EP4675106A1

EP4675106A1 - Housing for an internal gear pump and electric pump comprising such housing

Info

Publication number: EP4675106A1
Application number: EP25186520.0A
Authority: EP
Inventors: Alexander LEHNERT
Original assignee: Valeo Embrayages SAS
Current assignee: Valeo Embrayages SAS
Priority date: 2024-07-03
Filing date: 2025-07-01
Publication date: 2026-01-07
Also published as: FR3164255A1

Abstract

Pump housing (10) for an internal gear pump (13), having a receiving space (18) for an outer rotor (14) and an inner rotor (15) arranged inside the outer rotor (14), the outer rotor (14) and an inner rotor (15) having a same axial length, the receiving space (18) having a circumferential wall (19) which defines a circular cylindrical bearing space for the outer rotor (14), and two end walls (1, 2), at least one suction opening (16) and one pressure opening (17) being provided in one of the end walls (1, 2), a base surface (3) and at least one axial bearing surface (4) being provided on one of the end walls (1, 2), the axial bearing surface (4) lies against the inner rotor (15) with an axial play P1 and the base surface (3) is at distance from the internal gear pump (13) with an axial play P2, the axial play P2 is greater than the axial play P1.

Description

The present subject matter relates to fluid pump and especially a housing for an internal gear pump, for example a gerotor pump.
Such pumps are increasingly made of plastic, both for the motor housing and the pump housing. The use of this material offers advantages in terms of weight, but manufacturing tolerances are fairly wide, which can generate problems of premature noise.
On existing pumps, for example the pump disclosed in document DE 10 2022 117 208 A1 , the axial contact surface between the pump housing and the gerotor is a flat surface, see in particular surface reference 16. This flat surface is typical to get low volume losses and get high pressure.
The motor shaft linked to the gerotor is guided in rotation with a plastic part from the motor housing or the pump housing. Due to the tolerances inherent in the plastic part, the shaft may tilt slightly in some cases, e.g. when subjected to high radial loads. This can causes noises if gerotor inner ring teeths hit the flat axial surface between high pressure and low pressure chamber.
It is therefore necessary to remedy this problem by proposing an electric fluid pump that can be as silent as possible while avoiding very precise assembly tolerances, which increase production costs.
For electric cars pressure is around 1 bar, and tests showed that best efficiency is with a gap between the gerotor the flat surface of the pump housing axially at roughly 0,1mm. This gap allows to add extra axial bearing surfaces that can use some of the axial gap 0,1mm.
Therefore, the present invention relates to an housing for an internal gear pump rotatable around an axis X, having a receiving space for an outer rotor which has a circular cylindrical outer circumference, and an inner rotor arranged inside the outer rotor, the outer rotor and an inner rotor having a same axial length, the receiving space having a circumferential wall which defines a circular cylindrical bearing space for the outer rotor, and two end walls, at least one suction opening and one pressure opening being provided in one of the end walls. A base surface and at least one axial bearing surface being provided on one of the end walls, the axial bearing surface lies against the inner rotor with an axial play P1 and the base surface is at distance from the internal gear pump with an axial play P2, the axial play P2 is greater than the axial play P1.
According to this design, if the motor shaft is tilted which is highly likely in plastic housing, the inner rotor teeth are only touching the axial bearing surface and not the base surface which results in a controlled noise level.
According to the invention, the first end wall is on the pump housing, in particular the bottom of the receiving space of the internal gear pump. The second end wall is on the pump cover.
According to the invention, the internal gear pump is a gerotor pump.
According to an aspect of the invention, the base surface and the axial bearing surface are provided on the two end walls.
According to another aspect of the invention the base surface and the at least one axial bearing surface are axially offset, preferably by a distance of between 0.02mm and 0.005mm and more preferably between 0,01mm and 0,007mm.
According to the invention, there are two bearing surfaces, the second bearing surface is in contact with the outer rotor. The two bearing surfaces being coplanar. The base surface being radially between the two bearing surfaces.
According to the invention, the at least one axial bearing surface is an annular planar surface. In other words, the at least one axial bearing surface has a flat ring shape.
According to the invention, the at least one axial bearing surface is integrally formed with the end walls material. For example the end walls material is made from plastic. This feature facilitates the assembly by minimizing the number of components.
According to the invention, the annular planar surface is provided with a plurality of protuberance. This feature reduces the amount of material used without compromising the function of the at least one axial bearing surface.
According to a specific embodiment of the invention each protuberance has an inclined plan whose low point of the slope is on the side of the axis of rotation X. This special feature has the advantage of forming an axial hydrodynamic bearing.
According to the invention, the at least one axial bearing surface is an added part, for example a plastic or metal ring. Although this leads to increased assembly complexity, it does allow the pump components to be standardized and the axial bearing surface length to be adapted as required.
The invention also concerns an electric fluid pump with a housing according to one of the preceding features.
The present invention can be better understood with reference to the following description and drawings. The components in the figures are not necessarily to scale. In the drawings:

[Figure 1] illustrates a cut-section of an electric fluid pump configured in accordance with the present invention;
[Figure 2] illustrates an enlarged view of the base surface and the axial bearing surface from the [Figure 3];
[Figure 3] illustrates a top view of the housing body according to the invention;
[Figure 4] illustrates a top view of the pump cover according to the invention;
[Figure 5] illustrates a second embodiment of the invention focused on the housing body.

In the description that follows, reference is made to accompanying drawings, which form part thereof, and in which is shown by way of illustration specific implementations in which the invention may be practiced. These implementations are described in sufficient detail to enable that skilling in the art to practice the invention, and it is to be understood that the implementations may be combined, or that other implementations may be utilized, and that structural and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.
It can be seen on [Figure 4] an electric fluid pump 20 according to the invention. The electric pump 20 is suitable for providing a supply of a hydraulic fluid to a transmission of an electric or hybrid drive module of a motor vehicle, for example to lubricate bearing points, to provide a coolant flow for a clutch, or to generate a pressure medium flow for activating an actuator.
The electric pump 20 comprises a motor housing 21 enclosing an electric motor with a stator 22 and a rotor 23. The electric motor is driven with a circuit board 26. The circuit board 26 can be located in a specific circuit board housing 25 or can be directly located in the motor housing 21. The circuit board 26 is electrically linked to the stator 22 with electrical links not represented.
A motor shaft 24 is rotationally linked to the rotor 23 such that when the rotor 23 rotates the motor shaft 24 also rotates around an axis X. At the end of the motor shaft 24 opposite that connected to the rotor 23 is a pump device, notably an internal gear pump 13 also known as a gerotor.
Such internal gear pump 13 comprises an inner rotor 15 arranged inside an outer rotor 14. The inner rotor 15 is rotationally linked to the motor shaft 24 such that when the motor shaft 24 rotates the inner rotor 15 also rotates. The outer rotor 14 and an inner rotor 15 have a same axial length or from another perspective a same width which avoid internal leakages and reduce wear of the pump.
The electric pump 20 comprises a pump housing 10 which receives the pump device. The pump housing 10 has a first end wall 1, a housing body 11 and a second end wall 2. In the embodiment shown on [Figure 5], the housing body 11 and the second end wall 2 are designed as one piece and the first end wall 1 is part of a pump cover 12. The housing body 11 is preferably made of plastic.
The pump housing 10 has a receiving space 18 for the outer rotor 14 which has a circular cylindrical outer circumference, and the inner rotor 15 is arranged inside the outer rotor 14. The receiving space 18 has a circumferential wall 19 visible on [Figure 3] which defines a circular cylindrical bearing space for the outer rotor 14.
On the suction side, the fluid to be pumped by the internal gear pump 13 is supplied via a suction opening 16, which is formed in the first end wall 1. On the pressure side, the pumped fluid is discharged via a pressure opening 17, which is formed in the first end wall 1. In other words, the pump cover 12 comprises both suction 16 and pressure 17 openings, as visible on [Figure 4].
The [Figure 2] provides a better understanding of the invention where a base surface 3 and at least one axial bearing surface 4 are provided on one of the end walls 1, 2.
In the embodiment of the [Figure 2] there are one base surface 3 located on the first end wall 1 i.e. the pump cover 12 and two axial bearing surface 4, 5 also located on the first end wall 1 i.e. the pump cover 12.
The first axial bearing surface 4 lies against the inner rotor 15 with an axial play P1. For example, this axial play P1 is comprised between 0,05mm and 0,1mm and is preferably 0,09mm in the context of the [Figure 2]. The second axial bearing surface 5 lies against the outer rotor 14 with the same axial play P1.
The base surface 3 is at distance from the internal gear pump 13 with an axial play P2 and the axial play P2 is greater than the axial play P1. For example, this axial play P2 is comprised between 0,16mm and 0,25mm and preferably 0,21mm in the context of the [Figure 2].
Due to the tolerances inherent in the housing body 11 made of plastic, the motor shaft 24 may tilt slightly in relation to the X axis. The purpose of the first axial bearing surface 4 is to prevent the inner rotor 15 teeth to hit the base surface 3 to avoid generating noise or vibrations that could hinder the electric fluid pump's operation. The purpose of the second axial bearing surface 5 is to avoid the outer rotor 14 teeth to hit the base surface 3 as the outer rotor 14 might also tilt with the inner rotor 15 due to their contact in operation.
The two axial bearing surfaces 4, 5 are coplanar. The base surface 3 is radially between the two bearing surfaces 4, 5. The two axial bearing surfaces 4, 5 are made of an annular planar surface. The two axial bearing surfaces 4, 5 are continuous or uninterrupted surfaces.
The two axial bearing surfaces 4, 5 are integrally formed with the end walls 1, 2 material, for example from plastic. As an alternative, the two axial bearing surfaces 4, 5 are an added part, for example a plastic or metal ring.
The base surface 3 and two axial bearing surfaces 4, 5 are axially offset, preferably by a distance of between 0.02mm and 0.005mm. In other words, the two axial bearing surfaces 4, 5 have a thickness of between 0.02mm and 0.005mm in relation to the base surface 3.
The [Figure 3] shows the housing body 11 with a focus on the receiving space 18 where we can clearly see the two axial bearing surfaces 4, 5. The first axial bearing surfaces 4 is at the center of the receiving space 18 coaxial to the motor shaft bearing 7 of the housing body 11. The second axial bearing surfaces 5 is at the periphery of the receiving space 18 adjacent to its circumferential wall 19.
A similar arrangement is disclosed on the [Figure 4] where the first axial bearing surfaces 4 is at the center, coaxial to the motor shaft bearing 7 and the second axial bearing surfaces 5 is more at the periphery.
In the embodiment from [Figure 1] to [Figure 4], the base surface 3 and the two axial bearing surfaces 4, 5 are provided on the two end walls 1, 2 i.e. the housing body 11 and the cover 12. This means that the inner rotor 15 teeth can follow the tilt of the shaft without touching the base surface 3.
The [Figure 5] shows a second embodiment where the first annular planar surface 4 is provided with a plurality of protuberances 8 and the second annular planar surface 5 is also provided with a plurality of protuberance 8. The protuberances 8 are spaced so as to form a discontinuous annular planar surface performing the same function as the annular planar surface referred to in the previous embodiment.
According to another embodiment not shown, each protuberance 8 has an inclined plan whose low point of the slope is on the side of the axis of rotation X in order to form an axial hydrodynamic bearing surface.

Claims

Pump housing (10) for an internal gear pump (13) rotatable around an axis X, having a receiving space (18) for an outer rotor (14) which has a circular cylindrical outer circumference, and an inner rotor (15) arranged inside the outer rotor (14), the outer rotor (14) and an inner rotor (15) having a same axial length, the receiving space (18) having a circumferential wall (19) which defines a circular cylindrical bearing space for the outer rotor (14), and two end walls (1, 2), at least one suction opening (16) and one pressure opening (17) being provided in one of the end walls (1, 2), characterized in that a base surface (3) and at least one axial bearing surface (4) being provided on one of the end walls (1, 2), the axial bearing surface (4) lies against the inner rotor (15) with an axial play P1 and the base surface (3) is at distance from the internal gear pump (13) with an axial play P2, the axial play P2 is greater than the axial play P1.
Pump housing (10) according to claim 1, characterized in that the base surface (3) and the axial bearing surface (4) are provided on the two end walls (1, 2).
Pump housing (10) according to claim 1 or 2, characterized that the base surface (3) and the at least one axial bearing surface (4) are axially offset, preferably by a distance of between 0.02mm and 0.005mm and more preferably between 0,01mm and 0,007mm.
Pump housing (10) according to one of the preceding claims, characterized in that there are two bearing surfaces (4, 5), the second bearing surface is in contact with the outer rotor (14), the two bearing surfaces (4, 5) being coplanar, the base surface (3) being radially between the two bearing surfaces (4, 5).
Pump housing (10) according to one of the preceding claims, characterized in that the at least one axial bearing surface (4, 5) is an annular planar surface.
Pump housing (10) according to claim 5, characterized in that the at least one axial bearing surface (4, 5) is integrally formed with the end walls (1, 2) material, for example from plastic.
Pump housing (10) according to claim 6, characterized in that the annular planar surface is provided with a plurality of protuberance (8).
Pump housing (10) according to claim 7, characterized in that each protuberance (8) has an inclined plan whose low point of the slope is on the side of the axis of rotation X.
Pump housing (10) according to claim 5, characterized in that the at least one axial bearing surface (4, 5) is an added part, for example a plastic or metal ring.
Electric fluid pump (20) characterized in that it comprises a pump housing (10) according to one of the preceding claims.