JPH05287777A - Hydraulic circuit of construction machinery - Google Patents

Abstract

PURPOSE:To enable the fine control of a turning speed by providing a flow controlling valve to a main circuit communicating with a selector valve, and providing a pilot opening and closing valve to operate pilot pressure to make main pressure oil branch. CONSTITUTION:A hydraulic circuit is so formed that a turning motor and a working hydraulic actuator are connected to one pump in parallel. A flow controlling valve 45 is provided to a main circuit communicating with a turning selector valve 6, and a pilot opening and closing valve 45, a solenoid valve 46 and a solenoid 47 are provided to connect with a power supply 49 through a switch 48. After that, in the case of a normal turning speed, the switch 48 is turned OFF state. In the case a turning speed is finely controlled, the switch 48 is turned ON, the solenoid 47 is energized to switch and operate the pilot opening and shutting valve 45, and pressure oil of the flow controlling valve 44 is made to branch. In addition, surplus flow branching to a center by-pass oil path of the pilot selector valve 45 controlling the working actuator is bled, and a turning speed is finely controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for turning equipped on construction machines such as hydraulic excavators and work vehicles.

[0002]

2. Description of the Related Art FIG. 2 is a conventional hydraulic circuit diagram of a hydraulic excavator having a turning priority function. In the figure, 1
Is a swing motor, 2 is an arm cylinder, 3 is a bottom side oil chamber of the arm cylinder 2, 4 is a rod side oil chamber, 5L and 5R are travel switching valves for controlling left and right travel motors (not shown), 6 Is a pilot switching valve for swivel (hereinafter referred to as swivel switching valve), 7 is a pilot switching valve for arm (hereinafter, referred to as
Arm switching valve), 8 is a boom pilot switching valve for controlling a boom cylinder (not shown) (hereinafter referred to as boom switching valve), and 9 is a bucket cylinder (not shown).
A control bucket pilot switching valve (hereinafter referred to as a bucket switching valve) 10L is a center bypass oil passage communicating with the traveling switching valve 5L, the swing switching valve 6, and the arm switching valve 7,
Reference numeral 10R is a center bypass oil passage communicating with the traveling switching valve 10R, the boom switching valve 8 and the bucket switching valve 9, and 11L and 1L.
1R is a pilot cut valve provided on the outlet side of each of the center bypass oil passages 10L and 10R, 12 is a straight traveling valve,
Reference numerals 13 and 14 denote first and second discharges of main pressure oil, respectively.
Pump, 15 is a pilot pump, 16 is an oil tank, 1
7L and 17R are left and right hydraulic remote control valves, 18L and 18R
Is a working machine operation lever for each of the hydraulic remote control valves 17L and 17R, and 19 is a load check valve with a swing priority piston provided for exhibiting a swing priority function (hereinafter,
(Check valve with piston), 20 is a piston chamber of the check valve with piston 19, and symbols EE, ..., and CH are connections of pilot lines. The swing motor 1, arm cylinder 2, boom cylinder, and bucket cylinder are so-called various hydraulic actuators for working machines.

Next, a conventional hydraulic circuit will be described with reference to FIG. Two group A (5L, 5L, directional control valves for controlling various hydraulic actuators equipped in the hydraulic excavator
6, 7) and B (5R, 8, 9), which are driven by the first pump 13 and the second pump 14, respectively, and the left and right traveling switching valves 5L, 5R are arranged in the front row of the groups A and B. It is located in. Therefore, the main pressure oil from the first pump 13 can be sent to the swing switching valve 6 and the arm switching valve 7 in parallel.

In the hydraulic circuit of FIG. 2, the operating lever 18
When L is moved to perform an independent turning operation, the turning switching valve 6 is switched to the re-position or the N-position. The pressure oil from the first pump 13 is supplied to the pipe line 21, the oil line 22, the travel position of the straight travel valve 12,
Oil passage 23, neutral position of switching valve 5L for travel, oil passages 24, 2
5, the check valve 26, the oil passages 27, 28, 29, the check valve 30, the oil passage 31, the re-position or the n-position of the swing switching valve 6,
It is supplied to the turning motor 1 via the oil passage 32 or 33 and the pipe passage 34 or 35. As a result, the swing motor 1 rotates left or right.

Next, the turning operation and the arm pulling operation are performed simultaneously. The swing switching valve 6 is switched to the re-position or the null position, and the arm switching valve 7 is switched to the off position. At the same time, the pilot pressure for turning derived from the oil passage 32 or 33 is selected by the shuttle valve 36, and the throttle portion 37,
It acts on the piston chamber 20 through the oil passage 38. The piston in the piston chamber 20 operates to narrow the passage of the piston check valve 19. A part of the pressure oil from the first pump 13 is branched at the oil passage 28, and the oil passages 39, 40,
After passing through the narrowed passage in the piston check valve 19, the oil passage 41, the position of the arm switching valve 7, the oil passage 42,
The oil is supplied to the bottom side oil chamber 3 of the arm cylinder 2 via the pipe 43. In the above case, the pressure in the oil passages 40, 39 on the upstream side is increased by the operation of narrowing the check valve with piston 19, so that the main pressure oil is reliably supplied from the oil passage 29 side to the turning motor 1. .. Therefore, at the time of simultaneous operation of turning the hydraulic excavator and pulling the arm, it is possible to secure a high turning working pressure, and to perform diagonal landing work by the arm, excavation work by turning and pressing, etc. without any trouble.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
When simultaneously operating a swing motor connected in parallel to one hydraulic pump and a hydraulic actuator for another work machine, the main pressure oil is supplied to multiple hydraulic actuators in parallel, so the swing speed is low. Is. However, when the turning operation is independently performed, the pressure oil from one hydraulic pump is supplied only to the turning motor, so that the turning speed is considerably high. However, in a hydraulic excavator, there is a case where it is desired to perform fine speed turning in a narrow space, for example, but the conventional hydraulic circuit has not taken such means. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a hydraulic circuit that enables fine speed turning.

[0007]

In a hydraulic circuit in which a swing motor of various hydraulic actuators equipped on a construction machine and a hydraulic actuator for another working machine are connected in parallel to one hydraulic pump, 1 above
A flow control valve is provided in the main pressure circuit that communicates with the swing pilot switching valve from one hydraulic pump, and a pilot opening / closing valve is provided so that the pilot pressure from the main pressure circuit acts on the flow control valve. When switching the pilot on-off valve by switch operation, a part of the main pressure oil is diverted in the flow control valve, and the surplus flow that is diverted is used to control the hydraulic actuator for the working machine on the downstream side. By bleeding to the center bypass oil passage of the switching valve, the turning speed is adjusted to a fine speed.

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention. In the figure, the same reference numerals are given to those using the same configuration as the conventional technique. 44 is a flow control valve, 45
Is a pilot opening / closing valve, 46 is an electromagnetic switching valve, 47 is a solenoid of the electromagnetic switching valve 46, 48 is a switch, and 49 is a power source.

Next, the hydraulic circuit of the present invention will be described with reference to FIG. Of the various hydraulic actuators equipped on the hydraulic excavator, the swing motor 1 and the arm cylinder 2 are the first pump 1
3 is a hydraulic circuit that is connected in parallel with the main pressure circuit that communicates with the swing switching valve 6 from the first pump 13, and a flow rate control valve 44 is provided between the main pressure circuit and the flow rate control valve 44. A pilot opening / closing valve 45 is provided so as to act the pilot pressure from the main pressure circuit, and when the pilot opening / closing valve 45 is switched to operate by operating a switch (48), one of the main pressure oil is supplied in the flow control valve 44. The part is diverted, and the diverted excess flow is bleed to the center bypass oil passage 50 of the arm switching valve 7 on the downstream side, so that the turning speed is adjusted to a very small speed.

Next, the operation of the hydraulic circuit of the present invention will be described. First, as the first case, when it is desired to turn at a normal turning speed, the switch 48 is turned off.
Since the solenoid 47 is not energized, the electromagnetic switching valve 46 is in the tank communication oil passage position w. Since pilot pressure does not act on the pilot port 51 of the pilot on-off valve 45, the pilot on-off valve 45 is in the open oil passage position due to the spring force of the built-in spring. When the operation lever 18L is turned here, the turning switching valve 6 is switched to the re-position or the n-position. In this case, the pressure in the main pressure circuit of the first pump 13 is
9 through the pilot oil passage 52, the opening oil passage position of the pilot opening / closing valve 45, and the pilot oil passage 53.
4, the main passage 54 in the flow control valve 44 keeps the main pressure circuit fully open, but the flow dividing passage 55
Is cut off from the oil passage 56 on the downstream side. Therefore, the pressure oil from the first pump 13 passes from the oil passage 28 to the oil passage 5
7, main passage 54 of flow control valve 44, oil passage 58, throttle portion 5
9, the oil passage 60, the check valve 30, the oil passage 31, the re-position or the n-position of the swing switching valve 6, the oil passage 32 or 33, and the pipe passage 34 or 35 to supply the fluid to the swing motor 1. Thereby, the turning motor 1 rotates left or right at a normal turning speed.

Then, in the second case, when it is desired to turn at a very low turning speed, the switch 48 is turned on. Since the solenoid 47 is energized, the electromagnetic switching valve 46 is switched from the tank communication oil passage position w to the opening oil passage position f.
Since the pilot primary pressure from the pilot pump 15 acts on the pilot port 51 via the pipelines 61, 62, 63, 64, the position of the electromagnetic switching valve 46, and the pipeline 65,
The pilot on-off valve 45 switches from the open oil passage position to the shutoff oil passage position. As a result, the pressure of the main pressure circuit acting through the pilot on-off valve 45 ceases to act on the flow control valve 44, so that the spool (not shown) in the flow control valve 44 has a constant differential pressure across the throttle portion 59. Thus, the flow dividing passage 55 comes into communication with the oil passage 56. Therefore, a part of the main pressure oil branches from the main passage 54 in the flow control valve 44, and the flow dividing passage 55, the oil passage 56,
50, the oil tank 1 through the neutral position of the arm switching valve 7.
Flowed to 6. Therefore, the flow rate of the pressure oil that passes through the main passage 54 in the flow rate control valve 44 and is supplied to the swing motor 1 through the swing switching valve 6 is reduced, so that the swing speed can be made very small.

[0012]

Among various hydraulic actuators mounted on a hydraulic excavator, in a hydraulic circuit in which a swing motor and an arm cylinder are connected in parallel to one hydraulic pump, when the swing is independently operated, the hydraulic pump is operated. Since the pressure oil from is supplied only to the swing motor, the swing speed is considerably high. In the conventional hydraulic excavator, for example, even if it is desired to make a fine speed turn in a narrow space, fine operation cannot be performed. However, in the present invention, the flow control valve is provided in the main pressure circuit that communicates with the swing switching valve from the hydraulic pump,
A pilot opening / closing valve is provided so that the pilot pressure from the main pressure circuit acts on the flow control valve.
When the pilot on-off valve is switched by a switch operation, a part of the main pressure oil is diverted in the flow control valve, and the diverted excess flow is bleed to the center bypass oil passage of the arm switching valve on the downstream side. I did it. As a result, the flow rate of the pressure oil that passes through the main passage in the flow control valve and is supplied to the swing motor via the swing switching valve is reduced.
The turning speed can be made very small. Therefore, in the hydraulic excavator equipped with the hydraulic circuit of the present invention, the turning in a narrow place, the turning requiring the movement of a fine range, and the like can be performed at a very low speed, and the turning fine operability and safety can be improved.

[Brief description of drawings]

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

FIG. 2 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 1 Swing Motor 2 Arm Cylinder 6 Swing Pilot Changeover Valve 7 Arm Pilot Changeover Valve 10L, 10R Center Bypass Oil Path 13, 14 First and Second Pumps 15 Pilot Pump 44 Flow Control Valve 45 Pilot Open / Close Valve 46 Electromagnetic Changeover Valve 48 Switch 54 Main passage 55 Dividing passage

Claims (1)

[Claims] 1. Various hydraulic actuators mounted on a construction machine are driven by a single hydraulic pump and a plurality of hydraulic pumps, and a swing motor of the various hydraulic actuators is provided.
In a hydraulic circuit in which any other hydraulic actuator for working machine is connected in parallel to one hydraulic pump, a flow control valve is connected to a main pressure circuit communicating with the swing pilot switching valve from the one hydraulic pump. When the pilot on-off valve is installed so that the pilot pressure from the main pressure circuit acts on the flow control valve, and the pilot on-off valve is switched by the switch operation, the main flow control valve is operated. A part of the pressure oil is diverted, and the diverted excess flow is bleed to the center bypass oil passage of the pilot switching valve that controls the hydraulic actuator for the working machine on the downstream side, so that the turning speed can be adjusted to a fine speed. The hydraulic circuit of construction machinery characterized by