JPH0717356B2 - Control valve for tilt cylinder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt control valve for controlling a tilt cylinder for tilting a mast forward and backward of a forklift, and more particularly to limiting a forward tilt speed when tilting the mast backward. A telto lock plunger assembled in a tilt spool for

(Prior Art) FIGS. 3 and 4 show an oil control valve for a tilt cylinder equipped with a conventional tilt lock plunger. The valve body 1 includes a center bypass 2 that communicates with a discharge line of a hydraulic pump 9, left and right pump ports 3 and 4 that communicate with the center bypass 2 via check valves (not shown), and a bottom side of a tilt cylinder 10. Cylinder bottom port 5 that communicates with the oil chamber and tilt cylinder 10
Cylinder rod port 6 communicating with the rod side oil chamber of
It is provided with left and right tank ports 7 and 8 communicating with the tank 11. And this valve body 1 has a tilt spool
12 is slidably mounted in the axial direction and is always held in the neutral position shown in FIG. 3 to close the bottom port 5 and the rod port 6 of the tilt cylinder 10.

The tilt lock plunger 13 for controlling the tilting speed when the mast is tilted forward is slidably inserted in the tilt spool 12 in the axial direction. The position of the tilt lock plunger 13 is controlled by the pump pressure in the damper chamber 14 acting on one end in the axial direction and the spring 16 acting on the other end.
Although it is held in the shut-off position on the left side shown in FIG. 3 by 16, the pressure of the damper chamber 14 becomes the pressing force of the spring 16 when the tilt spool 12 is operated to the forward tilt side (the right side in the figure) while the engine is driven. When the tilt spool 12 is moved to the communicating position on the right side by overcoming, the tilt spool 12 is operated to the forward tilt side, and the tilt lock plunger 13 is displaced to the communicating position.

That is, the tilt spool in the engine driven state
When 12 is operated forward, the left pump port 3 communicates with the cylinder bottom port 5, so the hydraulic fluid discharged from the hydraulic pump 9 is sent to the bottom chamber of the tilt cylinder 10. At this time, a part of the hydraulic oil enters the outer peripheral space 20 between the central flange 18 and the left flange 17 of the tilt lock plunger 13 from the right pump port 4 through the through hole 15 of the tilt spool 12. As a result, it flows into the damper chamber 14 through the gap s between the outer peripheral surface of the left flange portion 17 and the inner peripheral surface of the tilt spool hole, and displaces the tilt lock plunger 13 against the spring 16 to the communicating position.

At this time, a part of the hydraulic oil that has flowed into the outer peripheral space 20 is a passage formed in the center of the tilt lock plunger 13.
It flows into the spring accommodating chamber 22 through 21 and further out through this through the through hole 23 provided in the tilt spool 12 to the tank port 8 on the right side in the drawing. This is done for the purpose of suppressing a sudden displacement of the tilt lock plunger 13.

Then, the tilt of the tilt lock plunger 13 to the communicating position causes the central flange portion of the tilt lock plunger 13 to move.
The outer circumference space 24 between the 18 and the right collar 19 is the tilt spool.
Since the cylinder rod port 6 and the right side tank port 8 are communicated with each other through the small holes 25 and 26 formed in 12, the hydraulic oil in the rod chamber flows out to the tank 11 and the tilt cylinder 10 is extended and actuated. Is leaned forward. In this case, the mast always tries to abruptly tilt due to the load acting in the forward tilting direction, but as described above, the hydraulic oil flow on the outflow side becomes the restricted flow due to the small holes 25, 26, The forward tilt speed of the mast can be suppressed to an appropriate speed. In other words, the tilt lock plunger acts to control the forward inclination of the mast at an appropriate speed. Then, once the tilt lock plunger 13 is displaced to the communication position, the damper chamber 14 is moved to the tank side even if the tilt spool 12 is returned to the neutral position while the engine is being driven or is operated to the backward tilt position. Since they are not communicated with each other, they are held in the communication position.

On the other hand, when the engine is stopped, the pump pressure of the pump port 4 disappears as the hydraulic pump 9 stops,
The hydraulic oil in the damper chamber 14 flows out to the pump port 4 through the gap s between the outer peripheral surface of the left flange 17 and the inner peripheral surface of the tilt spool hole, and the tilt lock plunger 13 is returned to the initial shutoff position by the spring 16. Thus, the hydraulic oil is prevented from flowing out of the oil chamber on the rod side of the tilt cylinder 10 to hold the mast from the load in the forward tilt direction. In other words, the mast fluctuates and self-propelling (tilting forward) is prevented.

(Problems to be Solved by the Invention) By the way, in the case of the conventional tilt cylinder control valve described above, the operation of the tilt lock plunger 13 is performed between the outer peripheral surface of the left collar portion 17 and the inner peripheral surface of the tilt spool hole. The control is performed depending on the clearance s. Therefore, when the clearance s is small, the inflow of the hydraulic oil into the damper chamber 14 is throttled, and the tilt lock plunger 13 is delayed in operation. When the clearance s is large, the tilt lock plunger 13 vibrates due to the reaction of the spring 16, destabilizing the pressure of the pump port 4 and causing the pump port 4 and the cylinder rod port to become unstable. Opening and closing operations are repeated between 6
There is a problem that the followability of the flow rate becomes difficult and the mast vibrates. Then, it is technically very difficult to set the gap s so as to prevent both of these problems.

Therefore, in view of the above problems, the present invention provides a tilt cylinder control valve having a structure effective in preventing the occurrence of an operation delay and vibration when the mast is tilted forward,
To that end.

(Means for Solving the Problems) The present invention is configured as follows to solve the above problems.

It is slidably inserted in the tilt spool in order to control the tilting speed at the time of tilting the mast, and by the pump pressure in the damper chamber acting on one end in the axial direction and the spring acting on the other end. A tilt cylinder control valve provided with a tilt lock plunger that is displaced between a position in which the rod-side oil chamber of the tilt cylinder communicates with a tank and a position in which the oil chamber closes to the tank, wherein the tilt lock plunger itself has the damper chamber and the pump. An introduction passage for communicating with the port is formed, and a check valve for preventing the flow from the damper chamber to the pump port side is provided in the introduction passage.

Further, the width of the collar portion formed in the tilt lock plunger for partitioning the damper chamber and the gap between the outer peripheral surface of the collar portion and the inner peripheral surface of the tilt spool hole allow oil to flow into and out of the damper chamber. It is set to be restricted to.
Specifically, it is desirable to set the width of the collar portion larger than that of the conventional one, while setting the gap between the outer peripheral surface of the collar portion and the inner peripheral surface of the tilt spool hole to be narrower than the conventional one.

(Operation) According to the tilt cylinder control valve configured as described above, when the tilt spool is operated to the forward tilt side, the hydraulic oil flowing from the pump port is non-returned from the passage formed in the tilt lock plunger itself. It flows into the damper chamber through the valve and displaces the tilt lock plunger to the communicating position against the spring. In this case,
It is possible to set the size of the introduction passage so that the tilt lock plunger can be displaced quickly without causing a delay in operation, and the pressure inside the damper chamber is reversed even though the introduction passage is large enough. Due to the presence of the stop valve, the tilt lock plunger is kept constant without being affected by the reaction of the spring or the pressure fluctuation of the pump port, so that the vibration of the tilt lock plunger is suppressed.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIGS. 1 and 2. The same components as those of the above-described conventional device are designated by the same reference numerals and the description thereof will be omitted.

1 shows a state in which the tilt spool 12 is in the neutral position and the tilt lock plunger 13 is held in the initial blocking position by the spring 16, and FIG. 2 shows that the tilt spool 12 is operated to the forward tilt position. The state in which the tilt lock plunger 13 is displaced to the communication position against the spring 16 is shown.

As shown in the figure, in the left part of the tilt lock plunger 13 shown in the figure, an introduction passage 27 for introducing hydraulic oil into the damper chamber 14 is formed at the center of the shaft, and an inlet 27a of the introduction passage 27 is formed.
Is opened in the outer peripheral space 20 between the left flange 17 and the central flange 18, and the outlet 27b is opened in the damper chamber 14. A check ball 28 as a check valve is incorporated in the introduction passage 27 to prevent oil from flowing out from the damper chamber 14 side to the outer peripheral space 20 side. In addition, 29 is a plug.

On the other hand, the gap s between the outer peripheral surface of the left collar portion 17 that defines the damper chamber 14 and the inner peripheral surface of the tilt spool hole is conventionally 15 to 30 μ (micron), but is narrowed to 10 to 20 μ. The width of the left collar 17 has been increased from 3 mm to 3 mm, which was conventionally 1 mm, which allows the oil flow passing between the outer peripheral surface of the left collar 17 and the inner peripheral surface of the tilt spool hole to the maximum extent possible. It is configured to be limited to.

Therefore, when the tilt spool 12 is operated to the forward tilt side shown in FIG. 2, the tilt spool 12 flows from the right pump port 4 through the through hole 15 into the outer peripheral space portion 20 between the left collar portion 17 and the central collar portion 18. The working oil pushes open the check ball 28 of the introduction passage 27 and flows into the damper chamber 14, and resists the spring 16 to move the tilt lock plunger 13 to the communicating position shown in FIG. 2, that is, the cylinder rod port 6 and the tank on the right side. The port 8 is displaced to a position where it communicates with the outer peripheral space 24 between the central flange 18 and the right flange 19 and the small holes 25, 26. Therefore, the hydraulic pump 9
The hydraulic oil from the pump is sent to the bottom side oil chamber of the tilt cylinder 10 via the pump port 3 and the cylinder bottom port 5 on the left in the figure, while the hydraulic oil in the rod side oil chamber flows out to the tank 11 and the tilt cylinder 10 extends. It is activated and the mast is tilted forward.

Therefore, in the present embodiment, the hydraulic oil is introduced into the damper chamber 14 through the introduction passage 27 having the check ball 28 formed in the tilt lock plunger 13 itself. Unlike the conventional case where the hydraulic oil is introduced through the gap s between the inner surface of the tilt spool hole, the area of the introduction passage 27 can be set so that the tilt lock plunger 13 can be displaced quickly. It is possible to eliminate the operation delay of. In addition, check balls 28 are provided in the introduction passage 27.
Is provided to prevent the reverse flow of the hydraulic oil in the damper chamber 14, it is possible to avoid the reaction of the spring 16 or the pressure fluctuation of the pump port 4 to suppress the vibration of the tilt lock plunger 13, so that the cylinder rod port Stabilization of hydraulic oil outflow from 6 to tank 11
10 can be operated smoothly.

Then, when the engine is stopped, the hydraulic oil in the damper chamber 14 returns to the tank port side through the slight clearance s between the outer peripheral surface of the left flange 17 and the inner peripheral surface of the tilt spool hole, and the tilt lock plunger 13 causes the spring 16 to rotate. The rod-side oil chamber of the tilt cylinder 10 and the tank 11 are shut off by returning to the initial position by the above, and the fluctuation and self-propelling (forward tilting) of the mast that is always loaded on the forward tilt side are prevented.

The inlet 27a of the introduction passage 27 is preferably set smaller than the inlet 21a of the passage 21 communicating with the spring accommodating chamber 22 within a range that does not cause an operation delay.
It is effective in suppressing a sudden inflow into the tilt lock plunger 13 and preventing the vibration of the tilt lock plunger 13.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to provide a control valve for a tilt cylinder that can prevent operation delay and vibration and can obtain stable operation with good responsiveness. Is. Also, for conventional control valves, it is possible to replace the tilt spool with the tilt lock plunger installed as a tilt spool assembly, so not only for newly manufactured vehicles but also for operation delays and vibration problems. It can be easily applied to existing existing vehicles.

[Brief description of drawings]

1 and 2 are sectional views showing an embodiment of a control valve for a tilt cylinder according to the present invention, and FIGS. 3 and 4 are sectional views showing a conventional control valve for a tilt cylinder. 1 …… Valve body, 3,4 …… Pump port 9 …… Hydraulic pump, 10 …… Tilt cylinder 12 …… Tilt spool 13 …… Tilt lock plunger 14 …… Damper chamber, 16 …… Spring 17,18,19 …… Mitsuba 27 …… Introduction passage, 28 …… Check ball

Claims (1)

[Claims] 1. A pump pressure in a damper chamber which is slidably inserted in a tilt spool in an axial direction to control a tilting speed when the mast is tilted forward, and a pump pressure in a damper chamber which acts on one end in the axial direction and another end. A tilt cylinder control valve having a tilt lock plunger that is displaced between a position in which the rod-side oil chamber of the tilt cylinder communicates with a tank and a position in which the oil chamber is shut off by a spring that acts on the damper chamber and the pump port. The tilt lock plunger itself is formed with an introduction passage for communicating the
A check valve for blocking the flow from the damper chamber to the pump port is provided in the introduction passage, and the width of the collar portion formed on the tilt lock plunger for partitioning the damper chamber and the outer peripheral surface of the collar portion and the tilt portion. A control valve for tilt cylinders with a clearance between the inner surface of the spool hole and the damper chamber that is set to limit the flow of oil into and out of the damper chamber.