Steering column for a motor vehicle

Abstract

The present invention relates to a steering column (1) for a motor vehicle, comprising a steering shaft (4) which is mounted in a steering column housing (3) to rotate about a longitudinal axis (L) extending in a longitudinal direction, a rotation limiter (5) for limiting the rotation of the steering shaft (4), and a feedback actuator (6) for coupling a feedback moment into the steering shaft (4), comprising an actuator housing (61) and an actuator shaft (62) which can be rotationally driven relative thereto by a motor. In order to permit an optimised design and improved manufacture and assembly, the invention proposes that the feedback actuator (6) and the steering column (1) have a releasable connection.

Description

[0001] Steering column for a motor vehicle

[0002] State of the art

[0003] The invention relates to a steering column for a motor vehicle, comprising a steering shaft rotatably mounted in a steering column housing about a longitudinal axis extending in a longitudinal direction, a rotation limiter for limiting the rotation of the steering shaft, and a feedback actuator for coupling a feedback torque into the steering shaft, comprising an actuator housing and an actuator shaft that can be driven in rotation relative thereto by a motor.

[0004] To steer the motor vehicle, a manual steering command can be input by turning a steering wheel mounted on the driver's side, at the rear end of the steering shaft in the direction of travel. This command is translated into a steering angle of the vehicle's steerable wheels. The steering shaft is rotatably mounted in a steering column housing, also known as a steering column housing or guide box. The steering column housing is typically held by a support unit that can be connected to the vehicle body and can be adjustable relative to it.

[0005] While in a conventional steering system the steering shaft is mechanically connected to the wheels via a steering gear, in a steer-by-wire steering system the rotation of the steering shaft is detected by a rotation sensor that has a rotation angle and / or torque sensor and converted into an electrical control signal to actuate electrical steering actuators. Due to the lack of mechanical coupling to the wheels, the rotation of the steering shaft is not limited by the mechanical end stop of the wheels when the maximum steering angle is reached. To avoid excessive steering and to simulate a realistic steering feel, it is known to limit the maximum possible angle of rotation of the steering wheel using a rotation limiter, which forms a limiting device with an end stop to restrict the maximum possible rotation of the steering shaft.

[0006] A further effect of the lack of mechanical coupling is that the driver receives no direct mechanical feedback from the steered wheels via the steering system. In mechanically coupled steering systems, this feedback is fed back to the steering wheel via the steering gear and the mechanically continuous steering shaft as a reaction or restoring torque depending on the road surface, 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 perform appropriate steering maneuvers, thereby impairing vehicle steerability and thus driving safety.

[0007] To create a realistic driving experience, it is known in the 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. From these, a feedback signal is generated, which is fed into a feedback actuator. This actuator has an electrical controller and an electric motor connected to it, which drives an actuator shaft connected to the steering shaft. During driving, the motor is activated to couple a feedback torque corresponding to the actual reaction torque into the steering wheel via the steering shaft. Such "force feedback" systems give the driver the impression of a real driving situation, similar to a conventional steering system, which facilitates intuitive response. The feedback actuator can also be referred to as a handwheel actuator (HWA) or manual force adjuster.

[0008] From WO 2022 / 175278 A1 or EP 3 620 350 A1, it is known to equip a steering column with a rotation limiter and a feedback actuator. This can, in principle, solve the aforementioned problems. However, the disadvantage is the relatively complex design and assembly, particularly considering the testing and calibration routines required during production, for example, for running in the feedback actuator, which is complicated by the rotation limiter.

[0009] In view of the problems explained above, it is an object of the present invention to enable an optimized design and improved production and assembly.

[0010] Description of the invention

[0011] This object is achieved according to the invention by the steering system having the features of claim 1. Advantageous further developments emerge from the subclaims.

[0012] In a steering column for a motor vehicle, comprising a steering shaft rotatably mounted in a steering column housing about a longitudinal axis extending in a longitudinal direction, a rotation limiter for limiting the rotation of the steering shaft, and a feedback actuator for coupling a feedback torque into the steering shaft, comprising an actuator housing and an actuator shaft that can be driven in rotation by a motor relative thereto, it is provided according to the invention that the feedback actuator and the steering column have a detachable connection.

[0013] By definition, the longitudinal direction is axial. The actuator shaft, which can also be referred to as the drive shaft, extends coaxially, or at least essentially coaxially, with the longitudinal axis. In other words, the steering shaft and the actuator shaft are aligned. The feedback actuator has an electric motor, which can drive the actuator shaft to rotate around the longitudinal axis, preferably via a gear.

[0014] According to the invention, at least one mechanical interface is formed between the steering column and the feedback actuator, which has a detachable connection. This is arranged between the rotation limiter and the feedback actuator.

[0015] The detachable connection can be created and separated. This makes it possible, for example, to mount the feedback actuator as a whole on the steering column and disassemble it again as needed, or to at least effectively couple and decouple individual functional parts of the steering shaft and the feedback actuator.

[0016] The decoupling or loosening of the connection can preferably be achieved by spatial separation.

[0017] The detachable connection simplifies the production and assembly of the steering column. Furthermore, different types of feedback actuators and steering column housings can be combined with minimal effort.

[0018] It is advantageous that the actuator housing is connectable to the steering column housing. The actuator housing and the steering column housing can have connecting elements that enable the creation of a preferably detachable connection. This makes it possible to mount and dismount the feedback actuator on the steering column. A further advantage is that during production of the steering column, the actuator housing or the steering column housing can be temporarily connected to production and / or testing equipment via detachable connecting elements, for example, in a test bench for recording operating parameters or for coupling test loads, running-in torques, and the like. Alternatively or additionally, non-detachable connecting elements can be provided. In the aforementioned embodiment, it can be provided that an axial connection is arranged between the actuator housing and the steering column housing.The axial connection is characterized in that the actuator housing and the steering column housing can be joined together in the axial direction, i.e. in the longitudinal direction, preferably in a linear axial relative movement. The axial connection can, for example, have form-fitting elements that can be brought into positive engagement with one another in the axial direction, in order to create a form-fitting connection that is effective in the longitudinal direction and / or in the circumferential direction with respect to a rotation about the longitudinal axis. For example, corresponding flange elements can be provided which are attached to the opposing end faces of the steering column and actuator housing and can be axially clamped together. The connection can be detachable, for example by means of screw bolts or the like, or alternatively or additionally comprise non-detachable connecting means, for example riveted, adhesively bonded, welded connections or the like.

[0019] Preferably, it can be provided that an axially connectable shaft coupling is arranged between the steering shaft and the actuator shaft. The shaft coupling serves to transmit the feedback torque to the steering shaft. It forms a detachable connection and is accordingly designed as a separable shaft coupling, i.e. it can be engaged and disengaged. Preferably, the shaft coupling comprises coupling parts which are attached to the steering shaft and the actuator shaft in a rotationally fixed manner and which can be axially coupled to create a torque-locking connection. This means that the shaft coupling can be brought into coupling engagement by an axial, preferably a purely axial, relative movement of the steering shaft and actuator shaft. This design of the shaft coupling can also be referred to as an axial coupling. This has the advantage of simple assembly.

[0020] Preferably, the aforementioned axial connection between the actuator housing and the steering column housing and the axially connectable shaft coupling can be arranged and combined in such a way that the shaft coupling is automatically brought into engagement by attaching the actuator housing to the steering column housing. To assemble the feedback actuator, only the actuator housing needs to be axially connected and fixed to the steering column, and no additional fixing of the shaft coupling is required. This advantageously reduces manufacturing and assembly costs. A further advantage is that the steering column and actuator housings can be designed to be closed and connected to one another in a sealed manner, so that the steering shaft and the actuator shaft can be housed together with the shaft coupling with optimal protection against external influences.The aforementioned embodiment can advantageously be realized by designing the shaft coupling as an axially joinable form-locking coupling. The form-locking coupling has form-locking elements which can be brought into form-locking engagement by a preferably linear relative movement in the longitudinal direction. The form-locking engagement thus generated is effective in the circumferential direction with respect to rotation about the longitudinal axis, thus enabling form-locking torque transmission between the steering shaft and actuator shaft. For example, the form-locking coupling can be designed as a claw coupling with coupling projections projecting axially from the end faces of the coupling parts and offset in the circumferential direction, which can be engaged with one another by simply axially plugging them together, thereby forming a form-locking engagement effective with respect to rotation. Such a design can be provided with little effort and in a functionally reliable manner.

[0021] It can preferably be provided that the shaft coupling is constructed in two parts. In the two-part design, exactly two coupling parts are provided, namely the two coupling halves. One coupling half is connected to the steering shaft, and the other coupling half is connected to the actuator shaft in a rotationally fixed manner. The two coupling halves are arranged on the axially opposing end faces of the steering shaft and actuator shaft. This allows them to be easily engaged by axially joining them together when attaching the feedback actuator.

[0022] It is advantageous that the shaft coupling can be connected without tools. This allows the torque-locking coupling engagement to be achieved without the use of external tools or other aids. Accordingly, the steering shaft and the actuator shaft can be connected to each other in a rotationally locked manner without tools, for example, by simply axially plugging the two coupling halves together. Preferably, the shaft coupling can also be separated without tools. This allows the steering shaft and the actuator shaft to be easily connected and separated from each other without the use of tools, so that the feedback actuator can be easily installed and just as easily removed from the steering column housing.

[0023] An advantageous development can be that the shaft coupling has a damping element. One or more damping elements can be provided, which are arranged between the torque-transmitting coupling parts. They can be designed to dampen a relative rotational movement and / or axial movement between the steering shaft and the actuator shaft. This can advantageously reduce the transmission of vibrations or torque peaks. A damping element can, for example, have an elastomer or rubber element, which is arranged between the torque-transmitting

[0024] can be arranged with form-locking elements, for example a claw coupling.

[0025] It is possible for the shaft coupling to have a spring element. One or more spring elements can be provided, which can be arranged axially and / or circumferentially between the steering shaft and the actuator shaft. Elastomer or rubber elements and / or metallic springs such as coil springs, leaf springs, or the like can be used as spring elements between the torque-transmitting coupling parts. This allows torque peaks to be cushioned when the feedback actuator starts up relative to the steering shaft, thus generating a pleasant tactile feedback. It is possible to functionally combine spring and damping elements.

[0026] The shaft coupling can be designed to compensate for offsets. This allows the coupling to compensate for any radial and / or angular misalignment between the steering shaft and the actuator shaft that may occur due to tolerances. Accordingly, the acceptable tolerance range can be increased, manufacturing and assembly costs can be reduced, and operational reliability can be improved.

[0027] Preferably, the rotation limiter can be integrated into the steering column housing. The rotation limiter is designed to limit the maximum possible angle of rotation of the steering shaft relative to the steering column housing. Various designs are known for this purpose. For example, stops that can be brought into contact with each other in the circumferential direction can be provided on the steering shaft and in the steering column housing, or wound-up band elements can be attached between the steering shaft and the steering column housing, or the like. Housing the rotation limiter in the steering column housing enables a compact design.

[0028] It can be provided that the rotation limiter can be mounted axially on the steering shaft, for example, from the end of the steering shaft where the shaft coupling according to the invention is arranged. In this way, the rotation limiter can be mounted through the axial opening of the steering column housing, onto which the feedback actuator is subsequently mounted axially.

[0029] The feedback actuator may be provided with a reduction gear. This is integrated between the motor shaft and the relatively slower-rotating actuator shaft and may comprise a belt drive, a worm gear, or another suitable gear design.

[0030] It is possible for the shaft coupling to be structurally combined with the rotation limiter and the feedback actuator. The rotation limiter can, for example, have a stop element on a shaft or hub part connected to the steering shaft. The feedback actuator can, for example, have a gear wheel connected to the actuator shaft. By having such a shaft or hub part, a gear wheel, or another functional element of the rotation limiter or the feedback actuator have a coupling part, for example, a coupling half attached to it or integrated therewith, an advantageously compact design can be realized.

[0031] It can advantageously be provided that the rotation limiter has a limiting torque that is higher than the maximum feedback torque of the feedback actuator. The limiting torque can be supported directly against the steering column housing and is therefore not transmitted via the shaft coupling. This has the advantage that the shaft coupling only has to transmit the relatively smaller feedback torque and can therefore be designed smaller and lighter.

[0032] Description of the drawings

[0033] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail:

[0034] Fig. 1 shows a steering column according to the invention in a schematic perspective view,

[0035] Fig. 2 shows the steering column according to Fig. 1 in a schematic representation, axially exploded in the direction of the longitudinal axis,

[0036] Fig. 3 is a detailed view of the rotation limiter of the steering column according to Fig. 1 in a schematic, axially exploded view,

[0037] Fig. 4 shows a longitudinal section through the steering column according to Fig.1, Fig. 5 shows a steering column according to the invention in a second embodiment in a schematic perspective view analogous to Fig.1,

[0038] Fig. 6 shows a section of a longitudinal section through the steering column according to Fig. 5,

[0039] Fig. 7 shows a steering column according to the invention in a third embodiment in a schematic perspective view analogous to Fig.1,

[0040] Fig. 8 shows a section of a longitudinal section through the steering column according to Fig.7.

[0041] Embodiments of the invention

[0042] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0043] Fig. 1 shows a steering column 1 in a schematic perspective view, viewed diagonally from top right to front with respect to the installation position in the direction of travel.

[0044] The steering column 1 has a support unit 2 which has fastening means 21 for attachment to a body of a motor vehicle (not shown here) and carries a casing unit 3 which forms a steering column housing.

[0045] In the casing unit 3, a steering shaft 4, which can be synonymously referred to as a steering spindle, is rotatably mounted about a longitudinal axis L extending axially in the longitudinal direction. At its rear end, directed towards the driver's position, the steering shaft 4 has a connecting section 41 to which a steering wheel (not shown here) can be mounted in a rotationally fixed manner.

[0046] Fig.2 shows a schematic representation of the steering column 1, exploded in the longitudinal direction of the longitudinal axis L.

[0047] The casing unit 3 is designed to be longitudinally adjustable in that it has an inner casing 32 that is coaxially telescopically adjustable in the longitudinal direction within an outer casing 31, as indicated by the double arrow. The steering shaft 4 is also designed to be longitudinally adjustable and has an inner shaft 43 that is telescopically and rotationally mounted in an outer shaft 42. Figure 3 shows a longitudinal section through the steering column 1.

[0048] A rotation limiter 5 limits the maximum possible rotation of the steering shaft 4 relative to the support unit 2. This has a hub part 51 which is rotationally connected to the inner shaft 43 of the steering shaft 4 and which has radially outwardly projecting stop elements 52. The hub part 52 is arranged in an axial passage of an annular or tubular outer part 53 which is rotationally fixed in the outer casing 31 of the casing unit 3 with respect to rotation about the longitudinal axis L and has radially inwardly projecting counter-stop elements 54. These can be stopped in the circumferential direction against the stop elements 52, whereby the relative rotation of the hub part 51 relative to the outer part 53 and thus the maximum of the steering shaft 4 relative to the casing unit 3 is limited.

[0049] A feedback actuator 6 enables the coupling of a feedback torque into the steering shaft 4. It has an actuator housing 61 in which an actuator shaft 62 is mounted so as to rotate about the longitudinal axis L in the installed position according to Fig. 1 or 3, i.e. it is arranged in alignment with the steering shaft 4. The actuator shaft 62 can be driven in rotation by an electric motor 63, namely via a gear which comprises a gear wheel 64 mounted in a rotationally fixed manner on the actuator shaft 62. In the embodiment according to Fig. 1, 2 and 3, the gear is designed as a belt gear, and the gear wheel 64 is correspondingly designed as a belt wheel around which a belt 65, which can be driven by the motor 63 and can preferably be designed as a toothed belt, rotates. The feedback actuator 6 comprises a control unit 68 which is set up and electrically connected to the motor 63 so as to operate the motor 63.

[0050] The electrical control unit 68 is also referred to as an ECU (Electronic Control Unit). The main function of an ECU is to control and monitor the operation of the motor 63 by receiving electronic signals from the vehicle or an installed rotation sensor 8, processing them, and regulating the motor 63 based on them.

[0051] To transmit the feedback torque, a shaft coupling 7 is arranged between the revolution limiter 5 and the feedback actuator 6. According to the invention, this is designed as a detachable or separable coupling, specifically as a two-part claw coupling. It comprises a first coupling half 71, which is attached to the actuator shaft 62, and a second coupling half 72, which is attached to the steering shaft 4, specifically to the inner shaft 43. The two coupling halves 71 and 72 have axially projecting, segment-shaped coupling claws 73 on their axially opposing end faces. These claws can be brought into a positive, torque-locking coupling engagement with respect to rotation about the longitudinal axis L by an axially directed assembly movement M, with which the feedback actuator 6 is moved towards the casing unit 3, as indicated by the arrow in Fig. 2.

[0052] During assembly, the actuator housing 61 is axially fixed to the casing unit 3 by means of fastening means not explicitly shown here, for example, screw bolts or the like, in order to realize the fully assembled state according to Fig. 1 or 4. In this case, the coupling halves 71 and 72 are brought into engagement so that the shaft coupling 7 is coupled.

[0053] In the example shown, the second coupling half 72 is rotationally fixed to the inner shaft 43 and can be axially supported on the hub part 51. However, it is also conceivable and possible to form the second coupling half 72 together with the hub part 51 as a single or integral component.

[0054] Figs. 5 and 6 show a second embodiment of a steering column 1 according to the invention, wherein the same reference numerals are used for identically functioning parts. Fig. 6 shows an enlarged partial view of a longitudinal section in the region of the rotation limiter 6 and the feedback actuator 6. The feedback actuator 6 comprises a control unit 68, which is configured and electrically connected to the motor 63 to operate the motor 63.

[0055] The difference from the first embodiment lies in the design of the gear mechanism of the feedback actuator 6, which is embodied here as a worm gear. This comprises a worm 66, which is connected to the motor shaft of the motor 63 and which is in gear engagement with the gear wheel 65, embodied here as a worm gear, which, as in the first embodiment, is connected to the actuator shaft 62.

[0056] The third embodiment shown in Figs. 7 and 8 in views analogous to Figs. 5 and 6 differs from the two aforementioned embodiments in that a direct drive is implemented. In this case, no gear is provided between the motor 63 and the actuator shaft 62. Instead, the rotor 67 is mounted directly on the actuator shaft 62, as can be seen in Fig. 8. In the example shown, the actuator housing 61 is identical to the motor housing of the motor 63. The feedback actuator 6 comprises a control unit 68 which is configured and electrically connected to the motor 63 to operate the motor 63. In all embodiments shown here, the shaft coupling 7 is brought into coupling engagement automatically and without tools during the axial assembly of the feedback actuator 6 on the steering column 1. According to the invention, the shaft coupling 7 is designed to be separable.This allows the feedback actuator 6 to be easily removed from the casing unit 3 if necessary, whereby the shaft coupling 7 is automatically separated.

[0057] In all embodiments shown, a rotation sensor 8, which is shown as an example in Fig. 8, can be provided. This can measure the rotation of the steering shaft 4 relative to the steering column housing 3 and, for example, comprise a position and / or torque sensor. Alternatively or additionally, a rotation sensor 8 can be attached to the feedback actuator 6, as indicated in Figs. 4 and 6.

[0058] List of reference symbols

[0059] 1 steering column

[0060] 2 carrying unit

[0061] 21 Fasteners

[0062] 3 jacket unit

[0063] 31 Outer jacket

[0064] 32 inner jacket

[0065] 4 Steering shaft

[0066] 41 connecting section

[0067] 42 inner shaft

[0068] 43 Outer shaft

[0069] 5 revolution limiters

[0070] 51 Hub part

[0071] 52 stop elements

[0072] 53 Outdoor part

[0073] 54 Counter stop element

[0074] 6 Feedback actuator

[0075] 61 Actuator housing

[0076] 62 Actuator shaft

[0077] 63 Engine

[0078] 64 gear wheel

[0079] 65 belts

[0080] 66 snail

[0081] 67 Rotor

[0082] 68 Control unit (ECU)

[0083] 7 Shaft coupling

[0084] 71 first coupling half

[0085] 72 second coupling half

[0086] 73 clutch claws

[0087] 8 rotation sensor

[0088] L Longitudinal axis

[0089] M assembly movement

Claims

PATENT CLAIMS 1. Steering column (1) for a motor vehicle, comprising a steering shaft (4) rotatably mounted in a steering column housing (3) about a longitudinal axis (L) extending in a longitudinal direction, a rotation limiter (5) for limiting the rotation of the steering shaft (4), and a feedback actuator (6) for coupling a feedback torque into the steering shaft (4), comprising an actuator housing (61) and an actuator shaft (62) which can be driven in rotation relative to the latter by a motor, characterized in that the feedback actuator (6) and the steering column (1) have a detachable connection.

2. Steering column according to claim 1, characterized in that the actuator housing (61) can be connected to the steering column housing (31).

3. Steering column according to one of the preceding claims, characterized in that an axial connection is arranged between the actuator housing (61) and the steering column housing (3).

4. Steering column according to one of the preceding claims, characterized in that an axially connectable shaft coupling (7) is arranged between the steering shaft (4) and the actuator shaft (62).

5. Steering column according to claim 4, characterized in that the shaft coupling (7) is designed as an axially joinable form-fitting coupling.

6. Steering column according to one of the preceding claims, characterized in that the shaft coupling (7) is formed in two parts.

7. Steering column according to one of the preceding claims, characterized in that the shaft coupling (7) can be connected without tools.

8. Steering column according to one of the preceding claims, characterized in that the shaft coupling (7) has a damping element.

9. Steering column according to one of the preceding claims, characterized in that the shaft coupling (7) has a spring element.

10. Steering column according to one of the preceding claims, characterized in that the shaft coupling (7) is designed to compensate for offsets.

11. Steering column according to one of the preceding claims, characterized in that the rotation limiter (5) is integrated in the steering column housing (3).

12. Steering column according to one of the preceding claims, characterized in that the feedback actuator (6) has a gear.

13. Steering column according to one of the preceding claims, characterized in that the shaft coupling (7) is structurally combined with the revolution limiter (5) and the feedback actuator (6).

14. Steering column according to one of the preceding claims, characterized in that the rotation limiter (5) has a limiting torque which is higher than a maximum feedback torque of the feedback actuator (6).

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