JPH0241646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to variations in the discharge fluid pressure of a pressure fluid source;
Alternatively, the present invention relates to a flow control device equipped with a pressure compensating valve that operates in response to fluctuations in the load acting on an actuator and always compensates for a fluid pressure difference between upstream and downstream sides of a directional switching valve to a constant pressure.

Conventionally, this type of flow control device was developed by
It is proposed to be disclosed in Publication No. 47-28839. As shown in FIG. 2, this consists of a directional control valve 4 equipped with a spool 3 forming a restriction δ2 between an inlet 1 and an outlet 2a or 2b, and a directional control valve 4 provided with a spool 3 on the discharge side of a pressure fluid source 5. a pressure chamber 7 connected to the inflow port 1; a spring chamber 10 connected to the outflow port 2a or 2b and having a spring 9; A control spool 1 in which a pressing force obtained by adding a pressing force of
1 and a pressure compensating valve 13.
In addition, 12 is a cylinder, and its cylinder chamber 1
2a, 12b are the outlet ports 2a, 12b of the directional control valve 4;
2b, and a load W acts on the rod 12c. Further, 2c and 2c' are discharge ports connected to the outlet ports 2a and 2b, respectively, by a spool 3, and are connected to the tank 6. 8 is a shuttle valve that connects the high pressure side of the cylinder 12 to the inside of the spring chamber 10 of the pressure compensation valve 13.

In the conventional flow rate control device having this configuration, first, when the directional control valve 4 is in the state shown in the figure (neutral position), the pressure fluid discharged from the pressure fluid source 5 is discharged when the inlet 1 of the directional control valve 4 is closed. Therefore, the fluid flows into the pressure chamber 7 of the pressure compensating valve 13 and increases the fluid pressure within the pressure chamber 7. Then, the control spool 11 applies the pressure of the spring 9 to the pressing force due to the fluid pressure in the pressure chamber 7 and the fluid pressure in the cylinder chamber 12b (load pressure of the load W) acting on the spring chamber 10 via the shuttle valve 8. It moves to the position indicated by the broken line in the figure where the applied pressing force is balanced, and the left shoulder part 14a of the large diameter part 14 forms a restriction δ1 to discharge the discharged pressurized fluid from the pressurized fluid source 5 to the tank 6, The fluid pressure on the upstream side of the directional switching valve 4 is compensated to be higher than the load pressure of the load W by the fluid pressure corresponding to the pressing force of the spring 9.

Next, when the spool 3 of the directional control valve 4 is operated to the left in the figure and moved to the position shown by the broken line in the figure, the right shoulder part 15b of the large diameter part 15 is connected to the inlet 1 and the outlet 2.
A throttle δ2 is formed between the outlet 2a and the outlet 2C, and the outlet 2a and the outlet 2C are connected. Then, the discharged pressure fluid from the pressure fluid source 5 flows into the cylinder chamber 12b of the cylinder 12 through the pressure compensation valve 13, the inlet 1 of the directional control valve 4, the throttle δ2, and the outlet 2b. 13 compensates for the fluid pressure on the upstream side of the directional control valve 4 to be higher than the load pressure of the load W by the fluid pressure corresponding to the pressing force of the spring 9, that is, the throttle δ2
In order to compensate for the fluid pressure on the upstream side of , which is higher than the fluid pressure on the downstream side (load pressure of the load W) by the fluid pressure corresponding to the pressing force of the spring 9,
Pressure fluid flows into the cylinder chamber 12b of the cylinder 12 at a flow rate corresponding to the opening area of the throttle δ2, and the cylinder 12 moves the load W to the left in the figure at a speed corresponding to the flow rate.

However, in this flow control device,
When the cylinder 12 is operated to collect speed, if the directional control valve 4 is operated to make the opening area of the throttle δ2 very small, a flow rate corresponding to the opening area cannot be obtained due to the flow resistance of the throttle δ2. However, there is a drawback that the operating speed of the cylinder 12 cannot be arbitrarily controlled. This applies to construction machinery, etc., for example.
When a heavy object suspended by a crane is moved up and down by a small distance, the problem arises that the positioning accuracy of the heavy object deteriorates.

The present invention solves the above problems,
The purpose of this invention is to arbitrarily control the speed of an actuator that operates at a very low speed without being affected by a restriction formed in a directional switching valve.

In order to achieve the above object, the present invention provides a pressure compensating valve with an internal passage that is always connected to the inlet of the directional control valve, and connects one end of the internal passage to the pressure chamber and the other end that connects the spring chamber. The actuator is connected to the spring chamber through a forward direction check valve and a fixed throttle, and the actuator and the With this configuration, when the directional control valve is operated, a part of the pressure fluid discharged from the pressure fluid source is transferred to the internal passage of the control spool of the pressure compensation valve. A bypass supply is supplied to the actuator via a check valve, a fixed throttle, and a spring chamber, and the flow rate supplied to the actuator is fixed by using the fluid pressure difference before and after the fixed throttle as a fluid pressure value corresponding to the pressing force of a spring provided in the spring chamber. The value corresponds to the aperture area of the diaphragm.

The present invention has the following unique effects due to the above-described structure.

The object of the present invention is to increase the number of notches formed in the lands of the spool 3 to the configuration of the prior art (FIG. 2) to reduce the rate of change in the opening area of the aperture δ2. The speed of the slow operation of the cylinder 12 can be arbitrarily controlled within an operation range that is not affected by the flow resistance of the cylinder 12, and the positional accuracy of the load W is improved. However, this configuration has the drawback that since the distance between the notches is long, the land width of the spool 3 must be made long, and the operating range of the directional control valve 4 becomes large, leading to an increase in the size of the valve body.

The present invention provides a pressure compensating valve with an internal passage that is always connected to an inlet of a directional switching valve, and has one end of the internal passage connected to a pressure chamber, and the other end of the internal passage as a check valve whose forward direction is in the direction of the spring chamber. , and the spring chamber of the pressure compensating valve before forming the throttle which can obtain a flow rate corresponding to at least the opening area when the directional control valve is operated. Because the configuration connects
Bypassing the pressure fluid to the actuator via the internal passage of the control spool of the pressure compensating valve, the check valve, the fixed throttle and the spring chamber before the discharge pressure fluid of the pressure fluid source flows through the throttle of the directional valve. This allows effective use of the operating range of the directional control valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the flow rate control device is provided between a supply body 18 to which the pressure fluid source 5 is connected, a discharge body 19 to which the tank 6 is connected, and the supply body 18 and the discharge body 19. It is composed of a pressure compensation valve 2 and a directional switching valve 21.

The pressure compensating valve 20 has a valve body 22 that is connected to the pressure fluid source 5 via the supply body 18 on the upstream side and to the tank 6 via the inlet 23 of the directional control valve 21 on the downstream side, A control spool 26 is slidably fitted into the valve body 22. A pressure chamber 24 and a spring chamber 40 provided with a spring 25 are formed at both ends of the control spool 26, and the pressing force due to the fluid pressure in the pressure chamber 24 and the pressing force on the spring chamber 40 side are opposed to each other. The control spool 26 is moved in the left and right directions in the figure. The control spool 26 has an inflow hole 23 of the directional control valve 21,
A check valve 28 that is always connected through the hole 26a, one end of which is connected to the pressure chamber 24, and the other end of which is directed toward the spring chamber 40, and a fixed throttle 29.
An internal passage 30 is provided which connects the spring chamber 40 to the passage 31 of the directional control valve 21.
Connect to. The control spool 26 is also provided with a large diameter portion 27 having a shoulder 27b, which forms a restriction δ1 between the pressure fluid source 5 and the tank 6.

The directional switching valve 21 has a passage 33 connecting its inlet 23 to the tank 6 via the discharge body 19;
It has a valve body 36 that includes an outlet 34a, 34b connected to the actuator 32 to which the load W is connected, an outlet 35a, 35b connected to the tank 6, and a passage 31. ，
A spool 37 provided with large diameter portions 38 and 39 having a diameter of 39b is slidably fitted therein.

Thus, when spool 37 is in the neutral position of FIG. 1, it connects inlet 23 to passage 33 and
When the outflow ports 34a and 34b are closed and the operation is performed in the right direction in the figure, the space between the inflow port 23 and the passage 33 is closed, the outflow port 34a and the discharge port 35a are connected, and the outflow port 34b and the passage 31 are closed. Connect with. At this time, the left shoulder portion 38a of the large diameter portion 38 provided on the spool 37 is inserted between the inflow port 23 and the passage 31 with a restriction δ2.
However, before that, the outlet 34b and the passage 31 are connected to each other.

Further, when the spool 37 is operated to the left in the drawing, the space between the inlet 23 and the passage 33 is closed, the outlet 34b and the outlet 35b are connected, and the outlet 34a and the passage 31 are connected. At this time,
Right shoulder portion 39b of large diameter portion 39 provided on spool 37
forms a restriction δ'2 between the inlet 23 and the passage 31, but as before, the outlet 34
a and the passage 31 are connected to each other.

The operation of the embodiment of the present invention having the above-mentioned configuration will be explained.

First, when the spool 37 of the directional control valve 21 is in the neutral position shown in FIG. The liquid is discharged into the tank 6 via the passage 33 and the discharge body 19, and the actuator 32 is in a stopped state.

Now, operate the spool 37 of the directional control valve 21 to the left in the figure to close the space between the inlet 23 and the passage 31 without forming the restriction δ'2, and at the same time close the space between the inlet 23 and the passage 31.
When a and the passage 31 are connected, and the outlet 34b and the outlet 35b are connected, the fluid pressure in the inlet 23 increases because the inlet 23 and the passage 33 are closed, and the fluid pressure in the inlet 23 increases. The pressure fluid flows through the hole 26a of the control spool 26 of the pressure compensation valve 20, the internal passage 30, the check valve 28, the fixed throttle 29, the spring chamber 40,
It flows into the actuator 32 through the outlet 34a. Then, the pressure fluid passing through the fixed throttle 29 creates a fluid pressure difference between the upstream side and the downstream side of the fixed throttle 29, and the fluid pressure on the upstream side is applied to the pressure chamber 24 through the internal passage 30. However, the fluid pressure on the downstream side acts on the spring chamber 40. Therefore, the pressing force obtained by adding the pressing force of the spring 25 to the pressing force due to the fluid pressure in the spring chamber 40 and the pressing force due to the fluid pressure in the pressure chamber 24 act on the control spool 26 in opposition, and the control spool 26 to the left in the figure, the shoulder 27b of the large diameter portion 27 is connected to the pressure fluid source 5.
A control spool 26 is configured to form a restriction δ1 between the pressure fluid source 5 and the tank 6, and discharge the discharged pressure fluid from the pressure fluid source 5 into the tank 6 so that the fluid pressures in the spring chamber 40 and the pressure chamber 34 are the same. balance. Therefore, the fluid pressure in the inlet 23 is compensated to be higher than the load pressure of the actuator 32 on which the load W acts by the fluid pressure value corresponding to the pressing force of the spring 25. Pressure fluid flows through hole 2
The actuator 32 is supplied with a flow rate corresponding to the opening area of the internal passage 30 and the fixed throttle 29, and the actuator 32 can be started in the direction of arrow A in the figure at a speed corresponding to the flow rate.

Furthermore, when the spool 37 of the directional control valve 21 is operated to the left in the figure to form a restriction δ'2 between the inlet 23 and the passage 31, the pressure fluid in the inlet 23 is caused to flow through the restriction δ'2, Since it flows into the actuator 32 through the passage 31 and the outlet 34a, the speed of the actuator 32 can be controlled in response to the operation of the directional switching valve 21.

In this embodiment, the actuator 32 and the spring chamber 40 of the pressure compensation valve 20 are connected before connecting the inlet 23 of the directional control valve 21 and the passage 31, but the present invention , the actuator 32 and the spring chamber 40 are connected before the throttle δ'2 formed between the inlet 23 and the passage 31 becomes large enough to obtain a flow rate corresponding to its opening area. Therefore, any state may be used before that, so for example, at the same time as connecting the inlet 23 and the passage 31 in the form of a simple micro passage, or after connecting the inlet 23 and the passage 31. , the actuator 32 and the spring chamber 40 may be connected, and the present invention is not limited to this embodiment.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram including a sectional view of a flow rate control device with a pressure compensation valve according to an embodiment of the present invention, and FIG. 2 is a circuit diagram including a sectional view of a conventional flow rate control device with a pressure compensation valve. 5... Pressure fluid source, 6... Tank, [24...
Pressure chamber, 25... spring, 26... control spool,
28... Check valve, 29... Fixed throttle, 30... Internal passage, 40... Spring chamber, δ1... Throttle, 23...
...Inflow port] 20...Pressure compensation valve, [34a, 34
b... Outlet, 37... Spool, δ2, δ'2...
... Throttle] 21 ... Directional switching valve.

Claims (1)

[Claims] 1. A directional control valve including an inlet to which a pressure fluid source is connected, an outlet to which an actuator is connected, a spool that forms a restriction between the outlet and the inlet, and a pressure fluid source. a pressure chamber provided between the fluid source and the directional control valve and connected to the inflow port; a spring chamber connected to the outflow port and having a spring; a pressure compensating valve comprising a control spool on which the applied pushing force and the pushing force due to the fluid pressure in the pressure chamber act against each other and form a restriction between the pressure fluid source and the tank; In the flow control device with a valve, the pressure compensating valve is provided with an internal passage that is always connected to the inflow port of the directional switching valve, one end of this internal passage is connected to the pressure chamber, and the other end is configured such that the spring chamber direction is the forward direction. The directional control valve is connected to the spring chamber through a check valve and a fixed throttle, and when the spool is operated, the actuator and pressure are A flow control device with a pressure compensation valve configured to be connected to the spring chamber of the compensation valve.