CN110998064A

CN110998064A - Pump assembly

Info

Publication number: CN110998064A
Application number: CN201880053022.0A
Authority: CN
Inventors: A.施泰纳; H.黑歇尔; M.因纳比希勒; A.德尼科洛; O.弗兰切斯基; T.马洛戈夫斯基
Original assignee: GKN Sinter Metals SpA
Current assignee: GKN Sinter Metals SpA
Priority date: 2017-06-16
Filing date: 2018-06-15
Publication date: 2020-04-10
Also published as: EP3638883A1; US20210140427A1; DE102018108192A1; JP2020528521A; WO2018229244A1; IT201700067438A1

Abstract

The invention relates to a pump assembly (1) comprising at least one housing (2) and two gears (6, 7) as transmission means and a drive shaft (15). The housing (2) comprises at least one base (3) and one cover element (4) which can be connected together to form a pressure chamber (5). Each of the two gears (6, 7) has a tooth portion (8) on an outer circumferential surface and meshes with each other via the tooth portion (8) to transmit fluid. The gears (6, 7) are arranged in the pressure chamber (5) between the base (3) and the cover element (4) along the axial direction (9). The drive shaft (15) extends in the axial direction (9) into the housing (2) via an opening (16) in the cover element (4). The first gear (6) is arranged on a first bearing bush (10), wherein the first bearing bush (10) is mounted only in the base part (3) and the first gear (6) is connected to the drive shaft (15) in the circumferential direction (25) via a form-fit connection.

Description

Pump assembly

Technical Field

The present invention relates to a pump assembly. Pump assemblies are envisaged for the purpose of delivering fluids. The pump assembly includes a housing, a transfer device in the housing for conveying fluid from a fluid inlet to a fluid outlet, and a drive shaft for driving the transfer device. The fluid inlet and the fluid outlet are disposed on the housing. At least one of the transmission devices is driven by a drive shaft extending from outside the housing into the housing. Two gears which mesh with one another are envisaged as transmission means. Each gear has a toothing on a circumferential surface, wherein the gears are connected to one another via the toothing. The drive shaft is assigned to an electric drive, which is arranged, for example, outside the housing of the pump assembly.

Background

The gear has a rotational axis, which is specifically oriented in the axial direction. The gears are arranged next to each other in the radial direction and overlap in the axial direction, wherein the rotational axes are arranged parallel to each other.

The drive shaft likewise has an axis of rotation which is arranged, in particular, parallel to and preferably coaxial with the axis of rotation of the gear.

In such a pump assembly, the transmission can be arranged on the shaft, and the shaft can be mounted on either side of the transmission in the housing at the location of the bearing. Furthermore, the drive shaft can be directly connected to the transmission means, and the transmission means can be mounted on the drive shaft at the bearing location. The expression mounting is used here to indicate in particular that forces acting in the radial direction (if appropriate additionally in the axial direction) can be transmitted at least in the radial direction (if appropriate also in the axial direction) via the transmission means onto the shaft or onto the bearing of the shaft in the housing (that is to say, for example, onto the base or cover element). However, supporting the shafts on both sides of the transfer device requires accurate adjustment of the positional tolerances of the bearing positions on the housing. In particular, uneven loading of the bearing locations and bending loads of the shaft can occur.

In view of this, it is an object of the present invention to at least partially solve the problems described in relation to the prior art. In particular, the simplest, lightest possible embodiment of the pump assembly is proposed, and the aim is to reduce or even prevent uneven loading of the bearing locations.

Disclosure of Invention

In order to achieve said object, a pump assembly according to the features of patent claim 1 is proposed. Advantageous further developments are the subject matter of the dependent patent claims. The features listed individually in the patent claims can be combined with one another in a technically expedient manner and can be supplemented by explanatory facts from the description and details from the drawings, in which further variant embodiments of the invention are proposed.

This is assisted by a pump assembly, wherein the pump assembly comprises at least the following parts:

-a housing having at least one base part and one cover element which can be connected together to form a pressure chamber;

- (at least) two gears (as transmission means) each having a tooth portion on an outer circumferential surface and meshing with each other via the tooth portions so as to transmit fluid; wherein the gear is arranged in the pressure chamber in the axial direction between the base and the cover element; and

a drive shaft extending in an axial direction through an opening in the cover element into the housing.

At least a first of the two gears can be driven by the drive shaft as an input gear. At least the first gear is embodied as a ring gear, wherein the first gear is arranged on the first bearing bush. The first bearing bush is mounted only in the base. The first gear wheel is connected to the drive shaft in the circumferential direction via a form-fit connection.

In particular, the second gear is also embodied as a ring gear, wherein the second gear can be arranged on the second bearing bush. The second bearing bush can (merely or alternatively) be mounted in the base or in the cover element.

Two gears which mesh with one another are envisaged as transmission means. Each gear has a tooth portion on an outer circumferential surface, wherein the gears are connected to each other via the tooth portions. Each of the gears has an axis of rotation, which is specifically oriented in the axial direction. The gears are arranged next to each other in the radial direction and overlap each other in the axial direction, wherein the rotational axes are arranged parallel to each other.

The drive shaft likewise has an axis of rotation which is arranged in particular parallel to and preferably coaxial with the axis of rotation of the gear wheel.

The housing is formed by at least one base part and a cover element. These are arranged one after the other in the axial direction, with the gear wheel positioned between them. The base and the cover element surround the gear wheel on the outside in the radial direction and thus form a pressure chamber. The pressure chamber is connected to the fluid inlet and the fluid outlet such that fluid can be supplied to the fluid outlet via the fluid inlet and the pressure chamber.

In particular, the bearing bushing is embodied as a so-called plain bearing or friction bearing. In a plain/friction bearing, the two parts which move relative to one another (in this case the gear and the bearing bush or the bearing bush and the housing, that is to say the base and the cover element) are in direct contact. They slide on each other against the resistance caused by the sliding friction. This can be kept at a low level by selecting a low friction material combination, by lubrication or by creating a lubrication film separating the two contact surfaces from each other (full fluid film lubrication). However, rolling bearings are also conceivable, wherein one rolling bearing is arranged between the housing and the bearing bushing or between the bearing bushing and the gear.

In particular, the fluid supplied by the pump acts as a lubricant for the bearings. In this case, special fluid passages in the base and/or cover element can be envisaged, through which a portion of the fluid supplied by the pump is guided to the bearing location.

It is proposed here that at least a first gearwheel, and in particular each gearwheel serving as a transmission, is mounted in the housing on the bearing bush only on one side (or unilaterally) of the gearwheel (that is to say either in the base part or in the cover element, and in the case of the first gearwheel in the base part). The bearing bushes envisaged for supporting each gearwheel extend from the gearwheel only to the base or cover element. As a result, the bearing bushing is mounted or fixed in the housing only on one side of the gear and therefore has only one (single) bearing position. The forces acting in the radial direction are thus transmitted from the gear to the bearing bush (via the bearing location between the gear and the bearing bush) and from the bearing bush to the housing via the bearing location present on only one side of the gear (between the bearing bush and the housing).

In particular, the two components of the group consisting of the first bearing bush and the second bearing bush are mounted or fixed only in the base. In particular, the two bearing bushes extend in the direction of the same part of the housing (that is to say also in the same axial direction) from the respective gear wheel.

This arrangement is particularly advantageous because in this way only on one of the parts of the housing (that is to say on the base) must the appropriate tolerances of position be guaranteed.

In particular, it is proposed to envisage sliding contact bearings between the (each) bearing bush and the (respective) gear wheel implemented as a ring gear. The bearing bush is preferably arranged in the housing (that is to say in the base or in the cover element) in a fixed or non-detachable manner, so that in particular a new bending load of the bearing bush can be reduced or a defined transmission of forces from the bearing bush onto the housing can take place between the bearing bush and the housing via the bearing position.

In particular, an intermediate element is arranged in the axial direction between the base part and the cover element, wherein the intermediate element surrounds the gear wheel in the radial direction on the outside and forms a pressure chamber together with the base part and the cover element. The intermediate element is in particular a disk element which has a tolerance with respect to the width of the gear wheel and thus defines the length of the pressure chamber in the axial direction.

In particular, at least the base and the cover element (and, if appropriate, additionally the intermediate element) are aligned with one another and connected to one another via a connecting element. In particular, at least one of the connecting elements extends in the axial direction through the intermediate element and connects the base and the cover element.

It is proposed here that at least the first gear wheel can be driven as an input gear wheel via a drive shaft, wherein the drive shaft is (directly) connected to the input gear wheel through an opening in the cover element.

Each of the gears may be driven separately via a drive shaft.

In particular, via the drive shaft, forces which do not act in the radial direction are transmitted from the gear wheel via the drive shaft to the housing. In particular, the drive shaft therefore transmits only the drive torque acting in the circumferential direction to the input gear.

In particular, the drive shaft is arranged with free play in the radial direction with respect to the first gear wheel and the first bearing bushing. The expression free play is used in this context to indicate that the rotation of the drive shaft in the radial direction relative to the first gear wheel may have a certain displacement without forces being transmitted in the radial direction by the drive shaft onto the first gear wheel or vice versa. In particular, a free play of at least 0.2 mm [ millimeter ] and preferably at least 0.5 mm is envisaged, so that a displacement of at least 0.2 mm (or at least 0.5 mm) in the radial direction in the above-described manner is possible with a concentric arrangement of the drive shaft and the first gearwheel.

In particular, the drive shaft is arranged to be mounted only outside the housing with respect to forces acting in the radial direction.

The drive shaft is preferably an integral part of an electric drive or a gearbox, for example, wherein the drive shaft is mounted on at least two bearing locations which are at a distance from one another in the axial direction (although always outside the housing).

The positive connection (acting in the circumferential direction) by the inner circumferential surface of the first gearwheel and the outer circumferential surface of the drive shaft preferably consists, for example, of an inner toothing of the first gearwheel and an outer toothing of the drive shaft.

In particular, the drive shaft and the first gear or the drive shaft and the first bearing bush constitute an abutment against displacement in the axial direction. The positioning of the drive shaft and the first gear in the axial direction can be achieved by means of an abutment. In particular, a free play between the drive shaft and the first gearwheel or between the drive shaft and the first bearing bushing is envisaged in the operation of the pump assembly, so that no axial forces can be transmitted.

In particular, the drive shaft has a reduction on its end face, so that the drive shaft can be guided, for example, by the first bearing bush with respect to the radial direction when it is introduced into the housing. In particular, the reduction on the end face serves only to ensure a free clearance between the drive shaft and the first bearing bush in operation of the pump assembly. As a result, it can be ensured that no forces acting in the radial direction are transmitted.

In particular, the first bearing bushing is connected to the base via a press fit. The second bearing bushing is (alternatively) connected to the base or the cover element, preferably via a press fit. The expression press fit is used in this context to indicate that the outer diameter of the bearing bush is (slightly) larger than the inner diameter of the positioning hole (in the housing) for the bearing bush before the bearing bush and the housing are joined together.

In particular, the first bearing bushing is connected to the base in an integral bond and is formed integrally with the base. The second bearing bushing is preferably connected to the base part or the cover element in an integrally bonded manner and is formed integrally therewith (for example embodied as a one-part or multi-part green body and then sintered together). The expression integrally bonded is used to indicate all connections in which the connection partners are held together by atomic or molecular forces. At the same time, they are inseparable connections which can only be separated by destruction of the connecting means.

In particular, at least the base and the cover element are at least partially embodied as sintered components. In particular, at least the first bearing bushing is embodied as a sintered component. Preferably, the two bearing bushes are at least partially embodied as sintered components. Most preferably, at least one of the following constituents and, if appropriate, a plurality or all of the following constituents are implemented as sintered components: a base, a cover element, an intermediate element, a bearing bush, a gear, a connecting element.

Sintered parts are components (green bodies) pressed from a material in powder form, which are subsequently subjected to a sintering process. In particular, at least one and preferably all of the base, the cover element, the intermediate element, the bearing bushing, the gear, the connecting element are produced from metal powder by pressing and sintering. In particular, the bearing bushing and the part of the housing receiving the bearing bushing (preferably of different materials) are produced as separate green bodies which are joined to one another as green bodies (preferably including the creation of a press fit) and then sintered together.

It should be noted that, for the avoidance of any doubt, the words "first", "second", … … as used herein are principally intended (merely) to distinguish between similar objects or dimensions, that is to say that they do not necessarily define, inter alia, any dependency and/or order of such objects or dimensions relative to one another. If dependencies and/or sequences are required, they are explicitly specified here or will become apparent to the skilled person when studying the embodiments described in specific terms.

Drawings

The invention and the technical environment are explained in more detail below on the basis of the drawings. It should be noted herein that the present invention is not intended to be limited by the illustrative embodiments shown herein. In particular, unless explicitly stated to the contrary, some aspects of the facts presented in the figures may also be extracted and combined with other constituents and findings from the present description and/or the figures. In particular, it must be pointed out that the figures and in particular the dimensional ratios represented are purely schematic. Like reference numerals refer to like objects so that explanations from other figures can be used in a complementary manner where appropriate. In the drawings:

FIG. 1 depicts a first pump assembly in perspective and exploded view;

FIG. 2 depicts a cross-section of the pump assembly according to FIG. 1 in a side view;

FIG. 3 depicts a cross-section of another pump assembly in a side view;

FIG. 4 depicts the pump assembly according to FIG. 3 in another side view;

FIG. 5 depicts a pump assembly in perspective and exploded views;

FIG. 6 depicts a detail of the pump assembly according to FIG. 5 in a side view;

FIG. 7 depicts further details of the pump assembly according to FIG. 5 in a side view; and

fig. 8 depicts a detail according to fig. 7 in a further side view.

Detailed Description

Fig. 1 depicts a first known pump assembly 1 in a perspective view and in an exploded view. Fig. 2 depicts a cross section of the pump assembly 1 according to fig. 1 in a side view. Fig. 1 and 2 will be described jointly below.

The pump assembly 1 comprises a housing 2 and a transfer device in the housing 2 for transferring fluid from a fluid inlet 20 to a fluid outlet 21. The fluid inlet 20 and the fluid outlet 21 are arranged on or in the housing 2. The housing 2 comprises a base part 3 and a cover element 4 as well as an intermediate element 12, which can be connected together by means of a connecting element 24 in order to form a pressure chamber 5. The transmission means are arranged in the pressure chamber 5 between the base part 3 and the cover element 4 in the axial direction 9. The intermediate element 12 surrounds the

gears

6, 7 externally in the radial direction 13. The intermediate element 12 is a disc element which has a tolerance with respect to the width of the

gears

6, 7 and thus defines the length 17 of the pressure chamber 5 in the axial direction 9. One of the transmission devices is driven via a drive shaft 15, which drive shaft 15 extends from outside the housing 2 into the housing 2. Two

gears

6, 7 which mesh with one another are envisaged here as transmission means. Each

gear

6, 7 has a toothing 8 on the outer circumferential surface, wherein the

gears

6, 7 are connected to each other via the toothing 8 for transferring fluid.

The

gears

6, 7 have an axis of rotation 22 oriented in the axial direction 9. The

gears

6, 7 are arranged next to each other in the radial direction 13 and overlap in the axial direction 9, wherein the rotational axes 22 are arranged parallel to each other.

The transmission means are arranged on the

shafts

15, 23, and the

shafts

15, 23 are mounted on either side of the transmission means in the housing 2 (that is to say in the base 3 and in the cover element 4 in this case) on bearing locations 19 (for example via sliding contact bearings 18). Furthermore, the drive shaft 15 is directly connected to the transmission means, and the transmission means is mounted on the drive shaft 15 on a bearing location 19. The expression mounted in this context is used to indicate that forces acting in the radial direction 13 (and, if appropriate, additionally in the axial direction 9) are transmitted by the transmission means at least in the radial direction 13 (and, if appropriate, also in the axial direction 9) to the

shafts

15, 23 or to the bearing locations 19 of the

shafts

15, 23 in the housing 2. However, supporting the

shafts

15, 23 on both sides of the transfer device requires accurate adjustment of the position tolerances of the bearing locations 19 on the housing 2. Uneven loading of the bearing location 19 and bending loading of the

shafts

15, 23 can occur here.

Fig. 3 depicts a cross section of another pump assembly 1 in a side view. Fig. 4 depicts a cross section of the pump assembly 1 according to fig. 3 in another side view. Fig. 3 and 4 will be described jointly below. Reference is made to the embodiments in figures 1 and 2.

The pump assembly 1 comprises a housing 2 and two

gears

6, 7 as transmission means. The housing 2 comprises a base 3, an intermediate element 12 and a cover element 4, which can be connected together by means of a connecting element 24 (as depicted in fig. 1 and 2) so as to constitute a pressure chamber 5. Each of the two

gears

6, 7 has a tooth portion 8 on an outer circumferential surface and meshes with each other via the tooth portion 8 so as to transmit fluid. The

gears

6, 7 are arranged in the pressure chamber 5 between the base 3 and the cover element 4 in the axial direction 9. The first gear 6 and the second gear 7 are each embodied as a ring gear, wherein the second gear 7 is arranged on the second bearing bush 11 and the first gear 6 is arranged directly on the drive shaft 15. The second bearing bush 11 is arranged only in the cover element 4. The

gears

6, 7 have an axis of rotation 22 oriented in the axial direction 9. The

gears

The base part 3, the intermediate element 12 and the cover element 4 are arranged one after the other in the axial direction 9, with the

gears

6, 7 positioned between them. The intermediate element 12 surrounds the

gears

6, 7 on the outside in the radial direction 13 and thus, together with the other parts of the housing 2, forms the pressure chamber 5. The intermediate element 12 is a disc element which has a tolerance with respect to the width of the

gears

6, 7 and thus defines the length 17 of the pressure chamber 5 in the axial direction 9.

The second bearing bush 11 is embodied as a so-called sliding contact bearing 18. The two parts moving relative to each other, in this case the second gear wheel 7 and the second bearing bushing 11, are in contact with each other in a sliding contact bearing 18. They slide on each other against the resistance caused by the sliding friction and constitute bearing locations 19 for the second gear wheel 7.

The second gearwheel 7 is thus mounted in the housing 2 only on one side of the second gearwheel 7, in this case via the bearing location 19 in the cover element 4. The second bearing bush 11 envisaged for supporting the second gearwheel 7 extends from the second gearwheel 7 only to the cover element 4. The second bearing bush 11 is therefore mounted or fixed in the housing 2 only on one side of the second gear wheel 7 and therefore has only one bearing point 19. The forces acting in the radial direction 13 are thus transmitted from the second gear wheel 7 to the second bearing bush 11 and from the second bearing bush 11 to the housing 2 via the bearing locations 19 which are present on only one side of the second gear wheel 7.

The first gear 6 is in this case arranged directly on the drive shaft 15 as input gear 14. The drive shaft 15 transmits a drive torque acting in a circumferential direction 25 (see arrow in fig. 4) to the input gear 14. The first gear 6 is not mounted in the housing 2. The drive shaft 15 extends into the housing 2 in the axial direction 9 via an opening 16. The drive shaft 15 is mounted in the electric drive 31 only outside the housing 2. The two bearing locations 19 are arranged there at a distance from each other in the axial direction 9. The force acting in the radial direction 13 (see arrow in fig. 4) is guided via the drive shaft 15 into the electric drive 31, for example starting from the first gearwheel 6.

Fig. 5 depicts the pump assembly 1 (without the drive shaft 15 in this case) in a perspective view and an exploded view. The embodiments in fig. 1 and 3 can be used in a complementary manner.

The pump assembly 1 comprises a housing 2 and two

gears

6, 7 as transmission means. The housing 2 comprises a base 3, an intermediate element 12 and a cover element 4, which can be connected together by means of a connecting element 24 (as depicted in fig. 1 and 2) so as to constitute a pressure chamber 5.

Each of the two

gears

6, 7 are arranged in the pressure chamber 5 between the base 3 and the cover element 4 in the axial direction 9. The first gear 6 and the second gear 7 are each embodied as a ring gear, wherein the first gear 6 is arranged on a first bearing bush 10 and the second gear 7 is arranged on a second bearing bush 11. The first bearing bush 10 and the second bearing bush 11 are each arranged only in the base part 3. The

gears

6, 7 have an axis of rotation 22 oriented in the axial direction 9. The

gears

6, 7 positioned between them. The intermediate element 12 surrounds the

gears

6, 7 and thus defines the length 17 of the pressure chamber 5 in the axial direction 9. The pressure chamber 5 is connected to the fluid inlet 20 and the fluid outlet 21 such that fluid can be supplied to the fluid outlet 21 via the fluid inlet 20 and the pressure chamber 5.

The bearing

bushes

10, 11 are designed as so-called sliding contact bearings 18. The two parts moving relative to each other, in this case the

gear wheels

6, 7 and the bearing

bushes

10, 11, are in contact with each other in a sliding contact bearing 18. They slide on each other against the resistance caused by the sliding friction and form bearing locations 19 for the

gears

6, 7.

Each

gear

6, 7 is thus mounted in the housing 2 only on one side of the

gear

6, 7, in this case in the base 3, on the bearing location 19. The bearing

bushes

10, 11 envisaged for supporting each

gear wheel

6, 7 extend from the

gear wheel

6, 7 only to the base 3. The bearing

bushes

10, 11 are therefore mounted or fixed in the housing 2 only on one side of the

gears

6, 7 and they therefore have only one bearing point 19.

A sliding contact bearing 18 is envisaged between each bearing

bush

10, 11 and the

gear wheel

6, 7 embodied as a ring gear, respectively. The bearing

bushes

10, 11 are arranged fixedly in the housing 2 (that is to say in the base 3).

The base part 3 and the cover element 4 and additionally the intermediate element 12 are oriented relative to one another and are connected to one another by means of a connecting element 24. The connecting element 24 extends in the axial direction 9 through the intermediate element 12 and connects the base 3 and the cover element 4.

One of the

gears

6, 7 can be driven as an input gear 14 via a drive shaft 15 (see fig. 6), wherein the drive shaft 15 can be connected to the input gear 14 through an opening 16 in the cover element 4. It can be seen that an internal toothing 26 is arranged on the input gear wheel 14, which internal toothing 26 interacts with the drive shaft 15 for the purpose of driving the input gear wheel 14.

Fig. 6 depicts a detail of the pump assembly 1 according to fig. 5 in a side view. Fig. 7 depicts further details of the pump assembly 1 according to fig. 5 in a side view. Fig. 6 and 7 will be described jointly below. Reference is made to the embodiment in fig. 5.

Only the

gears

6, 7, the bearing

bushes

10, 11 and the drive shaft 15 are represented in fig. 6. The base 3 is also presented in fig. 7. The drive shaft 15 extends in the axial direction 9 into the housing 2 through an opening 16 in the cover element 4 (see fig. 5). The first gear wheel 6 is connected to the drive shaft 15 in the circumferential direction 25 via a form-fit connection (in this case via an internal toothing 26).

Via the drive shaft 15, no forces acting in the radial direction 13 are transmitted from the

gears

6, 7 via the drive shaft 15 to the housing 2. The drive shaft 15 therefore transmits only one drive torque acting in the circumferential direction 25 to the input gear 14.

The form-fit connection acting in the circumferential direction 25 is formed by an inner circumferential surface 28 of the first gear wheel 6 and an outer circumferential surface 29 of the drive shaft 15, in this case via an inner toothing 26 (see fig. 5) of the first gear wheel 6 and an outer toothing of the drive shaft 15.

The drive shaft 15 and the first bearing bushing 10 form an abutment 30 which resists displacement in the axial direction 9. The positioning of the drive shaft 15 and the first gear wheel 6 in the axial direction 9 can be effected via the abutment 30. Free play in the axial direction 9 between the drive shaft 15 and the first gearwheel 6 and between the drive shaft 15 and the first bearing bushing 10 is envisaged in the operation of the pump assembly 1.

The drive shaft 15 also has a reduction 32 on its end face, so that the drive shaft 15 is guided, for example, when it is introduced into the housing 2, via the first bearing bushing 10 relative to the radial direction 13.

The drive shaft 15 is arranged with a free clearance 27 in the radial direction 13 with respect to the first gear wheel 6 and the first bearing bushing 10. The expression free play 27 indicates that the drive shaft 15 can have a certain displacement in the radial direction 13 relative to the first gearwheel 6 (and relative to the first bearing bushing 10) without forces being transmitted in the radial direction 13 from the drive shaft 15 onto the first gearwheel 6 or vice versa. The free play 27 between the first gear wheel 6 and the drive shaft 15 is equal to half the difference in diameter of the first gear wheel 6 and the drive shaft 15 in the circumferential direction 25 in the region of the positive connection between the first gear wheel 6 and the drive shaft 15. This positive connection is formed by an internal toothing 26 on an inner circumferential surface 28 of the first gearwheel 6 and an external toothing on an outer circumferential surface 29 of the drive shaft 15. Thus, a displacement of 0.2 mm in the radial direction 13 can be achieved in the above-described manner for a concentric arrangement of the drive shaft 15 and the first gear wheel 6, if a free play of 0.2 mm is envisaged. The free play 27 is in this case (only) so large that in any case or in any event a positive-fit connection between the first gearwheel 6 and the drive shaft 15 in the circumferential direction 25 is satisfied for a displacement of the drive shaft 15 relative to the first gearwheel 6 in the radial direction 13.

Fig. 8 depicts a detail according to fig. 7 in a further side view. Reference is made to the embodiment in fig. 7. The drive shaft 15 is arranged to be mounted only outside the housing 2 with respect to forces acting in the radial direction 13 (see arrows in fig. 8). The drive shaft 15 is therefore a component of the electric drive 31, wherein the drive shaft 15 is mounted on two bearing locations 19 which are arranged separately from one another in the axial direction 9 (although always outside the housing 2). No force acting in the radial direction 13 is therefore transmitted from the

gear wheels

6, 7 via the drive shaft 15 by the drive shaft 15 to the housing 2. The drive shaft 15 transmits only the drive torque acting in the circumferential direction 25 to the input gear 14.

List of reference numerals:

1 Pump Assembly

2 casing

3 base part

4 cover element

5 pressure chamber

6 first gear

7 second gear

8 tooth part

9 axial direction

10 first bearing bush

11 second bearing bush

12 intermediate element

13 radial direction

14 input gear

15 drive shaft

16 opening

17 length

18 sliding contact bearing

19 bearing position

20 fluid inlet

21 fluid outlet

22 axis of rotation

23 shaft

24 connecting element

25 in the circumferential direction

26 internal tooth part

27 free clearance

28 inner circumferential surface

29 outer circumferential surface

30 abutting part

31 electric driver

32 reduced portion.

Claims

1. A pump assembly (1) comprising at least:

-a housing (2), said housing (2) having at least one base (3) and one cover element (4) connectable together to form a pressure chamber (5);

-two gears (6, 7), the two gears (6, 7) having respective teeth (8) on an outer circumferential surface and meshing with each other via the teeth (8) for transferring a fluid; wherein the gear wheel (6, 7) is arranged in the pressure chamber (5) in an axial direction (9) between the base part (3) and the cover element (4); and

-a drive shaft (15), which drive shaft (15) extends in the axial direction (9) through an opening (16) in the cover element (4) into the housing (2);

wherein at least a first gear (6) is drivable by the drive shaft (15) as an input gear (14); wherein at least the first gear (6) is embodied as a ring gear, wherein the first gear (6) is arranged on a first bearing bush (10), wherein the first bearing bush (10) is mounted only in the base part (3); wherein the first gear wheel (6) is connected to the drive shaft (15) in the circumferential direction (25) via a form-fit connection.

2. Pump assembly (1) according to claim 1, wherein the drive shaft (15) is arranged with a free clearance (27) in radial direction (13) with respect to the first gear wheel (6) and the first bearing bushing (10).

3. Pump assembly (1) according to one of the preceding claims, wherein the drive shaft (15) is arranged to be mounted only outside the housing (2) with respect to forces acting in a radial direction (13).

4. Pump assembly (1) according to one of the preceding claims, wherein the form-fit connection is constituted by an inner circumferential surface (28) of the first gear wheel (6) and an outer circumferential surface (29) of the drive shaft (15).

5. Pump assembly (1) according to one of the preceding claims, wherein the drive shaft (15) and the first gearwheel (6) or the drive shaft (15) and the first bearing bushing (10) constitute an abutment (30) that resists displacement in the axial direction (9).

6. Pump assembly (1) according to one of the preceding claims, wherein the first bearing bushing (10) is connected to the base (3) via a press fit.

7. Pump assembly (1) according to one of the preceding claims 1 to 5, wherein the first bearing bushing (10) is connected to the base part (3) in an integrated manner and is formed integrally with the base part (3).

8. Pump assembly (1) according to one of the preceding claims, wherein at least the base (3) and the cover element (4) are at least partially implemented as sintered components.

9. Pump assembly (1) according to one of the preceding claims, wherein at least the first bearing bushing (10) is implemented as a sintered component.

10. Pump assembly (1) according to one of the preceding claims, wherein the second gear (7) is also embodied as a ring gear, wherein the second gear (7) is arranged on a second bearing bushing (11), wherein the second bearing bushing (11) is mounted only in one or the other of the base (3) and the cover element (4).