JPH0611875Y2 - 4-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a four-wheel steering system.

(Prior art and its problems) In order to improve the maneuverability during high-speed running of the vehicle and the small turning ability that facilitates entry into narrow alleys, etc., in addition to steering the front wheels, steering the rear wheels simultaneously 4 Wheel steering systems have been proposed. As for this steering device, steering of the front wheels is performed by a conventional steering device such as a power steering device, and steering of the rear wheels is supplied with hydraulic pressure to hydraulic cylinders or power cylinders attached to the left and right rear wheel hubs or trailing arms. A hydraulic type is known.

It is known that this hydraulic steering device electronically controls the working hydraulic pressure supplied to the hydraulic cylinder, and an electromagnetic switching valve or the like is provided in the middle of the working hydraulic pressure supply path to the hydraulic cylinder. The hydraulic pressure to the hydraulic cylinder is controlled by controlling the electronic control unit according to the vehicle speed signal detected by the vehicle speed sensor and the steering angle signal detected by the steering angle sensor.

The electronic control type does not complicate the hydraulic path even if the number of control parameters increases, and it has the advantage that fine control can be performed, but in order to electronically control the steering device which is an important safety component However, there is a risk of malfunction due to radio interference, disconnection, short circuit, etc., and there is an important problem of lack of reliability.

Instead of the hydraulic type described above, a pure mechanical type has also been proposed. This mechanical steering system connects the steering gear box on the front wheel side and the steering gear box on the rear wheel side by a mechanism such as an eccentric shaft and planetary gears. The steering angle is controlled by steering the front wheels and the rear wheels in the same phase up to a predetermined turning angle of the steering wheel, and when the turning angle exceeds the predetermined angle, steering is performed in the opposite phase. . Steering the rear wheels purely mechanically makes the mechanism extremely complicated, and in order to realize the steering of the rear wheels by the pure mechanical mechanism, the number of control parameters is limited as described above, and the steering angle outside the steering wheel is cut off. In addition, there is a problem that it is difficult to control the rear wheel steering angle by a plurality of parameters such as vehicle speed and steering force.

The present invention has been made in order to solve such a problem, and is a highly reliable full hydraulic control type that does not have a risk of malfunction due to radio interference, etc., has a high degree of control freedom, and has a simple configuration. An object is to provide a four-wheel steering device.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the four-wheel steering system of the present invention is
A hydraulic operating device for steering the rear wheels; and a hydraulic control valve device controlling the supply of hydraulic oil to the hydraulic operating device, wherein the hydraulic control valve device includes first and second variable displacement piston chambers,
A piston mechanism that changes the capacity of each of these piston chambers in conjunction with each other according to the vehicle speed, and is slidably and liquid-tightly fitted in each of the piston chambers, and the first piston chamber is connected to the first piston chamber. A first piston that divides the second pressure chamber into a third pressure chamber and a second piston that divides the second piston chamber into a third pressure chamber, and the first piston that divides the second piston chamber into a third pressure chamber and a fourth pressure chamber. A first oil passage connecting the pressure chamber and the fourth pressure chamber and connected to the hydraulic operating device, and connecting the second pressure chamber and the third pressure chamber to the hydraulic operating device. A second oil passage connected to the first and second pistons, the first and second pistons change their respective piston areas in accordance with changes in the volume of the corresponding piston chambers, and the first pistons are connected to the first pressure chambers. To increase the capacity of the second pressure chamber and decrease the capacity of the second pressure chamber When moved, the second piston moves in a direction to increase the capacity of the third pressure chamber and decrease the capacity of the fourth pressure chamber, and the first piston moves to the capacity of the first pressure chamber. In the direction of increasing the capacity of the second pressure chamber, the second piston decreases the capacity of the third pressure chamber and increases the capacity of the fourth pressure chamber. And the first and second pistons move in conjunction with each other according to the steering wheel angle.

(Operation) The hydraulic operating device steers the rear wheel to the right or left depending on whether the hydraulic oil is supplied from the first or second oil passage. When the volumes of the first and second piston chambers are equal, no matter which direction the first and second pistons are moved, the space between the first pressure chamber and the fourth pressure chamber and the second pressure chamber The hydraulic oil only moves between the first and second pressure chambers, the hydraulic oil is not supplied to the hydraulic operating device via the first and second oil passages, and the rear wheels are not steered in either direction. . However, when the piston mechanism operates to cause a difference in the volume of the first piston chamber and the volume of the second piston chamber, the displacement of the pressure chamber having a large volume from the pressure chamber having a large volume as the first and second pistons move. Part of the hydraulic oil discharged toward the small pressure chamber is also supplied to the hydraulic operating device, and the rear wheels are steered in the direction corresponding to the oil passage through which the hydraulic oil is supplied. It becomes possible to steer the rear wheels in the same phase or in the opposite phase with respect to the steering direction of the front wheels according to which volume of the second piston chamber is increased, that is, according to the vehicle speed. The steering ratio of the front and rear wheels is determined according to

(Embodiment) An embodiment of the present invention will be described below in detail with reference to the drawings.

First, referring to FIG. 1, a hydraulic circuit for steering the rear wheels of the four-wheel steering system according to the present invention will be described. The front wheel steering device is omitted in the four-wheel steering device shown in FIG.

The rear wheels 1, 1 are steered by the operation of the power cylinder 2,
The hydraulic oil discharged from the oil pump 6 and regulated by the displacement follow-up type servo valve 4 is supplied to the power cylinder 2. More specifically, the rear wheels 1, 1 are suspended on the vehicle body by, for example, a trailing arm type suspension device,
The tips of the left and right trailing arms 1a are connected to a subframe (neither is shown) via joints that can be bent only in the horizontal direction, and the pistons of the power cylinder 2 are connected to the tips of the trailing arms 1a. Tie rods 2b, 2b extending from the left and right from 2a are connected. The power cylinder 2 has a left pressure chamber 2c defined by a piston 2a.
A right pressure chamber 2d is formed, and springs 2g and 2h are contracted in the pressure chambers 2c and 2d. Left and right pressure chambers 2c, 2d
When the piston 2a is displaced according to the differential pressure of the hydraulic oil supplied to the rear wheel 1, the tie rod 2b presses the trailing arm 1a in the direction in which the piston 2a is displaced, and the rear wheel 1 is steered in the displacement direction.

The displacement follow-up type servo valve 4 is configured to include a valve body 40 and a spool 41 slidably fitted in the valve body 40, and a right end surface of the spool 41 has a rod 44.
Is connected to a piston 8a of a hydraulic actuator 8 described later via. The servo valve 4 has four ports 4a-
4d, an oil passage 22 communicating with the discharge side of the oil pump 6 is connected to the port 4a, and an oil passage 26 communicating with the oil tank 18 is connected to the port 4b.
The port 4c of the servo valve 4 communicates with the left pressure chamber 2c of the power cylinder 2 through the oil passage 23, and the port 4d communicates with the right pressure chamber 2d through the oil passage 24.

The valve body 40 of the servo valve 4 is relatively movable along the axial direction of the spool 41, and the valve body 40 is engaged with the above-mentioned left tie rod 2b via the arm 3 and is connected to the piston 2a of the power cylinder 2. When the arm 3 swings about the fulcrum 3a in response to the displacement, the valve body 40 is also displaced along with the displacement of the piston 2a in the direction opposite to the displacement direction of the piston 2a.

The oil pump 6 is constantly driven by the engine E,
The hydraulic oil in the oil tank 18 is pumped up through the oil filter 18a and the oil passage 21 and discharged to the servo valve 4 side. The oil passage 22 and the oil passage 26 are connected by the branch oil passage 22a, and the operating oil pressure discharged from the oil pump 6 is regulated to a predetermined value by the relief valve 19 arranged in the middle of the branch oil passage 22a. ing.

The spool 41 of the servo valve 4 is controlled and driven by the hydraulic actuator 8, and the operating hydraulic pressure supplied to the hydraulic actuator 8 is controlled by the variable displacement hydraulic control valve device 7. More specifically, the hydraulic actuator 8 is a spring that presses the pressure-receiving surfaces of the piston 8a, the cylinder 8b, and the piston 8a described above to hold the piston 8a in the neutral position.
8c, 8d, and the left end surface of the piston 8a in the drawing is the spool 41 of the servo valve 4 via the rod 44 as described above.
It is connected to the. The cylinder 8b in which the piston 8a is slidably fitted defines a left pressure chamber 8e and a right pressure chamber 8f by the piston 8a, and when the working hydraulic pressure of the left pressure chamber 8e exceeds the working hydraulic pressure of the right pressure chamber 8f, the piston 8a 8a moves to the right to displace the spool 41 of the servo valve 4 in the same direction as the piston 8a by the same movement amount, and conversely, when the working oil pressure of the right pressure chamber 8f exceeds the working oil pressure of the left pressure chamber 8e, the piston 8a moves. It moves to the left to displace the spool 41 to the left.

Two piston chambers 7a and 7b are formed in the cylinder 70 of the variable displacement hydraulic control valve device 7, and the piston chambers 7a and 7b are formed in the same shape, and have a rectangular parallelepiped shape with an opening at the top. (See Figures 1 and 2). Each of the piston chambers 7a and 7b has a piston 74 of a planar rectangular shape at the opening.
The a and 74b are fitted in a vertically slidable and liquid-tight manner. The pistons 74a and 74b move up and down in the piston chambers 7a and 7b, respectively.
Increase or decrease the capacity of 7b. These pistons 74a, 7
4b is a vehicle speed sensitive actuator 2 by a link mechanism 75.
It is connected to 0 and moves up and down in conjunction with the operation of the actuator 20 as described later.

One end of the link mechanism 75 is connected to the piston 74a, and the other end thereof is the piston 20 of the vehicle speed sensitive actuator 20 described later.
b, a rod 75c connected to the piston 74b, and a rod 75b connecting these rods 75a, 75c.
Each connecting portion between c and the rod 75b is rotatably supported, and the center position of the rod 75b is rotatably supported by a support shaft 75d.

The pistons 71 and 72 are provided in the piston chambers 7a and 7b defined by the cylinder 70 and the pistons 74a and 74b.
Are slidably fitted in a horizontal direction and are fitted in a liquid-tight manner. These pistons 71 and 72 are connected by a rod 73b that penetrates a partition wall 70a that divides the piston chamber 7a and the piston chamber 7b. Piston chamber 7 on the right side in the figure
The right end surface of the piston 72 fitted in b is connected to one end of a rod 73a, and this rod 73a penetrates the side wall 70b of the cylinder 70 and projects outward,
Connected to 11. The rotation of the steering wheel 11 causes the pistons 71 and 72 to interlock with each other to form each piston chamber 7a.
And 7b. That is, the steering wheel 1
When 1 is rotated to the right, the pistons 71 and 72 move to the left, and when rotated to the left, the steering wheel 1 moves to the right.
Move the same distance according to the cutting angle (handle angle) of 1.

The piston 71 divides the piston chamber 7a into a left pressure chamber 7A and a right pressure chamber 7B, and is composed of a main body portion 71a and a movable portion 71b. The main body portion 71a has a thickness larger than the plate thickness of the movable portion 71b, and a groove 71d into which the movable portion 71b is fitted is formed over the entire area in the width direction. A plate-shaped movable portion 71b having the same width as the main body portion 71a (that is, substantially the same width as the piston chamber 7a) is inserted into and retracted from the groove 71d, and the movable portion 71b is provided between the bottom and the groove bottom. Is pressed upward by a spring 71c housed in the groove 71d of the piston 74a.
In response to the up-and-down movement of the groove 71d, the groove 71d is projected and retracted, and the upper edge of the movable portion 71b is brought into sliding contact with the lower surface of the piston 74a to keep the left pressure chamber 7A and the right pressure chamber 7B liquid-tight.

Similarly, the piston 72 moves the piston chamber 7b into the left pressure chamber 7C.
And the right pressure chamber 7D, and the main body 72a and the movable portion 72b
Composed of and. The main body portion 72a has a thickness larger than the plate thickness of the movable portion 72b, and a groove 72d into which the movable portion 72b is fitted is formed over the entire area in the width direction. This groove 7
2d has the same width as the main body 72a (that is, the piston chamber 7b
A plate-shaped movable portion 72b having a width substantially the same as that of the movable portion 72b is inserted and retracted so that the movable portion 72b is pressed upward by a spring 72c housed in a groove 72d between the bottom portion and the groove bottom.
In response to the vertical movement of the piston 74b, the groove 72d appears and disappears,
While the piston area is increased / decreased, the upper edge of the movable portion 72b is in sliding contact with the lower surface of the piston 74b to maintain liquid tightness between the left pressure chamber 7C and the right pressure chamber 7D.

The left pressure chamber 7A of the piston chamber 7a and the right pressure chamber 7D of the piston chamber 7b communicate with each other through an oil passage 32, and the oil passage 32 is also connected to the left pressure chamber 8e of the hydraulic actuator 8.
The right pressure chamber 7B of the piston chamber 7a and the left pressure chamber 7C of the piston chamber 7b are connected by an oil passage 34, and the oil passage 34 is also connected to the right pressure chamber 8f of the hydraulic actuator 8.

The speed-sensitive actuator 20 displaces the rod 75a according to the vehicle speed V, and the piston 20b is slidably fitted in the valve body 20a.
0a and the lower end surface of the piston 20b in the drawing define a spring chamber, and the spring chamber is further partitioned into a lower spring chamber 20h and an upper spring chamber 20i by an annular partition wall 20c. The rod 75a is loosely fitted in the lower spring chamber 20h, and the partition wall 20c
The spring receiver 20d whose upward movement is restricted by the above and the spring 20e which presses the spring receiver 20d toward the partition wall 20c are housed. The upper spring chamber 20i has one end pressing the spring receiver 20d and the other end. A spring 20f for pressing the piston 20b is housed therein. The valve body 20a has a piston 20b.
A pressure chamber 20g defined by the upper end surface of the is formed.

The oil passage 1 is provided in the pressure chamber 20g of the speed sensitive actuator 20.
5 is connected to one end, and the other end of the oil passage 15 is connected to the oil pump 1
6 port 16a. The oil pump 16 is a bidirectional variable displacement pump and is driven by a transmission output shaft, a differential gear case, and the like as a drive source. Port 16b of oil pump 16
Is connected to an oil filter 18a in an oil tank 18 via an oil passage 17. A circulating oil passage 17a is branched from the middle of the oil passage 17, and the oil passage 17a is connected to the oil passage 15. A check valve 17b is arranged in the middle of the oil passage 17a. The check valve 17b is provided on the oil passage 1 on the port 16a side of the pump 16 via the oil passage 17a.
Only allow the flow of hydraulic oil flowing into No. 5.

From the middle of the oil passage 15, oil passages 15a and 15c respectively communicating with the oil tank 18 are branched and connected, and a relief valve 15b is arranged in the oil passage 15a, and an operating hydraulic pressure discharged from the oil pump 16 to the oil passage 15 is provided. Is specified below a predetermined value. An orifice 15d is provided in the oil passage 15c, and a part of the hydraulic oil discharged from the oil pump 16 to the port 16a side is supplied to the oil tank 18 through the orifice 15d.
Returned to.

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

The oil pump 6 is driven by the engine E and generates a predetermined hydraulic pressure as long as the engine E is operating. The servo valve 4 regulates the operating hydraulic pressure supplied from the oil pump 6 according to the relative displacement amount of the valve body 40 and the spool 41, and supplies this to the left and right pressure chambers 2c and 2d of the power cylinder 2. More specifically, when the hydraulic actuator 8 is held in the neutral state, the relative displacement amount between the valve body 40 of the servo valve 4 and the spool 41 becomes 0, which is in the neutral state.
The hydraulic pressure supplied to the left pressure chamber 2c of the power cylinder 2 via c and the hydraulic pressure supplied from the port 4a to the right pressure chamber 2d via the port 4d become substantially equal, and the power cylinder 2 is also in a neutral state. The steering angle of the rear wheels 1 is 0, that is, the rear wheels 1 are held in the neutral state.

Next, the piston 8a of the hydraulic actuator 8 moves to the left,
When the spool 41 of the servo valve 4 is displaced leftward with respect to the valve body 40, hydraulic oil easily flows between the ports 4d and 4b, and the hydraulic pressure in the right pressure chamber 2d of the power cylinder 2 decreases, while the port 4a And the flow of hydraulic oil between the ports 4b and 4c and 4b is restricted, and the hydraulic oil easily flows between the ports 4a and 4c,
The hydraulic pressure of the left pressure chamber 2c of the power cylinder 2 rises, and the differential pressure corresponding to the relative displacement amount of the spool 41 and the valve body 40 acts on the piston 2a, the piston 2a moves right, and the tie rod 2b moves. The right trailing arm 1a is pressed to steer the rear wheel 1 to the right. That is, the rear wheel 1 is steered to the right by the left movement of the piston 8a of the hydraulic actuator 8.

When the tie rod 2b is displaced to the right by the right movement of the piston 2a of the power cylinder 2, the arm 3 swings counterclockwise around the fulcrum 3a, and the valve body 40 of the servo valve 4 in the opposite direction to the rod 2b, that is, , Spool 41
Move in the same direction as was displaced. Therefore, the relative displacement amount between the spool 41 and the valve body 40 becomes small, and the pressure difference between the right pressure chamber 2d and the left pressure chamber 2c of the power cylinder 2 becomes small. Then, the piston 2a moves to a position where the spring force of the springs 2g and 2h compressed in the pressure chambers 2c and 2d and the differential pressure balance with each other, and is held at that position. The piston 2a is held at the equilibrium position corresponding to the position, and the rear wheel 1 is also held in the steering state.

Since the servo valve 4 is a displacement follow-up type, the rear wheel steering angle can be accurately controlled regardless of the road surface reaction force even if the road surface reaction force changes according to the road surface state or the running state.
That is, when the tie rod 2b is about to be displaced to a new equilibrium position due to a change in road surface reaction force, the arm 3 is rotated with this displacement, and the valve body 40 is moved in the direction opposite to the displacement direction of the tie rod 2b. And spool 41
Since the relative displacement amount is increased or decreased so as to correct the displacement of the tie rod 2b, the tie rod 2b is held at a position corresponding to the moving position of the spool 41 set by the hydraulic actuator 8.

Next, when the piston 8a of the hydraulic actuator 8 returns to the neutral position, the spool 41 of the servo valve 4 and the valve body 4
This means that relative displacement has occurred between the valve body 40 and the valve body 40 and the valve body 40 has moved to the right, and contrary to the above case, the operating hydraulic pressure supplied to the right pressure chamber 2d of the power cylinder 2 is the left pressure chamber 2c.
The hydraulic pressure is higher than the hydraulic pressure supplied to the piston 2a, and the piston 2a moves toward the neutral position. By the movement of the piston 2a, the valve body 40 of the servo valve 4 is displaced so as to follow the displacement of the spool 41, and the valve body 4
0 returns to the position where the relative displacement amount of the spool 41 and the valve body 40 becomes 0, that is, returns to the original neutral position, and when the valve body 40 returns to the neutral position, the piston 2 of the power cylinder 2
a, that is, the rear wheel 1 has also returned to the neutral position.

When the piston 8a of the hydraulic actuator 8 moves right and the spool 41 of the servo valve 4 also moves right, and the spool 41 is displaced rightward with respect to the valve body 40, hydraulic oil easily flows between the ports 4c and 4b. While the hydraulic pressure in the left pressure chamber 2c of the power cylinder 2 decreases, the flow of hydraulic oil between the ports 4a and 4b or between the ports 4d and 4b is restricted and the hydraulic oil flows between the ports 4a and 4d. The right pressure chamber 2d of the power cylinder 2 becomes easier.
The hydraulic pressure rises and a differential pressure corresponding to the relative displacement amount between the spool 41 and the valve body 40 acts on the piston 2a, the piston 2a moves left, and the tie rod 2b presses the left trailing arm 1a. Then, the rear wheel 1 is steered to the left. That is, the rear wheel 1 is steered to the left by the right movement of the piston 8a of the hydraulic actuator 8. The detailed operation of the valve body 40 and the like of the servo valve 4 at this time is performed by the piston 8 of the hydraulic actuator 8 described above.
Since it can be easily inferred from the description of the case where a moves to the left, the description thereof will be omitted.

The oil pump 16 is not driven when the vehicle is stopped, and does not generate operating hydraulic pressure in its ports 16a and 16b. However, when the vehicle starts, the oil pump 16 generates hydraulic pressure in accordance with the vehicle speed V in the port 16a, and this is applied to the speed-sensitive actuator. Two
Supply to the pressure chamber 20g of 0. When the vehicle is moving backward, the oil pump 16 rotates in the reverse direction to discharge the natural oil to the port 16b side, and the hydraulic oil is supplied to the oil passage 17a → check valve 17b → oil passage 15
→ The oil pump 16 → the oil passage 17a is circulated, and the working oil pressure is not substantially supplied to the pressure chamber 20g of the vehicle speed sensitive actuator 20.

The spring 20f housed in the upper spring chamber 20i of the speed sensitive actuator 20 is the spring 20 housed in the lower spring chamber 20h.
The spring constant is set to a value smaller than that of e. Therefore, the piston 20b moves to a position where the resultant force of the spring forces of the springs 20e and 20f and the hydraulic oil pressure of the pressure chamber 20g balance until the spring receiver 20d contacts the annular partition wall 20c. When the spring 20e expands and the spring receiver 20d abuts against the partition wall 20c as the operating oil pressure of the pressure chamber 20g decreases, the expansion of the spring 20e is prevented and the balance position is set to the spring 20e.
It is determined by the spring force of f and the hydraulic oil pressure. When the equilibrium position is determined by the spring force of the spring 20f and the hydraulic pressure of the pressure chamber 20a, compared to the case where the equilibrium position is determined by the resultant force of the spring forces of the springs 20e and 20f and the hydraulic oil pressure of the pressure chamber 20g. The piston 20b changes greatly even with a small change in the working oil pressure, and the piston 20b is displaced with a non-linear characteristic with respect to the change in the working oil pressure acting on the pressure chamber 20g. As a result, depending on the hydraulic pressure supplied to the pressure chamber 20g of the actuator 20,
That is, depending on the vehicle speed V, if the vehicle speed V is 0, the piston 20
b moves to the upper limit position, the piston 20b moves downward with a large displacement degree as the vehicle speed V increases, and the predetermined speed V
Upon reaching o, the piston 20b moves to the neutral position. When the vehicle speed V further increases and becomes higher than the predetermined speed Vo, the piston 20b moves further downward from the neutral position with a small displacement degree.

When the piston 20b is in the neutral position, the piston 74a
And 74b are also in the neutral state shown in FIG.
The left and right piston chambers 7a and 7b have the same capacity. When the piston 20b moves upward from the neutral position,
The rod 75a of the link mechanism 75 is pulled upward,
Along with the movement of the rod 75a, the rod 75b moves toward the spindle 7.
The rod 75c is pushed downward by swinging clockwise around 5d. As the rods 75a and 75c move, the piston 74a moves upward and the piston 74b moves downward, and the piston chamber 7a increases its capacity by the stroke amount of the pistons 74a and 75b.
b will be reduced. On the contrary, when the piston 20b moves downward from the neutral position, the rod 75a of the link mechanism 75 is pushed downward, and with the movement of the rod 75a, the rod 75b swings counterclockwise around the support shaft 75d. By moving, the rod 75c is pulled upward. As the rods 75a and 75c move, the piston 74a moves downward and the piston 74b moves upward, so that the piston chamber 7a decreases its capacity and the piston 7b increases by the stroke amount of the pistons 74a and 75b. Become.

When the steering wheel 11 is in the neutral position, the third
As shown, the pistons 71 and 72 are also in the neutral position.
In this state, even if the vehicle speed sensitive actuator 20 moves the piston 20b upward or downward according to the vehicle speed V, substantially no hydraulic oil is output to the oil passages 32 and 34. That is, assuming that the piston 20b of the actuator 20 is pushed downward and the capacity of the piston chamber 7a decreases and the capacity of the piston chamber 7b increases, for example, the left pressure chamber 7A and the right pressure chamber 7B of the piston chamber 7a are increased. The hydraulic oil is discharged by the amount of decrease in the volume, but the piston chamber 7b
The left pressure chamber 7C and the right pressure chamber 7D have a capacity of the piston chamber 7
Since the volumes of the left pressure chamber 7A and the right pressure chamber 7B of a are increased by the same amount as the volume is reduced, all the hydraulic oil discharged from the left pressure chamber 7A and the right pressure chamber 7B passes through the oil passages 32 and 34. Will be sucked into the right pressure chamber 7D and the left pressure chamber 7C. Therefore, the piston 8a of the hydraulic actuator 8
Is held in the neutral position, and the rear wheel 1 is also held in the neutral position.

Next, when the vehicle speed V is lower than the predetermined speed Vo and the piston 20b of the actuator 20 is displaced upward from its neutral position, the piston 74a is displaced upward while the piston 74b is displaced downward as shown in FIG. And the capacity of the piston chamber 7a is larger than the capacity of the piston chamber 7b. When the steering wheel 11 is rotated to the left in this state, the pistons 71 and 72 move to the right, and a part of the hydraulic oil removed by the piston 71 from the right pressure chamber 7B is in the oil passage.
Although it is sucked into the left pressure chamber 7C via 34, the left pressure chamber 7C
The remaining hydraulic oil that could not be sucked is supplied to the right pressure chamber 8f of the hydraulic actuator 8 via the oil passage 34. On the other hand, the amount of hydraulic oil sucked by the left pressure chamber 7A due to the movement of the piston 71 is insufficient only by the amount of hydraulic oil removed from the right pressure chamber 7D by the piston 72, and the insufficient amount of hydraulic oil is the left pressure chamber of the hydraulic actuator 8. It is covered by the hydraulic oil removed from 8e. Therefore, the piston 8a of the hydraulic actuator 8 moves to the left, and the left movement of the piston 8a causes the rear wheel 1 to be steered in the right direction opposite to the steering wheel 11, that is, in the opposite phase to the front wheel, as described above. Become.

On the contrary, when the steering wheel 11 is rotated to the right, the pistons 71 and 72 of the hydraulic control valve device 7 are moved to the left contrary to the above, and the hydraulic oil is transferred from the left pressure chamber 7A to the left pressure chamber 8e of the hydraulic actuator 8. The hydraulic oil supplied and removed from the right pressure chamber 8f of the hydraulic actuator 8 is sucked into the right pressure chamber 7B. As a result, the piston 8a of the hydraulic actuator 8 moves to the right, and as a result of this right movement of the piston 8a, the rear wheel 1 is steered in the left direction opposite to the steering wheel 11, that is, in the opposite phase to the front wheel. become.

It should be noted that the more the piston 20b of the vehicle speed sensitive actuator 20 is displaced above the neutral position, that is, the lower the vehicle speed is, and the larger the steering wheel 11 is cut, the more the hydraulic control valve device 7 is discharged. As a result, the amount of hydraulic oil is increased, and the rear wheels 1 are steered at a larger steering angle.

Next, when the vehicle speed V is higher than the predetermined speed Vo and the piston 20b of the actuator 20 is displaced downward from its neutral position, the piston 74a is displaced downward while the piston 74b is displaced upward as shown in FIG. And the capacity of the piston chamber 7a is smaller than the capacity of the piston chamber 7b. When the steering wheel 11 is rotated to the left in this state, the pistons 71 and 72 are moved to the right, hydraulic oil is supplied from the right pressure chamber 7D to the left pressure chamber 8e of the hydraulic actuator 8, and the right pressure chamber 8f of the hydraulic actuator 8 is supplied. The hydraulic oil removed from the above is sucked into the left pressure chamber 7C. As a result, the piston 8a of the hydraulic actuator 8 moves to the right,
By the right movement of the piston 8a, the rear wheel 1 is steered to the left in the same direction as the steering wheel 11, that is, in the same phase as the front wheel, as described above.

On the contrary, when the steering wheel 11 is rotated to the right, the pistons 71 and 72 of the hydraulic control valve device 7 are moved to the left contrary to the above, and the right pressure of the hydraulic actuator 8 is moved from the left pressure chamber 7C via the oil passage 34. The hydraulic oil is supplied to the chamber 8f, and the hydraulic oil removed from the left pressure chamber 8e of the hydraulic actuator 8 is sucked into the right pressure chamber 7D via the oil passage 32. As a result,
The piston 8a of the hydraulic actuator 8 moves to the left, and the left movement of the piston 8a causes the rear wheel 1 to be steered to the right in the same direction as the steering wheel 11, that is, in the same phase as the front wheel.

It should be noted that the more the piston 20b of the vehicle speed sensitive actuator 20 is displaced below the neutral position, that is, the higher the vehicle speed is, and the larger the cutting angle of the steering wheel 11 is, the discharge is performed from the hydraulic control valve device 7. As a result, the amount of hydraulic oil is increased, and the rear wheels 1 are steered at a larger steering angle.

When the vehicle speed V is the predetermined speed Vo, as described above,
The pistons 74a and 74b of the hydraulic control valve device 7 have moved to the neutral position shown in FIG.
The capacities of b are equal, and in such a case, even if the steering wheel 11 is rotated in either the left or right direction, the total amount of hydraulic oil is between the left pressure chamber 7A and the right pressure chamber 7D and between the right pressure chamber 7B.
The amount of hydraulic oil supplied to the hydraulic actuator 8 does not change only by moving between the left pressure chamber 7C and the left pressure chamber 7C. Therefore, the hydraulic actuator 8 remains in the neutral state, and the rear wheel 1 is also held in the neutral position.

In the above-mentioned embodiment, the piston chambers 7a and 7b are arranged in series, and the pistons 71 and 72 are also connected in series by the rod 73b. However, the present invention is not limited to this, and the piston chambers 7a and 7b are connected to each other. The pistons 71 and 72 may be arranged in parallel so as to be interlocked with each other and moved by separate rods.
When the capacity of A is increased and the capacity of the pressure chamber 7B is decreased, the piston 72 moves in the direction of increasing the capacity of the pressure chamber 7C and the capacity of the pressure chamber 7D is decreased, and the piston 71 is pressed. When the volume of the chamber 7A is reduced and the volume of the pressure chamber 7B is increased, the piston 72 is configured to reduce the volume of the pressure chamber 7C and increase the volume of the pressure chamber 7D. Good.

In addition, in the above-described embodiment, the speed sensitive actuator 2
The piston 20b of 0 needs to be accurately displaced by a predetermined amount according to the vehicle speed V, and the displacement amount of the piston 20b of the actuator 20, for example, the vertical movement amount of the rod 75c is constantly monitored by the position sensor 65, When the amount of displacement detected by the position sensor 65 is outside the allowable error range as compared with the value corresponding to the vehicle speed detection value V, it is desirable to take necessary necessary post-treatment. As a post-treatment, for example, the oil passage 22
And the oil passage 26 are connected by an oil passage 69, and a normally open type electromagnetic cutoff valve 68 is arranged in this oil passage 69. A solenoid 68a of the electromagnetic cutoff valve 68 is electrically connected to the output side of the controller 66. Keep connected. Then, during normal operation, the controller 66 supplies an energizing signal to the solenoid 68a to maintain the electromagnetic shutoff valve 68 in the closed state (the state in which the oil passage 69 is shut off), and the input vehicle speed signal V and the position sensor 65 detect it. Piston 2
When the displacement amount of 0b is out of the allowable error range, the solenoid 68a is deenergized to open the electromagnetic cutoff valve 68, and the working oil discharged from the oil pump 6 is passed through the electromagnetic cutoff valve 68 to the oil passage 26. It is desirable that the rear wheel 1 is kept in a neutral state by releasing the hydraulic oil to the servo valve 4 to shut off the supply of the hydraulic oil to the servo valve 4 to deactivate the servo valve 4 and the power cylinder 2.

Alternatively, the solenoid 68a of the electromagnetic shutoff valve 68 may be deenergized when the vehicle is moving backward to deactivate the servo valve 4 and the power cylinder 2 and keep the rear wheel 1 in a neutral state.

Furthermore, the steering angle of the rear wheel 1 is controlled by the turning angle (steering wheel angle) of the steering wheel 11 and the vehicle speed V, but the steering control of the rear wheel 1 is not limited to these parameters, and other parameters in addition to these parameters May be additionally controlled by. When additional control is performed using other parameters, for example, as shown by a virtual line in FIG. 1, the right end surface of the piston 8a of the hydraulic actuator 8 is connected to the rear wheel control addition mechanism 47 via the rod 45, The rear wheel connection adding mechanism 47 presses the piston 8a of the hydraulic actuator 8 in accordance with parameter values such as yaw rate, braking / driving force, and steering wheel angular velocity to move the balanced position of the piston 8a to change the rear wheel steering angle. It may be controlled.

(Effect of the Invention) As described in detail above, according to the four-wheel steering system of the present invention, a hydraulic actuator for steering the rear wheels and a hydraulic control valve device for controlling the supply of hydraulic oil to the hydraulic actuator. The hydraulic control valve device includes a first and a second variable capacity piston chambers, a piston mechanism for changing the capacities of these piston chambers in conjunction with each other according to the vehicle speed, and a slide mechanism for each of the piston chambers. The first piston and the second piston chamber, which are movably and liquid-tightly fitted and partition the first piston chamber into a first pressure chamber and a second pressure chamber, are provided with a third pressure chamber and a third pressure chamber. A second piston that is divided into four pressure chambers, a first oil passage that connects the first pressure chamber and the fourth pressure chamber, and that is also connected to the hydraulic actuator, and a second pressure chamber. A second oil passage connected to the third pressure chamber and connected to the hydraulic actuator,
And the second piston changes the piston area respectively with the change in the volume of the corresponding piston chamber, and the first piston increases the volume of the first pressure chamber and decreases the volume of the second pressure chamber. The second piston increases the capacity of the third pressure chamber and decreases the capacity of the fourth pressure chamber, the first piston moves the capacity of the first pressure chamber. When the second piston moves in a direction of decreasing the volume of the second pressure chamber and increasing the capacity of the second pressure chamber, the second piston moves in a direction of decreasing the capacity of the third pressure chamber and increasing the capacity of the fourth pressure chamber, Since the first and second pistons are configured to move in association with each other according to the steering wheel angle, the rear wheels are steered in the opposite phase or the same phase with respect to the front wheels according to the vehicle speed, and the vehicle speed and the steering wheel are rotated. The steering ratio of the front and rear wheels is controlled according to the angle. It can be made to a circuit which performs the steering angle ratio control in all hydraulic control circuit, high reliability without fear of malfunction due to interference or the like different from those of the electronic control is obtained. Further, as compared with the case where the steering ratio control is performed by the pure mechanical link mechanism, the structure is simple, the size can be reduced, and the control freedom is high, which is an excellent effect.

[Brief description of drawings]

FIG. 1 shows an embodiment of a four-wheel steering system according to the present invention,
FIG. 2 is a hydraulic circuit diagram showing the circuit configuration of the device, FIG. 2 is a sectional view taken along the line II-II shown in FIG. 1, and FIGS. 3 to 5 are operation explanatory views of the hydraulic control valve device 7. 1 ... rear wheel, 2 ... power cylinder, 4 ... servo valve, 6
... oil pump, 7 ... hydraulic control valve device, 7A ... left pressure chamber (first pressure chamber), 7B ... right pressure chamber (second pressure chamber),
7C ... left pressure chamber (third pressure chamber), 7D ... right pressure chamber (fourth pressure chamber), 7a ... piston chamber, 7b ... piston chamber,
20 ... Vehicle speed sensitive actuator, 8 ... Hydraulic actuator, 32, 34 ... Oil passage, 71 ... Piston (first piston), 72 ... Piston (second piston), 75 ... Link mechanism.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-85063 (JP, A) JP-A-62-71759 (JP, A) JP-A-60-94870 (JP, A) Actual development Sho--60- 45266 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A hydraulic operating device for steering a rear wheel, and a hydraulic control valve device for controlling supply of hydraulic oil to the hydraulic operating device, wherein the hydraulic control valve device comprises first and second variable displacements. A piston chamber, a piston mechanism for changing the capacity of each of the piston chambers in accordance with the vehicle speed, and a piston mechanism slidably and liquid-tightly fitted in each of the piston chambers. A first piston for partitioning the chamber into a first pressure chamber and a second pressure chamber and the second piston chamber for a third chamber
Second piston that divides the second pressure chamber and the fourth pressure chamber, and a first oil passage that connects the first pressure chamber and the fourth pressure chamber and is connected to the hydraulic actuator. , A second oil passage that connects the second pressure chamber and the third pressure chamber and is connected to the hydraulic operating device.
And the second piston changes the piston area with the change in the volume of the corresponding piston chamber, and the first piston increases the volume of the first pressure chamber,
When moving in the direction of decreasing the capacity of the pressure chamber of
The piston moves in a direction to increase the capacity of the third pressure chamber and decrease the capacity of the fourth pressure chamber, and the first piston decreases the capacity of the first pressure chamber, When the second piston moves in the direction of increasing the capacity of the second pressure chamber, the second piston moves in the direction of decreasing the capacity of the third pressure chamber and increases the capacity of the fourth pressure chamber, and A four-wheel steering system in which the first and second pistons move in conjunction with each other according to the steering wheel angle.