JP2001193709A - Hydraulic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device which prevents pressure oil in a back pressure chamber of a poppet valve from leaking through an outer periphery of a spool to prevent a lift from inadvertently lowering cased by the leakage. SOLUTION: An operate check calve 23 is disposed in a passage connecting the back pressure chamber 11b of the poppet valve 11 with a tank. High pressure from a high pressure passage 7 acts on a pilot chamber 32 of the operation check valve 23 at a spool switching position where an actuator port 2 communicates with a tank side. When the high pressure acts on the pilot chamber 32, the operate check valve opens to connect the back pressure chamber 11b with a tank passage 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic control device for an industrial vehicle, and more particularly to a control device for a single-acting cylinder such as a lift cylinder of a forklift.

[0002]

2. Description of the Related Art FIG. 3 shows a hydraulic control device for a lift cylinder of a forklift. This hydraulic control device forms an actuator port 2 in a valve body 1,
The actuator port 2 is connected to the bottom chamber C1 of the lift cylinder C. The spool 3 is slidably incorporated in the valve body 1. The spool 3 is formed with first to third annular grooves 4 to 6 from the left in the drawing.

Further, a high pressure passage 7 connected to a pump, a tank passage 8 connected to a tank, and passages 9 and 10 are formed around the spool 3. A poppet valve 11 is provided between the passage 9 and the actuator port 2, and the opening and closing of the poppet 11a opens and closes the actuator port 2 and the passage 9. The back pressure chamber 11b of the poppet valve 11 has a throttle 12
And the pilot port 13 is connected to the actuator port 2. This pilot passage 13 is connected to a passage 10 formed around the spool 3. Note that a passage 14 is also formed in the valve body 1.

Next, a method of controlling the lift cylinder C, that is, moving the lift up and down with this apparatus will be described. First, when pressure oil is supplied to the actuator port 2 to raise the lift, the spool 3 is moved in the direction of arrow A. Then, the high pressure passage 7 is formed by the second annular groove 5.
And the passage 14 communicate with each other, and further, the first annular groove 4 allows the passage 14 and the passage 9 to communicate with each other. Then, the high pressure from the high pressure passage 7 acts on the poppet 11a. When the poppet 11a moves against the spring 11c, pressure oil is supplied to the actuator port 2 via the passage 9. Therefore, pressurized oil is supplied to the bottom chamber C1 of the lift cylinder C, and the lift is raised.

When the spool 3 is returned to the neutral position in this state, the passage 9 and the high-pressure passage 7 are shut off, and the pilot passage 13 is also closed. Therefore, the poppet valve 11 is also closed, and the lift cylinder C changes its state. Can hold. On the other hand, when lowering the lift, the spool 3 is moved in the direction of arrow B. The tank passage 8 communicates with the passage 10 via the third annular groove 6 and the notch 15. Since the passage 10 is connected to the pilot passage 13, the back pressure chamber 11 b of the poppet valve 11 communicates with the tank passage 8 via these passages.
The passage 9 on the poppet valve 11 side communicates with the tank passage 8 through the first annular groove 4.

When the pilot passage 13 communicates with the tank passage 8 as described above, the back pressure chamber 11b of the poppet valve 11
The pressure inside decreases. On the other hand, a pressure due to the load W and the weight of the piston C2 acts on the bottom chamber C1 of the lift cylinder C, and this pressure acts on the inclined portion 11d of the poppet 11a via the actuator port 2. That is, the high pressure from the actuator port 2 acts on the poppet 11a upward in the drawing. At this time, since the back pressure chamber 11b communicates with the tank passage 8, the poppet 11a moves upward to open the valve. Then, the pressure oil in the bottom chamber C1 of the lift cylinder C flows to the tank passage 8 via the passage 9, and the lift cylinder C is lowered.

[0007]

In the above-described apparatus, when the spool 3 is maintained at the illustrated neutral position and the state of the lift cylinder C is maintained, the pressure oil in the pilot passage 13 is supplied to the passage 10 through the passage 10. May leak to the tank passage 8 through the outer periphery of the spool 3. As described above, the leak of the pressure oil from the pilot passage 13 means the leak of the pressure oil in the bottom chamber C1 via the actuator port 2. In other words, there was a problem that the lift could not hold the position and was gradually lowered.

An object of the present invention is to prevent pressure oil in a back pressure chamber of a poppet valve from leaking through the outer periphery of a spool.
An object of the present invention is to provide a hydraulic control device in which a lift is not inadvertently lowered by this leakage.

[0009]

According to the present invention, an actuator port is formed in a valve body, a pressure chamber of a single-acting cylinder is communicated with the actuator port, and a spool incorporated in the valve body is moved. The port is connected to the pump side or the tank side, and the actuator port is provided with a poppet valve.
The free flow is allowed for the flow from the pump to the actuator port, and the check function is demonstrated for the flow from the actuator port to the tank.The back pressure chamber of the poppet valve is moved according to the spool movement position. When the back pressure chamber becomes tank pressure, a load pressure acts around the poppet of the poppet valve to open the poppet valve and allow the flow from the actuator to the tank side. It is based on a hydraulic control device.

A first aspect of the present invention is based on the above-mentioned apparatus, and an operation check valve is provided in a passage for communicating the back pressure chamber of the poppet valve with the tank, and a spool switching position for communicating the actuator port with the tank side. The high pressure from the high pressure passage acts on the pilot chamber of the operating check valve, and when high pressure acts on the pilot chamber, the operating check valve opens and the back pressure chamber communicates with the tank passage. It is characterized in that it is configured as follows.

A second invention is based on the first invention, and includes a passage hole formed in a spool and a pair of through holes opened in the passage hole, wherein the spool is provided between the actuator port and the tank side. When the spool is switched to the spool switching position, the high pressure passage is communicated with the pilot chamber of the operated check valve via the pair of through holes and the passage hole.

A third aspect of the invention is based on the first and second aspects of the invention, wherein a supply pressure control means for the pump is provided between the high-pressure passage and the pump, and the pressure in the pilot chamber is changed according to the opening of the operation check valve. It is characterized in that the pressure is changed and the supply pressure control means controls the pump flow rate according to the pilot pressure of the operating check valve.

[0013]

1 and 2 show an embodiment of the present invention. As shown in FIG. 1, the valve body 1 has an actuator port 2 connected to the bottom chamber C1 of the lift cylinder C and a spool 16 provided therein. Around the spool 16, in addition to the high-pressure passage 7, the tank passage 8, and passages 9 and 14, as in the conventional example,
A poppet valve 11 is incorporated between the passage 9 and the actuator port 2. This poppet valve 11 is the same as that of the conventional example.

On the outer periphery of the spool 16, first to third annular grooves 17 to 19 are formed from the left side of the drawing. Also,
A passage hole 20 extending in the axial direction is formed inside the spool 10, and through holes 21 and 22 are opened near both ends thereof. These through holes 21 and 22 are a pair of through holes of the present invention. The back pressure chamber 1 of the poppet valve 11
An operation check valve 23 is incorporated in the pilot passage 13 communicating with 1b. The operation check valve 23 is provided with a sleeve 24 incorporated in the valve body 1.
, A small spool 25 and a spring 26. The sleeve 24 has first to third through holes 27 to
The small spool 25 has first and second annular grooves 30 and 31 formed therein.

The small spool 25 has one end face facing the pilot chamber 32 in the sleeve 24 and
A passage 33 communicating from the pilot chamber 32 to the second annular groove 31 is formed in 5. In the illustrated neutral state, the seat portion 34 is closed by the spring force of the spring 26. In addition, the above-mentioned operation check valve 2
3, a passage 3 connecting the outer periphery of the spool 16 is provided.
5, 36 are formed. The passage 35 is provided with the spool 1
6 is a passage communicating with the tank passage 8 via the third annular groove 19 when the switch 6 is switched in the direction of arrow B. Passage 3 above
6 communicates with the tank passage 8 via the third annular groove 19 when the spool is switched in the direction of the arrow A, and through the through hole 21 → the passage hole 20 → the through hole 22 when the spool is switched in the direction of the arrow B. It communicates with the high pressure passage 7.

Further, a pressure compensating valve 50 is provided in the high-pressure passage 7 as shown in FIG. The pressure of the pilot relief valve upstream of the pressure compensating valve 50 and the small spool 25
Of the pilot chambers 32 is selected and guided. The pressure in the pilot chamber 32 is guided through the passage 33 → the through hole 28 → the pilot passage 37. The pressure in the high-pressure passage 7 downstream of the pressure compensating valve 50 is led to the opposite side of the spring chamber. Further, in the circuit of FIG. 2, parts corresponding to the elements of FIG. 1 are denoted by the same reference numerals.

The operation of this device will be described below. In order to extend the lift cylinder C and raise the lift, the spool 16 is switched in the direction of arrow A in FIG. In FIG. 2, it is the right switching position. Then, the passage 9 communicates with the passage 14 via the first annular groove 17 of the spool 16, and further, the passage 1 communicates via the second annular groove 18.
4 and the high pressure passage 7 communicate with each other. Therefore, the high pressure acts on the poppet 11a, the poppet valve 11 opens, and the pressure oil is supplied to the bottom chamber C1 of the lift cylinder C.

At this time, the passage 36 is
It communicates with the tank passage 8 via an annular groove 19. That is, the tank pressure acts on the pilot chamber 32 of the operation check valve 23. When the spool 16 is returned from this state to the neutral state shown in FIG.
6 communicates with the tank passage 8. Therefore, no high pressure acts on the pilot chamber 32. That is, when the spool 16 is switched to the neutral position or the direction of the arrow A, the operation check valve 23 is kept closed. Therefore, the back pressure chamber 11 of the poppet valve 11
The lift position can be held without the pressure oil leaking from b.

On the other hand, when lowering the lift, the spool 16 is switched in the direction of arrow B in FIG. FIG.
Then, it is the left switching position. Then spool 1
6, the passage 35 communicates with the tank passage 8 via the third annular groove 19, and the high-pressure passage 7 communicates with the passage 36 via the through hole 21 → the passage hole 20 → the through hole 22. Passage 36
High pressure acts on the pilot chamber 32 of the operation check valve 23 through the through hole 29. When high pressure acts on the pilot chamber 32, the small spool 25 moves against the spring 26 and opens the seat portion 34. The switching position of the operation check valve 23 is the right position in FIG. Therefore, the back pressure chamber 11b is connected to the pilot passage 13 →
Operate check valve 23 → passage 35 → third annular groove 19
Through the tank passage 8.

As described above, when the pressure in the back pressure chamber 11b decreases, the poppet 11a moves by the pressure of the actuator port 2 and the poppet valve 1 similarly to the conventional example.
1 opens. At this time, since the passage 9 and the tank passage 8 communicate with each other via the first annular groove 17, the pressure oil in the bottom chamber C 1 flows from the actuator port 2 → the passage 9 → the first annular groove 17.
Is discharged to the tank passage 8 via the, and the lift is lowered. As described above, only when switching to the spool position for lowering the lift, the pressure in the high pressure
2 to open the operation check valve 23. Therefore, except at the spool position for lowering the lift, the pressure oil in the back pressure chamber of the poppet valve 11 does not leak, and the lift does not lower unexpectedly.

When a high pressure acts on the pilot chamber 32 to open the operation check valve 23, the large-diameter portion 25a behind the small spool 25 moves to reduce the opening of the through hole 29. As described above, when the opening degree of the through hole 29 is reduced, the supply amount from the high-pressure passage 7 is reduced, and the pressure in the pilot chamber 32 is reduced. That is, the pressure in the pilot chamber 32 is adjusted according to the amount of movement of the small spool 25, and the switching position of the pressure compensating valve 50 that guides the pilot pressure is adjusted.

That is, when lowering the lift, the supply flow rate of the pump is used only for opening the operation check valve 23. When the pressure in the high-pressure passage 7 acts on the pilot chamber 32 to open the operation check valve 23, the large-diameter portion 25a of the small spool 25 narrows the opening of the through hole 29, so that the pilot pressure rises rapidly. Nothing. Then, the pressure compensating valve 50 controls the supply amount to the high-pressure passage 7 in accordance with the pilot pressure, and causes the remainder to flow to the tank flow path. If the pilot pressure is reduced, the pressure compensating valve 50 is switched to the right switching position, so that an excessive flow rate is not supplied to the high-pressure passage 7.

In this embodiment, the pressure compensating valve 50 is used as the pump supply pressure control means. However, instead of the pressure compensating valve 50, a system for adjusting the discharge amount of the pump using a regulator is used. You can also. Also in this case, if the regulator is controlled in accordance with the pilot pressure of the operate check valve, the pump pressure can be increased unnecessarily, and control can be performed so as not to supply an unnecessary flow rate to the high-pressure passage. In the above embodiment, the actuator port 2 is connected to the bottom chamber C1, but when the cylinder C is used upside down, the actuator port 2 is connected to the rod chamber side. In short, the actuator port 2 must be connected to a pressure chamber below the piston C2.

[0024]

According to the first and second aspects of the present invention, oil leakage can be prevented by providing the operation check valve, so that the lift does not drop carelessly due to oil leakage. In the third invention, the pilot pressure for opening the operate check valve is guided to the supply pressure control means of the pump, and the supply amount to the high pressure passage is adjusted according to the pilot pressure. As a result, the pilot chamber does not have an excessively high pressure, and the pump does not supply an excessive flow rate to the high-pressure passage.
Therefore, energy loss is reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an apparatus according to an embodiment.

FIG. 2 is a circuit diagram of an embodiment.

FIG. 3 is a cross-sectional view of a conventional device.

[Explanation of symbols]

 C Lift cylinder C1 Bottom chamber W Load 1 Valve body 2 Actuator port 7 High pressure passage 8 Tank passage 11 Poppet valve 11a Poppet 11b Back pressure chamber 11c Spring 11d Inclined portion 13 Pilot passage 16 Spool 20 Passage hole 21 Through hole 22 Through hole 23 Operate Check valve 25 Small spool 32 Pilot chamber 37 Pilot passage 50 Pressure compensation valve

Continuation of the front page F term (reference) 3F333 AA02 AB13 BD02 FA15 FA21 FH05 FH08 3H089 AA02 AA21 AA58 BB01 CC06 DA02 DB02 DB12 DB34 DB47 DB49 DB73 DB75 DB79 FF07 GG02 JJ09

Claims (3)

[Claims] An actuator port is formed in a valve body, a pressure chamber of a single-acting cylinder is communicated with the actuator port, and a spool incorporated in the valve body is moved to communicate the actuator port with a pump. The actuator port is provided with a poppet valve, and this poppet valve allows free flow for the flow from the pump to the actuator port, and allows the free flow from the actuator port to the tank. The back pressure chamber of the poppet valve communicates with the tank in accordance with the moving position of the spool, and when the back pressure chamber reaches tank pressure, the poppet of the poppet valve The load pressure acts on the surroundings, the poppet valve opens, and the flow from the actuator to the tank In an oil pressure control device configured to allow a pressure, an operation check valve is provided in a passage communicating the back pressure chamber of the poppet valve with the tank, and a high pressure is provided at a spool switching position for communicating the actuator port with the tank. The high pressure from the passage acts on the pilot chamber of the operating check valve, and when high pressure acts on the pilot chamber, the operating check valve opens and the back pressure chamber communicates with the tank passage. Hydraulic control device. And a passage hole formed in the spool, and a pair of through holes opened in the passage hole.
A structure in which the high pressure passage and the pilot chamber of the operated check valve communicate with each other through the pair of through holes and the passage hole when the spool switching position is such that the actuator port communicates with the tank side. 2. The hydraulic control device according to 1. 3. A supply pressure control means for a pump is provided between the high-pressure passage and the pump, and the pressure in the pilot chamber is changed according to the opening degree of the operation check valve. 3. The hydraulic control device according to claim 1, wherein the pump flow rate is controlled according to the pilot pressure.