JP2001200805A - Hydraulic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device capable of assuring the responsiveness of a fork when the fork is operated in forward-bent posture and the function thereof as a lock valve while controlling the sudden forward-bent operation of the fork. SOLUTION: A flow control valve FV is installed in pilot pressure feed paths 30 and 33, an orifice 34 is provided between the flow control valve FV and a pilot chamber 17, and a flow rate fed from a feeding path 4 to a pilot chamber 17 of a sub spool 9 is controlled to a constant by the flow control valve FV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device used for a tilt cylinder of a forklift.

[0002]

2. Description of the Related Art In a conventional example shown in FIG. 3, a pair of first and second actuator ports A and B are formed in a valve body 1 and these first and second actuator ports A and B are formed.
Is connected to a tilt cylinder C of a forklift. The tilt cylinder C adjusts the angle of the fork F. For example, when the pressure oil is supplied to the first pressure chamber 2 and the pressure oil in the second pressure chamber 3 is discharged to the tank, the tilt cylinder C The fork F contracts, and the fork F tilts rearward with the support G as a fulcrum. Conversely, pressurized oil is supplied to the second pressure chamber 3,
When the pressure oil in the first pressure chamber 2 is discharged to the tank, the tilt cylinder C extends, and the fork F tilts forward about the support G.

A supply passage 4, a tank passage 5, and a spool hole 7 are formed in the valve body 1 to which the tilt cylinder C is connected, and the main spool 6 is slidably incorporated in the spool hole 7. Also, the valve body 1
Has a pump passage p to which a pump (not shown) is connected,
p and a neutral passage n. The pump passages p, p and the neutral passage n communicate with each other when the main spool 6 is at the neutral position, and the communication is cut off when the main spool 6 is switched. When the communication between the pump passages p and p and the neutral passage n is interrupted, the pressure in the bypass passage b increases, and the pressure oil is supplied from the bypass passage b to the supply passage 4 via the check valve c. I am trying to.

A shaft hole 8 is formed in the main spool 6 from the left side in the drawing, and a sub-spool 9 is slidably incorporated in the shaft hole 8. The shaft hole 8 is closed by a plug member 10, and a spring 11 is interposed between the plug member 10 and the sub-spool 9. The sub-spool 9 has first to third small-diameter portions 12 to 14, and a discharge hole 15 formed in the main spool 6 communicates with the first small-diameter portion 12 at a normal position shown in FIG. The communication hole 16 and the second small diameter portion 13 communicate with each other. A pilot chamber 17 is formed in the shaft hole 8 provided with the third small-diameter portion 14, and the pilot chamber 17 and the second small-diameter portion 13 are connected to the sub-spool 9 and the shaft hole 8.
Are communicated with each other via a clearance damper 18 formed by a gap with the gap.

[0005] The sub-spool 9 as described above closes the throttle passage 19 formed in the main spool 6 at the normal position shown in the figure, but when it is switched to the left against the spring 11, the throttle passage 19 is opened. The throttle passage 19 communicates with the discharge hole 15 through one small diameter portion 12. The communication between the throttle passage 19 and the tank passage 5 is interrupted when the main spool 6 is at the neutral position in the drawing, but communicates with the tank passage 5 when the main spool 6 is switched to the left side in the drawing. Therefore, when the main spool 6 and the sub-spool 9 are switched to the left, the first actuator port A and the tank passage 5 move from the discharge hole 15 to the first small-diameter portion 12.
→ It communicates via the throttle passage 19.

When the main spool 6 is at the neutral position, the communication with the supply passage 4 is interrupted. However, when the main spool 6 is switched to the left, the communication hole 16 communicates with the supply passage 4. I am trying to do it. The main spool 6 has a passage 23 formed therein. The passage 23 guides the pressure in the first actuator port A to the spring chamber 22 when the main spool 6 is at the neutral position. is there. If the pressure in the spring chamber 22 is maintained at the pressure in the first actuator port A, the sub-spool 9 keeps the illustrated normal state by the spring force of the spring 11 when the main spool 6 is at the neutral position. When the sub spool 9 switches to the left in the drawing, the pressure oil in the spring chamber 22 is discharged to the tank passage 5 through the passage 23.

Next, a case where the tilt cylinder C is controlled by the above-described device will be described. Main spool 6
Is switched from the neutral position shown to the right in the drawing, the second actuator port B and the tank passage 5 communicate with each other through the first annular groove 20 of the main spool 6, and the first through the second annular groove 21. The actuator port A communicates with the supply passage 4. Therefore, the pressure oil from the supply passage 4 is supplied to the second annular groove 21 → the first actuator port A → the first pressure chamber 2 of the tilt cylinder C, and the pressure oil of the second pressure chamber 3 of the tilt cylinder C is Is discharged to the tank via the second actuator port B → the first annular groove 20 → the tank passage 5. Therefore, the tilt cylinder C contracts, and the fork F tilts backward about the support G.

When the main spool 6 is switched to the left in the drawing, on the contrary, the second actuator port B and the supply passage 4 communicate with each other through the first annular groove 20. Further, the first actuator port A does not directly communicate with the tank passage 5 through the second annular groove 21, but communicates with the tank passage 5 through the main spool 6. That is, when the main spool 6 is switched to the left, the communication hole 16 opens to the supply passage 4, and the pressure oil from the supply passage 4 is supplied to the pilot chamber 17 via the communication hole 16 → the second small diameter portion 13 → the clearance damper 18. It is led to. And this pilot room 17
The sub-spool 9 moves the spring 1
The diaphragm path 19 moves to the left while bending, and the throttle passage 19 and the first small diameter portion 12 communicate with each other.

At this time, the throttle passage 19 communicates with the tank passage 5 as the main spool 6 moves. Therefore, the first actuator port A communicates with the tank via the discharge hole 15 provided in the main spool 6, the first annular groove 12, the throttle passage 19, and the tank passage 5.
That is, the first actuator port A communicates with the tank via the inside of the main spool 6. Then, the second actuator port B communicates with the supply passage 4 as described above,
When the first actuator port A communicates with the tank passage 5, the tilt cylinder C extends, and the fork F tilts forward about the support G. The main spool 6
Since the pressurized oil is discharged through the inside, the pressurized oil in the first pressure chamber 2 is not discharged at a stretch, and the fork F does not tilt forward rapidly.

On the other hand, the sub-spool 9 has a function as a lock valve for preventing danger. That is, when the engine is stopped, no pump pressure is generated, so that even if the main spool 6 is switched, the sub-spool 9 is not switched. Therefore, even if the main spool 6 is switched by mistake when the engine is stopped, the first actuator port A and the tank passage 5
The communication with the fork F is maintained in a disconnected state, and the fork F can be prevented from leaning forward.

Then, the sub-spool 9 as described above
The reason why the pilot chamber 17 and the clearance damper 18 are provided is as follows. For example, when the load W is placed on the fork F and the fork F is tilted forward, the load due to the load W acts on the rod-side chamber 2 of the tilt cylinder C as a counter load. For this reason, the extension speed of the tilt cylinder C increases, and the supply of the pressure oil to the second pressure chamber 3 cannot be performed in time, and the second actuator port B side may become negative pressure.

When the pressure in the second actuator port B becomes negative as described above, the supply passage 4 becomes slightly negative, and the sub-spool 9 is pushed back by the spring force of the spring 11. Therefore, the communication between the discharge hole 15 and the throttle passage 19 is interrupted, and the forward tilt of the fork F stops. When the forward tilt of the fork F stops, the pressure of the second actuator port B increases, so that the sub-spool 9 is switched, whereby the fork F starts to lean forward again.

That is, when the fork F is tilted forward,
Since the pressure in the supply passage 4 fluctuates due to the counter load W, the so-called hunting phenomenon occurs in the sub-spool 9, and the fork F may not be able to smoothly lean forward. Therefore, a clearance damper 18 is provided on the sub-spool 9 to prevent the hunting phenomenon of the sub-spool 9.

The clearance damper 18 not only prevents hunting of the sub-spool 9 but also prevents the sub-spool 9 from being switched at once when the fork F is tilted forward. That is, when the main spool 6 is switched to the left side in the drawing to tilt the fork F forward, the second actuator port B and the communication hole 16 communicate with the supply passage 4 almost simultaneously. Has not yet communicated with the tank passage 5. Therefore, the tilt cylinder C does not move, and the pressure in the supply passage 4 increases instantaneously. This high pressure acts on the sub-spool 9 via the communication hole 16.

If the high pressure as described above is applied to the sub-spool 9
, The sub-spool 9 is switched at once. When the sub-spool 9 is switched at a stroke, the pressure oil in the first pressure chamber 2 of the tilt cylinder C is discharged at a stretch via the throttle passage 19 in the fully opened state. As a result, the tilt cylinder C rapidly extends, and the fork F sharply leans forward. That is, when the fork F is tilted forward, there is a problem that the fork is tilted forward at a speed higher than expected by the operator. For this reason, the interval between the clearance dampers 18 is set to be small,
The rapid movement of the sub spool 9 is restricted.

[0016]

However, as described above, if the clearance between the clearance dampers 18 is set to be small, when the oil temperature becomes low, such as in winter, the sub-spool 9 is not used.
Movement becomes extremely bad. Therefore, there is a problem that a response delay occurs when the fork F is tilted forward.
Further, as described above, the sub-spool 9 functions as a danger-preventing lock valve.
Is smaller, the return of the sub-spool 9 becomes worse.

Therefore, for example, even if the engine is stopped immediately after the fork F is tilted forward, it takes time until the sub-spool 9 returns to the normal state. I sometimes leaned. That is, there is a problem that the function as the lock valve cannot be sufficiently exhibited. As mentioned above,
If the interval between the clearance dampers 18 is set to be small, there is a problem that a response delay occurs in the forward tilting operation of the fork and a function as a lock valve is not sufficiently exhibited. SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic control device capable of restricting a sharp forward leaning operation of a fork, and further maintaining a responsiveness at the time of a fork forward leaning operation and a sufficient function as a lock valve. It is.

[0018]

According to the present invention, a valve body has a first actuator port connected to a first pressure chamber of a cylinder on which a counter load acts, and a second actuator port connected to a second pressure chamber of the cylinder. An actuator port, and a main spool that communicates one of the actuator ports to the supply passage and communicates the other actuator port to the tank passage in accordance with the switching position. When the main spool is switched in a direction that allows the second actuator port to communicate with the supply passage, the supply passage communicates with the pilot chamber. The pilot pressure supply passage and the sub-spool When switched, and a discharge passage communicating with the first actuator port and the tank passage.

When the main spool is switched in a direction in which the second actuator port communicates with the supply passage, the pressure oil in the first pressure chamber of the cylinder flows from the first actuator port to the tank via the discharge passage. It is assumed that the hydraulic control device is discharged. The first invention presupposes the above-mentioned device, and the pilot pressure supply passage includes:
A flow control valve is provided, an orifice is provided between the flow control valve and the pilot chamber, and the flow supplied to the pilot chamber is controlled to be constant by the flow control valve.

According to a second aspect, in the first aspect,
The pilot pressure supply passage comprises an axial hole communicating with the pilot chamber, and a throttle hole communicating with the supply passage when the main spool is switched in a direction for communicating the second actuator port with the supply passage. A control spool in which a flow control valve is slidably incorporated in the axial hole, a control spring in which a spring force is applied to one end of the control spool, and a sub-pilot chamber provided in the other end of the control spool. An annular groove formed in the control spool, an orifice passage for guiding the pressure oil in the annular groove to the sub-pilot chamber side, and a pilot passage for guiding the pressure oil in the annular groove to the pilot chamber. An orifice is provided in the hole.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIGS. 1 and 2, a flow control valve FV is incorporated in
The FV communicates with the pilot chamber 17 through an axial hole 33, and an orifice 34 for preventing hunting is provided in the axial hole 33. This embodiment is the same as the conventional example except that the communication passage 16 and the clearance damper 18 are omitted. Therefore, only the internal configuration of the main spool 6 will be described below.
The same reference numerals are given to the same components as in the related art, and the description thereof will be omitted. In this embodiment, the discharge passage of the present invention is constituted by the discharge hole 15 and the throttle passage 19.

As shown in FIG. 1, the main spool 6 incorporates a flow control valve FV.
FIG. 2 is an enlarged view of a portion incorporating the FV. A shaft hole 24 is formed in the main spool 6, and a control spool 25 is slidably incorporated in the shaft hole 24. The control spool 25 divides a spring chamber 26 and a sub-pilot chamber 27. Note that a control spring 28 is provided in the spring chamber 26, and the spring force acts on the control spool 25.

An annular groove 29 is formed in the control spool 25, and the annular groove 29 and the spring chamber 28 communicate with each other through an orifice passage 31.
7 is communicated through a pilot passage 32. The annular groove 29 communicates with a throttle hole 30 formed in the main spool 6 at a normal position shown in the figure.
However, the throttle hole 30 does not communicate with either the pump passage 4 or the tank passage 5 when the main spool 6 is at the neutral position in the drawing, and when the main spool 6 switches to the left, the supply passage 4 To the main spool 6
Is connected to the second actuator port B when is switched to the right.

Further, an axial hole 33 is formed in the main spool 6, and the spring chamber 26 and the pilot chamber 17 are communicated via the axial hole 33. And
The axial hole 33 is provided with an orifice 34 for preventing hunting.

Next, the operation of this embodiment will be described. Since the point of tilting the fork F backward is the same as that of the conventional example, only the case where the fork F is tilted forward will be described. When the main spool 6 is switched leftward from the illustrated neutral position, the supply passage 4 communicates with the throttle hole 30, and the pressure oil in the supply passage 4 is guided to the annular groove 29. The pressure oil guided to the annular groove 29 is guided to the spring chamber 26 through the orifice passage 31 and further to the axial hole 3.
3 is led to the sub-pilot chamber 17. When the pressure oil flows through the orifice passage 31 as described above, a differential pressure is generated before and after that. Then, the pressure on the upstream side of the orifice passage 31 is guided to the sub-pilot chamber 27 via the pilot passage 32.

Therefore, the control spool 25 moves to a position where the pressure action on the pilot chamber 27 side, the pressure action on the spring chamber 26 and the spring force of the control spring 28 are balanced. That is, the control spool 25 applies a differential pressure generated before and after the orifice passage 31 to the control spring 28.
The opening degree of the throttle hole 30 is adjusted so as to keep the spring force equivalent to the above. With this configuration, the differential pressure across the orifice passage 31 is maintained at a level corresponding to the spring force of the control spring 28, so that a constant flow rate is always supplied to the spring chamber 26.

Therefore, a constant flow rate is always supplied to the pilot chamber 17 communicating with the spring chamber 26. In this way, even if the pressure in the supply passage 4 increases instantaneously, the sub-spool 9 does not move rapidly. Therefore, there is no problem that the fork F suddenly leans forward due to the opening of the throttle passage 19 at a stretch. When the sub-spool 9 is fully stroked leftward in the drawing, the flow in the orifice passage 31 stops, and the control spool 25 is returned to the state shown in the figure by the control spring 28.

When the engine is stopped while the main spool 6 is switched as described above and the fork is tilted forward, the pressure in the second actuator port B becomes negative and the inside of the supply passage 4 is also reduced. Negative pressure. Therefore, the pressure oil in the pilot chamber 17 is sucked out, and the sub-spool 9 returns to the normal position. Therefore, the discharge of the pressure oil from the first pressure chamber 2 of the tilt cylinder C is restricted, and the forward tilting operation of the fork F is stopped. That is, according to this embodiment, when the engine is stopped, the lock function of the sub-spool 9 can be obtained instantaneously.

When the main spool 6 is returned to the neutral position while the fork is being tilted forward, the throttle hole 30
However, at this time, since the passage 23 communicates with the supply passage 4, the load pressure of the first actuator port A is guided to the spring chamber 22 via the passage 23. Therefore, the sub-spool 9 is forcibly returned to the illustrated state by the pressure action on the spring chamber 22 side. Since the load pressure guided to the spring chamber 22 propagates to the pilot chamber 17 with the passage of time, after the both end faces of the sub-spool 9 have the same pressure, the spring pressure of the spring 11 The spool 9 returns to the illustrated state.

As described above, according to this embodiment, the pilot chamber 17 of the sub-spool 9 is controlled by the flow control valve FV.
, The opening of the orifice 34 for preventing hunting need not be so small. That is, the opening degree of the orifice 34 is
Can be set only to prevent the hunting phenomenon. Accordingly, the movement of the sub-spool 9 becomes smooth, and a response delay occurs in the forward tilting operation of the fork,
The problem that the function as the lock valve cannot be sufficiently exhibited can be prevented.

[0031]

According to the first and second aspects of the present invention, even when high pressure is generated in the supply passage at the start of the forward tilting operation of the fork, the flow rate flowing into the pilot chamber can be regulated by the flow rate control valve. Therefore, it is possible to prevent the sub spool from being switched at once, and the fork does not suddenly tilt forward. Since the pressure oil is supplied to the pilot chamber via the flow control valve in this manner, the opening degree of the orifice can be set to a size sufficient to prevent the hunting phenomenon of the sub spool. Therefore, the responsiveness when the fork is tilted forward can be maintained, and the function as the lock valve can be sufficiently obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a partially enlarged view of the flow control valve FV of FIG.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

 FV flow control valve A 1st actuator port B 2nd actuator port 1 Valve body 2 First pressure chamber 3 Second pressure chamber 4 Supply passage 5 Tank passage 6 Main spool 9 Subspool 15 Discharge hole constituting discharge passage of the present invention Reference Signs List 17 pilot chamber 19 throttle passage constituting discharge passage of the present invention 25 control spool 27 sub pilot chamber 28 control spring 29 annular groove 30 throttle hole 31 orifice passage 32 pilot passage 33 axial hole 34 orifice

Claims (2)

[Claims] The valve body has a first actuator port connected to a first pressure chamber of a cylinder on which a counter load acts, a second actuator port connected to a second pressure chamber of the cylinder, and a switching position. A main spool that communicates one of the actuator ports with the supply passage and communicates one of the other actuator ports with the tank passage. A pilot chamber provided at one end of the sub-spool, a pilot pressure supply passage for communicating the supply passage with the pilot chamber when the main spool is switched in a direction for communicating the second actuator port with the supply passage, When the sub-spool is switched by the action of pressure in the room, the first When the main spool is switched in a direction in which the second actuator port communicates with the supply passage, the pressure oil in the first pressure chamber of the cylinder becomes the first oil. In the hydraulic pressure control device discharged from the actuator port to the tank via the discharge passage, a flow control valve is provided in the pilot pressure supply passage, and an orifice is provided between the flow control valve and the pilot chamber. A hydraulic control device, wherein a flow rate supplied to a pilot chamber is controlled to be constant by a control valve. 2. A throttle hole communicating with the supply passage when the main spool is switched to an axial hole communicating the pilot pressure supply passage with the pilot chamber and a direction in which the second actuator port communicates with the supply passage. On the other hand, the flow control valve has a control spool slidably incorporated in the axial hole, a control spring in which a spring force acts on one end of the control spool, and a control spool on the other end of the control spool. A sub-pilot chamber provided, an annular groove formed in the control spool, an orifice passage for guiding the pressure oil in the annular groove toward the sub-pilot chamber, and a pilot passage for guiding the pressure oil in the annular groove to the pilot chamber. The hydraulic control device according to claim 1, wherein an orifice is provided in the axial hole.