Independent steering device and vehicle

Abstract

Individual wheel steering device (100) for a steerable vehicle axle, comprising two separately controllable individual wheel adjusters (200) which are operatively connected to each wheel of the vehicle axle for individual adjustment of a steering angle and which are operatively connected to each other by means of a backlash connecting device (400), wherein the backlash connecting device (400) comprises two connecting rods (410) which are each operatively connected at a first end to an individual wheel adjuster (200) and are connected to each other at a second end by means of a backlash coupling (420), characterized in that the backlash coupling (420) comprises two coupling halves (423, 424) which are freely rotatable about a vehicle-fixed axis (A) and which are rotatable relative to each other within a structurally defined angular range.

Description

[0001] The invention relates to a single-wheel steering device with the features of the preamble of claim 1 and a vehicle with the features of the preamble of claim 6.

[0002] In steer-by-wire systems, there is no direct mechanical connection between the steering wheel and the steering linkage, and the vehicle wheels are moved directly by a servo motor. The steerable wheels of such systems are typically mechanically coupled to tie rods.

[0003] In a steer-by-wire system with independent wheel steering, the steering angle of each of the two steered wheels is implemented by an actuator. Each of these actuators must be designed to withstand the maximum tie rod forces acting on the wheel to which it is connected. The actuators must therefore be particularly powerful to provide the maximum pivoting forces required to turn the steerable wheels.

[0004] From the generic document DE 10 2021 206 473 A1, an individual wheel steering system for a vehicle is known, in which at least one spring is attached to each steering actuator, via which the forces generated at the wheel during driving are transmitted. The document further discloses that the steering actuators can be connected to each other by the spring.

[0005] DE 10 2020 203 362 A1 discloses an individual wheel steering system for a vehicle's steer-by-wire system, comprising a first electric actuator that moves a first steering rod and a second electric actuator that moves a second steering rod. The steering rods are each connected to one of the wheels via a tie rod. The second actuator is located at one end of the first steering rod, so that the second actuator and the second steering rod move together with the first steering rod.

[0006] In contrast, WO 2017 / 198549 A1 proposed a steer-by-wire steering system for motor vehicles with at least two steering actuators acting on the steered wheels, electronically controlled depending on a driver's steering input. In this system, the at least two steering actuators each have an actuator with an output shaft. In a normal case, each steerable vehicle wheel is assigned a single steering actuator with an actuator in the form of individual wheel steering. A rotation of the actuator's output shaft causes the respective steerable vehicle wheel to rotate about a pivot axis. A switchable clutch is provided, designed to be open in the normal case and closed in a special case. In the closed state, the clutch connects the individual wheel steering systems.that drive power can be transferred from one individual wheel steering system to another to rotate a steerable vehicle wheel. By connecting the actuators in special cases where particularly high tie rod forces are present, such as during parking, the actuators can be made smaller while still providing the required high pivoting forces.

[0007] One object of the invention is to improve a single-wheel steering device in such a way that the vehicle remains maneuverable even if one of the steering actuators fails.

[0008] The problem is solved according to the invention by a single-wheel steering device having the features of the characterizing part of claim 1 and a vehicle having the features of the characterizing part of claim 4. Advantageous embodiments of the invention are the subject of the dependent claims.

[0009] In a single-wheel steering device for a steerable vehicle axle, comprising two separately controllable single-wheel actuators, each operatively connected to a wheel of the vehicle axle for individual steering angle adjustment, it is proposed that the single-wheel actuators be operatively connected to one another by means of a backlash-prone connecting device. According to the invention, the backlash-prone connecting device comprises two connecting rods, each operatively connected at a first end to a single-wheel actuator and connected to one another at a second end by means of a backlash-prone coupling. Furthermore, the backlash-prone coupling comprises two coupling halves, freely rotatable about a vehicle-fixed axis and rotatable relative to each other within a structurally defined angular range.In this case, the specified angular range defines the limits of the relative movement of the connecting rods, and thus also of the individual wheel adjusters and the wheels of the vehicle axle. The angular range, in this case, is the play that the coupling of the connecting device provides for independent positioning of the two wheels.

[0010] Each individual wheel actuator can be operatively connected to a wheel of the motor vehicle axle by means of a steering lever, which is arranged at the first end of the respective connecting rod, and a tie rod, so that an actuator of the individual wheel actuator transmits a steering movement via the steering lever to the tie rod, and the tie rod transmits the steering movement to the corresponding wheel.

[0011] In previously known independent wheel steering systems, the individual wheel actuators, and thus the wheels of the vehicle axle, are, as described above, either completely independent of one another, or they are rigidly coupled to one another, or they can be connected or disconnected as needed by means of a switchable clutch. In the proposed independent wheel steering system, however, the individual wheel actuators, or rather the wheels of the vehicle axle, are normally independent of one another due to the play in the connecting device, so that each wheel is moved by only one of the two individual wheel actuators. If, however, one of the individual wheel actuators fails, the intact individual wheel actuator also acts on the wheel associated with the defective actuator as soon as the steering angle error of this other wheel is so large that the play in the connecting device is exhausted.

[0012] The backlash-prone coupling is designed to allow relative movement of the two individual wheel actuators, and thus of the wheels of the vehicle axle, within defined limits. However, upon reaching these limits, a forced coupling of the two individual wheel actuators, and thus of the wheels of the vehicle axle, occurs, whereby one of the individual wheel actuators then acts on both wheels. The relative movement can be translational or rotational.

[0013] Furthermore, the coupling may include a return element that holds the coupling halves centered within the angular range when no external load is applied. The return element could, for example, be a spring element.

[0014] The object of the invention is further achieved by a vehicle with at least one steerable vehicle axle, in which the vehicle axle comprises at least one single-wheel steering device of the type described above.

[0015] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0016] This shows: Fig. 1 schematically an embodiment of the single wheel steering device, Fig. 2 schematically an enlarged representation of a single wheel actuator of the exemplary embodiment, Fig. 3 schematically an enlarged representation of a coupling of the exemplary embodiment, Fig. 4 schematically a mounting diagram of the coupling made of Fig. 3, and Fig. 5 schematically a cross-sectional view of the coupling from Fig. 3.

[0017] Corresponding parts are marked with the same reference symbols in all figures.

[0018] The embodiment describes a single-wheel steering device 100 for a motor vehicle with steered front wheels that can be controlled individually and are connected via a coupling on the right and left.

[0019] The single-wheel steering device 100 comprises two single-wheel actuators 200, which are fixedly arranged in the vehicle and transmit the steering torque to the steered front wheels by means of steering lever 310 and tie rod 320, wherein the tie rods 320 are each connected to a steering lever 310 by means of a ball joint 321.

[0020] In the exemplary embodiment, the individual wheel actuators 200 are designed as double worm gear steering drives, i.e., two worm gears 220 connected in series, which allows for a very high gear ratio. This high gear ratio makes it possible to use smaller motors with lower drive torque as actuators 210, resulting in weight and cost advantages. The individual wheel actuators 200 also include control electronics 211 with a sensor 212 that detects the angular position of the steering lever 310 and thus the wheel angle.

[0021] The design of the single wheel actuator 200 is not relevant to the invention; other solutions, such as single wheel actuators 200 with gear stages, with harmonic drive, with cycloidal gear or planetary gear, which are not self-locking, can also be used.

[0022] The object of the invention is to support the individual wheel adjusters 200 in the event of external force or failure, in order to minimize steering input of the wheels or to prevent complete wheel rotation. For this purpose, the two sides of the vehicle axle are connected to each other by means of a loose-connecting device 400. In the exemplary embodiment, each of the two individual wheel adjusters 200 is connected to an inwardly arranged connecting rod 410, which is connected on the opposite side to a vehicle-mounted coupling 420.

[0023] The connecting rods 410 to the individual wheel adjuster 200, more precisely to the steering lever 310, and to the coupling 420 are advantageously connected via ball joints 411 to allow spatial movement of the connecting rod 410. The position of the coupling 420 on the vehicle is determined, for example, so that the connecting rods 410 have the same length. Individual adjustment of the length of the connecting rods 410 is possible.

[0024] The coupling 420 comprises two coupling halves 423, 424. The coupling halves 423, 424 and the vehicle-mounted pivot axis are advantageously combined in a single assembly. In the exemplary embodiment, the coupling halves 423, 424 are rotatably arranged on a bearing journal 422 of a coupling bearing 421, which is mounted to the vehicle by means of screws 427. The coupling halves 423, 424 can rotate on the coupling bearing 421 about a vehicle-mounted axis A defined by the bearing journal 422 in the same or opposite directions to each other, and they can rotate together about the vehicle-mounted axis A, i.e., about the bearing journal 422. This assembly is referred to herein as the coupling 420.

[0025] The coupling halves 423, 424 are pre-tensioned relative to each other in the direction of rotation by a return element 426 in the form of a spring element. The return element 426 generates a pre-tension that is transferred to the connecting rods 410, thus counteracting vibration effects. The connecting rods 410 are each connected to a coupling half 423, 424, with the connecting rods being attached on one side, above or below the axis of rotation, i.e., the bearing journal 422.

[0026] The two coupling halves 423, 424 are designed such that a first coupling half 423 engages with its outer contour in an inner contour of a second coupling half 424 defined by two stops 425, thereby structurally determining the maximum angle of rotation of both coupling halves 423, 424 relative to each other.

[0027] During a steering maneuver – with both wheels moving in the same direction – both coupling halves 423, 424 are rotated together in the corresponding steering direction. Different wheel angles (Ackermann condition) are possible because the coupling halves 423, 424 can rotate freely relative to each other within the structurally defined angle of rotation.

[0028] By designing the coupling 420 and the fixed rotation angle of both coupling halves 423, 424 to each other, the steering can also be adjusted in opposite directions within the limits of the rotation angle, for example to optimize the track setting while driving, to reduce steering error or to implement anti-Ackermann.

[0029] The key advantage of coupling both sides of the vehicle axle by a loose-connecting device 400 is that, if one of the individual wheel adjusters 200 fails, the wheel associated with that individual wheel adjuster 200 does not rotate completely, since the associated connecting rod 410 of the failed wheel side can be supported by the coupling 420 on the functioning wheel side. In this process, the corresponding coupling half 423, 424 of the failed wheel side rotates relative to the coupling half 423, 424 of the functioning wheel side within the design-defined angle of rotation until both coupling halves 423, 424 are rotated relative to each other at stop 425.

[0030] The resulting deviation between the left and right wheel angles, increasing toe-in or toe-out, can be reduced by the functioning individual wheel adjuster 200, for example, when driving straight ahead. Furthermore, the wheel angle of the failed individual wheel adjuster 200 can be modified by the functioning individual wheel adjuster 200 to increase the driving time or at least to enable limp-aside.

Claims

[1] Individual wheel steering device (100) for a steerable vehicle axle, comprising two separately controllable individual wheel actuators (200) which are operatively connected to each wheel of the vehicle axle for individual adjustment of a steering angle and which are operatively connected to each other by means of a backlash connecting device (400), wherein the backlash connecting device (400) comprises two connecting rods (410) which are each operatively connected at a first end to an individual wheel actuator (200) and are connected to each other at a second end by means of a backlash coupling (420), characterized by , that the play-in coupling (420) comprises two coupling halves (423, 424) which are freely rotatable about a vehicle-fixed axis (A) and which can be rotated relative to each other within a structurally defined angular range. [2] Single-wheel steering device (100) according to claim 1, characterized by, that each individual wheel adjuster (200) is operatively connected to a wheel of the motor vehicle axle by means of a steering lever (310) and a tie rod (320). [3] Single-wheel steering device (100) according to claim 1 or claim 2, characterized by , that the coupling (420) includes a restoring element (426) by which the coupling halves (423, 424) are held centrally within the angular range when no external load is acting. [4] Vehicle with at least one steerable axle, characterized by , that the vehicle axle comprises at least one single-wheel steering device (100) according to one of claims 1 to 3.

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