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

Abstract

Steering device (1) for steering a vehicle, comprising a first steering rod (2) and a second steering rod (3), wherein the steering rods (2, 3) can each be coupled to an actuator (4) at one of their axial end faces, wherein at least one of the steering rods (2, 3) has a locking mechanism (5) which is configured to decouple this steering rod (2, 3) from a predetermined position, characterized in that the locking mechanism (5) is provided inside at least one of the steering rods (2, 3).

Description

Field of invention 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. Background of the invention 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. DE 10 2016 006 088 A1 discloses a steer-by-wire steering system for motor vehicles with at least two electronically controlled steering actuators, a feedback actuator for transmitting restoring torques to a steering wheel, and a control unit that controls the feedback actuator and the steering actuators to generate drive power. The at least two steering actuators each have an actuator with an output shaft; normally, each steerable wheel is assigned an individual steering actuator in the form of an individual wheel steering system, the output shaft of which causes the rotation of the respective wheel. Furthermore, a switchable clutch is provided, which is normally open and closed in a special case, for example, when parking. In the closed state, the clutch connects the individual wheel steering systems to each other in such a way that drive power can be transmitted from one individual wheel steering system to the other to rotate a steerable wheel. DE 10 2007 002 266 A1 discloses a method for operating a motor vehicle in which, during a driving maneuver, the steering is at least partially automatically actuated, and the assignment of certain steering positions of the wheels to corresponding positions of the steering control device is changed from a standard assignment. To restore the standard assignment, the steering position of the wheels is adjusted depending on the deviation from the standard assignment. This is intended to ensure that the steering remains intuitively controllable by the driver after the driving maneuver. DE 10 2016 208 775 A1 discloses a steer-by-wire system for a motor vehicle with at least two wheels that can be steered independently of each other in normal operation, each with its own steering actuator, and steering electronics connected to the steering actuators via a signal system. The steering electronics are designed to individually control the steering actuators based on steering commands and to detect whether one of the steering actuators has failed. If a steering actuator failure is detected, the system provides for controlling at least one further steering actuator with a steering ratio whose directness differs from the directness of the steering ratio in normal operation. 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. Summary of the invention It is therefore an object of the present invention to provide an improved steering device for steering a vehicle, in particular 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. According to the invention, this problem is solved by a steering device for steering a vehicle, comprising a first steering rod and a second steering rod, wherein the steering rods can each be coupled to an actuator at one of their axial end faces, wherein at least one of the steering rods has a locking mechanism which is configured to decouple this steering rod from a predetermined position. 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 steering rods together in a predetermined position by means of the locking mechanism, without moving relative to each other. The Ackermann relationship can be released by deactivating the locking mechanism, which is provided on at least one of the steering rods.For this purpose, the rigid connection of the steering rods is decoupled using the locking mechanism, allowing the wheels to freely adjust their steering angle. This design makes it possible to perform a so-called crabwalk and / or to steer the wheels in the opposite direction. 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, between the vehicle body and the wheels, since the entire assembly can be arranged between the wheels. According to one embodiment of the invention, the steering rod with the locking mechanism comprises a first rod section and a second rod section, which are coupled by means of a tie rod spring element. The first and second rod sections are aligned coaxially with each other and are axially displaceable relative to each other. Preferably, these are designed as cylindrical rod sections, wherein the first rod section is at least partially hollow and the second rod section is arranged to be axially displaceable at least partially within the first rod section. Preferably, the tie rod spring element is provided within the hollow rod section. According to one embodiment of the invention, the locking mechanism comprises a locking actuator and at least one pre-tensioned locking element. As soon as the locking mechanism is deactivated, the locking actuator is activated, which in turn releases the pre-tension of the locking element. This release causes the two rod sections to no longer be rigidly connected to each other by means of the tie rod spring element and consequently to be axially displaceable. Preferably, the locking element is arranged on the two rod sections such that axial displacement of the rod sections is prevented. In an advantageous embodiment, the pre-tension is achieved by means of a spring element. For example, a solenoid can be provided as the locking actuator. Preferably, the locking mechanism includes at least one clamping element that releases the at least one pre-tensioned locking element. The clamping element can be actuated directly by the locking actuator to release the pre-tension of the locking element. Depending on the available space and application, the locking mechanism is provided inside at least one of the steering rods or on an external side of at least one steering rod. 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. Brief description of the drawing Three exemplary embodiments of the invention are illustrated below with reference to six figures. These show: Fig. 1 a schematic representation of a steering device according to the invention, Fig. 2 a detailed view of section I from Fig. 1, Fig. 3 a locking mechanism of the steering device according to a first embodiment, Fig. 4 a locking mechanism of the steering device according to a second embodiment, Fig. 5 a locking mechanism of the steering device according to a third embodiment, and Figs. 6a-6e a schematic description of a decoupling process of the steering device according to the invention. Detailed description of the drawings Fig. 1 schematic representation of a steering device 1 according to the invention. The steering device 1 has a first steering rod 2 and a second steering rod 3, wherein the steering rods 2, 3 can each be coupled to an actuator 4 at one of their axial end faces. A locking mechanism 5 is provided on at least one of the steering rods 2, 3, in this example the first steering rod 2, which is configured to decouple the first steering rod 2 from a predetermined position. It is also possible to provide the locking mechanism additionally or only on the second steering rod 3. Furthermore, the two steering rods 2, 3 are connected via pivot points 6 to a track rod 7 each. Each track rod is in turn connected either to an axle body 8 or directly to the respective wheel 9. The axle body 8 can also be a frame or other chassis structure. The track rod 7 is also connected via pivot points 6. Fig. 2 shows an enlarged view of the assembly of the steering rod 2, which includes the locking mechanism 5. The following assembly refers primarily to the first steering rod 2, but is not limited to it. The same assembly can also refer to the second steering rod 3. The steering rod 2 comprises a first section 10 and a second section 11, which are coupled by means of a tie rod spring element 12. The tie rod spring element 12 can be designed as a spring or other elastomer. The first and second sections 10, 11 are aligned coaxially with each other and are axially displaceable relative to each other. The first section 10 is at least partially hollow, and the second section 11 is arranged to be axially displaceable at least partially within the first section 10. As can also be seen, the tie rod spring element 12 is arranged within the hollow section 10. The tie rod spring element 12 is supported on one side by the second section 11 and on the other side by a pivot point 6. The locking mechanism 5 is provided between the first section 10 and the second section 11. For a detailed explanation of the locking mechanism 5, reference is now made to Figures 3, 4 to 5, which illustrate three different embodiments of the locking mechanism. The actuated locking mechanism 5 allows the prevailing rigid steering geometry to be temporarily overridden. This eliminates the Ackermann steering angle relationship between the two wheels 9, making the desired crab steering maneuver, for example, possible. A detailed description of the process is given with reference to Figures 6a to 6e. Fig. 3 describes a first embodiment of the locking mechanism 5. This is a locking mechanism that acts from the inside out, meaning that the locking mechanism 5 is arranged inside the two rod sections 10, 11. To release the rigid connection between the two rod sections 10, 11, a locking actuator 13 is provided inside one of the rod sections 10, 11, which releases a pre-tensioned locking element 15. The pre-tensioning is achieved by means of spring elements 16. When the connection is to be released, the locking actuator 13 is actuated and moves a clamping element 14 connected to it, so that the pre-tensioned locking elements 15 are pushed radially R inwards via the spring elements 16. Consequently, the locking mechanism 5 is deactivated. As soon as the locking elements are back in their pre-tensioned position, the locking mechanism 5 is activated.Advantageously, the clamping elements 14 are provided with a ramp structure against which the spring elements 16 rest, making it easier to release the preload. Once the connection is released, the two partial rods 10, 11 are only "softly" connected to each other via the tie rod spring element 12 and can be moved axially A into each other. Fig. 4 shows another embodiment of the locking mechanism 5. Its operation is identical to that described in Fig. 3. The main difference lies in the arrangement of the locking mechanism 5. This is a locking mechanism that acts from the outside in, meaning that the locking mechanism 5 is located outside the two connecting rods 10 and 11. The process for releasing the connection is the same as described in Fig. 3, whereby the pre-tensioned locking elements 15 are pressed radially outwards by the spring elements 16. Fig. 5 shows another embodiment of the locking mechanism 5. Its operation is identical to that described in Fig. 3 or Fig. 4. The difference lies in the operative connection between the locking actuator 13 and the pre-tensioned locking element 15. In this embodiment, no clamping element is interposed; the locking actuator 13 acts directly on the spring element 16 and consequently releases the pre-tension directly. Such a variant can be provided in either the assembly shown in Fig. 3 or the assembly shown in Fig. 4. Figures 6a to 6e show a schematic description of a decoupling process of the steering device 1. Figure 6a shows the steering system, for example, for driving straight ahead. The locking mechanism is active here, meaning that the steering rods 2 and 3 are geometrically rigidly connected to each other. Since no steering is taking place, the steering angle relationship is not relevant at this point. Figure 6b shows the beginning or start of a parking maneuver or a turn. The locking mechanism 5 remains active, and the two steering rods 2, 3 are geometrically rigidly connected. The vehicle is steered using the Ackermann steering angle relationship. This relationship is still sufficient for the parking maneuver described in the application at this point. As soon as a parking maneuver using the crab-like trajectory is to be performed, as shown in Fig. 6c, this is no longer possible based on the Ackermann relationship. The locking mechanism 5 is deactivated, as described in Figs. 3, 4 to 5, whereby the two steering rods 2, 3 are no longer rigidly connected geometrically. There is a leading (steered) wheel and a following wheel. The steered wheel is set to the desired steering angle for the crab-like trajectory (steering angle > 10°) via the actuator 4. Due to the disconnected connection of the steering rods 2, 3 and the caster angle in the axle kinematics, the following wheel will follow the steered wheel, thus enabling the described crab-like trajectory maneuver. Once the described process, i.e., for example, the parking maneuver, is completed (Fig. 6d), the wheels 9 (in preparation for the exit maneuver) are moved back from the set steering angle of the crab steering position to the straight-ahead position. Since there is no vehicle movement, only the leading wheel is actively moved. As soon as the locking mechanism 5 reaches its engagement point, the locking mechanism 5 is reactivated and the Ackermann relationship between the left and right wheels is restored. Fig. 6e then shows parking or driving straight ahead, which corresponds to Fig. 6a. Reference symbol list 1 Steering mechanism 2 First steering rod 3 Second steering rod 4 Actuator 5 Locking mechanism 6 Joint point 7 Track lever 8 Axle housing 9 Wheel 10 First connecting rod 11 Second connecting rod 12 Tie rod spring element 13 Locking actuator 14 Clamping element 15 Locking element

Claims

Steering device (1) for steering a vehicle, comprising a first steering rod (2) and a second steering rod (3), wherein the steering rods (2, 3) can each be coupled to an actuator (4) at one of their axial end faces, wherein at least one of the steering rods (2, 3) has a locking mechanism (5) which is configured to decouple this steering rod (2, 3) from a predetermined position, characterized in that the locking mechanism (5) is provided inside at least one of the steering rods (2, 3). Steering device according to claim 1, wherein the steering rod (2, 3) with the locking mechanism (5) has a first partial rod (10) and a second partial rod (11), wherein these are coupled by means of a tie rod spring element (12). Steering device according to one of the preceding claims, wherein the locking mechanism (5) comprises a locking actuator (13) and at least one pre-tensioned locking element (15). Steering device according to one of the preceding claims, wherein the locking mechanism (5) provides at least one clamping element (14) which releases the at least one pre-tensioned locking element (15). Steering device according to claims 1 to 4, wherein the locking mechanism (5) is provided on an outer surface of at least one steering rod (2, 3). Steering device according to one of the preceding claims, wherein the steering rods (2, 3) are coupled to an axle body (8) and / or a wheel (9) by means of a track lever (7). Use of a steering device (1) according to one of the preceding claims in a vehicle. Vehicle comprising at least two parallel spaced-apart wheels (9) and a steering device (1) according to one of claims 1 to 6, wherein the steering device (1) is coupled to one of the two wheels (9) at each axial end face.

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