Stator carrier, drive arrangement and motor vehicle

Abstract

The invention relates to a stator carrier (40) for receiving a stator (32) of an electrical machine (30) designed as an internal rotor, in particular a traction machine for a motor vehicle, comprising a hollow cylindrical sleeve with a sleeve wall surrounding a stator chamber, which has a radially inwardly facing inner side carrying an inner joining surface (402) and a radially outwardly facing outer side carrying an outer joining surface (401), The invention is characterized in that the sleeve wall carries a plurality of pressure equalization grooves (441) distributed over the circumference of the sleeve, each of which extends predominantly axially over a predominant part of the axial length of the sleeve and is in direct fluidic connection with the stator chamber at least on both sides.

Description

The invention relates to a stator carrier for receiving a stator of an electric machine designed as an internal rotor, in particular a traction machine for a motor vehicle, comprising a hollow cylindrical sleeve having a sleeve wall which extends around a stator space and which has an inner side facing radially inward and bearing an inner joining surface and an outer side facing radially outward and bearing an outer joining surface, wherein the sleeve wall bears a plurality of pressure compensation grooves which are arranged distributed over the circumference of the sleeve and each extend predominantly axially over a predominant part of the axial length of the sleeve and are in direct fluidic connection at least terminally with the stator space.The invention further relates to a drive arrangement for a motor vehicle, comprisinga housing having a cylindrical housing interior space which runs around from an inner joining surface,a stator support comprising a hollow cylindrical sleeve with a sleeve wall surrounding a stator space, which has an inner side facing radially inward and carrying an inner joining surface and an outer side facing radially outward and carrying an outer joining surface, anda hollow cylindrical stator of an electric machine, which stator runs round from an outer joining surface,wherein the stator is joined into the stator space with its outer joining surface resting against the inner joining surface of the stator carrier and with the sleeve wall projecting axially beyond both sides beyond the stator, wherein the stator carrier is joined into the housing interior with its outer joining surface resting against the inner joining surface of the housing, and wherein the sleeve wall carries a plurality of pressure compensation channels arranged distributed over the circumference of the sleeve, which channels together with a radially adjacent joining surface form a plurality of pressure compensation channels arranged distributed over the circumference of the sleeve, which channels each extend predominantly axially, axially span the stator and are connected terminally in direct fluidic connection with the stator space.A stator support of the generic type is known from DE 196 35 196 A1.DE 10 2020 207 236 A 1 discloses an electric traction drive for a motor vehicle with a water-cooled, dry-running electric machine. The drive arrangement comprises a housing with a substantially cylindrical housing interior, which can also be referred to as machine space since the electric machine is arranged therein. The inner side of the cylinder jacket of the housing serves as a joining surface for the indirect fixing of the stator of the electric machine. The end faces of the housing support the bearings of the rotor shaft of the rotor of the electric machine. The latter, as named for electric machines of the internal rotor type, is arranged concentrically within the stator which is substantially hollow-cylindrical. As mentioned, the stator is not joined directly, but indirectly to the housing. For this purpose, a sleeve-like stator carrier is arranged between the stator and the housing. This sleeve carries on its outer side an outer joining surface which is joined to the inner joining surface of the housing. On its inner side, the sleeve carries an inner joining surface which is joined to the outer surface of the stator acting as an outer joining surface. In particular, said joints can be designed as press connections. The outer joining surface of the stator carrier is not formed as a uniform, contiguous cylinder surface. Rather, the sleeve outer side carries a plurality of parallel ribs extending in the circumferential direction, so that a channel structure open radially outwards is formed on the outer side of the stator carrier. The crowns of said ribs serve as the actual joining surface and are in fluid-tight contact with the inner joining surface of the housing in the final assembly state. In this way, a cooling channel system is formed which is radially closed-apart from an optionally provided inlet and / or outlet and can be supplied with a cooling fluid flow in order to act as a so-called water jacket, with which waste heat produced during operation of the electric machine can be reliably dissipated. Axially terminally, two closely adjacent ribs each form a sealing groove, into which an O-ring seal is inserted. In order to avoid stress peaks during the joining process, i.e. during the insertion of the stator carrier into the machine space of the housing, a respective groove wall of the two sealing grooves is formed from a rib with a height varying over the circumference. This rib or sealing groove wall therefore does not lie fully on the inner joining surface of the housing. This is intended to avoid stress peaks without the sealing effect being impaired.DE 10 2019 116 941 A1 also discloses a stator carrier with a radially open channel structure in its outer side, which forms a closed cooling channel system together with the inner joining surface of the housing. However, the cooling channels run meanderingly here.As an alternative or in addition to cooling via a water jacket, internal oil cooling is known in so-called wet-running electric machines. For this purpose, oil is pumped into the hollow rotor shaft and spun via axial openings onto the end windings of the stator. This oil then runs off by gravity into an oil sump through suitably placed overflow bores. Reliable removal of the oil is desirable in order to avoid penetration of oil into the air gap between the rotor and the stator of the electric machine.The drive arrangement known from the above-mentioned DE 10 2020 207 236 A1 is not suitable for the installation of such an additional oil cooling system. During operation of the known device, pressure differences will always build up in the two end spaces, i.e. in the intermediate spaces axially adjacent to the rotor between the electric machine and the housing end wall. These may have their causes in the mechanical movement of the rotor itself and / or in temperature differences occurring during operation. In the case of an additional, internal oil cooling, the problem of a distribution of the cooling oil from the rotor shaft into the two end spaces, which distribution is unequal depending on the driving situation, and the problem of an unequal increase or decrease of the oil level in the case of a driving situation-dependent oblique position of the drive are added.From DE 10 2013 200 105 A1, it is known to connect the two end spaces fluidically to one another by channels guided in the housing in order to achieve an air pressure compensation between the two end spaces. However, this known drive arrangement is likewise a purely dry-running electric machine in which an air pressure difference in the end spaces per se is not disadvantageous; on the contrary, in the known device, by arranging a blade wheel in an axial channel of the rotor, a pressure difference is specifically built up which is compensated again for (air) cooling purposes by said pressure compensation channel in the housing and in the process generates a continuous cooling air flow in a predetermined flow direction.The generic DE 196 35 196 A1 mentioned at the beginning discloses a similar concept in which, however, the pressure compensation channels are not formed as closed channels in the material of the housing wall, but as radially open channels in the inner wall of the stator carrier sleeve, which channels form closed channels together with the outer joining surface of the stator only in the final assembly state. These end openings into the respective radially inner space: on one side of the stator, this is the stator space itself; on the other side of the stator, this is a cover region delimited by a bearing shield, which, however, is in turn connected to the stator space again via axial apertures.DE 10 2022 207 130 A1 likewise discloses a stator carrier having open grooves which are axially elongated in its inner wall and which, however, are connected to one another via an annular gap which runs around the stator in its axial central region and together with the annular gap form a cooling space through which cooling oil can flow, driven by gravity, from top to bottom.It is the object of the present invention to further develop a stator support of the generic type or a drive arrangement of the generic type for a motor vehicle in such a way that an internal oil cooling system can be installed, i.e. that a wet-running electric machine can be used as a drive unit.It is a further object of the invention to propose a production method for a stator carrier according to the invention and a motor vehicle having a drive arrangement according to the invention.This object is achieved in conjunction with the features of the preamble of claim 1 in that the sleeve wall carries the pressure compensation grooves on its outer side, wherein these grooves are designed to be open radially outwards and their raised groove edges form part of the outer joining surface, wherein the direct fluidic connections of the pressure compensation grooves to the stator space are designed as radial through openings through the sleeve wall which are arranged terminally on both sides.The object is further achieved in conjunction with the features of the preamble of claim 5 in that the sleeve wall of the stator carrier carries the pressure compensation channels on its outer side, wherein these are designed to be open radially outwards, their raised channel edges form part of the outer joining surface of the stator carrier, and the direct fluidic connections of the pressure compensation channels to the stator space are designed as radial through openings through the sleeve wall, which are arranged on both sides of the stator, so that the pressure compensation channels together with the inner joining surface of the housing form pressure compensation channels which are radially closed in their respective axial central region and are open axially terminally radially inwards towards the stator space.A motor vehicle having a drive arrangement according to the invention is subject matter of claim 9.As likewise known, provision is made here to provide the stator support alone with additional elements which, in the final assembly state, i.e. when the stator is joined into the stator support and the stator support is in turn joined into the housing, create a corresponding pressure compensation system. In particular, contours are proposed on the stator carrier on its outer side, i.e. in its outer joining surface, which contours form the said pressure compensation system in interaction with the inner joining surface of the housing. The inner joining surface of the housing and the outer joining surface of the stator can therefore be designed particularly simply, in particular as uniform, contiguous cylinder jackets. Complicated contours are found only on the stator carrier, which, however, is designed as a sleeve with a comparatively large diameter (approximately the same order of magnitude as its axial length) and therefore an inner side and an outer side that can easily be reached and can be designed as a sheet metal forming or cast part. Preferably, a blank of the stator carrier is provided as a hollow cylindrical sleeve with a sleeve wall surrounding the stator space and the pressure compensation grooves according to the invention are produced by subsequent machining. The latter applies preferably also to the coolant guiding structure of a water jacket, if such a water jacket is desired.Water jacket variants are the preferred embodiment of the invention. For this purpose, it is provided that the sleeve wall of the stator carrier carries on its outer side a coolant conducting structure which is open radially outwards and the raised structure edges of which form part of the outer joining surface. In the final assembly state, this coolant guiding structure forms, together with the inner joining surface of the housing, a radially closed cooling channel system, namely said water jacket. The skilled person will understand that the term "radially closed" relates only to the guidance of the cooling fluid over the circumference of the stator carrier or of the stator. Possible inflows and outflows, via which the cooling fluid is discharged to or from the cooling duct structure and which are optionally connected radially to the cooling duct system, are expressly not to be excluded by this formulation.For the special arrangement and configuration of the pressure compensation channels, different variants are conceivable, which can be realized alone or in combination with one another. Thus, in one embodiment of the invention which is particularly simple to implement, it is provided that the sleeve wall of the stator carrier carries the pressure equalization grooves on its inner side, wherein these grooves are designed to be open radially inwards and their raised groove edges form part of the inner joining surface. In the final assembly state, this means that said pressure compensation channels on the inner side of the sleeve wall together with the joining surface of the stator form a pressure compensation channel system which is radially closed over the length of the stator and is open radially inward toward the stator space axially to the side of the stator. Expressed simply, the inner side of the stator carrier is provided with axially extending longitudinal grooves which are longer than the axial length of the stator, so that in the final assembly state they extend on both sides beyond the stator positioned in the stator space. Over the length of the stator, these slots are closed by the outer wall of the stator. In this axial region of the drive arrangement, they thus form a system of circumferentially distributed, discontinuous, individual, closed channels for pressure compensation. In the areas where they protrude laterally beyond the stator, however, these channels are open radially inward and are in fluidic connection with the respective face space of the electric machine. As a result, the two end spaces are fluidically connected to one another.According to the invention, for the arrangement of pressure compensation grooves on the sleeve inner side, it is provided that the sleeve wall carries the pressure compensation grooves on its outer side, wherein these grooves are designed to be open radially outwards and their raised groove edges form part of the outer joining surface, wherein the direct fluidic connections of the pressure compensation grooves to the stator space are designed as radial through-openings through the sleeve wall. In the final assembly state, this means that the pressure compensation channels, together with the inner joining surface of the housing, form pressure compensation channels in their respective axial central region that are radially closed and axially terminally open radially inward toward the stator space. The pressure compensation channels thus run on the outside on the stator carrier and are covered over their entire length radially outwards by the inner wall of the housing. Their fluidic connection to the two end spaces of the electric machine, which they are intended to connect to one another for the purpose of pressure compensation, is realized by corresponding radial through-openings through the sleeve wall, wherein these openings, in the final assembly state, naturally have to be located outside the length of the stator, i.e. open into said end spaces.By means of the channels lying above the oil level in the final assembly state, air can be exchanged between the two end spaces and any pressure difference can be compensated. Channels, on the other hand, which run below the oil level, permit an exchange of oil between the two end spaces according to the principle of the communicating tubes. In this way, a level difference between the end spaces which builds up, for example, on account of a different distribution of the oil from the rotor shaft can be reduced and penetration of the oil into the air gap between the rotor and stator can be avoided.In the particularly preferred case, in addition to the pressure compensation channels according to the invention, a water jacket, i.e. a cooling channel system, is also provided on the outer side of the stator carrier sleeve, spatial conflicts between cooling and pressure compensation channels must be avoided. A particularly preferred shape therefore provides that the cooling channel system has meandering cooling channels with predominantly axially extending longitudinal legs and predominantly circumferentially extending transverse legs, each connecting two longitudinal legs, while the pressure compensation channels each extend between two adjacent longitudinal legs. In such an arrangement, no intersections are formed between the two kinds of channel structures. Cooling and pressure compensation channels can be located adjacent to one another in the circumferential direction at the same radial height.For both types of channel structures, it applies that they are most easily formed as depressions buried in the sleeve wall. Such depressions can be created in particular by machining a hollow cylindrical blank of a stator carrier provided as a cast or sheet metal formed part.Further features and advantages of the invention will become apparent from the following specific description and the drawings.The following are shown: FIG. 1 is a schematic sectional view through a drive arrangement not according to the invention, FIG. 2 : a detail development of a stator carrier not according to the invention and a sectional illustration through its sleeve wall, FIG. 3 : a detail development of a stator carrier likewise not according to the invention and two sectional representations through its sleeve wall, and FIG. 4 : a detail development of a stator carrier according to the invention and two sectional representations through its sleeve wall.Like reference numerals in the figures indicate like or analogous elements.FIG. 1 shows a highly diagrammatic representation of a section through a drive arrangement 10 which is not according to the invention, said drive arrangement comprising a substantially cylindrical, hollow housing 20 having a casing wall 22 and two end walls 24. An electric machine 30 is arranged in the housing interior 26, said electric machine comprising a stator 32 and a rotor 34.The stator 32 is indirectly fixed in the housing interior 26 via a sleeve-like stator carrier 40. The stator carrier 40 has an outer joining surface 401 on its outer side and an inner joining surface 402 on its inner side. The latter interacts with an outer joining surface 321 of the stator 32. The former interacts with an inner joining surface 221 of the casing wall 22 of the housing 20, with the result that overall an indirect fixing of the stator 32 in the housing 20 is produced, preferably realized by pressing. Alternatively or additionally, the stator carrier 40 can also be fixed in the housing 20 by means of a screw connection 50.In the configuration shown, the outer joining surface 401 of the stator carrier 40 is interrupted in order to form a system of cooling channels 42. The sleeve wall of the stator carrier 40 has in this region a recessed coolant guiding structure 421, which can be buried into the sleeve wall, for example, as recessed grooves or as a planar recess region.The inner joining surface 402 of the stator carrier 40 is likewise designed to be interrupted. In particular, it has axially extending pressure compensation channels 441, which, in cooperation with the outer joining surface 321 of the stator 32, form a system of separate pressure compensation channels 44. The pressure compensation channels 44 extend axially on both sides beyond the stator 32 so that they fluidically connect the end spaces 261, 262, i.e. the subspaces of the housing interior 26 axially adjacent to the electric machine 30. In particular, a pressure difference which occurs between the end spaces 261, 262 during operation of the electric machine 30 can be compensated for via the pressure compensation channels 44. This is illustrated in FIG. 1 by the dashed double arrows.In the configuration shown in FIG. 1, the electric machine 30 is a wet-running electric machine cooled by oil supplied through the rotor shaft 341. As shown by the solid arrows, oil is pumped into the hollow rotor shaft 341 and may be spun off through radial through openings 342 in the housing interior 26. If the oil in the housing interior 26 reaches a certain level, it can flow off via outlet openings 241 in the end walls 24 of the housing 20 into an oil sump, not shown. Any level difference occurring in the two end spaces 261, 262 may be compensated for via those pressure compensation channels 44 (at the bottom in FIG. 1 ) which are below the oil level. This balancing oil flow is illustrated in FIG. 1 by full double arrows.FIGS. 2 to 4 show further configurations of the pressure equalizing grooves 441 and the coolant guiding structure 421, only that of FIG. 4 representing an embodiment of the present invention. For this purpose, a developed view of the stator carrier 40 in a detail and one or two sectional representations through its sleeve wall along the respective dashed-dotted line of intersection are shown.FIG. 2 shows a particularly simple design, not according to the invention, in which the coolant guiding structure 421 is shown on the outer side of the stator carrier 40 as a circumferential, flat depression. The resulting water jacket is therefore in the form of a hollow cylinder. The pressure compensation grooves 441, on the other hand, are arranged on the inner side of the stator carrier 40. They have the shape of axially extending grooves.In the design of FIG. 3 which is not according to the invention, the coolant guide structure 421 and the pressure compensation grooves 441 are also arranged on different sides of the sleeve wall of the stator carrier 40. However, the coolant guiding structure 421 is designed here in the form of a meandering coolant guiding channel with axially extending longitudinal legs 422 and transverse legs 423 extending in the circumferential direction. The pressure compensation grooves 441, which are formed as individual axially extending grooves as in the configuration of FIG. 2, extend between two longitudinal legs 422 in each case. Since intersections between the coolant guiding structure 421 and the pressure equalizing grooves 441 are avoided in such an arrangement, both structures can be arranged at approximately the same radial height, as a result of which the necessary wall thickness of the sleeve wall of the stator carrier 40 can be reduced.An arrangement according to the invention is shown in FIG. 4. Here, the pressure compensation grooves 441 run on the same, namely on the outer side of the sleeve wall of the stator carrier 40. In order to create a fluidic connection to the end spaces 261, 262 in the housing interior 26, the pressure compensation grooves 441 have terminal radial through-openings 442, which in the final assembly state open into the end spaces 261, 262, i.e. axially outside the stator extension.In this configuration, too, the wall thickness of the stator carrier 40 can be kept low. In addition, the advantage results that the stator carrier 40 only has to be machined on one side for the introduction of the various channel structures.List of reference characters10 Drive arrangement 20 Housing 22 Jacket wall of 20 221 Inner joining surface of 22 24 End wall of 20 241 Outlet opening 26 Housing interior 261 End space 262 End space 30 Electric machine 32 Stator 321 Outer joining surface of 32 34 Rotor 341 Rotor shaft 342 Radial through opening in 341 40 Stator carrier 401 Outer joining surface of 40 402 Inner joining surface of 40 42 Cooling channel 421 Coolant guiding structure 422 Longitudinal limb of 421 423 Transverse limb of 421 44 Pressure compensation channel 441 Pressure compensation channel 442 Radial through opening in 441 50 Screw connection

Claims

Stator carrier (40) for receiving a stator (32) of an electric machine (30) designed as an internal rotor, in particular of a traction machine for a motor vehicle, comprising a hollow cylindrical sleeve having a sleeve wall which surrounds a stator space and which has an inner side which faces radially inwards and carries an inner joining surface (402) and an outer side which faces radially outwards and carries an outer joining surface (401), wherein the sleeve wall carries a plurality of pressure compensation grooves (441) which are arranged distributed over the circumference of the sleeve and each extend predominantly axially over a predominant part of the axial length of the sleeve and are in direct fluidic connection at least terminally with the stator space, characterized in that the sleeve wall carries the pressure compensation grooves (441) on its outer side, wherein these are designed to be open radially outwards and their raised channel edges form part of the outer joining surface (401), wherein the direct fluidic connections of the pressure compensation channels (441) to the stator space are formed as radial through openings (442) through the sleeve wall, which openings are arranged terminally on both sides.Stator carrier (40) according to Claim 1, characterized in that the sleeve wall carries on its outer side a coolant guiding structure (421) which is open radially outwards and the raised structure edges of which form part of the outer joining surface (401).Stator carrier (40) according to Claim 2, characterized in that - the coolant-guiding structure (421) has meandering coolant-guiding channels with predominantly axially extending longitudinal limbs (422) and transverse limbs (421) which predominantly extend in the circumferential direction and in each case connect two longitudinal limbs (422), and - the pressure-equalizing channels (441) in each case extend between two adjacent longitudinal limbs (422) of the coolant-guiding channels.Stator support (40) according to one of the preceding claims, characterized in that the pressure compensation grooves (441) and / or - if present - the coolant guiding structure (421) are formed as depressions buried in the sleeve wall.Drive arrangement (10) for a motor vehicle, comprising - a housing (20) having a cylindrical housing interior (26) which runs round by an inner joining surface (221), - a stator carrier (40) comprising a hollow cylindrical sleeve having a sleeve wall which runs round a stator space and has an inner side which faces radially inwards and carries an inner joining surface (402) and an outer side which faces radially outwards and carries an outer joining surface (401), and - a hollow cylindrical stator (32) of an electric machine (30) which runs round by an outer joining surface (321), wherein the stator (32) is joined into the stator space under contact of its outer joining surface (321) on the inner joining surface (402) of the stator carrier (40) and under axial protrusion of the sleeve wall on both sides beyond the stator (32), wherein the stator carrier (40) is joined into the housing interior (26) with its outer joining surface (401) resting against the inner joining surface (221) of the housing (20), and wherein the sleeve wall carries a plurality of pressure compensation channels (441) distributed over the circumference of the sleeve, which forms, together with a radially adjacent joining surface (221), a plurality of pressure compensation channels (44) distributed over the circumference of the sleeve, which each predominantly extend axially, axially span the stator (32) and are connected terminally in direct fluidic connection to the stator space, characterized in that the sleeve wall of the stator carrier (40) carries the pressure compensation channels (441) on its outer side, wherein these are designed to be open radially outwards, their raised channel edges form part of the outer joining surface (401) of the stator carrier (40) and the direct fluidic connections of the pressure compensation channels (441) to the stator space are formed as radial through-openings (442) through the sleeve wall arranged on both sides of the stator (32), so that the pressure compensation channels (441), together with the inner joining surface (221) of the housing (20), form pressure compensation channels (44) which are radially closed in their respective axial central region and are axially terminally open radially inward toward the stator space.Drive arrangement (10) according to Claim 5, characterized in that the sleeve wall of the stator carrier (40) carries on its outer side a coolant-conducting structure (421) which is open radially outwards and the raised structure edges of which form part of the outer joining surface (401) of the stator carrier (40) and which, together with the inner joining surface (221) of the housing (20), forms a cooling-duct system (42) which is radially closed - apart from an optionally provided inlet and / or outlet.Drive arrangement (10) according to Claim 6, characterized in that - the cooling duct system has meandering cooling ducts (42) with predominantly axially extending longitudinal limbs and transverse limbs which extend predominantly in the circumferential direction and in each case connect two longitudinal limbs, and - the pressure compensation ducts (44) in each case extend between two adjacent longitudinal limbs of the cooling ducts.Drive arrangement (10) according to one of Claims 6 to 7, characterized in that a rotor (34) which is mounted on the housing (20) is arranged in a rotationally movable manner in the interior of the stator (32), with the result that the stator (32) and the rotor (34) together form an electric machine (30), in particular a traction machine for a motor vehicle which runs in a wet state.Motor vehicle having a drive arrangement (10) according to Claim 8.

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