JPH05321301A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To improve the safety and working efficiency of a construction machine, by a method wherein both a lock valve for an arm and a check valve therefor are, in parallel, provided in the circuit in which an oil chamber on the loaded side of an arm-cylinder communicates with a pilot-operated directional control valve while the arm-cylinder is not operated, and a side pilot line is provided for the pilot-operated directional control valve. CONSTITUTION:While an arm-cylinder 40 is not operated, a pilot-operated directional control valve 44 for an arm is allowed to be at its neutral position and a side pilot 44p is allowed to be at a position (f) where an oil way communicates with a tank. Therefore, a passage in a lock valve 52 for the arm is closed since a pilot pressure is not applied to a piston chamber 52p. As the result of it, the circuit between an oil chamber 42b on the loaded side of the arm-cylinder 40 and the pilot-operated directional control valve 44 is oiltightly closed by both the lock valve 52 and a check valve 54, and the arm- cylinder 40 is locked. In this way, when a construction machine is used as a crane by attaching a lifting device in the vicinity of the top end part of the arm, such a trouble that a lifted load lowers by its dead weight can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit capable of locking a hydraulic cylinder mounted on a work attachment of a construction machine such as a hydraulic excavator.

[0002]

2. Description of the Related Art FIG. 2 is a side view of a hydraulic excavator to which a lifting device for crane work is attached. In the figure, 1
Is an upper revolving structure which is the body of the hydraulic excavator, 2 is a lower traveling structure, 3 is a work attachment mounted on the front part of the upper revolving structure 1, 4 is a boom of the work attachment 3, 5 is an arm, and 6 is a work tool. Bucket, 7 is a boom cylinder, 7a is a bottom side oil chamber which is a load side oil chamber when the boom cylinder 7 is not operated, 7b is a rod side oil chamber, 8 is an arm cylinder, 8a is a bottom side oil chamber, and 8b is an arm. A rod side oil chamber which is a load side oil chamber when the cylinder 8 is not operated, 9 is a bucket cylinder, 10 is a swing motor, and 11
L and 11R are left and right traveling motors, 12 is a crane attachment mounted near the tip of the arm 5, and 13 is a suspended load.

FIG. 3 is a hydraulic circuit diagram of a main part of a hydraulic excavator having a lock valve 19 of the prior art. In the figure,
19 is a lock valve for the boom (4), 20 is a boom remote control valve, 21 is an operating lever of the boom remote control valve 20,
22 and 23 are pilot valves, 24 is a main pump, 25 is a pilot pump, 26 is a plunger provided inside the lock valve 19, 27 is a seat portion, 28 is a spool, and 29 is a relief valve for overload. ..

Next, a conventional hydraulic circuit is shown in FIGS.
I will describe. In the backhoe type hydraulic excavator as shown in FIG. 2, a work attachment 3 in which a boom 4, an arm 5 and a bucket 6 are sequentially connected to each other so as to be rotatable in the front-rear direction is attached to the front part of the upper swing body 1, It is equipped with a lock valve 19 for locking 4. In the hydraulic circuit shown in FIG. 3, the boom remote control valve 20 is used.
Since the pilot pressure (pilot secondary pressure) does not act on the pilot pressure receiving portions 30 and 31 of the pilot switching valve 17 when the operation lever 21 of is in the neutral position,
The pilot switching valve 17 is in the neutral position. At this time, the load side pressure of the boom cylinder 7, that is, the bottom side pressure (referred to as the pressure in the bottom side oil chamber 7a) acts on the back of the plunger 26 inside the lock valve 19 via the pipe line 33.
Since the plunger 26 is in close contact with the seat portion 27, it is possible to prevent leakage and lock the boom. Next, when the boom is lowered, if the operation lever 21 is operated from the neutral position toward the position a, the pilot pressure derived from the pilot valve 22 passes through the conduits 34 and 35, and the pilot pressure receiving portion 30 of the pilot switching valve 17 is reached. Act on. At the same time, the pilot pressure is branched in the pipe line 34,
6 and acts on the port Z1 of the lock valve 19. Since the spool 28 operates from the low position to the high position, the rear side of the plunger 26 communicates with the oil tank 37 via the high position of the spool 28. As a result, the seat portion 27 of the plunger 26 is opened, so that the boom cylinder 7 is contracted and the boom can be lowered.

[0005]

When the hydraulic excavator having the work attachment mounted on the front portion of the vehicle body is parked for a long time, the boom pilot switching valve is in the neutral position, but the boom pilot switching valve is in the neutral position. Since the work attachment drops due to the leak from the gap between the spool hole and the spool, the boom lock valve has been attached only to the boom. However, in hydraulic excavators, crane work may be carried out by attaching slings near the tip of the arm. In that case, when the suspended load is suspended, the tip of the arm and the suspended load drop due to internal leakage of the arm pilot switching valve, which is unsafe and unsafe. Further, the boom lock valve of the prior art has a complicated structure and is expensive to manufacture as shown in FIG. 3, for example. Further, when unlocking the boom lock valve, the pilot secondary pressure derived from the pilot valve of the hydraulic remote control valve is made to act on the port of the lock valve. Since the pilot secondary pressure fluctuates according to the operation angle amount of the operation lever, the operation of the lock valve may become unstable. The present invention aims to solve the above problems.

[0006]

According to the hydraulic circuit of the present invention,
A circuit that communicates the load side oil chamber when the boom cylinder is not operated with the boom pilot switching valve, and a circuit that communicates the load side oil chamber when the arm cylinder is not operated with the arm pilot switching valve, Boom and arm lock valves are respectively installed, check valves are installed in parallel for the boom and arm lock valves, and side pilot lines are installed for the boom and arm pilot switching valves. When the boom raising operation and the arm pulling operation are performed, the pilot primary pressure from the pilot pressure hydraulic source is applied to the boom lock valve and the arm lock valve piston chambers via the side pilot lines, respectively. The lock valve for the arm and the lock valve for the arm are configured to be opened.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of the present invention. In the figure, 39 is a boom cylinder, 39a is a bottom side oil chamber of the boom cylinder 39, 39b is a rod side oil chamber, 40 is an arm cylinder, 40a is a bottom side oil chamber of the arm cylinder 40, 40b is a rod side oil chamber, 41 Is a swing motor, 4
2L and 42R are traveling switching valves for controlling left and right traveling motors (not shown), 43 is a boom pilot switching valve for controlling the boom cylinder 39 (hereinafter, referred to as boom switching valve), and 43P is a boom switching valve 43. Side pilot lines (hereinafter, referred to as side pilots) that perform switching operation in conjunction with each other, 44 is an arm pilot switching valve for controlling the arm cylinder 44 (hereinafter, referred to as arm switching valve), 4
4P is a side pilot line (hereinafter, referred to as a side pilot) that performs switching operation in conjunction with the arm switching valve 44,
45 is a pilot switching valve for turning, 46 is a pilot switching valve for bucket, 47 is a load check valve with a turning priority piston, 48 is a straight traveling valve, and 49L and 49R are arranged on the outlet side of the left and right center bypass oil passages 50L and 50R. Pilot on-off valves, 51 and 52 are boom and arm lock valves, 51p and 52p are piston chambers of the boom lock valve 51 and arm lock valve 52, and 53 and 54 are check valves. 55 and 56 are first and second pumps which are main pumps respectively, 57 is a pilot pump which is a pilot hydraulic pressure source, 58 is an oil tank, 59L and 59R are left and right hydraulic remote control valves, and 60
L and 60R are operating levers of the hydraulic remote control valves 59L and 59R, respectively, and reference numerals Ni, ..., And 7-7 indicate connection of pilot lines.

Next, the structure of the hydraulic circuit of the present invention will be described with reference to FIG. In the hydraulic circuit of the present invention, the boom cylinder 3
Bottom side oil chamber 3 which is a load side oil chamber when 9 is not operated
A boom lock valve 51 is provided in a circuit connecting the 9a and the boom switching valve 43 to connect the rod side oil chamber 40b, which is a load side oil chamber when the arm cylinder 40 is not operated, and the arm switching valve 44. The arm lock valve 52 is provided in the circuit, the check valves 53 and 54 are connected in parallel to the boom lock valve 51 and the arm lock valve 52, respectively, and the boom switch valve 43 is connected to the boom switch valve 43.
When a side pilot 43p that performs a switching operation in conjunction with the above is provided, and a side pilot 44p that performs a switching operation in conjunction with the arm switching valve 44 is provided in the arm switching valve 44, respectively, when performing boom raising operation and arm pulling operation of the hydraulic excavator. By operating the pilot primary pressure from the pilot pump 57 on the piston chambers 51p and 52p of the boom lock valve 51 and the arm lock valve 52 via the side pilots 43p and 44p, respectively, the boom lock valve 51, Each of the arm lock valves 52 is configured to be opened.

Next, the operation of the hydraulic circuit of the present invention will be described. First, as the first case, when the boom cylinder 40 is not operated, the boom switching valve 43 is in the neutral position and the side pilot 43p is in the cutoff oil passage position c. Therefore, since the pilot pressure does not act on the piston chamber 51p, the passage of the boom lock valve 51 is closed. The circuit between the load side oil chamber (39a) of the boom cylinder 39 and the boom switching valve 43 is a boom lock valve 51.
Also, the boom valve 39 can be locked because it is oil-tightly shut off by the check valve 53.

Next, as a second case, the boom switching valve 43
To the boom raising position force, the boom switching valve 4
The side pilot 43p is interlocked with 3 and the cutoff oil passage position d
Switch to. Since the pilot pressure does not act on the piston chamber 51p, the boom lock valve 51 remains closed.
However, the pressure oil from the second pump 56 is transferred to the pipe line 61 and the oil line 6.
2, the neutral position of the switching valve 42R for traveling, the oil passages 63, 64,
Check valve 65, oil passages 66, 67, 68, 69, check valve 70, boom switching valve 43 position, oil passages 71, 7
2, the oil is sent to the bottom side oil chamber 39a via the check valve 53, the oil passage 74, and the pipe 75. At the same time, the return oil from the rod-side oil chamber 39b passes through the pipe line 76, the oil line 77, the position of the boom switching valve 43, the oil lines 78, 79, and the pipe lines 80, 81.
After that, it is returned to the oil tank 58. Therefore, since the boom cylinder 39 is extended, the boom raising operation can be performed without any trouble.

Next, as a third case, the boom switching valve 43
To the boom lowering position, the boom selector valve 4
In conjunction with 3, the side pilot 43p opens the oil passage position e
Switch to. The pilot primary pressure from the pilot pump 57 is applied to the pipelines 82, 83, 84 and the side pilot 43.
through the opening oil passage position e of p and the oil passage 85.
Acts on 1p. The boom lock valve 51 operates to open the passage. Therefore, the pressure oil from the second pump 56 is sent to the rod-side oil chamber 39b via the yaw position of the boom switching valve 43, and at the same time, the return oil from the bottom-side oil chamber 39b is returned to the pipe 75 and the oil passage. 74, 86, the opening passage of the boom lock valve 51, the oil passages 87, 71, the boom switching valve 4
After passing through the 3rd position, oil passages 78 and 79, and pipelines 80 and 81,
It is returned to the oil tank 58. Therefore, the boom cylinder 3
Since 9 is reduced, the boom lowering operation can be performed without any trouble.

Next, as a fourth case, the arm switching valve 44
When is not operated, when the arm cylinder 39 is not operated, the arm switching valve 44 is in the neutral position, and the side pilot 44p is in the tank communication oil passage position f. Therefore, since the pilot pressure does not act on the piston chamber 52p, the passage of the arm lock valve 52 is closed. Load side oil chamber of arm cylinder 40 (40b)
The circuit between the arm switching valve 44 and the arm switching valve 44 is the lock valve 5 for the arm.
2 and the check valve 54 are oil-tightly shut off, so that the arm cylinder 40 can be locked.

Next, as a fifth case, the arm switching valve 44
To the arm push position, the arm switching valve 4
4, the side pilot 44p is switched to the tank communication oil passage position g. Since the pilot pressure does not act on the piston chamber 52p, the arm lock valve 52 remains closed. However, the pressure oil from the first pump 55 is
Oil passage 89, straight position of travel straight valve 48, oil passage 90, neutral position of travel switching valve 42L, oil passages 91 and 92, check valve 93, oil passages 94, 95, 96 and 97, load with turning priority piston Check valve 47, oil passage 98, arm switching valve 44
Position, oil passages 99 and 100, check valve 54, oil passage 1
01, 102, the pipe 103, and the rod-side oil chamber 40b
Sent to. At the same time, the return oil from the bottom side oil chamber 40a is returned to the pipe line 104, the oil line 105, and the arm switching valve 44.
Through the oil passages 106, 107 and the pipe 108,
It is returned to the oil tank 58. Therefore, arm cylinder 4
Since 0 is reduced, the arm pushing operation can be performed without any trouble.

Next, as a sixth case, the arm switching valve 44
To the arm pull position, the arm switching valve 4
The side pilot 44p is switched to the switching position h in conjunction with the position 4 of FIG. The primary pilot pressure from the pilot pump 57 acts on the piston chamber 52p through the pipe lines 82, 83, 109, 110, the switching position h of the side pilot 44p, and the oil passage 111. The arm lock valve 52 operates to open the passage. Therefore, the first pump 55
The pressure oil from the oil is sent to the bottom side oil chamber 40a via the position of the arm switching valve 44, and at the same time, the rod side oil chamber 40a.
The return oil from b is pipe 103, oil passages 102, 112,
An opening passage of the arm lock valve 52, the oil passages 113, 99,
It is returned to the oil tank 58 through the repositioned position of the arm switching valve 44, the oil passages 106 and 107, and the pipeline 108. Therefore, since the arm cylinder 40 is extended, the arm pulling operation can be performed without any trouble.

When the boom cylinder 39 and the arm cylinder 40 are not operated as described above, the lock valve (51,
52) and the check valves (53, 54) can lock the cylinders (39, 40), respectively, so that when the hydraulic excavator mounts the sling near the tip of the arm and performs crane work, the suspended load drops due to its own weight. It is possible to prevent the trouble. Further, during lifting and lowering operations of the suspended load, the lock valve can be released and the check valve can be operated so that the suspended load can be lifted and lowered without trouble.

[0016]

EFFECTS OF THE INVENTION In a hydraulic excavator having a work attachment mounted on the front portion of a vehicle body, a boom lock valve is conventionally attached only to the boom in order to prevent the boom from dropping when parked. However, in hydraulic excavators, crane work may be carried out by attaching slings near the tip of the arm. In that case, when the suspended load is suspended, the tip of the arm and the suspended load drop due to internal leakage of the arm pilot switching valve, which is unsafe and unsafe. Further, the conventional boom lock valve has a complicated structure and is expensive to manufacture. Further, when the lock valve is unlocked, the pilot secondary pressure derived from the remote control pilot valve is made to act on the port of the lock valve, so that the operation of the lock valve may become unstable. However, in the hydraulic circuit of the present invention, a circuit that communicates the load side oil chamber when the boom cylinder is not operated with the boom pilot switching valve, and the load side oil chamber when the arm cylinder is not operated and the arm pilot switching Boom and arm lock valves are installed in the circuit that communicates with the valve, check valves are installed in parallel for the boom and arm lock valves, and side valves are installed for the boom and arm pilot switching valves. Pilot line is provided, and when boom raising operation and arm pulling operation of construction machine are performed, pilot primary pressure from the hydraulic pressure source is supplied to each piston of boom lock valve and arm lock valve through the side pilot line. By operating the chamber, the boom lock valve and arm lock valve are opened respectively. It was allowed to so. Thereby, when the boom cylinder and the arm cylinder are not operated, the cylinders can be locked by the lock valve and the check valve, respectively. Therefore, when the hydraulic excavator is mounted with a sling near the tip of the arm for crane work, it is possible to prevent the suspended load from falling due to its own weight. Further, since the stable pilot primary pressure from the pilot pump is applied to the piston chamber of the lock valve, the lock valve can be reliably unlocked. Further, since the lock valve of the present invention has the piston chamber, the structure thereof is simple, so that the control valve (multiple valve of pilot switching valve)
It can be manufactured at a low cost because it has a compact structure that does not require connection piping and space by being integrally configured.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of the present invention.

FIG. 2 is a side view of a hydraulic excavator to which a fishing tackle for crane work is attached.

FIG. 3 is a hydraulic circuit diagram of a main part of a hydraulic excavator having a lock valve according to a conventional technique.

[Explanation of symbols]

 3 Work Attachment 4 Boom 5 Arm 7,39 Boom Cylinder 7a, 8a, 39a, 40a Bottom Oil Chamber 7b, 8b, 39b, 40b Rod Oil Chamber 8, 40 Arm Cylinder 19 Lock Valve 25, 57 Pilot Pump 43 For Boom Pilot switching valve 43p, 44p Side pilot line 44 Pilot switching valve for arm 51 Boom lock valve 51p, 52p Piston chamber 52 Lock valve for arm

Claims (1)

[Claims] 1. A hydraulic circuit of a construction machine, comprising a work attachment, in which a boom, an arm, and a work tool are sequentially connected to each other so as to be rotatable in the front-rear direction, mounted on the front part of a vehicle body, and having means for locking the boom. , A circuit that connects the load side oil chamber when the boom cylinder is not operated and the boom pilot switching valve, and a circuit that connects the load side oil chamber when the arm cylinder is not operated and the arm pilot switching valve , The boom and arm lock valves are respectively installed, the boom and arm lock valves are respectively provided with check valves, and the boom and arm pilot switching valves are respectively provided with side pilot lines. When the boom is raised and the arm is pulled, the pilot primary pressure from the hydraulic pressure source is The passages of the boom lock valve and the arm lock valve can be opened by acting on the piston chambers of the boom lock valve and the arm lock valve respectively via the side pilot lines. Hydraulic circuit of construction machinery to be used.