JPH0739372Y2 - Hydraulic control valve mechanism of tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a configuration of a hydraulic control valve for controlling a work implement lifting device of a tractor.

(B) Conventional Technology Conventionally, the technology related to the hydraulic control valve of the tractor has been known.

For example, it is like the technique described in Japanese Utility Model Laid-Open No. 59-31807.

(C) Problems to be solved by the invention However, in the conventional technology, the main spool of the hydraulic control valve V is too sensitively slid back and forth due to the back and forth movement of the draft operation bar and the position operation bar, so that the disc plow Attach a towing work machine such as a plow or a soil-repellent plate,
When performing draft control, the traction resistance applied to the work implement changes drastically, and if the change in traction force is transmitted from the draft feedback arm as it is, the main spool moves too far back and forth due to the draft operation bar, and indefinitely. A chattering state occurs in which the main spool vibrates without coming to the neutral position.

The present invention eliminates the chattering phenomenon by providing a damper spool that provides resistance to sliding of the main spool that is too sensitive.

(D) Means for Solving the Problems The purpose of the present invention is as described above, and the configuration for achieving the purpose will be described below.

In the main spool 7 that can be switched between three positions of the raising position, the neutral position, and the lowering position, the main spool 7 is biased in the lowering direction, and is interlocked with the main spool 7 to be released by the contact pressure of the push pin 14 to open the hydraulic cylinder (S). A lowering check valve 8 for draining the hydraulic pressure inside the drain circuit is provided, and a back chamber A that interlocks with the main spool 7 to generate a reaction force in the direction opposite to the lowering direction of the main spool 7 and the main spool 7 are in the raised position. Occasionally, hydraulic oil flows into the back chamber A, and a land portion 21 is formed to prevent oil from entering and exiting from before the neutral position to the lowered position. At the same time when the lowered position is reached, the pressure oil in the back chamber A is discharged. The damper spool 1 provided with the small holes 20 is interposed.

(E) Embodiment The purpose and construction of the present invention are as described above. Next, the construction of the embodiment shown in the accompanying drawings will be described.

FIG. 1 is a hydraulic circuit diagram of the hydraulic control valve V of the present invention, and FIG.
The figure is also a developed sectional view, FIG. 3 is a developed sectional view of the main spool 7, the lowering check valve 8 and the damper spool 1, and FIG. 4 is a lowering check of the main spool 7 from a raised position to a position just before the neutral position. FIG. 5 is a sectional view showing the state of the valve 8 and the damper spool 1, and FIG.
6 is a cross-sectional view showing the position of the damper spool 1 after reaching the lowered position, FIG. 6 is a view showing a pressure change by a conventional valve to which the damper spool 1 is not attached, and FIG. 7 is a damper spool 1 of the present invention. 5 is a view showing a pressure change of a valve attached with.

In FIG. 1, the entire hydraulic circuit will be described.

A hydraulic pump P is attached to the engine mounted on the tractor, and pressure oil discharged from the hydraulic pump P passes through a relief valve L provided outside the hydraulic control valve V,
It is supplied into the hydraulic control valve V.

Inside the hydraulic control valve V, an unload valve 5, a main spool 7, a flow control valve 6, a raising check valve 9 and a lowering check valve 8 are provided together. In the present invention, in order to slow down the movement of the interlocking rod 13 that operates the main spool 7 in the lowering direction by the downward biasing spring 10, the damper spool 1 is interposed at a position that restricts the movement of the interlocking rod 13. is there.

The damper spool 1 is constantly urged by the damper urging spring 2 toward the interlocking rod 13.

The overall configuration will be described with reference to FIG. 2 in a developed sectional view.

The pressure oil from the hydraulic pump P is sent to the pressure oil port m of the hydraulic control valve V.

Oil is sent from the pressure oil port m to the unload valve 5, the main spool 7, and the flow control valve 6, respectively.

The unload valve 5 is urged by the urging spring 5a, and when the main spool 7 is operated to the neutral position, the pressure oil in the back chamber of the unload valve 5 is drained to the drain circuit and automatically opened. Since the pressure oil in the pressure oil port m is drained to the drain circuit before reaching the main spool 7, the main spool 7 is configured so that a load state in which the pressure oil is trapped does not occur.

The flow control valve 6 is urged by an urging spring 6a, and a throttle hole 6b is opened in the back chamber. The pressure oil after passing through the main spool 7 is introduced from the throttle hole 6b to apply the pressure oil. The total pressure of the spring 6a and the pressure oil port m
The flow control valve 6 is opened at a position that balances the pressure from, and the flow rate after passing through the main spool 7 to the pressure oil port n is variable depending on the degree to which the discharge pork 7a of the main spool 7 is opened to the pressure oil port n. Is there.

The pressure oil after passing through the main spool 7 is introduced into the hydraulic cylinder S through the cylinder port C by pushing the biasing spring 9a of the lifting check valve 9 to open it.

When the main spool 7 is in the lowered position, both the draft operation bar 17 and the position operation bar 18 pushing the right end of the main spool 7 are retracted.
A lowering direction urging spring 10 that abuts 11 and presses the main spool 7 in the lowering direction acts to slide the main spool 7 in the left lowering direction.

By sliding the main spool 7 in the lowering direction, the interlocking rod 13 integrally formed with the main spool 7 is pushed leftward to push the push pin 14 and the damper spool push pin 3.

When the lowering check valve 8 is pressed by the push pin 14, the lowering check valve 8 is released to the left against the biasing spring 8a, and the pressure oil in the hydraulic cylinder S is transferred to the cylinder port C. Through the valve case.

The structure of the interlocking rod 13, the push pin 14 and the lowering check valve 8 is the same as the conventional one.

In the present invention, a damper spool push pin 3 fixed to the interlocking rod 13 and a damper spool 1 pressed by the damper spool push pin 3 are separately provided.

The damper spool 1 is pushed by a damper urging spring 2 and is urged to a position where it comes into contact with the left end face of the damper spool push pin 3.

A land portion 21 and a small hole 20 are formed on the damper spool 1. The discharge oil of the flow control valve 6 is made to flow into the back chamber A that houses the damper biasing spring 2 through the drain oil passage D. At the raised position of the main spool 7, when the damper spool push pin 3 is retracted and the damper spool 1 is retracted, the land portion 21 is opened from the drain oil passage D to allow the oil to flow into the back chamber A. The land portion 21 closes the drain oil passage D at the neutral position of the main spool 7, and the small hole 20 communicates with the drain oil passage D at the lowered position.

FIG. 3 shows the state in which the main spool 7 is in the lowered position. In this state, the passage of the pressure oil in the back chamber A of the damper spool 1 to the drain oil passage D is opened, so that the damper When the position operation bar 18 and the draft operation bar 17 shown in FIG. 2 are moved to the left and the downward bias spring 10 starts to move the main spool 7 to the left, there is no interference. Therefore, since the resistance is not given, the movement of the main spool 7 to the lower side can be performed without delay.

Damper spool 1 due to the pressing force of the downward biasing spring 10
4 is gradually pushed to move the main spool 7 to the neutral position in FIG. 4, the land portion 21 is blocked with the drain oil passage D, and is closed by overlapping the distance b, and the pressure oil in the back chamber A is released. However, since the damper effect is exhibited, the switching from the neutral position to the lowered position of the main spool 7 is delayed.

The delay time t2 of the movement from the neutral position to the lowered position of the main spool 7 is shown in FIG.

In the conventional structure in which the damper spool 1 is not provided, as shown in FIG. 6, the lowering direction biasing spring 10 causes the main spool 7 to move to the lowering position at a time t1. In this case, since the resistance force of the damper spool 1 is exerted, the sliding of the main spool 7 to the lowered position by the lowering direction biasing spring 10 is delayed.

As a result, during draft control, the draft sensor suddenly switches between raising and lowering, whereas the actual switching of the main spool 7 becomes slow because a time delay occurs.

When the main spool 7 moves to the lowered position due to the oil leaking from the slight gap between the land 21 and the valve case, the overlapping portion of the land 21 of the damper spool 1 disappears. Since the small hole 20 is opened to the drain hole, the resistance of the damper spool 1 is lost and the main spool 7 can slide to the left side at a stroke. As a result, the pressure oil is immediately discharged to the drain circuit to the lowered position, so that the descending speed is the same as the conventional one.

On the contrary, when the main spool 7 moves from the lowered position toward the neutral position and the raised position, the damper spool 1 does not provide any resistance force, so that the switching action is performed as in the conventional case.

(F) Effect of the Invention Since the present invention is configured as described above, it has the following effects.

First, even if the operator operates the position operation lever to the lower side rapidly, the movement of the main spool 7 is restricted by the damper spool 1, so that the switching operation is performed slowly, and the working machine sharply drops. As a result, the work machine is not damaged.

Secondly, when the hydraulic control valve V of the present invention is used for draft control, the switching of the hydraulic control valve V does not respond immediately even if a draft feedback lowering signal is input, so chattering that has conventionally occurred. The phenomenon could be stopped.

Third, by changing the overlapping distance between the damper spool 1 and the land portion 21, the timing of the lowering damper,
Further, by changing the diameter of the small hole 20, the speed at the time of the lowering damper can be adjusted to form a lowering cushion that matches the work and the machine.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of the hydraulic control valve V of the present invention, and FIG.
The figure is also a developed sectional view, FIG. 3 is a developed sectional view of the main spool 7, the lowering check valve 8 and the damper spool 1, and FIG. 4 is a lowering check of the main spool 7 from a raised position to a position just before the neutral position. FIG. 5 is a sectional view showing the state of the valve 8 and the damper spool 1, and FIG.
6 is a cross-sectional view showing the position of the damper spool 1 after reaching the lowered position, FIG. 6 is a view showing a pressure change by a conventional valve to which the damper spool 1 is not attached, and FIG. 7 is a damper spool 1 of the present invention. 5 is a view showing a pressure change of a valve attached with. 1 …… Damper spool 2 …… Damper bias spring 3 …… Damper spool push pin 7 …… Main spool 20 …… Small hole 21 …… Land part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-28501 (JP, A) JP-A-58-191302 (JP, A) JP-A-54-160604 (JP, A) Actual development Sho-59- 31807 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A main spool 7, which can be switched between three positions of a raised position, a neutral position, and a lowered position, biases a biasing spring 10 in the direction of the lowered position, and interlocks with the main spool 7 to contact a push pin 14. Provided is a lowering check valve 8 which is opened by the pressing and releases the pressure oil in the hydraulic cylinder S to the drain circuit.
The back chamber A, which interlocks with the main spool 7 to generate a reaction force in the direction opposite to the lowering direction of the main spool 7, and the hydraulic oil flows into the back chamber A when the main spool 7 is in the raised position, and is in front of the neutral position. From the lower position to the lowered position, a land portion 21 is formed to prevent oil from entering and exiting, and the damper spool 1 having the small hole 20 for discharging the pressure oil in the back chamber A at the same time when the lowered position is provided is interposed. The hydraulic control valve mechanism of the tractor.