ELECTRIC MACHINE

Abstract

An electric machine for a vehicle is disclosed. The electric machine includes a stator and a rotor rotatable relative to the stator about a rotational axis that defines an axial direction. A housing at least partially surrounds a housing interior and includes a first housing part and a second housing part that bound the housing interior. The rotor is rotatably mounted on the first housing part and the second housing part via a bearing device. At least one heat transmission body is arranged along the axial direction between at least one of the first and second housing parts and the rotor. The heat transmission body bounds, together with the at least one of the first and second housing parts, a coolant space through which a coolant can flow.

Claims

1. An electric machine for a vehicle, comprising: a stator and a rotor rotatable relative to the stator about a rotational axis that defines an axial direction, a housing at least partially surrounding a housing interior, wherein the housing includes a first housing part and a second housing part that bound the housing interior and the rotor is rotatably mounted on the first housing part and the second housing part via a bearing device, at least one heat transmission body is arranged along the axial direction between at least one of the first housing part and the second housing part and the rotor, the at least one heat transmission body bounds, together with the at least one of the first housing part and the second housing part, a coolant space through which a coolant can flow.

2. The machine as claimed in claim 1, wherein the at least one heat transmission body is provided separately from the first housing part and the second housing part.

3. The machine as claimed in claim 1, wherein at least one of: the at least one heat transmission body and the first housing part and the second housing part are provided non-uniformly in respect of material, a material of the at least one heat transmission body has a higher thermal conductivity than a material of at least one of the first housing part and the second housing part, and a material of at least one of the first housing part and the second housing part has at least one of a higher upper yield strength and a higher creep limit than a material of the at least one heat transmission body.

4. The machine as claimed in claim 1, wherein the at least one heat transmission body and the rotor comprise a heat transmission structure for transmitting heat from the rotor to the at least one heat transmission body.

5. The machine as claimed in claim 4, wherein the heat transmission structure and the first housing part and the second housing part are provided non-uniformly in respect of material.

6. The machine as claimed in claim 4, wherein a material of the heat transmission structure has a higher thermal conductivity than a material of at least one of the first housing part and the second housing part.

7. The machine as claimed in claim 4, wherein the at least one heat transmission body and the heat transmission structure are provided uniformly in respect of material.

8. The machine as claimed in claim 1, wherein the rotor is mounted directly on the first housing part and the second housing part.

9. The machine as claimed in claim 4, wherein the rotor is not mounted on the first housing part and the second housing part via the heat transmission structure or via the at least one heat transmission body.

10. The machine as claimed in claim 1, wherein a wall thickness, measured in the axial direction, of at least one of the first housing part and the second housing part is at least twice a wall thickness of the at least one heat transmission body.

11. The machine as claimed in claim claim 1, wherein the at least one heat transmission body includes two heat transmission bodies bounding the coolant space, wherein a first heat transmission body of the two heat transmission bodies is arranged along the axial direction between the first housing part and the rotor, and a second heat transmission body of the two heat transmission bodies is arranged along the axial direction between the rotor and the second housing part.

12. The machine as claimed in claim 1, wherein: the bearing device comprises a first bearing element and a second bearing element that are arranged at an axial distance from one another, such that the rotor is arranged axially between the first bearing element and the second bearing element, and the axial position of the first bearing element and the second bearing element is defined such that that less than 35% of the radial forces taken up by the first bearing element and the second bearing element are passed on to the at least one heat transmission body.

13. The machine as claimed in claim 1, wherein: the bearing device comprises a first bearing element via which the rotor is mounted on the first housing part, and comprises a second bearing element arranged axially at a distance from the first bearing element and via which the rotor is mounted on the second housing part, a distance measured along the axial direction between the at least one heat transmission body and the first housing part is larger than a distance measured along the axial direction between the first bearing element and the first housing part, and a distance measured along the axial direction between a second heat transmission body and the second housing part is larger than a distance measured along the axial direction between the second bearing element and the second housing part.

14. The machine as claimed in claim 1, wherein the stator is attached to at least one of the first housing part and the second housing part.

15. The machine as claimed in claim 1, wherein the stator is arranged at a distance from the at least one heat transmission body.

16. The machine as claimed in claim 1, wherein one of: the at least one heat transmission body is attached to the at least one of the first housing part and the second housing part; and the at least one heat transmission body and the at least one of the first housing part and the second housing part are provided in one piece.

17. The machine as claimed in claim 1, wherein the heat transmission structure comprises at least two projections that protrude axially from the rotor toward the at least one heat transmission body and engage in complementary recesses that are provided on the at least one heat transmission body.

18. The machine as claimed in claim 1, wherein the heat transmission structure comprises at least two projections that protrude axially from the at least one heat transmission body to the rotor and engage in complementary recesses that are provided on the rotor.

19. The machine as claimed in claim 17, wherein the at least two projections are structured as a comb.

20. The machine as claimed in claim 1, wherein a distance, which is measured in a region of the heat transmission structure, between the at least one heat transmission body and the rotor along the axial direction, is at maximum 1 mm.

21. The machine as claimed in claim 1, wherein the at least one heat transmission body is a deep-drawn component extending at least in certain sections transversely to the axial direction with a wall thickness measured along the axial direction at maximum 3 mm.

22. The machine as claimed in claim 21, wherein at least one of a recess depth and a projection height of recesses or projections, which form the heat transmission structure on the at least one heat transmission body, is at least three times the wall thickness of the deep-drawn component.

23. The machine as claimed in claim 1, wherein at least one of the first housing part and the second housing part has an attachment section to which the at least one heat transmission body is attached, wherein the bearing device for rotatably mounting the rotor is also provided on the attachment section.

24. The machine as claimed in claim 23, wherein the attachment section is a sleeve that projects inward into the housing interior along the axial direction from the at least one of the first housing part and the second housing part, and on the inner side of the sleeve a bearing element of the bearing device is arranged.

25. The machine as claimed in one of the preceding claims claim 1, wherein the first housing part and the second housing part are composed of a different material than the at least one heat transmission body.

26. The machine as claimed in claim 1, wherein a material of at least one of the first housing part and the second housing part has a thermal conductivity which is lower than a thermal conductivity of the at least one heat transmission body.

27. The machine as claimed in claim 1, wherein a material of the at least one heat transmission body has a thermal conductivity of at least 100 W/(m*k).

28. The machine as claimed in claim 1, wherein the housing further includes a third housing part formed radially limited and from plastic via encapsulation of the stator by injection molding.

29. The machine as claimed in claim 1, wherein an annular gap, which is part of the coolant space, is provided between winding end sections that project into the coolant space.

30. The machine as claimed in claim 1, wherein the at least one heat transmission body is locked exclusively via axial compression.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In the drawings, in each case in a schematic form:

[0048] FIG. 1 shows an example of an electric machine according to the invention in a longitudinal section along the rotational axis of the rotor, and

[0049] FIG. 2 shows a view of a detail of FIG. 1 in the region of the heat transmission body.

DETAILED DESCRIPTION

[0050] FIG. 1 illustrates an example of an electric machine 1 according to the invention. The machine 1 comprises a housing 2 which surrounds a housing interior 3. A stator 4 and a rotor 5 are arranged in the housing interior 3. The stator 4 can have a stator body 12 and a plurality of stator coils 13 (not illustrated in more detail in FIG. 1) which are embedded into the stator body 12 and can be energized electrically to drive the rotor 5. The stator 4 is permanently provided on a circumferential wall 14 of the housing 2.

[0051] The rotor 5 comprises a rotor shaft 6 and a plurality of permanent magnets 7 (not illustrated in more detail in FIG. 1) which are arranged in a co-rotational fashion on the rotor shaft 6. The rotor 5 can rotate relative to the stator 3 about a rotational axis D which is defined by the center longitudinal axis M of the rotor shaft 6. An axial direction A of the electric machine 1 is defined by the rotational axis D. A radial direction R extends away perpendicularly from the rotational axis D. A circumferential direction U runs around the rotational axis D. The permanent magnets 7 of the rotor 5 can be arranged with alternating magnetic polarization along the circumferential direction U of the rotor shaft 6. In other words, magnetic north poles N and magnetic south poles S alternate along the circumferential direction U.

[0052] As is apparent from FIG. 1, the housing 2 comprises a first and a second housing part 8a, 8b. These two housings parts 8a, 8b are also known to a person skilled in the art as what are referred to as “end plates” which bound the housing interior 3 along the axial direction A. A further third housing part 8c, which bounds the machine radially, is formed by an injection-molded encapsulation of the stator 5, which is made of plastic. The first and second housing parts 8a, 8b can also be embodied separately with respect to the third housing part 8c. The rotor 5 with the rotor shaft 6 is rotatably mounted on the housing 2 by means of a bearing device 9. For this purpose, the bearing device 9 comprises a first bearing element 10a, by means of which the rotor shaft 6 is rotatably mounted on the first housing part 7a. Correspondingly, the bearing device 9 comprises a second bearing element 10b, which is axially arranged at a distance from the first bearing element 10a, so that the rotor is arranged axially between the two bearing elements 10a, 10b, and by means of which second bearing element 10b the rotor shaft 6 is rotatably mounted on the second housing part 8b.

[0053] The two bearing elements 10a, 10b—also known to a person skilled in the art by the term “shaft bearing”—are for this purpose permanently connected to the first or second housing part 8a, 8b. The stator 4 with the stator body 12 and the stator coils 13 is also attached to the housing parts 8a, 8b, 8c.

[0054] Furthermore, a first and a second heat transmission body 11a, 11b for conducting away waste heat generated by the rotor 5 including its permanent magnets 7 during operation are provided in the housing interior 3. The two heat transmission bodies 11a, 11b are formed separately with respect to the two housing parts 8a, 8b and bound, together with the two housing parts 8a, 8b, a coolant space 15 which is formed as a cooling duct and through which a coolant K can flow. The first and second heat transmission bodies 11a, 11b and the housing parts 8a, 8b which are respectively assigned to the heat transmission bodies 11a, 11b are therefore each embodied in two parts. The first heat transmission body 11a can be attached to the first housing part 8a, for example by means of a materially joined connected. Correspondingly, the second heat transmission body 11b can preferably also be attached to the second housing part 8b by means of a materially joined connection. As an alternative to a materially joined connection it is also possible to consider a suitable releasable connection. The two heat transmission bodies 11a, 11b of the heat transmission structure 18 are preferably locked here exclusively by axial pressure. The rotor 5 is expediently mounted directly on the housing parts 8a, 8b. In particular, the rotor 5 is, as is apparent in FIG. 1, not mounted on the housing parts 8a, 8b via the heat transmission structure 18 and also not via the heat transmission bodies 11a, 11b.

[0055] The first heat transmission body 11a is arranged along the axial direction A between the first housing part 8a and the rotor 5. The second heat transmission body 11b is arranged along the axial direction A between the rotor 5 and the second housing part 8b. The coolant K can take up, via the two heat transmission bodies 11a, 11b, heat generated by the rotor 5 during the operation of the machine 1, so that overheating and associated damage to or even destruction of the machine 1 can be avoided. A coolant inlet 16 for feeding the coolant K into the coolant space 15 is provided on the external circumference of the housing 2 in the first housing part 8a, and a coolant outlet 17 for discharging the coolant K from the coolant space 15 is provided in the second housing part 8b. Heat is passed on to the coolant K flowing through the coolant space 15 and carried away from said space out of the machine 1 via the two heat transmission bodies 11a, 11b which each partially bound the coolant space 15.

[0056] The two heat transmission bodies 11a, 11b can both be embodied as cooling plates 22a, 22b which extend at least in certain sections transversely with respect to the axial direction A, that is to say along the radial direction R, and their wall thickness W measured along the axial direction A, in the region of the heat transmission structure 18, is at maximum 3 mm. The cooling plates 22a, 22b can be implemented by means of deep-drawn shaped sheet metal parts. As is apparent from FIG. 1, the two heat transfer bodies 11a and 11b are arranged at a distance from the stator 4 with the stator body 12 and only rest loosely against the latter with their contact sections 19. For example, a wall thickness, which is measured in the axial direction A, of the first and second housing parts 8a, 8b is at least twice, preferably at least five times, a wall thickness of the first and second heat transmission bodies 11a, 11b.

[0057] The heat transmission structure 18 and the two housing parts 8a, 8b are embodied non-uniformly in respect of the material. Likewise, the two heat transmission bodies 11a, 11b are embodied non-uniformly in respect of material in comparison with the two housing parts 8a, 8b. In comparison, the two heat transmission bodies 11a, 11b and the heat transmission structure 18 are embodied uniformly in respect of material. The material of the heat transmission structure 18 expediently has a higher thermal conductivity than the material of the first and second housing part 8a, 8b. Moreover, the material of the heat transmission body has a higher thermal conductivity than the material of the two housing parts 8a, 8b. The material of the two housing parts 8a, 8b has a thermal conductivity which is lower than the thermal conductivity of the heat transmission body 8a, 8b. In this way, costs can be saved during the production of the machine 1, since suitable materials with a high thermal conductivity are usually more expensive than materials with a low thermal conductivity. In order to ensure a high heat transmission performance from the rotor 5 to the respective housing part 8a, 8b via the heat transmission body 11a, 11b, the material of the heat transmission body 11a, 11b has a thermal conductivity of at least 100 W/(m*k), preferably of at least 150 W/(m*k).

[0058] The axial position of the bearing elements 10a, 10b along the axial direction A is expediently defined such that less than 35%, preferably less than 10%, of radial forces taken up by the bearing elements 10a, 10b is passed on to the heat transmission bodies 8a, 8b. This avoids overloading of the respective heat transmission body 8a, 8b.

[0059] The material of the first and second housing parts 8a, 8b can also have a higher upper yield strength and a higher creep limit than the material of the heat transmission bodies 11a, 11b.

[0060] In the text which follows, reference is made to FIG. 2 which is an illustration of a detail of FIG. 1 in the region of the first heat transmission body 11a. As is illustrated by FIG. 2, a heat transmission structure 18 for transmitting waste heat from the rotor 5 to the heat transmission body 11a is formed on the first heat transmission body 11a and on the rotor 5. According to FIG. 2, the heat transmission structure 18 comprises a plurality of projections 21 which protrude from the rotor 5 toward the first heat transmission body 11 a along the axial direction A and engage in complementary recesses 20 provided on the heat transmission body 11a. In an alternative variant (not illustrated in more detail in FIGS. 1 and 2), it is conceivable that the first heat transmission body 11a comprises a plurality of projections 21 which protrude axially from the heat transmission body toward the rotor 5 and which engage in recesses 20 which are complementary to the projections 21 and are provided on the rotor 5. The projections 21 can preferably be embodied in the manner of a comb. A distance X measured in the region of the heat transmission structure 18 between the heat transmission body 11a and the rotor 5 along the axial direction is at maximum 1 mm, preferably at maximum 0.5 mm. A recess depth T1 of the recesses T1 which form the heat transmission structure 18 on the first heat transmission body 11a and a projection height H1 of the projections 21 which form the heat transmission structure 18 on the first heat transmission body 11a is at least three times, preferably at least five times, the abovementioned wall thickness W of the cooling plate.

[0061] The illustration in FIG. 2 also indicates that the first housing part 8a has a (first) attachment section 23a to which the first heat transmission body 11a is attached. In addition, the bearing device 9 for rotatably mounting the rotor 5 is provided on the (first) attachment section 23a. The (first) attachment section 23a is expediently embodied as a sleeve 24 which projects axially inward from the first housing part 11a into the housing interior 3 and on whose inner side 25 the first bearing element 10a of the bearing device 9 is arranged. The second housing part 8b also has such a (second) attachment section (23b) to which the second heat transmission body 11b and the rotor 5 are attached. Likewise, the second bearing element 10b of the bearing device 9 can be provided on the second attachment section 23b.

[0062] The preceding considerations explained above with reference to FIG. 2, relating to the first heat transmission body 11a and to the first housing part 8a assigned to this first heat transmission body 11a also apply mutatis mutandis to the second heat transmission body 11b and to the second housing part 8b which is assigned to the second heat transmission body 11b.

[0063] An annular gap 27 can be respectively formed between winding end sections 26 of the stator coils 13, which project into the coolant space 15, and the heat transmission bodies 11a, 11b, said annular gap 27 being part of the coolant space 15.