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

Abstract

The invention provides a steer-by-wire driving wheel actuator anti-rotation mechanism. 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 also includes an anti-rotation device disposed proximate an outer surface of the rack at a mounting location of the rack and disposed within the housing, the anti-rotation device including a bearing disposed within a groove of the rack. The system additionally includes an anti-backlash bearing assembly in contact with the rack to radially bias the rack to a desired position.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 636,951, filed April 22, 2024, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The disclosure of the present application relates to steering systems, and more particularly to a road wheel actuator anti-rotation mechanism for a steering system. BACKGROUND

[0004] Various electric power steering (EPS) systems have been developed for assisting an operator in steering a vehicle. One type of EPS system is referred to as a rack electric power steering (REPS) system, which utilizes an electric motor that drives a ball nut and a rack. Some examples of steer-by-wire (SbW) road wheel actuators (RWAs) are simple ball screw based rack electric power steering systems without an input shaft. In this configuration, the pinion shaft can still engage the rack teeth to act as an anti-rotation feature, thus avoiding unwanted rotation / twisting of the rack during translation.

[0005] During the development of steer-by-wire systems, OEMs can be interested in removing the pinion for better packaging and cost. In a steer-by-wire system for a vehicle, if a pinion is not used in the steering system, an anti-rotation device is needed to resist rotation of the ball screw formed by the loading of the ball nut threads. SUMMARY

[0006] According to one aspect of the present disclosure, 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 a mounting location of the rack and disposed within the housing, the anti-rotation device including a bearing seated within the groove of the rack. The system additionally includes a lash bearing assembly in contact with the rack to radially bias the rack to a desired position.

[0007] According to another aspect of the disclosure, an anti-rotation assembly includes a linear translation component movable in an axial direction, the linear translation component defining an axial groove defined by a curved groove surface. The anti-rotation assembly further includes a bearing in contact with the linear translation component to prevent rotation of the linear translation component. The bearing assembly includes an inner race. The bearing assembly further includes an 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, wherein the outer race has a curvature in both the axial direction of the groove and the circumferential direction of the groove. The anti-rotation assembly further includes an anti-backlash bearing assembly. The anti-backlash bearing assembly includes an anti-backlash bearing having a curved inner surface in contact with an outer surface of the linear translation component to radially bias the linear translation component. The anti-backlash bearing assembly further includes a spring in contact with the anti-backlash bearing. The anti-backlash bearing assembly further includes an adjuster plug in contact with the anti-backlash bearing to adjust a force of the anti-backlash bearing to radially bias the linear translation component.

[0008] These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0009] The sum of the claims particularly pointed out in the concluding portion of this specification are to be construed in connection with the embodiments described, but are to be considered as illustrative only, and not restrictive of the disclosure. The embodiments of the disclosure will be described with reference to the drawings in which:

[0010] Figure 1 A steer-by-wire steering assembly is shown; and

[0011] Figure 2 is a perspective view of an anti-rotation mechanism for a rack electric power steering system disposed within a housing. DETAILED DESCRIPTION

[0012] Reference will now be made to the drawings in which the various embodiments of present disclosure will be described. It should be understood that the embodiments are only examples of the disclosure and are not intended to limit the present disclosure in any way. It will be apparent to those skilled in the art that substantial variations can be practiced in form and detail without affecting the scope or essence of the present disclosure. Thus, the disclosed embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the disclosure to be indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein. It will be apparent to one of ordinary skill in the art that aspects of the application can be practiced without

[0013] Embodiments described herein are used in connection with a steering assembly of a vehicle, such as a car, truck, sport utility vehicle, crossover, van, watercraft, aircraft, all-terrain vehicle, recreational vehicle, or other suitable vehicle including various steering system schemes. As discussed herein, an electric power steering (EPS) system (e.g., including a steer-by-wire system) includes an anti-rotation device where a pinion gear is not used in the steering system. The anti-rotation device resists rotation of a linear translation component. For example, such rotation is caused by loading of an actuation component in contact with the linear translation component, such as a threaded connection of a ball screw.

[0014] Referring initially to Figure 1 , a power steering system 20 is generally shown. The power steering system 20 can be configured as a driver interface steering system, an autonomous driving system, or a system that allows both driver interface and autonomous steering. The steering system can include an input device 22, such as a steering wheel, where a driver can mechanically provide steering input by turning the steering wheel. A steering column 26 extends from the input device 22 along an axis to an output assembly 28. Embodiments disclosed herein are used in steering systems where the output assembly 28 is in operable communication with an actuator 34 coupled to a linear translation component 40 (e.g., steer-by-wire, autonomous system, etc.). The output assembly 28 has a wired electrical communication 36 with the actuator 34. The actuator 34 drives the linear translation component 40 to provide steering control of the vehicle.

[0015] The linear translation component 40 is any component having a generally cylindrical cross-section along at least a portion of its length and is driven in a substantially linear manner to effect adjustment of the vehicle running wheels 49. In some embodiments, the linear translation component 40 is a ball screw. In other embodiments, the linear translation component 40 is a lead screw. The foregoing examples are not limiting of the linear translation component 40.

[0016] In existing steer-by-wire steering systems, pinions are utilized on the outer surface of the linear translation member 40 (e.g., a "rack") to provide steering input control of the linear translation member 40. Such pinions also provide anti-rotation reaction forces on the linear translation member 40 to counteract the forces applied by the actuator 34 (such as a ball nut), for example. However, pinions and associated required components (e.g., pinion upper and lower bearings, rack bearings, adjuster plug, lower rotor, and rack teeth, etc.) can be undesirable in certain steering systems, for example, based on packaging requirements, cost, and manufacturing complexity. Embodiments of the anti-rotation device disclosed herein provide the anti-rotation benefits of the previously required pinions while eliminating many of the components described above. In steer-by-wire steering systems, the above-described steering input control of the linear translation member 40 utilizing pinions is not required, and such systems would benefit from the embodiments disclosed herein.

[0017] While the embodiments disclosed herein are described in connection with EPS systems located at the lower / front portion of a vehicle, EPS systems located at other locations of a vehicle (such as rear steering) can also benefit from the disclosed embodiments. Furthermore, the anti-rotation device disclosed herein can be used in any system that relies on a substantially cylindrical member that is driven in translation and that requires or would benefit from rotation limitation.

[0018] Referring to Figure 2 A portion of the rack housing 50 is shown with the boot removed to show a portion of the linear translation member 40. The rack housing 50 houses at least a portion of the linear translation member 40. The rack housing 50 includes a cover 54 that can be repeatedly removed to access the interior region of the rack housing 50. In some embodiments, the cover can be formed of plastic.

[0019] The linear translation member 40 extends longitudally about an axis A, which direction of extension is referred to herein as the axial direction. The ends of the linear translation member 40 are operably coupled to one or more components that connect the linear translation member 40 to the road wheels of the vehicle. Tie rods and other components can be used in a conventional manner, for example. This connection allows for axial movement of the linear translation member 40 to adjust the road wheels in a manner required to perform a steering maneuver.

[0020] A rotation prevention assembly 60 is included to prevent rotation of the linear translation member during operation. For example, the rotation prevention assembly 60 is arranged to counteract the forces applied by the actuation member 34, such as a ball nut. The rotation prevention assembly 60 includes an anti-rotation bearing 62 and an anti-backlash bearing assembly 64. The rotation prevention assembly 60 is at least partially disposed within the rack housing 50, such as within the compartment covered by the cover 54. The bearing 62 can be a standard bearing that is machined or otherwise modified to provide the features disclosed herein. Alternatively, the bearing 62 can be a specially manufactured bearing. Regardless of the process by which the bearing 62 is manufactured, the bearing 62 includes an inner race 68, an outer race 70, and a plurality of balls disposed between the inner race 68 and the outer race 70.

[0021] The outer race 70 is seated within a groove 74 defined in the linear translation member 40. The groove 74 extends longitudinally in the same direction as the longitudinal axis A of the linear translation member 40 to accommodate axial movement of the linear translation member 40 relative to the outer race 70 of the bearing 62 while allowing the outer race 70 to remain seated within the groove 74.

[0022] 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 the radius of the curved groove surface 76. In other words, the outer race 70 has a curvature in both the axial direction of the groove 74 and the circumferential direction of the groove 74 when installed within the groove 74. While in some embodiments the radius of curvature of each of the curved groove surface 76 and the outer race 70 are not identical, the curvature of each component is similarly matched to allow the bearing 62 to prevent rotation of the linear translation member 40. In operation, when the linear translation member 40 (e.g., a ball screw) is biased to rotate due to torque from the actuation member (e.g., a ball nut), the curved outer race 70 seated within the groove 74 acts on the curved groove surface 76 to prevent rotation of the linear translation member 40. The inner race 68 is in contact with a component such as a flange bolt 82 that is threaded or otherwise secured to a flange 84 extending from the rack housing 50. The contact between the inner race 68 and the flange bolt 82 secures the bearing 62 to the surrounding structure.

[0023] The anti-backlash bearing assembly 64 includes a rack bearing 90 having a curved inner surface that contacts an outer surface of the linear translation member 40 so as to radially bias the linear translation member 40 to a desired position in an anti-backlash manner. The force applied by the rack bearing 90 can be adjusted by any suitable assembly, including a spring 92 and an adjuster plug 94. In the illustrated embodiment, the anti-backlash bearing assembly 64 and the rotation prevention assembly 60 are located at axially overlapping positions of the linear translation member 40. Further, in some embodiments, the anti-backlash bearing assembly 64 and the rotation prevention assembly 60 are located on opposite sides of the linear translation member 40 (e.g., 180 degrees apart from one another).

[0024] The embodiments disclosed herein allow for a reduction in the packaging space required for an EPS system based on the removal of several components, including the pinion, pinion upper and lower bearings, lower rotor, and rack teeth in the case of a REPS system. Additionally, the use of the anti-rotation assembly 60 disclosed herein, particularly when used in conjunction with the anti-backlash bearing assembly 64, reduces the cost and complexity associated with the manufacture and assembly of the overall system. The anti-rotation assembly also couples with the mating wear components to meet NVH and friction requirements.

[0025] While the application has been described in detail herein in reference to only a limited number of embodiments, it should be understood that the application is not limited to these disclosed embodiments. Rather, references can be made to any variations and modifications to these embodiments that can become apparent to those skilled in the art after reading the foregoing description. Additionally, while a variety of embodiments of the present application have been described, it should be understood that aspects of the application can include only some of the described embodiments. Accordingly, the present application is not to be seen as limited by the foregoing description.

Claims

1. A by-wire steering 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 a mounting location of the rack and within the housing, the anti-rotation device comprising a bearing seated within the groove of the rack; and a lash compensation bearing assembly in contact with the rack to radially bias the rack to a desired position. the lash compensation bearing assembly comprising:

2. The steer-by-wire system of claim 1, wherein, a rack bearing having a curved inner surface that contacts an outer surface of the rack to radially bias the rack; a spring in contact with the rack bearing; and an adjuster plug in contact with the rack bearing to adjust a force with which the rack bearing radially biases the rack. the rack is a ball screw, the by-wire steering system further comprising a ball nut threadably coupled to the ball screw, wherein rotation of the ball nut actuates translation of the ball screw.

3. The steer-by-wire system of claim 2, wherein, an outer surface of the bearing is disposed within the groove to prevent rotation of the rack.

4. The steer-by-wire system of claim 2, wherein, the groove of the rack is defined by a curved groove surface.

5. The steer-by-wire system of claim 2, 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.

6. The steer-by-wire system of claim 5, wherein, the curvature of the outer surface of the bearing in the circumferential direction of the groove corresponds to a curvature of the curved groove surface.

7. The steer-by-wire system of claim 6, wherein, the bearing extends through an opening of a rack housing.

8. The steer-by-wire system of claim 2, wherein, the bearing of the anti-rotation device and the rack bearing of the lash compensation bearing assembly contact the rack at overlapping axial locations of the rack.

9. The steer-by-wire system of claim 2, wherein, the bearing of the anti-rotation device and the rack bearing of the lash compensation bearing assembly are located on opposite sides of the rack.

10. The steer-by-wire system of claim 2, wherein, 11. 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; and an 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, wherein outer race has a curvature in both an axial direction of the groove and a circumferential direction of the groove; and a lash compensation bearing assembly comprising: a lash compensation bearing having a curved inner surface that contacts an outer surface of the linear translation component to radially bias the linear translation component; a spring in contact with the lash compensation bearing; and an adjuster plug in contact with the lash compensation bearing to adjust a force with which the lash compensation bearing radially biases the linear translation component. the groove of the linear translation component is defined by a curved groove surface.

12. The anti-rotation assembly of claim 11, 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.

13. The anti-rotation assembly of claim 12, wherein, the curvature of the outer surface of the bearing in the circumferential direction of the groove corresponds to a curvature of the curved groove surface.

14. The anti-rotation assembly of claim 13, wherein, the bearing extends through an opening of the housing.

15. The anti-rotation assembly of claim 11, further comprising a housing for containing at least a portion of the linear translation component, wherein, ​ 16. The anti-rotation assembly of claim 15, wherein, The opening is covered with a cover formed of at least one of plastic and metal.

17. The anti-rotation assembly of claim 11, wherein, The bearing of the anti-rotation device and the rack bearing of the anti-backlash bearing assembly contact the rack at overlapping axial positions of the rack.

18. The anti-rotation assembly of claim 11, wherein, The bearing of the anti-rotation device and the rack bearing of the anti-backlash bearing assembly are located on opposite sides of the rack. The bearing of the anti-rotation device and the rack bearing of the anti-backlash bearing assembly are located on opposite sides of the rack.

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