Sensor unit for steering unit, and steering unit

Abstract

The invention relates to a sensor unit (6) for ascertaining a force-feedback signal for a steering unit (2), in particular a steer-by-wire steering unit (2), of a vehicle, comprising: a ball screw nut (8) which is designed to be couplable to a spindle portion (12) of a steering rod (3) of the steering unit (2) so as to transmit a load, a driver element (7) which is coaxial to the ball screw nut (8) and can be rotated relative thereto and which is designed to be couplable to an actuator (4) of the steering unit (2) so as to transmit a load, a sensor device (10) for detecting a relative rotation between the driver element (7) and the ball screw nut (8), and a restoring element (9) which is provided between the ball screw nut (8) and the driver element (7) and which is designed to generate a restoring torque in order to restore the driver element (7) and / or the ball screw nut (8) to a neutral position (15) in the event of a relative rotation between the driver element (7) and the ball screw nut (8).

Description

[0001] Sensor unit for steering unit and steering unit

[0002] The present invention relates to a sensor unit for determining a force feedback for a steering unit, in particular a steer-by-wire steering unit, of a vehicle, such as a passenger car, a truck or another commercial vehicle, as well as a steering unit, in particular a steer-by-wire steering unit, for a vehicle, such as a passenger car, a truck or another commercial vehicle.

[0003] State of the art

[0004] Today, both mechanical steering systems or steering units and so-called steer-by-wire steering systems or steering units are known. Steering systems can be divided into two subsystems: the steering shaft system with a steering element, such as a steering wheel, which is also referred to as a "hand wheel actuator" (HWA) system, and the steering actuator system for steering the wheels, which is also referred to as a "road wheel actuator" (RWA) system. In mechanical steering systems, these two subsystems are mechanically connected via the steering column and, if necessary, a steering gear. Thus, in mechanical steering systems, the two subsystems are directly, i.e., physically, connected. Thus, when operating the steering element in mechanical steering systems, a user or operator always experiences a noticeable resonance, known as force feedback, in the form of noticeable resistance on the steering element, for example when cornering, hitting a curb, etc., but also regarding the condition of the road surface, etc.

[0005] In steer-by-wire steering systems, the mechanical connection between the two subsystems via the steering column is dispensed with, and the steering of the wheels, in response to movement of the steering element, is controlled by transmitting corresponding signals between the two subsystems, HWA and RWA. In other words, with steer-by-wire steering systems, the physical steering column, which transmits the "input signals" or driver inputs from the steering wheel directly via the steering gear, tie rod, and wheel carrier to the wheel, is replaced by electrically redundant "by wire," i.e., signal transmission via cable. Conversely, in line with the signal transmission from the driver to the wheels, the driver also needs information or feedback, the so-called force feedback, from the wheels to the steering wheel. Force feedback systems, e.g., force feedback actuators, are currently commonly used for this purpose, for example, to measure (steering) restoring torques, road surface conditions such as slippery surfaces, potholes, etc., tire slip, etc., to be made perceptible to the driver again via the steering element on a mechatronic basis. Various sensor units are known for detecting or determining force feedback on the steering element. For example, the current required to energize the actuator on the steering gear unit to maintain the desired steering position can be used as a force feedback signal, since the magnitude of the electrical current is essentially linear to the torque applied by the actuator. DE 10 2020 212 557 A1 describes an inductive sensor combination for axially parallel driven steering systems, which enables the determination of an absolute position and / or the determination of a force from the belt stretch. US 10,962,429 B2 describes a method for estimating steering force on the RWA system by determining a differential travel on the elastic reduction gear, and US 11,279,398 B2 describes the use of a torsion bar sensor.

[0006] It has now become apparent that there is a further need to improve a known sensor unit for determining force feedback, in particular a force feedback signal, for a steering unit, in particular for a steer-by-wire steering unit, of a vehicle. In particular, there is a further need to provide a sensor unit for determining force feedback, in particular a force feedback signal, for a steering unit, in particular for a steer-by-wire steering unit, which enables improved, in particular more detailed, force feedback.

[0007] Against this background, it is an object of the present invention to provide an improved sensor unit for determining a force feedback, in particular a force feedback signal for a steering unit, in particular for a steer-by-wire steering unit, of a vehicle, which in particular enables an improved, in particular more detailed, force feedback.

[0008] Disclosure of the invention

[0009] These and other objects, which will be mentioned upon reading the following description or which can 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 subclaims and the following description. The sensor unit according to the invention for determining a force feedback, in particular a force feedback signal for a steering unit, in particular a steer-by-wire steering unit, of a vehicle comprises a ball screw nut, a driver element, a sensor device and a return element. The ball screw nut is designed to be coupled to a spindle section of a steering rod of the steering unit in a load-transmitting manner. The driver element is arranged coaxially to the ball screw nut and rotatable relative thereto, and is designed to be coupled to an actuator of the steering unit in a load-transmitting manner.The sensor device is used to detect a relative rotation between the driver element and the ball screw nut. The return element is provided between the ball screw nut and the driver element and is configured to generate a return torque for returning the driver element and / or the ball screw nut to a neutral position upon the relative rotation between the driver element and the ball screw nut.

[0010] The ball screw nut is part of a linear drive, particularly a ball screw drive, for converting rotational motion into translational motion. Alternatively, other linear drive types are also conceivable, e.g., a trapezoidal screw drive, a planetary roller screw drive, etc.

[0011] The driver element is to be understood as a generic term for elements that can be arranged coaxially to the ball screw nut, rotatable relative to it, and which can also be coupled to the actuator in a load-transmitting manner. For example, the driver element can be designed as a driver disk or a driver sleeve, with or without circumferential toothing, in particular circumferential external toothing. For example, the driver element can be designed as a pulley that is configured to be coupled to the actuator in a torque-transmitting manner via a belt. In particular, the driver element can be arranged radially outside the ball screw nut. Alternatively, the driver element can be arranged adjacent to the ball screw nut in the axial direction.

[0012] The return element is provided between the ball screw nut and the driver element in such a way that the relative rotation between the ball screw nut and the driver element is limited to a predetermined angular extent, e.g., a predetermined degree, by the return torque, or alternatively by a return force. If the driver element is rotated beyond this predetermined angular extent, the ball screw nut is also rotated via the return element due to its coupling with the driver element, and vice versa. In a load-free state, the return torque returns the driver element and / or the ball screw nut to the neutral position, i.e., to a relaxed, in particular load-free, state of the return torque.In other words, one can say that the restoring torque limits the relative rotation between the ball screw nut and the driver element and, if the maximum relative rotation is exceeded, the ball screw nut and the driver element are coupled in a rotationally fixed manner.

[0013] The advantage of the solution according to the invention lies in the fact that the sensor unit detects the relative rotation between the driver element and the ball screw nut, allowing the currently applied torque to be determined. This means that the sensor unit makes it possible to determine forces and / or torques originating from the road surface, in particular rapid and / or short torque pulses, and thus to improve the force feedback that a driver of the vehicle perceives on a steering element, making it more authentic. The steering feel in vehicles with a mechanical, and thus direct, connection between the wheels to be steered and the steering element is considered the "benchmark" or original for the steering feel perceived by the driver on a steering element.

[0014] Some forces and / or moments acting from the road onto the wheels to be steered and thus onto the steering rod, in particular fast and / or short torque impulses, are filtered by an inertia in the previously known, non-mechanically coupled systems, e.g. by an inertial mass of a rotor of the actuator designed as an electric motor, whereby the feedback signal is unintentionally smoothed to a certain extent.

[0015] The sensor unit according to the invention is provided in particular between the steering rod and the actuator in order to detect or determine these, in particular fast and / or short, moments and / or forces by detecting the relative rotation between the driver element and the ball screw nut and thus to achieve a more detailed force feedback signal quality.

[0016] One could also say that the sensor unit is designed as a sensor unit for torque detection (torque sensor unit) arranged between the actuator and the steering rod. According to one embodiment, the sensor device is configured to output a signal based on the relative rotation detected between the driver element and the ball screw nut. The output signal is transmitted, for example, to a central control unit, which is configured to determine the torque based on the received signal and to output a control signal corresponding to the torque to a control unit for controlling a force feedback system on the steering element.Alternatively, it is also conceivable for the sensor unit to further comprise a control unit that determines the torque based on the signal output by the sensor device and outputs a control signal based thereon to the control unit for controlling the force feedback system. Further alternatively, it is conceivable for the signal output by the sensor device to be received directly by the control unit for controlling the force feedback system, which converts it into a corresponding signal required to control the force feedback system.

[0017] According to one embodiment, the sensor device comprises at least one multipole magnetic ring, a pole plate pair device, in particular an annular one, and a fixed sensor, e.g., fixed to the housing, for detecting a change in the magnetic field. The multipole magnetic ring is rotationally fixedly coupled, in particular directly or indirectly, to one of the ball screw nut and the driver element, and the pole plate pair device is rotationally fixedly coupled, in particular directly or indirectly, to the other of the ball screw nut and the driver element.The pole plate pair device has two pole plate rings which form a circumferential air gap between them, in which the sensor is arranged at least partially, in particular without contact, wherein the sensor is designed to detect a change in a magnetic field formed between the pole plate rings caused by the relative rotation between the ball screw nut and the driver element, and thus the relative rotation between the magnetic ring and the pole plate pair device.

[0018] This means that the multi-pole magnetic ring is either rotationally fixed to the ball screw nut or rotationally fixed to the driver element, in particular directly or indirectly, and the pole plate pair device is rotationally fixed to the other component, in particular directly or indirectly. The coupling can be selected depending, among other things, on the available installation space for the sensor unit. The magnetic field changes depending on the relative positioning of the multi-pole magnetic ring and the pole plate pair device. The change in the magnetic field detected by the sensor can thus be used to determine the relative rotation between the driver element and the ball screw nut, and from this to determine the applied torque. The detection of the change in the magnetic field is, in particular, contact-free, which prevents a deterioration in the measuring accuracy of the sensor due to wear, e.g., due to contact friction, etc.

[0019] According to one embodiment, the circumferential air gap formed by the pole plate pair device is designed as an annular circumferential, axial air gap or as an annular circumferential, radial air gap. With the annular circumferential, axial air gap, it is possible to position the sensor in the axial direction adjacent to the pole plate pair device such that it protrudes at least partially into the air gap in the axial direction. This makes it possible, in particular, to reduce the radial installation space for the sensor unit, in particular to keep it as small as possible. With an annular circumferential, radial air gap, the multi-pole magnetic ring is generally arranged radially inside the pole plate pair device and the radial air gap is open radially outwards, such that the sensor is arranged protruding at least partially into the air gap from the radial outside.This makes it possible, in particular, to reduce the axial installation space for the sensor unit, in particular to keep it as small as possible. If the magnetic ring is arranged radially within the pole plate pair device, the magnetic ring is typically non-rotatably coupled to the ball screw nut, and the pole plate pair device is typically non-rotatably coupled to the driver element.

[0020] According to one embodiment, the sensor device further comprises a fixed sensor PCB, e.g., one fixed to the housing, for determining or detecting an angular position of the driver element and a sensor target, e.g., a target plate, an impeller, an annular target PCB, etc., wherein the sensor target is rotationally fixedly coupled to the driver element, in particular directly or indirectly, and is configured to interact with the sensor PCB to determine or detect the angular position. Thus, it is possible, in particular through constant comparison with a rotor position signal of the actuator, to detect discontinuities, e.g., belt slippage, tooth jump, etc.

[0021] According to one embodiment, the sensor unit further comprises end stops for limiting the relative rotation between the ball screw nut and the driver element. The end stops serve, in particular, to protect the return element from plastic deformation and / or damage / breakage due to exceptionally high forces and / or moments, particularly those that are too high for the return element. Exceptionally high forces and / or moments can be caused, for example, by large potholes, driving against an obstacle, e.g., a curb, etc.

[0022] According to one embodiment, the return element is designed as a spring element. With a spring element, the return force or the return moment can be defined by means of the spring constant. For example, the spring element can be designed as a wrap spring, a compression spring, an arrangement of several small compression springs, or an elastomer element. Alternatively, it is also conceivable to design the return element as a ball-ramp mechanism or as a claw clutch mechanism.

[0023] According to one embodiment, the spring element is designed as a, in particular pot-shaped, spring finger plate that is non-rotatably coupled to the ball screw nut. The spring finger plate has an annular disk-shaped base plate and a plurality of spring fingers that are arranged on the base plate along its circumference, in particular substantially evenly distributed, and extend in the axial direction. The free ends can also be referred to as spring finger heads. In particular, the spring finger heads have a convex shape because the spring fingers elastically deform under load, i.e., during relative rotation between the ball screw nut and the driver element, and thus cause pivoting movements at the spring finger heads. The spring fingers of the pot-shaped spring finger plate can be arranged between the ball screw nut and the driver element, viewed in the radial direction.The spring finger plate therefore represents a particularly space-saving variant for the return element.

[0024] According to one embodiment, the sensor unit further comprises a preload element configured to preload the driver element and the spring finger plate in the axial direction. This allows any play that may occur, for example, due to tolerances, to be compensated or avoided. It can therefore be said that the driver element and the spring finger plate are arranged axially free of play relative to one another. This prevents unwanted noises, such as rattling or clattering.

[0025] According to one embodiment, the prestressing element is designed as a disc spring.

[0026] The disc spring can be arranged, particularly in the axial direction, between the driver element and the annular disk-shaped base plate of the spring finger plate. Since the disc spring can rotate relative to the driver element during operation, a non-metallic friction ring, e.g., made of a plastic, is provided between the driver element and the disc spring to prevent metal-to-metal contact.

[0027] According to one embodiment, the sensor unit further comprises a plain bearing configured to rotatably mount the driver element relative to the ball screw nut. The plain bearing can, for example, be arranged as a plain bearing sleeve in the radial direction between the driver element and the ball screw nut, thus enabling a particularly space-saving arrangement or assembly of the sensor unit. Alternatively, it is also conceivable to mount the driver element rotatably relative to the ball screw nut in a housing of the steering unit. A further alternative is to use a rolling bearing instead of the plain bearing.

[0028] A further aspect of the invention relates to a steering unit, in particular a steer-by-wire steering unit, for a vehicle, comprising a handlebar, a control actuator, a sensor unit, in particular according to the invention, and a steering element. The handlebar is configured to be coupled to a wheel of the vehicle at each of its axial ends. The control actuator is coupled to the handlebar such that a rotational movement of the control actuator causes a translational movement of the handlebar. The driver element of the sensor unit is coupled to the control actuator in a load-transmitting manner, and the ball screw nut of the sensor unit is coupled to a spindle section of the handlebar in a load-transmitting manner. The steering element has a force feedback system that serves to generate force feedback on the steering element based at least on the force feedback signal output by the sensor device of the sensor unit.

[0029] The steering rod, the actuator, and the sensor unit can be summarized under the term steering gear or road wheel actuator (RWA) system. The actuator is used to move the steering rod along its longitudinal axis and thus change and / or maintain the wheel position of the wheels to be steered, which are coupled to the steering rod. The actuator is designed, in particular, as an electric motor and is controlled via a control unit. The steering element with the force feedback system can also be referred to as a steering unit or a hand wheel actuator (HWA) system. The steering element is designed, for example, as a steering wheel and serves a vehicle driver to perform steering movements. The steering movements performed on the steering element are transmitted to the steering gear, in particular the control unit for controlling the actuator, where they are implemented accordingly by means of the actuator on the steering rod.Conversely, the force feedback detected by the sensor unit is transmitted as a corresponding signal to the steering unit, in particular to the force feedback system, and is implemented accordingly by the force feedback system on the steering element in order to give the driver the most authentic steering feel possible.

[0030] Detailed description based on drawing

[0031] Further measures improving the invention are described in more detail below, together with the description of preferred embodiments of the invention, with reference to the figures. It shows:

[0032] Fig. 1 is a schematic representation of a steering gear of a steering unit according to an embodiment of the invention,

[0033] Fig. 2 is a schematic partial representation of a steering gear with a sensor unit according to an embodiment of the invention in a perspective view,

[0034] Fig. 3 is a schematic partial representation of a steering gear with a sensor unit according to an embodiment of the invention in an exploded view,

[0035] Fig. 4 is a schematic partial representation of a steering gear with a sensor unit according to an embodiment of the invention in an exploded view,

[0036] Fig. 5 schematic representations of a partial assembly of a sensor unit according to an embodiment to illustrate a first assembly step,

[0037] Fig. 6 schematic representations of a partial assembly of a sensor unit according to an embodiment of the invention to illustrate a further assembly step,

[0038] Fig. 7 schematic representations of partial sections to illustrate an axial preload of components of a sensor unit according to an embodiment of the invention,

[0039] Fig. 8 schematic representations of a partial assembly of a sensor unit according to an embodiment of the invention to illustrate a further assembly step,

[0040] Fig. 9 is a schematic representation of a magnetic ring of a sensor unit according to an embodiment of the invention in a perspective view from behind, Fig. 10 is a schematic representation of a partial assembly of a sensor unit according to an embodiment of the invention to illustrate a further assembly step,

[0041] Fig. 11 schematic representations of a partial assembly of a sensor unit according to an embodiment of the invention to illustrate a further assembly step,

[0042] Fig. 12 schematic representations of a pole plate pair device of a sensor unit according to an embodiment of the invention,

[0043] Fig. 13 schematic representations of a partial assembly of a sensor unit according to an embodiment of the invention to illustrate a further assembly step,

[0044] Fig. 14 is a schematic representation of a partial section of a steering gear to illustrate an arrangement of a sensor unit according to an embodiment of the invention in a housing,

[0045] Fig. 15 schematic representations of a partial section of a steering gear to illustrate the mounting of a sensor unit according to an embodiment of the invention in a housing,

[0046] Fig. 16 schematic representations of a spring finger plate of a sensor unit according to an embodiment of the invention,

[0047] Fig. 17 is a schematic representation of a subassembly of a sensor unit according to an embodiment of the invention,

[0048] Fig. 18 is a schematic representation of a subassembly of a sensor unit according to an embodiment of the invention, and

[0049] Fig. 19 is a schematic block diagram of a steering unit according to an embodiment of the invention.

[0050] The figures are merely schematic, not to scale, and serve only to clarify the invention. Identical elements are designated by the same reference numerals.

[0051] Fig. 1 shows schematically and by way of example a steering gear 1 of a steering unit 2 (see also Fig. 19) according to an embodiment of the invention. The steering gear 1 comprises a steering rod 3, a control actuator 4, of which only a drive wheel 5 is shown in Fig. 1, and a sensor unit 6. The sensor unit 6 comprises a driver element 7, a ball screw nut 8, a return element 9, and a sensor device 10 (see, for example, Fig. 2). The driver element

[0052] 7 is coupled here, for example, via a belt 11 in a torque-transmitting manner to the actuating actuator 4, and the ball screw nut 8 is coupled to the handlebar 3, more precisely to a spindle section 12 of the handlebar 3, in a load-transmitting manner, so that a rotation of the ball screw nut 8 causes a translational movement of the handlebar 3 along its longitudinal axis L. The return element 9 is designed here, for example, as a spring element 13 which is arranged between the ball screw nut 8 and the driver element 7 in such a way that it generates a return torque upon relative rotation between the ball screw nut 8 and the driver element 7.

[0053] In addition, end stops 14 are provided in Fig. 1 for the spring element 13, which limits the relative rotation between the ball screw nut 8 and the driver element 7 to an angular range of 2α, where α corresponds to a predetermined maximum torsion angle, i.e. the maximum permissible relative rotation between the driver element 7 and the ball screw nut 8, from a neutral position 15 of the spring element 13 in one or the other direction of rotation. The end stops 14 protect the spring element 13 during operation from plastic deformation and / or damage due to excessively high loads, e.g. due to high moments caused by large potholes, driving against a curb, etc. The torsion angle α is, for example, up to ± 20°, in particular up to ± 10°, more particularly up to approximately ± 5°.

[0054] The sensor device 10 serves to measure the relative rotation between the ball screw nut

[0055] 8 and the driver element 7. Based on the detected relative rotation, a currently applied torque causing the relative rotation can be determined. The detection of the relative rotation between the ball screw nut 8 and the driver element 7 and thus the detection of the torque causing the relative rotation makes it possible to improve force feedback on a steering element 16 (see Fig. 19) of the steering unit 2. To apply the force feedback to the steering element 16, a force feedback system 17 is provided on the steering element 16, which, based on at least the force feedback signal output by the sensor unit 6, in particular on a plurality of force feedback signals, applies force feedback to the steering element 16 in order to generate a steering feel on the steering element 16 that is as authentic and perceptible as possible for a driver of the vehicle (not shown). With reference to Fig. 2 to Fig.18, a structure of the sensor unit 6 according to an exemplary embodiment of the invention is described below. Fig. 2 to Fig. 4 show the sensor unit 6 arranged on the steering rod 3 in various views. The ball screw nut 8 is rotatably mounted in a housing 19 (see Fig. 14 and Fig. 15) of the steering gear 1 via a rolling bearing 18. The driver element 7 is arranged coaxially and in the radial direction R outside the ball screw nut 8, surrounding it, wherein a relative rotation between the driver element 7 and the ball screw nut 8 is possible. This means that the driver element 7 can rotate relative to the ball screw nut 8 and vice versa. Viewed in the axial direction A, the sensor device 10 is arranged at a first axial end of the driver element 7, likewise fixed to the housing (see Fig. 14 and Fig. 15).The driver element 7 is designed here, for example, as a driver sleeve which has a toothing on an outer circumference which serves for torque-transmitting engagement with the belt 11.

[0056] The sensor device 10 here has, for example, a sensor 20 for detecting the relative rotation between the driver element 7 and the ball screw nut 8, as well as a sensor PCB 21 for detecting an angular position of the driver element. The sensor 20 is configured to detect a change in the magnetic field caused by the relative rotation between the ball screw nut 8 and the driver element 7. The sensor PCB 21 determines the angular position of the driver element 7 using a sensor target 22, here embodied, for example, as a wing plate that is rotationally fixedly coupled to the driver element 7. A magnetic field or a change in the magnetic field that can be detected by the sensor 20 is generated using a multi-pole magnetic ring 23 (see Fig. 8 and Fig. 9) and a pole plate pair device 24, which are described in more detail below. It should be noted that the sensor device is shown in simplified form in the figures without a housing.However, it is particularly possible that the sensor device 10 has a housing and is accommodated together with this housing in the housing 19 of the steering gear 1.

[0057] Fig. 5 shows a partial assembly of the sensor unit 6 according to an embodiment to illustrate a first assembly step, in an exploded view (Fig. 6(a)) and in an assembled, perspective view (Fig. 6(b)). More specifically, Fig. 5 shows the partial assembly of several components that are mounted with or on the driver element 7 of the sensor unit 6. Therefore, this assembly can also be referred to as a driver element assembly. The driver element assembly in the first assembly step comprises the driver element 7 and a first thrust washer 25, which is arranged at the first axial end of the driver element 7, viewed in the axial direction A.The first thrust washer 25 has a plurality of axial projections 26, so-called protrusions, distributed over its circumference, which engage in openings 27, in particular bores, provided for this purpose on the driver element 7, thus ensuring torque transmission from the driver element 7 to the first thrust washer 25. In the exemplary embodiment shown here, the first thrust washer 25 is formed integrally with the sensor target 22, which is designed as a wing plate. Furthermore, in the first assembly step, the driver element assembly comprises a friction ring 28 and a disc spring 29, which serves as an axial preload element. The friction ring 28 is arranged between the first thrust washer 25 and the disc spring 29, as viewed in the axial direction A, in order to avoid metal-to-metal contact, i.e. direct contact between the first thrust washer 25 and the disc spring 29.The disc spring 29 serves to axially preload the driver element assembly to prevent rattling and / or clattering during operation. The disc spring 29 has radially inwardly projecting disc fingers 30, which generate the axial preload in the next assembly step (see Fig. 6).

[0058] The next assembly step of the driver element assembly is described with reference to Fig. 6. In the next assembly step, a second thrust washer 31 and a return element 9 designed as a spring finger plate 32 are mounted on the driver element assembly. The second thrust washer 31 is arranged in the axial direction A at a second axial end of the driver element 7 and, analogous to the first thrust washer 25, is connected to the driver element 7 in a torque-transmitting manner via axial through-positions 26 (see Fig. 6(d) and (e)) which engage in openings 27 in the driver element 7. In addition, the second thrust washer 31 has radially inwardly projecting, bead-like receiving extensions 33 which are arranged along an inner circumference of the second thrust washer 33.The spring finger plate 32 has an annular disk-shaped base body 34 and a plurality of spring fingers 35 extending over the circumference of the base body 34 and away from the base body 34 in the axial direction A. The spring fingers 35 each have a spring finger head 36 with a spring finger eye 37 at their free axial ends facing away from the base body 34.

[0059] The spring finger plate 32 is pushed in the axial direction A from the first axial end of the driver element 7 into the driver element 7. The spring fingers 35 are pressed radially inward and inserted into receiving recesses 38 provided for the spring fingers 35 on an inner circumference of the driver element 7 (see in particular Fig. 6(b)) until they snap into the receiving extensions 33 on the second thrust washer 31 at the second axial end of the driver element 7 with the spring finger eyes 37 (see Fig. 6(c)). At the same time, the spring finger plate 32 is subjected to a force axially such that the disc spring 29 is pressed flat. After the spring fingers 35 have snapped into the respective receiving extensions 33 (see Fig.6(c)), the spring finger plate 32 is then pressed away from the driver element 7 in the axial direction by the disc spring 29, whereby the driver element assembly is now axially preloaded (see arrows P1 and P2) and thus free of play (see Fig. 7). In a later assembly step, the spring finger plate 32 is coupled in a rotationally fixed manner to the ball screw nut 8 via the base body 34, here by screwing as an example (see Fig. 3 and Fig. 4). Side walls or flanks of the receiving recesses 38 serve here as end stops 14, against which the spring fingers 35 come to rest during the relative rotation between the ball screw nut 8 and the driver element 7, whereby the relative rotation is limited to a predetermined angle, here by way of example approximately ± 4° from the neutral position 15.

[0060] In the next assembly step (see Fig. 8), the multi-pole magnetic ring 23 is added to the driver element assembly. The multi-pole magnetic ring 23 has a plurality of poles, in particular north and south poles, which are arranged in the circumferential direction on one end face of the magnetic ring 23, in particular alternating. In particular, the magnetic ring 23 is made of a magnetizable plastic, e.g., a plastic provided with ferro-particles. The multi-pole magnetic ring 23 is arranged in the radial direction R between the first thrust washer 25 and the spring finger plate 32 and is coupled here in a rotationally fixed manner to the spring finger plate 32 and thus to the ball screw nut 8 by means of positive-locking connections.In order to ensure a secure fit of the magnetic ring 23 between the first thrust washer 25 and the spring finger plate 32, the magnetic ring 23 can have a contour shaped according to the installation space between the first thrust washer 25 and the spring finger plate 32 on an end face opposite the end face provided with the plurality of poles (see Fig. 9).

[0061] In a next step (see Fig. 10), a cover plate 39 is added to the driver element assembly, which secures the magnetic ring 23 against falling out in the axial direction A. For this purpose, the cover plate 39 has, for example, holes corresponding to the base body 34 of the spring finger plate 32, so that the cover plate 39 can be screwed together with the spring finger plate 32 to the ball screw nut 8. Alternatively, it is also conceivable to connect the magnetic ring 23 to the spring finger plate 32 without play by partial thermoplastic deformation. Subsequently, the pole plate pair device 24 is added to the driver element assembly (see Fig. 11), which is described in more detail with reference to Fig. 12.

[0062] The pole plate pair device 24 (see Fig. 12) has a first pole plate 40 and a second pole plate 41, both of which are ring-shaped. An annular base body 42 of the first pole plate 40 has a larger diameter than an annular base body 43 of the second pole plate 41. Furthermore, the first pole plate 40 has first pole tabs 44, which are bent over from the annular base body 42 on an axial end face, projecting radially inward. The second pole plate 41 has second pole tabs 45, which are bent over from the annular base body 43 on an axial end face, in particular the same axial end face as the first pole plate 40, projecting radially outward.Furthermore, the pole plate pair device 24 has a carrier 46 that arranges the first pole plate 40 and the second pole plate 41 coaxially to one another such that the first pole plates 44 and the second pole plates 45 are arranged essentially in the same plane and alternately along a circumferential direction. Due to the different diameters of the two base bodies 41, 43, they form an axial air gap LS between them, into which the sensor 20 later projects at least partially. The pole plates 40, 41 are then fixed in position on the carrier 46 by means of thermoplastic deformation 47 (see Fig. 12(c) and (d)).

[0063] With reference back to Fig. 11 and with reference to Fig. 13, the pole plate pair device 24 is arranged adjacent to the magnetic ring 23 in the axial direction A and is connected in a form-fitting and thus rotationally fixed manner to the first thrust washer 25 by means of thermoplastic deformation or caulking 48 of the carrier 46 (see Fig. 13 in general and in particular Fig. 13(d)). The pole plate pair device 24 and the magnetic ring 23 are coordinated with one another such that the alternately arranged pole tabs 44, 45 are arranged to cover the several poles of the magnetic ring 23. A plain bearing sleeve 49 is then added to the driver element assembly (see Fig. 13). The plain bearing sleeve 49 is pressed in particular into the inner circumference of the driver element 7 in order to be rotationally fixedly coupled to the driver element 7. The sleeve shown in Fig.The plain bearing sleeve 49 shown as an example in Figure 13 has tabs 50 bent radially outward at one axial end, which, when the plain bearing sleeve 49 is pressed in, provide security against the risk of the spring fingers 35 radially disengaging from the receiving extensions 33 (see in particular Figures 13(e) and (f)). The driver element assembly is then pushed onto the ball screw nut 8 and, thanks to the plain bearing sleeve 49, is arranged so as to be rotatable relative to it. The spring finger plate 32 (and the cover plate 39) is then screwed to an end face of the ball screw nut 8 (see Figures 3 and 4) and thus connected to it in a rotationally fixed manner. From this point on, the relative rotation between the ball screw nut 8 and the driver element 7 or the driver element assembly is limited to a predetermined angular dimension by the elastic spring force of the spring finger plate 32 and, for example, additionally by the flanks of the receiving recesses 38.

[0064] As illustrated in Fig. 15, the ball screw nut 8 and the driver element assembly are installed in a first part 50 of the housing 19, and the sensor device 10 is installed in a second part 51 of the housing 19. The two housing parts 50, 51 are then brought together and, for example, screwed together. Joining the housing 19 together then results in the sensor 20 being arranged at least partially within the air gap LS, where it detects a change in the magnetic field when the magnetic ring 23 and the pole plate pair device 24, and thus the ball screw nut 8 and the driver element 7, rotate relative to one another. The strength or extent of the change in the magnetic field is directly related to the currently applied torque that causes the relative rotation. Thus, the detected change in the magnetic field can be used to determine the currently applied torque.

[0065] Fig. 16 again shows various views of the spring finger plate 32 described above. The receiving extensions 33 on the second thrust washer 31 are designed in particular as rocker pressure pieces (see Fig. 16(c) and (d)), whereby the small pivoting movements of the finger heads 36 in contact with the receiving extensions 33 are purely rolling and therefore not sliding. The bearing points formed by the receiving extensions 33 are therefore almost wear-free even without lubrication. Flanks of the spring fingers 35, in particular in the attachment area, i.e. close to the base body 34 of the spring finger plate 32, together with flanks of the receiving recesses 38 of the driver element 7 form a rotation stop in order to limit component stresses of the spring fingers 35 in the event of excessive torque, e.g. due to potholes, driving against curbs, etc., and thus to protect the spring fingers 35 from damage.Depending on the design, the angle of rotation up to the stop can be up to ± 20°, in particular between ± 1° and ± 7°. In the exemplary embodiment shown in the figures, the permissible angle of rotation is approximately ± 4°. Therefore, the flanks of the receiving recesses 38 can also be referred to as the end stops 14, as already explained above. Fig. 17 and Fig. 18 show alternative embodiments of the spring finger plate 32, which differ from the embodiment described above in the shape of the finger heads 36. In general, it can be said for all spring fingers 35 that, since the spring fingers 35 deform under load and thus lead to pivoting movements at the spring finger heads 36, the lateral contours of the spring finger heads 36, viewed in the circumferential direction, have a convex shape which is supported on both sides, possibly with some tolerance-related play, on the flanks of the receiving recesses 38 of the driver element 7.Since the torque is transmitted at this point, the second thrust washer 31 serves only to axially fix the driver element assembly. Even in the embodiments shown in Fig. 17 and Fig. 18, it is necessary to press the spring fingers 35 radially inward during assembly so that they can snap into the second thrust washer 31, particularly after pressing in the plain bearing sleeve 49.

[0066] List of reference symbols

[0067] 1 steering gear

[0068] 2 steering unit

[0069] 3 Handlebar

[0070] 4 actuator

[0071] 5 drive wheel

[0072] 6 Sensor unit

[0073] 7 Driving element

[0074] 8 ball screw nut

[0075] 9 Reset element

[0076] 10 Sensor device

[0077] 11 belts

[0078] 12 spindle section

[0079] 13 Spring element

[0080] 14 End stop

[0081] 15 Neutral position

[0082] 16 Steering element

[0083] 17 Force feedback system

[0084] 18 rolling bearings

[0085] 19 housings

[0086] 20 sensors

[0087] 21 Sensor PCB

[0088] 22 Sensor target

[0089] 23 Magnetic ring

[0090] 24 pole sheet pair device

[0091] 25 first thrust washer

[0092] 26 axial adjustment

[0093] 27 Opening

[0094] 28 Friction ring

[0095] 29 Disc spring

[0096] 30 plate fingers

[0097] 31 second thrust washer

[0098] 32 spring finger plate

[0099] 33 Recording extension

[0100] 34 basic bodies

[0101] 35 spring fingers 36 spring finger head

[0102] 37 Feather Finger Eye

[0103] 38 Recording recess

[0104] 39 Cover plate

[0105] 40 first pole sheet

[0106] 41 second pole plate

[0107] 42 basic bodies

[0108] 43 basic bodies

[0109] 44 first Polashen

[0110] 45 second pole lashes

[0111] 46 carriers

[0112] 47 thermoplastic deformation

[0113] 48 thermoplastic deformation

[0114] 49 plain bearing sleeve

[0115] 50 tabs

[0116] 51 first part

[0117] 52 second part

[0118] A axial direction

[0119] L Longitudinal axis

[0120] LS air gap

[0121] P1 , P2 arrows

[0122] R radial direction

Claims

Claims 1. A sensor unit (6) for determining a force feedback signal for a steering unit (2), in particular a steer-by-wire steering unit (2), of a vehicle, comprising: a ball screw nut (8) configured to be coupled to a spindle section (12) of a handlebar (3) of the steering unit (2) in a load-transmitting manner, a driver element (7) arranged coaxially to the ball screw nut (8) and rotatable relative thereto, and configured to be coupled to an actuator (4) of the steering unit (2) in a load-transmitting manner, a sensor device (10) for detecting a relative rotation between the driver element (7) and the ball screw nut (8), and a return element (9) provided between the ball screw nut (8) and the driver element (7) and configured toto generate a restoring moment for returning the driver element (7) and / or the ball screw nut (8) to a neutral position (15) during the relative rotation between the driver element (7) and the ball screw nut (8).

2. Sensor unit (6) according to claim 1, wherein the sensor device (10) is configured to output a signal based on the detected relative rotation between the driver element (7) and the ball screw nut (8).

3. Sensor unit (6) according to claim 1 or 2, wherein the sensor device (10) comprises at least one multi-pole magnetic ring (23), a pole plate pair device (24), and a stationary sensor (20) for detecting a change in the magnetic field, wherein the multi-pole magnetic ring (23) is coupled in a rotationally fixed manner to one of the ball screw nut (8) and the driver element (7), and the pole plate pair device (24) is coupled in a rotationally fixed manner to the other of the ball screw nut (8) and the driver element (7), wherein the pole plate pair device (24) comprises two pole plate rings (40, 41) which form a circumferential air gap (LS) between them, in which the sensor (20) is at least partially arranged, and wherein the sensor (20) is designed to detect a change produced by the relative rotation between the ball screw nut (8) and the driver element (7) by means of a gap formed between the pole plate rings (40, 41). to detect magnetic field.

4. Sensor unit (6) according to claim 3, wherein the circumferential air gap (LS) formed by the pole plate pair device (24) is designed as an annular circumferential, axial air gap or as an annular circumferential, radial air gap.

5. Sensor unit (6) according to one of claims 1 to 4, further comprising end stops (14) for limiting the relative rotation between the ball screw nut (8) and the driver element (7).

6. Sensor unit (6) according to one of claims 1 to 5, wherein the return element (9) is designed as a spring element (13).

7. Sensor unit (6) according to claim 6, wherein the spring element (13) is designed as a spring finger plate (32) which is coupled in a rotationally fixed manner to the ball screw nut (8), wherein the spring finger plate (32) has an annular disk-shaped base plate (34) and a plurality of spring fingers (35) which are arranged on the base plate (34) along its circumference and extend in the axial direction (A), and are coupled at their free ends in a rotationally fixed manner to the driver element (7).

8. Sensor unit (6) according to claim 7, further comprising a prestressing element (29) which is configured to prestress the driver element (7) and the spring finger plate (32) in the axial direction (A).

9. Sensor unit (6) according to one of claims 1 to 8, further comprising a sliding bearing (49) which is designed to rotatably support the driver element (7) relative to the ball screw nut (8).

10. Steering unit (2), in particular a steer-by-wire steering unit (2), for a vehicle, comprising: a steering gear unit (1), comprising: a steering rod (3) which is designed to be coupled at its axial ends to a wheel of the vehicle, a control actuator (4) which is coupled to the steering rod (3) such that a rotational movement of the control actuator (4) causes a translational movement of the steering rod (3), and a sensor unit (6) according to one of claims 1 to 9, wherein the driver element (7) of the sensor unit (6) is coupled to the control actuator (4) in a load-transmitting manner, and wherein the ball screw nut (8) of the sensor unit (6) is coupled to a spindle section (12) of the handlebar (3) in a load-transmitting manner, a steering element (16) with a force feedback system (17) for generating a force feedback on the steering element (16) based on at least the force feedback signal output by the sensor device (10) of the sensor unit (6).

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