JPH04297628A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To raise the efficiency of heavy excavating operation by a method in which when the operating lever of bucket is greatly operated, an interlock valve and straight traveling valve are switched for operation, and pressure oils from the first and second pumps are joined and supplied to a bucket cylinder. CONSTITUTION:The upstream side port 45 of a subvalve 19 for bucket valve is connected with a pilot pump 27 through an interlocked valve 37. Pilot secondary pressure acting on the valve 13 is applied to the port 38 and the valve 38 is switched, during which period a straight traveling valve 20 is allowed to be switched. The pilot secondary pressure of pilot valve for controlling actuator other than the bucket cylinder 7 is applied to the port 39, and the valve 37 is allowed to be switched to return. When the operating lever 34 is greatly inclined, the pilot secondary pressure of the valve 13 is increased to higher one, the valves 20 and 37 are switched, and pressure oils in the pumps 25 and 26 are joined and supplied to the cylinder 7. The operating speed of the bucket can thus be increased and the efficiency of heavy excavation can be raised.

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 rapidly changing the operating speed of a working hydraulic actuator of a tracked construction machine such as a hydraulic excavator or a working vehicle.

0002

2. Description of the Related Art FIG. 2 is a hydraulic circuit diagram of a conventional tracked hydraulic excavator (not shown). In the figure, 1 is the work attachment attached to the front part of the hydraulic excavator, 2 is the boom of work attachment 1, 3 is the arm, 4 is the bucket, 5 is the boom cylinder, 6 is the arm cylinder, 7 is the bucket cylinder, 8L and 8R are left and right travel motors, 9 is a swing motor, 10L and 10R are travel motor control switching valves (hereinafter referred to as travel valves), 11 is a pilot switching valve for boom cylinder control (hereinafter referred to as boom valves), and 12 is an arm cylinder. Control pilot switching valve (
13 is a pilot switching valve for bucket cylinder control (hereinafter referred to as bucket valve); 14 is a pilot switching valve for swing motor control (hereinafter referred to as swing valve)
, 15, to, 19 are the respective valves 10L, 10R, 11, 1
Sub-valve connected to 2 and 13, 20 is a straight travel valve, 2
1 and 22 are pilot on-off valves (hereinafter referred to as on-off valves), 23 and 24 are low pressure relief valves for setting negative control pressure, 25 and 26 are first and second pumps, respectively, 27 is a pilot pump, and 28 and 29 are respectively Center bypass oil passage, 30 is remote control valve for bucket, 3
1 is a remote control valve for the arm, 32 is a remote control valve for swinging, 3
3 is an oil tank. Further, the symbols E-I, Ro-Ro, Ha-Ha, Ni-Ni, Ho-Ho, and He-He indicate the connections of the pilot pipes, respectively.

In the conventional hydraulic circuit shown in FIG. 2, various hydraulic actuators (8L,
6, 9, 8R, 5, 7) are divided into two groups A and B, each driven by a first pump 25 and a second pump 26, and various hydraulic actuator control switching valves (
10L, 12, 14, 10R, 11, 13), each sub-valve (15, 18, 16, 17) is configured to pass or block the pilot primary pressure in conjunction with its switching valve (excluding the swivel valve 14). , 19), and the center bypass oil passages 28 of groups A and B, respectively.
On-off valves 21 and 22 are arranged at the outlets of
are placed.

When the hydraulic excavator performs work, the bucket 4, arm 3, The upper revolving body (not shown) can be moved. Furthermore, when the hydraulic excavator travels, the travel valves 10L, 10
Operate R. When the travel valves 10L and 10R are simultaneously operated and any of the other actuators is operated, the straight travel valve 20 is switched from the single oil passage position G to the multiple oil passage position G. This allows the hydraulic excavator to travel straight without meandering.

[0005]

When a hydraulic excavator excavates soil or performs inching excavation, the tilt angle of the operating lever 34 of the bucket remote control valve 30 is operated to be small. In this case, the pressure oil from the first pump 25 is applied to the single oil passage position of the straight travel valve 20.
It is supplied to the bucket cylinder 7 through the neutral position of the travel valve 10R, the neutral position of the boom valve 11, the switching position of the bucket valve 13, and the pipe line 35 or 36. However, when the hydraulic excavator performs heavy excavation and discharge, the operating lever 34 of the bucket remote control valve 30 is operated from the neutral position in the R direction or N direction to the full tilt angle. However, only the pressure oil discharged from the first pump 25 is supplied to the bucket cylinder 7. Therefore, the operating speed of the bucket cylinder 7 was slow, making it impossible to perform heavy excavation at the required high speed. The problem to be solved by the present invention is the above problem.

[0006]

[Means for Solving the Problems] The present invention communicates the upstream side port of a sub-valve of a pilot switching valve for controlling a bucket cylinder with a pilot pump via an interlock valve, and connects the pilot pump to one side port of the interlock valve. In this case, the pilot secondary pressure applied to the bucket cylinder control pilot switching valve is applied to switch the interlock valve, and when the interlock valve is switched, the straight travel valve is switched by the pilot primary pressure. Further, the interlock valve is configured to switch the interlock valve to its original position by applying a pilot secondary pressure to the other side port of the interlock valve to act on a pilot switching valve for controlling a hydraulic actuator other than the bucket cylinder. Further, the interlock valve is set to switch when the pilot secondary pressure acting on one side port of the interlock valve in the hydraulic circuit exceeds a predetermined pressure.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a hydraulic circuit diagram of the present invention. In the figure, the same reference numerals are given to the same components as in the prior art. 37 is an interlock valve, 38 is a port on one side of the interlock valve 37, 39 is a port on the other side, 4
0 is a check valve, 41 is a shuttle valve for high pressure selection that selects the pilot secondary pressure that acts on the left and right pilot ports (numerals are omitted) of the bucket valve 13, and 42 acts on the left and right pilot ports of the arm valve 12, respectively. 43 is a shuttle valve that selects the pilot secondary pressure that acts on the left and right pilot ports of the swivel valve 14, and 44 is an arm valve 1.
2 and a shuttle valve for selecting the pilot secondary pressure acting on the swing valve 14; 45 a spool (not shown) inside the interlock valve 37 when the pilot secondary pressure acts on the port 38 on one side of the interlock valve 37; It is a built-in spring that is biased to resist movement.

Next, the configuration of the hydraulic circuit of the present invention will be described with reference to FIG. The upstream port 45 of the sub-valve 19 of the bucket valve 13 and the pilot pump 27 are communicated via an interlock valve 37, and one side port 38 of the interlock valve 37 has a pilot secondary pressure applied to the bucket valve 13. is actuated to switch the interlock valve 37, and when the interlock valve 37 switches, the pilot primary pressure causes the straight travel valve 20 to switch.
is switched, and pilot secondary pressure is applied to the other side port 39 of the interlock valve 37 to act on a pilot switching valve for controlling a hydraulic actuator other than the bucket cylinder, thereby switching the interlock valve 37 to its original position. It was configured as follows. Further, the interlock valve 37 is set to switch when the pilot secondary pressure acting on the one side port 38 of the interlock valve 37 exceeds a predetermined pressure P. The above pressure P is set using the built-in spring 4.
5 can be determined by selecting the required force.

Next, the operation of the hydraulic circuit of the present invention will be described. When the hydraulic excavator starts excavating soil or performs inching excavation, the tilt angle of the operating lever 34 of the bucket remote control valve 3 is operated to be small. In this case, the pilot secondary pressure acting on the left and right pilot ports of the bucket valve 13 is a low pressure below the set pressure P. Therefore, the low pilot secondary pressure is
Even if it acts on the one side port 38 via the shuttle valve 41 and the conduit 46, the interlock valve 37 will not switch due to the spring force of the built-in spring 45. The interlock valve 37 is in its original position, which is the same as in the prior art.

Next, when the hydraulic excavator performs heavy excavation and discharge, the operation lever 34 of the bucket remote control valve 30 is pressed.
Tilt the lever significantly from the neutral position in the R direction or N direction. In this case, the pilot secondary pressure acting on the left and right pilot ports of the bucket valve 13 becomes a high pressure higher than the set pressure P. Therefore, the high pilot secondary pressure acts on the one side port 38, and the interlock valve 37 is switched from the original position L to the open oil passage position O. Pilot pump 2
The pilot primary pressure from 7 is the open oil passage position O of the interlock valve 37, the pipe line 47, the check valve 40, the pipe line 48,
(At this time, since the bucket valve 13 is in the switching operation, its sub-valve 19 is in the cut-off oil path position) Oil passage 49, the opening oil passage position of the sub-valve 17 of the boom valve 11, the oil passage 50,
Through the pipes 51 and 52 and the shuttle valve 53, the straight travel valve 2
0 port 54. The straight travel valve 20 is switched from the single oil passage position G to the plural oil passage position H. 1st pump 2
The pressure oil from 5 is connected to the pipe 55, the position of the straight travel valve 20,
Oil passages 65, 66, check valve 67, oil passages 68, 61, 6
2. It is supplied to the bucket cylinder 7 via the check valve 63, the oil line 64, the switching position of the bucket valve 13, and the pipe line 35 or 36. At the same time, the pressure oil from the second pump 26 is supplied to the pipes 69 and 70, to the position of the straight travel valve 20, and to the oil passage 56.
, passes through the neutral position of the travel valve 10R, oil passages 57 and 58, check valve 59, and oil passage 61, and merges into oil passage 62. Therefore, the pressure oil discharged from the first pump 25 and the second pump 26 is jointly supplied to the bucket cylinder 7, so that the operating speed of the bucket 4 during heavy excavation and discharge is increased.

As described above, while performing heavy excavation and discharge by largely tilting the operation lever 34 of the bucket remote control valve 30, other hydraulic actuators such as the arm valve 12, the swing valve 14, etc. may be operated. There is. When the arm remote control valve 31 and the swing remote control valve 32 are operated, the pilot secondary pressure acting on the arm valve 12 and the swing valve 14 is selected as a high pressure by the shuttle valves 42 and 43, and is further led out from the shuttle valve 44 to It passes through channel 71 and acts on the other side port 39. Since the interlock valve 37 returns from the open oil path position O to its original position L, the bucket 4 and the arm 3 can be operated or rotated without any hindrance.

Note that even if the operating lever 34 of the bucket remote control valve 30 is tilted greatly, the operating lever 34
When the is returned to near the neutral position, the pilot secondary pressure acting on the one side port 38 of the interlock valve 37 decreases from the set pressure P, so the interlock valve 37 is automatically returned to its original position by the spring force of the built-in spring 45. Return to Le. Further, in the embodiment of the present invention, the speed of the bucket 4 is increased, but it may be adapted to other actuators such as the arm 3.

[0013]

As explained above, in the present invention, the upstream port of the sub-valve of the pilot switching valve for controlling the bucket cylinder is communicated with the pilot pump via the interlock valve, and the port on one side of the interlock valve is connected to the pilot pump. In this case, the pilot secondary pressure applied to the pilot switching valve for controlling the bucket cylinder is applied to switch the interlock valve, and when the interlock valve switches, the straight travel valve is switched by the pilot primary pressure. Further, the interlock valve is configured to switch the interlock valve to its original position by applying a pilot secondary pressure to the other side port of the interlock valve to act on a pilot switching valve for controlling a hydraulic actuator other than the bucket cylinder. Further, the interlock valve is set to switch when the pilot secondary pressure acting on one side port of the interlock valve in the hydraulic circuit exceeds a predetermined pressure. As a result, when the operating lever of the bucket remote control valve is tilted significantly, the interlock valve and the straight travel valve are switched, and the pressure oil discharged from the first and second pumps is combined and supplied to the bucket cylinder. Therefore, when the hydraulic excavator performs heavy excavation and discharge, the operation of the bucket can be speeded up and work efficiency can be improved.

[Brief explanation of drawings]

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

FIG. 2 is a hydraulic circuit diagram of the prior art.

[Explanation of symbols]

4 Bucket 7 Bucket cylinders 10L, 10R Travel motor control switching valve 11, ~,
14 Pilot switching valves 15, -, 19 Sub-valve 20 Direct travel valves 25, 26 First and second pumps 27 Pilot pumps 30, 31, 32 Remote control valve 37 Interlock valve 38 One side port 39 Other side port 45 Built-in spring

Claims (2)

[Claims] Claim 1: Various hydraulic actuators installed on construction machinery are divided into two groups A and B, each driven by a first and second pump, and each hydraulic actuator control switching valve is provided with a switching valve. A sub-valve is connected to the valve to allow the pilot primary pressure to pass or be blocked, and a pilot on-off valve is arranged at the outlet of each of the center bypass oil passages of groups A and B,
In a hydraulic circuit in which straight-travel valves are arranged on the discharge sides of the first and second pumps, the upstream port of the sub-valve of the pilot switching valve for controlling the bucket cylinder is communicated with the pilot pump via an interlock valve. Pilot secondary pressure, which is applied to the bucket cylinder control pilot switching valve, is applied to one side port of the interlock valve to switch the interlock valve, and when the interlock valve switches, the pilot The straight travel valve is switched by pressure, and the interlock valve is returned to its original position by applying pilot secondary pressure that acts on the pilot switching valve for controlling hydraulic actuators other than the bucket cylinder to the other side port of the interlock valve. A hydraulic circuit for construction machinery, characterized in that it is configured to switch to. Claim 2: In the hydraulic circuit for construction machinery according to claim 1, the interlock valve switches when the pilot secondary pressure acting on one port of the interlock valve exceeds a predetermined pressure. A hydraulic circuit for construction machinery, characterized in that it is set to.