JPH01172061A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To steer the front and rear wheels by opposite phases in the early period of steering and by the same phase in the later period of steering, by connecting a first order delay circuit between a plurality of control cylinders in communication with a power cylinder for front wheels, and thereby changing over a control valve with a certain delay. CONSTITUTION:When front wheels are steered to the right, pressure fluid flows into a pressure chambers 49 of No.2 control cylinder S2 upon passing though a passage 50 and further into a pressure chamber 44 of No.1 control cylinder S1. At this time, the rise of the pressure in this pressure chamber 44 is delayed by a first order delay circuit consisting of an orifice 52 and an accumulator 59. Accordingly the pressure in the pressure chamber 49 rises earlier to cause movement of a piston 43 in the direction 62, so that a spool 40 of a control valve V is changed over to the left position through the action of a rod 41. As a result, the pressure fluid flows into a pressure chamber of a power cylinder C2 for rear wheels to steer them to the left. when thereafter the accumulator 56 is filled, the rear wheels are steered to the right.

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 15.16 of the rear wheel power cylinder C2 has a passage 17.18. It is connected to the control valve 20 via. This control valve 20 has its pilot chamber 2
1.22 is communicated with the pressure chamber 4.5 of the front wheel power cylinder CI via a passage 23.24.

The spool 25 of this control valve 20 is attached to a centering spring 26.27 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 switch accordingly, one pressure chamber 4 of the front wheel power cylinder C1 will be connected to the pump 8, and the other pressure chamber 5 will be connected to the tank. Connects to 11. Therefore, pump 10
The pressure fluid from 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 stored in the tank 11. The piston rod 1 of the front wheel power cylinder C1 moves in the direction of arrow 33, steering the front wheel 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 rear wheel power cylinder C2 is connected to the It moves in the same direction as the piston rod 1 of the front wheel power cylinder C1, and steers the rear wheel 13 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) - Inside the vehicle, it is said that when the vehicle is running at medium to high speeds, the steering stability is better if the front and rear wheels are switched in the same phase mode. However, even when driving at medium and high speeds, at the beginning of switching the steering wheel, the front and rear wheels switch in reverse phase mode.
After that, switching the front and rear wheels in the same phase mode provides the best steering stability. In other words, when the front and rear wheels are steered in the opposite phase mode at the beginning of steering, the orientation of the vehicle body changes to the steered direction at that moment, so subsequent followability becomes very good. If the front and rear wheels are steered in the same phase mode while maintaining tracking ability in this way, the rear wheels will not skid at this time, and the steering performance will be further improved.

However, in the conventional device as described above, the front wheels and the rear wheels can always be steered only in the same phase mode, so there is a problem in that the above-mentioned steering stability cannot be improved.

An object of the present invention is to improve the steering performance of the device by steering the front and rear wheels in an anti-phase mode at the beginning of steering, and then in an in-phase mode afterwards.

(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-mentioned device, the present invention links a first control cylinder and a second control cylinder to the control valve, and makes the pressure receiving area of the first control cylinder larger than the pressure receiving area of the second control cylinder. Shichieru. Further, one pressure chamber of the front wheel power cylinder is communicated with the other pressure chamber of the second control cylinder, and the other pressure chamber of the front wheel power cylinder is communicated with one pressure chamber of the second control cylinder. There is. Moreover, one pressure chamber of the second control cylinder is communicated with the other pressure chamber of the first control cylinder, and the other pressure chamber of the second control cylinder is communicated with the one pressure chamber of the first control cylinder, A first-order delay circuit consisting of an orifice and an accumulator provided downstream of the orifice is provided in the communication process between the pressure chamber of the second control cylinder and the pressure chamber of the first control cylinder. When the pressure of the front wheel power cylinder is introduced into the other pressure chamber of the second control cylinder, the second control cylinder operates to switch the control valve, and then the first control cylinder operates, The control valve is configured to switch in the opposite direction.

(Operation of the present invention) Since the present invention is configured as described above, when pressure fluid is supplied to one pressure chamber of the front wheel power cylinder, the pressure fluid is transferred to the other pressure chamber of the second control cylinder. and operates this second control cylinder to switch the control valve in a predetermined direction. Thereafter, the pressure fluid of this second control cylinder flows into one pressure chamber of the first control cylinder via the first-order delay circuit, so that the pressures of both cylinders become equal. When the pressures of both cylinders become equal, the first control cylinder, which has a larger pressure receiving area, operates and switches the control valve in the opposite direction to the initial direction of steering.

Therefore, at the beginning of steering, the front and rear wheels are steered in the opposite phase mode, and then the front and rear wheels are steered in the in-phase mode.

(Effects of the present invention) As described above, according to the device of the present invention, at the initial stage of steering, the front and rear wheels are steered in the opposite phase mode, and after the vehicle is directed in the running direction, the front and rear wheels are steered in the opposite phase mode. Since it steers in in-phase mode,
Its maneuverability is greatly improved.

(Embodiment of the present invention) In the first embodiment of the present invention shown in FIG. .36 is connected. A pump port 37 of this control valve V is directly connected to the pump 10, and a tank port 38 thereof 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 Sl 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. By the action of the centering springs 46, 47, when the piston 42 is in the illustrated neutral position, the control valve V also maintains the illustrated neutral position.

Further, the second control cylinder S2 has a piston 43 defining pressure chambers 48,49. The other pressure chamber 48 communicates with one pressure chamber 4 of the front wheel power cylinder C1 via a passage 50.
is communicated with the other pressure chamber 5 of the front wheel power cylinder CI. Further, the other pressure chamber 48 of the second control cylinder S2 is communicated with the one pressure chamber 44 of the first control cylinder S1, and the one pressure chamber 48 of the second control cylinder S2 is connected to the other pressure chamber 48 of the first control cylinder S1. It communicates with the pressure chamber 45.

An orifice 52.53 is provided in the communication process between the second control cylinder S2 and the first control cylinder S1, and a check valve 54.55 is connected to the orifice 52.53.
It is installed in parallel with 3. Moreover, this orifice 5
Branch passage 57.5 between 2.53 and pressure chamber 44.45
8 are connected, and 7 cumulators 59.80 are connected to this branch passage 57.58. The orifice 52, 53 and the accumulator 59, 60 constitute the first-order lag circuit of the present invention.

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.

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.

At this time, the pressure fluid in the pressure chamber 4 flows into the other pressure chamber 48 of the second control cylinder S2 via the passage 50, and via this pressure chamber 48, the pressure fluid flows into the other pressure chamber 48 of the first control cylinder S1. It also flows into the pressure chamber 44 of. but,
The pressure increase in one pressure chamber 44 of the first control cylinder S1 is as follows:
There will be a slight delay due to the action of the first-order delay circuit. In other words,
The pressure fluid flowing into the pressure chamber 44 from the other pressure chamber 49 of the second control cylinder S2 is throttled by the orifice 52 and has a pressure drop, and the fluid that has passed through the orifice 52 flows into the accumulator 58. Therefore, unless the fluid flows by the capacity of the accumulator 58, the pressure within the pressure chamber 44 will not increase significantly.

However, the other pressure chamber 48 of the second control cylinder S2 is
Since it is in direct communication with the passage 50, the pressure fluid flowing into the passage 50 immediately acts on the pressure chamber 48. For this purpose, the other pressure chamber 48 of this second control cylinder S2
The pressure effect overcomes the pressure effect in the pressure chamber 44 of the first control cylinder S1, and the piston 43 of the second control cylinder S2 moves in the direction of the arrow 62. When the piston 43 moves in the direction of the arrow 62 in this manner, the rod 41 moves accordingly and switches the spool portion 40 of the control valve V to the left position II in the drawing.

When the control valve V is switched to the left position H, pressure fluid from the pump 10 flows into the other pressure chamber 16 of the rear wheel power cylinder C2 via the pump port 37 → actuator port 36 → passage 18. , the piston rod 12 is moved in the opposite direction to the front wheel power cylinder C1, and the rear wheel 13 is steered to the left. That is, in this case, the front wheels 2 and the rear wheels 13 are steered in the opposite phase mode.

When the capacity of the accumulator 58 is filled, the pressure in one pressure chamber 44 of the first control cylinder S1 increases and eventually becomes equal to the pressure in the other pressure chamber 48 of the second control cylinder S2. In this way, both pressure chambers 44.4
If the pressures at 9 are equal, both pistons 42, 43
The thrust force of the piston 42 is overcome by the pressure receiving area difference, and the rod 41 is moved in the opposite direction to the arrow 62, and the control valve V is switched to the right position (3).

As a result, 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, and the piston rod 12 is transferred to the front wheel power cylinder C2. It steers in the same direction as the piston rod l of the power cylinder CI, and the rear wheel 1
3 to the right, which is the same direction as the front wheels 2.

Therefore, according to this first embodiment, at the initial stage when the front wheels 2 are steered, the rear wheels 13 are steered in the opposite direction to the front wheels 2, but after that, the rear wheels 13 are steered in the same direction as the front wheels. The ship is steered to In this way, when the front and rear wheels are steered in the opposite phase mode at the beginning of steering, the orientation of the vehicle body changes in the steered direction at that moment, so subsequent tracking performance becomes very good. If the front and rear wheels are steered in the same phase mode while maintaining the followability in this way, the skidding of the rear wheels 13 at this time will be eliminated, and the steering performance will be further improved.

The second embodiment shown in FIG.
A first control cylinder S1 and a second control cylinder S2 are integrated at both ends of the cylinder 0.

In other words, there is a pump port 37 and a tank port 38 on the valve body.
．． 39 and an actuator port 35.3G, and a spool hole 63 is formed in this valve body. The spool portion 40 is slidably housed in the spool hole 63, and both ends of the spool portion 400 are exposed to the pressure chambers 44, 45. This pressure chamber 44.
45 has centering springs 46 and 47 interposed therebetween. These two pressure chambers 44.45 and the centering spring 48.47 constitute the first control cylinder S1 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 64.65 are formed which function as pistons of the second control cylinder S2, and the protrusions 64.65 are connected to the pressure chambers 48, 49.
I'm making it happen. These protrusions 64, 65 and pressure chambers 48, 48 constitute a second control cylinder S2.

The pressure chambers 44, 45 of the first control cylinder S1 are
As in the embodiment, the pressure chamber 49. of the second control cylinder S2.
48, and an orifice 52, 53 and a check valve 55, 56 are provided at each of the connection processes,
Further, an accumulator 59,
GO is connected.

If the handle 9 is turned to the right in the same manner as above, the pressure fluid in one pressure chamber 4 of the front wheel power cylinder C1 flows into the other pressure chamber 49 of the second control cylinder S2, and this pressure It also flows into one pressure chamber 44 of the first control cylinder S1 via the chamber 49.

Also in this second embodiment, due to the action of the first-order delay circuit consisting of the orifice 52 and the accumulator 59,
The pressure increase in one pressure chamber 44 of the first control cylinder S1 will be delayed. Therefore, at the initial stage of steering, the pressure action of the other pressure chamber 49 of the second control cylinder S2 overcomes the pressure action and moves the spool portion 40 to the right in the drawing, causing the pump port 37 and the actuator port 36 to communicate with each other.

Therefore, the pressure fluid of the pump 10 flows into the other pressure chamber 18 of the rear wheel power cylinder C2, and the front and rear wheels are steered in the reverse phase mode, as in the first embodiment. After that, one pressure chamber 44 of the first control cylinder S1
As the pressure increases, the spool portion 40 moves to the left in the drawing, communicates the pump port 37 with the actuator port 35, and connects the piston rod 12 of the rear wheel cylinder C2 to the front wheel power cylinder C1. The vehicle moves in the same direction as the vehicle, and steers the front and rear wheels in the same phase mode.

Therefore, in this second embodiment as well, at the initial stage when the front wheels 2 are steered, the rear wheels 13 are steered in the opposite direction to the front wheels 2, but after that, the rear wheels 13 are steered in the same direction as the front wheels. It is something that is steered.

[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. C1...Power cylinder for front wheels, 4.5...Pressure chamber, 8...Switching valve for front wheels, 9...Handle, 10...
・Pump, 11...tank, ■...control valve, SL・
...First control cylinder, 44.45...Pressure chamber, 52
．． 53... Orifice, 58.60... Accumulator, S2... Second control cylinder, 48.49...
pressure chamber.

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
The pressure receiving area of the first control cylinder is made larger than the pressure receiving area of the second control cylinder, and one pressure chamber of the front wheel power cylinder is connected to the other pressure chamber of the second control cylinder. the other pressure chamber of the front wheel power cylinder is communicated with one pressure chamber of the second control cylinder, and the one pressure chamber of the second control cylinder is communicated with the other pressure chamber of the first control cylinder. communication,
The other pressure chamber of the second control cylinder is communicated with one pressure chamber of the first control cylinder, and an orifice is provided in the communication process between the pressure chambers of the second control cylinder and the pressure chamber of the first control cylinder. A first-order delay circuit consisting of an accumulator provided on the downstream side of the second delay circuit is provided.
When the pressure of the front wheel power cylinder is introduced into the other pressure chamber of the control cylinder, the second control cylinder operates to switch the control valve, and then the first control cylinder operates to switch the control valve. A four-wheel steering device configured to switch in the opposite direction.