STEER-BY-WIRE STEERING COLUMN FOR A MOTOR VEHICLE

Description

State of the art

[0001] The invention relates to a steer-by-wire steering column for a motor vehicle, which has a steering shaft rotatably mounted relative to a housing about a longitudinal axis and which is operatively connected to a gearbox, wherein the gearbox has at least two gearbox elements that interact in gearbox engagement, wherein a rotation limiter for limiting the rotation of the steering shaft relative to the housing is integrated with the gearbox, and wherein the gearbox is operatively connected to a torque generating device of a feedback actuator.

[0002] The steering shaft is rotatably mounted within the steering column housing, which is typically held to the vehicle body by a support structure. Steering commands for steering the vehicle can be entered by manually turning the steering wheel, which is attached to the rear end of the steering shaft on the driver's side, thus causing the steerable wheels of the vehicle to turn.

[0003] While in a conventional steering system the steering shaft is mechanically connected to the steerable wheels via a steering gear, in a steer-by-wire steering system the rotation of the steering shaft is detected by sensors and converted into an electrical control signal to control electric steering actuators that adjust the steering angle of the steerable wheels.

[0004] In a steer-by-wire steering system, the driver receives no direct mechanical feedback from the steered wheels via the steering linkage. In conventional mechanically coupled steering systems, this feedback is transmitted to the steering wheel via the steering gear and the mechanically continuous steering shaft as a reaction or restoring torque, depending on road surface conditions, vehicle speed, the current steering angle, and other operating conditions. The lack of haptic feedback makes it difficult for the driver to reliably assess current driving situations and execute appropriate steering maneuvers, thus impairing vehicle handling and, consequently, driving safety.

[0005] To generate a realistic driving feel, it is known in the prior art for a steer-by-wire steering column 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 feedback actuator. The feedback actuator has a torque generation device coupled to the steering shaft, for example, a drive with an electric motor whose motor shaft is coupled to the steering shaft via a gearbox. The motor can be controlled by a control unit to couple a restoring torque (feedback torque) corresponding to the actual response torque into the steering wheel via the steering shaft.Such "force feedback" systems can give the driver the impression of a real driving situation, similar to a conventional steering system, which facilitates an intuitive reaction.

[0006] In a steer-by-wire steering column, the lack of a mechanical connection to the wheels means that the steering wheel's rotation is not limited by the wheels' end stop when maximum steering angle is reached. To prevent excessive steering input and simulate a realistic steering feel, it is known to limit the maximum possible steering wheel rotation angle using a rotation limiter that restricts the maximum possible rotation of the steering shaft.

[0007] A steer-by-wire steering column of this type is known from DE 603 ​​03 081 T2, in which a feedback actuator is mounted externally on the steering column housing. The electric motor of the feedback actuator is coupled to the steering spindle via a gearbox. A disadvantage of this design is that an end stop to limit the rotation of the steering wheel cannot be provided.

[0008] German patent DE 10 2019 210 096 A1 describes a steering column with a mechanical rotation limiter to restrict the steering wheel's rotation. However, this column lacks a feedback actuator and therefore no gearbox. Integrating such a rotation limiter into a standard steer-by-wire steering column would be structurally impossible or would require significant design complexity and a relatively large installation space.

[0009] US patent 2019 / 092374 A1 discloses a steer-by-wire steering column of the type mentioned above, in which a rotation limiter is integrated into a gearbox. However, this requires a complex additional gear arrangement. German patents DE 10 2013 004 055 A1 and DE 10 2017 008 651 A1 also show relatively complexly implemented rotation limiters.

[0010] In view of the problem explained above, it is an object of the present invention to enable a rotation limiting of the steering shaft in a compact design with low structural effort in a steer-by-wire steering column. Description of the invention

[0011] This problem is solved according to the invention by the steering column with the features of claim 1. Advantageous further developments result from the dependent claims.

[0012] In a steer-by-wire steering column for a motor vehicle, which has a steering shaft rotatably mounted relative to a housing about a longitudinal axis and which is operatively connected to a gearbox, wherein the gearbox has at least two gearbox elements that interact in gearbox engagement, wherein a rotation limiter for limiting the rotation of the steering shaft relative to the housing is integrated with the gearbox, and wherein the gearbox is operatively connected to a torque generating device of a feedback actuator, it is provided according to the invention that the rotation limiter has a winding core on which a flexible band element can be wound, wherein the winding core is rotatable relative to the housing or a gearbox element, and the band element is fixed between the winding core and the housing or gearbox element.

[0013] The steering shaft of the steer-by-wire steering column according to the invention has no mechanical connection to the steerable wheels of a motor vehicle. Accordingly, no means or devices are provided that could convert a rotation of the steering shaft into a steering input of the steerable wheels solely through a mechanical transmission.

[0014] The invention provides a rotation limiter that limits the possible rotation angle of the steering shaft, and thus of a steering wheel attached to it, to a predetermined maximum value. This limiter is integrated into a steering column, which is designed for connecting a feedback actuator via the transmission that interacts with the steering shaft. An advantageous embodiment may provide that the steering column according to the invention includes a feedback actuator. This actuator may advantageously be connected to, or include, the transmission itself. Such a feedback actuator may have a drive and / or braking device, which may preferably be structurally integrated with the steering column; in other words, it may be detachably or permanently connected to it.It is also conceivable and possible that the gearbox of the steering column according to the invention has a clutch or another mechanical interface which makes it possible to couple an external torque or an external force into the steering shaft.

[0015] The speed limiter is integrated into the gearbox. This means that the speed limiter and the gearbox together form a single integrated unit. The functions of torque transmission (feedback torque) to the steering shaft and rotation limiting of the steering shaft, which are implemented in separate assemblies in the prior art, can now be combined. One advantage is that the design and manufacturing effort can be reduced. Another advantage is that a more compact design with less installation space and reduced weight is achievable.

[0016] It is also advantageous that the torque-transmitting properties of the gearbox can be used to create a specific rotation angle limitation. For example, depending on a given gear ratio or reduction ratio, a possible rotation angle of the steering shaft, even greater than 360°, can be easily implemented through design. This also makes it possible to better control the forces that occur when limiting the rotation at the end stop.

[0017] The speed limiter is operatively connected to a transmission component. The speed limiter is designed to directly or indirectly restrict the movement of a transmission component that occurs during torque transmission. For this purpose, a mechanical stop can preferably be arranged between a transmission component and the housing, which is stationary relative to it. When the movement of the transmission component connected to the speed limiter is stopped at the stop, the movement of all other engaged transmission components is also stopped, in particular the transmission component connected to the steering shaft. An advantage of this arrangement is that the speed limiter can be flexibly positioned within the transmission with a high degree of design freedom, allowing for optimized function and adaptation to the available installation space.

[0018] The transmission is operatively connected to a torque-generating device of a feedback actuator. The steering column according to the invention preferably includes a feedback actuator. This actuator has at least one torque-generating device. This device is preferably connected to the transmission on the input side, to which the steering shaft is connected on the output side. This allows a torque generated by the torque-generating device to be coupled into the steering shaft, preferably as a feedback torque to simulate mechanical feedback from steerable wheels.

[0019] According to the invention, the speed limiter has a winding core onto which a flexible band element can be wound, the winding core being rotatable relative to the housing or a gear element, and the band element being fixed between the winding core and the housing or gear element. The flexible band element comprises an elongated band and is flexibly deformable transversely to its longitudinal extent. The winding core is rotatable about its winding axis relative to the housing or gear element. A first section, for example, a first end or a first intermediate section of the band element, is fixed to a circumference of the winding core. A second section of the band element, spaced apart from the first section, is fixed to a part of the gear element that is fixed relative to the rotation of the winding core about its winding axis.This results in the winding trough, which is formed by a section of the band element that can be wound onto the winding core, extending as a tension trough between the winding core and the part that is fixed relative to it.

[0020] The rotation limiter is achieved by winding the strip element onto the core as it rotates. This winding action shortens the length of the winding between the core and the stationary part of the gearbox. When the maximum rotation angle possible for limiting the rotation is reached, the strip element is wound onto the core to such an extent that it is tensioned and subjected to tensile stress between the rotating circumferential sections of the core and the stationary part. This creates a mechanical end stop, halting the relative rotation of the core. An advantage of this design is that a relative rotation of several revolutions can be reliably achieved with minimal effort. Furthermore, the assembly can be designed to be compact and virtually maintenance-free.

[0021] In the aforementioned embodiment, the winding core can be arranged coaxially with a gear wheel. The winding core can, for example, be fixed to the gear wheel in a rotationally fixed manner. A first section of the tape element is fixed to a coaxial circumference of the winding core. A second section of the tape element is fixed to the housing, which is stationary relative to the core, so that the winding strand extends between the winding core and the housing. Alternatively, the winding core can be rotationally fixed relative to the gear wheel with respect to rotation about the winding axis, which is identical to the axis of rotation of the gear wheel, and the tape element extends with its winding strand between the winding core and the gear wheel.

[0022] The winding core can be attached to or inside a gear wheel in a space-saving manner, for example within the interior of a hollow, drum-shaped belt or gear wheel where the teeth are arranged coaxially on the outside relative to the interior.

[0023] An advantageous design can provide that the winding core is firmly connected to a gear wheel, for example by means of a one-piece construction. This enables a particularly space-saving design and efficient manufacturing, for example as a plastic injection-molded part or a metal die-cast part.

[0024] Alternatively, it can be provided that the winding core is connected to the housing in a rotationally fixed manner, whereby the band element is also wound up to the end stop when the gear wheel is rotated relatively.

[0025] An advantageous embodiment may provide that the transmission has at least two meshing gear wheels. Gear wheels comprise rotating transmission elements, such as pulleys, toothed belt pulleys, gears, or even worms, worm gears, or the like. In a belt or toothed belt drive, the belt or toothed belt itself, which serves as the traction element, also constitutes a rotating transmission element. Because the speed limiter can interact directly or indirectly with each of the gear wheels to limit its rotation, a better design adaptation is possible than in the prior art, where the speed limiter engages the steering shaft.

[0026] It can be advantageous for a transmission element to be rotationally fixed to the steering shaft. Preferably, for example, a first gear wheel can be mounted on the steering shaft, so that the shaft itself then forms a transmission shaft of the gearbox. This allows for a compact design.

[0027] The torque-generating device may include a motor drive. Such an active drive may, for example, comprise an electric motor that drives a transmission device, such as a gear wheel mounted on the motor shaft.

[0028] Alternatively or additionally, another type of torque generation device can be provided, such as a passive braking device that can generate a braking torque through friction without an external energy supply, which can counteract a manually applied steering torque at the steering shaft. An energy storage device can also be provided, for example a spring accumulator, which can store torque applied manually via the steering wheel and release it back to the steering shaft as feedback torque when needed.

[0029] In a further advantageous design, the speed limiter can be integrated with a transmission component. For example, the speed limiter can be directly or indirectly connected to a gear wheel, or to a traction element or other torque-transmitting transmission element of the gearbox. This integrated design gives the transmission component a dual function: torque transmission and speed limiting. This allows for particularly space-saving integration into the steering column.

[0030] One advantageous possibility is that a gear element has a stop element, and the housing has a counter-stop element that interacts with the stop element.

[0031] The stop element moves along with the transmission element during torque transmission, for example, in accordance with the rotation of a gear wheel. The counter-stop element is fixed relative to this movement and positioned within the stop element's path of motion, thus blocking it. This allows the stop element to mechanically strike the counter-stop element in the direction of its movement, thereby blocking, for example, the further rotation of a gear wheel and thus limiting its movement. The stop and counter-stop elements can, for example, have axially or radially projecting projections, cams, or the like, whose cross-sections extend into a common relative path of movement, enabling them to create a positive-locking limit via a mechanical stop.

[0032] It is also possible that stop and counter-stop elements are coupled to a gear mechanism via a spindle drive or a differently constructed stop mechanism, so that they can be moved relative to each other and brought into position. Description of the drawings

[0033] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. Specifically, they show: Figure 1 shows a gearbox according to the invention in a schematic perspective view, Figure 2 shows a schematically separated view of the gearbox according to the invention. Figure 1 Figure 3 shows a schematic axial view of the gearbox according to Figure 2 within the permissible rotational range, Figure 4 shows a schematic axial view of the gearbox as in Figure 3 With rotation limiter, Figure 5 shows another schematically separated representation of the gearbox according to Figure 2 Figure 6 shows another representation of the gearbox similarly Figure 5Figure 7 shows a second embodiment of a transmission according to the invention in a schematic axial view similar to the Figure 3 Figure 8 shows a schematic perspective view of the casing made of Figure 7 Figure 9 shows a schematic perspective view of the gear wheel. Figure 7 . Embodiments of the invention

[0034] In the various figures, identical parts are always marked with the same reference symbols and are therefore usually only named or mentioned once.

[0035] Fig. 1 Figure 1 shows an external view of a gearbox 1, which is attached to a steering shaft 2 that is rotatably mounted about a longitudinal axis L in a housing of a steer-by-wire steering column (not shown).

[0036] Parallel to the longitudinal axis L, a motor axis M is arranged at a distance. This axis denotes the axis of rotation of a motor shaft (not shown) of an electric motor of a motor feedback actuator (also not shown), which is known in principle. For the purpose of explaining the function according to the invention, it is sufficient that a torque about the motor axis M can be coupled into the transmission 1 and transmitted to the steering shaft 2 by means of a motor or other torque-generating device.

[0037] The gearbox 1 has a housing 11. This can be a casting, for example made of aluminum or magnesium, and have fastening means 12 for attachment to the steering column.

[0038] The following Figures 2 to 6 Figures 1 show a first embodiment of the gearbox 1 in different views, with the exploded views shown in the figures. Figures 2 , 3 and 4are pulled apart axially in the direction of the longitudinal axis L, and Figures 5 and 6 an axial view into the interior of the housing 11 is shown.

[0039] The transmission 1 comprises a belt drive, namely a toothed belt drive, with a first belt pulley 3, which forms a first gear wheel, a second belt pulley 4, which forms a second gear wheel, and a toothed belt 5 which runs around these belt pulleys 3 and 4 as a traction element.

[0040] The pulley 3 is fixed to the steering shaft 2 in a rotationally fixed manner, and in Figures 2 , 3 and 4 The belt pulley 4 is shown pulled apart axially. It is connected to a motor shaft or drive shaft of a torque generating device (not shown).

[0041] In the execution according to the Figures 2 to 4According to the invention, a rotation limiter 6 is provided, comprising a coaxial winding core 61, which is rotationally fixed to the pulley 3, retaining elements 62 fixed to the housing 11, and a flexible band 63. The band 63 is designed as a closed loop, which is guided radially through the winding core 61 via radial slots 64. This allows the band 63 to be wound circumferentially and fixed to the winding core 61. Winding strands 65 extend from the winding core 61 to a section of the band 63 that is looped around the retaining elements 62. This fixes the band 63 to the housing 11 via the winding strands 65, with the section of the band 63 being spaced apart from the winding core 61.

[0042] Figure 3This shows an operating state within the permissible rotation of the steering shaft 2. In this state, the shaft, together with the pulley 3 and the attached winding core 61, is freely rotatable in both directions, as indicated by the double arrow. The winding strands 65 are free of tensile stress.

[0043] By rotating the steering shaft 2 counterclockwise, the Figure 4The limiting or stop state of the rotation limiter 6 shown has been reached. This state is characterized by the fact that the tape 63 is wound so far onto the winding core 61 that the winding strands 65 are tightly stretched between the circumference of the winding core 61 and the fixed retaining elements 62 of the housing 11 relative to it. As a result, they oppose a counterclockwise torque introduced into the steering shaft 2 and block further rotation in this direction, as indicated by the crossed arrow. The rotation limiter 6 is in an end stop position.

[0044] By rotating in the opposite direction, i.e., in the view of the Figures 3 and 4In a clockwise direction, the tape 63 can be wound onto the winding core 61 in the reverse direction until the winding strands 65 are taut in the opposite direction between the winding core 61 and the retaining elements 62. This allows the number of turns to be limited in the reverse direction.

[0045] As in Figure 5 As can be seen, the pulley 3 can be hollow, either pot-shaped or drum-shaped, with the winding core 61 fixed coaxially in the interior space around which the toothed belt 5 runs circumferentially. In the assembled state, the pin-shaped retaining elements 62 of the housing 11 project axially into this interior space of the pulley 3 such that they are positioned at the axial position of the winding core 61 and engage in the Figure 5 The recognizable loop-shaped band 63 engages. This enables a compact integration of the rotation limiter 6 into the pulley 3.

[0046] The retaining elements 62 can be integrally formed on the housing 11, for example in a casting process. The winding core 62 can be firmly connected to the pulley 3 via suitable fasteners, and a one-piece design is also possible.

[0047] For band 63, a highly flexible, tensile-resistant material can be used, for example a spring steel band.

[0048] In the Figures 7 to 9 A second embodiment of a rotation limiter 6 according to the invention is shown. This has axially projecting stop cams 66 and 67 attached to the pulley 3, and corresponding counter-stop cams 68 and 69 projecting axially in the opposite direction from the housing 11.

[0049] During relative rotation, the stop cams 66 and 67 are moved circumferentially relative to the counter-stop cams 68 and 69 until they mechanically abut against them circumferentially. This limits the angle of rotation of the pulley 3 relative to the housing. Reference symbol list

[0050] 1 Gearbox 11 Housing 12 Fastening device 2 Steering shaft 3 Pulley 4 Pulley 5 Timing belt 6 Speed ​​limiter 61 Winding core 62 Retaining element 63 Belt 64 Radial slot 65 Winding leg 66, 67 Stop cam 68, 69 Counter stop cam Longitudinal axis, engine axle

Claims

1. Steer-by-wire steering column for a motor vehicle, which has a steering shaft (2) which is mounted rotatably relative to a housing (11) about a longitudinal axis (L) and is operatively connected to a transmission (1), the transmission (1) having at least two transmission means (3, 4), wherein a rotation limiter (6) for limiting the rotation of the steering shaft (2) relative to the housing (11) is integrally formed with the transmission (1), wherein the transmission (11) is operatively connected to a torque generating device of a feedback actuator, characterized in in that the rotation limiter (6) has a winding core (61) on which a flexible band element (63) can be wound, the winding core (61) being rotatable relative to the housing (11) or a transmission means (3), and the band element (63) being fixed between the winding core (61) and the housing (11) or transmission means (3).

2. Steering column according to claim 1, characterized in that the rotation limiter (6) is operatively connected to a transmission means (3).

3. Steering column according to one of the preceding claims, characterized in that the transmission (11) has at least two intermeshing transmission gears (3, 4).

4. Steering column according to one of the preceding claims, characterized in that a transmission means (3) is non-rotatably connected to the steering shaft (2).

5. Steering column according to claim 1, characterized in that the torque generating device has a motor drive.

6. Steering column according to one of the preceding claims, characterized in that the rotation limiter (6) is designed to be integrated with a transmission means (3).

7. Steering column according to claim 6, characterized in that the rotation limiter (6) is structurally integrated with a gear wheel (3).

8. Steering column according to one of the preceding claims 6 or 7, characterized in that a transmission means (3) has a stop element (66, 67), and the housing (11) has a counter-stop element (68, 69) interacting with the stop element (66, 67).

9. Steering column according to one of the preceding claims, characterized in that the winding core (61) is arranged coaxially to a transmission gear (3).

10. Steering column according to one of the preceding claims, characterized in that the winding core (61) is non-rotatably connected to a transmission gear (3).