JPH053702A - Hydraulic device for lifting tractor working machine or the like - Google Patents

Abstract

PURPOSE:To delicately control the position of a working machine with a spool- formed solenoid valve by placing a flow priority valve, a lift control valve and a stop valve in a specific state. CONSTITUTION:A flow priority valve 3 and a lift control valve 4 are placed in a hydraulic circuit 2 of a lift cylinder 1. The excess oil flow of the valve 3 is discharged to a tank port T with the stop valve 5 or switched to a bypass circuit 6 to pass through a check valve 7 to the control valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device for lifting a tractor working machine or the like.

[0002]

2. Description of the Related Art Up-and-down control by an up-and-down cylinder of a working machine or the like is performed by switching a lift control valve. In order to improve the operability, a proportional control form or a high-speed digital control There are some forms, but the cost tends to increase. The present invention is intended to perform the same position control control with these control modes at a low cost by using a spool type valve.

[0003]

According to the present invention, a hydraulic circuit 2 of an elevating cylinder 1 for elevating and lowering a working machine is provided with a flow priority valve 3 and a lift control valve 4, and the surplus flow rate of the flow priority valve 3 is adjusted. , Discharge to tank port T, check valve 7
A hydraulic system for lifting and lowering a tractor working machine or the like is provided with a stop valve 5 that switches to a bypass 6 so as to bypass the control valve 4 via the control valve 4.

[0004]

When the position control of the working machine is performed, the stop valve 5 is used so that the hydraulic pressure sent from the hydraulic pump side is changed from the flow priority valve 3 to the lift control valve 4. The elevating cylinder 1 is expanded and contracted only by the control flow rate passing through, and the excess flow rate in the flow priority valve 3 is discharged from the stop valve 5 to the tank port T. By the control flow rate of the flow priority valve 3, the position control of the working machine can be finely controlled by the lift control valve 4 which is a spool type solenoid valve.

When the working machine is operated at high speed, by closing the stop valve 5, the surplus flow rate in the flow priority valve 3 is joined from the bypass 6 to the lift control valve 4 side by opening the check valve 7. ..

[0006]

EXAMPLE In FIG. 1, P is a hydraulic pump and T is a tank port. Reference numeral 8 is a relief valve, 9 and 10 are throttles, and 7 and 11 are check valves. In the hydraulic stroke in which the lift cylinder 1 is operated upward by the check valve 11 and the throttle 10, the check valve 11 is opened to increase the amount of hydraulic pressure supplied to the lift cylinder 1, and in the hydraulic stroke in which the lift cylinder 1 is operated downward. The slow return valve 12 is configured to limit the descending speed only by draining oil from the throttle 10.

The flow rate in the hydraulic circuit 2 is determined by the branch flow from the flow priority valve 3 and the throttle 9, and the excess branch flow is discharged to the tank port T by opening the stop valve 5. When the stop valve 5 is closed, the excess flow rate opens the check valve 7 and joins the hydraulic circuit 2 from the bypass 6 to be supplied to the lifting cylinder 1.

The lift control valve 4, the stop valve 5 and the like for controlling the elevation are solenoid valves in the form of spools. In FIG. 2, the lifting cylinder 1
In the control of raising and lowering the working machine by the method, even if the load of the working machine changes, the lowering speed is to be made constant.
Therefore, the plunger 15 for changing the opening degree of the pilot check valve 14 controlled by the high-speed response valve 13 is provided and controlled by the cylinder port C pressure of the lifting cylinder 1.

Reference numeral 16 is a high-speed response valve for raising, and by this switching operation, hydraulic pressure can be sent from the hydraulic circuit 2 into the lift cylinder 1 via the check valve 17 to raise the working machine. In the valve cylinder 17 which communicates with the lifting cylinder 1 through the cylinder ports C1 and C2, a plunger 15 elastically urged by a spring 18 and a poppet 14 elastically urged between the plunger 15 and the spring 19 are slidably provided. There is. The cylinder port C1 exerts hydraulic pressure on the head of the plunger 15 and operates against the spring 18. Poppet 1
4 communicates with the spring chamber 20 containing the spring 19 from the cylinder port C2 through the needle hole 21.
To the high-speed response valve 13 for lowering communication. When the poppet 14 moves against the spring 19, the poppet 14 communicates with the tank port T.

If the displacement amount of the plunger 15 is θ and the displacement amount between the plunger 15 and the poppet 14 is θ + α, the displacement amount θ + α of the poppet 14 is changed by the load of the working machine. The pressure of the cylinder port C1 acts on the plunger 15, and the plunger 15 is displaced by an amount higher than the pressure of the spring 18 and operates up to a θ amount at the maximum. When the movement amount of the poppet 14 becomes α at the maximum load and the load of the lifting cylinder 1 becomes maximum, the movement amount of the poppet 14 becomes minimum, and the lowering speed can be made constant regardless of the load.

As described above, when the lifting cylinder 1 descends, the amount of oil drained to the tank port T is adjusted according to the weight of the working machine to maintain the descending speed constant. 3 to 5 show the configuration of the lifting arm 22 that is lifted and lowered by the lifting cylinder 1. The lifting arm 22 and the lifting cylinder 1 are provided at the rear portion of the vehicle body 23. The tractor vehicle body 23 has an engine 24 mounted on a front portion thereof, a cockpit 25 supported on a rear portion thereof, and a steering wheel 26 which transmits steerable front wheels 27 and rear wheels 28 to form a four-wheel drive traveling mode. And

The elevating arm 22 has a base portion supported on a rear axle housing 29 below the vehicle body 23 by a shaft 30, and a rear end portion having a hitch 31 for connecting a working machine. The lifting cylinder 1 is provided along the inside of the frame of the vehicle body 23,
One end is pivotally supported on the vehicle body 23, the other end is pivotally attached to the elevating arm 22, and the hydraulic cylinder of the elevating cylinder 1 causes the shaft 30 to pivot up and down to elevate the working machine to be connected. ..

A connecting pipe 31 is fixed between the left and right elevating arms 22, and stop pins 32 which are movable in the lateral direction are provided at both left and right ends of the connecting pipe 31, and the connecting pipe 31 and the stop pin 32 are connected to each other. The stop pin 32 is taken in and out by inserting and removing the pin 33 into and from the pin hole provided. A pin seat 34 is fixed to a position of the vehicle body 23 facing the stop pin 32, and the stop pin 32 is projected and received by the pin seat 34 to lock the lowered position of the elevating arm 22. For example, when a chemical control liquid tank is mounted on the vehicle body 23 or the upper part of the elevating arm 22, the elevating arm 22 is fixed at a raised position and a heavy liquid tank is supported at a fixed position. The work can be performed in this state.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of the present invention.

FIG. 2 is a hydraulic circuit diagram of another invention.

FIG. 3 is a side view of a lifting arm unit.

FIG. 4 is a front sectional view thereof.

FIG. 5 is a side view of the tractor.

[Explanation of symbols]

 1 Lifting Cylinder 2 Hydraulic Circuit 3 Flow Priority Valve 4 Lift Control Valve 5 Stop Valve 6 Bypass 7 Check Valve T Tank Port

Claims (1)

Claims: 1. A hydraulic circuit 2 of an elevating cylinder 1 for elevating and lowering a working machine is provided with a flow priority valve 3 and a lift control valve 4, and the surplus flow rate of the flow priority valve 3 is adjusted to a tank. An elevating hydraulic device for a tractor working machine or the like provided with a stop valve 5 for discharging to a port T or switching to a bypass 6 so as to bypass the control valve 4 via a check valve 7.