JPH05254452A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To hold the steering angle of a rear wheel by providing a double cut valve wherein a first cut valve is put in connection between the ports on one side of a front power cylinder and that of a peer steering valve and a second cut valve is put in connection between the ports on respective other sides thereof. CONSTITUTION:In rightward turning of a wheel, an oil pressure in the left chamber FL of a front power cylinder 3 is fed through an oil passage 63 to a power cylinder 42 on the left side of a rear power cylinder 40. A piston 48 is pressed to the right against the spring force of a spring 54, and along with the rightward press of the piston, rear wheels RW is leftward steered in a reverse direction to front wheels FW. The power cylinder 42 is moved along with displacement of the front power cylinder 3. In this case, the left chamber FL of the front power cylinder 3 is closed, whereby the power cylinder 42 is prevented from being pushed back through the spring reaction force of the spring 54 and a steering angle can be maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel steering system,
In particular, the present invention relates to an all-hydraulic large steering angle reverse phase four-wheel steering system.

[0002]

2. Description of the Related Art A four-wheel steering (4WS) function provides a rear wheel with a steering angle in phase with or in the opposite phase of the front wheels in response to the steering angle of the front wheels and in synchronization with the front wheels to reduce the minimum turning radius. Therefore, it has been adopted for work vehicles that frequently enter into narrow alleys or turn in narrow places, but in recent years it has also been adopted for passenger cars.

As a four-wheel steering system, for example, there is an all-hydraulic large steering angle reverse-phase four-wheel steering system as shown in FIG. This four-wheel steering system includes a power staying valve 2 that operates according to a steering angle of a steering wheel 1, a front power cylinder 3 that is driven by the power staying valve 2 to give a steering angle to a front wheel FW, and a rear wheel RW. It is driven by a rear power cylinder 4 that gives a steering angle, return springs 5 and 6 built in the left and right oil chambers FL and FR of the rear power cylinder 4, and a rack 7 that operates in conjunction with the power steering valve 2. It comprises a cut valve 8 that opens and closes and controls the hydraulic pressure to the rear power cylinder 4, an oil pump P, a reservoir tank T, and the like.

Then, the front power cylinder 3 and the rear power cylinder 4 are connected in series by closing the cut valve 8 at a certain steering angle or more by the movement of the rack 7, and the front power cylinder 3 and the rear power cylinder 4 are connected at a pressure receiving area ratio of both cylinders. The cylinder 3 and the rear power cylinder 4 move in a certain proportional relationship to steer the front wheels FW and the rear wheels RW. That is, when traveling straight ahead, the cut valve 8 is opened as shown in FIG. 1, and the front power cylinder 3 and the rear power cylinder 8 are held at the neutral position. When the steering wheel 1 is turned to the right, the cut valve 8 is closed as shown in FIG. 2, hydraulic pressure is supplied from the power steering valve 2 to the right chamber FR of the front power cylinder 3, and the power cylinder 3 moves to the left to move the front wheels. The FW is steered to the right and the left ventricle FL
Of the rear power cylinder 4 flows into the left chamber RL of the rear power cylinder 4 to move the rear power cylinder 4 to the right against the spring force of the return spring 6 in the right chamber RR, and the rear wheel RW is moved to the front wheel F.
Steer to the left opposite to W. At this time, the hydraulic pressure in the right chamber RR is returned to the tank T via the power steering valve 2.

When the steering wheel 1 is turned to the left, the cut valve 8 is closed as shown in FIG.
Hydraulic pressure is supplied to the right chamber RR of the rear power cylinder 4 from
The rear power cylinder 4 is moved to the left against the spring force of the return spring 5 in the left chamber RL, the rear wheel RW is steered to the right, and the hydraulic pressure in the left chamber RL is left to the left of the front power cylinder 3. It flows into the room FL and steers the front wheels FW to the left in the opposite direction to the rear wheels RW. At this time, the hydraulic pressure in the right chamber FR is
It is returned to the tank T via the power steering valve 2.

[0006]

By the way, in the above-described four-wheel steering system, when the vehicle is turned to the right as shown in FIG. 2, even if the hydraulic pressure in the left chamber RL on the cutting side of the rear power cylinder 4 is reduced, the left side of the front power cylinder 3 is left. Because the chamber FL is closed,
It is not pushed back by the spring reaction force F of the spring 6 of the right chamber RR of the rear par cylinder 4, so the rear wheel steering angle is held at the right turning position.

On the other hand, in the case of the left turn shown in FIG. 3, the hydraulic pressure in the right chamber RR of the rear power cylinder 4 is high at the time of turning, and the rear wheel RW is steered to the right as shown by the solid line. However, when the hydraulic pressure in the right chamber RR on the notch side of the rear power cylinder 4 decreases, the rear power cylinder 4 is neutral as indicated by the dotted line because there is no hydraulic pressure for receiving the spring reaction force F of the spring 5 in the left chamber RL. There is a problem that the steering angle of the rear wheels is returned to the neutral position by being pushed back to the position, the steering position is not maintained, and a complete steering angle proportional system is not achieved.

The present invention has been made in view of the above points, and enables hydraulic circuits from the power steering valve to each of the front and rear power cylinders to be independently turned on and off, and the power steering of the rear power cylinder is also possible. An object of the present invention is to provide a four-wheel steering device that prevents the cylinder from returning to the neutral position due to a decrease in pressure and maintains the steering angle of the rear wheels.

[0009]

To achieve the above object, according to the present invention, a left cylinder for turning the rear wheels to the left, a right cylinder for turning the rear wheels to the right, and each of these cylinders are returned to the neutral position. A front power cylinder in which a spring for driving the left cylinder and a spring for moving the piston of the right cylinder to the right and a port for moving the piston of the right cylinder to the left are steered to accommodate the front wheels. In the left and right chambers of the vehicle, the other side ports are connected to the respective ports of the power steering valve, the rear power cylinder, and the rack of the steering mechanism. A first cut valve that is closed when steering to the other side and a second cut valve that is closed when steering to the other side are integrally housed, and the first cut valve is the front cut valve. The second cut valve includes a double cut valve connected between the work cylinder and each port of the power steering valve, and the second cut valve connected between the front power cylinder and the other port of the power steering valve, respectively. It has a different configuration.

[0010]

When the vehicle runs straight, the two cut valves of the double cut valve are both open, the rear power cylinder does not operate, and only the front power steering functions. When the steering angle of the front wheels exceeds a certain steering angle, the cut valve on the corresponding side is closed by the rack, and the front power cylinder and the rear power cylinder on the corresponding side are placed in series, and depending on the displacement of the front power cylinder. The rear power cylinder is displaced, and reverse phase steering is performed at a large steering angle. Since the rear power cylinders are left and right independent double piston power cylinders, even if the power steering pressure is released, the racks are not displaced unless they are displaced, and the rear wheels are held at the steered positions corresponding to the front wheels.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 4 shows a cut valve applied to the four-wheel steering system of the present invention. The cut valve 10 is a double cut valve, and one surface of the body 11 has two holes 11a and 11a.
b are arranged side by side, and holes 11c are formed on the bottom side of these holes 11a and 11b so as to be orthogonal to these holes 11a and 11b. And the holes 11a, 11 of the body 11
Cut valves 12 and 13 are housed in b, and one end of a control shaft 14 is fitted in a hole 11c so as to be liquid-tight and rotatable. The cut valves 12 and 13 are formed in the same shape, and one cut valve 12 will be described below for convenience of description.

A small hole 11 is formed on the bottom surface of the hole 11a of the body 11.
d is bored concentrically, and the hole 11d is
It is opened on the inner surface of c. Further, ports A ₁ and A ₂ are opened at the lower and upper positions of the side surface of the hole 11a, respectively. The valve 1 is inserted into the hole 11a through the spacer 15.
6 is fitted in a liquid-tight manner. The plug 17 is screwed to the opening end of the hole 11a, the lower end of which abuts the upper end of the valve 16 to fix the valve 16, and the upper end of the plug 17 projects from the hole 11a and is screwed through an O-ring, a washer, and a spring washer. It is fixed to the body 11 in a liquid-tight manner by the combined nut 18.

The valve 16 has ports A _{1 of} the holes 11a,
A lower portion and an upper portion corresponding to A ₂ have a slightly smaller diameter, and holes 16 a and 16 b are formed on each side surface so as to communicate with the ports A ₁ and A ₂ . This valve 16 has an O
It is fitted into the hole 11a in a liquid-tight manner via a ring, and the ports A ₁ and A ₂ are blocked. A spool 20 is built in the valve 16 so as to be movable in the axial direction. The pin 21 penetrating the hole of the spacer 15 with a slight gap in the small hole 11d is liquid-tight through the O-ring,
In addition, it is slidably inserted in the axial direction.

The upper portion of the pin 21 has a slightly smaller diameter to form a step, and the lower end surface thereof is a concave surface having a substantially hemispherical shape. A spring seat 22 is fitted on the small-diameter upper portion of the pin 21, and a spring 23 is contracted between the spring seat 22 and the spool 20. A tip of the spool 20 can be projected upward from a hole at an upper end of the valve 16, and is in contact with one end of a spring seat 24 housed in the plug 17. A spring 25 is contracted between the other end surface of the spring seat 24 and the opposite end surface of the plug 17. The spring force of the spring 25 is set to be slightly stronger than the spring force of the spring 23.

On the outer peripheral surface of the control shaft 14, a V groove 14a having a predetermined length is formed along the circumferential direction at a position corresponding to the lower end surface of the pin 22.
A ball 26 is interposed between the lower end surface of the V groove and the V groove. In the control shaft 14, the ball 26 has the V groove 1
4a, the cut valve 12 is opened, and when the ball 26 is pushed up from the V groove 14a with the rotation, the spring 23 is compressed via the pin 21 and the spring 25
The spool 20 is moved against the spring force to close the valve.

The cut valve 13 is also constructed similarly to the cut valve 12, and the control shaft 14 is formed with a V groove 14b for opening and closing the cut valve 13. Then, the groove 1 of the control shaft 14
As shown in FIG. 5, 4a and 14b are formed symmetrically with respect to the neutral position in the rotational direction. Cut valve 1
2 ports Port A ₁ and A ₂ and corresponding cut valve 1
The respective ports of 3 are designated as B ₁ and B ₂ , respectively.

The base ends of brackets 27, 27 are fixed to the other end of the control shaft 14, and rollers 28 are rotatably supported at the tips of the brackets 27, 27 so as to be rotatable in parallel with the control shaft 14. Has been done. The roller 28 is in contact with a cam surface 30a formed on the rack 30 of the steering mechanism as shown in FIG. The cam surface 30a is formed by cutting out the central outer peripheral surface of the rack 30 along the axial direction over a predetermined length.

On the side opposite to the cam surface 30a of the rack 30, the teeth 30 are provided at a predetermined pitch over a predetermined length along the longitudinal direction.
b is engraved, and the pinion PG of the power steering valve 2 is meshed with the tooth 30b. As shown in FIG. 10, one end of the rack 30 has one front wheel FW.
, And the other end is connected to one end of the piston rod of the front power cylinder 3, and the other end of the piston rod is connected to the arm of the front wheel FW on the other side.

FIG. 7 shows a rear power cylinder. The rear power cylinder 40 is a double piston power cylinder in which two power cylinders 41 and 42 and a spring chamber 43 are integrally connected along a rod 45. The right power cylinder 41 is a cylinder for turning to the right, and the power cylinder 42 on the left is a cylinder for turning to the left. Further, the oil chamber on the left side of the power cylinder 42 and the spring chamber 43 are communicated with each other.

Disc-shaped stoppers 50 and 51 are fixed to a portion of the rod 45 located in the spring chamber 43 with a predetermined space therebetween, and a large-diameter spring is provided between the stoppers 50 and 51. Seats 52 and 53 are slidably interposed in the axial direction, and a spring 54 is contracted between the spring seats 52 and 53. In addition, the spring chamber 4
Annular stoppers 55 and 56 are provided on the inner surface of 3 to restrict the movement of the spring seats 52 and 53.

Ports 40a and 40b are provided on both left and right sides of the power cylinder 41, and ports 40c and 40d are provided on the right side of the power cylinder 42 and substantially in the center of the spring chamber 43. Further, both ends of the piston rod 45 are connected to the arms of the left and right rear wheels RW, respectively. The double cut valve 10 and the rear power cylinder 40 are connected as shown in FIG. In the figure, the ports 2a and 2b of the power steering valve 2 are connected to the oil pump P and the reserve tank T, and the ports 2c and 2d are connected to the ports 40c and 40b of the rear power cylinder 40 via oil passages 60 and 61, respectively. The port of the right chamber FR of the front power cylinder 3 is connected to the port 40a of the rear power cylinder 40 via the oil passage 62, and the port of the left chamber FL is
Port 40d of rear power sillin 40 via oil passage 63
Connected to.

In the double cut valve 10, the port A ₁ of the cut valve 12 on one side is connected to the middle of the oil passage 63 and the port A ₂ is connected to the middle of the oil passage 60, and the cut valve 13 on the other side is connected. Port B ₁ of the
₂ are connected in the middle of the oil passage 61, respectively. The operation will be described below.

First, the operation of the cut valve 10 will be described. When the steering wheel 1 is in the neutral position, the rack 30 is in the neutral position as shown in FIG. 8A, and the roller 28 of the control shaft 14 of the double cut valve 10 is located at the center of the cam 30a of the rack 30. ing. The cut valve 10 is in the state shown in FIG.
a and 14b are at the positions shown in FIGS. 5A and 5B, respectively.
The cut valves 12 and 13 are open. Therefore, when traveling straight ahead, the rear power cylinder 40 does not operate and only the front power cylinder 3 functions.

When the steering wheel is cut to the right, for example, the rack 30 moves to the right as shown in FIG. 8 (b), and the steering wheel 1 is steered to a predetermined steering angle or more. The cam 30a rotates the control shaft 14 clockwise in the drawing. When the control shaft 14 rotates in the clockwise direction, the ball 26 of the cut valve 12 is pushed out from the V groove 14a as shown in FIG. 9, the pin 21 is pushed up accordingly, the spring 23 is compressed, and the spool 20 is rotated. Spring 25
It is pushed up against the spring force of and closes the valve. On the other hand, the ball of the cut valve 13 is in the V groove 14b of the control shaft 14 and is kept open.

When the steering wheel 1 is turned to the left and the steering angle exceeds a predetermined steering angle, the cut valve 13 is closed contrary to the above. Then, the cut valve 12 is held in the open state. When the steering angle by the steering wheel becomes equal to or larger than the predetermined steering angle in this way, the corresponding one cut valve is closed and the other valve is held in the open state.

Next, the operation of the four-wheel steering system will be described with reference to FIGS. When the steering wheel 1 is in the neutral position, as shown in FIG. 10, the cut valves 12 and 13 of the double cut valve 10 are opened, and the oil passages 61 and 62 and the oil passages 60 and 63 are in communication with each other. The front power cylinder 3 and the rear power cylinder 40 are respectively held in neutral positions, and the front wheels FW and the rear wheels RW are held in neutral positions.

When the steering wheel 1 is turned to the right, that is, when the steering wheel 1 is turned to the right and steered at a predetermined steering angle or more, FIG.
As shown in FIG. 2, the double cut valve 10 has the cut valve 12 closed, the power steering valve 2 and the oil passage 6
Hydraulic pressure is supplied from 1 to the right chamber FR of the front power cylinder 3 through the cut valve 13. As a result, the piston of the front power cylinder 3 is pushed to the left, and the front wheels FW are steered to the right.

The hydraulic pressure in the left chamber FL of the front power cylinder 3 is supplied to the power cylinder 42 on the left side of the rear power cylinder 40 through the oil passage 63, and the piston 48 pushes rightward against the spring force of the spring 54. As a result, the rear wheels RW are steered leftward in the opposite direction to the front wheels FW. Then, the power cylinder 42 moves according to the displacement of the front power cylinder 3. At this time, since the left chamber FL of the front power cylinder 3 is closed, the power cylinder 42 is not pushed back by the spring reaction force of the spring 54, and the steered angle is maintained.

When turning to the left, that is, when the steering wheel 1 is turned to the left and steered at a predetermined steering angle or more, FIG.
As shown in FIG. 5, the double cut valve 10 has the cut valve 13 closed, the power steering valve 2 and the oil passage 6.
From 0, hydraulic pressure is supplied to the left chamber FL of the front power cylinder 3 through the cut valve 12. As a result, the piston of the front power cylinder 3 is pushed to the right, and the front wheels FW are steered to the left.

The hydraulic pressure in the right chamber FR of the front power cylinder 3 is supplied to the power cylinder 41 on the right side of the rear power cylinder 40 through the oil passage 62, and the piston 47 pushes to the left against the spring force of the spring 54. Driven, rear wheel R
W is steered to the right, which is the opposite direction to the front wheel FW. And
The power cylinder 41 moves according to the displacement of the front power cylinder 3.

At this time, since the right chamber FR of the front power cylinder 3 is closed, even if the hydraulic pressure on the cutting side is lowered, it is not pushed back by the spring reaction force of the spring 54 and the turning angle is maintained. That is, when the rear power cylinder 40 is steered in either left or right direction,
The oil chamber that is pushed back by the spring force of the spring 54 is communicated with the oil chamber that is closed on the front power cylinder 3. Therefore, even if the hydraulic pressure on the cut side decreases, the oil chamber does not push back due to the spring force of the spring. Held in rudder position. In this way, in proportion to the steering angle,
At the time of a large steering angle, the rear wheels RW are steered in an opposite phase to the front wheels FW and are held at the steered positions.

FIG. 13 shows the steering characteristics of the rear wheels RW. When the steering angle of the front wheels FW becomes equal to or greater than a predetermined steering angle θ _R or θ _L , the rear wheels RW are steered in a phase opposite to that of the front wheels FW. And the steering angle θ
_R indicates the operating point of the cut valve 12, and the steering angle θ _L indicates the operating point of the cut valve 13. By changing the steering angle characteristic of the rear wheels according to the operating point of the cut valve and the pressure receiving area ratio of the pistons of the front power cylinder 3 and the rear power cylinder 40, not only the reverse phase control at the time of the large steering angle described above is performed. It is also possible to form an in-phase / opposite-phase system by converting the movement of the rear power cylinder 40 by, for example, a cam.

[0033]

As described above, according to the present invention, the rear power cylinder can be held in the steered position even when the hydraulic pressure on the cutting side of the steering wheel is reduced, and a complete steering angle proportional system can be provided. It is possible to configure the structure, and there is an effect that the steerability is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a vehicle steering mechanism to which a conventional four-wheel steering device is applied.

FIG. 2 is a diagram showing an operation of the steering mechanism of FIG. 1 when turning to the right.

FIG. 3 is a diagram showing an operation of the steering mechanism of FIG. 1 when turning to the left.

FIG. 4 is a cross-sectional view showing an embodiment of a double cut valve applied to the four-wheel steering system of the present invention.

5 is a cross-sectional view of the control shaft of FIG.

FIG. 6 is an assembled perspective view showing the relationship between the double cut valve and the rack of FIG.

FIG. 7 is a cross-sectional view showing an embodiment of a rear power cylinder applied to the four-wheel steering system of the present invention.

8 is a diagram showing a relationship between the rack and the control shaft shown in FIG.

9 is a diagram showing the relationship between the rack and the cut valve of FIG.

FIG. 10 is a configuration diagram of a vehicle steering mechanism to which the four-wheel steering system according to the present invention is applied.

FIG. 11 is a diagram showing an operation of the steering mechanism of FIG. 10 when turning to the right.

FIG. 12 is a diagram showing an operation of the steering mechanism of FIG. 10 when turning to the left.

13 is a characteristic diagram showing steering characteristics of rear wheels of the steering mechanism of FIG.

[Explanation of symbols]

 1 Steering Wheel 2 Power Steering Valve 3 Front Power Cylinder 10 Double Cut Valve 11 Body 12, 13 Cut Valve 14 Control Shaft 30 Rack 40 Rear Power Cylinder 41, 42 Power Cylinder 43 Spring Chamber 45 Rod 54 Spring FW Front Wheel RW Rear Wheel P Oil Pump T Reservoir tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Masuda No. 1 Nakashiniri, Hashime-cho, Okazaki City, Aichi Prefecture Mitsubishi Motors Engineering Co., Ltd. Okazaki Plant

Claims (1)

[Claims] 1. A left cylinder for turning a rear wheel to the left, a right cylinder for turning a rear wheel to the right, and a spring for returning each of these cylinders to a neutral position are integrally housed side by side in the axial direction. One port that moves the piston to the right and one port that moves the piston of the right cylinder to the left respectively steer the front wheels to the left chamber and right chamber ports of the front power cylinder, and the ports on the other side are powered. A rear power cylinder connected to each port of the steering valve, a first cut valve that is driven when a steering angle exceeds a predetermined value in conjunction with a rack of a steering mechanism, and is closed when steering to one side, and to the other side. The second cut valve, which is closed when the vehicle is steered, is integrally housed, and the first cut valve is
A second cut valve connected between the front power cylinder and one port of the power steering valve; and a second cut valve connected between the front power cylinder and the other port of the power steering valve, respectively. A four-wheel steering system including: