Hydraulic pump with variable delivery rate

Abstract

The invention relates to a hydraulic pump (4) with a drive motor (6) that can be operated in two directions of rotation, an adjustable positive displacement pump (10, 12, 18, 20) that is coupled to the drive motor (6) and has a housing (20), a stator (18) adjustable therein and a rotor (10) arranged inside the stator (18), wherein the stator (18) is adjustable between a first and a second operating position under the influence of the pressure generated in a first and a second pressure chamber (26, 28), in which the delivery volume of the positive displacement pump (10, 12, 18, 20) differs, wherein the positive displacement pump (10, 12, 18, 20) has two delivery outlets (34, 46), each of which is connected to one of the two pressure chambers (26, 28). The invention also relates to a hydraulic power unit (2) with such a hydraulic pump (4) and a supply output (V) and an actuation output (B) via which a hydraulic fluid can be provided.

Description

[0001] The invention relates to a hydraulic pump for a hydraulic unit that can be used in a drive train of a motor vehicle. The invention also relates to a hydraulic unit with such a hydraulic pump.

[0002] A hydraulic unit of the type to which the invention relates can be used in particular for the hydraulic actuation of a clutch, a gear selector, etc., and for transmission lubrication and / or transmission cooling in a motor vehicle. The hydraulic fluid can also be used to cool an electric motor.

[0003] It is known to use a single hydraulic unit for both the lubrication or cooling of components and the hydraulic actuation of actuators. In a first operating state, the hydraulic unit delivers hydraulic fluid via the supply output to the transmission or electric motor for the purpose of cooling and / or lubrication. In a second operating state, the hydraulic unit delivers the hydraulic fluid via the actuation output to a hydraulic actuator. This actuator can actuate a clutch, a transmission actuator, or any other component that is actuated with hydraulic pressure. In general, the first operating state is characterized by a high volume flow and a low discharge pressure, while the second operating state is characterized by a low volume flow and a high discharge pressure.

[0004] An example of a hydraulic unit of the type mentioned above can be found in DE 10 2018 007 459 A1.

[0005] The object of the invention is to provide a hydraulic pump in which the hydraulic unit can be switched between the first and second operating states with little effort.

[0006] To achieve this object, the invention provides a hydraulic pump with a drive motor that can be operated in two directions of rotation, with an adjustable positive displacement pump that is coupled to the drive motor and has a housing, a stator that can be adjusted therein and a rotor arranged inside the stator, wherein the stator is adjustable between a first and a second operating position under the effect of the pressure generated in a first and a second pressure chamber, in which the delivery volume of the positive displacement pump differs, wherein the positive displacement pump has two delivery outlets, one of which is connected to one pressure chamber and the other to the other pressure chamber.

[0007] To achieve the invention, a hydraulic unit is also provided with such a hydraulic pump and a supply output and an actuation output via which a hydraulic fluid can be provided.

[0008] The invention is based on the basic idea of ​​using a positive displacement pump that can be operated in two directions of rotation, with each output of the positive displacement pump being connected to exactly one of the two pressure chambers. Therefore, depending on the operating direction, either one or the other pressure chamber is subjected to the pump's delivery pressure. Accordingly, the stator is moved into one or the other of the two operating positions, with the operating positions differing in that the positive displacement pump has a comparatively high delivery volume in one operating position and a comparatively low delivery volume in the other operating position. The operating position with the high delivery volume is then used to provide a high volume flow at a comparatively low delivery pressure. The hydraulic fluid can then be used for lubrication and / or cooling.In the second operating position, a hydraulic fluid with a comparatively lower flow rate but higher discharge pressure is provided. The hydraulic fluid can then be used to operate or switch actuators, for example, to engage a clutch or operate a gear selector or parking lock. The particular advantage is that no internal switching valves or control valves are required to switch the pump between the two operating positions; only the direction of rotation needs to be changed. In response to the changed direction of rotation and the change in pressure conditions, the stator is then moved from one operating position to the other.

[0009] According to one embodiment, the stator is accommodated in the housing in a translationally displaceable manner. In this configuration, the housing can form the guide for the stator without the need for additional bearings.

[0010] According to an alternative embodiment, it is provided that the stator is accommodated in the housing in a rotationally adjustable manner.

[0011] The pressure chambers can act on opposite sides of the stator, so that the pressure acting there moves the stator into the desired operating position without the need to redirect the generated forces.

[0012] If the stator forms a boundary wall of each pressure chamber, the design effort is lowest, since the stator closes the corresponding pressure chamber similar to the piston of a piston / cylinder drive and the pressure acting there directly acts on the stator into the desired operating position.

[0013] According to one embodiment of the invention, the stator defines a pre-chamber in each pressure chamber when the pressure chamber has its minimum volume, into which the connection to the corresponding discharge outlet opens. This results in the fact that, after a change in the direction of rotation of the hydraulic pump, initially only the pre-chamber is subjected to the discharge pressure, and only when the stator has begun to move from the current to the new operating position is the entire pressure chamber subjected to the discharge pressure. This ensures that the adjustment movement of the stator into the other operating position begins more smoothly than if the stator were subjected to the discharge pressure across the entire surface of the pressure chamber at once.

[0014] According to one embodiment of the invention, a throttle is arranged in the connection from the discharge outlet to the pressure chamber, which throttle limits the fluid flow when the stator is adjusted to reduce the volume of the corresponding pressure chamber. In particular, the throttle is assigned to the pressure chamber whose volume is reduced during the transition from the operating state with a high discharge volume to the operating state with a low discharge volume. The throttle represents a resistance to switching, so that the stator briefly remains in the operating position resulting in a high discharge volume in the direction of rotation corresponding to a low discharge volume.In this way, an actuator that requires a high actuating pressure can be pre-filled with a large volume flow shortly after switching the direction of rotation, whereby the stator is then adjusted to the operating position with the low delivery volume but high delivery pressure, so that the operating pressure required to switch the actuator is generated.

[0015] A check valve can be connected in parallel with the throttle, which opens when the corresponding pressure chamber is filled. The check valve ensures that the corresponding pressure chamber can be filled with hydraulic fluid sufficiently quickly when switching in the opposite direction, despite the throttle.

[0016] The positive displacement pump can be a vane pump, where the delivery volume can be adjusted particularly easily by moving the stator between different operating positions.

[0017] The invention is described below with reference to two embodiments illustrated in the accompanying drawings, in which: - Fig. 1 schematically shows a hydraulic unit with a hydraulic pump according to a first embodiment of the invention; - Fig. 2 the hydraulic unit of Fig. 1 in a first operating state of the hydraulic pump in which it has a large delivery volume and a low delivery pressure; - Fig. 3 the hydraulic unit of Fig. 1 in a second operating state in which the hydraulic pump has a low delivery volume and a high delivery pressure; and - Fig. 4 schematically shows a hydraulic pump for a hydraulic unit according to a second embodiment.

[0018] In Fig. 1 schematically shows a hydraulic unit 2 which has a hydraulic pump 4, a drive motor 6 and a supply for hydraulic fluid.

[0019] The drive motor 6 is an electric motor coupled to the hydraulic pump 4. The electric motor can be operated in two directions of rotation, so that the hydraulic pump 4 can also be driven in two opposite directions of rotation.

[0020] The hydraulic fluid supply can be a reservoir 8, which in the illustrated embodiment is integrated into the hydraulic unit 2. However, the hydraulic fluid supply can also consist solely of connections on the hydraulic unit through which hydraulic fluid is drawn in from an external source, for example, a collection area in a transmission.

[0021] The hydraulic pump 4 is a positive displacement pump, which in the embodiment shown is designed as a vane pump.

[0022] The hydraulic pump 4 has a stator 10 in which several rotary vanes 12 are slidably accommodated. These valves rest with their radially outer end against the inner wall 16 of a stator 18. When the drive motor 6 is operated, the stator 10 is driven in one direction or the other.

[0023] The stator is accommodated in a housing 20 so as to be translationally displaceable along the direction of the double arrow P. Each end position, which corresponds to an operating state of the hydraulic pump 4, is defined by a stop 22, 24 in the housing 20.

[0024] On the side of each stop 22, 24, a pressure chamber 26, 28 is defined, which is delimited by the housing 20 and the corresponding end wall of the stator 18.

[0025] Within the volume delimited by the inner wall 16 of the stator 18, two fluid openings 30, 32 are provided either in only one end wall of the housing 20 or in both end walls, which serve as a suction opening or as a pressure outlet depending on the direction of rotation of the hydraulic pump 4.

[0026] On the “back side” of the fluid openings 30, 32, a compensation opening 33 is provided.

[0027] The fluid openings 30, 32 are connected to the storage tank 8 via lines 34, 36 and check valves 38, 40.

[0028] Output lines 42, 44 are also connected to the lines 34, 36, which lead to an actuation output B and a supply output V of the hydraulic unit 2.

[0029] Actuators that are to be actuated with the provided hydraulic fluid, such as a transmission actuator, a clutch actuator, an actuator for actuating a parking lock, or the like, can be connected to actuating output B of hydraulic unit 2. Generally speaking, components that require a comparatively high fluid pressure to perform the desired function are connected to actuating output B.

[0030] The supply outlet V is intended to supply a lubrication and / or cooling system, for example, the lubrication points of a gearbox, the friction discs of a wet clutch, or an electric motor. Generally speaking, the supply outlet V serves to supply a system with a high volume flow of hydraulic fluid at low delivery pressure.

[0031] Switching lines 46 and 48 also branch off from lines 34. Switching line 46 connects line 34 and thus the fluid line leading to actuation outlet B with pressure chamber 26, and switchover line 48 connects the fluid line leading to supply outlet V with pressure chamber 28.

[0032] Based on Fig. Figure 2 illustrates a first operating state of the hydraulic unit 2 and the hydraulic pump 4. The fluid flow is symbolized here by a second line along the corresponding line.

[0033] In the first operating state, the supply outlet V is supplied with hydraulic fluid. The fluid opening 32 serves as the pressure outlet of the hydraulic pump 4. Accordingly, the hydraulic fluid is sucked from the reservoir 8 by the fluid opening 30 via the line 34 and the check valve 38.

[0034] The discharge pressure of the output line 44 is applied to the pressure chamber 28 via the switching line 48. The pressure generated there acts on the stator 18 within the stationary housing 20 against the stop 22. The distance between the center axis M of the contour defined by the inner wall 16 of the stator 18 and the rotational axis of the stator 10 is designated here by s.

[0035] In this first operating state, the hydraulic pump 4 has a comparatively high delivery volume but provides a low delivery pressure.

[0036] In Fig. 3 shows a second operating state in which the hydraulic fluid is provided with a high delivery pressure, but the delivery volume of the hydraulic pump 2 is smaller than in the first operating state.

[0037] In the second operating state, the actuating output B is supplied with hydraulic fluid. In this state, the drive motor 6 drives the stator 10 in the state of Fig. 2 in the opposite direction of rotation. Accordingly, suction occurs via fluid opening 32, and fluid opening 30 serves as the pressure outlet.

[0038] In the second operating state, the hydraulic fluid is provided with a high delivery pressure, but the delivery volume of the hydraulic pump 2 is smaller than in the first operating state.

[0039] Mirror image of the first operating state, which is Fig. 2, in the second operating state, the pressure chamber 26 is pressurized with hydraulic pressure. Accordingly, the stator 18 rests against the stop 24. In this state, the distance t between the center axis M of the contour delimited by the inner wall 16 in the stator 18 and the rotational axis of the stator 10 is smaller than the distance s in the first operating state. By comparing the Fig. 2 and Fig. 3 it can also be seen that the rotary valve, which is located at the 9 o'clock position, is in the first operating state of Fig. 2 protrudes further from the corresponding receptacle in the rotor 10 than in the second operating state, which is Fig. 3 is shown.

[0040] The hydraulic pump 4 is automatically switched from the current operating state to the other operating state when the direction of rotation of the drive motor 6 is changed. However, it is possible to influence the speed of the switching through design measures.

[0041] On the one hand, it is possible to define a pre-chamber 50, 52 within each pressure chamber, for example, by means of the corresponding stop 22, 24. When hydraulic fluid flows into the pre-chamber 50, 52 via the corresponding switching line 46, 48, the pressure initially acts on the stator 18 over a smaller area. Accordingly, the stator initially moves more slowly toward the other operating position.

[0042] Another possibility is to provide a throttle device 54 as shown in Fig. 1 for the pressure chamber 28.

[0043] The throttle device 54 includes a throttle 56 arranged between the switching line 48 and the pressure chamber 28, as well as a check valve 58 which opens toward the pressure chamber 28 but blocks fluid flow from the pressure chamber 28.

[0044] If from the first operating state of Fig. 2 is switched to the second operating state, the flow resistance generated by the throttle 56 ensures that the stator 18 is not suddenly shifted from the first operating state to the second. As a result, the hydraulic pump 4 initially delivers a large delivery flow to the actuation output B, so that an actuator connected there is pre-filled very quickly. Meanwhile, the second pressure chamber 28 is emptied via the throttle 56, so that the stator is shifted into the second operating position under the effect of the delivery pressure present in the pressure chamber 26. In this position, the high delivery pressure is then provided at the actuation output B.

[0045] By dimensioning the throttle 56, it is possible to adjust how quickly the transition from the first operating state to the second operating state occurs after a change in the direction of rotation of the drive motor 6.

[0046] The check valve 58 present in the throttle device 54 ensures that the stator 18 is quickly filled when the pressure chamber 28 is supplied with fluid pressure, so that the stator 18 is quickly adjusted to the other operating position.

[0047] If desired, a corresponding throttle device 60 can also be realized on the side of the pressure chamber 26, which is only indicated schematically here.

[0048] In Fig. Figure 4 schematically shows a second embodiment. The same reference numerals are used for the features and components known from the first embodiment, and reference is made to the above explanations.

[0049] The essential difference between the first and second embodiments is that in the second embodiment, the stator 18 is pivotally mounted within the housing 20. A pivot point 62 is provided for this purpose.

[0050] In the same way as in the first embodiment, two pressure chambers 26, 28 are provided on opposite sides of the stator 18, which are supplied with hydraulic fluid depending on the operating direction of the hydraulic pump.

[0051] On the side opposite the pivot point 62, the gap between the housing 20 and the stator 18 is sealed in a suitable manner, for example by a correspondingly tight fit between the two components or by a separate sealing element. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 007 459 A1

[0004]

Claims

[1] Hydraulic pump (4) with a drive motor (6) which can be operated in two directions of rotation, an adjustable positive displacement pump (10, 12, 18, 20) which is coupled to the drive motor (6) and has a housing (20), a stator (18) which can be adjusted therein and a rotor (10) arranged within the stator (18), wherein the stator (18) is adjustable between a first and a second operating position under the effect of the pressure generated in a first and a second pressure chamber (26, 28), in which the delivery volume of the positive displacement pump (10, 12, 18, 20) differs, wherein the positive displacement pump (10, 12, 18, 20) has two delivery outlets (34, 46), each of which is connected to one of the two pressure chambers (26, 28). [2] Hydraulic pump (4) according to claim 1, characterized by that the stator (18) is accommodated in the housing (20) in a translationally displaceable manner. [3] Hydraulic pump (4) according to claim 1, characterized bythat the stator (18) is rotatably adjustable and accommodated in the housing (20). [4] Hydraulic pump (4) according to one of the preceding claims, characterized by that the two pressure chambers (26, 28) act on opposite sides of the stator (18). [5] Hydraulic pump (4) according to one of the preceding claims, characterized by that the stator (18) forms a boundary wall of each pressure chamber (26, 28). [6] Hydraulic pump (4) according to claim 5, characterized by that the stator (18) defines a pre-chamber (50) in each pressure chamber (26, 28) when the latter has its minimum volume, into which the connection to the corresponding delivery outlet opens. [7] Hydraulic pump (4) according to one of the preceding claims, characterized bythat a throttle (56) is arranged in the connection from the delivery outlet to the pressure chamber, which throttle limits the fluid flow when the stator (18) is adjusted in order to reduce the volume of the corresponding pressure chamber (28). [8] Hydraulic pump (4) according to claim 7, characterized by that a check valve (58) is connected in parallel with the throttle (56), which opens when the corresponding pressure chamber is filled. [9] Hydraulic pump (4) according to one of the preceding claims, characterized by that the positive displacement pump (10, 12, 18, 20) is a vane pump. [10] Hydraulic unit (2) with a hydraulic pump (4) according to one of the preceding claims and a supply outlet (V) and an actuation outlet (B) via which a hydraulic fluid can be provided.

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