US2986872A - Overcenter hydraulic pump-motor engine starter - Google Patents

Description

States This invention relates to starting devices for internal combustion engines.

Budzich and Manning copending application Serial No. 789,996, filed January 29, 1959, discloses and claims a reciprocating piston hydraulic starting engine which includes a cam plate that governs the length of the piston strokes and which is movable between maximum strokeestablishing positions on opposite sides of a neutral or Zero stroke-establishing position. The cam plate is biased toward the maximum stroke-establishing position on the motoring side of neutral by resilient means and is moved in the opposite direction by a shifting motor which is controlled by a device that is responsive to the speed of the internal combustion engine. When the speed is below that value at which the engine is capable of accelerating under its own power (termed the starter cut-out speed), the hydraulic engine operates as a starting motor. When engine speed exceeds the starter cut-out speed, the hydraulic engine becomes a pump and the speed responsive device energizes the shifting motor thereby causing it to shift the cam plate toward the maximum stroke-establishing position on the pumping side of neutral. This shift of the cam plate enables the engine to operate as a pump without reversing the functions of the inlet and outlet ports.

The overcenter starting device disclosed in the Budzich and Manning application is particularly useful in aircraft but it has a characteristic which, under one condition that can arise during such use, impairs that usefulness. If, during flight, the internal combustion engine associated with the hydraulic engine ceases to operate and its speed drops below the starter cut-out speed, the speed responsive device deenergizes the shifting motor thereby permitting the cam plate to move back to the motoring side of neutral. When this happens, the hydraulic engine becomes a motor and withdraws high pressure fluid from the hydraulic system. This waste of high pressure fluid, at a time when conservation may be essential, is undesirable.

The object of this invention is to provide an improved overcenter starting and pumping device in which reconversion from pumping to motoring operation is accomplished only by positive action on the part of the operator. With this improvement, failure of the internal combustion engine does not cause the hydraulic engine to impose a needless demand on the hydraulic system.

The preferred embodiment of the invention will now be described in detail with reference to the accompanying drawings, in which:

FIG. 1 is an axial sectional view of the hydraulic engine showing the cam plate in its maximum stroke-establishing position on the pumping side of neutral; in this figure the bidirectional torque-transmitting device has een rotated into the plane of section.

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1 showing the structure of one of the one-way overrunning clutches.

FIG. 3 is a sectional view taken on line 3-3 of FIG. 1.

P16. 4 is a sectional view taken on line 4-4 of FIG. 3 showing the front face of the valve plate.

FIG. 5 is a diagram, partly in schematic form, showing the control system for the hydraulic engine; the parts atent O Patented June 6, 1961 ICC being shown in the positions they assume when the hydraulic engine is at rest.

The hydraulic engine is the same as the one disclosed in the Budzich and Manning application referred to above. As shown in FIG. 1, it comprises a housing having separable sections 21 and 22 which are connected together by bolts 23 and which, when assembled, locate and rigidly hold an intermediate wall 24. A valve plate 25, containing arcuate high and low pressure ports 26 and 27 (see FIGS. 3 and 4) which communicate with the high and low pressure ports 28 and 29 of the hydraulic engine, is freely seated within a bore formed in housing section 22 and is prevented from rotating by pin 31. The valve plate disclosed and claimed in Tadeusz Budzich application Serial No. 677,636, filed August 12, 1957, is suitable for use in this engine. A drive shaft 32 is journalled in intermediate wall 24 and in valve plate 25 for supporting and driving rotary cylinder barrel 33. The cylinder barrel is formed with an axial bore 34 which is in great circle engagement with spherical enlargement 35 carried by shaft 32 for providing a universal and axially slidable support for the cylinder barrel. A torque tube 36, connected by splines 37 and 38 at its opposite ends with the cylinder barrel 33 and with the drive shaft 32, joins these members in driving relationship. This method of supporting and driving the cylinder barrel is fully described and claimed in Tadeusz Budzich application Serial No. 656,574, filed May 2, 1957, now Patent No. 2,925,046, issued February 16, 1960. The cylinder barrel 33 contains a circumferential series of through longitudinal cylinder bores 39 which are arranged to register sequentially with the arcuate ports 26 and 27 as the cylinder barrel rotates. A spring 41, reacting between split ring 42 carried by the torque tube and collar 43 carried by the cylinder barrel, biases the cylinder barrel 33 into engagement with the valve plate 25. The spring load imposed on the torque tube is transmitted to the shaft by splines 38 and ring 44.

Pistons 45, formed with spherical heads 46 for supporting shoes 47, are mounted in cylinder bores 39 for reciprocation by cam plate 48 and nutating plate 49. Nutating plate 49 is seated on a collar 51 having a spherical outer surface which engages a similarly shaped rec ss formed in the nutating plate. The center of this spherical surface, as well as the center of spherical enlargement 35, is located at the point of intersection 52 of the axis of the drive shaft and the plane of the centers of spherical piston heads 46. Snap ring 53, seated in a groove formed in drive shaft 32, prevents longitudinal movement of collar 51 under the action of the piston inertia loads and thus serves to transmit these loads into shaft 32. The loads are conveyed from the shaft to the housing section 22 by thrust bearing 54. This method of handling the inertia forces is fully described and claimed in Tadeusz Budzich application Serial No. 665,387, filed June 13, 1957, now Patent No. 2,953,099, issued Sept. 20, 1960.

Cam plate 48 is supported in housing section 22 by yokes 55, 55 and trunnions 56, 56' for angular movement about an axis extending in a direction normal to the axis of drive shaft 32 and intersecting that axis at the point 52. The angular position of the cam plate determines the length of the strokes of pistons 45 and the cam plate is free to move between maximum strokeestablishing positions on opposite sides of a neutral or zero stroke-establishing position (a vertical position as viewed in FIG. 1). A spring plunger 57, connected with the lower end of the cam plate 48 by an articulated connecting rod 58, biases the cam plate toward is maximum stroke-establishing position on the right or motoring side of neutral. The cam plate 48 is moved to the opposite or pumping side of neutral against the bias of spring plunger 57 by a shifting motor 59. This motor comprises a cylinder 61, a reciprocable piston 62, and a closed motor working chamber 63. The piston 62 is connected with the cam plate by articulated connecting rod 64. Surrounding the cylinder 61 is a coaxial cylinder 65 which defines an annular space for receiving the shiftable spring seat 66. This seat slides along and is in sealing engagement with the surfaces of the cylinders 61 and 65. A cap 67, threaded on the left end of cylinder 65, serves as a stop which limits the leftward movement of spring seat 66. The space 68 to the right of the spring seat 66 is connected with the working chamber of the shifting motor 59 by a passage 69. A biasing spring 71, reacting between the seat 66 and the piston 62, urges the cam plate 48 toward its maximum stroke-establishing position on the pumping side of neutral. A control motor 72 comprising a cylinder 73, a working chamber 74, and a reciprocable piston 75 connected with the cam plate 48 by articulated connecting rod 76, serves to shift the cam plate toward its neutral position against the bias of spring 71 and shifting motor 59.

Journalled in housing sections 21 and 22 is a power shaft 77 which is connected with the internal combustion engine (not shown) by a splined coupling 78. Encircling power shaft 77 are two spur gears 79 and 81 whose hubs 82 and 83 are journalled in intermediate housing wall 24. The hub portion 80 of gear 81 is journalled in housing section 22 and supports the right end of power shaft 77. These gears are connected with the power shaft by one-way overrunning clutches 84 and 85 and are arranged to engage spur gears 86 and 87 which are formed as an integral part of drive shaft 32. The cam elements 88 of clutches 84 and 85 are set in reverse senses so that when the shaft 32 is driving the shaft 77, a torque is transmitted through gears 86 and '79, and when power shaft 77 is driving drive shaft 32, torque is transmitted through gears 81 and 87. Both gear pairs 79, 86 and 81, 87 effect a step-down in speed; the pair 79, 86 having the higher ratio.

As shown in FIG. 5, the working chamber 63 of the shifting motor 59 is connected by passage 89 with a distributing valve 91. This valve comprises a housing con taining an outlet port 92 which is connected with the passage 89, and inlet port 93 which is connected with the high pressure port 28 by passages 94 and 95, and an exhaust port 96 which is connected with a sump 97 by passage 98. A valve plunger 99 reciprocates within a bore formed in the housing of valve 91 and is provided with three spaced reduced diameter portions 101, 102 and 103 which define the two valve lands 104 and 105. Seated on the reduced diameter portion 103 is a motor piston 106 which reciprocates within cylinder bore 187 under the action of the fluid pressure in working chamber 108 and the spring 109. This spring, acting through piston 1106 and land 105, urges valve plunger 99 to the position shown in FIG. against the bias of a weaker spring 111. During those times when the pressure in working chamber 108 is sufiicient to move piston 106 out of engagement with land 105, the position of plunger 99 is determined by spring 111 and the centrifugal ball governor 11 2 which is driven by the internal combustion engine.

The working chamber 74 of the control motor 72 is connected with a control valve 113 by passage 114. This valve is of the same basic type as the one described and claimed in Tadeusz Budzich application Serial No. 685,- 530, filed September 23, 1957, now Patent No. 2,921,560, issued January 19, 1960. As shown in FIG. 5, it comprises a housing having an inlet passage 115 connected with passage 95, a motor passage 116 connected with passage 114, and two exhaust passages 117 and 118 which are connected with sump 97 via passages 119 and 121, respectively. The valve housing is formed with a longitudinal bore 122 having enlarged end portions which are closed and sealed by plug 123 and solenoid casing 124, and an intermediate portion which receives two abutting valve sleeves 125 and 126. These sleeves are held in place by snap ring 127 and shoulder 128. The sleeve 125 contains two ports 129 and 131 which communicate, respectively, with passages 116 and 117, and a passage 132 which communicates with inlet passage through an annular groove 133 formed in the outer periphery of sleeve 126. Mounted in valve sleeve is a slidable valve plunger 134 carrying annular lands 135, 136 and 137 which are separated by annular grooves 138 and 139. The land contains a longitudinal slot 141 which connects annular groove 138 with passage 132. Slidable in the right end of bore 122 is a spring seat 142 which, with valve plunger 134 and sleeve 125, defines a spring chamber 143. This chamber 143 is in continuous communication with sleeve port 129 via longitudinal and radial passages 144 and 145. A spring 146, reacting between seat 142 and valve plunger 134, biases the plunger to the left into contact with the end wall of sleeve 125.

Valve sleeve 126 contains two ports 147 and 148; the former communicating with inlet passage 115 through annular groove 133, and the latter communicating with the space 149 between plug 123 and seat 142 via passage 151. Reciprocable in sleeve 126 is a valve plunger 152 which is formed with two spaced annular grooves 153 and 154 that define an annular valve land 155. The left end of the plunger 152 is enlarged to form a shoulder :156 and the plunger is biased by spring 157 to a position in which this shoulder abuts the left end of sleeve 126. A solenoid 158, having a movable armature 159 which is connected with plunger 152, is mounted in casing 124 and serves, when energized, to shift the plunger 152 to the left against the bias of spring 157. Passages 161, extending through the shoulder 156, establish continuous communication between groove 153 and the space 162 inside the solenoid casing.

Before describing the operation of the complete starter device, it will be helpful to consider separately the operation of each of its major components. For convenience, these components will be divided into three groups: the rotating group, comprising drive shaft 32, torque tube 36, cylinder barrel 33, pistons 45, and nutating plate 49; the motor-to-pump conversion group comprising cam plate 48, shifting motor 59, spring 71, distributing valve 91, and centrifugal governor 112; and the discharge pressure compensator group comprising cam plate 48, control motor 72, spring 71, shifting motor 59, and control valve 113.

When cam plate 48 is on the right side of neutral (as shown in FIG. 5), the high pressure fluid delivered to port 28 flows into those cylinder bores 39 which are in communication with arcuate port 26 and forces the pistons 45 against cam plate 48. The reaction force supplied by the cam plate produces a torque on the cylinder barrel 33 which causes the rotating group to rotate in the direction of the arrow in FIG. 4. As the cylinder barrel rotates, the fluid in cylinder bores 39 is discharged through arcuate port 27 and low pressure port 29. The torque developed by the rotating group is delivered to the internal combustion engine by spur gears 86 and 79, clutch 84, power shaft 77, and splined coupling 78. Since the cam elements 88 of clutches 84 and 85 are set in reverse senses, no torque will be transmitted to power shaft 77 through spur gears 81 and 87. After the internal combustion engine has started, it will drive the power shaft 77 in the direction of the arrow in FIG. 2, and when this engine has accelerated to the speed at which power shaft 77 begins to exceed the speed established by gears 79 and 86, the cam elements 88 of clutch 84 will automatically disengage. When power shaft 77 reaches the speed at which gear 81 begins to overrun gear 87, the cam elements 88 of clutch 85 will engage and the internal combustion engine will supply torque for driving the rotating group as a pump.

If the cam plate 48 is in the maximum stroke-establishing position of FIG. 5 when clutch 85 engages and the direction of torque transmission between the hydraulic engine and the internal combustion engine reverses, the magnitude of the torque will be large and a severe shock load will be imposed on the gear train and its clutch. Furthermore, since the rotating group will be moving in the direction of the arrow in FIG. 4, fluid will be Withdrawn from high pressure port 28 and arcuate 26 and will be discharged under high pressure through arcuate port 27 and low pressure port 29. This reversal of the functions of ports 28 and 29 is obviously undesirable because sump 97 is in direct communication with port 29. The motor-to-pump conversion group functions to reduce the magnitude of the torque at the time of its reversal of direction and also to prevent this port reversal.

At the time the hydraulic engine is started, high pressure hydraulic fluid is transmitted to working chamber 108 of distributing valve 91, in a manner to be described later, where it acts upon and moves piston 166 to the right, out of contact with land 1195 of valve plunger 99. Thus working chamber 63 of shifting motor 59 is vented to sump 97 by passages 89 and 98 and outlet port 92, reduced diameter portion 191, and exhaust port 96 of distributing valve 91, and spring plunger 57 moves cam plate 48 to the maximum stroke-establishing position on the motoring side of neutral. Since the space 68 to the right of annular spring seat 66 is in communication with working chamber 63 via passage 69, this space also will be vented. When the internal combustion engine has started and reached a speed at which it can accelerate under its own power, centrifugal governor 112 moves plunger 99 of distributing valve 91 to a position in which land 164 interrupts the vent path and reduced diameter portion 102 interconnects inlet and outlet ports 93 and 92. Fluid in passage 94 can now flow to and thus pressurize working chamber 63 and space 65;. The speed at which communication between ports 92 and 93 is first established (called the starter cut-ou speed), must not be greater than, and preferably is less than, the speed at which spur gear 79 begins to overrun spur gear 86. Under the action of the pressure in working chamber 63 and Space 68, piston 62 and annular spring seat 66 will move to the left thereby shifting the cam plate 48 toward neutral and compressing spring 71. The spring 71 and the piston 62 are capable of moving the cam plate to its maximum stroke-establishing position on the pumping side of neutral but, as will appear below, at this point in the operation they simply move it to neutral and hold it in that position.

As the cam plate 48 moves toward its neutral position, the torque developed by the hydraulic engine, and consequently the speed at which it is capable of driving the internal combustion engine, decreases. When the cam plate is within a few degrees of neutral, spur gear 79 will begin to overrun spur gear 86 and the cam elements 88 of clutch 84 will disengage. Simultaneously, or approximately simultaneously, spur gear 81 will begin to overrun spur gear 87 and the cam elements 88 of clutch 85 will engage. At the time of this reversal of the direction of torque transmission, the magnitude of the torque will be quite small. Furthermore, since the cam plate will be in its neutral position when the hydraulic engine is being driven as a pump, the functions of the ports 28 and 29 will not be reversed.

The components in the discharge pressure compensating group function, when the hydraulic engine is operating as a pump, to maintain the cam plate 48 in its maximum stroke-establishing position until discharge pressure reaches a limit very close to the desired maximum and then, as the discharge pressure increases above this limit, they serve to move the cam plate 48 progressively toward its neutral position. When the desired maximum pressure is reached, piston stroke, and consequently pump displacement, will be zero. Since this hydraulic engine may, in vehicles having multiple propulsion engines, be used to provide the motive fluid for operating starter devices associated with other engines and since it is de- '6 sirable, from the standpoint of conserving size and Weight, to use a higher pressure when the hydraulic engine is operating as a motor than when it is operating as a pump, the compensator group provides a selection between two maximum pressures.

Although the control motor 72 performs a useful function when the cam plate 48 is on the motoring side of neutral and is moving toward neutral, for present purposes its operation will be described only with reference to the conditions which arise when the cam plate is on the pumping side of neutral. As shown in FIG. 5, the working chamber 74 of this motor 72 is normally vented by passage 114, motor passage 116, port 129, plunger groove 139, port 131, exhaust passage 117, and passage 119. The pressure in passage is transmitted through inlet passage and groove 1 33 to the passage 132 of control valve 113 where it acts upon the end of valve plunger 13 and urges this plunger to the right against the bias of spring 146. The preload in spring 146, which determines which maximum pressure will be established, depends upon the position of valve plunger 152. When the solenoid 1511 is energized and the plunger 152 has moved to the left, the space 149, to the right of shiftable valve seat 142, is connected with passage 95 via passage 151, port 1455, plunger groove 154, port 147, annular groove 133, and inlet passage 115. The pressure in space 149 acts against the right face of seat 142 and causes this seat to compress, and therefore preload, spring 146. On the other hand, when solenoid 158 is deenergized and spring 157 moves plunger 152 to the FIG. 5 position, the space 14 9 is vented to sump 97 via passage 151, port 143, plunger groove 153, passages 161, chamber 162, exhaust passage 113, and passage 121. Thus, depending on Whether solenoid 153 is energized or deenergized, the compensator group will establish either the higher or the lower maximum discharge pressure.

Since the working chamber 108 is connected with passage 151 and space 149 by conduit 150, the condition of solenoid 151% also affects the operation of distributing valve 91. When solenoid 158 is energized (as it is during the starting operation), high pressure fluid is transmitted to working chamber 168 where it is eifective to move piston 166 to the right against the bias of spring 199. As a result, spring 111 moves the valve plunger 99 into operative engagement with governor 112 and renders this governor eifective to control the action of the valve. When solenoid 158 is deenergized, working chamber 108 is vented to sump 97 and spring 109 shifts piston 106 and valve plunger 99 to the position shown in FIG. 5. The significance of this action will become apparent as the description proceeds.

When the discharge pressure effective in passage 132 produces a pressure force on the left end of valve plunger 134 suflicient to overcome the bias of spring 146, this valve plunger moves to the right to a lap position in which plunger land 136 interrupts communication between ports 129 and 131. For convenience, the pressure required to hold valve plunger 134 in this lap position against the bias of spring 146 will be called the reference pressure. When discharge pressure exceeds the reference pressure, valve plunger 134 moves further to the right to thereby interconnect port 129 and passage 132 through slot 141 and plunger groove 138. Pressure fluid is now transmitted to the working chamber 74 of control motor 72 and through radial passages 145 and longitudinal passage 144 to spring chamber 143. When the pressure in these two chambers rises to a value at which the sum of the force of spring 146 and the pressure force acting on the right end of valve plunger 134 exceeds the pressure force acting on the left end of this plunger, the valve plunger will move to the left toward its lap position. When it has again reached the lap position, the pressures established in working chamber 74 and spring chamber 143 will be equal to the difference between discharge pressure in passage 95 and the reference pressure. Further increases in discharge pressure produce equal increases in pressure in working chamber 74 and spring chamber 143.

The pressure in working chamber 74, acting on control piston 75, urges the cam plate 48 toward its neutral position against the bias of spring 71 and shifting motor piston 62. The parts are so dimensioned that when the discharge pressure in passage 95 reaches either of the two maximums, the cam plate 48 will be in its neutral position. The following numerical example will illustrate this point:

Let it be assumed that (1) The lower maximum discharge pressure is 3000 p.s.i. and the higher maximum discharge pressure is 4000 p.s.1.',

(2) The control pressure differential of cam plate 48,

i.e., the difference in pressure in working chamber 74 which will cause cam plate 48 to move between its maximum and neutral positions, is 30 psi;

(3) The effective area of piston 75 of control motor 72 is 1 square inch;

(4) The effective area of piston 62 of shifting motor 59 is 0.495 square inch;

(5) Spring 71 exerts no force on cam plate 40 when the cam plate is in its maximum stroke-establishing position; and

(6) Spring 71 exerts a force of 15 pounds when cam plate 48 is in its neutral position.

Using these values and considering first the operation when solenoid 158 is deenergized and space 149 is vented, it will be seen that a pressure of 1500 psi. will be required in working chamber 74 of control motor 72 in order to hold cam plate 48 in its neutral position when discharge pressure is 3000 psi. Since the pressure in this working chamber equals the difference between discharge pressure and the reference pressure, the reference pressure in this case must be 1500 p.s.i. This means that spring 146 will vent Working chamber 74 until discharge pressure reaches 1500 p.s.i. and that when the discharge pressure exceeds this value, the pressure in that working chamber will increase at the same rate as the discharge pressure. When the discharge pressure reaches 2970 psi, the pressure in working chamber 74 will have increased to 1470 psi. and at this point the force developed by control motor 72 will just balance the sum of the forces developed by spring 71 and shifting motor 59. The next 30 psi. increase in discharge pressure will cause control motor 72 to move the cam plate from its maximum to its neutral stroke-establishing position. If discharge pressure should now decrease, valve plunger 134 will be shifted to the left from its lap position by spring 146 and the fluid pressure in spring chamber 143, thereby interconnecting ports 129 and 131 and venting working chamber 74. When the pressure in this chamber again equals the difference between discharge pressure and the reference pressure," valve plunger 134 will again move to the right to its lap position. If discharge pressure should drop below the reference pressure of 1500 p.s.i., valve plunger 134 will take up a position to the left of its lap position.

When solenoid 158 is energized and the space 149 to the right of shiftable spring seat 142 is pressurized, this seat will move to the left and compress spring 146. The area of spring seat 142, which is subject to the pressure in space 149, is so selected that the preload induced in spring 146 will establish a reference pressure of 2005 p.s.i. Operation of the discharge pressure compensator under high pressure conditions is basically the same as it is under low pressure conditions. When discharge pressure is below the reference pressure of 2005 psi, working chamber 74 is vented and when discharge pressure rises above this value, the pressure established in working chamber 74 equals the difference between discharge pressure and the reference pressure. At a discharge pressure of 3970 p.s.i., the pressure in working chamber 74 will be 1965 p.s.i. and the force developed by 8 control motor 72 will just balance the forces exerted by shifting motor 59 and spring 71. As the discharge pressure rises to 4000 p.s.i., the pressure in working chamber 74 will increase progressively to 1995 psi. and the cam plate 48 will be moved gradually toward its neutral position. When discharge pressure reaches 4000 p.s.i., the force developed by control motor 72 will just balance the sum of the forces developed by spring 71 and shifting motor 59 and the cam plate 48 will be in its neutral position.

Operation For purposes of description, let it be assumed that the vehicle has two propulsion engines and that each is provided with the starter unit shown in FIG. 1 and the control valve 113, governor 112 and distributing valve 91 shown in FIG. 5. The splined couplings 78 and the centrifugal governor 112 are connected with the associated internal combustion engines and the components of each starting device are interconnected in the manner shown in FIG. 5. It will also be assumed that the first engine to be started is the one associated with the illustrated starter device and that that starter device will supply the motive fiuid for starting the second internal combustion engine.

The passage 94 of this device is connected with a pump 163 via selector valve 164 and passage 165. The pump 163 supplies the 4000 psi. motive fluid for starting the first engine and it can be mounted in or external to the vehicle. Selector valve 164 has a start position in which passages 165 and 94 are interconnected and a pump position in which passages 94 and 166 are interconnected. The passage 166 leads to the vehicle hydraulic system and in this case, that system includes the hydraulic engine associated with the second propulsion engme.

Prior to the starting operation, the parts of the starting device assume the positions shown in FIG. 5. The working chamber 63 of shifting motor 59 is connected with high pressure port 28 via passage 89, port 92, re-

duced diameter portion 102, port 93, and passages 94 and 95. Because of the presence of passage 69, which interconnects working chamber 63 and the space 68 to the right of annular valve seat 66, this space also is connected with the high pressure port. When the hydraulic engine is idle, there is no pressure in port 28 so spring plunger 57 is able to shift cam plate 48 to the maximum stroke-establishing position on the motoring side of neutral (shown in FIG. 5). The working chamber 74 of control motor 72 is vented to sump 97 by control valve 113 along a path comprising passage 114, motor passage 116, port 129, plunger groove 139, port 131, and exhaust passage 117. The space 149, to the right of shifting valve seat 142, is vented by the solenoid-operated valve plunger 152 along a path comprising passage 151, port 148, plunger groove 153, passages 161, chamber 162, and exhaust passage 118. This same path vents conduit 150 and working chamber 108.

When it is desired to start the first propulsion engine, solenoid 158 is energized to shift valve plunger 152 to the left, and concurrently selector valve 164 is shifted to its start position. Pressure fluid delivered by pump 163 is now transmitted to the high pressure port 28 of the hydraulic engine via passages 165, 94 and 95. In the manner described above, the fluid passing through the hydraulic engine from high pressure port 28 to low pres sure port 29 causes rotation of the rotating group and produces the starting torque for the internal combustion engine. Simultaneously a portion of the fluid in passage flows to the space 149 of control valve 113 and to the working chamber 108 of distributing valve 91. The pressure in working chamber 108 shifts piston 106 to the right out of contact with land and permits spring 111 to shift plunger 99 to a position in which reduced diameter portion 101 connects outlet and exhaust ports 92 and 96, respectively. This vents working chamber 63 9 and space 68. The pressure in space 149, acting on the right face of spring seat 142, shifts this seat to the left thereby compressing spring 146 and causing it to establish a reference pressure of 2005 psi Although at this point in the operation the pressure in working chamber 74 may be as high as 1,995 p.s.i., the control motor 72 will not be effective to vary the displacement of the engine because this motor can move the cam plate 48 only in the clockwise direction and the cam plate has already reached the limit of movement in that direction.

Once the internal combination engine has started and has reached the starter cut-out speed, centrifugal governor 112 moves valve plunger 99 to the left against the bias of spring 111 to a position in which land 104 interrupts communication between ports 92 and 96 and reduced diameter portion 102 connects port 92 with port 93. Pressure fluid in passage 94 can now flow to working chamber 63 and space 68. Piston 62 and seat 66 (acting through spring 71) now move the cam plate 48 toward its neutral position. Since the angular position of the cam plate determines the length of the stroke of pistons 45, this movement of the cam plate reduces the displacement of the hydraulic engine and consequently increases the pressure in passages 94 and 95. As a result, the shifting force exerted by piston 62 and spring 71 will increase as the cam plate moves to the neutral position and, in the absence of the discharge pressure compensator, these forces would cause the cam plate to over-shoot the neutral position. However, in the present device, as the pressure in passage 95 rises so too does the pressure which control valve 113 establishes in control motor working chamber 74. Since the area of piston 72 is twice the area of piston 62 and since once the reference pressure is exceeded the rate of change of pressure in working chamber 74 equals the rate of change of pressure in working chamber 63, it is seen that the force developed by control motor 72 which resists movement of the cam plate increases at a faster rate than the shifting forces of piston 66 and spring 71. The cam plate then is moved to neutral with a progressively decreasing force and over-shoot is minimized. When the cam plate 48 reaches neutral, the pressures in passages 95 and in working chamber 63 will be 4000 p.s.i. and the pressure in working chamber 74 will be 1,995 p.s.i. Because of this, the force developed by motor 72 will just balance the sum of the forces developed by spring 71 and motor 59 and the cam plate will come to rest in the neutral position.

During the movement of cam plate 48 toward its neutral position, the motoring speed of the hydraulic engine decreases until, when the cam plate is within a few degrees of neutral, all motoring operation stops. At this point, power shaft 77, which is driven by the internal combustion engine, will commence to drive shaft 32 through clutch 85 and spur gears 81 and 87; the cam elements 88 of clutch 84 now being overrun. It is thus seen that at the time the direction of torque transmission between the starting device and the engine is reversed, the stroke of the pistons and consequently the magnitude of the torque will be small. Because of this, the transition from motoring to pumping operation is smooth. Furthermore, since the cam 48 will be held in its neutral position, a minimum load will be imposed on the internal combustion engine by the starter device and therefore that engine can accelerate rapidly to its idling speed.

When the internal combustion engine is idling, selector valve 164 is shifted to its pump position so that motive fluid can be supplied to the starting device of the second propulsion engine. Shifting of selector valve 164 to this position produces a decrease in pressure in passages 94 and 95 and this change in pressure is immediately effective in the passage 132 of control valve 113. The pressure in spring chamber 143, together with the force developed by spring 146, shifts valve plunger 134 to the left from its lap position, thereby connecting ports 129 and 131 through groove 139'to vent working chamber 74 of control motor 72. The pressures in working chamber 74 and in spring chamber 143 will decrease, and as they do, spring 71 and motor piston 62 will move the cam plate 48 toward its maximum stroke-establishing position on the pumping side of neutral. When the pressure in working chamber 74 is below 1965 p.s.i., the cam plate will be in that stroke-establishing position.

When the second propulsion engine has been started and the displacement of its starter device decreases, the pressures in passages 94 and 95 will increase and control valve 113 will again serve to progressively increase the pressure in working chamber 74 of control motor 72. Cam plate 48 will be moved back toward its neutral position and when the pressure in passages 94 and 95 reaches 4000 p.s.i., the cam plate will be in its neutral position. After both propulsion engines have reached their idling speeds, the solenoid 158 of each starter device will be deenergized to thereby allow spring 157 to shift valve plunger 152 to its FIG. 5 position. This action vents space 149 to the right of spring seat 142 and allows spring 146 to move that seat to the right into contact with plug 123. Control valve 113 will now function to limit discharge pressure to 3000 p.s.i.

Deenergization of solenoid 158 has another effect, namely, it vents Working chamber 108 and allows spring 109 to move piston 106 into contact with land 105. As a result, valve plunger 99 is held in the FIG. 5 position and the governor 112 is rendered ineffective. Therefore, even if the propulsion engine ceases to operate during flight and its speed drops below the starter cutout speed, spring 109 will prevent valve 91 from venting working chamber 63 and the cam plate 48 will remain on the pumping side of neutral. Because of this, the hydraulic engine associated with the inoperative propulsion en gine will not impose a demand for hydraulic fluid on the remaining hydraulic engine or on those accumulators which may be present in the system and high pressure fluid will be conserved at a time when conservation is essential. As stated previously, the drawings and description relate only to a preferred embodiment of the invention. Since many changes can be made in the structure of this embodiment without departing from the inventive concept, the following claims should provide the sole measure of the scope of the invention.

What is claimed is:

1. In an hydraulic starting and pumping device for an internal combustion engine of the type including a rotary cylinder barrel longitudinally reciprocating piston hydraulic engine capable of operating as both a pump and a motor and having high and low pressure ports, a cam plate for moving the pistons on their discharge strokes and for governing the length of these strokes, means supporting the cam plate for angular movement between maximum stroke-establishing positions on opposite sides of a zero stroke-establishing position, resilient means biasing the cam plate toward one of said maximum strokeestablishing positions, a shifting motor for moving the cam plate toward its other maximum stroke-establishing position against the bias of the resilient means, and a speed responsive device responsive to the speed of the internal combustion engine for energizing the shifting motor when engine speed is above a certain speed and for deenergizing that motor when engine speed is below said certain speed, the improvement which comprises override means associated with the shifting motor for preventing its deenergization; and means connected with the override means for selectively rendering it effective and ineffective.

2. In an hydraulic starting and pumping device for an internal combustion engine of the type including a rotary cylinder barrel longitudinally reciprocating piston hydraulic engine capable of operating as both a pump and a motor and having high and low pressure ports, a cam plate for moving the pistons on their discharge strokes 1 1 and for governing the length of these strokes, means supporting the cam plate for angular movement between maximum stroke-establishing positions on opposite sides of a zero stroke-establishing position, resilient means biasing the cam plate toward one of said maximum strokeestablishing positions, an hydraulic shifting motor for moving the cam plate toward its other maximum strokeestablishing position against the bias of the resilient means, a distributing valve having a movable element shiftable between first and second positions in which, respectively, it connects the shifting motor with the high and low pressure ports, a spring biasing the movable element toward its second position, and a governor responsive to the speed of the internal combustion engine for shifting the movable element to its first position, the improvement which comprises an override motor including a cylinder, a piston reciprocable in the cylinder and defining therewith a working chamber, and a spring reacting between the cylinder and the piston, the piston being arranged to move into engagement with said movable element and shift same to the first position under the action of the override spring and to move in the opposite direction out of engagement with said movable element under the action of the pressure in the working chamber of the override motor; and a control valve having an inlet port connected with the high pressure port, an outlet port connected with the working chamber of the override motor, an exhaust port, and a movable element shiftable between a first position in which the inlet and outlet ports are interconnected and a second position in which the outlet and exhaust ports are interconnected.

No references cited.

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