JPH01172062A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To steer the front and rear wheels by the same and opposite phases and enhance the maneuvering stability and small radis turning performance by changing over a mode changeover cylinder according to the car running condition, i.e., either at intermediate/high speed or low speed, and by supplying pressure fluid selectively to a plurality of control cylinders. CONSTITUTION:When the front wheels are steered for ex. to the right, the pressure of a power cylinder for front wheels does not rise while the car is running at intermediate/high speed, so that a mode changeover cylinder 52 is shutting a leadout port 62 with a piston 56 out of motion Accordingly the pressure fluid in a passage 50 flows all into a pressure chamber 49 of No.2 control cylinder S2. Therefore, a piston 43 moves in the direction 66 to change over a spool 40 of a control valve V to the left position II with the aid of a rod 41. As a result, the pressure fluid flows into a pressure chamber 15 of a power cylinder C2 for rear wheels so as to steer the rear wheels to the right with the aid of a rod 12. while the car is running at a low speed, on the other hand, the abovementioned leadout port 62 is opened, and the control valve V is changed over to the right position III to steer the rear wheels to the left.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering device that also steers rear wheels in conjunction with front wheel steering.

(Prior art) Front wheel power cylinder C1 of the conventional device shown in Fig. 3
connects both ends of the piston rod 1 to the knuckle arm 3 of the front wheel 2, and the pressure chamber 4.5 of the front wheel power cylinder C1 is connected to the front wheel switching valve 8 via a passage 6.7. ing. This front wheel switching valve 8 switches according to the direction of rotation of the handle 9, and communicates one of the pressure chambers 4.5 with the pump 10 and the other with the tank 11.

Further, the rear wheel power cylinder C2 has both ends of its piston rod 12 connected to the knuckle arm 14 of the rear wheel 13, and the pressure chamber 15.1e of the rear wheel power cylinder C2 has a passage 17.1. It is connected to the control valve 20 via. This control valve 20 has a pilot chamber 21
．． 22 is communicated with the pressure chamber 4.5 of the front wheel power cylinder C] via a passage 23.24.

The spool 25 of this control valve 20 is connected to the centering springs 2G and 27 provided in the pilot chamber 21.22.
When held in the neutral position shown by the pump 10, the pump port 28 connected to the pump 10 is closed and the tank port 29.30 communicates with the actuator port 31.32 which communicates with the passageway 17.18. I have to. Then, when pilot pressure acts on either one of the pilot chambers 21, 22, the spool 25 moves to communicate one of the actuator ports 31 or 32 with the pump port 28, and connects the other actuator port 32 or 32 with the pump port 28. 31 to tank port 20.3
0.

Now, if we turn the handle 9 to the right, the front wheel switching valve 8 will change accordingly, one pressure chamber 4 of the front wheel power cylinder C will be connected to the pump 8, and the other pressure chamber 5 will be connected to the pump 8. It communicates with the tank 11. Therefore, pump 10
The pressure fluid from the front wheel is supplied to the pressure chamber 4 of the front wheel power cylinder C1 via the front wheel switching valve 8 and the passage 6, and the working fluid in the pressure chamber 5 is returned to the tank 11. The piston rod 1 of the power cylinder C1 moves in the direction of arrow 33, steering the front wheels 2 to the right.

When the front wheel power cylinder C1 operates as described above, the pressure in one pressure chamber 4 acts on one pilot chamber 21 of the control valve 20, and the other pilot chamber 21 acts on the other pilot chamber 21 of the control valve 20.
2 communicates with the tank 11 via the pressure chamber 5,
The spool 25 of the control valve 20 is switched in the direction of the arrow 34. When the spool 25 is switched in this way, the pump port 28 communicates with one actuator port 31 and the tank port 30 communicates with the other actuator port 32, so that the piston rod 12 of the eM power cylinder C2 is connected to the front wheel. The rear wheel 13 is moved in the same direction as the piston rod 1 of the power cylinder C1, and the rear wheel 13 is steered in the same direction as the front wheel 2.

Note that when the steering wheel 9 is switched to the left, the front and rear wheels are steered in the same direction based on the same principle.

(Problems to be Solved by the Invention) In the conventional steering device as described above, the front and rear wheels are always steered in the same phase mode regardless of the vehicle speed of the vehicle. However, when driving at low speeds, the front and rear wheels are steered in reverse phase mode, which improves the ability to turn in a tight corner, but with this device,
There was a problem in that it was not possible to achieve tight turning characteristics when driving at low speeds.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device capable of steering the front and rear wheels in an in-phase mode when traveling at high speeds, and steering the front and rear wheels in an opposite phase mode when traveling at low speeds.

(Means for solving the problem) This invention switches a front wheel switching valve according to the steering direction of a steering wheel, supplies pressurized fluid to one pressure chamber of a front wheel power cylinder, and connects the other pressure chamber to a tank. The present invention is based on a four-wheel steering system that is equipped with a control valve that controls a power cylinder for the rear wheels.

Based on the above device, the present invention links the first control cylinder and the second control cylinder to the control valve, and also connects one pressure chamber of the front wheel power cylinder to $
The pressure chamber of the second control cylinder is connected to the other pressure chamber of the second control cylinder, and the other pressure chamber of the front wheel power cylinder is connected to one pressure chamber of the second control cylinder. It is made larger than the pressure receiving area of the control cylinder, and the introduction port of the mode switching cylinder is connected to the communication process between the pressure chamber of the front wheel power cylinder and the pressure chamber of the second control cylinder, and the piston of this mode switching cylinder is An outlet port that communicates with the introduction port during the movement of the piston, and a tank port that closes during the movement of the piston communicate with the pressure chamber of the first control cylinder.

(Operation of the present invention) According to the present invention, since the steering torque is small during medium-high speed driving, the pressure generated in one pressure chamber of the front wheel power cylinder does not become so high. Therefore, the outlet port remains closed by the piston of the mode switching cylinder, and the pressure fluid supplied to one pressure chamber of the front wheel power cylinder is supplied to the other chamber of the second control cylinder. When the second control cylinder operates in this manner, the control valve switches in a predetermined direction to steer the front and rear wheels in the same phase mode.

When the vehicle is running at low speed, the steering torque increases, so the pressure of the fluid supplied to one pressure chamber of the front wheel power cylinder also increases. For this purpose, the piston of the mode switching cylinder moves greatly, communicating its inlet port and outlet port, and transfers the pressure fluid supplied to one pressure chamber of the front wheel power cylinder to one pressure chamber of the first control cylinder. We also supply Therefore, one pressure chamber of the first control cylinder and the other pressure chamber of the second control cylinder have the same pressure, but the first control cylinder operates due to the difference in pressure receiving area between the two cylinders, causing the control valve to operate as described above. is switched in the opposite direction, steering the front and rear wheels in reverse phase mode.

(Effects of the Present Invention) According to the device of the present invention, when driving at medium to high speeds, the front and rear wheels are steered in the same phase mode, eliminating the side-slip phenomenon of the rear wheels and improving the steering performance. Additionally, when driving at low speeds, the front and rear wheels are steered in reverse phase mode to improve turning ability.

Furthermore, since all of these controls are performed using fluid force, there is also the advantage that the reliability is extremely high.

(Embodiment of the present invention) In the first embodiment of the present invention shown in FIG. .Connected to 3G. The pump port 37 of this control valve V
is directly connected to the pump 10, and its tank port 38 is connected to the tank 11.

The control valve V thus constructed has a rod 41 connected to its spool portion 40, and the rod 41 is passed through each piston 42, 43 of the first control cylinder S1 and the second control cylinder S2.

The piston 42 of the first control cylinder S1 is
The diameter is made larger than that of the piston 43 of the second control cylinder S2, and the pressure receiving area of the first control cylinder S1 is made larger.

The first control cylinder S1 as described above has pressure chambers 44,45 defined on both sides of its piston 42, and
Centering springs 46 in these pressure chambers 44, 45
．． 47 is interposed. When the piston 42 is in the neutral position shown in the figure due to the action of the centering springs 4B and 47, the control valve (2) is also maintained in the neutral position shown in the figure.

Further, the second control cylinder S2 has its piston 43
The pressure chambers 48 and 49 are divided into pressure chambers 48 and 49, and one pressure chamber 48 is communicated with the other pressure chamber 5 of the front wheel power cylinder C1 through a passage 51, and the other pressure chamber 48 is connected to the other pressure chamber 5 of the front wheel power cylinder C1.
communicates with one pressure chamber 4 of the front wheel power cylinder C1 via a passage 50.

It should be noted that the front wheel side steering device, including its front wheel power cylinder C1, has the same configuration as the conventional one, so a detailed explanation thereof will be omitted.

The introduction ports 54.55 of the mode switching cylinders 52.53 are connected to each of the passages 50.51 as described above, and the configuration of the mode switching cylinders 52.53 is as follows.

That is, this mode switching cylinder 52.53 is equipped with a piston 56.57, and a spring chamber 58.
．． The action of springs 80, 81 in 58 normally holds the piston 56, 57 in the position shown.

When pressure from the inlet port 54.55 acts on the piston 56.57, the piston moves against the spring 60.61 and in the process of movement opens the outlet port 82.63. This lead-out port 6
2.63 are in communication with the pressure chambers 44.45 of the first control cylinder S1. This mode switching cylinder 52.53 also has a tank port 64.
65 and communicates with the pressure chamber 44, 45 of the first control cylinder S1. This tank port 64.65 opens into the spring chamber 58.59 when the piston 56.57 is in the position shown, and connects the pressure chamber 44.45 to the tank 11 via the spring chamber 58.59. communicate. However, piston 56
．． 57 moves against the spring 80.61, the piston 56.57 closes this tank port 64.85.

When the handle 9 is turned to the right and one pressure chamber 4 of the front wheel power cylinder C1 is communicated with the pump 10 and the other pressure chamber 5 is communicated with the tank 11, the front wheel 2 is opened in the same way as in the conventional case. is steered to the right.

If the vehicle is running at medium to high speeds at this time, the steering torque is not large, so the front wheel power cylinder C
The pressure in one pressure chamber 4 of 1 does not become so high. Therefore, even if the pressure fluid in the pressure chamber 4 flows into the passage 50, the piston 56 of the mode switching cylinder 52 does not move much, and the outlet port 62 is maintained in a closed state.

Therefore, all the pressure fluid that has flowed into the passage 50 as described above flows into the other pressure chamber 49 of the second control cylinder S2. When pressure fluid flows into the pressure chamber 49 in this way,
As the piston 43 moves in the direction of arrow 66,
The rod 41 moves to switch the spool portion 40 of the control valve (2) to the left position II in the drawing.

When the control valve ■ is switched to the left position H, pressure fluid from the pump 10 flows into one pressure chamber 15 of the rear wheel power cylinder C2 via the pump port 37 → actuator port 35 → passage 17. , moving the piston rod 12 in the same direction as the front wheel power cylinder C1,
The rear wheels 13 are steered to the right. That is, in this case, the front wheels 2 and the rear wheels 13 are steered in the same phase mode.

Further, when the vehicle is running at a low speed, the steering torque increases, and the pressure in one pressure chamber 4 of the front wheel power cylinder C1 increases accordingly. For this purpose, the piston 58 of the mode switching cylinder 52 moves against the spring 60 to open the outlet port 62 and close the tank port 64.

Therefore, the pressure fluid flowing into the passage 50 is also guided to one pressure chamber 44 of the first control cylinder S1 via the introduction port 54 and the outlet port 62 of one mode switching cylinder 52. Therefore, the pressure in one pressure chamber 44 of this first control cylinder S1 is lower than that of the second control cylinder S2.
becomes equal to the pressure in the other pressure chamber 49. When the pressures in both pressure chambers 44 and 49 become equal in this way, the thrust of the piston 42 overcomes the pressure receiving area difference between the two pistons 42 and 43, and the rod 41 is moved in the opposite direction to the arrow 66. Then, switch the control valve V to the right position ■.

As a result, the pressure fluid from the pump IO flows into the other pressure chamber 16 of the rear wheel power cylinder C2 via the pump port 37 → actuator port 36 → passage 18, and the piston rod 12 is transferred to the front wheel power cylinder C2. The power cylinder C1 is steered in the opposite direction to the piston rod 1, and the rear wheels 13 and front wheels 2 are steered in a reverse phase mode.

Therefore, according to the first embodiment, when the vehicle is running at medium to high speeds, the front and rear wheels are steered in the same phase mode, and the rear wheels are steered in the same phase mode.
3 skidding is prevented. Also, while driving at low speed,
Since the front and rear wheels are steered in reverse phase mode, the turning ability is greatly improved.

In this embodiment, when the handle 9 is turned to the left, pressure fluid is first introduced into one pressure chamber 48 of the second control cylinder S2, and the mode switching cylinder 5
3 operates, and its operating principle is the same as when the handle 9 is turned to the right.

The second embodiment shown in FIG.
A first control cylinder S] and a second control cylinder S2 are integrally provided at both ends of the cylinder.

In other words, there is a pump port 37 and a tank port 38 on the valve body.
．． 39 and an actuator port 35.3, and a spool hole 67 is formed in this valve body. A spool portion 40 is slidably housed in the spool hole 67, and both ends of the spool portion 40 are exposed to the pressure chambers 44, 45. This pressure chamber 44.
45 has centering springs 4G and 47 interposed therebetween. These two pressure chambers 44.45 and the centering spring 48.47 constitute the first control cylinder sJ in the first embodiment, and both ends of this spool portion 40 are connected to the piston of the first control cylinder S1. It functions as a

Further, at both ends of this spool portion 40, protrusions 68.88 are formed which function as pistons of the second control cylinder S2, and these protrusions 68.89 are connected to the pressure chamber 48.48.
I am making it happen. These protrusions 68, 68 and pressure chambers 48, 48 constitute a second control cylinder S2.

One pressure chamber 48 of the second control cylinder S2 is connected to the passage 5
1 to the other pressure chamber 5 of the front wheel power cylinder C1.
The other pressure chamber 49 communicates with one pressure chamber 4 of the front wheel power cylinder C1 via a passage 50.

Further, one pressure chamber 44 of the first control cylinder Sl is connected to the outlet port 62 of the mode switching cylinder 52 and the tank port 6.
4, and the other pressure chamber 45 communicates with the outlet port 63 of the mode switching cylinder 53 and the tank port 65.

Therefore, when the steering wheel 9 is turned to the right in the same manner as described above during medium-high speed driving, the pressure fluid in one pressure chamber 4 of the front wheel power cylinder C1 is transferred to the second control cylinder and the other pressure chamber 49 of the cylinder S2. , the spool portion 40 is switched to the left in the drawing, and the pump port 37 and the actuator port 35 are brought into communication. Therefore, the pressure fluid of the pump 10 is transferred to one pressure chamber 15 of the rear wheel power cylinder C2.
As in the first embodiment, the front and rear wheels are steered in the same phase mode.

Then, when the vehicle is running at low speed, the pressure in one pressure chamber 44 of the first control cylinder S1 increases, as in the first embodiment, so that the spool portion 40 moves rightward in the drawing. Then, the pump port 37 and the actuator port 36 are communicated, the piston rod 12 of the rear wheel cylinder C2 is moved in the opposite direction to the front wheel power cylinder C1, and the front and rear wheels are steered in a reverse phase mode.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a first embodiment of the invention, and Figure 2 is a circuit diagram showing a first embodiment of the present invention.
The figure is a sectional view of a control valve showing a second embodiment, and FIG. 3 is a circuit diagram of a conventional steering system. CI...Power cylinder for front wheels, 4.5...Pressure chamber, 8...Switching valve for front wheels, 9...Handle, 10...
・Pump, 11...Tank, ■...Control valve, SI・
...First control cylinder, 44.45...Pressure chamber, S2
...Second control cylinder, 48.48...Pressure chamber, 5
2.53...Mode switching cylinder, 54.55...
Introducing port, 62.63... Outgoing port, 64.65
...tank port.

Claims (1)

[Claims] The front wheel switching valve is switched depending on the steering direction of the steering wheel,
A four-wheel steering system comprising a control valve that supplies pressurized fluid to one pressure chamber of a front wheel power cylinder, communicates the other pressure chamber with a tank, and controls a rear wheel power cylinder, the control valve as described above. the first control cylinder and the second
At the same time, one pressure chamber of the front wheel power cylinder is connected to the other pressure chamber of the second control cylinder, and the other pressure chamber of the front wheel power cylinder is connected to the second control cylinder. It communicates with one pressure chamber, and the pressure receiving area of the first control cylinder is made larger than the pressure receiving area of the second control cylinder, and the introduction port of the mode switching cylinder is connected to the pressure chamber of the front wheel power cylinder and the second control cylinder.
Connected to the communication process with the pressure chamber of the control cylinder, and
An outlet port that communicates with the introduction port during the movement process of the piston of this mode switching cylinder and a tank port that closes during the movement process of the piston are communicated with the pressure chamber of the first control cylinder, and these first and second control A four-wheel steering device configured to switch control valves by operating cylinders.