JPS63280125A - Fluid-pressure circuit for dozer working vehicle - Google Patents

Abstract

PURPOSE:To permit operation to be continued without touch to dozer lever by a method in which a switch valve is automatically operated to raise the dozer blade in case where a traveling motor becomes an overload state due to overmuch lowering of dozer blade. CONSTITUTION:When dozer blade advances under a condition of overmuch lowering during the soil discharging operation, the load of a traveling motor 15 is increased, and the pressure of an oil-pressure supply circuit for advancing is raised. When the pressure becomes more than a set pressure, the first switch valve 27a switched to a cylinder supply state and the second switch valve 27b is to a flow path open state. The pressure oil of the circuit 16a is supplied through the first bypath 28 into a cylinder chamber 6a for raising the dozer cylinder 6, and the pressure oil of the cylinder chamber 6b for lowering is discharged through the second bypath 29 to a drain circuit 20. The dozer blade can thus rise automatically, permitting the continuation of operation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a hydraulic circuit for a traveling motor of a crawler type traveling device, which operates in a forward operating position, reverse operating position, and neutral operating position in conjunction with a traveling operating lever. In addition to interposing a travel switching valve that can be selectively switched, there is also a dozer switch in the fluid pressure circuit of the dozer cylinder that can be selectively switched to a raise operation position, a lower operation position, and a neutral operation position in conjunction with a dozer operation lever. This invention relates to a fluid pressure circuit for a dozer vehicle that includes a valve.

[Conventional technology]

Conventionally, in the fluid pressure circuit of this type of dozer work vehicle, when the pressure in the forward pressure fluid supply circuit from the travel switching valve to the travel motor increases to a set pressure or higher, the fluid is supplied from the pump to the travel switching valve. There was a relief valve that was automatically switched to supply pressure fluid to the drain circuit (I can't find any references).

[Problem that the invention seeks to solve]

In the case of this conventional fluid pressure circuit, even if the dozer blade is forced to travel with the dozer blade lowered too much during earth removal work, the pressure in the forward pressure fluid circuit will exceed the setting of the relief valve as the load on the travel motor increases. The pressure increases, and the operation of this relief valve makes it impossible to drive. Therefore, if the dozer blade is lowered too much, you must switch from the travel control lever to the dozer control lever and raise the dozer blade in small steps until it is at a height that allows travel, making the operation complicated. At the same time, lifting the dozer blade too high may lead to a decrease in soil removal efficiency.

An object of the present invention is to make it possible to accurately and easily perform a dozer raising operation when the dozer blade is lowered too much by rationally modifying the travel system fluid pressure circuit and the dozer system fluid pressure circuit. The point is to make it.

[Means for solving problems]

In the fluid pressure circuit of the dozer work vehicle according to the present invention, when the pressure in the forward pressure fluid supply circuit from the travel switching valve to the travel motor increases to a set pressure or higher, the pressure fluid in the forward pressure fluid supply circuit The invention is characterized by being provided with a pilot type switching valve that can automatically switch to a state in which the dozer cylinder is supplied to a rising cylinder chamber of the dozer cylinder and a state in which the descending cylinder chamber of the dozer cylinder is connected to a drain circuit. The effects and effects thereof are as follows.

[For production]

During earth removal work, if the dozer blade is moved forward while being lowered too much, the pressure in the forward pressure fluid circuit will also increase as the load on the travel motor increases. When the pressure in the forward pressure fluid circuit becomes equal to or higher than the set pressure, the pilot type switching valve operates, and the pressure fluid in the forward pressure fluid supply circuit is supplied to the ascending cylinder chamber of the dozer cylinder. A lowering cylinder chamber is connected to a drain circuit, and the dozer blade is automatically raised without touching the dozer operating lever.

When the load on the travel motor decreases due to this lifting of the dozer blade, and the pressure in the forward pressure fluid circuit decreases below the set pressure, the pilot type switching valve automatically returns, and the dozer blade lifts automatically. will be stopped.

〔Effect of the invention〕

As a result, even if the dozer blade is lowered too much during earth removal work, there is no need to switch from the travel control lever to the dozer control lever and raise the dozer blade in small increments, unlike in the conventional method. This enabled the dozer blade to be raised accurately and easily.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 2, a dozer working device (A) is provided on a traveling vehicle body (2) equipped with a crawler type traveling device (1), and a swivel table (3) is attached to the traveling vehicle body (2) to center the vertical axis. The drive unit (3) is attached to the drive unit (
B) and a backhoe working device (C) are provided to constitute a working vehicle that can perform both excavation and earth removal work.

The dozer working device (A) is configured by an arm (
4), and a dozer blade (5) is fixed to the tip of this arm (4), and a dozer cylinder (6) is installed between the traveling vehicle body (2) and the arm (4). .

To configure the backhoe working device (C), a bracket (7) that is swingable around the vertical axis is attached to the front part of the swivel base (3), and a bracket (7) that can swing around the horizontal axis A boom (8) that can swing up and down is attached to the boom (8), and an arm (9) is attached to the tip of the boom (8), and a bucket (10) is attached to the tip of the arm (9). It is mounted so that it can swing vertically around the horizontal axis.

Moreover, between the swivel base (3) and the bracket (7),
A bracket cylinder (11) that drives and moves this bracket (7) is installed, and the bracket (7) is
) and the boom (8), an arm cylinder (13) between the boom (8) and the arm (9), and an arm cylinder (13) between the boom (8) and the arm (9). A packet cylinder (14) is installed between each bucket (10).

As shown in FIG. 1, the hydraulic circuit (16) of the travel motor (15) of the crawler type traveling device (1) is linked to the travel control lever (17) provided in the driving section (B). When the pressure in the travel switching valve (18) is selectively switched to a forward operation position, a reverse operation position, or a neutral operation position, and the pressure in the travel hydraulic circuit (16) exceeds the set pressure, the hydraulic pump (19) ) is provided with a relief valve (21) that relieves pressure oil supplied from the drain circuit (20) to the drain circuit (20).

Further, a dozer operating lever (23) provided in the driving section (B) is connected to the hydraulic circuit (22) of the dozer cylinder (6).
When the pressure in the dozer hydraulic circuit (22) and the dozer switching valve (24) are selectively switched to the ascending operating position, descending operating position, and neutral operating position in conjunction with A relief valve (26) that relieves pressure oil supplied from the pump (25) to the drain circuit 20)
and a forward pressure oil supply circuit (16a) from the travel switching valve (18) to the travel motor (15).
When the pressure increases to a set pressure that is lower than the set operating pressure of the relief valve (21), the pressure oil in the forward pressure oil supply circuit (16a) is transferred to the ascending cylinder chamber of the dozer cylinder (6). (6a) and a pilot type switching valve (27) which can be automatically switched to a state where the descending cylinder chamber (6b) of the dozer cylinder (6) is connected to the drain circuit (20). There is.

This pilot type switching valve (27) controls the motor supply state in which pressurized oil from the travel hydraulic pump (19) is supplied to the travel motor (15) and the dozer cylinder (6) through the first bypass passage (28). A two-position pilot type first switching valve (27a) that can be switched to a cylinder supply state that supplies the cylinder to the ascending cylinder chamber (6a), and a descending cylinder chamber (6b) of the dozer cylinder (6) and a drain. Circuit (2
0), and a two-position biloft type second switching valve (27b) that opens and closes the second bypass flow path (29).
).

In the hydraulic circuit configured as described above, if the dozer blade (5) is moved forward while being lowered too much during earth removal work, the load on the travel motor (15) increases and the forward hydraulic supply circuit (16a) is Pressure also increases. When the pressure of the forward hydraulic pressure supply circuit (16a) becomes equal to or higher than the set pressure, the viroft type first switching valve (27a) is switched to the cylinder supply state, and at the same time, the pilot type second switching valve (27a) is switched to the cylinder supply state.
7b) is switched to the flow path open state, and the pressure oil in the forward hydraulic pressure supply circuit (16a) flows into the first bypass flow path (28).
) of the dozer cylinder (6) through the lifting cylinder chamber (
6a) and the dozer cylinder (6)
Pressure oil in the lowering cylinder chamber (6b) is discharged to the drain circuit (20) through the second bypass passage (29), and the dozer blade (5) is automatically operated without touching the dozer operating lever (23). The drive is raised.

The load on the travel motor (15) is reduced by driving the dozer blade (5) upward, and the forward hydraulic pressure supply circuit (16) is reduced.
When the pressure in a) decreases below the set pressure, the pilot type first switching valve (27a) is switched to the motor supply state, and at the same time, the pilot type second switching valve (27b) is switched to the flow path closing state. The dozer blade (5) is actuated, and the driving upward movement of the dozer blade (5) is stopped, and at the same time, the machine moves forward by driving the travel motor (15).

Therefore, even if the dozer blade (5) is lowered too much during soil removal work, the dozer blade (5) can be switched from the travel control lever (17) to the dozer control lever (23).
) in small increments, and such raising operations of the dozer blade (5) can be performed accurately and easily.

[Another example]

In the above-mentioned embodiment, when the pressure in the forward hydraulic pressure supply circuit (16a) increases beyond the setting, the pressure oil in the forward hydraulic pressure supply circuit (16a) is transferred to the ascending cylinder chamber (6a) of the dozer cylinder (6). ) and a state in which the lowering cylinder chamber (6b) of the dozer cylinder (6) is connected to the drain circuit (20). Pilot type switching valve (27a).

(27b), but these two switching valves (27a)
.

It may be constructed from one switching valve having the function (27b).

Further, in the above embodiments, a hydraulic circuit has been described, but the technology of the present invention can also be applied to a circuit that uses other pressure fluids such as water pressure.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings show an embodiment of a fluid pressure circuit for a dozer work vehicle according to the present invention, and FIG. 1 is a hydraulic circuit diagram for traveling and lifting the dozer;
FIG. 2 is a side view of the entire working vehicle. (1)... Crawler type traveling device, (6)...
... Dozer cylinder, (6a) ... Cylinder chamber for ascending, (6b) ... Cylinder chamber for descending, (
15)...Travel motor, (16)...
Fluid pressure circuit, (16a)... Pressure fluid supply circuit for forward movement, (17)... Travel operation lever, (18
)... Travel switching valve, (20)... Drain circuit, (22)... Fluid pressure circuit, (23)
...Dozer operation lever, (24)...
Dozer switching valve, (27) Old pilot type switching valve.

Claims (1)

[Claims] The hydraulic circuit (16) of the travel motor (15) of the crawler type traveling device (1) is connected to the travel control lever (17) to selectively switch the forward operation position, reverse operation position, and neutral operation position. With a switching valve (18) for
The fluid pressure circuit (22) of the dozer cylinder (6) is provided with a dozer switching valve (24) that can be selectively switched to an ascending operating position, a descending operating position, and a neutral operating position in conjunction with the dozer operating lever (23). When the pressure of the forward pressurized fluid supply circuit (16a) from the traveling switching valve (18) to the traveling motor (15) in the intervening fluid pressure circuit of the dozer work vehicle increases to a set pressure or more. , the pressure fluid in the forward pressure fluid supply circuit (16a) is supplied to the dozer cylinder (6).
in a state where it is supplied to the rising cylinder chamber (6a), and
Lowering cylinder chamber (6b) of the dozer cylinder (6)
A fluid pressure circuit of a dozer work vehicle, which is equipped with a pilot type switching valve (27) that is automatically switched to connect the drain circuit (20) to the drain circuit (20).