Electric motor of a motor vehicle

Abstract

The invention relates to an electric motor (10) of a motor vehicle (2), comprising a housing (18) to which an end shield (26) is fastened, a bearing (28) which is retained on the end shield (26) and by means of which a shaft (30) is mounted for rotation about an axis of rotation (16), and a sensor system (50) for determining a position of the shaft (30). The sensor system (50) includes two sensor units (58), which are each equipped with a contact maker (56), and a sensor gear mechanism (62) comprising a gear wheel (61) that is fastened to the shaft (30) and meshes with another gear wheel (70) that is fastened to another shaft (63) which is mounted for rotation about another axis of rotation (66). The sensor system (50) is designed in such a way that the two contact makers (56) move when the shaft (30) rotates, the rotational speeds of the contact makers (56) differing from each other, wherein the sensor gear mechanism (62) includes a mechanical backlash compensation element (72). The invention further relates to an auxiliary unit (8) of a motor vehicle (2).

Description

[0001] Description

[0002] electric motor

[0003] The invention relates to an electric motor with a housing that includes a bearing plate on which a bearing is mounted. The electric motor is a component of a motor vehicle. Furthermore, the invention relates to an auxiliary unit of a motor vehicle.

[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 (and possibly rear 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, designed as an electric motor, is usually also present. This assists the driver's steering movement, thus 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. A sensor detects the angular position of the steering wheel or other control element, and the steering motor, which drives the steering rack, is controlled based on this position. Such a system is also referred to as a "steer-by-wire" system.This requires that the angular position specified by the control element / control device is always converted into the corresponding angular position of the wheels, with tolerances as small as possible. This, in turn, requires the position of a shaft of the electric motor to be determined relatively precisely so that the electric motor can be supplied with appropriate current. A sensor is usually used to determine the position of the shaft. A contactor of the sensor, such as a permanent magnet, is usually attached to the shaft. A Hall sensor of the sensor is fixedly attached and records the temporal change in the provided magnetic field when the shaft rotates. However, this only allows a relatively inaccurate determination of the position of the shaft. At the very least, this is not sufficient for the application in this type of steering system.

[0006] An alternative involves using multiple poles and / or multiple Hall sensors for the permanent magnet. As a result, a rotating magnetic field is detected several times per shaft revolution, which in principle improves resolution. However, it is also possible, for example, that the time-varying magnetic fields generated during operation of the electric motor have a significant impact on the functioning of the Hall sensors, or that the inertia of the Hall sensors is too great to correctly detect all changes. Thus, the generated sensor data may contain at least minor errors. Therefore, comparatively expensive Hall sensors are required.

[0007] An alternative is to integrate the sensors into the rack. However, this requires an additional assembly step, which increases production time. The rack is also relatively unprotected, requiring precautions to protect the sensors, which increases production costs.

[0008] The invention is based on the object of specifying a particularly suitable electric motor of a motor vehicle and a particularly suitable auxiliary unit of a motor vehicle, wherein manufacturing costs and / or manufacturing time are advantageously reduced.

[0009] With regard to the electric motor, 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 13. Advantageous further developments and refinements are the subject of the respective subclaims.

[0010] The electric motor is a component of a motor vehicle. In other words, the electric motor is suitable, in particular intended and configured, to form a component of the motor vehicle when assembled. The motor vehicle is in particular land-based and preferably designed with multiple tracks. 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.

[0011] The electric motor 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 motor is particularly preferably a component of an auxiliary unit of the motor vehicle, by means of which the motor vehicle is therefore not directly driven. In particular, the electric motor is a component of an adjustment drive, such as an electric seat adjustment or an electric window lifter. Alternatively, the electric motor is, for example, a component of a pump, such as a water pump or an oil pump. In a further alternative, the electric motor is, for example, a component of a transmission actuator, and the auxiliary unit is, in particular, a transmission. In a further alternative, the electric motor is, for example, a component of an air conditioning compressor. However, the auxiliary unit that comprises the electric motor is particularly preferably a steering system.For example, the electric motor forms a steering motor. When operated, the electric 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 electric motor preferably acts on the steerable / controllable wheels via a rack or the like. Expediently, a gearwheel that engages with the rack is driven by the electric motor.Preferably, a sensor is assigned to the steering wheel or other control device, which is connected electrically and / or signal-wise, in particular, to the electric motor. The connection is, for example, direct or via a control unit, by means of which the electric motor is operated based on the signals / data provided by the sensor. At least preferably, the electric motor is operated depending on the data and / or signals generated / provided by the sensor.

[0012] The electric motor comprises a housing which is, for example, designed in one piece or in multiple pieces. In particular, the housing is essentially hollow-cylindrical and expediently pot-shaped. Preferably, the housing is made of a metal, such as aluminum, and is expediently an aluminum die-cast part or produced by aluminum extrusion. The housing extends in particular along an axis of rotation and / or is in particular arranged at least in sections concentrically to the axis of rotation. A bearing shield is fastened to the housing. Preferably, the housing is closed, at least on one side, by means of the bearing shield. The bearing shield is in particular arranged essentially perpendicular to the axis of rotation. For example, the bearing shield is an A--side bearing shield. However, the bearing shield is particularly preferably a B--side bearing shield.

[0013] A bearing is held on the bearing shield. Preferably, the bearing is fastened to the bearing shield or, for example, loosely inserted in a bearing seat. For example, the bearing is a plain bearing. Preferably, however, the bearing is a rolling bearing, such as a ball bearing or a needle bearing. A shaft of the electric motor is rotatably mounted about the axis of rotation by means of the bearing. The shaft is preferably connected to the bearing shield by means of the bearing. For example, an inner ring of the bearing is fastened to the shaft if the shaft is designed as a rolling bearing. The shaft is expediently cylindrical and made of steel, for example. The shaft expediently extends along the axis of rotation and is preferably concentric with it. A rotor of the electric motor is suitably fastened to the shaft in a rotationally fixed manner.The rotor is preferably arranged concentrically to the rotational axis and comprises, for example, a number of magnets. The electric motor suitably comprises a stator, which is also arranged concentrically to the rotational axis. The stator is preferably substantially partially hollow-cylindrical and surrounds the rotor, for example, circumferentially. In particular, the stator is attached to the housing.

[0014] The electric motor further comprises a sensor system for determining the position of the shaft. The sensor system is suitable, in particular provided and configured, for this purpose. The sensor system in turn comprises two sensor units, each of the sensor units comprising a contactor. In particular, each sensor unit additionally comprises a sensor that is operatively connected to the respectively assigned contactor. In this case, in particular, only a contactless coupling is present. The position of the respective contactor can expediently be detected by means of each sensor. In particular, at least one of the sensors is a Hall sensor. The contactor is designed in particular in the manner of a magnet. This means that manufacturing costs are comparatively low. Alternatively or in combination with this, one of the sensor units is, for example, a so-called contactless inductive position sensor (“Contactless Inductive Position Sensor”).This particularly comprises a leaf- or flower-shaped contactor, which is formed, for example, from a magnetic material or a conductor loop that forms a closed contour. The sensor, on the other hand, comprises an excitation coil. In particular, these are spaced apart from one another parallel to the rotation axis and arranged perpendicular to it. For example, the two sensor units are designed in the same way and, in particular, are structurally identical to one another. This allows the use of identical parts. Alternatively, the two sensors are constructed differently or, in particular, operate according to different principles. This increases robustness, and adverse environmental conditions, for example, do not lead to the failure of both sensor units.

[0015] The sensor system further comprises a sensor gear that includes a gearwheel attached to the shaft. The gearwheel is arranged on the side opposite the bearing, if present, from that side. The gearwheel therefore does not obstruct the rotor or stator. The gearwheel, in turn, engages with another gearwheel that is attached to another shaft. The other shaft, in turn, is mounted so that it can rotate about another axis of rotation. Thus, when the shaft rotates, the other shaft also rotates. The other axis of rotation is parallel to the axis of rotation but laterally offset from it. The distance is predetermined, in particular, by means of the two gearwheels. For example, the other gearwheel and / or the gearwheel is made of metal or plastic. The gearwheel is, for example, made of a metallic material, for example by sintering. This increases robustness.The other gear is conveniently made of plastic, which improves acoustics.

[0016] The sensor system is designed in such a way that the two contact sensors are moved when the shaft rotates. In other words, the contact sensors are arranged in such a way that they also rotate when the shaft rotates. However, their rotation speeds are different from one another. Thus, if the angular position of the shaft changes by a certain amount, the position of the two contact sensors is also changed, whereby the change is different between the two contact sensors. In particular, the different movements of the contact sensors are due to the sensor gear. In summary, the sensor system is designed at least partially according to the vernier principle. This enables a comparatively precise determination of the position of the shaft, whereby only two sensor units are required.

[0017] The sensor gear further comprises a mechanical backlash compensation element. The backlash compensation element serves to compensate for backlash between the two rotational axes and / or between the two shafts. The backlash compensation element thus compensates, in particular, for manufacturing tolerances and / or offset during operation. Consequently, the backlash compensation element serves to compensate for changes in the distance / tilting of the two shafts / gears / rotational axes, for example, due to different thermal expansion. The backlash compensation element is suitable, in particular provided and configured, for this purpose. The backlash compensation element also ensures, in particular, that the two gears are always in engagement with each other, even if there is a slight movement of the two rotational axes relative to each other, such as tilting. Since the backlash compensation element is mechanically designed, its construction is simplified.It is also advantageous that no adjustment or adjustment of the play compensation element is required when the electric motor is in operation.

[0018] The electric motor suitably comprises electronics or at least a printed circuit board, which is arranged in particular perpendicular to the axis of rotation. At least one, preferably both sensors of the respective sensor unit are expediently attached to the printed circuit board so that the latter is held in place. Expediently, the two sensors are assigned to the same printed circuit board, which simplifies assembly. Preferably, the printed circuit board is arranged within an electronics compartment of the electric motor. This prevents the ingress of foreign particles, thus preventing malfunction of the two sensor units. For example, other electronics or preferably the electronics also serve in particular to supply current to the other components of the electric motor, preferably the stator. The electronics are operated in particular as a function of the data provided by the sensors.Preferably, the electronics comprise a bridge circuit, such as a B6 circuit. For example, the electric motor is a brushed commutator motor. However, the electric motor is particularly preferably brushless and expediently a brushless direct current (BLDC) motor. Expediently, the electronics comprise a B12 circuit, and the electric motor has twice the number of phases, each of which is connected in a star configuration.

[0019] Preferably, a holder is connected, in particular fastened, to the additional shaft. One of the contactors is held by means of the holder. For example, the holder is designed like a sleeve, at one end of which the contactor is arranged. The other end of the sleeve is placed on the additional shaft and secured there, for example, using adhesive. Alternatively, the sleeve is pressed onto the additional shaft.

[0020] In the electric motor, the two sensor units enable comparatively precise determination of the shaft position using just two sensor units. This means that the number of components required is comparatively low, which reduces manufacturing costs and space requirements. Because the sensors are attached to the bearing shield, no additional assembly step is required, as is the case, for example, when assigning the electronics to a component driven by the electric motor, such as a gear rack. This reduces manufacturing time. In addition, the sensors are stabilized by the bearing shield and are thus at least partially surrounded by the electric motor housing, which means the sensors are arranged in a comparatively protected manner. This increases robustness.Thanks to the mechanical backlash compensation element, the engagement of the two gears is maintained even in the event of vibrations from the electric motor and / or a wide variety of environmental conditions, so that a reproducible arrangement of the contactors relative to one another is always present, each corresponding to a predetermined position of the shaft. This enables a comparatively precise determination of the position of the shaft. The backlash compensation element preferably compensates for backlash in the event of wear on the gears in the area of ​​the teeth, and the backlash compensation element thus suitably closes / reduces the enlarged "gaps" that arise due to wear, resulting in reduced backlash over the service life. The backlash compensation element is particularly suitable, expediently provided and configured for this purpose.

[0021] For example, the additional gear is ring-shaped. For example, the additional gear is rigidly attached to the additional shaft. Due to the ring-shaped design, inertia is reduced. In particular, the additional gear is arranged essentially concentrically to the additional axis of rotation. Particularly preferably, the additional gear is attached to the additional shaft by means of the play compensation element. Thus, compensation is carried out by means of the play compensation element, in particular if the center of the gear is not directly on the additional axis of rotation. Due to the play compensation element, the engagement between the additional gear and the gear is maintained. Thus, comparatively high manufacturing tolerances can be used for both gears, so that manufacturing costs are reduced, while the functionality of the sensor system is still maintained.For example, the center point of the additional gear is deliberately chosen to be slightly offset from the additional rotational axis, particularly in the direction of the rotational axis. Thus, even with different expansions, such as during cooling, which leads to a reduction in the diameter of the additional gear, the engagement with the gear remains intact. In other words, in this case, the play compensation element preloads the additional gear in the direction of the gear.

[0022] For example, the play compensation element comprises one or more springs. Particularly preferably, a circumferential gap is formed between the further gear and the further shaft, in which gap the play compensation element is arranged. This means that the space requirement is comparatively small. In particular, the play compensation element is made of an elastomer. Preferably, a material-to-material connection between the further gear and the further shaft is achieved by means of the play compensation element, and this is injection-molded in particular onto the further shaft and / or the further gear to establish the mechanical connection. This ensures a captive connection and increases robustness. The number of required assembly steps is also reduced.

[0023] In an alternative embodiment, the additional gear is preferably rigidly attached to the additional shaft. The contactor is held by means of the holder. However, the holder is connected to the additional gear via the play compensation element. In particular, the play compensation element is made of an elastomer and is preferably injection-molded onto the additional gear and / or the holder. This ensures a captive connection. It is also possible to design the play compensation element to be at least partially encapsulated, thus increasing robustness. In an alternative, the play compensation element is designed as a plug-in element. This has the advantage that different play compensation elements, for example with different Shore hardnesses, can be selected depending on the application and load requirements. The play compensation element is expediently an elastomer insert.

[0024] For example, the holder is essentially ring-shaped or pot-shaped. Particularly preferably, the holder has circumferential teeth that also engage with the gear. This reduces the load on the play compensation element because the holder is also driven by the gear. In particular, the teeth of the holder are different from the teeth of the other gear, with one tooth size being changed, for example. During normal operation, the holder is suitably driven directly by the gear. Only under comparatively unfavorable operating conditions is it possible for the holder to come out of engagement with the gear, or for the mechanical contact area between them to be comparatively greatly reduced.In this case, the rotational movement of the shaft is transmitted to the bracket mainly via the additional gear and the play compensation element, so that the load on it is reduced.

[0025] For example, the holder is mechanically spaced from the further gear, and mechanical contact is made solely via the play compensation element. However, the holder is particularly preferably braced or clipped to the further gear. In this case, the further gear in particular has a locking lug that engages an undercut of the holder. For assembly, the holder is in particular placed on the shaft and rusted to the corresponding locking lug or lugs of the further gear. This enables assembly without tools. By means of the rusting, in particular only the position of the holder with respect to the further gear parallel to the further axis of rotation is stabilized. A movement in the radial and / or tangential direction with respect to the further axis of rotation, however, remains possible, at least within certain limits, due to the rusting.This reduces the requirements for corrosion protection, which simplifies its design and construction.

[0026] For example, the gears are each designed as a wheel (spur gear), and the sensor gear is in particular a spur gear. This reduces manufacturing costs. The gears are in particular straight-toothed. This simplifies construction. Alternatively, the two gears are meshed with each other using beveloid gearing. Due to the beveloid gearing, the two gears are in particular spur gears with variable profile shift over the respective gear width. In this case, one of the gears, in particular, is truncated cone-shaped. The backlash compensation element is formed by the beveloid gearing. This means that no additional components are required, which reduces material costs and increases robustness. In particular, the two gears are each rigidly attached to the respective associated shaft, which increases robustness.

[0027] Particularly preferably, the additional shaft is rotatably supported by means of an additional bearing held on the bearing shield. During manufacture of the bearing shield, in particular a bearing shield is created for the bearing as well as for the additional bearing. Expediently, the bearing shield is remachined, in particular to reduce manufacturing tolerances, wherein during remachining both the bearing seat for the bearing and for the additional bearing can be remachined in a single work step. This means that manufacturing time is not significantly extended. The additional bearing is, for example, a plain bearing or, particularly preferably, a rolling bearing such as a ball bearing or a needle bearing. This means that breakaway torques during rotation of the additional shaft are comparatively low, which is why even small changes in the position of the shaft can be detected comparatively reliably by the sensors.

[0028] For example, the end shield is covered by an electronics housing or the like on the side on which the sensors or at least the sensor gear is arranged. In particular, the electronics housing, by means of which, for example, the possible electronics compartment is provided and / or which, for example, has a pot-shaped design and is closed by the end shield, and the possible circuit board is arranged. Particularly preferably, a cover cap is attached to the end shield, by means of which the sensor gear is covered. In this case, the cover cap is made in particular from a plastic. The cover cap is expediently glued or rusted to the end shield. Alternatively, the cover cap is screwed to the end shield, for example. However, the cover cap is particularly preferably permanently connected to the end shield, for example by rivets. A wobble riveting method is preferably used for assembly.

[0029] For example, the cover cap covers the entire sensor system, in particular with the exception of any sensors in each sensor unit. This reliably prevents dirt particles from reaching the sensor system. Alternatively, the additional shaft is connected to the cover cap by means of an additional bearing, whereby the additional shaft is expediently guided through the cover cap, which simplifies construction. In other words, the additional shaft is rotatably mounted about the additional axis of rotation by means of the additional bearing that is connected to the cover cap. In this case, for example, the additional bearing is present so that the additional shaft as a whole is rotatably mounted by means of two bearings. This means that the additional axis of rotation is specified relatively precisely and the additional shaft is stabilized. Alternatively, the additional shaft is rotatably mounted only by means of the additional bearing.Thus, in particular, an assembly or module is provided which has the cover cap, the additional bearing, the further shaft and at least one of the contactors. This can be assembled in particular in a single work step. Particularly preferably, the assembly also has an auxiliary bearing, by means of which a shaft extension is rotatably mounted. This is expediently pin-shaped and, in the assembled state, is inserted in particular into a corresponding receptacle in a stub shaft of the shaft. The gear is fastened to the shaft extension. Thus, with the exception of any sensors, the sensor system is essentially present as a single assembly (module) which can be attached to the bearing shield for assembly in a single work step and can be manufactured independently of the latter. The shaft is completed in this process, namely the shaft extension is inserted into the stub shaft.The assembly is in particular independent of the play compensation element and is considered as an independent invention.

[0030] Conveniently, an additional bracket is attached to the shaft, which holds one of the contactors. Thus, when the shaft rotates, this contactor rotates with it, so that the rotational speed is equal to the rotational speed of the shaft. In particular, the other contactor is driven by the additional shaft and, for example, attached to the additional shaft by means of the bracket. This requires comparatively few components, thus reducing manufacturing costs and space requirements.

[0031] In one further development, the sensor gear comprises in particular a second further shaft to which a second further gear is fastened. The second further shaft is mounted so as to be rotatable about a second further axis of rotation, which is expediently parallel to the further axis of rotation. In particular, the sensor system, preferably the sensor gear, is designed such that when the shaft rotates, the second further shaft also rotates. For this purpose, for example, the second further gear is in engagement with the gear or only in engagement with the further gear. In particular, one of the contactors is assigned to the second further shaft and the other contactor is assigned to the further shaft. In this case, for example, when the shaft rotates, the contactors are rotated, wherein, for example, the rotational speed of one of the two further contactors is the same as the rotational axis of the shaft.Alternatively, all contactors are rotated at a rotational speed different from the rotational speed of the shaft, thus enabling a comparatively accurate determination of the position of the shaft. Suitably, the two further shafts, the two further gears and the associated contactors are of identical construction, each being held on the respective further shaft by means of a corresponding holder. This creates two structural units which are in particular identical or at least of a similar type. In particular, they differ only in the number of teeth on the respective further gears, so that different rotational speeds are achieved. This makes it possible to use at least some of the same parts, which reduces manufacturing costs.

[0032] In a further development, several additional gears are provided, each of which is assigned a corresponding contactor. Preferably, the sensor gear is designed like a planetary gear. In particular, the additional gears rotate at different speeds during operation.

[0033] 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 lorry, bus, or preferably a passenger car. The auxiliary unit comprises an electric motor with a housing to which a bearing plate is attached, on which a bearing is held, by means of which a shaft is mounted so as to be rotatable about a rotational axis, and with a sensor system for determining a position of the shaft. The sensor system comprises two sensor units, each comprising a contactor, and a sensor gear which comprises a gear attached to the shaft and which engages with a further gear attached to a further shaft which is mounted so as to be rotatable about a further rotational axis.The sensor system is designed in such a way that when the shaft rotates, the two contactors are moved, whereby their rotation speeds are different, and wherein the sensor gear comprises a mechanical play compensation element.

[0034] In particular, another component of the auxiliary unit is driven by the electric motor, such as an adjustment part. For example, the electric motor is a component of an electromotive pump, such as a water pump, a coolant pump or a lubricant pump, for example 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 motor acts, for example, to support a force applied manually by a driver. However, the steering system is particularly preferably designed as a steer-by-wire system. In particular, the electric motor drives a component by means of which a steering angle of wheels of the motor vehicle is predetermined.In particular, a rack which is connected to at least one of the wheels of the motor vehicle is driven by means of the electric motor, wherein the position of the rack determines the steering angle of the associated wheel. 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 the steering angle can be specified by a driver of the motor vehicle. Preferably, a signal-based coupling / connection of the electric motor to a sensor associated with the operating device is present. Alternatively, or in combination with this, the electric motor is coupled to an on-board computer or another assistance system of the motor vehicle, by means of which, in particular, semi-autonomous movement of the motor vehicle can take place.Furthermore, the invention relates to a motor vehicle with such an auxiliary unit. The developments and advantages explained in connection with the electric motor are also applicable mutatis mutandis to the auxiliary unit / the motor vehicle / the assembly, as well as to each other, and vice versa.

[0035] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawings:

[0036] Fig. 1 schematically shows a motor vehicle with a steering system having an electric motor,

[0037] Fig. 2 shows a schematic sectional view of the electric motor, which includes a sensor system,

[0038] Fig. 3-6 in a perspective sectional view, showing different embodiments of the sensor system, and

[0039] Fig. 7 shows a perspective view of another gear of the sensor system according to Fig. 6.

[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 in the example, 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 motor 10, by means of which a rack (not shown in detail) is driven, which is mounted on the two front wheels.When the electric motor 10 is operated, the rack is moved transversely, namely in a horizontal plane and perpendicular to a longitudinal axis of the motor vehicle 2, wherein, due to the connection to the front wheels, their steering angle relative to the body 6 is changed. The auxiliary unit 8 further comprises a sensor 12 which is assigned to an operating device 14, wherein a 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 motor 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.

[0042] Figure 2 shows a schematic sectional view of the electric motor 10 along a rotational axis 16. The electric motor 10 comprises a pot-shaped housing 24 made of aluminum and thus having a hollow cylindrical section 20 arranged concentrically to the rotational axis 16. The pot-shaped housing 18 has a base 22 arranged perpendicular to the rotational axis 16, to which an A-bearing 24 is attached.

[0043] On the side opposite the base 22, the housing 18 is closed by a bearing plate 26 that is fastened to the housing 18. A bearing 28, designed as a ball bearing, is held on the bearing plate 26. A shaft 30, which is arranged concentrically to the axis of rotation 16 and extends along it, is rotatably mounted about the axis of rotation 16 by means of the A-bearing 24 and the bearing 28. A rotor 32, which is arranged concentrically to the axis of rotation 16 and is fastened to the shaft 30 in a rotationally fixed manner, is arranged between the A-bearing 24 and the bearing 28. The rotor 32 comprises a number of permanent magnets (not shown in detail). The rotor 32 is surrounded on the circumference by a stator 34, which comprises a number of electromagnets (not shown in detail). The stator 34 is fastened to the hollow cylindrical section 20.Here, the electric motor 10 is designed as a brushless direct current (BLDC) motor, and the electromagnets of the stator 34 are connected to form several electrical phases, namely two times three phases (6-phase system). The electromagnets of the stator 34 are energized via several phase connections 36, which are led from the stator 34 through corresponding passages 38 of the bearing plate 26 and extend into an electronics compartment 40 located on the side of the bearing plate 26 opposite the rotor 32. The electronics compartment 40 is defined by a pot-shaped electronics housing 42, the opening of which is closed by the bearing plate 26.

[0044] Arranged within the electronics compartment 40 is an electronics unit 44 comprising a printed circuit board 46 arranged perpendicular to the rotation axis 16. A bridge circuit 48 is connected to the printed circuit board 46, which is electrically connected to the phase terminals 36 and comprises a plurality of semiconductor switches (not shown in detail). The electronics unit 44 also has a driver circuit (not shown in detail) for controlling the bridge circuit 48, a control, regulation, and / or the like. A sensor unit 50 for determining the position of the shaft 30, namely its angular position, is arranged between the printed circuit board 46 and the bearing plate 26. The stator 34 is energized by means of the additional components of the electronics unit 44, depending on the position of the shaft 30, so that it is always in the desired position. Consequently, the steering angle of the wheels 4 always corresponds to the position specified by the control device 14.

[0045] The sensor system 50, which is shown in Figure 3 in a partial perspective view in a sectional view along the axis of rotation 16, has an additional holder 54 arranged on the side of the bearing plate 26 opposite the rotor 32 and placed on the end of the shaft 30 located there. The additional holder 54 is designed in the manner of a sleeve and is pressed onto the end of the shaft 30. By means of the additional holder 54, a contactor 56 of a sensor unit 58, which is arranged perpendicular to the axis of rotation 16 and which also has a sensor 60 that is fastened on the side of the circuit board 46 facing the bearing plate 26. Thus, when the shaft 30 rotates, the contactor 56 also rotates relative to the sensor 60, which is detected by the sensor 60.Here, the sensor unit 58 operates, for example, according to the inductive principle and is designed, in particular, as a CIPOS unit (Contactless Inductive Position Sensor). Thus, a comparatively precise position determination is already possible using this sensor unit 58. The additional bracket 54, by means of which one of the contactors 56 is held, is attached to the shaft.

[0046] Between the bearing 28 and the additional holder 54, a gear 61 is arranged, which is placed on the shaft 30 and fastened thereto in a rotationally fixed manner. The gear 61 is thus rigidly fastened to the shaft 30. The gear 61 is a spur gear and a component of a sensor gear 62 of the sensor system 50. The gear 61 is made, for example, from a metallic material, e.g., by sintering. The gear 61 also drives a further shaft 63 of the sensor gear 62, which is connected to the bearing plate 26 by means of a further bearing 64. The further shaft 63 is rotatably mounted about a further rotation axis 66 by means of the further bearing 64, which is a ball bearing. The further axis of rotation 66 is parallel to the rotation axis 16, but radially offset from it. The further shaft 63 is thus rotatably mounted by means of the further bearing 64 held on the bearing plate 26.

[0047] A holder 68 is placed on the end of the further shaft 63 opposite the bearing plate 26 and pressed into place. The holder 68 is designed like a sleeve, and by means of this sleeve, the further shaft 63 is gripped circumferentially. A contactor 56 is also held by the holder 68, so that the sensor system 50 has a total of two corresponding sensor units 58. This sensor unit 68 also comprises a sensor 60, which is fastened to the circuit board 46 on the side facing the bearing plate 26 and is located on the further rotation axis 66. The two sensor units 58 are identical in construction or operate according to different principles, with one of the sensor units 58 being like a Hall sensor and the other a CIPOS unit.

[0048] The sensor gear 62 further comprises a further gear 70, which is ring-shaped and surrounds the further shaft 63, forming a gap between them. The further gear 70 is rotationally fastened to the further shaft 63 by means of a mechanical play compensation element 72, which is made of an elastomer and fills the gap. The play compensation element 72 compensates for the case in which the center of the ring-shaped further gear 70 is not completely located on the further rotation axis 66 due to manufacturing tolerances or different expansion upon heating, so that an engagement between the further gear 70 and the gear 61 nevertheless remains.

[0049] The sensor gear 62 is designed such that the two contactors 56 are moved during a rotational movement of the shaft 30, but at different rotational speeds. Due to the rigid coupling, the contactor 56 assigned to the shaft 30 is moved at the rotational speed of the shaft 30. Due to the toothing of the two gears 61, 70, the contactor 56 assigned to the other shaft 63 is moved at a lower speed. The data provided by the sensors 60 is evaluated by the additional components of the sensor system 50, which are provided, for example, in part by the electronics 40, using the vernier principle. This enables a comparatively precise determination of the position of the shaft 30.

[0050] In summary, in the sensor gear 62, the gear 61 engages with the further gear 70, and the sensor system 50 is designed such that when the shaft 30 rotates, the two contactors 56 are moved, their rotational speeds being different, and the sensor gear 62 comprises the mechanical play compensation element 72. The further gear 70 is annular and is fastened to the further shaft 63 by means of the play compensation element 72, wherein the circumferential gap is formed between the further gear 70 and the further shaft 63, within which the play compensation element 72 made of elastomer is arranged. The play compensation element 72 is injection-molded onto the shaft 63 and fastened to the further gear 70, for example by means of an adhesive (not shown in detail). Furthermore, a cover cap 74, which is a plastic injection-molded part, is fastened to the bearing plate 26.The sensor gear 62 is covered by the cover cap 74. In other words, the sensor gear 62 is arranged in the space formed between the cover cap 74 and the bearing plate 26. The two holders 54, 68 and the two contactors 56 are also located in the space enclosed by the cover cap 74. The electronics 44, however, is arranged outside the cover cap 74. The cover cap 74 thus keeps any abrasion particles generated during operation of the sensor gear 62 away from the electronics 44, thus protecting it. Any particles penetrating from the rotor 32 via the bearing 28 are also kept away from the electronics 44 by the cover cap 74.Thus, a connection between the electronics compartment 40 and the space provided by the housing 18 is only present in the area of ​​the passages 38, with the passages 38 being closed by sealing elements (not shown in detail) and the phase connection 36. Thus, the electronics compartment 40 is relatively securely sealed.

[0051] Figure 4 shows a modification of the sensor system 50, wherein the cover cap 74, the shaft 30, the bearing plate 26, the bearing 28, the additional holder 54, the two contactors 56, and the additional bearing 46 are essentially unchanged. The holder 68 is also slightly modified, but its functionality remains essentially the same. The two contactors 56 are still covered by the cover cap 74.

[0052] The additional shaft 63 is now also rotatably mounted by means of an additional bearing 76 connected to the cover cap 74, which is identical in construction to the additional bearing 46 and is also arranged concentrically to the axis of rotation. The additional gear 70 is also still attached to the additional shaft 63, whereby this now mechanically rests directly on the shaft 63 and is pressed onto it. The gear 61 attached to the shaft 30 is also still present and engages with the additional gear 70. Here, there is direct engagement, with the play compensation element 72 being formed by means of beveloid toothing, by means of which the two gears 61, 70 are toothed. In other words, the two gears 61, 70 are no longer straight-toothed, but have an inclined contour on their circumferential side, so that the two gears 61, 70 are conical.The beveloid gearing compensates for play in the event of differential expansion upon heating, ensuring that the two gears 61 and 70 are always in engagement. This sensor 50 also operates according to the vernier principle.

[0053] Figure 5 shows a further modification of the sensor system 50, wherein the cover cap 74 is still present, to which the additional bearing 76 is connected, by means of which the additional shaft 63 is rotatably mounted about the additional rotation axis 66. The additional bearing 64 is not present, and the additional shaft 63 protrudes through the cover cap 74. Thus, the holder 68 and the associated contactor 56, which essentially correspond to the variants shown in Figure 3, are located outside the space formed by the cover cap 74 and the bearing plate 26.

[0054] The additional holder 54 and the contactor 56 held thereby also correspond to the variant shown in Figure 3. However, the shaft 30 has now been modified and has a shaft stub 78 which is shorter than the one-piece shaft 30 and which is connected to the bearing 28. The shaft stub 78 has a receptacle 80 formed concentrically to the axis of rotation 16, into which a pin-shaped shaft extension 82 is inserted or pressed. The gear 61 is fastened to the shaft extension 82, which, like the additional gear 70 and the play compensation element 72, corresponds to the variant shown in Figure 3. Thus, the gear 61 and the additional gear 70 continue to mesh. The shaft extension 82 is fastened to the cover cap by means of an auxiliary bearing 84 and extends through the cover cap 74.In other words, the gear 61 and the additional holder 54 are located on different sides of the cover cap 74. This sensor 50 also works according to the vernier principle.

[0055] By means of the cover cap 74, the bearings 76, 84 attached to it and the sensor gear 62 attached thereto, which has the two gears 61, 70 and the further shaft 63, the play compensation element 72, the two holders 54, 68, the shaft extension 72 and the contactor 56, an assembly 86 is formed which can be produced independently of other components of the electric motor 10. The assembly 86 is present as a pre-assembled module and, after the housing 18 has been closed, is placed onto the bearing plate 26 as a whole and fastened thereto by means of the bearing plate 26. For this purpose, the cover cap 74 is fastened to the bearing plate 26 by means of fastening means (not shown in detail), such as rivets or screws, with the shaft extension 32 being inserted into the receptacle 80 of the shaft stub 78. This enables comparatively quick assembly.

[0056] Figure 6 shows a further modification of the sensor system 50, which also operates according to the vernier principle. The shaft 30 is again made in one piece and is rotatably mounted on the bearing plate 26 by means of the bearing 28. The gear 61 is also mounted on the shaft 30, but none of the contactors 56 are assigned to the shaft 30 anymore. The sensor system 50 now has two structural units 88 that are essentially identical in construction. Each of the two structural units 88 comprises the additional bearing 64, which is fastened to the bearing plate 26 and by means of which the associated additional shaft 63 is rotatably mounted about the respective additional rotation axis 66. Consequently, a total of two additional shafts 63 are present.

[0057] Rigidly attached to each additional shaft 63 is a respective additional gear 70 which meshes with gear 61, which in turn has straight teeth. The two additional rotational axes 66 and the rotational axis 16 lie on a common line. Since the number of teeth on the two additional gears 70 is different, the two additional rotational axes 66 are at different distances from the rotational axis 16. However, this essentially represents the only difference between the two structural units 88. The additional gears 70 are expediently made of a plastic, which improves acoustics. The gear 61 is made of a metallic material (sintered metal) due to the loads exerted on both sides by the additional gears 70. Each structural unit 88 further comprises one of the contactors 56, each of which is held by means of the respectively associated holder 68 and connected to the respective additional gear 70.Each holder 68 is connected to the respectively associated further gear 70 via the play compensation element 72, which is made of an elastomer. In summary, each further gear 70 is rigidly attached to the respectively associated further shaft 63, wherein each further gear 70 is connected to one of the holders 68 via the respectively associated play compensation element 72, and wherein one of the contactors 56 is held by means of each of the holders 68. In summary, the sensor gear 62 thus has the two further shafts 63, wherein one of the further gears 70 is attached to each of the further shafts 63, and wherein each further shaft 63 is rotatably mounted about one of the further rotation axes 66. The sensor system 50 is designed such that when the shaft 30 rotates, the two further shafts 63 are moved, but at different rotational speeds.

[0058] Figure 7 shows a perspective view of one of the two additional gears 70. The associated backlash compensation element 72 is molded onto this element, forming a hollow cylindrical structure. Alternatively, the backlash compensation element 72 is designed as a plug-in element, with a Shore hardness adapted to the application. The backlash compensation element 72 is an elastomer insert.

[0059] The play compensation element 72 is arranged on the circumference by three locking lugs (locking tongues) 90 which are connected to the further gear 70 and which extend parallel to the further axis of rotation 66. In the assembled state, the locking lugs 90 are secured to an undercut 92 of the holder 68, which is made of a plastic. In other words, the holder 68 is thus secured to the further gear 70. For assembly, the respective holder 68 is placed onto the further shaft 63 parallel to the further axis of rotation 66 until the locking lugs 90 secure to the respectively associated undercut 92. In this case, each holder 68 engages around the end of the respectively associated further shaft 63, wherein the holders 68 are merely placed onto the free end of the respective further shafts 63, but not directly attached to them, which facilitates assembly.Due to the locking, detachment of the holders 68 from the respective associated further gear 70 is prevented, whereby movement of these relative to one another is possible at least to a limited extent.

[0060] The holders 68 each have a circumferential toothing 94, which also engages with the gear 61. Thus, the holder 68 is driven not only via the additional gear 70, but also directly. This reduces the load on the 34 play compensation elements 72, ensuring that the additional shaft 63, or at least the contactor 56, is driven even with high manufacturing tolerances or deformations.

[0061] 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.

[0062] List of reference symbols

[0063] 2 motor vehicles

[0064] 4 wheel

[0065] 6 Body

[0066] 8 Auxiliary unit

[0067] 10 Electric motor

[0068] 12 Sensor

[0069] 14 Control unit

[0070] 16 Rotation axis

[0071] 18 housings

[0072] 20 hollow cylindrical section

[0073] 22 Floor

[0074] 24 A-bearing

[0075] 26 Bearing shield

[0076] 28 warehouses

[0077] 30 wave

[0078] 32 rotors

[0079] 34 Stator

[0080] 36 phase connection

[0081] 38 passage

[0082] 40 Electronics compartment

[0083] 42 electronics housings

[0084] 44 Electronics

[0085] 46 circuit board

[0086] 48 bridge circuit

[0087] 50 Sensors

[0088] 54 additional bracket

[0089] 56 contactors

[0090] 58 Sensor unit

[0091] 60 sensors

[0092] 61 gear

[0093] 62 Sensor gear 63 additional shaft

[0094] 64 additional camps

[0095] 66 additional rotation axes

[0096] 68 Bracket 70 additional gear

[0097] 72 Play compensation element

[0098] 74 Cover cap

[0099] 76 additional warehouse

[0100] 78 Shaft stub 80 Mount

[0101] 82 Wave process

[0102] 84 relief camps

[0103] 86 assembly

[0104] 88 Assembly unit 90 Locking lug

[0105] 92 undercut

[0106] 94 Gearing

Claims

Claims 1. Electric motor (10) of a motor vehicle (2), comprising a housing (18) to which a bearing plate (26) is fastened, on which a bearing (28) is held, by means of which a shaft (30) is mounted rotatably about a rotational axis (16), and comprising a sensor system (50) for determining a position of the shaft (30), wherein the sensor system (50) has two sensor units (58), each comprising a contactor (56), and a sensor gear (62) comprising a gear (61) fastened to the shaft (30), which is in engagement with a further gear (70) fastened to a further shaft (63) which is mounted rotatably about a further rotational axis (66), wherein the sensor system (50) is designed such that upon rotation of the shaft (30), the two contactors (56) are moved, their rotational speeds being different, and wherein the sensor gear (62) comprises a mechanical Play compensation element (72).

2. Electric motor (10) according to claim 1, characterized in that the further gear (70) is ring-shaped and is fastened to the further shaft (63) by means of the play compensation element (72).

3. Electric motor (10) according to claim 2, characterized in that a circumferential gap is formed between the further gear (70) and the further shaft (62), in which the play compensation element (72) is arranged, which is made of an elastomer.

4. Electric motor (10) according to claim 1, characterized in that the further gear (70) is rigidly fastened to the further shaft (63), and in that a holder (68) is connected to the further gear (70) via the play compensation element (72), one of the contactors (56) being held by means of the holder (68).

5. Electric motor (10) according to claim 4, characterized in that the holder (68) has a circumferential toothing (94) which is in engagement with the gear (61).

6. Electric motor (10) according to claim 4 or 5, characterized in that the holder (68) is connected to the further gear (70).

7. Electric motor (10) according to claim 1, characterized in that the two gear wheels (61, 70) are toothed by means of a beveloid toothing, by means of which the play compensation element (72) is formed.

8. Electric motor (10) according to one of claims 1 to 7, characterized in that the further shaft (63) is rotatably mounted by means of a further bearing (64) held on the bearing plate (26).

9. Electric motor (10) according to one of claims 1 to 8, characterized in that a cover cap (74) is fastened to the bearing plate (26), by means of which the sensor gear (62) is covered.

10. Electric motor (10) according to claim 9, characterized in that the further shaft (63) is connected to the cover cap (74) by means of an additional bearing (76).

11. Electric motor (10) according to one of claims 1 to 10, characterized in that an additional holder (54) is fastened to the shaft (30), by means of which holder one of the contactors (56) is held.

12. Electric motor (10) according to one of claims 1 to 10, characterized in that the sensor gear (62) has a second gear (70) fastened to a second further shaft (63), which is rotatably mounted about a second further rotation axis (66), wherein the sensor system (50) is configured such that it is moved upon rotation of the shaft (63).

13. An auxiliary unit (8) of a motor vehicle (2), in particular a steering system, comprising an electric motor (10) according to one of claims 1 to 12.

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