US20050008499A1 - Displacement control mechanism for variable displacement compressor - Google Patents
Displacement control mechanism for variable displacement compressor Download PDFInfo
- Publication number
- US20050008499A1 US20050008499A1 US10/851,870 US85187004A US2005008499A1 US 20050008499 A1 US20050008499 A1 US 20050008499A1 US 85187004 A US85187004 A US 85187004A US 2005008499 A1 US2005008499 A1 US 2005008499A1
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- Prior art keywords
- valve
- chamber
- spool
- control valve
- displacement
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/16—Filtration; Moisture separation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B53/00—Component parts, details or accessories not provided for in, or of interest apart from, groups F04B1/00 - F04B23/00 or F04B39/00 - F04B47/00
- F04B53/20—Filtering
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/1809—Controlled pressure
- F04B2027/1813—Crankcase pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/1822—Valve-controlled fluid connection
- F04B2027/1827—Valve-controlled fluid connection between crankcase and discharge chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/1822—Valve-controlled fluid connection
- F04B2027/1831—Valve-controlled fluid connection between crankcase and suction chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/184—Valve controlling parameter
- F04B2027/1854—External parameters
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/184—Valve controlling parameter
- F04B2027/1859—Suction pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/1863—Controlled by crankcase pressure with an auxiliary valve, controlled by
- F04B2027/1868—Crankcase pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/14—Control
- F04B27/16—Control of pumps with stationary cylinders
- F04B27/18—Control of pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B27/1804—Controlled by crankcase pressure
- F04B2027/1863—Controlled by crankcase pressure with an auxiliary valve, controlled by
- F04B2027/1881—Suction pressure
Definitions
- the present invention relates to a displacement control mechanism for controlling the displacement of a variable displacement compressor that forms a part of a refrigerant circulation circuit of an air-conditioner.
- the displacement of the compressor is varied in accordance with the pressure in a crank chamber of the compressor.
- crank chamber 153 (or crank pressure Pc).
- the crank chamber 153 communicates with a suction chamber 155 via a bleed passage 154 .
- a discharge chamber 151 of the compressor communicates with the crank chamber 153 via a supply passage 152 on which a control valve 156 is arranged.
- the amount of refrigerant gas introduced into the crank chamber 153 via the supply passage 152 is controlled by adjusting the opening degree of the control valve 156 , and the crank pressure Pc is determined in accordance with the relation between the amounts of refrigerant gas introduced into and bleeding from the crank chamber 153 .
- a fixed throttle 158 is formed in the bleed passage 154 so that the refrigerant gas bleeds slowly from the crank chamber 153 to the suction chamber 155 .
- the crank pressure Pc is steadily increased. Therefore, when the control valve 156 increases the opening degree of the supply passage 152 , the crank pressure Pc is rapidly increased. Consequently, appropriate response in decreasing the compressor displacement is obtained.
- an amount of blow-by gas from a cylinder bore 157 to the crank chamber 153 leaks to the suction chamber 155 via the bleed passage 154 .
- the refrigerant gas moves from the discharge chamber 151 to the suction chamber 155 via the crank chamber 153 as mentioned above, such movement of the refrigerant being a kind of internal leaking.
- the amount of the above leaking blow-by gas and the amount of the above moving refrigerant gas are reduced as much as possible by the provision of the fixed throttle 158 . Consequently, decrease in efficiency of the compressor caused by the provision of the displacement control mechanism is prevented.
- the fixed throttle 158 provided in the bleed passage 154 causes the pressure in the crank chamber 153 to be slowly reduced, thereby deteriorating the response of the compressor in increasing the displacement.
- the crank pressure Pc tends to be increased excessively because the liquid refrigerant accumulated in the crank chamber 153 evaporates and the fixed throttle 158 prevents smooth flow of refrigerant gas from the crank chamber 153 . Therefore, even when the control valve 156 closes the supply passage 152 so as to increase the displacement of the compressor in response to the requirement for cooling shortly after starting the compressor, it takes time before the displacement of the compressor is actually increased, so that the cooling performance shortly after a start-up of an air-conditioner deteriorates.
- a second control valve 161 for controlling the opening degree of the bleed passage 154 in addition to the control valve (first control valve) 156 , as shown in FIG. 16 (e.g. Japanese Unexamined Patent Publication 2002-21721).
- a region K is provided in the supply passage 152 downstream of the position of first control valve 156 (i.e. the position of valve opening adjustment) and upstream of the fixed throttle 169 , as shown in FIG. 16 .
- the second control valve 161 is a spool type valve that includes a spool 162 and a backpressure chamber 166 into which the pressure in the region K Is introduced.
- a valve chamber 167 of the second control valve 161 forms a part of the bleed passage 154 and communicates with the suction chamber 155 .
- the valve chamber 167 also communicates with the crank chamber 153 via a valve hole 168 that forms the upstream part of the bleed passage 154 .
- the spool 162 is movably disposed in a spool-supporting recess 164 that is formed in a compressor housing.
- the spool 162 includes a valve portion 162 a that is located in the valve chamber 167 and a back surface 162 b that is located in the backpressure chamber 166 .
- the spool 162 (or the valve portion 162 a ) is positioned by various forces applied thereto such as urging force based on the pressure in the backpressure chamber 166 acting on the back surface 162 b in the direction to close the valve, urging force of a spring 165 acting in the valve opening direction and force of the crank pressure Pc that is applied in the valve opening direction.
- a pressure PdK in the backpressure chamber 166 of the second control valve 161 is substantially the same as the crank pressure Pc and, therefore, the spool 162 of the second control valve 161 is positioned by the spring 165 where the valve hole 168 is wide opened at a maximum opening degree.
- the bleed passage 154 is wide opened by the second control valve 161 , flowing of the refrigerant from the crank chamber 153 to the suction chamber 155 is promoted. Therefore, closing the supply passage 152 by the first control valve 156 so as to increase the displacement of the compressor shortly after starting the compressor, the displacement of the compressor is immediately increased, so that the cooling performance shortly after a start-up of air conditioner is improved.
- a spring having a small spring force is utilized as the spring 165 .
- the spool 162 moves against the urging force of the spring 165 , and the valve portion 162 a sets the valve hole 168 at a minimum opening degree that is not zero. Therefore, when the valve hole 168 is thus set at the minimum opening degree that is not zero, the second control valve 161 functions similarly as the above-described fixed throttle 158 shown in FIG. 15 , and the decrease in the efficiency of the compressor which is caused by having the displacement control mechanism is prevented.
- the second control valve 161 is arranged such that the clearance between the outer peripheral surface of the spool 162 and the inner peripheral surface of the spool-supporting recess 164 is small, so that the fluid communication between the backpressure chamber 166 and the valve chamber 167 via the clearance is blocked, and the decrease in the efficiency of the compressor due to the leak of the refrigerant gas from the backpressure chamber 166 to the valve chamber 167 is prevented.
- foreign substances tend to be caught between the outer peripheral surface of the spool 162 and the inner peripheral surface of the spool-supporting recess 164 , thereby causing poor sliding movement of the spool 162 .
- the alternative embodiment of the above prior art reference proposes the use of a bellows instead of the spool 162 and the spring 165 .
- the bellows that is elastic and stretchable and serves as a partition wall shutting off the communication between the back pressure chamber and the valve chamber without any sliding contact of moving part of the second control valve with the compressor housing, the clearance between the moving part of the second control valve and the compressor housing is set large enough.
- the bellows becomes larger with a decrease of its spring constant.
- the second control valve having incorporated therein a bellows is disadvantageously large-sized.
- the present invention provides a displacement control mechanism for a variable displacement compressor that prevents the operation failure of the spool of a second control valve that adjusts the opening degree of the bleed passage.
- a displacement control mechanism is used in a variable displacement compressor for controlling a displacement of the compressor.
- the compressor partially forms a refrigerant circulation circuit of an air-conditioner.
- the displacement of the compressor is varied in accordance with a pressure in a crank chamber of the compressor.
- the refrigerant circulation circuit includes a suction pressure region and a discharge pressure region.
- the displacement control mechanism includes a first bleed passage, a supply passage, a first control valve and a second control valve.
- the first bleed passage interconnects the crank chamber and the suction pressure region.
- the supply passage interconnects the crank chamber and the discharge pressure region.
- the first control valve is located on the supply passage for controlling an opening degree of the supply passage.
- the second control valve is located on the first bleed passage.
- the second control valve also includes a backpressure chamber and a spool.
- the backpressure chamber has substantially the same pressure atmosphere as a region of the supply passage downstream of the first control valve.
- the spool includes a back surface that is located in the backpressure chamber.
- the spool has a cylindrical outer peripheral surface.
- the spool reduces an opening degree of the first bleed passage when a pressure in the backpressure chamber that is applied to the back surface is increased.
- the spool blocks a communication between the backpressure chamber and the first bleed passage via a clearance formed around the cylindrical outer peripheral surface of the spool in the second control valve when the spool sets the first bleed passage at a minimum opening degree.
- FIG. 1 is a longitudinal cross-sectional view of a variable displacement compressor according to a first preferred embodiment
- FIG. 2 is a cross-sectional view of a first control valve
- FIG. 3A is a partially enlarged cross sectional view of the variable displacement compressor around a second control valve
- FIG. 3B is a schematic view showing cross section areas of a valve chamber and a valve hole for explaining conditional inequalities
- FIG. 4A is a cross-sectional view explaining an action of the second control valve
- FIG. 4B is a cross-sectional view explaining the action of the second control valve
- FIG. 5 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a second preferred embodiment
- FIG. 6 is a cross-sectional view explaining an action of the second control valve
- FIG. 7 is a cross-sectional view of a first control valve including a second control valve therein according to a third preferred embodiment
- FIG. 8 is a partially enlarged cross-sectional view of the first control valve including the second control valve therein according to the third preferred embodiment
- FIG. 9 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a first alternative embodiment
- FIG. 10 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a second alternative embodiment
- FIG. 11 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a third alternative embodiment
- FIG. 12 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a fourth alternative embodiment
- FIG. 13 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a fifth alternative embodiment
- FIG. 14 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a sixth alternative embodiment
- FIG. 15 is a schematic view of a variable displacement compressor according to prior art.
- FIG. 16 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to prior art.
- the present invention is applied to a swash plate type variable displacement compressor (hereinafter the compressor) that is used in a vehicle air-conditioner for compressing refrigerant gas.
- the compressor swash plate type variable displacement compressor
- the compressor includes a cylinder block 1 , a front housing 2 , a valve plate assembly 3 and a rear housing 4 .
- the left side and the right side respectively correspond to the front side and the rear side of the compressor.
- the front housing 2 is fixed to the front end of the cylinder block 1
- the rear housing 4 is fixed to the rear end of the cylinder block 1 via the valve plate assembly 3 .
- a compressor housing includes the cylinder block 1 , the front housing 2 and the rear housing 4 .
- a crank chamber 5 is defined by the cylinder block 1 and the front housing 2 .
- a drive shaft 6 is rotatably supported in the crank chamber 5 .
- a lug plate 11 is rotatably fixed to the drive shaft 6 in the crank chamber 5 .
- the front end of the drive shaft 6 is operatively connected to a vehicle engine E as an external drive source via a power transmission mechanism PT.
- the power transmission mechanism PT is a clutch mechanism (e.g. an electromagnetic clutch) that selectively transmits and blocks driving power according to electric control from an external device, or a continuous transmission type clutchless mechanism (e.g. the combination of belt and pulley) that dispenses with the above clutch mechanism.
- the clutchless type power transmission mechanism PT is utilized.
- a swash plate 12 as a cam plate is accommodated in the crank chamber 5 .
- the swash plate 12 is slidably and inclinably supported by the drive shaft 6 .
- a hinge mechanism 13 is interposed between the lug plate 11 and the swash plate 12 .
- a plurality of cylinder bores 1 a are formed in the cylinder block 1 extending axially through the cylinder block 1 and arranged around the drive shaft 6 .
- Single-headed pistons 20 are each accommodated in the respective cylinder bores 1 a for reciprocation therein.
- the front and rear openings of the cylinder bores 1 a are respectively closed by the valve plate assembly 3 and the pistons 20 .
- Compression chambers are defined in the cylinder bores 1 a , and the volume of the compression chambers is varied in accordance with the reciprocating movement of the pistons 20 .
- Each of the pistons 19 is engaged with the swash plate 12 via a pair of shoes 19 , so that the rotation of the swash plate 12 in accordance with the drive shaft 6 is converted into reciprocating linear movement of the pistons 20 .
- a suction chamber 21 and a discharge chamber 22 are defined between the valve plate assembly 3 and the rear housing 4 .
- the suction chamber 21 is located in the middle region of the rear housing 4 and is surrounded by the discharge chamber 22 .
- a suction port 23 and a suction valve 24 are formed in the valve plate assembly 3 for each of the cylinder bores 1 a .
- the suction valve 24 is adapted to open and close the suction port 23 .
- a discharge port 25 and a discharge valve 26 are also formed in the valve plate assembly 3 for each of the cylinder bores 1 a .
- the suction chamber 21 communicates with each of the cylinder bores 1 a via the corresponding suction port 23
- each of the cylinder bores 1 a communicates with the discharge chamber 22 via the corresponding discharge port 25 .
- the refrigerant gas is drawn into the corresponding cylinder bore 1 a via the suction port 23 and the suction valve 24 .
- the refrigerant gas introduced into the cylinder bore 1 a is compressed to a predetermined pressure and is discharged into the discharge chamber 22 via the discharge port 25 and the discharge valve 26 .
- An inclination angle of the swash pate 12 which is defined as an angle made between the swash plate 12 and a hypothetical plane perpendicular to an axis L of the drive shaft 6 is varied in accordance with the pressure in the crank chamber 5 (a crank pressure Pc).
- the inclination angle of the swash plate 12 is randomly determined between a minimum inclination angle as indicated by a solid line in FIG. 1 and a maximum inclination angle as indicated by a chain double-dashed line in FIG. 1 .
- a displacement control mechanism for controlling the crank pressure Pc which is concerned with the controlling of the inclination angle of the swash plate 12 includes a first bleed passage 27 , a second bleed passage 28 , a supply passage 29 , a first control valve CV 1 and a second control valve CV 2 .
- the first and second bleed passages 27 and 28 interconnect the crank chamber 5 and the suction chamber 21 as a suction pressure (Ps) region.
- the second control valve CV 2 is arranged on the first bleed passage 27 .
- the second bleed passage 28 has a fixed throttle 28 a and extends through the cylinder block 1 and the valve plate assembly 3 .
- the fixed throttle 28 a located in the second bleed passage 28 is formed such that the part of the second bleed passage 28 extending through the valve plate assembly 3 is narrower than that extending through the cylinder block 1 .
- the supply passage 29 interconnects the discharge chamber 22 as a discharge pressure (Pd) region and the crank chamber 5 .
- the first control valve CV 1 is arranged on the supply passage 29 for adjusting the opening degree of the supply passage 29 .
- the supply passage 29 extends through the valve plate assembly 3 downstream of the first control valve CV 1 or on a side of the crank chamber 5 .
- the first control valve CV 1 and the second control valve CV 2 respectively adjust the opening degree of the supply passage 29 and the first bleed passage 27 .
- the balance between the amount of high-pressure discharge gas introduced from the discharge chamber 22 into the crank chamber 5 via the supply passage 29 and the amount of the refrigerant gas flowing from the crank chamber 5 into the suction chamber 21 via the first and second bleed passages 27 and 28 is controlled, and the crank pressure Pc is determined, accordingly.
- Pressure difference between the crank pressure Pc and the internal pressure in the cylinder bores 1 a via the pistons 20 is changed in accordance with the variation of the crank pressure Pc, and the inclination angle of the swash plate 12 is varied, accordingly. Consequently, the stroke of pistons 20 , that is, the displacement of the compressor is adjusted.
- the first control valve CV 1 reduces the opening degree of the supply passage 29 and the crank pressure Pc is decreased, the inclination angle of the swash plate 12 is increased, and the displacement of the compressor is increased.
- the first control valve CV 1 increases the opening degree of the supply passage 29 and the crank pressure Pc is increased, the inclination angle of the swash plate 12 is decreased, and the displacement of the compressor is decreased.
- a refrigerant circulation circuit (or refrigerant cycle) of the vehicle air-conditioner includes the above-described compressor and an external refrigerant circuit 30 .
- the external refrigerant circuit 30 includes a gas cooler 31 , an expansion valve 32 and an evaporator 33 .
- a circulation pipe 35 for the refrigerant is provided on the downstream side of the external refrigerant circuit 30 , interconnecting the outlet of the evaporator 33 and the suction chamber 21 of the compressor.
- a circulation pipe 36 for the refrigerant is provided on the upstream side of the external refrigerant circuit 30 , interconnecting the discharge chamber 22 of the compressor and the inlet of the gas cooler 31 .
- the first control valve CV 1 includes a supply valve portion in the upper half thereof as seen on the drawing of FIG. 2 and a solenoid portion 60 in the lower half.
- the supply valve portion adjusts the opening degree (throttle degree) of the supply passage 29 that interconnects the discharge chamber 22 and the crank chamber 5 .
- the solenoid portion 60 is an actuator for controlling the operation of a valve rod 40 arranged in the control valve CV 1 in response to a control signal from an external device.
- the valve rod 40 is a rod-like member which includes a partition wall portion 41 at the top of the valve rod 40 , a connection part 42 , a valve body 43 at the middle of the valve rod 40 and a guide rod 44 at the base of the valve rod 40 .
- the valve body 43 is a part of the guide rod 44 .
- a valve housing 45 for the first control valve CV 1 includes a valve body housing 45 a forming its upper part and an actuator housing 45 b forming its lower part.
- a valve accommodation chamber 46 , a communication passage 47 and a pressure sensing chamber 48 are defined in the valve body housing 45 a in this order as seen from the lower side of FIG. 2 .
- the valve rod 40 is arranged in the valve accommodation chamber 46 and the communication passage 47 for movement in the direction of the axis of the valve housing 45 , that is, movement in the vertical direction as seen in FIG. 2 .
- the partition wall portion 41 of the valve rod 40 is inserted through the communication passage 47 thereby to shut off the communication between the pressure sensing chamber 48 and the communication passage 47 .
- Ports 51 and 52 are formed through the peripheral wall of the valve body housing 45 a .
- the port 51 communicates with the valve accommodation chamber 46
- the port 52 communicates with the communication passage 47 , respectively.
- the valve accommodation chamber 46 communicates with the discharge chamber 22 of the compressor via the port 51 and the upstream part of the supply passage 29 .
- the communication passage 47 communicates with the crank chamber 5 of the compressor via the port 52 and the downstream part of the supply passage 29 .
- the valve accommodation chamber 46 and the communication passage 47 form a part of the supply passage 29 .
- the valve body 43 of the valve rod 40 is located in the valve accommodation chamber 46 .
- a valve seat 53 is formed at the step portion located between the valve accommodation chamber 46 and the communication passage 47 , and the communication passage 47 functions as a valve hole.
- a bellows 50 is accommodated in the pressure sensing chamber 48 .
- the upper end of the bellows 50 is fixed to the valve housing 45 .
- the top of the partition wall portion 41 of the valve rod 40 is fitted into the lower end of the bellows 50 .
- a first pressure chamber 54 that is located inside the bellows 50 and a second pressure chamber 55 that is located outside the bellows 50 are defined in the pressure sensing chamber 48 by the bellows 50 that has a cylindrical shape with a bottom.
- a throttle 36 a is formed in the circulation pipe 36 between the discharge chamber 22 and the external refrigerant circuit 30 .
- the first pressure chamber 54 communicates via a first pressure introducing passage 37 with the discharge chamber 22 at a first pressure monitoring point P 1 that is located upstream of the throttle 36 a .
- the second pressure chamber 55 communicates via a second pressure introducing passage 38 with the circulation pipe 36 at a second pressure monitoring point P 2 that is located downstream of the throttle 36 a .
- a monitored pressure PdH at the first pressure monitoring point P 1 is introduced into the first pressure chamber 54
- a monitored pressure PdL at the second pressure monitoring point P 2 is introduced into the second pressure chamber 55 .
- the lower end of the bellows 50 vertically moves in accordance with the pressure difference (PdH ⁇ PdL) between the pressures on opposite sides of the throttle 36 a .
- positioning of the valve rod 40 (the valve portion 43 ) is determined by varying the pressure difference.
- the pressure difference (PdH ⁇ PdL) between the pressures on opposite sides of the throttle 36 a varies depending on the refrigerant flow rate in the refrigerant circulation circuit. For example, when the refrigerant flow rate is increased, the pressure difference (PdH ⁇ PdL) is increased. On the other hand, when the refrigerant flow rate is decreased, the pressure difference (PdH ⁇ PdL) is decreased.
- the bellows 50 operates on the valve body 43 such that the displacement of the compressor is changed so as to cancel the variation of the pressure difference (PdH ⁇ PdL).
- the solenoid portion 60 of the first control valve CV 1 includes an accommodation cylinder 61 that has a cylindrical shape with a bottom in the middle of the actuator housing 45 b .
- a fixed core 62 of a column shape is fitted in the upper opening of the accommodation cylinder 61 .
- a solenoid chamber 63 is defined in the lower portion of the accommodation cylinder 61 .
- a movable core 64 is axially movable and accommodated in the solenoid chamber 63 .
- a guide hole 65 extends through the center of the fixed core 62 in the axial direction of the valve rod 40 .
- the guide rod 44 of the valve rod 40 is arranged in the guide hole 65 so as to move in the axial direction of the valve rod 40 .
- the guide rod 44 is fitted into the movable core 64 .
- a spring 66 is accommodated between the fixed core 62 and the movable core 64 in the solenoid chamber 63 for urging the valve rod 40 in such direction that causes the valve body 43 to move away from the valve seat 53 .
- a coil 67 is wound around the outer periphery of the accommodation cylinder 61 over a range covering the fixed core 62 and the movable core 64 .
- Driving signal is transmitted from a driving circuit 68 a to the coil 67 , based on the command from a control device 68 in accordance with air-conditioning load.
- a magnitude of the electromagnetic force (or electromagnetic attraction) in accordance with an amount of electric power supplied to the coil 67 is generated between the fixed core 62 and the movable core 64 .
- the electromagnetic force is transmitted to the valve rod 40 (the valve body 43 ) through the movable core 64 .
- Controlling to energize the coil 67 is performed by adjusting the voltage applied across the coil 67 , and duty ratio is utilized in the first preferred embodiment.
- the solenoid portion 60 of the first control valve CV 1 varies the electromagnetic force that is applied to the valve body 43 in accordance with the amount of the electric power supplied from an external device.
- control target set pressure difference
- PdH ⁇ PdL pressure difference between the pressures on opposite sides of the throttle 36 a
- a standard for positioning the valve body 43 by the bellows 50 is changed by varying the electromagnetic force that is applied to the valve body 43 .
- the first control valve CV 1 is constructed to internally autonomously position the valve rod 40 (the valve body 43 ) in accordance with the variation of the pressure difference (PdH ⁇ PdL) between the first and second pressure monitoring points P 1 and P 2 such that the set pressure difference determined by the amount of the electric power supplied to the coil 67 is maintained.
- the set pressure difference of the first control valve CV 1 is varied by adjusting the amount of the electric power supplied to the coil 67 from the external device. For example, when the duty ratio that is commanded from the control device 68 to the driving circuit 68 a is increased, electromagnetic urging force of the solenoid portion 60 is increased, and the set pressure difference of the first control valve CV 1 is increased, accordingly. With the set pressure difference of the first control valve CV 1 thus increased, the displacement of the compressor is increased. On the other hand, when the duty ratio that is commanded from the control device 68 to the driving circuit 68 a is decreased, electromagnetic urging force of the solenoid portion 60 is decreased, and the set pressure difference of the first control valve CV 1 is decreased. When the set pressure difference of the first control valve CV 1 is decreased, the displacement of the compressor is decreased.
- an accommodation hole 70 is formed in the rear housing 4 for accommodating therein the second control valve CV 2 .
- the rear housing 4 functions also as a valve housing for the second control valve CV 2 .
- the cross section showing the second control valve CV 2 is different from that showing the first control valve CV 1 and the suction chamber 21 .
- the first control valve CV 1 protrudes from a rear end 4 a of the rear housing 4 toward the rear side, and the accommodation hole 70 is not covered with the first control valve CV 1 .
- the accommodation hole 70 is formed extending through the rear end 4 a and a front end of 4 b of the rear housing 4 in parallel with the axis L of the drive shaft 6 or in the horizontal direction of as viewed in FIGS. 1, 3A , 4 A and 4 B.
- the front opening of the accommodation hole 70 on the front end 4 b of the rear housing 4 is closed by the valve plate assembly 3 .
- the accommodation hole 70 includes a valve chamber 71 that is a small-diameter hole, a middle-diameter hole 72 whose diameter is greater than that of the valve chamber 71 , and a large-diameter hole 73 whose diameter is still greater than that of the hole 73 , in this order as seen from the left side on the drawings.
- the valve chamber 71 , the middle-diameter hole 72 and the large-diameter hole 73 are formed coaxially.
- a valve hole 27 a is formed in the valve plate assembly 3 that partially defines the valve chamber 71 and the cylinder block 1 .
- the valve chamber 71 communicates with the crank chamber 5 via the valve hole 27 a .
- the valve chamber 71 also communicates with a communication hole 27 b that is formed in the rear housing 4 .
- the communication hole 27 b is opened into the valve chamber 71 through a cylindrical inner peripheral surface 71 a of the valve chamber 71 .
- the valve hole 27 a , the valve chamber 71 and the communication hole 27 b form the first bleed passage 27 .
- a spool 75 is received in the valve chamber 71 and the middle-diameter hole 72 for movement in the horizontal direction as seen in FIGS. 1, 3A , 4 A and 4 B.
- a stopper 76 is fixedly fitted in the large-diameter hole 73 .
- the stopper 76 is positioned by the step portion that is located between the large-diameter hole 73 and the middle-diameter hole 72 in the rear housing 4 for restricting the movement of the spool 75 beyond the rear end of the middle-diameter hole 72 .
- the spool 75 has a small-diameter portion 75 a located on the side of the valve chamber 71 and a large-diameter portion 75 b formed coaxially with the small-diameter portion 75 a and located on the side of the middle-diameter portion 72 .
- the spool 75 has also an annular-shaped movable step 78 formed between outer peripheral surfaces 77 a and 77 b of the small-diameter portion 75 a and the large-diameter portion 75 b of the spool 75 .
- the movable step 78 includes a wall surface 78 a that faces toward a side of the valve plate assembly 3 .
- the large-diameter portion 75 b of the spool 75 has a cylindrical shape with an opening to the rear side, that is, to the side of the stopper 76 .
- the small-diameter portion 75 a of the spool 75 is almost located in the valve chamber 71 , and the large-diameter portion 75 b is accommodated in the middle-diameter hole 72 for movement in the axial direction of the spool 75 .
- the small-diameter portion 75 a is coaxial with the valve hole 27 a , and the diameter of the small-diameter portion 75 a is larger than that of the valve hole 27 a .
- the front end of the small-diameter portion 75 a forms a first valve portion 79 that adjusts the opening degree of the valve hole 27 a that communicates with the valve chamber 71 , that is, the opening degree of the first bleed passage 27 .
- the opening degree of the valve hole 27 a is decreased.
- the opening degree of the valve hole 27 a is increased.
- a backpressure chamber 80 is defined between the stopper 76 and the large-diameter portion 75 b of the spool 75 in the middle-diameter hole 72 .
- the backpressure chamber 80 includes a cylindrical inner space of the large-diameter portion 75 b .
- the spool 75 has a back surface 81 which includes the end surface of the opening portion of the large-diameter portion 75 b and the inner bottom surface of the large-diameter portion 75 b .
- the back surface 81 of the spool 75 is located in the backpressure chamber 80 .
- a pressure introducing passage 82 branches from the supply passage 29 at the region K that is located on the side of the crank chamber 5 , that is, downstream of the position of valve opening adjustment in the first control valve CV 1 (or the valve seat 53 ).
- the pressure introducing passage 82 communicates with the large-diameter hole 73 and is opened into an inner peripheral surface 73 a of the large diameter hole 73 .
- a communication groove 76 a and a communication hole 76 b are formed in the stopper 76 to interconnect the pressure introducing passage 82 and the middle-diameter hole 72 .
- the communication groove 76 a is formed annularly throughout the outer peripheral surface of the stopper 76 at a position facing the opening of the pressure introducing passage 82 .
- the communication hole 76 b extends through the stopper 76 between the communication groove 76 a and an end surface 76 c of the stopper 76 on the side of the valve plate assembly 3 ,
- the communication hole 76 b is open at the center of the end surface 76 c.
- Pressure PdK in the region K of the supply passage 29 is introduced into the backpressure chamber 80 via the pressure introducing passage 82 , the communication groove 76 a and the communication hole 76 b .
- the backpressure chamber 80 has the same pressure atmosphere as the region K that is located downstream of the position of valve opening adjustment in the control valve CV 1 in the supply passage 29 .
- Force from the pressure PdK in the backpressure chamber 80 urges the spool 75 toward the valve plate assembly 3 , that is, in the direction that causes the valve to be closed.
- the spool 75 has the characteristics of decreasing the opening degree of the valve hole 27 a with an increase in the pressure PdK in the backpressure chamber 80 that is applied to the back surface 81 .
- the outer diameter of the large-diameter portion 75 b of the spool 75 is larger than the inner diameter of the valve chamber 71 .
- An annular fixed step 83 is formed between the valve chamber 71 and the middle-diameter hole 72 in the second control valve CV 2 .
- the fixed step 83 includes a wall surface 83 a that faces the wall surface 78 a of the movable step 78 of the spool 75 .
- the axial length of the small-diameter portion 75 a of the spool 75 is slightly smaller than that of the valve chamber 71 .
- the wall surface 78 a of the movable step 78 contacts the wall surface 83 a of the fixed step 83 , and a slight clearance is formed between the first valve portion 79 and the valve plate assembly 3 . Since the first bleed passage 27 is not closed even when the opening of the valve hole 27 a is reduced to the minimum and, therefore, the crank chamber 5 keeps fluid communication with the suction chamber 21 via the first bleed passage 27 .
- the minimum opening degree of the valve hole 27 a is slightly larger than zero.
- the minimum clearance between the first valve portion 79 and the valve plate assembly 3 functions as a throttle of the first bleed passage 27 .
- the diameter of the throttle 28 a of the second bleed passage 28 is set smaller than that when the second control valve CV 2 and the first bleed passage 27 are not hypothetically provided.
- a spring 85 such as coil spring is located in a clearance 84 between the outer peripheral surface 77 a of the small-diameter portion 75 a of the spool 75 and the inner peripheral surface 71 a of the valve chamber 71 .
- the movable end of the spring 85 is in contact with the wall surface 78 a of the movable step 78 at a region that is located radially inward from the region where the wall surface 78 a faces the wall surface 83 a of the fixed step 83 .
- the inner region of the wall surface 78 a that is located radially inward from the annular region of the wall surface 78 a that faces the wall surface 83 a of the fixed step 83 forms a spring seat 86 for the movable end of the spring 85 .
- the fixed end of the spring 85 is in contact with the valve plate assembly 3 at a position surrounding the opening of the valve hole 27 a .
- the spring 85 urges the spool 75 in the direction that causes the first valve portion 79 to move so as to increases the opening degree of the valve hole 27 a.
- a clearance 87 is formed between an outer peripheral surface 77 b of the large-diameter portion 75 b of the spool 75 and an inner peripheral surface 72 a of the middle-diameter hole 72 , and the clearance 87 is narrower than the clearance 84 between the outer peripheral surface 77 a of the small-diameter portion 75 a and the inner peripheral surface 71 a of the valve chamber 71 .
- a clearance 84 a is formed between the spring 85 and the inner peripheral surface 71 a of the valve chamber 71 and, especially, is provided such that the spring 85 freely extends and contracts in accordance with the movement of the spool 75 .
- the clearance 87 is also narrower than the clearance 84 a . Namely, the clearance 87 is the narrowest of the all clearances that are around the cylindrical outer peripheral surface 77 of the spool 75 .
- the valve chamber 71 communicates with the backpressure chamber 80 via the clearance between the wall surfaces 78 a and 83 a and the clearance 87 of the spool 75 .
- the wall surface 78 a of the movable step 78 contacts the wall surface 83 a of the fixed step 83 as shown in FIG. 3A , the communication between the backpressure chamber 80 and the valve chamber 71 via the clearance 87 of the spool 75 is shut off.
- the annular region of the wall surface 78 a of the movable step 78 that faces the wall surface 83 a of the fixed step 83 forms a second valve portion 88 for shutting off the communication between the backpressure chamber 80 and the valve chamber 71 via the clearance 87 of the spool 75 .
- a valve seat 89 for the second valve portion 88 is formed by an annular region of the wall surface 83 a of the fixed step 83 that faces the second valve portion 88 .
- a filter 90 is arranged in the supply passage 29 on the side of the discharge chamber 22 , that is, upstream of the first control valve CV 1 for removing foreign substances in the refrigerant gas.
- the width of the clearance 87 between the large-diameter portion 75 b of the spool 75 and the inner peripheral surface 72 a of the accommodation hole 70 is larger than the diameter of the foreign substances that pass through the filter 90 .
- the width of the clearance 87 is larger than the diameter of the mesh openings of the filter 90 .
- the clearance 87 that is the narrowest clearance around the cylindrical outer peripheral surface 77 of the spool 75 is formed with a width that is larger than the diameter of the foreign substances flowing through the clearance 87 .
- the cross sectional area of the valve chamber 71 that is perpendicular to the axial direction of the spool 75 is represented as SA
- the cross sectional area of the valve hole 27 a that is also perpendicular to the axial direction of the spool 75 is represented as SB, which is smaller than SA.
- a force for urging the spool 75 toward the valve plate assembly 3 that is, in the direction in which the opening degree of the valve hole 27 a is decreased in response to the varying pressure difference between the pressure PdK and the crank pressure Pc is expressed by “(PdK ⁇ PC)SB”.
- a force for urging the spool 75 in the direction which causes the opening degree of the valve hole 27 a to be decreased in accordance with the pressure difference between the pressure PdK and the suction pressure Ps, is expressed by “(PdK ⁇ Ps)(SA ⁇ SB).”
- the urging force of the spring 85 is represented as “f”.
- Conditional inequality (1) for the minimum opening degree of the valve hole 27 a in the second control valve CV 2 is expressed as follows: ( PdK ⁇ Ps )( SA ⁇ SB )+( Pdk ⁇ Pc ) SB>f (1)
- the backpressure chamber 80 is in constant communication with the crank chamber 5 via the supply passage 29 and has the same pressure atmosphere as the crank chamber 5 .
- the pressure PdK is substantially the same as the pressure Pc. Therefore, the above inequality (1) is expressed as the following conditional inequality (2): ( Pc ⁇ Ps )( SA ⁇ SB )> f (2)
- the spring 85 for use in the illustrated embodiment has a small set load and a low spring constant. It is understood, therefore, from the above conditional inequality (2) that the valve portion 79 reduces the opening degree of the valve hole 27 a to the minimum opening degree when the crank pressure Pc somewhat exceeds the suction pressure Ps.
- the pressure is equalized at a low value in the refrigerant circulation circuit and, therefore, the crank pressure Pc becomes substantially the same as the suction pressure Ps. Since the conditional inequality (2) is no more effective, the spool 75 is moved by the urging force of the spring 85 until the spool 75 is brought into contact with the stopper 76 , as shown in FIG. 4A . With the spool 75 thus fully urged by the spring 85 , the valve portion 79 sets the opening degree of the valve hole 27 a at its maximum.
- liquid refrigerant existing on the low pressure side of the external refrigerant circuit 30 with the vehicle engine E kept at a stop for a long time, flows into the crank chamber 5 via the suction chamber 21 due to the fluid communication between the crank chamber 5 and the suction chamber 21 via the first and second bleed passages 27 and 28 .
- the temperature in the engine room where the compressor is located is lower than that in the vehicle interior, a large amount of the liquid refrigerant flows into the crank chamber 5 via the suction chamber 21 and is accumulated in the crank chamber 5 .
- the control device 68 is operated in response to the cooling demand from the occupant of the vehicle to command maximum duty ratio to the drive circuit 68 a , and the set pressure difference of the first control valve CV 1 is set at the maximum value for performing cooling as required. Accordingly, the first control valve CV 1 closes the supply passage 29 , and no high pressure refrigerant gas is supplied from the discharge chamber 22 to the crank chamber 5 and the backpressure chamber 80 of the second control valve CV 2 .
- the spool 75 of the second control valve CV 2 is maintained in such a state that the first valve portion 79 fully opens the first bleed passage 27 by the urging force f of the urging spring 85 , and the liquid refrigerant in the crank chamber 5 , as well as the refrigerant gas evaporated from a part of the liquid refrigerant, is immediately flown into the suction chamber 21 via the fully-opened first bleed passage 27 .
- the crank pressure Pc is maintained at a low value corresponding to that the first control valve CV 1 is closed, the compressor increases the inclination angle of the swash plate 12 thereby to increase the displacement of the compressor to its maximum.
- the first bleed passage 27 is fully opened by the first valve portion 79 of the second control valve CV 2 as described above.
- the crank pressure Pc is maintained at substantially the same level as the suction pressure Ps, and the maximum inclination angle of the swash plate 12 , that is, the maximum displacement operation (100% displacement operation) of the compressor is maintained.
- the second valve portion 88 is moved away from the valve seat 89 , and the backpressure chamber 80 communicates with the valve chamber 71 via the clearance 87 (refer to FIG. 4B ).
- the first control valve CV 1 is in its closed state when the backpressure chamber 80 is in communication with the valve chamber 71 , no refrigerant gas in the discharge chamber 22 flows into the backpressure chamber 80 via the first control valve CV 1 , and hence there is no fear of a decrease in efficiency of the refrigerant cycle caused by leakage of the refrigerant gas from the backpressure chamber 80 to the valve chamber 71 .
- the control device 68 reduces the duty ratio that is commanded to the drive circuit 68 a from the maximum. Accordingly, the first control valve CV 1 is changed from the closed state and opens the supply passage 29 so that the crank pressure Pc becomes higher than the suction pressure Ps.
- the conditional inequality (2) is satisfied, so that spool 75 moves against the urging force of the spring 85 in the direction to reduce the valve opening and the first bleed passage 27 , that is, the valve hole 27 a is substantially throttled by the first valve portion 79 .
- Amount of the compressed refrigerant gas that leaks from the discharge chamber 22 to the crank chamber 5 further to the suction chamber 21 is reduced by decreasing the opening degree of the first bleed passage 27 by the second control valve CV 2 , so that the decrease in the efficiency of the refrigerant cycle is prevented.
- the refrigerant circulation circuit in the first preferred embodiment is formed such that the refrigerant circulation stops by operating the compressor at the minimum displacement (so called an OFF operation of the clutchless compressor), the OFF operation of the compressor is reliably performed due to the substantial decrease in the opening degree of the first bleed passage 27 by the second control valve CV 2 .
- the second valve portion 88 contacts the valve seat 89 as described above. Accordingly, the communication between the valve chamber 71 and the backpressure chamber 80 is shut off. Thus, the refrigerant gas in the discharge chamber 22 is prevented from leaking from the backpressure chamber 80 to the suction chamber 21 via the clearance 87 , the valve chamber 71 and the communication hole 27 b . Therefore, the decrease in the efficiency of the refrigerant cycle is prevented.
- the second valve portion 88 is formed by the wall surface 78 a of the movable step 78 on the cylindrical outer peripheral surface 77 of the spool 75 , and the valve seat 89 for the second valve portion 88 is formed by the wall surface 83 a of the fixed step 83 .
- the functions of the second valve portion 88 and the valve seat 89 are provided to the second control valve CV 2 by simple structure such as the movable and fixed steps 78 and 83 in the first preferred embodiment. Therefore, the structure of the second control valve CV 2 is simplified.
- the second control valve CV 2 includes the spring 85 for urging the spool 75 in the direction to increase the valve opening, and the urging force f of the spring 85 relates to the positioning of the spool 75 .
- the operating characteristics of the second control valve CV 2 is easily adjusted by changing the urging force f of the spring 85 , that is, by selecting an appropriate spring from a group of springs having different characteristics.
- the wall surface 78 a of the movable step 78 that forms the second valve portion 88 is also utilized as the spring seat 86 for the spring 85 . Accordingly, in comparison to a case in which a spring seat (a step) is provided separately from the movable step 78 , the structure of the spool 75 and the structure of the second control valve CV 2 is simplified.
- the filter 90 is provided between the discharge chamber 22 and the first control valve CV 1 , and the width of the clearance 87 of the spool 75 is larger than the diameter of the foreign substances that pass through the filter 90 .
- the foreign substances whose diameter is larger than the width of the clearance 87 of the spool 75 will not be caught in the clearance 87 , and the operation failure of the spool 75 in the second control valve CV 2 is prevented successfully.
- the valve hole 27 a of the above-described first preferred embodiment is arranged so as to interconnects the crank chamber 5 and the valve chamber 71 .
- the valve hole 27 a in the second preferred embodiment is arranged so as to interconnects the suction chamber 21 and the valve chamber 71 as shown in FIGS. 5 and 6 .
- the communication hole 27 b which is arranged so as to interconnect the suction chamber 21 and the valve chamber 71 in the above-described first preferred embodiment, is modified in the second preferred embodiment such that the communication hole 27 b interconnects the crank chamber 5 and the valve chamber 71 .
- the accommodation hole 70 of the second control valve CV 2 extends in the vertical direction in FIGS. 5 and 6 and is open to the outside of the compressor.
- the valve chamber 71 is located in the upper side of the accommodation hole 70
- the large-diameter hole 73 is located in the lower side of the accommodation hole 70
- the middle-diameter hole 72 is removed from the accommodation hole 70 .
- the valve hole 27 a is open in a ceiling surface 71 b of the valve chamber 71 .
- the communication hole 27 b is open in the inner peripheral surface 71 a of the valve chamber 71 .
- the communication hole 27 b serves as a part of the region of the supply passage 29 on the side of the crank chamber 5 with respect to the second control valve CV 2 .
- the connection in the supply passage 29 between the first and second control valves CV 1 and CV 2 is open in the inner peripheral surface 73 a of the large-diameter hole 73 of the second control valve CV 2 .
- a spool 91 having a cylindrical shape with a cover is accommodated in the valve chamber 71 for movement in the vertical direction as seen in FIGS. 5 and 6 .
- the spool 91 is placed so as to have its opening that faces downward.
- the diameter of the top surface of the cylindrical spool 91 is larger than that of the valve hole 27 a .
- a region of the top surface of the spool 91 that faces the ceiling surface 71 b of the valve chamber 71 forms a valve portion 92 .
- a region of the ceiling surface 71 b of the valve chamber 71 that faces the valve portion 92 forms a valve seat 93 for the valve portion 92 .
- the spool 91 is formed with a flange 94 protruding radially outwardly from the opening portion of the spool 91 .
- a cylindrical outer peripheral surface 77 of the spool 91 includes an outer peripheral surface 77 a of the flange 94 and an outer peripheral surface 77 b of the cylindrical portion that is located above the flange 94 in the spool 91 as seen in FIGS. 5 and 6 .
- the spool 91 inserts into the spring 85 that is located in the clearance 84 formed between the outer peripheral surface 77 b of the spool 91 and the inner peripheral surface 71 a of the valve chamber 71 .
- the upper surface of the flange 94 forms the spring seat 86 for receiving the movable end of the spring 85 .
- a region on the ceiling surface 71 b outward from the valve seat 93 forms a spring seat for receiving the fixed end of the spring 85 .
- a slope 91 a is formed in the lower peripheral surface of the flange 94 .
- the slope 91 a is formed such that the distance from its sloped surface to the end surface 76 c of the stopper 76 is increasing as the diameter of the slope 91 a is larger.
- the back surface 81 of the spool 91 includes the inner ceiling surface of the spool 91 , the lower surface of the spool 91 and the slope 91 a of the spool 91 .
- the back surface 81 is located in the backpressure chamber 80 .
- valve chamber 71 and the backpressure chamber 80 in the second preferred embodiment are in constant communication with each other and share the same space, a region adjacent to the back surface 81 of the spool 91 is referred to as the backpressure chamber 80 .
- the backpressure chamber 80 has the same pressure atmosphere as the region K that is located downstream of the position of valve opening adjustment (the valve seat 53 ) of the first control valve CV 1 in the supply passage 29 .
- the clearance 87 between the outer peripheral surface 77 a of the flange 94 and the inner peripheral surface 71 a of the valve chamber 71 is narrower than the clearance 84 between the spring 85 and the inner peripheral surface 71 a of the valve chamber 71 .
- the width of the clearance 87 is larger than the diameter of the foreign substances that are around the cylindrical outer peripheral surface 77 of the spool 91 and pass through the filter 90 .
- the communication hole 27 b partially forms the supply passage 29 together with the valve chamber 71 and the backpressure chamber 80 .
- the refrigerant gas that flows into the backpressure chamber 80 via the first control valve CV 1 flows into the crank chamber 5 via the valve chamber 71 and the communication hole 27 b .
- the refrigerant gas flowing into the valve chamber 71 is guided by the slope 91 a of the spool 91 so as to flow smoothly into the communication hole 27 b.
- valve portion 92 of the spool 91 closes the valve hole 27 a , the communication between the backpressure chamber 80 and the valve hole 27 a via the clearance 87 of the spool 91 is shut off simultaneously by the valve portion 92 .
- the refrigerant gas in the discharge chamber 22 is prevented from leaking from the region K to the suction chamber 21 via the backpressure chamber 80 , the valve chamber 71 and the valve hole 27 a , so that the decrease in the efficiency of the refrigerant cycle is prevented.
- the valve portion 92 of the spool 91 closes the valve hole 27 a or the first bleed passage 27 and also simultaneously shuts off of the communication between the backpressure chamber 80 and the valve hole 27 a via the clearance 87 of the spool 91 .
- the clearance 87 is set to be small, and the operation failure of the spool 91 caused by foreign substances caught in the clearance 87 is prevented.
- the first bleed passage 27 and the supply passage 29 share the communication hole 27 b as a common part of the passages.
- the communication hole 27 b serves as the part of the first bleed passage 27 and the supply passage 29 between the crank chamber 5 and the valve chamber 71 .
- the third preferred embodiment differs from the second preferred embodiment mainly in that the second control valve CV 2 is installed in the valve housing 45 of the first control valve CV 1 .
- the relationship of upstream or downstream between the ports 51 and 52 is reverse of the relationship in the first control valve CV 1 of FIG. 2 . That is, the supply passage 29 is connected at the upstream side thereof (or the side of the discharge chamber 22 ) to the port 52 and at the downstream side thereof (or the side of the crank chamber 5 ) to the port 51 .
- a spool 96 , a valve seat body 97 and the spring 85 of the second control valve CV 2 are accommodated in the valve accommodation chamber 46 of the first control valve CV 1 .
- a through hole 96 a is formed in the middle of the spool 96 .
- the valve rod 40 is inserted into the through hole 96 a , and the spool 96 moves in the axial direction of the valve rod 40 .
- the valve seat body 97 is located below the spool 96 and in contact with the fixed core 62 in the valve accommodation chamber 46 .
- the part of the valve accommodation chamber 46 located above the top surface of the valve seat body 97 forms the valve chamber 71 .
- a recess 96 b is formed on the top surface of the spool 96 around the through hole 96 a.
- a port 98 is formed in the peripheral wall of the valve housing 45 that surrounds the lower portion of the valve accommodation chamber 46 .
- the port 98 is connected to the first bleed passage 27 on the side of the suction chamber 21 .
- the valve hole 27 a is formed in the valve seat body 97 and interconnects the port 98 and the valve chamber 71 .
- the valve hole 27 a is open at the top surface of the valve seat body 97 between the inner peripheral surface and the outer peripheral surface of the valve seat body 97 .
- a groove 96 c is formed in the lower surface of the spool 96 .
- the groove 96 c has an annular shape surrounding the through hole 96 a and has a part that faces the valve hole 27 a of the valve seat body 97 .
- valve portion 92 An annular region in the lower surface of the spool 96 that is located radially outward of the groove 96 c forms the valve portion 92 .
- An annular region in the top surface of the valve seat body 97 that is located radially outward of the valve hole 27 a and faces the valve portion 92 forms the valve seat 93 for the valve portion 92 .
- valve portion 92 With the valve portion 92 brought in contact with the valve seat 93 , the valve portion 96 d contacts the valve seat 97 a , thereby shutting off the communication between the valve hole 27 a and the backpressure chamber 80 via the clearance formed between the inner peripheral surface of the of the through hole 96 a of the spool 96 and the outer peripheral surface of the guide rod 44 in the valve rod 40 .
- a flange 94 is formed at the top of the spool 96 .
- the lower surface of the flange 94 forms the spring seat 86 for receiving the movable end of the spring 85 .
- a region in the top surface of the valve seat body 97 that is located radially outward of the valve seat 93 forms the valve seat for receiving the fixed end of the urging spring 85 .
- the back surface 81 of the spool 96 is formed by the top surface of the spool 96 and the bottom surface of the recess 96 b .
- the backpressure chamber 80 that is located between the back surface 81 and the position of valve opening adjustment, or the valve seat 53 , of the first control valve CV 1 forms a part of the region K that is located downstream, that is, on the side of the crank chamber 5 , of the position of valve opening adjustment of the first control valve CV 1 in the supply passage 29 .
- the backpressure chamber 80 has the same pressure atmosphere as the region K.
- the cylindrical outer peripheral surface 77 of the spool 96 includes the outer peripheral surface 77 a of the flange 94 and the outer peripheral surface of the spool 96 that is located below the flange 94 .
- the spring 85 is located in the clearance 84 between the outer peripheral surface 77 b and the inner peripheral surface 71 a of the valve chamber 71 .
- the clearance 87 between the outer peripheral surface 77 a of the flange 94 and the inner peripheral surface 71 a of the valve chamber 71 is narrower than the clearance 84 a between the spring 85 and the inner peripheral surface 71 a of the valve chamber 71 .
- the same advantageous effects are obtained as those which have been described in the second preferred embodiment.
- the first and second control valves CV 1 and CV 2 are formed as a single unit, the first and second control valves CV 1 and CV 2 are easily assembled to the rear housing 4 during manufacturing of the compressor.
- FIG. 9 A first alternative embodiment is shown in FIG. 9 and is a modification of the second preferred embodiment.
- the spool 91 is formed in the top surface thereof with a recess 91 b .
- a cross sectional area SC of the recess 91 b that is perpendicular to the axis of the spool 91 is larger than the cross sectional area SB of the valve hole 27 a that is perpendicular to the axis of the spool 91 .
- the pressure difference (Pc ⁇ Ps) is multiplied by the cross sectional area SC of the recess 91 b instead of the cross sectional area SB of the valve hole 27 a .
- valve hole 27 a is wide opened for allowing the liquid refrigerant that is accumulated in the crank chamber 5 to flow out thereof.
- the air-conditioner is stated, the refrigerant gas in the suction chamber 21 is drawn into the cylinder bores 1 a and the suction pressure Ps is instantaneously decreased, so that the spool 91 of the second control valve CV 2 may be moved toward the valve hole 27 a thereby to decrease the opening degree of the valve hole 27 a . In the result, the efficiency of flowing the liquid refrigerant is decreased.
- the communication hole 27 b extends obliquely upward from the valve chamber 71 .
- a wall 99 protrudes from the stopper 76 in the vertical direction as seen on the drawing to the ceiling surface 71 b of the valve chamber 71 .
- the wall 99 divides the valve chamber 71 into a space that accommodates the spool 91 and a communication passage 100 that extends in the vertical direction on the drawing and communicates with the communication hole 27 b.
- a hole 99 a is formed through the wall 99 so that the refrigerant gas that flows from the first control valve CV 1 into the backpressure chamber 80 via the communication hole 76 b of the stopper 76 and is guided toward the wall 99 by the slope 91 c flows toward the crank chamber 5 via the communication passage 100 and the communication hole 27 b .
- another hole 99 b is formed through the wall 99 so that, when the second control valve CV 2 is opened, the refrigerant that flows from the crank chamber 5 into the communication passage 100 via the communication hole 27 b flows into the suction chamber 21 via the valve chamber 71 and the valve hole 27 a .
- the hole 99 b is formed above the hole 99 a .
- the provision of the communication passage 100 and the though holes 99 a and 99 b helps to facilitate the flow of the refrigerant gas in the first bleed passage 27 and the supply passage 29 .
- FIG. 10 A second alternative embodiment that is a modification of the second preferred embodiment is shown in FIG. 10 .
- This alternative embodiment differs from the second preferred embodiment in that the spool 91 is disposed in upside down relation, the flange 94 is removed, and the spring 85 is accommodated within the spool 91 .
- the inner and outer diameters of the spool 91 are enlarged by the length of the removed flange 94 for the valve chamber 71 having the same diameter as in the second preferred embodiment.
- the second alternative embodiment of FIG. 10 prevents a decrease in the efficiency of flowing the liquid refrigerant, while ensuring the ease of closing operation of the second control valve CV 2 .
- the minimum opening degree of the valve hole 27 a by the first valve portion 79 of the second control valve CV 2 is not zero. However, it is so arranged, as shown in FIGS. 11 through 14 , that the minimum opening degree of the valve hole 27 a by the first valve portion 79 is zero and also that elasticity is provided to at least one of the first valve portion 79 , the valve seat or the valve plate assembly 3 for the first valve portion 79 , the second valve portion 88 and the valve seat 89 for the second valve portion 88 . In this case, the element provided with the elasticity out of the above-named parts is elastically deformable.
- the opening of the two valve portions 79 and 88 formed in the single spool 75 can be reduced to zero simultaneously without the need of machining the spool 75 and the valve seat 89 (or the valve plate assembly 3 ) at a very high accuracy.
- the second valve portion 88 of the second control valve CV 2 is formed by a ring-shaped lead 101 .
- the small-diameter portion 75 a has an engaging protrusion 75 c
- the large-diameter portion 75 b has an engaging recess 75 d .
- the large-diameter portion 75 b and the small-diameter portion 75 a are combined together such that the engaging protrusion 75 c is inserted into the engaging recess 75 d with the lead 101 held between the small-diameter portion 75 a and the large-diameter portion 75 b .
- a slope 78 b is formed in the region of the wall surface 78 a of the movable step 78 and is located outside the spring seat 86 for allowing the lead 101 to be deformed toward a space provided by forming the slope 78 b.
- the first valve portion 79 of the second control valve CV 2 is formed by a lead 102 .
- the lead 102 has a ring shape and is fitted around a protrusion 75 e formed at the center of the end surface of the small-diameter portion 75 a on the side thereof adjacent to the valve plate assembly 3 .
- a slope 75 f is formed on the end surface of the small-diameter portion 75 a in the radially outward region thereof for the same purpose as the slope 78 b of FIG. 11 .
- the large-diameter portion 75 b of the spool 75 that is, the second valve portion 88 is made of rubber.
- the small-diameter portion 75 a instead of the large-diameter portion 75 b (the second valve portion 88 ), of the spool 75 is made of rubber.
- FIG. 14 A sixth alternative embodiment that is a modification of the fifth alternative embodiment is shown in FIG. 14 .
- the large-diameter portion 75 b is fitted in a cylinder 103 that is made of metal.
- the width of the clearance 87 between the outer peripheral surface of the cylinder 103 and the inner peripheral surface 72 a of the middle-diameter hole 72 is larger than the diameter of the foreign substances that pass through the filter 90 .
- the second valve portion 88 is formed protruding beyond the cylinder 103 .
- the cylinder 103 functions to restrict the deformation of the rubber large-diameter portion 75 b in the radially outward direction.
- the clearance 87 is formed without considering the deformation of the rubber large-diameter portion 75 b.
- the foreign substances are less liable to be attached to the surface of the metallic cylinder 103 than to the surface of rubber. Even if the foreign substances are accumulated in the clearance 87 when the second valve portion 88 contacts the valve seat 89 , such foreign substances are easily flown from the clearance 87 by the refrigerant gas when the second valve portion 88 is moved away from the valve seat 89 . Additionally, since the outer peripheral surface of the metallic cylinder 103 is less susceptible to damage by the foreign substances, the endurance of the spool 75 is extended.
- the entire spool 75 is made of rubber to provide elasticity to both the first and second valve portions 79 and 88 .
- the valve seat for the first valve portion 79 is formed by a lead or rubber to be provided with elasticity.
- the valve seat 89 for the second valve portion 88 is formed by a lead or rubber for the same purpose.
- elasticity is provided to both the valve seat for the first valve portion 79 and the valve seat 89 for the second valve portion 88 .
- the backpressure chamber 80 of the second control valve CV 2 has the same pressure atmosphere as the region K that is located downstream of the position of valve opening adjustment (the valve seat 53 ) of the first control valve CV 1 in the supply passage 29 , and the backpressure chamber 80 is in constant communication with the crank chamber 5 via the part of the supply passage 29 .
- a passage that interconnects the backpressure chamber 80 and the crank chamber 5 is provided independently of the supply passage 29 .
- the backpressure chamber 80 has the same pressure atmosphere via the above passage and the crank chamber 5 as the region K that is located downstream of the position of valve opening adjustment (the valve seat 53 ) in the supply passage 29 .
- the backpressure chamber 80 of the second control valve CV 2 is in constant communication with the crank chamber 5 via the part of the supply passage 29 , and it is presumed that the pressure PdK in the backpressure chamber 80 is substantially the same as the crank pressure Pc.
- a fixed throttle is formed in the valve plate assembly 3 on the supply passage 29 , so that the pressure PdK in the backpressure chamber 80 is larger than the crank pressure Pc when the first control vale CV 1 is opened.
- the first control valve CV 1 is so constructed that the pressure difference (PdH ⁇ PdL) is detected between the pressure monitoring points P 1 and P 2 .
- the first control valve CV 1 is so constructed that only the suction pressure Ps is detected in a ninth alternative embodiment.
- the first control valve CV 1 is constructed to internally autonomously position the valve rod 40 in response to the variation of the suction pressure Ps such that a control target or a set suction pressure for the suction pressure Ps that is determined by the electromagnetic urging force of the solenoid 60 is maintained.
- the spring 85 of the second control valve CV 2 is provided by a coil spring in the above-described preferred embodiments, the spring 85 includes a plate spring in a tenth alternative embodiment.
- the spring 85 in each of the above-described preferred embodiments is removed from the second control valve CV 2 .
- the provision of the spring 85 in the second control valve CV 2 is desired because such spring assists in smooth opening of the valve hole 27 a and it is preferable that the spring 85 is provided for stabilizing the operation of the second control valve CV 2 .
- the second bleed passage 28 in the above-described first preferred embodiment is removed.
- clutch mechanism such as an electromagnetic clutch is utilized as the power transmission mechanism PT.
- the present invention is applied to a wobble plate type variable displacement compressor.
Abstract
Description
- The present invention relates to a displacement control mechanism for controlling the displacement of a variable displacement compressor that forms a part of a refrigerant circulation circuit of an air-conditioner. The displacement of the compressor is varied in accordance with the pressure in a crank chamber of the compressor.
- There is known a control mechanism shown in
FIG. 15 . According to the mechanism, the compressor displacement is controlled by adjusting the pressure in crank chamber 153 (or crank pressure Pc). Namely, in a swash plate type variable displacement compressor (hereinafter the compressor), thecrank chamber 153 communicates with asuction chamber 155 via ableed passage 154. Adischarge chamber 151 of the compressor communicates with thecrank chamber 153 via asupply passage 152 on which acontrol valve 156 is arranged. The amount of refrigerant gas introduced into thecrank chamber 153 via thesupply passage 152 is controlled by adjusting the opening degree of thecontrol valve 156, and the crank pressure Pc is determined in accordance with the relation between the amounts of refrigerant gas introduced into and bleeding from thecrank chamber 153. - A
fixed throttle 158 is formed in thebleed passage 154 so that the refrigerant gas bleeds slowly from thecrank chamber 153 to thesuction chamber 155. Thus, even when the amount of the refrigerant gas supplied from thedischarge chamber 151 to thecrank chamber 153 via thesupply passage 152 is small, the crank pressure Pc is steadily increased. Therefore, when thecontrol valve 156 increases the opening degree of thesupply passage 152, the crank pressure Pc is rapidly increased. Consequently, appropriate response in decreasing the compressor displacement is obtained. - Also, an amount of blow-by gas from a cylinder bore 157 to the
crank chamber 153 leaks to thesuction chamber 155 via thebleed passage 154. The refrigerant gas moves from thedischarge chamber 151 to thesuction chamber 155 via thecrank chamber 153 as mentioned above, such movement of the refrigerant being a kind of internal leaking. However, the amount of the above leaking blow-by gas and the amount of the above moving refrigerant gas are reduced as much as possible by the provision of the fixedthrottle 158. Consequently, decrease in efficiency of the compressor caused by the provision of the displacement control mechanism is prevented. - However, the
fixed throttle 158 provided in thebleed passage 154 causes the pressure in thecrank chamber 153 to be slowly reduced, thereby deteriorating the response of the compressor in increasing the displacement. Especially, upon starting the compressor, the crank pressure Pc tends to be increased excessively because the liquid refrigerant accumulated in thecrank chamber 153 evaporates and thefixed throttle 158 prevents smooth flow of refrigerant gas from thecrank chamber 153. Therefore, even when thecontrol valve 156 closes thesupply passage 152 so as to increase the displacement of the compressor in response to the requirement for cooling shortly after starting the compressor, it takes time before the displacement of the compressor is actually increased, so that the cooling performance shortly after a start-up of an air-conditioner deteriorates. - To solve such problems, it is proposed to provide a
second control valve 161 for controlling the opening degree of thebleed passage 154 in addition to the control valve (first control valve) 156, as shown inFIG. 16 (e.g. Japanese Unexamined Patent Publication 2002-21721). In the proposed structure, a region K is provided in thesupply passage 152 downstream of the position of first control valve 156 (i.e. the position of valve opening adjustment) and upstream of thefixed throttle 169, as shown inFIG. 16 . Thesecond control valve 161 is a spool type valve that includes aspool 162 and abackpressure chamber 166 into which the pressure in the region K Is introduced. Avalve chamber 167 of thesecond control valve 161 forms a part of thebleed passage 154 and communicates with thesuction chamber 155. Thevalve chamber 167 also communicates with thecrank chamber 153 via avalve hole 168 that forms the upstream part of thebleed passage 154. - The
spool 162 is movably disposed in a spool-supportingrecess 164 that is formed in a compressor housing. Thespool 162 includes avalve portion 162 a that is located in thevalve chamber 167 and aback surface 162 b that is located in thebackpressure chamber 166. The spool 162 (or thevalve portion 162 a) is positioned by various forces applied thereto such as urging force based on the pressure in thebackpressure chamber 166 acting on theback surface 162 b in the direction to close the valve, urging force of aspring 165 acting in the valve opening direction and force of the crank pressure Pc that is applied in the valve opening direction. - When the
first control valve 156 closes thesupply passage 152, a pressure PdK in thebackpressure chamber 166 of thesecond control valve 161 is substantially the same as the crank pressure Pc and, therefore, thespool 162 of thesecond control valve 161 is positioned by thespring 165 where thevalve hole 168 is wide opened at a maximum opening degree. When thebleed passage 154 is wide opened by thesecond control valve 161, flowing of the refrigerant from thecrank chamber 153 to thesuction chamber 155 is promoted. Therefore, closing thesupply passage 152 by thefirst control valve 156 so as to increase the displacement of the compressor shortly after starting the compressor, the displacement of the compressor is immediately increased, so that the cooling performance shortly after a start-up of air conditioner is improved. - A spring having a small spring force is utilized as the
spring 165. Thus, when thesupply passage 152 is opened even slightly by thefirst control valve 156 and the pressure PdK in the region K exceeds the crank pressure Pc, thespool 162 moves against the urging force of thespring 165, and thevalve portion 162 a sets thevalve hole 168 at a minimum opening degree that is not zero. Therefore, when thevalve hole 168 is thus set at the minimum opening degree that is not zero, thesecond control valve 161 functions similarly as the above-describedfixed throttle 158 shown inFIG. 15 , and the decrease in the efficiency of the compressor which is caused by having the displacement control mechanism is prevented. - However, the
second control valve 161 is arranged such that the clearance between the outer peripheral surface of thespool 162 and the inner peripheral surface of the spool-supportingrecess 164 is small, so that the fluid communication between thebackpressure chamber 166 and thevalve chamber 167 via the clearance is blocked, and the decrease in the efficiency of the compressor due to the leak of the refrigerant gas from thebackpressure chamber 166 to thevalve chamber 167 is prevented. However, foreign substances tend to be caught between the outer peripheral surface of thespool 162 and the inner peripheral surface of the spool-supportingrecess 164, thereby causing poor sliding movement of thespool 162. - In order to solve such problems, the alternative embodiment of the above prior art reference proposes the use of a bellows instead of the
spool 162 and thespring 165. Using the bellows that is elastic and stretchable and serves as a partition wall shutting off the communication between the back pressure chamber and the valve chamber without any sliding contact of moving part of the second control valve with the compressor housing, the clearance between the moving part of the second control valve and the compressor housing is set large enough. However, the bellows becomes larger with a decrease of its spring constant. Thus, in comparison to the case that thespool 162 and thespring 165 are used in combination, the second control valve having incorporated therein a bellows is disadvantageously large-sized. - The present invention provides a displacement control mechanism for a variable displacement compressor that prevents the operation failure of the spool of a second control valve that adjusts the opening degree of the bleed passage.
- According to the present invention, a displacement control mechanism is used in a variable displacement compressor for controlling a displacement of the compressor. The compressor partially forms a refrigerant circulation circuit of an air-conditioner. The displacement of the compressor is varied in accordance with a pressure in a crank chamber of the compressor. The refrigerant circulation circuit includes a suction pressure region and a discharge pressure region. The displacement control mechanism includes a first bleed passage, a supply passage, a first control valve and a second control valve. The first bleed passage interconnects the crank chamber and the suction pressure region. The supply passage interconnects the crank chamber and the discharge pressure region. The first control valve is located on the supply passage for controlling an opening degree of the supply passage. The second control valve is located on the first bleed passage. The second control valve also includes a backpressure chamber and a spool. The backpressure chamber has substantially the same pressure atmosphere as a region of the supply passage downstream of the first control valve. The spool includes a back surface that is located in the backpressure chamber. The spool has a cylindrical outer peripheral surface. The spool reduces an opening degree of the first bleed passage when a pressure in the backpressure chamber that is applied to the back surface is increased. The spool blocks a communication between the backpressure chamber and the first bleed passage via a clearance formed around the cylindrical outer peripheral surface of the spool in the second control valve when the spool sets the first bleed passage at a minimum opening degree.
- The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. Aspect of the invention may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
-
FIG. 1 is a longitudinal cross-sectional view of a variable displacement compressor according to a first preferred embodiment; -
FIG. 2 is a cross-sectional view of a first control valve; -
FIG. 3A is a partially enlarged cross sectional view of the variable displacement compressor around a second control valve; -
FIG. 3B is a schematic view showing cross section areas of a valve chamber and a valve hole for explaining conditional inequalities; -
FIG. 4A is a cross-sectional view explaining an action of the second control valve; -
FIG. 4B is a cross-sectional view explaining the action of the second control valve; -
FIG. 5 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a second preferred embodiment; -
FIG. 6 is a cross-sectional view explaining an action of the second control valve; -
FIG. 7 is a cross-sectional view of a first control valve including a second control valve therein according to a third preferred embodiment; -
FIG. 8 is a partially enlarged cross-sectional view of the first control valve including the second control valve therein according to the third preferred embodiment; -
FIG. 9 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a first alternative embodiment; -
FIG. 10 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a second alternative embodiment; -
FIG. 11 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a third alternative embodiment; -
FIG. 12 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a fourth alternative embodiment; -
FIG. 13 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a fifth alternative embodiment; -
FIG. 14 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to a sixth alternative embodiment; -
FIG. 15 is a schematic view of a variable displacement compressor according to prior art; and -
FIG. 16 is a partially enlarged cross-sectional view of a variable displacement compressor around a second control valve according to prior art. - The following will describe a preferred embodiment of the present invention. In the first preferred embodiment, the present invention is applied to a swash plate type variable displacement compressor (hereinafter the compressor) that is used in a vehicle air-conditioner for compressing refrigerant gas.
- Referring to
FIG. 1 , the compressor includes acylinder block 1, a front housing 2, avalve plate assembly 3 and arear housing 4. InFIG. 1 , the left side and the right side respectively correspond to the front side and the rear side of the compressor. The front housing 2 is fixed to the front end of thecylinder block 1, and therear housing 4 is fixed to the rear end of thecylinder block 1 via thevalve plate assembly 3. A compressor housing includes thecylinder block 1, the front housing 2 and therear housing 4. Acrank chamber 5 is defined by thecylinder block 1 and the front housing 2. Adrive shaft 6 is rotatably supported in thecrank chamber 5. Alug plate 11 is rotatably fixed to thedrive shaft 6 in thecrank chamber 5. - The front end of the
drive shaft 6 is operatively connected to a vehicle engine E as an external drive source via a power transmission mechanism PT. The power transmission mechanism PT is a clutch mechanism (e.g. an electromagnetic clutch) that selectively transmits and blocks driving power according to electric control from an external device, or a continuous transmission type clutchless mechanism (e.g. the combination of belt and pulley) that dispenses with the above clutch mechanism. In the first preferred embodiment, the clutchless type power transmission mechanism PT is utilized. - A
swash plate 12 as a cam plate is accommodated in thecrank chamber 5. Theswash plate 12 is slidably and inclinably supported by thedrive shaft 6. Ahinge mechanism 13 is interposed between thelug plate 11 and theswash plate 12. Thus, a hinge connection between thelug plate 11 and theswash plate 12 via thehinge mechanism 13 and the support of theswash plate 12 by thedrive shaft 6 allow theswash plate 12 to rotate integrally with thelug plate 11 and thedrive shaft 6 as well as to incline with respect to thedrive shaft 6 in accordance with the sliding movement of the swash plate 1.2 relative to thedrive shaft 6 in the axial direction of thedrive shaft 6. - A plurality of cylinder bores 1 a are formed in the
cylinder block 1 extending axially through thecylinder block 1 and arranged around thedrive shaft 6. Single-headedpistons 20 are each accommodated in the respective cylinder bores 1 a for reciprocation therein. The front and rear openings of the cylinder bores 1 a are respectively closed by thevalve plate assembly 3 and thepistons 20. Compression chambers are defined in the cylinder bores 1 a, and the volume of the compression chambers is varied in accordance with the reciprocating movement of thepistons 20. Each of thepistons 19 is engaged with theswash plate 12 via a pair ofshoes 19, so that the rotation of theswash plate 12 in accordance with thedrive shaft 6 is converted into reciprocating linear movement of thepistons 20. - A
suction chamber 21 and adischarge chamber 22 are defined between thevalve plate assembly 3 and therear housing 4. Thesuction chamber 21 is located in the middle region of therear housing 4 and is surrounded by thedischarge chamber 22. Asuction port 23 and asuction valve 24 are formed in thevalve plate assembly 3 for each of the cylinder bores 1 a. Thesuction valve 24 is adapted to open and close thesuction port 23. Adischarge port 25 and adischarge valve 26 are also formed in thevalve plate assembly 3 for each of the cylinder bores 1 a. Thesuction chamber 21 communicates with each of the cylinder bores 1 a via the correspondingsuction port 23, and each of the cylinder bores 1 a communicates with thedischarge chamber 22 via thecorresponding discharge port 25. - As each of the
pistons 20 moves from the top dead center toward the bottom dead center, the refrigerant gas is drawn into the corresponding cylinder bore 1 a via thesuction port 23 and thesuction valve 24. As each of thepistons 20 moves from the bottom dead center toward the top dead center, the refrigerant gas introduced into the cylinder bore 1 a is compressed to a predetermined pressure and is discharged into thedischarge chamber 22 via thedischarge port 25 and thedischarge valve 26. - An inclination angle of the
swash pate 12, which is defined as an angle made between theswash plate 12 and a hypothetical plane perpendicular to an axis L of thedrive shaft 6 is varied in accordance with the pressure in the crank chamber 5 (a crank pressure Pc). The inclination angle of theswash plate 12 is randomly determined between a minimum inclination angle as indicated by a solid line inFIG. 1 and a maximum inclination angle as indicated by a chain double-dashed line inFIG. 1 . - A displacement control mechanism for controlling the crank pressure Pc which is concerned with the controlling of the inclination angle of the
swash plate 12 includes afirst bleed passage 27, asecond bleed passage 28, asupply passage 29, a first control valve CV1 and a second control valve CV2. The first andsecond bleed passages crank chamber 5 and thesuction chamber 21 as a suction pressure (Ps) region. The second control valve CV2 is arranged on thefirst bleed passage 27. Thesecond bleed passage 28 has a fixedthrottle 28 a and extends through thecylinder block 1 and thevalve plate assembly 3. The fixedthrottle 28 a located in thesecond bleed passage 28 is formed such that the part of thesecond bleed passage 28 extending through thevalve plate assembly 3 is narrower than that extending through thecylinder block 1. - The
supply passage 29 interconnects thedischarge chamber 22 as a discharge pressure (Pd) region and thecrank chamber 5. The first control valve CV1 is arranged on thesupply passage 29 for adjusting the opening degree of thesupply passage 29. Thesupply passage 29 extends through thevalve plate assembly 3 downstream of the first control valve CV1 or on a side of thecrank chamber 5. The first control valve CV1 and the second control valve CV2 respectively adjust the opening degree of thesupply passage 29 and thefirst bleed passage 27. By so doing, the balance between the amount of high-pressure discharge gas introduced from thedischarge chamber 22 into thecrank chamber 5 via thesupply passage 29 and the amount of the refrigerant gas flowing from thecrank chamber 5 into thesuction chamber 21 via the first andsecond bleed passages pistons 20 is changed in accordance with the variation of the crank pressure Pc, and the inclination angle of theswash plate 12 is varied, accordingly. Consequently, the stroke ofpistons 20, that is, the displacement of the compressor is adjusted. - For example, when the first control valve CV1 reduces the opening degree of the
supply passage 29 and the crank pressure Pc is decreased, the inclination angle of theswash plate 12 is increased, and the displacement of the compressor is increased. On the other hand, when the first control valve CV1 increases the opening degree of thesupply passage 29 and the crank pressure Pc is increased, the inclination angle of theswash plate 12 is decreased, and the displacement of the compressor is decreased. - A refrigerant circulation circuit (or refrigerant cycle) of the vehicle air-conditioner includes the above-described compressor and an external
refrigerant circuit 30. The externalrefrigerant circuit 30 includes agas cooler 31, anexpansion valve 32 and anevaporator 33. Acirculation pipe 35 for the refrigerant is provided on the downstream side of the externalrefrigerant circuit 30, interconnecting the outlet of theevaporator 33 and thesuction chamber 21 of the compressor. Acirculation pipe 36 for the refrigerant is provided on the upstream side of the externalrefrigerant circuit 30, interconnecting thedischarge chamber 22 of the compressor and the inlet of thegas cooler 31. - As shown in
FIG. 2 , the first control valve CV1 includes a supply valve portion in the upper half thereof as seen on the drawing ofFIG. 2 and asolenoid portion 60 in the lower half. The supply valve portion adjusts the opening degree (throttle degree) of thesupply passage 29 that interconnects thedischarge chamber 22 and thecrank chamber 5. Thesolenoid portion 60 is an actuator for controlling the operation of avalve rod 40 arranged in the control valve CV1 in response to a control signal from an external device. Thevalve rod 40 is a rod-like member which includes apartition wall portion 41 at the top of thevalve rod 40, aconnection part 42, avalve body 43 at the middle of thevalve rod 40 and aguide rod 44 at the base of thevalve rod 40. Thevalve body 43 is a part of theguide rod 44. - A
valve housing 45 for the first control valve CV1 includes avalve body housing 45 a forming its upper part and anactuator housing 45 b forming its lower part. Avalve accommodation chamber 46, acommunication passage 47 and apressure sensing chamber 48 are defined in thevalve body housing 45 a in this order as seen from the lower side ofFIG. 2 . Thevalve rod 40 is arranged in thevalve accommodation chamber 46 and thecommunication passage 47 for movement in the direction of the axis of thevalve housing 45, that is, movement in the vertical direction as seen inFIG. 2 . Thepartition wall portion 41 of thevalve rod 40 is inserted through thecommunication passage 47 thereby to shut off the communication between thepressure sensing chamber 48 and thecommunication passage 47. -
Ports valve body housing 45 a. Theport 51 communicates with thevalve accommodation chamber 46, and theport 52 communicates with thecommunication passage 47, respectively. Thevalve accommodation chamber 46 communicates with thedischarge chamber 22 of the compressor via theport 51 and the upstream part of thesupply passage 29. Thecommunication passage 47 communicates with thecrank chamber 5 of the compressor via theport 52 and the downstream part of thesupply passage 29. Thevalve accommodation chamber 46 and thecommunication passage 47 form a part of thesupply passage 29. - The
valve body 43 of thevalve rod 40 is located in thevalve accommodation chamber 46. Avalve seat 53 is formed at the step portion located between thevalve accommodation chamber 46 and thecommunication passage 47, and thecommunication passage 47 functions as a valve hole. When thevalve rod 40 moves upward from the position ofFIG. 2 , where the communication passage 47 (or the supply passage 29) is opened, to a position where thevalve body 43 contacts thevalve seat 53, that is, aplanar surface 43 a of thevalve body 43 contacts aplanar surface 53 a of thevalve seat 53, the communication passage 47 (the supply passage 29) is closed. - A bellows 50 is accommodated in the
pressure sensing chamber 48. The upper end of thebellows 50 is fixed to thevalve housing 45. The top of thepartition wall portion 41 of thevalve rod 40 is fitted into the lower end of thebellows 50. Afirst pressure chamber 54 that is located inside thebellows 50 and asecond pressure chamber 55 that is located outside thebellows 50 are defined in thepressure sensing chamber 48 by thebellows 50 that has a cylindrical shape with a bottom. - As shown in
FIG. 1 , athrottle 36 a is formed in thecirculation pipe 36 between thedischarge chamber 22 and the externalrefrigerant circuit 30. Referring back toFIG. 2 , thefirst pressure chamber 54 communicates via a firstpressure introducing passage 37 with thedischarge chamber 22 at a first pressure monitoring point P1 that is located upstream of thethrottle 36 a. Thesecond pressure chamber 55 communicates via a secondpressure introducing passage 38 with thecirculation pipe 36 at a second pressure monitoring point P2 that is located downstream of thethrottle 36 a. Thus, a monitored pressure PdH at the first pressure monitoring point P1 is introduced into thefirst pressure chamber 54, and a monitored pressure PdL at the second pressure monitoring point P2 is introduced into thesecond pressure chamber 55. - The lower end of the
bellows 50 vertically moves in accordance with the pressure difference (PdH−PdL) between the pressures on opposite sides of thethrottle 36 a. Thus, positioning of the valve rod 40 (the valve portion 43) is determined by varying the pressure difference. The pressure difference (PdH−PdL) between the pressures on opposite sides of thethrottle 36 a varies depending on the refrigerant flow rate in the refrigerant circulation circuit. For example, when the refrigerant flow rate is increased, the pressure difference (PdH−PdL) is increased. On the other hand, when the refrigerant flow rate is decreased, the pressure difference (PdH−PdL) is decreased. The bellows 50 operates on thevalve body 43 such that the displacement of the compressor is changed so as to cancel the variation of the pressure difference (PdH−PdL). - The
solenoid portion 60 of the first control valve CV1 includes anaccommodation cylinder 61 that has a cylindrical shape with a bottom in the middle of theactuator housing 45 b. A fixedcore 62 of a column shape is fitted in the upper opening of theaccommodation cylinder 61. Thus, asolenoid chamber 63 is defined in the lower portion of theaccommodation cylinder 61. - A
movable core 64 is axially movable and accommodated in thesolenoid chamber 63. Aguide hole 65 extends through the center of the fixedcore 62 in the axial direction of thevalve rod 40. Theguide rod 44 of thevalve rod 40 is arranged in theguide hole 65 so as to move in the axial direction of thevalve rod 40. Theguide rod 44 is fitted into themovable core 64. Thus, themovable core 64 and thevalve rod 40 vertically move together. Aspring 66 is accommodated between the fixedcore 62 and themovable core 64 in thesolenoid chamber 63 for urging thevalve rod 40 in such direction that causes thevalve body 43 to move away from thevalve seat 53. - A
coil 67 is wound around the outer periphery of theaccommodation cylinder 61 over a range covering the fixedcore 62 and themovable core 64. Driving signal is transmitted from a drivingcircuit 68 a to thecoil 67, based on the command from acontrol device 68 in accordance with air-conditioning load. A magnitude of the electromagnetic force (or electromagnetic attraction) in accordance with an amount of electric power supplied to thecoil 67 is generated between the fixedcore 62 and themovable core 64. The electromagnetic force is transmitted to the valve rod 40 (the valve body 43) through themovable core 64. Controlling to energize thecoil 67 is performed by adjusting the voltage applied across thecoil 67, and duty ratio is utilized in the first preferred embodiment. - The
solenoid portion 60 of the first control valve CV1 varies the electromagnetic force that is applied to thevalve body 43 in accordance with the amount of the electric power supplied from an external device. In the first control valve CV1, therefore, control target (set pressure difference) for the pressure difference (PdH−PdL) between the pressures on opposite sides of thethrottle 36 a, that is, a standard for positioning thevalve body 43 by thebellows 50 is changed by varying the electromagnetic force that is applied to thevalve body 43. To put in other words, the first control valve CV1 is constructed to internally autonomously position the valve rod 40 (the valve body 43) in accordance with the variation of the pressure difference (PdH−PdL) between the first and second pressure monitoring points P1 and P2 such that the set pressure difference determined by the amount of the electric power supplied to thecoil 67 is maintained. - The set pressure difference of the first control valve CV1 is varied by adjusting the amount of the electric power supplied to the
coil 67 from the external device. For example, when the duty ratio that is commanded from thecontrol device 68 to the drivingcircuit 68 a is increased, electromagnetic urging force of thesolenoid portion 60 is increased, and the set pressure difference of the first control valve CV1 is increased, accordingly. With the set pressure difference of the first control valve CV1 thus increased, the displacement of the compressor is increased. On the other hand, when the duty ratio that is commanded from thecontrol device 68 to the drivingcircuit 68 a is decreased, electromagnetic urging force of thesolenoid portion 60 is decreased, and the set pressure difference of the first control valve CV1 is decreased. When the set pressure difference of the first control valve CV1 is decreased, the displacement of the compressor is decreased. - As shown in
FIGS. 1, 3A , 4A and 4B, anaccommodation hole 70 is formed in therear housing 4 for accommodating therein the second control valve CV2. Therear housing 4 functions also as a valve housing for the second control valve CV2. In the drawings, the cross section showing the second control valve CV2 is different from that showing the first control valve CV1 and thesuction chamber 21. The first control valve CV1 protrudes from arear end 4 a of therear housing 4 toward the rear side, and theaccommodation hole 70 is not covered with the first control valve CV1. - The
accommodation hole 70 is formed extending through therear end 4 a and a front end of 4 b of therear housing 4 in parallel with the axis L of thedrive shaft 6 or in the horizontal direction of as viewed inFIGS. 1, 3A , 4A and 4B. The front opening of theaccommodation hole 70 on thefront end 4 b of therear housing 4 is closed by thevalve plate assembly 3. Theaccommodation hole 70 includes avalve chamber 71 that is a small-diameter hole, a middle-diameter hole 72 whose diameter is greater than that of thevalve chamber 71, and a large-diameter hole 73 whose diameter is still greater than that of thehole 73, in this order as seen from the left side on the drawings. As seen fromFIG. 3 a, thevalve chamber 71, the middle-diameter hole 72 and the large-diameter hole 73 are formed coaxially. - A
valve hole 27 a is formed in thevalve plate assembly 3 that partially defines thevalve chamber 71 and thecylinder block 1. Thevalve chamber 71 communicates with thecrank chamber 5 via thevalve hole 27 a. Thevalve chamber 71 also communicates with acommunication hole 27 b that is formed in therear housing 4. Thecommunication hole 27 b is opened into thevalve chamber 71 through a cylindrical innerperipheral surface 71 a of thevalve chamber 71. Thevalve hole 27 a, thevalve chamber 71 and thecommunication hole 27 b form thefirst bleed passage 27. - A
spool 75 is received in thevalve chamber 71 and the middle-diameter hole 72 for movement in the horizontal direction as seen inFIGS. 1, 3A , 4A and 4B. Astopper 76 is fixedly fitted in the large-diameter hole 73. Thestopper 76 is positioned by the step portion that is located between the large-diameter hole 73 and the middle-diameter hole 72 in therear housing 4 for restricting the movement of thespool 75 beyond the rear end of the middle-diameter hole 72. - The
spool 75 has a small-diameter portion 75 a located on the side of thevalve chamber 71 and a large-diameter portion 75 b formed coaxially with the small-diameter portion 75 a and located on the side of the middle-diameter portion 72. Thespool 75 has also an annular-shapedmovable step 78 formed between outerperipheral surfaces diameter portion 75 a and the large-diameter portion 75 b of thespool 75. Themovable step 78 includes awall surface 78 a that faces toward a side of thevalve plate assembly 3. - The large-
diameter portion 75 b of thespool 75 has a cylindrical shape with an opening to the rear side, that is, to the side of thestopper 76. The small-diameter portion 75 a of thespool 75 is almost located in thevalve chamber 71, and the large-diameter portion 75 b is accommodated in the middle-diameter hole 72 for movement in the axial direction of thespool 75. The small-diameter portion 75 a is coaxial with thevalve hole 27 a, and the diameter of the small-diameter portion 75 a is larger than that of thevalve hole 27 a. The front end of the small-diameter portion 75 a forms afirst valve portion 79 that adjusts the opening degree of thevalve hole 27 a that communicates with thevalve chamber 71, that is, the opening degree of thefirst bleed passage 27. When thefirst valve portion 79 approaches thevalve plate assembly 3, the opening degree of thevalve hole 27 a is decreased. On the other hand, when thefirst valve portion 79 moves away from thevalve plate assembly 3, the opening degree of thevalve hole 27 a is increased. - A
backpressure chamber 80 is defined between thestopper 76 and the large-diameter portion 75 b of thespool 75 in the middle-diameter hole 72. Thebackpressure chamber 80 includes a cylindrical inner space of the large-diameter portion 75 b. Thespool 75 has aback surface 81 which includes the end surface of the opening portion of the large-diameter portion 75 b and the inner bottom surface of the large-diameter portion 75 b. Thus, theback surface 81 of thespool 75 is located in thebackpressure chamber 80. - In the
supply passage 29, apressure introducing passage 82 branches from thesupply passage 29 at the region K that is located on the side of thecrank chamber 5, that is, downstream of the position of valve opening adjustment in the first control valve CV1 (or the valve seat 53). Thepressure introducing passage 82 communicates with the large-diameter hole 73 and is opened into an innerperipheral surface 73 a of thelarge diameter hole 73. - A
communication groove 76 a and acommunication hole 76 b are formed in thestopper 76 to interconnect thepressure introducing passage 82 and the middle-diameter hole 72. Thecommunication groove 76 a is formed annularly throughout the outer peripheral surface of thestopper 76 at a position facing the opening of thepressure introducing passage 82. Thecommunication hole 76 b extends through thestopper 76 between thecommunication groove 76 a and anend surface 76 c of thestopper 76 on the side of thevalve plate assembly 3, Thecommunication hole 76 b is open at the center of theend surface 76 c. - Pressure PdK in the region K of the
supply passage 29 is introduced into thebackpressure chamber 80 via thepressure introducing passage 82, thecommunication groove 76 a and thecommunication hole 76 b. Namely, thebackpressure chamber 80 has the same pressure atmosphere as the region K that is located downstream of the position of valve opening adjustment in the control valve CV1 in thesupply passage 29. Force from the pressure PdK in thebackpressure chamber 80 urges thespool 75 toward thevalve plate assembly 3, that is, in the direction that causes the valve to be closed. Namely, thespool 75 has the characteristics of decreasing the opening degree of thevalve hole 27 a with an increase in the pressure PdK in thebackpressure chamber 80 that is applied to theback surface 81. - The outer diameter of the large-
diameter portion 75 b of thespool 75 is larger than the inner diameter of thevalve chamber 71. An annular fixedstep 83 is formed between thevalve chamber 71 and the middle-diameter hole 72 in the second control valve CV2. The fixedstep 83 includes awall surface 83 a that faces thewall surface 78 a of themovable step 78 of thespool 75. When thespool 75 has reached the position closest to thevalve plate assembly 3, thewall surface 78 a of themovable step 78 is brought into contact with thewall surface 83 a of the fixedstep 83 to seat thespool 75. The axial length of the small-diameter portion 75 a of thespool 75 is slightly smaller than that of thevalve chamber 71. Thus, with thespool 75 positioned closest to thevalve plate assembly 3, thewall surface 78 a of themovable step 78 contacts thewall surface 83 a of the fixedstep 83, and a slight clearance is formed between thefirst valve portion 79 and thevalve plate assembly 3. Since thefirst bleed passage 27 is not closed even when the opening of thevalve hole 27 a is reduced to the minimum and, therefore, thecrank chamber 5 keeps fluid communication with thesuction chamber 21 via thefirst bleed passage 27. The minimum opening degree of thevalve hole 27 a is slightly larger than zero. - The minimum clearance between the
first valve portion 79 and thevalve plate assembly 3 functions as a throttle of thefirst bleed passage 27. Thus, in consideration of the throttle of the refrigerant gas in thefirst bleed passage 27 when thevalve hole 27 a is at the minimum opening degree, the diameter of thethrottle 28 a of thesecond bleed passage 28 is set smaller than that when the second control valve CV2 and thefirst bleed passage 27 are not hypothetically provided. - A
spring 85 such as coil spring is located in aclearance 84 between the outerperipheral surface 77 a of the small-diameter portion 75 a of thespool 75 and the innerperipheral surface 71 a of thevalve chamber 71. The movable end of thespring 85 is in contact with thewall surface 78 a of themovable step 78 at a region that is located radially inward from the region where thewall surface 78 a faces thewall surface 83 a of the fixedstep 83. That is, the inner region of thewall surface 78 a that is located radially inward from the annular region of thewall surface 78 a that faces thewall surface 83 a of the fixedstep 83 forms aspring seat 86 for the movable end of thespring 85. The fixed end of thespring 85 is in contact with thevalve plate assembly 3 at a position surrounding the opening of thevalve hole 27 a. Thespring 85 urges thespool 75 in the direction that causes thefirst valve portion 79 to move so as to increases the opening degree of thevalve hole 27 a. - A
clearance 87 is formed between an outerperipheral surface 77 b of the large-diameter portion 75 b of thespool 75 and an inner peripheral surface 72 a of the middle-diameter hole 72, and theclearance 87 is narrower than theclearance 84 between the outerperipheral surface 77 a of the small-diameter portion 75 a and the innerperipheral surface 71 a of thevalve chamber 71. Aclearance 84 a is formed between thespring 85 and the innerperipheral surface 71 a of thevalve chamber 71 and, especially, is provided such that thespring 85 freely extends and contracts in accordance with the movement of thespool 75. Theclearance 87 is also narrower than theclearance 84 a. Namely, theclearance 87 is the narrowest of the all clearances that are around the cylindrical outerperipheral surface 77 of thespool 75. - When the
wall surface 78 a of themovable step 78 is moved away from thewall surface 83 a of the fixedstep 83 as shown inFIG. 4B , thevalve chamber 71 communicates with thebackpressure chamber 80 via the clearance between the wall surfaces 78 a and 83 a and theclearance 87 of thespool 75. On the other hand, when thewall surface 78 a of themovable step 78 contacts thewall surface 83 a of the fixedstep 83 as shown inFIG. 3A , the communication between thebackpressure chamber 80 and thevalve chamber 71 via theclearance 87 of thespool 75 is shut off. Namely, the annular region of thewall surface 78 a of themovable step 78 that faces thewall surface 83 a of the fixedstep 83 forms asecond valve portion 88 for shutting off the communication between thebackpressure chamber 80 and thevalve chamber 71 via theclearance 87 of thespool 75. Avalve seat 89 for thesecond valve portion 88 is formed by an annular region of thewall surface 83 a of the fixedstep 83 that faces thesecond valve portion 88. - As shown in
FIGS. 1 and 2 , afilter 90 is arranged in thesupply passage 29 on the side of thedischarge chamber 22, that is, upstream of the first control valve CV1 for removing foreign substances in the refrigerant gas. As shown inFIGS. 3A and 4 , the width of theclearance 87 between the large-diameter portion 75 b of thespool 75 and the inner peripheral surface 72 a of theaccommodation hole 70 is larger than the diameter of the foreign substances that pass through thefilter 90. In other words, the width of theclearance 87 is larger than the diameter of the mesh openings of thefilter 90. Namely, theclearance 87 that is the narrowest clearance around the cylindrical outerperipheral surface 77 of thespool 75 is formed with a width that is larger than the diameter of the foreign substances flowing through theclearance 87. - Referring to
FIG. 3B , in the second control valve CV2, the cross sectional area of thevalve chamber 71 that is perpendicular to the axial direction of thespool 75 is represented as SA, and the cross sectional area of thevalve hole 27 a that is also perpendicular to the axial direction of thespool 75 is represented as SB, which is smaller than SA. A force for urging thespool 75 toward thevalve plate assembly 3, that is, in the direction in which the opening degree of thevalve hole 27 a is decreased in response to the varying pressure difference between the pressure PdK and the crank pressure Pc is expressed by “(PdK−PC)SB”. - A force for urging the
spool 75 in the direction which causes the opening degree of thevalve hole 27 a to be decreased in accordance with the pressure difference between the pressure PdK and the suction pressure Ps, is expressed by “(PdK−Ps)(SA−SB).” The urging force of thespring 85 is represented as “f”. Conditional inequality (1) for the minimum opening degree of thevalve hole 27 a in the second control valve CV2 is expressed as follows:
(PdK−Ps)(SA−SB)+(Pdk−Pc)SB>f (1) - The
backpressure chamber 80 is in constant communication with thecrank chamber 5 via thesupply passage 29 and has the same pressure atmosphere as thecrank chamber 5. Thus, it is presumed that the pressure PdK is substantially the same as the pressure Pc. Therefore, the above inequality (1) is expressed as the following conditional inequality (2):
(Pc−Ps)(SA−SB)>f (2) - The
spring 85 for use in the illustrated embodiment has a small set load and a low spring constant. It is understood, therefore, from the above conditional inequality (2) that thevalve portion 79 reduces the opening degree of thevalve hole 27 a to the minimum opening degree when the crank pressure Pc somewhat exceeds the suction pressure Ps. - When a predetermined length of time or more has passed after a stop of the vehicle engine E, the pressure is equalized at a low value in the refrigerant circulation circuit and, therefore, the crank pressure Pc becomes substantially the same as the suction pressure Ps. Since the conditional inequality (2) is no more effective, the
spool 75 is moved by the urging force of thespring 85 until thespool 75 is brought into contact with thestopper 76, as shown inFIG. 4A . With thespool 75 thus fully urged by thespring 85, thevalve portion 79 sets the opening degree of thevalve hole 27 a at its maximum. - In a conventional compressor for a vehicle air-conditioner, liquid refrigerant, existing on the low pressure side of the external
refrigerant circuit 30 with the vehicle engine E kept at a stop for a long time, flows into thecrank chamber 5 via thesuction chamber 21 due to the fluid communication between thecrank chamber 5 and thesuction chamber 21 via the first andsecond bleed passages crank chamber 5 via thesuction chamber 21 and is accumulated in thecrank chamber 5. Therefore, when the vehicle engine E is started and the compressor is also started thereby through the clutchless type power transmission mechanism PT, the liquid refrigerant evaporates under the influence of heat generated by the vehicle engine E and also of the stirring effect due to stirring the liquid refrigerant by theswash plate 12, with the result that the crank pressure Pc tends to be increased regardless the opening degree of thevalve hole 27 a. - For example, when the vehicle engine E is started while the vehicle interior is hot, the
control device 68 is operated in response to the cooling demand from the occupant of the vehicle to command maximum duty ratio to thedrive circuit 68 a, and the set pressure difference of the first control valve CV1 is set at the maximum value for performing cooling as required. Accordingly, the first control valve CV1 closes thesupply passage 29, and no high pressure refrigerant gas is supplied from thedischarge chamber 22 to the crankchamber 5 and thebackpressure chamber 80 of the second control valve CV2. Therefore, even if evaporation of the liquid refrigerant occurs in thecrank chamber 5, the state where the pressure difference between the crank pressure Pc and the suction pressure Ps does not exceed the urging force f, that is, the state where the conditional inequality (2) is not effective, continues. - Consequently, the
spool 75 of the second control valve CV2 is maintained in such a state that thefirst valve portion 79 fully opens thefirst bleed passage 27 by the urging force f of the urgingspring 85, and the liquid refrigerant in thecrank chamber 5, as well as the refrigerant gas evaporated from a part of the liquid refrigerant, is immediately flown into thesuction chamber 21 via the fully-openedfirst bleed passage 27. Thus, the crank pressure Pc is maintained at a low value corresponding to that the first control valve CV1 is closed, the compressor increases the inclination angle of theswash plate 12 thereby to increase the displacement of the compressor to its maximum. - If the first control valve CV1 remains closed even after the liquid refrigerant is flown out from the
crank chamber 5, thefirst bleed passage 27 is fully opened by thefirst valve portion 79 of the second control valve CV2 as described above. Thus, even if the amount of blow-by gas from the cylinder bores 1 a to the crankchamber 5 is more than the amount initially designed, for example, due to wornpistons 20, the blow-by gas is immediately flown into thesuction chamber 21 via the first andsecond bleed passages swash plate 12, that is, the maximum displacement operation (100% displacement operation) of the compressor is maintained. - As described above, when the
first valve portion 79 of the second control valve CV2 sets the opening degree of thefirst bleed passage 27 larger than the minimum opening degree, thesecond valve portion 88 is moved away from thevalve seat 89, and thebackpressure chamber 80 communicates with thevalve chamber 71 via the clearance 87 (refer toFIG. 4B ). However, since the first control valve CV1 is in its closed state when thebackpressure chamber 80 is in communication with thevalve chamber 71, no refrigerant gas in thedischarge chamber 22 flows into thebackpressure chamber 80 via the first control valve CV1, and hence there is no fear of a decrease in efficiency of the refrigerant cycle caused by leakage of the refrigerant gas from thebackpressure chamber 80 to thevalve chamber 71. - When the vehicle interior is cooled to a certain extent due to the above maximum displacement operation of the compressor, the
control device 68 reduces the duty ratio that is commanded to thedrive circuit 68 a from the maximum. Accordingly, the first control valve CV1 is changed from the closed state and opens thesupply passage 29 so that the crank pressure Pc becomes higher than the suction pressure Ps. The conditional inequality (2) is satisfied, so thatspool 75 moves against the urging force of thespring 85 in the direction to reduce the valve opening and thefirst bleed passage 27, that is, thevalve hole 27 a is substantially throttled by thefirst valve portion 79. - Namely, when the
supply passage 29 is opened by the first control valve CV1 and the introduction of the refrigerant gas from thedischarge chamber 22 into thecrank chamber 5 starts, the amount of the refrigerant gas flown out from thecrank chamber 5 to thesuction chamber 21 via thefirst bleed passage 27 is substantially decreased in accordance with the above gas introduction into thecrank chamber 5. Thus, the crank pressure Pc is rapidly increased, and the compressor immediately reduces the inclination angle of theswash plate 12 so that the displacement of the compressor is reduced. - Amount of the compressed refrigerant gas that leaks from the
discharge chamber 22 to the crankchamber 5 further to thesuction chamber 21 is reduced by decreasing the opening degree of thefirst bleed passage 27 by the second control valve CV2, so that the decrease in the efficiency of the refrigerant cycle is prevented. Furthermore, although the refrigerant circulation circuit in the first preferred embodiment is formed such that the refrigerant circulation stops by operating the compressor at the minimum displacement (so called an OFF operation of the clutchless compressor), the OFF operation of the compressor is reliably performed due to the substantial decrease in the opening degree of thefirst bleed passage 27 by the second control valve CV2. - When the
first valve portion 79 of the second control valve CV2 sets thefirst bleed passage 27 at the minimum opening degree, thesecond valve portion 88 contacts thevalve seat 89 as described above. Accordingly, the communication between thevalve chamber 71 and thebackpressure chamber 80 is shut off. Thus, the refrigerant gas in thedischarge chamber 22 is prevented from leaking from thebackpressure chamber 80 to thesuction chamber 21 via theclearance 87, thevalve chamber 71 and thecommunication hole 27 b. Therefore, the decrease in the efficiency of the refrigerant cycle is prevented. - While the first control valve CV1 is opened, fine foreign substances that are not removed by the
filter 90 flow into the second control valve CV2 together with the refrigerant gas and possibly further into theclearance 87 of thespool 75. However, since the width of theclearance 87 of thespool 75 is larger than the diameter of the foreign substances that have passed through thefilter 90, the foreign substances are prevented from being caught in theclearance 87, so that thespool 75 moves smoothly without any operation failure. Even if the foreign substances remain in theclearance 87 at thesecond valve portion 88 in contact with thevalve seat 89, such foreign substances are removed from theclearance 87 by the flow of the refrigerant gas occurring when the second control valve CV2 is opened as shown inFIG. 4B . - The following advantageous effects are obtained according to the above-described first preferred embodiment of the present invention.
- (1) When the
first valve portion 79 sets thevalve hole 27 a at the minimum opening degree, thesecond valve portion 88 of thespool 75 shuts off the communication between thebackpressure chamber 80 and thevalve chamber 71 via theclearance 87 of thespool 75 in the second control valve CV2. Thus, it is unnecessary that theclearance 87 is set small, and the operation failure of thespool 75 caused by the foreign substances caught in theclearance 87 is prevented. - (2) The
second valve portion 88 is formed by thewall surface 78 a of themovable step 78 on the cylindrical outerperipheral surface 77 of thespool 75, and thevalve seat 89 for thesecond valve portion 88 is formed by thewall surface 83 a of the fixedstep 83. In other words, the functions of thesecond valve portion 88 and thevalve seat 89 are provided to the second control valve CV2 by simple structure such as the movable andfixed steps - (3) The minimum opening degree of the
valve hole 27 a by thefirst valve portion 79 of the second control valve CV2 is not zero. Thus, it is not necessary to machine thefirst valve portion 79 and thesecond valve portion 88 in thespool 75 at a very high accuracy, and the manufacture of thespool 75 is easier. Accordingly, in a structure in which thevalve portions spool 75 are required to be brought into contact simultaneously with thevalve plate assembly 3 and thevalve seat 89 so as to shut off the fluid communication and, parts of the control valve are required to be manufactured to a very high standard of accuracy. Apparently, the structure will make it troublesome and hence costly to manufacture valve parts such as spool, valve seat and valve plate assembly. - (4) The second control valve CV2 includes the
spring 85 for urging thespool 75 in the direction to increase the valve opening, and the urging force f of thespring 85 relates to the positioning of thespool 75. Thus, the operating characteristics of the second control valve CV2 is easily adjusted by changing the urging force f of thespring 85, that is, by selecting an appropriate spring from a group of springs having different characteristics. - (5) In the second control valve CV2, the
wall surface 78 a of themovable step 78 that forms thesecond valve portion 88 is also utilized as thespring seat 86 for thespring 85. Accordingly, in comparison to a case in which a spring seat (a step) is provided separately from themovable step 78, the structure of thespool 75 and the structure of the second control valve CV2 is simplified. - (6) The
filter 90 is provided between thedischarge chamber 22 and the first control valve CV1, and the width of theclearance 87 of thespool 75 is larger than the diameter of the foreign substances that pass through thefilter 90. Thus, the foreign substances whose diameter is larger than the width of theclearance 87 of thespool 75 will not be caught in theclearance 87, and the operation failure of thespool 75 in the second control valve CV2 is prevented successfully. - The following will describe a second preferred embodiment according to the present invention. In the following description about the second preferred embodiment, only the difference thereof from the first preferred embodiment will be described. Like or corresponding elements or parts are referred to by like reference numerals, and the detailed description thereof is omitted.
- The
valve hole 27 a of the above-described first preferred embodiment is arranged so as to interconnects thecrank chamber 5 and thevalve chamber 71. However, thevalve hole 27 a in the second preferred embodiment is arranged so as to interconnects thesuction chamber 21 and thevalve chamber 71 as shown inFIGS. 5 and 6 . Further, thecommunication hole 27 b, which is arranged so as to interconnect thesuction chamber 21 and thevalve chamber 71 in the above-described first preferred embodiment, is modified in the second preferred embodiment such that thecommunication hole 27 b interconnects thecrank chamber 5 and thevalve chamber 71. - The
accommodation hole 70 of the second control valve CV2 extends in the vertical direction inFIGS. 5 and 6 and is open to the outside of the compressor. Thevalve chamber 71 is located in the upper side of theaccommodation hole 70, the large-diameter hole 73 is located in the lower side of theaccommodation hole 70, and the middle-diameter hole 72 is removed from theaccommodation hole 70. - The
valve hole 27 a is open in aceiling surface 71 b of thevalve chamber 71. Thecommunication hole 27 b is open in the innerperipheral surface 71 a of thevalve chamber 71. Thecommunication hole 27 b serves as a part of the region of thesupply passage 29 on the side of thecrank chamber 5 with respect to the second control valve CV2. The connection in thesupply passage 29 between the first and second control valves CV1 and CV2 is open in the innerperipheral surface 73 a of the large-diameter hole 73 of the second control valve CV2. - A
spool 91 having a cylindrical shape with a cover is accommodated in thevalve chamber 71 for movement in the vertical direction as seen inFIGS. 5 and 6 . Thespool 91 is placed so as to have its opening that faces downward. The diameter of the top surface of thecylindrical spool 91 is larger than that of thevalve hole 27 a. A region of the top surface of thespool 91 that faces theceiling surface 71 b of thevalve chamber 71 forms avalve portion 92. A region of theceiling surface 71 b of thevalve chamber 71 that faces thevalve portion 92 forms avalve seat 93 for thevalve portion 92. - The
spool 91 is formed with aflange 94 protruding radially outwardly from the opening portion of thespool 91. A cylindrical outerperipheral surface 77 of thespool 91 includes an outerperipheral surface 77 a of theflange 94 and an outerperipheral surface 77 b of the cylindrical portion that is located above theflange 94 in thespool 91 as seen inFIGS. 5 and 6 . Thespool 91 inserts into thespring 85 that is located in theclearance 84 formed between the outerperipheral surface 77 b of thespool 91 and the innerperipheral surface 71 a of thevalve chamber 71. The upper surface of theflange 94 forms thespring seat 86 for receiving the movable end of thespring 85. A region on theceiling surface 71 b outward from thevalve seat 93 forms a spring seat for receiving the fixed end of thespring 85. - A
slope 91 a is formed in the lower peripheral surface of theflange 94. Theslope 91 a is formed such that the distance from its sloped surface to theend surface 76 c of thestopper 76 is increasing as the diameter of theslope 91 a is larger. Theback surface 81 of thespool 91 includes the inner ceiling surface of thespool 91, the lower surface of thespool 91 and theslope 91 a of thespool 91. Theback surface 81 is located in thebackpressure chamber 80. Although thevalve chamber 71 and thebackpressure chamber 80 in the second preferred embodiment are in constant communication with each other and share the same space, a region adjacent to theback surface 81 of thespool 91 is referred to as thebackpressure chamber 80. Thebackpressure chamber 80 has the same pressure atmosphere as the region K that is located downstream of the position of valve opening adjustment (the valve seat 53) of the first control valve CV1 in thesupply passage 29. - In the second control valve CV2, the
clearance 87 between the outerperipheral surface 77 a of theflange 94 and the innerperipheral surface 71 a of thevalve chamber 71 is narrower than theclearance 84 between thespring 85 and the innerperipheral surface 71 a of thevalve chamber 71. The width of theclearance 87 is larger than the diameter of the foreign substances that are around the cylindrical outerperipheral surface 77 of thespool 91 and pass through thefilter 90. - It is presumed that the pressure PdK in the
backpressure chamber 80 is substantially the same as the crank pressure Pc. Thus, thespool 91 closes thevalve hole 27 a in such a manner that thevalve portion 92 contacts thevalve seat 93 when the conditional inequality (3) below is satisfied. Therefore, when the crank pressure Pc somewhat exceeds the suction pressure Ps, the second control valve CV2 closes thefirst bleed passage 27. In the conditional inequality (3), the weight of thespool 91 is ignored, and “SB” denotes the cross sectional area of thevalve hole 27 a.
(Pc−Ps)SB>f (3) - With the first control valve CV1 opened, the crank pressure Pc is increased, so that the above conditional inequality (3) is effective. Thus, the
spool 91 is moved upward until thevalve portion 92 contacts thevalve seat 93, so that thevalve hole 27 a or thefirst bleed passage 27 is closed, as shown inFIG. 5 . The constant communication between thecrank chamber 5 and thesuction chamber 21 is ensured by thesecond bleed passage 28. - The
communication hole 27 b partially forms thesupply passage 29 together with thevalve chamber 71 and thebackpressure chamber 80. Thus, the refrigerant gas that flows into thebackpressure chamber 80 via the first control valve CV1 flows into thecrank chamber 5 via thevalve chamber 71 and thecommunication hole 27 b. The refrigerant gas flowing into thevalve chamber 71 is guided by theslope 91 a of thespool 91 so as to flow smoothly into thecommunication hole 27 b. - When the
valve portion 92 of thespool 91 closes thevalve hole 27 a, the communication between thebackpressure chamber 80 and thevalve hole 27 a via theclearance 87 of thespool 91 is shut off simultaneously by thevalve portion 92. Thus, the refrigerant gas in thedischarge chamber 22 is prevented from leaking from the region K to thesuction chamber 21 via thebackpressure chamber 80, thevalve chamber 71 and thevalve hole 27 a, so that the decrease in the efficiency of the refrigerant cycle is prevented. - When the first control valve CV1 is closed, that is, when the
supply passage 29 is closed, as shown inFIG. 6 , the crank pressure Pc is lowered, and the above conditional inequality (3) is no more effective, so that thespool 91 moves downward and thevalve portion 92 moves away from thevalve seat 93. Thus, thevalve hole 27 a communicates with thecommunication hole 27 b via thevalve chamber 71, and thefirst bleed passage 27 is wide opened. Therefore, the refrigerant in thecrank chamber 5 is immediately flown out into thesuction chamber 21. - The following advantageous effects are obtained according to the second preferred embodiment.
- (7) In the second control valve CV2, the
valve portion 92 of thespool 91 closes thevalve hole 27 a or thefirst bleed passage 27 and also simultaneously shuts off of the communication between thebackpressure chamber 80 and thevalve hole 27 a via theclearance 87 of thespool 91. Thus, it is unnecessary that theclearance 87 is set to be small, and the operation failure of thespool 91 caused by foreign substances caught in theclearance 87 is prevented. - (8) The
first bleed passage 27 and thesupply passage 29 share thecommunication hole 27 b as a common part of the passages. Namely, thecommunication hole 27 b serves as the part of thefirst bleed passage 27 and thesupply passage 29 between thecrank chamber 5 and thevalve chamber 71. Thus, since a part of thesupply passage 29 between the branch point of thepressure introducing passage 82 and thecrank chamber 5 in the first preferred embodiment is removed from thesupply passage 29, the arrangement of the passages is simplified, and the structure of the displacement control mechanism is simplified. - Now, a third preferred embodiment will be described with reference to
FIGS. 7 and 8 . The third preferred embodiment differs from the second preferred embodiment mainly in that the second control valve CV2 is installed in thevalve housing 45 of the first control valve CV1. In the first control valve CV1 in the third preferred embodiment, the relationship of upstream or downstream between theports FIG. 2 . That is, thesupply passage 29 is connected at the upstream side thereof (or the side of the discharge chamber 22) to theport 52 and at the downstream side thereof (or the side of the crank chamber 5) to theport 51. - A
spool 96, avalve seat body 97 and thespring 85 of the second control valve CV2 are accommodated in thevalve accommodation chamber 46 of the first control valve CV1. A through hole 96 a is formed in the middle of thespool 96. Thevalve rod 40 is inserted into the through hole 96 a, and thespool 96 moves in the axial direction of thevalve rod 40. Thevalve seat body 97 is located below thespool 96 and in contact with the fixedcore 62 in thevalve accommodation chamber 46. The part of thevalve accommodation chamber 46 located above the top surface of thevalve seat body 97 forms thevalve chamber 71. Arecess 96 b is formed on the top surface of thespool 96 around the through hole 96 a. - A
port 98 is formed in the peripheral wall of thevalve housing 45 that surrounds the lower portion of thevalve accommodation chamber 46. Theport 98 is connected to thefirst bleed passage 27 on the side of thesuction chamber 21. Thevalve hole 27 a is formed in thevalve seat body 97 and interconnects theport 98 and thevalve chamber 71. Thevalve hole 27 a is open at the top surface of thevalve seat body 97 between the inner peripheral surface and the outer peripheral surface of thevalve seat body 97. Agroove 96 c is formed in the lower surface of thespool 96. Thegroove 96 c has an annular shape surrounding the through hole 96 a and has a part that faces thevalve hole 27 a of thevalve seat body 97. - An annular region in the lower surface of the
spool 96 that is located radially outward of thegroove 96 c forms thevalve portion 92. An annular region in the top surface of thevalve seat body 97 that is located radially outward of thevalve hole 27 a and faces thevalve portion 92 forms thevalve seat 93 for thevalve portion 92. - An annular region in the lower surface of the
spool 96 that is located radially inward of thegroove 96 c forms avalve portion 96 d for the through hole 96 a. An annual region in the top surface of thevalve seat body 97 that is located radially inward of thevalve hole 27 a and faces thevalve portion 96 d forms thevalve seat 97 a for thevalve portion 96 d. With thevalve portion 92 brought in contact with thevalve seat 93, thevalve portion 96 d contacts thevalve seat 97 a, thereby shutting off the communication between thevalve hole 27 a and thebackpressure chamber 80 via the clearance formed between the inner peripheral surface of the of the through hole 96 a of thespool 96 and the outer peripheral surface of theguide rod 44 in thevalve rod 40. - A
flange 94 is formed at the top of thespool 96. The lower surface of theflange 94 forms thespring seat 86 for receiving the movable end of thespring 85. A region in the top surface of thevalve seat body 97 that is located radially outward of thevalve seat 93 forms the valve seat for receiving the fixed end of the urgingspring 85. Theback surface 81 of thespool 96 is formed by the top surface of thespool 96 and the bottom surface of therecess 96 b. Thebackpressure chamber 80 that is located between theback surface 81 and the position of valve opening adjustment, or thevalve seat 53, of the first control valve CV1 forms a part of the region K that is located downstream, that is, on the side of thecrank chamber 5, of the position of valve opening adjustment of the first control valve CV1 in thesupply passage 29. Namely, thebackpressure chamber 80 has the same pressure atmosphere as the region K. - The cylindrical outer
peripheral surface 77 of thespool 96 includes the outerperipheral surface 77 a of theflange 94 and the outer peripheral surface of thespool 96 that is located below theflange 94. Thespring 85 is located in theclearance 84 between the outerperipheral surface 77 b and the innerperipheral surface 71 a of thevalve chamber 71. Theclearance 87 between the outerperipheral surface 77 a of theflange 94 and the innerperipheral surface 71 a of thevalve chamber 71 is narrower than theclearance 84 a between thespring 85 and the innerperipheral surface 71 a of thevalve chamber 71. - As shown in.
FIG. 7 , with the first control valve CV1 opened, the crank pressure Pc, which is considered to be substantially the same as the pressure PdK in thebackpressure chamber 80, is increased, so that thespool 96 is moved downward until thevalve portion 92 contacts thevalve seat 93. Thus, thevalve hole 27 a is closed and thefirst bleed passage 27 is closed, accordingly. Thus, the refrigerant gas that flows from thedischarge chamber 22 into thebackpressure chamber 80 via theport 52 and thecommunication passage 47 flows into thecrank chamber 5 via theport 51. - As shown in
FIG. 8 , with the first control valve CV1 closed, that is, when thesupply passage 29 is closed, on the other hand, the crank pressure Pc is decreased. Accordingly, thespool 96 is moved upward by the urging force of thespring 85, that is, thevalve portion 92 is moved away from thevalve seat 93, so that thevalve hole 27 a communicates with theport 51 and thefirst bleed passage 27 is wide opened. Thus, the refrigerant in thecrank chamber 5 is immediately flown into thesuction chamber 21 via theport 51, thevalve chamber 71 and thevalve hole 27 a. - According to the third preferred embodiment, the same advantageous effects are obtained as those which have been described in the second preferred embodiment. In addition, since the first and second control valves CV1 and CV2 are formed as a single unit, the first and second control valves CV1 and CV2 are easily assembled to the
rear housing 4 during manufacturing of the compressor. - The preferred embodiment according to the present invention is not limited to the above-described preferred embodiments, but it may be modified in various ways as follows.
- A first alternative embodiment is shown in
FIG. 9 and is a modification of the second preferred embodiment. In this embodiment, thespool 91 is formed in the top surface thereof with arecess 91 b. A cross sectional area SC of therecess 91 b that is perpendicular to the axis of thespool 91 is larger than the cross sectional area SB of thevalve hole 27 a that is perpendicular to the axis of thespool 91. In the conditional inequality (3) for closing thevalve hole 27 a, the pressure difference (Pc−Ps) is multiplied by the cross sectional area SC of therecess 91 b instead of the cross sectional area SB of thevalve hole 27 a. Thus, even if the urging force f of thespring 85 is set relatively large with respect to a predetermined value of the pressure difference (Pc−Ps), the second control valve CV2 closes. - As described above, when the air-conditioner is started, it is desirable that the
valve hole 27 a is wide opened for allowing the liquid refrigerant that is accumulated in thecrank chamber 5 to flow out thereof. However, when the air-conditioner is stated, the refrigerant gas in thesuction chamber 21 is drawn into the cylinder bores 1 a and the suction pressure Ps is instantaneously decreased, so that thespool 91 of the second control valve CV2 may be moved toward thevalve hole 27 a thereby to decrease the opening degree of thevalve hole 27 a. In the result, the efficiency of flowing the liquid refrigerant is decreased. Thus, a relatively large amount of the urging force of thespring 85 that acts on thespool 91 in the direction which increases the opening degree of thevalve hole 27 a is required. Therefore, the embodiment ofFIG. 9 , wherein thespool 91 is formed in the top surface thereof with therecess 91 b, prevents a decrease in the efficiency of flowing the liquid refrigerant, while ensuring the ease of closing operation of the second control valve CV2. - Furthermore, in the first alternative embodiment shown in
FIG. 9 , thecommunication hole 27 b extends obliquely upward from thevalve chamber 71. There is a large space in thevalve chamber 71 and the large-diameter hole 73 on the side of thecommunication hole 27 b. A wall 99 protrudes from thestopper 76 in the vertical direction as seen on the drawing to theceiling surface 71 b of thevalve chamber 71. The wall 99 divides thevalve chamber 71 into a space that accommodates thespool 91 and acommunication passage 100 that extends in the vertical direction on the drawing and communicates with thecommunication hole 27 b. - A hole 99 a is formed through the wall 99 so that the refrigerant gas that flows from the first control valve CV1 into the
backpressure chamber 80 via thecommunication hole 76 b of thestopper 76 and is guided toward the wall 99 by theslope 91 c flows toward thecrank chamber 5 via thecommunication passage 100 and thecommunication hole 27 b. In addition to the hole 99 a, anotherhole 99 b is formed through the wall 99 so that, when the second control valve CV2 is opened, the refrigerant that flows from thecrank chamber 5 into thecommunication passage 100 via thecommunication hole 27 b flows into thesuction chamber 21 via thevalve chamber 71 and thevalve hole 27 a. Thehole 99 b is formed above the hole 99 a. Even though thecommunication hole 27 b extends obliquely upward from thevalve chamber 71, the provision of thecommunication passage 100 and the though holes 99 a and 99 b helps to facilitate the flow of the refrigerant gas in thefirst bleed passage 27 and thesupply passage 29. - A second alternative embodiment that is a modification of the second preferred embodiment is shown in
FIG. 10 . This alternative embodiment differs from the second preferred embodiment in that thespool 91 is disposed in upside down relation, theflange 94 is removed, and thespring 85 is accommodated within thespool 91. In this case, the inner and outer diameters of thespool 91 are enlarged by the length of the removedflange 94 for thevalve chamber 71 having the same diameter as in the second preferred embodiment. In the second alternative embodiment ofFIG. 10 , above conditional inequality (3) is used in such a way that the pressure difference (Pc−Ps) is multiplied, not by the cross sectional area SB of thevalve hole 27 a, but by a cross sectional area SD of the inner space of thespool 91 that is perpendicular to the axis of thespool 91 and is larger than the cross sectional area SC of therecess 91 b of thespool 91 having theflange 94 as shown inFIG. 9 . Therefore, the second alternative embodiment ofFIG. 10 prevents a decrease in the efficiency of flowing the liquid refrigerant, while ensuring the ease of closing operation of the second control valve CV2. - In the second alternative embodiment shown in
FIG. 10 , if theslope 91 c is further formed in the inner periphery and at the open end of thespool 91, in the above conditional inequality (3), the pressure difference (Pc−Ps) is multiplied by a cross sectional area SE of the opening of thespool 91 that is perpendicular to the axis of thespool 91 and is larger than the cross sectional area SD of the inner space of thespool 91 that is located below theslope 91 c. Therefore, the second alternative embodiment ofFIG. 10 prevents a decrease in the efficiency of flowing the liquid refrigerant, while ensuring the ease of closing operation of the second control valve CV2. - In the first preferred embodiment, the minimum opening degree of the
valve hole 27 a by thefirst valve portion 79 of the second control valve CV2 is not zero. However, it is so arranged, as shown inFIGS. 11 through 14 , that the minimum opening degree of thevalve hole 27 a by thefirst valve portion 79 is zero and also that elasticity is provided to at least one of thefirst valve portion 79, the valve seat or thevalve plate assembly 3 for thefirst valve portion 79, thesecond valve portion 88 and thevalve seat 89 for thesecond valve portion 88. In this case, the element provided with the elasticity out of the above-named parts is elastically deformable. By so arranging, the opening of the twovalve portions single spool 75 can be reduced to zero simultaneously without the need of machining thespool 75 and the valve seat 89 (or the valve plate assembly 3) at a very high accuracy. - In a third alternative embodiment shown in
FIG. 11 , thesecond valve portion 88 of the second control valve CV2 is formed by a ring-shapedlead 101. The small-diameter portion 75 a has an engagingprotrusion 75 c, and the large-diameter portion 75 b has an engagingrecess 75 d. In thespool 75, the large-diameter portion 75 b and the small-diameter portion 75 a are combined together such that the engagingprotrusion 75 c is inserted into the engagingrecess 75 d with thelead 101 held between the small-diameter portion 75 a and the large-diameter portion 75 b. Aslope 78 b is formed in the region of thewall surface 78 a of themovable step 78 and is located outside thespring seat 86 for allowing thelead 101 to be deformed toward a space provided by forming theslope 78 b. - In a fourth alternative embodiment shown in
FIG. 12 , thefirst valve portion 79 of the second control valve CV2 is formed by alead 102. Thelead 102 has a ring shape and is fitted around aprotrusion 75 e formed at the center of the end surface of the small-diameter portion 75 a on the side thereof adjacent to thevalve plate assembly 3. Aslope 75 f is formed on the end surface of the small-diameter portion 75 a in the radially outward region thereof for the same purpose as theslope 78 b ofFIG. 11 . - Furthermore, in a fifth alternative embodiment shown in
FIG. 13 , the large-diameter portion 75 b of thespool 75, that is, thesecond valve portion 88 is made of rubber. As a further alternative embodiment of the fifth alternative embodiment, the small-diameter portion 75 a, instead of the large-diameter portion 75 b (the second valve portion 88), of thespool 75 is made of rubber. - A sixth alternative embodiment that is a modification of the fifth alternative embodiment is shown in
FIG. 14 . In this embodiment, the large-diameter portion 75 b is fitted in acylinder 103 that is made of metal. The width of theclearance 87 between the outer peripheral surface of thecylinder 103 and the inner peripheral surface 72 a of the middle-diameter hole 72 is larger than the diameter of the foreign substances that pass through thefilter 90. Thesecond valve portion 88 is formed protruding beyond thecylinder 103. - In this embodiment, even though the rubber large-
diameter portion 75 b is deformed when the rubber large-diameter portion 75 b contacts thevalve seat 89 or thestopper 76, thecylinder 103 functions to restrict the deformation of the rubber large-diameter portion 75 b in the radially outward direction. Thus, theclearance 87 is formed without considering the deformation of the rubber large-diameter portion 75 b. - Also, the foreign substances are less liable to be attached to the surface of the
metallic cylinder 103 than to the surface of rubber. Even if the foreign substances are accumulated in theclearance 87 when thesecond valve portion 88 contacts thevalve seat 89, such foreign substances are easily flown from theclearance 87 by the refrigerant gas when thesecond valve portion 88 is moved away from thevalve seat 89. Additionally, since the outer peripheral surface of themetallic cylinder 103 is less susceptible to damage by the foreign substances, the endurance of thespool 75 is extended. - In addition to the third through sixth alternative embodiments shown in
FIGS. 11 through 14 , for example, theentire spool 75 is made of rubber to provide elasticity to both the first andsecond valve portions first valve portion 79 is formed by a lead or rubber to be provided with elasticity. Furthermore, thevalve seat 89 for thesecond valve portion 88 is formed by a lead or rubber for the same purpose. In still further alternative embodiment, elasticity is provided to both the valve seat for thefirst valve portion 79 and thevalve seat 89 for thesecond valve portion 88. - In the above-described first and second preferred embodiments, the
backpressure chamber 80 of the second control valve CV2 has the same pressure atmosphere as the region K that is located downstream of the position of valve opening adjustment (the valve seat 53) of the first control valve CV1 in thesupply passage 29, and thebackpressure chamber 80 is in constant communication with thecrank chamber 5 via the part of thesupply passage 29. However, in a seventh alternative embodiment, a passage that interconnects thebackpressure chamber 80 and thecrank chamber 5 is provided independently of thesupply passage 29. Namely, thebackpressure chamber 80 has the same pressure atmosphere via the above passage and thecrank chamber 5 as the region K that is located downstream of the position of valve opening adjustment (the valve seat 53) in thesupply passage 29. - In each of the above-described preferred embodiments, the
backpressure chamber 80 of the second control valve CV2 is in constant communication with thecrank chamber 5 via the part of thesupply passage 29, and it is presumed that the pressure PdK in thebackpressure chamber 80 is substantially the same as the crank pressure Pc. However, in an eighth alternative embodiment, a fixed throttle is formed in thevalve plate assembly 3 on thesupply passage 29, so that the pressure PdK in thebackpressure chamber 80 is larger than the crank pressure Pc when the first control vale CV1 is opened. - In this modification, when decreasing the displacement of the compressor in a state in which the second control valve CV2 is opened, the pressure PdK in the
backpressure chamber 80 is rapidly increased by opening the first control valve CV1, so that the second control valve CV2 is closed. Thus, the displacement of the compressor is immediately decreased. - In each of the above-described preferred embodiments, the first control valve CV1 is so constructed that the pressure difference (PdH−PdL) is detected between the pressure monitoring points P1 and P2. However, the first control valve CV1 is so constructed that only the suction pressure Ps is detected in a ninth alternative embodiment. Namely, the first control valve CV1 is constructed to internally autonomously position the
valve rod 40 in response to the variation of the suction pressure Ps such that a control target or a set suction pressure for the suction pressure Ps that is determined by the electromagnetic urging force of thesolenoid 60 is maintained. - Although the
spring 85 of the second control valve CV2 is provided by a coil spring in the above-described preferred embodiments, thespring 85 includes a plate spring in a tenth alternative embodiment. - In an eleventh alternative embodiment, the
spring 85 in each of the above-described preferred embodiments is removed from the second control valve CV2. However, the provision of thespring 85 in the second control valve CV2 is desired because such spring assists in smooth opening of thevalve hole 27 a and it is preferable that thespring 85 is provided for stabilizing the operation of the second control valve CV2. - In a twelfth alternative embodiment, the
second bleed passage 28 in the above-described first preferred embodiment is removed. In a thirteenth alternative embodiment, clutch mechanism such as an electromagnetic clutch is utilized as the power transmission mechanism PT. - In a fourteenth alternative embodiment, the present invention is applied to a wobble plate type variable displacement compressor.
- The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.
Claims (20)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2003146952A JP4100254B2 (en) | 2003-05-23 | 2003-05-23 | Capacity control mechanism of variable capacity compressor |
JP2003-146952 | 2003-05-23 |
Publications (1)
Publication Number | Publication Date |
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US20050008499A1 true US20050008499A1 (en) | 2005-01-13 |
Family
ID=33095504
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US10/851,870 Abandoned US20050008499A1 (en) | 2003-05-23 | 2004-05-21 | Displacement control mechanism for variable displacement compressor |
Country Status (3)
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US (1) | US20050008499A1 (en) |
EP (1) | EP1479908A2 (en) |
JP (1) | JP4100254B2 (en) |
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US20070116578A1 (en) * | 2005-11-16 | 2007-05-24 | Kabushiki Kaisha Toyota Jidoshokki | Control Device for a Vehicular Refrigeration, Vehicular Variable Displacement Compressor, and A Control Valve for the Vehicular Variable Displacement Compressor |
US20070264131A1 (en) * | 2006-05-12 | 2007-11-15 | Masaki Ota | Variable displacement compressor |
US20080131297A1 (en) * | 2006-11-10 | 2008-06-05 | Sokichi Hibino | Suction throttle valve of a compressor |
US20090142202A1 (en) * | 2007-11-29 | 2009-06-04 | Yoshinori Inoue | Structure for mounting a filter in a compressor |
US20090269216A1 (en) * | 2008-04-28 | 2009-10-29 | Kabushiki Kaisha Toyota Jidoshokki | Variable displacement type compressor with displacement control mechanism |
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US11098703B2 (en) * | 2017-04-06 | 2021-08-24 | Sanden Automotive Components Corporation | Variable displacement compressor with variation in discharge capacity |
US11149722B2 (en) * | 2016-12-01 | 2021-10-19 | Sanden Automotive Components Corporation | Variable displacement refrigerant compressor having a control valve adapted to adjust an opening degree of a pressure supply passage and a switching valve in the pressure supply passage closer to a controlled pressure chamber than the control valve and switching between a first state and a second state |
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-
2003
- 2003-05-23 JP JP2003146952A patent/JP4100254B2/en not_active Expired - Fee Related
-
2004
- 2004-05-21 EP EP04012097A patent/EP1479908A2/en not_active Withdrawn
- 2004-05-21 US US10/851,870 patent/US20050008499A1/en not_active Abandoned
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Also Published As
Publication number | Publication date |
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EP1479908A2 (en) | 2004-11-24 |
JP2004346880A (en) | 2004-12-09 |
JP4100254B2 (en) | 2008-06-11 |
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