JPH0113885Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a counterbalance valve that ensures mode switching.

(Conventional Counterbalance Valve) The conventional counterbalance valve shown in FIG. 4 is on the way.

When pilot pressure is introduced into the pilot chamber 4, the spool 2 moves against the spring 5 and opens its control orifice 6. When the control orifice 6 opens, the pressure oil flowing in from the first port 7 enters a counterflow state in which it flows out from the second port 8 while being subjected to throttling resistance by the control orifice 6 .

Further, when no pilot pressure is introduced into the pilot chamber 4 and pressure oil flows in from the second port 8, the pressure oil pushes open the check valve 9 and flows out from the first port 7 in a free flow state.

This type of counterbalance valve is usually used in cranes and the like, but it is also used in power shovels. In other words, since the power shovel is sometimes used for crane work, a counterbalance valve such as the one described above is required for this crane work.

However, in the above-mentioned crane mode, the counterbalance valve must function sufficiently, but in the power shovel mode, when the counterbalance valve functions, the return resistance increases, so there is a corresponding loss of power. Become.

For this purpose, the counterbalance valve has conventionally been switched depending on the mode of use, but conventionally the mode has been switched manually.

For example, in the counterbalance valve shown in FIG. 1, when in the power shovel mode, the pilot piston is forcibly pushed from the outside to stop the spool at the fully open position.

However, after maintaining the spool 2 in the fully open state as described above, when using the power shovel in the crane mode, the fully open state must be released each time.

However, with the conventional counterbalance valve described above, it is possible to forget to change the spool when changing the mode. In particular, when switching from power shovel to crane mode, forgetting to switch the spool has the drawback of increasing the danger of crane work.

(Purpose of the present invention) The purpose of this invention is to provide a counterbalance valve that allows mode switching to be controlled remotely and maintains the counterbalance valve function unless the mode is intentionally switched.

(Embodiment of this invention) The embodiment of this invention shown in FIG.
A bore 12 is formed in the longitudinal direction of the bore 1, and both ends of this bore are closed with covers 13 and 14. A first port 15 and a second port 16 are formed in the valve body 11, and the first port 15 and the second port 16 are formed in the valve body 11.
The port 15 is directly connected to the bottom side chamber 18 of the cylinder 17, and the second port 16 is connected to the directional switching valve 19.

The rod side chamber 20 of the cylinder 17 is connected to the directional control valve 19.

A main spool 21 is slidably housed in the bore 12 as described above, and both ends of the main spool 21 are exposed to the damper chambers 22 and 23. The pressure-receiving area of the main spool in the damper chamber is slightly different.
That is, the pressure receiving area D ₂ of the other damper chamber 23 is made slightly smaller than the pressure receiving area D ₁ of one damper chamber 22 . Furthermore, this other damper chamber 23
A spring 24 is interposed therein, and a stopper 25, which is usually an annular protrusion formed on the main spool 21, contacts the seat portion 26 of the valve body 11, so that the main spool 21 maintains the state shown in the figure. I have to.

Damper orifices 27 and 28 are provided at the inlet and outlet ports of the damper chambers 22 and 23 as described above, and both damper chambers are communicated with each other via a flow path 29. And in this flow path 29,
A pilot passage 30 is connected, and this pilot passage 30 is connected to a pilot passage switching valve a, which will be described later.

Further, inside the main spool 21, a through hole 31 is formed which is separated from the damper chambers 22 and 23. Furthermore, in this main spool 21,
A first communication port 32 and a second communication port 33 are formed, and each of these communication ports 32 and 33 is connected to the above-mentioned through hole 31. A check valve 34 is provided in the passage hole 31 to permit flow only from the second communication port 33 to the first communication port 32.

When the main spool 21 constructed as described above is in the illustrated state, the control throttle 35 formed on its outer periphery is closed, and the spring 24 is closed.
When it moves against the above, the control diaphragm 35 opens according to the amount of movement.

The pilot flow path switching valve a has a spool 37 built into its main body 36, and one end of the valve a is connected to a push rod 39 of a solenoid 38.
I am facing it.

When the solenoid 38 is in a non-energized state, the spool 37 is held at the neutral position shown in the figure by the action of the spring 40. In this neutral position, the pilot passage 41 and the passage 30 communicating with the flow passage 29 communicate with each other. The pilot passage 41 communicates with a passage 43 connecting the directional control valve 19 and the rod side chamber 20 of the cylinder 17.

Furthermore, when the solenoid 38 is energized, the spool 37 moves against the spring 40, cutting off communication between the pilot passage 41 and the passage 30, and also communicating the passage 42 communicating with the first port 15 with the passage 30. let

Therefore, unless the solenoid 38 is energized, the spool 37 will maintain the neutral position shown.

When the solenoid 38 is de-energized and the directional control valve 19 is switched to the left side position in the drawing, the oil discharged from the pump 44 passes through the second port 16 → second communication port 33 → through hole 31 to the check valve. 3
4 is pushed open and flows into the bottom side chamber 18 of the cylinder 17 through the first communication port 32 and the first port 15.

On the other hand, the return oil in the rod side chamber 20 passes through the directional control valve 19 and returns to the tank 41 as it is.

Therefore, when the solenoid 38 is maintained in a de-energized state and the directional control valve 19 is switched to the left position, the cylinder 17 is expanded and becomes in a free flow state in which the load W is increased.

Furthermore, when the directional control valve 19 is switched to the right side position in the drawing with the solenoid 38 in a de-energized state, the oil discharged from the pump 44 flows directly into the rod side chamber 20, and the pilot passage 41→pilot passage switching valve a→passage. 30→Flows into both damper chambers 22, 23 via flow path 29, and maintains the insides of both damper chambers 22, 23 at the same pressure.

When the pressure in both damper chambers becomes the same, the main spool 21 moves against the spring 24 because the pressure-receiving area of the main spool 21 in the damper chamber is in the relationship D ₁ >D ₂ as described above.

When the main spool 21 moves as described above, the control throttle 35 opens in proportion to the amount of movement, in other words, in proportion to the pilot pressure. Since the control aperture 35 opens in this way, the bottom side chamber 18
The return oil is sent to the tank 41 via the first port 15 → control throttle 35 → opening between the stopper 25 and the seat part 26 → second port 16 → directional control valve 19.
Return to

Therefore, when the directional control valve 19 is switched to the right position shown in the figure, the cylinder 17 contracts to lower the load W, but a counterflow state is created in which the control throttle 35 functions.

Also, when the solenoid is energized, the spool 37
moves against the spring 40, blocks the pilot passage 41, and connects the passage 30 and the passage 4.
2 and communicate with each other.

When the directional control valve 19 is switched to the right position as shown in the figure in this state, the oil discharged from the pump 44 flows into the rod side chamber 20, and the return oil in the bottom side chamber 18 flows from the first port 15 to the passage 42 to the pilot flow. It flows into both damper chambers 22 and 23 via the path switching valve a → passage 30 → flow passage 29.

Since the counter load pressure that has flowed into the damper chambers 22, 23 as described above is higher than the above-mentioned pilot pressure, the main spool 21 is fully opened due to the high counter load pressure.

If the main spool 21 remains fully open,
There is less resistance to the return flow from the bottom side chamber 18, and energy loss is correspondingly reduced.

Note that when the directional control valve 19 is switched to the left position with the solenoid 38 energized, the same effect as described above occurs when the solenoid 38 is de-energized.

Therefore, when the solenoid 38 is de-energized, the counterbalance valve functions exactly as a counterbalance valve, but when the solenoid 38 is energized, the counterbalance valve function is canceled. It turns out.

(Structure of the present invention) In this invention, the main spool moves according to the pressure in the passage connecting the hydraulic source and the cylinder, and the opening area of the control throttle is determined in proportion to the amount of movement of the main spool. This method is based on a counterbalance valve that controls counterflow by .

Based on the above counterbalance valve,
This idea allows both ends of the main spool to face the damper chamber, communicates the two damper chambers with each other, and makes the pressure receiving area of the main spool different in the damper chamber. A thrust force is obtained, and a flow path is provided to communicate these damper chambers with the passage, and a pilot flow path switching valve for switching the flow path is provided in this flow path,
This pilot flow path switching valve is characterized in that it is configured to guide the load pressure of the cylinder to the damper chamber and cancel its function as a counterbalance valve only when the solenoid is energized.

With the above configuration, the function as a counterbalance valve will not be canceled unless the solenoid of the pilot flow path switching valve is energized.

(Effects of the Present Invention) With the above configuration, when this counterbalance valve is used in a power shovel, for example, remote control becomes possible for switching between the power shovel mode and the crane mode.

Moreover, when the solenoid is in a de-energized state, it functions as a counterbalance valve.
Unless the solenoid is consciously energized, its function as a counterbalance valve will not be released, making it safer than conventional valves.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a sectional view showing an embodiment of this invention. 21... Main spool, 22, 23... Damper chamber, 27, 28... Damper orifice, 35...
...Control throttle, a...Pilot flow path switching valve,
38...Solenoid.

Claims (1)

[Scope of utility model registration request] The main spool moves according to the pressure in the passage connecting the hydraulic source and the cylinder, and the opening area of the control throttle is determined in proportion to the amount of movement of the main spool, and the control throttle controls the counterflow. In the counterbalance valve, both ends of the main spool are faced to the damper chamber, and
These damper chambers are made to communicate with each other, and the pressure receiving areas of the main spools in the damper chambers are made different, so that the thrust of the main spool is obtained by the difference in the pressure receiving areas, and furthermore, these damper chambers are made to communicate with the above passage. A flow path is provided, and a pilot flow path switching valve for switching the flow path is provided in this flow path, and the pilot flow path switching valve only operates when the solenoid is excited.
A counterbalance valve configured to guide the load pressure of the cylinder to the damper chamber and cancel its function as a counterbalance valve.