Cooling of electric drive devices in electrically driven vehicles

Abstract

The invention relates to an electric drive device (10) of an electrically driven vehicle. The electric drive device (10) comprises a rotor (22) and a stator (24), which rotor is surrounded by a housing (25). The housing (25) is formed by an outer part (48) and an inner part (50), which outer part and inner part have axial ribs (62, 64), respectively, which extend in an axial direction (78) of the housing (25).

Description

TECHNICAL FIELD

[0001] The invention relates to an electric drive device of an electrically driven vehicle, having a rotor and a stator, which is surrounded by a housing. Furthermore, the invention relates to the use of an electric drive device in an E-axle module of an electrically driven vehicle. BACKGROUND

[0002] DE 10 2018 200 365 AL discloses a cooling unit for cooling an electric machine. The cooling unit has a hollow-cylindrical cooling jacket and cooling channels configured on the cooling jacket. The cooling channels are embodied on the radially outer surface of the cooling jacket with respect to the central axis of the cooling unit.

[0003] DE 10 2012 008 209 AL relates to an electric machine having a housing and a jacket concentrically surrounding the housing. Between the housing and the jacket there extends an annular, liquid-tightly closed and coolant-flowable cooling jacket. The cooling jacket has a plurality of coolant channels arranged next to one another in the axial direction and extending in the circumferential direction of the housing, which extend between ribs arranged on the outer circumference of the housing.

[0004] DE 10 2010 029 986 AL relates to an electric machine having a housing in which a stator and a rotor are arranged. The housing has an outer jacket and an inner jacket which points to the stator in sectionally spaced manner from the outer jacket. Between the outer jacket and the inner jacket a cooling jacket is embodied. The cooling jacket comprises a plurality of channels extending around the axis of rotation of the electric machine for guiding a cooling medium through.

[0005] In electric machines used in electrically driven axles of electric vehicles, the stator is usually cooled with liquid. For this purpose, the stator is mounted in an aluminum housing manufactured by an extrusion method. The housing is usually embodied double-walled and has a web extending in the longitudinal direction of the housing between the two walls. Cooling water channels extending parallel to one another are formed by the partition webs. In each of the two bearing covers of the electric machine there is a diverting pocket which diverts the liquid flowing out of the longitudinal channels by 180° and into the adjacent channel. Thereby, the electric machine is circulated in a meandering manner over the entire circumference of the housing jacket and is thus cooled.

[0006] It is furthermore known that the cooling water guide is formed in a cost-effective manner by a lengthened front bearing cover and by a lengthened rear bearing cover. Thereby, an outer wall and an inner wall of the cooling housing can be formed. In this way, the housing itself is saved. In said possibility, the first bearing cover is configured as a die casting, while the second bearing cover is usually configured as a stamped part. SUMMARY

[0007] According to the application, an electric drive device of an electrically driven vehicle is proposed, wherein the electric drive device comprises an electric machine having a rotor and a stator, and the stator is surrounded by a housing. The housing comprises an outer part and an inner part, which have axial ribs extending in the axial direction of the housing, respectively.

[0008] By dividing the housing of the electric machine into an inner part and an outer part, a turning bag required so far can be saved in terms of manufacturing technology, on the one hand. Furthermore, by means of the solution according to the application, an overflow of the cooling fluid from a cooling channel into an adjacent cooling channel can be avoided, so that the cooling power available overall for the dissipation of heat from the electric machine can be kept essentially constant.

[0009] In an advantageous design variant of the solution according to the application, the electric drive device is designed in such a way that the axial ribs form an intermediate space in the joined state of the outer part or the inner part of the housing, through which the cooling medium flows exclusively in the tangential direction. The meandering portion of the cooling medium flow present in the previous solution can be significantly reduced and ideally completely avoided by means of the solution according to the application, so that an exclusively tangential flow of the cooling medium occurs.

[0010] In a further advantageous design variant of the solution according to the application, the inlet and the outlet for the cooling medium are located on the outer part, which are arranged at an axial spacing relative to one another. By means of the distance that can be achieved between the inlet and the outlet due to the axial spacing, a short circuit of the flow of the cooling medium can be avoided, so that the flow of the cooling medium through the cooling channels that extend accordingly in the axial direction is imposed more precisely, which is accompanied by a constant dissipation of heat.

[0011] In an advantageous design variant of the solution according to the application, the inlet and the outlet are arranged on the outer part of the housing at an advantageous offset relative to one another, for example, of 180°. Thereby, it can be achieved that the inlet and the outlet for the cooling medium are opposite one another and impose a flow path of the cooling medium exclusively in the tangential direction under the assistance of gravity. An offset angle of 180° is also possible, however.

[0012] In an advantageous implementation variant of the solution according to the application, the inlet for the cooling medium is located in a first axial plane, while the outlet for the cooling medium is preferably located in a second axial plane spaced apart from the first axial plane in the axial direction; the inlet and the outlet can also be arranged in the same axial plane.

[0013] By means of this arrangement of the inlet and the outlet for the cooling medium, an optimization of the tangentially extending flow path of the cooling medium can be achieved, so that a maximum of the heat loss can be dissipated from the electric machine.

[0014] The electric drive according to the application further comprises axial ribs which are embodied on the demolding bevels of the outer part and the inner part of the housing. The configuration of the demolding bevels on the outer part and the inner part of the housing, which form the coolant channel in the engaged state and extend in the axial direction, makes it possible to produce the housing comprising the inner part and the outer part of the electric machine by means of the die casting method.

[0015] In an advantageous manner, in the solution according to the application, the outer part and the inner part of the housing can each be embodied as a taper, which likewise facilitates easier demolding of the outer part and the inner part of the housing, provided that these are produced by means of the die casting method.

[0016] In the solution according to the application, the axial ribs are embodied in the machining region in the inner peripheral surface of the outer part, wherein the axial ribs of the outer part comprise in particular a cylindrical run-on on the inner peripheral surface of the outer part. In contrast, the axial ribs are configured in the machining region on the outer peripheral surface of the inner part of the housing in such a way that a conical run-on is configured there, in particular. By means of the subsequent, in particular chip-removing machining of the inner part and the outer part in the region of the axial ribs inside the demolding bevels, the coolant channel which extends substantially in the axial direction can be kept particularly flat in terms of its geometry, which on the one hand leads to optimum dissipation of the loss heat from the electric machine and on the other hand leads to a particularly space-saving configuration of the coolant channel.

[0017] In the solution according to the application, the electric drive is configured in such a way that the taper is determined by a first diameter and a second diameter of the inner part of the housing, for example. The respective taper of the outer part of the housing is complementary thereto.

[0018] In an advantageous manner, the electric drive is configured in such a way that the stator of the electric machine is fixed in the inner part of the housing, in particular shrunk into said inner part. This allows the stator of the electric machine to be particularly simply assembled in the inner part of the housing without the need for fixing elements, etc.

[0019] In an advantageous embodiment variant of the electric drive according to the application, the axial ribs of the inner part of the housing are provided with interruptions. Thereby, a turbulent flow state is imposed on the flow of the cooling medium, by means of which a significant improvement in the dissipation of heat from the electric machine can be achieved.

[0020] Furthermore, the application relates to the use of an electric drive in an E-axis module of a drive train of an electrically driven vehicle.

[0021] The advantages of the present application, in an advantageous manner, a very large surface is achieved by the ribbed design of both the outer part and the inner part of the housing of the electric machine, which leads to an optimal heat transfer to the cooling medium, for example cooling water. Furthermore, as very advantageously to be emphasized, by the axial ribs provided on the outer part and on the inner part, seen in the axial direction of the housing, the flow assumes a state of turbulence, which is accompanied by a significant improvement of the achievable heat transfer. Since the cooling channel is not shown as a cavity in one part, for example in a casting core, in the solution according to the present application, the cooling channel can be implemented very flat by the dimensioning of the outer part and the inner part. By the flat configuration of the cooling channel, the largest possible amount of the cooling medium flowing is connected with the surface on which the heat should be dissipated, so that the heat can be absorbed or transferred to the cooling medium in the best possible way. Due to the very flat configuration of the channel shown for the flow of the cooling medium as an intermediate space or flat gap between the axial ribs on the inner part and the outer part of the housing, a very high flow rate of the cooling medium can be achieved.

[0022] In the solution according to the present application, the design of the cooling is such that, in the case of the smallest cross section due to tolerances, on the one hand, the permissible flow resistance is not exceeded, and on the other hand, in the case of the largest cross section, a sufficient cooling power is ensured.

[0023] In the solution according to the present application, the cooling water guidance is optimized in such a way that the cooling water flows in at the inlet and is discharged again from the cooling channel geometry at the outlet connection, which is opposite the inlet at 180° offset. In this way, the cooling water is guided around the two sides of the electric machine in a tangential manner, respectively, half. The intermeshing axial ribs on the inner part and the outer part of the housing ensure the necessary flow influence of the cooling medium and the optimization of the achievable cooling effect. Since the inlet and the outlet of the cooling medium are as far apart as possible from each other in the axial direction, a substantially complete circulation of the two-part housing comprising the inner part and the outer part is achieved. In principle, the two interfaces, i.e. the inlet and the outlet for the cooling medium, can also be arranged on the same axial plane.

[0024] The outer part of the housing can be produced as a casting, for example, and is provided with a demolding slope. The inner part of the housing is designed cylindrically due to the manufacture. In order that the channel cross section, i.e. the intermediate space in which the cooling medium flows, does not become too large, the protruding part of the axial ribs is machined completely or partially, respectively, in the inner part and the outer part, so that, for example, with regard to the axial ribs, the axial ribs can be machined in such a way that they are implemented either conically over-turned or cylindrically over-turned. In both cases, the presence of the demolding slope on the inner part and the outer part can be used in an advantageous manner for optimizing the geometry of the intermediate space in the form of the gap between the inner part and the outer part of the housing. Attached Figure Description

[0025] Embodiments of the present invention are described in more detail with the aid of the accompanying drawings and the following description.

[0026] Figure 1 A perspective view of an electric drive unit with a transmission device having a side flange connection is shown.

[0027] Figure 2 It shows that according to Figure 1 A partial cross-sectional view of the electric drive unit.

[0028] Figure 3 The flow of cooling medium on a housing having outer and inner components according to the present invention is illustrated.

[0029] Figure 4 A top view shows an internal component with a constricted stator being pushed into the outer component of the housing.

[0030] Figure 5 A perspective view of the outer components of the housing is shown.

[0031] Figure 6 A first embodiment variant with an internal member having an externally located axial rib is shown, and

[0032] Figure 7 A second embodiment of the internal component with an interrupted portion having axial ribs is shown. Detailed Implementation

[0033] Figure 1 An electric drive unit 10 is shown in perspective, the electric drive unit having a first bearing cover 12 and a second bearing cover 16. A motor housing 14 is arranged between the first bearing cover 12 and the second bearing cover 16, the motor housing having a transmission device 18 with a lateral flange connection. The motor of the electric drive unit 10 (not shown in detail) is housed in the motor housing 14.

[0034] Figure 2 It shows that according to Figure 1 A partial cross-sectional view of the electric drive unit 10 in the perspective view.

[0035] Figure 2It is shown that the rotor shaft 20 is rotatably supported in a first bearing 26 and a second bearing 28, in which the rotor 22 of the electric machine is accommodated. The rotor shaft 20 of the electric machine rotates relative to the stator 24 of the electric machine, which is fixedly assembled on the housing. The first bearing 26 is accommodated in the first bearing cover 12. The second bearing 28 is supported in the laterally flanged transmission 18. The transmission 18 comprises an intermediate shaft 30, on which a gear wheel is accommodated, which meshes with a drive pinion of the rotor shaft 20. Cooling channels 32 extend in the motor housing 14. The individual cooling channels 32 are formed in the longitudinal direction by a partition 34. Each of the cooling channels 32 opens into a first or a second diverting pocket 36, 38, which is either machined into the material of the first bearing cover 12 or into the material of the second bearing cover 16.

[0036] In the following description of embodiments of the application, identical or similar elements are denoted by the same reference signs, wherein a repeated description of these elements is dispensed with in individual cases. The drawings merely schematically show the subject matter of the application.

[0037] Figure 3 A schematic representation of the flow 46 of the cooling medium through the housing 25 is shown. The cooling medium enters the cooling system of the housing 25 via the inlet 42 and exits the cooling system at the outlet 44. As is known from the illustration according to Figure 3 , the housing 25 is formed by an outer part 48 and an inner part 50. In the joined state, the outer part 48 and the inner part 50 define a channel geometry, as will also be described in more detail below. It can be seen from Figure 3 that the inlet 42 and the outlet 44 can be oriented relative to one another with a misalignment 52 of, for example, 180°. Misalignment angles other than 180° are also possible. Furthermore, it is shown from the illustration according to Figure 3 that there is an axial spacing 54 between the inlet 42 and the outlet 44 for the cooling medium. The inlet 42 for the cooling medium is located in a first axial plane 56, while the outlet 44 for the cooling medium is located in a second axial plane 58, which is further spaced apart in the axial direction from the first axial plane 56. Due to the spacing between the inlet and the outlet 42 / 44 for the cooling medium, a particularly long flow path can be imposed on the cooling medium, so that the cooling medium can transport the maximum amount of heat from the electric drive 10. Alternatively, the possibility also exists of arranging the inlet 42 and the outlet 44 in one and the same axial plane.

[0038] Furthermore, it is shown from the illustration according to Figure 3As can be seen in the illustration according to Fig. 1, the flow 46 of the cooling medium takes place substantially in tangential direction and is divided behind the inlet 42. Since the inlet 42 and the outlet 44 for the cooling medium are located far apart from one another as viewed in axial direction 78, an almost complete circulation of the housing 25 of the electric drive 10 is achieved. In principle, the inlet 42 and the outlet 44 can also be arranged in the same axial plane.

[0039] Figure 4 It is shown that the inner part 50 is pushed into the outer part 48 of the housing 25 of the electric drive 10. An annular gap-like intermediate space 60 is created between the outer part 48 on the one hand and the inner part 50 on the other hand. The geometry of the annular gap-like intermediate space 60 is substantially flat, so that a large contact surface between the cooling medium and the surface to be cooled is created and an optimum heat transfer to the cooling medium can be achieved. As Figure 4 It is shown that the individual sections of the annular gap-like intermediate space 60 are formed on the one hand by axial ribs 62 of the inner part 50 and on the other hand by axial ribs 64 of the outer part 48. Figure 4 It is further shown that the stator 24 of the electric machine is shrunk into the inner part 50 by means of a shrink connection 66 and is thus fixed without the need for additional fixing elements.

[0040] Figure 4 It is further shown that the stator 24 of the electric machine surrounds the rotor 22 of the electric machine which is accommodated on the rotor shaft 20.

[0041] Figure 5 A perspective view of the outer part 48 of the housing 25 is shown. From the perspective view according to Figure 5 As can be seen from the perspective view according to Fig. 2, the outer part 48 of the housing 25 can be produced, for example, as a casting, for example an aluminum die casting. For this purpose, the outer part 48 has a demolding bevel 68. Due to the demolding bevel 68, the finished cast blank of the outer part 48 can be removed more easily from the mold or casting tool. As Figure 5 As is further shown, the outer part 48 comprises axial ribs 64 on its inner circumferential surface, which consist of individual axial ribs which are spaced apart from one another in circumferential direction, which respectively comprise a base 72.

[0042] Furthermore, Figure 5 It is shown that the individual ribs of the axial ribs 64 of the outer part 48 have a cylindrical overrunning portion 71 in a machining region 74. By means of this machining of the respective upper side of the individual ribs of the axial ribs 64 on the inner circumference of the outer part 48, the annular gap-like intermediate space 60 is defined relative to the outer part 48.

[0043] Analogous to the illustration according to Fig. 1, the housing 25 according to Fig. 2 has an inlet 42 and an outlet 44 for the cooling medium, which are arranged in axial direction 78 at a distance from one another. Figure 5 Figure 6 ​The internal component 50 shown in the illustration has axial ribs 62 on its outer peripheral surface. The individual ribs 62 extend substantially parallel to each other on the outer periphery of the internal component 50. As shown in the illustration... Figure 6 As further seen in the illustration, the internal component 50 of the housing 25 is constructed as a cone 82 when viewed along the axial direction 78. This means that the internal component 50 is configured according to... Figure 6 The diagram, viewed along the axial direction 78, shows a variable diameter that tapers from a first diameter 84 to a second diameter 86. (See diagram 78 for reference.) Figure 6 As also shown, the stator 24 is fixed to the inner circumferential surface of the inner component 50, for example via... Figure 4 The shrink-fit connection 66 shown in the figure is fixed between the stator 24 of the motor and the internal component 50 of the housing 25.

[0044] Figure 6 It is also shown that the axial ribs 62 of the internal component 50 of the housing 25 also have machined areas 74. The machined areas 74 of the axial ribs 62 of the internal component 50 are provided with tapered turning portions 70. Within the tapered turning portions 70, the upper edges of each rib of the axial ribs 62 are cut, i.e., worn.

[0045] Inside the housing 25, part 50 and Figure 5 When the outer component 48 shown is engaged, it produces Figure 4 The annular, gap-shaped intermediate space 60 shown is in which the cooling medium flows tangentially (see [reference]). Figure 3 (Position 46 in the diagram). Figure 7 The alternative design possibilities for the internal component 50 of the housing 25 are shown. According to... Figure 7 As illustrated in the diagram, the inner component 50 includes an end side 80. Axial ribs 62, extending substantially in the axial direction 78, extend along the outer periphery of the inner component 50. Each rib of the axial ribs 62 of the inner component 50 has a respective interruption 76. According to... Figure 7 As illustrated in the diagram, the interruptions 76 of individual ribs of the axial ribs 62 of the inner component 50 are aligned with the interruptions 76 of adjacent individual ribs of the axial ribs 62. This creates introduced grooves 88 that extend circumferentially along the inner component 50 and introduce turbulent flow conditions into the cooling medium when flowing through the arrangement formed by the outer component 48 and the inner component 50. According to... Figure 3 The turbulent flow state of the cooling medium in the annular gap-shaped intermediate space 60 through the flow 46 improves heat dissipation from the housing 25 of the electric drive device 10 according to the present invention.

[0046] By according to Figure 7The embodiment variants of the inner part 50 achieve a significant increase in the surface area and a flow regime with respect to the application of turbulence to the cooling medium which flows through the annular gap-like intermediate space 60 between the outer part 48 on the one hand and the inner part 50 of the housing 25 on the other hand.

[0047] The application is not limited to the embodiments described herein and the aspects emphasized therein. Rather, a number of variants are possible within the scope of the claims, which are within the skill of the person skilled in the art.

Claims

1. An electric drive unit (10) for an electric vehicle, the electric drive unit having a rotor (22) and a stator (24), the stator being surrounded by a housing (25), characterized in that, The housing (25) has an outer part (48) and an inner part (50), the outer part and the inner part having axial ribs (62, 64) extending along the axial direction (78) of the housing (25), wherein the outer part (48) and the inner part (50) of the housing (25) are respectively implemented as cones (82), wherein the axial rib (64) has a machining area (74) on the inner circumferential surface of the outer part (48) or on the first outer circumferential surface of the inner part (50), the machining area being formed as a turning part (70, 71).

2. The electric drive device (10) according to claim 1, characterized in that, The axial ribs (62, 64) form an intermediate space (60) in the engagement state of the outer component (48) and the inner component (50), through which the cooling medium flows substantially tangentially.

3. The electric drive device (10) according to claim 1 or 2, characterized in that, The outer component (48) has an inlet (42) and an outlet (44) for a cooling medium, the inlet and outlet being positioned relative to each other at an axial distance (54).

4. The electric drive device (10) according to claim 3, characterized in that, The inlet (42) and the outlet (44) are misaligned (52) relative to each other.

5. The electric drive device (10) according to claim 3, characterized in that, The inlet (42) is located in a first axial plane (56), and the outlet (44) is located in a second axial plane (58) spaced apart from the first axial plane along the axial direction (78).

6. The electric drive device (10) according to claim 1 or 2, characterized in that, The axial ribs (62, 64) are provided on the demolding ramps (68) of the outer part (48) and inner part (50) of the housing.

7. The electric drive device (10) according to claim 1, characterized in that, The processing area (74) is made into a cylindrical rotating part (71).

8. The electric drive device (10) according to claim 1, characterized in that, The processing area (74) is implemented as a conical turning section (70).

9. The electric drive device (10) according to claim 1 or 2, characterized in that, The cone (82) is defined by the first diameter (84) and the second diameter (86) of the inner part (50) of the housing (25).

10. The electric drive device (10) according to claim 1 or 2, characterized in that, The stator (24) of the electric drive device is fixed in the internal part (50) of the housing (25) by a shrink connection (66).

11. The electric drive device (10) according to claim 2, characterized in that, The axial ribs (62) of the internal components (50) of the housing (25) have interruptions (76) that impose a turbulent state on the flow (46) of the cooling medium.

12. The application of the electric drive device (10) according to any one of the preceding claims in the E-axis module of an electric drive vehicle.

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