JPH0630602Y2 - Four-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 for steering front and rear wheels of a vehicle.

(Prior Art) Conventionally, as a four-wheel steering device, for example, JP-A-59-1
The one described in Japanese Patent No. 28054 is known.

This conventional four-wheel steering device is a rear wheel steering actuator that is driven by the switching operation of the switching control valve to steer the rear wheels,
A return spring for urging the piston of the rear wheel steering actuator to a neutral position, the switching control valve supplies hydraulic pressure to one pressure chamber and drains the other pressure chamber in a steering control state, and In the neutral control state, both pressure chambers and the supply liquid pressure are drained.

Therefore, at the neutral position, both pressure chambers have a drain pressure, and the piston of the rear wheel actuator is supported by the set load of the return spring.

Further, this conventional device is provided with a switching valve for communicating and blocking the pressure chambers on both sides of the piston in the cylinder separately from the switching control valve, and when the switching valve is actuated to the communicating position, the piston operates as a return spring. It was configured to forcibly return to the neutral position by elastic force.

(Problems to be solved by the invention) However, in such a conventional four-wheel steering system, when the rear-wheel steering actuator is set to the neutral position, both pressure chambers become drain pressure and the piston is the return spring. However, there is a problem described below because it is restricted to the neutral position only by the set load of.

That is, when the rear wheel is in the neutral position (straight-run state), it is necessary to increase the set load of the return spring in order to fix the piston so that the rear wheel will not be shaken by the lateral load from the road surface side.

When the set load is increased in this way, when steering the rear wheels to the left and right, it is also necessary to increase the hydraulic pressure introduced into the pressure chamber so as to overcome the set load, resulting in a large energy loss with respect to the set load. However, there is a problem that a pump that generates high pressure is required, which leads to an increase in cost.

(Means for Solving Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this object, in the present invention, the liquid in the pressure chambers on both sides of the piston is A rear wheel steering actuator that steers the rear wheel by sliding the piston based on the pressure difference, a biasing means that biases the piston to the neutral position, and the rear wheel is switched to steer the rear wheel based on a predetermined condition. In a four-wheel steering system provided with a switching control valve for supplying or draining hydraulic pressure to the chamber, a communication path for communicating the both pressure chambers in a neutral control state of the switching control valve is provided, and the communication path In addition, an opening / closing mechanism is provided which closes the communication path when the piston is in the neutral position and opens the communication path when the piston is in the left-right steered position.

(Operation) (a) During left / right steering When the switching control valve is switched from the neutral position according to the steering direction, hydraulic pressure is introduced from the switching control valve side into either one of the pressure chambers and the other is drained. A differential pressure is generated between the pressure chambers, the piston slides, and the rear wheel is steered in a desired direction.

In this steering state of the switching control valve, the communication path closed by the opening / closing mechanism at the neutral position is opened according to the sliding of the piston, but in the steering control state of the switching control valve, the communication path is cut off and the pressure chambers of both pressure chambers are closed. Since the communication is cut off, the hydraulic pressure in one pressure chamber is not transmitted from the communication path side to the other pressure chamber, and a differential pressure is generated in both pressure chambers as described above.

(B) Neutral state When the switching control valve is switched from the above-mentioned steering state to the neutral control state, the communication path is opened, and both pressure chambers are shut off from the hydraulic pressure supply and the drain side.

That is, both pressure chambers are cut off from hydraulic pressure supply and drain,
The communication path and the path via the switching control valve are in a state of mutual communication.

Therefore, the piston is slid in the direction of the neutral position by the urging force of the urging means, and as the piston slides, the pressure difference causes the liquid pressure to be equalized in both pressure chambers through the communication path. The pressure moves.

Then, when the piston returns to the neutral position, the opening / closing mechanism is closed, the communication via the communication path and the switching control valve is cut off, and both pressure chambers are shut off at the same pressure.

Therefore, the two pressure chambers are shut off by the same pressure, so that the piston is locked and fixed at its neutral position, and does not slide even if a lateral load is input from the road surface side.

As described above, in the present invention, the piston in the neutral state is not fixed by the set load of the biasing means such as the return spring but is held by locking both pressure chambers. It is possible to reduce the load, that is, it is sufficient if there is an urging force for returning the piston from the left and right sliding positions to the neutral position, and by lowering the urging force of the urging means in this way, the hydraulic fluid It is possible to reduce the pressure and use a pump having a low output.

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

First, the configuration of the embodiment will be described.

FIG. 1 is an overall view showing a four-wheel steering system according to an embodiment of the present invention, in which reference numeral 10 denotes a front wheel steering actuator. The front wheel steering actuator 10 has left and right pressure chambers 12 and 13 with a piston 11 interposed therebetween, and the left and right pressure chambers 12 and 13 are connected to a power steering device 20. That is, the power steering device 20 is connected to the hydraulic pressure supply circuit 2 from the pump 1 and the drain circuit 4 to the reserve tank 3, and when the steering wheel 30 is turned to the right, the hydraulic pressure is supplied to the right pressure chamber 13 and the left side. Pressure chamber 12
Is drained, and when the steering wheel 30 is turned counterclockwise, hydraulic pressure is supplied to the left pressure chamber 12, the right pressure chamber 13 is drained, the piston 11 slides, and the front wheel 5 is steered left and right. It is supposed to be done. The supplied hydraulic pressure is configured to be a hydraulic pressure that corresponds to the steering angle of the steering wheel 30.

In the figure, reference numeral 40 denotes a rear wheel steering actuator, which is connected to the power steering device 20 via a first hydraulic pressure transmission circuit 6 and a second hydraulic pressure transmission circuit 7.
Further, the switching control valve 50 is provided in the middle of both hydraulic pressure transmission circuits 6 and 7.
Is provided, and the rear wheel 8 is steered by connecting or disconnecting the power steering device 20 and the rear wheel steering actuator 40.

FIG. 2 shows the rear wheel steering actuator 40 and the switching control valve 5.
As shown in the drawing, the rear wheel steering actuator 40 is provided with a piston 42 and a piston rod 43 on a cylinder tube 41, and the piston rod 43 slides on both ends of the cylinder tube 41. Guide members 44 and 45 that guide and seal the inside of the cylinder tube 41 are provided. The piston rod 43 is connected to the rear wheel 8. Further, the cylinder tube 41 is formed by connecting a large-diameter tube 411, which is a sliding portion of the piston 42, and a small-diameter tube 412, which houses a return spring 60 described later.

A right pressure chamber 46 and a left pressure chamber 47 are formed on the left and right sides of the piston 42, and a spring storage chamber 48 is formed next to the right pressure chamber 46 and communicates with the right pressure chamber 46.

The spring storage chamber 48 is provided with a return spring 60 as a biasing means for biasing the piston 42 to the neutral position. That is, both ends of the return spring 60 are slidable with respect to the piston rod 43, and are abutted against the stopper surfaces 481 and 482 at the ends of the spring accommodating chamber 48 so that the right retainer 61 and the left retainer 62 are restricted from sliding. And the retainer 61, 62 is provided on the piston rod 43 at the neutral position of the piston 42 shown in the figure.
And the retainers 61 and 6 are arranged so as to abut each other.
A right side stopper 431 and a left side stopper 432 capable of restricting the sliding of 2 are provided. Therefore, in the neutral position, the elastic force of the return spring 60 causes the stopper surfaces 481,
Piston 4 transmitted from 482 to the cylinder tube 41 side
Although it does not act on the second side, when the piston 42 slides from the neutral position to the left or right, for example, to the left, the right retainer 61 separates from the stopper surface 481, and the elastic force of the return spring 60 passes through this right retainer 61. And acts on the piston rod 43 from the right side stopper 431 toward the neutral position.

Also, on both stopper surfaces 481 and 482, the right side port 7
1 and the left port 72 are opened, and both ports 71 and 7
2 is connected to the switching control valve 50 by a communication passage 73. That is, both ports 71, 72 are connected to the spring storage chamber 4
8 is communicated with the right pressure chamber 46 via 8 and is opened / closed by both retainers 61, 62. The return spring 60 and both retainers 61, 62 allow the ports 71, 72 at the neutral position of the piston 42. Is formed, and a port opening / closing mechanism (opening / closing mechanism) 80 that opens either of the ports 71 and 72 at a position where it is slid to the left and right is formed. Also,
Desirably, in the communication passage 73, as shown in the figure, a one-way valve 731 is provided near the right side port 71 to allow only hydraulic pressure movement from the spring storage chamber 48 (right pressure chamber 46) side to the switching control valve 50 side. Also, a one-way valve 732 is provided near the left port 72 to allow only hydraulic pressure movement from the switching control valve 50 side to the spring storage chamber 48 (right pressure chamber 46) side.

The switching control valve 50 supplies hydraulic pressure from the power steering device 20 side to the rear wheel steering actuator 40,
The rear wheel steering actuator 40 may be disconnected by disconnecting the communication.
Is controlled by the controller 90.

That is, the switching control valve 50 is connected to both of the hydraulic pressure transmission circuits 6 and 7 on one side, and on the other side to the right side transmission path 461 connected to the right pressure chamber 46 and the left side connected to the left pressure chamber 47. In the neutral control state in which the transmission passage 471 and the communication passage 73 are connected and the solenoid 51 is not operating, both hydraulic pressure transmission circuits 6 and 7 and the right transmission passage 461 are shut off as shown in the drawing, and the communication passage 73 and the left side The transmission path 471 (left pressure chamber 47) is communicated with the solenoid 51.
In the steering control state in which the second hydraulic pressure transmission circuit 7 is operated, the first hydraulic pressure transmission circuit 6 and the left transmission path 471 are communicated with each other, and
And the right transmission path 461 are communicated with each other, and the communication path 73 is blocked.

Therefore, in the neutral control state in which the solenoid 51 is operated, the left and right pressure chambers 47 and 46 are routed through the spring accommodating chamber 48 to the port 71 or 72 to the communication passage 73 to the switching control valve 50 to the left transmission passage 471. That is, the communication paths 70 are in communication with each other.

Therefore, in the steering control state of the switching control valve 50, the front wheels 5 and the rear wheels 8 are steered in opposite phases.

The controller 90 receives a steering angle signal h indicating a steering angle from a steering angle sensor 91 provided on a column shaft 31 of the steering wheel 30 and a vehicle speed signal i from a vehicle speed sensor 92 provided in a drive transmission system. When the vehicle speed is low below a predetermined speed, the operation signal s is output to the switching control valve 50 in order to steer the rear wheels 8 in a phase opposite to that of the front wheels 5. The steering angle of the rear wheels 8 is proportional to the steering angle of the front wheels 5.

Next, the operation of the embodiment will be described.

(A) At the time of steering left and right When the front wheels 5 are steered, the operation signal s is output from the controller 90 accordingly, and the switching control valve 50 is switched from the neutral position. By this switching operation, the first hydraulic pressure transmission circuit 6 and the left side transmission passage 471 are communicated with each other, and the second hydraulic pressure transmission circuit 7 and the right side transmission passage 461 are communicated with each other. Pressure chamber 46, 47
The hydraulic pressure is introduced into one side and the other side is drained, a differential pressure is generated in both pressure chambers 46 and 47, the piston 42 slides, and the rear wheel 8 is steered in the opposite direction to the front wheel 5.

In the steering control state of the switching control valve 50, for example,
When the piston 42 slides to the right, the left retainer 62 separates from the stopper surface 482 to open the left port 72, and when the piston 42 slides to the left, the right retainer 61 separates from the stopper surface 481 and the right port 71 opens. Opened,
The communication passage 73 is in communication with the spring accommodating chamber 48, and has the same pressure as the right pressure chamber 46. The communication passage 73 is closed by the switching control valve 50 in the steering control state.

(B) Neutral state When the front wheels 5 are returned to the straight traveling state, the output of the operation signal s from the controller 90 is stopped, and the switching control valve 50 switches from the above steering control state to the neutral control state shown in FIG.

By this switching, both the hydraulic pressure transmission circuits 6 and 7 and the right side transmission path 461 are shut off, and the left side transmission path 471 and the communication path 73.
And are communicated.

That is, both the pressure chambers 46 and 47 are cut off from the power steering device 20 side, and the spring storage chamber 48 to the port 7 are closed.
1,72 (when steering to the right, right port 71,
When steering to the left, the left port 72) ~ communication passage 7
3 ~ switching control valve 50 ~ path via the left transmission path 471,
That is, the communication paths 70 are in communication with each other.

Therefore, the urging force of the return spring 60 allows the piston 42 to slide toward the neutral position, and when the piston 42 slides to the left (steers to the right), the hydraulic pressure in the right pressure chamber 46 changes. To the left pressure chamber 47 through the communication passage 73 via the one-way valve 731, that is, the communication passage 70, and when sliding to the right (steering to the left), the left pressure chamber The hydraulic pressure of 47 moves from the communication passage 73 to the right pressure chamber 46 through the left port 72 via the one-way valve 732, that is, the communication passage 70, and the piston 42 slides to the neutral position and both pressures are increased. The hydraulic pressure in the chamber becomes equal.

Then, when the piston 42 returns to the neutral position, the port opening / closing mechanism 80 opens both ports 71, 7
One of the two pressure chambers is closed, the communication through the communication path 70 is cut off, and the pressure chambers 46 and 47 are shut off at the same pressure.

Therefore, since the pressure chambers 46 and 47 are shut off by the same pressure, the piston 42 is locked and fixed at its neutral position, and can slide even when a lateral load is input from the road surface side. There is no.

Thus, in the embodiment of the present invention, the piston 4 in the neutral state is
2 is not fixed by the set load of the biasing means such as a return spring, but is held by locking the hydraulic pressures of both pressure chambers 46 and 47 at the same pressure. Therefore, in the embodiment, the return spring 60 is fixed. The urging force may be a force for returning the piston 42 from the left and right sliding positions to the neutral position, and the urging force (set load) can be reduced.

Therefore, by lowering the biasing force (set load) of the return spring 60, energy loss during steering operation can be reduced and efficiency can be improved.

By lowering the biasing force of the return spring 60 in this way, the hydraulic fluid pressure from the power steering device 20 side can be reduced and a low output pump 1 can be used, thereby reducing the cost. The feature that can be obtained is obtained.

Further, since both ports 71, 72 are opened and closed by the movement of both titeners 61, 62 according to the sliding of piston 42, reliable control can be performed with a simple configuration, and a special configuration such as a valve is provided. It also has the feature that complicated control is not required.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to this embodiment. For example, in the embodiment apparatus, when one return spring slides to the left or right. However, although the spring is biased in the neutral direction, a spring that exerts a biasing force when sliding to the right and a spring that exerts a biasing force when sliding to the left may be separately provided. Further, the spring may be provided outside the cylinder tube. Further, although the return spring is used as the biasing means in the embodiment, another elastic body such as rubber or a fluid capable of accumulating pressure may be used.

Further, in the embodiment, the device for steering the rear wheels in the opposite phase to the front wheels has been shown, but it may be applied to a device for steering in the same phase, or a device for steering both in the same phase and opposite phase depending on the situation. .

Further, in the embodiment, the one-way valve is provided in the communication passage, but this one-way valve is not necessarily provided.

Further, in the embodiment, the opening and closing mechanism is opened and closed by using the retainer, but the present invention is not limited to this, as long as the cylinder is closed in the neutral state and opened in the steering state. , For example, includes a valve mechanism that opens and closes as the piston rod moves.

(Effect of the Invention) As described above, in the four-wheel steering system of the present invention, in the neutral state, the means for closing both pressure chambers of the rear wheel steering actuator to lock the piston is used. Since the piston is not fixed by the set load of the biasing means such as the return spring, it is possible to reduce the load of the biasing means set to reduce energy loss. It is possible to reduce the cost by using a pump having a low output and a low output.

Further, in the four-wheel steering system of the present invention, since the opening / closing mechanism is operated in conjunction with the sliding of the piston to lock the piston, the control is simple and highly reliable without using complicated valve control. The effect is obtained.

[Brief description of drawings]

FIG. 1 is an overall view showing a four-wheel steering system according to one embodiment of the present invention,
FIG. 2 is a cross-sectional view showing the main part of the embodiment apparatus. 8 ... Rear wheel 40 ... Rear wheel steering actuator 42 ... Piston 46 ... Right pressure chamber 47 ... Left pressure chamber 50 ... Switching control valve 60 ... Return spring (biasing means) 71 ... Right port 72 ...... Left side port 73 ...... Communication passage 80 ...... Port opening / closing mechanism (opening / closing mechanism)

Claims (1)

[Scope of utility model registration request] 1. A rear wheel steering actuator for steering a rear wheel by sliding the piston based on a hydraulic pressure difference between pressure chambers on both sides of the piston, a biasing means for biasing the piston to a neutral position, and a predetermined condition. A four-wheel steering system including a switching control valve that is switched to steer the rear wheels and supplies or drains hydraulic pressure to both pressure chambers. A communication path for communicating in a state is provided, and an opening / closing mechanism that closes the communication path when the piston is in the neutral position and opens the communication path when the piston is steered to the left or right is provided in the communication path. A characteristic four-wheel steering system.