Electric drive system for a motor vehicle

Abstract

The invention relates to an electric drive device (10) for a motor vehicle, comprising at least one electric machine (12) for driving the motor vehicle, a planetary gear set (26) having a ring gear (28) via which the motor vehicle can be driven by the electric machine (12), and a housing (32) in which the planetary gear set (26) is arranged, wherein the electric machine (12) is designed as an axial flux machine, which has two rotors (14, 16) and a stator (18) which is arranged in the axial direction (22) of the electric machine (12) between the rotors (14, 16) which are rotatable relative to the stator (18). The stator (18) has a partial area (TB) projecting outwards beyond the rotors (14, 16) in a radial direction (24) of the electric machine (12), on which a projection (36) is provided which extends in an axial direction (22) of the electric machine (12) over one of the rotors (14, 16).

Description

[0001] The invention relates to an electric drive device for a motor vehicle, in particular for a motor vehicle, according to the preamble of patent claim 1.

[0002] DE 10 2009 018 409 A1 discloses a ring gear comprising a wall with teeth along a periphery of the wall. It is also provided that the wall of the ring gear is provided with at least one reinforcing material layer in the area where the teeth are present on the periphery.

[0003] The object of the present invention is to provide an electric drive device for a motor vehicle so that a particularly advantageous noise behavior of the drive device can be realized.

[0004] This object is achieved by an electric drive device having the features of patent claim 1.

[0005] Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0006] The invention relates to an electric drive device for a motor vehicle, also simply referred to as a vehicle. This means that the motor vehicle, preferably designed as a motor vehicle, in particular as a passenger car, in its fully manufactured state has the electric drive device and can be driven, in particular purely electrically, by means of the electric drive device. For this purpose, the electric drive device has at least one electric machine, by means of which the motor vehicle can be driven, in particular purely electrically. The drive device also has a planetary gear set, also referred to as a planetary set or planetary gear, via which the motor vehicle can be driven by the electric machine. The planetary gear set has a ring gear. For example, the planetary gear set also has a sun gear and a planet carrier as well as planetary gears which are rotatably mounted on the planet carrier.The sun gear meshes with the respective planetary gear, whereby meshing of the sun gear with the ring gear does not occur. For example, the ring gear meshes with the respective planetary gear. The electric drive device also has a housing in which the planetary gear set is arranged. For example, the ring gear is connected, in particular permanently, in a rotationally fixed manner to the housing. The sun gear and the planet carrier are rotatable, for example, about a planetary gear set rotation axis relative to the housing. For example, the sun gear is an input of the planetary gear set, also referred to as the drive, via whose input torques that can be provided or are provided by the electric machine can be introduced into the planetary gear set.Preferably, the planet carrier is an output of the planetary gear set, also referred to as output, via whose output a respective output torque resulting from the respective drive torque introduced into the planetary gear set can be diverted from the planetary gear set, i.e. can be provided by the planetary gear set.

[0007] The housing is preferably formed from a die-cast component. In other words, the housing is preferably designed as a die-cast component and thus manufactured by a die-casting process. In particular, the ring gear is arranged at least partially, in particular at least predominantly and thus at least more than half or entirely, in the housing.

[0008] In order to be able to achieve particularly advantageous noise behavior of the electric drive device and thus particularly high driving comfort of the motor vehicle, it is provided according to the invention that the electric machine is designed as an axial flux machine having two rotors and a stator, by means of which the rotors can be driven and are thus rotatable about a machine axis of rotation relative to the stator. The rotors are also referred to as rotor elements and are, for example, components of an overall rotor which has the rotors as the rotor elements. In particular, the rotors are connected to one another in a rotationally fixed manner, in particular permanently. For example, the rotors, and thus the rotor elements, are designed as rotor disks.The stator is arranged in the axial direction of the electric machine, the radial direction of which is perpendicular to the axial direction of the electric machine, between the rotors, which are rotatable relative to the stator about the machine's axis of rotation, wherein the axial direction of the electric machine coincides with the machine's axis of rotation. Thus, for example, the rotors each have a first partial region, wherein the first partial regions are spaced apart from one another in the axial direction of the electric machine.The stator is arranged at least partially between the first subregions in the axial direction of the electric machine, so that at least a second subregion of the stator is arranged between the first subregions of the rotors in the axial direction of the electric machine, such that the first subregion of a first of the rotors is overlapped by the third subregion along the machine's rotational axis and, as viewed from the first rotor to the second rotor. Accordingly, for example, the first subregion of the second rotor is overlapped, i.e., covered, by the third subregion along the machine's rotational axis and, as viewed from the second rotor to the first rotor.

[0009] When reference is made above and below to the axial direction, this means, unless otherwise stated, the axial direction of the electric machine and thus of the ring gear and the planetary gear set as a whole. When reference is made above and below to the radial direction, this means, unless otherwise stated, the radial direction of the electric machine and thus of the ring gear and the planetary gear set. Thus, the term “axial” refers to the axial direction of the electric machine and thus of the electric drive device as a whole, and the term “radial” refers to the radial direction of the electric machine and thus of the ring gear and the planetary gear set. The stator has a sub-region that projects outwards beyond the rotors in the radial direction of the electric machine, the circumferential direction of which runs around the axial direction and thus around the machine axis of rotation, and is also referred to as the stator sub-region.When reference is made above and below to the sub-region, this means the stator sub-region unless stated otherwise. This means that the sub-region is arranged further outwards than the rotors, viewed in the radial direction of the electric machine. A projection is provided on the sub-region of the stator and extends in the axial direction of the electric machine over one of the rotors. In other words, the projection projects in the axial direction from an end face of the stator facing the planetary gear set in the axial direction, in such a way that the projection extends in the axial direction away from the end face and towards the planetary gear set, wherein the projection extends in the axial direction over one of the rotors. The projection extends in the axial direction over one of the rotors in such a way that the projection projects over one of the rotors in the radial direction of the machine.overlaps towards the outside, in particular completely, i.e. is covered. In this case, one rotor is arranged in the axial direction between the planetary gear set and the stator, i.e. the axial end face. The projection forms a ring gear carrier, in particular such that the ring gear carrier is connected integrally to the projection. In the context of the present disclosure, the feature that two components are formed integrally with one another is to be understood as meaning that the components are formed integrally with one another, i.e. from a single piece. In other words, the components are not formed separately from one another or connected to one another, but the components are formed from a single piece, so that the components are formed by a one-piece, i.e. one-part and thus formed from a single piece and thus integrally manufactured monoblock.

[0010] The ring gear, which is formed separately from the hollow carrier, is connected to the ring gear carrier in a rotationally fixed manner. In particular, the ring gear, which is formed separately from the ring gear carrier, is also connected to the ring gear carrier in such a way that relative movements in the axial direction between the ring gear and the ring gear carrier are prevented. Furthermore, the projection has a spline, which is also referred to as the first spline. The spline of the projection is also referred to as the first spline. Whenever spline is mentioned above and below, this refers to the first spline of the projection, unless otherwise stated. The spline, i.e. the first spline, engages with a corresponding second spline of the housing, for example as the second spline or the second spline.In particular, the spline, i.e. the first spline, is arranged on an axial end face of the projection, the axial end face of which faces the second spline in the axial direction. In particular, the axial end face of the projection faces an axial end face of the housing, on whose axial end face the second spline can be formed. The spline extends, for example, in the radial direction. In other words, the teeth of the spline, for example, extend in the radial direction. This means that the respective tooth of the spline protrudes in the axial direction from the axial end face of the projection and extends, in particular elongated, in the radial direction. Because the spline engages with the second spline of the housing, a particularly advantageous rotationally fixed connection of the ring gear carrier and thus of the ring gear to the housing can be realized.In addition, a particularly precise and easily realizable alignment of the ring gear carrier and thus of the ring gear relative to the housing can be achieved.

[0011] In order to achieve particularly advantageous noise characteristics for the drive system, one embodiment of the invention provides for the ring gear carrier to be made of a fiber-reinforced plastic. This can prevent, for example, excessive transmission of vibrations from the ring gear carrier to the housing, thereby preventing unwanted noises that can be perceived by people inside the vehicle.

[0012] In principle, it would be conceivable for the projection to be formed separately from the partial area and thus separately from the stator and, in particular, to be permanently connected to the partial area and thus to the stator in a rotationally fixed manner.

[0013] To achieve particularly advantageous noise behavior, a further embodiment of the invention also provides for the projection to be formed integrally with the partial region and integrally with the stator. In other words, it is preferably provided that the stator and the projection are formed from a single piece, thus integrally with each other. In other words, the stator and the projection are thus not formed separately from each other and connected to each other; rather, the stator and the projection are preferably formed by a single-piece, thus one-piece and thus formed from a single piece, i.e., integrally manufactured monoblock.

[0014] Thus, it is preferably conceivable that the stator is formed from the aforementioned fiber-reinforced plastic, whereby a particularly advantageous noise behavior can be achieved.

[0015] A further embodiment of the invention is characterized in that the spline is designed as a segmented spline. In this case, planar intermediate segments are arranged, for example, in the circumferential direction between the teeth of the spline, in particular such that a respective one of the planar intermediate segments is arranged, in particular precisely, between two teeth of the spline that are immediately adjacent in the circumferential direction. In particular, the respective planar intermediate segment is to be understood as a respective wall region of the projection, wherein the wall region extends, for example, in a plane that is perpendicular to the axial direction. This enables a particularly advantageous connection of the projection to the housing to be realized, whereby a particularly advantageous noise behavior can be achieved.

[0016] In order to achieve particularly advantageous noise behavior, it has proven particularly advantageous if the spline is designed as a Hirth spline.

[0017] In a further, particularly advantageous embodiment of the invention, it is provided that in the circumferential direction of the electrical machine, the circumferential direction of which runs around the axial direction and thus around the machine's axis of rotation, screws are arranged between the teeth of the spline, by means of which screws the spline is tensioned against the second toothing in the axial direction of the electrical machine. For example, the screws pass through the planar intermediate segments, whereby the projection can be connected to the housing in a particularly advantageous and rotationally fixed manner. Very preferably, one of the screws is provided for each planar intermediate segment, in particular precisely, so that the projection can be connected to the housing in a particularly advantageous and rotationally fixed manner to create particularly advantageous noise behavior.

[0018] In a further embodiment of the invention, the ring gear is connected to the ring gear carrier in a rotationally fixed manner via an additional spline. This allows for a particularly simple and secure connection of the ring gear to the ring gear carrier, while simultaneously achieving particularly advantageous noise characteristics.

[0019] A further embodiment of the invention is characterized by a sleeve formed separately from the ring gear and separately from the ring gear carrier, which sleeve is arranged, in particular directly, on an outer circumference of the ring gear carrier facing away from the ring gear in the radial direction of the electric machine, in particular such that the sleeve directly contacts the outer circumference and thus the ring gear carrier. The sleeve is firmly connected to the ring gear carrier, so that relative rotations between the ring gear carrier and the sleeve as well as relative movements in the axial direction between the ring gear carrier and the sleeve are prevented. By means of the sleeve, at least one respective longitudinal region of the ring gear carrier and the ring gear extending in the axial direction of the electric machine, and thus running in the axial direction of the electric machine, overlaps radially outwards.This can, for example, prevent excessive radial outward expansion or fanning of the ring gear carrier, thereby achieving particularly advantageous noise behavior.

[0020] In order to advantageously avoid excessive fanning out or expansion of the ring gear carrier in the radial outward direction, it is provided in a further embodiment of the invention that the sleeve is formed from a steel.

[0021] Finally, it has been shown to be particularly advantageous for realizing a particularly advantageous noise behavior if the housing and the ring gear carrier are arranged radially spaced from one another, whereby an air gap is provided in the radial direction between the housing and the ring gear carrier, which air gap extends completely circumferentially around the ring gear carrier in the circumferential direction of the electric machine.

[0022] Furthermore, it is preferably provided that the ring gear carrier has a free end which is opposite the stator in the axial direction, that is to say the axial end face of the stator, at which free end the ring gear carrier and the projection as a whole end in the axial direction, wherein the free end is spaced apart from the housing, in particular completely, both in the radial direction and in the axial direction.

[0023] The invention is based in particular on the following findings and considerations: A particularly efficient way of being able to reduce the speed of a high-speed electric motor, such as an axial flux machine, by an appropriate amount is to use a single-stage planetary gear set. Thus, the planetary gear set is preferably provided as a single-stage planetary gear set. For example, the sun gear can be driven by the electric machine, in particular by the overall rotor, whereby the electric machine can provide the respective drive torque, for example via its overall rotor. The sun gear meshes with a suitable number of planet gears carried by the planet carrier, which is the output of the planetary gear set. The ring gear, which likewise meshes with the planet gears, is also provided.A potential risk of such an arrangement can be a rigid fixation of the ring gear to, and particularly within, the housing of the electric drive device, also referred to as the electric drive unit. This can lead to unsatisfactory noise behavior of the electric drive device, also referred to as NVH behavior (noise vibration harshness), since vibrations of the ring gear can be transmitted to the housing via an excessively strong connection between the ring gear and the housing if no appropriate countermeasures are taken. Furthermore, an excessively rigid attachment of the ring gear to the housing can potentially lead to an undesirably low efficiency of the planetary gear set, particularly due to an overdetermination of the planetary gear set with a large number of planet gears. The number of planet gears is, for example, 3 or 4.Such excessive vibration transmission can be avoided by sufficiently large gear play and / or bearing play, but this comes with the disadvantage of increased to excessive play in the planetary gear set, which can severely impair ride comfort. The aforementioned problems and disadvantages can now be avoided by the invention.

[0024] The sleeve is also referred to as a collar and is, for example, pressed and / or shrunk onto the ring gear carrier. Thus, it is conceivable, for example, for the sleeve and the ring gear carrier to form a transverse interference fit, by means of which the sleeve is firmly connected to the ring gear carrier. For example, the sleeve is shrunk onto the ring gear carrier and is thereby firmly connected to the ring gear carrier. For example, the sleeve is made from a first material, with the ring gear, for example, being made from a second material. The second material can be the same material as the first material. Preferably, the first material and the second material have the same modulus of elasticity and / or the same coefficient of thermal expansion. Thus, it is conceivable for the sleeve and the ring gear to be made from the same steel.

[0025] In particular, when the ring gear carrier is formed from the aforementioned fiber-reinforced plastic, the ring gear carrier is manufactured, for example, by injection molding, i.e., formed from an injection-molded polymer reinforced by reinforcing fibers, in particular by short reinforcing fibers, in particular in a random and / or arbitrary direction, in particular such that the reinforcing fibers are embedded in the polymer. The reinforcing fibers can comprise glass fibers and / or carbon fibers.In order to realize an advantageously rotationally fixed connection between the ring gear and the ring gear carrier, it is conceivable for an outer circumference of the ring gear, which points outwards in particular in the radial direction of the electric machine and faces the ring gear carrier, to be micro-toothed, i.e. to be provided with micro-toothing which, for example, has axially aligned micro-toothings running in the axial direction, for example with a height running in the radial direction of a few tenths of a millimeter. Alternatively or additionally, for example, the outer circumference of the ring gear facing the ring gear carrier in the radial direction and the ring gear carrier form a press fit, by means of which the ring gear is firmly connected to the ring gear carrier, so that relative rotations between the ring gear and the ring gear carrier as well as relative movements in the axial direction between the ring gear and the ring gear carrier are prevented.For example, during assembly of the electric drive device, the ring gear is firmly connected to the ring gear carrier in such a way that the ring gear is pressed axially into the ring gear carrier. During assembly of the ring gear to the ring gear carrier, for example, the micro-toothings themselves cut into the ring gear carrier, in particular into the fiber-reinforced plastic, in such a way that the micro-toothing cuts micro-notches into the ring gear carrier, in particular the fiber-reinforced plastic, whereby a positive connection is or will be formed between the ring gear and the ring gear carrier, by means of which the ring gear carrier is particularly firmly connected to the ring gear.

[0026] It is conceivable for the projection to have a first wall thickness, also referred to as the first wall thickness, in a first longitudinal region of the projection running in the axial direction, the first longitudinal region of which forms the ring gear carrier. For example, the projection to have a second wall thickness, also referred to as the second wall thickness, which is smaller than the first wall thickness, in a second longitudinal region extending in the axial direction. The second longitudinal region adjoins the ring gear carrier in the axial direction towards the axial end face of the stator. For example, the first longitudinal region and / or the second longitudinal region of the projection is tubular. On the one hand, this allows for advantageous rigidity of the ring gear carrier. On the other hand, it is possible to ensure a particularly low weight of the output as a whole.Furthermore, it is conceivable that the first length region has the greater, first wall thickness compared to the second wall, in particular only when the ring gear is mounted on the ring gear carrier, wherein, for example, after the ring gear has been mounted on the ring gear carrier, the first length region is machined, in particular milled, in such a way that the first length region is reduced in terms of its wall thickness, in particular in such a way that the finished state of the drive device, the first length region and the second length region have the same wall thickness.

[0027] Furthermore, it is conceivable that the plug-in toothing of the projection is arranged on an outer circumference of the projection facing the housing in the radial direction, so that, for example, the second toothing is arranged on an inner circumference of the housing facing the first toothing in the radial direction.

[0028] If the ring gear carrier formed, for example, from the fiber-reinforced plastic is arranged adjacent to a component of the drive device formed from a composite material, such as the stator, it is advantageous to form this component and the ring gear carrier or the projection from a single piece and from fiber-reinforced plastic.

[0029] The invention can realize at least the following advantages: - particularly advantageous noise behavior of the drive device, in particular through the use of fiber-reinforced plastic, which can advantageously dampen vibrations; the fiber-reinforced plastic can, in particular, prevent natural vibrations of the ring gear induced by tooth engagement of the ring gear from being transmitted to the housing, in particular to its surfaces; - particularly high efficiency of the planetary gear with low backlash due to the particularly radially flexible ring gear carrier, which enables advantageous self-alignment of the ring gear via the planetary gears with which the ring gear meshes; - lightweight design and advantageously low number of parts in the drive system.

[0030] Further findings underlying the invention are that axial flux machines (AFMs), particularly those with a flat, cylindrical central stator whose diameter is significantly larger than its axial thickness and which is located between two disc-shaped parts that are particularly round axially due to a central bore in the stator, can drive a motor vehicle particularly efficiently and effectively. The stator is usually firmly connected to the housing, also referred to as the motor housing, which contains, for example, the entire electric machine and possibly other components to form the electric drive device that can deliver the respective drive torque, also referred to as motor torque, to drive the motor vehicle.For example, a reaction torque of the stator, whose reaction torque is equal in magnitude to the drive torque provided by the electric machine but opposite in its direction of action, is absorbed by the housing. Typically, the reaction torque is introduced into the housing via a multi-bolted flange connection between the stator and the housing, with the flange connection located outside the rotor or the entire rotor.

[0031] In most applications, for example in automotive engineering, aviation, shipping, etc., it is advantageous from several points of view such as overall efficiency, size, mass, etc. if the axial flux machine runs at an advantageously high speed, which is, for example, a factor of 5 to 8 inclusive higher than an output speed of a drive element formed, for example, as a vehicle wheel or propeller, etc.

[0032] The use of a coaxial planetary transmission gear, such as that formed by the planetary gear set, to enable such a rotating part difference is advantageous.

[0033] A particularly advantageous arrangement for such a transmission gear is a single-stage planetary gear, in particular in the form of a planetary gear set, wherein, for example, the central sun gear in particular can be driven or is driven by the overall rotor.

[0034] The planet gears, which are rotatably mounted on, in particular, the common planet carrier, would have an advantageously small diameter with the sun gear. Furthermore, the planet gears, in particular with the central ring gear, would have an advantageously large diameter, which is larger than the advantageously small diameter. In order to achieve an advantageous gear ratio range, in particular such that, as described above, the axial flux machine or the entire rotor rotates 5-8 times faster than the drive element, it is advantageous if the ring gear is connected, in particular permanently, to the housing in a rotationally fixed manner, with the planet carrier forming the output and thus, for example, a concentric output shaft of the planetary gear set. A reaction torque of the ring gear, which is stationary relative to the housing and whose reaction torque is equal to the output torque minus the drive torque, is supported by the housing.A fixed and in particular direct metallic fastening of the ring gear to the housing, which is made of light metal casting, for example, can lead to noise problems because vibrations of the ring gear can be transmitted via surfaces of the housing to an area surrounding the drive device and amplified.

[0035] Furthermore, an epicyclic arrangement as described above is overdetermined due to the numerous load paths through the multitude of planetary gears. As a result, the load carried by each planetary gear does not equal the theoretical value of the transmitted torque divided by the number of planetary gears (also known simply as planets) through which it is passed, but is likely to be different for each planet due to unavoidable manufacturing tolerances. This implies susceptibility to higher torque loading for each of the planetary gears. The gearing should therefore be designed to be able to bear a higher torque than theoretically possible, which to some extent loses the advantage of load distribution across the multitude of planetary meshes. Such overdetermined designs are also susceptible to increased tooth flank friction or even jamming.It is conceivable and known to provide sufficient toothing clearance and / or sufficient clearance in bearings such as planetary gear bearings to avoid these disadvantages. However, it should be noted that while increased tooth flank friction or even jamming can be successfully avoided, the uneven load distribution caused by the large number of planetary gears can only be reduced to a certain, limited extent. This must be taken into account when dimensioning planetary gear seats according to the state of the art and leads, for example, to a larger tooth width than would be required for an ideal over-tuned gear with even torque distribution across the large number of planets with the same safety factor for the same application.

[0036] The invention makes it possible to avoid the disadvantages mentioned above and listed again below: - the uneven load distribution on the multitude of planetary gears with its effects on the dimensioning of the planetary gear (planetary gear set); - the noise problems mentioned above.

[0037] In order to achieve a space-saving design, it is advantageous to design the planetary gear set, also known as a planetary gear, in such a way that an outer diameter of the ring gear is slightly larger than an outer diameter of the rotors and significantly larger than an outer diameter of the stator.

[0038] For example, it is conceivable for the stator to enclose the windings and pole cores in a fiber-reinforced polymer housing, with the polymer housing being formed integrally with the projection. The stator's reaction torque, for example, can be transferred into the housing via the polymer housing. Given the magnitude of magnetic forces between the stator and the rotors of the axial flux machine, a rigid stator attachment to the housing is highly advantageous.

[0039] In order to avoid excessive noise problems, the projection formed in the ring gear carrier is preferably made of the fiber-reinforced plastic, also referred to as fiber-reinforced polymer, from which the ring gear carrier is formed. For example, a micro-toothed connection is provided between the preferably metallic ring gear and the ring gear carrier, preferably formed from the fiber-reinforced plastic. For this purpose, the ring gear, also referred to as the ring gear, has, for example, the aforementioned micro-toothing, in particular in the form of micro-wedges, particularly on its outer circumference facing the ring gear carrier in the radial direction. The respective micro-toothing has, for example, a height running in the radial direction and a width running in the circumferential direction of the electric machine, each of a few tenths of a millimeter.For example, the micro-toothings are arranged evenly distributed in the circumferential direction of the electric machine. In the circumferential direction between the micro-toothings, for example, in particular smooth sections, in particular of the outer circumference of the ring gear, are provided. These sections of the outer circumference of the ring gear form a respective press fit with an in particular smooth inner circumference of the ring gear carrier facing the outer circumference of the ring gear in the radial direction, whereby the ring gear rotates and is connected to the ring gear carrier in such a way that relative movements in the axial direction between the ring gear and the ring gear carrier are prevented. A radial extent or extension of the ring gear carrier can, for example, be only a few millimeters.The sleeve, designed as a steel sleeve, for example, which is mounted on the outer circumference of the ring gear carrier, can stabilize the ring gear carrier and, via it, the ring gear, particularly in the radial direction. Since, for example, the thermal expansion coefficient of the ring gear is equal to the thermal expansion coefficient of the sleeve, no problems arise during a thermal cycle, especially as long as the limit operating temperature of one of the materials involved, for example, the fiber-reinforced plastic, is not exceeded.

[0040] Even if, for example, the planetary gear set, also referred to as a planetary drive, is arranged as close as possible to or adjacent to the axial flux machine, particularly in the axial direction of the electric machine, an axial expansion of one rotor and an unavoidable play between the one rotor and the planetary gear set can define a minimal axial distance between the stator, in particular its stator housing, and the ring gear. By utilizing this particularly unavoidable axial distance, the axial length of the input device can be advantageously kept small.

[0041] The projection is, for example, a preferably thin-walled, axial and preferably tubular extension of the stator, in particular of the stator housing. The projection extends over the one rotor, which is on the planetary gear set and thus on the transmission side, and for example even further to one end of an axial end face or end surface of the planetary gear, which faces away from the stator in particular in the axial direction. The projection, which forms, for example, a tubular extension, is, for example, formed integrally with the stator housing and thus with the stator, so that it is conceivable that the stator, in particular the stator housing, and the projection are formed from the same fiber-reinforced plastic. One purpose of the projection, which is designed, for example, as an axial tubular extension, is to enable particularly favorable mounting of the ring gear.To achieve this, the ring gear, for example, is fixed to, particularly in, the projection by the aforementioned micro-toothing. The projection, designed, for example, as a polymer ring gear bearing, cannot transmit the reaction torque of the ring gear radially into the housing. Instead, it has, for example, the aforementioned air gap and thus a radial play with the housing. It transmits the reaction torque of the ring gear, possibly together with axial forces, across an axial distance between a planetary gearing and the stator or stator housing. The axial forces result, for example, from helical gearing of the ring gear.The invention enables a particularly high reactive torque load of the stator housing, in particular its structure, since in comparison to conventional solutions in which the stator-housing connection is only loaded by the motor drive torque, while the ring gear reaction torque and the axial force are introduced radially directly into the housing, the arrangement according to the invention disclosed here loads the stator-housing connection with the full drive torque of the drive device and with the axial ring gear force.To cope with this load on the particularly separable connection of the particularly fiber-reinforced projection to the particularly cast housing, which is formed, for example, from a light metal alloy bonded to an aluminum alloy, in particular a cast aluminum alloy, or a magnesium alloy, in particular a cast magnesium alloy, a Hirth toothing is used, for example, as the spline, in order to achieve a particularly axial positive connection between the projection and the housing. A radial extension of the spline, in particular the Hirth toothing, can extend from just above the outer diameter of the rotor up to the outer diameter of the stator.This leaves the overall radial dimensions of the stator unaffected, and the segmentation of the spline (toothed segments alternate repeatedly with smooth sectors) provides the necessary space for a large number of clamping screws for axially securing the spline within the same inner and outer diameter. These screws are advantageously designed as tapered shaft screws. This also allows for stiffening and increased flatness of the stator assembly in the housing. Similar to the radial dimension, the axial dimension of the stator-housing connection and the overall mass remain unaffected by the described design.

[0042] In addition to the possibly provided, torque-loaded connections between metallic and non-metallic components described above, attention can be paid, for example, to the equally torque-loaded axial extension of the stator's overhang, in particular of the stator housing, which is designed, for example, as a tubular extension. For example, the overhang can accommodate the ring gear at its axial end facing away from the axial end face of the stator. The torque load absorbed by the overhang can correspond to the reaction torque of the sun gear. The axial load transmitted by the overhang corresponds to the axial gear force of the helical gearing of the ring gear. Due to the large outer diameter of the overhang, typical of axial flux machines, the reaction torque-induced shear stresses are very low.The same applies to the tensile or compressive stresses induced by the axial force of the ring gear, so that the resulting von Mises stress ends up well below the load-bearing capacity of the cantilever. Therefore, the cantilever, designed, for example, as a tubular extension, can be thin-walled. This achieves sufficient torsional rigidity while simultaneously achieving appropriate radial compliance, which is particularly advantageous. Using finite element analysis (FEA), this radial compliance can be optimized, for example, by considering a plurality of tangential, axial, or 45° inclined slots, particularly in the cantilever, to further increase the radial compliance of the cantilever, in particular up to a customized, favorable amount, without compromising sufficient axial stiffness of the cantilever.

[0043] Theoretically, the radial forces of the meshing between the multiple planets and the sun gear cancel each other out. In practice, this will not be the case in every position of the ring gear due to unavoidable tolerances such as gearing errors on rotating parts, leading to the uneven load distribution among the multiple planet gears described above. Because the overhang of the stator, particularly the stator housing, exhibits and enables advantageous radial compliance, the ring gear acquires the ability to align itself with the planet gears with which it meshes. This self-alignment autonomously tends to achieve the equilibrium position of the acting forces, which is achieved when the load is evenly distributed across all planets.This self-alignment occurs because the aforementioned equilibrium position coincides with the position of minimum energy, achieving an equal or at least significantly more even load distribution across the multitude of planetary gears, thus avoiding overload situations in one of the shared torque paths. The maximum remanent magnitude of the uneven planetary gear loading is determined by the tailored radial stiffness of the ring gear carrier or overhang. Advantageous results are achieved with planetary gear sets with three equally spaced planets with synchronous meshing, as such a design enables stable self-alignment, comparable to the stability of a tripod.The reaction moment-loaded projection of the stator, in particular of the stator housing, which is designed, for example, as a tubular extension, wherein the projection is not rigidly radially supported over a suitable axial length and accommodates the ring gear, in particular at the end of the projection opposite the axial end face of the stator and preferably offers a tailor-made radial compliance for the ring gear for self-alignment, is particularly advantageous, whereby in particular an advantageous noise behavior of the drive device can be realized.

[0044] The extent of the radial self-alignment of the ring gear via the planetary meshing will be on the order of the position and gearing tolerances of precision gear components, i.e., in the low to mid-double-digit range of micrometers. The maximum frequency of self-alignment corresponds to the output speed of the drive system. For example, in automotive applications, the self-alignment frequency is typically below 25 hertz and reaches a maximum of 50 hertz during high-speed highway driving.

[0045] Since there is preferably no rigid metallic contact between the ring gear and the housing in the invention, an advantageous noise behavior of the drive device can be realized.

[0046] Due to the self-aligning capability of the ring gear, the clearance and / or bearing clearance need not be increased beyond a favorable minimum value, which improves driving comfort by reducing the overall gear clearance.

[0047] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the single figure, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0048] The drawing shows in the only figure a partial schematic longitudinal sectional view of an electric drive device for a motor vehicle.

[0049] The single figure shows a detail in a schematic longitudinal sectional view of an electric drive device 10 for a motor vehicle, also simply referred to as a vehicle. This means that the motor vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car, has the electric drive device 10 in its fully manufactured state and can be driven, in particular purely electrically, by means of the electric drive device 10. For this purpose, the electric drive device 10 has at least one electric machine 12, which is designed as an axial flux machine (AFM). The electric machine 12 has two rotors, also referred to as rotor elements, namely a first rotor 14 and a second rotor 16. For example, the respective rotor 14, 16 is disk-shaped and thus designed as a respective disk, also referred to as a rotor disk.The rotors 14 and 16 are, for example, in particular permanently, connected to one another in a rotationally fixed manner. The electric machine 12 also has a stator 18, which is arranged at least partially between the rotors 14 and 16 in the axial direction of the electric machine 12, the radial direction of which runs perpendicular to the axial direction of the electric machine 12. The rotors 14 and 16 are, for example, components of an overall rotor 20 of the electric machine 12, which can provide drive torques for driving the motor vehicle via its overall rotor 20. The axial direction of the electric machine 12 and thus of the drive device 10 as a whole is illustrated in the figure by a double arrow 22, and the radial direction of the electric machine 12 and thus of the drive device 10 as a whole is illustrated by a double arrow 24.

[0050] The drive device 10 also has a planetary gear set 26, also referred to as a planetary gear set or planetary transmission, which includes a ring gear 28. Furthermore, the planetary gear set 26 has a sun gear (not visible in the figure) and a planet carrier (not visible in the figure). Furthermore, the planetary gear set 26 includes planetary gears, also referred to as planets. Of the planetary gears of the planetary gear set 26, a planetary gear designated 30 can be seen in detail in the figure. The respective planetary gear 30 meshes simultaneously with the sun gear and with the ring gear 28, whereby meshing of the sun gear with the ring gear 28 is omitted.

[0051] The drive device 10 also has a housing 32 in which the planetary gear set 26 is arranged. For example, the housing 32 is designed as a die-cast component and thus manufactured by die casting.

[0052] The sun gear and the planet carrier are rotatable about a planetary gear set rotation axis relative to the housing 32. The electric machine 12, whose overall rotor 20 is rotatable about a machine rotation axis relative to the housing 32, can provide the aforementioned drive torques for driving the motor vehicle via its overall rotor 20, which can be driven by the overall rotor 20 via the planetary gear set 26 and thus by means of the electric machine 12. In this case, for example, the sun gear is or can be connected to the overall rotor 20 in a torque-transmitting manner, in particular in a rotationally fixed manner. In particular, it is conceivable for the sun gear to be permanently connected to the overall rotor 20 in a torque-transmitting manner, in particular in a rotationally fixed manner. The sun gear is an input of the planetary gear set 26, also referred to as the drive, via whose input the respective drive torque provided or capable of being provided by the overall rotor 20 can be introduced into the planetary gear set 26.The ring gear 28 is permanently connected to the housing 32 in a rotationally fixed manner. The planet carrier of the planetary gear set 26 is an output of the planetary gear set 26, also referred to as the output. Via the output of the planetary gear set 26, a respective output torque resulting from the respective drive torque introduced into the planetary gear set 26 via its input can be output from the planetary gear set 26, thus being provided by the planetary gear set 26, whereby the motor vehicle can be driven by means of the respective output torque.

[0053] In order to be able to realize particularly advantageous noise behavior of the drive device 10, the stator 18, in particular its stator housing 34, has a partial region TB which projects outwards beyond the rotors 14 and 16 in the radial direction of the electric machine 12 and thus projects outwards from the rotors 14 and 16 in the radial direction of the electric machine 12. A projection 36 is provided on the partial region TB, which projection 36, in the embodiment shown in the figure, is formed integrally with the stator housing 34 and thus with the stator 18. This means that the stator housing 34 and the projection 36, i.e. the stator 18 and the projection 36, are formed from a single piece. In the embodiment shown in the figure, the projection 36 and thus the stator housing 34 are formed from a fiber-reinforced plastic.

[0054] As can be seen from the figure, the projection 36 extends from an axial end face 38 of the stator 18, in particular of the stator housing 34, pointing in the axial direction of the electric machine 12 towards the planetary gear set 26, away in the direction of the planetary gear set 26, in such a way that the projection 36 extends in the axial direction of the electric machine 12 away from the axial end face 38 and extends over the rotor 16, whereby the rotor 16, which is arranged in the axial direction of the electric machine 12 between the planetary gear set 26 and the stator 18, that is to say the stator housing 34 and in the present case the axial end face 38, is overlapped outwards in the radial direction of the electric machine 12 by the projection 36, in particular completely.In the present case, the projection 36 surrounds the rotor 16 in the circumferential direction of the electric machine 12, in particular completely encircling it. The entire rotor 20 is driven by the stator 18 and is thus rotatable about a machine rotation axis relative to the stator 18. For example, the planetary gear set rotation axis coincides with the machine rotation axis, so that the electric machine 12 is arranged coaxially with the planetary gear set 26.

[0055] The projection 36, which is essentially formed in one piece, i.e., made from a single piece and in this case formed integrally with the stator housing 34, forms a ring gear carrier 40, to which the ring gear 28, which is formed separately from the ring gear carrier 40 and thus separately from the projection 36, is connected, in particular permanently, in a rotationally fixed manner. Furthermore, the projection 36 is connected, in particular permanently, in a rotationally fixed manner to the housing 32, so that the ring gear 28 is permanently connected in a rotationally fixed manner to the housing 32 via the ring gear carrier 40. Furthermore, the projection 36 has a spline 42 as the first spline, which engages with a corresponding second spline 44 of the housing 32. The second spline 44 is preferably designed as a second spline.It can be seen that the spline 42 is arranged on an axial end face 46 of the projection 36 facing the spline 44 in the axial direction of the electric machine 12, with teeth of the spline 42 extending away from the axial end face 46 in the axial direction of the electric machine 12. One of the teeth of the spline 42 can be seen in the figure and is designated by 48. The second spline 44 is arranged on an axial end face 50 of the housing 32 facing the axial end face 46 of the projection 36 in the axial direction of the electric machine 12, with teeth of the spline 44 projecting from the axial end face 50 of the housing 32 towards the axial end face 46 in the axial direction of the electric machine 12. One of the teeth of the spline 44 can be seen in the figure and is designated by 52.

[0056] An outer circumference of the ring gear 28, which points outwards in the radial direction of the electric machine 12 and faces the ring gear carrier 40 in the radial direction of the electric machine 12, is designated by 54 in the figure. An inner circumference of the ring gear carrier 40, which points inwards in the radial direction of the electric machine 12 and faces the outer circumference 54 in the radial direction of the electric machine 12, is designated by 56, wherein the outer circumference 54 faces the inner circumference 56 in the radial direction of the electric machine 12. For example, the ring gear 28 has, on its outer circumference 54, a toothing which is particularly designed as micro-toothing and is also referred to as connecting toothing. For example, the ring gear carrier 40 and the ring gear 28 are connected to one another in a rotationally fixed manner such that the ring gear 48 is pressed into the ring gear carrier 40 or the ring gear carrier 40 is pressed onto the ring gear 28.When the ring gear 28 is pressed into the ring gear carrier 40 or when the ring gear carrier 40 is pressed onto the ring gear 28, teeth of the connecting toothing of the ring gear 28 intersect, i.e. independently, into the ring gear carrier 40, in particular into the fiber-reinforced plastic and very particularly into its plastic matrix, thereby forming a positive connection between the ring gear 28 and the ring gear carrier 40, in particular between the outer circumference 54 and the inner circumference 56. Thus, the ring gear 28 and the ring gear carrier 40 are positively connected to one another in a rotationally fixed manner. In particular, the ring gear 28 and the ring gear carrier 40 are connected to one another in such a way that both relative rotations between the ring gear 28 and the ring gear carrier 40 and relative movements occurring in the axial direction of the electric machine 12 between the ring gear 28 and the ring gear carrier 40 are prevented.In addition, because the spline 42 engages with the spline 44, the projection 36 is positively connected to the housing 32 in a rotationally fixed manner.

[0057] For example, the spline 42 is designed as segmented spline, wherein it is preferably provided that, in particular, the spline 44 is also designed as segmented spline. This means that first partial regions of the axial end face 46 are arranged in the circumferential direction between the teeth of the spline 42. The first partial regions of the axial end face 46 are also referred to as first intermediate segments. The first partial regions of the axial end face 46 are first wall regions of the projection 36. For example, the first partial regions of the axial end face 46 are flat or planar. This means, for example, that the first partial regions of the axial end face 46 extend in a plane that is perpendicular to the axial direction of the electrical machine 12.Accordingly, for example, in the circumferential direction of the electric machine 12, second subregions of the axial end face 50 are arranged between the teeth of the toothing 44, the second subregions of which are also referred to as second intermediate segments. Thus, the second subregions of the axial end face 50 are second wall regions of the housing 32. For example, the second subregions are planar or planar regions. This means that, for example, the second subregions of the axial end face 50 extend in a second plane that runs perpendicular to the axial direction of the electric machine 12. For example, the first subregions are separated from the second subregions in the axial direction, for example by an air gap.

[0058] Exactly one of the second sub-regions of the axial end face 50 is assigned to the respective first sub-region of the axial end face 46, wherein the respective first sub-region and the respective second sub-region assigned to the respective first sub-region form a respective sub-region pair. For example, at least one or exactly one screw 58 is assigned to the respective sub-region pair, which screw 58 penetrates the respective sub-regions of the respective sub-region pair. By means of the screws 58, the spline 42 is clamped against the toothing 44 in the axial direction of the electric machine 12, wherein in the present case it is provided, for example, that the first sub-regions are clamped against the second sub-regions in the axial direction by means of the screws 58. For example, the spline 42 and / or the toothing 44 is designed as a Hirt toothing.For example, the ring gear 28 is formed from a metallic material, in particular from a steel.

[0059] The drive device 10 has a sleeve 60 which is formed separately from the ring gear 28 and separately from the ring gear carrier 40 and thus separately from the projection 36 and which is formed, for example, from the same metallic material, in particular from the same steel, from which the ring gear 28 is formed. An outer circumference of the ring gear carrier 40 which points outwards in the radial direction of the electric machine 12 and points away from the outer circumference 54 in the radial direction of the electric machine 12, and away from the inner circumference 56 and the ring gear 28 and faces the sleeve 60 in the radial direction of the electric machine 12 is designated by 62 in the figure. The sleeve 60 is arranged on the outer circumference 62 in such a way that the sleeve 60 directly touches the outer circumference 62 and thus the ring gear carrier 40.With respect to the ring gear carrier 40 and the ring gear 28, the sleeve 60 is positioned in the axial direction of the electric machine 12 such that at least one respective length region of the ring gear carrier 40 and the ring gear 28 running in the axial direction of the electric machine 12 is overlapped outwards in the radial direction of the electric machine 12 by the sleeve 60. In the present case, the ring gear 28 and the ring gear carrier 40 are overlapped outwards in the radial direction of the electric machine 12 by the sleeve 60 over more than half of their respective length running in the axial direction of the electric machine 12, in particular over their respective entire length running in the axial direction of the electric machine 12, whereby an advantageous connection of the ring gear 28 to the ring gear carrier 40 can be ensured.

[0060] Furthermore, in the drive device 10, an air gap L is arranged in the radial direction of the electric machine 12 between the housing 32 and the ring gear carrier 40, and in the present case, in the radial direction of the electric machine 12 between the sleeve 60 and the housing 32. This air gap L is delimited outwards in the radial direction of the electric machine 12 directly by the housing 32 and inwards in the radial direction of the electric machine 12 directly by the sleeve 60. The air gap L extends completely around the sleeve 60 and the ring gear carrier 40 in the circumferential direction of the electric machine 12, which runs around the machine's axis of rotation and thus around the axial direction of the electric machine 12. In the present case, the air gap L extends over more than half of the respective lengths of the ring gear carrier 40, the ring gear 28, and the sleeve 60 running in the axial direction of the electric machine 12.In the present case, it is provided that the air gap L extends in the axial direction of the electric machine 12 over the respective entire length of the ring gear 28, the ring gear carrier 40 and the sleeve 60 running in the axial direction of the electric machine 12.

[0061] The projection 36 has a free axial end E, which is opposite the axial end face 38 of the stator 18, i.e., the stator housing 34, in the axial direction of the electric machine 12. The projection 36 and the ring gear carrier 40 terminate at the end E in the axial direction of the electric machine 12, wherein the end E is completely spaced from the housing 32 in both the radial direction and the axial direction of the electric machine 12. List of reference symbols 10 electric drive device 12 electric machine 14 Rotor 16 Rotor 18 Stator 20 total rotor 22 Double arrow 24 double arrow 26 planetary gear set 28 ring gear 30 Planetary gear 32 housings 34 Stator housing 36 cantilever 38 axial end face 40 ring gear carriers 42 spline 44 second gearing 46 axial end face 48 tooth 50 Axial front side 52 teeth 54 outer circumference 56 inner circumference 58 screw 60 sleeve 62 outer circumference E End L Air gap TB sub-area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2009 018 409 A1

[0002]

Claims

[1] Electric drive device (10) for a motor vehicle, with at least one electric machine (12) for driving the motor vehicle, with a planetary gear set (26) having a ring gear (28) via which the motor vehicle can be driven by the electric machine (12), and with a housing (32) in which the planetary gear set (26) is arranged, characterized by , that: - the electrical machine (12) is designed as an axial flux machine having two rotors (14, 16) and a stator (18) which is arranged in the axial direction (22) of the electrical machine (12) between the rotors (14, 16) which are rotatable relative to the stator (18); - the stator (18) has a partial region (TB) projecting outwardly beyond the rotors (14, 16) in the radial direction (24) of the electric machine (12), on which a projection (36) is provided, which: o extends in the axial direction (22) of the electric machine (12) over one of the rotors (14, 16), o the one rotor (16) arranged in the axial direction (22) of the electric machine (12) between the planetary gear set (26) and the stator (18) overlaps outwards in the radial direction (24) of the electric machine (12), o forms a ring gear carrier (40) to which the ring gear (28) formed separately from the ring gear carrier (40) is connected in a rotationally fixed manner, and o has a plug-in toothing (42) as the first toothing, which engages in a corresponding second toothing (44) of the housing (32). [2] Electric drive device (10) according to claim 1, characterized by that the ring gear carrier (40) is formed from a fiber-reinforced plastic. [3] Electric drive device (10) according to claim 1 or 2, characterized by that the stator (18) is formed integrally with the projection (36). [4] Electric drive device (10) according to one of the preceding claims, characterized by that the spline (42) is designed as a segmented spline [5] Electric drive device (10) according to one of the preceding claims, characterized by that the plug-in toothing (42) is designed as a Hirth toothing. [6] Electric drive device (10) according to one of the preceding claims, characterized by that in the circumferential direction of the electrical machine (12) between teeth (48) of the spline (42) screws (58) are arranged, by means of which the spline (42) is tensioned in the axial direction (22) of the electrical machine (12) against the second spline (44). [7] Electric drive device (10) according to one of the preceding claims, characterized by that the ring gear (28) is connected to the ring gear carrier (40) in a rotationally fixed manner via a further spline. [8] Electric drive device (10) according to one of the preceding claims, characterized by a sleeve (60) which is formed separately from the ring gear (28) and separately from the ring gear carrier (40), is arranged on an outer circumference (62) of the ring gear carrier (40) facing away from the ring gear (28) in the radial direction (24) of the electrical machine (12) and is fixedly connected to the ring gear carrier (40), by means of which sleeve at least one respective longitudinal region of the ring gear carrier (40) and of the ring gear (28) running in the axial direction (22) of the electrical machine (12) is overlapped outwards in the radial direction (24) of the electrical machine (12). [9] Electric drive device (10) according to claim 8, characterized by that the sleeve (40) is made of steel. [10] Electric drive device (10) according to one of the preceding claims, characterized bythat in the radial direction (24) of the electrical machine (12) between the housing (32) and the ring gear carrier (40) an air gap (L) is provided, which extends in the circumferential direction of the electrical machine (12) completely circumferentially around the ring gear carrier (40).

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