JPH07279905A - Controller for operating cylinder - Google Patents

Abstract

PURPOSE:To make a compact controller and to make common use of a main relief valve among a plurality of operating cylinders. CONSTITUTION:A first actuator port 26 of a directional control valve 23 is connected to a holding pressure generating chamber 31 of an operating cylinder 30 through a lock valve 34, and a pressure receiving part 36 for pressing the lock valve 34 in the shut-off direction by holding pressure is connected to a tank 42, and a switching valve 40 is made in the shut-off position by spring force and in the communication position by pressure of the pressure receiving port 44. And, pilot pressure for switching a directional switching valve is supplied to the pressure receiving part 44, and the output side of the lock valve 34 is connected to a main relief valve 45 through check valves 47.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a working cylinder for controlling expansion and contraction by supplying pressure oil to working cylinders such as boom cylinders, arm cylinders and bucket cylinders of hydraulic excavators.

[0002]

2. Description of the Related Art As a control device for supplying pressure oil to an operating cylinder, a discharge pressure oil of a hydraulic pump is supplied to one of a first chamber and a second chamber of the operating cylinder by a directional control valve.
In general, the pressure oil in the other of the first chamber and the second chamber flows out into the tank to extend the operating cylinder and contract the operation.

In the above-mentioned directional control valve, the spool is slidably fitted in the spool hole of the valve block, and the spool is switched from the neutral position to the first position and the second position, so that the pump port has the first and second actuators. By communicating with one of the ports and communicating the tank port with the other of the first and second actuator ports, the pressure oil is supplied as described above,
When the spool is in the neutral position, it shuts off each port and
The return oil from the working cylinder that has flowed into the second actuator port is prevented from flowing out to the tank.

However, there is a small gap between the spool hole of the valve block and the spool, and oil leaks, while a holding pressure is generated in the first chamber or the second chamber of the working cylinder by an external load. Due to the holding pressure, a part of the return oil flows into the tank through the above-mentioned gap, and the working cylinder expands or contracts (hereinafter referred to as "natural drop").

For this reason, conventionally, a lock valve is provided in the circuit connecting the chamber where the holding pressure of the working cylinder is generated and the actuator port of the directional control valve. When the directional control valve is in the neutral position, the lock valve is used to remove the pressure from the working cylinder. The return oil is prevented from flowing to the actuator port of the directional control valve to prevent natural drop, and when the directional control valve is in the 1st and 2nd positions, the lock valve is opened and pressure is applied between the directional control valve and the working cylinder. Allows oil to flow.

However, if the lock valve is provided as described above, the holding pressure is abnormally increased when an inertial load or an external force acts on the working cylinder.

As a working cylinder control device for solving this, for example, as shown in FIG. 3 of Japanese Utility Model Application Laid-Open No. 2-91201, one actuator port of a directional control valve and a holding pressure generating chamber of a working cylinder are connected. A lock valve called a sequence valve is provided in the circuit, and a relief valve is provided in the circuit between this lock valve and the operating cylinder so that when the holding pressure rises when an inertial load or external force acts, the relief valve operates to relief the tank. It is known to have been made.

Further, the first of Japanese Utility Model Laid-Open No. 2-91201
The one shown in the figure is known. That is, as shown in FIG. 1, a lock valve 6 called a logic valve is provided in a circuit 5 connecting one actuator port 2 of the directional control valve 1 and the holding pressure generating chamber 4 of the working cylinder 3, and the spring of this lock valve 6 is provided. A pilot valve 9 that connects and disconnects the chamber 7 and the tank 8 is provided, and when the holding pressure in the holding pressure generating chamber 4 of the working cylinder 3 becomes high, the pilot relief valve 10 operates in a relief manner, and the pilot oil is relieved by the pilot oil. 9, the spring chamber 7 of the lock valve 6 is connected to the tank 8 to open the lock valve 6, the holding pressure generating chamber 4 is connected to the circuit 5, and the holding pressure of the working cylinder 3 is relieved from the main relief valve 11. It is known that it is activated.

[0009]

With the former type, the relief valve becomes large because a large capacity flows, and the unit in which the relief valve and the lock valve are combined becomes large,
When a plurality of working cylinders are provided, as many units as the working cylinders are installed, so that the set area becomes large.

In the latter case, the lock valve 6, the pilot valve 9 and the pilot relief valve 10 are used, so that the number of components is large, the cost is high, and the size is large. If you have one, the installation area will increase.

Therefore, it is an object of the present invention to provide a control device for an operating cylinder which can solve the above-mentioned problems.

[0012]

An actuator port of a directional control valve 23 and a holding pressure generating chamber 31 of an operating cylinder 30.
Is provided in a circuit connecting the directional control valve 23, and is pushed in the communication direction by the output pressure of the directional control valve 23 and the holding pressure of the working cylinder 30,
Further, the holding pressure of the working cylinder 30 acting on the pressure receiving portion 36 and the lock valve 34 which is pushed in the closing direction by the spring 35, the switching valve 40 which connects and disconnects the pressure receiving portion 36 of the lock valve 34 with the tank 42, and this switching The valve 40 is always closed and the holding pressure generating chamber 31 of the working cylinder is brought into the communicating position when communicating with the tank, and the lock valve 34 in the circuit is located upstream of the main relief valve 45 near the holding pressure generating chamber 31. A control device for a working cylinder, which comprises a check valve 47 connected to a side circuit 46.

[0013]

[Operation] If the switching valve 40 is set to the shutoff position, the lock valve 3
Since 4 is at the cutoff position due to the holding pressure, it is possible to prevent the working cylinder 30 from dropping naturally,
When an external force is applied, the high-pressure oil is relieved by the check valve 47 from the main relief valve 45, so that an abnormally high pressure can be prevented. When the switching valve 40 is set to the communicating position, the lock valve 34 is set to the communicating position by the holding pressure, that is, the return oil of the working cylinder 30, so that the return oil from the working cylinder 30 is fed to the directional control valve 2.
Can be leaked to 3. Since it is connected to the upstream circuit 46 of the main relief valve 45 via the check valve 47, the output side of the lock valves 34 provided in the plurality of working cylinders 30 is connected to one main relief valve 45 and the main relief valve 45 is connected. The valve 45 can be common.

[0014]

[Example] As shown in FIG. 2, a plurality of pressure compensating valves 22 are provided in the discharge passage 21 of the hydraulic pump 20, and a directional control valve 23 is provided on the output side of each pressure compensating valve 22. The directional control valve 23 includes a pump port 24, a tank port 25, first and second actuator ports 26, 2
7. The load pressure detection port 28 is connected or disconnected, and the first actuator port 26 thereof is connected to the first circuit 29.
Is connected to the holding pressure generating chamber 31 of the working cylinder 30 with the second
The actuator port 27 is connected by a second circuit 32 to the other chamber 33 of the working cylinder 30.

A lock valve 34 is provided in the first circuit 29. The lock valve 34 is pushed in the communicating direction by the pressure oil of the first circuit 29, and is pushed in the closing direction by the pressure of the spring 35 and the pressure receiving portion 36. , A circuit 38 having a diaphragm 37 in its pressure receiving portion 36.
The pressure in the holding pressure generating chamber 31 of the working cylinder 30 acts on the drain passage 41 including the throttle 39 and the switching valve 40.
The switching valve 40 is connected to the tank 42 by means of a spring 43, and is held in the shut-off position by the spring 43.

An upstream side circuit 46 of the main relief valve 45 is connected to the working cylinder 30 side of the lock valve 34 in the first circuit 29 and a second circuit 32 via a check valve 47, and each first circuit 29 is connected. When the highest pressure in the second circuit 32 becomes equal to or higher than the set pressure of the main relief valve 45, the main relief valve 45 is operated for relief. By doing so, it is possible to use only one main relief valve in a circuit including a plurality of working cylinders.

The directional control valve 23 shuts off the pump port 24 and the first and second actuator ports 26 and 27, respectively, and is held at the neutral position A where the load pressure detection port 28 communicates with the tank port 25. The first pressure oil supply position B is reached by the pressure oil supplied to the chamber 48, and the second pressure reception chamber 49
The pressure oil is supplied to the second pressure oil supply position C.

When the directional control valve 23 is at the first pressure oil supply position B, the pump port 24 becomes the first actuator port 26.
And the load pressure detection port 28, the second actuator port 27 communicates with the tank port 25, and when the second pressure oil supply position C is reached, the pump port 24 communicates with the second actuator port 27 and the load pressure detection port 28. , The first actuator port 26 communicates with the tank port 25.

The pressure compensating valve 22 is provided with a check valve portion 50 and a pressure reducing valve portion 51, and the check valve 50 is pushed in the communicating direction by the pressure on the inlet side acting on the pressure receiving portion a and acts on the outlet side acting on the pressure receiving portion b. It is pushed in the blocking direction by pressure, its inlet 52 is connected to the discharge passage 21, and its outlet 53 is in communication with the pump port 24 of the directional control valve 23.

The pressure reducing valve portion 51 is pushed in a direction in which the inlet 54 and the outlet 55 communicate with each other by the pressure acting on the pressure receiving portion c, the pressure receiving portion d and the spring 56 shut off the inlet 54 and the outlet 55, and the check valve portion The pressure receiving portion c is connected to the load pressure detecting port 28 of the directional control valve 23, the pressure receiving portion d is connected to the outlet 55, and the inlet 54 is pressed.
Is connected to the discharge passage 21, and the outlet 55 of each pressure compensation valve 22 is connected to be connected to the load pressure detection passage 57, whereby a plurality of directional control valves 23 are simultaneously operated to operate a plurality of operating cylinders 30. When operating simultaneously, each pressure compensating valve 22 is set by the highest load pressure so that the pressure oil discharged from one hydraulic pump can be simultaneously supplied to the operating cylinders 30 having different load pressures.

The hydraulic pump 20 is of a variable displacement type in which the capacity is increased or decreased by changing the tilt angle of the swash plate 58. The cylinder 60 for controlling the tilt angle of the swash plate 58 is pumped by a control valve 61 through a pump. Pressure is supplied, and the control valve 61 is switched by the pump discharge pressure and the load pressure in the load pressure detection path 57.

The pressure compensating valve 22, the cylinder 60 that tilts the swash plate 58, and the control valve 61 are provided to supply the pressure oil discharged from one hydraulic pump 20 to a plurality of operating cylinders 30 at the same time. This is unnecessary when only one working cylinder 30 is operated or when it is not necessary to simultaneously operate a plurality of working cylinders 30. The directional control valve 2
The pilot valve 62 is provided in the first and second pressure receiving chambers 48 and 49 of No. 3.
The pilot pressure oil in the second pressure receiving chamber 49 is supplied to the pressure receiving portion 44 of the switching valve 40.

Next, the operation will be described. When the directional control valve 23 is in the neutral position A, the pilot pressure is not supplied to the pressure receiving portion 44 of the switching valve 40 and the switching valve 40 is in the shut-off position. Therefore, the pressure in the holding pressure generating chamber 31 of the working cylinder 30 (holding pressure )
Acts on the pressure receiving portion 36 of the lock valve 34, and the lock valve 34 is held in the shut-off position by the spring 35, and the holding pressure is changed to the directional control valve 2
Since it does not flow into the tank 3, it does not leak into the tank, and the working cylinder 30 can be prevented from falling naturally. At this time, the holding pressure acts on the main relief valve 45, but the main relief valve 45 does not operate because it is lower than the set pressure.

When the pressure in the holding pressure receiving chamber 31 is abnormally increased by the inertial load or the external force in the above-described state, the pressure is actuated from the check valve 47 to the main relief valve 45 and becomes equal to or higher than the set pressure of the main relief valve 45. Then, the relief operation is performed and the gas flows out into the tank, so that the holding pressure can be prevented from becoming an abnormally high pressure.

The directional control valve 2 is operated by operating the pilot valve 62.
When pilot pressure oil is supplied to the first pressure receiving chamber 48 of No. 3,
The pressure oil supply position B is reached, pressure oil is supplied to the first circuit 29, and the lock valve 34 is opened.

The directional control valve 2 is operated by operating the pilot valve 62.
When pilot pressure oil is supplied to the second pressure receiving chamber 49 of No. 3,
At the pressure oil supply position C, the pressure receiving portion 44 of the switching valve 40
When pressure oil is supplied to the lock valve 34, the drain valve 41 of the lock valve 34 communicates with the tank 42.
Is opened, and the pressure oil in the holding pressure generating chamber 31 of the working cylinder 30 flows out from the tank port 25 of the direction control valve 23 to the tank.

Next, a specific structure will be described. Direction control valve 23
3 includes a valve block 70 as shown in FIG. 3, and the spool 71 of the valve block 70 has a pump port 24, a first
Second load pressure detection ports 28-1, 28-2, first and second
Actuator ports 26 and 27 and first and second tank ports 25-1 and 25-2 are formed, and these ports are communicated / blocked by sliding a spool 72 fitted in a spool hole 71. The first and second load pressure detection ports 28-1 and 28-2 communicate with each other through an oil hole (not shown).

The spool 72 has the first and second small diameter portions 7
3, 74 and the intermediate small diameter portion 75 are formed, each port is shut off when the spool 72 is in the neutral position shown in FIG. 3, and the pump moves when the spool 72 slides to the right in FIG. 3 to the first pressure oil supply position. The port 24 communicates with the second load pressure detection port 28-2, the first load pressure detection port 28-1 communicates with the first actuator port 26, and the second actuator port 2
The pressure oil that has communicated with the second tank port 25-2 by 7 and flows into the pump port 24 flows into the first actuator port 26, and the return oil flows from the second actuator port 27 to the second tank port 25-2. .

When the spool 72 is slid to the left from the state of FIG. 3 to the second pressure oil supply position, the pump port 24 is moved to the first position.
The second load pressure detecting port 28-2 communicates with the load pressure detecting port 28-1, the second load pressure detecting port 28-2 communicates with the second actuator port 27, and the pressure oil of the pump port 24 flows into the second actuator port 27, so that the first actuator port 26 communicates with the first tank port 25-1.

A first spring box 76 is attached to one end surface 70a of the valve block 70 in the spool longitudinal direction, and a first spring receiver 77 and a second spring receiver 78 are mounted in the first spring box 76.
The first spring receiver 77 contacts the one end surface 70a of the valve block 70 and the end surface of the spool 72, and the second spring receiver 78 contacts the bottom wall 76a and the stepped portion 79 of the spool 72. A spring 80 is provided between the second spring receivers 77 and 78 to hold the spool 72 at the neutral position, and the inside of the first spring box 76 serves as the first pressure receiving chamber 48. A second spring box 81 is attached to the other end surface 70b of the valve block 70 to form a second pressure receiving chamber 49. A spool 8 that constitutes the check valve unit 50 is provided below the valve block 70.
2 and the spool 83 that constitutes the pressure reducing valve portion 51 are fitted so as to face each other.

The mating surface 70c of the valve block 70 is joined and connected to the mating surface 90a of the block 90, and the first oil hole 9 opened in the first mating surface 90a is connected to the block 90.
1 and a second oil hole 92 are formed, the first oil hole 91 communicates with the first actuator port 26 opened in the mating surface 70c of the valve block 70, and the second oil hole 92 aligns with the valve block 70. A lock valve 34 is provided in the first oil hole 91, which opens in the second actuator port 27 that opens in the surface 70c.

The lock valve 34 is a poppet 94 fitted in a valve hole 93 opened in the second mating surface 90b of the block 90.
The poppet 94 is pushed in the closing direction by the spring 35, and the spring 35 is supported by the lid 95 attached to the second mating surface 90b of the block 90 to move the spring chamber 96 (pressure receiving portion 36 in FIG. 2). This spring chamber 96 is opened in the first oil hole 91 by a shaft hole 97 and a pore 98 (circuit 38 having the diaphragm 37 in FIG. 2) formed in the poppet 94, and the shaft hole 97 is formed in the pore 9.
9 communicates with the port 100 of the valve hole 93.

The block 90 is formed with a hole 101 opened to the first mating surface 90a and the second mating surface 90b. The hole 101 communicates with the port 100 by an oil hole 102 and the mating surface of the valve block 70. Recess 103 formed in 90a
Is communicated with the tank 42, and the hole 101 is provided in the switching valve 4
The valve 104, which constitutes 0, is inserted and the valve 10
4 faces the blind hole 105 of the lid 95 and is biased in one direction by a spring 106 so that the conical portion 107 has a seat 108 with a hole 101.
The port 100 and the recess 103 are closed by being pressed to the spring chamber 109 (pressure receiving portion 44 in FIG. 2) of the oil hole 1 of the lid 95.
10, the oil hole 111 of the block 90 and the oil hole 112 of the valve block 70 communicate with the second pressure receiving chamber 49, and the pressure oil in the second pressure receiving chamber 49 is springed from the oil hole 112, the oil hole 111, and the oil hole 110. It flows into the chamber 109 and pushes down the valve 104 to move the conical portion 107 away from the seat 108 so that the port 100 and the recess 103 communicate with each other, and the pressure oil in the first oil hole 91 is transferred to the tank 42.
The above-mentioned switching valve 40 is configured so as to flow out to the.

The drain port 1 is provided in the valve block 70.
13 is formed, the drain port 113 communicates with the first oil hole 91 by the first check valve 114, and the second check valve 11 is formed.
5 to communicate with the second actuator port 27,
-The second check valves 114 and 115 use the valve 116 for the spring 11
7, the first check valve 114 allows pressure oil flow from the first oil hole 91 to the drain port 113, and the second check valve 115 connects the second actuator port 27 to the drain port. Allow pressure oil flow to 113.

As shown in FIG. 4, the drain port 113 is opened at the joint surfaces 70d on both sides in the width direction of the valve block 70, and the valve blocks 70 of the plurality of directional control valves 23 are joined to each other so that each valve block 70 is joined. Drain port 11
3 communicates with each other, and the main relief valve 45 is attached to the valve block 70 located at the end thereof.

Because of the above, the circuit shown in FIG. 2 can be constructed by connecting the block 90 provided with the lock valve 34 and the switching valve 40 with the valve block 70, so that the directional switching valve 23 and the lock valve 34 are connected. It is not necessary to connect the switching valve 40 with piping.

[0037]

Since the main relief valve 45 for preventing an abnormally high pressure in the holding pressure generating chamber 31 can be provided separately, the lock valve 3
4 and the switching valve 40 only, and the main relief valve 45 can be shared by the plurality of working cylinders 30, so that the installation area of the unit for preventing the working cylinders from being naturally lowered can be reduced. The cost can be reduced because only one main relief valve needs to be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional example.

FIG. 2 is an explanatory diagram showing an example of the present invention.

FIG. 3 is a sectional view showing a specific structure of the directional control valve.

FIG. 4 is a right side view of FIG.

[Explanation of symbols]

23 ... Direction control valve, 24 ... Pump port, 25 ... Tank port, 26 ... First actuator port, 27 ... Second
Actuator port, 29 ... First circuit, 30 ... Working cylinder, 31 ... Holding pressure generating chamber, 32 ... Second circuit, 33 ...
Other chamber, 34 ... Lock valve, 35 ... Spring, 36 ... Pressure receiving portion,
40 ... Switching valve, 43 ... Spring, 44 ... Pressure receiving part, 45 ... Main relief valve, 46 ... Upstream circuit, 47 ... Check valve.

Claims (3)

[Claims] 1. A circuit provided to connect an actuator port of the directional control valve 23 and a holding pressure generating chamber 31 of the working cylinder 30, and is pushed in a communication direction by an output pressure of the directional control valve 23 and a holding pressure of the working cylinder, Also, the holding pressure of the working cylinder acting on the pressure receiving portion 36 and the lock valve 34 pushed in the closing direction by the spring 35, and the pressure receiving portion 36 of the lock valve 34.
Switching valve 40 for connecting / disconnecting the fuel to / from the tank 42, and the switching valve 4
0 is always the shutoff position, and the holding pressure generation chamber 3 of the working cylinder
When the 1 is communicated with the tank, the switching means for bringing the switching valve 40 into the communication position and the circuit 46 upstream of the main pressure relief valve 45 near the holding pressure generating chamber 31 from the lock valve 34 in the circuit.
A control device for a working cylinder, which is composed of a check valve 47 connected to the. 2. A pump port 24, a tank port 25, and first and second actuator ports 26, 27, wherein the first and second actuator ports 26, 27 are in a neutral position.
27 is cut off, the pump port 24 and the first actuator port 26 are communicated with each other at the first pressure oil supply position, and the second actuator port 27 is communicated with the tank port 25, and the pump port is at the second pressure oil supply position. 24 and second
A directional control valve 23 communicating the actuator port 27 and communicating the first actuator port 26 with the tank port 25, and the first actuator port 26 with the operating cylinder 30.
Circuit 29 connected to the holding pressure generating chamber 31 of the above, a second circuit 32 connecting the second actuator port 27 to another chamber 33, and a directional control valve output pressure and a holding pressure provided in the first circuit 29. Of the lock valve 34, which is pushed in the communicating direction by the pressure of 1 and is pushed in the closing direction by the holding pressure of the working cylinder acting on the spring 35 and the pressure receiving portion 36, and the drain passage 4 connected to the pressure receiving portion 36 of the lock valve 34.
1 and is held in the shut-off position by the spring 43 and the pressure receiving portion 4
The switching valve 40, which is in the communicating position under the pressure of 4, and the first circuit 29 and the second circuit 32 between the lock valve 34 and the holding pressure generating chamber 31 are connected to the upstream circuit 46 of the main relief valve 45, respectively. A control device for a working cylinder, comprising a check valve 47, and a second pressure receiving chamber 49 having the directional control valve 23 at a second pressure oil supply position connected to a pressure receiving portion 44 of the switching valve 40. 3. A valve block 70 of a directional control valve 23 is connected to a block 90 equipped with a lock valve 34 and a switching valve 40 to open the inlet side of the lock valve 34 to a first actuator port 26 of the valve block 90. Further, the outlet side of the lock valve 34 is used as an actuator port, and the block 90 and the valve block 70 are provided with an oil hole for communicating the spring chamber 109 of the switching valve 40 with the second pressure receiving chamber 49 of the direction switching valve 23. Control device for the working cylinder described.