Vehicle steering device

Abstract

This vehicle steering device comprises: a rotating member having a male thread portion and a first cylindrical surface portion; a nut that moves in an X direction with respect to the rotating member in a non-rotating state; a first annular member inserted into the first cylindrical surface portion and movable in the X direction; a wave washer which abuts against the first annular member, thereby being able to elastically deform in the X direction; and a housing. The housing has: a holding portion that holds the elastic member; and a nut abutment portion which can abut against the nut when the nut moves and transmits, to the rotating member, a reaction force toward an X1 side that is generated when the nut abuts.

Description

Vehicle steering device

[0001] The present disclosure relates to a vehicle steering system.

[0002] In a steer-by-wire vehicle steering device, the steering wheel and the steered wheels are mechanically disconnected. In this configuration, the steering reaction force is not transmitted from the steering mechanism including the steered wheels to the steering wheel. For this reason, a steering reaction force device and a stopper mechanism are provided on the steering shaft connected to the steering wheel.

[0003] The steering reaction force device applies a reaction force to the steering wheel in the opposite direction to the rotational direction (steering direction) of the steering wheel, giving the driver a natural steering feel. The steering reaction force device includes, for example, a motor and a speed reduction mechanism, and the steering reaction force generated by the motor is transmitted to the steering shaft via the speed reduction mechanism. The speed reduction mechanism includes, for example, a worm shaft and a worm wheel, and the rotation of the motor is transmitted to the worm wheel via the worm shaft as the shaft teeth of the worm shaft mesh with the wheel teeth of the worm wheel.

[0004] The steering wheel is connected to a steering shaft. The stopper mechanism communicates the limit range of the steering angle of the steered wheels to the driver. The stopper mechanism includes, for example, a rotating member connected to the steering shaft, a nut attached to the rotating member and linearly moving in the axial direction relative to the rotating member, and a stopper portion that prevents the nut from linearly moving. When the linearly moving nut abuts against the stopper portion, the rotation of the rotating member stops, and as a result, rotation (steering) of the steering wheel is also prevented via the steering shaft. In this way, the rotation angle of the steering wheel is limited.

[0005] Here, immediately after the linearly moving nut abuts on the stopper, the motor of the steering reaction force device does not immediately stop rotating but continues to rotate for a short time due to inertia. This applies force to the meshing portion between the worm shaft and the worm wheel in the reduction mechanism, which may cause damage to the meshing portion. In Patent Document 1, to prevent such damage, the stopper against which the nut abuts is made of an elastic material.

[0006] German Patent No. 102020126785

[0007] However, in Patent Document 1, elastic members are arranged on both sides of the rotating member in the axial direction, which makes the stopper mechanism longer in the axial direction, and ultimately may result in the vehicle steering device becoming larger.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a vehicle steering device that is more compact.

[0009] In order to achieve the above object, one aspect of the present invention provides a vehicle steering device in which steered wheels and a steering wheel are mechanically disconnected, and the vehicle steering device includes a stopper mechanism that restricts the range of rotation angle of the steering wheel when the steering wheel is rotated, the stopper mechanism including a rotating member that has a male threaded portion having a male thread on its outer periphery, and a first cylindrical surface portion that is adjacent to one side of the male threaded portion in the axial direction of a central axis, extends along the circumferential direction around the central axis, and has a cylindrical surface with a diameter smaller than the outer diameter of the male threaded portion, and that rotates in the circumferential direction in response to the rotation of the steering wheel, and a nut that is arranged on the outer periphery of the rotating member, and has a female thread that engages with the male threaded portion on its inner periphery, and that, in a non-rotating state, prevents the rotation of the rotating member from rotating. The rotary member includes a nut that moves axially relative to the rotary member upon rotation; a first annular member that is inserted into the first cylindrical surface portion of the rotary member and that abuts against the nut or the male thread portion and is movable axially; an elastic member that is arranged adjacent to one axial side of the first annular member and abuts against the first annular member and is elastically deformable in the axial direction; and a housing that is arranged on the outer periphery of the rotary member, the nut, the first annular member, and the elastic member, wherein the housing has a holding portion that holds the elastic member, and a nut abutment portion that is arranged opposite the other axial side of the nut, is abuttable against the nut when the nut moves, and transmits a reaction force toward one side in the axial direction that is generated when the nut abuts to the rotary member.

[0010] In a steer-by-wire steering system, a steering reaction force device is provided on a steering shaft connected to the steering wheel to apply a steering reaction force to the steering wheel in a direction opposite to the steering direction of the steering wheel. A stopper mechanism is also provided to notify the driver of the limit range of the steering angle of the steered wheels. The stopper mechanism is provided to prevent the steering wheel from rotating beyond a certain angle, for example, to notify the driver of the end stop position or to prevent an airbag harness connected to the steering wheel from breaking due to excessive rotation. The stopper mechanism includes, for example, a rotating member connected to the steering shaft, a nut attached to the rotating member and linearly moving axially relative to the rotating member, and a stopper portion that prevents the nut from linearly moving. When the linearly moving nut abuts on the stopper portion, rotation of the rotating member stops, and therefore rotation (steering) of the steering wheel is also prevented via the steering shaft.

[0011] Immediately after the linearly moving nut abuts on the stopper portion, the motor of the steering reaction force device continues to rotate for a short time due to inertia, which may apply force to the meshing portion between the worm shaft and the worm wheel in the reduction mechanism, resulting in possible damage. Therefore, as described above, in Patent Document 1, the stopper portion against which the nut abuts is made of an elastic member in order to prevent damage to the meshing portion. Specifically, because elastic members are disposed on both sides of the rotating member in the axial direction, the stopper mechanism becomes longer in the axial direction, which may result in an increase in the size of the vehicle steering device.

[0012] In this disclosure, only one elastic member is used. That is, an elastic member is provided on one axial side of the nut, and no elastic member is provided on the other axial side of the nut, resulting in fewer elastic members than in Patent Document 1. This shortens the axial distance of the stopper mechanism, thereby enabling the vehicle steering device to be made more compact. Below, we will briefly explain why the stopper mechanism functions effectively even when only one elastic member is used.

[0013] First, in a first mode, when the nut moves linearly in one axial direction, the nut compresses the elastic member in the axial direction via the first annular member, causing the elastic member to elastically deform.

[0014] In a second mode, when the nut moves linearly in the other axial direction, the nut abuts on the nut abutment portion, generating a reaction force from the nut abutment portion toward one axial direction. This reaction force is transmitted to the male thread, causing the rotating member to move toward one axial direction. The first annular member then compresses the elastic member in the axial direction, elastically deforming the elastic member.

[0015] In this way, in both the first mode in which the nut moves linearly to one side in the axial direction and the second mode in which the nut moves linearly to the other side in the axial direction, the one elastic member is elastically deformed to absorb the impact when the first annular member or the nut abutment portion and the nut come into contact with each other. As described above, in the present disclosure, the number of elastic members is smaller than in Patent Document 1, so that the axial distance of the stopper mechanism is shorter, and therefore the vehicle steering device can be made smaller.

[0016] In a preferred embodiment, the rotating member has a second cylindrical surface portion adjacent to the other axial side of the male threaded portion, extending circumferentially, and having a cylindrical surface with a diameter smaller than the outer diameter of the male threaded portion, and the nut abutment portion is a second annular member inserted into the second cylindrical surface portion.

[0017] In the second embodiment, when the nut moves linearly in the other axial direction, the nut abuts against the second annular member, generating a reaction force from the second annular member toward one axial direction. This reaction force is transmitted to the male thread, and the rotating member 31 moves toward one axial direction. In this way, the second annular member functions properly as a nut abutment. Furthermore, if the second annular member is damaged, its function as a nut abutment can be easily restored by replacing it with a new one.

[0018] In a preferred embodiment, the elastic member has an annular shape extending circumferentially, the rotating member has a cylindrical shape extending circumferentially, the retaining portion of the housing is provided with an annular through hole that penetrates in the axial direction and extends circumferentially, the inner diameter of the elastic member is equal to or greater than the inner diameter of the rotating member, and the inner diameter of the through hole of the retaining portion is equal to or greater than the inner diameter of the elastic member.

[0019] Therefore, a part such as a shaft extending in the axial direction can be fitted onto the inner periphery of the rotating member by passing through the through hole and the inner periphery of the elastic member.

[0020] In a preferred embodiment, the first annular member and the first cylindrical surface portion are capable of relative movement in the axial direction, and the second annular member and the second cylindrical surface portion are capable of relative movement in the axial direction.

[0021] In the first aspect, the nut moves linearly in one axial direction, pushing the first annular member to move it to one axial direction and compressing the elastic member. In the second aspect, the nut moves linearly in the other axial direction, pushing the second annular member to move it to the other axial direction. This allows the first and second annular members to move smoothly, making it easy to compress the elastic member.

[0022] In a preferred embodiment, the male thread of the rotating member and the second annular member can come into contact with each other. In the second embodiment, the reaction force is transmitted to the male thread, and the rotating member is directed toward one side in the axial direction. Therefore, by allowing the male thread and the second annular member to come into contact with each other, the elastic deformation of the elastic member becomes smoother.

[0023] In a preferred embodiment, the holding portion of the housing has a flat surface extending along the radial direction, and an axial gap is provided between the flat surface and the first annular member. In the first embodiment described above, the nut moves linearly in one axial direction, pushing the first annular member to move it in one axial direction and compress the elastic member. Therefore, by providing an axial gap between the flat surface and the first annular member, the first annular member can move smoothly, making it easy to compress the elastic member.

[0024] In a preferred embodiment, the elastic member has an annular shape extending in the circumferential direction, and a radially extending disk portion is provided at one axial end of the holding portion of the housing, and the holding portion holds the elastic member by abutting against the disk portion. This makes it possible to hold the elastic member more stably, thereby making compression of the elastic member smoother.

[0025] In a preferred embodiment, at least one of the first annular member and the second annular member has a protruding portion that protrudes axially toward the nut and is capable of coming into contact with the nut.

[0026] This reduces the axial movement distance of the nut relative to the first annular member and the second annular member, which do not have protrusions, thereby reducing the limit range of the steering angle of the steered wheels and allowing the steering wheel to be rotated at a smaller angle.

[0027] In a preferred embodiment, the first annular member includes a main body and a coating layer provided on a surface layer of the main body, and the elastic modulus of the coating layer is smaller than the elastic modulus of the main body.

[0028] This makes it possible to reduce contact noise (interference noise) when the nut hits the first annular member.

[0029] According to the present disclosure, it is possible to provide a more compact vehicle steering device.

[0030] FIG. 1 is a schematic diagram showing the overall configuration of a vehicle steering device according to a first embodiment. FIG. 2 is a cross-sectional view showing a portion of FIG. 1. FIG. 3 is a cross-sectional view showing a portion of FIG. 2. FIG. 4 is an enlarged cross-sectional view of a portion of FIG. 3. FIG. 5 is an enlarged cross-sectional view of a portion of FIG. 4. FIG. 6 is an exploded perspective view of a stopper mechanism according to the first embodiment. FIG. 7 is a perspective view of the wave washer of FIG. 6. FIG. 8 is a cross-sectional view of the stopper mechanism when the nut is positioned at one end in the axial direction. FIG. 9 is a cross-sectional view of the stopper mechanism when the nut is positioned at the other end in the axial direction. FIG. 10 is a cross-sectional view of a stopper mechanism according to a first modified example. FIG. 11 is a cross-sectional view of a stopper mechanism according to a second modified example. FIG. 12 is a cross-sectional view of a stopper mechanism according to a second embodiment. FIG. 13 is a cross-sectional view of a stopper mechanism according to a third embodiment. FIG. 14 is a cross-sectional view of a stopper mechanism according to a fourth embodiment. FIG. 15 is an enlarged cross-sectional view of the first annular member shown in FIG. 14.

[0031] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially identical. Furthermore, the components described below can be combined as appropriate. Furthermore, parts with the same structure are given the same reference numerals and their description will be omitted. In the coordinate system, the X direction indicates the axial direction of the rotating member, the X1 side is one side of the axial direction, and the X2 side is the other side of the axial direction.

[0032] [First embodiment] A first embodiment will be described below. Fig. 1 is a schematic diagram showing the overall configuration of a vehicle steering device of the first embodiment. Fig. 2 is a cross-sectional view showing a part of Fig. 1. Fig. 3 is a cross-sectional view showing a part of Fig. 2.

[0033] As shown in FIG. 1 , the vehicle steering device 100 includes a steering unit 4 , a control device (ECU) 14 , and a steering unit 20 .

[0034] As shown in FIGS. 1 to 3 , the steering unit 4 is provided with a steering reaction force device 13. When the steering wheel 10 is steered, the steering reaction force device 13 applies a steering reaction force to the steering wheel 10 in a direction opposite to the steering direction of the steering wheel 10. The control device (ECU) 14 calculates a reaction torque corresponding to the vehicle's driving state based on operation information, adjusts the power value supplied to the motor 110 of the steering reaction force device 13 based on the reaction torque, and operates the motor 110 according to the power value, thereby transmitting the steering reaction force of the steering wheel 10 to the operator. The control device (ECU) 14 also calculates a current command value based on the operation information and controls the current supplied to the steering motor 21 of the steering unit 20. In the steering unit 20, the steered wheels 22 are steered via various gears connected to the steering motor 21. Each component of the vehicle steering device 100 will be described in detail below. In the steer-by-wire vehicle steering device 100, the steering wheel 10 and the steered wheels 22 are mechanically disconnected from each other. However, in the present invention, "disconnected" also includes a mode in which the steering wheel 10 and the steered wheels 22 can be connected by a clutch device or the like in an emergency, for example.

[0035] As shown in FIG. 1 , the steering unit 4 includes a steering wheel 10 , a steering shaft 11 , a steering housing 12 , and a steering reaction force device 13 .

[0036] 2 and 3 , the steering shaft 11 extends in the X direction (axial direction). The steering wheel 10 is rotatably connected to the steering shaft 11. The steering shaft 11 is housed inside a steering housing 12. The steering shaft 11 has a column shaft 15, an output shaft 16, and a torsion bar 17.

[0037] The column shaft 15 and the output shaft 16 are connected via a torsion bar 17. Specifically, an insertion hole is provided in the X1 side end of the column shaft 15 in the axial direction, and the torsion bar 17 is inserted into this insertion hole. The column shaft 15 and the torsion bar 17 are connected to each other via a pin 122 so as not to rotate relative to each other. A through hole that passes through the output shaft 16 in the axial direction is provided, and the X1 side end of the torsion bar 17 is fitted into this through hole. In this way, the output shaft 16 and the torsion bar 17 are connected to each other so as not to rotate relative to each other. As described above, when the steering wheel 10 is rotated, the steering shaft 11 is connected and rotates.

[0038] The steering housing 12 also includes a shaft holding member 121 , rotation support members 123 and 124 , and a sub-housing 127 .

[0039] A rotation support member 123 is located on the X1 side of the shaft holding member 121, and a rotation support member 124 is located on the X1 side of the rotation support member 123. A sub-housing 127 is located on the X1 side of the rotation support member 124. A bearing 125 is provided radially inside the rotation support member 124, and a bearing 126 is provided radially inside the sub-housing 127. The output shaft 16 is rotatably supported via the bearings 125 and 126. In addition, a torque sensor 128 is provided between the rotation support member 123 and the rotation support member 124. The torque sensor 128 detects the rotational torque transmitted between the column shaft 15 and the output shaft 16.

[0040] Here, the steering reaction force device 13 has a steering shaft 11 , a worm wheel 18 , a worm shaft 19 , and a motor 110 .

[0041] A worm wheel 18 is attached to the outer periphery of the output shaft 16 of the steering shaft 11. The worm wheel 18 has a core metal portion 18a and wheel teeth portion 18b. The wheel teeth portion 18b is provided on the outer periphery of the core metal portion 18a. A worm shaft 19 and a motor 110 are located on the Y2 side (see FIG. 6) of the worm wheel 18. The worm shaft 19 is attached to the output shaft of the motor 110. The worm shaft 19 has shaft teeth portion 19a. The shaft teeth portion 19a mesh with the wheel teeth portion 18b.

[0042] The motor 110 generates a steering reaction force. That is, the output of the motor 110 becomes a reaction torque, and the reaction torque is transmitted from the steering shaft 11 to the steering wheel 10 via the worm wheel 18 and the worm shaft 19.

[0043] As shown in Figures 2 and 3, a stopper mechanism 3 is provided on the X1 side of the output shaft 16 of the steering shaft 11. The stopper mechanism 3 will be described in detail below. Figure 4 is an enlarged cross-sectional view of a portion of Figure 3. Figure 5 is an enlarged cross-sectional view of a portion of Figure 4. Figure 6 is an exploded perspective view of the stopper mechanism according to the first embodiment. Figure 7 is a perspective view of the wave washer of Figure 6.

[0044] As shown in Figures 2 and 3, the rotating member 31 has a central axis AX, and the axial direction of the central axis AX coincides with the X direction. The rotating member 31 included in the stopper mechanism 3 is spline-fitted to the X1-side end of the output shaft 16 of the steering shaft 11. That is, a female spline 319 extending in the X direction is provided on the inner periphery of the rotating member 31, and a male spline extending in the X direction is provided on the outer periphery of the X1-side end of the output shaft 16. The male spline of the output shaft 16 is fitted into the female spline 319 of the rotating member 31. As a result, the rotating member 31 is movable in the X direction relative to the output shaft 16 but is unable to rotate in the circumferential direction around the central axis AX. That is, the rotating member 31 rotates integrally with the output shaft 16.

[0045] As shown in FIG. 4 , the stopper mechanism 3 includes a rotating member 31 , a nut 32 , a first annular member 331 , an elastic member 34 , and a housing 35 .

[0046] The rotating member 31 has a central axis AX. The axial direction of the central axis AX is the X direction. The direction around the central axis AX is the circumferential direction. The direction perpendicular to the central axis AX is the radial direction. The rotating member 31 includes a male thread portion 311, a first cylindrical surface portion 312, and a second cylindrical surface portion 312A.

[0047] The male thread portion 311 has a male thread 314 on its outer periphery. Of the male threads 314, a male thread 315 is located at the end closest to the X1 side, and a male thread 316 is located at the end closest to the X2 side. The first cylindrical surface portion 312 is adjacent to the male thread portion 311 on the X1 side. The first cylindrical surface portion 312 has a cylindrical surface 313. The cylindrical surface 313 extends circumferentially around the central axis AX. The diameter of the cylindrical surface 313 is smaller than the outer diameter of the male thread portion 311. In other words, the crest of the thread of the male thread 314 is located radially outward from the cylindrical surface 313. In other words, the radial position of the bottom portion 315a is substantially the same as the radial position of the cylindrical surface 313, and the male thread 315 protrudes radially outward from the bottom portion 315a.

[0048] The second cylindrical surface portion 312A is adjacent to the male thread portion 311 on the X2 side. The second cylindrical surface portion 312A has a cylindrical surface 313. The radial position of the bottom portion 316a is substantially the same as the radial position of the cylindrical surface 313, and the male thread 316 protrudes radially outward from the bottom portion 316a. The end of the rotating member 31 on the X1 side has an axial end face 317, and the end of the rotating member 31 on the X2 side has an axial end face 318.

[0049] The nut 32 is provided on the outer periphery of the rotating member 31. The nut 32 has an internal thread 321 on its internal circumference. The internal thread 321 meshes with the external thread 314 of the rotating member 31. The outer periphery 324 of the nut 32 is a cylindrical surface extending in the circumferential direction. The end of the nut 32 on the X1 side has an axial end face 322, and the end of the nut 32 on the X2 side has an axial end face 323.

[0050] The first annular member 331 has an annular shape extending in the circumferential direction. The first annular member 331 is inserted into the first cylindrical surface portion 312. The inner diameter of the first annular member 331 is larger than the outer diameter of the first cylindrical surface portion 312. Therefore, the first annular member 331 is movable in the X direction while inserted into the first cylindrical surface portion 312. The first annular member 331 has a vertical wall portion 332 and a tubular portion 333. The vertical wall portion 332 extends in the radial direction. The tubular portion 333 extends in the circumferential direction. The vertical wall portion 332 and the tubular portion 333 are connected via a corner portion 334. An axial end face 335 is provided at the end of the tubular portion 333 on the X1 side.

[0051] A wave washer 341, which is an example of the elastic member 34, is disposed adjacent to the first annular member 331 on the X1 side. The elastic member 34 is not limited to the wave washer 341, and various elastic members such as a disc spring can be used. The wave washer 341 overlaps the axial end face 335 when viewed from the X direction. The wave washer 341 abuts against the axial end face 335 and is elastically deformable in the X direction by abutting against the first annular member 331. The wave washer 341 and the axial end face 317 of the rotating member 31 are spaced apart in the X direction. That is, the wave washer 341 and the axial end face 317 of the rotating member 31 do not abut against each other.

[0052] 4 and 7 , wave washer 341 has an inner peripheral edge 345 on the radially inner side and an outer peripheral edge 344 on the radially outer side. Also, bent portions 342 and 343 are alternately arranged along the circumferential direction. Bent portion 342 is convex toward the X2 side, and bent portion 343 is convex toward the X1 side. Bent portion 342 abuts against axial end surface 335, and bent portion 342 abuts against disk portion 352g (described later).

[0053] 4 , the housing 35 is disposed on the outer circumferential side of the rotating member 31, the nut 32, the first annular member 331, and the wave washer 341. The housing 35 includes a first housing 351 and a second housing 352.

[0054] 4 and 6, the first housing 351 is disposed on the X2 side of the housing 35. The first housing 351 has a connecting portion 351a, a vertical wall portion 351b, a cylindrical portion 351c, and a flange 351d (see FIG. 6).

[0055] The coupling portion 351a fits into and is coupled to a coupled portion 352a of the second housing 352. The vertical wall portion 351b extends radially, and the cylindrical portion 351c extends circumferentially. As shown in FIG. 6 , the first housing 351 has flanges 351d that protrude toward the Y1 side and the Y2 side. A second bolt hole H2 is formed in the flange 351d. An internal thread is formed on the inner periphery of the second bolt hole H2, and the internal thread engages with the external thread of the bolt BL.

[0056] As shown in FIGS. 4 and 6, the second housing 352 has a cylindrical portion 352b, a protruding portion 352d, a disk portion 352g, a flange 352h, and a protruding portion 352i.

[0057] The cylindrical portion 352b extends in the circumferential direction. The disk portion 352g extends in the radial direction and seals the opening of the cylindrical portion 352b on the X1 side. The cylindrical portion 352b and the disk portion 352g are connected via a protrusion 352d. The protrusion 352d protrudes toward the inside of the second housing 352. Specifically, the protrusion 352d protrudes radially inward and toward the X2 side. The protrusion 352d has a flat surface 352e and a cylindrical surface 352f. The flat surface 352e is the axial end surface of the protrusion 352d on the X2 side, and the cylindrical surface 352f is the inner circumferential surface of the protrusion 352d.

[0058] As shown in Fig. 5, a gap G in the X direction is defined between the flat surface 352e and the vertical wall portion 332 of the first annular member 331. The size of the gap G is, for example, a distance that allows the wave washer 341 to deform in the axial direction. As shown in Fig. 4, the disk portion 352g and the protrusion 352d form the retaining portion 352c. That is, the X2 side of the disk portion 352g and the inner peripheral side of the protrusion 352d form the retaining portion 352c that retains the wave washer 341.

[0059] Furthermore, as shown in FIG. 6 , the second housing 352 has flanges 352h that protrude toward the Y1 side and the Y2 side. A first bolt hole H1 is provided in the flange 352h. A through hole is provided on the inner periphery of the first bolt hole H1, and the shank of the bolt BL passes through the through hole. A protrusion 325 that protrudes radially outward is provided on the outer circumferential surface 324 of the nut 32. The protrusion 325 extends in the X direction. The second housing 352 also has a protrusion 352i that protrudes radially outward. A groove 352j is provided on the inner periphery of the protrusion 352i. The protrusion 325 is fitted into the groove 352j. In this way, the protrusion 352i and the protrusion 325 prevent the nut 32 from rotating relative to the housing 35.

[0060] As shown in FIG. 4 , a second annular member 331A is inserted into the second cylindrical surface portion 312A. The second annular member 331A is an example of a nut abutment portion 350. The second annular member 331A has a vertical wall portion 332A and a tubular portion 333A. The vertical wall portion 332A extends radially. The vertical wall portion 332A is disposed facing the X2 side of the nut 32. The tubular portion 333A extends circumferentially. The vertical wall portion 332A and the tubular portion 333A are connected via a corner portion 334A. The second annular member 331A is constantly abutting against the male thread 316 of the rotating member 31. Specifically, a bottom portion 316a of the male thread 316 abuts against the corner portion 334A of the second annular member 331A. In other words, the second annular member 331A is sandwiched between the first housing 351 and the male thread 316 in the X direction. The second annular member 331A can abut against the axial end surface 323 of the nut 32 when the nut 32 moves toward the X2 side. Here, the second annular member 331A and the rotating member 31 are capable of relative movement in the axial direction (X direction). Therefore, when the nut 32 moves toward the X2 side and the axial end surface 323 compresses the vertical wall portion 332A of the second annular member 331A in the X direction, a reaction force is generated that returns the vertical wall portion 332A to its original position, and this reaction force is transmitted to the rotating member 31. As a result, the second annular member 331A pushes the rotating member 31 toward the X1 side.

[0061] Next, with reference to FIG. 6 , the assembly procedure for the stopper mechanism 3 will be briefly described. As shown in FIG. 6 , first, the rotating member 31 is fastened to the inner periphery of the nut 32, the first annular member 331 is inserted into the first cylindrical surface portion 312 of the rotating member 31, and the second annular member 331A is inserted into the second cylindrical surface portion 312A. Next, in this state, the rotating member 31, the nut 32, the first annular member 331, and the second annular member 331A are inserted into the inside of the second housing 352. At this time, the protrusion 325 is fitted into the groove 352j. Then, the first housing 351 is bolted to the second housing 352. Specifically, the flange 351d is butted against the flange 352h, and the second bolt hole H2 and the first bolt hole H1 are connected. Then, the bolt BL is passed through the first bolt hole H1 and engaged with the female thread of the second bolt hole H2, thereby completing the assembly of the stopper mechanism 3.

[0062] Next, a brief description will be given of the behavior of the stopper mechanism 3. Fig. 8 is a cross-sectional view of the stopper mechanism when the nut is positioned at one end in the axial direction. Fig. 9 is a cross-sectional view of the stopper mechanism when the nut is positioned at the other end in the axial direction.

[0063] (First embodiment) The nut 32 is non-rotatably supported by the housing 35. Therefore, as shown in FIG. 8 , when the rotating member 31 rotates, the nut 32 moves (linearly moves) toward the X1 side relative to the rotating member 31, as indicated by arrow D1. The axial end face 322 of the nut 32 abuts against the vertical wall portion 332 of the first annular member 331. As described with reference to FIG. 5 , there is a gap G in the X direction between the flat surface 352e and the vertical wall portion 332 of the first annular member 331. Therefore, the first annular member 331 moves toward the X1 side as indicated by arrow D2, and the axial end face 335 compresses the wave washer 341 in the X direction, elastically deforming the wave washer 341.

[0064] (Second Mode) As shown in FIG. 9 , when the rotating member 31 rotates in the opposite direction to the first mode, the nut 32 moves (linearly moves) toward the X2 side relative to the rotating member 31, as indicated by arrow D11. Therefore, the axial end surface 323 of the nut 32 abuts against the vertical wall portion 332A of the second annular member 331A. Because the second annular member 331A is supported by the first housing 351 in the X direction, a reaction force is generated from the second annular member 331A toward the X1 side. This reaction force is transmitted to the male thread 316, and the rotating member 31 moves toward the X1 side, as indicated by arrow D12. Because the rotating member 31 has a male thread 315, the male thread 315 also moves toward the X1 side, as indicated by arrow D13. The bottom portion 315a of the male thread 315 abuts against the corner portion 334 of the first annular member 331. 5, there is a gap G in the X direction between the flat surface 352e and the vertical wall portion 332. Therefore, the first annular member 331 moves toward the X1 side as shown by arrow D14. The axial end surface 335 compresses the wave washer 341 in the X direction, causing the wave washer 341 to elastically deform.

[0065] As described above, the vehicle steering device according to the first embodiment includes the rotating member 31 having the male thread portion 311 and the first cylindrical surface portion 312, the nut 32 that moves in the X direction relative to the rotating member 31 in a non-rotating state, the first annular member 331 that is inserted into the first cylindrical surface portion 312 and is movable in the X direction, the wave washer 341 (elastic member 34) that abuts against the first annular member 331 and is elastically deformable in the X direction, and the housing 35. The housing 35 includes a holding portion 352c that holds the elastic member 34, and a second annular member 331A (nut abutment portion 350) that can abut against the nut 32 when the nut 32 moves and that transmits a reaction force toward the X1 side that is generated when the nut 32 abuts against the second annular member 331A to the rotating member 31.

[0066] As described above, in this embodiment, only one wave washer 341 is provided as the elastic member 34. That is, the wave washer 341 is provided at the X1 side of the nut 32, and no wave washer 341 is provided at the X2 side of the nut 32. As a result, the number of elastic members 34 is smaller than in Patent Document 1, and the axial distance of the stopper mechanism 3 is shorter, which in turn makes it possible to reduce the size of the vehicle steering device 100. Below, it will be briefly explained that the stopper mechanism 3 can function effectively even when only one wave washer 341 is provided.

[0067] First, in the first mode, when the nut 32 moves linearly toward the X1 side, as shown in Figure 8, the axial end face 322 of the nut 32 compresses the wave washer 341 in the X direction via the first annular member 331, causing the wave washer 341 to elastically deform.

[0068] Next, in a second mode, when the nut 32 moves linearly toward the X2 side, as shown in FIG. 9 , the axial end surface 323 of the nut 32 abuts against the second annular member 331A (nut abutment portion 350). Because the second annular member 331A is supported by the first housing 351 in the X direction, a reaction force is generated from the second annular member 331A toward the X1 side. This reaction force is transmitted to the male thread 316, and the rotating member 31 moves toward the X1 side. Thereafter, the axial end surface 335 of the first annular member 331 compresses the wave washer 341 in the X direction, elastically deforming the wave washer 341 and thereby absorbing the impact.

[0069] In this way, in both the first mode in which the nut 32 moves linearly toward the X1 side and the second mode in which the nut 32 moves linearly toward the X2 side, one wave washer 341 is elastically deformed. As described above, in this embodiment, the number of wave washers 341 is smaller than in Patent Document 1, so the axial distance of the stopper mechanism 3 is shorter, and therefore the vehicle steering device 100 can be made smaller.

[0070] The rotating member 31 has a second cylindrical surface portion 312A. The nut abutment portion 350 is a second annular member 331A that is inserted into the second cylindrical surface portion 312A.

[0071] As described above, in the second mode, when the nut 32 moves linearly toward the X2 side, as shown in FIG. 9 , the nut 32 abuts against the second annular member 331A, generating a reaction force from the second annular member 331A toward the X1 side. This reaction force is transmitted to the male thread 316, and the rotating member 31 moves toward the X1 side. In this manner, the second annular member 331A functions properly as the nut abutment portion 350. Note that if the second annular member 331A is damaged, its function as the nut abutment portion 350 can be easily restored by replacing it with a new one. Furthermore, replaceable parts are not limited to the second annular member 331A; for example, the wave washer 341 and other parts can also be replaced.

[0072] [First Modification] The following describes the first modification: Fig. 10 is a cross-sectional view of the stopper mechanism according to the first modification.

[0073] In the first embodiment, the second annular member 331A is used as the nut abutment portion 350, but in the first modified example, the first housing 351A is used as the nut abutment portion 350. A brief description will be given below.

[0074] The stopper mechanism 3A according to the first modification does not include the second annular member 331A of the first embodiment. That is, a first housing 351A is used as the nut abutment portion 350. The first housing 351A serving as the nut abutment portion 350 is disposed on the X2 side of the housing 35. The first housing 351A has a connecting portion 351a, a vertical wall portion 351Ab, and a cylindrical portion 351Ac.

[0075] The coupling portion 351a is fitted into and coupled to the coupled portion 352a of the second housing 352. The vertical wall portion 351Ab extends radially, and the cylindrical portion 351Ac extends circumferentially. The cylindrical portion 351Ac abuts against the male thread 316. The coupling portion 351a, the vertical wall portion 351Ab, and the cylindrical portion 351Ac are integrally molded.

[0076] The behavior of the first modified example will be described below. The first aspect is the same as the behavior described in the first embodiment. The second behavior will be described. First, the axial end face 323 of the nut 32 abuts against the vertical wall portion 351Ab of the first housing 351A. This generates a reaction force from the vertical wall portion 351Ab toward the X1 side. This reaction force is transmitted to the male thread 316, and the rotating member 31 moves toward the X1 side. Since the male thread 315 also moves toward the X1 side, the first annular member 331 moves toward the X1 side. Then, the axial end face 335 compresses the wave washer 341 in the X direction, causing the wave washer 341 to elastically deform.

[0077] As described above, the vehicle steering device according to the first modified example includes the first housing 351A as an example of the nut abutment portion 350. The first housing 351A can abut against the nut 32 when the nut 32 moves, and transmits to the rotating member 31 the reaction force toward the X1 side that is generated when the nut 32 abuts against the first housing 351A.

[0078] As described above, when the nut 32 moves linearly toward the X2 side, the nut 32 abuts against the first housing 351A, and a reaction force is generated from the first housing 351A toward the X1 side. In this way, even when the first housing 351A is used as the nut abutment portion 350, the stopper mechanism 3A functions properly.

[0079] [Second Modification] A second modification will now be described. Fig. 11 is a cross-sectional view of a stopper mechanism according to the second modification.

[0080] A seal member S is provided in the stopper mechanism 3B according to the second modification. A brief description follows. As shown in FIG. 11 , the second housing 352B has a protrusion 352Bd at its end on the X1 side. A recess 354 is provided on the inner periphery of the protrusion 352Bd. The recess 354 extends annularly in the circumferential direction. In the cross section shown in FIG. 11 , the recess 354 has a generally trapezoidal shape whose distance in the X direction decreases as it moves radially outward. An annular seal member S is housed inside the recess 354. A through-hole 353 is provided in the disc portion 352Cg of the second housing 352B. The through-hole 353 has a circular shape extending in the circumferential direction around the central axis AX.

[0081] The first annular member 331B also has a vertical wall portion 332 and a tubular portion 333B. The tubular portion 333B of the first annular member 331B is different from that of the first annular member 331. Specifically, the distance in the X direction of the tubular portion 333B of the first annular member 331B is greater than the distance in the X direction of the tubular portion 333B of the first annular member 331. The tubular portion 333B seals the opening on the inner circumferential side of the recess 354. An inner circumferential tip end S10 of the seal member S abuts against the tubular portion 333B.

[0082] As described above, in the vehicle steering device according to the second modified example, the second housing 352B has the protrusion 352Bd in which the recess 354 is provided, and the annular seal member S is housed in the recess 354. The tip S10 on the inner circumferential side of the seal member S abuts against the tubular portion 333B. The through hole 353 is provided in the disc portion 352Cg of the second housing 352B.

[0083] There is a possibility that foreign matter such as dust may enter the inside of the second housing 352B through the through-hole 353. However, the tip S10 of the seal member S abuts against the first annular member 331B, making it possible to prevent the entry of such foreign matter. Furthermore, the seal member S can prevent oil inside the second housing 352B from leaking to the outside.

[0084] Second Embodiment A second embodiment will now be described with reference to Fig. 12, which is a cross-sectional view of a stopper mechanism according to the second embodiment.

[0085] In the stopper mechanism 3C according to the second embodiment, a through hole 353 is provided in a disk portion 352Cg of a second housing 352C. The through hole 353 has a circular shape extending in the circumferential direction around the central axis AX. The through hole 353 has an inner diameter DI1.

[0086] Additionally, an annular wave washer 341 is disposed on the X2 side of the disk portion 352Cg, and the wave washer 341 has an inner diameter DI2. Furthermore, as described above, the female spline 319 is provided on the inner circumference of the rotating member 31. The rotating member 31 has an inner diameter DI3. The inner diameter DI2 of the wave washer 341 is equal to or greater than the inner diameter DI3 of the rotating member 31, and the inner diameter DI1 of the through hole 353 is equal to or greater than the inner diameter DI2 of the wave washer 341.

[0087] As described above, in the vehicle steering device according to the second embodiment, the retaining portion 352c of the second housing 352C is provided with the annular through-hole 353. The inner diameter DI2 is equal to or greater than the inner diameter DI3, and the inner diameter DI1 is equal to or greater than the inner diameter DI2.

[0088] Therefore, a part such as a shaft extending in the axial direction can be fitted into the female spline 319 on the inner periphery of the rotating member 31 by passing through the through hole 353 and the inner periphery of the wave washer 341 .

[0089] Third Embodiment A third embodiment will now be described with reference to Fig. 13, which is a cross-sectional view of a stopper mechanism according to the third embodiment.

[0090] A stopper mechanism 3D according to the third embodiment differs from the stopper mechanism 3 according to the first embodiment in a first annular member 331C and a second annular member 331D.

[0091] The first annular member 331 according to the first embodiment has a vertical wall portion 332 and a cylindrical portion 333. In contrast, the first annular member 331C according to the third embodiment further has a protruding portion 336. That is, the first annular member 331C has the vertical wall portion 332, the cylindrical portion 333, and the protruding portion 336. The protruding portion 336 extends in the circumferential direction. The protruding portion 336 extends from the radially outer end of the vertical wall portion 332 toward the X2 side.

[0092] The second annular member 331D has a vertical wall portion 332A, a cylindrical portion 333A, and a protrusion 337. The protrusion 337 extends in the circumferential direction. The protrusion 337 extends from the radially outer end of the vertical wall portion 332A toward the X1 side.

[0093] As such, the first annular member 331C has a protruding portion 336 that protrudes toward the nut side in the X direction (axial direction) and can abut against the nut 32. The second annular member 331D has a protruding portion 337 that protrudes toward the nut side in the X direction (axial direction) and can abut against the nut 32.

[0094] As described above, in the vehicle steering device of the third embodiment, each of the first annular member 331C and the second annular member 331D has a protrusion 336 or a protrusion 337 that protrudes toward the nut side in the X direction and can abut against the nut 32.

[0095] Therefore, in the third embodiment, the distance that the nut 32 can move in the X direction is short compared to the first annular member 331 and the second annular member 331A that do not have the protrusion 336 or the protrusion 337 according to the first embodiment. This reduces the limit range of the steering angle of the steered wheels, and makes it possible to set the rotatable angle of the steering wheel 10 to a smaller value.

[0096] [Fourth embodiment] A fourth embodiment will be described below. Fig. 14 is a cross-sectional view of a stopper mechanism according to the fourth embodiment. Fig. 15 is an enlarged cross-sectional view of the first annular member shown in Fig. 14.

[0097] A stopper mechanism 3E according to the fourth embodiment differs from the stopper mechanism 3 according to the first embodiment in a first annular member 331E.

[0098] 14 and 15 , the first annular member 331E has a vertical wall portion 332 and a tubular portion 333. Each of the vertical wall portion 332 and the tubular portion 333 has a main body portion 338 and a coating layer 339.

[0099] The coating layer 339 is provided on the surface layer of the main body 338. The main body 338 is made of, for example, metal, and the coating layer 339 is made of, for example, resin. The main body 338 has an elastic modulus of, for example, 205 GPa. The coating layer 339 has an elastic modulus of, for example, 650 MPa. Thus, the elastic modulus of the coating layer 339 is smaller than that of the main body 338.

[0100] As described above, in the vehicle steering device according to the fourth embodiment, the first annular member 331E includes the main body 338 and the coating layer 339 provided on the surface layer of the main body 338. The elastic modulus of the coating layer 339 is smaller than the elastic modulus of the main body 338.

[0101] This makes it possible to reduce contact noise (interference noise) when the nut 32 contacts the first annular member 331E. Furthermore, the coating layer 339 reduces friction between the tubular portion 333 of the first annular member 331E and the second cylindrical surface portion 312A of the rotating member 31. This prevents the first annular member 331E from getting caught on the second cylindrical surface portion 312A when the nut 32 contacts the first annular member 331E. Furthermore, applying grease to the coating layer 339 can further reduce the contact noise (interference noise) and prevent the first annular member 331E from getting caught.

[0102] 3 Stopper mechanism 3A Stopper mechanism 3B Stopper mechanism 3C Stopper mechanism 3D Stopper mechanism 3E Stopper mechanism 4 Steering unit 10 Steering wheel 11 Steering shaft 12 Steering housing 13 Steering reaction force device 14 Control device (ECU) 15 Column shaft 16 Output shaft 17 Torsion bar 18 Worm wheel 18a Core metal portion 18b Wheel tooth portion 19 Worm shaft 19a Shaft tooth portion 20 Turning unit 21 Turning motor 22 Turned wheel 31 Rotating member 32 Nut 34 Elastic member 35 Housing 100 Vehicle steering device 110 Motor 121 Shaft holding member 122 Pin 123 Rotation support member 124 Rotation support member 125 Bearing 126 Bearing 127 Sub-housing 128 Torque sensor 311 Male thread portion 312 First cylindrical surface portion 312A Second cylindrical surface portion 313 Cylindrical surface 314 Male thread 315 Male thread 315a Bottom portion 316 Male thread 316a Bottom portion 317 Axial end face 318 Axial end face 319 Female spline 321 Female thread 322 Axial end face 323 Axial end face 324 Outer circumferential surface 325 Projection portion 331 First annular member 331A Second annular member (nut abutment portion) 331B First annular member 331C First annular member 331D Second annular member 331E First annular member 332 Vertical wall portion 332A Vertical wall portion 333 Cylinder portion 333A Cylinder portion 334 Corner portion 334A Corner portion 335 Axial end surface 336 Protruding portion 337 Protruding portion 338 Main body portion 339 Coating layer 341 Wave washer 342 Bent portion 343 Bent portion 344 Outer periphery 345 Inner periphery 350 Nut abutting portion 351 First housing 351a Joining portion 351b Vertical wall portion 351A First housing (nut abutting portion) 351Ab Vertical wall portion 351c Cylindrical portion 351d Flange 352 Second housing 352a Joined portion 352b Cylindrical portion 352c Holding portion 352d Projecting portion 352e Flat surface 352f Cylindrical surface 352g Disc portion 352h Flange 352i Protruding portion 352j Groove portion 352B Second housing 352Bd Protrusion portion 352C Second housing 352Cg Disk portion 353 Through hole354 Recess BL Bolt G Gap H1 First bolt hole H2 Second bolt hole S Sealing member S10 Tip

Claims

1. A steering device for a vehicle in which steerable wheels and a steering wheel are mechanically uncoupled, the steering device comprising: a stopper mechanism for restricting the range of a rotation angle of the steering wheel when the steering wheel is rotated, the stopper mechanism comprising: a rotating member having a male threaded portion having a male thread on its outer periphery, and a first cylindrical surface portion adjacent to one axial side of a central axis relative to the male threaded portion, extending in a circumferential direction around the central axis, and having a cylindrical surface with a diameter smaller than the outer diameter of the male threaded portion, the rotating member rotating in a circumferential direction in response to the rotation of the steering wheel; a nut disposed on the outer periphery of the rotating member, the nut having a female thread on its inner periphery which meshes with the male thread, the nut moving in the axial direction relative to the rotating member as the rotating member rotates in a non-rotating state; a first annular member inserted into the first cylindrical surface portion of the rotating member, and abutting against the nut or the male threaded portion to be movable in the axial direction; and an elastic member disposed adjacent to one axial side of the first annular member, abutting against the first annular member to be elastically deformable in the axial direction. a housing arranged on the outer circumferential side of the rotating member, the nut, the first annular member and the elastic member, wherein the housing has: a holding portion that holds the elastic member; and a nut abutment portion that is arranged facing the other axial side of the nut, is able to abut against the nut when the nut moves, and transmits a reaction force toward one side in the axial direction that is generated when the nut abuts, to the rotating member.

2. A vehicle steering device as described in claim 1, wherein the rotating member has a second cylindrical surface portion adjacent to the other axial side of the male threaded portion, extending circumferentially, and having a cylindrical surface with a diameter smaller than the outer diameter of the male threaded portion, and the nut abutment portion is a second annular member inserted into the second cylindrical surface portion.

3. A vehicle steering device as described in claim 1 or 2, wherein the elastic member has an annular shape extending in the circumferential direction, the rotating member has a cylindrical shape extending in the circumferential direction, the retaining portion of the housing is provided with an annular through hole that penetrates in the axial direction and extends in the circumferential direction, the inner diameter of the elastic member is equal to or greater than the inner diameter of the rotating member, and the inner diameter of the through hole in the retaining portion is equal to or greater than the inner diameter of the elastic member.

4. A vehicle steering device as described in claim 2, wherein the first annular member and the first cylindrical surface portion are capable of relative movement in the axial direction, and the second annular member and the second cylindrical surface portion are capable of relative movement in the axial direction.

5. The vehicle steering device according to claim 2, wherein the male thread of the rotating member and the second annular member are capable of abutting against each other.

6. A vehicle steering device as set forth in claim 1, wherein the retaining portion of the housing has a flat surface extending along a radial direction, and an axial gap is provided between the flat surface and the first annular member.

7. A vehicle steering device as claimed in claim 1 or 2, wherein the elastic member has an annular shape extending in the circumferential direction, and one axial end of the retaining portion of the housing is provided with a radially extending disk portion, and the retaining portion retains the elastic member by the elastic member abutting against the disk portion.

8. A vehicle steering device as set forth in claim 2, wherein at least one of the first annular member and the second annular member has a protruding portion that protrudes axially towards the nut and is capable of abutting against the nut.

9. A vehicle steering device as described in claim 1 or 2, wherein the first annular member comprises a main body and a coating layer provided on a surface layer of the main body, and the elastic modulus of the coating layer is smaller than the elastic modulus of the main body.

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