JPH0516569U - Hydraulic lifting device for work vehicles - Google Patents

Abstract

(57) [Summary] [Purpose] It is possible to lower the working part at a high speed after traveling the machine to improve working efficiency, and lower the working part at a low speed during automatic plowing depth control. Improve work accuracy. [Structure] A poppet 13a for regulating and allowing the discharge and a floating poppet 28 which is closed before the poppet 13a is closed are provided in the oil discharge path in the cylinder, and the poppet 13a is opened and the floating poppet is opened. 28
A lower orifice 29a is provided for discharging a small amount in the closed state.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic lifting device for a work vehicle such as a tractor.

[0002]

[Problems to be Solved by Prior Art and Invention]

 Generally, there is a traveling vehicle of this type provided with a hydraulic cylinder for moving up and down the working part, and the oil in the hydraulic cylinder is discharged by the own weight of the working part to lower the working part by its own weight. In consideration of work efficiency in such a case, it is desirable to lower the working unit at a high speed so that the work can be quickly returned after the aircraft has traveled. However, when the working height of the working part is automatically controlled like the automatic control of the working depth of the tractor, if the above-mentioned high descending speed is adopted, the descending speed is too fast, and the working part moves up and down beyond the target height. There is an inconvenience that a so-called hunting phenomenon that vibrates in the direction occurs and the working accuracy is reduced. Therefore, in the past, the lowering speed was adjusted by the lowering speed adjusting valve provided separately from the control valve of the hydraulic cylinder, but it is necessary to adopt an intermediate compromise speed, so both of the above conditions are sufficiently satisfied. As a result, it was not possible to combine excellent work efficiency and work precision as a result.

[0003]

[Means for Solving the Problems]

 The present invention was devised in view of the above circumstances to provide a hydraulic lifting device for a working traveling vehicle capable of eliminating these drawbacks. In a traveling vehicle for work, a hydraulic cylinder for raising and lowering is provided, and a control valve for the hydraulic cylinder is provided with a descending valve for discharging oil in the hydraulic cylinder by its own weight of the working portion to lower the hydraulic cylinder. The descending valve includes a main valve that opens and closes the descending discharge path, a sub valve that closes the descending discharge path earlier than the main valve when the main valve is closed, and a main valve opens and a sub valve. And a throttle discharge means for discharging a smaller amount of oil when the sub valve is opened when the sub valve is closed. Further, the present invention is capable of significantly improving work efficiency and work accuracy with this configuration.

[0004]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 is a traveling machine body of a tractor, and a rotary tillage type working section 3 is movably connected to a rear portion of the traveling machine body 1 via an elevating link mechanism 2, and the working section 3 Moves up and down by the vertical swing of the lift arm 5 based on the expansion and contraction of the single-acting hydraulic cylinder 4, but the basic structure of each of these is the same as before.

Reference numeral 6 denotes a hydraulic mechanism provided in the traveling machine body 1. The hydraulic mechanism 6 has a working unit lifting hydraulic mechanism 7 and a power steering hydraulic mechanism 8. The working unit lifting hydraulic mechanism 7 is The hydraulic pump P for pumping the oil in the hydraulic tank T, the relief valve 9 for returning the surplus oil to the hydraulic tank T when the pressure in the working unit lifting hydraulic mechanism 7 becomes equal to or higher than a predetermined pressure, and the hydraulic cylinder 4 The control valve 10 controls the extension operation, the contraction operation, and the stop operation, and the descending speed adjusting valve 11 capable of variably narrowing the oil discharge path of the hydraulic cylinder 4.

The control valve 10 is configured by incorporating a spool valve 12, a poppet valve 13, an unload valve 14, a check valve 15 and the like into a valve body. The spool shaft 16 of the spool valve 12 and the poppet valve of the poppet valve 13 are The shaft 17 is connected via a connecting member 18, and the connecting member 18 includes an elevating operation lever 20 provided in a driver's seat 19 and a rear cover 21 provided in the working unit 3 for swinging up and down for swinging. Is linked to. In other words, both shafts 16 and 17 are pushed and pulled to the raising position, the neutral position, and the lowering position, which will be described later, based on the operation of the raising and lowering operation lever 20, and the raising and lowering fine movement position based on the vertical swing of the rear cover 21. By pushing and pulling a small amount to the neutral position and the lower side fine movement position peculiar to the present invention, manual and automatic hydraulic switching can be supported.

The movement of the control valve 10 will be described below. First, in the neutral position, the pressure oil supplied from the pump port 22 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 Since the biasing force is set to be larger than that of the spring 14b, the check valve 15 is closed, the unload valve 14 is opened, and the oil is discharged from the first return port 23. In this unloaded operation state, the check valve 15 is closed. The valve 15 shuts off the other path to stop the hydraulic cylinder 4.

Further, in the raised position, only the spool shaft 16 is pushed into the valve chamber of the spool valve 12 and the front chamber 24 and the rear chamber 25 of the unload valve 14 so that the same pressure is applied to the poppet 15a from the front and rear. Although the hydraulic pressure is applied, the unload valve 14 is closed by the urging force of the spring 14b. Then, all the hydraulic pressure acts on the check valve 15. However, since the pump pressure exceeds the pressure in the hydraulic cylinder 4 here, the check valve 15 is opened and oil is supplied to the hydraulic cylinder 4 to cause the hydraulic cylinder 4 to operate. It will be extended.

On the other hand, in the lowered position, the spool shaft 16 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. However, as in the neutral position, The load valve 14 opens and the first return port 23 discharges. Also, 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. become.

Further, in the fine movement position on the raising side, the spool shaft 16 is slightly pushed in, the spool valve 12 is closed and the check valve 15 is opened as in the case of the raising position described above. Since the hydraulic pressure from P flows to the hydraulic cylinder 4 via the notch portion 27 of the spool valve 12, the hydraulic pressure is throttled and the hydraulic cylinder 4 extends at a low speed.

Further, at the lower side fine movement position, as in the case of the lower position, as the poppet 13a of the poppet valve 13 opens, the oil in the hydraulic cylinder 4 is discharged from the second return port 26 and the hydraulic pressure is reduced. Although the cylinder 4 is contracted, the second return port 26 is closed by a floating poppet 28, which will be described later, so that the oil in the hydraulic cylinder 4 is discharged little by little through a separate lower orifice 29a. Based on this, the hydraulic cylinder 4 is reduced at a low speed. That is, a small-diameter extension shaft 29 extends toward the second return port 26 on the poppet shaft 17, and the second return port 26 is attached to the extension shaft 29 only in the lowered position. In the state in which the poppet 13 is opened and the poppet 13a is opened and the poppet 28 is closed while the floating poppet 28 that closes the second return port 26 by the biasing force of the spring 30 is slidably fitted on the outside. A small diameter down orifice 29a is formed to squeeze out the oil in the hydraulic cylinder 4. Reference numeral 31 is a retaining ring provided at the tip of the extension shaft 29 to prevent the floating poppet 28 from coming off.

In the embodiment of the present invention constructed as described above, when the raising / lowering operation lever 20 is operated to be lowered, the poppet shaft 17 is pulled out to the lowered position to open the poppet 13a, and the floating poppet 28 is also moved to this position. Following this, the second return port 26 is opened, so that a large amount of oil in the hydraulic cylinder 4 is discharged, and the hydraulic cylinder 4 is reduced at high speed. On the other hand, when the poppet shaft 17 is pulled out to the lower side fine movement position based on the swing of the rear cover 21, the poppet 13a opens but the floating poppet 28 maintains the closed state, so that the oil in the hydraulic cylinder 4 is lowered. The hydraulic cylinder 4 is discharged little by little from the orifice 29a, and the hydraulic cylinder 4 is reduced at a low speed. Therefore, it is possible to surely prevent the problem that the working part 3 causes a so-called hunting phenomenon in the automatic plowing depth control state like the hydraulic cylinder 4 which is constantly reduced at a high speed. It is possible to prevent the inconvenience that it takes a long time to recover the work at the time of traveling, such as the case where the reduction operation is performed by, and as a result, the work accuracy and work efficiency can be remarkably improved.

Moreover, in the automatic tilling depth control state, since the working unit 3 does not move up and down at a low speed and the tilling load does not change abruptly, the engine load is reduced and the so-called rotating drop phenomenon is surely prevented. be able to.

It should be noted that the present invention is not limited to the above-described embodiment, and can be configured as a second embodiment shown in FIG. 4, for example. That is, the second embodiment is provided with the floating poppet 28 as in the first embodiment, and the outer end surface of the floating poppet 28 is in contact with the retractable pilot screw 32. Then, when the poppet shaft 17 is pulled out to the lower side fine movement position, the floating poppet 28 maintains a closed state with a slight gap, so that the inside of the hydraulic cylinder 4 is the same as in the first embodiment. The oil can be discharged little by little and the hydraulic cylinder 4 can be reduced at a low speed. Further, the speed adjustment of the reduction operation at the lower side fine movement position is performed by the clearance adjustment based on the forward and backward operation of the pilot screw 32. It can be performed. Therefore, even when the working unit 3 having a different weight is exchanged, the working unit 3 can be lowered at the optimum speed by the gap adjustment.

[0015]

[Operation effect]

 In short, since the present invention is configured as described above, the oil in the hydraulic cylinder is discharged by the weight of the working part to lower the hydraulic cylinder, but the lowering valve of the hydraulic cylinder is It is possible to switch between a high speed descent state in which the main valve and the sub valve are provided, and the main valve and the sub valve are opened, and a low speed descent state in which the main valve is opened and the sub valve is closed to go through the throttle discharge means. Therefore, after the machine has traveled, the working part can be lowered at a high speed to perform quick work recovery, and in the case of automatically controlling the working height of the working part such as the automatic control of the working depth of the tractor. By lowering the working part at a low speed, the so-called hunting phenomenon can be reliably prevented, and as a result, work efficiency and working accuracy are significantly improved compared to the conventional one in which the working part was lowered at a single speed. be able to.

[Brief description of 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.

FIG. 4 is a sectional view showing the second embodiment.

[Explanation of symbols]

 1 Traveling aircraft 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)

[Scope of utility model registration request] 1. A traveling machine body is provided with a hydraulic cylinder for raising and lowering a working unit, and a control valve of the hydraulic cylinder is a lowering unit for discharging oil in the hydraulic cylinder by the weight of the working unit to lower the hydraulic cylinder. In a working vehicle provided with a valve for operation, a main valve that opens and closes a discharge passage for lowering the lower valve, and a sub valve that closes the lower discharge passage earlier than the main valve when the main valve is closed. A hydraulic lifting device for a working vehicle, comprising: a valve; and a throttle discharge means for discharging a smaller amount of oil when the main valve is open and the sub valve is closed than when the sub valve is opened. ..