Gerotor Pump

Abstract

A gerotor pump having an inner rotor and an outer rotor, which is also the rotor of an electric drive, having a housing and a flange which closes the housing with the motor compartment, the rotor being arranged on a shaft and sealing against the flange at a gap, wherein, in addition to the gap, there is at least one device with which at least a partial pressure compensation takes place between the suction region of the gerotor pump and the motor compartment of the gerotor pump.

Claims

1. A gerotor pump comprising: a housing; a flange which closes the housing to define a compartment; an inner rotor; an outer rotor in driving engagement with the inner rotor, the inner rotor and the outer rotor being positioned within the compartment; an electric drive positioned within the compartment and including an electric rotor fixed for rotation with the outer rotor, the outer rotor being arranged on a shaft that is supported for rotation within the compartment, a first end of the outer rotor being positioned against the flange, the gerotor pump including a suction region and a pressure region, wherein medium within the pressure region is at a higher pressure than medium within the suction region and the compartment; a gap between the flange and the inner and outer rotors allowing medium in the pressure region to enter the compartment; and a cavity in the shaft in fluid communication with the suction region and in fluid communication with the compartment.

2. The gerotor pump according to claim 1, wherein the cavity in the shaft has a taper which serves as a throttle.

3. A gerotor pump comprising: a housing; a flange which closes the housing to define a compartment; an inner rotor; an outer rotor in driving engagement with the inner rotor, the inner rotor and the outer rotor being positioned within the compartment; an electric drive positioned within the compartment and including an electric rotor fixed for rotation with the outer rotor, the outer rotor being arranged on a shaft that is supported for rotation within the compartment, a first end of the outer rotor being positioned against the flange, the gerotor pump including a suction region and a pressure region, wherein medium within the pressure region is at a higher pressure than medium within the suction region and the compartment; a gap between the flange and the inner and outer rotors allowing medium in the pressure region to enter the compartment; and a cavity in the shaft in fluid communication with the compartment and in fluid communication with an eccentric bearing of the gerotor pump.

4. The gerotor pump according to claim 3, wherein the cavity in the shaft has a taper which serves as a throttle.

Description

DRAWINGS

[0025] FIG. 1 shows an exploded illustration of the gerotor pump,

[0026] FIG. 2 shows a section through a gerotor pump according to the disclosure with bore to the suction region,

[0027] FIG. 3 shows a section through a gerotor pump according to the disclosure, with shaft bore and throttle cross-section,

[0028] FIG. 4 shows a section through a gerotor pump according to the disclosure with motor compartment outflow via the bearing of the eccentric for the purposes of improving the lubrication and cooling thereof,

[0029] FIG. 5 shows a section through a pump according to the disclosure with increased play at the axial bearing of the rotor for the purposes of relieving the pressure compartment of load in the presence of pressure peaks,

[0030] FIG. 6 shows a section through a pump according to the disclosure with a gap under the rotor for the purposes of relieving the pressure compartment of load in the presence of pressure peaks.

DETAILED DESCRIPTION

[0031] FIG. 1 shows, in an exploded illustration, the housing 2, which is closed by means of a flange 3. In the interior, it is possible to see an inner rotor 4 and an outer rotor 5 with a shaft 6. The outer rotor 5 is illustrated separately. Inlet and outlet openings can be seen on the flange 3.

[0032] FIGS. 2 to 4 illustrate a gerotor pump 1 with a housing 2 in various sectional views.

[0033] In the housing 2, an inner rotor 4 and an outer rotor 5 are rotatably arranged in a pump working compartment of the gerotor pump 1.

[0034] In the housing 2, a shaft 6 is mounted rotatably about an axis of rotation 28 by means of a bearing devices 9.

[0035] A flange 3 serves as housing cover, by means of which the housing 2, which is of substantially pot-shaped form, is closed off.

[0036] An electric motor 30 with a rotor 31 and a stator is integrated into the housing 2 of the gerotor pump 1. The stator comprises a stator laminated core with windings which are embedded together with the stator laminated core into a plastics material. The plastics material is, for example in an injection molding process, shaped so as to constitute the housing 2 of the gerotor pump 1.

[0037] The rotor 31 of the electric motor 30 comprises a rotor laminated core 32 and cast-in magnets. The rotor laminated core is, together with the magnets 36, encapsulated with a plastics material. The rotor 31 of the electric motor 30 is integrally connected, by means of the plastics material, to the outer rotor 5 of the gerotor pump 1. Stator and rotor of the electric motor form a motor compartment 33, in which no pressure prevails.

[0038] The plastics material thus serves both for realizing the rotor 31 of the electric motor 30 and for realizing 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.

[0039] Here, the rotor 31 of the electric motor 30 is mounted, together with the outer rotor 5 of the gerotor pump 1, 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. As a result, the inner rotor 4 of the gerotor pump 1 is arranged eccentrically with respect to the shaft 6 and the outer rotor 5.

[0040] The gerotor pump 1 has an suction region 22 in the upper region and has a pressure region 21 in the lower region. The housing cover, the flange 3, is formed from a plastics material or metal.

[0041] A connection 10 between the motor compartment 33 of the electric machines 30 and the suction region 22 is arranged in the flange 3.

[0042] The motor compartment 33 of the gerotor pump, which is operated by electric motor, is pressurized to an intermediate pressure level, which lies above atmospheric pressure, by means of an inflow of the medium through the gap 35 from the pressure region 21.

[0043] By means of a targeted build-up of pressure in the otherwise unpressurized motor compartment 33 of the gerotor pump, the axial bearing 9 is relieved of load, whereby friction losses decrease, and the gap 35 between rotor 5 and flange 3 decreases in size, whereby leakage decreases.

[0044] The inflow of the medium into the motor compartment 33 is caused by the leakage in the gap itself. A greater inflow thus gives rise to a higher internal pressure in the motor compartment and thus to an improved sealing action of the rotor 5 against the flange 3, which, in terms of closed-loop control technology, equates to negative feedback.

[0045] FIG. 3 shows a further embodiment of the gerotor pump 1.

[0046] An inflow of the medium into the motor compartment takes place via the gap 35. By means of a connection 11, the motor compartment 33 is connected to the shaft 6, which has a cavity 25 which extends along the axis 28.

[0047] The outflow out of the motor compartment 33 takes place through the cavity 25 into the region of the suction port 7 or a leakage path with a connection 12 directly to the suction region 22.

[0048] For the adjustment of the pressure level that results in the motor compartment, a throttle cross-section 26 is provided in the outflow path, that is to say for example in the shaft. The flow through the motor compartment 33 of the gerotor pump, which has come about through a hollow shaft, has the secondary effect that heat losses of electric motor 30 and electronics are dissipated by the flow that is generated, and supply of lubricant a supply to the bearings can be improved.

[0049] By relieving an axial bearing in the electric motor of load, the friction of the rotor is minimized, wherein, at the same time, by means of an increase of the contact pressure in a gap between rotor and side wall, the leakage is minimized.

[0050] FIG. 4 describes an embodiment which produces a connection 11 between motor compartment 33 and shaft 6 and has a cavity 25 in the shaft 6, which cavity opens out in a connecting bore 13 which produces a connection of the shaft 6 to the eccentric bearing 27. The connecting bore 13 is of reduced diameter and constitutes a throttle 13a for the return flow of the medium.

[0051] By means of a targeted build-up of pressure in the otherwise unpressurized motor compartment of the pump, the axial bearing is relieved of load, whereby the friction thereof decreases, and the gap between rotor and flange is compressed, whereby leakage decreases. Said intermediate pressure level is high enough to ensure adequate sealing of the pump but permits a load-relieving lift-off of the rotor assembly in the presence of pressure peaks.

[0052] The above-described effect of the compensation by internal pressure is based on leakage in the motor compartment of the pump. If only a temporally brief pressure peak arises at the inlet of the pump, the rotor assembly immediately recoils from the pressure plate, because, at the time of arrival of the pressure peak, it has not yet been possible for a pressure of corresponding magnitude to be built up in the motor compartment. To permit such recoiling, it is merely necessary to ensure that the rotor assembly has such amount of axial play that an opening of the pressure compartment is thus permitted, without the rotor assembly being allowed so much play that, in the event of vibrations, without or with low working pressure, destruction can occur owing to impacting against the axial stops, that is to say the axial bearing or the pressure plate.

[0053] This requirement is met with a gap 37 that is provided between a retaining ring 40 and a bearing washer 41 on the shaft 6.