JPH06128983A - Dozer device for service car - Google Patents

Abstract

PURPOSE:To improve the finish by permitting the free expansion and contraction movement of a hydraulic cylinder driving and lifting and lowering a dozer and conducting land grading work under the state, in which the dozer is floated. CONSTITUTION:A changeover switch 11 is pushed and operated while a changeover valve 9 is changed over from a normal position H to a floating position F. A pair of oil supply-discharge passages 6a, 6b are short-circuited mutually by the changeover valve 9 at that time while being connected to a drain passage 14. A hydraulic cylinder 6 is changed over to the state of automatic expansion and contraction while a dozer is brought to a floating state. Levelling work is performed while a backhoe is moved backward. Accordingly, the finishing state of excellent levelling work can be obtained because the dozer is not brought to a fixed state, and operationability can be improved because the dozer can be transferred to the floating state regardless of the position of the changeover of a control valve 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a backhoe, a carrier,
Alternatively, it relates to a dozer device for a work vehicle with a dozer such as a wheel loader.

[0002]

2. Description of the Related Art As a work vehicle of this type, for example, as disclosed in Japanese Unexamined Patent Publication No. 4-209216, a dozer has a three-position switching type control valve to switch its operation between upward, downward and neutral. It was something that was done.

[0003]

Among the ground leveling work by the dozer, it is convenient to carry out the work of leveling the soft soil and sand on the so-called back dozer using the back face of the dozer by moving the machine body backward. In other words, the dozer's discharge surface usually has a tilt angle that tilts backward, so when performing the dozer work in reverse, the dozer work can be carried out while pressing down the soil and scraping the soil Compared with work, it is easy to obtain a clean finish. However, in the past, the leveling work was performed with the dozer fixed, so if there is undulation on the ground, the pressing force on the ground will change and the leveling will tend to differ partially, depending on the state of the undulation. May cause the dozer to leave the ground and become unleveled, or to press it too much to scoop the ground, leaving room for improvement to obtain a better finish. It was An object of the present invention is to further improve the finish condition of the leveling work.

[0004]

To achieve the above object, the present invention provides a pair of oil supply / drainage for a hydraulic cylinder in the middle of an oil passage connecting a hydraulic cylinder for driving a dozer up and down and a control valve for the hydraulic cylinder. A switching valve having a floating position that allows free expansion and contraction of the hydraulic cylinder by short-circuiting the paths and connecting to the drain path is provided, and a sub-operation tool for switching the switching valve is used as the main operation for the control valve. It is characterized by being provided separately from the ingredients.

[0005]

According to the above-mentioned characteristic structure, when the switching valve is operated to the floating position, the state where the dozer freely moves up and down appears. Therefore, when moving backward in the floating state, the downward pressing force due to the weight of the dozer acts on the ground. The dozer can follow the ground surface even if the ground is uneven,
It becomes possible to perform a uniform leveling work without any unpressable or gouged part. Since the switching valve is between the control valve and the hydraulic cylinder, and the sub-operation tool and the main operation tool are different, the floating state is defined as the operation position of the main operation tool or the switching position of the control valve. Since it can appear regardless of the height of the dozer, it is suitable for leveling work.
Of course, when the lifting and lowering is stopped, the dozer can be directly switched to the floating state while the dozer is being lowered or raised. For example, in the case where the switching valve is provided on the pressure oil supply side of the control valve, the floating state cannot be obtained unless the control valve is operated to either the ascending or descending position. And is excellent in operability when shifting to leveling work.

[0006]

As a result, it is possible to obtain a better finish of leveling work in the floating state, and
It was possible to provide a dozer device excellent in operability that can shift to a floating state regardless of whether the dozer is raised or lowered.

[0007]

Embodiments of the present invention will be described below with reference to the drawings when applied to a backhoe which is an example of a work vehicle. A backhoe is shown in FIG. 2, 1 is an excavation work device, 2 is a swivel platform, 3 is a traveling machine platform, 4 is a crawler traveling device, and 5 is a dozer. The dozer 5 is configured by attaching an earth-discharging plate 5b curved in a vertical direction in a side view to the tip of an arm 5a supported by the traveling machine base 3 at the left-right axis P, and can be driven and moved up and down by a hydraulic cylinder 6.

FIG. 1 shows a drive operation system of the dozer 5,
Is a control valve having an ascending position U, a neutral position N and a descending position D, and 8 is an operating lever (corresponding to a main operating tool) for operating the control valve 7. In the middle of the pair of oil passages connecting the hydraulic cylinder 6 and the control valve 7, the pair of oil supply / discharge passages 6a and 6b for the hydraulic cylinder 6 are short-circuited and connected to the drain passage 14 so that the hydraulic cylinder 6 is free to move freely. A switching valve 9 having a floating position F that allows expansion and contraction is provided, and a sub-operation tool for switching the switching valve 9 is provided separately from the operation lever 8. That is, the switching valve 9 has a normal position H and a floating position F, and the floating position F is provided with a short circuit 9c connecting the pair of supply / discharge paths 9a and 9b in the valve, and this short circuit 9c. Is configured to be connectable to the tank port 9t that continues to the drain passage 14. Then, the switching valve 9 is configured as an electromagnetic valve, and the control device 1
A push operation type changeover switch (corresponding to a sub operation tool) 11 connected via 0 is provided on the top of the operation lever 8. That is, when the changeover switch 11 is pushed in, the changeover valve 9 is changed over from the normal position H to the floating position F,
The hydraulic cylinder 6 switches to the free expansion / contraction state regardless of the switching position of the control valve 7.

[Other Embodiments] As shown by a broken line in FIG. 1, an orifice 12 is provided in the short circuit 9c of the switching valve 9 so as to be located between the pair of supply / discharge passages 9a and 9b, and back pressure is applied to the hydraulic circuit. It is convenient if the pressing force generated by the dozer 5 in the floating state is lowered and set in a floating state. Further, as shown in FIG. 3, if the orifice 12 is made variable and adjustable by the setting device 13, the downward pressing force in the floating state can be arbitrarily adjusted and set, which is more convenient.

It should be noted that although reference numerals are given in the claims for convenience of comparison with the drawings, the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram for driving a dozer.

[Fig. 2] Side view of backhoe

FIG. 3 is a hydraulic circuit diagram showing another structure of the switching valve.

[Explanation of symbols]

 5 Dozer 6 Hydraulic cylinders 6a, 6b Oil supply / drain passage 7 Control valve 8 Main operation tool 9 Switching valve 11 Sub-operation tool 14 Drain path F Floating position

Claims (1)

[Claims] 1. A pair of oil supply / discharge passages for the hydraulic cylinder (6) in the middle of an oil passage connecting a hydraulic cylinder (6) for driving a dozer (5) up and down and a control valve (7) thereof. A switching valve (9) having a floating position (F) which allows free expansion and contraction of the hydraulic cylinder (6) by short-circuiting 6a) and (6b) and connecting to the drain passage (14) is provided. , This switching valve (9)
The sub-operation tool (11) for switching operation of the control valve (7)
A dozer device for a work vehicle provided separately from the main operation tool (8) for the.