JPH0437974Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a lift control device for a front loader.

(Prior art) In a front loader mounted on a tractor, the boom is pivoted to the vehicle body so that it can be raised and lowered, and the boom is raised and lowered by a boom cylinder that is controlled by a control valve such as a solenoid valve. That's what I do.

(Problem to be solved by the invention) In this type of front loader, if you try to speed up the cycle time of raising and lowering the boom, the boom will go up and down at almost the same speed over the entire stroke, so for example, in the rising range. If the speed becomes too high, it will come to a sudden stop, and there is a great risk that the earth and sand in the bucket will spill out due to inertia.

Therefore, in view of the above problems, the present invention aims to smoothly reduce the rising speed of the boom as it rises.

(Means for solving the problem) The technical means is that a boom 3, which is pivotally attached to the vehicle body 1 so that it can be raised and lowered, is raised and lowered by a boom cylinder 4 that is controlled by an elevator control valve 15. In the loader, a variable resistor 19 is provided to detect the rise of the boom 3, and a variable resistor 19 is provided in the oil path from the lift control valve 15 to the boom cylinder 4 in order to gradually reduce the flow rate as the boom 3 rises. A proportional control valve 18 is provided which is controlled in conjunction with changes in the resistance of the variable resistor 19.

(Function) According to the present invention, the rise of the boom 3 is detected by the change in resistance of the variable resistor 19, and
Proportional control valve 1 by a signal due to the change in resistance of 9
8 is activated, the flow rate of pressure oil supplied to the boom cylinder 4 on the rising side of the boom 3 is gradually reduced, and the rising speed of the boom is gradually reduced.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings. In Figs. 1 to 3, 1 is a tractor body, 2 is a mounting frame, 3 is a pair of left and right booms, and It is pivoted so that it can be raised and lowered, and can be raised and lowered by a pair of left and right boom cylinders 4. 5 is a bucket, with a horizontal shaft 6 at the tip of the boom 3.
A pair of left and right bucket cylinders 7
It is possible to move up and down. 8 is a three-point link mechanism, and 9 is a hydraulic device for raising and lowering the working machine attached via the three-point link mechanism 8. 10
1 is a driver's seat, and 11 is a cabin that covers the driver's seat 10, etc.

Further, FIG. 1 shows a hydraulic circuit, and 13 is a hydraulic pump, which is driven by an engine 14. 12 is a relief valve.

Reference numeral 15 denotes an elevation control valve for controlling the boom cylinder 4, which can be freely switched between a raised position and a lowered position of the boom 3.

Reference numeral 16 denotes a rotary operation control valve for controlling the bucket cylinder 7, which can be freely switched between a dump position and a scooping position of the bucket 5.

A check valve 17 and a proportional control solenoid valve 18 for controlling the flow rate of pressure oil are provided in the oil path from the lifting control valve 15 to the boom cylinder 4.

A variable resistor 19 is provided at the pivot point between the boom 3 and the mounting frame 2.
The resistance is changed in conjunction with the rise of the boom 3, and the rise position of the boom 3 is continuously detected. Then, as shown in FIG. 2, the variable resistor 1
The signal detected by 9 is sent to a control circuit 20, and the signal output from the control circuit 20 operates the proportional control solenoid valve 18 to adjust the flow rate. The proportional control solenoid valve 18 is configured to gradually reduce the flow rate as the boom 3 rises, for example by restricting the flow rate.

The embodiment of the present invention is constructed as described above, and if pressure oil is supplied to the boom cylinder 4 to gradually raise the boom 3, the resistance of the variable resistor 19 will increase as the boom 3 rotates upward. is gradually changing. A signal is continuously sent from the control circuit 20 to the proportional control solenoid valve 18 by detecting a change in the resistance of the variable resistor 19, and the proportional control solenoid valve 18 is continuously operated to raise the boom 3. Accordingly, the flow rate of the pressure oil supplied to the boom cylinder 4 through the proportional control solenoid valve 18 is continuously and gradually reduced, and the rising speed of the boom 3 is continuously and gradually reduced.

As described above, the rising speed of the boom 3 is continuously decelerated as it rises, and a smooth speed change of the boom 3 is obtained, and when the boom 3 is raised, the spillage of earth and sand from the bucket 5 is effectively prevented. Damage to the vehicle body 1 side, such as the bonnet, can be prevented. It also makes driving easier.

In the above embodiment, the variable resistor 19 is shown as being provided at the pivot portion of the boom 3, but it may be provided at a location linked to the expansion and contraction of the pivot portion of the boom cylinder 4 or the cylinder rod.

Moreover, although the configuration in which the ascending speed is gradually decelerated during the ascending operation of the boom 3 is shown, the descending speed may be similarly configured to be configured to gradually reduce the descending speed during the descending operation.

Furthermore, in the lifting trajectory of the boom 3, the boom 3 may be raised at a constant speed in the middle and gradually decelerated in the upper rising region.

(Effects of the invention) According to the invention, the variable resistor 19 is provided to detect the rise of the boom, and the flow rate is gradually controlled in the oil path from the lift control valve to the boom cylinder as the boom rises. A proportional control valve is provided that is controlled in conjunction with changes in the resistance of the variable resistor to reduce the increase in resistance. When the boom is raised, it is possible to effectively prevent soil and sand from falling out of the bucket, and operation is also facilitated.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a hydraulic circuit diagram, FIG. 2 is an explanatory diagram of a control section, and FIG. 3 is an overall side view. DESCRIPTION OF SYMBOLS 1... Tractor body, 3... Boom, 4... Boom cylinder, 15... Lifting control valve, 18...
Proportional control solenoid valve, 19...variable resistor.

Claims (1)

[Scope of utility model registration request] A variable resistor 1 detects the rise of the boom 3 in a front loader in which a boom 3 pivotably attached to a vehicle body 1 is raised and lowered by a boom cylinder 4 controlled by an elevation control valve 15.
9 is provided in the oil path from the lifting control valve 15 to the boom cylinder 4 in order to gradually reduce the flow rate as the boom 3 rises, in conjunction with the change in resistance of the variable resistor 19. An elevation control device for a front loader, characterized in that a controlled proportional control valve 18 is provided.