JPH0579060A - Hydraulic circuit of hydraulic shovel - Google Patents

Abstract

PURPOSE:To turn a hydraulic shovel so effectively at low speed by installing a turning pilot selector valve in a hydraulic circuit for a turning motor and also a flow controlling pilot selector valve and a flow control valve both in a turning motor working pressure pipeline, respectively. CONSTITUTION:A turning pilot selector valve 15 is set up in the rearmost row of a hydraulic circuit group C where a turning motor 5 is installed, and a turning motor working pressure pipeline 62 is installed there in parallel with a center bypass oil passage 60 of the group C. Next, a flow controlling pilot selector valve 28 and a flow control valve 31 are installed in the pipeline 62, operating them with operation of a switch 39. Then, a piston chamber part is installed in the flow control valve 31, and in this case, it may be done that pilot pressure is made so as to act on the piston chamber part via a solenoid proportional pressure reducing valve. With this constitution, turning speed in the hydraulic shovel is reducible to sane extent, thus it is selectively settable to the specified low speed.

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 adjusting the turning speed of a small shovel to a high speed or a low speed.

[0002]

2. Description of the Related Art FIG. 3 is a side view of a hydraulic excavator.
In the figure, 1 is a lower traveling body of a hydraulic excavator, 2L and 2R are left and right traveling motors, 3 is an upper swing body, 4 is a hydraulic remote control valve, 5 is a swing motor, and 6 is a front portion of the upper swing body 3. Work attachment, 7 boom of work attachment 6, 8 arm, 9 bucket, 10
Is a boom cylinder, 11 is an arm cylinder, 12 is a bucket cylinder, 13 is a dozer device, and 14 is a dozer device 1.
3 dozer cylinders.

FIG. 4 is a conventional hydraulic circuit diagram of a hydraulic excavator. In the figure, reference numeral 15 is a turning pilot switching valve for controlling the turning motor 5, 16L and 16R are left and right traveling switching valves, and 17, ..., 19 are other actuators (for convenience of explanation, other actuators are not shown in FIG. 4). ) Control pilot control valves, 20 dozer directional control valves 21, 22, 23 are first, second and third valves, respectively.
The hydraulic pump, 24 is a pilot pump, 25 is an oil tank, 26 is a turning hydraulic remote control valve of the hydraulic remote control valve 4 in FIG. 3, and 27 is an operating lever of the turning hydraulic remote control valve 26. Further, reference numerals YY and LOW indicate connections of pilot lines connecting the turning hydraulic remote control valve 26 and the turning pilot switching valve 15 (hereinafter referred to as turning valve 15).

Next, a conventional hydraulic circuit is shown in FIGS.
I will describe. In conventional hydraulic circuits of hydraulic excavators, various hydraulic actuators (16L, 17, 18, 1
6R, 19, 15, 20) into three groups A, B, C
Divided into a first hydraulic pump 21 and a second hydraulic pump 2, respectively.
The second and third hydraulic pumps 23 are used for driving.

[0005]

It is desired to reduce the turning speed when the hydraulic excavator performs a work requiring high working accuracy, or when turning to prevent the work attachment from colliding with a surrounding structure in a narrow work site or the like. There are cases. In a hydraulic excavator equipped with a conventional hydraulic circuit, if the hydraulic remote control valve for turning is operated normally,
Since the upper revolving structure makes standard high-speed revolving, work requiring low-speed revolving becomes difficult and dangerous.

[0006]

According to the present invention, a turning pilot switching valve is arranged in the last row of a group in which a turning motor is arranged, and a turning pilot switching valve and a directional switching valve in the group are arranged. A swing motor working pressure conduit is provided in parallel with the center bypass oil passage that communicates therethrough, and a flow control pilot switching valve is provided in the swing motor working pressure conduit. Side and the tank communication circuit are communicated via a flow control valve, while the pilot pump and the pilot pressure receiving portion of the flow control pilot switching valve are communicated via an electromagnetic switching valve. The flow rate control pilot switching valve is activated by switching the switch. Further, the flow control valve is provided with a piston chamber part for adjusting the built-in spring of the flow control valve, and the port of the piston chamber part and the pilot pump are communicated via an electromagnetic proportional pressure reducing valve. The current value acting on the solenoid is adjusted by an adjustment switch.

[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 claim 1 according to 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. 60 is group C
Center bypass oil passage, 61 is a swing motor operating pressure circuit, 28 is a flow rate control pilot switching valve, 29 is a pilot pressure receiving portion of the flow rate control pilot switching valve 28 (hereinafter referred to as flow rate control valve 28), and 30 is a throttle. Part, 31 is a flow control valve, 32 is a flow control valve 31
Built-in spring (hereinafter referred to as flow control valve 31), 33 and 3
4 is a throttle part, 35 is a tank communication circuit, 36 is an electromagnetic switching valve, 37 is a solenoid of the electromagnetic switching valve 36, 38 is an electric circuit, 39 is a switch, and 40 is a power source.

Next, the structure of the hydraulic circuit according to the first aspect of the present invention will be described with reference to FIG. In the last row of the group C in which the turning motor 5 is arranged, the turning pilot switching valve 1 is provided.
5 (hereinafter referred to as a slewing valve 15), and a slewing motor in parallel with a center bypass oil passage 60 which communicates with the slewing valve 15 and the directional switching valve 20 for a dozer (hereinafter referred to as a dozer valve) in the group C. Is provided with a flow control valve 28 for the swing motor, and the upstream side of the flow control valve 28 is communicated with the tank communication circuit 35 via a flow control valve 31. On the other hand, the flow rate control is performed by connecting the pilot pump 24 and the pilot pressure receiving portion 29 of the flow rate control valve 28 via an electromagnetic switching valve 36, and switching the electromagnetic switching valve 36 by operating a switch (39). The valve 28 was made to operate.

Next, the operation of the hydraulic circuit according to the first aspect of the present invention will be described. When the switch 39 is off, the solenoid 37 is not energized.
Since the electromagnetic switching valve 36 is at the tank communication oil passage position C, the pilot pressure does not act on the pilot pressure receiving portion 29 of the flow control valve 28. Since the flow rate control valve 28 is located at the open oil passage position e, when the turning hydraulic remote control valve 26 is operated in this case, the pressure oil from the third hydraulic pump 23 is released from the flow rate control valve 28.
It is supplied to the turning motor 5 through the opening oil passage position E and the switching position of the turning valve 15. In this case, since a large amount of pressure oil is sent to the swing motor, the hydraulic excavator makes a standard high-speed swing. Further, when the dozer valve 20 is independently operated without operating the turning hydraulic remote control valve 26, the arrow tension 3rd.
Due to the large amount of pressure oil supplied from the hydraulic pump 23, the dozer cylinder operates at standard speed. In the above case, when the swing motor 5 and the dozer cylinder are simultaneously operated, the operating speeds of the both are slightly lower than the standard speed, but the pressure oil from the third hydraulic pump 23 is sufficient.
Almost no hindrance.

Next, when the turning speed is reduced to a low speed, the switch 39 is turned on. Since the solenoid 37 is energized, the electromagnetic switching valve 36 is switched from the tank communication oil passage position C to the opening oil passage position D. The pilot pressure from the pilot pump 24 acts on the pilot pressure receiving portion 29 via the pipe lines 41 and 42, the two positions of the electromagnetic switching valve 36, and the pipe line 43. The flow rate control valve 28 has a throttle portion (3
0) Switch to the attached oil passage position. When the turning hydraulic remote control valve 26 is operated in this state, the hydraulic pressure in the turning motor working pressure line 61 upstream of the flow control valve 28 rises,
The increased hydraulic pressure is applied to the flow control valve 31 via the throttle portion 33.
Act on. When the hydraulic pressure rises above the spring force set in the built-in spring 32, the flow control valve 31 opens against the spring force. The pressure oil from the third hydraulic pump 23 is supplied to the pipeline 4
4, 62, 61 and a part of the pressure oil flows through the flow control valve 2
The oil is supplied to the swivel motor 5 to the oil passage position with the throttle portion 8 through the conduit 61 ′ and the switching position of the swirl valve 15. Further, the other part of the pressure oil branched from the pipe 61 is returned to the tank communication circuit 35 via the pipe 63, the opening passage of the flow control valve 31, and the pipe 50. Since a small amount of pressure oil is sent to the swing motor 5 as described above, the swing speed can be reduced to a low speed. Even when the swing motor and the dozer cylinder are simultaneously operated in the above case, the operating speed of the dozer cylinder is hardly disturbed as described above.

Next, FIG. 2 is a hydraulic circuit diagram of claim 2 according to the present invention. In the figure, the same components as those in claim 1 are designated by the same reference numerals. Reference numeral 51 is a flow control valve, 52 is a built-in spring of the flow control valve 51 (hereinafter referred to as flow control valve 51), 53 is a piston chamber portion, 54 is a port of the piston chamber portion 53, 55 is an electromagnetic proportional pressure reducing valve, and 56 is an electromagnetic proportional pressure reducing valve. Solenoid of valve 55, 5
Reference numeral 7 is a diaphragm portion, 58 is a current value setting device, and 59 is an adjusting switch of the current value setting device 58.

Next, the construction of the hydraulic circuit according to the second aspect of the present invention will be described with reference to FIG. 2. The hydraulic circuit according to claim 1, wherein the flow control valve 51 is provided with a piston chamber portion 53 for adjusting the spring force of the built-in spring 52, the port 54 of the piston chamber portion 53, and the pilot pump 2.
4 is communicated with the electromagnetic proportional pressure reducing valve 55, and the current value acting on the solenoid 56 of the electromagnetic proportional pressure reducing valve 55 can be adjusted by the adjusting switch 59.

Next, the operation of the hydraulic circuit according to the second aspect of the present invention will be described. The movements of the electromagnetic switching valve 36 and the flow rate control valve 28 when the switch 39 is turned off or on are the same as in the hydraulic circuit of claim 1. However, in the hydraulic circuit of the second aspect, by operating the adjustment switch 59, it is possible to adjust the value of the current supplied to the solenoid 56. As a result, the pilot pressure can be applied to the piston chamber 53 to change the spring force of the built-in spring. That is, since the pressure at which the flow control valve 51 opens can be selected by the adjusting switch 59, the turning speed can be reduced to a required low speed.

[0014]

When a hydraulic excavator having a hydraulic circuit according to the prior art performs work requiring precision, or when operating a hydraulic remote control valve for turning normally when working on a narrow site, the upper turning body is standard. Since it makes a high-speed turn, it became difficult and dangerous. However, in the present invention, the turning pilot switching valve is arranged in the last row of the group in which the turning motor is arranged, and the center bypass oil which communicates through the turning pilot switching valve and the direction switching valve in the group. The working pressure pipeline for the swing motor is provided in parallel with the flow path, and the pilot switching valve for flow control and the flow control valve are provided for the working pressure pipeline for the swing motor, while the solenoid switching valve provided in the pilot circuit is switched. The pilot switching valve for flow rate control is operated by switching it by operation. Further, a piston chamber portion for adjusting the built-in spring of the flow control valve is provided, and the pilot pressure is applied to the piston chamber portion via the electromagnetic proportional pressure reducing valve. As a result, when the electromagnetic switching valve is switched by the switch operation, part of the pressure oil discharged from the hydraulic pump is supplied to the swing motor, and the other part is returned to the oil tank through the flow control valve. Therefore, the turning speed of the hydraulic excavator can be reduced to a low speed. Further, in the hydraulic circuit in which the flow control valve is provided with the piston chamber portion and the electromagnetic proportional pressure reducing valve is adjusted and operated by the adjusting switch, the turning speed can be selectively set to a required low speed. Therefore, the hydraulic excavator provided with the hydraulic circuit of the present invention improves low-speed turning performance and safety.
Further, even when the swing motor and the hydraulic actuator in the group in which the swing motor is arranged are simultaneously operated, the operating speed of the hydraulic actuator is not hindered.

[Brief description of drawings]

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

FIG. 2 is a hydraulic circuit diagram of claim 2 according to the present invention.

FIG. 3 is a side view of the hydraulic excavator.

FIG. 4 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 5 Swing motor 15 Pilot switching valve for swiveling 21, 22, 23 First, second, third hydraulic pump 24 Pilot pump 26 Hydraulic remote control valve for swiveling 28 Pilot switching valve for flow control 31, 51 Flow control valve 36 Electromagnetic switching valve 39 Switch 53 Piston Chamber 55 Electromagnetic Proportional Pressure Reducing Valve 59 Adjustment Switch 60 Center Bypass Oil Path 62 Swing Motor Working Pressure Circuit

Claims (2)

[Claims] 1. Various hydraulic actuators mounted on a hydraulic excavator are divided into a plurality of groups, each driven by a plurality of hydraulic pumps, and a swiveling pilot switching valve is arranged in one of the groups. In the hydraulic circuit in which the swing motor is controlled via the swing pilot switching valve by operating the hydraulic remote control valve, the swing pilot switching valve is arranged in the last row of the group in which the swing motor is arranged. , A swing motor working pressure line is provided in parallel with the center bypass oil passage that communicates with the swing pilot changeover valve and the direction changeover valve in the group, and the swing motor working pressure line is used for flow control pilot changeover. A valve is installed, and the upstream side of the flow control pilot switching valve and the tank communication circuit are connected via the flow control valve. On the other hand, with the pilot pump,
It is characterized in that the pilot pressure receiving portion of the flow rate control pilot switching valve is communicated via an electromagnetic switching valve, and the flow rate control pilot switching valve is operated by switching the electromagnetic switching valve by a switch operation. The hydraulic circuit of a hydraulic excavator. 2. A hydraulic circuit for a hydraulic excavator according to claim 1, wherein the flow control valve is provided with a piston chamber portion for adjusting a built-in spring of the flow control valve, and a port of the piston chamber portion, A hydraulic circuit for a hydraulic excavator, which is configured to communicate with a pilot pump via an electromagnetic proportional pressure reducing valve, and a current value acting on a solenoid of the electromagnetic proportional pressure reducing valve can be adjusted by an adjusting switch.