Control unit and steer-by-wire system

Abstract

The invention relates to an operating unit (1) for influencing the driving direction of a motor vehicle (2) by a user, comprising a rotatably mounted steering shaft (3) which can be coupled to a steering device (4), and an actuator (5) which generates a restoring torque against a rotational movement of the steering shaft (3) from a neutral rotational position (15), wherein the steering shaft (3) is rotationally fixed to a coupling element (6) from which a first group of contact bodies (7) and a second group of contact bodies (8) extend radially and the actuator (5) has a coil spring (9).wherein the first group of contact elements (7) bears against the coil (11) of the helical spring (9) on a first axial side (10) and the second group of contact elements (8) bears against the coil (11) of the helical spring (9) on a second axial side (12) and the helical spring (9) is detachably supported at its first axial end (13) and detachably supported at its second axial end (14), such that when the coupling element (6) is rotated in a first direction of rotation, the helical spring (9) is compressed in a first axial direction and when the coupling element (6) is rotated in a second direction of rotation, the helical spring (9) is compressed in a second axial direction.

Description

[0001] The present invention relates to an operating unit for influencing the direction of travel of a motor vehicle by a user, comprising a rotatably mounted steering shaft that can be coupled to a steering means, and an actuator that generates a restoring torque that counteracts a rotational movement of the steering shaft from a neutral position. The invention further relates to a steer-by-wire system.

[0002] Electric steering systems are used - among other things in motor vehicles - to receive a driver's directional command and translate it into corresponding movements of one or more wheels. In contrast to purely mechanical steering systems, electric steering systems are divided into electrically assisted steering systems and fully electric steering systems, so-called "steer-by-wire" steering systems. These steer-by-wire steering systems in particular have the advantage that the control unit can be positioned relatively freely within the vehicle, independent of mechanical connecting components. This not only saves costs when distinguishing between, for example, right- and left-hand drive vehicles, but also improves accident behavior due to the absence of a steering column. Furthermore, the control unit can be moved into a stowed position, which is also used, for example, in fully automatic steering.

[0003] A steer-by-wire steering system, as defined in the present invention, is a steering system that essentially consists of a so-called handwheel actuator (HWA), for example, the actuator system around the commanding vehicle steering wheel, and a roadwheel actuator (RWA), i.e., the actuator system acting on the steering mechanism connected to the vehicle wheels. The steering signal is transmitted from the HWA to the RWA via a cable ("by wire").

[0004] To create a realistic driving experience, it is also known in the prior art to record parameters such as vehicle speed, steering angle, steering reaction torque, and the like from an actual, current driving situation or to calculate them in a simulation, and to use these to generate a feedback signal that is fed into a force feedback actuator. The force feedback actuator is integrated into the input unit and has an actuator unit that includes an actuator that serves as a manual torque or steering wheel actuator and, depending on the feedback signal, couples a feedback torque that at least partially corresponds to the actual reaction torque via the steering shaft into the steering wheel. A partial feedback torque is particularly suitable when other, possibly controllable, components such as springs or brakes provide supplementary feedback torques.Feedback torque refers to both directions of action, meaning that the feedback actuator can be rotated by the driver as an adjustable load. Such "force feedback" systems give the driver the impression of a real driving situation, similar to a conventional steering system, facilitating intuitive response.

[0005] DE 10 2008 036 730 A1 discloses a steer-by-wire steering system with an input unit that includes an actuator unit driven by an electric motor. The electric motor can be controlled by an electronic control unit, which adjusts the motor current depending on measured values ​​that characterize the respective driving situation. The motor shaft is directly coupled to the steering shaft, thus the motor torque is identical to the manual torque coupled to the steering shaft. The electric motor is flanged axially to the casing unit with respect to its longitudinal axis, and the motor shaft is connected via a coupling to the steering shaft mounted in the casing unit. An actuator unit of a similar design is described in EP 2414211 B1. In the embodiment described therein, the steering shaft itself forms the motor shaft of the electric motor, allowing for a more compact design.

[0006] To achieve the most realistic steering feel possible in such steer-by-wire systems, it is also known to place a magnetorheological brake in the torque flow of a steering device to increase the resistance torque. In combination, this allows for a higher total restoring torque with active steering return and lower energy consumption within the same installation space. However, such combinations are still comparatively large and expensive to manufacture.

[0007] The object of the invention is to provide an improved control unit for influencing the direction of travel of a motor vehicle by a user. Furthermore, the object of the invention is to implement an optimized steer-by-wire system.

[0008] This object is achieved by an operating unit for influencing a driving direction of a motor vehicle by a user, comprising a rotatably mounted steering shaft which can be coupled to a steering means, and an actuator which generates a restoring moment counter to a rotational movement of the steering shaft from a neutral rotational position, wherein the steering shaft is connected in a rotationally fixed manner to a coupling element from which a first group of contact bodies and a second group of contact bodies extend radially, and the actuator has a helical spring, wherein the first group of contact bodies bears against the winding of the helical spring on a first axial side and the second group of contact bodies bears against the winding of the helical spring on a second axial side, and the helical spring is releasably supported at its first axial end and releasably supported at its second axial end,such that upon rotation of the coupling element in a first direction of rotation, the coil spring is compressed in a first axial direction and upon rotation of the coupling element in a second direction of rotation, the coil spring is compressed in a second axial direction.

[0009] This provides the advantage that a restoring and / or resisting torque can be provided by a mechanical actuator. The advantage of this actuator is that it can provide a two-stage characteristic curve with a decreasing gradient, which will be explained in more detail below.

[0010] Furthermore, the actuator allows the steering shaft to rotate by 360° or more in either direction. Another key advantage of the actuator is that it allows for essentially identical characteristics in both directions of rotation. The actuator can also be designed with virtually no backlash, which can contribute to a particularly smooth steering feel for the driver. Furthermore, it has been demonstrated that the actuator can be configured and operated with virtually no hysteresis.

[0011] The coil spring allows the actuator to utilize a comparatively large travel and small forces of a moving thread. In order to maintain the torque in two stages and with a variable pitch, the contact bodies of the coupling element are coupled to the coil spring's winding. These contact bodies, designed as pins, for example, are present for both actuation directions of the steering shaft. In the neutral rotational position (center position) of the steering shaft, the coil spring is preferably clamped between these contact bodies, as further rotation of the mechanism from the opposite side is prevented. This means that the coil spring can advantageously not expand to its original height.

[0012] When the mechanism is rotated from its neutral position, additional coils of the coil spring are pressed beneath the contact bodies. This has two effects: The coil spring acquires a variable number of springy coils. This means that the more springy coils, the softer the spring becomes. As more coils are pressed beneath the contact bodies, the pitch of the screw thread changes because the coil spring is used directly as part of the thread. This makes it possible, in particular, to influence the rise of the actuator's torque characteristic. The smaller the initial number of springy coils, the greater the change when a springy coil is added, for example, when the mechanism is rotated by 360°.

[0013] By using the coil spring in this way, it is now possible to freely design the torque characteristic without the need for additional mechanical components, such as additional pre-transmissions or a larger number of springs. It would even be possible to design the coil spring so that it hits the spring ends after a certain angle of rotation, thus implementing a defined angle limit (stop).

[0014] The actuator can preferably be arranged in a telescopic extension device of the operating unit. In this case, the extension device can comprise a first extension tube that can be translated relative to a guide tube. It is understood that the telescopic extension device can also have more than just a first extension tube. For example, a second or a third extension tube can also be present, which are then arranged telescopically between the guide tube and the first extension tube. Preferably, the first extension tube has an outer surface that has a substantially rectangular cross-sectional contour. Most preferably, the first extension tube is cuboid-shaped and, when installed in a motor vehicle, is aligned with its wide side in cross-section perpendicular to the direction of gravity. Preferably, the first extension tube can be designed in several parts.It is further preferred that the first extension tube is formed from one or more shaped sheet metal parts.

[0015] Corresponding to the first extension tube, the guide tube can preferably have an inner surface with a substantially rectangular cross-sectional contour, so that the first extension tube is accommodated in the guide tube in a rotationally and tilt-proof manner and can be displaced translationally. In this context, it is further preferred that the guide tube be cuboid-shaped.

[0016] The actuator can be arranged in a pull-out tube so that it can be moved with it, or it can be arranged in a guide tube so that it can be fixed in place.

[0017] According to an advantageous embodiment of the invention, the coil spring can be accommodated in an actuator housing and supported axially and detachably on both sides of the actuator housing. The advantage of this embodiment is that it allows for the creation of a modular unit, which is particularly easy to assemble, particularly due to this modular design.

[0018] According to a further preferred development of the invention, it can also be provided that the coil spring is supported axially on both sides of the actuator housing in the neutral rotational position of the steering shaft, which can also contribute to a modular design of the actuator.

[0019] Furthermore, according to a similarly advantageous embodiment of the invention, the coil spring can be preloaded in the neutral rotational position of the steering shaft. The advantageous effect of this embodiment is that the preload in the center position enables a safe return to the center position and is modeled on the restoring torque directly experienced on steering wheels. This tends to cause the vehicle to travel straight ahead. This can also be reflected in an increased force gradient in the center position. The preload ensures that the unit remains free of play, even under different tolerance levels.

[0020] According to another particularly preferred embodiment of the invention, the coupling element can be provided to axially penetrate the coil spring. This allows for a particularly compact design of the actuator, since the radially inner space of the coil spring is utilized accordingly.

[0021] Furthermore, the invention can also be further developed such that the coil spring is designed such that the steering shaft has a rotation angle of at least 360° in the first direction of rotation and a rotation angle of at least 360° in the second direction of rotation. For this purpose, the coil spring then has a corresponding number of turns.

[0022] In a likewise preferred embodiment of the invention, it can also be provided that the first group of contact bodies and / or the second group of contact bodies are designed as pins. The pins have a cylindrical basic shape with a circumferential surface that is partially in contact with the coil(s) of the coil spring. This allows for particularly low-wear actuation of the coil spring. Furthermore, the contact surfaces of the contact bodies can be adapted to the coil spring in order to keep the surface pressure low.

[0023] It may also be advantageous to further develop the invention in such a way that at least one of the pins, preferably a plurality of pins, most preferably all pins in the coupling element is / are rotatably mounted about its longitudinal axis via a respective plain bearing and / or rolling bearing, which may also contribute to a reduction of wear phenomena on the pins or the coil spring.

[0024] According to a further preferred embodiment of the subject matter of the invention, the first group of contact bodies and the second group of contact bodies rest against the coil spring without play in any rotational position of the steering shaft. This can create a particularly harmonious and safe steering feel for the driver. This freedom from play can also be at least supported by the preload of the coil spring.

[0025] The object of the invention is further achieved by a steer-by-wire system for a motor vehicle comprising an operating unit according to one of claims 1-9. This allows the generation of a mechanical restoring torque in a steer-by-wire steering system.

[0026] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0027] It shows: Fig. 1 an operating unit in a neutral rotational position in an axial section view, Fig. 2 an operating unit in a second rotational position in an axial section view, Fig. 3 a first embodiment of an actuator of an operating unit in a neutral rotational position in a perspective partial sectional view, Fig. 4 a first embodiment of an actuator of an operating unit in a second rotational position in a perspective partial sectional view, Fig. 5 a first embodiment of an actuator of an operating unit in a third rotational position in a perspective partial sectional view, Fig. 6 a rotation angle-torque diagram of an actuator, Fig. 7 a motor vehicle with a steer-by-wire system in a schematic representation, Fig. 8 shows a second embodiment of an actuator of an operating unit in a neutral rotational position in an axial section, Fig. 9 a second embodiment of an actuator of an operating unit in a second rotational position in an axial sectional view.

[0028] The Fig. 1-2 show an operating unit 1 for influencing a driving direction of a motor vehicle 2 by a user, comprising a rotatably mounted steering shaft 3, which can be coupled to a steering means 4, as is also shown in the Fig. 7. The control unit 1 is telescopic and has a fixed tube 19 in which the inner tube 18 is guided in a translationally displaceable manner.

[0029] The control unit 1 has an actuator 5 arranged in the inner tube 18, which generates a restoring torque counter to a rotational movement of the steering shaft 3 from a neutral rotational position 15. For this purpose, the steering shaft 3 is connected to a coupling element 6 in a rotationally fixed manner or is formed monolithically with it, from which a first group of contact bodies 7 and a second group of contact bodies 8 extend radially, which can also be clearly seen from the synopsis of the Fig. 1-2 with the Fig. 3-5. The coupling element 6 is axially fixed.

[0030] The actuator 5 further comprises a helical spring 9, wherein the first group of contact bodies 7 bears against the winding 11 of the helical spring 9 on a first axial side 10, and the second group of contact bodies 8 bears against the winding 11 of the helical spring 9 on a second axial side 12. The helical spring 9 is releasably supported at its first axial end 13 and at its second axial end 14, such that upon rotation of the coupling element 6 in a first direction of rotation, the helical spring 9 is compressed in a first axial direction, and upon rotation of the coupling element 6 in a second direction of rotation, the helical spring 9 is compressed in a second axial direction.

[0031] When the steering shaft 3 and thus also the axially fixed coupling element 6 rotate from the neutral rotational position 15, additional windings 11 of the coil spring 9 are pressed under the contact bodies 7,8, which can be seen particularly well from the Fig. 3-5. The coil spring 9 thus receives a variable number of spring coils 9. In the Fig. 4, these are in a first direction of rotation of the steering shaft 3 the windings 9 below the contact bodies 7,8 and in the Fig. 5 for the second direction of rotation of the steering shaft 3 the windings 9 above the contact bodies 7,8.

[0032] If more coils 9 are pressed under the contact bodies 7, 8, the pitch of the screw thread also changes, because the coil spring 9 is used directly as part of the thread. This makes it possible, in particular, to influence the increase in the torque characteristic of the actuator 5. The smaller the initial number of spring coils 9, the greater the change when a spring coil 9 is added, for example, when the mechanism is rotated by 360°. This behavior of the actuator 5 can also be determined using the angle of rotation-torque characteristic in the Fig. 6 understand.

[0033] One can see from the overview of the Fig. 3-5 with the Fig. 6, it is good that the coil spring 9 changes its angle of inclination under or above the contact bodies 7,8 when actuated (compressed), thus resulting in a changed force-to-torque ratio. This results in the flattening characteristic curve M = f(angle), as shown in the Fig. 6. As the steering angle increases, the pitch angle of the coil spring 9 becomes smaller and the increasing spring force produces a less rapidly increasing torque.

[0034] In the embodiment of the Fig. 3-5, the coil spring 9 is accommodated in an actuator housing 16 and is supported axially and detachably on both sides of the actuator housing 16. In the neutral rotational position 15 of the steering shaft 3, which is in the Fig. As can be seen in Figure 3, the coil spring 9 is supported axially on both sides of the actuator housing 16. The coil spring 9 has a preload in this neutral rotational position 15 of the steering shaft 3.

[0035] The coupling element 6 extends axially through the coil spring 9. The coil spring 9 is designed such that the steering shaft 3 has a rotation angle of at least 360° in the first direction of rotation and a rotation angle of at least 360° in the second direction of rotation.

[0036] The first group of contact bodies 7 and the second group of contact bodies 8 are designed as pins 17 in the illustrated embodiments. The pins 17 are each mounted in the coupling element 6 via a plain bearing and / or roller bearing, rotatable about their longitudinal axis, and rest against the coil spring 9 without play.

[0037] In the Fig. 8-9, a second embodiment of an actuator 5 is shown in two different rotational positions. Fig. 8, the actuator 5 is shown in a neutral or center position. It can be clearly seen that the pins 17, 18 radially penetrate the coupling element 6 and are rotatably mounted in the coupling element 6 via plain and / or roller bearings. The pins 17, 18 have a contact profile adapted to the contour of the coil spring 9. In the neutral rotational position 15, both ends 13, 14 of the coil spring 9 rest against the housing 16 and the coil spring 9 is preloaded. Fig. 9, the coupling element 6 was rotated so that the Fig. 9 lower part of the helical spring 9 is displaced upwards by the pins 17, 18 and the helical spring 9 is thus compressed above the pins 17, 18. The first group of contact bodies 7 is located on the first axial side 10 of the coil 11 of the helical spring 9, while the second group of contact bodies 8 rests on the second axial side 12 of the coil 11 of the helical spring 9. The helical spring 9 is releasably supported at its first axial end 13 and at its second axial end 14 on the housing 16. The coupling element 6 is mounted at both of its axial ends via rolling bearings in the housing 16.

[0038] Fig. 7 shows a steer-by-wire system 20 for a motor vehicle 2 comprising an operating unit 1, as shown in the Fig. 1-5 or the Fig. 8-9 is known.

[0039] If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a ranking. List of reference symbols 1 control unit 2 motor vehicles 3 Steering shaft 4 Steering devices 5 Actuator 6 coupling element 7 Asset bodies 8 Investment bodies 9 coil spring 10 pages 11 turns 12 pages 13 End 14 End 15 rotation position 16 actuator housings 17 pen 18 pipe 19 pipe 20 Steer-by-Wire System

Claims

[1] Operating unit (1) for influencing a driving direction of a motor vehicle (2) by a user, comprising a rotatably mounted steering shaft (3) which can be coupled to a steering means (4), and an actuator (5) which generates a restoring torque counter to a rotational movement of the steering shaft (3) from a neutral rotational position (15), characterized by , that the steering shaft (3) is connected in a rotationally fixed manner to a coupling element (6) from which a first group of contact bodies (7) and a second group of contact bodies (8) extend radially and the actuator (5) comprises a helical spring (9), wherein the first group of contact bodies (7) bears against the winding (11) of the helical spring (9) on a first axial side (10) and the second group of contact bodies (8) bears against the winding (11) of the helical spring (9) on a second axial side (12) and the helical spring (9) is releasably supported at its first axial end (13) and releasably supported at its second axial end (14), such that upon rotation of the coupling element (6) in a first direction of rotation, the coil spring (9) is compressed in a first axial direction and upon rotation of the coupling element (6) in a second direction of rotation, the coil spring (9) is compressed in a second axial direction. [2] Control unit (1) according to claim 1, characterized by that the helical spring (9) is accommodated in an actuator housing (16) and is supported axially and detachably on both sides on the actuator housing (16). [3] Control unit (1) according to claim 2, characterized by that the coil spring (9) is supported axially on both sides on the actuator housing (16) in the neutral rotational position (15) of the steering shaft (3). [4] Control unit (1) according to one of the preceding claims, characterized bythat the coil spring (9) has a preload in the neutral rotational position (15) of the steering shaft (3). [5] Control unit (1) according to one of the preceding claims, characterized by that the coupling element (6) passes axially through the helical spring (9). [6] Control unit (1) according to one of the preceding claims, characterized by that the coil spring (9) is designed such that the steering shaft (3) has an angle of rotation in the first direction of rotation of at least 360° and an angle of rotation in the second direction of rotation of at least 360°. [7] Control unit (1) according to one of the preceding claims, characterized by that the first group of contact bodies (7) and / or the second group of contact bodies (8) are designed as pins (17). [8] Control unit (1) according to claim 7, characterized bythat at least one of the pins (17) is / are mounted in the coupling element (6) via a respective plain bearing and / or rolling bearing so as to be rotatable about its longitudinal axis. [9] Control unit (1) according to one of the preceding claims, characterized by that the first group of contact bodies (7) and the second group of contact bodies (8) rest against the coil spring (9) without play in every rotational position of the steering shaft (3). [10] Steer-by-wire system (20) for a motor vehicle (2) comprising an operating unit (1) according to one of claims 1-9.

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