JPH01168550A - Hydraulic control valve for fork-lift truck - Google Patents

Abstract

PURPOSE:To contrive at reduction in effect on brake force due to pulsation in a lift cylinder by installing an annular ring and a throttle passage in a spring bearing of a control piston for a fork-lift truck hydraulic control valve which proportionally controls the extent of braking pressure in response to the load of freight mounted on a fork. CONSTITUTION:Brake fluid pressure out of a master cylinder is fed to an inlet chamber 11 of a stepped piston 8 from an inlet 6, and also fed to a brake cylinder from an outlet chamber 12 and an outlet 7, whereby braking takes place. Fluid pressure at the side of a lift cylinder pressure chamber of a fork is fed to a control room 28 from a connection 28a, thereby operating the stopped piston 8 via a control piston 24, a spring bearing 23 and springs 32, 33, and brake pressure is proportionally controlled in response to load of freight mounted on the fork. An annular ring 29 and a throttle passage 30 are installed in this spring bearing 23, through which pressure variations in the control room 28 due to pulsation in the lift cylinder is absorbed, thus reduction in effect on brake force is contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic pressure control valve for a forklift vehicle that performs cargo handling work.

[Conventional technology]

As shown in Japanese Utility Model Application Publication No. 62-29395, this type of device includes a main body formed with an inlet communicating with a master cylinder and an outlet "1" communicating with a wheel cylinder;
A stepped hole formed by connecting the inlet and the outlet, a piston slidably inserted into the stepped hole to partition the inlet chamber and the outlet chamber, and a passage provided in the passage connecting the inlet chamber and the outlet chamber. a control piston that can be pressed to increase the biasing force of the spring against the piston; a spring that biases the piston in a direction in which the valve opens; It is known that the pressure of a lift cylinder that drives the fork is applied to the control piston.

[Problem that the invention seeks to solve]

In the above conventional system, the pressure of the lift cylinder is applied directly to the control piston, so when the forklift truck is running with a load placed on the fork, the external force acting on the fork may fluctuate due to vibration etc. The internal pressure of the lift cylinder also fluctuates, and this causes fluid pressure pulsations that act on the control piston, making fluid pressure control unstable.
Brake force cannot be properly controlled.

SUMMARY OF THE INVENTION In view of these problems, an object of the present invention is to provide a hydraulic pressure control valve for a forklift vehicle that can be appropriately controlled.

[Means of invention]

The present invention provides a reduction mechanism to reduce pressure pulsations from the lift cylinder.

[Effect of means]

Even if the pressure in the lift cylinder pulsates for some reason and this acts on the control piston, the pulsation is reduced by the reduction mechanism, making it possible to perform control without pulsation.

[Embodiment] FIG. 1 is a sectional view of a hydraulic pressure control valve for a forklift vehicle, which is an embodiment of the present invention.

In the figure, the hydraulic pressure control valve is indicated as a whole by 1, and this hydraulic pressure control valve 1 has a valve section 2 on the left side and a control section 3 on the right side.

The valve part 2 has a main body 5 in which a stepped hole 4 is formed that is open on the right side, and a large diameter part 4a of the stepped hole 4 is connected to a pipe to a master cylinder (not shown). Inlet 6 and stepped hole 4
A lower outlet is connected to the small diameter portion 4b of the front axle to which a pipe to a wheel cylinder (not shown) of a brake device of the front axle is connected.

A single stepped piston 8 is slidably inserted into the stepped hole 4, and the large diameter portion 8a is fitted into the small diameter portion 4b of the stepped hole 4, and the small diameter portion 8b is fitted into the large diameter portion 4a of the stepped hole 4. They are slidably fitted to the attached sealing member 9 and plug 10, respectively, and partition a population chamber 11 that communicates with the inlet 6 and an outlet chamber 12 that communicates with the outlet lower. 13 is a stop ring for preventing the plug 10 from being removed; 1
4 is a spacer with a hole for holding down the sealing member 9, and 15 is a sealing member. A passage 16 is formed in the stepped piston 8 and connects the inlet chamber 11 and the outlet chamber 12.
6 has a valve spring 1 facing toward a valve seat 17 formed in a passage 16.
A valve body 19 is provided which is biased by the valve body 19.
The end of the valve seat 1 is brought into contact with the bottom of the stepped hole 4.
It is far from 7.

The valve portion 2 has the same function as the valve portion of the well-known P valve.

In contrast to such a valve part 2, the control part 3 has a main body 21 that is fitted to the main body 5 via a rolling 2o, and a stepped hole 22 that is open on the left side is formed in the main body 21. It is designed to be closed by the main body 5.

The stepped hole 22 of the main body 21 has a spring support 2 on the opening side.
The inside of the large diameter part 22a has a large diameter part 22a into which a control piston 24 which can come into contact with the spring receiver 23 is slidably inserted. A damper chamber 27 is connected to the drain side of the rift 1 cylinder (not shown) through a connection part 25 and to the hydraulic oil tank side through a connection part 26, and the small diameter part 22b is connected to a damper chamber 27 by a control piston 24. A control chamber 28 is provided which is divided and communicates with the pressure chamber side of the lift cylinder through a connecting portion 28a.

The spring receiver 23 is equipped with an annular ring 29 made of a rubber material on the outer periphery of the cylindrical portion 23a, which closely divides both sides of the spring receiver 23 and between the spring receiver 23 and the inner circumferential surface of the large diameter portion 22a. It is designed to provide a relatively large frictional resistance between the Further, the plate portion 23b of the spring receiver 23 is formed with a throttle passage 30 that communicates both sides of the spring receiver 23. Therefore, the spring receiver 23 also has the role of a damper piston that acts within the damper chamber 27.

Of the connection parts 25 and 26 to the damper chamber 27, the one on the lift cylinder side has a small inner hole in the piping tube sheet 25a to have a throttling effect to suppress pulsation on the drain side of the lift cylinder, and the inside of the damper chamber 27 is This prevents pressure pulsations.

Preload springs 32 and 33 are tensioned between the plate portion 23b of the spring receiver 23 and the main body 5 of the valve portion 2, and between the spring receiver 31 fitted to the stepped piston 8, respectively. The ratio of change in pressure reduction start pressure in valve portion 2 to pressure increase is set to be greater than 1 (this point is conventionally known).

In the map, 34 indicates a sealing member, 34a indicates a backup ring, and 35 indicates an air bleeding bleeder screw.

The operation of the above embodiment will be described below.

Now, assuming that the pressure from the lift cylinder is sufficiently low and the brake is not applied, each member assumes the position shown. That is, the stepped piston 8 and the spring receiver 23 are returned to the positions where they contact the main body 5 and the main body 21, respectively, by the tension of the springs 32 and 33, and the valve body 19 is separated from the valve seat 17 in the passage 16 of the stepped piston 8. The control piston 24 freely communicates the inlet chamber 11 and the outlet chamber 12 with each other.
The control chamber 28 is in a position where it is pushed to its minimum volume.

After that, when the vehicle attempts to travel with a load placed on the fork, the pressure in the pressure chamber of the lift cylinder increases due to the driver's operation, causing the fork to rise along with the load.

At this time, pressure opposite to the weight of the cargo is supplied to the pressure chamber of the lift cylinder, and this pressure is applied to the control chamber 28.
is supplied to. The control piston 24 receives this pressure and moves the spring receiver 23 to the left against the tension of the spring 32, 33, increasing the load of the spring 32 on the stepped piston 8.

Suppose you drive a forklift truck under these conditions and apply the brakes. Then, brake pressure is supplied from the master cylinder to the wheel cylinder through the inlet chamber 11, the first passage 16, and the outlet chamber 12 in order, and the brake starts to be applied. Thereafter, when the brake pressure increases, the force acting to the right due to the pressure acting on the membrane area S1 of the small diameter portion 8b of the stepped piston 8 and the force acting leftward by the spring 32 are balanced out. Then, the single-stage piston 8 moves to the right and seats the valve body 19 on the valve seat 17. Next, when the master cylinder side pressure further increases, the force exerted by the outlet chamber 12 pressure Pw on the large diameter portion 8a of the stepped piston 8 to move it to the right causes the inlet chamber 11 pressure Pw to The acting force acting on the area obtained by subtracting the cross-sectional area S of the small diameter portion 8b from the cross-sectional area S2 of the large diameter portion 8a of the piston 8 (S2-S) to move it leftward and the acting force by the spring 32 The stepped piston 8 moves so as to repeat the seating and unseating of the valve body 19 and the valve seat 17 so as to be evenly matched with respect to the sum of the sum. As a result, the outlet chamber 12 pressure Pw is controlled to be reduced. This can be expressed in the following equation.

When Pm<Pg=(F+ΔF)/S, Pw=
PmPm) When Pg, Pv=Pm ・(S, -S,)/S, +(F+ΔF)
/S□ However, Pg: Pressure to start pressure reduction F: Preload of spring 32 ΔF: Increase in load on spring 32 due to movement of control piston 24 As can be understood from this equation, pressure to start pressure reduction control by valve part 2 Pg spring 3 due to movement of control piston 24
The larger the increase in load ΔF in step 2, the greater the increase, and the smaller the increase in load ΔF, the smaller the decrease control pressure Pg can be changed in proportion to the load of the load placed on the fork. be.

When the spring receiver 23 compresses the springs 32 and 33 due to the movement of the control piston 24 in this manner, if the load on the fork moves up and down due to unevenness of the road surface, this up and down movement is caused by the lift cylinder. The pressure in the pressure chamber is moved up and down, and this is.

The pulses are transmitted to the control chamber 28 in the form of pulsations, and try to vibrate the control piston 24 from side to side. However, even if an attempt is made to move the control piston 24 to the left, the spring receiver 23 functions as a damper piston due to the annular ring 29 on its outer periphery and the throttle passage 30, and the vibrational movement of the control piston 24 does not occur. Moreover, the load on the spring 32 is not vibrated and the valve portion 2 is not adversely affected. In particular, the spring receiver 23 is connected to the control piston 2
4 during slow normal movement, the throttle passage 30
Even if there is, the throttling effect is quite small and the spring receiver 23 moves smoothly, but the throttling effect is large and the damper effect is large against sudden movements caused by pulsation or the like. As a result, even if the pulsation is transmitted to the control room 28,
Brake pressure reduction control can be performed appropriately.

Although the above embodiments have produced useful effects, it goes without saying that the following embodiments can also be used.

(2) An example in which the damper chamber 27 is a single sealed pressure chamber to prevent liquid from moving to the control chamber 28 or the inlet chamber 11.

(2) An example in which, instead of providing the damper chamber 27, a throttle passage is provided in the connecting portion 28a like a tube sheet 25a.

(2) An example in which the annular ring 29 has a trapezoidal cross section or a rectangular cross section.

(2) An example in which only one of the throttle passages 30 and the annular ring 29 is used in combination.

〔Effect of the invention〕

According to the present invention, since a reduction mechanism is provided to reduce pressure pulsations from the lift cylinder, even if the pressure in the lift cylinder pulsates for some reason and this acts on the control piston side, the reduction mechanism reduces the pressure pulsations from the lift cylinder. Because pulsation can be reduced.

Control can be performed without pulsation, and brake control can be performed appropriately.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Hydraulic pressure control valve for forklift vehicles, 23... Spring receiver, 29... Annular ring, 30... Throttle passage.

Claims (1)

[Claims] A main body formed with an inlet communicating with the master cylinder and an outlet communicating with the wheel cylinder, a stepped hole formed by communicating the inlet and the outlet, and an inlet chamber formed by being slidably inserted into the stepped hole. a piston that partitions the outlet chamber; a valve that is provided in a passage that communicates the inlet chamber and the outlet chamber and that opens and closes according to the movement of the piston; and a spring that biases the piston in a direction in which the valve opens. , a control piston that can be pressed to increase the biasing force of the spring against the piston, and a hydraulic pressure control valve for a forklift vehicle, the control piston being configured to apply pressure from a lift cylinder that drives a fork to the control piston. A hydraulic pressure control valve for forklift trucks equipped with a reduction mechanism that reduces pressure pulsation from the cylinder.