JPS5920442Y2 - Hydraulic excavator hydraulic circuit - Google Patents

Description

[Detailed description of the invention] The invention relates to a hydraulic circuit for a hydraulic excavator that excavates earth and sand using a packet by rotating each of the boom, arm, and packet using a hydraulic cylinder. .

Generally, this type of hydraulic excavator is used for civil engineering work such as excavating and loading earth and sand, and when used as a crane, it has a lifting capacity greater than its limit load.

For this reason, crane work is not permitted as is for occupational safety reasons.

Therefore, in order to use a hydraulic excavator as a crane, it must be modified to meet the structural standards for a crane.

In particular, the design must be such that objects exceeding the maximum limit load cannot be lifted.

For this reason, when a conventional hydraulic excavator is used as a crane, a boom cylinder or arm cylinder with a diameter corresponding to the lifting load is prepared separately in advance, and this cylinder is replaced depending on the work.

However, this method had the following drawbacks.

That is, (1) it takes nearly one day of man-hours and labor to change setups during civil engineering work and crane work.

Furthermore, since a separate hydraulic cylinder is required, the cost is high.

(2) Hydraulic circuits are sensitive to contamination by foreign matter such as dirt, so setup changes must be carried out carefully in a dust-free area while avoiding the effects of rain and wind.
Requires high skill and mental strain on workers.

(3) Oil always boils over during setup changes, and work tools require measures to prevent oil from scattering.

(4) After completing the work, check the operating □ oil level and replenish the hydraulic oil.

(5) Since each piping joint is disassembled and reassembled each time a setup is changed, the joints are easily damaged and problems such as oil leaks are easily visible.

The present invention was developed in consideration of the above-mentioned problems, and it is possible to change the setup between excavation work and crane work by simply opening and closing the valve without replacing any hydraulic cylinders. It is an object of the present invention to provide a hydraulic circuit for a hydraulic excavator that overcomes the drawbacks of the conventional hydraulic excavator.

The configuration will be explained below based on the embodiment shown in the drawings.

In the figure, 1 is the arm cylinder, 2 is the form cylinder, 3 is the bucket 1 to cylinder, 4 a and 4 b are the left and right travel motors, 5 is the swing motor, and 6 is the first operation valve group. The valve group 6 includes a swing operation valve 8, an arm operation valve 9, a preliminary operation valve 10, and a left travel operation valve 11, and the second operation valve group 7 includes a boom operation valve 12, a packet operation valve 13, and a right travel operation valve 14. There is.

Hydraulic pumps 15a and 15b supply pressure oil to each actuator via the first and second operation valve groups 6 and 7, respectively.

Further, 16a, 16b, 16C, . . . are safety valves that operate when abnormal pressure occurs in each actuator, and 17a, 17b are main circuit relief valves.

The above configuration is the same as the hydraulic circuit of a conventional hydraulic excavator.

The hydraulic circuit according to the present invention includes the hydraulic pump 15 a of the above circuit.
, 15b and the first and second operation valve groups 6 and 7.
There are on-off valves 18a, 18b and check valve 19 in the main circuit.
The main circuit relief valve 17 via a, 19 b
A and 17b were connected in parallel with a relief valve 20 for limiting the hanging load.

The set pressure of this suspension load limiting relief valve 20 is lower than the set pressure of the main circuit relief valves 17 a and 17 b;
It is also designed to provide relief when the hanging load exceeds a predetermined value.

On the other hand, 21 is a counterbalance valve for preventing arm fall, 22
1 is a boom fall prevention counterbalance valve, which is provided according to crane structural standards to prevent suspended loads from falling due to damage to hydraulic hose connections, etc.

In the above configuration, during civil engineering work, the on-off valves 18a, 18
Close b.

This allows the hydraulic excavator to perform normal civil engineering work.

At this time, the two counterbalance valves 21, 22 have no influence.

During crane work, the on-off valves 18a and 18b are opened.

As a result, the relief valves 17a, 17 in the main circuit
b and the suspension load limiting relief valve 20 are placed in parallel, but the latter has a lower set value and is relieved before the former when the suspension load reaches the limit value, preventing further pressure from being generated. This prevents lifting of loads with a higher load.

FIG. 2 shows another embodiment, in which hanging load limiting relief valves 20, 20 are connected to each main circuit via separate on-off valves 18a, 18b, respectively.

In this case, a check valve is not required.

In each of the above embodiments, an example is shown in which the relief valve 20 for limiting the hanging load is connected to both the main circuit communicating with the arm cylinder 1 and the main circuit communicating with the boom cylinder 2 via the on-off valves 18 a and 18 b. However, by limiting the hanging load of either arm cylinder 1 or boom cylinder 2, the entire hanging load is limited, so the on-off valves 18a, 18b and the relief valve for limiting hanging load are 20 may be connected to either one of the main circuits.

The present invention is as described above, and includes actuators such as an arm cylinder 1, a boom cylinder 2, a packet cylinder 3, etc.
In the hydraulic circuit of a hydraulic excavator consisting of an operating valve that selectively supplies pressure oil to these, hydraulic pumps 15 a and 15 b, etc., the arm cylinder 1 and the boom cylinder 2
In addition to main circuit relief valves 17 a and 17 b that set the operating pressure during excavation work, at least one of the main circuits leading to Valve 20 open/close valve 1
Since they are connected through 8a and 18b, when a hanging load of a predetermined load or more is applied during crane work, the relief valves 17a and 17b for limiting the hanging load operate in relief to prevent lifting of a load of a predetermined load or more. All you can do is prevent it.

According to the present invention, setup changes during civil engineering work and crane work can be performed by simply opening and closing the on-off valves 18a and 18b, and the number of man-hours and labor can be extremely reduced.

Further, since the hydraulic circuit is not exposed to the outside air during setup change, conventional drawbacks such as no dirt or the like getting mixed into the circuit can be solved.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram showing main parts of another embodiment. 1 is an arm cylinder, 2 is a boom cylinder, 3 is a bucket I cylinder, 15 a and 15 b are hydraulic pumps, 1
7a, 17b are main circuit relief valves, 18a, 18
b is an on-off valve, and 20 is a relief valve for limiting hanging load.

Claims (1)

[Scope of utility model registration request] In the hydraulic circuit of a hydraulic excavator, which includes actuators such as arm cylinder 1, arm cylinder 2, and packet cylinder 3, an operation valve that selectively supplies pressure oil to these, and hydraulic pumps 15a and 15b, the arm cylinder 1 and at least one of the main circuits leading to the boom cylinder 2,
Main circuit relief valve 17 that sets the operating pressure during excavation work
In addition to a and 17 b, this main circuit relief valve 17
A hydraulic circuit for a hydraulic excavator, characterized in that a lifting load limiting relief valve 20 with a set pressure lower than that of the opening/closing valves 18 a and 18 b is connected to the relief valve 20 having a lower set pressure than that of the hydraulic excavator.