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 (52) for determining a position of the shaft (30). The sensor system (52) includes two sensor units (58), which are each equipped with a contact maker (56), and a sensor gear mechanism (64) comprising a gear wheel (62) that is fastened to the shaft (30) and meshes with another gear wheel (66). The other gear wheel (66) is mounted, by means of a journal (70) that is secured to the end shield (26) and extends parallel to the axis of rotation (16), on the end shield (26) for rotation about another axis of rotation (74). The sensor system (52) is designed in such a way that the two contact makers (56) move when the shaft (30) rotates, the rotational speeds of the two contact makers (56) differing from each other. The invention also relates to an auxiliary unit (8) of a motor vehicle (2).

Description

[0001] Description

[0002] Electric motor of a motor vehicle

[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 8. 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, preferably 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 assigned to the control device.

[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 a rotational axis and / or is in particular arranged at least in sections concentrically to the rotational axis. 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 rotational axis. 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 operate in the same manner and, in particular, are structurally identical to one another. This allows the use of identical parts. Alternatively, the two sensors can be 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, which includes a gearwheel attached to the shaft. The gearwheel is arranged, in particular, on the side opposite the bearing from any rotor. Thus, the gearwheel does not interfere with the rotor and stator. The gearwheel, in turn, meshes with another gearwheel mounted for rotation 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 determined, in particular, by the two gearwheels.

[0016] The additional gear is supported by means of a journal which is held on the bearing shield and arranged parallel to the axis of rotation. The journal is thus arranged parallel to the additional axis of rotation and preferably concentric with it. In this case, the journal is offset outwards with respect to the shaft, in particular in a radial direction with respect to the axis of rotation. Since the journal is held on the bearing shield, it does not rotate when the shaft rotates. Therefore, when the shaft rotates, the additional gear rotates with respect to the journal. In particular, the additional gear is placed on the journal and surrounds it circumferentially. For example, the journal is made in one piece with other components of the bearing shield. Thus, in particular, the journal is made of the same material as the bearing shield. However, it is particularly preferred that the journal be made of a separate material.This makes it possible to optimize the journal with regard to the bearing support of the gear, while the material of the bearing plate is adapted to the other requirements of the bearing plate. In particular, the journal is made of steel. For example, the journal is glued or welded to the bearing plate. In another alternative, the journal is screwed to the bearing plate. However, it is particularly preferred that the journal be pressed into a corresponding opening in the bearing plate, creating a press fit. In other words, the journal is held force-locking to the bearing plate. This means that no additional components are required for assembly, and robustness is increased.

[0017] The sensor system is designed such that the two contactors are moved when the shaft rotates. In other words, the contactors are arranged such that they also rotate when the shaft rotates. However, their rotation speeds differ from one another. Thus, if the angular position of the shaft changes by a certain amount, the position of the two contactors also changes, although the change differs between the two contactors. In particular, the different movements of the contactors are due to the sensor gear. In summary, the sensor system is designed at least partially according to the vernier principle.

[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 it is held stationary. 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 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] 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.

[0020] Because the journal is held, or in particular fastened, to the bearing shield, its stability is increased, so that even if the electric motor is subjected to vibration, the position of the journal relative to the remaining components of the bearing shield and the shaft remains constant. As a result, the position of the two gears relative to each other, in particular their centers, does not change, which is why the two gears are always in mesh. This ensures that the position of the shaft can be reliably determined even under adverse conditions. It is also possible to adjust / check the position of the journal accordingly during remachining of the bearing shield to ensure that the bearing, in particular any bearing seat, is in the desired position.No separate work step is required for this, which is why the manufacturing time is not extended, but due to the comparatively precise alignment of the pin with respect to the shaft, it is ensured that the two gears are always in mesh with each other and that the two gears rotate together.

[0021] For example, the gear is made of a plastic or, preferably, of a metal. For example, the additional gear is made of a plastic. This reduces manufacturing costs and weight. However, the additional gear is preferably made of a metal so that robustness is increased and wear is reduced. For example, the additional gear is cast or milled. However, the additional gear is particularly preferably sintered, in particular from a metal powder. This enables production with comparatively close manufacturing tolerances, and no post-processing is necessary after demolding. Also, no machining is required to produce the additional gear, which means that no tools are required that are subject to comparatively high wear. This reduces manufacturing costs.Furthermore, during the manufacturing of the additional gear, there is no comparatively high temperature change that could lead to the development of mechanical stresses and / or deformation. This further increases precision. Furthermore, the forces acting on the additional gear during operation of the sensor system are comparatively low, which means wear is comparatively low.

[0022] For example, the additional gear is simply placed on the journal, creating a plain bearing between them. This further reduces material costs and, in particular, makes it possible to select tight manufacturing tolerances, especially since only two different components are required: the additional gear and the journal. Particularly preferably, however, the additional gear is connected to the journal by means of an additional bearing. The additional bearing is, in particular, a rolling bearing, such as a ball bearing or a needle bearing. An outer ring of the additional bearing is advantageously attached to the additional gear, for example, using an adhesive. Particularly preferably, the additional bearing is pressed into a corresponding receptacle in the additional gear, creating a frictional connection. Preferably, the additional bearing is connected to the additional gear during its manufacture and is suitably integrated into the gear manufacturing process.For example, the additional bearing is overmolded with a plastic that forms the additional gear. This enables a relatively precise alignment of the additional bearing with respect to the additional gear and the journal, simplifying assembly. The additional bearing, in particular, reduces static friction, so that even a relatively small change in the shaft position leads to rotation of the additional gear. This makes it possible to reliably detect relatively small changes in the shaft position using electronics.

[0023] For example, a further holder is attached to the further gear, by means of which the contactor is held. This means that the further holder and therefore also the contactor rotate with the further gear. Due to the further holder, it is possible to space the contactor from the further gear, so that there are comparatively few restrictions on the design. However, one of the contactors is particularly preferably attached to the further gear, for example by means of a further component or particularly preferably directly. For this purpose, the further gear in particular has a corresponding receptacle. The further gear is preferably at least partially pot-shaped, so that the pin engages over the end by means of the gear. In particular, the contactor is arranged on the pot base on the side opposite the pin in the assembled state, so that it is concentric with the further axis of rotation.This design prevents the pin from being inserted too far, simplifying assembly and increasing robustness. It also eliminates the need for additional components, thus reducing manufacturing costs.

[0024] 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, is pot-shaped and closed by the end shield, is where 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.For example, the cover cap covers the entire sensor system, with the exception of any sensors in each sensor unit. This reliably prevents dirt particles from penetrating the sensor system.

[0025] Conveniently, a 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 shaft's rotational speed. In particular, the other contactor is driven by the additional gear and, for example, attached to it. This requires comparatively few components, thus reducing manufacturing costs and space requirements.

[0026] In a further development, the sensor gear comprises in particular a second further gear which is rotatably mounted about a second further axis of rotation, which is expediently parallel to the further axis of rotation. The second further gear is rotatably mounted by means of a second pin which is held on the bearing plate and arranged parallel to the axis of rotation. The second pin is arranged in particular parallel to the pin and / or preferably concentrically to the second further axis of rotation. In particular, the sensor system, preferably the sensor gear, is designed such that when the shaft rotates the second further gear is also moved, in particular rotated. For this purpose, for example, the second further gear is in engagement with the gear or merely in engagement with the further gear. In particular, one of the contactors is assigned to the second further gear and the other contactor is assigned to the further gear.For example, when the shaft rotates, the contactors rotate, with the rotational speed of one of the two contactors equal to the rotational speed of the shaft. Alternatively, all contactors rotate at a different rotational speed than the rotational speed of the shaft, allowing a comparatively accurate determination of the shaft position.

[0027] Suitably, the two additional gears, the two pins, and the associated contactors are identical in design. This creates two structural units that are, in particular, identical in design or at least similar in type. In particular, they differ only in the number of teeth on the respective additional gears, allowing for different rotational speeds. This makes it possible to use at least partially identical parts, which reduces manufacturing costs.

[0028] Particularly preferably, one of the contact sensors is each assigned to each of the two further gears, each of which is in particular designed as a so-called contactless inductive position sensor (CIPOS). This enables a comparatively precise determination of the position of the shaft. Suitably, one of the contact sensors is also assigned to the shaft, so that at least three contact sensors are present. For example, the contact sensor assigned to the shaft is also designed as a CIPOS unit. Particularly preferably, however, this is designed as a Hall sensor, which is why accuracy is increased (if only this were used to determine the position) but also manufacturing costs are reduced. Due to the three contact sensors, reliability is increased, and higher manufacturing tolerances can also be selected, whereby precise determination of the position of the shaft is still possible.In this case, the two pins are arranged on different sides of the shaft, resulting in comparatively efficient use of space. In particular, all three rotational axes lie on a common straight line. In a further development, several additional gears are provided, each of which is assigned a corresponding contactor. The sensor gear is preferably designed like a planetary gear. In particular, the additional gears rotate at different speeds during operation.

[0029] 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 comprising a gearwheel attached to the shaft, which engages with another gearwheel which is mounted so as to be rotatable about a further rotational axis by means of a pin held on the bearing plate and arranged parallel to the rotational axis.The sensor is designed in such a way that when the shaft rotates, the two contactors are moved, whereby their rotation speeds are different.

[0030] 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.

[0031] The further developments and advantages explained in connection with the electric motor can also be transferred to the auxiliary unit / the as well as to each other and vice versa.

[0032] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In the drawings:

[0033] Fig. 1 schematically shows a motor vehicle with a steering system having an electric motor,

[0034] Fig. 2 shows a schematic sectional view of the electric motor, which includes a sensor system, and

[0035] Fig. 3 shows a perspective sectional view of a modification of the sensor system.

[0036] Corresponding parts are provided with the same reference numerals in all figures.

[0037] 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, whereby due to the connection to the front wheels, their steering angle with respect to the body 6 is changed.

[0038] 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 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.

[0039] 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 18 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.

[0040] 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 rotatably fastened to the shaft 30, 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 motor (BLDC), and the electromagnets of the stator 34 are connected to several electrical phases, namely 2 times three phases (6-phase system).

[0041] The electromagnets of the stator 34 are energized via several phase connections 36, which are guided from the stator 34 through corresponding passages 38 of the bearing plate 26 and which 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. The bearing plate 26 has a hollow-cylindrical, circumferential collar 44, by means of which both the electronics housing 42 and the housing 18 are encompassed at their ends.

[0042] Arranged within the electronics compartment 40 is an electronics unit 46 comprising a printed circuit board 48 arranged perpendicular to the rotation axis 16. A bridge circuit 50 is connected to the printed circuit board 48, which is electrically connected to the phase terminals 36 and which comprises a plurality of semiconductor switches (not shown in detail). The electronics unit 46 also has a driver circuit (not shown in detail) for controlling the bridge circuit 50, a control, regulation, and / or the like. A sensor unit 52 for determining the position of the shaft 30, namely its angular position, is arranged between the printed circuit board 48 and the bearing plate 26. The stator 34 is energized by means of the additional components of the electronics unit 46, 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.

[0043] The sensor system 52 has a holder 54 arranged on the side of the bearing plate 26 opposite the rotor 32 and placed onto the end of the shaft 30 located there. The holder 54 is designed, for example, in the manner of a sleeve and is pressed onto the end of the shaft 30. A contactor 56 of a sensor unit 58, arranged perpendicular to the axis of rotation 16, is arranged by means of the holder 54. The sensor unit 58 also has a sensor 60 attached to the side of the circuit board 48 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. 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 holder 54 is thus attached to the shaft, by means of which one of the contactors 56 is held.

[0044] A gear 62 is arranged between the bearing 28 and the holder 54, which is placed on the shaft 30 and fastened thereto in a rotationally fixed manner. The gear 62 is thus rigidly fastened to the shaft 30. The gear 62 is a spur gear and a component of a sensor gear 64 of the sensor system 52. A further gear 66 meshes with the gear 62. The further gear 66 has external teeth and is essentially cup-shaped. The further gear 66 surrounds a further bearing 68 that is pressed into the cup opening of the further gear 66. The further bearing 68 is designed as a rolling bearing, and due to the press-fitting, an interference fit is realized between an outer ring of the further bearing 68 and the further gear 66. In an alternative, the outer ring of the further bearing 68 is overmolded using the plastic of the further gear 66.The additional bearing 68, namely its inner ring, is connected to a journal 70 made of steel and arranged parallel to the rotational axis 16. The journal 70 is pressed into an opening 72 of the bearing plate 26, which is offset radially outward from the bearing 28 with respect to the rotational axis 16. Thus, the journal 70 is held firmly on the bearing plate 26 and thus non-rotatably attached thereto.

[0045] In summary, the additional gear 66 is connected to the journal 70 by means of the additional bearing 68. By means of the journal 70 and with the aid of the additional bearing 68, the additional gear 66 is rotatably mounted about an additional rotation axis 74, which is parallel to the rotation axis 16 but laterally offset from it. The journal 70 and the additional bearing 68 are arranged concentrically to the additional rotation axis 74. Due to the engagement with the gear 62, the additional gear 66 rotates about the additional rotation axis 74 when the shaft 30 rotates.

[0046] The additional gear 66 is sintered and thus made of a metal powder that was filled into a corresponding mold during production and pressed there. Thus, the outer contour of the additional gear 66 is determined by the mold used, with only minor deviations. Alternatively, the additional gear 66 can be plastic-injected.

[0047] A contactor 56 of a sensor unit 58 is also attached to the end of the further gear 66 opposite the pin 70, so that the sensor system 52 has a total of two corresponding sensor units 58. This sensor unit 58 also includes a sensor 60, which is attached to the circuit board 48 on the side facing the bearing plate 26 and is located on the further rotation axis 74. The two sensor units 58 are either structurally identical or operate according to different principles, with one of the sensor units 58 being designed as a Hall sensor and the other as a CIPOS unit.

[0048] The sensor gear 64 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 interlocking of the two gears 62, 66, the other contactor 56 is moved at a lower speed. The data provided by the sensors 60 is evaluated by the additional components of the sensor system 52, which are provided, for example, in part by the electronics 46, using the vernier principle. This enables a comparatively precise determination of the position of the shaft 30.

[0049] In summary, in the sensor gear 64, the gear 62 engages with the further gear 66, which is rotatably mounted about the further rotation axis 74 by means of the pin 70 secured to the bearing plate 26 and arranged parallel to the rotation axis 16. One of the contactors 56 is attached to the further gear 66. The sensor system 64 is designed such that when the shaft 30 rotates, the two contactors 56 are moved, with their rotation speeds being different.

[0050] Furthermore, a cover cap 76, which is a plastic injection-molded part, is attached to the bearing plate 26. The sensor gear 64 is covered by the cover cap 76. In other words, the sensor gear 64 is arranged in the space formed between the cover cap 76 and the bearing plate 26. The two contactors 56 are also located in the space enclosed by the cover cap 76. The electronics 46 and the sensors 60, however, are arranged outside the cover cap 76. The cover cap 76 thus keeps any abrasion particles generated during operation of the sensor gear 64 away from the electronics 46, thus protecting it. Any particles penetrating from the rotor 32 via the bearing 28 are also kept away from the electronics 46 by the cover cap 76.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 3 shows a perspective sectional view of a modification of the sensor system 52 along a sectional plane along the rotation axis 16 and the further rotation axis 74. Here, too, the shaft 30 is connected to the bearing plate 26, which has the collar 44, by means of the bearing 28. In this variant, however, the cover cap 76 is essentially flat and fastened to the collar 44. The cover cap 76 again covers the entire sensor gear 64, which also has the gear 62 fastened to the shaft 30. The shaft 30 has a blind-hole-like recess at its end, and the modified holder 54 is pressed into this recess. The holder 54 is designed as a pin arranged parallel and concentrically to the rotation axis 16. One of the contactors 56, which is an annular permanent magnet arranged perpendicular to the rotation axis 16, is fastened to the pin at the end opposite the shaft 30.The associated sensor 60, not shown in detail, of this sensor unit 58 is a Hall sensor.

[0052] Instead of just one pin 70, there are now two identical pins 70, each pressed into a corresponding opening 72 in the bearing plate 26. The construction essentially corresponds to the previous embodiment, and a corresponding additional bearing 68 is connected to each of the pins 70. Each additional bearing 68 is pressed into a corresponding opening of a respective additional gear 66, or injected into the plastic, which are thus each mounted about a corresponding additional axis of rotation 74. The additional axes of rotation 74 and the axis of rotation 16 lie in a common plane and are parallel to one another. However, the distance of the two axes of rotation 74 from the axis of rotation 16 is different, and thus also the distance of the two pins 70 from the shaft 30. The axis of rotation 16 is arranged between the two additional axes of rotation 74.

[0053] Each additional gear 66 meshes with gear 62, which is thus arranged between the two additional gears 66. Due to the different spacing of the associated pins 70 and thus also the centers of the additional gears 66, the number of teeth on the two gears 66 differs. Therefore, when the shaft 30 rotates, the two gears 66 rotate at different speeds. As in the previous embodiment, the two gears 66 are sintered, namely from a metal powder. In a variant not shown in detail, the additional gears 66 are made of a plastic.

[0054] On each of the additional gears 66, on the side facing away from the respective pin 70, the associated contactor 56 is attached, which is designed as a CIPOS unit. In this variant, the sensor system 52 thus has a total of three sensor units 58, with the sensor units 58 associated with the additional gears 66 comprising the CIPOS units. Here, too, the sensor system 52 operates according to the vernier principle, with the position of the shaft 30 being determined during normal operation of the auxiliary unit 8 by means of the sensor units 58 associated with the additional gears 66. Due to the sensor units 58 used, a comparatively precise determination of the position of the shaft 30 is possible. The sensor unit 58 associated with the shaft 30, on the other hand, is only used in the event of a failure of one of the other sensor units 58 and / or for plausibility checks.It is also possible by means of this sensor unit 58 to compensate for any inaccuracies in the other sensor units 58, so that comparatively high manufacturing tolerances can be selected during the manufacture of the electric motor 10.

[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.

[0056] List of reference symbols

[0057] 2 motor vehicles

[0058] 4 wheel

[0059] 6 Body

[0060] 8 Auxiliary unit

[0061] 10 Electric motor

[0062] 12 Sensor of the control unit

[0063] 14 Control unit

[0064] 16 Rotation axis

[0065] 18 housings

[0066] 20 hollow cylindrical section

[0067] 22 Floor

[0068] 24 A-bearing

[0069] 26 Bearing shield

[0070] 28 warehouses

[0071] 30 wave

[0072] 32 rotors

[0073] 34 Stator

[0074] 36 phase connection

[0075] 38 passage

[0076] 40 Electronics compartment

[0077] 42 electronics housings

[0078] 44 collar

[0079] 46 Electronics

[0080] 48 circuit board

[0081] 50 bridge circuit

[0082] 52 Sensor technology

[0083] 54 bracket

[0084] 56 contactors

[0085] 58 Sensor unit

[0086] 60 sensors

[0087] 62 Gear 64 Sensor gear

[0088] 66 additional gear

[0089] 68 additional camps

[0090] 70 Pin 72 Opening

[0091] 74 additional rotation axis

[0092] 76 Cover cap

Claims

Claims 1. An 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 for rotation about a rotation axis (16), and comprising a sensor system (52) for determining a position of the shaft (30), wherein the sensor system (52) has two sensor units (58), each comprising a contactor (56), and a sensor gear (64) comprising a gear (62) fastened to the shaft (30), which is in engagement with a further gear (66) which is mounted for rotation about a further rotation axis (74) by means of a pin (70) held on the bearing plate (26) and arranged parallel to the rotation axis (16), wherein the sensor system (52) is designed such that upon rotation of the shaft (30), the two contactors (56) are moved, wherein their rotation speeds are different.

2. Electric motor (10) according to claim 1, characterized in that the further gear (66) is sintered.

3. Electric motor (10) according to claim 1 or 2, characterized in that the further gear (66) is connected to the pin (70) by means of a further bearing (68).

4. Electric motor (10) according to one of claims 1 to 3, characterized in that one of the contactors (56) is fastened to the further gear (66).

5. Electric motor (10) according to one of claims 1 to 4, characterized in that a cover cap (76) is fastened to the bearing plate (26), by means of which the sensor gear (64) is covered.

6. Electric motor (10) according to one of claims 1 to 5, characterized in that a holder (54) is fastened to the shaft (30), by means of which holder one of the contactors (56) is held.

7. Electric motor (10) according to one of claims 1 to 6, characterized in that the sensor gear (64) has a second further gear (66) which is rotatably mounted about a second further axis of rotation (74) by means of a second pin (70) which is held on the bearing plate (26) and arranged parallel to the axis of rotation (16), wherein the sensor system (52) is designed such that the second further gear (66) is moved when the shaft (30) rotates.

8. Auxiliary unit (8) of a motor vehicle (2), in particular a steering system, with an electric motor (10) according to one of claims 1 to 7.

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