Steering device for a vehicle, use and vehicle with steering device

Abstract

Steering device (1) for steering a vehicle, comprising: an extendable steering rod (2) comprising a first and a second coaxially aligned partial rod (6, 7), characterized in that the first partial rod (6) is at least partially hollow and the second partial rod (7) is arranged at least partially axially displaceable within the first partial rod (6), wherein the steering rod (2) can be coupled to each of its axial end faces (8, 9) with a wheel (24, 26) of the vehicle; a first non-self-locking actuator (3) configured to displace at least the first section rod (6) in the axial direction; and a second self-locking actuator (4) configured to displace the second section rod (7) relative to the first section rod (6) in an axial direction; and a locking device (5) which is designed to fix the first actuator (3) in a predetermined position.

Description

[0001] The present invention relates to a steering device for steering a vehicle, the use of a steering device in a vehicle, and a vehicle with such a steering device. State of the art

[0002] Steering systems for vehicles are known in the prior art in a multitude of embodiments. Both central steering systems and independent wheel steering systems are known. In a central steering system with a steering rod, two wheels are connected via a tie rod and connecting rods and moved by one or more drives. The wheels always move in the same direction, but to different degrees, resulting in the so-called Ackermann steering angles, which ensure that the inner wheel turns more sharply than the outer wheel. In an independent wheel steering system, the wheels are typically not connected via a tie rod, but are moved independently of each other by means of a module. An independent wheel steering system is known, for example, from DE 10 2018 107 358 A1.

[0003] DE 10 2020 108 459 A1 discloses an electromechanical steering actuator with an electric drive motor designed as a hollow motor and a planetary roller screw drive, the rotating nut of which is rotationally fixed to the rotor of the drive motor. The rotating nut is arranged axially next to the rotor, resulting in a compact design. The combination of these features enables a cost-effective design while simultaneously reducing the space required.

[0004] DE 10 2020 203 362 A1 discloses an individual wheel steering system based on the steer-by-wire principle for a motor vehicle, in which a first and a second electric actuator each translationally displace a first and second steering rod, respectively. The first steering rod is connected to a first steerable wheel via a tie rod, while the second steering rod is coupled to a second steerable wheel via another tie rod. The second electric actuator is arranged together with the second steering rod at one end of the first steering rod, so that it moves along with the first steering rod when it is displaced.

[0005] DE 10 2017 106 671 A1 discloses a steering gear for the individual wheel steering of a motor vehicle in a steer-by-wire system, in which each steerable wheel is assigned a threaded spindle unit with its own electric motor. The spindle nut, driven by the electric motor, is rotatably but axially immovably mounted in the gearbox housing, while the corresponding threaded spindle is arranged to be rotationally fixed but axially displaceable. By rotating the spindle nut, the threaded spindle is displaced along its longitudinal axis, thereby pivoting the vehicle wheel; the two threaded spindles can be moved independently of each other.

[0006] DE 10 2016 119 595 A1 discloses a steering system for a vehicle that drives a first actuator which steers a first wheel via a first movable means, and a second actuator which steers a second wheel via a second movable means. The two wheels can be steered independently of each other. The document also describes how either both actuators, both movable means, or all of the aforementioned components are arranged together in a single housing.

[0007] DE 10 2013 222 251 A1 discloses a steering gear for a steerable motor vehicle axle with a first and a second rack segment, each of which positions a corresponding steering knuckle. A gear arrangement with a first and a second actuator engages with the respective rack segments, the actuators being geared together within the gear arrangement. This coupling is adjustable by means of an actuator, so that the two rack segments can be displaced relative to each other within a limited adjustment range.

[0008] It has now become apparent that there is a further need to improve a known steering device for steering a vehicle, in particular a further need to provide a steering device for steering a vehicle that enables both the functions of a central steering system and the functions of individual wheel steering.

[0009] It is therefore an object of the present invention to provide an improved steering device for steering a vehicle, in particular to provide a steering device for steering a vehicle that enables both the functions of a central steering system and the functions of an individual wheel steering system. Disclosure of the invention

[0010] The problem is solved by a steering device for steering a vehicle and a vehicle with such a steering device according to the independent claims. Advantageous embodiments and further developments can be found in the dependent claims and the following description.

[0011] The steering device according to the invention for steering a vehicle comprises an extendable steering rod, a first non-self-locking actuator, a second self-locking actuator, and a locking device. The extendable steering rod has a first and a second coaxially aligned, axially displaceable, preferably cylindrical, section, wherein the first section is at least partially hollow and the second section is arranged to be axially displaceable at least partially within the first section. The steering rod can be coupled to a wheel of the vehicle at each of its axial end faces. The first non-self-locking actuator is configured to displace at least the first, preferably outer, section in the axial direction. The second self-locking actuator is configured to displace a second, preferably inner, section relative to the first section in the axial direction.The locking device is designed to selectively fix the first actuator in a predetermined position.

[0012] The advantage of the solution according to the invention lies particularly in the fact that the steering device enables both central steering, i.e., steering that effects coupled wheel movement, and individual wheel steering, i.e., steering that allows independent movement of the wheels. The coupling of the two wheels by means of the steering rod allows for compensation of differing force application to the wheels coupled by the steering rod. The Ackermann steering angles, as are typical for central steering, are implemented by moving the two sections of the steering rod together, e.g., by activating an actuator, without moving relative to each other. The two sections thus move like a single steering rod.

[0013] Simultaneously, the function of lateral movement is enabled by a 90° steering maneuver, achieved by moving the two steering rods relative to each other, for example, by activating both actuators. Preferably, the extendable steering rod is in a fully extended or retracted position to implement the 90° steering of both wheels.

[0014] In comparison to a single-wheel steering system, the steering device according to the invention requires less installation space in the assembled state, particularly above the wheel, i.e., between the vehicle body and the wheels, since the actuators can be arranged between the wheels, and improves the force transmission through a lower coupling point of the wheels on the steering rod.

[0015] The coupling of both wheels via the steering rod, and the resulting compensation of differing force inputs at the coupled wheels, allows the use of force lever arms greater than 0 mm. This simplifies the design of the steering system. The non-self-locking actuator ensures automatic wheel return within the Ackermann steering angle range. The self-locking actuator has no influence on the steering movement within the Ackermann steering angle range during operation, thus not hindering the automatic wheel return in this range and acting as a fixed connection; that is, the two connecting rod sections function as a single steering rod. The self-locking mechanism of the second actuator ensures that the second connecting rod section does not move unintentionally relative to the first.

[0016] To implement the individual wheel steering mode, both actuators work actively, enabling steering angles outside the Ackermann steering angle range, such as crab steering and / or 90° steering. This also allows the vehicle to move sideways. The locking device ensures a smooth, consistent steering angle setting for the individual wheel steering mode and locks the first, non-self-locking actuator. This allows the entire steering assembly to be fixed relative to the vehicle body and absorbs the opposing forces of the two actuators that occur in individual wheel steering mode. The first actuator is preferably locked when the wheels are in the straight-ahead position within the Ackermann steering angle range.

[0017] According to a preferred embodiment, the first actuator comprises a first drive, a first gearbox, and a first mechanical actuator. The second actuator comprises a second drive, a second gearbox, and a second mechanical actuator. The first and second mechanical actuators are each configured as a gear geometry or a thread geometry on a respective outer circumferential surface of the first and second rod sections. The respective gearbox couples the respective mechanical actuator to the respective drive. The gearbox and the mechanical actuator interact in such a way that a rotational movement of the drive is converted into a translational movement of the steering rod or the respective rod section.

[0018] According to one embodiment, the first mechanical actuator and the first rod section are integrally formed as a single piece, and the second mechanical actuator and the second rod section are integrally formed as a single piece. The integral, one-piece design of the mechanical actuators with their respective rod sections enables functional integration, thereby reducing the total number of components.

[0019] According to one embodiment, the first mechanical actuator and the first gearbox are coupled in such a way that they form a non-self-locking spindle drive, e.g. a planetary roller screw drive, a ball screw drive, a trapezoidal screw drive, or a steep-pitch screw drive, or a non-self-locking rack and pinion drive.

[0020] The first mechanical actuator can be, for example, a roller screw, a ball screw, a trapezoidal screw, a high-helix screw, or a rack, and the first gear can be a screw nut, such as a ball screw nut, a roller screw nut, a trapezoidal screw nut, or a high-helix screw nut, or a gear. The non-self-locking screw drives allow the vehicle's wheels to automatically return to the straight-ahead position and enable a compact, space-saving design.

[0021] According to one embodiment, the second mechanical actuator and the second gearbox are coupled such that they form a self-locking spindle drive, e.g., a planetary roller screw drive or a trapezoidal screw drive, or a worm linear drive. Alternatively, the second mechanical actuator and the second gearbox can be coupled such that they form a non-self-locking spindle drive, e.g., a planetary roller screw drive, a ball screw drive, a trapezoidal screw drive, or a high-pitch screw drive, or a non-self-locking rack and pinion drive, and the second gearbox has a self-locking feature, e.g., in the form of a worm or wave drive. The degree of self-locking of the planetary roller screw drive or the trapezoidal screw drive can be adjusted via the thread pitch and / or the preload.The self-locking mechanism in the second actuator ensures that the relative movement between the two sections of the steering rod only occurs when force is actively applied, thus preventing relative movement in the range of the Ackermann steering movement.

[0022] The second mechanical actuator can be designed as a roller screw spindle, a ball screw spindle, a trapezoidal screw spindle, a high-helix screw spindle or a rack and the second gear can have a spindle nut, e.g. a ball screw nut, a roller screw nut, a trapezoidal screw nut, or a high-helix screw nut, or a gear.

[0023] According to one embodiment, the first and second drives are designed as a single, combined drive. This combined drive is coupled to both gearboxes or actuators, for example, via a coupling unit. By engaging one coupling, the respective actuator coupled to that coupling can be operated. Rapid switching between the two couplings allows for nearly uniform movement, similar to simultaneous operation of both actuators. This reduces the number of drives required. The first and / or second drive are preferably designed as electric motors.

[0024] According to one embodiment, the locking device is configured to fix the first actuator in a predetermined position by means of a positive locking mechanism, a frictional locking mechanism, or, preferably, an electronic control system. The locking device is preferably designed with the default position "open." The positive locking mechanism can be achieved, for example, by means of a solenoid, a DC motor with end-stop control, or a displacement-controlled motor. The frictional locking mechanism can be implemented as a linear freewheel, linear lamella packs, or another linear surface pairing. The electronic control system allows the locking device to be activated in any position of the steering rod and causes the steering rod to be moved into the predefined locking position after an activation request.

[0025] Further aspects of the invention relate to the use of a steering device according to the invention in a vehicle, as well as a vehicle with at least two wheels spaced parallel to each other, and a steering device according to the invention, wherein the steering device is coupled to one of the two wheels at each axial end face. Detailed description based on drawing

[0026] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show: Fig. 1 a schematic representation of a steering device according to an embodiment of the invention, Fig. 2a to 2c schematic representations of various exemplary steering angle positions in the area of ​​the Ackermann steering movement, and Fig. 3 A schematic representation of a steering angle position for a sideways movement of a vehicle.

[0027] Fig. Figure 1 shows a schematic representation of a steering device 1 according to one embodiment. The steering device 1 comprises an extendable steering rod 2, a first actuator 3, a second actuator 4, and a locking device 5.

[0028] The steering rod 2 comprises a first section 6 and a second section 7, the first section 6 being essentially hollow. The second section 7 is designed such that it can be at least partially inserted into the first section 6 and is arranged to be axially movable relative to the first section 6. The steering rod 2 has a wheel coupling point 8, 9 on each of its two axial end faces, to which a wheel of a vehicle (not shown in the figures) can be coupled. A first wheel coupling point 8 is arranged on an axial end face of the first section 6, and a second wheel coupling point 9 is arranged on an axial end face of the second section 7.

[0029] The first actuator 3 comprises a first drive 10, a first gearbox 11, and a first mechanical actuator 12. The first mechanical actuator 12 is designed as a gear geometry 13 on a circumferential surface of the first section rod 6. The first drive 10 can be an electric motor that transmits torque to the first gearbox 11 via an output shaft 14. The first gearbox 11 has a counter-geometry 15 designed corresponding to the gear geometry 13 of the first mechanical actuator 12, which interacts with the gear geometry 13 of the first mechanical actuator 12 in such a way that the rotational movement of the output shaft 14 of the first drive 10 is converted into a translational movement of the first section rod 6. The first mechanical actuator 12 and the first gearbox 11 are preferably designed as a spindle drive that does not have self-locking capability.Examples of such a non-self-locking spindle drive are a planetary roller screw drive, a ball screw drive, a trapezoidal screw drive, or a high-helix screw drive. A rack and pinion drive is also conceivable. The first actuating element 3 is configured to move the first section rod 6 back and forth in the axial direction A.

[0030] The second actuator 4 comprises a second drive 16, a second gearbox 17, and a second mechanical actuator 18. The second mechanical actuator 18 is configured as a gear geometry 19 on an outer circumferential surface of the second section rod 7. The second drive 16 can be an electric motor that transmits torque to the second gearbox 17 via an output shaft 20. The second gearbox 17 has a counter-geometry 21 configured corresponding to the gear geometry 19 of the second mechanical actuator 18, which interacts with the gear geometry 18 of the second mechanical actuator 18 in such a way that the rotational movement of the output shaft 20 of the second drive 16 is converted into a translational movement of the second section rod 7. The second mechanical actuator 18 and the second gearbox 17 are preferably configured as a spindle drive with self-locking capability.Examples of such a self-locking spindle drive are a planetary roller screw drive or a trapezoidal screw drive, where the thread pitch and / or the preload influence the degree of self-locking. A worm linear drive is also conceivable. Furthermore, it is also conceivable that the second mechanical actuator 18 and the second gear 17 form a non-self-locking spindle drive, and that the second gear 17 incorporates a self-locking element, e.g., a worm or wave gear. It is also conceivable that the second gear 17 and the spindle drive formed by the coupling of the second gear 17 and the second mechanical actuator 18 are each designed to be non-self-locking, but interact with each other to cause self-locking of the second actuator 4.

[0031] The self-locking mechanism of the second actuator 4 causes the second rod section 7 to move along with the first rod section 6 as long as the second actuator 4 is not actively operated and / or the locking device 5 is not closed. In the embodiment shown here, both gearboxes 11, 17 have a housing 22, 23, wherein the housing 23 of the second gearbox 17 is rotationally and axially fixed to the second rod section 7.

[0032] The locking device 5 is in Fig. The locking device 5 is represented symbolically by two arrows and is designed with the default position "open". This means that the locking device 5 is open in a load-free state and closes upon activation, e.g., the application of a load, remaining closed as long as the activation is active. The locking device 5 serves to fix the first mechanical actuator 3, in this case the first section 6, in a predetermined position. If the second actuator 4 is activated while the locking device 5 is closed, the locking device 5 absorbs the opposing forces of the first and second actuators 3, 4, thereby displacing the second section 7 relative to the first section 6. The locking device 5 can be implemented in various ways. For example, the locking device 5 can be configured so that the locking is achieved by means of a positive locking or a frictional locking mechanism.Alternatively, it is also possible to design the locking device 5 in such a way that the locking is implemented in a software-controlled manner.

[0033] When the locking device 5 is open, the second connecting rod 7 moves axially with the first connecting rod 6, particularly due to the self-locking mechanism of the second actuator 4, and steering of the two coupled wheels is implemented within the range of the Ackermann steering movement. To implement, for example, sideways movement, the wheels must each be steered by 90° in opposite directions relative to a straight-ahead direction. For this purpose, the locking device 5 is closed and the second actuator 4 is activated to move the second connecting rod 7 relative to the first connecting rod 6 so that the length of the steering rod 2 increases.

[0034] The Fig. Figures 2a to 2c illustrate different steering angle positions for a wheel 24, which is coupled to the first partial rod 6 via connecting rods 25, in the area of ​​the Ackermann steering movement according to an embodiment of the invention. Fig. 2a shows a steering angle position in a first curve direction, Fig. 2b shows a steering angle position for driving straight ahead and Fig. Figure 2c shows a steering angle position for a second turning direction. To set these three steering positions, the locking device 5 is open and only the first actuator 3 is activated. The steering rod 2 acts like a single steering rod and, together with the connecting rods 25, steers the coupled wheels analogously to a central steering system and within the Ackermann steering angles.

[0035] Fig.Figure 3 schematically illustrates a steering angle position for lateral movement of the vehicle. To set these 90° steering angles for each of the two wheels 24, 26, the locking device 5 is closed, and both the first actuator 3 and the second actuator 4 are active. The second actuator 4 thus exerts a force on the second section 7 of the steering rod 2, causing the second section 7 to move relative to the first section 6, here by way of example, into an extended position (of the steering rod 2). By activating both actuators 3, 4, the wheels 24, 26 can be steered independently of each other, in particular in opposite directions.

[0036] The steering device 1 described above is one possible embodiment. In this embodiment, the second actuator 4 is only active to effect a relative movement of the second rod section 7 to the first rod section 6. However, it is also conceivable that the actuators 3 and 4 are fixed to the vehicle body and that both actuators 3 and 4 are active to adjust the steering positions, both within the range of Ackermann steering angles, in which the two wheels 24 and 26 are steered together in the same direction relative to each other, and for independent movement, e.g., for lateral movement. Furthermore, it is also conceivable that the drives 10 and 16 are fixed and coupled to the respective transmissions 11 and 17 via variable-travel couplings.Furthermore, it is also conceivable to design both actuators 3, 4 as non-self-locking and to effect self-locking of the second actuator 4 by means of a locking mechanism, whereby the locking mechanism can be implemented both mechanically and control-technically. Reference symbol list 1 Steering device 2 handlebars 3 first actuator 4 second actuator 5 Locking device 6 first section rod 7 second section rod 8 Wheel coupling point 9 Wheel coupling point 10 first drive 11 first gearbox 12 first mechanical actuator 13 Gear geometry 14 Output shaft 15 Counter-geometry 16 second drive 17 second gearbox 18 second mechanical actuator 19 Gear geometry 20 Output shaft 21 Opposite geometry 22 cases 23 cases 24-inch wheel 25 Connecting rod 26-inch wheel A Axial direction

Claims

Steering device (1) for steering a vehicle, comprising: an extendable steering rod (2) having a first and a second coaxially aligned sub-rod (6, 7), characterized in that the first sub-rod (6) is at least partially hollow and the second sub-rod (7) is arranged to be axially displaceable at least partially within the first sub-rod (6), wherein the steering rod (2) can be coupled to a wheel (24, 26) of the vehicle at each of its axial end faces (8, 9); a first non-self-locking actuator (3) configured to displace at least the first sub-rod (6) in the axial direction; and a second self-locking actuator (4) configured to displace the second sub-rod (7) relative to the first sub-rod (6) in the axial direction; and a locking device (5) configured to fix the first actuator (3) in a predetermined position. Steering device (1) according to claim 1, wherein the first actuator (3) comprises a first drive (10), a first transmission (11) and a first mechanical actuator (12) and the second actuator (4) comprises a second drive (16), a second transmission (17) and a second mechanical actuator (18), wherein the first mechanical actuator (12) and the second mechanical actuator (18) are each formed as a toothed geometry or as a threaded geometry (13, 19) on a respective outer circumferential surface of the first partial rod (6) and the second partial rod (7). Steering device (1) according to claim 2, wherein the first mechanical actuator (12) and the first partial rod (6) are formed in one piece and the second mechanical actuator (18) and the second partial rod (7) are formed in one piece. Steering device (1) according to claim 2 or 3, wherein the first mechanical actuator (12) and the first transmission (11) are coupled such that they form a non-self-locking spindle drive or a non-self-locking rack and pinion drive. Steering device (1) according to one of claims 2 to 4, wherein the second mechanical actuator (18) and the second transmission (17) are coupled in such a way that they form a self-locking spindle drive or a worm linear drive. Steering device (1) according to one of claims 2 to 4, wherein the second mechanical actuator (18) and the second transmission (17) are coupled such that they form a non-self-locking spindle drive or a non-self-locking rack and pinion drive and the second transmission (17) has a self-locking mechanism. Steering device (1) according to one of claims 2 to 6, wherein the first drive (10) and the second drive (16) are designed as a common drive. Steering device (1) according to one of claims 1 to 7, wherein the locking device (5) is configured to fix the first actuator (3) in a predetermined position by means of a positive locking, a frictional locking or by means of a control. Use of a steering device (1) according to one of the preceding claims in a vehicle. Vehicle comprising at least two parallel spaced wheels (24, 26) and a steering device (1) according to one of claims 1 to 8, wherein the steering device (1) is coupled to one of the two wheels (24, 26) at each axial end face (8, 9).

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