Steering unit of a vehicle

Abstract

Steering unit (1), in particular a steer-by-wire steering unit, for a vehicle, comprising: a steering rod (2) configured to be coupled to a wheel of the vehicle at each of its axial ends (7, 8), wherein the steering rod (2) has at least a section with a toothed section (5), an actuator coupled to the steering rod (2) such that a rotational movement of the actuator causes a translational movement of the steering rod (2) to change the position of the steering rod (2) along a predetermined steering rod travel path (9), an anti-rotation device (3) for torque support of the steering rod (2), and a sensor unit (4) for determining the position of the steering rod (2), wherein the anti-rotation device (3) has a first toothed device (10) which engages with the toothed section (5) of the steering rod (2) and is axially fixed and rotatable in a steering rod housing (16).wherein the sensor unit (4) has at least one sensor arrangement (25) for detecting the steering rod travel (9), wherein the sensor arrangement (25) has a sensor wheel (21) which is coupled directly or indirectly to the first toothed assembly (10) of the anti-rotation device (3) such that the sensor wheel (21) rotates by a predetermined angle over the entire steering rod travel (9), characterized in that the anti-rotation device (3) has a second toothed assembly (19) which rotates together with the first toothed assembly (10), wherein the second toothed assembly (19) is in engagement with the sensor wheel (21), wherein the second toothed assembly (19) has a smaller pitch circle than the first toothed assembly (10), wherein the sensor arrangement (25) further comprises a sensor wheel receiving device (24) for rotatably coupling the sensor wheel (21) with the steering rod housing (16),wherein the sensor wheel receiving device (24) has an opening (31) for rotatably mounting the sensor wheel (21) and is configured to be fixedly connected to a sensor unit housing (26), wherein the sensor wheel receiving device (24) further comprises a centering element (30) which is configured to be received in a corresponding centering opening (32) of the steering rod housing (16), wherein the sensor wheel (21) is preloaded relative to the second gearing device (19) by means of a coil spring (33), wherein the sensor wheel receiving device (24) further comprises a locking element (38) which is configured to hold the sensor wheel (21) in a preloaded state.

Description

[0001] The present invention relates to a steering unit, in particular a steer-by-wire steering unit, for a vehicle. State of the art

[0002] Nowadays, both mechanical steering systems and steering units, as well as steer-by-wire systems, are common. Steering systems can be divided into two subsystems: the steering shaft system with a steering element, such as a steering wheel, also known as a "Hand Wheel Actuator" (HWA) system, and the steering actuator system for steering the wheels, also known as a "Road Wheel Actuator" (RWA) system. In mechanical steering systems, these two subsystems are mechanically connected via the steering column and, if applicable, a steering gear. Thus, in mechanical steering systems, the two subsystems are directly, i.e., physically, connected. Therefore, in these mechanical steering systems, a position of the steering element is always uniquely linked to a position of the steering actuator, in particular a steering rod.This means that a specific position of the steering element is uniquely assigned to a specific position of the steering rod, so that each position of the steering rod is assigned to a specific position of the steering element.

[0003] In steer-by-wire steering systems, the mechanical connection between the two subsystems via the steering column is eliminated. Instead, the steering of the wheels, corresponding to a movement of the steering element, is controlled by the transmission of corresponding signals between the two subsystems, HWA (heading and rear steering). In other words, steer-by-wire systems replace the physical steering column, which transmits the steering movement or driver input directly from the steering wheel to the wheel via the steering gear, tie rod, and wheel carrier, with an electrically redundant "by-wire" system, i.e., signal transmission via cable. This means that the position of the steering element is no longer physically linked to the position of the steering column. Therefore, with steer-by-wire systems, it is necessary to constantly know the absolute steering angle of the wheels or the position of the steering column. Since there is no mechanical connection to the steering wheel, the steering angle sensor on the steering column cannot be used for this purpose, as is the case, for example, with other systems.This is common with conventional EPS systems. A steering angle sensor on the steering shaft pinion is also (usually) not present in a steer-by-wire steering system. A loss of steering angle measurement leads, in the simplest case, only to a misalignment of the steering wheel, but in more serious cases to dangerous steering errors (especially with regard to driver assistance systems) or damage to mechanical components. Changes in the steering angle can also occur when the vehicle is switched off / without power (e.g., in a workshop). Therefore, a sensor or combination of sensors is required, usually integrated into the smoke and heat exhaust ventilation (SHEV) system, to absolutely determine the actual steering column position. Various sensor configurations are known, such as those described in DE 11 2020 002 949 T5 and DE 10 2021 212 470 A1. Depending on the application, customer requirements, and safety concept, high demands are placed on the functional safety and reliability of the sensor.In some cases, for redundancy reasons, a duplicate displacement sensor may be required to meet the requirements.

[0004] DE 10 2020 101 481 A1 discloses a steering system for a motor vehicle, designed as a steer-by-wire system. The system comprises a rack that is longitudinally displaceable by an electric drive, and a rotatably mounted support element that is spaced from the electric drive along the longitudinal axis of the rack. The rotatably mounted support element engages with the rack in a toothed mesh. These features enable precise control of the steering movements without a mechanical connection between the steering wheel and the wheels.

[0005] JPH1183415A discloses a cost-effective stroke detection device for a gear that is easy to assemble and suppresses the occurrence of errors. The device comprises a first bracket attached to a rack to transmit a steering force by axial movement, and a second bracket attached to a cylinder of a power steering gear. A rotary position detection sensor is provided, equipped with a rotating arm for detection on one side of the first and second brackets. Furthermore, engagement means are provided that are displaceable with the rotating arm along its length and engage axially along the rack shaft between the other side and the rotary position detection sensor.

[0006] JP H0729 413 U discloses a technical solution relating to [a brief description of the invention or the technical field, if known]. This disclosure includes, in particular, [important features or aspects of the invention described in claim 1]. The features described in JP H0729 413 U could be relevant for assessing the novelty and inventive step of the present application. Therefore, this prior art is analyzed in more detail below to evaluate its relevance to the claimed invention.

[0007] DE 20 2022 103 825 U1 discloses a steering system for a vehicle comprising a housing section, a rack section penetrating the housing section, a box section mounted within the housing section, and a sensor section. The sensor section is mounted within the box section and configured to detect the amount of movement of the rack section as it rotates and engages with the rack section. These features enable precise detection of the rack section's movement, which is important for controlling the steering system.

[0008] DE 10 2012 202 639 A1 discloses a sensor arrangement for detecting rotation angles on a rotating component in a vehicle. The arrangement comprises a measuring element coupled to a peripheral part of the rotating component and connected to a distance sensor to generate a signal representing the rotation angle of the rotating component. The measuring element acts as a motion converter, transforming the rotation of the component into a translation, with the sensor determining the distance traveled by the measuring element. The distance sensor can be designed as an eddy current sensor, a capacitive sensor, or an ultrasonic sensor.

[0009] US 5,353,004 A discloses a sensor for detecting a steering angle, comprising a steering shaft that is rotated by a steering wheel. The sensor includes a first shaft element connected to the steering shaft and a first potentiometer that generates initial steering angle information in the form of a voltage. Additionally, a second shaft element is connected to the first shaft element via a reduction gear, and a second potentiometer generates secondary steering angle information that corresponds one-to-one to the steering wheel's rotation angle.

[0010] WO 2023 / 002 779 A1 discloses a power steering device comprising several gears and angle sensors for precisely detecting the absolute angle of rotation of a rotating shaft. The device includes a first gear that rotates with the rotation of a rotating shaft element, as well as a second and third gear that rotate with the first gear and have different numbers of teeth. Each of the three gears is equipped with its own angle sensor that detects the respective angle of rotation. By combining the detected angles of rotation from the three sensors, the absolute angle of rotation of the rotating shaft is determined, thus preventing a deterioration in detection accuracy due to backlash.

[0011] DE 10 2022 209 105 A1 discloses a sensor device for a component, in particular a longitudinally displaceable component, preferably for a steering rod of a vehicle. The steering rod is driven by a wheel actuator of a steer-by-wire system, the wheel actuator controlling the steering rod according to a steering request. The sensor device comprises a housing for mounting on a transmission unit and a sensor unit for determining the position of the component, the sensor unit comprising a transmission element and a signal transmitter that is rotationally fixed to the transmission element in order to indicate the angle of the transmission element.

[0012] It has now become apparent that there is a further need to improve a known steering unit, in particular a steer-by-wire steering unit, for a vehicle. Specifically, there is a further need to provide a steering unit that allows the position of the steering column to be determined absolutely, and especially even after the vehicle has been switched off or without power.

[0013] Against this background, it is an object of the present invention to provide an improved steering unit, in particular a steer-by-wire steering unit, for a vehicle which in particular enables an absolute, and furthermore in particular constant, determination of the steering rod position. Disclosure of the invention

[0014] These and other problems, which will be mentioned in the following description or which can be recognized by a person skilled in the art, are solved by the subject matter of the independent claim. Advantageous embodiments and further developments can be found in the dependent claims and the following description.

[0015] The steering unit according to the invention, in particular a steer-by-wire steering unit, for a vehicle comprises a steering rod, an actuator, an anti-rotation device, and a sensor unit. The steering rod is configured to be coupled to a wheel of the vehicle at each of its axial ends, wherein the steering rod has at least a section of a toothed section, in particular a flattened section. The actuator is coupled to the steering rod such that a rotational movement of the actuator causes a translational movement of the steering rod to change its position along a predetermined steering rod travel path. The anti-rotation device for torque support of the steering rod comprises a first toothed element, in particular a first gear, and further in particular a pinion, which engages with the toothed section of the steering rod and is mounted axially fixed in a steering rod housing so as to be rotatable.The sensor unit for determining the position of the steering rod has at least one sensor arrangement for detecting the steering rod travel path, wherein the sensor arrangement has a sensor wheel that is coupled directly or indirectly to the first toothed device of the anti-rotation device in such a way that the sensor wheel rotates over the entire steering rod travel path by a predetermined angle, in particular an angle of less than 360°.

[0016] The gear engagement between the first gear of the anti-rotation device and the gear section of the steering rod is modeled on an anti-rotation device used in steering gears or steering units mechanically coupled to the steering wheel. Particularly in steer-by-wire steering units, this gear engagement is generally no longer necessary due to the elimination of the mechanical coupling between the steering wheel and steering gear. However, it is retained here as an anti-rotation device and supplemented with a coupling to the sensor assembly. The first gear, designed as a pinion, provides the necessary torque support for the steering rod, preventing it from rotating unintentionally, as is required, for example, when using a ball screw drive to convert the rotation of the actuator into a translation of the steering rod.

[0017] The term "directly or indirectly coupled" here means that the sensor wheel is coupled either directly, i.e., immediately, to the first gear element of the anti-rotation device, or indirectly, i.e., indirectly, in particular via another element. Specifically, "directly coupled" means that the sensor wheel and the first gear element are in direct engagement with each other. "Indirectly coupled" means, in particular, that the sensor wheel is in engagement with another element, which in turn is coupled to the first gear element. This other element can be a separate element from the anti-rotation device or an integral element of the anti-rotation device.

[0018] The anti-rotation device can further comprise a pressure piece arranged on the steering rod opposite the first toothed assembly. The pressure piece is, in particular, pre-tensioned against the steering rod and can thus ensure the tooth engagement between the first toothed assembly and the toothed section of the steering rod in essentially all operating positions of the steering rod. In particular, the pressure piece can prevent the steering rod from deflecting significantly in the area of ​​tooth engagement between the first toothed assembly and the toothed section of the steering rod due to external forces, such as those transmitted from the road to the steering rod via the tie rods.

[0019] The actuator, also known as a positioning actuator, is designed, for example, as an electric motor. An output shaft of the electric motor can be coupled to the steering rod via a conversion gear in such a way that the rotation, and in particular the torque, of the output shaft is converted into a translational movement, specifically an axially acting actuating force for moving the steering rod along its travel path. Furthermore, the actuator can include a power pack and a steering gear. It is also conceivable that the actuator incorporates hydraulic force amplification and / or control systems.

[0020] Furthermore, it is also conceivable to couple the actuator, particularly directly, with the first gearing element of the anti-rotation device in a torque-transmitting manner, thus achieving a conversion of the actuator's rotational movement into a translational movement of the steering rod via the gear mesh between the first gearing element of the anti-rotation device and the gear section of the steering rod. In other words, instead of a conversion gear with a wrap-around drive and ball screw, the axial movement of the steering rod is effected by driving the first gearing element. Due to the steering forces to be transmitted, two gearing elements, in particular two pinions, of which at least one is part of the anti-rotation device, are used. In particular, both gearing elements can each form part of an anti-rotation device.This means that in such a case, two anti-rotation devices can be provided, which further serve, in particular, as bearing points for the steering rods. In other words, one bearing point would be arranged at each axial end, i.e., left and right, of the steering rod.

[0021] The advantage of the solution according to the invention lies particularly in the fact that the movement of the steering rod along its longitudinal axis, i.e., the movement of the steering rod along the predetermined steering rod travel path, is detected with high accuracy. The conversion of the linear steering rod travel path into a rotation, particularly with an angle of less than 360°, of the sensor wheel enables a compact design of the sensor arrangement and thus of the sensor unit. This allows for position determination of the steering rod, especially absolute position determination, with reduced installation space, particularly compared to the use of linear displacement sensors. Since the movement of the steering rod along its entire travel path is detected as a rotation of the sensor wheel, it can be said that the position determination of the steering rod is implemented as directly as possible.Furthermore, the sensor unit also enables the determination of the absolute position of the steering rod, in particular by rotating the sensor wheel by less than 360° for the entire steering rod travel distance.

[0022] The total steering rod travel is defined as the path the steering rod travels when moving along its longitudinal axis from one maximum wheel deflection position (e.g., maximum possible wheel tilt to the left) to another maximum wheel deflection position (e.g., maximum possible wheel tilt to the right). Therefore, the total steering rod travel can also be referred to as the maximum steering rod travel.

[0023] In other words, the absolute position of the steering column can be determined with high accuracy using the sensor unit comprising the sensor array. Furthermore, strategies exist that, in combination with the steering motor's RPS signal, allow for precise determination of the steering column's absolute position even with relatively imprecise displacement measurement. However, precise direct measurement—that is, measurement solely via the sensor array—opens up new possibilities for steering angle control strategies. Currently, it is common practice to control the steering angle based on the angular position of the steering motor, assuming a primarily proportional relationship between the motor angle and the steering angle. However, belt stretch, bearing play, lead screw play, wear, etc., can lead to significant deviations between the calculated and actual steering column position.If a precise sensor signal of the actual steering rod position is available, the control system can be designed in such a way that a direct and therefore more accurate control of the steering rod position takes place.

[0024] Direct measurement means that linear path conversions are reduced, ideally minimized or even avoided altogether, because these conversions often lead to a series of tolerances that can negatively impact measurement accuracy. To reduce, minimize, or even eliminate these tolerances, the sensor assembly can be designed to be backlash-free and coupled to the steering rod, so that linear path conversions have minimal, ideally negligible or no, influence on measurement accuracy. Absolute position means that the absolute position of the steering rod can be determined at any given time from the measurement signal or a combination of several measurement signals, such as a signal from a rotor position sensor of the actuator (motor-RPS).In particular, so-called incremental measurement methods, which require a reference run or calibration to determine the absolute position for correct operation, are not desired in steering applications.

[0025] The compact design of the sensor assembly, and thus the sensor unit, offers a significant advantage over measurements with linear displacement sensors, as it can be used even in confined or limited installation spaces. Direct measurement of the steering rod position with linear displacement sensors is particularly challenging due to limited installation space, because in most methods the sensor length is at least equal to the measuring distance, i.e., the steering rod travel, but is usually considerably greater. Especially with steering actuators that have a large travel range, the available installation space—that is, the distance between the threaded drive and the opposite bearing point (e.g., pressure piece / plain bearing)—is smaller than the travel distance. Therefore, a directly measuring linear displacement sensor cannot be easily installed in such cases. The situation is similar on the steering rod itself.The free installation space between the thread and the opposing bearing surfaces is often even much smaller than the travel distance. In other words, the sensor unit described above and below can be designed compactly and therefore requires only a small installation space compared to other sensor units, especially those comprising linear displacement sensors.

[0026] In particular, the sensor unit can have a separate sensor unit housing, distinct from the steering rod housing, which can be easily attached to the steering rod housing from the outside. This requires only a small opening in the steering rod housing to couple the sensor wheel with the anti-rotation device. This avoids larger openings in the steering rod housing (e.g., long slots) and thus prevents weakening of the steering rod housing (otherwise, additional reinforcements, a solid cover, etc., would be necessary). Because the sensor assembly, especially the sensor wheel, is coupled to the steering rod via the anti-rotation device, deflection of the steering rod caused by external forces from the tie rods, which leads to radial displacement, particularly between the bearing points (threaded drive and plain bearing), has little to no effect on the measurement accuracy of the sensor assembly.Even a twisting of the steering rod around its longitudinal axis, which can be up to 4° under unfavorable conditions, is compensated for by the anti-rotation device to such an extent that the measuring accuracy of the sensor arrangement is only negligibly affected or not affected at all.

[0027] According to the invention, the anti-rotation device comprises a second gear element, in particular a second gear, which rotates together with the first gear element, the second gear element being in tooth engagement with the sensor wheel. This means that the first gear element and the second gear element are arranged on a common shaft, in particular integrally as a single piece, and thus form a stepped gear. The sensor wheel is therefore coupled to the steering rod via the anti-rotation device, i.e., via the stepped gear formed by the first and second gear elements, such that the sensor wheel rotates when the steering rod moves along its travel path. In particular, the second gear element can be described as an element formed integrally with the anti-rotation device.

[0028] According to the invention, the second gear assembly has a smaller pitch circle than the first gear assembly. In particular, the pitch circles of the first and second gear assemblies are selected such that the sensor wheel completes slightly less than one full rotation, i.e., slightly less than 360°, over the entire steering rod travel distance. This makes it possible to use even simple sensors, such as Hall sensors.

[0029] According to one embodiment, the sensor arrangement further comprises a sensor target mounted on the sensor wheel and a sensor configured to detect the sensor target, in particular its position. The sensor can be, in particular, a non-contact sensor, such as an inductive sensor, a Hall sensor, or a magnetoresistive sensor (xMR sensor). Non-contact sensors exhibit little to no susceptibility to wear and therefore offer higher reliability than contact sensors. In particular, the sensor target can be designed as a magnetic sensor located in the center of the sensor wheel, i.e., concentrically to the sensor wheel.The sensor, which is arranged essentially opposite and facing the magnetic encoder, can in particular be designed as a Hall sensor, which determines the angular position of the sensor wheel via the changing orientation of the magnetic field caused by the rotation of the sensor wheel (and thus of the sensor target). The sensor unit then determines the position of the steering rod based on the angular position of the sensor wheel.

[0030] According to the invention, the sensor arrangement further comprises a sensor wheel mounting device for rotatably coupling the sensor wheel to a steering rod housing. The sensor wheel mounting device makes it possible to pre-assemble a module comprising the sensor wheel and to arrange or mount it as a pre-assembled sub-assembly on the steering rod housing.

[0031] According to the invention, the sensor wheel receiving device has an opening for rotatably mounting the sensor wheel and is designed to be rigidly connected to a sensor assembly housing. In one embodiment, the sensor wheel receiving device further comprises a centering element, particularly a projecting one, e.g., a centering pin, which is designed to be received or inserted into a corresponding centering opening in the steering rod housing. In particular, the opening for rotatably mounting the sensor wheel can be located within the centering element, and furthermore, can be concentric with the centering element. By inserting the centering element into the corresponding centering opening of the steering rod housing, the correct axial distance between the sensor wheel and the second gear assembly can be ensured.In particular, the centering element and the centering opening are aligned such that the centering element is positively engaged and free of play within the centering opening. To attach the sensor wheel mounting device to the sensor unit housing, the sensor wheel mounting device can be longer, especially deeper, than the sensor wheel and thus project beyond it. This allows it to be firmly connected to the sensor unit housing, for example, by screws, by thermal deformation of mounting pins, or by adhesive bonding.

[0032] According to the invention, the sensor wheel is preloaded relative to the second gear assembly. In other words, the sensor wheel is arranged with no backlash relative to the second gear assembly. This prevents slippage, etc., due to backlash in the tooth engagement between the second gear assembly and the sensor wheel, thus ensuring high measuring accuracy of the sensor arrangement. According to one embodiment, the sensor wheel is preloaded relative to the second gear assembly by means of a coil spring. The coil spring is particularly cost-effective and easy to install. In particular, the coil spring can be axially fixed and torque-transmitting to the sensor wheel mounting device, and especially to the centering pin.

[0033] According to the invention, the sensor wheel receiving device further comprises a locking element designed to hold the sensor wheel in a pre-tensioned state, particularly during assembly. The locking element can also be referred to as a blocking element or a holding element. The locking element is, for example, located in the plane of the sensor wheel receiving device, in the form of an elastically deformable, in particular compressible, finger, and engages positively in the teeth of the sensor wheel. The sensor wheel is pre-set to the predetermined restoring torque, e.g., wound up by approximately 360°, in particular by more than 400°. The locking element is then bent axially and elastically into the underlying tooth gap of the sensor wheel teeth.The restoring preload of the coil spring now presses the tooth flank against the locking element, with contact friction preventing the finger from springing back to its starting position. After the sensor unit is mounted, the steering rod is actuated a short distance so that the sensor wheel is further wound up via the stepped gearing, i.e., the first and second gearing sections. This immediately releases the locking element, causing it to fully disengage and return to its starting position. The sensor unit, and in particular the sensor assembly, is now free and ready for operation. It should be noted that the use of the teeth is merely an example. The locking element can also engage at other points, such as a designated undercut on the sensor wheel. In this case, the springback is independent of contact friction.Furthermore, it is also conceivable that the locking element is released mechanically, for example, by providing a projection, such as a cam. The projection is specifically provided extending from the steering rod housing, and the locking element is released when, during the mounting of the sensor unit to the steering rod housing, the projection presses against the locking element, thereby returning it to its initial position. In other words, the projection is positioned on the steering rod housing such that the release of the locking element occurs due to the projection's orientation, particularly axially to the sensor or anti-rotation device axis, during the positioning of the locking element onto the projection.

[0034] According to one embodiment, the sensor unit for determining the position of the steering rod is configured to determine the steering rod's position based on the position of the sensor wheel detected by the sensor. The gear ratio of the stepped toothing is specifically selected such that the rotation of the sensor wheel for the entire steering rod travel distance is less than 360°. This allows for precise and absolute determination of the steering rod's position, even using relatively simple sensors such as Hall effect sensors. Therefore, it can be said that the sensor unit for determining the steering rod's position, particularly its absolute position, generally operates autonomously and can determine the steering rod's position with sufficiently high accuracy, resolution, and reliability, essentially on its own, and output it as a signal.

[0035] According to one embodiment, the sensor unit further comprises a position sensor, in particular a rotor position sensor, for detecting the rotational position of the actuator. The rotor position sensor typically provides a highly precise signal corresponding to an electrical or mechanical angle of the rotor, which is required for controlling the actuator, particularly in the form of an electric motor.

[0036] The angle of the rotor is highly proportional to the position of the steering rod, usually about 2-5 mm / rev, but - considered on its own - does not allow a determination of the absolute position of the steering rod, since the angle of the rotor completes several full revolutions over the entire travel distance of the steering rod, i.e., over the entire steering rod travel distance, e.g. on the order of about 20-100 revolutions.

[0037] According to one embodiment, the sensor unit for determining the position of the steering rod is further configured to determine the steering rod's position based on the position of the sensor wheel detected by the sensor and the rotational position of the actuator detected by the position sensor. The combination of the output signal from the sensor arrangement for detecting the steering rod position with the signal from the rotor position sensor of the actuator enables precise position determination of the steering rod, in particular its absolute position. In this case, the sensor arrangement only needs to have a low resolution or accuracy, since it only needs to perform a rough determination of the steering rod's position, while the rotor position sensor provides the high resolution or accuracy, i.e., the decimal places. Such a combination can make it possible to further improve the resolution and accuracy.

[0038] Furthermore, the costs for the sensor array, and thus for the steering unit, can be reduced because the requirements placed on the sensor array are lower than in a case where the sensor array alone, i.e., independently, must provide the high accuracy or resolution. For example, precise, especially absolute, determination of the steering rod position in combination with the rotor position sensor is also possible if the rotation of the sensor wheel over the entire steering rod travel is equal to or greater than 360°. Even if the rotor position sensor fails during operation, it is possible to control the actuator temporarily using the signal from the sensor array, even if the resolution or accuracy of the sensor array with respect to the angle of the actuator's rotor is rather low.Conversely, it is also possible to compensate for a failure of the sensor arrangement for determining the position of the steering rod during operation by incrementally “counting” the signal of the rotor position sensor, especially at least as long as a current supply to the rotor position sensor and, if applicable, an associated control unit is ensured. Detailed description based on drawing

[0039] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to the figures. The figures show: Fig. 1 a schematic sectional view of a steering unit according to an embodiment of the invention, Fig. 2 a schematic partial representation of a steering unit according to an embodiment of the invention in a side view, Fig. 3 a schematic partial representation of a sensor unit according to an embodiment of the invention in a sectional view, and Fig. 4 schematic partial representations of a sensor unit according to an embodiment of the invention in a longitudinal section view (a) and a top view (b).

[0040] The figures are purely schematic and serve only to illustrate the invention. The same elements are identified by the same reference symbols.

[0041] Fig. 1, Fig. 2, Fig. 3 to Fig. Figure 4 shows a schematic and exemplary representation of a steering unit 1 or partial representations of the steering unit 1 according to an embodiment of the invention, wherein the steering unit 1 is here exemplified as a steer-by-wire steering unit. Although not everything is shown in every figure, the steering unit 1 comprises a steering rod 2, an actuator (not shown), an anti-rotation device 3 for torque support of the steering rod 2, and a sensor unit 4 for determining the position of the steering rod 2.

[0042] As in Fig. As can be clearly seen, the steering rod 2 has a flat toothed section 5, which is formed in a flattened area 6 of the essentially round steering rod 2 and can therefore also be referred to as a flattened toothed section. The steering rod can be coupled to the wheels of a vehicle at its axial ends 7, 8 and is arranged to be movable along its longitudinal axis L for a predetermined steering rod travel path 9. To move the steering rod 2 along the steering rod travel path 9, the steering rod 2 is coupled to an actuator (not shown here) such that a rotational movement of the actuator causes a translational movement of the steering rod 2 to change its position along the predetermined steering rod travel path 9.

[0043] With reference to Fig. In Figure 1, the anti-rotation device 3 for torque support of the steering rod 2 comprises a first gearing device 10 and a pressure piece 11. The first gearing device 10 engages with the toothed section 5 of the steering rod 2. The pressure piece 11 is arranged on an outer circumferential surface of the steering rod 2 opposite the flattened area 6 of the steering rod and is mounted against the steering rod 2 with a predetermined preload by means of a spring element 12 and an adjusting screw 13. The first gearing device 10 is shown here by way of example as a pinion 14, which is integrally formed in one piece with a shaft 15. The shaft 15 is rotatably but axially fixed in a steering rod housing 16, here by way of example by a needle bearing 17 and a ball bearing 18.At one axial end of the shaft 15, a second gearing element 19 is formed, in particular integrally as a single piece, wherein the second gearing element 19 has a smaller pitch circle than the first gearing element 10 and projects at least partially, in particular completely, from the steering rod housing 16. Thus, the shaft 15, the first gearing element 10, and the second gearing element 19 form a stepped gearing. Not shown in the figures, but conceivable, it is possible to form the first gearing element 10 and / or the second gearing element 19 separately from the shaft 15 and to arrange them on the shaft 15 in a rotationally and axially fixed manner. The second gearing element 19 is shown here by way of example as a gear 20.

[0044] The sensor unit 4, as in Fig. Figure 1 shows an example of a sensor wheel 21, a sensor target 22, a sensor 23, and a sensor wheel mounting device 24. The sensor wheel 21, the sensor target 22, and the sensor 23 can also be referred to together as a sensor assembly 25 for detecting the steering rod travel 9. The sensor unit 4 is at least partially enclosed by a sensor unit housing 26, wherein the sensor assembly can be pre-assembled in the sensor unit housing 26 and arranged as a pre-assembled sub-assembly together with the sensor housing 26 on the steering rod housing 16. This avoids the need for complex modification of the steering rod housing 16. The sensor wheel 21 has an external toothing 27 which engages with the second toothing device 19 of the anti-rotation device 3. The sensor target 22 is designed as a magnetic encoder and is arranged concentrically to the sensor wheel 21.The sensor 23 is designed as a Hall sensor, which is arranged on a circuit board 28 that is rigidly connected to the sensor unit housing 26. The sensor unit housing 26 is made of a plastic, such as a single-material plastic, a plastic mixture, or a fiber-reinforced plastic or a fiber-reinforced plastic mixture, whereas the steering rod housing 16 is made of a metal, more specifically aluminum or an aluminum alloy. If required for EMC compatibility, metallic shielding would be necessary. For example, the sensor unit housing 26 could be made of metal, e.g., die-cast aluminum, or a suitable additional film could be inserted between the sensor unit housing 26 and the circuit board 28. It is also possible to spray the inside of the sensor unit housing 26 with a shielding lacquer.

[0045] The sensor wheel receiving device 24 is parallel in an extension direction to the longitudinal axis L of the steering rod 2 (in Fig. 1 the direction into the plane of the leaf, into Fig. 4(b) the left-right direction) longer than the sensor wheel 21 and fixed, here exemplified by thermal deformation of receiving pins 29 (see Fig. 3 and Fig. 4), which are integrally formed in one piece with the sensor unit housing 26, are firmly connected to the sensor unit housing 26. The sensor wheel receiving device 24 has a centering pin 30 which has a cavity 31, the cavity 31 serving for the rotatable mounting of the sensor wheel 21. During assembly of the sensor unit 4, the centering pin 30 is inserted into a corresponding centering opening 32 formed on the steering rod housing 16 (see Fig. 1), which is designed in particular as a centering bore. This ensures the correct axial distance of the sensor wheel 21 with the second gearing device 19.

[0046] As particularly in Fig. 1 and Fig. As can be seen in Figure 3, the sensor wheel is coupled to the steering rod 2 via the stepped gearing formed by the first gearing element 10 and the second gearing element 19, such that a movement of the steering rod 2 along the steering rod travel path 9 is converted into a rotation of the sensor wheel 21. The gear ratio of the stepped gearing is selected such that the sensor wheel 21 performs a predetermined rotation, in particular of less than 360°, over the entire steering rod travel path 9. The ratio of the stepped gearing, i.e., the ratio of the pitch circles of the first gearing element 10 and the second gearing element 19, is selected, in particular, depending on the steering rod travel path 9 and / or the design of the gear section 5 of the steering rod, and thus also on the design of the first gearing element 10. The design of the gearing is also referred to as the "coarseness of the gearing".In particular, a gear ratio of 3:1, further in particular of 3.5:1, and further in particular of 4:1, is selected for the first gearing device 10 to the sensor wheel 21. The gear ratio 4:1 means that for one complete revolution of the sensor wheel 21, the first gearing device 10 makes four complete revolutions.

[0047] When the sensor wheel 21 rotates, the sensor target 22, designed as a magnetic encoder, also rotates, which is detected as a change in the magnetic field by the Hall sensor 23. Detecting the angular position of the sensor wheel 21 enables the determination of the position of the steering rod 2 along its travel path 9.

[0048] To increase the measuring accuracy of the sensor arrangement 25, the gear mesh between the sensor wheel 21 and the second gearing device 19 is, in particular, backlash-free. The backlash-free operation is described here (see Fig. 1 and Fig. 2) achieved by mounting the sensor wheel 21 on the sensor wheel mounting device 24 with a preload from a coil spring 33. As in Fig. As can be seen in Figure 2, one end 34 of the spiral spring 33, in particular an inner end, is axially fixed to the sensor receiving device 24 via a positive-locking connection area 35. The other end 36 of the spiral spring 33, in particular an outer end, is also axially fixed to the sensor wheel 21, in particular via a positive-locking connection area 37.

[0049] As in Fig.As shown in Figure 4(b), the sensor wheel receiving device 24 further includes, by way of example, a locking element 38, which here is designed in the form of an elastically bendable locking finger 39. The locking finger 39 can, by way of example, be pressed into the plane of the blade and engage there in a positive-locking manner with the external teeth 27 of the sensor wheel 21. This allows for easy mounting of the sensor unit 4 to the steering rod housing 16. For this purpose, the sensor wheel 21 is set to the specified restoring torque, e.g., "wound" 360° in the direction indicated by arrow P1. The locking finger 39 is then bent axially and elastically into the tooth gap of the external teeth 27 of the sensor wheel 21 below (here into the plane of the blade).Due to the restoring preload torque, a corresponding tooth flank now presses against the locking finger 39, whereby the contact friction between this tooth flank and the locking finger 29 prevents the locking finger 39 from springing back to its initial position on its own. The sensor unit 4 is mounted in this position held by the locking finger 39. After the sensor unit 4 is mounted, the steering rod 2 is actuated a short distance so that the sensor wheel 21 is wound further via the first gearing element 10 and the second gearing element 19. This releases the locking finger 39, allowing it to fully disengage and spring back to its initial position. In this state, the steering unit 1, and in particular the sensor unit 4, is ready for operation. Reference symbol list 1 steering unit 2 handlebars 3 Anti-rotation device 4 sensor units 5 Gear section 6 flattened area 7 axial end 8 axial end 9 Steering rod travel 10 first gearing device 11 Printed piece 12 spring element 13 Adjusting screw 14 sprockets 15 wave 16 steering rod housings 17 needle bearings 18 ball bearings 19 second gearing device 20 gear 21 Sensor wheel 22 Sensor target 23 Sensor 24 Sensor wheel recording device 25 Sensor arrangement 26 Sensor unit housing 27 External teeth 28 circuit boards 29 Recording pen 30 Centering pin 31 Cavity 32 Centering opening 33 spiral spring 34 End of the spiral spring 35 positive locking connection area 36 End of the spiral spring 37 Form-fitting connection area 38 Locking element 39 locking fingers

Claims

Steering unit (1), in particular a steer-by-wire steering unit, for a vehicle, comprising: a steering rod (2) configured to be coupled to a wheel of the vehicle at each of its axial ends (7, 8), wherein the steering rod (2) has at least a section with a toothed section (5), an actuator coupled to the steering rod (2) such that a rotational movement of the actuator causes a translational movement of the steering rod (2) to change the position of the steering rod (2) along a predetermined steering rod travel path (9), an anti-rotation device (3) for torque support of the steering rod (2), and a sensor unit (4) for determining the position of the steering rod (2), wherein the anti-rotation device (3) has a first toothed element (10) which engages with the toothed section (5) of the steering rod (2) and is axially fixed and rotatable in a steering rod housing (16).wherein the sensor unit (4) has at least one sensor arrangement (25) for detecting the steering rod travel (9), wherein the sensor arrangement (25) has a sensor wheel (21) which is coupled directly or indirectly to the first toothed assembly (10) of the anti-rotation device (3) such that the sensor wheel (21) rotates by a predetermined angle over the entire steering rod travel (9), characterized in that the anti-rotation device (3) has a second toothed assembly (19) which rotates together with the first toothed assembly (10), wherein the second toothed assembly (19) is in engagement with the sensor wheel (21), wherein the second toothed assembly (19) has a smaller pitch circle than the first toothed assembly (10), wherein the sensor arrangement (25) further comprises a sensor wheel receiving device (24) for rotatably coupling the sensor wheel (21) with the steering rod housing (16) exhibitswherein the sensor wheel receiving device (24) has an opening (31) for rotatably mounting the sensor wheel (21) and is configured to be fixedly connected to a sensor unit housing (26), wherein the sensor wheel receiving device (24) further comprises a centering element (30) which is configured to be received in a corresponding centering opening (32) of the steering rod housing (16), wherein the sensor wheel (21) is preloaded relative to the second gearing device (19) by means of a coil spring (33), wherein the sensor wheel receiving device (24) further comprises a locking element (38) which is configured to hold the sensor wheel (21) in a preloaded state. Steering unit (1) according to claim 1, wherein the sensor arrangement (25) further comprises a sensor target (22) arranged on the sensor wheel (21) and a sensor (23) configured to detect the sensor target (22). Steering unit (1) according to one of claims 1 or 2, wherein the sensor unit (4) further comprises a position sensor for detecting a rotational position of the actuator.

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