JPH06220895A - Hydraulic circuit for small sized shovel - Google Patents

Abstract

PURPOSE:To provide a rectilinear running hydraulic circuit having a maintainability by providing a sample valve for performing change-over operation in association with a running change-over valve, in the latter, and by locating a supply pilot-operated selector valve at the final row of a group. CONSTITUTION:When right and left running valves 15'L, 15'R are operated, subvalves 48L, 48R are both changed over into an oil passage opening position. Next, in this running condition, when either one of pilot operated selector valves 16 to 19 is operated, pilot pressures fed from hydraulic remote control valves 4L, 4R is applied to a pilot pressure receiving part 50 by way of a pipe line 52 or the like, thereby a replenish valve 49 changes over from a position X to a position Y. Then, pressure oil from a third pump 24 flows through the position X and a pipe line 53, and is fed into another operated hydraulic actuator for rectilinear running so as to preform a straight running. Accordingly, it is possible to eliminate the necessity of a rectilinear running electric circuit, and a rectilinear advancing valve, thereby it is possible to provide a hydraulic circuit having a large maintainability.

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 traveling straight ahead of a small shovel.

[0002]

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

FIG. 3 is a prior art circuit diagram of a small excavator. In the figure, 15L and 15R are travel switching valves for controlling the left and right travel motors 2L and 2R, respectively.
6 is a boom pilot switching valve, 17 is a bucket pilot switching valve, 18 is an arm pilot switching valve, 19
Is a pilot switching valve for turning, 20 is a switching valve for a dozer, 2
1 is a straight traveling valve, 22, 23 and 24 are first, second and third pumps respectively, 25 is an oil tank, 26 is a pilot pump, 27 is pilot pressure derived from hydraulic remote control valves 4L and 4R (in this case, A shuttle valve for selecting high pressure (which is the pilot secondary pressure), 28 is an electromagnetic switching valve, 29 is a solenoid of the electromagnetic switching valve 28, 30 is an electric circuit, 31 is a power source, 32 and 33 are switching valves for traveling 15L and 15R. These limit switches are turned on in association with the switching operation of the traveling valves 15L and 15R. Further, reference numerals Y, R, L, H, ..., Teach indicate connections of pilot lines connecting the hydraulic remote control valves 4L, 4R and the pilot switching valves 14 ,.

A prior art circuit will now be described with reference to FIGS. In the prior art circuit of a small shovel, various actuators (reference numerals 2L, 2R, 5, 1 shown in FIG. 2 are used).
(0, 11, 12, 14) are divided into three groups A, B, C so that they are respectively driven by the first pump 22, the second pump 23, and the third pump 24, and the left and right traveling valves 15L, 15L,
15R is arranged in the front row of each of the groups A and B, and the left and right traveling valves 15L and 15R and other actuator control pilot switching valves (pilot switching valve of any one of 16, to 19) are simultaneously operated. When it does, the small excavator is equipped with a means for traveling straight ahead.

When the left and right running valves 15L and 15R are operated, the small shovel runs. Travel valves 15L and 15
Since R is switched, the limit switches 32 and 33 are turned on in conjunction with the switching operation. Solenoid 2
Since 9 is energized, the electromagnetic switching valve 28 is switched from the tank communication oil passage position R to the opening oil passage position N. In this state, the pilot switching valve for controlling other actuators (16, ~, 1
9), the pilot pressure derived from the hydraulic remote control valves 4L and 4R causes the pilot pressure derived from the hydraulic remote control valves 4L and 4R to be changed to the opening oil passage position of the shuttle valve 27, the pipe 34, and the electromagnetic switching valve 28, and the pipe 35. After that, it acts on the pilot pressure receiving portion 36 of the straight travel valve 21. Therefore, the straight-travel valve 21
Changes from the second pump discharge oil passage position to the straight traveling position (e). The pressure oil from the first pump 22 passes through the pipe line 37, one of which passes through the pipe line 38 and the traveling valve 15L, and the traveling motor 2
L and the other branch in the pipe line 37 and are supplied in parallel to the traveling motor 2R via the pipe line 39, the travel position of the straight travel valve 21, the pipe line 40 and the traveling valve 15R. Also the second pump 2
The pressure oil from 3 is supplied to the pipelines 41 and 42, the position of the straight traveling valve 21, the pipeline 43, 44 or 45, and the check valve 46 or 4.
It is supplied to the other hydraulic actuator that has been operated through 7. When the traveling valves 15L and 15R and the pilot switching valve for controlling other actuators are simultaneously operated as described above, the small shovel can travel straight.

[0006]

Since the small shovel has a low vehicle height, water such as muddy water easily enters the electric circuit for straight traveling during excavation work, and the limit switch and the solenoid rust and cause a failure. Also, since it has an expensive straight valve for traveling, the manufacturing cost of the small shovel was inevitably high. The problem to be solved by the present invention is to provide a hydraulic circuit for straight traveling which does not require an electric circuit for straight traveling and a straight traveling valve, has good maintainability and is inexpensive.

[0007]

According to the present invention, the left and right traveling switching valves are each provided with a sub-valve that operates in conjunction with the traveling switching valve, and the sub-valve is shut off when the traveling switching valve is in the neutral position. The sub valve is set to the oil passage position, and when the traveling switching valve is in the switching position, the sub valve is set to the open oil passage position, and both sub valves are communicated with each other through the oil passage, while the last row of group C is replenished. A pilot switching valve for supply is provided, and the pilot pressure receiving part of the supplementary pilot switching valve is connected to the downstream sub-valve of the above two sub-valves, and it is derived when the hydraulic remote control valve for operating another actuator is operated. The pilot pressure to be generated is communicated to the upstream sub-valve of the above two sub-valves, and the left and right traveling switching valves and pilot switching for controlling other actuators are controlled. Pressurized oil from the third pump when co operate the door and configured to example by supplying to the other actuator through a pilot switching valve for the supply.

[0008]

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 numerals 15'L and 15'R are left and right traveling switching valves, and 48L and 48R are traveling switching valves 1.
Sub-valves of 5'L and 15'R (hereinafter referred to as traveling valves 15'L and 15'R), 49 is a supplementary pilot switching valve, 50 is a pilot pressure of a supplemental pilot switching valve 49 (hereinafter referred to as supplemental valve 49). It is a pressure receiving part.

Next, the structure of the hydraulic circuit of the present invention will be described with reference to FIG. The left and right traveling valves 15'L and 15'R are provided with sub-valves 48L and 48R that are switched and operated in conjunction with the traveling valves 15'L and 15'R, respectively.
When L and 15'R are in the neutral position, the sub valve 48L,
48R is in the shutoff oil passage position, and traveling valves 15'L, 15 '
When R is in the switching position, the sub-valves 48L and 48R are set so as to switch to the open oil passage position, and both sub-valves 48L and 48R are connected to each other through the oil passage 51, while the replenishment valve 49 is provided in the last row of the group C. The pilot pressure receiving portion 50 of the supply valve 49 and the downstream side sub-valve 48R are communicated with each other via the oil passages 53 and 54, and the other actuator operating hydraulic remote control valves 4L and 4R are operated. The left and right traveling valves 15′L and 15′R and the pilot switching valve for controlling other actuators (either one of 16, to 19) are arranged so that the pilot pressure derived at this time is communicated to the upstream side sub-valve 48L. When the pilot switching valve) is simultaneously operated, the pressure oil from the third pump 24 is supplied to the other actuator via the supply valve 49.

Next, the operation of the hydraulic circuit of the present invention will be described. In the hydraulic circuit of the present invention, the pressure oils from the first pump 22, the second pump 23, and the third pump 24 are sent to the groups A, B, and C, respectively. Is the same as. However, the operation when traveling straight ahead is different from the case of the prior art. When the left and right traveling valves 15'L and 15'R are operated, the sub-valves 48L and 48R are both switched to the open oil passage position in conjunction with the switching operation. When the pilot switching valve for controlling the other actuators (one of the pilot switching valves 16, 16, ... 19) is operated in this traveling state, the pilot pressure derived from the hydraulic remote control valves 4L, 4R becomes the shuttle valve 27, It acts on the pilot pressure receiving section 50 via the pipe line 52, the opening oil passage position of the sub valve 48L, the pipe line 51, the opening oil passage position of the sub valve 48R, and the pipe lines 53 and 54. The supply valve 49 is switched from the wheel position to the power position. Therefore, the pressure oil from the third pump 24 is supplied to the pipe 55, the group C.
Oil passage (the oil passage (the flow of pressure oil changes depending on whether the dozer switching valve 20 or the swiveling pilot switching valve 19 is switched) depending on whether the dozer switching valve 20 or the swiveling pilot switching valve 19 is switched), a supply valve It is supplied to the other hydraulic actuator that has been operated through the position 49, the pipeline 53, 44 or 45, the check valve 46 or 47. The traveling valves 15L and 15R and the pilot switching valve for controlling the other actuators as described above. When operating simultaneously, the small shovel can travel straight ahead.

[0011]

As described above, according to the present invention, the left and right traveling switching valves in the hydraulic circuit equipped in the small excavator,
Each of the valves is provided with a switching valve that operates in conjunction with the travel switching valve.When the travel switching valve is in the neutral position, the sub valve is in the shutoff oil passage position, and when the travel switching valve is in the switching position, the sub valve is in the open oil passage position. The sub-valves are connected to each other through an oil passage, and a supplementary pilot switching valve is arranged in the last row of group C. The supplementary pilot switching valve is connected to the pilot pressure receiving portion. , The pilot pressure derived when communicating the downstream sub-valve of the both sub-valves and operating the other actuator operating hydraulic link control valve is communicated to the upstream sub-valve of the both sub-valves. When the traveling switching valve and the pilot switching valve for controlling other actuators are simultaneously operated, the pressure oil from the third pump is supplied to the replenishment pilot. Through the valve and configured to supply to the other actuator. As a result, the electric circuit for traveling straight ahead and the traveling straight ahead valve, which are equipped in the conventional small-sized shovel, can be eliminated. Therefore, in the small excavator having the hydraulic circuit of the present invention, it is possible to improve the maintainability of the straight traveling system, reduce the manufacturing cost of the small excavator, and reduce the manufacturing cost of the shovel. it can.

[Brief description of drawings]

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

FIG. 2 is a side view of a small excavator.

FIG. 3 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 2L, 2R Travel motor 4L, 4R Hydraulic remote control valve 15L, 15R, 15'L, 15'R Travel switching valve 16, 17, 18, 19 Pilot switching valve 21 Traveling straight valve 22, 23, 24 1st, 2nd , 3rd pump 26 Pilot pump 48L, 48R Sub valve 49 Refueling pilot switching valve

Claims (1)

[Claims] 1. A hydraulic excavator mounted on a small excavator is divided into three groups A, B and C, which are driven by first, second and third pumps respectively, and left and right traveling switching valves are provided. In a hydraulic circuit provided with traveling straight traveling means such that the small shovels are arranged in the front row of each of the groups A and B so that the small excavator can travel straight when the traveling switching valves on the left and right and the pilot switching valves for controlling other actuators are simultaneously operated. , The left and right travel switching valves are provided with sub-valves that perform switching operations in conjunction with the travel switching valve.When the travel switching valve is in the neutral position, the sub valve switches to the cutoff oil passage position and the travel switching valve switches. When set to the position, the sub-valve is set so as to switch to the open oil passage position so that both sub-valves communicate with each other through the oil passage. This is derived when a pilot switching valve is provided, the pilot pressure receiving portion of the supplementary pilot switching valve is connected to the downstream sub-valve of both sub-valves, and another hydraulic actuator remote control valve is operated. The pilot pressure is supplied to the upstream sub-valve of both sub-valves, and when the left and right traveling switching valves and the pilot switching valve for controlling other actuators are simultaneously operated, the pressure oil from the third pump is replenished. A hydraulic circuit for a small excavator, characterized in that the hydraulic circuit is configured to be supplied to another actuator via a pilot pilot switching valve.