Steering unit for vehicle with relative sliding between sensor teeth and steering rod

Abstract

Steering unit (1), in particular a steer-by-wire steering unit, for a vehicle, comprising: a steering rod (2) which is configured to be coupled at each of its axial ends to a wheel of the vehicle, wherein the steering rod (2) has at least a section of sensor teeth (15), an actuator (3) which is coupled to the steering rod (2) such that a rotational movement of the actuator (3) 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 (VWL), a sensor gearing device (4) which at least sectionally has a counter-gear corresponding to the sensor gearing (15) of the steering rod (2) which is in tooth engagement with the sensor gearing (15) of the steering rod (2) in such a way that the translational movement of the steering rod (2) causes a change in position of the sensor gearing device (4) along a predetermined sensor travel path, characterized by the fact that in the tooth engagement between the sensor toothing device (4) and the sensor toothing (15) of the steering rod (2) a relative sliding occurs which is equal to or greater than 80% of the steering rod travel (VWL) of the steering rod (2), and a sensor device (5) for determining the position of the steering rod (2), which is configured to detect a position of the sensor gear device (4) along the predetermined sensor travel path (15).

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 (head-wheel steering) and RWA (tail-wheel 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" signal transmission via cable. As a result, the position of the steering element is no longer physically coupled to the position of the steering column. This one-to-one coupling of the steering element's position with the steering column's position is typically achieved using sensors integrated into the RWA system to determine the steering column's position.Various sensor arrangements are known, such as those from DE 11 2020 002 949 T5, DE 10 2021 212 470 A1.

[0004] German patent DE 102 38 640 A1 describes a compact multiturn angle measuring device that provides an absolute angular position over many revolutions after being switched on, without requiring a reference run. The starting point is the realization that conventional spur gear reductions require considerable installation space with large shaft diameters or generate high gear speeds and thus wear. The invention solves this problem with a first gear stage whose gear axis is crossed at 90° relative to the input shaft; preferably a helical gear or, alternatively, a worm gear is used. This achieves a high reduction ratio in the first stage, enabling reliable measurement even at high input speeds. Subsequent spur gear stages drive three code gears, each equipped with diametrically magnetized permanent magnets.The magnetic position is detected by semiconductor magnetic sensors, while the angular position within one revolution is recorded via an optical code disk with Gray or sequential code. All scanning units – optics and magnetics – are arranged on the same circuit board, enabling a particularly flat, monolithic design and cost-effective chip-on-board contacting. The entire gear and magnet assembly can be positioned outside or, optionally, partially within the circumference of the optical disk.

[0005] German patent DE 198 41 913 A1 describes an electromechanical steering actuator for steer-by-wire vehicle systems in which, under normal operating conditions, only an electric actuator generates the wheel steering angle. To ensure reliable vehicle steering even in the event of a power failure or other faults, a switchable clutch is proposed that positively engages the steering wheel with the steered link – preferably the rack of a rack and pinion steering system – in the event of a malfunction. The clutch is open against the force of a pre-tensioned spring; if the supply voltage fails or another fault occurs, it closes automatically, establishing a de-energized emergency operation. Position sensors detect both the steering wheel angle and the deflection of the steered link or the motor and transmit actual signals to a process computer. This computer calculates motor control signals, monitors battery voltage and system status, and controls the clutch.Driving condition data and comfort / stability commands can be incorporated via a vehicle bus system, enabling variable steering ratios, vehicle stabilization, automatic lane guidance and an adjustable steering feel.

[0006] German patent DE 10 2016 208 317 A1 describes a compact steering gear unit for vehicles, particularly for active rear-axle steering systems, in which the steering angle sensor is an integral part of the assembly. The electric motor, gearbox, electronic control unit (ECU), and steering angle sensor are housed together in a multi-part casing. The sensor element—e.g., a Hall effect, magnetic resonance, gamma, or torsion energy sensor (GMR) IC—is soldered directly onto the ECU's circuit board; a separate sensor housing, additional cables, and individual assembly steps are eliminated, thus reducing costs, installation space, and the risk of failure (cable breakage). The sensor element, preferably a permanent magnet, is rotatably mounted and detects the translational movement of the tie rod via a sensing device. Two variants are mentioned: (a) a worm-spur gear pair, in which a worm connected to the spindle sleeve drives a spur gear on the magnetic shaft; (b) a spur gear directly on the spindle, which acts as a rack.The gear ratio creates a large absolute measuring range (>160°) that can cover linear paths of ±40 mm. A pre-tensioned coil spring always presses the spur gear against the same tooth flank and eliminates backlash, so that changes in direction do not distort the measurement result.

[0007] It has now become apparent that there is a further need to improve a known device for determining the position of the steering rod in a steering unit, particularly a steer-by-wire steering unit, of a vehicle. Specifically, there is a further need to provide a device for determining the position of the steering rod that allows the position of the steering rod to be determined absolutely, and especially even after the vehicle has been switched off or de-energized.

[0008] Against this background, it is an object of the present invention to provide an improved device for determining the position of a steering rod for a steering unit, in particular a steer-by-wire steering unit, of a vehicle, which in particular enables an absolute, and furthermore in particular a continuous, determination of the steering rod position. Disclosure of the invention

[0009] 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.

[0010] The steering unit according to the invention, in particular a steer-by-wire steering unit, for a vehicle comprises a steering rod, an actuator, a sensor gear assembly, and a sensor assembly for determining the position of the steering rod. The steering rod is configured to be coupled to a wheel of the vehicle at each of its axial ends and has sensor gears at least partially. The actuator is coupled to the steering rod such that a rotational movement of the actuator causes a translational movement of the steering rod along its longitudinal axis to change the position of the steering rod along a predetermined steering rod travel path.The sensor gear assembly has, at least in sections, a mating tooth profile corresponding to the sensor tooth profile of the steering rod. This mating tooth profile engages with the sensor tooth profile of the steering rod in such a way that the translational movement of the steering rod along its longitudinal axis causes a change in the position of the sensor gear assembly along a predetermined sensor travel path. During this engagement, relative sliding occurs between the sensor gear assembly and the sensor tooth profile, which is equal to or greater than 80% of the steering rod travel path. The sensor assembly for determining the position of the steering rod is configured to detect the position and / or a change in the position of the sensor gear assembly along the predetermined sensor travel path.

[0011] The sensor gearing device and / or the sensor gearing on the steering rod each have, in particular, a tooth height of less than 3 mm, and furthermore, in particular, less than 2 mm, wherein the tooth height is defined from a tooth tip to a tooth root. Furthermore, the tooth engagement has, in particular, a tooth engagement angle of greater than 25°.

[0012] The sensor teeth are provided only in local zones, i.e., section by section, on the steering rod, particularly outside other sliding and / or rolling zones provided on the steering rod. With regard to the circumference of the steering rod or a surface of the steering rod, the sensor teeth can be provided section by section or completely circumferentially, in particular in a helical screw configuration.

[0013] Relative sliding of more than 80% of the predetermined sensor travel path enables tooth engagement with low frictional resistance because the contact force of the sensor gearing device is low. This reduces frictional force, frictional energy, and / or frictional wear.

[0014] 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 is detected with high accuracy. The required measuring path, here the maximum sensor travel path that the sensor gearing device must be able to cover in order to determine the position, in particular the absolute position, of the steering rod, is smaller than the maximum travel path that the steering rod can cover. The maximum travel path is defined as the path that the steering rod travels when it is moved along its longitudinal axis from a maximum deflected position of the wheels, e.g., the maximum possible tilt of the wheels to the left, to another maximum deflected position of the wheels, e.g., the maximum possible tilt of the wheels to the right.This makes it possible to determine the position of the steering rod, in particular an absolute position determination of the steering rod, with reduced installation space, especially compared to directly measuring linear displacement sensors.

[0015] It can therefore be said that the sensor device for determining the position of the steering rod, in particular the absolute position of the steering rod, generally works independently and can essentially determine the position of the steering rod with sufficiently high accuracy, resolution and reliability and output it as a signal.

[0016] Furthermore, it is also possible to combine the output signal of the sensor device for determining the position of the steering rod with another signal, in particular the signal from a rotor position sensor in the actuator. The rotor position sensor typically provides a highly precise signal corresponding to the electrical or mechanical angle of the rotor, which is required to control the actuator, especially an electric motor. The rotor angle is highly proportional to the position of the steering rod, typically around 2-5 mm / rev, but—considered on its own—does not allow for a determination of the absolute position of the steering rod, since the rotor angle completes several full rotations over the entire travel range of the steering rod, which can also be referred to as the steering rod travel range, e.g., on the order of approximately 20-100 revolutions.In combination with the sensor device of the steering unit described above, particularly according to the invention, a precise determination of the steering rod's position, especially its absolute position, is now possible, whereby the sensor device 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.

[0017] Such a combination can make it possible to further improve resolution and accuracy.

[0018] This reduces the costs for the sensor system used to determine the position of the steering rod, and thus for the steering unit, because the requirements for the sensor system are lower than in a case where the sensor system alone, i.e., independently, has to provide the high accuracy or resolution. Even if the rotor position sensor fails during operation, it is possible to control the actuator temporarily using the signal from the sensor system, even if the resolution or accuracy of the sensor system 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 system used to determine the position of the steering rod during operation by incrementally "counting" the signal from the rotor position sensor, especially as long as the rotor position sensor and, if applicable, the steering unit are powered.a corresponding control unit is ensured.

[0019] Furthermore, continuous monitoring of the rotor position sensor signal and the steering rod position sensor signal can detect implausible discrepancies in the signals, which could indicate, for example, a belt slippage and / or belt wear. This allows for the early detection of an impending mechanical failure.

[0020] Furthermore, it is conceivable to determine the position of the steering rod, in particular its absolute position, using the vernier scale principle. In this case, the sensor device for position determination could be designed not to determine the absolute position of the steering rod, but rather to cover only a small, and in particular high-resolution, measuring range on the steering rod, which repeats periodically over the entire travel path of the steering rod. The period length should be selected such that it differs only slightly from that of the rotor position sensor, and the difference or phase shift between the signals should allow for an unambiguous determination of the position, especially the absolute position, of the steering rod at all times. This reduces the requirements regarding the detection accuracy of the sensor device, since a significantly smaller measuring range needs to be covered, but this range is repeated multiple times.Inductive sensor devices are particularly suitable for this purpose.

[0021] According to one embodiment, the sensor teeth of the steering linkage have a helix angle of approximately 45° to 85°, particularly approximately 65° to 85°, and more specifically approximately 80°. This means that the sensor teeth are oriented almost along the steering linkage instead of, as with conventional rack and pinion gears, perpendicular to the spindle. Such an inclination of the teeth facilitates the relative sliding of the sensor gear assembly relative to the sensor teeth.

[0022] According to one embodiment, the steering unit further comprises a bearing unit for the radial support of the steering rod. The bearing unit is designed to reduce or even prevent radial deflection of the steering rod and / or rotation of the steering rod about its own longitudinal axis, while still allowing linear movement of the steering rod along its longitudinal axis. In particular, the bearing unit is arranged on a flattened section of the steering rod. This arrangement on a flattened section of the steering rod enables a simple and therefore cost-effective implementation of the bearing unit, since a flattened section particularly simplifies the implementation of an anti-rotation device.

[0023] According to one embodiment, the bearing unit comprises a pressure piece and a pressure roller, which are arranged opposite each other, guiding the steering rod between them so that it can move longitudinally. The pressure piece generally serves to prevent the steering rod from rotating about its own longitudinal axis. The pressure roller is generally designed to reduce or even prevent radial deflection of the steering rod, particularly in the area of ​​the pressure piece, in order to ensure contact between the steering rod and the pressure piece.

[0024] According to one embodiment, the sensor teeth of the steering rod are essentially flat. This simplifies the manufacturing of the sensor teeth because the steering rod does not need to be rotated for manufacturing, particularly by machining.

[0025] According to one embodiment, the sensor gear assembly comprises at least one spur gear configured to rotate by a specific angle, particularly less than 360°, over the entire travel range of the steering rod. The rotation of the spur gear corresponds to the sensor's travel range. The sensor assembly detects the spur gear's angle of rotation, for example, by sensing a sensor target that is fixed to the spur gear, and this angle can be uniquely assigned to a position of the steering rod. Unique assignment here means that each angular position of the spur gear corresponds to only one position of the steering rod, allowing the steering rod's position to be easily determined from the detected angular position. A rotation of less than 360° over the entire travel range of the steering rod enables the use of simple, and therefore cost-effective, sensors.For rotations of 360° or more over the entire travel distance of the steering rod, so-called multiturn sensors are usually used to enable a unique correlation between the rotation angle and the position of the steering rod.

[0026] Furthermore, it is also conceivable that the sensor gear assembly has two or more spur gears, all meshing with the same sensor gear, or that the steering rod has multiple sensor gear sections, with each of the two or more spur gears meshing with one of these multiple sensor gear sections. The spur gears can all have the same configuration or different configurations, particularly regarding the number of teeth and / or the helix angle.

[0027] According to one embodiment, the spur gear is preloaded and / or the teeth of the spur gear have a helix angle of up to approximately 45°. Furthermore, the spur gear is mounted, in particular, axially and / or radially, by means of sliding or rolling bearings. The spur gear is preloaded against the steering rod, particularly with a preload force greater than 100 N, to ensure that the tooth engagement between the spur gear and the sensor teeth of the steering rod is backlash-free under all operating conditions. In particular, the teeth of the gearing on the spur gear are also conical or tapered, or have another gear helix angle of up to approximately 45°. The rotational axis of the spur gear is oriented almost parallel, in particular substantially parallel, to the longitudinal axis of the steering rod.Alternatively, the axis of rotation of the spur gear can also be inclined at an angle of up to 45°, in particular less than 45°, to the longitudinal axis of the steering rod, which allows the use of a straight-toothed spur gear.

[0028] According to one embodiment, the sensor gearing device is designed as a two-stage spur gear transmission comprising two meshing gears, wherein a first gear of the two-stage spur gear transmission is further meshed with the sensor gearing of the steering rod, and the spur gear transmission has a gear ratio such that a second gear of the spur gear transmission rotates through a predetermined angle, in particular less than 360°, over the entire travel distance of the steering rod. With such a spur gear transmission, it is possible to design the sensor gearing on the steering rod as a straight gear, which simplifies the manufacturing of the sensor gearing.Therefore, both the first and second gears can be straight-cut, and the rotational movement of the second gear over the entire travel of the steering rod is essentially defined by a gear ratio between the first and second gears. This means that the rotational movement of the second gear corresponds to the sensor's travel distance.

[0029] The rotation angle of the second gear is detected – analogous to the spur gear described above – by the sensor device, for example, by sensing a sensor target that is fixed to the second gear. This angle can then be uniquely assigned to a position of the steering rod. Uniquely, this means that each angular position corresponds to only one position of the steering rod, allowing the steering rod position to be easily determined from the detected angular position. Rotations of less than 360° across the entire travel range of the steering rod allow the use of simple, and therefore cost-effective, sensors. For rotations of 360° or more across the entire travel range of the steering rod, so-called multiturn sensors are typically used to ensure a unique correlation between the rotation angle and the steering rod position.

[0030] According to one embodiment, the spur gear unit, particularly on the output side, is preloaded. This ensures backlash-free gear meshing between the spur gear unit and the steering rod. For example, the second spur gear can be preloaded by means of a coil spring. Alternatively, the second gear can be made in two parts, with the two parts of the second gear being preloaded against each other. The output-side preload ensures that even when the direction changes, the same flank remains in contact with the gear teeth, making the preload less sensitive to tolerances, especially manufacturing tolerances. In other words, the preload can be applied rotationally, particularly via the angle of rotation of the second gear, or via the radial distance of the second gear to the steering rod.Additionally or alternatively, the toothing of the first gear can have a helix angle of up to approximately 45°.

[0031] According to one embodiment, the sensor gear assembly comprises at least one internally toothed ring gear, which is rotatably arranged around the steering rod, particularly not coaxially, wherein an internal toothing of the ring gear engages with the sensor toothing of the steering rod, and wherein the ring gear is configured to rotate through a predetermined angle, particularly less than 360°, over the entire steering rod travel path. Thus, in this embodiment as well, the rotational movement of the ring gear corresponds to the sensor travel path. The design as an internally toothed ring gear allows for mounting within the housing, particularly by means of plain or roller bearings, and thus enables a particularly space-saving implementation of the sensor gear assembly.Furthermore, the internally toothed ring gear can have a high number of teeth, thereby achieving a high contact ratio that ensures reliable contact between the sensor gearing device and the sensor teeth. Additionally, the ring gear can be made of a plastic, such as a single-material plastic, a plastic blend, or a fiber-reinforced plastic or blend, wherein the ring gear—analogous to the spur gears described above—includes a sensor target that is fixed to the ring gear and configured to be detected by the sensoring device.

[0032] According to one embodiment, the sensor teeth are spirally formed on the outer surface of the steering rod. In particular, the sensor teeth are helically screwed around the outer surface. The grooves of the sensor teeth are very long, as they run almost along the entire length of the steering rod.

[0033] According to one embodiment, the sensor gearing device comprises a rack, in particular a helical-toothed rack, which engages with the sensor teeth of the steering rod, the rack being arranged substantially perpendicular or orthogonal to the steering rod. Thus, a movement of the steering rod along its longitudinal axis is converted into a longitudinal movement of the rack that is orthogonal or tangential to it. By selecting a transmission ratio between the teeth of the rack and the sensor teeth of the steering rod, the length of the total sensor travel can be influenced. In this embodiment, the sensor travel corresponds to the longitudinal movement of the rack.In purely mathematical terms, a rack arranged perpendicular to the steering rod results in a relative sliding, i.e., a slippage, of over 100%, which can be reduced to less than 100% by a slight inclination, i.e., a non-perpendicular, especially skew, orientation to the longitudinal axis of the steering rod, the rack.

[0034] According to one embodiment, the rack is arranged in or near the bearing unit for the radial support of the steering rod. The arrangement of the rack in, and in particular its orientation essentially perpendicular to the steering rod's movement, can almost completely prevent distortion of the measured value detected by the sensor device due to steering rod deformation. If the rack is arranged near, but adjacent to, the bearing unit, such distortion can be minimized. Specifically, the rack can be arranged or supported in the pressure piece of the bearing unit, with the rack in contact with the steering rod in the central region of the pressure piece. In the central region, the pressure piece, and in particular a sliding bearing of the pressure piece, does not bear any load.In this area, no load is borne by the steering rod, and therefore this area can be left out and used for the rack bearing. Furthermore, the pressure piece is always in contact with the steering rod due to spring force, thus preventing any distortion of the measured value or signal, even under external force or deflection of the steering rod.

[0035] According to one embodiment, the rack and the sensor teeth of the steering rod are meshed such that the total rack travel is smaller than the total steering rod travel. This means that the gear ratio between the rack and the sensor teeth is selected such that the total rack travel, i.e., the sensor travel, is smaller than the total steering rod travel along its longitudinal axis. The smaller or shorter rack movement simplifies the steering rod position determination by the sensor device, as the smaller movement is easier to measure. In particular, the rack travel is less than one-third of the steering rod travel.

[0036] According to one embodiment, the rack is arranged to be axially displaceable relative to the bearing unit. The axial relative movement with respect to the bearing unit enables the rack to move perpendicularly relative to the steering rod when the steering rod is moved along its longitudinal axis.

[0037] According to one embodiment, the sensor device comprises an inductive sensor, an xMR sensor, or a Hall sensor. The sensor type can depend on the operating conditions, such as environmental influences, interference, etc. The type of target is generally selected depending on the sensor type of the sensor device. The term "xMR sensor" encompasses all magnetoresistive (MR) sensors, such as GMR, TMR, AMR, etc. In other words, the "x" is a placeholder for the various types of magnetoresistive sensors.

[0038] According to one embodiment, the sensor device comprises at least one moving-coil sensor arranged at an axial end of the rack, surrounding the rack. The moving-coil sensor is an example of an inductive sensor. In particular, the sensor device comprises two moving-coil sensors, one of which is arranged at each axial end of the rack, surrounding the rack. For this purpose, at least the axial ends of the rack are made of a metallic material, e.g., iron or steel. Furthermore, the externally arranged moving-coil sensors are connected to the pressure piece of the bearing unit, so that the moving-coil sensors follow any movement of the pressure piece, e.g., due to external forces on the steering rod, and thus avoid distortions of the measured value or the measurement signal due to a shift in the relative position of the rack to the moving-coil sensors.

[0039] Alternatively, as mentioned above, other sensor types are also conceivable, e.g. capacitive, magnetic, resistive, etc. sensors.

[0040] In general, the rack can be made mostly of a plastic, such as a single-material plastic, a plastic mixture, or a fiber-reinforced plastic or mixture, which can reduce the cost and / or weight of the rack compared to a rack made of metal.

[0041] According to one embodiment, the rack is pre-tensioned in the axial and / or radial direction. This ensures that the rack is pre-tensioned parallel and / or orthogonal to the steering rod and thus arranged without backlash. Particularly with large gear ratios between the rack and the sensor teeth, even small deviations in the rack's movement or position can lead to significant measurement errors, which can be reduced or even prevented by the backlash-free meshing between the rack and the sensor teeth of the steering rod. Detailed description based on drawing

[0042] 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 Schematic representations of a steering unit according to an embodiment of the invention in a perspective view (a), a side view (b), a top view (c), and a perspective enlarged detail view (d), Fig. 2 a schematic, enlarged representation of a partial section of a steering unit according to an embodiment of the invention in a front view, Fig. 3 schematic, enlarged representations of a partial section of a steering unit according to an embodiment of the invention in a side view (a) and a top view (b), Fig. 4 a schematic representation of a steering unit according to an embodiment of the invention in a side view, Fig. 5 a schematic representation of a steering unit according to an embodiment of the invention in a perspective view, Fig. 6 schematic representations of a steering unit according to an embodiment of the invention in a perspective view (a) and a side view (b), Fig. 7 A schematic, enlarged representation of a partial section of a steering unit according to an embodiment of the invention in a front view, Fig. 8 a schematic partial representation of a steering unit according to an embodiment of the invention in a perspective view, Fig. 9 a schematic cross-sectional representation of a steering unit according to an embodiment of the invention, Fig. 10 a schematic partial representation of a steering unit according to an embodiment of the invention in a perspective view, and Fig. 11 a schematic longitudinal sectional view of a steering unit according to an embodiment of the invention,

[0043] The figures are purely schematic and serve only to illustrate the invention. The same elements are identified by the same reference symbols.

[0044] Fig. 1 to Fig. Figure 11 shows schematically and exemplarily a steering unit 1 or sections thereof according to various embodiments of the invention. Although not everything is shown for every embodiment, the steering unit 1 according to all the illustrated exemplary embodiments comprises a steering rod 2 and an actuator 3 (see, for example, Figure 11). Fig. 8), a sensor gear unit 4, and a sensor unit 5 for determining the position of the steering rod (see example) Fig. 8 and Fig. 9) on. The ones in the Fig. 1 to Fig. The embodiments shown in Figure 11 differ essentially in the design and measuring principle of the sensor gearing device 4. Thus, the embodiments can be broadly categorized according to the measuring principle for determining the position of the steering rod 2 as a rotary measuring principle ( Fig. 1 to Fig. 7) and a translational measurement principle ( Fig. 8 to Fig. 11) are subdivided.

[0045] Fig. 1 to Fig. Figure 3 shows a steering unit 1 according to an exemplary embodiment of the invention in various views. The steering rod 2 according to the one shown in Fig. The embodiment shown in Figure 1 has a spindle section 6 and a section 7 that is flattened on one side. The spindle section 6 has a screw contour 8 with a typical pitch of approximately 8 mm and is part of a ball screw drive (not shown) that serves to convert the rotational movement of the actuator 3 into a translational movement of the steering rod 2 along its longitudinal axis L. A bearing unit 9 is arranged on the flattened section 7, which supports a pressure piece 10 (in Fig. 1(d) not shown) and comprises a pressure roller 11. The flattened section 7 has several functional zones distributed around its circumference. For example, a partial circular section 12 of the steering rod 2, on which the pressure piece 10 is arranged, is designed as a sliding surface over which the steering rod 2 is axially displaceable relative to the pressure piece 10 along its longitudinal axis L. A section 13 arranged opposite the sliding surface, which is flattened on one side, serves, among other things, as a rolling surface 14 (see in particular ). Fig. 1(d)), on which the pressure roller 11 rolls to prevent rotation of the steering rod 2 about its longitudinal axis L (see also Fig. 2).

[0046] Furthermore, section 13 also features a sensor gear 15, which is a strong helical gear with a helix angle β of approximately 80° (see Fig. 3(b)). In particular, the sensor toothing 15 can have a helix angle β of approximately 60° to approximately 85°. Such a strong helix angle of the sensor toothing 15 enables or causes the sensor toothing device 4, which engages with the sensor toothing 15 of the steering rod 2, to slide rather than roll in this tooth engagement. In particular, a relative sliding of more than 80% is possible here, and in particular even desirable.

[0047] In the Fig. In the embodiment shown in Figure 1, the pressure roller 11 is recessed in the area of ​​the sensor teeth 15, so that the sensor teeth 15 can, so to speak, pass under the pressure roller 11 when the steering rod 2 moves along its longitudinal axis L. Thus, the pressure roller 11 does not contact the sensor teeth 15, thereby preventing wear of the sensor teeth 15 from rolling contact with the pressure roller 11. In principle, the sensor teeth 15 can also be formed in other areas of Section 13 (see, for example, Figure 1). Fig. 4 or Fig. 6). As especially in Fig. 1(b) and Fig. As can be seen in Figure 1(c), it is possible that a manufacturing-related run-out zone 19 of a rolling tool required for the production of the sensor gear 15 projects into the spindle section 6. More precisely, a run-out zone 20 of the screw contour 8 formed on the spindle section 6 and the run-out zone 19 of the sensor gear 15 can overlap. Furthermore, it is even conceivable that an operating zone of the sensor gear 15 overlaps with the run-out zone 20 of the screw contour 8, provided the spur gear 16 is sufficiently wide, e.g., 20 mm with a pitch of approximately 8 mm.

[0048] The sensor gear unit 4 is located in the Fig. 1 to Fig. 3 shown embodiment is designed as a helical spur gear 16 which engages with the sensor teeth 15 of the steering rod 2 in such a way that, when the steering rod 2 moves along its longitudinal axis L about an axis of rotation R (see in particular Fig. 3(a)) rotates. The axis of rotation R is oriented almost parallel to the longitudinal axis L of the steering rod 2. The helix angle of the helical gear of the spur gear 16, which can also be referred to as the sensor gear 17, is approximately 45° as an example. A sensor target 18, e.g., a magnet, is fixedly mounted on the spur gear 16. The sensor target 18 is configured to receive a reading from the sensor device 5 (in Fig. 1 to Fig. 3 (not shown, but designed, for example, as a sensor PCB or sensor chip and arranged opposite the sensor target 18) to be detected. Since the sensor target 18 rotates together with the spur gear 16, the sensor device 5 detects a rotational movement or angle of rotation of the spur gear 16 via the sensor target 18, based on which the position of the steering rod 2 can be determined. In particular, the tooth engagement between the spur gear 16 and the sensor teeth 15 is selected such that the spur gear 16 rotates by less than 360° over the entire travel range of the steering rod 2. This allows the use of simple and cost-effective sensors for the sensor device 5 to determine the position of the steering rod 2.

[0049] Fig. Figure 4 shows an embodiment of the steering unit 1 in which the sensor teeth 15 are arranged or formed on both sides between the pitched circular section 12, which serves as a sliding zone for the pressure piece 10, and the rolling surface 14 for the pressure roller 11. Since the sensor teeth 15 are not located on the rolling surface 14, the pressure roller 11 does not need to be recessed. Furthermore, the sensor device 5 here has several, for example three, spur gears 16, each of which serves as a sensor wheel 17. This creates redundancy, which provides protection in the event of a failure or defect of one of the sensor wheels 17. The multiple sensor wheels 17 do not have to be identical, but can, for example, have different numbers of teeth.

[0050] The bearing unit 9, as shown here, comprises a pressure piece 10 and a pressure roller 11, where the pressure piece 10 is designed here by way of example as a sliding element and the pressure roller 11 by way of example as a rolling element. However, it is also conceivable that both the pressure piece 10 and the pressure roller are designed as sliding elements, or alternatively, both as rolling elements. Furthermore, it is conceivable that the bearing unit 9 has additional sliding and / or rolling elements. It is also conceivable that the anti-rotation device for the steering rod 2, which is implemented here by means of the pressure roller 11 rolling on the rolling surface 13, could instead be implemented by non-circular sliding contours, so-called "V-grooves".

[0051] Fig. Figure 5 shows an embodiment of the steering unit 1 in which the sensor gearing device 4 is designed as a two-stage spur gear 21. The two-stage spur gear 21 comprises a first gear 22 and a second gear 23, which mesh with each other in a predetermined gear ratio. The first gear 22 is also in mesh with the sensor gearing 15 of the steering rod 2, and the second gear 23 functions as the sensor wheel 17. Due to the gear ratio between the first gear 22 and the second gear 23, the first gear 22 can engage over the entire travel range VWL of the steering rod 2, i.e., from the point where the steering rod is in the center of the steering column to the end of the steering column. Fig. 5 from the leftmost position of the first gear 22 (marked 22') to the rightmost position of the first gear (marked 22"), in particular several 360° rotations, since the gear ratio between the first gear 22 and the second gear 23 can be selected such that the entire travel of the steering rod 2 is translated into a rotation of the second gear 23, designed as a sensor wheel 17, of less than 360°. As described above, this allows the use of simple and inexpensive sensors for the sensor device 5 to determine the position of the steering rod 2. Of course, here, as also in the section relating to Fig. 1 to Fig. In the embodiment described in 3, the use of so-called multiturn sensors is also possible, by means of which the position determination of the steering rod 2 is possible even with a rotational movement of 360° or more on the sensor wheel 17.

[0052] Furthermore, the sensor gearing device 4, designed as a two-stage spur gear 21, makes it possible to also design the sensor gearing 15 of the steering rod 2 with straight teeth. Also in Fig. 5 The pressure roller 11 (schematically indicated to the right of the first gear 22) must be partially recessed to prevent it from rolling on the sensor teeth 15 formed in the rolling surface 14. Fig. 5 The second gear 23 is further pre-tensioned by means of a spiral spring 24 to ensure backlash-free gear meshing under all operating conditions. As in Fig. As indicated in Figure 5, the two-stage spur gear unit 21 requires only a small opening or bulge in a housing 25 of the steering rod 2, in the contact area with the steering rod 2.

[0053] Fig. 6 and Fig. Figure 7 shows an embodiment of the steering unit 1 in which the sensor teeth 15 are designed as spiral or helical grooves 26 that essentially circumferentially run around the steering rod 2, and the sensor tooth assembly 4 is designed as an internally toothed ring gear 27. Typically, six to twenty grooves 26 are provided, ten grooves 26 are shown here by way of example, and they have a pitch of approximately 200–400 mm / rev, 300 mm / rev by way of example, resulting in a helix angle β of approximately 60° to approximately 85°. This means that the teeth of the sensor teeth 15 run parallel to the steering rod 2 to within approximately 10°. The internally toothed ring gear 27 engages with the sensor teeth 15 and, due to a comparatively high number of teeth, has a high contact ratio, which improves the tooth engagement. Thus, the internally toothed ring gear 27 serves here as the sensor wheel 17.The ring gear 27 itself is mounted in the housing 25 of the steering rod 2 by means of a sliding or rolling bearing and in particular comprises a plastic, such as a single-type plastic, a plastic mixture, a fiber-reinforced plastic or mixture.

[0054] In the Fig. 6 and Fig. In the embodiment shown in Figure 7, the sensor target 18 is designed as a cylindrical metal target ring that serves as the outer surface of the ring gear 27. Alternatively, a disc-shaped sensor target 18 is also possible. As shown in particular in Fig. As shown in Figure 7, the internally toothed ring gear 27 is designed eccentrically to the steering rod 2. Alternatively, a nut concentric to the steering rod 2 could be used instead of the ring gear 27. The ring gear 27 can, for example, be inserted into the housing 25 of the steering rod from the right or from the left. A split housing would also be conceivable to simplify the installation of the ring gear 27.

[0055] Fig. 8 to Fig. Figure 11 shows an embodiment of the steering unit 1 in which the sensor toothing device 4 is designed as a rack 28, which is arranged perpendicular to the sensor toothing 15 of the steering rod 2 and engages with it. The sensor toothing 15 is shown here as a strong helical toothing in the area of ​​the bearing unit 9, more precisely, in the area of ​​the pressure piece 10. The tooth engagement between the rack 28 and the sensor toothing 15 converts the longitudinal movement of the steering rod 2 along its longitudinal axis L into a longitudinal movement of the rack 28 that is essentially orthogonal or tangential to it. The transmission ratio between the sensor toothing 15 of the steering rod 2 and the toothing of the rack 28 is selected such that the longitudinal movement of the rack 28 is, in particular, less than one-third of the longitudinal movement of the steering rod 2 and is therefore much smaller.shorter and easier to measure.

[0056] The rack 28 is helical and, as an example, is mounted in the pressure piece 10. This means that the rack 28 is in contact with the steering rod 2 via a central area 29 of the pressure piece 10. The function of the pressure piece 10 is not affected, as the pressure piece 10 is only load-bearing in its outer areas 30, but not in the central area 29. The movement of the rack 28 can be, for example, as shown in Fig. 8 and Fig. Figure 9 shows that the movement of the rack 28 is measured or detected by means of moving-coil sensors 31 arranged on both sides. The moving-coil sensors 31 are inductive sensors, which means that the rack 28 must have a metallic material, e.g., iron or steel, at least in the region of its axial ends. Otherwise, the rack 28 can also be made predominantly of a plastic or similar material. The moving-coil sensors 31 are connected to the pressure piece 10 so that they follow any movement of the pressure piece 10, e.g., due to external forces on the steering rod 2.

[0057] The arrangement of the rack 28 within the pressure piece 10 is particularly suitable because the pressure piece is pre-tensioned against the steering rod 2 by a spring element 32 and thus always bears against the steering rod 2. This prevents any distortion of the measurement signal generated by the moving-coil sensors 31, even in the event of external force or deflection of the steering rod 2. Furthermore, by positioning the rack 28 in or near the bearing unit 9, combined with its orientation perpendicular to the steering rod 2, any distortion of the measured value due to deformation of the steering rod 2 can be almost entirely avoided.

[0058] Additionally, the rack is 28, as in Fig.Figure 9 shows that the rack 28 is pre-tensioned both axially and radially to achieve backlash-free operation. This means that the rack 28 is pre-tensioned both parallel to the steering rod 2, here exemplified by a spring element 33 that presses the rack 28 onto the steering rod 2 via a piston-like component 34 (see arrow P1), and perpendicular to the steering rod 2, here exemplified by a spring element 34. To reduce friction between the piston-like component 34 and the rack 28, rolling elements, e.g., balls, needles, rollers, etc., can be arranged in the contact area as so-called "rollers" (not shown), which can reduce the friction and / or resistance in the tooth engagement between the rack 28 and the steering rod 2. Reference symbol list 1 steering unit 2 handlebars 3 Actuator 4 Sensor gearing device 5 Sensor setup 6 Spindle section 7 flattened section 8 screw contour 9 storage units 10 printed pieces 11 Pressure roller 12 partial circle section Section 13 14 rolling surface 15 Sensor gearing 16 Spur gear 17 Sensor wheel 18 sensor target 19 Run-off area 20 Run-off area 21 two-stage spur gear unit 22 first gear 23 second gear 24 spiral springs 25 cases 26 groove 27 Ring gear 28 Rack and pinion 29 middle range 30 outer area 31 Moving coil sensor 32 spring element 33 Spring element 34 stamp-like components 35 Spring element L Longitudinal axis VWL steering rod travel P1 Arrow

Claims

[1] Steering unit (1), in particular a steer-by-wire steering unit, for a vehicle, comprising: a steering rod (2) which is configured to be coupled at each of its axial ends to a wheel of the vehicle, wherein the steering rod (2) has at least a section of sensor teeth (15), an actuator (3) which is coupled to the steering rod (2) such that a rotational movement of the actuator (3) 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 (VWL), a sensor gearing device (4) which at least sectionally has a counter-gear corresponding to the sensor gearing (15) of the steering rod (2) which is in tooth engagement with the sensor gearing (15) of the steering rod (2) in such a way that the translational movement of the steering rod (2) causes a change in position of the sensor gearing device (4) along a predetermined sensor travel path, characterized by , that in the tooth engagement between the sensor toothing device (4) and the sensor toothing (15) of the steering rod (2) a relative sliding occurs which is equal to or greater than 80% of the steering rod travel (VWL) of the steering rod (2), and a sensor device (5) for determining the position of the steering rod (2), which is configured to detect a position of the sensor gear device (4) along the predetermined sensor travel path (15). [2] Steering unit (1) according to claim 1, wherein the sensor toothing (15) of the steering rod (2) has a helix angle (β) of about 45° to 85°. [3] Steering unit (1) according to claim 1 or 2, further comprising a bearing unit (9) for radially supporting the steering rod (2). [4] Steering unit (1) according to one of claims 1 to 3, wherein the sensor toothing (15) of the steering rod (2) is essentially planar. [5] Steering unit (1) according to one of claims 1 to 4, wherein the sensor gearing device (4) is designed as a spur gear (16) which is configured to rotate by a predetermined angle over the entire steering rod travel (VWL). [6] Steering unit (1) according to claim 5, wherein the spur gear (16) is mounted with preload. [7] Steering unit (1) according to one of claims 1 to 3, wherein the sensor gearing device (4) has at least one internally toothed ring gear (27) which is arranged to be rotatable about the steering rod (2), wherein an internal toothing of the ring gear (27) is in tooth engagement with the sensor toothing (15) of the steering rod (2), and wherein the ring gear (27) is arranged to rotate over the entire steering rod travel path (VWL) by a predetermined angle. [8] Steering unit (1) according to any one of claims 1 to 7, wherein the sensor device (5) comprises an inductive sensor (31), an xMR sensor or a Hall sensor.

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