Actuator for steering unit

Abstract

The invention relates to an actuator (4) for a steering unit (1) of a vehicle, comprising: a drive unit (5) configured to output torque, a worm gear (6) comprising a worm shaft (9) and a worm wheel (10) with a first toothing (12) which is in tooth engagement with the worm shaft (9), wherein the worm shaft (9) is further coupled to the drive unit (5) in a torque-transmitting manner, and the worm wheel (10) is configured to be coupled to a steering shaft (3) of the steering unit (1) in a torque-transmitting manner, a rotation angle sensor unit (7) configured to detect a rotation angle of the worm wheel (10), and a torque sensor unit (8) configured to detect a torque of the steering shaft (3), wherein the rotation angle sensor unit (7) is configured to detect an absolute angular position of a multiturn of the worm wheel (10) of at least approximately ± to capture 360°and the torque sensor unit (8) is configured to detect the torque of the steering shaft (3) based on the inverse magnetostrictive effect. Furthermore, the invention also relates to a steering unit (1) comprising a steering shaft (3), a steering wheel (2), and an actuator (4) according to the invention.

Description

[0001] The present invention relates to an actuator, in particular a force feedback actuator, for a steering unit of a vehicle, as well as a steering unit for a vehicle with such an actuator. State of the art

[0002] Actuators are used in vehicle steering units, among other things, to reduce the effort required by the driver when performing a steering movement. Such steering units are also colloquially referred to as power steering. Steer-by-wire steering units are also known in the art. Steer-by-wire steering units no longer have a mechanical connection between the steering wheel and the wheels to be steered, such as through a steering column. In such steer-by-wire steering units, actuators are used to artificially generate the steering feel for the driver. The artificial generation of the steering feel makes it possible to adapt the steering feel to the driver's needs. In this regard, freedom from play and minimal torque fluctuations in the actuators are particularly important in order to make the artificially generated steering feel appear "natural."

[0003] It has now become apparent that there is a further need to improve a known actuator for a vehicle steering unit. In particular, there is a further need to provide an actuator for a vehicle steering unit that can be mounted in a space-saving manner and produces a steering feel that the driver perceives as natural or authentic.

[0004] DE 11 2014 001 505 T5 discloses a vehicle steering device for steering a vehicle according to the operation of a steering wheel. This device comprises first and second steering assist devices, each equipped with a steering torque sensor, an assist motor, and a control unit. The control units perform drive control of the assist motors independently of each other, making it possible to maintain operation even if one of the control units fails. This ensures reliable steering assistance even in the event of an abnormal condition of one of the control units.

[0005] DE 10 2020 104 136 A1 discloses a steering unit comprising a one-piece sensor shaft and a torque sensor unit for detecting a torque introduced into the sensor shaft. The sensor shaft has a connection region for connection to a steering means in a first end region and is rotatably mounted in a transmission housing in its second end region. The torque sensor unit includes a magnetoelastic torque sensor and at least two magnetically coded zones on the sensor shaft, the permeability of which changes depending on a mechanical load. The magnetoelastic torque sensor is designed to measure a magnetic field change corresponding to the introduced torque, which is caused by the magnetically coded zones.

[0006] DE 10 2005 007 357 A1 discloses an electric power steering device comprising a worm gear mounted on a steering shaft for rotation therewith. The device includes a brushless electric motor with an output shaft capable of generating a current to assist the rotation of the steering shaft when energized. Furthermore, a worm gear is provided, which is coaxially connected to the output shaft of the motor to form a unified shaft assembly, wherein the worm gear meshes with the worm gear. Two bearings support the axially opposite end portions of the unified shaft assembly, respectively.

[0007] DE 10 2018 117 155 A1 discloses a steering assistance device for a motor vehicle, comprising a steering wheel-side steering shaft and a wheel-side steering shaft coupled thereto. A gear coupled to an assistance drive is mounted on the wheel-side steering shaft. A sensor element is integrated into the gear and interacts with a second, stationary sensor counter-element via a first sensor counter-element mounted on the steering wheel-side steering shaft. This arrangement enables precise detection of the steering movements and supports the control of the vehicle.

[0008] DE 10 2013 213 708 A1 discloses a worm gear for a power steering device of a motor vehicle that enables backlash compensation. The worm gear comprises a housing for accommodating a worm shaft and a worm gear meshing with the worm shaft, wherein the worm shaft is mounted for radial movement. A key feature of the invention is at least one torsion element, which is fixed on the one hand relative to the worm shaft and on the other hand relative to a component fixed to the housing, in order to preload the worm shaft toward the worm gear. This design enables simple manufacture and assembly, as well as quiet operation.

[0009] Against this background, it is an object of the present invention to provide an improved actuator for a steering unit of a vehicle, in particular to provide an actuator for a steering unit of a vehicle which can be mounted in a space-saving manner and which produces a steering feel which is perceived by the driver as natural or authentic. Disclosure of the invention

[0010] These and other objects, which will be mentioned upon reading the following description or which may be recognized by a person skilled in the art, are achieved by the subject matter of the independent claims. Advantageous embodiments and further developments can be found in the dependent claims and the following description.

[0011] The actuator according to the invention, in particular a force feedback actuator, for a steering unit of a vehicle, comprises a drive unit, a worm gear, a rotation angle sensor unit, and a torque sensor unit. The drive unit, in particular an electric motor, is configured to output a torque. The worm gear has a worm shaft and a worm wheel with a first toothing, wherein the toothing of the worm wheel meshes with the worm shaft. The worm shaft is further coupled to the drive unit in a torque-transmitting manner. The worm wheel is configured to be torque-fixedly coupled to the steering unit, in particular to a steering shaft of the steering unit. The rotation angle sensor unit is configured to detect a rotation angle of the worm wheel, and the torque sensor unit is configured to detect a torque of the worm wheel.The rotation angle sensor unit is configured to detect an absolute angular position of a multi-turn of the worm wheel (10) of at least approximately ± 360°, and the torque sensor unit is configured to detect the torque of the steering shaft based on the inverse magnetostrictive effect.

[0012] The advantage of the solution according to the invention lies in particular in the fact that the actuator comprises a rotation angle sensor unit and a torque sensor unit, thus offering a highly integrated solution that is compact and space-saving, particularly compared to known actuators. Furthermore, the actuator, particularly due to the worm gear, enables the haptic character of the steering feel to be improved for the driver. Furthermore, the actuator can adapt the haptic character of the steering feel to the driver's individual needs.

[0013] The torque of the drive unit can also be referred to as the drive torque. Because the worm gear is designed to be torque-fixedly coupled to the steering unit, in particular to the steering shaft of the steering unit, the angle of rotation of the worm gear detected by the angle of rotation sensor unit essentially corresponds to the angle of rotation of the steering unit, in particular the steering shaft, and the torque of the worm gear detected by the torque sensor unit essentially corresponds to the torque of the steering unit, in particular the steering shaft. The worm gear transmission can also be referred to as a helical gear transmission, in which case the worm gear is referred to as a helical gear.

[0014] According to the invention, the rotation angle sensor unit further comprises a first spur gear, a second spur gear, a first target, a second target, and a stationary plate. The first spur gear is torque-locked to a first shaft, and the second spur gear is torque-locked to a second shaft. The first target is torque-locked to the first spur gear, and the second target is torque-locked to the second spur gear. The stationary plate has at least one sensor element configured to detect contact with the first target and / or the second target. The first spur gear and the second spur gear each mesh with a second, in particular smaller, toothing of the worm gear, the first spur gear having a first number of teeth and the second spur gear having a second number of teeth that differs from the first number of teeth.Furthermore, the first target and the second target are each pre-tensioned in the direction of the fixed board by means of a spring element.

[0015] The second toothing of the worm gear can be formed integrally with the worm wheel. Alternatively, the second toothing of the worm gear can be designed as a separate spur gear that is coupled to the worm wheel in a torque- and axially fixed manner. The second toothing has, in particular, a smaller tip diameter than the first toothing that meshes with the worm shaft. The first spur gear and / or the second spur gear can also be referred to as a pinion. Due to the meshing engagement, the first spur gear and the second spur gear rotate according to their respective number of teeth when the worm wheel rotates. The angle of rotation of the worm gear and thus a steering angle of the steering unit, in particular the steering shaft, is detected via the first target, which is coupled to the first spur gear, and the second target, which is coupled to the second spur gear, in combination with the at least one sensor element of the circuit board.The underlying measuring principle is in particular an inductive measuring principle.

[0016] The spring elements bias the first target and the second target toward the circuit board, in particular toward the at least one sensor element. This ensures precise positioning of the respective target relative to the at least one sensor element under all operating conditions, i.e., independent of temperature, vibration, etc. This allows for high measurement accuracy.

[0017] The first spur gear and the second spur gear enable a phase shift between the first target and the second target, which enables the measurement of absolute angular positions of the worm gear of at least ± 360°.

[0018] The particularly accurate detection of the absolute angular position of at least ± 360°, in particular in a range of ± 900°, is particularly relevant for use in steering units, since a steering movement performed by the driver of the vehicle on a steering wheel, and thus on the steering shaft, can be over 360° for a strong steering angle.

[0019] The first spur gear and the second spur gear are made in particular from a plastic, whereby the term plastic is understood to mean both a pure plastic and a plastic mixture.

[0020] According to one embodiment, the actuator further comprises a protective cover which is arranged between a gear chamber and a sensor chamber and is designed to substantially prevent penetration of dirt particles, such as water, grease, dust, etc., into the sensor chamber.

[0021] The gear chamber is a space or area of ​​the actuator in which the worm shaft and the worm gear mesh. The sensor chamber is a space or area of ​​the actuator in which the angle sensor unit, in particular the circuit board and the first and second targets, is located.

[0022] In particular, the first shaft, which is torque-fixedly connected to the first spur gear, extends from the gear chamber, in which the first spur gear meshes with the second gearing of the worm gear, through the protective cover into the sensor chamber, where it is connected to the first target. In particular, the first shaft and the target can be connected to one another by overmolding. The first shaft is mounted and thus positioned in the protective cover by means of a sliding bushing. The second shaft, which is torque-fixedly connected to the second spur gear, and the second target are arranged in a similar manner. This protects the sensitive sensor system from the influence of dirt particles, particularly from the gear chamber.

[0023] According to one embodiment, the torque sensor unit further comprises a torsion bar and at least one sensor element. The torsion bar has a predetermined torsional resistance moment and is configured to be coupled to the worm gear. The at least one sensor element is arranged radially outside and spaced from the torsion bar and is configured to detect a torsion-induced stress change in a lateral surface of the torsion bar.

[0024] In particular, the torsion bar is designed as a shaft on which the worm gear is mounted in a torque-resistant manner. The torque of the worm shaft causes the torsion bar to twist, i.e., torsion, which in turn causes a change in stress in the outer surface of the torsion bar. This change in stress can be detected by the at least one sensor element, and, taking into account the predetermined torsional resistance moment of the torsion bar, the torque of the worm gear, and thus the torque of the steering unit, in particular the steering shaft of the steering unit, can be determined. The at least one sensor element can be arranged on a circuit board and, in particular, can be designed as a so-called SMD element (SMD = "surface mounted device").

[0025] According to one embodiment, the torque sensor unit comprises a plurality of sensor elements arranged substantially evenly distributed in the circumferential direction of the torsion bar. This allows the measurement accuracy of the torque sensor unit to be increased.

[0026] According to one embodiment, the at least one sensor element is arranged or accommodated in a main cover of the actuator. The torsion bar is mounted in the main cover of the actuator. Thus, the arrangement of the at least one sensor element in the main cover enables a short tolerance chain from the sensor element to the torsion bar. This can further improve the measurement accuracy of the torque sensor unit.

[0027] According to one embodiment, the torque sensor unit and the rotation angle sensor unit are configured to be coupled or capable of being coupled to the same control and / or power electronics, in particular electrically, for example, via a flexible ribbon cable, wherein the torque sensor unit can be positioned geometrically independently of the rotation angle sensor unit. This means that the torque sensor unit and the rotation angle sensor unit can be arranged geometrically independently of one another, i.e., at different positions, in the actuator, wherein they are both coupled to the same control and power electronics for further signal processing. This makes it possible to further reduce the required number of components and / or the required installation space of the actuator.

[0028] According to one embodiment, the torsion bar is designed as a hollow shaft or as a solid shaft. With an identical predetermined torsional resistance moment, the torsion bar designed as a hollow shaft has a larger diameter than the torsion bar designed as a solid shaft. Thus, the torsion bar designed as a hollow shaft, in particular, can be particularly easily integrated into the overall structure of the actuator.

[0029] According to one embodiment, the worm wheel is made of a plastic or a composite material and / or the worm shaft is made of steel. In this case, it is conceivable for the worm wheel to be made essentially entirely of a plastic in a so-called 1-component design. Alternatively, the worm wheel is made of a so-called 2-component design, i.e. a composite material. For example, the worm wheel can have a body made of a fiber-reinforced plastic and a toothing area, in particular a flank area, made of an unreinforced plastic. Another example of a worm wheel in the 2-component design has a sintered body with a flank area made of an unreinforced plastic. The term plastic here refers to both a single-material plastic and a plastic mixture.

[0030] The plastic gearing of the worm gear combined with the steel worm shaft enables reduced friction during contact, especially compared to steel-on-steel contact, and also provides improved damping behavior, as the plastic gearing is more elastic than steel gearing. Thus, the plastic-on-steel contact of the gearing engagement between the worm gear and the worm shaft enables good NVH (noise vibration harshness) behavior.

[0031] According to one embodiment, the worm shaft is preloaded radially toward the worm gear by means of a spring unit at one axial end and / or pivotally mounted at another axial end. The spring unit thus presses the worm shaft radially into flank contact with the worm gear, ensuring backlash-free tooth engagement between the worm shaft and the worm gear. This reliably prevents backlash in the torsional force flow in every operating condition, i.e., regardless of tolerances, temperature, wear, etc.

[0032] The pivoting bearing of the worm shaft at the other axial end can be achieved, for example, by a pivot bearing that separates the rotational function and the pivoting function of the worm shaft. This can prevent tilting effects in the worm shaft bearing. This can improve the NVH behavior and / or the friction behavior of the worm gear.

[0033] According to one embodiment, the worm shaft is coupled to the drive unit via a damping element. The damping element is designed, in particular, as a torsional damping element and serves to decouple the worm shaft from the drive unit. This means that torque peaks that may occur at the drive unit are dampened by the damping element, thus preventing the transmission of such torque peaks to the worm shaft. Such torque peaks at the worm shaft can be perceived by the vehicle driver as jerking. However, such jerking is undesirable. In other words, one can say that damping within the power flow from the drive unit to the worm shaft is improved.This enables an improved haptic experience for the driver of the vehicle, in particular it prevents the driver from perceiving jerking caused by torque peaks when performing a steering movement.

[0034] Another aspect of the invention relates to a steering unit for a vehicle. The steering unit comprises a steering shaft, a steering wheel, and an actuator according to the invention, in particular as described above and below. The steering wheel is coupled to a first axial end of the steering shaft in a torque-transmitting manner, and the actuator is coupled to a second axial end of the steering shaft in a torque-transmitting manner.

[0035] This allows the actuator to generate a torque that is perceived by the driver as a steering torque via the steering shaft and the steering wheel during a steering movement of the driver. Detailed description based on drawing

[0036] Further measures improving the invention are described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows: Fig. 1 a schematic representation of a steering unit according to an embodiment of the invention, Fig. 2 shows a schematic representation of an actuator according to an embodiment of the invention in a sectional view; Fig. 3 a schematic representation of a rotation angle sensor unit of an actuator according to an embodiment of the invention in a sectional view, Fig. 4 an enlarged schematic partial view of the rotation angle sensor unit from Fig. 3 in a perspective sectional view, and Fig. 5 a schematic representation of a torque sensor unit of an actuator according to an embodiment of the invention in a sectional view.

[0037] The figures are merely schematic and serve only to clarify the invention. The same elements are designated by the same reference numerals.

[0038] Fig. 1 shows a schematic representation of a steering unit 1 according to an exemplary embodiment of the invention. The steering unit 1 is designed, for example, as a steer-by-wire steering unit and has a steering wheel 2, a steering shaft 3 and an actuator 4. The steering wheel 2 is connected to the steering shaft 3 at least in a torque-fixed manner, and furthermore in particular in an axially fixed manner. The actuator 4 is designed as a force feedback actuator and is also connected to the steering shaft 3 in a torque-fixed manner. The actuator 4 in the steer-by-wire steering unit 1 is configured to transmit a torque to the steering shaft 3, which counteracts a steering movement of a driver on the steering wheel 2 in such a way that the steering feel during this steering movement is perceived by the driver as "authentic" or "natural". An "authentic" or"Natural" steering feel essentially corresponds to the steering feel found in steering units where the steering wheel is mechanically connected to the wheels via the steering shaft, and the torque generated by the driver's steering movement is transmitted to the wheels via the steering shaft, which is mechanically connected to the wheels. Resistances such as friction losses, etc., generated by the mechanical connection and depending on the steering angle, are perceived by the driver and result in the steering feel.

[0039] In the steer-by-wire steering unit 1, this steering feeling is generated synthetically by the actuator 4, which is described below with reference to the Fig. 2 to 5 are explained in more detail. Fig. Figure 2 shows the actuator 4 according to an exemplary embodiment of the invention in a schematic sectional view. The actuator 4 has a drive unit 5, which is designed as an electric motor, a worm gear 6, a rotation angle sensor unit 7 (see Fig. 3 and Fig. 4) and a torque sensor unit 8 (see Fig. 5).

[0040] The worm gear 6 has a worm shaft 9 and a worm wheel 10. The worm shaft 9 is coupled at one axial end to an output shaft 11 of the drive unit 5 in a torque-transmitting manner. Furthermore, the worm shaft 9 meshes with a first toothing 12, which can also be referred to as the main toothing 12, of the worm wheel 10 and thus transmits the torque generated by the drive unit 5 to the worm wheel 10. The worm wheel 10 is further connected to the steering shaft 3 in a torque-transmitting manner and thus transmits a steering torque, which results from the torque generated by the drive unit 5 and the transmission ratio of the worm gear 6, to the steering shaft 3.

[0041] The worm shaft 9 is made, in particular, of steel, and the worm gear 10 is made of a plastic, at least in a flank region of the main toothing 12. This results in a plastic-to-steel contact in the toothing engagement between the worm shaft 9 and the worm gear 10, which has reduced friction compared to steel-to-steel contact and also offers good damping properties. This makes it possible to achieve good NVH (noise-vibration-harshness) properties. This means that audible and / or perceptible vibrations in the vehicle can be dampened by the worm gear 6. The body of the worm gear 10 can be made of a plastic, a fiber-reinforced plastic, or a sintered metal. The term "plastic" encompasses both single-variety plastics and plastic mixtures.

[0042] In order to keep the tooth engagement between the worm shaft 9 and the worm wheel 10 essentially free of flank backlash, regardless of tolerances, temperature, wear, etc., the worm shaft 9 is spring-mounted by a spring unit 14 at an axial end 13 facing away from the drive unit 5. The spring unit 14 presses or preloads the worm shaft 9 radially into flank contact with the worm wheel 10. This prevents torsional backlash between the flanks of the worm shaft 9 and the flanks of the worm wheel 10. A pivoting movement of the worm shaft 9 required for the spring unit 14 is made possible by the worm shaft 9 being mounted at another axial end 15 via a pivot bearing 16. The pivot bearing 16 makes it possible to separate the rotational function and the pivoting function of the worm shaft 9 from one another, thus avoiding tilting effects in the bearing of the worm shaft 9.

[0043] Furthermore, the torque-transmitting connection between the worm shaft 9 and the output shaft 11 of the drive unit 6 is decoupled by means of a torsional damping element 17. The torsional damping element 17 is embodied here, for example, as a plug-in coupling 18 made of an elastic plastic and enables the damping within the power flow to be improved by compensating for torque peaks that may occur at the output shaft 11, thus improving the feel for a driver.

[0044] The rotation angle sensor unit 7 is described with reference to Fig. 3 and Fig. 4. The rotation angle sensor unit 7 has a stationary circuit board 19, a torque-transmitting spur gear 20 arranged coaxially with the steering shaft 3, and two additional spur gears 21, 22, each of which meshes with the spur gear 20. The two additional spur gears 21, 22 have a different number of teeth, in particular a number that differs by one tooth. The spur gear 20 is designed here, for example, as a second toothing of the worm gear 10, which has a smaller diameter than the main toothing 12 of the worm gear 10.

[0045] The additional spur gears 21, 22 are each arranged in a rotationally and axially fixed manner on a shaft 23, 24, which in turn are each rotatably mounted in a protective cover 26 via a sliding bushing 25. The protective cover 26 is designed to separate a gear chamber 27, i.e. an area in the actuator 4 in which the worm shaft 9 and the worm wheel 10 are in toothed engagement with one another, from a sensor chamber 28, i.e. an area in the actuator 4 in which the sensor system of the rotation angle sensor unit 7 is arranged. The circuit board 19, a first target 29, and a second target 30 are arranged in the sensor chamber 28. The first target 29 is connected to the shaft 23 of the additional gear 21 in a torque-fixed manner, and the second target 30 is connected to the shaft 24 of the additional gear 22 in a torque-fixed manner. Thus, the targets 29, 30 rotate with the additional spur gear 21, 22 assigned to them. Fig. 3 and Fig. 4, the targets 29, 30 and the respective shaft 23, 24 are overmolded, whereby production can be achieved in only one step.

[0046] The additional spur gears 21, 22 are each in meshing engagement with the spur gear 20, so that the two additional spur gears 21, 22 transmit a rotational movement of the worm gear 10, and thus of the steering shaft 3, to the additional spur gears 21, 22 and translate it according to the respective tooth ratio. Due to the different number of teeth of the additional spur gears 21, 22, the so-called vernier principle is applied, and a determination of the absolute angle of the worm gear 10 or the steering shaft 3 is possible. Thus, the rotation angle sensor unit 7 enables the determination of the absolute angular position during a multi-turn of the worm gear 10 and thus of the steering shaft 3, whereby, starting from a zero position, a rotation, i.e. a rotation angle, of at least ± 360° occurs. In particular, a determination of an absolute angle in a range of ± 900° is possible.

[0047] The targets 29, 30 can, for example, each be designed as a primary sensor, the position of which is detected by the circuit board 19, in particular by secondary sensors (not shown) arranged on the circuit board 19. To ensure positioning of the targets 29, 30 relative to the circuit board 19 or relative to a sliding surface provided for this purpose and arranged flush with the circuit board 19, independent of external influences such as temperature, vibration, etc., the targets 29, 30 are each preloaded towards the circuit board 19 via a spring element 31. This allows a high degree of measurement accuracy of the angle of rotation of the steering shaft 3 to be achieved. In particular, the targets 29, 30 and the circuit board 19 are configured to detect the angle of rotation of the steering shaft 3 using an inductive measuring principle.

[0048] The torque sensor unit 8 is in Fig.5 schematically shown. The torque sensor unit 8 has a torsion bar 32 with a predetermined torsional resistance moment, and a plurality of sensor elements 33 which are arranged radially outside and spaced from a lateral surface 34 of the torsion bar 32. The torsion bar 32 is designed as a hollow shaft and is part of the steering shaft 3. The lateral surface 34 has at least two circular magnetization regions (not shown) which serve as a primary sensor for determining the torque. The sensor elements 33 are designed in particular as magnetic field sensors which serve as secondary sensors for determining the torque. The primary sensors, i.e. the magnetization regions, serve to convert the torque to be measured into a corresponding magnetic field. The secondary sensors, i.e. the magnetic field sensors, are designed to convert this magnetic field into electrical signals which serve to determine the torque.

[0049] The magnetic field is caused by tensions that occur in the outer surface 34 of the torsion bar 32 due to the application of torque, which is also referred to as the inverse magnetostrictive effect. Thus, the measurement of the torque of the steering shaft 3, i.e., the steering moment, is based on the inverse magnetostrictive effect. The sensor elements 33 are arranged in a housing cover 35 that at least partially surrounds the steering shaft 3. This ensures a short tolerance chain from the sensor elements 33 to the torsion bar 32, thus increasing measurement accuracy. List of reference symbols 1 steering unit 2 steering wheel 3 Steering shaft 4 Actuator 5 Drive unit 6 worm gears 7 Angle sensor unit 8 Torque sensor unit 9 Worm shaft 10 Worm gear 11 Output shaft 12 first gearing / main gearing 13 axial end 14 Spring unit 15 axial end 16 swivel bearings 17 torsional damping element 18 plug-in coupling 19 circuit board 20 spur gear 21 Additional spur gear 22 Additional spur gear 23 Wave 24 Wave 25 sliding bushing 26 protective covers 27 Gearbox compartment 28 Sensor Room 29 first target 30 second target 31 spring element 32 Torsion bar 33 Sensor element 34 lateral surface 35 Housing cover

Claims

[1] Actuator (4) for a steering unit (1) of a vehicle, comprising: a drive unit (5) which is arranged to output a torque, a worm gear (6) comprising a worm shaft (9) and a worm wheel (10) with a first toothing (12) which is in toothed engagement with the worm shaft (9), wherein the worm shaft (9) is further coupled to the drive unit (5) in a torque-transmitting manner, and the worm wheel (10) is designed to be coupled to a steering shaft (3) of the steering unit (1) in a torque-transmitting manner, a rotation angle sensor unit (7) which is designed to detect a rotation angle of the worm wheel (10), and a torque sensor unit (8) which is designed to detect a torque of the steering shaft (3), wherein the rotation angle sensor unit (7) is configured to detect an absolute angular position of a multi-turn of the worm wheel (10) of at least ± 360°, and the torque sensor unit (8) is configured to detect the torque of the steering shaft (3) based on the inverse magnetostrictive effect, characterized by that the rotation angle sensor unit (7) further comprises: a first spur gear (21) which is torque-fixedly connected to a first shaft (23), a second spur gear (22) which is torque-fixedly connected to a second shaft (24), a first target (29) which is torque-fixedly coupled to the first spur gear (21), a second target (30) which is torque-fixedly coupled to the second spur gear (22), and a fixed circuit board (19) with at least one sensor element which is designed to detect contact with the first target (29) and / or the second target (30), wherein the first spur gear (21) and the second spur gear (22) mesh with a second toothing (20) of the worm gear (10), wherein the first spur gear (21) has a first number of teeth and the second spur gear (22) has a second number of teeth which is different from the first number of teeth, and wherein the first target (29) and the second target (30) are each prestressed in the direction of the fixed board (19) by means of a spring element (31). [2] Actuator (4) according to claim 1, further comprising a protective cover (26) arranged between a gear chamber (27) and a sensor chamber (28) and configured to substantially prevent dirt particles from penetrating into the sensor chamber (28). [3] Actuator (4) according to one of claims 1 or 2, wherein the torque sensor unit (8) further comprises: a torsion bar (32) having a predetermined torsional resistance moment and adapted to be coupled to the worm wheel (10), at least one sensor element (33) arranged radially outside and spaced from the torsion bar (32), wherein the sensor element (33) is configured to detect a torsion-induced stress change in a lateral surface (34) of the torsion bar (32). [4] Actuator (4) according to claim 3, wherein the torque sensor unit (8) has a plurality of sensor elements (33) which are arranged substantially uniformly distributed in the circumferential direction of the torsion bar (32). [5] Actuator (4) according to claim 3 or 4, wherein the at least one sensor element (33) is arranged in a main cover (35) of the actuator (4). [6] Actuator (4) according to one of claims 3 to 5, wherein the torsion bar (32) is designed as a hollow shaft or a solid shaft. [7] Actuator (4) according to claims 1 to 6, wherein the worm wheel (10) is made of a plastic or a composite material and / or the worm shaft (9) is made of steel. [8] Actuator (4) according to one of claims 1 to 7, wherein the worm shaft (9) is prestressed by means of a spring unit (14) at one axial end (13) in the radial direction towards the worm wheel (10) and / or is pivotally mounted at another axial end (15). [9] Steering unit (1) for a vehicle, comprising: a steering shaft (3), a steering wheel (2) which is coupled to a first axial end of the steering shaft (3) in a torque-transmitting manner, and an actuator (4) according to one of claims 1 to 8, wherein the actuator (4) is coupled to a second axial end of the steering shaft (3) in a torque-transmitting manner.

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