JPH02136432A - Oil-pressure circuit for backhoe working vehicle - Google Patents

Abstract

PURPOSE:To obtain an oil-pressure circuit having good operability without the needs for skill and free of temperature rise of oil by a method in which a bypass having a switch valve with throttle mechanism is provided between the first and second oil paths of a boom cylinder. CONSTITUTION:A bypass C having a switch valve V11 with a throttle mechanism 12 is provided between the first oil path (d) and the second oil path (e) of a boom cylinder C1. The valve V11 is opened by interrupting a tank oil path 9 and a pump oil path 10 and the paths (d) and (e) are led to each other through the mechanism 12. When the device is restored to original attitude for exchanging crawler belts, only the device is slowly contacted with the ground only by operating the valve V11. The operability thereof can thus be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a first oil passage and a second oil passage to a double-acting cylinder that raises and lowers a working device relative to a traveling machine body through a first switching valve. The present invention relates to a hydraulic circuit for a backhoe vehicle that is configured to be connectable to a pump oil path and a tank oil path, respectively.

[Conventional technology]

When performing routine maintenance work such as replacing crawler belts on this type of backhoe work vehicle,
As shown in Figure 2, the boom (4a) is routed around the side of the crawler (1) to ground the bucket) (4c), and the boom cylinder (C1) is shortened to make the bucket) (4c).
), one of the crawler devices (1) will be lifted. After the crawler was replaced, the work style was to extend the boom cylinder (Cυ) and push up the bucket (4c) to return it to its original position. Here, when the boom cylinder (C1) is extended and returned to its original position, it is necessary to ground it with less shock, so conventionally,
A throttling mechanism that performs an inching operation on the first switching valve (V2) and operates only when descending is interposed in one of the first oil passage or the second oil passage.

[Problem to be solved by the invention]

However, it has the disadvantage that considerable skill is required to inching the switching valve and grounding with less shock, and if you try to cover this with a throttling mechanism, the throttling mechanism will work even during normal trenching work. There was an inconvenience that the oil temperature rose.

An object of the present invention is to provide a device that can overcome the conventional drawbacks by adding a simple mechanism.

[Means to solve the problem]

Characteristic configurations according to the present invention include: (1) providing a bypass passage between the first oil passage and the second oil passage; and (2) communicating the first oil passage and the second oil passage with this bypass passage. The second switching valve switches between the closed state and the closed state, and the throttle mechanism throttles the bypassed oil.The functions and effects thereof are as follows.

[Function] In other words, when the first switching valve is set to the neutral state to disconnect the pump oil passage and the tank oil passage from the first oil passage and the second oil passage, and the second switching valve is set to the open state. The first oil passage and the second oil passage are brought into communication, and the double-acting cylinder is expanded under the weight of the aircraft body.

At this time, the oil passing through the bypass passage can be given a throttling effect by the throttling mechanism, and the crawler can be grounded gently.

〔Effect of the invention〕

Therefore, the operator only has to perform a simple operation of switching the first and second switching valves, and it is possible to provide a system with good operability that does not require any skill. During normal operations such as work, the blockage of the bypass path does not affect the throttling and does not cause an increase in oil temperature.

〔Example〕

Next, examples will be shown.

As shown in Figure 4, a swivel platform (2) and a dozer device (3) are attached to the crawler type traveling device (1), and the backhoe device (4), boarding and driving section (5), and driving section (6) are rotated. stand (
2), it constitutes a small backhoe work vehicle that can also be used for earth removal work.

A hydraulic circuit for driving a traveling device (1), a swivel table (2), a dozer device (3), a backhoe device (4) as a working vehicle, etc. will be described in detail below with reference to FIG.

The first to third pumps (+'+) are provided in the driving part (6).

(P2) and (P3) are arranged in conjunction with the same engine, and the first traveling operation valve (V1) of the hydraulic motor (Ml) for one of the left and right crawlers, and the hydraulic cylinder (C1) for the boom (4a) Operation valve as the first switching valve (V2
), bucket) The operation valves (V, ) of the hydraulic cylinder (C2) for 4C> are arranged in the order of a multiple valve type with a center bypass, and are connected in parallel to the first pump (p+).

The second hydraulic motor (M2) for the left and right crawlers
Travel operation valve (V4), boom speed increase operation valve (V,), merging spacer (7), hydraulic cylinder for arm (4b) (
The operation valve (Vs) of C6) and the operation valve (V,) for the service port (8) are connected in parallel to the second pump (P2) as a multiple valve type with a center bypass arranged in that order, and
The operating valve (V,
), the operation valve (VS) of the hydraulic motor for the swivel head (M3), and the operation valve (Lo) of the hydraulic cylinder for the dozer (C2) are arranged in that order in the center bypass Nobuta valve type, and the third pump (P3) is installed. are connected in parallel.

A first oil passage (d) connecting the double-acting type boom (4a) hydraulic cylinder (C+) and the boom operation valve (V2).
) and the second oil passage (e), and a two-position manually operated valve (Vll) as a second switching valve is provided in this bypass passage (C). In the oil communication passage that allows bypass of the manual operation valve (V, l),
A throttling mechanism (12
) is provided.

Therefore, as shown in Fig. 2, the boom (4a) is rotated laterally to the crawler traveling device (1) and
4c) to the ground, lift the crawler traveling device (1) on one side, and replace the crawler belt, etc., and then place the lifted crawler traveling device (1) on the ground. The valve operation (V2) is set to the neutral position to create a closed state, and the manually operated valve (L+) is switched to the bypass position to form a closed circuit with the boom cylinder (C3).

When the manual operation valve (V, 1) is switched to the bypass position, the boom hydraulic cylinder (C3) receives a force in the extension direction due to the weight of the aircraft body. Then, the oil in the descending side hydraulic chamber (a) of the cylinder (C1) passes through the first oil passage (d), the bypass passage (C), and the second oil passage (e) to the cylinder (C1).
C1) is put into the lifting hydraulic chamber (b). At this time, the crawler traveling device (1) gently lands on the ground due to the squeezing effect. The bypass l (C) is equipped with a tank (T).
This communication passage (13) is provided with a check valve (14) that allows suction from the tank (T) to the bypass passage (C), and the piston rod ( The negative pressure decreases due to the expansion of the volume required for the movement of the piston (15a) in the ascending hydraulic chamber (1+) compared to the amount of oil input from the descending hydraulic chamber (a) on the side through which the hydraulic pressure chamber 15b) penetrates.
A structure is adopted in which the insufficient amount is absorbed from the communication path (13) to eliminate it.

As shown in FIG. 5, a link (16) and an arm (
A drive cylinder (17) is placed between the packet (4b) and the packet (4C).
) is additionally configured and the bucket) (
4c) can be installed in the opposite direction to perform soil leveling work and loader work. Moreover, it is more effective than a general loader work vehicle because it is capable of turning, etc.

[Another example]

(2) Each operating valve (Vl)... is used to manually switch the spool, but may be driven by an actuator.

■ The throttle mechanism (12) includes a second switching valve (V11).
), but may be provided in the bypass path (C).

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 hydraulic circuit for a backhoe work vehicle according to the present invention, and FIG. 1 is a circuit diagram showing a state in which a bypass path is provided across a first oil path and a second oil path, and FIG. Fig. 3 is a front view showing a state in which one side of the crawler is lifted, Fig. 3 is an overall hydraulic circuit diagram, Fig. 4 is a side view of the backhoe working vehicle, and Fig. 5 is a side view showing a state in which the packets are attached in different directions. . (4)... Working equipment, (9)... Tank oil line, (10)... Pump oil line, (12)...
... Throttle mechanism, (C) ... Bypass path,
(d)...First oilway, (e)...Second
Oil passage, (C1)...Double acting cylinder, (V2)...
...First switching valve, (V,)...Second switching valve.

Claims (1)

[Claims] Pump oil is connected to the first oil passage (d) and second oil passage (e) to the double-acting cylinder (C_1) that raises and lowers the working device (4) relative to the traveling machine body through the first switching valve (V_2). A hydraulic circuit for a backhoe work vehicle configured to be connectable to a passage (10) and a tank oil passage (9) separately, wherein the first oil passage (d
) and the second oil passage (e), a bypass passage (C) is provided between the bypass passage (C) and the first oil passage (d) and the second oil passage (e). A hydraulic circuit for a backhoe work vehicle, which is provided with a second switching valve (V_1_1) that switches between a closed state and a closed state, and a throttle mechanism (12) that throttles bypassed oil.