JPH08260523A - Hydraulic circuit for working device - Google Patents

Abstract

PURPOSE: To provide a compact and inexpensive hydraulic circuit with good efficiency in which a lock valve is installed to each port of the bottom or head side of a boom lock cylinder, and the valve is connected to the pilot operating circuit of a boom main valve through a mode switching valve, and operated. CONSTITUTION: This circuit has a boom operating valve 8 connected to a boom operating lever 7 for pilot-operating a boom main valve 2; the boom main valve 2 switched by receiving the pressure from the boom operating valve 8; a two-port two-position spring offset pilot type lock valve 4 for connecting an oil passage which is inserted between a boom lock cylinder 5 and a tank 11; and a posture control valve 10 inserted to a pilot circuit between the lock valve 3 and the boom operating valve 8 to switch a working device 30 to either one of housing posture and working posture. At posture switching, the boom operating valve 8 is operated, and the lock valve 4 also is switched to suck the oil in the tank 11 into the boom lock cylinder 5 so that it can be expanded and contracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a working device, and more particularly to a hydraulic circuit of a working device used for a working vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, as a conventional example of this type of hydraulic circuit, a circuit for boom control of a work device used for a work vehicle or the like is shown in FIG. 6 is a side view showing the storage posture of the work device of the work vehicle to which FIG. 5 is applied, and FIG. 7 is a side view showing the work posture of the work device. In FIG. 5, a main hydraulic pump 1 and an auxiliary pump 6 connected to the main hydraulic pump 1
Are both driven by a power source of a work vehicle (not shown). The discharge oil of the main hydraulic pump 1 is supplied to the boom cylinder 3 via the boom main valve 2 connected to the main circuit 1a and to the boom lock cylinder 5 via the boom lock main valve 70. The oil discharged from the auxiliary pump 6 is the pilot circuit 6a.
It is supplied to the boom operation valve 8 and the attitude control valve 71 connected to.

The boom main valve 2 is a closed center 4-port 3-position pilot operated, spring offset switching valve, and has a boom raising position 2a, a closed center neutral position 2b, and a boom lowering position 2c. Further, the boom main valve 2 has a side end portion with a rising pilot pressure chamber 2d and a lower pilot pressure chamber 2e for switching the valve position of the boom main valve 2. The boom cylinder 3 is
It comprises a piston rod 3a, a head side 3b and a bottom side 3c, and supplies the discharge oil of the main hydraulic pump 1 to the bottom side 3c at a boom raising valve position 2a of the boom main valve 2. Further, the discharge oil of the main hydraulic pump 1 is supplied to the head side 3b at the boom lowering valve position 2c.

The boom lock main valve 70 has a boom retracting position 70a, a closed center neutral position 70b, a boom extending position 70c, a retracting side pilot pressure chamber 70d and an extending side pilot pressure chamber 70e. The valve has the same structure as. The boom lock cylinder 5 is composed of a piston rod 5a, a head side 5b and a bottom side 5c, and supplies the discharge oil of the main hydraulic pump 1 to the bottom side 5c and the head side 5b via a boom lock main valve 70. are doing.

The boom operating valve 8 is composed of a boom lowering valve 8a and a boom raising valve 8b connected to the boom operating lever 7, and the boom main valve is controlled according to the strokes of the boom operating lever 7 on the raising side and the lowering side. The boom main valve 2 is switched by causing pilot pressure oil to flow into the ascending side pilot pressure chamber 2d and the ascending side pilot pressure chamber 2e at the side end portion of 2. The boom operation valve 8 discharges pilot pressure oil that is substantially proportional to the operation stroke of the boom operation lever 7, and the discharge pressure causes the boom lowering valve 8a or the boom raising valve 8 to be discharged.
It is a proportional pressure control valve that pushes back b to balance the discharge pressure.

The attitude control valve 71 is composed of a boom extension valve 71a connected to the pedal 9 and a boom contraction valve 71b, and discharges pilot pressure oil that is substantially proportional to the pedaling angle of the pedal 9, and this discharge pressure causes the boom to move. It is a proportional pressure control valve similar to the boom operation valve 8 in which the extension valve 71a or the boom contraction valve 71b is pushed back to balance. In addition, this attitude control valve 71 is a boom extension valve 7 connected to the pedal 9.
1a and the expansion side pilot pressure chamber 70e at the side end of the attitude control valve 71 according to the stepping angle of the boom compression valve 71b.
And the boom lock main valve 70 is switched by flowing pilot pressure oil into the contraction side pilot pressure chamber 70d. Also, 1
1 is a hydraulic tank.

In FIG. 6, the work vehicle is the undercarriage 3
5, a swivel frame 37 is rotatably mounted at a swivel center 38 via a swirl circle 36. A driver seat 39, a work device 30, a drive source such as an engine, and the like are mounted on the upper portion of the revolving frame 37. The work device 30 is divided into a first boom 32 and a second boom 33, which are rotatably supported by a boom support pin 31 on a revolving frame 37.
The piece boom 33a, the second boom 33 connected and supported by the boom connecting pin 42 at the tip of the first boom 32, and the arm 3 pivotally attached to the tip of the second boom 33.
4, a bucket 43 is provided. Also, the working device 3
0 for the bottom side 3 for rotating the two-piece boom 33a
The first boom cylinder 3 in which c is pivotally attached to the revolving frame 37 and the piston rod 3a is pivotally attached to the second boom 33.
And the first boom cylinder 5 in which the bottom side 5c that sets the working device 30 to the storage posture 40 and the working posture 41 (FIG. 7) is pivotally attached to the first boom 32 and the piston rod 5a is swingably pivoted to the second boom 33. , An arm cylinder 44 for rotating the arm 34, arm links 45a and 45b, a bucket 43
A bucket cylinder 46 for pivoting is pivotally attached.

Next, the working device 3 will be described with reference to FIGS.
The operation of 0 will be described. In the boom lock main valve 70 shown in FIG. 5, when the boom extension valve 71a is stepped on by the pedal 9 of the attitude control valve 71, the extension side pilot pressure chamber 70e.
The discharge oil is discharged from the pilot circuit 6a to switch from the neutral position 70b to the boom extending position 70c. Then, the oil discharged from the main circuit 1a is supplied to the boom lock cylinder 5
To the head side 5b, and the piston rod 5a contracts. As a result, the working device 30 has the storage posture 40 in which the second boom 33 is folded on the first boom 32 as shown in FIG.
Then, the second boom 33 rotates clockwise around the connecting pin 42 as a fulcrum due to the contraction of the boom lock cylinder 5, and the second boom 33 moves away from the first boom 32 as shown in FIG.
Switch to.

Further, the attitude control valve 71 discharges the discharge oil from the pilot circuit 6a to the contraction side pilot pressure chamber 70d of the boom lock main valve 70 when the boom contraction valve 71b is stepped on with the pedal 9 and extends. The pilot pressure oil in the pilot pressure chamber 70e is drained to the tank 11. As a result, the boom lock main valve 70 switches from the closed center neutral position 70b or the boom extended position 70c to the boom retracted position 70a. Then, the pressure oil of the main circuit 1a flows to the bottom side 5c of the boom lock cylinder 5 and extends the piston rod 5a. At this time, the working device 30
The second boom 3 by the extension of the boom lock cylinder 5.
3 rotates counterclockwise about the connecting pin 42 as a fulcrum, and FIG.
As shown in FIG. 3, the first boom 32 is stored so as to be folded and is switched to the storage posture 40.

[0010]

In the above-mentioned conventional circuit, the discharge oil of the main circuit 1a of the main hydraulic pump 1 having a large discharge oil amount is supplied to the boom cylinder 3 and the boom lock cylinder 5, and further the boom main valve is used. 2 and the boom lock main valve 70 use the same closed center 4 port 3 position pilot operated and spring offset switching valve, the following problems occur. Two large switching valves are also used in the high-pressure pipe of the main circuit 1a, and each switching valve is pilot operated by an individual operation valve and attitude control valve. Therefore, a large space for installing these devices and a piping space are required, and a thick pipe becomes complicated. Further, the piping configuration of the pilot circuit of the operation valve and the attitude control valve, which individually operate each switching valve, becomes complicated. In addition, the space for mounting the device becomes large, the device configuration becomes complicated, and the cost increases.

The present invention focuses on the above-mentioned conventional problems and relates to a hydraulic circuit of a working device. Particularly, in a working vehicle or the like, a lock valve is provided between a tank and a boom lock cylinder, and oil in the tank is passed through the lock valve. An object of the present invention is to provide a simple and inexpensive hydraulic circuit that extends the boom lock cylinder by sucking it into the boom lock cylinder.

[0012]

In order to achieve the above object, in the first invention of the hydraulic circuit of the working apparatus of the present invention, the first boom 32 and the second boom 33 are rotatably connected to each other. The piece boom 33a and a boom lock cylinder that is inserted between the first boom 32 and the second boom 33 to control the opening amount of the first boom 32 and the second boom 33 by expansion and contraction to determine the storage posture 40 and the working posture 41. 5, 25, a boom cylinder 3 for raising and lowering the two-piece boom 33a in the vertical direction, and a boom main valve 2 for switching the boom cylinder 3 up and down so that the boom cylinder 3 can expand and contract freely.
Between the boom operation valve 8 connected to the boom operation lever 7 for pilot operating the boom main valve 2, the boom main valve 2 for switching by receiving the pressure from the boom operation valve 8, the boom lock cylinders 5, 25 and the tank 11. 2 port 2 position spring offset that connects the oil passage inserted in 2 port 2 position spring offset Operate lock valve 4, 20, 21, 26 and lock valve 4, 20, 21,
26 and the boom operation valve 8 are inserted in the pilot circuit, and the storage posture 40 and the work posture 41 of the working devices 30 and 50 are inserted.
And the attitude control valves 10 and 22 for switching to either of the above are provided, the boom operation valve 8 is operated at the time of attitude switching, and the lock valves 4, 20, 21, and 26 are switched so that the inside of the tank 11 and / or the bottom 5c, 25c Boil lock cylinders 5 and 25 are sucked with the return oil.

In the second invention, which is mainly based on the first invention,
One of the boom lock cylinders 5 has a lock valve 4 at one end.
To the tank 11 or the return oil pipe 12 and the other end to the tank 11 or the pipe 12 and the attitude control valve 10 to connect to the pilot hydraulic chamber 2e for lowering the boom main valve 2. The lock valve 4 has a pilot operate circuit.

In the third invention, which is mainly based on the first invention,
The extension side lock valve 20 and the contraction side lock valve 21 of the boom lock cylinder 5 are connected to the tank 11 and the boom lock cylinder 5, respectively, and the extension side pilot hydraulic chamber 20c of the extension side lock valve 20 is connected to the boom operation valve 2. The contraction side pilot hydraulic chamber 21c of the contraction side lock valve 21 is connected to the lowering pilot hydraulic chamber 2e of FIG.

In the fourth invention, which is mainly based on the first invention,
A lock valve 26 is connected between the boom lock cylinder 25 and the tank 11 by an oil passage 12, and a pilot hydraulic chamber 2c for lowering the boom main valve 2 is connected to a pilot hydraulic chamber 26c of the lock valve 26 via an attitude control valve 10. Are connected.

In the fifth invention, which is mainly based on the first invention,
The attitude control valves 10 and 22 are pedals or manual 2-position 2-connection directional control valves or 2-position 5-connection directional control valves.

[0017]

According to the above construction, in the hydraulic circuit of the working device, the oil is supplied to the boom lock cylinder for moving the boom from the retracted posture to the working posture by the suction oil passage connected to the tank and the oil passage and the boom lock. This is done with a lock valve connected between the cylinders. In addition, the switching of the lock valve is pilot operated via the attitude control valve, and this pilot circuit is connected to the control circuit of the boom operation valve. Therefore, since the discharge pressure of the main circuit of the main hydraulic pump is not supplied to the boom lock cylinder, the only piping connected to the high pressure main circuit from the main hydraulic pump is the boom main valve and the piping to the boom cylinder. Since it is good, it has a simple piping configuration. Further, only one large switching valve may be used in the high-pressure pipe of the main circuit 1a, and the space for mounting these devices may be small. Further, since the lock valve is pilot-operated by one boom operation valve via the attitude control valve, control of the lock valve is simplified by also using the boom operation valve. In addition, the attitude control valve inserted in the pilot circuit is cheaper than the conventional high-pressure piping for the boom lock cylinder main circuit and the boom lock main valve and the attitude control valve of the proportional pressure control valve type. It can be attached without removing.

Further, the lock valve provided between the head side of the boom lock cylinder and the tank locks the boom with the contraction force of the second boom due to the lowering of the boom cylinder or the dead weight of the bucket connected to the tip of the second boom. The working device is placed in the retracted position by acting on the cylinder to extend the piston rod connected to the second boom. Further, when the attitude control valve is unlocked (valve opened) and the boom operation lever is at the boom raising position, the extension force of the boom cylinder pushes down the piston rod that is the connecting portion between the second boom and the boom lock cylinder. At this time, in the boom lock cylinder, the oil in the tank is sucked to the head side by pushing down the piston rod, passes through the position of the lock valve in one direction via the oil passage, and the piston rod is contracted to work the working device. Take a posture.

Further, since the lock valve provided between the boom lock cylinder and the tank and the lock valve are connected to the control circuit of the boom operation valve for pilot operation via the attitude control valve, the boom lock cylinder The attitude control valve can be locked (valve closed) even during expansion and contraction of the boom lock cylinder even during the stroke of the boom lock cylinder. As described above, stopping the boom lock cylinder during the stroke allows the opening amounts of the first boom and the second boom to be arbitrarily set. Even at a work site where the height of the work range is limited, if the opening amounts of the first boom and the second boom are variable, the opening amount of the working machine can be arbitrarily set so as not to interfere with the height-limiting object. The work machine can be safely operated and the work can be continued.

Further, a boom lock cylinder for fixing the opening amount of the first boom and the second boom is arranged on the inner angle side of the first boom and the second boom, and oil is supplied to the boom lock cylinder by a tank. A suction oil passage connected to
The lock valve connected to the oil passage, the boom lock cylinder connected to the boom lock cylinder, and the lock valve connected to the control circuit of the boom operation valve for pilot operation via the attitude control valve are used. For the thick piping connected to the high-pressure main circuit from the hydraulic pump, only the boom main valve and the piping to the boom cylinder are sufficient, and simple piping can be used. Further, since the thick pipe to the boom lock cylinder needs only one oil passage between the tank and the lock valve, a simpler pipe configuration is possible. Further, the large switching valve used in the high-pressure pipe of the main circuit may be one of the boom main valves, and the space for mounting these devices may be small. Further, since the lock valve is pilot-operated via the attitude control valve by one boom operation valve, the configuration of the operation valve is simplified.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a hydraulic circuit of a working apparatus according to the present invention will be described in detail below with reference to the drawings. FIG.
FIG. 3 is a hydraulic circuit diagram showing the first embodiment. The same parts as those in FIG. 5 of the prior art are designated by the same reference numerals, and the description of the configuration will be omitted. In FIG. 1, a main hydraulic pump 1 and an auxiliary pump 6 connected to the main hydraulic pump 1 are both driven by a power source of a work vehicle (not shown). The oil discharged from the main hydraulic pump 1 is guided to the boom cylinder 3 via the boom main valve 2 connected to the main circuit 1a. The discharge oil of the auxiliary pump 6 is supplied to the boom operation valve 8 connected to the pilot circuit 6a.

The boom main valve 2 is a closed center 4-port 3-position pilot operated, spring offset switching valve, and has a boom raising position 2a, a closed center neutral position 2b, and a boom lowering position 2c. Further, the boom main valve 2 has a side end portion with a rising pilot pressure chamber 2d and a lower pilot pressure chamber 2e for switching the valve position of the boom main valve 2. The boom cylinder 3 is
It comprises a piston rod 3a, a head side 3b and a bottom side 3c, and the discharge oil of the main hydraulic pump 1 is supplied to the bottom side 3c at a boom raising valve position 2a of the boom main valve 2. Also, at the boom lowering valve position 2c, the main hydraulic pump 1
Is supplied to the head side 3b. Further, the boom cylinder 3 has the bottom side 3c on the swing frame 37,
The end portion of the piston rod 3a is pivotally attached to the second boom 33 so as to be swingable. The boom lock cylinder 5 is composed of a piston rod 5a, a head side 5b, and a bottom side 5c, and the head side 5b has an outlet port 4A of the lock valve 4.
It is connected to the. Further, the oil passage 12 is provided on the bottom side 5c.
Is connected. Further, the hydraulic circuit that operates the boom lock cylinder 5 is configured by the oil passage 12 that connects the tank 11 and the bottom side 5c of the boom lock cylinder 5, the lock valve 4, and the attitude control valve 10 that operates the lock valve 4. are doing.

The oil passage 12 is connected to the oil in the tank 11 so as to suck the oil in the tank 11. Lock valve 4
Has an inlet port 4P connected to the oil passage 12 and an outlet port 4A connected to the head side 5b of the boom lock cylinder 5, and has a one-way position 4a, a free flow position 4b, a pilot hydraulic chamber 4c, and a spring 4d. ing. Also,
The pilot hydraulic chamber 4c that operates the lock valve 4 is connected to a boom lowering pilot hydraulic chamber 2e that pilot-operates the boom main valve 2 via a posture control valve 10. The attitude control valve 10 is a switching valve provided with a 2-port 2-position having a lever 10a for offsetting a spring 10c or a pedal 10d, and includes an inlet port 10P and an outlet port 1.
0A, locked (valve closed) position 10a and unlocked (valve open)
10b and. In addition, the inlet port 10P,
Exit port 10A to boom lowering pilot hydraulic chamber 2e
Is connected to the pilot hydraulic chamber 4c.

Regarding the operation of the above construction, FIG. 1 and FIG.
And it demonstrates using FIG. To change from the work posture 41 of FIG. 7 to the storage posture 40 of FIG. 6, in the state of the work posture 41, the boom cylinder 3 is extended to the stroke end, and the first boom 32 is rotated clockwise. At this position, the lever or pedal 10d of the attitude control valve 10 shown in FIG. 1 is manually or stepped to the unlock (valve open) 10b position. Then, the pilot hydraulic chamber 4c of the lock valve 4 and the boom lowering pilot hydraulic chamber 2e of the boom main valve 2 are communicated with each other.

Next, when the boom operating lever 7 is set to the boom lowering position, the lowering valve 8a of the boom operating valve 8 operates,
The hydraulic oil from the pilot circuit 6a is pressurized in the boom lowering pilot hydraulic chamber 2e and the pilot hydraulic chamber 4c. Then, the boom main valve 2 causes pilot pressure oil to flow into the boom lowering pilot hydraulic chamber 2e and switches to the boom lowering position 2c according to the stroke of the boom operation lever 7. As a result, the pressure oil of the main circuit 1a is supplied to the head side 3b of the boom cylinder 3, so that the boom cylinder 3 is contracted. Further, the pilot pressure oil discharged from the lowering valve 8a causes the posture control valve 10 to be unlocked (valve open) at a position 10.
Since it is set to b, the lock valve 4 is pilot-operated to move the space between the head side 5b of the boom lock cylinder 5 and the tank 11 to the free flow position 4b. As a result, the oil on the head side 5b passes through the free flow position 4b and the oil passage 1
Connected to 2.

Therefore, when the boom cylinder 3 is contracted, the second boom 33 is contracted by lowering the boom cylinder 3, or the weight of the boom 43 connected to the tip of the second boom 33 is applied to the boom connecting pin. It rotates counterclockwise about 42 as a fulcrum. As a result, the second boom 33
In the boom lock cylinder 5 pivotally attached to the tip end of the piston rod 5a, the oil on the head side 5b passes through the free flow position 4b of the lock valve 4 and is drained to the oil passage 12. At this time, the bottom side 5 of the boom lock cylinder 5
Oil is sucked into c from the head side 5b or the tank 11 via the oil passage 12 until the piston rod 5a is fully extended. Then, when the piston rod 5a is fully extended, the rotation of the second boom 33 is stopped and the first boom 32 is further rotated in the clockwise direction, so that the second boom 33 shown in FIG. 6 is folded into the first boom 32. The storage device 40 is switched to the stored posture 40 of the working device 30.

When the storage posture 40 is switched to the work posture 41, the posture control valve 10 is in the lock (valve closed) position 1.
Regardless of the position 0a or the unlock (valve open) position 10b, when the boom raising valve 8b is pushed by the boom operation lever 7, the boom main valve 2 is switched to the boom raising position 2a and the main circuit 1a The pressure oil is supplied to the bottom side 3c of the boom cylinder 3. As a result, the boom cylinder 3 is extended, and the second boom 33 is rotated clockwise with the boom connecting pin 42 as a fulcrum when the boom cylinder 3 is raised. At this time, the piston rod 5a of the boom lock cylinder 5 connected to the end of the second boom 33 is pushed down to discharge the oil on the bottom side 5c to the oil passage 12. Also, the posture control valve 10 is unlocked (valve open).
When the position 10b is set, the pressure oil in the pilot hydraulic chamber 4c of the lock valve 4 is drained to the tank 11 via the boom lowering valve 8a to move the lock valve 4 to the one-way position 4a. Then, the head side 5b of the boom lock cylinder 5
The oil will be sucked from the tank 11. At this time, the oil required on the head side 5b is the amount discharged from the bottom side 5c or the one-way position 4 of the lock valve 4 from the tank 11.
It is sucked into the head side 5b through a. As a result, the boom lock cylinder 5 moves the piston rod 5a to the bottom side 5
It is reduced by pushing down to the end of c. On the other hand, when the attitude control valve 10 is in the lock (valve closed) position 10a,
The lock valve 4 remains in the free flow position 4b, and the oil in the tank 11 is sucked into the bottom side 5c of the boom lock cylinder 5. When the boom lock cylinder 5 is completely contracted, the opening amounts of the first boom 32 and the second boom 33 become maximum. At this time, the attitude control valve 10 is set to the locked (valve closed) position 10a so as not to be pressurized in the pilot hydraulic chamber 4c, and the lock valve 4 remains in the one-way position 4a. Therefore, due to the above operation, the work device 3
0 becomes the working posture 41 separated from the first boom 32 as shown in FIG. 7 from the storage posture 40 of the second boom 33 folded up on the first boom 32 as shown in FIG. Further, in the state of the work posture 41 in which the posture control valve 10 is set to the lock (valve closed) position 10a, when an external force to be reduced is applied to the boom cylinder 3, an action force for extending the boom lock cylinder 5 is exerted to act on the head side. 5b is trying to discharge the oil, but it is stopped at the one-way position 4a of the lock valve 4,
The boom lock cylinder 5 is not extended, and the working device 30 is
The work posture 41 is maintained.

As described above, in the first embodiment, the oil is supplied to the boom lock cylinder 5 by the suction oil passage 12 connected to the tank 11 and the lock connected between the oil passage 12 and the boom lock cylinder 5. Since the valve 4 and the lock valve 4 are connected to the control circuit of the boom operation valve 8 for pilot operation via the attitude control valve 10, the piping connected to the high-pressure main circuit 1a from the main hydraulic pump 1 is Since only the boom main valve 2 and the piping to the boom cylinder 3 are required, the piping configuration is simple. Further, only one boom main valve 2 needs to be a large switching valve used in the high-pressure pipe of the main circuit 1a, and the space for mounting these devices can be reduced. Further, since the lock valve 4 is pilot-operated via the attitude control valve 10 by one boom operation valve 8, the configuration of the operation valve is also simplified.

Next, the second embodiment will be described. Figure 2
FIG. 7 is a hydraulic circuit diagram of the second embodiment. The same parts as those in FIG. 5 of the first embodiment and the prior art are designated by the same reference numerals, and the description of the configuration will be omitted. In FIG. 2, a hydraulic circuit for operating the boom lock cylinder 5 includes a tank 11, an oil passage 12 connecting the tank 11 and the lock valve 4, and an extension side lock valve connecting the head side 5b of the boom lock cylinder 5. 20, a contraction-side lock valve 21 connected to the bottom side 5c of the boom lock cylinder 5, and the lock valves 20, 21
And an attitude control valve 22 for operating the.

The oil passage 12 is connected to the oil in the tank 11 so as to suck the oil in the tank 11. The extension-side lock valve 20 and the contraction-side lock valve 21 are spring-offset pilot-operated 2-port 2-position lock valves similar to the lock valve 4, and have inlet ports 20P, 21P and outlet ports 20A, 21A, 1-way position 20a, respectively. , 21a, free flow positions 20b, 21b, an extension side pilot hydraulic chamber 20c, a contraction side pilot hydraulic chamber 21c, and offset springs 20d, 21d. The attitude control valve 22 is a switching valve that is offset by a spring 22c and switches between 5 port 2 positions by a lever or a pedal 22d, has inlet ports 22P, 22R, 22T and outlet ports 22A, 22B, and has an ABT. It has a connected lock position 22a and an unlock (valve open) position 22b for opening PA and RB. Also, the entrance port 22
P is located in the hydraulic chamber 2d of the boom main valve 2 and has an inlet port 22R.
Is connected to the hydraulic chamber 2e of the boom main valve 2. Further, the inlet port 22T is connected to the tank 11, and the oil at the outlet ports 22A and 22B is drained to the tank 11 at the offset ABT connection position 22a. Further, the outlet port 22A is connected to the contraction side pilot hydraulic chamber 21c, and the outlet port 22B is provided.
Is connected to the extension side pilot hydraulic chamber 20c.

Regarding the operation of the above configuration, FIG. 2 and FIG.
And it demonstrates using FIG. Boom lock cylinder 5
The extension side lock valve 20 and the contraction side lock valve 21 connected between the head side 5b and the bottom side 5c of the tank 11 and the tank 11 are operated by operating the posture control valve 22 by manually operating the lever or the pedal 22d or stepping on the pedal. In the lock (valve open) position 22b, the inlet port 22P and the outlet port 22A
And the inlet port 22R and the outlet port 22B are communicated with each other. Then, when the boom operating lever 7 is set to the boom lowering position, the lowering valve 8a of the boom operating valve 8 is activated, and the pressure oil from the pilot circuit 6a is supplied to the boom lowering pilot hydraulic chamber 2e and the inlet port 22R of the attitude control valve 22. Discharge.
Then, according to the stroke of the boom operation lever 7, pilot pressure oil is flown into the pilot hydraulic chamber 2e to switch the boom main valve 2 to the boom lowering position 2c.

At this time, since the posture control valve 22 is switched to the unlock (valve open) position 22b, the pressure oil of the inlet port 22R is connected to the expansion side pilot hydraulic chamber 20c and the contraction side pilot hydraulic chamber is The pressure oil 21c is drained from the outlet port 22A to the tank 11 via the inlet port 22P and the boom raising valve 8b. Then, the extension side lock valve 20 is pilot-operated to move the space between the head side 5b of the boom lock cylinder 5 and the tank 11 to the free flow position 20b, and the oil on the head side 5b is transferred to the oil passage 12.
The tank 11 is drained via. On the other hand, the contraction side pilot hydraulic chamber 21c for operating the contraction side lock valve 21
Even if the attitude control valve 22 is in the unlock (valve open) position 22b, the lift valve 8 connected to the inlet port 22P
Since b is drained to the tank 11, it is not pressurized. Therefore, the compression-side lock valve 21 is located at the one-way position 21a.
Has become. Then, when the boom main valve 2 is at the boom lowering position 2c and the boom cylinder 3 is contracted, the second boom 33 is rotated counterclockwise about the boom connecting pin 42 as a fulcrum by the contracting force due to the lowering of the boom cylinder 3. Let
As a result, in the boom lock cylinder 5 pivotally attached to the end of the second boom 33, the oil on the head side 5b is locked by the lock valve 2
It is drained to the oil passage 12 through the free flow position 20b of 0, and on the bottom side 5c from the oil passage 12 and the tank 11 to the one-way position 21 from the inlet port 21P of the lock valve 21.
Oil is sucked in through the piston a until the piston rod 5a is fully extended. Then, the second boom 33 has the piston rod 5a.
When the extension is fully extended, the rotation of the second boom 33 is stopped, and the working posture of the working device 30 folded to the first boom 32 is switched to the retracted posture 40 as shown in FIG.

When the attitude control valve 22 is in the unlocked (valve open) position 22b and the boom operating lever 7 is on the boom raising side and the boom raising valve 8b is pushed, the pressure oil in the discharge circuit of the boom lowering valve 8a is released. While being drained to the tank 11, the boom raising valve 8b supplies the pressure oil from the pilot circuit 6a to the raising pilot pressure chamber 2d and the contracting pilot hydraulic chamber 21c. For this purpose, the boom main valve 2
According to the stroke of the boom operation lever 7, the pilot pressure oil is flown into the boom lowering pilot hydraulic chamber 2d to switch to the boom raising position 2a. As a result, the pressure oil of the main circuit 1a is supplied to the bottom side 3c of the boom cylinder 3, so that the boom cylinder 3 is extended. On the other hand, the expansion side pilot hydraulic chamber 20c is decompressed and switched to the one-direction position 20a. Then, the boom lock cylinder 5 has the piston rod 5 connected to the second boom 33 when the second boom 33 is rotated by the extension force of the boom cylinder 3.
Acts to push down a. Further, the oil on the bottom side 5c with the piston rod 5a pushed down is returned to the oil passage 12 through the free flow position 21b, and on one head side 5b, the oil flows from the oil passage 12 in one direction of the lock valve 20. Suction and fill through position 20a. Therefore, the second
The boom 33 rotates clockwise with the connecting rod 42 of the second boom 33 and the first boom 32 serving as a fulcrum as the piston rod 5a is contracted. As a result, the work device 30 switches from the storage posture 40 shown in FIG. 6 to the work posture 41 as shown in FIG.

Furthermore, when the attitude control valve 22 is set to the lock (valve closed) position 22a while the boom lock cylinder 5 is contracted, the boom lock cylinder 5 is pressurized with the decompressed extension side pilot hydraulic chamber 20c. The pilot circuit of the contraction side pilot hydraulic chamber 21c is connected to the outlet port 22
The contraction-side lock valve 21 is switched to the one-direction position 21a by draining the tank 11 via T. At this time, the second boom 33 is rotated clockwise about the boom connecting pin 42 as the boom cylinder 3 continues to extend. Therefore, the boom lock cylinder 5 has a contracting force, but the extension side lock valve 20 and the contraction side lock valve 21 are
Both are at one-way position 20a and one-way position 21a.
Therefore, the oil on the bottom side 5c is stopped at the one-direction position 21a. As a result, the boom lock cylinder 5 stops during the stroke, and thereafter, the first boom 32 and the second boom 33 rotate about the boom support pin 31 as a fulcrum.

Of course, the boom lock cylinder 5 switches the boom main valve 2 to the boom lowering position 2c and then reduces the boom cylinder 3 to rotate the second boom 33 counterclockwise while the boom lock cylinder 5 is locked. Although the cylinder 5 extends, if the posture control valve 22 is set to the lock (valve closed) position 22a at this time, the expansion side pilot hydraulic chamber 20c that is pressurized and the compression side pilot hydraulic chamber 21 that is depressurized.
Both of the pilot circuits of c are drained to the tank 11 via the outlet port 22T, and the compression side lock valve 21 is switched to the one-direction position 21a. At this time, the second boom 33 is rotated counterclockwise about the boom connecting pin 42 as the boom cylinder 3 continues to contract. Therefore, the boom lock cylinder 5 is acted on by the extension force, but both the extension side lock valve 20 and the contraction side lock valve 21 are set to 1
The directional position 20a and the unidirectional position 21a are set. Therefore, the oil on the head side 5b is stopped at the one-direction position 20a. As a result, the boom lock cylinder 5 stops during the stroke. Therefore, according to the second embodiment, the attitude control valve 22 can be locked (valve closed) even while the boom lock cylinder 5 is being expanded or contracted, and stopped during the stroke of the boom lock cylinder 5. In this way, it is possible to stop the boom lock cylinder 5 in the middle of the stroke.
Since the opening amounts of the boom 32 and the second boom 33 can be arbitrarily set, the work machine 30 does not interfere with the height-restricted object even at a work site where the height of the work range is restricted, and the work can be performed safely and the work can be continued. You can

Next, a third embodiment will be described. FIG.
FIG. 4 is a hydraulic circuit diagram showing a third embodiment, and FIG. 4 is a side view showing a working state of a working device operated by the hydraulic circuit of FIG.
The same parts as those of the first and second embodiments and the prior art of FIG. 5 are designated by the same reference numerals, and the description of the configuration will be omitted. In FIG. 3, an outlet port 26A of the lock valve 26 is provided on the head side 25b and the bottom side 25c of the boom lock cylinder 25.
Are connected respectively. Boom lock cylinder 25
Has the same structure as the boom lock cylinder 5, and detailed description thereof will be omitted.

The lock valve 26 is a spring offset pilot type two-port two-position lock valve having the same structure as the lock valve 4, and has an inlet port 26P and an outlet port 26A.
It has a unidirectional position 26a and a free flow position 26b, and is offset to the unidirectional position 26a by a spring 26d when there is no pressure in the pilot hydraulic chamber 26c.
The inlet port 26P is also connected to the oil in the tank 11 through the oil passage 12 so as to suck the oil in the tank 11. Further, the attitude control valve 10 is connected to the pilot hydraulic chamber 26c that operates the lock valve 26. The attitude control valve 10 is a lever or pedal 10d type 2-port 2-position switching valve offset by a spring 10c, and has an inlet port 10P and an outlet port 10.
A, lock (valve closed) position 10a and unlock (valve open) 1
0b and. The inlet port 10P is connected to the hydraulic chamber 2d of the boom main valve 2 that pilot-operates the boom main valve 2 to the boom lowering position. The outlet port 10A is connected to the pilot hydraulic chamber 26c.
It is connected to the.

In FIG. 4, the boom lock cylinder 25
Is pivotally attached to the first boom 52 at the front side on the bucket 43 side so that one end is swingably attached to the first boom 52 and the other end is swingably attached to the second boom 53. In addition, the boom lock cylinder 25 and the second
The pivot position with respect to the boom 53 may be the same position as the boom cylinder 3, or may be any position between the boom cylinder 3 and the boom connecting pin 42. The other components are the same as those in FIGS. 6 and 7, and the same reference numerals are given to omit the description.

The operation of the above configuration will be described with reference to FIGS. 3 and 4. To move from the working posture 41 of FIG. 4 to the storage posture 40 (not shown) corresponding to FIG. 6, in the state of the working posture 41, the boom cylinder 3 is extended to the stroke end, and the first boom 52 is rotated clockwise. Set to the position. At this position, the lever or pedal 10d of the attitude control valve 10 shown in FIG. 3 is manually or stepped on to the unlock (valve open) 10b position. Then, when the boom operation lever 7 is set to the boom lowering position, the pump 6
Of the oil passes through the boom lowering valve 8a and pressurizes the pilot hydraulic chamber 2e. As a result, the boom main valve 2 is switched to the boom lowering position 2c, and the lock valve 26 is moved to the free flow position 26b. When the boom main valve 2 reaches the boom lowering position 2c, the head side 3b is pressurized and the pressure oil on the bottom side 3c is released to the tank 11 to contract the piston rod 3a.

At this time, since the attitude control valve 10 is switched to the unlock (valve open) position 10b, the pressure oil of the inlet port 10P passes through the unlock (valve open) 10b position and the pilot hydraulic pressure of the lock valve 26 is reached. The chamber 26c is pressurized. When the lock valve 26 reaches the free flow position 26b, the pressure oil on the head side 25b and the bottom side 25c of the boom lock cylinder 25 is released to the tank 11 and the rod 25 is released.
a becomes free. Then, when the boom main valve 2 is at the boom lowering position 2c and the boom cylinder 3 is contracted, the second boom 53 is rotated counterclockwise about the boom connecting pin 42 as a fulcrum by the contracting force due to the lowering of the boom cylinder 3. Let At this time, the boom lock cylinder 25 has the lock valve 26 at the free flow position 26b due to the contracting force of the second boom 53 or the weight of the bucket 43 connected to the tip of the second boom 53. When the piston rod 25a is pushed by the second boom 53, the oil on the bottom side 25c is pushed by the piston rod 25a and sucked by the head side 25b, and a part of the oil is drained to the tank 11 via the oil passage 12. . As a result, the boom lock cylinder 25 is reduced. And the second boom 53
The second boom 53 when the piston rod 25a is fully contracted.
The rotation of the first boom 52 further rotates in the clockwise direction, and the work posture 41 of the work device 50 folded by the first boom 52 is switched to the storage posture 40 similar to that shown in FIG. Replace

When the storage posture 40 is switched to the working posture 41, the posture control valve 10 is in the lock (valve closed) position 1.
Regardless of which position is 0a or unlocked (valve open) 10b, when the boom raising valve 8b is pushed by the boom operating lever 7, the boom main valve 2 is switched to the boom raising position 2a and the main circuit 1a The pressure oil is supplied to the bottom side 3c of the boom cylinder 3. As a result, the boom cylinder 3 is extended, and the second boom 53 rotates clockwise with the boom connecting pin 42 as a fulcrum when the boom cylinder 3 is raised. At this time, boom lock cylinder 2
5, the piston rod 25a is pulled up by the second boom 53 and extended. When the posture control valve 10 is set to the unlock (valve open) position 10b, the pressure oil in the pilot hydraulic chamber 26c of the lock valve 26 is drained to the tank 11 via the boom lowering valve 8a, and the lock valve 26 26 is set to the one-direction position 26a. Then, the oil on the head side 25b of the boom lock cylinder 25 is locked by the lock valve 26
Since the oil is stopped at the one-direction position 26a ahead of the outlet port 26A, the oil on the head side 25b turns to the bottom side 25c. Further, on the bottom side 25c, oil corresponding to the volume of the rod 25a on the head side 25b is supplied from the tank 11 to the lock valve 26.
Through the one-direction position 26a and is sucked to the bottom side 25c. On the other hand, the attitude control valve 10 is locked (valve closed) at the position 10a.
When it is set, the lock valve 26 remains at the free flow position 26b, and oil corresponding to the volume of the rod 25a on the head side 25b of the boom lock cylinder 25 is sucked from the tank 11 to the bottom side 25c. Then, when the piston rod 25a is fully extended, the second boom 53 stops rotating in the clockwise direction about the connecting pin 42 with the first boom 52 as a fulcrum, and is separated from the first boom 52 as shown in FIG. The device 50 switches to the working position 41.

As described above, in the third embodiment, the oil is supplied to the boom lock cylinder 25 by the suction oil passage 12 connected to the tank 11, the lock valve 26 connected to the oil passage 12, and the lock valve. Boom lock cylinder 25 connected between Boom lock cylinder 25 and lock valve 26
Is connected to the control circuit for the boom operation valve 8 for pilot operation via the attitude control valve 10,
The thick pipe connected to the high-pressure main circuit 1a from the main hydraulic pump 1 may be a simple pipe structure as long as the pipes to the boom main valve 2 and the boom cylinder 3 are provided. Further, since the thick pipe to the boom lock cylinder 25 needs only one of the oil passage 12, the pipe configuration is simpler. Also,
Only one boom main valve 2 needs to be a large switching valve used in the high-pressure pipe of the main circuit 1a, and the space for mounting these devices can be reduced. Further, since the lock valve 26 is pilot-operated via the attitude control valve 10 by one boom operation valve 8, the configuration of the operation valve is also simplified.

[0043]

As described above, according to the present invention,
In the hydraulic circuit of the work device that moves the boom from the retracted posture to the working posture, the oil is supplied to the boom lock cylinder by a suction oil passage connected to the tank and a lock valve connected between the oil passage and the boom lock cylinder. Since the lock valve is connected to the control circuit of the boom operation valve that is pilot-operated via the attitude control valve, the piping connected to the high-pressure main circuit from the main hydraulic pump is connected to the boom main valve and the boom cylinder. Since only the piping is required, a simple piping configuration is sufficient. Moreover, only one large switching valve is required in the high-pressure pipe of the main circuit 1a, and the space for mounting these devices can be reduced. Further, since the lock valve is pilot-operated via the attitude control valve by one boom operation valve, the configuration of the operation valve is simplified.

Further, the lock valve provided between the boom lock cylinder and the tank causes the boom lock cylinder to receive the contraction force of the second boom due to the lowering of the boom cylinder or the own weight up to the bucket connected to the tip of the second boom. It is possible to cause the piston rod connected to the second boom to extend so that the working device can be switched to the retracted posture. Further, when the attitude control valve is unlocked (valve opened) and the boom operation lever is at the boom raising position, the extension force of the boom cylinder pushes down the piston rod that is the connecting portion between the second boom and the boom lock cylinder. At this time, the boom lock cylinder is designed so that the oil in the tank is sucked into the space on the head side by pushing down the piston rod through the oil passage to the head side through the one-way position of the lock valve. Thus, the working device can be switched to the working posture.

Further, since the lock valves provided between the boom lock cylinder and the tank and the lock valve are connected to the control circuit of the boom operation valve for pilot operation via the attitude control valve, the boom lock cylinder The attitude control valve can be locked (valve closed) even during expansion and contraction to stop during the stroke of the boom lock cylinder. In this way, since the boom lock cylinder can be stopped during the stroke, the opening amount of the first boom and the second boom can be arbitrarily set, so that the work machine is limited in height even at the work site where the height of the work range is limited. It will not interfere with the objects, the work machine can be operated safely, and the work can be continued.

Further, the boom lock cylinder for setting the opening amount of the first boom and the second boom is arranged on the inner angle side of the first boom and the second boom, and the oil is supplied to the boom lock cylinder by the tank. A suction oil passage connected to
Since the lock valve connected to the oil passage, the boom lock cylinder connecting the lock valve to the boom lock cylinder, and the lock valve connected to the control circuit of the boom operation valve for pilot operation via the attitude control valve, The thick piping connected to the high-pressure main circuit from the main hydraulic pump may have a simple piping configuration only by providing the boom main valve and piping to the boom cylinder. Further, since the thick pipe to the boom lock cylinder needs only one oil passage between the tank and the lock valve, the pipe structure becomes simpler. Moreover, the large switching valve used in the high-pressure pipe of the main circuit may be one of the boom main valves, and the space for mounting these devices can be reduced. Further, since the lock valve is pilot-operated via the attitude control valve by one boom operation valve, the configuration of the operation valve is simplified.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a first embodiment.

FIG. 2 is a hydraulic circuit diagram of a second embodiment.

FIG. 3 is a hydraulic circuit diagram of a third embodiment.

FIG. 4 is a side view showing a work posture of a work apparatus according to a third embodiment.

FIG. 5 is a hydraulic circuit diagram of a conventional working device.

FIG. 6 is a side view showing a storage posture of the work device.

FIG. 7 is a side view showing a work posture of the work device.

[Explanation of symbols]

2 ... Boom main valve, 3 ... Boom cylinder, 4, 20, 2
1, 26 ... Lock valve, 5, 25 ... Boom lock cylinder, 5b, 25b ... Head side, 5c, 25c ... Bottom side, 7 ... Boom operating lever, 8 ... Boom operating valve, 1
0,22 ... Attitude control valve, 10d, 22d ... Pedal or manual type, 11 ... Tank, 26A ... Discharge side, 26P
... Inlet side, 30,50 ... Working device, 32,52 ... First
Boom, 33, 53 ... Second boom, 33a ... Two-piece boom, 40 ... Storing posture, 41 ... Working posture.

Claims (5)

[Claims] 1. A two-piece boom in which a first boom and a second boom are rotatably connected to each other, and an opening amount of the first boom and the second boom which is inserted between the first boom and the second boom and extends and contracts. Hydraulic circuit of a working device consisting of a boom lock cylinder that controls the storage posture and working posture by controlling the boom, a boom cylinder that vertically raises and lowers the two-piece boom, and a boom main valve that telescopically switches the boom cylinder between up and down. The boom operation valve connected to the boom operation lever that pilot operates the boom main valve, the boom main valve that switches by receiving pressure from the boom operation valve, and the oil passage inserted between the boom lock cylinder and the tank. Insert the pilot operated lock valve to be connected and the pilot circuit between the lock valve and the boom operation valve to adjust the retracted posture and working posture of the work equipment. And a posture control valve for switching to any of the above, and when the posture is changed, the boom operation valve is operated and the lock valve is changed so that oil returned from the tank and / or the bottom is sucked into the boom lock cylinder. Hydraulic circuit of working equipment. 2. One of the boom lock cylinders is connected to a tank or a return oil pipe via a lock valve, and the other end is connected to a tank or a pipe, and the boom main cylinder is connected via a posture control valve. The hydraulic circuit of the working apparatus according to claim 1, further comprising a pilot operating circuit of the lock valve connected to the pilot hydraulic chamber for lowering the valve. 3. The extension side lock valve and the contraction side lock valve of the boom lock cylinder are respectively connected to the tank and the boom lock cylinder, and the extension side pilot hydraulic chamber of the extension side lock valve is used for lowering the boom operation valve. The hydraulic circuit of the working apparatus according to claim 1, wherein the compression side pilot hydraulic chamber of the compression side lock valve is connected to the hydraulic chamber to the raising pilot hydraulic chamber of the boom operation valve via an attitude control valve. 4. A lock valve is connected between the boom lock cylinder and the tank by an oil passage, and a pilot operating circuit for the lock valve is connected to a pilot hydraulic chamber for lowering the boom main valve via an attitude control valve. The hydraulic circuit of the working apparatus according to claim 1, wherein. 5. The attitude control valve is a pedal or a manual type 2 valve.
2. The hydraulic circuit for a working device according to claim 1, wherein the hydraulic circuit comprises a position 2 connection directional control valve or a 2 position 5 connection directional control valve.