Anti-rotation mechanism for ball screw of steer-by-wire road wheel actuator

Abstract

A steer-by-wire steering system for a vehicle includes a rack that is movable in an axial direction. The steer-by-wire steering system also includes an anti-rotation device disposed proximate an outer surface of the rack. The anti-rotation apparatus includes a yoke having a bearing journal extending therefrom. The anti-rotation device also includes a bearing disposed on the bearing journal. The anti-rotation device also includes a travel surface disposed within the rack housing and extending in a longitudinal direction of the rack, where the bearing is positioned to move along the travel surface during operation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 417,232 filed on October 18, 2022, U.S. Provisional Patent Application Serial No. 63 / 429,465 filed on December 1, 2022, U.S. Provisional Patent Application Serial No. 63 / 451,417 filed on March 10, 2023, and U.S. Patent Application Serial No. 18 / 458,217 filed on August 30, 2023, which claims priority to U.S. Provisional Patent Application Serial No. 63 / 402,325 filed on August 30, 2022, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] The subject matter disclosed herein relates to electric power steering (EPS) systems, and more particularly to road wheel actuator anti-rotation mechanisms for such EPS systems (electric power steering (EPS) systems). Background Art

[0004] Various electric power steering (EPS) systems have been developed to assist the operator in steering a vehicle. One type of EPS system is known as a rack electric power steering (REPS) system. Some examples of steer-by-wire (SbW) road wheel actuators (RWA) are simple rack electric power steering systems based on ball screws without an input shaft. In this configuration, the pinion shaft still engages the rack teeth cut into the rack bar of the ball screw. This gear meshing provides two main functions. First, the pinion is a convenient rotating member for ball screw position sensing. Second, the pinion serves as an anti-rotation feature to prevent rotation of the ball screw. If the steer-by-wire road wheel actuator is designed for a large vehicle, it may be necessary to use two ball nuts on the same ball screw to achieve the required output force. Since the center of the ball loop in each ball nut defines the axis of the ball screw, adding a rack and pinion meshing to this type of system will result in an over-constraint condition. Over-constraint is undesirable because it will result in friction changes if the parts are misaligned. Summary of the invention

[0005] According to one aspect of the present disclosure, a steer-by-wire steering system for a vehicle includes a rack that is capable of moving in an axial direction. The steer-by-wire steering system also includes an anti-rotation device that is disposed proximate an outer surface of the rack. The anti-rotation device includes a yoke having a bearing journal extending therefrom. The anti-rotation device also includes a bearing that is disposed on the bearing journal. The anti-rotation device also includes a travel surface that is disposed within the rack housing and extends in a longitudinal direction of the rack, wherein the bearing is positioned to move along the travel surface during operation.

[0006] According to another aspect of the present disclosure, a steering system for a vehicle includes a rack that is movable in an axial direction. The steering system also includes an anti-rotation device that is disposed around an outer surface of the rack. The anti-rotation device includes a yoke having a bearing journal extending therefrom. The anti-rotation device also includes a first bearing disposed on the bearing journal. The anti-rotation device also includes a second bearing disposed on the bearing journal. The anti-rotation device also includes a travel surface that is located in the rack housing, the travel surface extending in the longitudinal direction of the rack, the travel surface having a first side and a second side opposite to the first side, wherein the first bearing is positioned to contact the first side of the travel surface during operation and move along the first side, and the second bearing is positioned to contact the second side of the travel surface during operation and move along the second side.

[0007] According to another aspect of the present disclosure, a steering system for a vehicle includes a rack that is movable in an axial direction. The steering system also includes an anti-rotation device that is arranged around the outer surface of the rack. The anti-rotation device includes a yoke that has a bearing journal extending therefrom. The anti-rotation device also includes a first bearing that is arranged on the bearing journal. The anti-rotation device also includes a second bearing that is arranged on the bearing journal. The anti-rotation device also includes a pair of running plates that include a first plate and a second plate that are at least partially arranged in a rack housing, the running plate extending in the longitudinal direction of the rack, and the running plate arranged on opposite sides of the first bearing and the second bearing, wherein the first bearing is positioned to contact the first plate and move along the first plate during operation, and the second bearing is positioned to contact the second plate and move along the second plate during operation.

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

[0009] The subject matter regarded as the present invention is particularly pointed out and expressly claimed in the claims at the beginning of this specification. The foregoing and other features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 A steering assembly having a rack and pinion electric power steering system is illustrated;

[0011] Figure 2 A dual motor embodiment of a rack electric power steering system is schematically illustrated;

[0012] Figure 3 is a perspective view of an anti-rotation mechanism for a rack electric power steering system disposed within a housing;

[0013] Figure 4 is a perspective view of the anti-rotation mechanism;

[0014] Figure 5 is a first perspective view of a portion of an anti-rotation mechanism;

[0015] Figure 6 is a second perspective view of a portion of the anti-rotation mechanism;

[0016] Figure 7 is a perspective view of a ball screw having a mounting structure for a yoke of an anti-rotation mechanism;

[0017] Figure 8 is a perspective view of the yoke of the anti-rotation mechanism.

[0018] Fig. 9 is a side elevation view of the anti-rotation mechanism;

[0019] Fig.10 It is a top view of the anti-rotation mechanism;

[0020] Figures 11 to 22 An anti-rotation mechanism according to another embodiment is illustrated;

[0021] Figure 23 to Figure 27 An anti-rotation mechanism according to another embodiment is illustrated;

[0022] Figure 28 to Figure 33 An anti-rotation mechanism according to yet another embodiment is illustrated;

[0023] Fig.34 is a perspective view of a W-shaped wear plate; and

[0024] Fig.35 is a perspective view of an L-shaped wear plate. DETAILED DESCRIPTION

[0025] Referring now to the accompanying drawings, the embodiments described herein are used in conjunction with a steering assembly of a vehicle, such as a car, truck, sport utility vehicle, crossover, minivan, boat, aircraft, all-terrain vehicle, RV, or other suitable vehicle. As discussed herein, an electric power steering (EPS) system (e.g., including a steer-by-wire system) includes an anti-rotation mechanism in which a pinion is not used in the steering system. The anti-rotation mechanism prevents rotation of a ball screw, lead screw, rack, etc. Such rotation is caused by thread loading of one or more ball nuts or lead nuts.

[0026] As used herein, the terms screw, ball screw, and rack define a longitudinal member that is translated when another member (such as, for example, a ball nut) is rotated. It should be understood that the components may be used in various embodiments of the present disclosure and are not limited to other components that may be converted to perform steering maneuvers.

[0027] First reference Figure 1 , schematically illustrating an automated steering system 20 in general. The automated steering system 20 may be configured as a driver interface steering system, an automated driving system, or a system that allows both driver interface and automated steering. The steering system 20 may include an input device 22 (such as a steering wheel), wherein a driver may mechanically provide steering input by turning the steering wheel. A steering column 26 extends from the input device 22 to an output assembly 28 along an axis. The steering column 26 may include two or more axially adjustable portions and / or rake adjustable portions, such as a first portion 30 and a second portion 32 that are axially adjustable relative to each other. However, in some embodiments, only a single portion may be present. The embodiments disclosed herein are for a steering system in which the output assembly 28 is in operative communication with an actuator 34 that is coupled to a rack having a helical screw / linear rack configuration (such as a ball screw rack 1). The output assembly 28 is in operative communication with the actuator 34, such as a wired communication 36 (e.g., a steer-by-wire configuration). In some embodiments, translation of rack 1 adjusts road wheels 47 to perform steering maneuvers.

[0028] like Figure 2 As illustrated in , by way of example and not limitation, the rack 1 translates with at least one actuator and possibly two or more actuators 34. Each actuator 34 comprises a motor 21 and a ball nut 31 configured to drive the rack 1 to translate along the rack axis A1. The rack 1 is at least partially surrounded radially by a housing marked H. The anti-rotation mechanism 10 is disposed within a bore of the housing H and is described herein.

[0029] Reference now Figure 3, a rack 1 and an anti-rotation mechanism 10 for the rack 1 are shown disposed within a housing H. As disclosed herein, the anti-rotation mechanism 10 prevents rotation of the rack 1 during operation.

[0030] The anti-rotation mechanism 10 Figure 3 is illustrated in the hole 6 defined by the housing H, and the housing H is Figure 4 1 is removed to better illustrate various aspects of the anti-rotation mechanism 10. Figure 3 and Figure 4 , the anti-rotation mechanism 10 has a yoke 14 surrounding the rack 1, wherein the bearing 7 is attached to the yoke 14. The bearing 7 is positioned between the running plate structures 5. The running plate structures 5 are disposed within the hole 6 of the housing H and are adjacent to the wall defining the hole 6.

[0031] The yoke 14 defines a yoke hole having a yoke hole surface 15. In some embodiments, the yoke hole surface 15 is smooth. In other embodiments, the yoke hole surface 15 is textured (e.g., having knurling) to increase friction at the interface with the rack 1. The yoke 14 includes a breakout 16 to allow sufficient deflection to clamp the yoke 14 to the outer surface of the rack 1, such as Figure 5 and Figure 6 The yoke 14 is positioned between the two ball nuts 31 along the rack 1. In some embodiments, the yoke 14 is located at a central axial position of the rack 1, such as approximately at the midpoint of the rack 1 along the axial direction of the rack 1. The yoke 14 is positioned on the rack 1 by a clamping bolt 8 or any other suitable fastening mechanism to provide a clamping force sufficient to properly hold the yoke 14 to the rack 1.

[0032] like Figure 7 and Figure 8 As shown in , the rack 1 may have one or more recessed areas 40 to receive the yoke 14. The (one or more) recessed areas 40 may be any suitable geometry configured to receive the yoke 14 in a desired position. For example, a machined flat surface may be provided on each side of the rack 1. The yoke 14 includes a pair of holes 90 that align with holes 92 defined by the rack 1 to allow the clamping bolts 8 to clamp the yoke 14 to the rack 1. The connection of the yoke 14 to the rack 1 ensures that the yoke 14 translates together with the rack 1 in the axial direction of the rack 1. The connection between the yoke 14 and the rack 1 also prevents the yoke 14 from rotating relative to the rack 1.

[0033] Reference now Figure 3 and Figure 4As described above, the running plate structure 5 is positioned in the housing hole 6. As shown, the running plate structure 5 is a single integrally formed component. In the illustrated embodiment, the running plate structure 5 is a substantially U-shaped component having an end section 60, a first plate section 62, and a second plate section 64. In the illustrated embodiment, the first plate section 62 and the second plate section 64 are substantially parallel to each other and substantially perpendicular to the end section 60. Each plate section 62, 64 has an inner running plate surface, specifically a first inner running plate surface 68 for the first plate section 62 and a second inner running plate surface 70 for the second plate section 64. The running plate structure 5 is fixed in the housing hole 6 and adjacent to the housing H in any suitable manner. Although shown and described as a single component formed in a generally U-shape, it should be understood that in other embodiments, two separate components can be positioned relative to each other in the same manner as the first plate section 62 and the second plate section 64.

[0034] The bearing 7 attached to the yoke 14 is positioned between the first plate section 62 and the second plate section 64. The bearing 7 is configured to react against the running plate structure 5 during operation. The bearing 7 is pressed onto a journal 67 on the yoke 14 by a retaining ring or the like (not shown) positioned in a retaining ring groove 9 beside the bearing 7. In some embodiments, a retaining ring is not required, and the pressing load associated with pressing the bearing 7 onto the journal 67 is sufficient to retain the bearing 7 to the yoke 14. The distance between the first inner running plate surface 68 and the second inner running plate surface 70 is slightly greater than the outer diameter of the bearing 7, so that the bearing 7 will only contact one side of the steel running surface 5 (i.e., one of the inner running plate surfaces 68, 70) at a time and thus roll against it. The outer ring of the bearing 7 has a curved profile (e.g., spherical) that results in a point contact on one of the inner running plate surfaces 68, 70.

[0035] The biasing member 11 works in combination with the slider 80 to apply torque to the yoke 14. The biasing member 11 is positioned within a groove 82 defined by an axially extending portion 84 of the yoke 14. The biasing member 11 can be any type of resilient member capable of maintaining the slider 80 in a desired position, to which the end of the biasing member 11 is operably coupled, such as Figure 5 and Figure 6. In operation, when there is little or no torque on the rack 1 from the ball nut 31, the torque from the biasing member 11 forces the bearing 7 to remain in contact with one side of the running board structure 5 (i.e., one of the inner movable board surfaces 68, 70). When a large torque is applied to the rack 1 by the ball nut 31, the preload from the biasing member 11 is overcome, and the bearing 7 will rotate with the yoke 14 until it contacts the other side of the running board structure 5 (i.e., the other of the inner running board surfaces 68, 70). The biasing member 11 and the slider 80 are intended to prevent noise from being generated when road forces or driver input cause the torque on the rack 1 to reverse. The groove 82 on the yoke 14 at least partially guides the biasing member 11, and the retaining hole 12 positions the biasing member 11 by securing the end of the biasing member 11 therein.

[0036] In some embodiments, the slider 80 is formed of a material having a coefficient of friction that is lower than the coefficient of friction of the running board structure 5. As a non-limiting example, the slider 80 may be formed of plastic, but other materials are also contemplated. This allows the slider 80, and therefore the bearing 7 and yoke 14, to move along the running board structure 5 with little to no significant resistance.

[0037] The vertical walls of the inner running plate surfaces 68, 70 allow the yoke 14, and therefore the rack 1, to float radially in the direction of the axis of the bearing 7. The curved profile of the outer surface of the bearing 7 allows the rack 1 to shift side to side without generating side loads on the rack 1 due to such shifting. The disclosed embodiment allows the reaction forces between the bearing 7 and the running plate structure 5 to counteract any torque applied to the rack 1 by the ball nut 31, while not overconstraining the position of the rack 1.

[0038] The embodiments disclosed herein provide several structural features and benefits, including but not limited to: 1) a yoke and bearing mechanism that is clamped to the surface of the ball screw via a clamping bolt; 2) the torque applied to the ball screw by the ball nut is transmitted to the yoke via friction; 3) a reaction force is generated at the outer surface of the bearing against the travel surface, which reacts to the ball screw torque; 4) when the ball screw torque is low, the biasing member and the plastic slider force the bearing to travel against one side of the travel surface and prevent reverse noise; 5) the vertical wall of the travel surface allows the ball screw to move along the axis of the bearing without resistance; 6) the spherical profile of the outer ring of the bearing that travels on the flat travel surface allows the ball screw to move left and right without generating side loads on the ball screw; and 7) a mechanism prevents over-constraint of the ball screw axis.

[0039] Reference now Figures 11 to 22, an anti-rotation mechanism 101 according to another embodiment is shown. The anti-rotation mechanism 101 includes a rack, hereinafter referred to as a ball screw 104, which can be accommodated between at least one and shown as two actuators 149 (as an example and not limitation), wherein each actuator 149 includes a motor 102 and a ball nut 103. A running surface 105a is positioned in a housing bore 106 so that an anti-rotation member, shown as a bearing 107 of the anti-rotation mechanism 101, reacts against the running surface 105a. The running surface 105a can be made of any suitable material, such as steel, as an example and not limitation. Depending on the application, the bearing 107 can be provided as any desired type of bearing, including a roller bearing 107. The bearing 107 can be pressed onto a journal on the yoke 114, wherein a retaining ring (not shown) is positioned adjacent to the bearing 107 in a retaining ring groove 109. The yoke 114 is centrally positioned on the ball screw 104 by a retainer, such as a clamping retainer, and is shown as a clamping bolt 108 providing a clamping force, by way of example and not limitation. The distance D between the opposing, generally parallel travel sides of the travel surface 105a is Fig.13 ) is slightly larger than the outer diameter of the outer ring (race) of the bearing 107 so that the bearing 107 will only contact one side of the running surface 105a at a time and roll against it, thereby avoiding the application of opposing forces to the bearing 107. The outer ring of the bearing 107 can be configured to have a spherical profile to make point contact on the running surface 105a. The biasing member 111 works in combination with a lubricated slider (such as a lubricated plastic slider 110, as an example and not limitation) to apply torque to the yoke 114. When there is little torque from the ball nut 103 on the ball screw 104, the torque from the biasing member 111 will force the bearing 107 to remain in contact with one side of the running surface 105a. When increased torque is applied to the ball screw 104 by the ball nut 103, the preload from the biasing member 111 will be overcome, and the bearing 107 will rotate with the yoke 114 until it contacts the opposite side of the running surface 105a.

[0040] The biasing member 111 and slider 110 are intended to prevent noise from being generated when road forces or driver inputs cause torque on the ball screw 104 to reverse. A groove 113 may be provided on the yoke 114 to help retain the biasing member 111, and a retaining hole 112 may be provided to fixedly position and retain the end of the biasing member 111. The yoke hole 115 configured for engagement with the rack 104 may be smooth or textured (e.g., with knurling) to increase friction at the interface with the ball screw 104. The split portion 116 in the yoke 114 allows sufficient deflection to be generated to clamp the yoke hole 115 into fixed engagement with the outer surface of the ball screw 104.

[0041] The generally U-shaped vertical walls (including the opposing, generally parallel walls forming the travel surface 105a) allow the yoke 114, and therefore the ball screw 104, to float radially in the direction of the axis of rotation of the bearing 107. The spherical profile of the outer race of the bearing 107 allows the ball screw 104 to shift side to side without generating side loads on the ball screw 104 due to the displacement along the axis of rotation of the bearing. This arrangement allows the reaction force between the bearing 107 and the travel surface 105a to counteract any torque applied to the ball screw 104 by the ball nut 103, while not over-constraining the position of the ball screw 104.

[0042] According to another embodiment of the present disclosure, instead of Figures 11 to 13 Instead of forming the running surface 105a as shown in FIG. Fig.16 and Fig.17 , wherein the travel surface 105b may be made of the same material as discussed above for the travel surface 105a and function similarly. The travel surface 105b is shown as having a generally planar top surface TS, wherein the opposite side surfaces S extend from the top surface TS in a generally parallel relationship to each other. The opposite side surfaces S extend generally laterally from the top surface TS. As an example and not limitation, the travel surface 105b may be configured to fit in an undersized housing groove, which provides a preload on the side surfaces S of the travel surface 105b and a preload force on the top surface TS of the travel surface 105b, thereby effectively removing the clearance of the travel surface 105b in the housing groove from the radial and vertical clearances.

[0043] The embodiments disclosed herein provide several structural features and benefits, including but not limited to: 1) a yoke and bearing mechanism that is clamped to the surface of the ball screw via a clamping bolt; 2) the torque applied to the ball screw by the ball nut is transmitted to the yoke via friction; 3) a reaction force is generated against the travel surface at the outer surface of the bearing, which reacts to the ball screw torque; 4) when the ball screw torque is low, the biasing member and the plastic slider force the bearing to travel against one side of the travel surface and prevent reverse noise; 5) the vertical wall of the travel surface allows the ball screw to move along the axis of the bearing without resistance; 6) the spherical profile of the outer ring of the bearing that travels on the flat travel surface allows the ball screw to move left and right without generating side loads on the ball screw; 7) the mechanism prevents over-constraint of the ball screw axis; 8) during certain bending conditions, the mechanism can help support the load from the ball screw; and 9) the alternative travel surface design 105b self-removes the gap between itself and the mating groove geometry.

[0044] Reference now Figure 23 to Figure 27, shows an anti-rotation mechanism 210 according to another embodiment. The anti-rotation mechanism 210, which does not cause an over-constraint condition to the rack 201, can be placed at the end of the ball screw 201, or in the central area of ​​the housing 202 as needed. The running surface 203 made of a bearing grade material (such as steel, as an example and not limitation) is positioned in the side cover 204 or the housing 202 so that the first bearing 205a and the second bearing 205b of the mechanism will react against it. The bearings 205a, 205b are pressed onto the journal J on the yoke 206 by a retaining method (retaining ring, stake calibration, interference fit, etc.), wherein a spacer 207 can be set between the bearings 205a, 205b. Therefore, the first bearing 205a and the second bearing 205b rotate around a common rotation axis A.

[0045] If desired, the bearings 205a, 205b and the spacer 207 may be integrated into a single piece. The yoke 206 has a through hole B defined by an inner clamping surface S, and the rack 201 extends through the through hole B, wherein the inner clamping surface S is in clamping engagement with the rack 201 to prevent relative movement between the yoke 206 and the rack 201. By way of example and not limitation, the yoke 206 is centrally positioned on the rack 201, wherein the clamping bolt 208 provides sufficient clamping force to prevent relative movement between the yoke 206 and the rack 201. The through hole B may be textured (e.g., knurled) to increase friction between the rack 201 and the yoke 206. The distance D between the relative sides 203a, 203b of the running surface 203 is slightly larger than the OD of the outer races (also called outer rings) of the first bearing 205a and the second bearing 205b, wherein the relative sides 203a, 203b can be tilted (also called tapered) so that the relative sides 203a, 203b are not parallel to each other, so that each bearing 205a, 205b will only contact one side, wherein the bearing 205a contacts the side 203a and the bearing 205b contacts the side 203b, and therefore, each bearing 205a, 205b can roll against the corresponding side 203a, 203b of the running surface 203 respectively without contacting the relative sides 203b, 203a.

[0046] The outer rings of the bearings 205a, 205b may be configured to have a profile (spherical, curved, arched, etc.) that controls the contact point on the travel surface 203. The assembly forces the travel surface 203 to act as a spring and preloads the rack anti-rotation mechanism 210 to minimize any NVH issues. As noted, the yoke bore B may be smooth or textured (e.g., with knurling) to increase friction at the interface with the ball screw 201. The split portion S in the yoke 206 allows sufficient deflection to be generated to clamp on the outer surface of the ball screw 201. This arrangement allows the reaction force between the first and second bearings 205a, 205b and the travel surface 203 to offset any torque applied to the ball screw 201 by the ball nut 212 while minimizing constraints on the position of the ball screw 201. The running surface 203 will fit into an undersized groove in the side cover 204, which will provide a preload on the sides 203a, 203b of the running surface 203 and force a preload on the top surface 203c of the running surface 203, effectively removing the clearance of the running surface 203 in the housing groove from the radial and vertical clearances. The side cover 204 will be held to the housing 202 by screws 209 and will incorporate some kind of sealing joint (RTV, PIP seal, etc.). If additional compliance is desired, a pocket can be formed between the running surface 203 and the cover 204 to allow additional movement, or an additional spring element can be added in the pocket area to fine tune the desired system compliance.

[0047] Reference now Figure 28 to Figure 33 , shows an anti-rotation mechanism 310 according to another embodiment. Fig.28 and Fig.29, an anti-rotation mechanism 311 that does not cause an over-constraint condition to the ball screw 307 can be placed at the end of the ball screw 307, or in the central area of ​​the housing 313 as needed. The running plate 301 made of a bearing grade material (such as steel, as an example and not limitation) is positioned in the side cover 302 or the housing 313 so that the first bearing 305a and the second bearing 305b of the mechanism will react against it. The bearings 305a, 305b are pressed onto the journals on the yoke 304 by a retaining method (retaining ring, stake calibration, interference fit, etc.), wherein a spacer 306 can be set between the bearings 305a, 305b. Therefore, the first bearing 305a and the second bearing 305b rotate around a common axis of rotation. If desired, the bearings 305a, 305b and the spacer 306 can be integrated into a single piece. The yoke 304 has a through hole defined by an inner clamping surface, and the ball screw 307 extends through the through hole, wherein the inner clamping surface is in clamping fixed engagement with the ball screw 307 to prevent relative movement between the yoke 304 and the ball screw 307. By way of example and not limitation, the yoke 304 is centrally positioned on the ball screw 307, wherein the clamping bolt 308 provides sufficient clamping force to prevent relative movement between the yoke 304 and the ball screw 307. The through hole may be textured (e.g., knurled) to increase friction between the ball screw 307 and the yoke 304.

[0048] refer to Fig.30 and Fig.31, the running plate 301 can be divided into a pair of steel wear plates 301a, 301b fastened to the aluminum cover 302 by threaded fasteners 303. The steel wear plates 301a, 301b can be coupled to a pair of extensions or legs 302a, 302b of the side cover 302, wherein each of the pair of extensions 302a, 302b includes a different length to set the steel wear plates 301a, 301b at different positions. Specifically, the steel wear plates 301a, 301b can be set at a separation height, wherein one of the plates 301a contacts one of the bearings 305a, and the other of the plates 301b contacts the other of the bearings 305b, thereby applying force or preload to the bearings 305a, 305b in opposite directions. The wear plates 301a, 301b can be substantially L-shaped and extend obliquely to the pair of extensions 302a, 302b to contact the bearings 305. For example, the distance D between the opposite sides 301a, 301b of the running plate 301 is slightly larger than the OD of the outer races (also called outer rings) of the first bearing 305a and the second bearing 305b, wherein the opposite sides 301a, 301b may be tilted (also called tapered) so that the opposite sides 301a, 301b are not parallel to each other, so that each bearing 305a, 305b will contact only one side, wherein the bearing 305a contacts the side 301a and the bearing 305b contacts the side 301b, and therefore, each bearing 305a, 305b can roll against the corresponding side 301a, 301b of the running plate 301, respectively, without contacting the opposite sides 301b, 301a.

[0049] The outer rings of the bearings 305a, 305b can be configured to have a profile (spherical, curved, arched, etc.) that controls the contact point on the running plate 301. The assembly forces the running plate 301 to act as a spring and preloads the rack anti-rotation mechanism 311 to minimize any NVH issues. As noted, the yoke bore can be smooth or textured (e.g., with knurling) to increase friction at the interface with the ball screw 307. The split portion in the yoke 304 allows sufficient deflection to be generated to clamp on the outer surface of the ball screw 307. This arrangement allows the reaction force between the first bearing 305a and the second bearing 305b and the running plate 301 to offset any torque applied to the ball screw 307 by the ball nut 312, while minimizing constraints on the position of the ball screw 307.

[0050] The running plate 301 will fit into an undersized groove in the side cover 302, which will provide a preload on the wear plates 301a, 301b of the running plate 301 and force a preload on the top surface of the running plate 301, effectively removing the clearance of the running plate 301 in the housing groove from the radial and vertical clearances. The side cover 302 will be held to the housing 313 by screws and will incorporate some kind of sealing joint (RTV, PIP seal, etc.). If additional compliance is required, a pocket can be formed between the running plate 303 and the cover 302 to allow additional movement, or an additional spring element can be added in the pocket area to fine tune the desired system compliance.

[0051] refer to Fig.34 , depicts another embodiment of a running plate 301. The alternative running plate 301 includes a W-shaped wear plate 301a, 301b, wherein the central arch 309 of the wear plate 301a, 303b contacts the bearing 305, and the knees 309a on the opposite sides of the central arch 309 bear against the legs 310 of the side cover 302. The two contact points of the W-shaped running plate 301 achieved by the knees 309a of the wear plate 301 prevent deflection of the running plate 301 by contact with the bearing 305. Alternatively, as Fig.35 As shown in , an embodiment of an L-shaped running plate 301 may wear through contact with a bearing 305 to deflect toward a leg 310 of a side cover 302 .

[0052] The embodiments disclosed herein provide several structural features and benefits, including but not limited to: two steel wear plates 301 are fastened to an aluminum cover 302 by a plurality of threaded fasteners 303; a yoke 304 holds two bearings 305 spaced apart by spacers 306; the yoke 304 is clamped to a ball screw 307 by clamping bolts 308; the bearings 305 are standard deep groove Conrad type with a cylindrical outer surface. style) ball bearing; several possible shapes for the wear plate 301 are considered; L-shaped wear plate 301 is the preferred embodiment due to the resulting spring rate and required material thickness; W-shaped wear plate 309 is also suggested for situations where a higher spring rate is required; both embodiments are arranged so that when the unit is assembled, the wear plate will be deflected and provide a preload against the bearing 305; for both designs, the legs 310 of the cover supporting the wear plate can be parallel, which minimizes the manufacturing cost of the cover 302; the cover 302 and the wear plate are designed so that when one wear plate is compressed flat against the cover, the other wear plate will still have a preload on the opposing bearing; such design considerations are critical to the quiet operation of the steering mechanism; the initial deflection of the wear plate is designed to achieve a target preload and effective spring rate; the exact size and thickness of the wear plate and the number of fasteners can be varied to accommodate the required preload and spring rate for a given application.

[0053] Although the present invention has been described in detail in conjunction with only a limited number of embodiments, it should be readily understood that the present invention is not limited to these disclosed embodiments. On the contrary, the present invention may be modified to include any number of changes, modifications, permutations, or equivalent arrangements not previously described but commensurate with the spirit and scope of the present invention. In addition, although various embodiments of the present invention have been described, it should be understood that aspects of the present invention may include only some of the described embodiments. Therefore, the present invention should not be considered to be limited by the foregoing description.

Claims

1. A steer-by-wire steering system for a vehicle, comprising: a rack movable in an axial direction; as well as An anti-rotation device, the anti-rotation device is arranged close to the outer surface of the rack, the anti-rotation device comprises: a yoke having a bearing journal extending therefrom; a bearing disposed on the bearing journal; and A running surface is disposed within the rack housing and extends in a longitudinal direction of the rack, wherein the bearing is positioned to move along the running surface during operation. 2 . The steer-by-wire steering system of claim 1 , further comprising a biasing member that contacts the yoke and slider member during operation to apply torque to the yoke.

3. A steering system for a vehicle, comprising: a rack movable in an axial direction; An anti-rotation device, the anti-rotation device is arranged around the outer surface of the rack, the anti-rotation device comprises: a yoke having a bearing journal extending therefrom; a first bearing, the first bearing being disposed on the bearing journal; a second bearing disposed on the bearing journal; and A running surface is located in the rack housing, the running surface extending in the longitudinal direction of the rack, the running surface having a first side and a second side opposite to the first side, wherein the first bearing is positioned to contact the first side of the running surface and move along the first side during operation, and the second bearing is positioned to contact the second side of the running surface and move along the second side during operation. 4 . The steering system of claim 3 , wherein the first bearing does not contact the second side of the running surface.

5. The steering system of claim 3, wherein the second bearing does not contact the first side of the running surface.

6. The steering system of claim 3, wherein the first bearing and the second bearing rotate about a common axis of rotation.

7. The steering system of claim 3 wherein the yoke has a through hole defined by an inner clamping surface and the rack extends through the through hole such that the inner clamping surface is in clamping engagement with the rack to prevent relative movement between the yoke and the rack.

8. The steering system of claim 7, wherein the through hole is textured to increase friction between the rack and the yoke.

9. The steering system of claim 3, wherein the steering system is a steer-by-wire steering system.

10. A steering system for a vehicle, comprising: a rack movable in an axial direction; An anti-rotation device, the anti-rotation device is arranged around the outer surface of the rack, the anti-rotation device comprises: a yoke having a bearing journal extending therefrom; a first bearing, the first bearing being disposed on the bearing journal; a second bearing disposed on the bearing journal; and A pair of running plates, the pair of running plates including a first plate and a second plate at least partially disposed within the rack housing, the running plates extending in the longitudinal direction of the rack, the running plates being disposed on opposite sides of the first bearing and the second bearing, wherein the first bearing is positioned to contact the first plate and move along the first plate during operation, and the second bearing is positioned to contact the second plate and move along the second plate during operation.

11. The steering system of claim 10, wherein the first bearing does not contact the second plate.

12. The steering system of claim 10, wherein the second bearing does not contact the first plate.

13. The steering system of claim 10, wherein the first bearing and the second bearing rotate about a common axis of rotation.

14. The steering system of claim 10 wherein the yoke has a through hole defined by an inner clamping surface and the rack extends through the through hole such that the inner clamping surface is in clamping engagement with the rack to prevent relative movement between the yoke and the rack.

15. The steering system of claim 14, wherein the through hole is textured to increase friction between the rack and the yoke.

16. The steering system of claim 10, wherein the steering system is a steer-by-wire steering system.

17. The steering system of claim 10, wherein each plate is W-shaped.

18. The steering system of claim 10, wherein each plate is L-shaped.

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