JP2572152Y2 - Hydraulic lifting device for work vehicles - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic lifting device for a working vehicle such as a tractor.

[0002]

2. Description of the Related Art
In this type of traveling vehicle, there is a traveling vehicle provided with a hydraulic cylinder that raises and lowers the working unit, and the working unit is lowered by its own weight by discharging the oil in the hydraulic cylinder by its own weight, and In such a case, in consideration of work efficiency, it is desirable to lower the work unit at a high speed so that the work can be quickly returned after the body circulates. However, in the case of automatically controlling the working height of the working unit such as the automatic control of the cultivation depth of the tractor, when the high descending speed is adopted, the descending speed is too fast and the working unit moves up and down beyond the target height. The so-called hunting phenomenon, which vibrates at the same time, is disadvantageous in that the working accuracy is reduced.
Therefore, in the past, the descending speed was adjusted by a descending speed adjusting valve provided separately from the control valve of the hydraulic cylinder. However, an intermediate compromise speed must be adopted. I ca n’t,
As a result, in reality, it has not been possible to combine excellent work efficiency and work accuracy.

[0003]

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-described circumstances, and has as its object to provide a hydraulic lifting device for a working vehicle that can eliminate these disadvantages. The traveling machine is provided with a hydraulic cylinder for raising and lowering the working unit, and a control valve for the hydraulic cylinder is provided with a descent valve for discharging the oil in the hydraulic cylinder by its own weight and lowering the hydraulic cylinder. In the working traveling vehicle, the lowering valve includes a main valve that opens and closes a lowering discharge path, a sub-valve that closes the lowering discharge path earlier than the main valve with closing operation of the main valve, A throttle discharging means for discharging a smaller amount of oil than when the sub-valve is opened when the valve is open and the sub-valve is closed is provided. According to the present invention, the working efficiency and working accuracy can be remarkably improved by this configuration.

[0004]

Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a traveling body of a tractor, and a rotary tilling type working unit 3 is connected to a rear portion of the traveling body 1 via a lifting link mechanism 2 so as to be able to move up and down. The vertical movement of the lift arm 5 based on the expansion and contraction of the single-acting hydraulic cylinder 4 causes the lift arm 5 to move up and down. However, these basic configurations are all conventional.

Reference numeral 6 denotes a hydraulic mechanism provided in the traveling machine body 1. The hydraulic mechanism 6 includes a hydraulic mechanism 7 for elevating and lowering the working unit and a hydraulic mechanism 8 for power steering. A hydraulic pump P for pumping oil in the tank T, a relief valve 9 for returning surplus oil to the hydraulic tank T when the pressure in the working unit elevating hydraulic mechanism 7 becomes equal to or higher than a predetermined pressure, and an extension of the hydraulic cylinder 4 A control valve 10 that controls operation, reduction operation, and stop operation, and a descent speed adjustment valve 11 that can variably restrict the oil discharge path of the hydraulic cylinder 4 are provided.

The control valve 10 includes a spool valve 1
2, a poppet valve 13, an unloading valve 14, a check valve 15 and the like are incorporated in a valve body. The spool shaft 16 of the spool valve 12 and the poppet shaft 17 of the poppet valve 13 are connected via a connecting member 18. Further, the connecting member 18 is connected to an elevating operation lever 20 provided at the driver's seat 19 and a rear cover 21 provided at the working section 3 so as to be able to swing up and down. That is, both shafts 16 and 17 are
Based on the operation of the lifting / lowering operation lever 20, the push-pull is performed to an up position, a neutral position, and a down position, which will be described later. In this case, manual and automatic hydraulic pressure switching can be performed by pushing and pulling the hydraulic pressure in a small width.

Hereinafter, the operation of the control valve 10 will be described. First, in the neutral position, the pump port 2
2 acts on the poppet 14a of the unload valve 14 and the poppet 15a of the check valve 15, but the spring 15b of the check valve 15 is set to have a larger urging force than the spring 14b of the unload valve 14. Therefore, the check valve 15 is closed, the unload valve 14 is opened, and oil is discharged from the first return port 23. In this no-load operation state, other paths are cut off by the check valve 15 and the hydraulic pressure is reduced. The cylinder 4 will stop.

In the raised position, the spool shaft 1
6 is pushed in, the valve chamber of the spool valve 12 communicates with the front chamber 24 and the rear chamber 25 of the unload valve 14, and the same hydraulic pressure acts on the poppet 15a from front and rear. Spring 14b
Will be closed by the urging force. Then, all the hydraulic pressure acts on the check valve 15, but here the pump pressure exceeds the pressure in the hydraulic cylinder 4, so that the check valve 15 is opened, oil is supplied to the hydraulic cylinder 4, and the hydraulic cylinder 4 is turned on. It will extend.

On the other hand, in the lowered position, the spool shaft 1
6 and the poppet shaft 17 are pulled out and the hydraulic pressure from the pump P acts on the unload valve 14 and the check valve 15, but the unload valve 14 opens and is discharged from the first return port 23 as in the case of the neutral position. Will be done. The oil in the hydraulic cylinder 4 is discharged from the second return port 26 as the poppet 13a of the poppet valve 13 opens against the spring 13b, and the hydraulic cylinder 4 is contracted based on this.

Further, in the raising position, the spool shaft 16 is slightly pushed in, and the spool valve 12 is closed and the check valve 15 is closed as in the raising position.
However, since the hydraulic pressure from the pump P flows to the hydraulic cylinder 4 via the notch 27 of the spool valve 12, the hydraulic pressure is reduced and the hydraulic cylinder 4 extends at a low speed. .

Further, in the lower-side fine movement position,
When the poppet 13a of the poppet valve 13 is opened, the oil in the hydraulic cylinder 4 is discharged from the second return port 26 and the hydraulic cylinder 4 is contracted as in the case of the lower position. 26 is closed by a floating poppet 28 described later, so that the hydraulic cylinder 4
The oil inside is discharged little by little through a separately formed lowering orifice 29a, and based on this, the hydraulic cylinder 4 is operated to contract at a low speed. That is, the small-diameter extension shaft 2 is attached to the poppet shaft 17 toward the second return port 26.
9 is extended, and the extension shaft 29 opens the second return port 26 only in the lowered position, and otherwise closes the second return port 26 by the biasing force of the spring 30. A small-diameter lower orifice 29a is formed to discharge the oil in the hydraulic cylinder 4 in a throttle-like manner while the poppet 13a is open and the floating poppet 28 is closed. . Reference numeral 31 denotes a retaining ring provided at the distal end of the extension shaft 29 to prevent the floating poppet 28 from coming off.

In the embodiment of the present invention configured as described above, when the lifting operation lever 20 is lowered, the poppet shaft 17 is pulled out to the lowered position and the poppet 13a is pulled out.
And the floating poppet 28 follows the opening to open the second return port 26, so that a large amount of oil in the hydraulic cylinder 4 is discharged and the hydraulic cylinder 4 contracts at high speed. On the other hand, when the poppet shaft 17 is pulled out to the lower fine movement position based on the swing of the rear cover 21,
Although the poppet 13a opens but the floating poppet 28 remains closed, the oil in the hydraulic cylinder 4 is discharged little by little from the lowering orifice 29a, and the hydraulic cylinder 4 contracts at a low speed. Therefore, the hydraulic cylinder 4
As but always to shrink operate at high speed, based on the problem that the working unit 3 in tilling depth automatic control state would cause so-called hunting phenomenon can prevent Rika, as though always to shrink operated at low speed the hydraulic cylinder 4, times the line will also be prevented inconveniences takes time to work return in time, etc., as a result, Ru <br/> you to improve the working accuracy and working efficiency.

[0013] Moreover, in the tilling depth automatic control state, since the working unit 3 never tilling load is lifting at low speed abruptly changes, wear in preventing even a so-called rotational-drop phenomenon to reduce the engine load.

[0014]

[Effects] In summary, since the present invention is constructed as described above, the oil in the hydraulic cylinder is discharged by its own weight and the hydraulic cylinder is lowered, while the hydraulic cylinder is lowered. The main valve and the sub-valve are provided with a main valve and a sub-valve. Become. Therefore, after the aircraft circulates, the work unit can be lowered at a high speed to quickly return to the work, and when the work height of the work unit is automatically controlled as in the automatic control of the tractor plowing depth, the work must be performed. parts by lowering at a low speed will be able prevent a so-called hunting phenomenon,
As a result, cut with improved work efficiency and working precision as compared with the conventional one had to lower the working unit in a single rate.

[0015]

[Brief description of the drawings]

FIG. 1 is a side view of a tractor.

FIG. 2 is a hydraulic circuit diagram showing the entire hydraulic mechanism.

FIG. 3 is a sectional view of a control valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Traveling body 3 Working part 4 Hydraulic cylinder 10 Control valve 12 Spool valve 13 Poppet valve 13a Poppet 28 Floating poppet 29a Lowering orifice

Claims (1)

(57) [Scope of request for utility model registration] A traveling machine is provided with a hydraulic cylinder for elevating and lowering a working unit, and a control valve of the hydraulic cylinder is provided with a descent for discharging oil in the hydraulic cylinder by its own weight to lower the hydraulic cylinder. In the working traveling vehicle provided with a control valve, the descending valve includes a main valve that opens and closes a descending discharge path, and a sub valve that closes the descending discharge path prior to the main valve in accordance with the closing operation of the main valve. A hydraulic lift device for a working vehicle, comprising: a valve; and a throttle discharge means for discharging a smaller amount of oil than when the sub-valve is opened when the main valve is open and the sub-valve is closed. .