Single wheel actuator for a motor vehicle steering system

Abstract

The invention relates to an individual wheel actuator (10) (10) for a steering system (1), in particular a steer-by-wire steering system (1), of a motor vehicle, having a drive unit (12) comprising an electric machine (12a) and an electronic control unit (12b), a first gear stage (16) coupled to an output shaft of the electric machine (12a), and a second gear stage (20) coupled to the first gear stage (16) via an intermediate shaft (18), wherein the second gear stage (20) can be coupled by a joint (22), in particular a cardan joint, to a wheel suspension, in particular an upper wishbone (24) of the wheel suspension, in such a way that a wheel of the steering system (1) can be deflected by a rotational movement of the joint (22). The invention further relates to a wishbone for a wheel suspension of a motor vehicle and to a steering system (1), in particular a steer-by-wire steering system (1), for a motor vehicle.

Description

[0001] The invention relates to an individual wheel actuator for a steering system, in particular a steer-by-wire steering system, of a motor vehicle.

[0002] The invention further relates to a wishbone for a wheel suspension of a motor vehicle.

[0003] The invention further relates to a steering system, in particular a steer-by-wire steering system, for a motor vehicle. State of the art

[0004] In conventional steering systems, the desired steering angle is transmitted from the steering wheel to the two front wheels via a mechanical connection. The steering torque is amplified by a servo gear to enable easy steering.

[0005] Future steer-by-wire steering systems will eliminate the mechanical connection between the steering wheel and the steered wheels. The steering angle set on the steering wheel is detected by a sensor and transmitted electronically to the steering actuator, which then adjusts the front wheels accordingly.

[0006] The steering system can act centrally, meaning the steering actuator controls both wheels simultaneously. Typically, the translational movement of a rack is transferred to the tie rods, which pivot the wheels. However, the kinematics limit the maximum steering angle at the front wheels.

[0007] In decentralized steering systems, each steered wheel is assigned its own steering actuator, allowing each wheel to be controlled individually. This allows for an increase in the maximum steering angle. Since the central steering actuator in the center of the vehicle is eliminated, this can result in advantages for the vehicle manufacturer. Decentralized steering systems also enable new functions such as a parking brake function by turning the wheels in opposite directions.

[0008] Furthermore, it is known to transmit the rotation of an electric motor via a worm gear to pivot the steered wheel. Since the electric motor is attached to the chassis, a universal joint must be installed to transmit the rotational movement. This allows vertical movement of the wheel carrier caused by the spring compression to be compensated. Furthermore, movements in the x, y directions due to the spring compression can also be compensated.

[0009] DE 102020213664 A1 discloses an electric single-wheel actuator for a motor vehicle with a double-wheel carrier, which consists of an axle carrier and a pivoting carrier, and wherein the pivoting carrier is rotatably mounted within the axle carrier, with an electric motor which pivots the pivoting carrier via a gear, wherein the electric motor is arranged on the axle carrier.

[0010] Wheel suspensions with conventional steering systems, as well as the aforementioned independent wheel actuator, also exhibit a phenomenon called bump steer. The ideal situation would be that the steering angle does not change during vertical compression of a vehicle wheel. However, this cannot normally be prevented.

[0011] It is therefore an object of the invention to provide a compact single-wheel actuator which enables efficient steering torque transmission while simultaneously reducing or compensating for disruptive steering influences such as bump steer.

[0012] This object is achieved by an individual wheel actuator for a steering system, in particular a steer-by-wire steering system, of a motor vehicle having the features of patent claim 1.

[0013] The object is further achieved by a wishbone for a wheel suspension of a motor vehicle having the features of patent claim 11.

[0014] Furthermore, the object is achieved by a steering system, in particular a steer-by-wire steering system, for a motor vehicle having the features of patent claim 12. Disclosure of the invention

[0015] The present invention provides an individual wheel actuator for a steering system, in particular a steer-by-wire steering system, of a motor vehicle.

[0016] The single wheel actuator comprises a drive unit comprising an electric machine and an electronic control unit as well as a first gear stage coupled to an output shaft of the electric machine.

[0017] Furthermore, the independent wheel actuator comprises a second gear stage coupled to the first gear stage via an intermediate shaft, wherein the second gear stage can be coupled to a wheel suspension, in particular an upper wishbone of the wheel suspension, by a joint, in particular a cardan joint, in such a way that a wheel of the steering system can be deflected by a rotational movement of the joint.

[0018] The present invention further provides a wishbone for a wheel suspension of a motor vehicle, wherein the independent wheel actuator according to the invention is fastened to the wishbone.

[0019] The present invention further provides a steering system, in particular a steer-by-wire steering system, for a motor vehicle, having a plurality of individual wheel actuators according to the invention, which are designed to steer the wheel connected to a respective individual wheel actuator.

[0020] One idea of ​​the present invention is to provide a steering actuator or independent wheel actuator that can be integrated into double-wishbone wheel suspensions with a long steering axle. Furthermore, the wheel suspension's characteristics lie within a conventional and advantageous range.

[0021] The arrangement of the gear stages with intermediate shaft also reduces the required installation space within the rim, leaving sufficient space for a wheel brake and possibly a wheel hub drive.

[0022] The connection of the independent wheel actuator to the wheel suspension also advantageously exhibits lower elasticity. Furthermore, no bump steer effect occurs within the scope of the present invention. The steering angle is thus decoupled from the spring deflection.

[0023] Advantageous embodiments and further developments emerge from the subclaims and from the description with reference to the figures.

[0024] According to a preferred development, it is provided that the independent wheel actuator is arranged substantially vertically, wherein the drive unit is fastened to a wheel carrier adjacent to a lower wishbone of the wheel suspension, and wherein the second gear stage is arranged adjacent to an upper wishbone of the wheel suspension.

[0025] The steering actuator is thus attached to the wheel carrier, including the necessary bearing points, e.g. the intermediate shaft and the gear stages.

[0026] According to a further preferred embodiment, the first gear stage is formed by a transmission gear, in particular a harmonic drive. This advantageously allows a high transmission ratio to be achieved.

[0027] According to a further preferred development, the drive unit and the first gear stage can be positioned, at least in sections, within a circumference and an axial width of a rim of the motor vehicle. This arrangement thus makes it possible to utilize the available installation space within the rim.

[0028] According to a further preferred development, it is provided that the second gear stage can be positioned outside the circumference of the rim, in particular in an installation position of the individual wheel actuator above the rim, of the motor vehicle.

[0029] Due to the fact that the individual wheel actuator is moved vertically when the wheel is compressed, the vertical distance between the second gear stage and the wheel remains essentially constant.

[0030] According to a further preferred development, it is provided that an axial length of the intermediate shaft is designed such that the intermediate shaft connects the first gear stage, which can be positioned at least in sections within a circumference and an axial width of a rim of the motor vehicle, with the second gear stage, which can be positioned outside the circumference of the rim.

[0031] The use of a long intermediate shaft allows the drive unit and the first gear stage to be positioned inside the rim.

[0032] According to a further preferred development, it is provided that the second gear stage is formed by a spur gear which has an axial offset between a gear input shaft, in particular the intermediate shaft, and a gear output shaft.

[0033] This allows the transmission output shaft or drive shaft to be offset outward relative to the intermediate shaft. This results in a favorable position for the outer connection point of the upper wishbone, which, together with the two lower wishbones, defines the steering axis. The resulting values ​​for the spread angle and steering roll radius are thus within a typical and advantageous range.

[0034] According to a further preferred development, the transmission output shaft of the second transmission stage is offset outward in the direction of the vehicle, in particular positioned at least partially above the rim. Since the second transmission stage is positioned at least partially above the rim, this installation space can be utilized advantageously.

[0035] According to a further preferred development, it is provided that the individual wheel actuator is designed to support a steering torque at an outer connection point of the individual wheel actuator on the wheel carrier, and wherein the steering torque can be absorbed by the joint via the upper wishbone.

[0036] The joint provides the necessary degrees of freedom for the wheel's deflection movement and at the same time enables the transmission of the steering torque.

[0037] According to a further preferred development, it is provided that the intermediate shaft has a hollow wall profile.

[0038] In order to keep the additional weight for the individual wheel actuator attached to the wheel carrier as an unsprung mass to a minimum, it is conceivable, depending on the requirements and length of the intermediate shaft, that the intermediate shaft is designed with a hollow wall profile, for example as a hollow-drilled intermediate shaft.

[0039] The described designs and further training courses can be combined as desired.

[0040] Further possible embodiments, further developments and implementations of the invention also include combinations of features of the invention described previously or below with regard to the exemplary embodiments that are not explicitly mentioned. Short description of the drawings

[0041] The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention.

[0042] Other embodiments and many of the aforementioned advantages will become apparent upon review of the drawings. The elements illustrated in the drawings are not necessarily drawn to scale.

[0043] It shows: Fig. 1 a schematic representation of an individual wheel actuator in a steering system, in particular in a steer-by-wire steering system, of a motor vehicle according to a preferred embodiment of the invention.

[0044] In the figures of the drawings, the same reference symbols designate the same or functionally equivalent elements, parts or components, unless otherwise stated.

[0045] The Fig.1 comprises a drive unit 12 comprising an electric machine 12a and an electronic control unit 12b as well as a first gear stage 16 coupled to an output shaft of the electric machine 12a.

[0046] Furthermore, the individual wheel actuator 10 comprises a second gear stage 20 coupled to the first gear stage 16 via an intermediate shaft 18, wherein the second gear stage 20 can be coupled by a joint 22, in particular a cardan joint, to a wheel suspension, in particular an upper wishbone 24 of the wheel suspension, in such a way that a wheel of the steering system 1 can be deflected by a rotational movement of the joint 22.

[0047] The independent wheel actuator 10 is arranged substantially vertically, wherein the drive unit 12 is fastened to a wheel carrier 26 adjacent to a lower wishbone 28 of the wheel suspension, and wherein the second gear stage 20 is arranged adjacent to an upper wishbone 24 of the wheel suspension.

[0048] The first gear stage 16 is formed by a transmission gear, in particular a harmonic drive. Furthermore, the drive unit 12 and the first gear stage 16 can be positioned at least partially within a circumference and an axial width of a rim 30 of the motor vehicle.

[0049] The second gear stage 20 can be positioned outside the circumference of the rim 30, in particular in an installation position of the individual wheel actuator 10 above the rim 30 of the motor vehicle.

[0050] An axial length of the intermediate shaft 18 is designed such that the intermediate shaft 18 connects the first gear stage 16, which can be positioned at least partially within a circumference and an axial width of a rim 30 of the motor vehicle, with the second gear stage 20, which can be positioned outside the circumference of the rim 30.

[0051] The second gear stage 20 is formed by a spur gear which has an axial offset between a transmission input shaft, in particular the intermediate shaft 18, and a transmission output shaft 32.

[0052] In addition, the transmission output shaft 32 of the second transmission stage 20 is offset outwards in the direction of the vehicle, in particular can be positioned at least in sections above the rim 30.

[0053] The independent wheel actuator 10 is further configured to support a steering torque at an outer connection point of the independent wheel actuator 10 on the wheel carrier 26. The steering torque can be absorbed by the joint 22 via the upper wishbone 24. The intermediate shaft 18 preferably has a hollow-wall profile. Alternatively, the intermediate shaft 18 can, for example, have a solid profile. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 102020213664 A1

[0009]

Claims

[1] Individual wheel actuator (10) for a steering system (1), in particular a steer-by-wire steering system (1), of a motor vehicle, comprising: a drive unit (12) comprising an electric machine (12a) and an electronic control unit (12b); a first gear stage (16) coupled to an output shaft of the electric machine (12a); and a second gear stage (20) coupled to the first gear stage (16) via an intermediate shaft (18), wherein the second gear stage (20) can be coupled to a wheel suspension, in particular an upper wishbone (24) of the wheel suspension, by a joint (22), in particular a cardan joint, in such a way that a wheel of the steering system (1) can be deflected by a rotational movement of the joint (22). [2] Independent wheel actuator (10) according to claim 1, wherein the independent wheel actuator (10) is arranged substantially upright, wherein the drive unit (12) is fastened to a wheel carrier (26) adjacent to a lower wishbone (28) of the wheel suspension, and wherein the second gear stage (20) is arranged adjacent to an upper wishbone (24) of the wheel suspension. [3] Single wheel actuator (10) according to claim 1 or 2, wherein the first gear stage (16) is formed by a transmission gear, in particular a wave gear. [4] Single wheel actuator (10) according to one of the preceding claims, wherein the drive unit (12) and the first gear stage (16) can be positioned at least in sections within a circumference and an axial width of a rim (30) of the motor vehicle. [5] Independent wheel adjuster (10) according to claim 4, wherein the second gear stage (20) can be positioned outside the circumference of the rim (30), in particular in an installation position of the independent wheel adjuster (10) above the rim (30) of the motor vehicle. [6] Single wheel actuator (10) according to claim 5, wherein an axial length of the intermediate shaft (18) is designed such that the intermediate shaft (18) connects the first gear stage (16), which can be positioned at least in sections within a circumference and an axial width of a rim (30) of the motor vehicle, with the second gear stage (20), which can be positioned outside the circumference of the rim (30). [7] Single-wheel actuator (10) according to one of claims 4 to 6, wherein the second gear stage (20) is formed by a spur gear which has an axial offset between a transmission input shaft, in particular the intermediate shaft (18), and a transmission output shaft (32). [8] Single wheel actuator (10) according to claim 7, wherein the transmission output shaft (32) of the second transmission stage (20) is offset outwards in the direction of the vehicle, in particular at least partially positionable above the rim (30). [9] Independent wheel actuator (10) according to one of the preceding claims, wherein the independent wheel actuator (10) is designed to support a steering torque at an outer connection point of the independent wheel actuator (10) on the wheel carrier (26), and wherein the steering torque can be absorbed by the joint (22) via the upper wishbone (24). [10] Single wheel actuator (10) according to one of the preceding claims, wherein the intermediate shaft (18) has a hollow wall profile. [11] Wishbone (24, 28) for a wheel suspension of a motor vehicle, wherein an independent wheel adjuster (10) according to one of claims 1 to 10 is fastened to the wishbone (24, 28). [12] Steering system (1), in particular steer-by-wire steering system (1), for a motor vehicle, with a plurality of individual wheel actuators (10) according to one of claims 1 to 10, which are designed to steer the wheel connected to a respective individual wheel actuator (10).

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