Fluid pump with improved shaft bearing components

Abstract

The present invention relates to a fluid pump (100) comprising a housing (10) having an axial bore (13) extending axially along an X-axis, with a first bearing portion (11) and a second bearing portion (12) for supporting a drive shaft (1). A motor (7) is used to drive the drive shaft (1). A pump block (9) comprises a first pump rotor (3) having a plurality of external teeth and a second pump rotor (5) having a plurality of internal teeth. The first pump rotor (3) is configured to rotate with the drive shaft (1). The second pump rotor (5) is configured to rotate with the first pump rotor (3), forming a pump chamber for the fluid between the external and internal teeth. According to the invention, the first bearing portion (11) is not cylindrical, and the second bearing portion (12) is cylindrical. Figure for the abbreviation: [Figure 1]

Description

Title of the invention: Fluid pump with improved shaft bearing parts

[0001] The present invention relates to an electric fluid pump, in particular an electric fluid pump with improved shaft bearing parts

[0002] As is known, an electric fluid pump is an internal gear pump with a drive shaft on which an internal pump rotor is mounted. The internal pump rotor is assembled inside an external pump rotor. Generally, the drive shaft of the internal gear pump is mounted in the housing with a bearing contact. Similarly, the external pump rotor is also mounted in the housing with a bearing contact. The external pump rotor receives a load, for example, a drive force transmitted by the internal pump rotor, and hydraulic pressure from the lubricating fluid, since the rotor center distance is maintained within a tight tolerance. At this point, due to the rotation of the internal pump rotor, noise is generated as a result of the impact between the external teeth of the internal pump rotor and the internal teeth of the external pump rotor.

[0003] In view of the above situations, it is generally difficult to produce a plastic housing with reduced operating noise and given the narrow tolerance.

[0004] It is therefore necessary to solve the technical problem associated with the assembly described above.

[0005] The present invention therefore aims to provide an assembly which remedies the aforementioned and other disadvantages of known arrangements, and to provide an electric fluid pump shaft bearing offering improved efficiency with regard to friction between the shaft and the housing and operating noise due to the runout of the internal pump rotor.

[0006] The present invention relates to a fluid pump comprising: a housing having an axial bore extending axially along an axis X with a first bearing portion and a second bearing portion supporting a cylindrical drive shaft, a motor for driving the drive shaft, a pump block having a first pump rotor with a plurality of external teeth and a second pump rotor with a plurality of internal teeth, the first pump rotor being configured to rotate with the drive shaft and the second pump rotor being configured to rotate with the first pump rotor, forming a pump chamber for the fluid between the external and internal teeth, characterized in the first part of the bearing is not cylindrical and the second part of the bearing is cylindrical.

[0007] Thus, thanks to an assembly of the drive shaft in the first part of the housing bearing which is not cylindrical, the drive shaft equipped with the first pump rotor is supported and guided to move, in other words to exhibit a degree of movement, in a direction normal to the X axis. Consequently, the first pump rotor moves in the direction normal to the X axis, which makes it possible to reduce the noise generated by the impact between the external teeth of the first pump rotor driven by the drive shaft and the internal teeth of the second pump rotor.

[0008] According to the invention, the fluid pump is an electric fluid pump, in other words the motor used to drive the drive shaft is an electric motor.

[0009] According to one aspect of the invention, the first bearing portion is provided with at least two opposing flats parallel to the X-axis to support the drive shaft. Thanks to these at least two flats, the drive shaft is assembled between them so as to have linear contact with the first bearing portion along the X-axis. Consequently, the at least two flats limit the movement of the drive shaft in a direction normal to the eccentric direction. Thus, the movement of the first pump rotor equipped with the drive shaft is permitted in the direction normal to the X-axis.

[0010] According to another aspect of the invention, the first bearing portion is provided with a substantially elongated, oblong, oval, or rectangular shape. Advantageously, the first bearing portion with the aforementioned shape eliminates the circumferential support of the drive shaft and ensures movement in the direction normal to the X-axis. Thus, the problem related to manufacturing the bearing portion of the housing with tight tolerances is eliminated.

[0011] According to another aspect of the invention, the first part of the bearing is provided with at least one recess.

[0012] According to another aspect of the invention, the first bearing portion extends over a first distance in a direction Y1 and over a second distance in a direction Y2 normal to the direction Y1 between the at least two flats. The first distance is greater than the second distance, and the directions Y1 and Y2 are two distinct directions in a plane normal to the X-axis. In this way, the drive shaft equipped with the first pump rotor moves along the first distance in the direction Y1, that is, in the direction normal to the X-axis. Advantageously, the problem related to manufacturing the bearing portion of the housing with tight tolerances is eliminated.

[0013] According to another aspect of the invention, a hollow slide is positioned radially with respect to the X-axis between the drive shaft and the first bearing portion. Thanks to the hollow slide, surface contact, i.e., a plain bearing, is provided between the hollow slide and the housing in the Yl direction, which reduces the contact pressure between the hollow slide and the housing.

[0014] According to another aspect of the invention, the hollow slide is provided with an outer circumference configured to cooperate with the first bearing part and an inner cylindrical opening configured to receive the drive shaft.

[0015] According to another aspect of the invention, the outer circumference of the hollow slide is provided with at least one protrusion intended to pivot in at least one recess. The protrusion is assembled by pivoting in the recess so as to allow movement in the direction normal to the X-axis.

[0016] According to another aspect of the invention, the outer circumference of the hollow slide is provided with at least two surfaces, preferably two flats, opposite each other and parallel to the X axis, intended to cooperate with the at least two flats in the first part of the bearing.

[0017] A flat contact is thus provided between the outer circumference of the slide and the housing, which reduces the contact pressure between the hollow slide and the housing. This reduces wear between the slide and the housing.

[0018] According to another aspect of the invention, the hollow slide is provided with a substantially elongated or oblong or oval or rectangular shape.

[0019] According to another aspect of the invention, the outer circumference of the hollow slide extends over a third distance D3 in the direction Y1 and extends over a fourth distance D4 in the direction Y2 normal to the direction Y1 between the at least two surfaces.

[0020] According to another aspect of the invention, the third distance D3 is greater than the fourth distance D4 of the hollow slide.

[0021] According to another aspect of the invention, the first distance DI of the first bearing part is greater than the fourth distance D4 of the hollow slide.

[0022] According to another aspect of the invention, the pump block is placed axially along the X axis on the drive shaft between the first bearing part and the second bearing part.

[0023] According to another aspect of the invention, the casing material is a plastic or a fiber-reinforced plastic. This reduces friction between the casing and the drive shaft. According to the invention, the drive shaft and the pump block are made of metal.

[0024] According to another aspect of the invention, the material of the hollow slide is a plastic material or a fiber-reinforced plastic material or bronze. This allows to reduce friction between the housing and the hollow slide and between the hollow slide and the drive shaft.

[0025] According to another aspect of the invention, the housing comprises a housing body and a cover body mounted on the housing body, and the first bearing part is located in the cover body.

[0026] According to another aspect of the invention, the cover body comprising the first bearing part is an integral part of the housing body to form an integrated housing.

[0027] The present invention can be better understood with reference to the following description and drawings. The elements in the figures are not necessarily to scale, the emphasis being rather on illustrating the principles of the invention. In the drawings:

[0028] Fig. 1 illustrates a cross-sectional view of a first embodiment of a fluid pump, configured according to the invention;

[0029] [Fig.2] illustrates a detailed view of II as shown in [Fig.1] of the first embodiment of the fluid pump, configured according to the invention;

[0030] [Fig.3] illustrates a cross-sectional view of section III as shown in [Fig.1] of the first embodiment of the fluid pump, configured according to the invention;

[0031] Figure 4 illustrates a cross-sectional view of a second embodiment of the fluid pump, configured according to the invention;

[0032] [Fig.5] illustrates a detailed view of IV as shown in [Fig.3] of the first embodiment of the fluid pump, configured according to the invention;

[0033] [Fig.6] illustrates a detailed view of V as shown in [Fig.4] of the second embodiment of the fluid pump, configured according to the invention;

[0034] Figure 7 illustrates a cross-sectional view of a third embodiment of the fluid pump, configured according to the invention;

[0035] Figure 8 illustrates a cross-sectional view of a fourth embodiment of the fluid pump, configured according to the invention;

[0036] [Fig.9] illustrates a detailed view of VI as shown in [Fig.8] of the fourth embodiment of the fluid pump, configured according to the invention;

[0037] Fig. 10 illustrates a detailed view of VII as shown in Fig. 9 of the fourth embodiment of the fluid pump, configured according to the invention.

[0038] In the following description, reference is made to the accompanying drawings, which form part thereof, and in which specific embodiments in which the invention can be implemented are shown by way of illustration. These embodiments are described in sufficient detail to enable a person skilled in the art to implement 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 detailed description that follows should therefore not be interpreted in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0039] Unless otherwise specified, "axially" means parallel to the X-axis of the axial bore of the housing, "radially" means along a transverse axis intersecting the X-axis of the axial bore, and "circumferentially" means around the X-axis of the axial bore. For ease of understanding, and without limitation, the terms "internal / inside / inside" or "external / outside / outside" will be used with respect to the X-axis and in a radial orientation orthogonal to said X-axis.

[0040] The present description relates to [Fig.1], [Fig.2], [Fig.3], [Fig.4], [Fig.5] and [Fig.6] described together for the sake of brevity.

[0041] The fluid pump 100 is a gerotor-type pump. The fluid pump 100 comprises a housing 10 in which a cylindrical drive shaft 1 (hereinafter referred to as the drive shaft 1) and a pump block 9 are mounted. The housing 10, which is made primarily of plastic or fiber-reinforced plastic, has an axial bore 13 for receiving the drive shaft 1. The axial bore 13 extends axially along an axis X with a first bearing portion 11 and a second bearing portion 12. The housing 10 extends substantially transversely to the axis X, forming a chamber for receiving the pump block 9. The second bearing portion 12 is cylindrical, and the first bearing portion 11 is not cylindrical.The second bearing part 12 receiving the drive shaft 1 provides circumferential support to at least a partial length of the drive shaft 1 thanks to the cylindrical shape of the second bearing part 12 of the axial bore 13 of the housing 10.

[0042] The drive shaft 1 has a diameter D and is driven by the motor 7, which is an electric motor. The motor 7 is an internal rotor motor comprising a stator 6 and a rotor 8. The rotor 8 is received inside the stator 6, with an annular space providing clearance to facilitate its rotation. The rotor 8 is fixed to the drive shaft 1, so that the rotation of the rotor 8 rotates the drive shaft 1. The housing 10 extends axially, at least partially, inside the rotor 8.

[0043] By way of non-limiting example, as illustrated in [Fig. 1], the housing 10 comprises a housing body 15 and a cover body 19. The cover body 19 is assembled to the housing body 15 by means of a fastener, for example a screw or a nut and bolt. The first bearing portion 11 is located in the cover body 19 and the second bearing portion 12 is located in the housing body 15.

[0044] The pump block 9 comprises a first pump rotor 3 having a plurality of external teeth arranged sequentially on a radially external peripheral side and a second pump rotor 5 having a plurality of internal teeth arranged sequentially on a radially internal peripheral side. Said pump block 9 is housed in the housing body 15. The cover body 19 has a suction inlet and a discharge outlet. The housing body 15 has the chamber for receiving the pump block 9.

[0045] The first pump rotor 3 of the pump block 9 is connected by a drive link with the drive shaft 1. The drive link requires that the first pump rotor 3 be assembled onto the drive shaft 1 by press fitting such that the first pump rotor 3 is rotationally fixed to the drive shaft 1 about the X axis. The second pump rotor 5 is radially mounted outside the first pump rotor 3 such that the second pump rotor 5 rotates relative to the rotation of the first pump rotor 3 about a second axis X2 which is eccentric with respect to the X axis by a predetermined distance E in a direction Y1 as illustrated in [Fig. 1].

[0046] The second pump rotor 5 is provided with a plurality of recesses formed by the plurality of internal teeth. The number of recesses in the second pump rotor 5 is generally one more than the number of external teeth in the first pump rotor 3. The external teeth of the first pump rotor 3 mesh with the internal teeth of the second pump rotor 5 when the first pump rotor 3 rotates inside the second pump rotor 5. Consequently, the rotation of the first pump rotor 3 and the second pump rotor 5 creates a plurality of pump chambers for the fluid between the external teeth of the first pump rotor 3 and the internal teeth of the second pump rotor 5. The plurality of pump chambers are configured to have a range of volumes from a maximum to a minimum volume.Therefore, when the first pump rotor 3 rotates in a first direction relative to the X axis by means of the drive shaft 1, the fluid is drawn in through the suction inlet and pressurized by means of the plurality of pump chambers having the range of volumes from maximum to minimum volume, and then pumped out through the discharge outlet.

[0047] The pump block 9 is placed on the drive shaft 1 axially along the X axis between the first part of the bearing 11 and the second part of the bearing 12.

[0048] The first bearing portion 11 is provided with at least two opposing flats 16, 18 extending axially over a certain length in a direction parallel to the X-axis to support the drive shaft 1. The first bearing portion 11 receiving the drive shaft 1 ensures linear contact over a distance axial at least partial along the X axis between the drive shaft 1 and the first part of the bearing 11 by means of at least two flats 16, 18.

[0049] With reference to [Fig. 4] and [Fig. 6], the first bearing portion 11 extends radially over a first distance DI in the direction Y1 and over a second distance D2 in the direction Y2. The direction Y2 is normal to the direction Y1. The second distance D2 is defined as the distance between the at least two flats 16, 18 in the direction Y2. According to the present invention, the first distance DI of the first bearing portion 11 is configured to be greater than the second distance D2 of the first bearing portion 11. The direction Y1 and the direction Y2 are two distinct directions in a plane normal to the X-axis. According to the second embodiment, the second distance D2 of the first bearing portion 11 is equal to the diameter D of the drive shaft 1, and the first distance DI of the first bearing portion 11 is greater than the second distance D2 of the first bearing portion 11.Therefore, the drive shaft 1 supported in the first part of bearing 11 by means of at least two flats 16, 18 is guided to move in the direction Yl, so the axis X of the first pump rotor 3 which is press-fitted onto the drive shaft 1 is configured to move in the direction YL.

[0050] With reference to [Fig. 1] and [Fig. 6], the predetermined distance E is in an eccentric direction on a plane normal to the X-axis in the YL direction. The second axis X2 of the second pump rotor 5 is fixed, and the X-axis of the first pump rotor 3 moves in a direction normal to the X-axis, i.e., in the YL direction. The X-axis and the second axis X2 lie within the predetermined distance E; in other words, the displacement of the X-axis of the first pump rotor 3 defines an operating range for the first pump rotor 3. Thus, the operating range lies within the predetermined distance E in the YL direction.

[0051] In another embodiment not shown, the second pump rotor 5 is guided along its entire circumference on the radially outer peripheral side by the housing chamber 10, which limits the displacement of the second pump rotor 5 in the Y1 direction and in the Y2 direction. Thus, the second pump rotor 5 is fixed. Therefore, the X-axis of the first pump rotor 3, which is press-fitted onto the drive shaft 1, is configured to move in the Y1 direction within the predetermined distance E, and the displacement of the drive shaft 1 is limited along the X-axis of the first pump rotor 3, which is press-fitted onto the drive shaft 1, and the second X2 axis of the second pump rotor 5 in the Y2 direction.

[0052] In another embodiment not shown, the second pump rotor 5 is not guided over its entire circumference on the radially outer peripheral side by the housing chamber 10. In other words, the housing chamber 10 is configured so as to move the second pump rotor 5 in the direction Y1 within the predetermined distance E. In this way, the X axis and the second axis X2 are within the predetermined distance E, in other words the operating range of the first pump rotor 3 and the second pump rotor 5 is within the predetermined distance E in the direction Y1 and the displacement of the drive shaft 1 is limited along the X axis of the first pump rotor 3 which is press-fitted onto the drive shaft 1 and the second axis X2 of the second pump rotor 5 in the direction Y2.

[0053] With reference to [Fig. 1], [Fig. 2], [Fig. 3], and [Fig. 5], a hollow slide 21 is positioned radially with respect to the X-axis between the drive shaft 1 and the first bearing portion 11. Consequently, the drive shaft 1 is supported in the first bearing portion 11 by means of the hollow slide 21. The hollow slide 21 has an outer circumference 25 and an inner cylindrical opening 23. The drive shaft 1 is mounted on the inner cylindrical portion 23 of the hollow slide 21 so as to provide circumferential support for at least a partial length of the drive shaft 1. The outer circumference 25 has at least two opposing surfaces 27, 29 parallel to the X-axis designed to cooperate with the at least two flats 16, 18. in the first part of level 11. The at least two surfaces 27, 29 extend axially over a certain length along the X axis.The at least two surfaces 27, 29 of the hollow slide 21 are flats. In this way, when the at least two flats 16, 18 of the first part of the bearing 11 receive the at least two flats 27, 29 of the hollow slide 21, a surface contact, in other words a plain bearing, is formed between the hollow slide 21 and the first part of the bearing 11 of the housing 10.

[0054] With reference to [Fig. 5], the first bearing portion 11 extends radially over the first distance DI in the direction Y1 and over the second distance D2 in the direction Y2 (as illustrated in [Fig. 6]). The outer circumference 25 of the hollow slide 21 extends radially over a third distance D3 in the direction Y1 and over a fourth distance D4 in the direction Y2. The direction Y2 is normal to the direction Y1. The fourth distance D4 is defined as the distance between the at least two flats 27, 29 of the hollow slide 21 in the direction Y2. According to the present invention, the first distance DI of the first bearing portion 11 is configured to be greater than the second distance D2 of the first bearing portion 11.

[0055] The fourth distance D4 of the hollow slide 21 is equal to the second distance D2 of the first bearing part 11. The third distance D3 of the hollow slide 21 is greater than the fourth distance D4 of the hollow slide 21. The first distance DI is greater than the second distance D2, the third distance D3 and the fourth distance D4 of the hollow slide 21.

[0056] Consequently, the hollow slide 21 assembled with the drive shaft 1 supported in the first part of the bearing 11 by means of at least two flats 16, 18 is guided to move in the direction Yl. Thus, the first pump rotor 3 is configured to move in the direction Yl.

[0057] The first part of the bearing 11 is provided with an elongated or oval or rectangular shape with at least two flats 16, 18 opposed to each other and parallel to the axis X. The hollow slide 21 is provided with a substantially elongated or oblong or oval or rectangular shape.

[0058] With reference to [Fig. 8] and [Fig. 9], in the fourth embodiment, the first part of the bearing 11 is provided with a recess 30. The recess 30 extends radially over a certain distance in the direction Y2 normal to the direction YL. The outer circumference 25 of the hollow slide 21 is substantially cylindrical with a protrusion 31. The protrusion 31 extends over a certain distance in the direction Y2 normal to the direction YL.

[0059] As illustrated in [Fig. 8], [Fig. 9], and [Fig. 10], the protrusion 31 is shaped like a gear tooth, preferably an involute gear tooth 32. The recess 30 in the first part of the bearing 11 is shaped like a space 33 between the teeth of a straight rack, as illustrated in [Fig. 10], intended for the pivoting assembly of the protrusion 31, which is shaped like the involute gear tooth 32, thus allowing the hollow slide 21 to move in the YL direction.

[0060] According to the fourth embodiment, the drive shaft 1 is assembled on the inner cylindrical part 23 of the hollow slide 21 so as to provide circumferential support to at least a partial length of the drive shaft 1. The protrusion 31 on the outer circumference 25 of the hollow slide 21 is intended to pivot in the recess 30 of the first part of the bearing 11, which allows the hollow slide 21 to move in the direction YL. A clearance between the outer circumference 25 of the hollow slide 21 and the first part of the bearing 11 allows the hollow slide 21 to move in the direction YL. Therefore, the hollow slide 21 assembled with the drive shaft 1 is guided to move in the direction Y1 within the predetermined distance E.Thus, the first pump rotor 3 is configured to move in the Yl direction by means of the protrusion 31 of the hollow slide 21 assembled by pivoting with the recess 30 of the first part of the bearing 11.

[0061] The hollow slide 21 provided with the gear-tooth-shaped protrusion 31 is assembled by pivoting in the recess 30 of the first part of the bearing 11 so as to guide the movement of the hollow slider 21 in the direction Yl, in other words in the eccentric direction within the predetermined distance E according to the principle of Cardano's circles.

[0062] The principle of Cardano circles relates to a type of hypocycloid comprising a pair of Cardano circles of different diameters, a smaller circle rolling inside the larger circle whose diameter is twice that of the smaller circle, a trajectory described by a first point on a circumference of the smaller circle forming a straight line that passes through the diameter of the larger circle. In other words, the smaller circle rotates about its center and rotates around the center of the larger circle.

[0063] In accordance with the preceding description, the gear-tooth-shaped protrusion 31 has an imaginary pitch circle relative to the gear-tooth shape of the protrusion 31. The imaginary pitch circle acts as the smaller circle with a first point on the protrusion 31 and a second point located opposite the first point, substantially coinciding with the X-axis. The outer circumference 25 of the hollow slide 21 acts as the larger circle. The diameter of the imaginary pitch circle is equal to half the diameter of the hollow slide 21. Thus, the imaginary pitch circle of the gear-tooth shape of the protrusion 31 and the outer circumference 25 of the hollow slide 21 form the pair of Cardano circles. Therefore, the presence of the first point on the gear-tooth-shaped protrusion 31 and the second point substantially coinciding with the X-axis guides the movement of the hollow slide 21 in the YL direction

[0064] In another embodiment not shown, the first bearing portion 11 is provided with at least two flats 16, 18 as described above. The outer circumference 25 of the hollow slide 21 is provided with a protrusion 31 in the Y2 direction, and the flat 16 of the first bearing portion 11 is provided with a recess 30 in the Y2 direction. In this way, the protrusion 31 is assembled by pivoting with the recess 30. Consequently, the hollow slide 21 assembled with the drive shaft 1 is guided to move in the direction Yl, so the axis X of the first pump rotor 3 which is press fitted onto the drive shaft 1 is configured to move in the direction Yl by means of the protrusion 31 of the hollow slide 21 assembled by pivoting with the recess 30 of the first part of the bearing 11.The movement of the hollow slide 21 assembled with the drive shaft 1 in the Y2 direction is limited by the at least two flats 16, 18 of the first part of the bearing 11 of the housing 10.

[0065] In another embodiment not shown, the first part of the bearing 11 is not cylindrical, by way of non-limiting example of a cylindrical shape having a recess 30 in the Y2 direction. The outer circumference 25 of the hollow slide 21 is provided with a form complementary to the first part of the bearing 11, by way of non-limiting example the outer circumference 25 is provided with a protrusion 31 complementary to the recess 30. The protrusion 31 meshes with the recess 30 to cooperate with the first part of the bearing 11 of the axial bore 13 of the housing 10.

[0066] In another embodiment not shown, the first part of the bearing 11 is provided with a substantially elongated, oblong, oval, or rectangular shape. Any of the aforementioned shapes having at least one recess 30 in the Y2 direction is possible. The outer circumference 25 of the hollow slide 21 has at least one protrusion 31 complementary to the at least one recess 30. The protrusion 31 meshes with the recess 30.

[0067] In another embodiment not shown, the hollow slide 21 is provided with a substantially elongated, oblong, oval, or rectangular shape. Any of the aforementioned shapes having at least one protrusion 31 in the Y2 direction is conceivable.

[0068] In another embodiment not shown, more than one hollow slide 21 is mounted axially on the drive shaft 1 with respect to the X-axis, adjacent to the first pump rotor 3, and the first bearing portion 11 is provided with at least two opposing flats 16, 18. The flat 16 has a recess 30 and the flat 18 has a second recess 30a. By way of non-limiting example, the outer circumference 25 of the hollow slide 21 has a protrusion 31 and the outer circumference of a second hollow slide has a second protrusion as described above. The hollow slide 21 and the second hollow slide 21a are mounted axially on the drive shaft 1 such that the protrusion 31 of the hollow slide 21 is assembled by pivoting with the recess 30 of the flat 16 and that the second protrusion of the second hollow slide is assembled by pivoting with the recess of the flat 18.

[0069] In another example, as illustrated in [Fig.7], the housing 10 takes the form of an integrated housing 31. In other words, the cover body 19 provided with the first bearing part 11 is an integral part of the housing 10 to form a single integrated housing 31.

[0070] For all embodiments, the hollow slide 21 is made of plastic or fiber-reinforced plastic or bronze.

[0071] In all embodiments, the fluid is a lubricating oil. The electric fluid pump 100 circulates the lubricating oil for the lubrication of a vehicle transmission system.

Claims

Demands

1. Fluid pump (100), comprising: a housing (10) having an axial bore (13) extending axially along an axis X, with a first bearing portion (11) and a second bearing portion (12) supporting a cylindrical drive shaft (1), a motor (7) for driving the drive shaft (1), a pump block (9) having a first pump rotor (3) having a plurality of external teeth and a second pump rotor (5) having a plurality of internal teeth, the first pump rotor (3) being configured to rotate with the drive shaft (1) and the second pump rotor (5) being configured to rotate with the first pump rotor (3), forming a pump chamber for the fluid between the external and internal teeth, characterized in that the first bearing portion (11) is not cylindrical and the second bearing portion (12) is cylindrical cylindrical.

2. Fluid pump (100) according to claim 1, the first bearing part (11) being provided with at least two flats (16, 18) opposed to each other and parallel to the X axis to support the drive shaft (1).

3. Fluid pump (100) according to claim 1 or 2, the first bearing part (11) being provided with a substantially elongated or oblong or oval or rectangular shape.

4. Fluid pump (100) according to any one of claims 1 to 3, the first bearing part (11) being provided with at least one recess (30).

5. Fluid pump (100) according to any one of claims 1 to 4, a hollow slide (21) being positioned radially with respect to the X axis between the drive shaft (1) and the first bearing part (H).

6. Fluid pump (100) according to claim 5, the hollow slide (21) being provided with an outer circumference (25) configured to cooperate with the first bearing part (11) and an inner cylindrical opening (23) configured to receive the drive shaft (1).

7. Fluid pump (100) according to claims 4 and 6, the outer circumference (25) of the hollow slide (21) being provided with at least one protrusion (31) intended to pivot in at least one recess (30).

8. Fluid pump (100) according to claims 2 and 6, the outer circumference (25) of the hollow slide (21) being provided with at least two surfaces (27, 29), preferably two flats, opposite each other and parallel to the X axis intended to cooperate with the at least two flats (16, 18) in the first part of the bearing (11).

9. Fluid pump (100) according to claim 5, the hollow slide (21) being provided with a substantially elongated or oblong or oval or rectangular shape.

10. Fluid pump (100) according to any one of the preceding claims, the pump block (9) being placed on the drive shaft (1) axially along the X axis between the first bearing part (11) and the second bearing part (12).

11. Fluid pump (100) according to any one of the preceding claims, the casing material (10) being a plastic material or a fiber-reinforced plastic material.

12. Fluid pump (100) according to any one of claims 5 to 9, the material of the hollow slide (21) being a plastic material or a fiber-reinforced plastic material or a bronze.

13. Fluid pump (100) according to any one of the preceding claims, the housing (10) comprising a housing body (15) and a cover body (19) mounted on the housing body (15), and the first bearing part (11) being located in the cover body (19).

14. Fluid pump (100) according to claim 13, the cover body (19) comprising the first bearing part (11) forming an integral part of the housing (10) to form an integrated housing (31).

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