Housing for an internal gear pump and electric pump including such housing

Abstract

The present invention relates to a pump housing (10) for an internal gear pump (13), having a receiving space (18) for an external rotor (14) and an internal rotor (15) disposed inside the external rotor (14), the receiving space (18) having a circumferential wall (19) which defines a circular cylindrical bearing space for the external 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 disposed on one of the end walls (1, 2), the axial bearing surface (4) bearing against the internal rotor (15) with an axial clearance P1 and the base surface (3) being at a distance from the internal gear pump (13) with an axial clearance P2, the axial play P2 being greater than the axial play P1. Figure for the abbreviation: Figure 1

Description

Title of the invention: Housing for an internal gear pump and an electric pump comprising such a housing

[0001] The present invention relates to a fluid pump and particularly a housing for an internal gear pump, for example a gerotor type pump.

[0002] Such pumps are increasingly manufactured from plastic, both for the motor housing and the pump housing. The use of this material offers advantages in terms of weight, but the manufacturing tolerances are quite wide, which can lead to premature noise problems.

[0003] On existing pumps, for example the pump disclosed in document DE 10 2022 117 208 Al, 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 for obtaining low volume losses and high pressure.

[0004] The motor shaft connected to the gerotor is guided in rotation by a plastic part of the motor housing or pump housing. Due to inherent tolerances in the plastic part, the shaft may tilt slightly in certain cases, for example, when subjected to high radial loads. This can cause noise if the teeth of the gerotor's inner ring strike the flat axial surface between the high-pressure chamber and the low-pressure chamber.

[0005] It is therefore necessary to remedy this problem by proposing an electric fluid pump that can be as quiet as possible while avoiding very precise assembly tolerances, which increase production costs.

[0006] For electric cars, the pressure is approximately 1 bar, and tests have shown that the best efficiency is obtained with a gap of approximately 0.1 mm between the gerotor and the flat surface of the pump housing in the axial direction. This gap allows for the addition of extra axial bearing surfaces that can utilize a portion of the 0.1 mm axial space.

[0007] Therefore, the present invention relates to a housing for an internal gear pump rotating about an axis X, having a receiving space for an external rotor having a circular cylindrical outer circumference, and an internal rotor disposed inside the external rotor, the receiving space having a circumferential wall that defines a circular cylindrical support space for the external 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 support surface are disposed on one of the walls At the end, the axial bearing surface rests against the inner rotor with an axial clearance PI and the base surface is at a distance from the inner gear pump with an axial clearance P2, the axial clearance P2 being greater than the axial clearance PI.

[0008] According to this design, if the motor shaft is inclined, which is very likely in a plastic housing, the teeth of the inner rotor only touch the axial bearing surface and not the base surface, which allows the noise level to be controlled.

[0009] According to the invention, the first end wall is located on the pump housing, in particular at the bottom of the receiving space of the internal gear pump. The second end wall is located on the pump cover.

[0010] According to the invention, the internal gear pump is a gerotor type pump.

[0011] According to one aspect of the invention, the base surface and the axial support surface are arranged on the two end walls.

[0012] According to another aspect of the invention, the base surface and at least one axial support surface are axially offset by a distance of between 0.02 mm and 0.005 mm and preferably between 0.01 mm and 0.007 mm.

[0013] According to the invention, there are two bearing surfaces, the second bearing surface being in contact with the outer rotor. The two bearing surfaces are coplanar. The base surface lies radially between the two bearing surfaces.

[0014] According to the invention, at least one axial bearing surface is a flat annular surface. In other words, at least one axial bearing surface has the shape of a flat ring.

[0015] According to the invention, at least one axial bearing surface is formed in one piece with the material of the end walls. For example, the material of the end walls is made from plastic. This feature facilitates assembly by minimizing the number of components.

[0016] According to the invention, the annular flat surface is provided with a plurality of protrusions. This feature reduces the amount of material used without compromising the function of at least one axial bearing surface.

[0017] According to a specific embodiment of the invention, each protuberance has an inclined plane whose lowest point of the slope is located on the side of the axis of rotation X. This feature has the advantage of forming an axial hydrodynamic bearing.

[0018] According to the invention, at least one axial bearing surface is an added part, for example a plastic or metal ring. Although this increases the assembly complexity, it allows for the standardization of the pump components and for the adaptation of the axial bearing surface length according to requirements.

[0019] The invention also relates to an electric fluid pump with a housing according to one of the preceding characteristics.

[0020] 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:

[0021] Fig. 1 illustrates a cross-section of an electric fluid pump configured according to the present invention;

[0022] [Fig.2] illustrates an enlarged view of the base surface and the axial support surface of [Fig.1];

[0023] Fig. 3 illustrates a top view of the housing body according to the invention;

[0024] [Fig.4] illustrates a top view of the pump cover according to the invention;

[0025] [Fig.5] illustrates a second embodiment of the invention focused on the housing body.

[0026] In the following description, reference is made to accompanying drawings, which form part thereof, and in which specific embodiments in which the invention can be applied are illustrated. These embodiments are described in sufficient detail to enable a person skilled in the art to carry out the invention, and it will be understood that the embodiments can be combined, or that other embodiments can be used, and that structural and logical modifications can be made without departing from the scope of the present invention. The following detailed description should therefore not be interpreted in a restrictive manner, and the scope of the present invention is defined by the accompanying claims and their equivalents.

[0027] Figure 1 shows an electric fluid pump 20 according to the invention. The fluid pump 20 is adapted to supply hydraulic fluid to a transmission of an electric or hybrid drive module of a motor vehicle, for example to lubricate contact points, to provide a flow of coolant to a clutch or to generate a flow of pressurized fluid for the activation of an actuator.

[0028] The electric pump 20 includes a motor housing 21 containing an electric motor with a stator 22 and a rotor 23. The electric motor is driven by a printed circuit board 26. The printed circuit board 26 may be located in a specific printed circuit board enclosure 25 or may be located directly in the motor housing 21. The printed circuit board 26 is electrically connected to the stator 22 by electrical connections not shown.

[0029] A motor shaft 24 is rotationally linked to the rotor 23 such that when the rotor 23 rotates, the motor shaft 24 also rotates about an axis X. At the end of the motor shaft 24 opposite the end connected to the rotor 23 is a device pumping, including an internal gear pump 13 also known as a gerotor.

[0030] This internal gear pump 13 includes an internal rotor 15 disposed inside an external rotor 14. The internal rotor 15 is rotationally linked to the motor shaft 24, so that when the motor shaft 24 rotates, the internal rotor 15 also rotates.

[0031] The electric pump 20 includes a pump housing 10 which receives the pumping device. The pump housing 10 has a first end wall 1, a housing body 11 and a second end wall 2. In the embodiment illustrated in [Fig. 1], the housing body 11 and the second end wall 2 are made as a single unit and the first end wall 1 is part of a pump cover 12. The housing body 11 is preferably made of plastic.

[0032] 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 disposed inside the outer rotor 14. The receiving space 18 has a circumferential wall 19 visible on [Fig.3] which defines a circular cylindrical support space for the outer rotor 14.

[0033] 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 includes suction openings 16 as well as pressure openings 17 as seen in [Fig.4].

[0034] [Fig.2] allows for a better understanding of the invention where a base surface 3 and at least one axial bearing surface 4 are arranged on one of the end walls 1, 2. In the embodiment of [Fig.2], a base surface 3 is located on the first end wall 1, i.e. the pump cover 12, and two axial bearing surfaces 4, 5 are also located on the first end wall 1, i.e. the pump cover 12.

[0035] The first axial bearing surface 4 rests against the inner rotor 15 with an axial clearance PL. For example, this axial clearance PL is between 0.05 mm and 0.1 mm and is preferably 0.09 mm in the context of [Fig. 2]. The second axial bearing surface 5 rests against the outer rotor 14 with the same axial clearance PL.

[0036] The base surface 3 is at a distance from the internal gear pump 13 with an axial clearance P2 and the axial clearance P2 is greater than the axial clearance PL For example, this axial clearance P2 is between 0.16 mm and 0.25 mm and preferably 0.21 mm in the context of [Fig.2].

[0037] Due to inherent tolerances in the plastic housing 11, the motor shaft 24 may tilt slightly relative to the X-axis. The first axial bearing surface 4 is designed to prevent the teeth of the inner rotor 15 from striking the base surface 3, thereby avoiding the generation of noise or vibration that could interfere with the operation of the electric fluid pump. The second axial bearing surface 5 is designed to prevent the teeth of the outer rotor 14 from striking the base surface 3, as the outer rotor 14 could also tilt with the inner rotor 15 due to their contact during operation.

[0038] The two axial bearing surfaces 4, 5 are coplanar. The base surface 3 lies radially between the two bearing surfaces 4, 5. The two axial bearing surfaces 4, 5 are made of a flat annular surface. The two axial bearing surfaces 4, 5 are continuous or uninterrupted surfaces.

[0039] The two axial bearing surfaces 4, 5 are formed in one piece from the material of the end walls 1, 2, for example plastic. Alternatively, the two axial bearing surfaces 4, 5 are an added part, for example a plastic or metal ring.

[0040] The base surface 3 and the two axial bearing surfaces 4, 5 are axially offset by a distance of between 0.02 mm and 0.005 mm. In other words, the two axial bearing surfaces 4, 5 have a thickness of between 0.02 mm and 0.005 mm relative to the base surface 3.

[0041] Fig. 3 shows the housing body 11 with emphasis on the receiving space 18 where the two axial bearing surfaces 4, 5 can be clearly seen. The first axial bearing surface 4 is located in the center of the receiving space 18, coaxial with the bearing 7 of the motor shaft of the housing body 11. The second axial bearing surface 5 is located at the periphery of the receiving space 18, adjacent to its circumferential wall 19.

[0042] A similar arrangement is shown in [Fig.4] where the first axial bearing surface 4 is in the center, coaxial with the bearing 7 of the motor shaft and the second axial bearing surface 5 is further to the periphery.

[0043] In the embodiment of [Fig.1] to [Fig.4], the base surface 3 and the two axial bearing surfaces 4, 5 are arranged on the two end walls 1, 2, i.e. the housing body 11 and the cover 12. This means that the teeth of the inner rotor 15 can follow the inclination of the shaft without touching the base surface 3.

[0044] Figure 5 shows a second embodiment in which the first annular flat surface 4 is provided with a plurality of protrusions 8 and the second annular flat surface 5 is also provided with a plurality of protrusions 8. The protrusions 8 are spaced so as to form an annular flat surface discontinuous fulfilling the same function as the annular plane surface referred to in the previous embodiment.

[0045] According to another embodiment not shown, each protuberance 8 has an inclined plane whose lowest point of the slope is located on the side of the axis of rotation X in order to form an axial hydrodynamic support surface.

Claims

Demands

1. Pump housing (10) for an internal gear pump (13) rotating about an axis X, having a receiving space (18) for an external rotor (14) having a circular cylindrical outer circumference, and an internal rotor (15) disposed inside the external rotor (14), the receiving space (18) having a circumferential wall (19) that defines a circular cylindrical bearing space for the external 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) are disposed on one of the end walls (1, 2), the axial bearing surface (4) rests against the internal rotor (15) with an axial clearance PI and the base surface (3) is at a distance from the internal gear pump (13) with an axial clearance P2,The axial play P2 is greater than the axial play PL.

2. Pump housing (10) according to claim 1, characterized in that the base surface (3) and the axial bearing surface (4) are arranged on the two end walls (1, 2).

3. Pump housing (10) according to claim 1 or 2, characterized in that the base surface (3) and at least one axial bearing surface (4) are axially offset by a distance between 0.02 mm and 0.005 mm and preferably between 0.01 mm and 0.007 mm.

4. Pump housing (10) according to any 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).

5. Pump housing (10) according to any one of the preceding claims, characterized in that at least one axial bearing surface (4, 5) is an annular flat surface.

6. Pump housing (10) according to claim 5, characterized in that at least one axial bearing surface (4,5) is formed in one piece with the material of the end walls (1,2), for example plastic.

7. Pump housing (10) according to claim 6, characterized in that the annular flat surface is provided with a plurality of protrusions (8).

8. Pump housing (10) according to claim 7, characterized in that each protrusion (8) has an inclined plane whose lowest point of the slope is on the side of the axis of rotation X.

9. Pump housing (10) according to claim 5, characterized in that at least one axial bearing surface (4,5) is an added part, for example a plastic or metal ring.

10. Electric fluid pump (20), characterized in that it comprises a pump housing (10) according to any one of the preceding claims.

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