Electric drive

Abstract

The invention relates to an electric drive (10) of a motor vehicle (2), in particular a steering motor, comprising a housing (22) that has a motor compartment (30) and an electronics compartment (28). An electric motor (46) having a stator (48) and having a rotor (50) fastened to a shaft (38) that is arranged parallel to an axial direction (18) is arranged in the motor compartment (30). Electronics (52) for energizing the electric motor (46) are arranged in the electronics compartment (28). The motor compartment (30) and the electronics compartment (28) are separated by way of an end shield (26) to which there is attached a bearing (36) for mounting the shaft (38). A cover element (58) is arranged between the electronics (52) and the end shield (26) and rests against the inside (32) of the housing (22). A heat sink (56) is attached to the electronics (52) and is supported on the cover element (58). The invention also relates to an auxiliary unit (8) of a motor vehicle (2).

Description

[0001] Description

[0002] Electric drive

[0003] The invention relates to an electric drive of a motor vehicle and an auxiliary unit of a motor vehicle with such an electric drive. The electric drive is, in particular, a steering motor.

[0004] Motor vehicles, such as passenger cars, typically have a steering system that allows the direction of travel to be adjusted. The steering system typically comprises a steering wheel located inside the vehicle and connected to a steering column. Attached to the steering column is a gearwheel that meshes with a rack, which in turn is mounted on the pivoting front wheels of the vehicle. Thus, when the steering wheel rotates, the rack is moved transversely, changing the steering angle of the wheels.

[0005] To increase comfort, a steering motor is usually also present, which assists the driver's steering movement, reducing the force required by the driver to operate the steering wheel while still allowing the wheels to be adjusted appropriately. To reduce weight and increase safety in the event of an accident, steering systems are known in which there is no mechanical coupling between the steering wheel and the front wheels. In this case, the angular position of the steering wheel or other control element is detected by a sensor, and the steering motor, which drives the steering rack, is controlled accordingly. Such a system is also referred to as a "steer-by-wire" system. Both of these steering systems place comparatively high demands on the steering motor. For example, it should be relatively compact and insensitive to external vibrations.Therefore, the electric motor of the steering motor and the electronics used to power the electric motor are typically housed in a single housing, allowing the steering motor to be installed and replaced as a single module. The housing also protects the electrical connections between the electronics and the electric motor.

[0006] The disadvantage here is that abrasion particles or similar can be generated during operation of the electric motor, or that dirt particles or liquid can penetrate the housing on one of the drive sides of the electric motor, which then reach the electronics and accumulate there. This can cause a short circuit in the electronics or other operational impairment, leading to a failure of the steering motor. Depending on the design of the steering system, this can either suddenly increase the forces required for steering, surprising the driver, or make the vehicle impossible to control at all, or lead to incorrect steering (wheels turning in the opposite direction when steering).

[0007] To prevent this, a cover element is usually arranged in the housing, by means of which the electronics in the housing are separated from the other components of the steering motor. If this cover element is made of plastic, it has a different coefficient of thermal expansion than the housing. When the steering motor heats up, it is therefore possible that additional gaps arise, making particles permeable. To prevent this, the cover element is made of an elastic material and attached to the housing. However, this makes assembly more difficult and therefore increases manufacturing costs. Alternatively, the cover element is made of the same material as the housing and welded to it, which increases manufacturing costs and also the weight of the steering motor.The invention is based on the object of specifying a particularly suitable electric drive of a motor vehicle and a particularly suitable auxiliary unit of a motor vehicle, wherein operational reliability is advantageously increased, and wherein a failure rate, manufacturing costs and / or weight are expediently reduced.

[0008] With regard to the electric drive, this object is achieved according to the invention by the features of claim 1 and with regard to the auxiliary unit by the features of claim 9. Advantageous further developments and refinements are the subject of the respective subclaims.

[0009] The electric drive is a component of a motor vehicle. In other words, the electric drive is suitable, in particular intended and configured, to be connected to other components of the motor vehicle in the assembled state and / or to form a component of the motor vehicle. The motor vehicle is in particular land-based and preferably has a multi-track design. In this case, it is suitably possible to position the motor vehicle essentially freely, in particular on a corresponding roadway. For this purpose, the motor vehicle expediently has corresponding wheels. In summary, it is preferably possible to position the motor vehicle essentially independently of other conditions on land. In other words, the motor vehicle is suitably not rail-guided. Preferably, the motor vehicle is a passenger car (car) or a commercial vehicle, such as a lorry (truck) or bus.

[0010] The electric drive, also referred to as an electric motor unit, is, for example, a component of a main drive of the motor vehicle, by means of which the motor vehicle is driven during operation. However, the electric drive is particularly preferably a component of an auxiliary unit of the motor vehicle, by means of which the motor vehicle is not directly driven. In particular, the electric drive is a component of an adjustment drive, such as an electric seat adjustment or an electric window lifter. Alternatively, the electric drive is, for example, a component of a pump, such as a water pump or an oil pump. In a further alternative, the electric drive is, for example, a transmission actuator, and the auxiliary unit is in particular a transmission. In a further alternative, the electric drive is, for example, a component of an air conditioning compressor.

[0011] However, the electric drive is particularly preferably a steering motor, and the auxiliary unit is thus in particular a steering system. During operation, the steering motor, for example, assists a steering movement performed by a driver. In other words, the steering system is mechanically designed, with a mechanical coupling between an operating device, such as a steering wheel, and steerable / controllable wheels or the like. However, the steering system is particularly preferably designed as a so-called "steer-by-wire" system, and in particular there is no direct mechanical operative connection between the operating device and the steerable / controllable wheels. The steering motor preferably acts on the steerable / controllable wheels via a rack or the like.The steering motor expediently has a gear that engages with the rack, or that is at least driven by the steering motor. Preferably, a sensor is assigned to the steering wheel or other operating device, which is connected, in particular, electrically and / or signal-wise to the steering motor. The connection is, for example, direct or via a control unit, by means of which the steering motor is operated based on the signals / data provided by the sensor. At least preferably, the steering motor is operated depending on the data and / or signals generated / provided by the sensor.

[0012] The steering motor itself comprises a housing having a motor compartment and an electronics compartment. In particular, the housing is designed as a single piece and is expediently cylindrical, such as a hollow cylinder. The housing comprises at least one hollow cylindrical section. Suitably, the housing preferably extends along an axial direction, which is also referred to as the axial direction. The housing is suitably made of aluminum, in particular an aluminum die-cast part or aluminum cold-extruded part. An electric motor having a stator and a rotor is arranged in the motor compartment. The rotor is fastened to a shaft arranged parallel to the axial direction. In this case, the shaft forms, in particular, at least partially a component of the electric motor or of another component of the electric drive. Preferably, the shaft is arranged at least partially outside the motor compartment.The electric motor, however, is expediently arranged entirely within the motor compartment. In particular, the electric motor is designed as an internal rotor, so that the stator surrounds the rotor circumferentially. Preferably, the stator rests against one inner side of the housing or is at least attached thereto. In particular, the stator and rotor are hollow-cylindrical and arranged concentrically with the shaft.

[0013] For example, the electric motor is a brushed commutator motor. However, the electric motor is particularly preferably designed to be brushless and expediently a brushless direct current (BLDC) motor. This reduces any losses that may occur. The electric motor, preferably the stator, expediently has one or more electrical coils, each of which at least partially forms an electromagnet. In particular, the electrical coils are connected to form several phases, for example, three phases. The stator preferably comprises the electrical coils. Suitably, the electric motor has one or more permanent magnets, which are, for example, a component of the rotor.

[0014] Electronics are arranged in the electronics compartment. In particular, the electronics are arranged entirely within the electronics compartment, and the electronics serve to supply power to the electric motor. Electronics are suitable, in particular provided and configured for this purpose. The electronics are expediently electrically connected to the electric motor, in particular to the stator and / or any phases. The electronics comprise, in particular, a plurality of electrical and / or electronic components, which are suitably attached to a circuit board of the electronics. In this case, the individual components are expediently interconnected by means of the circuit board. If the electric motor is designed as a brushless DC motor, the electronics expediently has a bridge circuit, preferably a B6 circuit. However, the bridge circuit expediently corresponds at least to a number of any phases of the electric motor.The electric motor preferably comprises two sets of three phases, with the phase connection being a star or delta connection. The bridge connection is preferably a B12 connection.

[0015] A heat sink is connected to the electronics and is attached, for example, to any circuit board. In particular, the heat sink is in thermal contact with at least one component of the electronics, such as a (power) semiconductor, by means of which, for example, any bridge circuit is at least partially formed. For example, the heat sink is supported on the circuit board via the electronics component or is in direct mechanical contact with the circuit board. The heat sink is made, for example, from a metal such as aluminum. The heat sink dissipates any (waste) heat generated by the electronics during operation. For this purpose, the heat sink provides, in particular, a comparatively large surface area, so that waste heat dissipation is improved.

[0016] The motor compartment and the electronics compartment are separated by a bearing shield. The bearing shield is expediently a component of the housing or at least attached to it, preferably molded onto it, so that the bearing shield is particularly integrally connected to the remaining components of the housing. The bearing shield and any hollow cylindrical section of the housing are expediently formed together, thus increasing robustness. Due to the bearing shield, the motor compartment and the electronics compartment are suitably designed to be essentially pot-shaped. The bearing shield is preferably oriented perpendicular to the axial direction, and a bearing for supporting the shaft is expediently connected to the bearing shield. The bearing is in particular a rolling bearing, suitably a ball bearing.In particular, one end of the shaft protrudes through the bearing shield so that it is partially arranged within the electronics compartment. The bearing shield forms in particular a so-called B-side bearing shield. A cover element is arranged between the electronics below the bearing shield. This is therefore located in the electronics compartment. The cover element rests on the inside of the housing. For example, there is a frictional connection between the cover element and the inside of the housing, at least at certain temperatures, so that the cover element rests force-fittingly on the inside of the housing. In particular, the cover element is arranged perpendicular to the axial direction. Suitably, the cover element has a flat design. The cover element covers in particular the bearing shield and / or the electronics so that they are separated from one another.The cover element therefore suitably serves to separate the electronics from the bearing plate and, in particular, to protect it from particles, liquids, and / or dust. The cover element is suitable, preferably provided, and configured for this purpose. For example, the cover element has no perforations, other openings, or the like that are not sealed. Sealing is achieved, for example, by means of individual sealing elements.

[0017] Preferably, a plurality of electrical lines are routed through the cover element so that the electronics can supply power to the electric motor. The lines suitably comprise any phase connections of the electric motor or are at least electrically contacted with them. For example, a plurality of sealing elements or the like are provided in the region of the lead-throughs of any lines through the cover element. Suitably, the cover element has a flat base body made of a plastic. In particular, the base body forms a plastic body. Due to the plastic, weight and manufacturing costs are reduced. The lines are preferably routed through the base body, with a plurality of openings being provided, for example. For example, the base body is made of a single material.The openings are sealed in particular by means of a sealing element attached to the base body. However, the base body is particularly preferably made of different plastic components, which are manufactured in particular using a two-component process. For example, the sealing elements are overmolded with the plastic to create the base body. The sealing elements are, for example, elastic and preferably made of an elastomer or rubber. During the manufacture of the electric drive, the sealing elements are preferably pierced by any cables to establish the electrical connection between the electronics and the electric motor.

[0018] The heat sink connected to the electronics is supported by the cover element. Consequently, the position of the cover element is stabilized in at least one direction by the heat sink, and movement of the cover element toward the electronics is prevented in particular in this way. The cover element is expediently supported in the axial direction by the heat sink, so that movement of the cover element in the axial direction is prevented by the heat sink. The heat sink thus acts as a hold-down device for the cover element.

[0019] The cover element, which rests on the inside of the housing, prevents particles and / or fluids from the electric motor from penetrating the bearing shield and reaching the electronics. Therefore, the bearings have comparatively low requirements, and in particular, there is no need to design them with a seal, which, on the one hand, reduces friction. On the other hand, manufacturing costs are reduced. There are also no requirements for openings in the bearing shield, through which, in particular, any phase connections or other cables are routed.

[0020] Due to the direct contact of the cover element with the inside of the housing, a comparatively high level of tightness is achieved. If, when the electric drive heats up, which leads to a different expansion of the housing and the cover element, the cover element detaches slightly from the inside, for example, it is no longer fully stabilized by the housing. However, the position of the cover element is at least partially predetermined by the heat sink, so that even in this case a sealing effect, for example a reduced one, is still present. At the very least, complete detachment of the cover element is prevented, so that after the electric drive has cooled down again, it can be used essentially unchanged.In summary, the support provided by the heat sink ensures that the cover element always remains in the same position, even if, for example, a possible frictional connection between the inside of the housing and the cover element is not sufficient to stabilize the position of the cover element and / or no longer exists due to current operation.

[0021] Consequently, the cover element provides a comparatively high level of tightness, preventing foreign particles from penetrating the electronics. This reduces the failure rate of the electric drive and increases operational reliability. To stabilize the cover element, an existing or otherwise usable component, namely the heat sink, is used, thus maintaining the same manufacturing costs and weight. Furthermore, it is not necessary to design the cover element to be comparatively robust and / or with the same thermal expansion coefficient as the housing, thus also reducing manufacturing costs. Furthermore, the assembly requirements for the cover element are comparatively low.

[0022] For example, the inside of the housing is smooth. However, the inside is particularly preferably provided with a circumferential projection that projects inwards, particularly in the radial direction. The radial direction is perpendicular to the axial direction and is expediently determined by the shaft or at least one axis of rotation of the shaft. The projection is expediently a component of the housing and / or integrally formed on any hollow cylindrical section, preferably formed therewith. The projection in particular forms at least a local reduction in the inside diameter of the housing. Thus, the housing has at least two different inside radii, with the transition between these two occurring in the region of the projection. The projection is, for example, annular. In other words, the inside radius of the housing is the same on both sides of the projection in the axial direction.Alternatively, the projection is formed by a step or edge. The electronics compartment preferably has only two different inner radii, with one of the reduced inner radius expediently extending from the bearing plate to the end of the projection in the axial direction.

[0023] The cover element expediently rests on the projection on / with the side facing away from the electronics. For assembly, the cover element is inserted into the electronics compartment from the end of the housing opposite the bearing plate until it rests on the projection, which simplifies assembly. After production, the cover element is stabilized by means of the projection and the heat sink, and the cover element is located, in particular, at least in sections, between them. Suitably, the cover element rests mechanically directly on the projection and the heat sink. Consequently, the position of the cover element in the axial direction is predetermined by the heat sink and the projection. For example, the cover element is attached to the projection and / or the heat sink, e.g. by means of an adhesive.However, there is no additional fastening, and the stabilization of the position is achieved primarily due to the direct mechanical attachment.

[0024] The projection also provides a comparatively large contact surface for the cover element against the housing. Even if the cover element and the housing expand differently, they still contact each other (at the end face), even if a small circumferential gap forms between the cover element and the inner surface. The projection and the cover element act like a labyrinth seal, thus maintaining a tight seal.

[0025] For example, the cover element is pressed against the projection by means of the heat sink. Alternatively, the cover element merely rests on the projection. Particularly preferably, however, the cover element comprises a disc-shaped plastic body, which is formed in particular by means of the base body, if any. The plastic body is annular or flat. For example, the base body comprises one or more elevations that are offset toward the bearing plate or away from it. In particular, the elevations serve to increase the stability of the cover element and / or are located in the area of ​​any openings or feedthroughs for the cables / phase connections.

[0026] The plastic body is arranged flush with the projection on the side facing the electronics. The plastic body thus advantageously rests circumferentially against the projection and adjoins it in the radial direction. In other words, the plastic body is inserted into the projection. The cover element also has a collar arranged on the side of the plastic body facing the electronics, which protrudes in the axial direction and thus points towards the electronics. The collar overlaps the projection in sections. This reduces the material required for the cover element, while the collar still provides a labyrinth seal, thus increasing tightness.It is also possible, for example, to manufacture the collar and the plastic body from different materials, for example, using a two-component injection molding process, and / or to mold the plastic body onto the collar, which is made of a sealing material, such as an elastomer or rubber. At the very least, the collar preferably has increased elasticity, so that a high sealing effect is always maintained even with varying expansion. The collar is conveniently located on the inside of the housing.

[0027] For example, the collar is designed to be circumferential and in particular ring-shaped. For example, the heat sink is supported on the collar. However, the collar particularly preferably has a bulge running inwards in the radial direction, by means of which bulge a free end of the heat sink is encompassed. The free end itself rests in particular on the plastic body and partially on the projection. Thus, the position of the plastic body is predetermined by the heat sink, and the position of the heat sink is also predetermined by the housing, namely the projection. It is also possible in particular to mount the heat sink without exerting force on the electronics, thus reducing stress on the electronics. Due to the bulge, a sealing effect is nevertheless present. In particular, the collar rests mechanically directly on the heat sink in the region of the bulge.For example, the collar is made of a comparatively elastic material, in particular an elastomer or rubber.

[0028] Alternatively, or in combination with the collar, an additional collar projecting in the axial direction is advantageously arranged on the plastic body on the side facing away from the electronics. The additional collar is advantageously annular. For example, the annular additional collar has a smaller diameter than the projection. The additional collar, in particular, stabilizes the plastic body, which increases robustness, while only slightly increasing the weight and additional space required by the cover element.

[0029] For example, the additional collar rests directly on the inside of the housing, thus stabilizing the cover element. However, it is particularly preferred for a sealing element, such as an O-ring, to be arranged in the radial direction between the additional collar and the inside. The sealing element is expediently made of an elastomer or rubber. For example, the additional collar has a substantially rectangular cross-section parallel to the radial direction. However, it is particularly preferred for the collar to be chamfered and, in particular, to have a triangular cross-section at least in sections, with the width of the collar being increased in the region of the plastic body. When the cover element is inserted onto the projection, the sealing element is pressed against the additional collar and the inside of the housing, which increases the sealing effect.Alternatively or in combination with this, the sealing element is inserted, for example, into a groove in the collar or the plastic body, which is why the position of the sealing element is reliably determined. Particularly preferably, the sealing element is, for example, materially bonded to the plastic body, which have in particular been manufactured together using a 2K process. For example, the plastic of the plastic body is injection-molded onto the sealing element, so that the sealing element is captively attached to the plastic body. For example, the heat sink is spaced from the housing. However, it is particularly preferred that the heat sink is thermally contacted within the housing, so that the heat from the electronics is dissipated via the housing. This improves the cooling effect.Particularly preferably, the heat sink is at least partially attached to the inside of the housing, for example, via another component such as a thermal pad or thermal paste, or directly mechanically. In this way, the heat sink is also stabilized by the housing, thus reducing stress on the electronics.

[0030] For example, the electric drive comprises only a single such heat sink. However, the electric drive particularly preferably comprises at least a second corresponding heat sink, by means of which the cover element is also supported and which is connected to the electronics. For example, there are exactly two heat sinks that are connected to the electronics. Alternatively, more heat sinks are provided, the number preferably being less than ten. This reduces the space requirement. The electric drive particularly preferably comprises exactly three such heat sinks. By means of these, in particular the position of the cover element is precisely predetermined, so that tilting does not occur. There is also no overdetermination, which is why the desired support of the cover element by means of the heat sinks is always achieved, even with comparatively high manufacturing tolerances.For example, some, preferably all, of the heat sinks are identical to each other, allowing the use of identical parts. This reduces manufacturing costs. If the collar is present, the number of protrusions is appropriately corresponding to the number of heat sinks.

[0031] When assembled, the auxiliary unit is a component of a motor vehicle and is suitable, in particular provided and configured for this purpose. The motor vehicle is, for example, land-based and, for example, a truck, bus, or preferably a passenger car. The auxiliary unit has an electric drive. The electric drive comprises a housing having a motor compartment and an electronics compartment. Arranged in the motor compartment is an electric motor having a stator and a rotor fastened to a shaft that is arranged parallel to an axial direction. Arranged in the electronics compartment is electronics for supplying current to the electric motor, and the motor compartment and the electronics compartment are separated by a bearing shield to which a bearing for supporting the shaft is connected.A cover element is arranged between the electronics and the bearing plate, which rests on the inside of the housing, and a heat sink is connected to the electronics and supported on the cover element.

[0032] In particular, another component of the auxiliary unit is driven by the electric drive, such as an adjustment part. For example, the electric drive is a component of an electromotive pump, such as a water pump, a coolant pump, or a lubricant pump, such as an oil pump. For example, the auxiliary unit is a transmission. However, the auxiliary unit is particularly preferably a steering system. During operation, the electric drive, for example, supports a force applied manually by a driver. However, the steering system is particularly preferably designed as a steer-by-wire system. In particular, a component is driven by the electric drive, by means of which component a steering angle of wheels of the motor vehicle is predetermined.In particular, a rack connected to at least one of the wheels of the motor vehicle is driven by means of the electric drive, wherein a steering angle of the associated wheel is predetermined by the position of the rack. For example, the rack is a component of the auxiliary unit or is driven by the auxiliary unit. In particular, the steering system comprises an operating device, such as a steering wheel, by means of which, in particular, the steering angle can be predetermined by a driver of the motor vehicle. Preferably, a signal-based coupling / connection of the electric drive to a sensor assigned to the operating device is present. Alternatively, or in combination with this, the electric drive is coupled to an on-board computer or other assistance system of the motor vehicle, by means of which, in particular, semi-autonomous or fully autonomous movement or at least steering of the motor vehicle can take place.Furthermore, the invention relates to a motor vehicle with such an auxiliary unit.

[0033] The further developments and advantages explained in connection with the electric drive can also be transferred to the auxiliary unit / the motor vehicle as well as to each other and vice versa.

[0034] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawings:

[0035] Fig. 1 schematically shows a motor vehicle with a steering system having an electric drive,

[0036] Fig. 2, 3 each show a perspective sectional view along an axial direction of the electric drive having a cover element, wherein an electronics system is not shown,

[0037] Fig. 4 shows a sectional view of the electric drive with the electronics,

[0038] Fig. 5 perspective view of the cover element, and

[0039] Fig. 6 shows in perspective an alternative design of the cover element.

[0040] Corresponding parts are provided with the same reference numerals in all figures.

[0041] Figure 1 shows a simplified schematic representation of a motor vehicle 2 in the form of a passenger car (car). The motor vehicle 2 has a total of four wheels 4, which, in their intended state, rest on a roadway (not shown in detail), and which are connected to a body 6 of the motor vehicle 2 by means of a chassis. Two of the wheels 4, namely the two front wheels or, if applicable, the rear wheels, are coupled to an auxiliary unit 8, namely a steering system, by means of which a steering angle of these wheels 4 relative to the body 6 can be adjusted. For this purpose, the auxiliary unit 8 is operatively connected to these wheels 4. The auxiliary unit 8 comprises an electric drive 10, by means of which a rack (not shown in detail) is driven, which is mounted on the two front wheels.During operation of the electric drive 10, the rack is moved transversely, namely in a horizontal plane and perpendicular to a longitudinal axis of the motor vehicle 2, whereby due to the connection to the front wheels, their steering angle with respect to the body 6 is changed.

[0042] The auxiliary unit 8 further comprises a sensor 12, which is assigned to an operating device 14, wherein the position of the operating device 14 is detected by means of the sensor 12. The operating device 14 is designed as a steering wheel and arranged in an interior of the motor vehicle 2, which is provided by the body 6. The sensor 12 is signal-connected to the electric drive 10 via a control device / control unit (not shown in detail). There is no direct mechanical coupling between the operating device 14 and the front wheels of the motor vehicle 2, so that the steering system is designed as a so-called "steer-by-wire" system.

[0043] Figure 2 shows the electric drive 10 along a rotational axis 16, and Figure 3 shows a section of the electric drive 10, also in a perspective sectional view along the rotational axis 16. The rotational axis 16 runs parallel to an axial direction 18, and a radial direction 20 is also defined by the rotational axis 16. The radial direction 20 always intersects the rotational axis 16 at an angle of 90°.

[0044] The electric drive 10 has a housing 22 made in one piece from aluminum and having a hollow cylindrical section 24 arranged concentrically to the rotation axis 16. A bearing plate 26 arranged perpendicular to the axial direction 18 is surrounded by the hollow cylindrical section 24 and formed thereon. The bearing plate 26 divides the housing 22 into an electronics compartment 28 and a motor compartment 30. The inner diameter of the housing 22, namely of the hollow cylindrical section 24, is not constant in the electronics compartment 28; rather, an inner side 32 of the housing 22 has a circumferential projection 34 oriented inward in the radial direction 20, which is formed by a step. The inner diameter is constant from the step up to the bearing plate 26, as well as on the side of the step facing away from the bearing plate 26.

[0045] A bearing 36, namely a ball bearing, is held by the bearing plate 26. In other words, the bearing 36 is connected to the bearing plate 26. A shaft 38, which is essentially cylindrical and arranged concentrically to the rotation axis 16, is rotatably mounted by the bearing 36 with respect to the rotation axis 16. The shaft 38 projects through the bearing plate 20 and is located partially within the electronics compartment 28. The shaft 38 also extends through the entire motor compartment 30. The motor compartment 30 is closed at the end opposite the bearing plate 26 by another bearing plate 40, by means of which another bearing 42 is held. The shaft 38 is also mounted by the additional bearing and also extends through the additional bearing plate 40, which forms an A-side bearing plate.At the end of the shaft 38 passing through the further bearing plate 40, a gear 44 or pinion is connected, which in the assembled state is in engagement with the rack (not shown in detail) or a belt.

[0046] An electric motor 46, designed as a brushless direct current (BLDC) motor, is arranged in the motor compartment 30 and has a hollow cylindrical stator 48. The stator 48 is attached circumferentially to the inner side 32 of the housing 22 and surrounds a rotor 50, also designed as a hollow cylinder, which is attached to the shaft 38. The stator 48 and the rotor 50 are arranged concentrically with respect to the rotation axis 16. The stator 48 comprises a number of electromagnets (not shown in detail), each of which is formed at least partially by an electrical coil. The electrical coils are interconnected in a total of two times three phases, each forming a star connection. The rotor 50 has a laminated core into which permanent magnets (not shown in detail) are embedded. In summary, the electric motor 46 is arranged in the motor compartment 30, which has the stator 48 and the rotor 50 which is fixedly fastened to the shaft 38 in a rotationally fixed manner.The electric drive 10 comprises electronics 52, which is shown in Figure 4. There, a section of the electric drive 10 is shown in a sectional view along the rotation axis 16. The electronics 52 has a disk-shaped circuit board 54, which is arranged perpendicular to the axial direction 18 and is located in the electronics compartment 28. Electrical and / or electronic components (not shown in detail) are attached to the circuit board 54 and suitably interconnected, whereby a bridge circuit is also implemented. This is electrically connected to the stator 48 via lines (not shown in detail), so that the electric motor 46 is operated by means of the electronics 52. In summary, the electronics 52 serves to supply current to the electric motor 46.

[0047] A total of three heat sinks 56 are connected to the electronics 52, namely the circuit board 54, two of which are shown in a simplified schematic in Figure 4. The heat sinks 56 are structurally identical and made of aluminum. The heat sinks 56 are thermally contacted, for example, with the semiconductor switches forming the bridge circuit and are located on the side of the circuit board 54 facing the bearing plate 26. The heat sinks 56 are finger-shaped or similar and run parallel to the axial direction 18. Each of the heat sinks 56, which are offset from one another with respect to the rotation axis 16, also rests against the inner side 32 of the housing 22. Thus, during operation, the heat is dissipated from the heat sinks 56 to the housing 22 and from there into the environment.

[0048] A cover element 58 is arranged between the electronics 52 and the bearing plate 26 and is shown in perspective in Figure 5 from the side of the electronics 52. An additional space 60 of the electronics compartment 28 is formed between the cover element 58 and the bearing plate 26, in which additional space 60 the end of the shaft 38 and components for determining an angular position of the shaft 30 with respect to the housing 22 are located. In this case, the additional space 60 has a reduced inner diameter compared to the other components of the electronics compartment 28 due to the projection 34. The cover element 58 has a disc-shaped plastic body 62 which is arranged essentially perpendicular to the axial direction 18. In this case, the plastic body 62 does not lie merely in a single plane, but has three different elevations 64 which point in the direction of the bearing plate 26.Each of the elevations 64 has a plurality of openings 66 through which the lines are routed, by means of which the electronics 52 is electrically connected to the electric motor 46. The openings are incorporated into sealing elements 70, which consist of an additional elastomer and are overmolded with a rigid plastic that forms the remainder of the plastic body 62. The openings 66 have a smaller cross-section than the lines passing through them, so that a tight seal exists between them, thus preventing the passage of particles there. The plastic body 62 also has further inserts 72, which are also made of the elastomer and are used in the production of the cover element 58 using the two-component injection molding process.

[0049] The plastic body 62 is arranged flush with the projection 34 on the side facing the electronics 52. Consequently, the projection 34 surrounds the plastic body 62 circumferentially, and in the axial direction 18, the plastic body base body 62 ends at the same height as the projection 34. The plastic body 62 rests circumferentially against the projection 34. In addition, a collar 74 is attached to the plastic body 62 on the side facing the electronics 52. The collar 74 thus protrudes in the axial direction 18. The collar 74 is made, for example, from the rigid plastic or from the elastomer. The collar 74 is essentially annular, but has a larger diameter than the plastic body 62. As a result, the projection 34 is engaged by means of the collar 74.The collar 74 and thus the cover element 58 consequently rests on the projection 34 on the side facing away from the electronics 52, and by means of the cover element 58 and the projection 34 a type of labyrinth seal is formed, so that the passage of particles or a liquid is prevented or at least made more difficult.

[0050] In contrast to the ring shape, the collar 70 has three bulges 76 running inward in the radial direction 20. By means of the bulges 76, the collar 74 is therefore curved inward in a circular arc at three points. In the area of ​​the bulges 76, the collar 74 does not rest on the projection 34. The free end of one of the heat sinks lies in each bulge 76, so that each heat sink 56 rests on the front side against the projection 34 and the part of the plastic body 62 located there. In summary, the free end of one of the heat sinks 56 is thus encompassed by each of the bulges 76. Consequently, the heat sinks 56 are supported on the cover element 58. In summary, the three heat sinks 56, which are supported on the cover element 58, are connected to the electronics 52.

[0051] As a result, the position of the heat sink 56 is determined by means of the projection 34, which in turn determines the position of the plastic body 62 and thus of the cover element 58, namely the distance to the electronics 52. The position of the cover element 58 with respect to the bearing plate 26 is predetermined by means of the collar 74 and its contact with the projection 34. If the housing 22 and the cover element 58 heat up, leading to different expansion such that the collar 74 no longer rests against the inner side 32 of the housing 22, a circumferential gap is formed between the inner side 32 of the housing 22 and the collar 74. However, due to the support by the heat sink 56, the collar 74 continues to rest on the projection 34, so that the labyrinth seal still exists and the passage of particles is prevented.

[0052] To increase the seal, an additional collar 78 is arranged on the plastic body 62 on the side facing away from the electronics 52, which protrudes in the axial direction 20 and thus points in the direction of the bearing plate 26. The additional collar 78 is completely annular and made of rigid plastic. The additional collar 78 has an interface that is inclined with respect to the inner side 32, and a sealing element 80 is arranged between this interface and the inner side 32 of the housing 22. The sealing element 80 is formed by an O-ring made of a plastic or a rubber. Alternatively, the sealing element 80 is made of an elastomer, and the plastic body 62 is injection-molded onto this O-ring. Due to the inclined interface (bevel) of the additional collar 78, the sealing element 80 is pressed between the additional collar 78 and the inner side 32 when the cover element 58 is inserted into the electronics compartment 28, thus increasing the seal.In summary, the sealing element 80 is arranged in the radial direction 20 between the further collar 78 and the inner side 32.

[0053] Figure 6 shows a perspective view of an alternative embodiment of the cover element 58. The shape of the cover element 58 remains essentially the same. The cover element 58 still has the plastic body 62, the elevations 64, and the collar 74 with the three bulges 76. However, the cover element 58 is made solely from the rigid plastic. In other words, the sealing elements 70 and the inserts 72 are missing, and these are provided by the rigid plastic. The sealing element 80 is also not present. The openings 66 are still present, with their cross-sections matching the cross-sections of the respective cables used or being slightly larger. The type of assembly in the electric drive 10 corresponds to the previous embodiment. In particular, here too, the heat sinks 56 are supported on the cover element 58 in the region of the bulges 76.

[0054] Due to the simplified design of the cover element 58, manufacturing costs are reduced. However, sealing is slightly reduced. For example, to provide improved sealing after inserting the lines into the openings 66, these are surrounded by additional seals, further impeding the passage of particles.

[0055] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the individual exemplary embodiments can also be combined with one another in other ways without departing from the subject matter of the invention. List of reference symbols

[0056] 2 motor vehicles

[0057] 4 wheel

[0058] 6 Body

[0059] 8 Auxiliary unit

[0060] 10 Electric drive

[0061] 12 Sensor

[0062] 14 Control unit

[0063] 16 Rotation axis

[0064] 18 Axial direction

[0065] 20 Radial direction

[0066] 22 housings

[0067] 24 hollow cylindrical section

[0068] 26 Bearing shield

[0069] 28 Electronics compartment

[0070] 30 engine compartment

[0071] 32 Inside

[0072] 34 lead

[0073] 36 warehouses

[0074] 38 Wave

[0075] 40 additional bearing plate

[0076] 42 additional camps

[0077] 44 gear

[0078] 46 electric motor

[0079] 48 Stator

[0080] 50 rotor

[0081] 52 Electronics

[0082] 54 circuit board

[0083] 56 heat sinks

[0084] 58 Cover element

[0085] 60 additional space

[0086] 62 Plastic body 64 Elevation

[0087] 66 Opening

[0088] 70 sealing element

[0089] 72 insert 74 collar

[0090] 76 bulge

[0091] 78 additional collars

[0092] 80 sealing element

Claims

Claims 1. Electric drive (10) of a motor vehicle (2), in particular a steering motor, with a housing (22) which has a motor compartment (30) and an electronics compartment (28), - wherein an electric motor (46) having a stator (48) and a rotor (50) fixed to a shaft (38) is arranged in the motor compartment (30) and is arranged parallel to an axial direction (18), - wherein an electronics unit (52) for supplying current to the electric motor (46) is arranged in the electronics compartment (28), - wherein the motor compartment (30) and the electronics compartment (28) are separated by a bearing plate (26) to which a bearing (36) for supporting the shaft (38) is connected, - wherein a cover element (58) is arranged between the electronics (52) and the bearing plate (26), which cover element rests against the inside (32) of the housing (22), and - wherein a heat sink (56) is connected to the electronics (52) and is supported on the cover element (58).

2. Electric drive (10) according to claim 1, characterized in that the inner side (32) has a circumferential projection (34) on which the cover element (58) rests on the side facing away from the electronics (52).

3. Electric drive (10) according to claim 2, characterized in that the cover element (58) has a disc-shaped plastic body (62) which is arranged on the side facing the electronics (50) in alignment with the projection (34), and on which a collar (74) projecting in the axial direction (18) is arranged on the side facing the electronics (50) and at least partially overlaps the projection (34).

4. Electric drive (10) according to claim 3, characterized in that the collar (74) has a bulge (76) extending inwards in a radial direction (20), by means of which a free end of the heat sink (56) is encompassed.

5. Electric drive (10) according to one of the preceding claims, characterized in that a further collar (78) projecting in the axial direction (20) is arranged on the plastic body (62) on the side facing away from the electronics (52).

6. Electric drive (10) according to claim 5, characterized in that a sealing element (80) is arranged in the radial direction (20) between the further collar (78) and the inner side (32).

7. Electric drive (10) according to one of claims 1 to 6, characterized in that the cooling body (56) rests against the inner side (32) of the housing (22) at least in sections.

8. Electric drive (10) according to one of claims 1 to 6, characterized by three such heat sinks (56).

9. Auxiliary unit (8) of a motor vehicle (2), in particular a steering system, with an electric drive (10) according to one of claims 1 to 8.

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