EP1302663A1 - Electro-hydraulic motor pump unit and check valve unit - Google Patents

Abstract

The unit (G) includes an electric motor which drives at least one pump. There is a connection element (C) between a pressure discharge point of the pump and the oil return route. The device has an automatic hydraulic pressure relief unit (D).

Description

The invention relates to an electro-hydraulic motor pump unit according to the preamble Claim 1, an attachment element according to the preamble of claim 12 and a pressure relief valve according to the preamble of claim 13.

Electrohydraulic motor pump units according to DE 200 07 554 U are on Machine tools used to hydromechanical clamping or tool or To control workpiece holding devices. Furthermore, electrohydraulic motor pump units as transportable supply units for cutting or riveting devices, Tools or screwdrivers used. The motor pump unit is with one Add-on element equipped that has the at least one consumer connection, at the respective consumer, for example via hydraulic hoses or Piping, is connected. Because of the high tightness of the valve components and also the manufacturing precision of the connectable hydraulic consumers remains a considerable amount even after the motor pump unit has been switched off System pressure maintained for a long time. Especially with portable electrohydraulic Motor pump units with interchangeable motors and for maximum pressures up to 800 bar is the pressure holding capacity undesirable under certain circumstances Disadvantage of the high quality of the interacting hydraulic components. The maintained pressure makes starting an AC motor particularly difficult after a business interruption. There are also hose or pipe couplings can only be solved with a relatively large amount of effort, and the connected hydro consumer For example, do not reset by hand, although for certain Reasons would be desirable. A major reason for this Long-term pressure retention lies in the extensive freedom from leakage of the individual Valve components in their closed positions, and in particular the complete one Leakage-free pressure relief valves in poppet design. On the other hand This freedom from leakage for maximum pressures up to approx. 800 bar is a must, even with a AC motor and small delivery of the high pressure pump stage to reach necessary working pressures reliably and quickly.

In hydraulic control systems according to US 4 197 705 A or US 5 454 223 A, the one of which is dependent on the load in terms of its delivery volume and / or the delivery rate, i.e. pressure according to demand, regulated control pump is supplied, the start of the electric motor after a standstill then no problem if all directional control valves are in their neutral positions because of a largely unpressurized circulating flow to the tank. The control pump is spring loaded when starting set to its maximum delivery volume, however, the flow resistance the essential unpressurized circulating flow is low, so that in the case of a Electric motor as the drive motor of the control pump no excessive starting current arises. However, if one of the directional control valves is located after an interruption in operation in a control position, then the flow path for the unpressurized circulation flow blocked. The maximum delivery volume set by spring loading The control pump then has to overcome a considerable flow resistance, which is in an excessive starting current of the electric motor driving the control pump expresses.

Further prior art is contained in US 4,362,084 A.

The invention has for its object a hydraulic motor pump unit to create the type mentioned, in which the long-term pressure retention the hydraulic valve components is eliminated in a structurally simple manner, and an attachment for a hydraulic pump unit, in particular with a AC motor, to indicate with the starting problems of the AC motor are avoidable, and finally a pressure relief valve in seat valve design to indicate that there is leakage in the closed position.

The task is with the features of claim 1, the sibling Claim 12 and the independent claim 13 solved.

The pressure relief device automatically reduces the pressure as soon as the electric motor stands. This makes it much easier for the electric motor to restart. In particular in an AC motor, this effect is advantageous because of a AC motor otherwise requires a relatively high starting current, which if necessary could overload the fuses of the normal network. AC motors are used especially with portable motor pump units, so that Motor pump unit just connected to the normal network in mobile use can be. However, easy starting is also possible with other electric motors be desirable. Furthermore, hose or Loosen pipe couplings easily, and if necessary, the consumer reset by hand, for example in the event of an unexpected power failure is advantageous.

The attachment can be used to convert an electrohydraulic motor pump unit be attached to the electric motor, especially an AC motor, facilitate starting after a break. The permanently open bypass means only a negligible loss. None is used for this additional function uses its own valve component, but the pressure relief valve that is necessary anyway.

Despite the poppet valve design, the pressure relief valve creates leakage-free Shut-off position a leakage predetermined in its extent, however does not affect the pressure relief function. It can be used without an additional valve component the pressure held within a pressure relief valve Known period of time can be reduced, which is particularly the case with an electrohydraulic Motor pump unit with an AC motor as a drive source for The pump stage offers advantages to keep the starting current of the AC motor low to keep.

The pressure relief device is expediently incorporated into the attachment element. The permanently open bypass means a loss in operation, but it does is negligible. After switching off the electric motor, the pressure builds up automatically from.

To the desired function of the pressure relief device without additional valve components To obtain the bypass is advantageous in one of the pressure relief valves intended. The pressure relief valve fulfills its normal operation Pressure limiting function and the function at the beginning of a break the pressure relief.

Usually with an electrohydraulic motor pump unit with at least two consumer connections, the two pressure relief valves to different Set response pressures. The bypass in the pressure relief valve is useful arranged with the lower response pressure so that to reach no losses due to the higher working pressure. At a Reset or release stroke of a hydraulic consumer controlled by the motor pump unit the loss due to the bypass does not matter.

An AC motor as an electric motor offers the advantage of being connected to the normal AC network to be able to be connected. The dual circuit pump stage enables it, initially with the low-pressure pump stage with a relatively large delivery rate to reach lower pressure levels, and then with the high pressure pump stage low flow rate to get to very high working pressures, e.g. except for about 800 bar. The direction of movement of the hydraulic consumer is determined by means of the directional control valve controlled, each pressure relief valve the maximum working pressure monitored in one direction. To the pressure relief function the bypass is located in one of the pressure relief valves, expedient in that the less important function or the lower pressure monitoring Pressure relief valve.

The bypass in a cone seat valve is structurally simple by flattening the Cone jacket of the valve cone formed. The flattening forms in the shut-off position the pressure relief valve with the valve seat a passage or a throttle a predetermined size over which the leakage flows. The is expedient Flattened by a sanded surface, the manufacture of which is simple.

The flattening should be parallel to the cone generator, so that it is at the Grinding strokes when grinding the cone shell by interrupting the rotary movement of the valve cone can be precisely shaped by adjusting the grinding tool.

Alternatively, the bypass could be at least in the case of a cone or ball seat valve a notch may be formed in the valve seat.

The bypass is expediently dimensioned such that it has a leakage of approx. 0.3 to 0.4 Liters per minute at 150 bar. This allows an at least extensive Pressure relief, for example within a few seconds, e.g. approx. 5 Seconds, bring about.

It is favorable to design the valve cone with a damping piston to avoid a nervous one Avoid response behavior of the pressure relief valve.

The damping effect is enhanced when the cavity of the damping piston is open to the outside via at least one channel and contains a check valve.

Fig. 1

eine schematische Seitenansicht eines elektrohydraulischen Motorpumpenaggregats,

Fig. 2

das elektrohydraulische Motorpumpenaggregat symbolisiert durch ein Blockschaltbild, das auch einen Hydraulikverbraucher zeigt,

Fig. 3

einen Längsschnitt eines Anbauelements des Motorpumpenaggregats,

Fig. 4

ein Detail aus Fig. 3, teilweise im Schnitt,

Fig. 5

ein Detail zu Fig. 4, und

Fig. 6

einen Längsschnitt einer anderen Ausführungsform eines Anbauelements.

Embodiments of the subject matter of the invention are explained with the aid of the drawing. Show it:

Fig. 1

a schematic side view of an electrohydraulic motor pump unit,

Fig. 2

the electrohydraulic motor pump unit is symbolized by a block diagram that also shows a hydraulic consumer,

Fig. 3

3 shows a longitudinal section of an attachment element of the motor pump unit,

Fig. 4

3 shows a detail from FIG. 3, partly in section,

Fig. 5

a detail of Fig. 4, and

Fig. 6

a longitudinal section of another embodiment of an add-on element.

An electro-hydraulic motor pump unit G (Fig. 1) is used as a supply unit e.g. of a hydromechanical tool either installed stationary or as transportable unit used. In a housing 1, which is also an oil reservoir T can be an electric motor M with a fan 2 as the drive of at least one internal pump stage P is provided. The electric motor M can be a three-phase motor, a DC motor or also, especially for mobile applications, be an AC motor that can be supplied from the normal network.

An add-on element C is attached to the housing 1 or integrated therein stands with at least one, not shown, pressure side connection of the pump stage P in connection, and also with the return leading into the housing 1. The add-on element C has in Fig. 1 a block-like housing 7 on which a directional control valve 3 is attached with a switching magnet 4. On the attachment element C are a or two or more consumer connections A, B or 5, 6 are provided. the Consumer connection B or 6 is, preferably in the add-on element C, a hydraulic, assigned automatic pressure relief device D, via which when switched off Electric motor M the system pressure, at least in the electro-hydraulic motor pump unit G to at least the consumer connections A, B due to leakage is degradable, and possibly even up to the hydraulic consumer not shown in FIG. 1.

The block diagram of FIG. 2 shows the housing 1 and the housing in dash-dot lines 7, and a hydraulic consumer Z (for example a double-sided differential cylinder), for driving a tool, a clamping device, a holding device, or the like. Via an actuating element 17. The Hydraulic consumer Z is via hydraulic hoses or piping 8, 9 to the Consumer connections A, B or 5, 6 connected.

It is assumed that the electric motor M is an AC motor that has its Fan 2 and a high-pressure pump stage P1 with a small flow rate as well as one Low pressure pump stage P3 drives with a larger flow, which from the tank T suck. Both pump stages P1, P3 are connected to a common pressure line 10 connected, the low-pressure pump stage P3 via a check valve 11 secured and via a pressure control valve that is pilot-controlled from the pressure line 10 formed switching valve 12 can be connected to a return 13. The Pressure line 10 leads to an input of the directional control valve 3, which is by spring force durable in the switching position shown and by the switching magnet 4 in the other switch position is convertible. The consumer connection is in the switch position shown B connected to the pressure line 10 via a working line 15 (Reset movement or release stroke), while the consumer connection A via a Working line 14 is connected to the return 13 and is thus relieved of pressure. Both Working lines 14, 15 are each via a pressure relief valve R1, R2 to the return 13 secured. The hydraulic, automatic pressure relief device D is formed by a bypass 16 integrated in the pressure relief valve R2. Both Pressure relief valves R1, R2 are seat valves that are in the shut-off position Seal leak-free. Thanks to the bypass 16 occurs in the shut-off position of the Pressure relief valve R2 leakage to the return 13 through which the system pressure is broken down.

The bypass 16 is, for example, dimensioned so that it is at 150 bar (e.g. the response pressure of the pressure relief valve R2) a leakage between 0.3 and 0.4 Liters per minute, which enables the pressure to be generated in a few seconds, e.g. about 5 seconds.

The pressure reduction occurring in this way when the electric motor M stops is facilitated the electric motor M later starting. Furthermore, hose or Easily release pipe couplings to the hydraulic consumer Z or the Adjust hydraulic consumer Z by hand if necessary.

Fig. 3 is a longitudinal section of the extension element C in a plane in which the switching valve 12 and the pressure relief valve R2 are visible. The pressure relief valve R2 is installed in a chamber of the housing 7, the return 13 and the Working line 15 cuts. An insert element 18 is positioned in the chamber a valve seat 19 positioned between the return 13 and the working line 15. With the valve seat 19, a valve cone 20 works together by the response pressure generating spring 21 in the direction of the valve seat 19 and against Pressure in the working line 15 is loaded. The integrated pressure relief device D with the bypass 16 is between the valve cone 20 and the valve seat 10 formed, as will be explained with reference to FIGS. 4 and 5.

4, the valve cone 20 has e.g. a coaxial at the large diameter end Shaft 23 for pressing on a spring abutment 22. The small diameter End portion of the valve cone 20 is extended by a neck 27 which is a hollow damping piston 28 is arranged. A cavity 29 of the damping piston 28 is in a channel 30 with the environment of the valve cone 20 in Connection and contains a ball check valve with a valve ball 31 and one Closing spring 32. The lower, open-shaped end of the cavity 29 is through a Plug 33 closed.

The valve cone has a cone jacket 25 as a seating surface, which is in a seating area 24 cooperates with the valve seat 19. A flattened portion 26 is in the conical jacket 25 shaped, the bypass as an interruption of the cone jacket 25 with the valve seat 19 16 forms.

According to FIG. 5, the flattened area 26 is, for example, a ground surface in the cone jacket 25, the surface being at least approximately parallel to the cone-producing extends. A grinding depth Y of approx. 2 to 5% of the conical jacket diameter X im Seating area 24 results in a suitable size of the bypass. Alternatively, instead of the flattened portion 26 also has at least one longitudinal notch.

6 shows an alternative embodiment of the pressure relief valve R2, that as a ball seat valve with a valve ball 20 'in cooperation with the Valve seat 19 'is formed. In this embodiment, the bypass 16 is through at least one notch or ablation 34 in the valve seat 19 'when working with the spherical surface. The principle of providing a notch in the valve seat 19 ' could also be provided with a cone seat valve.

Claims (13)

Electrohydraulic motor pump unit (G), with a housing in which an electric motor (M) drives at least one pump stage (P, P1, P3), with an add-on element (C) which is connected between at least one pressure side connection of the pump stage and the unit oil return (13 ) and at least one consumer connection (A, B, 5, 6) and a directional control valve (3) between the consumer connection and the pressure side connection and between the consumer connection (A, B, 5, 6) and the return line (13) a pressure relief valve ( R1, R2) in seat valve design, characterized in that the motor pump unit (G) has a hydraulic, automatic pressure relief device (D). Electrohydraulic motor pump unit according to claim 1, characterized in that the pressure relief device (D) is incorporated into the attachment element (C) and has at least one permanently open bypass (16). Electrohydraulic motor pump unit according to claim 1, characterized in that the pressure relief device (D) is a permanently open bypass (16) in a pressure relief valve (R1, R2). Electrohydraulic motor pump unit according to claim 1, characterized in that two consumer connections (A, B, 5, 6) and two pressure relief valves (R1, R2) are provided, which are set to different response pressures, and that the bypass (16) in the pressure relief valve (R2 ) is arranged with the lower response pressure, preferably in the pressure limiting valve (R2) of the consumer connection (B) for a reset or release stroke of a double-acting hydraulic consumer (Z) connected to the consumer connections (A, B, 5, 6). Electrohydraulic motor pump unit according to claim 1, characterized in that the motor pump unit (G) as an electric motor (M) contains an AC motor which drives a two-circuit pump stage with at least one high pressure pump stage (P1) and at least one low pressure pump stage (P3), of which the low pressure pump stage (P3) is connected to a changeover valve (12) for the return (13), and that the pressure relief valve (R2) with the bypass (16) is arranged between the directional control valve (3) downstream of the changeover valve (12) and a consumer connection (B, 6). Electrohydraulic motor pump unit according to claim 3, characterized in that the pressure relief valve (R2) is a cone seat valve with a spring-loaded valve cone (20) and a, preferably conical, valve seat (19), and in that the bypass (16) is a flattened portion (26), preferably has a ground surface in the cone jacket (25) of the valve cone (20). Electrohydraulic motor pump unit according to claim 6, characterized in that the flattened portion (26) is parallel to the cone-producing end, preferably a ground surface with a grinding depth (Y) of approx. 2 to 5% of the conical jacket diameter (X) in the seat area (24). Electrohydraulic motor pump unit according to claim 3, characterized in that the pressure relief valve (R2) is a cone or ball seat valve, the valve cone (20) or valve ball (20 ') is pressed against a valve seat (19') by spring loading, and that the bypass ( 16) has at least one notch (34) in the valve seat (19 '). Electrohydraulic motor pump unit according to claim 2, characterized in that the bypass (16) is designed in its passage size for a leakage of approximately 0.3 to 0.4 liters per minute at 150 bar, preferably for an at least extensive pressure relief within approximately 5 seconds. Electrohydraulic motor pump unit according to claim 6, characterized in that the valve cone (20) has a holding shaft (23) for a spring abutment (22) at its large-diameter end and a neck (27) at its small-diameter end and adjacent to the flattened portion (26) in the cone jacket. with a smaller diameter than the cone diameter in the seat area (24) and on the neck (27) has a hollow damping piston (28). Electrohydraulic motor pump unit according to claim 10, characterized in that the cavity (29) of the damping piston (28) is open to the outside via at least one channel (30), and in that a ball check valve (31, 32) is arranged in the cavity (28). Attachment element (C) for an electrohydraulic motor pump unit (G), the attachment element (C) between at least one pressure side connection and a return (13) and at least one consumer connection (A, B, 5, 6) at least one directional control valve (3) and between the Consumer connection (A, B, 5, 6) and the return (13) contains a pressure relief valve (R1, R2) in seat valve design, characterized in that a permanently open bypass (16) is provided in the pressure relief valve (R2). Pressure limiting valve (R2) in a seat valve design, especially for a mounting member (C) of an electrohydraulic motor pump aggregate (G), said pressure relief valve comprises a spring-loaded valve cone (20) or a valve ball (20 ') and a valve seat (19, 19' in), characterized that the pressure relief valve (R2) contains a bypass (16) with which a permanent leakage of a predetermined magnitude can be generated in the leakage-free shut-off position.

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