JP2617723B2 - 4-wheel steering system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel steering device in which the rotation speeds of a front wheel pump and a rear wheel pump depend on the vehicle speed.

(Prior Art) The conventional device shown in FIG.
The front wheel power cylinder S ₁ provided, the power cylinder
Connecting the two chambers 3 and 4 of the S ₁ to the downstream side of the port of the front-wheel control valve V _1.

The pump port of the front-wheel control valve V ₁ was, but are connected to the front wheel pump P ₁ through the supply passage 5 is provided with a solenoid flow control valve 6 for the feed passage 5. Also,
The tank port of the front wheel control valve V ₁ is connected to the tank T via the return passage 7.

Front-wheel control valve V ₁ which is as described above, those switches in connection with the rotation of the handle 8, for example, if off the handle 8 to the right, front-wheel control valve V ₁ is switched in response, power The chamber 3 of the cylinder S ₁ communicates with the tank T, and the chamber 4
The communicating with the front wheel pump P _1. Therefore, the tie rod 2 is moved leftward, and the front wheel 1 is steered rightward.

If the handle 8 is turned to the left opposite to the above, the chamber 3 will be pumped.
Communicating with the P _1, because the chamber 4 communicates with the tank T, to steer front wheels 1 to the left.

Control valve V ₂ for the rear wheels to the steering wheel 8 as described above is also linked, connecting the rear wheel pump P ₂ via the supply passage 9 to the after pump port wheel control valve V ₂ However, an electromagnetic flow control valve 10 is provided in the supply passage 9. On the other hand, the tank port of the rear wheel control valve V ₂ is connected to the tank T via the return passage 11.

Such downstream ports wheel control valve V ₂ after, the
For the rear wheels via a passage 12, 13 power cylinder S ₂ chambers 14 and 15
While connected to, the wheel power cylinder S ₂ Thereafter, and so as to steer the rear wheels 16.

The wheel control valve V ₂ After this, also steered to the right rear wheel when turned the steering wheel 8 to the right, so that when the cut in the left steered also the rear wheels to the left, the front and rear wheels Switching is performed in the common mode.

The solenoid valves of the electromagnetic flow control valves 6 and 10 are electrically connected to a controller C, and a vehicle speed sensor 17 is connected to the controller C.

Pump front wheel pump P ₁ and rear wheels was as above P ₂
Are associated with an engine (not shown), and therefore the discharge amount depends on the vehicle speed.

The electromagnetic flow control valve 6 for controlling the supply flow rate with respect to the front-wheel power cylinder S ₁ may increase the flow rate at the time of low-speed running, during medium or high speed running, reducing its flow rate. The electromagnetic flow control valve 10 for controlling the supply flow rate with respect to the rear wheel power cylinder S _2, said reducing its supply flow rate at the time of low-speed running contrary to, during medium or high speed running, so as to increase its supply flow rate ing.

While the vehicle is running, the vehicle speed is detected by the vehicle speed sensor 17 and a vehicle speed signal output from the controller C is input to the electromagnetic flow control valve 6. And
In response to the vehicle speed signal, the electromagnetic flow control valve 6 operates to increase the supply flow rate at low speed traveling and increase the assist force, and reduce the supply flow rate at high speed traveling to prevent over-steering. I have.

The vehicle speed signal output from the controller C is also input to the electromagnetic flow control valve 10, which reduces the flow rate during low-speed running and suppresses turning of the rear wheels 16. On the other hand, when traveling at high speed, the flow rate is increased, and the rear wheels 16 are steered in the same direction as the front wheels 1.

The reason why the rear wheels 16 are steered in the same direction as the front wheels 1 during middle-high speed traveling is to prevent the rear wheels from skidding when changing lanes, for example, and to maintain steering stability. To do that.

(Problems to be solved by the present invention) In the conventional device as described above, in order to make the assist force of the front and rear wheel power cylinders S ₁ and S ₂ sensitive to vehicle speed,
The controller C and the vehicle speed sensor 17 must be provided. However, since the controller C and the vehicle speed sensor 17 are expensive, there is a problem that the cost of the entire apparatus increases accordingly.

In addition, there is a problem that this control system is rather complicated and thus lacks reliability.

An object of the present invention is to provide an apparatus which eliminates the need for a conventional electric control device such as a controller, reduces the overall cost, and improves the reliability thereof.

(Means for Solving the Problems) The present invention provides a front-wheel pump and a rear-wheel pump whose rotation speeds depend on the vehicle speed. A control valve for the front wheels that connects one of the chambers of the cylinder to the pump for the front wheels, and a control valve for the front wheels that connects the other chamber to the tank, and switches when the handle is operated. And a rear wheel control valve for communicating one of the chambers to the rear wheel pump and communicating one of the other chambers to the tank, and the rear wheel control valve connects the rear wheel to the front wheel. And a four-wheel steering device configured to switch to a common-mode position in which the vehicle is steered in the same direction.

On the premise of the above-described device, the present invention provides a front-wheel valve mechanism that controls the supply flow rate in inverse proportion to the vehicle speed, on the upstream side of the front-wheel control valve, and on the upstream side of the rear-wheel control valve,
A rear wheel valve mechanism for controlling the supply flow rate in proportion to the vehicle speed is provided.The rear wheel valve mechanism has an inflow port connected to the rear wheel pump, an outflow port connected to the rear wheel control valve, A fixed orifice and a variable orifice provided in the communication process between the inflow port and the outflow port are provided in the passage process between the variable orifice and the outflow port. And a flow control spool provided in parallel to the fixed orifice and the variable orifice and returning a flow rate equal to or greater than a set flow rate to the tank.

(Operation of the Present Invention) The front-wheel valve mechanism increases its flow rate during low-speed running of the vehicle, so that the supply flow rate to the front-wheel power cylinder increases, and the power assisting force increases.

At this time, the rear wheel valve mechanism operates in a direction to decrease the flow rate from the rear wheel pump, so that the rear wheels are not steered during low-speed traveling.

When the vehicle is traveling at a medium to high speed, the front wheel valve mechanism performs a control operation in the direction of reducing the supply flow rate, so that the assisting force of the front wheel power cylinder is reduced, and the vehicle enters a manual steering state.

At this time, the rear wheel valve mechanism performs a control operation in the direction of increasing the flow rate, so that the rear wheels are steered in the same direction as the front wheels.

Therefore, when the vehicle is running at a high speed, the front wheels are prevented from being over-steered, and the rear wheels are steered in the same direction as the front wheels to prevent skidding.

(Effects of the Present Invention) According to the four-wheel steering device of the present invention, electric control equipment such as a controller is not required, so that cost can be reduced and the control system is simplified, so that its reliability is improved. improves.

Further, since the rear wheel valve mechanism does not require a pilot pump or the like for operating the rear wheel valve mechanism, the number of pumps can be reduced accordingly.

(Example of the present invention) the first embodiment shown in the first to third drawing, the front wheel power cylinder S ₁ provided tie rod 2 of the front wheel 1, front wheel biventricular 3,4 of the power cylinder S ₁ It is connected to the downstream side of the boat of the control valve V _1.

The pump port of the front-wheel control valve V ₁ was, but are connected to the front wheel pump P ₁ through the supply passage 5 is provided with a front-wheel valve mechanism V _F in the feed passage 5. Also, the tank port of the front-wheel control valve V ₁ through a return passage 7 is connected to the tank T.

Incidentally, the front wheel pump P ₁ is one that is coordinated with the engine, thus, the discharge amount will depend on the vehicle speed.

Front-wheel control valve V ₁ which is as described above, those switches in connection with the rotation of the handle 8, for example, if off the handle 8 to the right, front-wheel control valve V ₁ is switched in response, power The chamber 3 of the cylinder S ₁ communicates with the tank T, and the chamber 4
The communicating with the front wheel pump P _1. Therefore, the tie rod 2 is moved leftward, and the front wheel 1 is steered rightward.

If the handle 8 is turned to the left opposite to the above, the chamber 3 will be pumped.
Communicating with the P _1, because the chamber 4 communicates with the tank T, to steer front wheels 1 to the left.

The specific configuration of the front wheel valve mechanism V _F, the second
As shown in the figure.

That is, a flow control spool 21 is slidably inserted into a valve hole 19 formed in the valve main body 18 with a spring 20 interposed between the flow control spool 21 and the inner end thereof.

Further, a hollow connector 22 is inserted outside the flow control spool, and a screw portion 23 thereof is tightened to press a flange 24 against a side surface of the valve body 18.

The connector 22 as described above has a small-diameter portion 25 at its distal end, and an annular space 26 between the small-diameter portion 25 and the valve hole 19.
And plug the tip of this connector 22
It is occupied by 27. The plug 27 has a fixed orifice communicating the space 26 with the hollow portion of the connector 21.
28 are formed.

A hollow plunger 29 is attached to the connector 22 as described above.
Is slidably inserted, but a spring 30 is interposed between the plunger 29 and the plug 27 so that the plunger 29 normally keeps the illustrated position.

The variable orifice 31 is provided in the small diameter portion 25 of the connector 22.
The variable orifice 31 is fully opened when the flanger 29 is at the normal position shown in the drawing, and the opening area of the variable orifice 31 is reduced when it moves against the spring 30. .

Further, on the outer periphery of the plunger 29, a pressure chamber 32 formed in combination with the connector 22 is provided.
The space 26 is communicated with the space 26 through a through hole 33.

Incidentally, the space 26 to the reference numeral 34 denotes a discharge oil of the front wheel pump P ₁
Inlet port leading to, 35 at outlet port formed in the connector 22, communicates with the pump port of the front-wheel control valve V _1.

The flow control spool 21 has first and second land portions 36 and 37.
Along with the action of the spring 20, usually
It is in pressure contact with the plug 27. When the flow control spool 21 is in pressure contact with the plug 27 as described above, the bypass passage 38 and the space 26
Communication with is interrupted.

In the above state, when the pressure in the space 26 rises and the acting force overcomes the spring force of the spring 20, the flow control spool 21 moves to connect the space 26 and the bypass passage 38.

Pump port 39 of the wheel control valve V ₂ after controlling the rear wheel power cylinder S _2, the pump for the rear wheels via a supply passage 40 P ₂
While connected to and connects the rear wheel valve mechanism V _R to the supply passage 40. Also, the tank port 41 of the control valve V ₂
Is connected to the tank T via the return passage 42.

Incidentally, the rear wheel pump P _2, like the front wheel pump P _1, those that are linked to the engine, thus, the pump P ₂ also depends the discharge amount to the vehicle speed.

Furthermore, cylinder port 43, 44 of the rear wheel control valve V ₂
The chamber 1 of the rear wheel power cylinder S ₂ via the passage 45
4 and 15 are connected.

Wheel control valve V ₂ after the above communicates the pilot chamber 47, 48 to the front wheel power cylinder S ₁ chamber of the chamber 3,4. When cut the handle 8 to the right to supply pressure oil to the chamber 4 of the front wheel power cylinder S _1, it acts on the pilot chamber 48 of the rear wheel control valve V ₂ is the pressure, the pump port
39 and switching the rear wheel control valve V ₂ so as to communicate the cylinder port 44.

With such switching the rear wheel control valve V _2, oil discharged from the rear wheel pump P ₂ is, the supply passage 40 → the pump port 39 → the power cylinder for the rear wheels via the cylinder port 44 → passage 46
It is supplied to the chamber 15 of S _2. Further, the hydraulic oil of the rear wheel power cylinder S ₂ of the chamber 14, so returned to the tank T via the passage 45 → cylinder port 43 → the tank port 41 → return passages 42, the rear wheel 16 and the front wheels 1 The vehicle is steered rightward, which is the same direction.

Also, cutting the handle 8 to the left, since the chamber 3 side of the front wheel power cylinder S ₁ is higher pressure, in turn, the rear wheel control valve V ₂ is switched in the opposite direction to the above, the rear wheel 16 Also steers to the left.

Specific configuration of the wheel valve mechanism F _R after connecting to the supply passage 40 is shown in Figure 3. That is, a flow control spool 52 is slidably inserted into a valve hole 50 formed in the valve body 49 with a spring 51 interposed between the valve hole 50 and the inner end thereof.

Further, a hollow connector 53 is inserted outside the flow control spool, and the screw portion 54 is tightened to press the flange 55 against the side surface of the valve body 49.

The connector 53 as described above has a small-diameter portion 56 at its distal end, and an annular space 57 between the small-diameter portion 56 and the valve hole 50.
And plug the end of this connector 53
Blocked at 58. The plug 58 has a fixed orifice communicating the space 57 with the hollow portion of the connector 52.
Form 59.

A hollow plunger 60 is connected to the connector 53 as described above.
Is slidably inserted, a spring 61 is interposed between the plunger 60 and the plug 58, and the plunger 60 normally keeps the position shown in the figure.

The small diameter portion 56 of the connector 53 has a variable orifice 62
The variable orifice 62 is fully closed when the plunger 60 is in the normal position shown in the figure, and when the plunger 60 moves against the spring 61, the variable orifice 62
Is trying to open.

Further, on the outer periphery of the flanger 60, a pressure chamber 63 is formed in conjunction with the connector 53, and the pressure chamber 63 is formed.
Communicates with the space 57 through the through hole 64.

Incidentally, the space 57 to discharge oil in the reference numeral 65 is a rear wheel pump P ₂
Inlet port leading to, 66 at the outlet port formed in the connector 53, communicates with the pump port of the rear wheel control valve V _2.

The flow control spool 52 has first and second land portions 67 and 68.
Along with the action of the spring 51, usually
It is in pressure contact with the plug 58. When the flow control spool 52 is in pressure contact with the plug 58 as described above, the bypass passage 69 and the space 57
Communication with is interrupted.

In the above state, when the pressure in the space 57 increases and the acting force overcomes the spring force of the spring 51, the flow control spool 52 moves, and connects the space 57 and the bypass passage 69.

Thus, the during running of the vehicle, since both pumps P _1, P ₂ is operated, the inlet port 65 of the discharge amount and the inlet port 34 of the front wheel valve mechanism V _F, the rear wheel valve mechanism V _R Flows into.

Then, the pressure oil which has flowed into the inlet port 34, through the fixed orifice 28 and the variable orifice 31 flows out from the outflow port 35, flows into the pump port of the front-wheel control valve V _1.

At this time if the vehicle is traveling at low speed, since the discharge quantity of the front wheel pump P ₁ is not so large, no differential pressure across the variable orifice 31 in the fixed orifice 28 and fully open state is hardly generated.

Therefore, the pressure in the pressure chamber 32 is also maintained relatively low, so that the plunger 29 holds the illustrated normal position,
The variable orifice 31 is kept fully open. Thus, almost all of the flow rate flowing from the inlet port 34 is supplied to the front wheel power cylinder S _1, the cylinder S ₁ exhibits a sufficient power assist force.

When the vehicle speed increases from the above state, since many discharge quantity of the front wheel pump P ₁ along with it, differential pressure across the fixed orifice 28 and the variable orifice 31 is increased. If the differential pressure increases, the pressure in the pressure chamber 32 increases relatively, so that the plunger 29 moves against the spring 30, but in the middle speed range, the opening of the variable orifice 31 is narrowed, and In the range, the variable orifice 31 is fully closed.

If small or the opening area thereof variable orifice 31 is closed as described above, the flow rate flowing out of the outflow port 35 is much less, the supply flow rate to the front wheel power cylinder P ₁ becomes less. Therefore, amount that the supply flow rate is reduced, the assist force of the front wheel power cylinder S ₁ is reduced, the manual steering in its fully closed state.

And, as described above, if the differential pressure across the orifice increases, the pressure acting on the flow control spool 21 also increases, so that the spool 21 moves against the spring 20,
The space 26 and the bypass passage 38 are communicated. Therefore,
The surplus flow rate flowing from the inflow port 34 is returned to the tank T from the bypass passage 38.

The discharge oil of the rear wheel pump P ₂ is flowing into the inlet port 65 of the rear wheel valve mechanism V _R, the traveling the vehicle as described above at low speed, the rear wheel pump P ₂ Does not increase, so the amount of inflow into the inflow port 65 also decreases.

If the amount of inflow is small as described above, the differential pressure does not increase before and after the fixed orifice 59, so that the pressure in the pressure chamber 63 does not increase. For this purpose, the plunger 60 holds the illustrated normal position and the variable orifice 62 is kept closed.

Accordingly, the flow rate flowing out of the outlet port 66 becomes very small amount of only passing portion of the fixed orifice 59, does not substantially activate the rear wheel power cylinder S _2. The excess flow at this time is pushed back to open the flow control spool 52 and returned to the tank T.

From the above state, when the vehicle shifts to the middle and high speed range,
Since the pressure difference around the fixed orifice 59 becomes large, the pressure in the pressure chamber 63 also becomes relatively high, and the plunger 60 moves against the spring 61 to open the variable orifice 62.
If this variable orifice 62 is opened, since a sufficient flow rate is supplied to the rear wheel power cylinder S _2, the rear-wheel power cylinder S ₂ is operated to steer the rear wheels in a predetermined direction .

At this time, the excess flow rate equal to or higher than the target flow rate is pushed back by opening the flow rate control spool 52 and returned from the bypass passage 69 to the tank T.

As described above, according to the device of the first embodiment, when the vehicle is traveling at low speed, only the front wheels 1 are steered, but when traveling at medium to high speed, the front wheels and the rear wheels are also steered in the same direction.

Second embodiment shown in 4 and 5 figure includes a front wheel power cylinder S ₁ chamber 3,4, the rear wheel control valve V _R pilot chamber 4
The passage 71 which connects the 7,48 obtained by connecting the directional control valve V _d, the specific structure of the directional control valve V _d are shown in Figure 5.

That is, the spool 73 is slidably mounted in the valve case 72, and one end of the spool 73 faces the spring chamber 74 and the other end faces the pilot chamber 75. Since the spring 76 is provided in the spring chamber 74, the spool 73 maintains the illustrated in-phase position by the action of the spring 76 unless pressure acts on the pilot chamber 75. That is, the upstream port 77 connected to the passage 70 communicates with the downstream port 78 connected to the pilot chamber 47, and the upstream port 79 connected to the passage 71 and the downstream port 80 connected to the pilot chamber 48 are connected. Communicate.

The pilot chamber 75 communicates with the supply passage 5 connected to the front wheel pump P _{1. When} the pressure action of the pilot chamber 75 overcomes the spring force of the spring 76,
The spool 73 moves to maintain the reverse phase mode position. That is, the upstream port 77 and the downstream port 80 communicate with each other, and the upstream port 79 is connected to the flow path 81 formed in the spool 73.
Through to the downstream port 78.

Directional control valve V _d which as described above, during low-speed running, when turned the steering wheel 8, switches to a reverse phase mode position by the pressure of the supply passage 5 side. That is, since during low-speed running large換向resistance, but also increases the pressure in the supply passage 5, in this raised pressure, that the directional control valve V _d is switched to a reverse phase mode, as described above It is.

Therefore, turn off the handle 8 during the low-speed running to the right, since the pressure oil in the chamber 4 of the front wheel power cylinder S ₁ is supplied, the passage 71 side becomes a high pressure.

At this time, since the directional control valve V _d is switched to the reverse phase mode as described above, the pressure oil of the passage 71, the directional control valve V _d of the upstream port 79, the passage 81 and the downstream port 78
Via, acting on one of the pilot chamber 47 of the rear wheel control valve V _2. At this time the other pilot chamber 48 communicates with the tank T via the downstream port 80 → the upstream port 77 → the passage 70 → the front-wheel control valve V ₁ → return path 7 of the directional control valve V _d.

Thus, the rear wheel control valve V ₂ is switched, the pump port 39 and cylinder port 43 communicates with the tank port
41 and the cylinder port 44 are communicated. Therefore, the hydraulic oil of the rear wheel power cylinder S ₂ of the chamber 14 to supply pressurized oil is chamber 15 so returned to the tank T, the rear wheel 16 from the front wheel 1 is steered to the left is a reverse direction.

Also, cutting the handle 8 to the left, since the pressure oil in the chamber 3 of the front wheel power cylinder S ₁ is supplied, the pressurized oil is, the rear wheel control valve via the other side of the passage and the V ₂ acts on the pilot chamber 48, switching the control valve V ₂ on the opposite to the above. Thus, although the pressure oil in the chamber 15 of the rear wheel power cylinder S ₂ is supplied, this rear wheel 16 by are steered to the right is the direction opposite to the front wheels.

On the other hand, when the vehicle is traveling at medium to high speeds, the turning resistance is small, so the pressure on the supply passage 5 side does not increase so much. Since not higher pressure in the pilot chamber 75 to the direction switching valve V _d holds the in-phase position is a normal position.

By holding this way directional control valve V _d is phase position, the rear wheel control valve V ₂ may instead outright along with it, to steer the rear wheels 16 to the front wheel 1 in the same direction.

The second embodiment as described above, by adding the directional control valve V _d, the rear wheel 16 and the front wheel 1 is obtained by allowing turning in the opposite direction.

 Other configurations are the same as in the first embodiment.

The third embodiment shown in FIG. 6 is the directional control valve V _d and solenoid control, but were electrically connected to the solenoid 82 to the controller C, the other configuration exactly the same as the second embodiment It is.

Then, the controller C outputs a signal corresponding to the vehicle speed, at the time of low-speed running, switching the switching valve V _d to reverse phase mode position, at the time of medium speed running, in which switches it to the in-phase mode position .

The fourth embodiment shown in FIG. 7, together with the rear wheel control valve V ₂ provided in connection with the handle 8 with the front-wheel control valve V _1, direction change at the downstream side of the rear wheel control valve V ₂ The valve _Vd is connected.

In other words, while the switched directly related to the rear wheel control valve V ₂ to the rotation of the handle 8, a flow path connecting the rear wheel cylinder S ₂ Thereafter the wheel control valve V _2, the direction change switching the valve V _d, it is obtained by be able to select one of the common-mode or reverse-phase mode.

The configurations of the directional control valve V _d and the two valve mechanisms 6 and 10 in the fourth embodiment are the same as those in the above embodiments.

The fifth embodiment shown in FIG.
_Vd is electromagnetically controlled, and its solenoid 82 is
The other configuration is completely the same as that of the fourth embodiment.

Then, the controller C outputs a signal corresponding to the vehicle speed, at the time of low-speed running, switching the switching valve V _d to reverse phase mode position, at the time of high-speed running, in which switches it to the in-phase mode position.

[Brief description of the drawings]

1 to 3 show a first embodiment of the present invention.
1 is a circuit diagram, FIG. 2 is a sectional view of a front wheel valve mechanism, and FIG.
4 and 5 show a second embodiment. FIG. 4 is a circuit diagram, FIG. 5 is a cross-sectional view of a directional control valve, and FIG. FIG. 7 is a circuit diagram of a fourth embodiment, FIG. 8 is a circuit diagram of a fifth embodiment, and FIG. 9 is a circuit diagram of a conventional device. P ₁ … front wheel pump, P ₂ … rear wheel pump, 1… front wheel, S ₁ … front wheel power cylinder, 3, 4… chamber, V ₁ …
... Front wheel control valve, T ... Tank, 8 ... Handle, V ₂ ...
… Rear wheel control valve, S ₂ … Rear wheel power cylinder, 14, 15
… Room, 16… Rear wheel, V _F … Front wheel valve mechanism, V _R … Rear wheel valve mechanism.

Claims (1)

(57) [Claims] 1. A front wheel pump and a rear wheel pump whose rotation speeds depend on the vehicle speed, and which are switched with the rotation of a steering wheel, and one of chambers of a front wheel power cylinder according to the switching position. To the front wheel pump, and to the front wheel control valve to connect one of the other chambers to the tank, and to switch when the steering wheel is operated, and to switch to one of the rear wheel power cylinders according to the switching position. And a control valve for the rear wheel that communicates the chamber with the pump for the rear wheel and communicates one of the other chambers with the tank. The control valve for the rear wheel steers the rear wheel in the same direction as the front wheel. In the four-wheel steering system configured to switch to the in-phase mode position, a front-wheel valve mechanism for controlling the supply flow rate in inverse proportion to the vehicle speed is provided upstream of the front-wheel control valve, while the upstream of the rear-wheel control valve is provided. Beside A rear wheel valve mechanism for controlling the supply flow rate in proportion to the vehicle speed is provided.The rear wheel valve mechanism has an inflow port connected to the rear wheel pump, an outflow port connected to the rear wheel control valve, A fixed orifice and a variable orifice provided in the communication process between the inflow port and the outflow port are provided in the passage process between the variable orifice and the outflow port. A plunger that controls the opening of the variable orifice
A four-wheel steering device comprising: a flow control spool provided in parallel with the fixed orifice and the variable orifice and returning a flow rate equal to or greater than a set flow rate to a tank.