Gerotor pump and the use of a gerotor pump to create pressure equalization

Abstract

Gerotor pump (1) with an inner rotor (4) and an outer rotor (5), which is also a rotor (31) of an electric drive, with a housing (2) and a flange (3) closing the housing (2) to the motor compartment (33), wherein the rotor (31) is arranged on a shaft (6), wherein at least one device is provided with which at least partial pressure equalization takes place between the suction area (22) of the gerotor pump (1) and the suction port (7) of the gerotor pump (1), wherein the pressure equalization is effected by a variable throttle, characterized in that the device consists of an outflow bore (26) in the shaft (6) and at least one recess (55) between the outflow bore (26) and the suction port (7), wherein a pressure-dependent control slide (50) is arranged in the recess (55), or the device consists of an outflow bore (26) in the shaft (6), and at least one connection (13) between the outflow bore (26) of the shaft (6) and the suction port (7) of the gerotor pump (1), wherein an opening (66) between suction chamber (22) and motor chamber (33) can be closed by a centrifugal control slide on the rotor (31).

Description

[0001] The invention relates to a gerotor pump with an inner rotor and an outer rotor, which is also the rotor of an electric drive, with a housing and a flange closing the housing with the motor compartment, wherein the rotor is arranged on a shaft, wherein at least one device is provided with which at least a partial pressure equalization takes place between the suction area of ​​the gerotor pump and the suction connection of the gerotor pump.

[0002] The invention further relates to the use of a gerotor pump for pressure equalization. State of the art

[0003] In transmissions, especially dual-clutch transmissions, gerotor pumps are required to actuate clutches. During operation of such a pump, a pressure builds up in the pressure channel corresponding to a downstream throttle. Within the pump's operating range, there is an almost linear increase in pressure with pump speed, with the required clutch actuation pressure being reached even at low speeds, especially at lower oil temperatures. This can lead to noticeable pulsations in the hydraulic system.

[0004] In conventional gerotor pumps, the displacement must be selected so small that pressure buildup only occurs at somewhat higher speeds, which result in acoustically less critical pulsations. The disadvantage of this is that such pumps are less efficient than larger pumps, especially at higher temperatures and with lower oil viscosity.

[0005] In gerotor pumps with a highly integrated design, as described in the not yet published DE 10 2017 223 715, the electro-motor rotor and external gerotor are designed as a common component.

[0006] In the gerotor pump, pressure is deliberately built up in the pump's motor compartment to seal the pump and relieve the thrust bearing. This pressure is established by the leakage between the outer gerotor and the front plate, as well as a throttle that relieves pressure in the space toward the suction chamber. When such pumps are used as clutch actuator pumps in a dual-clutch transmission, the pressure downstream of the pump is adjusted according to the downstream throttle in the pressure channel, as well as the throttle between the motor compartment and the suction chamber.

[0007] In any case, the two fixed throttles lead to a predetermined increase in pressure with speed that is approximately linearly dependent on the pump speed in the working range.

[0008] The inflow to this chamber is determined by the leakage in the gap itself; more inflow means more internal pressure and thus improved sealing, which in control terms is equivalent to negative feedback. The outflow from the engine compartment takes place through a hollow shaft into the area of ​​the intake port or a leakage path directly to it. To adjust the resulting pressure level in the engine compartment, a fixed throttle cross-section is provided in the outflow path, e.g., in the shaft.

[0009] Further pumps for conveying a fluid are known from US 5 317 999 A, DE 10 2017 104 063 A1, DE 1 650 819 A, DE 10 2012 223 920 A1 and DE 3 420 190 A1.

[0010] The object of the invention is to create a gerotor pump with improved pressure behavior. Description of the invention

[0011] The object is achieved with a gerotor pump with an inner rotor and an outer rotor, which is also the rotor of an electric drive, with a housing and a flange closing the housing with the motor compartment, wherein the rotor is arranged on a shaft, wherein at least one device is provided with which at least a partial pressure equalization takes place between the suction area of ​​the gerotor pump and the suction connection of the gerotor pump, wherein the pressure equalization takes place by means of a variable throttle.

[0012] The variable throttle ensures that the volume flow delivered by the pump does not increase as quickly with the pump speed.

[0013] In addition, the device consists of an outflow bore in the shaft and at least one recess between the outflow bore and the suction connection, wherein a pressure-dependent control slide is arranged in the recess.

[0014] Furthermore, the device consists of an outflow bore in the shaft, as well as at least one connection between the outflow bore of the shaft and the suction connection of the gerotor pump, wherein a centrifugal control slide on the rotor closes an opening between the suction chamber and the motor chamber.

[0015] The task also consists in using the gerotor pump to create pressure equalization, whereby an inflow of pressurized medium into the motor compartment of the gerotor pump takes place and there is at least one connection between the motor compartment and the suction area through which the medium is discharged, whereby a control slide regulates the flow by pressure build-up in the sense of a control-technical positive feedback.

[0016] The task alternatively consists in the use of the gerotor pump to create a pressure equalization, wherein an inflow of pressurized medium into the motor compartment of the gerotor pump takes place and at least one connection is present between the motor compartment and the suction area, via which the medium is discharged, wherein a centrifugal control slide controllably closes an opening by centrifugal forces as a result of rotation of the rotor. Description of the characters Fig. 1 shows a section through a pump with a fixed throttle in the downstream flow from the engine compartment to the suction chamber (SdT), Fig. 2 shows a section through a pump according to the invention with a pressure-operated valve in the open position (start), Fig. 3 shows a section through a pump according to the invention with a pressure-operated valve in the closed position (operation). Fig. 4 shows a section through a pump according to the invention with the valve in the open position at low speed (start), Fig. 5 shows a section through a pump according to the invention with the valve in the closed position at high speed (operation), Fig. 6 shows the flow rate curve as a function of the pump speed.

[0017] Fig. Figure 1 shows a housing 2, which is closed with a flange 3. Inside, an inner rotor 4 and an outer rotor 5 with a shaft 6 can be seen. Electrical connections can be seen on the flange 3. The gerotor pump has a pressure port 8 and a suction port 7.

[0018] In the housing 2, the inner rotor 4 and the outer rotor 5 are rotatably arranged in a pump working chamber of the gerotor pump 1.

[0019] A standing shaft 6 is mounted in the housing 2, allowing it to rotate about a rotational axis. The flange 3 serves as a housing cover, which closes the housing 2, which is essentially pot-shaped.

[0020] An electric motor 30 with a rotor 31 and a stator is integrated into the housing 2 of the gerotor pump 1. The stator 15 comprises a stator core with windings, which, together with the stator core, are embedded in a plastic material. The plastic material is shaped, for example, using an injection molding process, to form the housing 2 of the gerotor pump 1.

[0021] The rotor 31 of the electric motor 30 comprises a rotor core and cast-in magnets 36. The rotor core, along with the magnets 36, is overmolded with a plastic material. The rotor 31 of the electric motor 30 is integrally connected to the outer rotor 5 of the gerotor pump 1 by the plastic material. The stator and rotor of the electric motor form a motor chamber 33 in which there is no pressure.

[0022] The plastic material therefore serves both to represent the rotor 31 of the electric motor 30 and to represent the outer rotor 5 of the gerotor pump 1. Thus, the outer rotor 5 of the gerotor pump 1 is directly driven by the rotor 31 of the electric motor 30.

[0023] The rotor 31 of the electric motor 30, together with the outer rotor 5 of the gerotor pump 1, is mounted on the shaft 6 in the housing 2 of the gerotor pump 1. The inner rotor 4 of the gerotor pump 1 is mounted on an eccentric independently of the outer rotor 5. As a result, the inner rotor 4 of the gerotor pump 1 is arranged eccentrically to the shaft 6 and the outer rotor 5.

[0024] The gerotor pump 1 has a suction area 22 and a pressure area above the shaft 6.

[0025] Via the suction area 22, the engine compartment is connected at least via leakage gaps to the shaft 6, which has a cavity extending along the axis of rotation in the form of an outflow bore 26.

[0026] The outflow from the engine compartment takes place through the outflow hole 26 and the connecting hole 13 into the area of ​​the suction connection 7.

[0027] To adjust the resulting pressure level in the engine compartment, a defined cross-section is provided in the downstream path, e.g. in the shaft.

[0028] The flow through the motor compartment of the gerotor pump, created by a hollow shaft, has the side effect that heat loss from the electric motor 30 and the electronics is dissipated by the resulting flow, and the supply to the bearings can be improved.

[0029] By relieving the load on an axial bearing in the electric motor, the friction of the rotor is minimized, while at the same time leakage is minimized by increasing the surface pressure in a gap between the rotor and the side wall.

[0030] The inflow of the medium into the engine compartment is caused by a leak in a gap itself.

[0031] The invention provides for the fixed throttle cross-section to be made variable or to be replaced by a valve.

[0032] This can in turn be achieved by the pressure build-up itself in the sense of a control-technical feedback in the embodiment according to the Fig. 2 and Fig. 3 or by centrifugal forces resulting from rotation of the rotor to Fig. 4 and Fig. 5 can be operated.

[0033] In any case, such a valve leads to a delayed pressure build-up while the pump runs through a range of lower speeds and acoustically more critical frequencies, without requiring more speed in the range of larger to maximum pressure build-up, which in Fig. 6 is shown.

[0034] In the Fig. 2 shows the first embodiment of the inventive solution in the gerotor pump. The lower part of the Fig. Figure 2 is an enlarged section of the upper portion of the figure. It shows a pressure-actuated valve in the open position. It is a control slide 50 located in a horizontal recess 55. The horizontal recess 55 is connected to the discharge bore 26 of the shaft 6. Furthermore, the recess 55 connects the discharge bore 26 to the suction port 7 via the discharge connection of the suction chamber 51. The control slide 50 is displaced all the way to the left in the starting arrangement and rests against a ball 54.

[0035] The opening of the discharge bore 26 is thus free, and the fluid can flow into the suction port 7 via the right-hand area of ​​the horizontal recess 55. The control valve 53 does not close the opening of the discharge bore 26. A spring 52 is provided on the right side of the horizontal recess 55, against which the control slide 50 is arranged to slide.

[0036] In the Fig. Figure 3 shows the pressure-controlled valve when pump pressure is built up. The control slide 50 is displaced horizontally by the pressure toward the spring 52. The control edge 53 thus moves across the open cross-section of the discharge bore 26. If the pressure increases even further, the opening of the discharge bore 26 can be completely closed. This causes the control slide to press against the spring 52. When the pressure decreases, the spring 52 returns the control slide 50 to its rest position toward the ball 54.

[0037] This allows the outflow of the fluid to be controlled via the pressure that builds up as the pump speed increases.

[0038] In the Fig. Figure 4 shows a second embodiment with a valve that is actuated by centrifugal force. When the pump starts, i.e., at low speeds, the control slide 60 is open. The control slide 60 is part of a component of the rotor assembly and is installed above the rotor assembly. An opening 66 establishes the connection between the suction chamber 22 and the motor chamber 33 of the pump. The control slide 60 regulates the extent to which the opening is available for flow. Fig. In Figure 4, the control edge 63 can be seen offset relative to the opening 66. The centrifugal control slide 60 thus does not cover the opening. When not activated, it rests against a plug 65 and is limited on the right side by a spring 64.

[0039] In Fig. Figure 5 shows the situation when the pump speed is increased and the centrifugal control slide moves toward the spring 64. The control edge 63 then covers the opening 66 between the suction chamber 22 and the motor chamber 33.

[0040] The opening 66 is thus covert in an adjustable manner by the pump speed.

[0041] Regardless of the design, the advantages of a speed- or pressure-dependent valve arrangement are Fig. 6 shown.

[0042] The graph shows the flow rate of the pump according to the invention versus pump speed. The dashed line represents an idealized flow rate without flow resistance I.

[0043] Curve D shows the profile of an idealized flow rate through a fixed throttle element, as is known from the prior art. It can be seen that in the lower speed range, the flow rate is almost similar to the idealized flow rate without flow resistance. This is where the solution according to the invention comes into play.

[0044] Curve R shows the flow rate of a pump according to the invention with a speed-dependent throttling function. It can be seen that the flow rate is significantly reduced, especially at low pump speeds. Reference symbol 1 gerotor pump 2 housings 3 Flange 4 inner rotor 5 Outer rotor 6 Wave 7 Suction connection 8 Pressure connection 13 Connecting hole 15 Stator 22 Suction area 26 downstream borehole 30 electric motor 31 Rotor 33 Engine compartment 36 Magnet 50 control slides 51 Downstream connection suction chamber 52 spring 53 control edge 54 ball 55 recess 60 centrifugal control slides 63 control edge 64 spring 65 plugs 66 Opening

Claims

[1] Gerotor pump (1) with an inner rotor (4) and an outer rotor (5), which is also the rotor (31) of an electric drive, with a housing (2) and a flange (3) closing the housing (2) with the motor compartment (33), wherein the rotor (31) is arranged on a shaft (6), wherein at least one device is provided with which at least a partial pressure equalization takes place between the suction area (22) of the gerotor pump (1) and the suction connection (7) of the gerotor pump (1), wherein the pressure equalization takes place by means of a variable throttle, characterized by , that the device consists of an outflow bore (26) in the shaft (6) and at least one recess (55) between the outflow bore (26) and the suction connection (7), wherein a pressure-dependent control slide (50) is arranged in the recess (55), or the device consists of an outflow bore (26) in the shaft (6), and at least one connection (13) between the outflow bore (26) of the shaft (6) and the suction connection (7) of the gerotor pump (1), wherein an opening (66) between the suction chamber (22) and the motor chamber (33) can be closed in a controlled manner by a centrifugal control slide on the rotor (31). [2] Use of a gerotor pump (1) according to claim 1 for establishing pressure equalization in the gerotor pump (1), wherein the volume flow of the gerotor pump (1) increases non-linearly with the pump speed, the increase being subproportional. [3] Use of a gerotor pump (1) according to claim 1 for establishing pressure equalization, wherein an inflow of pressurized medium into the motor chamber (33) of the gerotor pump (1) takes place and at least one connection is present between the motor chamber (33) and the suction area (22), via which the medium is discharged, wherein a control slide (50) regulates the flow by pressure build-up in the sense of a control-technical positive feedback. [4] Use of a gerotor pump (1) according to claim 1 for establishing pressure equalization, wherein an inflow of pressurized medium into the motor chamber (33) of the gerotor pump (1) takes place and at least one connection is present between the motor chamber (33) and the suction region (22), via which the medium is discharged, wherein a centrifugal force control slide (60) controllably closes an opening (66) by centrifugal forces as a result of the rotation of the rotor.

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