Housing for a drive train, with adjustable thermal conductivity; and drive unit

Abstract

The invention relates to a housing (1) for a motor vehicle drive train, comprising an outer wall (3) enclosing an interior (2), wherein the outer wall (3) has a heat dissipation device (4) whose thermal conductivity is adjustable. The invention also relates to a drive unit (12) with this housing (1).

Description

The invention relates to a housing for a drive train / drive unit of a motor vehicle, having an outer wall which engages / surrounds / envelopes an interior space. The housing is preferably implemented as a housing of a drive unit, wherein the drive unit further preferably has an electric drive machine and / or a transmission. The housing thus always accommodates a component / structural unit which either generates waste heat to be dissipated during operation or must first be heated to a specific operating temperature. The housing is preferably used in purely electrically driven motor vehicles, so-called BEVs.Housings of the generic type are sufficiently known. It is also customary to manufacture the housing by casting, using metallic materials, such as aluminum. Owing to their high thermal conductivity, these materials allow primarily a suitable heat emission from the interior enclosed by the outer wall to the outside / to the environment. However, if there is a need for heating for the components located in the interior, this heat flow to the environment is in principle undesirable only once.It is therefore the object of the present invention to provide a housing by means of which an efficiency of a drive train of a preferably purely electrically driven motor vehicle is further improved as far as possible independently of the existing ambient temperatures.This is achieved according to the invention in that the outer wall has a heat dissipation device that is adjustable with regard to its thermal conductivity.Because the thermal conductivity of the outer wall can be adjusted directly / directly, a higher thermal conductivity can thus be selected at high ambient temperatures, while a lower thermal conductivity is selected at low ambient temperatures. A significantly more efficient operation of the drive unit results.Further advantageous embodiments are claimed with the dependent claims and are explained in more detail below.Accordingly, it is also advantageous if the heat dissipation device can be switched over (controlled in a targeted manner) between at least two states (controlled in a targeted manner) which set different thermal conductivities of the outer wall. Further preferably, the thermal conductivity is adjustable (continuously or discontinuously) between a completely emptied state and a completely filled state of the cavity. As a result, the thermal conductivity can be selected appropriately.In addition, it is advantageous if the outer wall is equipped with at least one cavity of the heat dissipation device that can be closed off from the environment. Such a hollow space enables a particularly simple construction of the outer wall.In this regard, it is also expedient if the at least one cavity (preferably via a valve device) is designed to be normally closed and is opened (briefly) only for changing the thermal conductivity, that is to say when switching between individual states.As a particularly simple and low-maintenance variant, it has been found that the heat dissipation device is designed such that a filling state / pressure state of a fluid, preferably air, located within the at least one cavity (during operation) can be adjusted. As a result, the heat dissipation device can be used in a skillful manner for vacuum generation. The construction is thus kept as simple as possible.It is furthermore expedient if the outer wall has a first (preferably annular) wall section and a second (preferably likewise annular) wall section spaced apart from the first wall section, and the at least one cavity is formed between the two wall sections. In this way, in particular the wall sections can preferably be produced easily from separate elements. The wall sections are further preferably connected to one another in a materially bonded manner, for example by means of an adhesive connection or a welded connection.If the wall sections are supported spaced apart from one another by means of a plurality of support webs which are arranged spaced apart from one another and are formed integrally with one of the wall sections or separately from the wall sections, a sufficiently robust outer wall is also provided.According to a preferred embodiment, the wall sections are of annular / sleeve-shaped design and are arranged radially one inside the other, wherein the supporting webs are arranged radially between the wall sections and distributed in the circumferential direction.If a plurality of self-contained cavities are present in the outer wall, the thermal conductivity of the outer wall can be set even more finely. If a plurality of interconnected cavities are present in the outer wall, the construction of the switching / control device is further simplified.In this regard, it is particularly advantageous if the heat dissipation device is fluidically connected to a vacuum pump arranged outside the at least one cavity. The vacuum pump is preferably connected to the at least one cavity by means of a valve. The construction is thus further simplified.If an open pore structure is introduced within the at least one cavity, a fluid volume to be conveyed into the cavity or a fluid volume that can be correspondingly removed from the cavity can be designed to be as small as possible, so that the switching process between the different states takes place quickly.It is furthermore advantageous if the outer wall is made at least partially of a plastic. For example, it is possible to form the first wall section and / or the second section from a plastic. Alternatively, however, it is also possible to form the corresponding wall sections (at least partially) from metal, such as aluminum.The invention further relates to a drive unit for a motor vehicle, having a housing according to the invention according to at least one of the embodiments described above and an electric machine arranged within the housing and / or a transmission arranged within the housing.The invention will now be explained in more detail below with reference to figures, in which context various exemplary embodiments are also shown.The following are shown: FIG. 1 shows a cross-sectional view of a detail region of a housing according to the invention according to a first exemplary embodiment, wherein, in addition to a section of an outer wall of the housing formed according to the invention, a drive unit having the housing is also partially illustrated, FIG. 2 shows a cross-sectional view of a detail area of the housing according to the invention according to a second exemplary embodiment, wherein a plurality of support webs supporting two wall sections of an outer wall are no longer integrally formed as in FIG. 1 on a first wall section designed as an inner ring, but rather on a second wall section (outer ring) arranged outside the first wall section, FIG. 3 shows a cross-sectional view of a detail region of the housing according to the invention according to a third exemplary embodiment, wherein the respective supporting web is now formed separately from the wall sections, and FIG. 4 shows a cross-sectional view of a detail region of the housing according to the invention according to a fourth exemplary embodiment, wherein a pore structure is introduced between the two wall sections.The figures are merely schematic in nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numerals.FIG. 1 shows a section of a housing 1 according to the invention according to a first exemplary embodiment. The housing 1 is normally part of a drive unit 12, which is only schematically shown in FIG. 1 for the sake of clarity. The drive unit 12 is preferably realized as an E-axis / electric axle drive unit, which has both an electric machine 13 / drive machine and a transmission 14 connected thereto. The electric machine 13 is shown in FIG. 1 in a simplified manner with regard to its stator 16 and rotor 17. The transmission 14 is merely indicated for the sake of clarity.With regard to the electric machine 13, it should be pointed out that its stator 16 is preferably accommodated in the housing 1 according to the invention. The stator 16 is realized substantially annularly. The housing 1 has in particular an annular outer wall 3 which radially surrounds the stator 16 from the outside (radial direction denoted by reference arrow 19). The rotor 17 is again arranged radially inside the stator 16. The transmission 14 can be realized, for example, as a planetary transmission and is usually connected downstream of the electric machine 13 along a torque transmission path. It should be pointed out in this regard that other components can also be present in the housing 1, however, for example exclusively the electric machine 13 or exclusively the transmission 14.The housing 1 is thus shown in sections in FIG. 1 on the side of its annularly extending outer wall 3.The outer wall 3 has a heat dissipation device 4 designed according to the invention, which is adjustable with regard to its thermal conductivity. The outer wall 3 can be adjusted in its entirety with regard to its thermal conductivity. The heat dissipation device 3 can generally be adjusted between a plurality of states, i.e. at least two states. The states differ in each case with respect to the thermal conductivity of the outer wall 3.In FIG. 1, the outer wall 3 is composed of two segments / elements. A first annular wall portion 7 is arranged radially inward of a second annular wall portion 8. The two wall sections 7 are supported / held spaced apart from one another via a plurality of support webs 9 arranged distributed in the circumferential direction 18. The supporting webs 9 extend axially (in FIG. 1 into the plane of the drawing). In this first embodiment, the support webs 9 are integrally formed on the first wall section 7 in a material-integral manner.The support webs 9 directly define the height of a plurality of cavities 6 arranged between the two wall sections 7, 8, which cavities are distributed in the circumferential direction 18. The hollow spaces 6 can in principle be fluidically connected to one another via connecting passages penetrating the supporting webs 9. If the cavities 6 are fluidically connected to one another, the plurality of cavities 6 can also be regarded as an overall cavity 6, which is closed off from the environment. The surrounding area of the outer wall 3 is to be understood in particular as meaning both a surrounding area radially outwards and inwards.In the first exemplary embodiment, the heat dissipation device 4 has a vacuum pump 10 by means of which an internal filling state / pressure state of a fluid within the cavities 6 can be adjusted. A filling medium is preferably air. Depending on the filling state of fluid within the respective cavity 6, the thermal conductivity of the outer wall 3 can be variably adjusted in its entirety.The vacuum pump 10 provided thus adjusts the fill level within the cavity 6 by means of targeted actuation (by means of a control device not shown in more detail). Preferably, a valve 15 is present between the vacuum pump 10 and a cavity 6, which valve is designed such that it is designed to close normally during normal operation of the drive unit 12 / of the housing 1 and thus permanently closes off the cavity 6 from the environment during normal operation. Only when the vacuum pump 10 is actuated does the valve 15 / the cavity 6 open to the environment in order to set the internal fill level / the pressure in the cavity 6 in a targeted manner. Once again a desired fill level has been reached, the valve 15 closes automatically.If a high thermal conductivity of the outer wall 3 is therefore intended to be implemented, the cavity 6 is filled with the fluid (first state); if, on the other hand, the thermal conductivity is intended to be kept low, the fill level of fluid within the cavity 6 is reduced (second state). Thus, in the first state, a higher fill level of fluid is present in the cavity 6 than in the second state. It is thus preferably possible to achieve any desired number of states which differ with respect to the fill level / pressure in the cavity 6.Due to the adjustable thermal conductivity, it is also possible to produce the wall sections 7, 8 from materials other than metal, such as aluminum, for example from plastic. In particularly preferred embodiments, however, the respective wall section 7, 8 is at least partially made of metal in order to ensure heat dissipation from the stator 16 as effectively as possible.In conjunction with FIGS. 2 to 4, alternative exemplary embodiments are then shown, which, however, correspond to the first exemplary embodiment with regard to their basic structure. For the sake of brevity, only the differences from the first embodiment will be described below.It can be seen from FIG. 2 that the second wall section 8 serving as an outer ring is now provided with the supporting webs 9. The support webs 9 are thus formed integrally on the second wall section 8 in a material-forming manner. In the first exemplary embodiment, the supporting webs 9 were also formed integrally on the first wall section 7 designed as an inner ring.In the third exemplary embodiment of FIG. 3, the supporting webs 9 are realized completely separately from the wall sections 7, 8 and are formed as separate strip-shaped elements. These may in turn consist of a metal or a plastic material. These supporting webs 9 are then preferably connected to the respective wall section 7, 8 in a materially integral manner.According to the fourth exemplary embodiment of FIG. 4, it is furthermore possible to introduce a pore structure 11 into the cavity 6, which pore structure is preferably realized as an open / open pore structure. The pore structure 11 can be formed in such a way that the supporting webs 9 can be completely dispensed with. A support of the wall sections 7, 8 relative to each other can thus be effected directly by the pore structure 11.In other words, the concept according to the invention consists in using a material with cavities 6 which can be subjected to vacuum. When the cavities are evacuated, a relatively low thermal conductivity is reacted, if they are not (completely) evacuated, the thermal conductivity is high.List of reference characters1 Housing 2 Interior space 3 Outer wall 4 Heat dissipation device 5 Environment 6 Cavity 7 First wall portion 8 Second wall portion 9 Supporting web 10 Vacuum pump 11 Pore structure 12 Drive unit 13 Electric machine 14 Transmission 15 Valve 16 Stator 17 Rotor 18 Circumferential direction 19 Radial direction

Claims

Housing (1) for a drive train of a motor vehicle, having an outer wall (3) which surrounds an interior space (2), characterized in that the outer wall (3) has a heat dissipation device (4) which is adjustable with respect to its thermal conductivity.Housing (1) according to Claim 1, characterized in that the heat dissipation device (4) can be switched over between at least two states which set different thermal conductivities of the outer wall (3).Housing (1) according to Claim 1 or 2, characterized in that the outer wall (3) is equipped with at least one cavity (6) of the heat dissipation device (4) which can be closed off from the environment (5).Housing (1) according to Claim 3, characterized in that the heat dissipation device (4) is designed in such a way that a filling state of a fluid located within the at least one cavity (6) is adjustable.Housing (1) according to Claim 3 or 4, characterized in that the outer wall (3) has a first wall section (7) and a second wall section (8) spaced apart from the first wall section (7), and the at least one cavity (6) is formed between these two wall sections (7, 8).Housing (1) according to Claim 5, characterized in that the wall sections (7, 8) are supported at a distance from one another by means of a plurality of mutually spaced supporting webs (9) which are formed integrally with one of the wall sections (7, 8) or are formed separately from the wall sections (7, 8).Housing (1) according to one of Claims 1 to 6, characterized in that a plurality of cavities (6) which are self-contained or are connected to one another are present in the outer wall (3).Housing (1) according to one of Claims 3 to 7, characterized in that the heat removal device (4) is fluidically connected to a vacuum pump (10) arranged outside the at least one cavity (6).Housing (1) according to one of Claims 2 to 7, characterized in that an open pore structure (11) is introduced within the at least one cavity (6).Drive unit (12) for a motor vehicle, having a housing (1) according to one of Claims 1 to 9 and an electric machine (13) arranged within the housing (1) and / or a transmission (14) arranged within the housing (1).

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