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 a control unit for influencing the driving direction of a motor vehicle by a user, comprising a rotatably mounted steering shaft which can be coupled to a steering device, and an actuator which generates a restoring torque against a rotational movement of the steering shaft from a neutral rotational position. The invention further relates to a steer-by-wire system.

[0002] Electric steering systems, used in motor vehicles among other applications, are designed to receive a driver's steering input and translate it into corresponding movements of one or more wheels. Compared to purely mechanical steering systems, electric steering systems are further divided into electrically assisted systems and fully electric systems, also known as "steer-by-wire" systems. Steer-by-wire systems, in particular, offer the advantage that the control unit can be positioned relatively freely within the vehicle, independent of mechanical linkages. This not only saves costs when distinguishing between, for example, right- and left-hand drive vehicles, but also improves crash safety due to the absence of a steering column. Furthermore, the control unit can be stowed away, a feature also used, for example, in fully automated steering systems.

[0003] A steer-by-wire steering system within the meaning of the present invention is understood to be a steering system which essentially consists of a so-called hand wheel actuator (HWA), for example, the actuators around the vehicle's steering wheel, and a road wheel actuator (RWA), i.e., the actuators acting on the steering mechanism connected to the vehicle's wheels. The steering signal is transmitted from the HWA to the RWA via a wire ("by wire").

[0004] To generate a realistic driving feel, it is also known in the prior art to acquire or calculate parameters such as vehicle speed, steering angle, steering response torque, and the like from an actual, instantaneous driving situation, and to generate a feedback signal from these parameters, which is fed into a force feedback actuator. The force feedback actuator is integrated into the input unit and comprises an actuator unit that includes a drive unit serving as a hand torque or steering wheel actuator. Depending on the feedback signal, this actuator couples a feedback torque (feedback torque) into the steering wheel via the steering shaft, at least partially corresponding to the actual response torque. A partial feedback torque is particularly suitable when other, potentially controllable components such as springs or brakes provide supplementary feedback torques.The term "feedback moment" encompasses both directions of action, meaning that the feedback actuator can also 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, which facilitates an intuitive response.

[0005] From DE 102008036730 A1, a steer-by-wire steering system with an input unit is known, which 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, so the motor torque is identical to the hand torque coupled into the steering shaft. The electric motor is axially flanged to the housing unit with respect to its longitudinal axis, and the motor shaft is connected to the steering shaft, which is mounted in the housing unit, via a coupling. A similarly constructed actuator unit is shown in EP 2414211 B1. In the embodiment described therein, the steering shaft itself forms the motor shaft of the electric motor, thus enabling a more compact design.

[0006] To achieve the most realistic steering feel possible in such steer-by-wire systems, it is also known to incorporate a magnetorheological brake into 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 to center within the same installation space and with lower energy consumption. Nevertheless, such combinations are still relatively large and expensive to manufacture.

[0007] The object of the invention is to provide an improved control unit for a user to influence the driving direction of a motor vehicle. It is also an object of the invention to implement an optimized steer-by-wire system.

[0008] This task is solved by an operating unit for influencing the driving direction of a motor vehicle by a user, comprising a rotatably mounted steering shaft which can be coupled to a steering device, and an actuator which generates a restoring torque against a rotational movement of the steering shaft from a neutral rotational position, wherein the steering shaft is rotationally fixed 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 coil of the helical spring on a first axial side and the second group of contact bodies bears against the coil of the helical spring on a second axial side, and the helical spring is detachably supported at its first axial end and detachably supported at its second axial end.so that when the coupling element is rotated in a first direction of rotation, the helical spring is compressed in a first axial direction, and when the coupling element is rotated in a second direction of rotation, the helical spring is compressed in a second axial direction.

[0009] This offers the advantage that a restoring and / or resistive 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 360° or more in either direction. Another significant advantage of the actuator is that it enables 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. It has also been shown that the actuator can be configured and operated with almost no hysteresis.

[0011] The helical spring allows the actuator to utilize a comparatively large travel distance and small forces of a helical thread. To maintain the torque in two stages and with variable pitch, the contact elements of the coupling are attached to the coil of the helical spring. These contact elements, for example, designed as pins, are present for both directions of steering shaft operation. In the neutral rotational position (center position) of the steering shaft, the helical spring is preferably pre-tensioned between these contact elements, as further rotation of the mechanism is prevented from the opposite side. This means that the helical spring is advantageously unable to extend to its original height.

[0012] When the mechanism is rotated from its neutral position, additional coils of the helical spring are pressed under the contact surfaces. This has two effects: First, the helical spring acquires a variable number of spring coils. That is, the more spring coils, the softer the spring becomes. Second, when more coils are pressed under the contact surfaces, the pitch of the screw thread changes because the helical spring is directly integrated into the thread. This makes it possible, in particular, to influence the slope of the actuator's torque characteristic. The smaller the initial number of spring coils, the greater the change when an additional spring coil is added, for example, when the mechanism is rotated 360°.

[0013] By using this helical spring, it is now possible to freely design the torque characteristic curve without using additional mechanical components, such as additional reduction gears or a larger number of springs. It would even be possible to design the helical spring so that it contacts the spring ends after a certain angle of rotation, thus creating a defined angular limit (stop).

[0014] The actuator can preferably be arranged in a telescopic extension device of the control unit. The extension device can comprise a first extension tube that is translationally displaceable relative to a guide tube. It is understood that the telescopic extension device can also have more than one first extension tube. For example, a second or a third extension tube can also be present, which are then telescopically arranged between the guide tube and the first extension tube. Preferably, the first extension tube has an outer surface that is essentially rectangular in cross-sectional contour. Most preferably, the first extension tube is cuboid in shape and, when installed in a motor vehicle, its wider side is oriented perpendicular to the direction of gravity. Preferably, the first extension tube can be made of multiple parts.It is further preferred that the first extraction tube is formed from one or more shaped sheet metal parts.

[0015] Corresponding to the first extension tube, the guide tube preferably has an inner surface that is essentially rectangular in cross-sectional contour, so that the first extension tube is mounted in the guide tube in a rotationally and tilt-proof manner and is translationally displaceable. In this context, it is further preferred that the guide tube be cuboid in shape.

[0016] The actuator can be moved within an extension tube or fixed in place within a guide tube.

[0017] According to an advantageous embodiment of the invention, the helical spring can be housed in an actuator housing and supported axially and detachably on both sides by the actuator housing. The advantage of this embodiment is that it allows for the creation of a modular assembly, which is particularly easy to install 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 axially supported 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 another 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 reliable return to the center position and mimics the restoring torque directly experienced on steering wheels. This makes the vehicle tend to drive straight ahead. This can also be reflected in an increased force gradient in the area of ​​the center position. The preload also ensures that the unit is free of play even under varying tolerances.

[0020] According to a further particularly preferred embodiment of the invention, the coupling element can extend axially through the helical spring. This allows for a particularly compact design of the actuator, since the radially inner space of the helical spring is utilized accordingly.

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

[0022] In a further preferred embodiment of the invention, the first group of contact elements and / or the second group of contact elements can also be designed as pins. The pins have a cylindrical shape with a circumferential surface that is in partial contact with the coil(s) of the helical spring. This allows for particularly low-wear actuation of the helical spring. Furthermore, the contact surfaces of the contact elements can be adapted to the helical spring to minimize surface pressure.

[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 are rotatably mounted about their longitudinal axis via a sliding bearing and / or rolling bearing, which can also contribute to a reduction of wear on the pins or the coil spring.

[0024] According to a further preferred embodiment of the invention, the first group of contact elements and the second group of contact elements can be arranged to bear against the coil spring without play in every rotational position of the steering shaft. This allows for a particularly smooth and safe steering feel for the driver. The absence of play can also be at least partially 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 enables the generation of a mechanical restoring torque in a steer-by-wire steering system.

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

[0027] It shows: Fig. 1. A control unit in a neutral rotational position in an axial section view. Fig. 2 a control unit in a second rotation position in an axial section view, Fig. 3 a first embodiment of an actuator of a control unit in a neutral rotational position in a perspective partial section view, Fig. 4 a first embodiment of an actuator of a control unit in a second rotation position in a perspective partial section view, Fig. 5 a first embodiment of an actuator of an operating unit in a third rotation position in a perspective partial section 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 a second embodiment of an actuator of a control unit in a neutral rotational position in an axial section view, Fig. 9 a second embodiment of an actuator of a control unit in a second rotational position in an axial section view.

[0028] The Fig. Figures 1-2 show a control unit 1 for influencing the direction of travel of a motor vehicle 2 by a user, comprising a rotatably mounted steering shaft 3, which can be coupled to a steering device 4, as is also the case in the Fig. Figure 7 shows that 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 against a rotational movement of the steering shaft 3 from a neutral rotational position 15. For this purpose, the steering shaft 3 is non-rotatably connected to a coupling element 6 or is monolithically formed with it, from which a first group of contact bodies 7 and a second group of contact bodies 8 extend radially, which is also clearly visible from the overall view of the Fig. 1-2 with the Fig. 3-5 can be understood. The coupling element 6 is designed to be axially fixed.

[0030] The actuator 5 further comprises a helical 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. The helical spring 9 is detachably supported at its first axial end 13 and at its second axial end 14, so 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.

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

[0032] Furthermore, when more coils 9 are pressed under the support bodies 7, 8, the pitch of the screw thread also changes because the helical spring 9 is used directly as part of the thread. This makes it possible, in particular, to influence the slope of 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 seen in the rotation angle-torque characteristic curve in the Fig. 6. Understand.

[0033] One can see from the overall view of the Fig. 3-5 with the Fig. It is good that the coil spring 9, through actuation (compression), changes its helix angle below or above the contact bodies 7, 8, thus exhibiting a changed force-to-torque ratio. This results in the flattening characteristic curve M = f(angle), as shown in the Fig. Figure 6 can be seen. As the steering angle increases, the helix angle of the coil spring 9 decreases and the increasing spring force produces a less steeply increasing moment.

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

[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 support bodies 7 and the second group of support bodies 8 are designed as pins 17 in the illustrated embodiments. The pins 17 are rotatably mounted about their longitudinal axis in the coupling element 6 via a sliding bearing and / or rolling bearing and bear against the helical spring 9 without play.

[0037] In the Fig. Figures 8-9 show a second embodiment of an actuator 5 in two different rotational positions. Fig. Figure 8 shows the actuator 5 in a neutral or center position. It is clearly visible that the pins 17, 18 extend radially through the coupling element 6 and are rotatably mounted in the coupling element 6 via sliding and / or rolling bearings. The pins 17, 18 have a contact profile adapted to the contour of the helical spring 9. In the neutral rotational position 15, both ends 13, 14 of the helical spring 9 rest against the housing 16 and the helical spring 9 is pre-tensioned. Fig. 9 the coupling element 6 was rotated so that the one in the Fig. The lower part of the helical spring 9 is displaced upwards by the pins 17, 18, and the helical spring 9 is compressed above the pins 17, 18. The first group of contact elements 7 is located on the first axial side 10 of the coil 11 of the helical spring 9, while the second group of contact elements 8 rests against the second axial side 12 of the coil 11 of the helical spring 9. The helical spring 9 is detachably supported at its first axial end 13 and at its second axial end 14 against the housing 16. The coupling element 6 is mounted at both its axial ends in the housing 16 via rolling bearings.

[0038] Fig. Figure 7 shows a steer-by-wire system 20 for a motor vehicle 2 comprising a control unit 1, as it consists of the Fig. 1-5 or the Fig. 8-9 is known.

[0039] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Insofar as the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy. List of reference symbols 1 control unit 2 motor vehicles 3 Steering shaft 4 Steering devices 5 Actuator 6 coupling element 7 Plant components 8 plant bodies 9 coil spring Page 10 11 turns Page 12 13 End 14 End 15 rotation position 16 actuator housings 17 pen 18 pipe 19 pipe 20 Steer-by-Wire system QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102008036730 A1

[0005] EP 2414211 B1

[0005]

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), preferably a plurality of pins (17), most preferably all 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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