Gerotor pump and method for creating pressure equalization in a gerotor pump

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) with the motor compartment (33), wherein the rotor (31) is arranged on a shaft (6) and seals against the flange (3) at a gap (35), characterized in that a bore in the flange (3) or a cavity (25) in the shaft (6) is provided for at least partial pressure equalization between the suction area (22) of the gerotor pump (1) and the motor compartment (33) of the gerotor pump (1), wherein a medium is supplied from the pressure area to an opposite second side of the outer rotor (5) in order to push the outer rotor (5) towards the flange (3) and to counteract a force acting on the outer rotor (5) in the pressure area by the medium, which pushes the outer rotor (5) away from the flange (3).

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 and seals against the flange at a gap.

[0002] Furthermore, the invention relates to a method for producing pressure equalization in a gerotor pump. State of the art

[0003] From the not yet published DE 10 2018 202 150 a gerotor pump is known which has a diaphragm and improves the tightness of a gerotor pump with a pump working chamber in which an inner rotor and an outer rotor are rotatably arranged and which is delimited by a housing cover with a pressure diaphragm.

[0004] In the specific case of such a highly integrated gerotor pump, in which the electric rotor and pump rotor are structurally combined, axial forces arise that are absorbed by a thrust bearing on the side of the shaft opposite the gerotor pump. At the same time, the displacement of the rotor toward said thrust bearing creates a gap between the rotor and the side plate. Pressure peaks are observed in gearboxes where such pumps are used, which can lead to component damage.

[0005] The movement generated by the axial forces causes mechanical friction in the axial bearing, as well as leakage in the gap between the rotor and the side plate.

[0006] Pressure peaks in the gearbox must be absorbed, so components must be designed to be significantly oversized.

[0007] International Patent Application WO 2016 / 096755 A1 discloses a gear pump with a housing. Within the housing, a side plate, through which a motor shaft passes, is fixedly arranged at the edge of a housing opening in the housing body. This side plate, preferably rigid, rests in an annular groove in the housing body at its edge or outer circumference. The rigid side plate has a circular arc-shaped opening extending over a circumferential section. A flexible pressure plate, also referred to as a diaphragm, is inserted into the housing between this side plate and the housing cover. This pressure plate, preferably circular, is clamped at its outer edge between the housing body and the housing cover at the opening or edge, and is thus also fixedly held in the housing.The flexible pressure plate is used to reduce and / or compensate for temperature-related expansion of the housing or pump components.

[0008] These gerotor pumps operate with two side plates between which the outer and inner rotors are guided with pressure compensation. This necessitates a bearing area between the hydraulic pump rotor and the electric rotor of the drive motor, which increases installation space and manufacturing costs.

[0009] The object of the invention is to create an electrically driven gerotor pump in which the pressure difference between the motor compartment and the pressure area is optimized in order to minimize leakage and axial forces. Description of the invention

[0010] 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 and seals against the flange at a gap, wherein in addition to the gap there is a device with which at least a partial pressure equalization takes place between the pressure area of ​​the gerotor pump and the motor compartment of the gerotor pump.

[0011] By deliberately building up pressure in the otherwise pressureless motor compartment of the gerotor pump, the axial bearing of the gerotor pump is relieved, thereby reducing its friction, and the gap between rotor and flange is compressed, thus reducing leakage.

[0012] The inflow into this space is caused by the leakage in the aforementioned gap itself; more inflow therefore means higher internal pressure and thus improved sealing, which is equivalent to negative feedback in terms of control technology. Reducing or eliminating pressure peaks relieves the load on other components, especially pressure sensors, whose accuracy can thereby be improved.

[0013] In an advantageous embodiment, the device is a connection between the engine compartment and the suction area, which is provided in the flange.

[0014] It is particularly advantageous if the device consists of a cavity in the shaft, as well as connections between the engine compartment and the cavity of the shaft and between the cavity of the shaft and the suction area.

[0015] The flow through the cavity in the shaft into the motor compartment of the gerotor pump has the side effect of dissipating waste heat from the electric motor and electronics. It is advantageous that the cavity in the shaft has a constriction that acts as a throttle. This allows for better adjustment of the intermediate pressure level in the motor compartment.

[0016] An advantageous embodiment is also if the device consists of a cavity in the shaft as well as connections between the motor compartment and the cavity of the shaft and the cavity of the shaft to an eccentric bearing of the gerotor pump.

[0017] In this embodiment, the flow through the motor compartment is not only advantageous for dissipating the waste heat from the electric motor, but the flow also serves to improve the supply to the eccentric bearing.

[0018] In all embodiments, it is advantageous that at least one of the connections has a reduction in cross-section, which serves as a throttle.

[0019] This allows the intermediate pressure and the flow rate to be adjusted more easily.

[0020] The problem is further solved by a method for creating pressure equalization in a gerotor pump, wherein a flow of pressurized medium occurs through the gap into the motor compartment of the gerotor pump and at least one connection exists between the motor compartment and the suction area or to the eccentric bearing, through which the medium is discharged.

[0021] It is advantageous that an intermediate pressure is created in the engine compartment via the inflow and outflow of the medium. Description of the characters Fig. 1: Exploded view of the gerotor pump, Fig. 2: Section through a gerotor pump according to the invention with bore to the suction area Fig. 3: Section through a gerotor pump according to the invention, with shaft bore and throttle cross-section, Fig. 4: Section through a gerotor pump according to the invention with motor compartment drain via the bearing of the eccentric to improve the lubrication and cooling thereof, Fig. 5: Section through a pump according to the invention with increased clearance at the axial bearing of the rotor to relieve the pressure chamber during pressure peaks, Fig. 6: Section through a pump according to the invention with a gap under the rotor to relieve the pressure chamber during pressure peaks.

[0022] Fig. Figure 1 shows an exploded view of the 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. The outer rotor 5 is shown separately. Inlet and outlet openings can be seen on the flange 3.

[0023] In the Fig. 2 to 4, a gerotor pump 1 with a housing 2 is shown in various sectional views.

[0024] In the housing 2, an inner rotor 4 and an outer rotor 5 are rotatably arranged in a pump working chamber of the gerotor pump 1.

[0025] In the housing 2, a shaft 6 is rotatably mounted about a rotation axis 28 by means of a bearing device 9.

[0026] A flange 3 serves as a housing cover with which the housing 2, which is essentially pot-shaped, is closed.

[0027] The housing 2 of the gerotor pump 1 incorporates an electric motor 30 with a rotor 31 and a stator. The stator comprises a stator lamination stack with windings, which, together with the stator lamination stack, are embedded in a plastic material. The plastic material is shaped, for example by an injection molding process, to form the housing 2 of the gerotor pump 1.

[0028] The rotor 31 of the electric motor 30 comprises a rotor lamination stack 32 and embedded magnets. The rotor lamination stack, together 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 means of this plastic material. The stator and rotor of the electric motor form a motor chamber 33 in which there is no pressure.

[0029] The plastic material thus serves both to represent the rotor 31 of the electric motor 30 and to represent the outer rotor 5 of the gerotor pump 1. The outer rotor 5 of the gerotor pump 1 is thus directly driven by the rotor 31 of the electric motor 30.

[0030] 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 independently of the outer rotor 5 on an eccentric 6. This positions the inner rotor 4 of the gerotor pump 1 eccentrically to the shaft 6 and the outer rotor 5.

[0031] The gerotor pump 1 has a suction area 22 in the upper area and a pressure area 21 in the lower area. The housing cover, the flange 3, is made of a plastic material or metal.

[0032] In the flange 3, a connection 10 is arranged between the motor compartment 33 of the electrical machines 30 and the suction area 22.

[0033] The motor compartment 33 of the electrically operated gerotor pump is brought to an intermediate pressure level above atmospheric pressure by the inflow of the medium through the gap 35 from the pressure area 21.

[0034] By selectively building up pressure in the otherwise unpressurized motor chamber 33 of the gerotor pump, the axial bearing 9 is relieved, thereby reducing friction losses and decreasing the gap 35 between rotor 5 and flange 3, thus reducing leakage.

[0035] The inflow of the medium into the motor compartment 33 is caused by the leakage in the gap itself. A higher inflow therefore means a higher internal pressure in the motor compartment and thus an improved sealing effect of the rotor 5 on the flange 3, which is equivalent to negative feedback in terms of control technology.

[0036] Fig. Figure 3 shows a further embodiment of the gerotor pump 1. The medium flows into the motor chamber via the gap 35. The motor chamber 33 is connected to the shaft 6 via a connection 11; the shaft 6 has a cavity 25 extending along the axis 28.

[0037] The outflow from the engine compartment 33 takes place through the cavity 25 into the area of ​​the suction connection 7 or a leakage path with a connection 12 directly to the suction area 22.

[0038] To regulate the resulting pressure level in the engine compartment, a throttle cross-section 26 is provided in the outflow path, e.g., in the shaft. The flow through the engine compartment 33 of the gerotor pump, achieved via a hollow shaft, has the side effect of dissipating waste heat from the electric motor 30 and electronics, and improving lubrication of the bearings.

[0039] 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.

[0040] In the Fig. Figure 4 describes an embodiment which establishes a connection 11 between the motor compartment 33 and the shaft 6 and has a cavity 25 in the shaft 6 that opens into a connecting bore 13, which establishes a connection from the shaft 6 to the eccentric bearing 27. The connecting bore 13 is reduced in diameter and acts as a throttle 13a for the return flow of the medium.

[0041] By deliberately building up pressure in the otherwise pressureless motor chamber of the pump, the thrust bearing is relieved, reducing friction, and the gap between the rotor and the plate is compressed, reducing leakage. This intermediate pressure level is high enough to ensure adequate sealing of the pump, but also allows the rotor core to lift off during pressure peaks.

[0042] The previously described effect of compensation through internal pressure is based on leakage into the pump's motor chamber. If only a short-term pressure spike arrives at the pump's inlet, the rotor assembly immediately retracts from the pressure plate, since a sufficiently high pressure has not yet built up in the motor chamber at the time the pressure spike arrives. To allow such retraction, it is only necessary to provide the rotor assembly with precisely enough axial play to allow the pressure chamber to open, without allowing so much play that, in the event of vibration, or with no or low operating pressure, damage can occur due to impact with the axial stops, i.e., the thrust bearing or the pressure plate.

[0043] This requirement is met by a gap 37 provided between a retaining ring 40 and a bearing disc 41 on the shaft 6. Reference symbol: 1 gerotor pump 2 housings 3 flange 4 inner rotor 5 Outer rotor 6 wave 7 Suction port 8 Pressure connection 9 radial-axial bearings 10 connection 11 Connection engine compartment 12 Connection Tank 13 Connecting hole 13a Throttle 21 Print area 22 Suction area 25 cavity 26 Throttle 27 eccentric bearings 28 axle 30 electric motor 31 Rotor 32 Rotor lamination package 33 Engine compartment 35 gap 36 Magnet 37 gap 40 retaining ring 41 Bearing washer

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) and seals against the flange (3) at a gap (35), characterized by that a bore in the flange (3) or a cavity (25) in the shaft (6) is provided for at least partial pressure equalization between the suction region (22) of the gerotor pump (1) and the motor chamber (33) of the gerotor pump (1), wherein a medium is supplied from the pressure region to an opposite second side of the outer rotor (5) in order to urge the outer rotor (5) towards the flange (3) and to counteract a force from the medium acting on the outer rotor (5) in the pressure region, which force urges the outer rotor (5) away from the flange (3). [2] Gerotor pump (1) according to claim 1, characterized bythat further connections (11, 12) are provided between the engine compartment and the hollow space of the shaft and the hollow space of the shaft to the suction area (22). [3] Gerotor pump (1) according to claim 1 or 2, characterized by that the cavity (25) in the shaft has a taper which serves as a throttle (26). [4] Gerotor pump (1) according to claim 1, characterized by that further connections (11, 13) are provided between the motor compartment (33) and the cavity (25) of the shaft (6) and the cavity (25) of the shaft to an eccentric bearing (27) of the gerotor pump (1). [5] Gerotor pump (1) according to one of the preceding claims, characterized by that at least one of the connections (10,11,25,13) has a reduction in cross-section which serves as a throttle (13a). [6] Method for establishing pressure equalization in a gerotor pump (1) according to one of the preceding claims, characterized bythat an intermediate pressure is created in the engine compartment via the inflow and outflow of the medium. [7] Method according to claim 6, wherein an additional gap (27) between a retaining ring (40) and a bearing disc (41) is used to adjust the pressure in the event of pressure peaks.

Images