JPS61127967A - Flush valve - Google Patents

Abstract

PURPOSE:To suppress production of surge pressure due to abrupt change of flow by selectively limiting the moving speed of poppet in poppet valve for communicating between main and low pressure conduits. CONSTITUTION:In case of low delivery flow from hydraulic pump 1, the solenoid valve 20 is held in the condition shown on the drawing where the rear section of push rod 4f is communicated with main conduit A to produce high moving speed of poppet 4c in poppet valve 4. Upon increase of the delivery flow from said pump 1 to setting level, a signal is fed from a controller 25 to the solenoid valve 20 which is switched to lower position thus to block between the rear section of push rod 4f and main conduit A. When the poppet valve 4 will transfer from open to close, the pressurized oil is restricted through a restrictor 19 thus to limit the moving speed of poppet 4c.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a flushing valve that replaces oil in a closed circuit connecting a hydraulic pump and an actuator in cooperation with an oil replenishing means such as a charge pump.

In particular, it relates to flushing valves with poppet valves.

[Background of the invention]

Figure W2B is a circuit diagram showing an example of a hydraulic circuit equipped with a conventional flushing valve.

1 is a variable displacement hydraulic pump; 2 is an actuator driven by this hydraulic pump 1; for example, a single rod cylinder forming an arm cylinder of a hydraulic excavator; A, B;
is a main pipe connecting these hydraulic pumps 1 and cylinders 2, C is a low pressure pipe, and 3 is connected to main pipes A and B and low pressure pipe C, and a pressure difference is created between the main pipes A and B. This is a conventional flushing valve that closes the main pipeline on the high-pressure side and connects the main pipeline on the low-pressure side to the low-pressure pipeline C.

This flushing valve 3 mainly consists of two poppet valves 4 and 5.
, a switching valve 6, and throttles 7 and 8. Each poppet valve 4, 5 has an inlet chamber 4a, 5a connected to the main conduit A or the main conduit B, and an outlet chamber 4 connected to the low pressure conduit C.
b, 5b, and the inlet chamber 4a by advancing due to the pressure of the inlet chambers 4a, 5a.

A poppet 4C communicates between the poppet 5a and the outlet chambers 4b and 5b.

5C, pressure chambers 4d, 5d that apply pressure in the direction of preventing the forward movement of 4C, 5C, and springs 4e, 5e set according to the maximum pressure of the main pipe A or main pipe B on the low pressure side.
It consists of Moreover, the switching valve 6 has pressure chambers 6a, 5b connected to the main pipe A or main pipe B, and pressure chambers 6a,
Weak springs 6f, 6g which return the poppets 6d, 6e to the neutral position when there is no differential pressure between the two poppets (6d, 6e) and the main pipes A, 8 which are pushed together via the bushing rod 6C under the pressure of the poppet 6b. , the common bow connected to the low pressure pipe CK) 6h, the pressure chamber 4 of the switching chamber 61 and the poppet valve 4゜5.
d, a switching boat 6j connected to 5d.

It consists of 6 and 6. The throttle 7 is provided between the main pipe A and the pressure chamber 4d of the poppet valve 4, and the throttle 8 is provided between the main pipe B and the pressure chamber 5d of the poppet valve 5. Also,
9 is a pilot relief valve provided between the outlet side of the throttle 7 and the low pressure pipe C, and 10 is a pilot relief valve provided between the outlet side of the throttle 8 and the low pressure pipe C.

The above-mentioned switching valve 6 and throttles 7, 8 are the main pipe A.

The differential pressure responsive means detects the differential pressure between 8 and closes the poppet valve connected to the main pipeline on the high pressure side, and enables the poppet valve connected to the main pipeline on the low pressure side to open. There is.

In addition, 11 is a charge pump, 12 and 13 are check valves, 14 is a relief valve for charging, 15 is an accumulator that compensates for the change in oil amount in the closed circuit due to the difference in area between the rod side and the bottom side of the single rod cylinder 2, and 16 is a tank.

As above! IC! The operation of the hydraulic circuit equipped with the flushing valve 3 is as follows.

That is, when there is no differential pressure between the main pipes A and B, the switching valve 6 is in the neutral position, and the common bow 6h communicates with both switching bows 6j and 6k via the switching chamber 61. However, the pressure chambers 4d and 5d of the poppet valves 4 and 5 communicate with the output port 16 via a low-pressure pipe C. This state is called the openable state. Therefore, in this state, when the pressure in the main pipes A and B becomes greater than the cracking pressure determined by the springs 4e and 5e of the poppet valve 4.5, the poppets 4c and 5c move forward to open the inlet chambers 4a and 5a and the outlet chamber 4b. , 5b,
That is, the poppet valves 4 and 5 are opened. This results in
Main lines A, B are connected to tank 16 and oil is discharged into tank 16.

K when there is no differential pressure between main pipes A and 8.

When the hydraulic pump 1 is operated to drive the cylinder 2, for example, when the pressure in the main line A increases, the switching valve 6 is driven by the differential pressure before the pressure reaches the cracking pressure of the poppet valve 4. As a result, the pressure chamber 4d of the poppet valve 4 is cut off from the tank 16, and the pressure chamber 5d of the poppet valve 5 is still communicated with the tank 16.

The pressure of the main pipe A is introduced into the pressure chamber 4d of the poppet valve 4 through the throttle 7, and the valve becomes closed, so the poppet valve 4 will not open even if the pressure of the main pipe A rises above the cracking pressure. do not have.

When the load of the inertial system is driven by the cylinder 2, when the discharge amount of the hydraulic pump 1 is reduced, if the main pipe A is on the high pressure side, the main pipe B is instantly switched to the high pressure side. However, the poppet valve 4.5 is a poppet 4c for increasing the oil passage area.

Since the amount of movement of 5C can be reduced, the switching operation is fast.
There is no need to worry about oil leakage, so the high pressure in main pipes A and B
Follows low pressure switching well. Therefore, the responsiveness of the operation is good.

By the way, FIG. 4 is a side view of a hydraulic excavator cited as an example of a hydraulic working machine equipped with the hydraulic circuit shown in FIG. 3 described above. In this figure, 2 is a single rod cylinder (arm cylinder) provided in the hydraulic circuit shown in FIG. 3, and 17 is an arm driven by this cylinder 2. For such hydraulic excavators,
When the arm 17 is operated to dump as shown by the arrow 18 in the figure, the cylinder 2 operates in the direction of contraction, but the direction of the load is reversed in the middle. That is, in the first half of rotation in the direction of arrow 18 from the state of the arm 17 shown by the broken line, the main pipe B connected to the bottom side of the cylinder 2 is under high pressure due to the weight of the arm 17, and the poppet valve 5 is in the closed state. , the boppet valve 4 is in an open state. Then, arm A17 further moves in the direction of arrow 18, and this arm 1
When the cylinder 7 is in a substantially vertical state, the main pipe connected to the rod side of the cylinder 2 is brought under high pressure in order to lift the arm 17, contrary to the above. At this time, main pipe A.

Due to the reversal of the pressure at B, the poppet valve 4 becomes closed,
On the contrary, the poppet valve 5 is in an open state.

FIG. 5 is an explanatory diagram showing the flow of oil during this period.

As shown in this figure, the piston area on the bottom side of cylinder 2 is 88. Assuming that the piston area on the rod side is SR, and for the sake of simplicity S□/S, w 2, and the discharge flow rate of the hydraulic pump 1 is Q, then in the first half when the main pipe B is at high pressure, the pressure of the cylinder 2 is The flow rate of Kfi on the Rondo side is Q/2
And the remaining Q/2 flow rate is returned to the low pressure pipe C. As soon as the main pipe becomes high pressure as described above, the poppet valve 4 is closed and the flow rate flowing into the hood of the cylinder 2 becomes Q. Due to the change in flow rate at this time, a surge pressure is generated in the main pipe, causing a shock, and this shock is more noticeable when the flow rate Q is large because the flow force also acts strongly.

In order to alleviate such shocks, it has been proposed that the seat portions of the poppet valves 4 and 5 have a cushioning function. The advantage of providing .degree. 5 will be lost.

[Purpose of the invention]

The present invention has been made in view of the actual situation in the prior art, and its purpose is to prevent the generation of surge pressure due to rapid changes in the flow rate flowing into the actuator when a large flow rate is supplied to the actuator. An object of the present invention is to provide a flushing valve that can suppress the above problems without changing the shape of the seat portion of the poppet valve.

[Summary of the invention]

To achieve this objective, the present invention provides for a variable displacement hydraulic pump and an actuator to be connected to two main lines communicating in a closed circuit and a low pressure line leading to a tank, and a differential between the two main lines. When pressure is generated, the main pipeline on the high pressure side is closed, the main pipeline on the low pressure side is connected to the low pressure pipeline, and it is installed between the main pipeline and the low pressure pipeline, and in the closed state, the main pipeline and the low pressure Select the moving speed of the poppet of the poppet valve for those with a poppet valve that cuts off communication with the pipeline and connects the main pipeline and the low-pressure pipeline when the pressure in the main pipeline is higher than the setting when it is openable. The structure is equipped with regulatory means to regulate the situation.

[Embodiments of the invention]

Hereinafter, the flushing valve of the present invention will be explained based on the drawings. FIG. 1 is a circuit diagram showing a hydraulic circuit equipped with an embodiment of the present invention, and FIG. 2 is a side view of a hydraulic excavator as an example of a hydraulic working machine equipped with the hydraulic circuit shown in FIG. 1.

The flushing valve 3 shown in FIG. 1 has a bushing rod 4f and a spring 4g housed in an inlet chamber 4a of a poppet valve 4, and the spring 4g biases the bushing rod 4f so that it is always in continuous contact with the bushing rod 4f. It's a shame. Note that the spring force of the spring 4g is set to be sufficiently smaller than that of the spring 4e. Also, 19 is the aperture, 2
Reference numeral 0 designates a solenoid valve, and the throttle 19 and the solenoid valve 20 are arranged in parallel in a conduit connecting the back of the bushing rod 4f and the main conduit A. The bush rod 4f and spring 4 mentioned above
Together with the throttle 19 and the electromagnetic valve 20, g constitutes a regulating means for selectively regulating the moving speed of the poppet valve 4c of the poppet valve 4. In addition, 21 shown in FIG. 1 is a low pressure pipe C.
This is a relief valve that sets the pressure of the pressure oil flowing through the valve.

Further, 22 shown in FIG. 2 is an engine that drives the hydraulic pump 1, 23 is a rotation speed detector that detects the rotation speed N of the engine 22, 24 is an angle detector that detects the tilt angle θ of the hydraulic pump 1, Reference numeral 25 denotes a control device having memory, calculation, and comparison functions, including a rotation speed detector 23 and an angle detector 24 . The above-mentioned solenoid valve 20 is connected to this control device 25. This control device 25 controls the displacement volume corresponding to the tilt angle θ of the hydraulic pump 1 output from the angle detector 24, the rotation speed N of the engine 22 output from the rotation speed detector 23, and the engine 22. A computation, N-I@D electric QA, is performed to determine the currently discharged flow rate QA from the reduction ratio I in the reduction gear (not shown) connected to the hydraulic pump 1. In addition, a flow rate of a magnitude corresponding to the generation of surge pressure expected from experience is stored as QT, and, for example, the above QA and QT are compared, and
When it becomes equal to T, a signal eA is output to the solenoid valve 20.

In the hydraulic circuit having the flushing valve 3 configured as shown in FIG. 1 above, when the flow rate discharged from the hydraulic pump 1 is small, the signal eA is not output from the control device 25. Therefore, the solenoid valve 20 is maintained in the state shown in FIG.
The movement speed of 4G is fast, ensuring quick response, and the arm 17 does not suffer from a breathing phenomenon.

In addition, the flow rate discharged from the hydraulic bonder 1 increases,
Rotation speed detector 23. θ output from the angle detector 24,
When the flow rate QA calculated by the control device [25 based on The bushing rod 4f is switched to the lower position, and the communication between the back of the bushing rod 4f and the main conduit A is cut off. In this state, when the poppet valve 4 transitions from the open state to the closed state, the bushing rod of the poppet valve 4.

Since the pressure oil flowing from the back of 4f to the main pipe is throttled by the throttle 19, the moving speed of 4c is regulated, and 4c closes the inlet chamber 4a and outlet chamber 4b at a gentle speed.

Therefore, as described above, when the arm 17 shown in FIG. 2 moves in the direction of the arrow 18 from the state indicated by the broken line and the direction of the load applied to the single cylinder cylinder 2 is reversed, that is, the main pipe B becomes high pressure first, When the main line A changes to high pressure when the arm 17 is in a substantially vertical state, the poppet valve 40 of the poppet valve 4 moves at a slow speed to close the inlet chamber 4a and the outlet chamber 4b, thereby closing the inlet chamber 4a and the outlet chamber 4b. The generation of surge pressure due to sudden changes in the flow rate flowing into the Rondo cylinder 2 is suppressed, and shock can be suppressed to a minimum.

In the above embodiment, the conduit connecting the back of the bushing rod 4f and the main conduit A is constricted 19. and ON, OF
Although the F-type solenoid valve 20 is provided, these throttles 19.
A proportional solenoid valve may be provided in place of the solenoid valve 20, so that the moving speed of the bobber 4c can be changed as appropriate. QAlso, in the above embodiment, the poppet 4G and the bushing rod 4f are provided separately, and the bushing rod 4f is biased by the spring 4g so as to come into contact with the poppet 4C, but the present invention is not limited to this. It is also possible to form the bushing rod 4C and the bushing rod 4f integrally and omit the spring 4g.

〔Effect of the invention〕

As described above, the flushing valve of the present invention is configured to include a regulating means for selectively regulating the moving speed of the poppet of the poppet valve. The generation of surge pressure caused by sudden changes in the flow rate flowing into the valve can be suppressed without changing the shape of the seat of the poppet valve, unlike conventional poppet valves.Therefore, the poppet valve's followability is ensured when necessary. This has the effect of minimizing the shock associated with the generation of surge pressure.
′

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a hydraulic circuit equipped with an embodiment of the flushing valve of the present invention, and Fig. 2 is a side view of a hydraulic excavator as an example of a hydraulic working machine equipped with the hydraulic circuit shown in Fig. 1. , FIG. 3 is a circuit diagram showing an example of a hydraulic circuit equipped with a conventional flushing valve, and FIG. 4 is a side view of a hydraulic excavator cited as an example of a hydraulic working machine equipped with the hydraulic circuit shown in FIG. , FIG. 5 is an explanatory diagram showing the flow of oil when the arm of the hydraulic excavator shown in FIG. 4 is operated to dump. 1...Variable displacement hydraulic pump, 2...Single rod cylinder, (actuator), 3...
Flushing valve, 4...Poppet valve, 4a...
...Entrance room, 4c...Poppet, 4f...
... Butsch rod, 4g ... Spring, 6.
...Switching valve, 7, 8... Throttle, 19...
...Aperture, 20...Solenoid valve, 22...
・・Engine, 23・・Rotation speed detector, 24・
... Angle detector, 25 ... Control device. Figure 1 Figure 3 Figure 5 Cause

Claims (1)

[Claims] It is connected to two main pipes that connect the variable displacement hydraulic pump and the actuator in a closed circuit, and a low-pressure pipe that leads to the tank, and when a differential pressure occurs between the two main pipes, the high-pressure side main pipe and connects the main pipeline on the low-pressure side to the low-pressure pipeline, and is disposed between the main pipeline and the low-pressure pipeline, and in the closed state cuts off communication between the main pipeline and the low-pressure pipeline, In a flushing valve having a poppet valve that connects the main pipeline and the low-pressure pipeline when the pressure in the main pipeline is equal to or higher than a set time in an openable state, the flushing valve includes a regulating means for selectively regulating the moving speed of the poppet of the poppet valve. A flushing valve characterized by comprising: