Anti-rotation mechanism for steer-by-wire road wheel actuator

Abstract

A steer-by-wire system for a vehicle includes a rack movable in an axial direction and defining a groove extending in the axial direction of the rack. The system also includes a housing surrounding at least a portion of the rack. The system further includes an anti-rotation device disposed proximate an outer surface of the rack at the mounting location of the rack and within the housing, the anti-rotation device comprising a bearing seated in the groove of the rack. The system further includes a lash adjuster bearing assembly in contact with the rack for radially biasing the rack to a desired position.

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] This application claims the priority benefits of the preliminary US patent application, serial no. 63 / 636,951, filed on April 22, 2024, the disclosure of which is hereby incorporated in its entirety by reference. AREA OF INVENTION

[0002] The disclosure of this application relates to steering systems and in particular to a rotation protection mechanism for a road wheel actuator for such steering systems. BACKGROUND

[0003] Various electric power steering systems (EPS systems) have been developed to assist a driver in steering a vehicle. One type of EPS system is called an electric rack and pinion power steering system (REPS system) and uses an electric motor to drive a ball screw and a rack. Some examples of steer-by-wire road wheel actuators (SbW-RWAs) are simply electric rack and pinion power steering systems based on ball screws without input shafts. In this configuration, a pinion shaft can still engage with the teeth of the rack and act as an anti-rotation feature to prevent unwanted rotation / twisting of the rack during translation.

[0004] OEMs might be interested in removing the pinion gear for reasons of better fit and cost savings when developing steer-by-wire systems. In a vehicle's steer-by-wire system, an anti-rotation device is required when the steering system does not use a pinion gear to counteract the rotation of the ball screw caused by the load on the ball nut thread. SUMMARY

[0005] According to one aspect of the disclosure, a steer-by-wire system for a vehicle includes a rack that is movable in an axial direction and defines a groove extending in the axial direction of the rack. The system also includes a housing that surrounds at least one section of the rack. The system further includes an anti-rotation device located near an outer surface of the rack at the rack's mounting location and within the housing, the anti-rotation device comprising a bearing seated in the rack's groove. The system further includes a backlash-compensating bearing arrangement in contact with the rack to radially preload the rack into a desired position.

[0006] According to another aspect of the disclosure, an anti-rotation device includes a linear translation component that is movable in an axial direction, wherein the linear translation component defines an axial groove defined by a curved groove surface. The anti-rotation arrangement also includes a bearing in contact with the linear translation component to prevent rotation of the linear translation component. The bearing arrangement includes an inner raceway. The bearing arrangement also includes an outer raceway with an outer surface located within the axial groove defined within the linear translation component to prevent rotation of the linear translation component, wherein the outer raceway has a curvature both in the axial direction of the groove and in the circumferential direction of the groove. The anti-rotation arrangement also includes a backlash compensation bearing arrangement.The backlash adjustment assembly includes a backlash adjustment bearing with a curved inner surface that contacts an outer surface of the linear translation component to radially preload the linear translation component. The backlash adjustment assembly also includes a spring in contact with the backlash adjustment bearing. Furthermore, the backlash adjustment assembly includes an adjusting plug in contact with the backlash adjustment bearing to adjust the force with which the backlash adjustment bearing radially preloads the linear translation component.

[0007] These and other advantages and features will become clearer from the following description in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The subject matter considered to be the invention is specifically highlighted and clearly claimed in the claims at the end of the patent specification. The foregoing and further features and advantages of the invention will become clear from the following detailed description in conjunction with the accompanying drawings, which: Fig. Figure 1 illustrates a steer-by-wire steering system; and Fig. Figure 2 shows a perspective view of a rotation protection mechanism for the electric rack and pinion power steering system, which is arranged inside a housing. DETAILED DESCRIPTION

[0009] With reference to the figures, which describe the present disclosure with reference to certain embodiments without limiting them, it is understood that the disclosed embodiments serve only to illustrate the present disclosure, which can be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of certain components. Therefore, the specific structural and functional details disclosed herein are not to be interpreted as a limitation, but merely as a representative basis for teaching a person skilled in the art the manifold uses of the present disclosure.

[0010] The embodiments described herein are used in conjunction with a steering arrangement of a vehicle, such as a passenger car, truck, sport utility vehicle (SUV), crossover, minivan, personal watercraft, aircraft, off-road vehicle, motorhome, or other suitable vehicles, which include various steering system schemes. As discussed herein, an electric power steering system (EPS system), which includes, for example, a steer-by-wire system, includes an anti-rotation device where no pinion is used in the steering system. The anti-rotation device resists the rotation of a linear translation component. Such rotation is caused by the loading of an actuating component in contact with the linear translation component, such as the thread of a ball screw.

[0011] First, with reference to Fig. Figure 1 illustrates a power steering system 20 in general terms. The power steering system 20 can be configured as a driver interface steering system, an autonomous driving system, or a system that enables both driver interface steering and autonomous steering. The steering system can include an input device 22, such as a steering wheel, whereby a driver can mechanically provide steering input by turning the steering wheel. A steering column 26 extends along an axis from the input device 22 to an output arrangement 28. The embodiments disclosed herein are used in steering systems in which the output arrangement 28 is in functional communication with an actuator 34 (e.g., steer-by-wire, autonomous system, etc.) that is coupled to a linear translation component 40. The output arrangement 28 has wired electrical communication 36 with the actuator 34.The actuator 34 drives the linear translation component 40 to provide the steering control of the vehicle.

[0012] The linear translation component 40 is any component that has a substantially cylindrical cross-section over at least one section of its length and is driven in a substantially linear manner to effect the adjustment of the vehicle road wheels 49. In some embodiments, the linear translation component 40 is a ball screw. In other embodiments, the linear translation component 40 is a leadscrew. The foregoing examples do not constitute a limitation of the linear translation component 40.

[0013] In previous steer-by-wire steering systems, a pinion on an outer surface of the linear translation component 40 (e.g., a "rack") is used to provide steering input control of the linear translation component 40. Such a pinion also provides anti-rotation reaction forces on the linear translation component 40 to counteract the forces exerted by the actuator 34, such as a ball screw nut. However, the pinion and the associated required components (e.g., upper and lower pinion bearings, rack bearings, adjusting plugs, lower rotor, and rack teeth, etc.) may be undesirable in certain steering systems, for example, due to space constraints, cost, and manufacturing complexity. The embodiments of an anti-rotation device disclosed herein provide the anti-rotation benefits of the previously required pinion while eliminating the numerous components mentioned above.The above-mentioned steering input control of the linear translation component 40 with a pinion is unnecessary in a steer-by-wire steering system, and such a system will benefit from the embodiments disclosed herein.

[0014] Although the embodiments disclosed herein are described in connection with an EPS system located in the lower / front section of a vehicle, an EPS system located elsewhere on the vehicle, such as at the rear steering system, can also benefit from the disclosed embodiments. Furthermore, the anti-rotation device disclosed herein can be used in any system based on a substantially cylindrical component that is translationally driven and that requires or would benefit from rotation limitation.

[0015] With reference to Fig.Figure 2 shows a section of a rack housing 50 with the sealing sleeve removed to illustrate a section of the linear translation component 40. The rack housing 50 contains at least one section of the linear translation component 40. The rack housing 50 includes a cover 54, which can be repeatedly removed to access an interior area of ​​the rack housing 50. The cover may be made of plastic in some embodiments.

[0016] The linear translation component 40 extends longitudinally about an axis A in a direction referred to herein as the axial direction. One end of the linear translation component 40 is functionally coupled to one or more components that connect the linear translation component 40 to the vehicle's road wheels. For example, tie rods and other components can be used in the conventional manner. This connection allows axial movement of the linear translation component 40 to adjust the road wheels in a manner required for the execution of steering maneuvers.

[0017] To prevent rotation of the linear translation component during operation, an anti-rotation arrangement 60 is included. The anti-rotation arrangement 60 is provided to counteract the forces exerted by the actuating component 34, such as a ball screw nut. The anti-rotation arrangement 60 includes an anti-rotation bearing 62 and a backlash compensation bearing arrangement 64. The anti-rotation arrangement 60 is located at least partially within the rack housing 50, such as in a compartment covered by the cover 54. The bearing 62 can be a standard bearing that has been machined or otherwise modified to provide the features disclosed herein. Alternatively, the bearing 62 can be a custom-made bearing.Regardless of the process by which the bearing 62 is manufactured, the bearing 62 includes an inner raceway 68, an outer raceway 70 and a plurality of balls arranged between the inner raceway 68 and the outer raceway 70.

[0018] The outer race 70 sits in a groove 74 defined in the linear translation component 40. The groove 74 extends longitudinally in the same direction as the longitudinal axis A of the linear translation component 40 to allow axial movement of the linear translation component 40 relative to the outer race 70 of the bearing 62, while the outer race 70 remains in the groove 74.

[0019] The groove 74 is defined by a curved groove surface 76. The outer race 70 of the bearing 62 is shaped to maximize contact with a radius of the curved groove surface 76. In other words, when installed in the groove 74, the outer race 70 exhibits curvature both axially and circumferentially. While the radius of curvature of the curved groove surface 76 and the outer race 70 is not identical in some embodiments, the curvature of each component is similarly adapted to enable the bearing 62 to prevent rotation of the linear translation component 40. During operation, the linear translation component 40 (e.g., the ball screw) is driven by the torque of the actuating component (e.g., the actuator).The ball screw nut is preloaded for rotation, whereby the curved outer race 70 in the groove 74 acts on the curved groove surface 76 and thus prevents rotation of the linear translation component 40. The inner race 68 is in contact with a component, such as a flange screw 82, which is threaded or otherwise attached to a flange 84 extending from the rack housing 50. The contact between the inner race 68 and the flange screw 82 secures the bearing 62 to surrounding structures.

[0020] The backlash-compensating bearing arrangement 64 includes a rack bearing 90 with a curved inner surface that contacts the outer surface of the linear translation component 40 to radially preload the linear translation component 40 into a desired position in a backlash-compensating manner. The force exerted by the rack bearing 90 is adjustable by any suitable arrangement, including a spring 92 and an adjusting plug 94. In the illustrated embodiment, the backlash-compensating bearing arrangement 64 and the anti-rotation arrangement 60 are arranged at axial locations on the linear translation component 40 that overlap each other. Furthermore, in some embodiments, the backlash-compensating bearing arrangement 64 and the anti-rotation arrangement 60 are arranged on opposite sides of the linear translation component 40 (e.g., spaced 180 degrees apart).

[0021] The embodiments disclosed herein enable a reduction in the installation space required for EPS systems by removing several components, including a pinion, an upper and lower pinion bearing, a lower rotor, and rack teeth in the case of a REPS system. In addition, the rotation protection arrangement 60 disclosed herein reduces the costs and complexity associated with the manufacture and assembly of the overall system, particularly when used in conjunction with the backlash compensation bearing arrangement 64. This arrangement is also coupled with a suitable wear component to meet NVH and friction requirements.

[0022] Although the invention has been described in detail in connection with only a limited number of embodiments, it should be readily apparent that the invention is not limited to the disclosed embodiments. Rather, the invention can be modified to include any number of variations, changes, substitutions, or equivalent arrangements not described herein, but which correspond to the basic concept and scope of protection of the invention. Even though various embodiments of the invention have been described, it is understood that aspects of the invention may only include some of the described embodiments. Accordingly, the invention is not to be considered as limited by the foregoing description. 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] US 63 / 636,951

[0001]

Claims

A steer-by-wire system for a vehicle, comprising: a rack movable in an axial direction and defining a groove extending in the axial direction of the rack; a housing surrounding at least a portion of the rack; an anti-rotation device disposed proximate an outer surface of the rack at the mounting location of the rack and within the housing, the anti-rotation device comprising a bearing seated in the groove of the rack; and a lash adjuster bearing assembly in contact with the rack for radially biasing the rack to a desired position. The steer-by-wire system of claim 1, wherein the lash adjuster bearing assembly comprises:a rack bearing having a curved inner surface contacting an outer surface of the rack to radially bias the rack;a spring in contact with the rack bearing; andan adjustment plug in contact with the rack bearing to adjust the force with which the rack bearing radially biases the rack. The steer-by-wire system of claim 2, wherein the rack is a ball screw, and the steer-by-wire system further comprises a ball nut threadedly coupled to the ball screw, rotation of the ball nut causing translation of the ball screw. Steer-by-wire system according to claim 2, wherein an outer surface of the bearing is disposed within the groove to prevent rotation of the rack. Steer-by-wire system according to claim 2, wherein the groove of the rack is defined by a curved groove surface. Steer-by-wire system according to claim 5, wherein the outer surface of the bearing has a curvature in both an axial direction of the groove and a circumferential direction of the groove. Steer-by-wire system according to claim 6, wherein the curvature of the outer surface of the bearing in the circumferential direction of the groove corresponds to the curvature of the curved groove surface. Steer-by-wire system according to claim 2, wherein the bearing extends through an opening of the rack housing. Steer-by-wire system according to claim 2 , wherein the bearing of the anti-rotation device and the rack bearing of the lash adjuster bearing assembly contact the rack at an axially overlapping location of the rack. Steer-by-wire system according to claim 2 , wherein the bearing of the anti-rotation device and the rack bearing of the lash adjuster bearing assembly are located on opposite sides of the rack. An anti-rotation assembly comprising:a linear translation component movable in an axial direction, the linear translation component defining an axial groove defined by a curved groove surface;a bearing in contact with the linear translation component to prevent rotation of the linear translation component, the bearing assembly comprising:an inner race; andan outer race having an outer surface disposed within the axial groove defined within the linear translation component to prevent rotation of the linear translation component, the outer race having a curvature in both an axial direction of the groove and a circumferential direction of the groove;anda lash adjuster bearing assembly comprising:a lash adjuster bearing having a curved inner surface contacting an outer surface of the linear translation component to radially preload the linear translation component;a spring in contact with the lash adjuster bearing; andan adjustment plug in contact with the lash adjuster bearing to adjust the force with which the lash adjuster bearing radially preloads the linear translation component.; The anti-rotation assembly of claim 11, wherein the groove of the linear translation component is defined by a curved groove surface. The anti-rotation assembly of claim 12, wherein the outer surface of the bearing has a curvature in both an axial direction of the groove and a circumferential direction of the groove. The anti-rotation assembly of claim 13, wherein the curvature of the outer surface of the bearing in the circumferential direction of the groove corresponds to the curvature of the curved groove surface. The anti-rotation assembly of claim 11, further comprising a housing for receiving at least a portion of the linear translation component, wherein the bearing extends through an opening of the housing. Anti-rotation assembly according to claim 15, wherein the opening is covered with a cover made of one of plastic and metal. Anti-rotation assembly according to claim 11, wherein the bearing of the anti-rotation device and the rack bearing of the lash adjuster bearing assembly contact the rack at an axially overlapping location of the rack. Anti-rotation assembly according to claim 11, wherein the bearing of the anti-rotation device and the rack bearing of the lash adjuster bearing assembly are located on opposite sides of the rack.

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