JPH05272508A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To prevent the generation of shock caused by fluctuations of pressure in a turning operation circuit by switching a sequence valve when the pressure in an arm bottom side oil passage is increased above a specified pressure at the time of arm pull operation, and joining a pilot pressure to an arm confluent valve. CONSTITUTION:The pressure from an arm bottom side oil passage 89 which is connected to an arm bottom side oil chamber 12 of an arm cylinder 10 and formed in a control valve constituted of a change-over valve group, is allowed to act on a pilot port 84 of a sequence valve 82. Further, when the pressure in the arm bottom side oil chamber 89 is increased above a specified pressure P during the operation of pulling an arm, the sequence valve 82 is operated to be switched. Thus, the pilot-primary pressure from a pilot pump 28 is allowed to act on an arm confluent valve 24 through a sub-valve 81 oil passage of an arm switching valve 15', the opened-oil passage position of the sequence valve 82, and to be joined to the bottom side oil chamber 12. As a result, the pilot port 84 of the sequence valve 82 is not affected by fluctuations of pressure in a turning operation circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arm-cylinder merging circuit equipped in a construction attachment such as a hydraulic excavator or a work attachment of a work vehicle.

[0002]

2. Description of the Related Art FIG. 2 is a side view of a hydraulic excavator.
In the figure, 1 is a lower traveling body, 2L and 2R are left and right traveling motors, 3 is an upper revolving body, 4 is a revolving motor, 5 is a work attachment mounted on the front part of the upper revolving body 3, and 6
Is a boom of the work attachment 5, 7 is an arm, 8 is a bucket, 9 is a boom cylinder, 10 is an arm cylinder,
Reference numeral 11 is a bucket cylinder. FIG. 3 is a hydraulic circuit diagram of a prior art hydraulic excavator. In the figure, 12 is a bottom side oil chamber of the arm cylinder 10, 13 is a rod side oil chamber, 14L and 14R are travel switching valves for controlling the travel motors 2L and 2R (see FIG. 2), and 15 is an arm cylinder 10.
Control arm pilot switching valve, 16 is a swing pilot switching valve for controlling the swing motor 4, 17 is a boom cylinder switching valve for controlling the boom cylinder 9 (see FIG. 2), and 18 is a bucket 8 (see FIG. 2). ) Control bucket pilot switching valve, 19 straight traveling valves, 20L, 20R
Are pilot opening / closing valves provided at the outlets of the center bypass oil passages 21L and 21R, 22 is a logic valve, 23 is a sequence valve, 24 is an arm merging valve, and 25 is a sub valve provided so as to be interlocked with the arm pilot switching valve 15, Two
6, 27 are first and second pumps, 28 is a pilot pump which is a pilot pressure hydraulic source, 29 is an oil tank,
30L and 30R are left and right hydraulic remote control valves, 31L and 31
Reference symbol R denotes a working machine operating lever of each of the hydraulic remote control valves 30L and 30R, and symbols EE, ...

FIG. 4 is an enlarged view of the arm pilot switching valve 15 in FIG. 3 (hereinafter referred to as arm switching valve 15). In the figure, 32 is a variable restrictor provided inside the arm pulling position of the arm switching valve 15, 33 is a variable throttle portion of the variable restrictor 32, and 34 is a check valve. When the operation lever 31L is moved in the hydraulic circuit of FIG. 3 to perform simultaneous operation of turning and arm pulling, the pilot secondary pressure derived from the hydraulic remote control valve 30L is supplied to the pilot port (for example, 35) of the turning switching valve 16 and the arm. It acts on the pilot port 36 of the switching valve 15. The swing switching valve 16 is switched to the open position, and the arm switching valve 1
5 is switched to the arm pulling position. At the same time, part of the pilot secondary pressure acting on the pilot port 35 of the swing switching valve 16 is passed through the shuttle valve 37, the pipelines 38 and 39, the logic valve 22, the pipeline 40, the sub-valve 25, and the pilot oil passage 41. , Acts on the variable diaphragm 33.
Therefore, the return oil circuit from the rod side oil chamber 13 of the arm cylinder 10 is narrowed down by the variable throttle portion 33. Therefore, the return oil is regenerated and flows into the supply circuit on the bottom oil chamber 12 side through the check valve 34. When the pressure in the bottom side oil chamber 12 rises, the supply flow rate for regeneration decreases, and the swing motor 4 is driven at the same pressure as the pump pressure at that time, so that the swing priority function can be exerted.

Next, the structure of the hydraulic circuit of the prior art will be described with reference to FIGS. Two groups A (14L, 15, 16) and B (14R, 17, 1) of directional control valves for controlling various hydraulic actuators mounted on the hydraulic excavator.
8), and is driven by the first pump 26 and the second pump 27, respectively, and the left and right switching valves 14L, 1 for traveling.
4R is arranged in the front row of each of the groups A and B, and the pressure oil from the first pump 26 can be sent in parallel to the arm switching valve 15 and the swing switching valve 16 so that the swirling and the arm pulling can be performed simultaneously. When the operating pressure acting on the bottom side oil chamber 12 of the arm cylinder 10 rises above a predetermined pressure during the arm pulling operation, the operation of the sequence valve 23 causes the arm converging valve 24 to operate. The pressure oil from the second pump 27 is supplied to the bottom side oil chamber 1
It is configured so as to join and supply the two.

In the hydraulic excavator, the operating speed of arm pulling is increased to enable heavy excavation. Therefore, when the arm pulling operation of the operation lever 31L is performed during excavation work,
The arm switching valve 15 is switched to the arm pull position. First
The pressure oil from the pump 26 is supplied to the pipe line 42, the oil line 43, the travel position of the straight traveling valve 19, the oil line 44, the neutral position of the traveling switching valve 14L, the oil lines 45 and 46, the check valve 47, and the oil line 48. ，
The oil is supplied to the bottom-side oil chamber 12 via 49, the check valve 50, the oil passages 51 and 52, the arm pulling position of the arm switching valve 15, and the pipe 53. Then, the arm cylinder 10 is extended so that the arm pulling operation is performed. In that case, the pressure in the bottom side oil chamber 12 corresponds to the load and the predetermined pressure P is reached.
When the pressure rises above (for example, 100 kg / cm ² ), the pressure rises due to the oil passages 54, 55, 56, 5 branched from the oil passage 48.
7 through the pilot port 58 of the sequence valve 23
Act on. The sequence valve 23 is switched from the power position to the power position. The pilot primary pressure from the pilot pump 28 passes through the conduits 59, 60, 61, 62, the throttle portion 63, the conduit 64, the position of the sequence valve 23, the conduit 65, the shuttle valve 66, and the conduit 67, and then the arm. It acts on the pilot port 68 of the merge valve 24. The arm merging valve 24 switches from the cutoff oil passage position to the open oil passage position. Therefore, the pressure oil from the second pump 27 is supplied to the pipe 69, the oil passage 70, the neutral position of the traveling switching valve 14R, the oil passages 71 and 72, the check valve 73,
The oil passages 74, 75, 76, the arm passage valve 24 open oil passage position, the oil passage 77, the check valve 78, and the oil passage 79 are joined to the oil passage 52. Therefore, since the pressure oil from the first pump 26 and the second pump 27 is jointly supplied to the bottom side oil chamber 12 of the arm cylinder 10, the arm pulling operation can be speeded up and heavy excavation can be performed.

[0006]

In the hydraulic circuit of the prior art, when the arm pulling operation is performed, the arm cylinder 1
When the operating pressure on the bottom side oil chamber 12 of 0 rises to a predetermined pressure P or more, the sequence valve 23 operates to activate the arm merging valve 24, and the pressure oil from the first pump 26 and the second pump 27 is activated. Are merged and supplied to the bottom side oil chamber 12. However, the above sequence valve 2
The oil passage 57 of pilot pressure for controlling the
Of the operating circuit 80 (see FIG. 3). Therefore, if the swing is moved while the hydraulic excavator is performing the arm pulling operation, the swing motor 4 is activated each time the swing is started and stopped.
The operating circuit 80 causes pressure fluctuation, and the changed pressure acts on the pilot port 58 of the sequence valve 23 via the oil passage 57. The operation of the sequence valve 23 became unstable, and a shock was generated in the arm pulling operation due to the pressure fluctuation of the swing operation circuit 80, and the working condition was poor. It is an object of the present invention to provide a hydraulic circuit that can solve the above problems.

[0007]

According to the hydraulic circuit of the present invention,
The pressure from the arm bottom side oil passage that is connected to the bottom side oil chamber of the arm cylinder and that is formed in the control valve that is composed of the switching valve group is applied to the pilot port of the sequence valve. When the pressure in the arm bottom side oil passage rises above a predetermined pressure, the pilot pressure from the pilot pressure hydraulic source is transferred by the sequence valve switching operation, and the sub valve oil passage of the arm pilot switching valve and the sequence valve opening oil passage position To act on the arm merging valve to join the bottom side oil chamber.

[0008]

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, the same reference numerals are given to those using the same constituent elements as those in the prior art. Reference numeral 15 'is an arm pilot switching valve (hereinafter referred to as arm switching valve), 81 is an arm switching valve 1
Reference numeral 5'is a sub valve interlocking with 5 ', reference numeral 16' is a pilot switching valve for turning (hereinafter referred to as turning switching valve), and reference numeral 82 is a sequence valve. Next, the configuration of the hydraulic circuit of the present invention will be described with reference to FIG. In the hydraulic circuit of the present invention, the arm cylinder 10
Arm bottom side oil passage formed in a control valve (a so-called multiple valve in which the switching valves are formed in a block shape, not shown) communicating with the bottom side oil chamber 12 of The pressure from 89 acts on the pilot port 84 of the sequence valve 82,
When the pressure in the oil passage 89 on the arm bottom side rises above the predetermined pressure P during the arm pulling operation, the pilot primary pressure from the pilot pump 28 is transferred to the oil in the sub-valve 81 of the arm switching valve 15 'by the switching operation of the sequence valve 82. The arm merging valve 24 is caused to act through the passage and the opening oil passage position of the sequence valve 82 so as to join the bottom side oil chamber 12.

Next, the operation of the hydraulic circuit of the present invention will be described. When the arm pulling operation of the operating lever 31L is performed, the arm switching valve 15 'is switched to the arm pulling position re'. The pressure oil from the first pump 26 is supplied to the pipe 42, the oil passage 43, the travel position of the straight travel valve 19, the oil passage 44, the neutral position of the travel switching valve 14L, the oil passages 45 and 46, the check valve 47, and the oil. Road 8
5, 86, 87, 88, check valve 50, oil passages 51, 5
2, the arm pulling position of the arm switching valve 15 ′, the arm bottom oil passage 89, and the pipe 90, and then the bottom oil chamber 12
Is supplied to. The arm cylinder 10 extends, but when the operating pressure rises above a predetermined pressure P, the rising pressure acts on the pilot port 84 through the oil passage 91 branched from the oil passage 89. The sequence valve 82 is switched from the cutoff oil passage position Y to the open oil passage position. The pilot primary pressure from the pilot pump 28 is supplied to the pipelines 59, 60, 9
2, 93, the position of the sub-valve 81, the oil passages 94, 95,
Position of sequence valve 82, oil passage 96, shuttle valve 9
7, the pipe line 98, and the pilot port 68. Therefore, the pressure oil from the second pump 27 joins the oil passage 52, as in the case of the conventional technique. Therefore, since the pressure oil from the first pump 26 and the second pump 27 is jointly supplied to the bottom side oil chamber 12 of the arm cylinder 10, the arm pulling operation can be speeded up and heavy excavation can be performed. If you perform a turning operation while performing this arm pulling operation,
The swivel switching valve 16 'is switched to, for example, the "nu" position. First
The pressure oil from the pump 26 is branched at the oil passage 86,
9, check valve 100, oil passage 101, swing switching valve 16 '
It is supplied to the turning motor 4 via the conduit position 102 and the conduit 102. Even if only the turning is stopped during the simultaneous operation of the arm pulling and the turning described above, the load holding check valve (load check valve) 100 is arranged on the operating pressure input port side of the turning switching valve 16 '. The pressure fluctuation in the swing operation circuit 102 does not act on the pilot port 84 of the sequence valve 82. Therefore, even if the turning operation is started and stopped while the arm pulling operation is performed, the turning operation circuit 102
There is no shock in the arm pulling operation due to the pressure fluctuation. In the sequence valve 82 of the present invention, the pilot pressure acting on the pilot port 84 is introduced from the arm bottom side oil passage 89 in the control valve, and the pilot primary pressure acting on the arm merging valve 24 is set in the arm switching valve 15. Since the sub-valve 81 'and the sequence valve 82 are made to pass through, the arm switching valve 15' and the sequence valve 82 are integrally formed into a compact structure (not shown) that does not require connection piping and space. You can

[0010]

In the hydraulic circuit of the prior art, when the pressure oils from the first and second pumps are jointly supplied to the bottom-side oil chamber of the arm cylinder during the arm pulling operation, when the swings are simultaneously operated, the swing start is started. , The swing fluctuating pressure due to the stop acted on the pilot port of the sequence valve for controlling the arm merging valve through its operating circuit. As a result, a shock was generated in the arm pulling operation, and the working condition was poor. However, in the hydraulic circuit of the present invention, the pressure from the bottom side oil passage which is communicated with the bottom side oil chamber of the arm cylinder and which is formed in the control valve formed by the switching valve group is applied to the pilot port of the sequence valve. When the pressure in the arm bottom side oil passage rises above a predetermined pressure during arm pulling operation, the pilot pressure from the pilot pressure hydraulic source is changed to the oil passage of the sub valve of the arm pilot changeover valve by the switching operation of the sequence valve, The arm merging valve is caused to act through the opening oil passage position of the sequence valve so as to join the bottom side oil chamber. As a result, the load check valve is arranged on the operating pressure input port side of the swing switching valve even if only the swing is started and stopped when the arm is pulled and the swing is operated simultaneously. Does not work on the pilot port. Therefore, it is possible to prevent a shock from occurring due to the pressure fluctuation of the turning operation circuit during the arm pulling operation. The pilot pressure acting on the pilot port of the sequence valve is guided from the oil passage on the arm bottom side in the control valve, and the pilot primary pressure acting on the arm merging valve passes through the sub valve of the arm switching valve and the sequence valve. With this configuration, the arm switching valve and the sequence valve can be integrated to form a compact structure that does not require connection piping and space.

[Brief description of drawings]

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

FIG. 2 is a side view of the hydraulic excavator.

FIG. 3 is a conventional hydraulic circuit diagram.

FIG. 4 is an enlarged view of the arm pilot switching valve in FIG.

[Explanation of symbols]

 4 Swing motor 10 Arm cylinder 12 Bottom side oil chamber 14L, 14R Travel switching valve 15, 15 'Arm pilot switching valve 16, 16' Rotation pilot switching valve 23, 82 Sequence valve 24 Arm confluent valve 25, 81 Sub valve 26 , 27 1st, 2nd pump 28 Pilot pump 31L, 31R Operation lever

Claims (1)

[Claims] 1. A directional control valve for controlling various hydraulic actuators mounted on a construction machine is divided into two groups A and B, which are driven by first and second pumps respectively, and left and right switching valves. Is arranged in the front row of each of the groups A and B, and the pressure oil from one of the first and second pumps can be sent in parallel to the pilot switching valves for arms and turning, When the swing operation and the arm pulling operation are simultaneously performed, the swing priority operation is performed, and when the operating pressure acting on the bottom side oil chamber of the arm cylinder during the arm pulling operation rises above a predetermined pressure, the operation of the sequence valve causes the arm It is a hydraulic circuit that joins and supplies the pressure oil from the other hydraulic pump to the bottom side oil chamber via a merging valve, and communicates with the bottom side oil chamber of the arm cylinder. The pressure from the oil passage on the arm bottom side formed in the control valve configured by the switching valve group to act on the pilot port of the sequence valve, and the pressure in the oil passage on the arm bottom side is set to a predetermined value when the arm is pulled. When the pressure rises above the pressure, the switching operation of the sequence valve causes the pilot pressure from the pilot pressure hydraulic source to act on the arm merging valve through the oil passage of the sub valve of the arm pilot switching valve and the opening passage of the sequence valve, and A hydraulic circuit for a construction machine, characterized in that it joins the side oil chamber.