JPH061508Y2 - Rear wheel steering system for front and rear wheel steering vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a rear wheel steering device that steers rear wheels in conjunction with steering of front wheels, and in particular, converts steering of front wheels into hydraulic pressure and The present invention relates to a rear wheel steering device for steering a front and rear wheel steering vehicle that steers rear wheels by utilizing the.

[Prior art]

Conventionally, this type of device is disclosed, for example, in Japanese Utility Model Application No. 60-45266
As disclosed in Japanese Patent Publication No. JP-A-2004-242242, a first hydraulic cylinder having a piston rod connected to a rack bar for steering left and right front wheels, and a left and right hydraulic cylinders connected to left and right oil chambers of the first hydraulic cylinder via a pair of conduits, respectively. A second hydraulic cylinder having an oil chamber and a rear wheel steering mechanism having a hydraulic servo mechanism driven by a piston rod of the second hydraulic cylinder to steer the left and right rear wheels are provided. 1 Displace the piston rod of the hydraulic cylinder,
In accordance with the displacement of the piston rod, the working oil in one of the oil chambers of the first hydraulic cylinder is sent out to one of the oil chambers of the second hydraulic cylinder via a conduit, and in the other oil chamber of the second hydraulic cylinder. The hydraulic oil is introduced into the other oil chamber of the first hydraulic cylinder via a conduit, and the piston rod of the second hydraulic cylinder is displaced by the movement of this hydraulic oil, and the rear wheel is moved to the front wheel via the rear wheel steering mechanism. The steering is performed in conjunction with the steering.

[Problems to be solved by the invention]

However, in the above-mentioned conventional device, in order to accurately convert the displacement of the piston rod of the first hydraulic cylinder into the displacement of the piston rod of the second hydraulic cylinder, each one of the first and second hydraulic cylinders and each other Although it is necessary to make the working oil in the oil chamber of the system including the working oil in the conduit closed, it is extremely difficult to completely maintain the closed working oil. That is, if air is not completely removed from the oil chamber or the conduit, or if air is later introduced into the oil chamber or the conduit, the completely closed state of the hydraulic oil cannot be realized. Then, in such a case, there is a problem that the volume elasticity modulus of the hydraulic oil mixed with air is reduced, the steering signal of the front wheels is not accurately transmitted to the rear wheels, and the steering of the rear wheels is not performed accurately. is there.

The present invention has been devised in view of the above problems, and an object thereof is to use a hydraulic means that does not require the sealed state of the hydraulic oil to ensure that the rear wheels are always synchronized with the steering of the front wheels. (EN) Provided is a rear wheel steering device that steers to the right, and in this rear wheel steering device, particularly, the steering characteristics of the rear wheels are improved when the front wheels are steered at a small steering angle.

[Means for solving problems]

In order to solve the above problems and achieve the object of the present invention, a structural feature of the present invention is to provide an input elliptical gear that rotates according to the turning of a steering wheel and an output elliptical gear that meshes with the input elliptical gear. A gear mechanism including an elliptical gear, a cam member that is connected to the rotation shaft of the output elliptical gear and that rotates according to the rotation of the output elliptical gear, and that is engaged with the cam surface of the cam member at one end A spool valve that has a valve spool that is displaced in the axial direction according to the rotation of the cam member and that generates hydraulic pressure according to the relative displacement of the valve spool and the valve sleeve; A pair of connected conduits for transmitting the hydraulic pressure, a pair of hydraulic chambers respectively connected to the other ends of the pair of conduits, and a hydraulic cylinder for driving a piston rod according to the hydraulic pressure; and the piston rod And a spring for urging the neutral position,
And a steering mechanism that steers the rear wheels by being driven according to the displacement from the neutral position of the piston rod.

[Function of device]

In the present invention configured as described above, when the steering wheel is rotated to steer the front wheels, the rotation of the steering wheel is transmitted to the cam member via the gear mechanism, and the cam member operates as a steering wheel. It rotates according to the rotation. In this case, since the gear mechanism is composed of the input elliptical gear and the output elliptical gear, the rotation speed of the cam member with respect to the rotation of the steering wheel becomes faster according to the change in the meshing position of the pair of elliptical gears, It will be late. Due to the rotation of the cam member, the valve spool engaged with the cam surface of the cam member at one end is displaced from the neutral position, and the valve spool is displaced between the valve spool and the valve sleeve, that is, the steering handle is rotated. Since relative displacement occurs depending on the mesh position of the pair of elliptical gears and the cam profile of the cam member, the spool valve controls the rotation of the steering handle, the hydraulic pressure corresponding to the mesh position of the pair of elliptical gears, and the cam profile. Supply to a hydraulic cylinder via a pair of conduits. The piston rod of the hydraulic cylinder is pressed by this hydraulic pressure, but since the urging force of the spring acts so as to oppose the hydraulic pressure, the piston rod should be displaced from the reference position by an amount proportional to the hydraulic pressure. become. Since the steering mechanism steers the left and right rear wheels in accordance with the displacement of the piston rod, the rear wheels are interlocked with the steering of the front wheels and the characteristics determined by the mesh position of the pair of elliptical gears and the cam profile of the cam member. Is steered by.

[Effect of device]

According to the present invention, as can be understood from the above description of the operation, the hydraulic pressure corresponding to the steering amount of the front wheels is generated by using the cam member and the spool valve, and this hydraulic pressure is used by the hydraulic cylinder and the steering mechanism. Since the rear wheels are steered in conjunction with the front wheels, there is no need to maintain the sealed state of the hydraulic oil as in the conventional device, and the problem caused by the incomplete sealing is eliminated and the The wheels can be accurately steered in conjunction with the steering of the front wheels.

Further, according to the present invention, since a pair of elliptical gears is used as the gear mechanism, by setting the meshing positions of both elliptical gears, the rotational speed of the cam member is increased when the valve spool is in the vicinity of the neutral position. can do. With this setting, the dead zone for hydraulic pressure generation in the vicinity of the neutral state of the spool valve can be made small without compromising the design of the cam surface of the cam member, and the steering characteristics of the rear wheels at the small steering angle of the front wheels can be improved. You can

Further, according to the present invention, only by changing the cam profile of the cam member, the displacement of the valve spool with respect to the steering amount of the front wheel is changed and the hydraulic pressure supplied to the hydraulic cylinder is changed. The steering characteristic with respect to can be easily changed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a front and rear wheel steering vehicle according to the present invention.

The front and rear wheel steering vehicle is a front wheel steering link mechanism that is supported by a housing 11 fixed to the vehicle body so as to be axially displaceable and axially displaced according to the rotation of a steering handle 12 to steer the left and right front wheels FW1 and FW2. Rack bar 1
Have three. The rack bar 13 is connected to the steering handle 12 via a pinion 14 housed in the housing 11 and a steering shaft 15 that fixes the pinion 14, and the left and right tie rods 16a, 16b and the left and right knuckle arms 17a, Left and right front wheels FW via 17b
1 and FW2 are connected. A control valve 18, which is a four-way valve, is attached to an intermediate portion of the steering shaft 15, and the valve 18 is a constant displacement hydraulic pressure driven by an engine 21 in accordance with a steering torque acting on the steering shaft 15. The supply of hydraulic oil from the pump 22 to the power cylinder 23 and the discharge of hydraulic oil from the cylinder 23 to the reservoir 24 are controlled. The power cylinder 23 is formed in the housing 11 and is fixed to the rack bar 13 by a piston 23.
has left and right oil chambers 23b, 23c partitioned by a,
The rack bar 13 is driven according to the supply and discharge of the hydraulic oil.

As shown in FIGS. 1 and 2, the lower end of the steering shaft 15 is
The cam member 2 in the housing 11 via the gear mechanism 25.
It is connected to 6 rotary shafts. As shown in FIGS. 1 to 3, the gear mechanism 25 includes first to fourth gears 25a, 25b, 25c, which are rotatably supported by the housing 11.
25d, the rotation of the steering shaft 14 is transmitted to the cam member 26 through the gears 25a, 25b, 25c, 25d in this order. First and second gears 25a, 2
Each of 5b is composed of a circular gear, and the radius of the first gear 25a is set smaller than that of the second gear 25b. As a result, the first and second gears 25a,
25b decelerates the rotation of the steering shaft 15 associated with the rotation of the steering wheel 12 so that the rotation of the third gear 25c with respect to the maximum rotation amount of the steering wheel 12 is less than one rotation. The third and fourth gears 25c and 25d are composed of elliptical gears of the same shape that mesh with each other, and when the steering handle 12 (steering shaft 15) is in the neutral state, the third gear 2
The major axis direction of 5c and the minor axis direction of the fourth gear 25d are set to coincide with each other. As a result, the steering wheel 12
The cam member 2 for changes in the rotation angle θ _H of the (steering shaft 15)
The change in the rotation angle θ _C of No. 6 becomes large in the vicinity of the neutral state of the steering wheel 12 as shown by the solid line A in FIG. The cam surface of the cam member 26 is formed so that the displacement S _F of the valve spool 27a, which will be described later, changes with the rotation of the cam member 26 from the reference position in accordance with the characteristics shown in FIG. That is, with respect to the rotation of the cam member 26 in the direction of the arrow in FIG. 1 (corresponding to the right rotation of the steering wheel 12), the valve spool 27a is displaced in the right direction in FIG. The spool 27a is displaced leftward in FIG. 1 in a range where the rotation amount is large. In addition, the cam member 26
1 in the opposite direction of rotation (corresponding to the left rotation of the steering wheel 12), the valve spool 27a is displaced leftward in FIG. And the spool 27 in the same range of large rotation amount.
a is displaced rightward in FIG.

As shown in FIGS. 1 and 2, a cam follower 28 rotatably supported at the tip end of a valve spool 27a that constitutes the spool valve 27 contacts the cam surface formed on the outer periphery of the cam member 26. Touching. Valve spool 2
7a is a valve sleeve 27 fitted in the housing 11.
It is incorporated in b so as to be displaceable in the axial direction, and its rear end is constantly urged toward the cam member 26 by a spring 31 supported at one end by a plug 29 fitted to the housing 11. The engine 2 is attached to the valve sleeve 27b.
The first and second discharge ports 27b2, 27b3 communicating with the reservoir 33 and the supply port 27b1 communicating with the constant displacement hydraulic pump 32 driven by the valve 1 are formed. Lands 27a1, 27a2, 27a3 facing the ports 27b1, 27b2, 27b3 are provided.
Further, first and second inflow / outflow ports 27b4 and 27b5 are formed between the supply port 27b1 of the valve sleeve 27b and the first and second exhaust ports 27b2 and 27b3. The spool valve 27 including the valve spool 27a and the valve sleeve 27b constitutes an underlap type four-way valve. When the valve spool 27a is in the neutral position, the first and second inlet / outlet ports 27b4 and 27b5 are connected to each other. The hydraulic pressure in the first inflow / outflow port 27b4 (or the second inflow / outflow port 27b5) when the spool 27a is displaced in the right (or left) direction in FIG. 2 is eliminated.
So that the higher by an amount corresponding to the displacement amount S _F of the valve spool 27a from a hydraulic in (or first inlet outflow port 27B4) (solid line B of FIG. 4).

First and second inflow / outflow ports 27b of the spool valve 27
4, 27b5 are left and right oil chambers 35a, 35b of a hydraulic cylinder 35 fixed to the vehicle body via a pair of conduits 34a, 34b.
Is in communication with. Springs 36a and 36b for urging the neutral position are housed in the left and right oil chambers 35a and 35b,
The springs 36a and 36b constantly urge the piston 35c and the piston rod 35d to the neutral position.

One end of the piston rod 35d has left and right rear wheels RW1, RW
2 is rotatably connected to an intermediate portion of a lever 37 provided in a rear wheel steering mechanism that steers 2 according to the displacement of the rod 35d. The rear wheel steering mechanism includes the lever 37, a steering link mechanism that connects the left and right rear wheels RW1 and RW2 in a steerable manner, and a copying servo mechanism that steers the left and right rear wheels RW1 and RW2.

In this steering link mechanism, a rear end of a lever 37 is rotatably connected and a housing 38 fixed to a vehicle body is provided.
And a relay rod 41 supported so as to be displaceable in the axial direction. Both ends of the relay rod 41 are left and right tie rods 42.
The left and right rear wheels RW1 and RW2 are connected via a and 42b and left and right knuckle arms 43a and 43b.

The copying servo mechanism has a zero-lap or overlap-type spool valve 44 and a power cylinder 45 as main components. The spool valve 44 is a tubular valve body 44a formed in the housing 38, and a valve spool 44b in which the front end of the lever 37 is rotatably connected at one end thereof so as to be slidably incorporated in the body 44a.
Have and. The valve body 44a includes a variable displacement hydraulic pump 46 driven by the engine 21 and a check valve 4
A supply port that communicates with each other through 7 and two discharge ports that communicate with the reservoir 48 are formed, and three lands corresponding to the respective ports are formed on the outer circumference of the valve spool 44b. The power cylinder 45 has left and right oil chambers 45b and 45c partitioned by a piston 45a fixed to the relay rod 41.
Respectively communicate with the inflow / outflow ports formed between the supply port and the exhaust port of the valve sleeve 44a.

Next, the operation of the embodiment configured as described above will be described.

First, a case where the vehicle is steered to the right will be described. When the steering wheel 12 is rotated rightward by θ _H , this rotation is transmitted to the pinion 14 via the steering shaft 15, and the pinion 14 moves the rack bar 13 leftward in FIG. The displacement X _F corresponding to the amount of rotation θ _H is displaced. The displacement X _F of the rack bar 13 is determined by the left and right tie rods 16a, 16b and the left and right knuckle arms 17
The left and right front wheels FW1 and FW2 are transmitted to the left and right front wheels FW1 and FW2 via a and 17b, and the left and right front wheels FW1 and FW2 are steered rightward by θ _F according to the turning amount θ _H of the steering wheel 12. In the steering of the left and right front wheels FW1 and FW2, the control valve 18 operates according to the steering torque acting on the steering shaft 15 to supply hydraulic oil to the right oil chamber 23c of the power cylinder 23 and the left oil chamber 23b. Since the discharge of hydraulic oil from the cylinders is controlled, the cylinder 23 pushes the rack bar 13 to the left via the piston 23a, and the left and right front wheels FW1 and FW described above are pressed.
Assist the steering of 2.

On the other hand, the rotation of the steering shaft 15 is also input to the gear mechanism 25, and the gear mechanism 25 uses the first and second gears 25a and 25b.
The rotation is decelerated by the action of the
By the action of the gears 25c and 25d, the rotation speed is changed according to the rotation angle θ _H of the steering handle 12 to rotate the cam member 26 in the arrow direction in FIG. In this case, the cam member 2
Assuming that the rotation angle of 6 is θ _C , the rotation angle θ _C changes so that the rotation speed increases near zero of θ _C , as indicated by the solid line A in FIG. The rotation of the cam member 26 is transmitted to the valve spool 27a via the cam follower 28, and the spool 27a is displaced by the displacement amount S _{F in the} axial direction according to the cam profile of the cam member 26. In this case, since the conversion characteristic of the cam member 26 is as shown in FIG. 5, the valve spool 27a is displaced rightward in FIG. 1 within a small range of the rotation angle θ _C (> 0) of the cam member 26. ,
Further, in the range where the rotation angle θ _C is large, the displacement is leftward in FIG.

The displacement of the valve spool 27a, the spool valve 27 is a hydraulic cylinder 3 hydraulic force via a conduit 34a, 34b having a differential pressure P to increase in accordance with the displacement amount S _F
Supply to 5. In this case, the change characteristic of the differential pressure P with respect to the displacement of the valve spool 27a in the spool valve 27 has a large dead zone near the reference position of the valve spool 27a, as shown by the solid line B in FIG.
Since the rotation characteristic of the cam member 26 is as shown by the solid line A in FIG. 4, the change characteristic of the differential pressure P with respect to the rotation θ _H of the steering wheel 12 is as shown by the solid line C in FIG. In addition, the dead zone in the vicinity of the neutral state of the steering wheel 12 is reduced and the cam profile of the cam member 26 is linear. However, in this case, if the rotation angle θ _C of the cam member 26, that is, the rotation angle θ _H to the right of the steering handle 12 is small, the operating hydraulic pressure in the conduit 34a is higher than that in the conduit 34b, and the rotation angle θ is the same. _C
If (θ _H ) is large, the hydraulic pressure in the conduit 34b is
It will be higher than that in 4a.

When such hydraulic pressure is supplied to the hydraulic cylinder 35,
The piston 35c and the piston rod 35d are displaced in the direction according to the supplied oil pressure, but the urging force of the springs 36a and 36b acts on the piston 35c and the piston rod 35d in the direction to return them to the neutral position, and the piston 35c and The piston rod 35d displaces to the position where the hydraulic pressure and the urging force of the springs 36a and 36b are equalized, that is, displaced from the reference position by S _{R and} stands still.

This displacement of the piston rod 35d is transmitted to the lever 37, but if the rotation angle θ _H of the steering handle 12 is small as described above, the operating oil pressure supplied to the left oil chamber 35a of the hydraulic cylinder 35 via the conduit 34a. Is high and the piston rod 35d is displaced rightward in FIG. 1, the lever 37 is pressed rightward in FIG. In such a case, first, the relay rod 41 is in a state in which it is difficult to displace due to the frictional force between the left and right rear wheels RW1, RW2 and the road surface, so the lever 37 rotates rightward in FIG. 1 with the connection point with the relay rod 41 as the fulcrum. . Due to this rotation, the valve spool 44b is displaced to the right in FIG. 1, and the spool valve 44 moves to the hydraulic pump 46.
The hydraulic oil discharged from the left oil chamber 4 of the power cylinder 45.
5b and the right oil chamber 45c of the cylinder 45
Since the discharge of the hydraulic oil from the reservoir to the reservoir 48 is allowed, the relay rod 41 is displaced rightward in FIG. Next, due to the rightward displacement of the relay rod 41, the lever 37 rotates leftward in FIG. 1 with the connection point with the piston rod 35d as a fulcrum. This rotation of the lever 37 displaces the valve spool 44b in the leftward direction in FIG. 1 contrary to the above, so that the spool valve 44 stops the supply and discharge of hydraulic oil to and from the power cylinder 45, and the relay rod 41 moves to the rightward direction. The displacement of is also stopped. The servomechanism copying comprising such a spool valve 44, a power cylinder 45, etc., the relay rod 41 is caused to undergo displacement in Figure 1 the right direction by X _R in accordance with the displacement amount S _R of the operating rod 35d of the hydraulic cylinder 35. Further, the displacement of the relay rod 41 is caused by the left and right tie rods 42a and 42b and the left and right knuckle arms 43.
It is transmitted to the left and right rear wheels RW1 and RW2 via a and 43b, and the left and right rear wheels RW1 and RW2 are steered rightward by θ _R.

On the other hand, as described above, when the rotation angle θ _H of the steering wheel 12 is large, the operating oil pressure supplied to the right oil chamber 35b of the hydraulic cylinder 35 via the conduit 34b is high and the piston rod 35d is left in FIG. Since it is displaced in the direction,
Is pulled to the left in FIG. In this case, the spool valve 44 and the power cylinder 45 act in the opposite manner to displace the relay rod 41 leftward in FIG. 1, so that the left and right rear wheels RW1 and RW2 are steered leftward.

In this way, when the steering handlebar 12 is rotated rightward and the left and right front wheels FW1 and FW2 are steered rightward,
As shown in the figure, if the turning amount θ _H of the steering handle 12 is small, the left and right rear wheels RW1, RW2 are steered in the right direction, that is, in the same phase as the left and right front wheels FW1, FW2, and if the turning amount θ _H is large, the left and right rear wheels are rotated. The wheels RW1 and RW2 are steered to the left, that is, in the opposite phase to the left and right front wheels FW1 and FW2.

Next, a case where the vehicle is steered to the left will be described. In this case, in this embodiment, the characteristic of the cam member 26, that is, the valve spool 27a with respect to the input rotation angle θ _C.
Since the displacement amount S _F of the steering wheel 12 is symmetrical with respect to the steering of the steering wheel 12 in the left-right direction due to the design of the cam profile of the cam member 26 (see FIG. 5), the steering wheel 12 rotates leftward. Left and right front wheels FW1 and FW2
When the vehicle is steered to the left, the left and right rear wheels RW1, RW
2 is steered in the opposite direction to the case described above in accordance with the front wheel steering. As a result, the rear wheels RW1 and RW2 are steered symmetrically with respect to the left-right rotation of the steering handle 12, as shown in FIG.

As can be understood from the above description, according to the above-described embodiment, the cam member 26 and the spool valve 27 forming the four-way valve are used to generate the hydraulic pressure corresponding to the turning amount of the steering handle 12, and the hydraulic pressure is generated. Hydraulic cylinder 35 corresponding to pressure
Left and right rear wheels RW according to the displacement of the piston rod 35d of
1 and RW2 are steered so that the left and right front wheels FW1 and FW2 are not required to use a hydraulic device that requires a sealed state of hydraulic oil.
Since the left and right rear wheels RW1 and RW2 can be steered in conjunction with W2, the problem associated with the incomplete sealing is solved, and the steering control of the rear wheels RW1 and RW2 becomes accurate.

Further, according to the above-described embodiment, the rotation speed of the cam member 26 is increased when the valve spool 27a is in the vicinity of the neutral position by using the third and fourth gears 25c and 25d that are elliptical gears as the gear mechanism. In this way, the hydraulic pressure P generated from the spool valve 27 is applied to the steering wheel 1
Since the rotation angle θ _{H of} 2 is changed as shown by the solid line C in FIG. 4, the hydraulic pressure generation in the vicinity of the neutral state of the spool valve 27 can be performed without oversighting the design of the cam surface of the cam member 26. It is possible to reduce the dead zone for, and to improve the steering characteristics of the rear wheels when the front wheels have a small steering angle. The broken lines D and E in FIG. 4 indicate the third and fourth gears 2.
Change characteristics of the rotation angle θ _C of the cam member 26 with respect to the rotation angle θ _H of the steering handle 12 and the change of the hydraulic pressure P generated by the spool valve 27 with respect to the rotation angle θ _H when the gears 5c and 25d are formed of circular gears. Characteristics are shown for comparison with the present example.

Further, in the above-described embodiment, if the cam profile of the cam member 26 is changed, the displacement characteristic of the valve spool 27a with respect to the rotation of the steering wheel 12 is changed, and the characteristic of the hydraulic pressure generated from the spool valve 27 can be changed. The left and right front wheels FW can be obtained only by changing the cam member 26 according to the above embodiment to another cam member having a different cam profile.
The steering characteristics of the left and right rear wheels RW1, RW2 with respect to 1, FW2 can be variously changed.

Further, according to the above-described embodiment, since the copying servo mechanism including the spool valve 44, the power cylinder 45 and the like is used as the rear wheel steering mechanism, the hydraulic pressure supplied from the spool valve 27 and the urging force of the springs 36a and 36b are changed. Based on the displacement of the piston rod 35d of the hydraulic cylinder 35 which is positioned by, the left and right rear wheels RW1, RW2 can be accurately steered without the influence of the reaction force from the rear wheels RW1, RW2. When the reaction force does not matter or the reaction force can be ignored, the left and right rear wheels RW of the piston rod 35d can be ignored.
If the steering force with respect to RW1 and RW2 can be obtained, the copying servo mechanism becomes unnecessary.

[Brief description of drawings]

FIG. 1 is an overall schematic view of a front and rear wheel steering vehicle equipped with a rear wheel steering device according to an embodiment of the present invention, and FIG. 2 is a cutaway view showing details of the gear mechanism, cam member and spool valve of FIG. ,
FIG. 3 is a third and a fourth view taken along the line III-III in FIG.
Gear mounting structure diagram, Figure 4 shows the steering wheel rotation angle,
FIG. 5 is a characteristic diagram of the rotation angle of the cam member, the amount of displacement of the valve spool, and the hydraulic pressure generated by the spool valve, FIG. 5 is a characteristic diagram of the cam, and FIG. 6 is a steering characteristic diagram of the left and right rear wheels for the left and right front wheels. Explanation of reference numerals 12 ... Steering handle, 15 ... Steering shaft, 25 ...
Gear mechanism, 25a, 25b, 25c, 25d ... gear, 26 ... cam member, 27 ... spool valve,
27a ... Valve spool, 27b ... Valve sleeve, 28 ... Cam follower, 32 ... Hydraulic pump, 34a, 34b ... Conduit, 35 ... Hydraulic cylinder, 35d ... Piston rod, 36a , 36b ...
-Spring, 37 ... Lever, 41 ... Relay rod, 44 ... Spool valve, 45 ... Power cylinder, 46 ... Hydraulic pump, FW1, FW2 ...
Front wheels, RW1, RW2 ... Rear wheels.

Claims (1)

[Scope of utility model registration request] 1. A gear mechanism comprising an input elliptical gear that rotates according to the turning of a steering wheel and an output elliptical gear that meshes with the input elliptical gear, and a gear shaft connected to a rotary shaft of the output elliptical gear. The valve spool includes a cam member that rotates in response to the rotation of the output elliptical gear, and a valve spool that engages with the cam surface of the cam member at one end and is axially displaced in response to the rotation of the cam member. Spool valve for generating hydraulic pressure according to relative displacement between the valve sleeve and the valve sleeve, a pair of conduits connected to the spool valve at each one end to transmit the hydraulic pressure, and the other end of each of the pair of conduits A hydraulic cylinder that has a pair of oil chambers respectively connected to each other to drive a piston rod according to the hydraulic pressure, a spring that urges the piston rod to a neutral position, and a neutral position of the piston rod. Steering the rear wheels are driven in accordance with the displacement of the fact that includes a steering mechanism rear wheel steering apparatus of the front and rear wheel steering vehicle according to claim.