JPH05280072A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To surely perform swing during at simultaneously operation of swing and arm-pull by applying pilot pressure for swing to a check valve having a restrictor of a main pressure working oil passage for an arm cylinder so as to raise working pressure on the upper stream side of the valve. CONSTITUTION:When arm-pull and swing are simultaneously operated, an arm changeover valve 34 is changed to a specified position and a swing changeover valve 33 is changed to another specified position. Next, pressure oil from a first pump 40 is fed to a swing motor 28 through a duct 52, an oil passage 53, a running rectilineal valve 37, an oil passage 9, a duct 93, and the like. Simultaneously pilot pressure for swing introduced from an oil passage 91 is selected by means of a shuttle valve 50 and applied on a spool part 47 for restriction through a restriction part 95 and an oil passage 96. Next, the spool part 47 is actuated so as to restrict the passage of a check valve 46 having a restrictor. Further, pressure in oil passages 49a, 60 on the upper stream side of the check valve 46 is raised, and high pressure oil from the pump 40 is branched at an oil passage 59, and fed to the motor 28 through the changeover valve 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit provided with a construction machine such as a hydraulic excavator or a working vehicle and having a turning priority function.

[0002]

2. Description of the Related Art In a hydraulic excavator (not shown), various excavation work is performed by operating a work attachment that connects a boom, an arm and a bucket. Among them are diagonal pulling and leveling of the arm and swivel excavation in which the side surface of the bucket is pressed against an inclined wall surface to excavate the wall surface.
In both cases, simultaneous turning and arm pulling operations are performed.

FIG. 2 is a hydraulic circuit diagram of a main part of a hydraulic excavator having a conventional turning priority function. In the figure,
1 is a remote control valve for turning, 2 is a remote control valve for arm, 3 is a turning motor, 4 is an arm cylinder, 5 is a pilot switching valve for turning (hereinafter referred to as a turning switching valve) for controlling the turning motor 3, and 6 is an arm cylinder 4. Control arm pilot switching valve (hereinafter referred to as arm switching valve), 7 is a variable restrictor provided in position a of the arm switching valve 6, 8 is a check valve, 9 is a shuttle valve, 10 is a main pump, 11
Is a pilot pump. In the hydraulic circuit as shown in FIG. 2, the operation lever 12 of the turning remote control valve 1 is simultaneously operated in the position b and the arm remote control valve 2 is operated in the direction c. This is an example of simultaneous operation of turning and arm pulling, and the pilot pressure derived from the pilot valve 14 of the remote control valve 1 acts on the pilot pressure receiving portion 15 of the turning switching valve 5, so the turning switching valve 5 is Switch to position. On the other hand, along with that, the arm switching valve 6 switches to the a position. The pressure oil from the main pump 10 is supplied to the pipe lines 16 and 1.
The turning motor 3 is rotated through the two positions of 7, the check valve 18, and the turning switching valve 5. Further, to the arm cylinder 4 connected in parallel, the pressure oil from the main pump 10 is branched by the pipe line 16, and the pipe lines 19, 20, and 21, the check valve 22, the pipe line 23, and the arm switching valve 6 are connected. The oil is supplied to the bottom side oil chamber 4a of the arm cylinder 4 via the position b and the pipe line 24. At the same time, part of the pilot pressure oil that has acted on the pilot pressure receiving portion 15 of the swivel switching valve 5 also acts on the variable position restrictor 7 in position a of the arm switching valve 6 via the shuttle valve 9 and the conduit 25. .. Therefore, the return oil circuit from the rod-side oil chamber 4b for the arm cylinder 4 is narrowed down by the variable throttle portion 26 of the variable restrictor 7. Therefore, the return oil is regenerated and flows into the bottom side oil chamber 4a for the arm cylinder 4 through the in-position check valve 8 of the arm switching valve 6. The pressure in the bottom side oil chamber 4a increases. Therefore, the swing motor 3 is driven by the same pressure as the increased pump pressure. Note that the pilot on-off valve 27
Are arranged to generate pump pressure during a single swing operation.

[0004]

In the hydraulic circuit of the prior art, the return oil circuit from the rod side oil passage of the arm cylinder is narrowed down at the time of simultaneous operation of turning and arm pulling, so that a single hydraulic pump is used. The pressure of the main pressure oil sent in parallel to each of the arm and turning pilot switching valves is the same. However, since the turning start torque is larger than that of the arm drive, the turning start may not be performed reliably. Further, when excavating work that requires relatively high operating accuracy of the hydraulic excavator, the engine speed is reduced to a low speed and the operation speed of the work attachment is reduced. In this case, the arm tries to move down by its own weight,
In some cases, the pressure oil supply from the hydraulic pump may not catch up. For this reason, when turning and arm pulling are simultaneously performed, for example, when performing diagonal pulling and leveling with an arm, arm pulling is possible but turning does not move, which hinders work. The present invention aims to solve the above problems.

[0005]

According to the hydraulic circuit of the present invention,
A check valve with a throttle is provided in the main cylinder hydraulic oil passage for the arm cylinder in the control valve that is connected to the input side port of the pilot pilot switching valve for the arm. By making the pilot pressure for turning act on the check valve with throttle, the upstream side working pressure of the check valve with throttle is increased.

[0006]

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, 28 is a swing motor, 29 is an arm cylinder, 3
Reference numeral 0 is a bottom side oil chamber of the arm cylinder 29, 31 is a rod side oil chamber, 32L and 32R are traveling switching valves for controlling left and right traveling motors (not shown), and 33 is a swinging pilot for controlling the swinging motor 28. A switching valve (hereinafter referred to as a swing switching valve) 34 is an arm pilot switching valve for controlling the arm cylinder 29 (hereinafter referred to as an arm switching valve) 3
5 is a boom pilot switching valve, 36 is a bucket pilot switching valve, 37 is a straight traveling valve, 38 is a sequence valve for arm joining, 39 is an arm joining valve, 40 and 41 are first and second pumps, and 42 is A pilot pump, 43 is an oil tank, 44L and 44R are a pair of left and right working machine remote control valves, and 45L and 45R are working machine remote control valves 44L and 44.
Each of R is a working machine operation lever, 46 is a check valve with a throttle, 47 is a spool for throttle of the check valve with a throttle 46, and reference numerals hoe, to, and o are pilot line connections. Show.

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 arm switching valve 34
Main hydraulic fluid passage 49a for the arm cylinder in a control valve (a so-called multiple valve in which the switching valves are formed in a block shape, not shown), which is connected to the input side port 48 of the switching valve group. -49b is provided with a check valve 46 with throttle, and by applying a pilot pilot pressure for rotation to the spool portion 47 for throttle of the check valve 46 with throttle at the time of simultaneous operation of turning and arm pulling, the check valve 46 with throttle is provided. The upstream side operating pressure of the check valve 46 is increased. In FIG. 1, the swing pilot pressure is supplied to the shuttle valve 5 from the operating circuit of the swing motor 28.
The working spool remote control valve 4 is operated by the turning operation of the working machine operating lever 45L, for example.
It is also possible to make the pilot secondary pressure derived from 4L act.

Next, the operation of the hydraulic circuit of the present invention will be described. First, as the first case, only the arm pulling operation is performed without operating the turning. By this operation, the arm switching valve 34 switches from the neutral position to the arm pulling position w. First
The pressure oil from the pump 40 is supplied to the pipe line 52, the oil line 53, the position of the traveling rectilinear valve 37, the oil line 54, the neutral position of the traveling switching valve 32L, the oil lines 55 and 56, the check valve 57, and the oil line 58. ,
59, 60, 49a, check valve 46 with narrowing down, oil passage 4
The oil is supplied to the bottom side oil chamber 30 via 9b, 61, the arm pulling position of the arm switching valve 34, the arm bottom side oil passage 62, and the pipe 63. Since the arm cylinder 29 is extended, the arm pulling operation of the hydraulic excavator is performed. At the time of the above-mentioned independent arm pulling operation, the spool portion 47 for narrowing down
Since the turning pilot pressure does not act on the throttle valve, the check valve 46 with throttle does not perform any throttle operation.

When the pressure in the oil passage 62 on the arm bottom side rises above a predetermined pressure P (for example, 100 kg / cm ² ) during the arm pulling operation, the oil passage 64 is branched from the oil passage 62. The rising pressure acts on the pilot port 65. The sequence valve 38 is switched from the cutoff oil passage position to the open oil passage position. Pilot pump 4
The pilot primary pressure from 2 is the lines 66, 67, 68,
69, the position of the sub valve 70, the oil passages 71 and 72, the position of the sequence valve 38, the oil passage 73, the shuttle valve 74, the pipe 75, and the pilot port 76. So the second
The pressure oil from the pump 41 is used to open the pipe 77, the oil passage 78, the neutral position of the travel switching valve 32R, the oil passages 79 and 80, the check valve 81, the oil passages 82, 83 and 84, and the arm merging valve 39. It joins the oil passage 61 through the road position, the oil passage 85, the check valve 86, and the oil passage 87. Therefore, the pressure oil flow rate supplied to the bottom side oil chamber 30 of the arm cylinder 29 can be maximized.

Next, as a second case, simultaneous turning and arm pulling operations are performed. Although the arm pulling operation has been described in the first case, when the turning operation is performed together with the arm pulling, the arm switching valve 34 switches to the wa position and the turning switching valve 33 switches to the so position or the to position. The pressure oil from the first pump 40 is supplied to the pipe line 52, the oil line 53, the travel position of the straight travel valve 37, the oil line 54, the neutral position of the travel switching valve 32L, the oil lines 55 and 56, the check valve 57, and the oil. Roads 58, 5
9, 88, check valve 89, oil passage 90, swing switching valve 33
The oil is supplied to the turning motor 28 via the hydraulic position 91 or 92, the oil passage 91 or 92, and the pipe 93 or 94. At the same time, the turning pilot pressure derived from the oil passage 91 or 92 is selected by the shuttle valve 50 and acts on the throttle spool portion 47 through the throttle portion 95 and the oil passage 96.
The throttle spool portion 47 is activated to throttle the passage of the check valve with throttle 46. The pressure in the oil passages 49a, 60 upstream of the check valve 46 with restriction is increased, and the high pump pressure oil from the first pump 40 is branched in the oil passage 59 to form the oil passage 88, the shuttle valve 89, Oil passage 9
0, turning motor 28 via the switching position of turning switch valve 33
Is supplied to. Therefore, at the time of simultaneous operation of turning the hydraulic excavator and pulling the arm, a high turning working pressure can be secured without being affected by the working pressure of the arm cylinder.
Diagonal pulling and leveling work by arm and excavation work by turning and pressing can be performed without any problems.

In the hydraulic circuit according to the present invention, the check valve 46 with a throttle is provided with the main pressure working oil passage 4 for the arm cylinder in the control valve constituted by the switching valve group.
9a-49b so that the turning pilot pressure introduced into the control valve is made to act on the throttle spool portion 47. Therefore, the arm switching valve 34 or the turning switching valve 33 and the check valve with throttle 46 are installed. It can be integrated into a compact structure (not shown) that does not require connection piping and space.

[0012]

In the conventional hydraulic circuit, the return oil circuit from the rod-side oil chamber of the arm cylinder is narrowed down when the swing operation and the arm pulling operation are performed simultaneously. The pump pressures sent in parallel are the same. However, since the turning start torque is larger than that of the arm drive, the turning start may not be performed reliably. However, in the hydraulic circuit according to the present invention, a check valve with a throttle is provided in the arm cylinder main pressure working oil passage communicating with the input side port of the arm pilot switching valve and provided in the control valve that is formed by the switching valve group. The pilot pressure for turning is adapted to act on the check valve with throttle when the arm and the arm are pulled simultaneously. As a result, the turning pilot pressure actuates the throttle spool portion, so that the passage of the check valve with throttle is throttled. The pressure of the oil passage on the upstream side of the check valve with restriction is increased, and high pump pressure oil flows toward the swing switching valve connected in parallel with the arm switching valve and is supplied to the swing motor. Therefore, when the hydraulic shovel is turned and the arm is pulled simultaneously, a high swing working pressure can be secured without being affected by the working pressure of the arm cylinders, so that there is no hindrance to the diagonal landing work by the arm or excavation work using the turning push. It can be carried out. Further, in the hydraulic circuit of the present invention, the check valve with throttling is provided in the arm cylinder main pressure working oil passage in the control valve so that the turning pilot pressure introduced into the control valve acts on the throttling spool portion. Therefore, the arm switching valve or the swivel switching valve and the check valve with a throttle can be integrally formed into 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 hydraulic circuit diagram of a main part of a hydraulic excavator having a prior art turning priority function.

[Explanation of symbols]

 3,28 Revolving motor 4,29 Arm cylinder 4a, 30 Bottom side oil chamber 4b, 31 Rod side oil chamber 5,33 Revolving pilot switching valve 6,34 Arm pilot switching valve 40,41 1st, 2nd pump 42 Pilot pump 44L, 44R Remote control valve for working machine 46 Check valve with throttle 47 Spool for throttle

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 respectively driven by first and second pumps, and first and second thereof. A hydraulic circuit that enables pressure oil from one of the hydraulic pumps to be sent in parallel to the pilot switching valves for the arm and the swing, and the swing priority operation is performed when the swing and arm pull operations are performed simultaneously. There
A check valve with a throttle is provided in the main cylinder hydraulic oil passage for the arm cylinder in the control valve that is connected to the input side port of the pilot pilot switching valve for the arm. A hydraulic circuit for a construction machine, characterized in that a pilot pressure for turning is applied to a check valve with a throttle to increase an upstream side working pressure of the check valve with a throttle.