WO2020165261A1

WO2020165261A1 - Electric drive unit and method of manufacturing the same

Info

Publication number: WO2020165261A1
Application number: PCT/EP2020/053616
Authority: WO
Inventors: Jan Willem van der Vecht; Alexander SCHÄFER
Original assignee: Punch Powertrain NV
Current assignee: Punch Powertrain NV
Priority date: 2019-02-12
Filing date: 2020-02-12
Publication date: 2020-08-20
Anticipated expiration: 2021-08-12
Also published as: CN113661639B; EP3925058A1; BE1027048B1; BE1027048A1; CN113661639A

Abstract

An electric drive unit (1) is provided that comprises a carrier body (5), a motor housing (20) with electric motor (2) and an electronic module housing (30) power electronic module (3). These components can be manufactured independently from each other and the readily assembled. Upon assembly a common cooling channel is formed for the electric motor (2) and the power electronic module (3).

Description

Electric drive unit and method of manufacturing the same

BACKGROUND

Field of the invention

The present invention relates to an electric drive unit.

The present invention further relates to a method of

manufacturing an electric drive unit.

Related Art

US 5.585.681 discloses an electric drive unit for an electric motor car which comprised an electric motor, a housing for the electric motor, a control housing having accommodated therein electronic controls for the electric motor and a cooling circuit for the electric motor and the electronic controls. The control housing has a bottom located on top of the motor housing. The coohng circuit having a cooling fluid flowing therethrough, has a first portion which cools the bottom of the control housing and a second portion which cools the motor housing. The first and second portions of the cooling circuit are connected in series so that the cooling fluid passes through the first portion of the cooling circuit to cool the control housing before passing through the second portion of the cooling circuit to cool the motor housing. The electric drive unit can be assembled from the various components so that these components can be manufactured independently from each other which renders possible a flexible and efficient production process.

SUMMARY

It is an object of the present invention to provide an improved electric drive unit, which also can me manufactured by assembly from components, at least comprising the electric motor as a first component and the electronic module as a second component, and wherein the construction of the cooling channel is simplified.

In accordance therewith, an electric drive unit is provided that comprises a carrier body, a motor housing accommodating an electric motor, an electronic module housing accommodating a power electronic module and a common cooling system for cooling the electric motor and the power electronic module with a cooling fluid.

The carrier body has a wall with an inner surface defining a cavity extending in an axial direction. A portion of an outer surface of the wall forms a mounting surface extending in the axial direction.

The motor housing accommodating the electric motor is arranged in the cavity. The electric motor has a motor axis extending in the axial direction defined by the cavity. The motor housing comprises a

circumferential wall that extends along the motor axis to circumferentially enclose the electric motor.

The electronic module housing is arranged on the mounting surface. The electronic module housing comprises a thermally conductive carrier for carrying one or more elements of the power electronic module. The power electronic module accommodated therein is electrically connected with the electric motor, to provide electric drive signals for driving the motor.

The common cooling system for cooling the electric motor and the power electronic module comprises a cooling channel with a cooling fluid input and a cooling fluid output and being formed by a space between an outer surface of the circumferential wall of the motor housing and the inner surface defining the cavity in the carrier body.

The electric drive unit as claimed herein is characterized in that the mounting surface defines one or more openings towards the cooling channel and in that the thermally conductive carrier is provided with protrusions extending through the one or more openings for allowing the cooling fluid to transfer heat from the power electronic module to the cooling fluid. As set out in more detail in the description of embodiments, the arrangement allows various options to control the relative contribution of the heat flow from the electric motor to the cooling fluid and from the power electronic module to the cooling fluid. Therewith the arrangement can be rapidly adapted to other changes in the design, for example in the design of the electric motor or in the design of the power electronic module that could result in different cooling requirements.

In an embodiment, the openings comprise inflow openings and outflow openings which are separated from each other by a bridge and wherein the outflow openings are arranged stream downward with respect to said inflow openings. The dimensioning of the bridge enables a further control of the distribution of the flow of coohng fluid for cooling of the motor and for cooling of the power electronic module. Alternatively or additionally, the circumferential wall of the motor housing may be provided with an axially extending rib facing outward that forces the cooling fluid to flow more towards the power electronic module depending on the height of the rib.

In an embodiment, the cooling channel includes a first axial channel extending in the axial direction from the cooling fluid input and a second axial channel extending in the axial direction from the cooling fluid output. Therewith the cooling channel can be easily coupled to a cooling fluid source and drain connection.

In an embodiment, the first axial channel and the second axial channel are formed as a respective groove in the inner wall of the cavity.

The axial channels, which are aligned with the direction defined by the cavity can be provided relatively easily in the wall of the carrier. Therewith they do not need to be provided in the wall of the motor housing, which simplifies the manufacturing of the latter component. In an embodiment, a cross-section of the first axial channel diminishes in a direction away from the cooling fluid input and a cross- section of the second axial channel diminishes in a direction away from the cooling fluid output. This contributes to a homogeneous distribution of the flow of cooling fluid.

In an embodiment the cooling channel comprises a plurality of tangential channels, which are spaced with respect to each other in the axial direction and which extend from the first axial channel to the second axial channel. The configuration of tangential channels enhances cooling.

In an embodiment, the tangential channels are formed by respective tangential grooves in the outer surface of the circumferential wall. This simplifies the manufacturing process of the carrier.

In an embodiment, a distance between the cooling fluid input and the mounting surface is shorter than a distance between the cooling fluid output and the mounting surface. Therewith it can be achieved that a relative large proportion of the cooling capacity of the cooling system is dedicated to the power electronic module.

According to a second aspect, a method for manufacturing an electric drive unit is provided. The method comprises the following steps.

A carrier body is provided that has a wah with an inner surface defining a cavity extending in an axial direction. The carrier body further has a mounting surface, which is a portion of an outer surface of the wah and which extends in the axial direction. The carrier body further has a cooling fluid input, and a cooling fluid output that communicate with the cavity.

A motor housing is provided that accommodates an electric motor with a motor axis, and the motor housing comprises a circumferential wall that extends along the motor axis to circumferentially enclose the electric motor, and has an outer surface. An electronic module housing is provided that comprises a thermally conductive carrier for carrying one or more elements of a power electronic module accommodated in the electronic module housing and which is to provide electric drive signals for driving the motor.

The motor housing is inserted inside the cavity of the carrier body with, the motor axis aligned with the axial direction of the cavity. Therewith an intermediate space is left free which forms a cooling channel between the outer surface of the motor housing and the inner surface of the cavity. The cooling channel communicates with the coohng fluid input and the cooling fluid output to allow a flow of coohng fluid from the cooling fluid input via the cooling channel to the cooling fluid output in a cooling system.

The electronic module housing is mounted with its thermally conductive carrier on the mounting surface of the carrier body and the power electronic module therein is electrically connected with the electric motor.

The mounting surface for the power electronic module defines one or more openings towards the cooling channel and the thermally conductive carrier is provided with protrusions extending through the one or more openings for enabling the cooling fluid to transfer heat from the power electronic module to the cooling fluid. Therewith the method is an efficient way to manufacture the electric drive unit in that its constituting

components can be manufactured independently from each other and be assembled in a final manufacturing stage.

In an embodiment of the method, the motor housing has electric contacts facing designed to face in a radial direction towards the mounting surface and the electronic module housing has complementary contacts designed to face radially inwards and to cooperate with the electric contacts of the motor housing, so as to form the electric connection between electronic module and the electric motor. Therewith the power electronic module therein is electrically connected with the electric motor already by the act of mounting the electronic module housing with its thermally conductive carrier on the mounting surface. Optionally, the electric connection may be further secured by a further means, e.g. by a further mechanical connection between the mutually cooperating contacts.

Alternatively a separate connection cable may be provided for the electrical connection for example.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention are described in more detail with reference to the drawings. Therein:

FIG. 1 schematically shows an electric drive unit in a cross- section through the longitudinal axis defined by the rotation axis of the rotor of the electric motor;

FIG. 1A shows an aspect in more detail;

FIG. 2 shows the same cross-section, in the absence of the electric motor;

FIG. 3 shows a perspective view without the power electronic module;

FIG. 4 schematically shows a cooling circuit;

FIG. 5 shows a perspective view in the absence of the electric motor;

FIG. 6 shows a cross-section of the electric motor along its rotation axis;

FIG. 7A shows a top-view of a mounting surface and FIG. 7B shows a cross-section according to VIIB-VIIB in FIG. 7 A.

DETAILED DESCRIPTION OF EMBODIMENTS

Like reference symbols in the various drawings indicate like elements unless otherwise indicated. FIG. 1 schematically shows an electric drive unit 1 that comprises a carrier body 5, a motor housing 20 accommodating an electric motor 2, an electronic module housing 30 accommodating a power electronic module 3 and a common cooling system comprising amongst others a cooling channel 43 for cooling the electric motor 2 and the power electronic module 3 with a cooling fluid.

As shown in more detail in FIG. 2, the carrier body 5 has a wall 50 with an inner surface 50i that defining a cavity 52 extending in an axial direction 51 (coinciding with the z-axis).

As shown further in FIG. 3, the carrier body 5 further has a mounting surface 53. The mounting surface 53 is a portion of an outer surface of the wall 50 (FIG. 1,2) and extends in the axial direction,

FIG. 1 schematically illustrates a motor housing 20 that accommodates an electric motor 2 arranged in the cavity. As schematically indicated, the motor 2 may have a stator 2S and a rotor 2R having a motor axis 22 extending in the axial direction 51, corresponding to the direction z, see also FIG. 5. The motor housing 20 comprises a circumferential wall 21 that extends along the motor axis 22 to circumferentially enclose the electric motor 2.

As shown in FIG. 1,2 the electronic module housing 30 is arranged on the mounting surface 53. The electronic module housing 30 comprises a thermally conductive carrier 31 for carrying one or more elements 33 of the power electronic module 3 accommodated in the electronic module housing 30. The power electronic module 3 is electrically connected with the electric motor (schematically illustrated by cable 35), to provide electric drive signals for driving the motor.

The common cooling system 4 for cooling the electric motor 2 and the power electronic module 3 of FIG. 1,2, with a cooling fluid F is shown schematically in FIG. 4, the cooling system comprises a cooling channel 43 which is formed by a space between an outer surface 211 of the circumferential wall 21 of the motor housing 20 and the inner surface 50i that defines the cavity for the motor. The cooling channel 43 extends between a cooling fluid input 41 for receiving a low temperature cooling fluid F from a heat exchanger 45 and fluid output 42 to return the heated cooling fluid to the heat exchanger 45. The cooling channel 43 is interrupted 44 at a position between the cooling fluid output 42 and the cooling fluid input 41. The flow of cooling fluid F through the cooling channel 43 provides for a transfer of heat from the electric motor. As shown in FIG. 3 and FIG. 4, the mounting surface 53 defines one or more openings 54a, 54b towards the cooling channel 43. The thermally conductive carrier 31 is provided with protrusions, comprising protrusions 314a, 314b extending through these openings 54a, 54b. Therewith the cooling fluid F is also enabled to transfer heat from the power electronic module to the cooling fluid.

The arrangement allows various options to control the relative contribution of the heat flow from the electric motor 2 to the coohng fluid and from the power electronic module 3, to be mounted on the thermally conductive carrier 31 as shown in FIG. 1,2, to the cooling fluid. In the example shown, the distance in a stream downward direction from the cooling fluid input 41 to the mounting surface 53 is shorter than the distance in the stream downward direction from the mounting surface 53 to the cooling fluid output 42. Therewith it is achieved that a relatively high portion of the cooling capacity is available for the power electronic module 3. Should it for example be the case however that the cooling capacity available for the power electronic module 3 is higher than necessary, but that a higher cooling capacity for the electric motor is desired, then it may be contemplated to provide the cooling fluid input, the interruption, and the cooling fluid output at a location 41’, 44’ and 42’ respectively which is further stream upwards with respect to the thermally conductive carrier 31 for the power electronic module 3. This may for example be the case if the power electronic module has some additional cooling, e.g. air cooling by its housing 30.

In the embodiment as shown in FIGs. 3, 4, the openings 54a, 54b comprise inflow openings 54a and outflow openings 54b which are separated from each other by a bridge 55. The outflow openings 54b are arranged stream downward with respect to the inflow openings 54a. This

arrangement as also shown in FIG. 3, enhances a flow of the cooling fluid F along the protrusions 314a, 314b. This is favorable if a relatively high cooling capacity for the power electronic module 3 is required. A still further increase in the contribution of the cooling capacity for the power electronic module 3 may be achieved if the outer wall 211 of the housing 20 of the motor is provided with an axially extending rib 26 facing the bridge 55, that partially or fully blocks a flow of cooling fluid F in the portion of the cooling channel facing the thermally conductive carrier 31, so that the cooling fluid is forced to flow more substantially or fully along the along the protrusions 314a, 314b. Alternatively or additionally this may be achieved by modifying the bridge 55 so that it protrudes into the cooling channel 43.

In an embodiment as illustrated in FIG. 5, the cooling channel includes a first axial channel 56 that extends in the axial direction 51 from the cooling fluid input 41 and a second axial channel 57 that extends in the axial direction 51 from the cooling fluid output 42. In this way an axial distribution of the flow through the cooling channel 43 (FIG. 4) is promoted. In the example shown in FIG. 5, the first axial channel 56 and the second axial channel 57 are formed as a respective groove in the wall of the cavity. Alternatively the axial channels 56, 57 may be provided in the outer surface of the motor housing.

In an embodiment a cross-section of the first axial channel 56 diminishes in a direction away from the cooling fluid input 41 and a cross- section of the second axial channel 57 diminishes in a direction away from the cooling fluid output 42. Therewith the cross-section of the axial channels 56, 57 is adapted to provide a relatively high flow capacity near the input and the output to conduct the accumulated flow for the entire cooling channel, and a lower flow capacity more remote from the input and the output where the axial channels 56, 57 only need to conduct the fluid flow for an end portion of the cooling channel.

As shown in FIG. 6 in conjunction with FIGs. 4 and 5, the cooling channel 43 may comprise a plurality of tangential channels 212 spaced with respect to each other in the axial direction and extending from the first axial channel 56 to the second axial channel 57. As shown in FIG. 7B, in this example, the tangential channels 212 are formed by respective tangential grooves 212 between tangentially extending ribs 214 in the outer surface 211 of the circumferential wall 21 of the motor housing 20. The presence of the tangential channels 212 as part of the cooling channel makes it possible to optimally control the flow of cooling fluid. Moreover, by providing the tangential grooves 212 in the outer surface 211 of the circumferential wall 21, the contact surface between the wall 21 and the cooling fluid is increased.

FIG. 7A shows a view of the mounting surface 53, according to VIIA-VIIA in FIG. 1.

FIG. 7B shows a cross-section according to VIIB-VIIB in FIG. 7 A. As shown therein, the protrusions 314 (314a, 314b) of the thermally conductive carrier 31 may be arranged opposite protrusions formed by the tangentially extending ribs 214 of the outer surface 211 of the

circumferential wall 21 of the motor housing 20 shown in FIG. 6 .

An electric drive unit as disclosed herein may be obtained with the following modular approach wherein the carrier body 5, the motor housing 20 accommodating the electric motor 2 and the electronic module housing 30 with the power electronic module 3 may be manufactured independent from each other, and then be assembled. Therewith the motor housing 20 may be inserted inside the cavity 52 of the carrier body. After insertion an intermediate space between the outer surface 211 of the motor housing and the inner surface 50i of the cavity remains that forms the cooling channel.

The electronic module housing 30 can then be mounted with its thermally conductive carrier 31 on the mounting surface 53 of the carrier body and the power electronic module 3 can be electrically connected to the electric motor. The motor housing may have electric contacts 35 la,...35 If that are designed to face in a radial direction towards the mounting surface and the electronic module housing 30 may have complementary contacts 352a,..., 352f designed to face radially inwards and to cooperate with the electric contacts of the motor housing, as shown schematically in FIG. 1A. Therewith it is achieved that the electric connection 35 between the electronic module and the electric motor is obtained already by mounting the electronic module housing 30. Optionally a further the electric

connection may be further secured with an additional mechanical

connection. Alternatively, the electric connection 35 may be provided in a separate manufacturing step. In that case it is alternatively possible to first mount the electronic module housing and subsequently insert the motor housing.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Claims

1. An electric drive unit (1) comprising:

a carrier body (5) having a wall (50) with an inner surface (50i) defining a cavity (52) extending in an axial direction (51); and having a mounting surface (53) being a portion of an outer surface of said wall extending in said axial direction,

a motor housing (20) accommodating an electric motor (2) arranged in the cavity, and having a motor axis (22) extending in said axial direction (51), the motor housing (20) comprising a circumferential wall (21) extending along said motor axis (22) to circumferentially enclose the electric motor;

an electronic module housing (30) being arranged on the mounting surface (53), the electronic module housing (30) comprising a thermally conductive carrier (31) for carrying one or more elements of the power electronic module (3) accommodated in the electronic module housing (30) and being electrically connected with the electric motor, to provide electric drive signals for driving the motor;

a common cooling system (4) for cooling the electric motor (2) and the power electronic module (3) with a cooling fluid (F), the cooling system comprising a cooling fluid input (41), a cooling fluid output (42) and comprising a cooling channel (43) formed by a space between an outer surface (211) of the circumferential wall (21) of the motor housing (20) and said inner surface (50i) for allowing the cooling fluid (F) to transfer heat from the electric motor, characterized in that the mounting surface (53) defines one or more openings (54a, 54b) towards the cooling channel (43), and in that the thermally conductive carrier (31) is provided with

protrusions extending through the one or more openings for enabling the cooling fluid (F) to transfer heat from the power electronic module to the cooling fluid.

2. The electric drive unit (1) according to claim 1, wherein the openings (54a, 54b) comprise inflow openings (54a) and outflow openings (54b) are separated from each other by a bridge (55) and wherein the outflow openings (54b) are arranged stream downward with respect to said inflow openings (54a) and/or wherein the circumferential wall of the motor housing is provided with an axially extending rib (26) facing outward.

3. The electric drive unit (1) according to claim 1 or 2, wherein the cooling channel (43) includes a first axial channel (56) extending in the axial direction (51) from the cooling fluid input (41) and a second axial channel (57) extending in the axial direction (51) from the cooling fluid output (42).

4. The electric drive unit (1) according to claim 3, wherein the first axial channel (56) and the second axial channel (57) are formed as a respective groove in the inner wall of the cavity.

5. The electric drive unit (1) according to claim 3 or 4, wherein a cross-section of the first axial channel (56) diminishes in a direction away from the cooling fluid input (41) and a cross-section of the second axial channel (57) diminishes in a direction away from the cooling fluid output (42).

6. The electric drive unit (1) according to claim 5, wherein the cooling channel (43) comprises a plurality of tangential channels (212) spaced with respect to each other in the axial direction and extending from the first axial channel (56) to the second axial channel (57).

7. The electric drive unit (1) according to claim 6, wherein the tangential channels (212) are formed by respective tangential grooves (212) in the outer surface (211) of the circumferential wall (21).

8. The electric drive unit (1) according to one of the previous claims, wherein a distance between the cooling fluid input (41) and the mounting surface (53) is shorter than a distance between the cooling fluid output (42) and the mounting surface (53).

9. A method for manufacturing an electric drive unit, the method comprising the steps of:

providing a carrier body (5) having a wall (50) with an inner surface (50i) defining a cavity (52) extending in an axial direction (51); and having a mounting surface (53) being a portion of an outer surface of said wall extending in said axial direction, the carrier body having a cooling fluid input (41), and a cooling fluid output (42) communicating with the cavity;

providing a motor housing (20) accommodating an electric motor (2), and having a motor axis (22) extending in said axial direction (51), the motor housing (20) comprising a circumferential wall (21) extending along said motor axis (22) to circumferentially enclose the electric motor, and having an outer surface (211);

providing an electronic module housing (30) comprising a thermally conductive carrier (31) for carrying one or more elements of the power electronic module (3) accommodated in the electronic module housing (30) to provide electric drive signals for driving the motor;

inserting the motor housing (20) inside the cavity (52) of the carrier body, therewith leaving free intermediate space forming a cooling channel between the outer surface (211) of the motor housing and the inner surface (50i) of the cavity, the cooling channel communicating with the cooling fluid input (41), and a cooling fluid output (42) to allow a flow of cooling fluid (F) from the cooling fluid input (41) via the coohng channel to the cooling fluid output (42) in a cooling system;

mounting the electronic module housing (30) with the thermally conductive carrier (31) on the mounting surface (53) of the carrier body and electrically connecting the power electronic module (3) to the electric motor, characterized in that the mounting surface (53) defines one or more openings (54a, 54b) towards the cooling channel (43), and in that the thermally conductive carrier (31) is provided with protrusions extending through the one or more openings for enabhng the coohng fluid (F) to transfer heat from the power electronic module to the cooling fluid.

10. The method according to claim 9, wherein the motor housing has electric contacts designed to face in a radial direction towards the mounting surface and the electronic module housing (30) has complementary contacts designed to face radially inwards and to cooperate with the electric contacts of the motor housing, so as to form the electric connection between electronic module and the electric motor.