JPH0580961U - Rear wheel steering system - Google Patents

Abstract

(57) [Summary] [Construction] The rotation of the input shaft 9 is converted into the movement of the rear wheel steering member 12 by the conversion mechanism to steer the rear wheels. The pressing members 76 and 77 are held by the cover member 72 that covers the reference surfaces 70 and 71 formed on the outer periphery of the input shaft 9. Compression coil springs 78 and 79 for pressing the pressing members 76 and 77 against the reference surfaces 70 and 71 are provided. By pressing the pressing members 76 and 77 against the reference surfaces 70 and 71, a force for returning the input shaft 9 to the straight steering position is generated. The rotation range of the input shaft 9 is within a range of ± 360 ° with respect to the straight-ahead steering position, and the pressing members 76 and 77 are at a position other than the position where the force for returning the input shaft 9 to the straight-ahead steering position is generated. , 71 is set so as not to be pressed. [Effect] The force for returning the input shaft to a position other than the straight steering position is not generated. A sufficient return force can be applied to the input shaft.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rear wheel steering system for a front and rear wheel steering vehicle, which reduces the force for returning a steering handle to a straight steering position.

[0002]

[Prior Art]

 In front and rear wheel steering vehicles, when returning both the front wheels and the rear wheels to the straight steering position, resistance acts on both the front wheels and the rear wheels from the contact surface, so compared to a normal vehicle that returns only the front wheels, A large amount of force is required to return the steering wheel to the straight traveling position.

Therefore, a reference surface is formed on the outer circumference of a handle shaft that connects the steering wheel and the front wheel steering device, and a pressing member is pressed against the reference surface by a spring to return the handle shaft to the straight steering position. A mechanism for generating force has been proposed (see Japanese Patent Application Laid-Open No. 62-181961).

Further, a torsion coil spring is wound around the outer peripheries of the connecting shafts of the front wheel steering device and the rear wheel steering device, one end of the torsion coil spring is fixed to the connecting shaft, and the other end is fixed to the vehicle body side. A mechanism for generating a force for returning to the straight steering position has been proposed (see Japanese Patent Laid-Open No. 181960/1987).

[0005]

[Problems to be solved by the device]

 Since the handle shaft that connects the steering wheel and the front wheel steering device generally rotates over ± 360 ° with respect to the straight steering position, it is pressed against the reference surface formed on the outer periphery of the handle shaft. When pressing, the pressing member is pressed against the reference surface even though the handle shaft is not in the straight steering position, and a force is generated to position the handle shaft at a position other than the straight steering position. Further, since the elastic force of the spring acts on the handle shaft only from one direction, the bearing supporting the handle shaft is unevenly worn.

When the connecting shaft that connects the front wheel steering device and the rear wheel steering device is returned to the straight steering position by the elastic force of the torsion coil spring, the displacement of the torsion coil spring becomes smaller as the connecting shaft approaches the straight steering position. , A sufficient restoring force cannot be generated near the linear steering position. Further, the spiral windings that form the torsion coil spring are rubbed against each other and are easily worn. Furthermore, the torsion coil spring is troublesome to fix, and even if it is fixed, it is easy to come off.

An object of the present invention is to provide a rear wheel steering system that can solve the above-mentioned problems of the conventional art.

[0008]

[Means for Solving the Problems]

 The first feature of the present invention is that the input shaft and a conversion mechanism that converts the rotation of the input shaft into the movement of the rear wheel steering member are provided, and the rear wheel is steered by the movement of the rear wheel steering member. In a rear wheel steering system for a front-rear wheel steering vehicle, a reference surface is formed on the outer periphery of the input shaft, a cover member is provided to cover the reference surface, and the pressing member is held by the cover member. A compression coil spring that can be pressed against is provided, and a force that returns the input shaft to the straight steering position is generated by pressing the pressing member against the reference surface, and the rotation range of the input shaft is ± 360 ° with reference to the straight steering position. It is set within the range of ° and within the range where the pressing member does not press the reference surface at a position other than the force that returns the input shaft to the straight steering position. That.

The feature of the second invention is that the input shaft and a conversion mechanism for converting the rotation of the input shaft into the movement of the rear wheel steering member are provided, and the rear wheel is driven by the movement of the rear wheel steering member. In the rear-wheel steering system for steering front and rear wheels of a vehicle, a pair of reference planes is formed on the outer periphery of the input shaft, and one reference plane is located apart from the other reference plane in the axial direction of the input shaft. A cover member that is located 180 ° apart in the circumferential direction and covers both reference surfaces is provided, and a pair of pressing members are held by this cover member, and one pressing member is pressed against one reference surface while the other is pressed. Is provided with a pair of compression coil springs that press the pressing member against the other reference surface.The pressing force of each pressing member against each reference surface generates a force to return the input shaft to the straight steering position, and the rotation of the input shaft. The circle indicates the range within ± 360 ° of the straight-ahead steering position, where each pressing member does not press the reference surface at a position other than the force that returns the input shaft to the straight-ahead steering position. Is set to.

[0010]

[Action]

 According to the configurations of the respective inventions, by pressing the pressing member against the reference surface formed on the input shaft of the rear wheel steering device by the compression coil spring, a force for returning the input shaft to the straight steering position is generated. The rotation range of the input shaft is less than 720 °, that is, within the range of ± 360 ° with reference to the straight-ahead steering position, and the pressing member presses the reference surface at a position other than the force that returns the input shaft to the straight-ahead steering position. The input shaft is not positioned at a position other than the straight-ahead steering position because the range is set so that it will not be lost. Further, since the pressing member is pressed against the reference surface by the elastic force of the compression coil spring, the input shaft can be returned to the straight-ahead steering position with a large force even in the vicinity of the straight-ahead steering position.

According to the configuration of the second aspect of the present invention, the reference surfaces formed on the outer periphery of the input shaft are located 180 ° apart in the circumferential direction, and the elastic force of the compression coil spring acts on each reference surface. , The elastic force acting on the input shaft is not biased. As a result, the bearing that supports the input shaft will not wear unevenly. In addition, since one reference surface is located away from the other reference surface in the axial direction of the input shaft, one pressing member should be pressed by the other pressing member when the input shaft rotates near 180 °. It does not push the surface and the input shaft is not positioned at a position other than the straight steering position.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows a schematic configuration of a front and rear wheel steering vehicle that controls the rear wheel steering angle in accordance with the front wheel steering angle. The left and right front wheels 1 are connected via a front wheel steering member 2, a tie rod 3, and a knuckle arm 14. A rack 4 is formed on the front wheel steering member 2, and a pinion 5 meshing with the rack 4 is connected to a steering handle 6 via a handle shaft 15. As a result, when the steering wheel 6 is operated, the front wheel steering member 2 moves left and right to steer the front wheels 1.

Further, a rack (not shown) is formed on the front wheel steering member 2 separately from the rack 4, and a connecting shaft 16 is connected to a pinion 7 that meshes with the rack. The input shaft 9 of the rear wheel steering device 8 is connected to the connecting shaft 16 via a coupling 17. The input shaft 9 is rotatable around the vehicle longitudinal axis. As a result, when the front wheel steering member 2 moves in the left-right direction by the steering operation input, the pinion 7 rotates, and the rotation of the pinion 7 causes the input shaft 9 to rotate by an amount corresponding to the front wheel steering angle. In this embodiment, the rotation range of the input shaft 9 is less than 360 °, that is, within a range of ± 180 ° with reference to the straight steering position.

The rear wheel steering device 8 includes a conversion mechanism 13 that converts the rotation of the input shaft 9 into a lateral movement of a rear wheel steering rack (rear wheel steering member) 12. The left and right rear wheels 10 are connected to each end of the rear wheel steering rack 12 via tie rods 11 and knuckle arms 18.

As shown in FIGS. 1 and 2, the conversion mechanism 13 includes a housing 32 that supports the input shaft 9 via a pair of bare rings 30 and 31. The housing 32 is configured by connecting a front member 32a and a rear member 32b with bolts 32c, and is fixed to a constituent member 33 of the vehicle body via a bracket 20. One bearing 31 that supports the input shaft 9 is attached to a block 32d screwed into the rear member 32b. A spline 19 is formed at the end of the input shaft 9 protruding from the block 32d, and the coupling 17 is connected via the spline 19.

Inside the housing 32, a screw shaft 34 is integrally formed on the outer periphery of the input shaft 9. In this embodiment, the screw shaft 34 is a ball screw. As shown in FIG. 2, the shaft center 34c of the screw shaft 34 is eccentric to the shaft center 9c of the input shaft 9 by an amount indicated by e in the figure.

A nut 35 is screwed onto the screw shaft 34. The nut 35 is a ball nut in this embodiment, and the ball 21 is interposed between the nut 35 and the screw shaft 34. A rack 36 is formed around the nut 35. The axial direction of the rack 36 is along the front-rear direction.

A pinion 37 that meshes with the rack 36 is provided. The axis of the pinion 37 extends along the vertical direction. The pinion 37 is supported by the housing 32 so as to be movable in the left and right directions. That is, the pinion 37 is rotatably supported by a pair of upper and lower arms (swing members) 38 and 39 via bearings 40 and 41. The arms 38 and 39 are rotatably supported by bearings 44 and 45 on vertical shafts 42 and 43 screwed into the housing 32. As a result, the arms 38, 39 swing about the axes of the support shafts 42, 43 as the center of rotation B 1, so that the pinion 37 moves in the left-right direction.

The pinion 37 and the rear wheel steering rack 12 mesh with each other. As a result, when the input shaft 9 rotates, the screw shaft 34 rotates, and the rotation of the screw shaft 34 moves the nut 35 in the front-rear direction. As the nut 35 moves back and forth, the rack 36 formed on the nut 35 moves back and forth. As the rack 36 moves back and forth, the pinion 37 meshing with the rack 36 rotates about the vertical axis as the rotation center A. The rotation of the pinion 37 moves the rear wheel steering rack 12 in the left-right direction.

Since the shaft center 9c of the input shaft 9 and the shaft center 34c of the screw shaft 34 are eccentric by e, the screw shaft 34 swings around the shaft center 9c of the input shaft 9 by the rotation of the input shaft 9. exercise. By the whirling of the screw shaft 34, the nut 35 moves in the vertical direction and the horizontal direction. The pinion 37 and the nut 35 are connected so that the rack 12 for steering the rear wheels is moved in the left-right direction by the left-right movement of the nut 35. That is, the roller 48 is rotatably supported by the pair of arms 38 and 39 via the bearing 49 with the vertical axis as the rotation center C. A nut 37 is arranged between the roller 48 and the pinion 37 on the left and right, and the nut 35 is sandwiched between the roller 48 and the pinion 37. As a result, when the nut 35 moves to the left and right due to the whirling of the screw shaft 34, the arms 38 and 39 swing about the axes of the support shafts 42 and 43 as the center of rotation B, and the swing of the arms 38 and 39. The pinion 37 moves in the left-right direction. The left-right movement of the pinion 37 moves the rear wheel steering rack 12 meshing with the pinion 37 in the left-right direction.

Therefore, when the input shaft 9 rotates, the screw shaft 34 also rotates and swings. The rotation of the screw shaft 34 moves the nut 35 in the front-rear direction, the front-rear movement of the nut 35 rotates the pinion 37, and the rotation of the pinion 37 moves the rear wheel steering rack 12 in the left-right direction. Also, the whirling of the screw shaft 34 moves the nut 35 in the left-right direction, the left-right movement of the nut 35 causes the arms 38, 39 to swing, and the swinging of the arms 38, 39 causes the pinion 37 to move in the left-right direction. The rear wheel steering rack 12 moves in the left-right direction by the left-right movement of the pinion 37. That is, the left-right movement of the rear wheel steering rack 12 is a combination of movement based on rotation of the screw shaft 34 and movement based on whirling of the screw shaft 34. Therefore, by adjusting the gear ratio between the pinion 37 and the racks 36, 12, and the eccentric amount e of the shaft center 34c of the shaft 34c with respect to the shaft center 9c of the input shaft 9, the rear wheel steering angle can be adjusted according to the front wheel steering angle. The movement of the steering rack 12 can be desired.

FIG. 5 shows the relationship between the front wheel steering angle and the rear wheel steering angle of the front and rear wheel steering vehicle. A one-dot chain line 60 in the figure shows the case where the rear wheel steering rack 12 moves based only on the rotation of the screw shaft 34, and the rear wheel steering angle changes linearly according to the front wheel steering angle. The two-dot chain line 61 in the figure shows the case where the rear wheel steering rack 12 moves based only on the whirling of the screw shaft 34, and the rear wheel steering angle periodically changes according to the front wheel steering angle. A solid line 62 in the figure shows a case where the rear wheel steering rack 12 moves based on the rotation of the screw shaft 34 and the whirling of the screw shaft 34, and shows the relationship shown by the one-dot chain line 60 and the relationship shown by the two-dot chain line 61. Is a composite of the above, and represents the relationship between the front wheel steering angle and the rear wheel steering angle of the front and rear wheel steering vehicle of the above embodiment. That is, while the front wheel steering angle is small, the front wheel 1 and the rear wheel 10 are steered in the same direction, and when the front wheel steering angle is large, the front wheel 1 and the rear wheel 10 are steered in opposite directions. Enter into phase. This relationship is favorable for front and rear wheel steering vehicles.

As shown in FIGS. 1 to 3, a pair of reference surfaces 70 and 71 is formed on the outer periphery of the input shaft 9 outside the housing 32. Each reference surface 70, 71 is covered with a cylindrical cover member 72. The cover member 72 is attached to the block 32d of the housing 32 by bolts 73, as shown in FIG. One reference surface 70 is located apart from the other reference surface 71 in the axial direction of the input shaft 9 and is located 180 ° apart in the circumferential direction.

A pair of through holes 74 and 75 are formed in the cover member 72. One of the through holes 74 extends from the outer periphery of the cover member 72 toward the one reference surface 70, and the other through hole 75 extends from the outer periphery of the cover member 72 toward the other reference surface 71. The pressing member 76 and the compression coil spring 78 are inserted into one of the through holes 74, and the pressing member 77 and the compression coil spring 79 are inserted into the other through hole 75. Each pressing member 76, 77 has a cylindrical shape and can be moved in the radial direction of the input shaft 9 while being guided by the inner peripheral surfaces of the through holes 74, 75. The openings of the through holes 74, 75 on the outer periphery of the cover member 72 are closed by screwing the plugs 80, 81. The compression coil springs 78, 79 are arranged between the plugs 80, 81 and the pressing members 76, 77. One pressing member 76 is pressed against one reference surface 70 by the elastic force of one compression coil spring 78, and the other pressing member 77 is pressed against the other reference surface 71 by the elastic force of the other compression coil spring 79. In the present embodiment, the reference surfaces 70, 71 and the tip surfaces of the pressing members 76, 77 are flat surfaces, and in the state where the tip surfaces of the pressing members 76, 77 and the reference surfaces 70, 71 are in surface contact with each other. The input shaft 9 is in the straight steering position. As a result, when the input shaft 9 is located at a position other than the straight steering position, the pressing members 76 and 77 press the reference surfaces 70 and 71 by the elastic force of the compression coil springs 78 and 79. The force to return to the position is generated.

By the elastic force of the compression coil springs 78 and 79, a force for returning the input shaft 9 to the straight steering position is generated, so that the operation force required to return the handle 6 to the straight steering position can be reduced. Further, since the rotation range of the input shaft 9 is less than 360 °, that is, within a range of ± 180 ° with respect to the straight-ahead steering position, the pressing members 76, 77 are located at positions other than the force for returning the input shaft 9 to the straight-ahead steering position. Does not press the reference surfaces 70, 71, and the input shaft 9 is not positioned at a position other than the straight steering position. Further, since the compression coil springs 78 and 79 can press the pressing members 76 and 77 against the reference surfaces 70 and 71 with a large force even when the input shaft 9 is in the vicinity of the straight steering position, a sufficient restoring force is generated. Can be made Further, the compression coil springs 78 and 79 can be fixed simply by inserting them into the through holes 74 and 75 of the cover member 72 and screwing the plugs 80 and 81 into the through holes 74 and 75, so that the fixing is easy and reliable. .. Further, the spiral windings that form the compression coil springs 78 and 79 do not rub against each other and do not wear. Further, since the pair of reference surfaces 70, 71 are located 180 ° apart from each other in the circumferential direction of the input shaft 9, the elastic forces of the compression coil springs 78, 79 acting on the input shaft 9 are balanced and are biased to the input shaft 9. Force is not applied, and the bearings 30 and 31 supporting the input shaft 9 are not unevenly worn. Further, since the pair of reference surfaces 70 and 71 are located apart from each other in the axial direction of the input shaft 9, one of the pressing members should press one reference surface 70 when the input shaft 9 rotates by nearly 180 °. 76 does not press the other reference surface 71, and the other pressing member 77 that should press the other reference surface 71 does not press one reference surface 70.

As shown in FIG. 1, a line segment connecting the rotation center C of the roller 48 and the rotation center A of the pinion 37 is an axis line extending in the left-right direction of the rear wheel steering rack 12 in the straight steering state shown. It is said to be parallel to. As a result, when the pinion 37 exerts a pushing force to the left and right on the rear wheel steering rack 12 based on the whirling of the screw shaft 34, the component force in a direction other than the left and right directions is minimized. The most effective action can be exerted on the rear wheel steering rack 12 from the pinion 37.

Since the movement of the pinion 37 in the left-right direction is based on the swing of the arms 38 and 39 around the rotation center B, the movement is on an arc locus. When the pinion 37 moves on the arc locus in this manner, the meshing amount between the teeth of the pinion 37 and the teeth of the rear wheel steering rack 12 tends to change. Therefore, the support yoke 50 and the spring 51 are inserted into the insertion hole 32f formed in the housing 32, and the adjusting screw 52 is screwed into the insertion hole 32f. The support yoke 50 is movable in the front-rear direction. As a result, the support yoke 50 presses the rear wheel steering rack 12 against the pinion 37 by the elastic force of the spring 51, and the amount of meshing between the teeth of the pinion 37 and the teeth of the rear wheel steering rack 12 changes. To prevent. By adjusting the screwing amount of the adjustment screw 52 into the insertion hole 32f, the elastic force of the spring 51 can be adjusted, and the rotation of the pinion 37 and the movement of the rear wheel steering rack 12 can be made smooth. Wear.

Further, as shown in FIG. 1, the line segment connecting the rotation center A of the pinion 37 and the rotation center B of the arms 38 and 39 is the right and left of the rear wheel steering rack 12 in the straight steering state shown in the drawing. It is perpendicular to the axis along the direction. Therefore, when the pinion 37 moves on the arc locus, the change in the meshing amount between the pinion 37 and the rear wheel steering rack 12 is minimized. As a result, fluctuations in the force with which the support yoke 50 presses the rear wheel steering rack 12 against the pinion 37 are minimized, so that the rotation of the pinion 37 and the movement of the rear wheel steering rack 12 become smooth.

Since the left and right movements of the pinion 37 and the roller 48 are based on the swing of the arms 38 and 39 around the rotation center B, they are moved on an arc locus. Therefore, the horizontal distance between the pinion 37 and the roller 48 changes as the swing amount of the arms 38 and 39 changes. That is, as shown in FIG. 6, in the straight steering state in this embodiment, the line segment L1 connecting the rotation center A of the pinion 37 and the rotation center B of the arms 38 and 39 is the axis 12c of the rear wheel steering rack 12. A line segment L2 connecting the center of rotation A of the pinion 37 and the center of rotation C of the roller 48 is parallel to the axis of the rear wheel steering rack 12. Therefore, in the straight steering state, the lateral distance W between the pinion 37 and the roller 48 becomes maximum. When the arms 38 and 39 sway while being steered to the left or right from the straight-ahead steering state, the left-right distance W ′ between the pinion 37 and the roller 48 becomes smaller than the left-right distance W in the straight-ahead steering state. In order to cope with the change in the left-right distance between the pinion 37 and the roller 48, unevenness is formed in the portion of the nut 35 that contacts the roller 48. That is, as shown in FIG. 1, the portion that contacts the roller 48 in the straight steering state is the convex portion 35a, and the portion that contacts the roller 48 in the left-right steering state is the concave portion 35b. In this embodiment, a stepped portion is formed between the convex portion 35a and the concave portion 35b. The step difference δ between the convex portion 35a and the concave portion 35b is determined based on the difference between the lateral distance W between the pinion 37 and the roller 48 in the straight steering state and the lateral distance W ′ between the pinion 37 and the roller 48 in the lateral steering state. .. As a result, the horizontal width of the nut 35 becomes smaller at the position where the horizontal distance between the pinion 37 and the roller 48 becomes smaller, and the horizontal width of the nut 35 becomes larger at the position where the horizontal distance between the pinion 37 and the roller 48 becomes larger. It is possible to prevent 37 from being pressed against the nut 35 with a large force, and to prevent a large gap from being formed between the pinion 37 and the nut 35. Therefore, the rear wheel steering rack 12 can be accurately made to follow the rotation of the screw shaft 34 and the whirling of the screw shaft 34, and desired steering characteristics can be obtained. It should be noted that the concavities and convexities at the contact portion of the nut 35 with the roller 48 may be the concavities and convexities that are smoothly continuous by a curved surface instead of the convex portions 35a and the concave portions 35b having steps.

The present invention is not limited to the above embodiment.

For example, a friction reducing synthetic resin material may be interposed between the input shaft 9 and the pressing members 76 and 77, or a friction reducing synthetic resin material may be coated on the pressing members 76 and 77. Alternatively, the pressing members 76 and 77 themselves may be molded from synthetic resin having a small friction coefficient. Further, the reference surface and the tip end surface of the pressing member are not limited to flat surfaces and may be curved surfaces. Further, the conversion mechanism 13 is not limited to the above embodiment as long as it converts the rotation of the input shaft into the movement of the rear wheel steering member. For example, an acme screw may be used as the screw shaft 34 and an acme nut may be used as the nut 35. Further, the rotation of the input shaft may be transmitted to the rear wheel steering member via a cam. Further, in the above embodiment, the rotation range of the input shaft 9 is less than 360 °, that is, within the range of ± 180 ° with respect to the straight-ahead steering position, but within the range of ± 360 ° with respect to the straight-ahead steering position, the input shaft If the range is such that the pushing member does not press the reference surface at a position other than the force that returns the steering shaft to the straight steering position, the input shaft exceeds the range of ± 180 ° based on the straight steering position. The rotation range of may be set.

[0033]

[Effect of the device]

 According to the rear wheel steering device of the present invention, no force is generated to return the input shaft to a position other than the straight steering position, and the elastic force of the compression coil spring returns the input shaft to the straight steering position. , A sufficient return force can be applied to the input shaft.

According to the rear wheel steering system of the second aspect of the present invention, an unbalanced load does not act on the input shaft, and the bearing of the input shaft can be prevented from being unevenly worn.

[Brief description of drawings]

FIG. 1 is a plan sectional view of a main part of a rear wheel steering system according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a main part of a rear wheel steering system according to an embodiment of the present invention.

FIG. 3 is a front view of a main part of a rear wheel steering system according to an embodiment of the present invention.

FIG. 4 is a structural explanatory view of a front and rear wheel steering vehicle according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a front wheel steering angle and a rear wheel steering angle of a front and rear wheel steering vehicle according to an embodiment of the present invention.

FIG. 6 is an operation explanatory view of a rear wheel steering device according to an embodiment of the present invention.

[Explanation of symbols]

 1 Front Wheel 9 Input Shaft 10 Rear Wheel 12 Rear Wheel Steering Rack 13 Conversion Mechanism 70, 71 Reference Surface 72 Cover Member 76, 77 Pressing Member 78, 79 Compression Coil Spring

Claims (2)

[Scope of utility model registration request] 1. A front and rear wheel steering vehicle, comprising: an input shaft; and a conversion mechanism for converting the rotation of the input shaft into a movement of a rear wheel steering member, wherein the rear wheels are steered by the movement of the rear wheel steering member. In the wheel steering device, a reference surface is formed on the outer periphery of the input shaft, a cover member is provided to cover the reference surface, the pressing member is held by the cover member, and the compression coil spring is capable of pressing the pressing member against the reference surface. Is provided, a force for returning the input shaft to the straight steering position is generated by pressing the pressing member against the reference surface, and the rotation range of the input shaft is within ± 360 ° with respect to the straight steering position. A rear wheel steering system characterized in that the pressing member is set in a range such that the pressing member does not press the reference surface at a position other than a position where a force for returning the input shaft to the straight steering position is generated. 2. A front and rear wheel steering vehicle, comprising: an input shaft; and a conversion mechanism for converting the rotation of the input shaft into a movement of a rear wheel steering member, wherein the rear wheels are steered by the movement of the rear wheel steering member. In the wheel steering system, a pair of reference planes are formed on the outer periphery of the input shaft, one reference plane is located away from the other reference plane in the axial direction of the input shaft, and the reference plane is 1 in the circumferential direction.
A cover member that is located at a distance of 80 ° and covers both reference surfaces is provided, and a pair of pressing members are held on the cover members. One pressing member is pressed against one reference surface and the other pressing member is pressed against the other reference surface. A pair of compression coil springs that press against the surface are provided, and a force that returns the input shaft to the straight steering position is generated by pressing each pressing member against each reference surface, and the rotation range of the input shaft is ± It is characterized in that each pressing member is set in a range that does not press each reference surface at a position other than a force for returning the input shaft to the straight-ahead steering position within a range of 360 °. Wheel steering device.