2100 The Crescent Oy/bec (2022006387)

Birmingham Business Park Q22010WQ00

Birmingham, West Midlands B37 7YE United Kingdom

Housing assembly and electric drive with such a housing assembly

Description

The invention relates to a housing assembly for an electric drive for driving a motor vehicle. Furthermore, the invention relates to an electric drive with such a housing assembly.

From US 2021 394600 A1 , an electric drive is known comprising a housing assembly, an electric machine with a hollow shaft, a planetary gearing, and a differential gearing. The housing assembly comprises a motor-sided first housing part, a gearing-sided second housing part, and an intermediate housing part disposed therebetween. The intermediate housing part includes, integrally formed, an intermediate wall, a motorside jacket portion and a gearing-side jacket portion. A sealed cavity for a coolant flowing therethrough is formed between an outer face of the motor-side jacket portion and the inner face of the first gearing part.

From WO 2019 182 622 A1 , a drive unit is known comprising an electric motor and a first circulation passage for a first coolant for cooling the electric motor and, separately therefrom, a second circulation passage for a second coolant. The second circulation passage has a heat exchange portion with the circulation passage for the first coolant. The drive unit is provided with an inverter for controlling the motor. The circulation passage for the second coolant has a cooling portion for cooling the inverter. The inverter comprises a power module with a switching transistor for converting the direct current for battery power source into a three phase alternating current for the electric motor. From US 2022 190 764 A1 , a motor-integrated inverter is known. The inverter includes a motor with a shaft disposed in a horizontal direction, and a power module configured to generate driving power for driving the motor and coupled to the motor in a direction in which the shaft is disposed.

From US 2022006349 A1 , a power generation module is known comprising: an electric motor that includes a motor housing, an inverter disposed at a first side of the motor housing and including an inverter housing configured to accommodate an insulated gate bipolar transistor (IGBT) and a capacitor, an inner housing disposed inside the motor housing and configured to accommodate a stator and a rotor. A dual flow path is provided at a circumferential surface of the motor housing. A similar module is known from US 2022 006350 A1 .

From DE 10 2020 207 101 A1 , an electric drive is known with a power electronic unit and electrical connectors. The power electronic unit is arranged on top of the housing thereby forming a T-structure.

From DE 10 2015 219 669 A1 , an electric machine is known with a stator, rotor and a power electronic unit for controlling the stator. The power electronic unit is arranged axially in front or behind the stator with respect to the motor axis.

In addition to the functionality and efficiency of the power electronics, space requirements and weight are important criteria in development. In order for electric and hybrid vehicles to operate at a particularly high level of efficiency, it is necessary to keep not only the temperature of the electric machine and the battery, but also that of the power electronics in an efficiency-optimized temperature range. To ensure this, a powerful thermal management system is needed that cools the components accordingly and keeps them within the optimum temperature window.

The present invention is based on the object to propose a housing assembly for an electric drive for a motor vehicle, which housing assembly ensures reliable cooling of the components of the electric drive and has a compact design. The object is further to provide a respective electric drive for a motor vehicle that has a high efficiency with good cooling properties and a compact design. According to the invention, a housing assembly for an electric drive for driving a motor vehicle is proposed to solve the object, which housing assembly comprises: a motor housing part with a jacket portion for accommodating a stator of the electric machine and a first gear case portion for accommodating parts of a gearing, wherein the jacket portion and the first gear case portion are integrally formed; an outer jacket part that is mountable to the jacket portion, wherein in a mounted condition, the outer jacket part and jacket portion are coaxially arranged with respect to a motor axis and include a motor cooling channel through which cooling fluid can flow for cooling the electric machine; an inverter housing part with an inverter case portion for accommodating an inverter of the electric machine and a second gear case portion integrally formed with the inverter case portion, wherein the inverter case portion is arranged axially adjacent to the second gear case portion and comprises a fluid connector that is fluid-connected to a cooling chamber within the inverter case portion, wherein the second gear case portion includes a gearbox cooling channel that is fluid-connected to the cooling chamber; wherein the first gear case portion and the second gear case portion are mechanically connectable with each other by connecting elements; wherein, in the connected condition, a closed cooling circuit is formed from the fluid connector of the inverter housing part, via the cooling chamber and the gearbox cooling channel to the motor cooling channel.

An advantage of the proposed housing assembly is that it has a compact design which can have a substantially cylindrical shape with respect to the motor axis. The housing volume can be concentrated at the same height or radial distance, avoiding unconformities in radial direction. Thus, a good packaging is achieved and the housing assembly allows it to reduce the number of housing parts to only three, for example two pots and one cover. The first and inverter housing parts and/or the outer jacket part can be cast from a light metal such as aluminum or an aluminum alloy, for example. In an example embodiment, the assembly can be configured as two pot and three cover housing assembly, with the motor and inverter housing parts forming the two pots, and the casing as well as two optional further covers of the inverter housing part forming the three covers.

In a preferred embodiment, the inverter case portion forms an axial end of the housing assembly with respect to the motor axis. The inverter case portion can be open in the axial direction, so that the inverter can be axially mounted. A cover can be provided to close the inverter case portion.

The motor housing part forms a casing for the electric machine and half of the casing for the gearing. The inverter housing part forms a casing for the inverter and the other half of the casing for the gearing. The motor and inverter housing parts are connected to each other with their gearing case portions. For this, the first and second gear case portions can include circumferentially distributed connecting elements, such as flanges and/or bolts, by which they can be mechanically connected to each other. In the assembled condition, the two halves of the gearing case jointly form an inner chamber in which the gearing is accommodated. The cooling structure of the inverter housing part is fluid-connected to the cooling structure of the motor housing part. In the assembled condition, both cooling structures form part of a closed cooling circuit through which a cooling fluid flows during operation of the assembly. Thus, the cooling fluid flows through the inverter housing part to cool the inverter and a portion of the gearing, and through the motor housing part to cool the electric machine.

The closed cooling system is arranged within the walls of the housing and has no contact to the inner chambers of the housing assembly. Thus, a gearing arranged within the gearbox casing can be cooled and lubricated by a second fluid different from the cooling fluid of the housing assembly. The cooling fluid can be water or a water based coolant, such as ethylene glycol. The fluid for lubricating the gearing can be an oil, for example. The electric machine can be cooled and lubricated with the same fluid as the gearing. It may however also be lubricant free in the case of a dry electric machine.

According to an embodiment, the first gear case portion can include a first through- opening for a first output shaft, and the second gear case portion can include a second through-opening for a second output shaft. The first and second shaft openings can be arranged such that the opening axes extend parallel to the motor axis. The gearbox cooling channel of the inverter housing part can have a C-shaped form in a cross sectional view. The C-shaped gearbox cooling channel can extend circumferentially over at least 180° with respect to the axis of the through-opening of at least one of the first and second gear case portions. The inverter housing part can have an intermediate cooling channel that can be arranged between the inverter cooling chamber and the gearbox cooling channel. Thus, the cooling fluid can flow from the inverter cooling chamber through the intermediate cooling channel to the gearbox cooling channel. With the intermediate cooling chamber, a larger portion of the inverter housing part is cooled. The intermediate cooling channel can have a C-shaped form in a cross sectional view. The intermediate cooling channel can be arranged axially and/or radially offset the gearbox cooling channel. In particular, the intermediate cooling channel can be arranged so as to extend in circumferential direction around the motor axis, for example over at least 180°.

A first connecting channel can be formed between the motor housing part and the inverter housing part so as to fluidically connect the cooling structure of the motor housing part with the cooling structure of the inverter housing part. A return path can be arranged between an outlet connector of the motor channel and an inlet connector of the inverter housing part. A heat exchanger can be arranged in the return path to cool the cooling fluid that has absorbed heat while flowing through the housing from the gearing and the motor. The first connecting channel can be formed from an end section of the gearbox cooling channel to an inlet section of the motor cooling channel.

According to a first embodiment, there is only one connecting channel between the motor housing part and the inverter housing part so that the cooling fluid flows throw them in series, first through the cooling structure of the inverter housing part and then through the cooling structure of the motor housing part.

According to another embodiment, a second connecting channel can be formed between the motor housing part and the inverter housing part. In this case, the cooling fluid flows functionally in parallel, with a first coolant stream flowing from the inverter cooling chamber to the motor housing part indirectly via the gearbox channel and a second coolant stream flowing to the motor housing part directly, bypassing the gearbox channel. During operation of an electric drive, more heat is generated by the electric machine. Thus, the cooling structure of the inverter housing part is formed preferably such that at least 30 %, in particular more than 40 % of the coolant flowing into the inverter housing part flows through the second connecting channel directly to the motor cooling channel, with the rest of the coolant flowing through the gearbox cooling channel indirectly to the motor cooling channel.

According to a specification, the second connecting channel can connect the intermediate cooling channel of the inverter housing part with a second inlet of the motor cooling channel. According to an alternative specification, the second connecting channel can connect the cooling chamber of the inverter housing part with a second inlet of the motor cooling channel.

Furthermore, with respect to the above object, an electric drive for driving a motor vehicle is proposed, comprising: a housing assembly that can be configured according to any one of the above embodiments; an electric machine including a stator and a rotor, wherein the stator is connected in a rotationally fixed manner to the jacket portion of the motor housing part, wherein the rotor is drivingly connected to a rotor shaft that is rotatably supported in the housing assembly about the motor axis; a gearing to transmit a rotary movement of the rotor shaft to a first output shaft and a second output shaft of the gearbox; and an inverter that is arranged in the inverter case portion of the inverter housing part. The stator can be connected axially to the motor housing part, in particular so as to be supported axially against it.

The electric drive has the same advantages as mentioned with respect to the housing assembly so that reference is hereby made to the above description.

The inverter that can also be referred to as power electronics is positioned functionally between the battery of the electric vehicle and the electric machine. The inverter controls and monitors the electric machine and ensures that torque supply and speed control of the powertrain meet the requirements. When the electric machine is operating in motor mode, the inverter supplies the electric motor with power from the battery. When the electric machine is working in generator mode, the inverter feeds power into the battery. In this process known as recuperation, the inverter converts the alternating current (AC) generated by the electric machine into direct current (DC) and thus charges the battery. In the motor mode, the inverter converts the battery's DC voltage into AC voltage required by the electric motor. Preferred embodiments of the invention are described below using the drawing figures.

Herein:

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

Figure 1 B shows the housing assembly of Figure 1A in a mounted condition in a 3D view (without cover);

Figure 1 C shows the cooling structure of the housing assembly of Figures 1 A and 1 B in a 3D view according to Figure 1 B;

Figure 1 D shows the housing assembly of Figure 1 A in an axial view;

Figure 1 E shows the cooling structure of the housing assembly in an axial view according to Figure 1 D;

Figure 1 F shows the inverter housing part in a longitudinal section according to section 1 F-1 F of Figure 1 D;

Figure 1 G shows the housing assembly of Figure 1A in a top view;

Figure 1 H shows the cooling structure of the housing assembly in a top view according to Figure 1 G;

Figure 1 J shows the housing assembly of Figure 1A in a cross section according to section line 1 J-1J of Figure 1 G;

Figure 1 K shows a connection between an inverter cooling channel and a motor cooling channel;

Figure 2A shows a housing assembly in a second embodiment according to the invention in a 3D view;

Figure 2B shows the cooling structure of the housing assembly of Figure 2A in a 3D view;

Figure 2C shows the cooling structure of the housing assembly in a top view;

Figure 3A shows a housing assembly in a third embodiment according to the invention in a 3D view; and

Figure 3B shows the cooling structure of the housing assembly of Figure 3A in a 3D view. Figures 1A to 1 K, which are described together below, show a housing assembly 2 according to the invention in a first embodiment. The housing assembly 2 is for an electric drive of a motor vehicle (not shown). The components of the housing assembly are shown in Figures 1 A, 1 B, 1 D, 1 F, 1 G, 1 J and 1 K. The cooling fluid hollow structure formed by the components is shown in Figures 1 C, 1 E and 1 H. The fluid sections are designated with F, supplemented by the respective reference sign of the associated component. This also applies to the embodiments shown in Figures 2A to 2C and Figures 3A to 3B.

The housing assembly 2 includes a motor housing part 3, a casing 4 and an inverter housing part 5.

The motor housing part 3 comprises a jacket portion 6 for accommodating a stator of the electric machine and a first gear case portion 7 for accommodating parts of a gearing. The jacket portion 6 and the first gear case portion 7 are integrally formed, for example by casting of a light metal.

The casing 4 can be mounted to the jacket portion 6 by suitable connectors 11 , for example by circumferentially distributed flange and/or bolt connectors. In the mounted condition, the casing 4 and inner jacket portion 6 are coaxially arranged and form a motor cooling channel 8 through which cooling fluid F can flow for cooling the electric machine (not shown). The cooling channel 8 is arranged radially between the inner jacket portion 6 and the outer casing 4 and extends helically around the motor axis A1 . In this manner, heat transferred from the electric machine to the inner jacket portion 6 can be absorbed by the cooling fluid F flowing through the motor jacket. The casing 4 can also be referred to as outer jacket part.

The first gear case portion 7 comprises circumferentially distributed connecting elements 9. The connecting elements 9 are configured as flange connectors which are to be mounted to corresponding second connecting elements 10 of the inverter housing part 5 that can be configured as flange connectors as well. The first gear case portion 7 further comprises a through-opening 12 for a first output shaft of the gearbox (not shown). The axis A2 of the through-opening 12 extends parallel to the motor axis A1 . Furthermore, the first gear case portion can optionally comprise a bearing seat 36 for an intermediate shaft of the gearing (not shown).

The inverter housing part 5 includes an inverter case portion 13 for accommodating an inverter of the electric machine (not shown) and a second gear case portion 14. The inverter case portion 13 and the second gear case portion 14 are integrally formed and can be made as a casting from light metal material, for example. The inverter case portion 13 is arranged axially adjacent to the second gear case portion. More particularly, the inverter case portion 13 forms an axial end of the housing assembly 2 with respect to the motor axis A1 . The inverter case portion 13 has an opening in the axial direction, so that the inverter can be axially mounted therein. A cover 15 can be provided to close the inverter case portion 13 so that the inverter is encapsulated in the inverter case. The cover 15 can be mounted to the inverter case portion 13 by respective connecting elements 24. The inverter case portion 13 can optionally comprise a chamber 39 to receive electronic components, for example, which can be closed by a cover 40.

An inverter supplies the electric machine with power from a battery, when the machine is operating in motor mode. When the electric machine operates in generator mode, the inverter feeds power into the battery of the motor vehicle. The inverter can convert alternating current generated by the electric machine into direct current to charge the battery, and vice versa. An inverter can comprise a capacitor, an intelligent power generation module (IPGM) and bus bars. During operation, the components of the inverter gets warm and the heat generated needs to be dissipated by the cooling system.

For this, the inverter housing part 5 comprises a fluid connector 16 that is fluidically connected to a cooling chamber 17 within the inverter case portion 13. The cooling chamber 17 has an inlet 18 and an outlet 19 so that cooing fluid can flow from the connector 16 through the cooling chamber 17 and then further to the gear case portion 14. The cooling chamber 17 includes a circumferential connecting face 20 to which a component of the inverter can be connected in a fluid-tight manner. Thus, the inverter component extending into the cooling chamber 17 is cooled by the fluid flowing through the chamber. The second gear case portion 14 includes a gearbox cooling channel 22 fluidically connected to the outlet 19 of the inverter cooling chamber 17. The gearbox cooling channel 22 has, in particular, a C-shaped form in a cross sectional view, as can be seen in Figures 1 C, 1 E and 1 J. The second gear case portion 14 further comprises a second through-opening 23 for a second output shaft, with the axis A2 of the shaft opening extending parallel to the motor axis A1 . The C-shaped gearbox cooling channel 22 extends in circumferential direction over at least 180° with respect to the axis A2 of the shaft opening of the second gear case portion 14. The second gear case portion 14 can optionally comprise a second bearing seat 37 for an intermediate shaft of the gearing, with the second bearing seat 37 and the first bearing seat 36 forming a rotational axis A3 in the mounted condition extending parallel to the motor axis A1 .

The inverter housing part 5 can optionally have an intermediate cooling channel 29 (shown in dashed lines in Figure 1 D) that can be arranged between the inverter cooling chamber 17 and the gearbox cooling channel 22. The cooling fluid thus can flow from the cooling chamber 17 through the intermediate cooling channel 29 to the gearbox cooling channel 22. The intermediate cooling channel 22 can have a C-shaped form in a cross sectional view, similar to the gearbox cooling channel 22. However, the intermediate cooling channel 29 is preferably arranged axially offset the gearbox cooling channel 22. In particular, the intermediate cooling channel 29 is arranged so as to extend in circumferential direction around the motor axis A1 , for example over at least 180°.

On its side directed towards the first gear case portion 7, the second gear case portion 14 includes, circumferentially distributed, the second connecting elements 10 for providing a mechanical connection to the motor housing part 3. Furthermore, a connecting channel 26 is formed between the motor housing part 3 and the inverter housing part 5 so as to fluidically connect the cooling structure of said housing parts.

The first connecting elements 9 and the second connecting elements 10 are connectable with each other so as to sealingly connect the motor housing part 3 and the inverter housing part 5. In the mounted condition, the motor housing part 3 forms a first half of the casing for the gearbox and the inverter housing part 5 forms the second half of the casing for the gearbox. In other words, the interface of the two housing parts 3, 5 is located in the region of the gearbox casing. The first and second connecting elements 9, 10 can include flanges and bolts without being limited thereto. For example, the two housing parts could also be welded to each other.

In the connected condition, the cooling structure 35 of the inverter housing part 5 is fluid-connected to the cooling structure 33 of the motor housing part 3 via the connecting channel 26. The first connecting channel 26 can be formed from an end section of the gearbox cooling channel 22 to an inlet section 28 of the motor cooling channel 8. The cooling structures of the motor and inverter housing part 3, 5 form part of a closed cooling circuit from the fluid connector 16 of the inverter housing part 5, via the inverter cooling chamber 17, the gearbox cooling channel 22, the motor cooling channel 8 and to a fluid connector 31 of the motor housing part 3. The flow path P of the cooling fluid F is shown by arrows in Figure 1 C. A return path (not shown) can be arranged between the motor housing connector 31 and the inverter housing connector 16. The return path may include a heat exchanger to cool the cooling fluid that has absorbed heat while flowing through the housing assembly 2. The heat exchanger can be arranged externally to the housing assembly 2.

An exemplary fluid coupling between inverter housing part 5 and the motor housing part 3 is shown as a detail in Figure 1 K. The fluid coupling can comprise a sleeve- formed connector 21 with a first portion 38 connected to the motor sided cooling channel and a second portion 38' connected to the inverter sided cooling channel. The connector 21 is configured in particular so as to form a liquid tight sealing between the motor sided cooling channel and the inverter sided cooling channel. The connector 21 can be made of an elastic material, such as rubber or other similar plastic material. The connector 21 can have sealing lips at its axial ends or other sealing features to sealingly contact a circumferential face of the channel connecting section 25 of the motor housing part 3 and the opposed channel connecting section 25' of the inverter housing part 5 respectively. The inverter housing part 5 can have an optional auxiliary bore 41 , which forms part of the connection channel 26 and can be closed to the outside with a plug (not shown). As an alternative, the two opposed channel connecting sections 25, 25' can also be fluidical ly connected to each other without separate connector, for example by including a sealing ring in the contact region between the two housing parts 3, 5. In the mounted condition, the housing assembly 2 is part of an electric drive that is configured for driving a motor vehicle. The electric drive includes an electric machine received in the motor housing part 3, a gearing for transmitting the rotary movement of the electric machine, and an inverter for controlling and monitoring the electric machine and ensuring torque supply and speed control to meet the requirements. The electric machine comprises a stator and a rotor (not shown), with the stator connected to the casing 4 of the motor housing part 3 in a rotationally fixed manner. The rotor is driving ly connected to a rotor shaft that is rotatably supported in the housing assembly 2 about the motor axis A1 . The gearing (not shown) is configured to transmit a rotary movement from the rotor shaft to a first and second output shaft. For this, the gearing can comprise a transmission unit with an optional intermediate shaft rotatable about the axis A3, and a differential unit to split the input movement to the two output shafts. The inverter (not shown) is arranged in the inverter case portion 13 of the inverter housing part 5.

In the following, the special features of the different embodiments will be described. In the first embodiment shown in Figures 1 A to 1 K, there is only one connecting channel 26 between the motor housing part 3 and the inverter housing part 5. The whole cooling fluid F flows from the inverter housing part 5 through channel 26 to the motor housing part 3, where it leaves the housing assembly 2 and can return through a return path (not shown) back again to the inverter housing part 5.

The embodiment shown in Figures 2A to 2C widely corresponds to the embodiment shown in Figures 1A to 1 K so that reference is made to the above description with respect to the shared features. In this connection, the same and/or corresponding details have been provided with the same reference signs as in Figures 1A to 1 K.

A special feature of the second embodiment shown in Figures 2A to 2C is that in addition to the first connecting channel 26 a second connecting channel 30 is provided to fluidically connect the first and second cooling structure. In this case, the cooling fluid F flows functionally in parallel, with a first coolant stream F26 flowing from the inverter cooling chamber 17 to the motor housing part 3 indirectly via the gearbox cooling channel 22, and a second coolant stream F30 flowing to the motor housing part 3 directly, i.e. bypassing the gearbox cooling channel 22. The cooling structure 35 of the inverter housing part 5 is formed such that preferably at least 30 %, for example 50 % of the coolant flowing into the inverter housing part 3 through the connector 16 is branched off in the flow path behind the cooling chamber 17 and directed through the second connecting channel 30 directly to the motor cooling channel 8. The other half of the coolant flows through the gearbox cooling channel 22 indirectly to the motor cooling channel 8. In the motor cooling channel 8, the two fluid streams F26, F30 are united and jointly flow through the motor jacket.

As can be seen in Figure 2B and 2C, a connecting channel (F32) is formed between the outlet 19 of the inverter cooling chamber 17 and the intermediate cooling channel 29. At an end portion (F34), the intermediate channel 29 is connected to the second cooling channel 30. Thus, the first coolant stream F1 flows through the intermediate channel 29 to the gearbox channel 22, and the second coolant stream F30 flows from the end portion (F34) of the intermediate channel 29 through the second connecting channel 30.

The embodiment shown in Figures 3A and 3B widely corresponds to the embodiment shown in Figures 2A to 2C so that reference is made to the above description with respect to the common features. In this connection, the same and/or corresponding details have been provided with the same reference signs as in Figures 2A to 2C and Figures 1A to 1 K, respectively.

The only difference of the embodiment shown in Figures 3A and 3B is that the outlet 19 of the cooling chamber 17 is directly connected through the second connecting channel 30 to the motor cooling channel 8. Reference Numerals

2 housing assembly

3 motor housing part

4 casing

5 inverter housing part

6 jacket portion

7 first gear case portion

8 motor cooling channel

9 first connecting elements

10 second connecting elements

11 connector

12 through-opening

13 inverter case portion

14 second gear case portion

15 cover

16 fluid connector (5)

17 cooling chamber

18 inlet

19 outlet

20 connecting face

21 fluid connector

22 gearbox cooling channel

23 through-opening

24 connecting elements

25, 25' connecting section

26 first connecting channel

27 end section (22)

28 inlet section (8) 29 intermediate cooling channel

30 second connecting channel

31 fluid connector

32 connecting channel

33 cooling structure (3)

34 end section (32)

35 cooling structure (5)

36 bearing seat (7)

37 bearing seat (14)

38, 38' portion

39 chamber

40 cover

41 auxiliary bore

A axis

F cooling fluid

P flow path