Description

The invention relates to a motor housing assembly for an electric machine for driving a motor vehicle, and an electric machine with such a motor housing assembly.

From EP 3859951 A1 , a motor housing assembly for cooling a motor assembly is known. The motor housing assembly includes a stator and a rotor. To reduce a weight and a manufacturing cost, the motor housing assembly includes an aluminum housing coupled to an outer circumferential surface of a motor assembly and configured to form a first space between the aluminum housing and the motor assembly, the first space including an oil flow channel, and a plastic housing coupled to an outer circumferential surface of the aluminum housing and configured to form a second space between the plastic housing and the aluminum housing, the second space including a water flow channel.

From US 2017/0302133 A1 , an electric pump motor is known comprising a permanent magnet rotor, a wound stator and a motor housing made of plastic material.

From US 2006/0071567 A1 , a housing assembly is known for a permanent magnet motor. The housing assembly includes a ferrous flux ring structure. A plastic housing encapsulates the exterior of the flux ring structure. A bearing is provided in a closed end of the housing.

From US 2019 0027993 A1 , an electric motor utilized in vehicle actuators is known including an electrically conductive plastic housing. From US 10 680 486 B2, an external rotor motor is known, including a rotary shaft, a plasticpackaged stator, a plastic-packaged body, and an external rotor sleeving on the plastic-pack- aged stator.

The present invention is based on the object to propose a housing assembly for an electric machine for driving a motor vehicle, which housing assembly provides low weight and contributes to energy efficiency and sustainability. A further object is to propose an electric machine with such a housing assembly that has a good efficiency.

According to the invention, a housing assembly for an electric machine for driving a motor vehicle is proposed, comprising: an inner housing part for receiving a stator of the electric machine, wherein the inner housing part comprises a base portion and an inner jacket portion which are integrally formed of a metal material that includes aluminum, wherein the inner jacket portion comprises on an outer circumferential face a channel structure for a cooling fluid; a side part made of a metal material that includes aluminum, wherein the side part is connected to an end of the inner housing part opposite to the base portion; and an outer housing part that comprises a base portion and an outer jacket portion which are integrally formed of a plastic material, wherein the outer housing part is mounted on the inner housing part such that the outer jacket portion covers the inner jacket portion, with the channel structure being closed so as to form a circumferential cooling fluid channel.

An advantage of the proposed housing assembly is that the inner housing part and the side part, which are both formed of a metal material, jointly form a closed mechanical structure thus providing a high stiffness, wherein at the same time the housing has a very low weight due to the outer housing part made of plastic material. Overall, the housing assembly contributes to a high energy efficiency and/or cost efficiency.

In the context of the present disclosure, the term outer housing part relates to the outer jacket portion into which the inner housing part is inserted with its inner jacket portion. The outer housing can also be referred to as plastic housing part, and the inner housing part as metal housing part. Both, the outer and the inner housing parts are preferably pot-shaped, in other words, they include a base portion and a jacket portion made in one piece. The material of the inner housing part and the side part can be the same or different from each other. The metal material of the inner housing part and the side part can have a higher stiffness than the plastic material of the outer housing part. The plastic material can have a lower density than the metal material.

The inner housing part can be made of pure aluminum or an aluminum alloy, which can comprise more than 90 % by weight of aluminum, for example, with further elements of together up to 10 weight % being optionally included. The outer housing part is made of a plastic material which can be a fibre reinforced plastic, for example. Preferred material properties of the plastic material are any type of high strength plastic or plastic composite.

According to an embodiment, the base portion of the inner housing part can have a through-opening to receive a first bearing for rotatably supporting a rotor shaft of the electric machine, and the side part connected to the inner housing part can have a side part opening to receive a second bearing for rotatably supporting the rotor shaft of the electric machine. Thus, in particular radial forces acting from the first and second bearings to the housing will be well supported, with dynamic and static forces efficiently accommodated by a closed force path due to the closed casing configuration of the metal inner housing part and the metal side part connected therewith. The axial forces of the rotor shaft are preferably supported only by the bearing of the base portion of the inner housing part.

The base portion of the inner housing part serves as a bearing carrier for the rotor shaft. It can also be referred to as A-shield. A particular high stiffness may be achieved in an embodiment where the base portion, on an outer side face thereof, comprises circumferentially distributed ribs that extend from an inner sleeve portion radially outwardly, in particular with a decreasing axial height.

A contribution to particularly high structural properties can be made in an embodiment, where the base portion of the inner housing part and/or the side part comprise a reinforcement ring for receiving the respective first or second bearing. The reinforcement ring can be made of a metal material, in particular steel, that has a greater strength than the respective metal material of the base portion and the side part. The side part is connected to the inner housing part in a rigid manner and serves as a bearing carrier for the rotor shaft. The side part can also be referred to as B-shield, bearing carrier, bearing fixation rim or simply rim. The connection can be achieved by axially mounting the side part to a side face of the first housing part, for example by circumferentially distributed connecting elements, such as screws.

The side part can be disc-shaped in one embodiment. As an alternative, the side part can also have an open structure to reduce weight. In particular, the side part can include an inner ring portion forming the opening for the shaft bearing, an outer ring portion or rim to be connected to the inner housing part and circumferentially distributed web portions that extend radially between the inner ring portion and the outer ring portion. In this case, axial through-openings are formed circumferentially between respective web portions which contributes to a reduced weight. The number of webs and through-openings can be, for example, between three and 15. The connecting elements for connecting the side part to the inner housing part can be arranged circumferentially in the region of the webs, without being limited thereto.

The webs and/or through-openings can have the same or different shapes and/or circumferential extensions. In an embodiment, one of the openings may have a greater circumferential extension so as to form a passage for electronic components, such as electric cables and/or connectors. The wall portion surrounding the opening can be used to attach one or more electronic components.

According to an embodiment, the base portion of the outer housing part is closed to form an isolated chamber together with the inner housing part. A space, respectively chamber may be formed between the closed base portion of the plastic housing part and a side face of the bearing carrier. This chamber can be configured to accommodate electronical and/or mechanical components of the electric machine, such as a resolver or electric connectors.

The plastic housing part can comprises a reinforcement ring at an end facing the base portion of the metal housing part. The reinforcement ring can comprise an inner circumferential face that is centered on an outer circumferential contact face of the metal housing part, such that the plastic housing part is coaxially arranged on the metal housing part. The coaxial connection section between the inner circumferential face of the plastic housing part, respectively reinforcement ring, and the outer contact face of the metal housing part is preferably an interference fit connection. Other sections between the plastic housing part and the metal housing part, in particular in the region along the cooling channel, may have clearance. The reinforcement ring is preferably made of a material that has a higher strength than the plastic material of the main body of the plastic housing part. In particular, a metal ring can be used as reinforcement ring. The reinforcement ring can include a plurality of circumferentially distributed radial projections that can be configured as flange connections for being connected to the metal housing part.

A first sealing can be provided between an inner circumferential face of the reinforcement ring and a circumferential groove of the inner housing part. However, the sealing can also be provided so as to contact an inner circumferential face of the plastic housing part instead of a reinforcement ring. The sealing can be axially shorter than the axial length of the reinforcement ring. Thus, the reinforcement ring is radially supported on the outer contact face of the metal housing part axially adjacent to the first sealing.

The plastic housing part can have a plurality of circumferentially distributed connecting elements for being connected with the base portion of the metal housing part. The connecting elements can be configured as flange portions into which bolts may be screwed to attach the plastic housing to the metal housing. The dimensions of the plastic and metal housing parts can be such, that in the mounted condition, at least in one axial section, preferably close to the open end of the plastic housing part, the inner circumferential surface of the plastic housing part is in pretension contact with the outer circumferential surface of the metal housing part. In other axial sections, in particular along the axial extension of the cooling channel, there may be radial clearance between the inner face of the plastic housing and the outer face of the metal housing. At the axial end of the metal housing part, there may be an interference fit again between the metal and plastic housing part.

Furthermore, with respect to the above object, an electric machine for driving a motor vehicle is proposed, comprising: a housing assembly that can be configured according to any one or more of the above embodiments; a stator connected in a rotationally fixed manner to the inner jacket portion of the inner housing part; and a rotor drivingly connected to a rotor shaft, with the rotor shaft being rotatably supported in the inner housing part and the side part about the rotor axis.

The electric machine has the same advantages as mentioned with respect to the housing assembly so that reference is hereby made to the above description. The electric machine has a low weight, high stiffness and thus overall a high energy efficiency.

Preferred embodiments of the invention are described below using the drawing figures. Herein:

Figure 1 shows a housing assembly according to the invention in a 3D exploded view;

Figure 2 shows the first housing part and side part of the housing assembly of Figure 1 in an assembled condition in a 3D sectional view;

Figure 3A shows the side part of the housing assembly of Figure 1 in a side view;

Figure 3B shows the side part of the housing assembly of Figure 1 in an axial view;

Figure 3C shows the side part of the housing assembly of Figure 1 in a sectional view according to 3C-3C of Figure 3B;

Figure 4A shows the second housing part of the housing assembly of Figure 1 in a 3D view from the bottom side;

Figure 4B shows the second housing part of the housing assembly of Figure 1 in a 3D view from the opening side;

Figure 5A shows an electric machine according to the invention in a longitudinal section with a housing assembly as shown in Figures 1 to 4;

Figure 5B shows the electric machine of Figure 5A in a 3D exploded view; and

Figure 6 shows a detail of the housing assembly of Figure 5A in a modified embodiment. Figures 1 to 4B, which are described together below, show a housing assembly 2 according to the invention. The housing assembly 2 is for an electric machine for driving a motor vehicle (not shown). The housing assembly 2 includes an inner housing part

3 for receiving a stator of the electric machine, a side part 4 connectable to an end section of the inner housing part 3, and an outer housing part 5 that is connectable to the inner housing part 3.

The inner housing part 3 comprises a base portion 6 and a jacket portion 7 which are integrally formed of a metal material, in particular a light metal material such as aluminum or an aluminum alloy. To that extent, the inner housing part 3 can also be referred to as metal housing part. The metal housing part can be produced by a casting process, for example. The metal material can contain aluminum, for example, with an amount of at least 90 weight %, wherein further elements of together up to 10 weight % can optionally be included. The side part 4 can be connected to an end section of the inner housing part 3 opposite to the base portion 6 by suitable connecting means 8 such as screws, without being limited thereto. The side part 4 is also made of a metal material, in particular a light metal material such as aluminum or an aluminum alloy. The inner housing part 3 and the side part 4 can be made of the same or different metal materials.

The base portion 6 of the metal housing forms a bearing carrier for a rotor shaft of the electric machine, and can also be referred to as A-shield. A through-opening 16 is provided in the base portion 6 through which a rotor shaft of the electric machine can extend, wherein the rotor shaft can be rotatably supported by means of a first bearing 17. A clamping ring 18 can be provided to axially fix the bearing 17. The base portion 6 can optionally comprise, on an outer side face thereof, circumferentially distributed ribs 21 that extend from an inner sleeve portion 31 radially outwardly with a decreasing axial height.

At the opposite end, the side part 4 serves as a second bearing carrier for the rotor shaft, and can also be referred to as B-shield. The side part 4 comprises an opening 19 to receive a second bearing 20 for rotatably supporting the rotor shaft. The side part

4 can optionally comprise a reinforcement ring 47 for receiving the bearing 20. The reinforcement ring 47 can be made of a metal material that has a greater strength than the metal of the side part 4.

Figure 2 shows the described unit comprising the inner housing part 3 with inserted first bearing 17 and side part 4 connected thereto with inserted second bearing 20 as a detail. Through this casing structure, forces acting from the first and second bearings 16, 20 to the metal housing and side part can be efficiently accommodated by a closed force path. The force path F is shown in Figure 5A. The bearing arrangement can be such that the first bearing 17 is configured as axially fixed bearing, whereas the second bearing at 20 can be configured as axially floating bearing.

The outer housing part 5 includes a base portion 9 and a jacket portion 10 which are integrally formed of a plastic material. To that extent, the outer housing part 5 can also be referred to as plastic housing part or simply plastic housing. The plastic material of the outer housing part can have a lower stiffness than the metal of the inner housing part 3 and/or side part 4. Furthermore, the plastic material can have a lower density than the metal material.

The plastic housing is mounted onto the metal housing such that the jacket portion 10 of the plastic housing covers the jacket portion 7 of the metal housing. The jacket portion 7 of the metal housing comprises, on an outer circumferential face thereof, a channel structure 12 with, for example, one or more circumferentially and/or helically extending channels formed by land portions 13. In the mounted condition, the channel structure 12 of the inner jacket portion 7 is closed by the outer jacket portion 10. The outer circumferential surface 14 of the land portions 13 can come into contact with the inner circumferential surface 15 of the outer jacket portion 10 and/or radial clearance may be provided. Thus, one or more closed cooling fluid channels 11 are formed between the inner and outer jacket portion 7, 10 through which a coolant can flow to cool the electric machine.

The side part 4, which is shown as a detail in Figures 3A to 3C, includes an inner ring portion 22 surrounding the cover opening 19 for the shaft bearing, an outer ring portion 23 to be connected to the metal housing part and circumferentially distributed web portions 24 that extend radially between the inner ring portion 22 and the outer ring portion 23. Axial through-openings 25 are respectively formed circumferentially between adjacent web portions 24. In the present embodiment, the side part 4 comprises a plurality of openings 25 that have the same shape, and one opening 25' that has a greater circumferential extension of in particular more than 30° around the longitudinal axis A2. The greater opening 25' can serve to attach and/or pass through one or more electronic components, such as cables and connectors 30 for the stator of the electric machine (as shown in Figure 5A).

At the radially outer ring portion 23, the side part 4 comprises circumferentially distributed connecting elements 27 for rigidly attaching the side part 4 to the metal housing. Furthermore, as can be seen in Figures 3A and 3C, the side part 4 can include a circumferentially extending centering portion 31 that interacts with a respective centering face of the inner housing part 3 such that, in the mounted condition, the side part 4 is coaxially connected to the inner housing part 3. The side part 4 can comprise, at a side face of the inner ring portion 22, attaching means 26 to attach an electronic component, in particular a resolver for the electric machine. The resolver is configured as a rotary electronical transformer for measuring rotation of the electric machine.

Figures 4A and 4B show the outer housing part 5 as a detail, where the base portion 9 and the jacket portion 10 can be seen. The base portion 9 is closed, so that in the mounted condition, the plastic housing forms a liquid-tight casing for the electric machine. The plastic housing is formed such that, in the mounted condition (as shown in Figure 5A), a space respectively chamber 28 is formed between the closed base portion 9 of the plastic housing and the side part 4 connected to the metal housing. This chamber 28 provides room for an electronic component 29 connected to the side part 4, for example a resolver.

The outer housing part 5 includes a plurality of circumferentially distributed connecting elements 32 for being connected with the base portion 6 of the metal housing part. In the present embodiment, the connecting elements are configured as circumferentially distributed flange sections into which bolts 33 can be engaged for attaching the plastic housing to the base portion 6 of the metal housing. The base portion 6 has respective flange sections 34 through which the bolts can pass through to engage with the end portion of the plastic housing. The outer housing part 5 further comprises a sealed connecting portion 35 for the bus bars 36 of the electric machine. The bus bars 36 can be overmolded into the connecting portion 35 of the plastic housing. Furthermore, the outer housing part 5 comprises fluid connectors 37, 37' for the supply respectively return of the cooling channel 11 of the cooling fluid. For a high stiffness, the plastic housing can optionally comprise longitudinally and/or circumferentially extending ribs 38, 39.

A first sealing ring 40 is provided between an inner circumferential face of the outer housing part 5 and a circumferential groove of the inner housing part 3. A second sealing ring 41 is provided at the axially opposite end between the inner circumferential face of the outer housing part 5 and a second circumferential groove of the inner housing part 3 (shown in Figures 2 and 5A).

Figures 5A and 5B show an electric machine 42 for driving a motor vehicle which includes a housing assembly according to the invention as described with respect to Figures 1 to 4. The same and/or corresponding components are provided with the same reference signs as in Figures 1 to 4 so that reference is made to the above description with regard to the structure and mode of operation.

The electric machine 42 comprises, in addition to the housing assembly 2, a stator 43 connected in a rotationally fixed manner to the jacket portion 7 of the metal housing part and a rotor 44 drivingly connected to a rotor shaft 45. One end of the rotor shaft 45 is rotatably supported in the base portion 6 of the inner housing part 3 and the opposite end of the rotor shaft 45 is rotatably supported in the side part 4. The shaft 45 is thus rotatably supported about the axis of rotation A2.

In a modified embodiment shown in Figure 6, the outer housing part 5 can comprise a reinforcement ring 46 at an end section thereof. The reinforcement ring 46 can be made of a metal material, such as steel, for example. The reinforcement ring 46 comprises an inner circumferential face that is centered on the outer circumferential contact face 14' of the metal housing part so that the two parts (3, 5) are coaxially arranged. In an embodiment with reinforcement ring 46, the sealing 40 can be arranged within the axial extension of the reinforcement ring. In this case, the reinforcement ring 46 is preferably axially longer than the sealing so that the reinforcement ring 46 is radially supported on the outer contact face 14' of the inner housing part 3 axially adjacent to the sealing ring 40.

Reference Numerals

2 housing assembly

3 inner housing part

4 side part

5 outer housing part

6 base portion (3)

7 jacket portion (3)

8 connecting means

9 base portion (5)

10 jacket portion (5)

11 cooling channel

12 channel structure

13 land portion

14, 14' circumferential surface (13)

15 circumferential surface (9)

16 through-opening

17 bearing

18 clamping ring

19 cover opening

20 bearing

21 ribs

22 inner ring portion

23 outer ring portion

24 web portion

25 opening (4)

26 attaching means

27 connecting elements

28 chamber 29 electronic component

30 connector

31 sleeve portion

32 connecting elements

33 bolts

34 flange sections

35 connecting portion

36 bus bars

37, 37' fluid connectors

38 ribs

39 ribs

40 sealing ring

41 sealing ring

42 electric machine

43 stator

44 rotor

45 rotor shaft

46 reinforcement ring

47 reinforcement ring

A axis

F force path