Electric drive device with thermally decoupled heat exchanger

Abstract

Electric drive device (1) for a motor vehicle, comprising an electric drive motor (2), a housing (3) accommodating the drive motor (2) and a heat exchanger (4) connected to the housing (3), characterized in that a fluid circuit (5) connected to the heat exchanger (4) passes through an interior (6) of a stator (17), providing at least partial cooling of the drive motor (2) in an operating state, wherein the heat exchanger (4) is arranged indirectly on an outer surface (8) of the housing (3) via at least one heat decoupling element (7) and the at least one heat decoupling element (7) has a lower thermal conductivity than the housing (3).

Description

[0001] The invention relates to an electric drive device, preferably in the form of a modular axle drive unit / axle drive module / e-axle, for a motor vehicle, such as a car, truck, bus or other commercial vehicle.

[0002] The overall goal is to achieve the most efficient possible cooling and lubrication of the drive unit components housed within the casing. For efficient cooling, it is also essential to position the heat exchanger as far away as possible from the heat-radiating casing. At the same time, the drive unit should, of course, be modular so that it can be installed as a pre-assembled unit in its intended position within the vehicle.

[0003] The generic patent DE 10 2011 084 038 A1 discloses an electromechanical drive unit with an electric motor, wherein a heat exchange fluid is conductive through a housing of the electric motor. A heat exchanger is connected in such a way that the heat exchange fluid can flow through it.

[0004] DE 10 2006 020 801 A1 discloses a cooling module for a gearbox, the shape of which, facing the interior of the gearbox, follows the shape of a rotating part or parts of the gearbox in order to improve heat dissipation from the interior of the gearbox by means of an enlarged surface area in the oil flow space between the part or parts and the housing. The cooling module comprises a casting in which a space for flowing coolant is provided, bounded by the casting and a housing plate tightly connected to the casting. Cooling fingers are attached to the casting, pointing towards the interior of the gearbox, and are either integrally formed or welded to the casting. The ends of the cooling fingers follow the shape of the rotating part of the gearbox and are arranged on a circular arc, the radius of which is determined by the radius of the rotating part.The space for the flowing coolant is designed as a meandering groove.

[0005] It can therefore be considered an object of the present invention to provide a drive device that is cooled as efficiently as possible, is designed as a module that is as compact as possible and can be used variably in different motor vehicles.

[0006] This is achieved according to the invention by the subject matter of claim 1, according to which an electric drive device is claimed, comprising an electric drive motor, a housing for the drive motor, and a heat exchanger connected to the housing. A fluid circuit connected to the heat exchanger passes through an interior space of the housing / stator of the drive motor, at least partially cooling the drive motor during operation. The heat exchanger is indirectly arranged on an outer surface of the housing via at least one thermal decoupling element. The at least one thermal decoupling element has a lower thermal conductivity than the housing.

[0007] By mounting the heat exchanger on the outside of the housing, a highly compact module is achieved. Simultaneously, the inclusion of a thermal decoupling element creates a protective shield against the heat emitted by the housing during operation. This allows the heat exchanger to operate as efficiently as possible while also positioning it as close as possible to the housing. The result is a compact and highly efficiently cooled drive unit.

[0008] Further advantageous embodiments are claimed in the dependent claims and are explained in more detail below.

[0009] Therefore, it is also advantageous if at least one thermal decoupling element has a significantly lower thermal conductivity than the housing. This further improves the shielding effect.

[0010] The housing and at least one thermal decoupling element can perform their functions as effectively as possible if the housing is made at least partially of an aluminum material and / or if at least one thermal decoupling element is made of a plastic.

[0011] The thermal decoupling is as effective as possible if at least one thermal decoupling element has a ring area that is inserted between a base area of ​​the housing and the heat exchanger, defining a screw point and / or forming a fluid passage between the interior of the housing and its exterior.

[0012] Alternatively, it is also advantageous if at least one thermal decoupling element has several ring sections, each positioned between the base area of ​​the housing and the heat exchanger, defining a screw-in point and / or forming a fluid passage between the interior and exterior of the housing. This further improves the shielding effect.

[0013] Furthermore, it is advantageous if at least one thermal decoupling element is shaped like a plate. This allows it to be installed in a particularly space-saving manner.

[0014] It is in principle possible to design at least one thermal decoupling element in multiple layers, for example with an additional damping layer that dampens the vibrations acting on the housing during operation.

[0015] It is further advantageous if the at least one thermal decoupling element has at least two ring sections, each resting on its own base area of ​​the housing, with a plate section of the at least one thermal decoupling element connecting the ring sections being spaced away from the housing. This further improves the shielding effect.

[0016] It is also advantageous if the heat exchanger has a mounting section with increased thermal conductivity compared to the at least one thermal decoupling element, and this mounting section rests against the at least one thermal decoupling element on a side facing away from the housing. This simplifies the installation of the heat exchanger.

[0017] In this context, it is advantageous if the mounting section is attached to the at least one thermal decoupling element using a first fastening element, and the at least one thermal decoupling element is attached to the housing using a second fastening element. This further improves the shielding effect. Alternatively, it is advantageous if the fastening element and the at least one thermal decoupling element are attached to the housing using common fastening elements. This again keeps the assembly as simple as possible.

[0018] Furthermore, it is advantageous if several heat decoupling elements (and thus a group / arrangement of several heat decoupling elements) are arranged between the heat exchanger and the housing, with each heat decoupling element preferably being arranged between a base area of ​​the housing and the heat exchanger.

[0019] The invention will now be explained in more detail below with reference to figures, in which context various embodiments are also indicated.

[0020] They show: Fig. 1 a perspective view of an in-section electric drive device according to the invention in a first embodiment, wherein an arrangement of a heat exchanger relative to a housing / a drive machine arranged inside the housing is clearly visible, Fig. 2 a perspective view of the drive device according to Fig. 1, where this is now presented in such a way that a fastening means securing the heat exchanger to the housing is shown in more detail, Fig. 3 another perspective view of the drive device according to Fig. 1, which allows components of a fluid circuit encompassing the heat exchanger to be identified in cross-section, Fig. 4 a perspective view of a scene in the Fig. 1, Fig. 2 to Fig. 3. a heat decoupling element arranged between the heat exchanger and the housing, wherein the heat coupling element is recognizable from its upper side facing the heat exchanger, Fig. 5 a perspective view of the heat decoupling element according to Fig. 4 from its underside facing away from the heat exchanger, Fig. 6 a top view of the heat decoupling element according to Fig. 4, Fig. 7 a top view of an assembly consisting of the heat decoupling element according to Fig. 4 and the heat exchanger, Fig. 8 a perspective view of a heat decoupling element designed according to a second embodiment, which can be used as an alternative to the heat decoupling element of the first embodiment, and Fig. 9 a perspective view of an arrangement of several individual heat decoupling elements designed according to a third embodiment, which can be used as an alternative to the heat decoupling element of the first embodiment.

[0021] The figures are purely schematic and serve solely to illustrate the invention. The same elements are identified by the same reference numerals. Furthermore, the various features of the different embodiments can, in principle, be freely combined.

[0022] In connection with the Fig. 1, Fig. 2 to Fig. Figure 3 describes the structure of an electric drive device 1 according to the invention. The electric drive device 1 is preferably modular in design and thus implemented as an e-axle, which is preferably mounted as a complete unit in a motor vehicle and drives at least two drive wheels of the motor vehicle during operation.

[0023] The drive device 1 therefore has a [missing information] in the Fig. 1 and Fig. Figure 3 shows an indicated electric drive motor 2. In particular, a stator 17 of this drive motor 2 can be seen. The drive motor 2 is inserted / mounted in a housing 3.

[0024] In the usual manner, further components are provided on or in the housing 3 and thus in the drive device 1, which, for the sake of clarity, are not shown in detail here. It should be noted in particular that a power electronics unit for controlling the drive motor 2 is preferably also used and is accordingly connected to this drive motor 2. Preferably, a gearbox, such as a planetary gearbox, is also installed in the housing 3 downstream of the drive motor 2 along the intended torque transmission path.

[0025] The housing 3 itself is made of a metal material, preferably an aluminum alloy. The drive motor 2, as well as the optionally provided components of the gearbox and the power electronics unit, are installed together in an interior space 6 of the housing 3. Regarding the power electronics unit, it should be noted that it is also possible, in principle, to mount it outside the housing 3.

[0026] The interior space 6 of the housing 3 (corresponding to the interior space 6 of the stator 17 due to its arrangement / allocation to the housing 3) is also part of a fluid circuit 5, which can be seen section by section in the figures. In other words, the interior space 6 is connected to the fluid circuit 5. The fluid circuit 5 flows through the interior space 6 in such a way that various components within the housing 3, for example the stator 17, are cooled. The fluid circuit 5 can also, in principle, be used to lubricate the components of the gearbox or additionally to cool the power electronics unit.

[0027] A heat exchanger 4 is attached to an outer surface 8 of the housing 3. Fig. Figure 2 shows that the heat exchanger 4 rests on so-called base areas 12a of the housing 3 and is partially fastened, namely screwed on. The base areas 12a are essentially designed as bushing-shaped projections.

[0028] It is assumed from the Fig. 1, Fig. 2 to Fig. 3 further states that the heat exchanger 4 has a mounting section 15 which is essentially plate-shaped. The mounting section 15 is preferably made of metal.

[0029] According to the invention, a thermal decoupling element 7 is arranged between the heat exchanger 4, namely the mounting section 15, and the housing 3. In other words, the heat exchanger 4 thus rests indirectly against the housing 3 via the thermal decoupling element 7. According to the invention, the thermal decoupling element 7 has a significantly lower thermal conductivity than the housing 3 itself. Preferably, the thermal decoupling element 7 is made of a plastic material.

[0030] The heat decoupling element 7 is preferably according to the Fig. 4, Fig. 5, Fig. 6 to Fig. 7 and has a plate area 14. The plate area 14 is preferably provided on its side facing the heat exchanger 4 with stiffening ribs that run between several ring areas 9. The plate area 14 therefore served to connect the ring areas 9 (also referred to as bore areas or through-flow areas).

[0031] The ring sections 9 project towards the side facing the housing 3 and thus extend beyond the plate section 14 in this direction. Each ring section 9 serves to rest against a base section 12a of the housing 3.

[0032] It can be seen that these ring areas 9 directly form fluid passages 11, which are connected to / transition into further fluid passages 10a, 10b of the base areas 12a. These fluid passages 10a, 10b form the fluid circuit 5.

[0033] While two ring areas 9 form directly straight fluid passages 11 and thus passages into the interior of the housing 3, ring areas 9 are also provided that connect directly to angled channels 18, which channels 18, however, do not open directly into the interior of the housing 3.

[0034] Furthermore, several through-holes 19 are provided on the thermal decoupling element 7, which, in conjunction with fasteners 16 (screws), are attached to base areas 12a forming screw points 13. In principle, common fasteners 16 can be provided for the joint attachment of the heat exchanger 4 and the thermal decoupling element 7 to the housing 3; alternatively, however, firstly, fasteners can be provided that only secure the heat exchanger 4 to the thermal decoupling element 7, and secondly, fasteners can be provided that only secure the thermal decoupling element 7 to the housing 3 / the screw points 13.

[0035] Regarding the further design of the housing 3, it should be noted that preferably, offset to the base areas 12a, a gap / airless space 20 is provided between the housing 3 and the plate area 14 of the heat decoupling element 7.

[0036] With the Fig. 8 and Fig. 9 It is pointed out that according to further alternative embodiments, which are largely constructed and function according to the first embodiment, the heat decoupling element 7 can also be designed in a different way.

[0037] Accordingly, the heat decoupling element 7 in Fig. 8 a substantially rectangular plate area 14 on.

[0038] In Fig. 9 The individual ring areas 9 can also directly form independent thermal decoupling elements 7, thus eliminating the need for the plate area 14. This corresponds to an arrangement of several thermal decoupling elements 7.

[0039] In other words, according to the invention, an intermediate component (thermal decoupling element 7 (also referred to as heat exchanger support)) is placed between the heat exchanger 4 and the housing 3, which, in addition to the necessary mechanical and chemical properties, has a thermal conductivity (in W / (m*K)) that is significantly lower (plastics typically 0.x W / (m*K) compared to aluminum alloys approximately 75-200 W / (m*K); therefore, a factor greater than 100).

[0040] In a simple version, the interfaces between heat exchanger 4 and heat exchanger support and between heat exchanger support and housing 3 are the same. Due to the screw connection (fastening means 16; usually steel screws with high thermal conductivity), a residual heat conduction path exists. A further preferred version therefore includes separate interfaces / fastening means 16 between heat exchanger 4 and heat exchanger support and between heat exchanger support and housing 3.

[0041] The heat conduction path extends completely over the heat exchanger support and is advantageously also longer.

[0042] In a particularly preferred embodiment, three damping (polymer) elements are advantageously integrated between the heat exchanger support and the housing. This may optimize both thermal and acoustic decoupling (this embodiment is omitted from the figures for clarity).

[0043] Decoupling can also be implemented between heat exchanger 4 and the heat exchanger support. The necessary sealing elements perform this function. Complex and therefore expensive (sealing) interfaces on housing 3 can be reduced, resulting in cost savings.

[0044] Alternatively, the (four) fluid interfaces (ring areas 9) required for the heat exchanger function can be represented by individual components instead of in one component as described above, either completely separated or partially combined.

[0045] The heat exchanger support preferably includes lines for two fluid connections, which are not shown or only partially shown in housing 3.

[0046] Furthermore, the heat exchanger support incorporates seals 21 that seal the contact points between the heat exchanger 4 and the heat exchanger support, and between the heat exchanger support and the housing 3, as well as other components involved in the fluid circuit (e.g., stator housing). Advantageously, the seals 21 / sealing elements are attached / injection-molded onto the heat exchanger support, thus reducing assembly effort.

[0047] As previously mentioned, a common interface (screw connection) between heat exchanger 4, heat exchanger support, and housing 3 is possible (heat exchanger support is located between heat exchanger 4 and housing 3), or separate interfaces (screw connections) between heat exchanger 4 and heat exchanger support and between heat exchanger support and housing 3 are possible. Pre-assembly and, if necessary, assembly testing of heat exchanger 4 and heat exchanger support are possible.

[0048] Furthermore, the heat exchanger support can include additional interfaces (mechanical, electrical or hydraulic). Reference symbol list 1 Drive device 2 Drive machine 3 cases 4 heat exchangers 5 Fluid circuit 6 Interior 7 Thermal decoupling element 8 Outside 9 ring area 10a first fluid passage 10b second fluid passage 11 Fluid passage 12a Base area 12b Fluid1 exit from stator housing 13. Screw-in point 14 plate area 15 Fastening section 16 Fasteners 17 Stator 18-channel 19 through hole 20 spaces 21 Seal

Claims

Electric drive device (1) for a motor vehicle, comprising an electric drive motor (2), a housing (3) accommodating the drive motor (2) and a heat exchanger (4) connected to the housing (3), characterized in that a fluid circuit (5) connected to the heat exchanger (4) passes through an interior (6) of a stator (17), providing at least partial cooling of the drive motor (2) in an operating state, wherein the heat exchanger (4) is arranged indirectly on an outer surface (8) of the housing (3) via at least one heat decoupling element (7) and the at least one heat decoupling element (7) has a lower thermal conductivity than the housing (3). Drive device (1) according to claim 1, characterized in that the at least one heat decoupling element (7) has a thermal conductivity that is many times lower than that of the housing (3). Drive device (1) according to claim 1 or 2, characterized in that the housing (3) is made at least partially of an aluminum material and / or that at least one heat decoupling element (7) is made of a plastic. Drive device (1) according to one of claims 1 to 3, characterized in that the at least one heat decoupling element (7) has a ring area (9) which is inserted between a base area (12a) of the housing (3) defining a screw point (13) and / or forming a fluid passage (10a, 10b) between the interior (6) of the housing (3) and its outer surface (8) and the heat exchanger (4). Drive device (1) according to one of claims 1 to 4, characterized in that the at least one heat decoupling element (7) has several ring areas (9) which are each inserted between a base area (12a) of the housing (3) defining a screw point (13) and / or a fluid passage (10a, 10b) between the interior (6) of the housing (3) and its outer surface (8) and the heat exchanger. Drive device (1) according to one of claims 1 to 5, characterized in that the at least one heat decoupling element (7) is shaped like a plate. Drive device (1) according to one of claims 1 to 6, characterized in that the at least one heat decoupling element (7) has at least two ring areas (9) each resting on its own base area (12a) of the housing (3), wherein a plate area (14) of the at least one heat decoupling element (7) connecting the ring areas (9) is spaced apart from the housing (3). Drive device (1) according to one of claims 1 to 7, characterized in that the heat exchanger (4) has a fastening section (15) having increased thermal conductivity compared to the at least one heat decoupling element (7), which fastening section (15) is located on a side facing away from the housing (3) on the at least one heat decoupling element (7). Drive device (1) according to claim 8, characterized in that the fastening section (15) is attached to the at least one heat decoupling element (7) by means of first fastening means (16) and the at least one heat decoupling element (7) is attached to the housing (3) by means of second fastening means. Drive device (1) according to one of claims 1 to 9, characterized in that several heat decoupling elements (7) are arranged between the heat exchanger and the housing (3).

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