JPH0425522Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in electro-hydraulic flow control valves used in industrial hydraulic equipment.

(Prior art) As such a conventional control valve, for example, the
There is a utility model disclosed in Japanese Patent No. 24972, which describes the first part of the claimed utility model, that is, the non-characteristic part (excluding the check valve 30 in FIGS. 1 and 2 of the present application). This product was greatly improved compared to previous products, but when the pressure at the outlet port 17 became higher than the pressure at the inlet port 12, the third port of the three-way servo valve 19 was removed from the oil line 16. Pressure oil flows back to 29, moves the spool 3 to the left in the diagram, and closes the control spool 2 of the throttle part 18, so the desired control spool cannot be opened regardless of the differential pressure before and after the throttle part 18. There was a problem in that it became impossible to send a controlled flow rate from the inlet port to the outlet port.

(Problems to be solved by the invention) The purpose of the invention is to solve the above-mentioned problems of the control valve disclosed in Japanese Patent Publication No. 57-24972. The electro-hydraulic flow rate is such that the closing operation of 2 can be prevented, and therefore a desired opening degree of the control spool can be obtained regardless of the differential pressure before and after the throttle part, and a controlled flow rate can be sent from the inlet port to the outlet port. The purpose of this invention is to provide a control valve.

(Means for Solving the Problems) Therefore, the present invention solves the above-mentioned problems by providing an electro-hydraulic flow control valve as claimed in the claims of the utility model registration.

(Embodiment) An embodiment of the present invention will be described below based on the drawings. In the position shown in FIG. 1, the valve is closed in the neutral position, and the force motor 24 is in a position where no current is applied. . The electro-hydraulic flow control valve of the present invention is composed of a force motor 24, a pressure compensator 1, a throttle section 18, and a three-way servo valve 19.

The throttle part 18 is internally installed in a control spool 2 having two lands and a connecting part, first and second oil chambers 15B and 15A partitioned by both end surfaces of the control spool 2, and a second oil chamber 15A. The oil passage 26 communicates the first oil chamber 15B with the inlet port 12, the inlet port 12, and the outlet port 17. Movement of the control spool 2 controls the amount of oil flowing from the inlet port 12 to the outlet port 17.

The pressure compensator 1 is placed in front of the throttle section 18, is connected to both the inlet port 12 and the outlet port 17, and has the function of keeping the differential pressure between the inlet port 12 and the outlet port 17 constant. The force motor 24 also includes an input wire 10, a coil 6, a rod 9, a single core 27, a zero point adjustment screw 7, and a zero point adjustment spring 8. The core 27 of the force motor 24 moves a predetermined amount left and right in proportion to the polarity and magnitude of the input current from the input wire 10.

The three-way servo valve 19 includes a spool 3 having three lands and a connecting portion, and a throttle 21 of the inlet port 12.
The first port 28 opens the oil passage 20 that communicates with the second oil chamber 15A of the throttle part 18, the second port 14 opens the oil passage 22 that communicates with the second oil chamber 15A of the throttle part 18, and the outlet port 17 and the throttle 23 and A third port 29 where the oil passage 16 communicates via the check valve 30 opens, a feedback spring 5 that biases the left end of the spool 3 toward the right, and a left end of the spring 5 and the right end of the control spool. It consists of a feedback pin 4 that is directly connected. Check valve 30 is throttle 2
3 to the third port 29. The three-way servo valve 19 is a zero-lap valve, that is, the central land 13 of the spool 3 is zero-lap, closing the second port 14, and when the spool 3 moves to the left or right, the second port 14 closes the first or third port. It communicates with ports 28 and 29. The zero point adjustment spring 8 and the zero point adjustment screw 7 are used to correctly set the zero lap.

Next, to explain the operating state, when there is no input current to the force motor 24, the control spool 2 is pushed by the spring 25 and closes the inlet port 12 as shown in FIG. 1, and oil flows before and after the throttle part 18. Not yet. The three-way servo valve 19 is also closed at zero wrap.

For example, if there is an input current to the force motor 24 and the plunger 27 moves to the left as shown by the arrow, it will be in the position shown in FIG. 2, and the rod 9 will push the right end of the spool 3 of the three-way servo valve 19 to the left. , the spool 3 is moved to the left against the feedback spring 5, so that the second port 14 and the third port 29 communicate with each other. In this case, the first oil chamber 15B of the control spool 2 communicates with the inlet port 12 through the oil passage 26, so the pressure is high, and the second oil chamber 15A communicates with the inlet port 12 through the oil passage 22 between the second and third ports 14. , 29, and the oil passage 16 via the throttle 23 and check valve 30, the pressure in the oil passage 16 is reduced by the differential pressure of the pressure compensator 1, that is, the pressure reduction due to the throttling action of the throttle part 18. Since the pressure in the oil chamber 15A is low, the pressure oil in the oil chamber 15A passes through the oil passage 22 and the three-way servo valve 19, then through the oil passage 16, then through the check valve 30 and the throttle, as shown by the arrow.
The control spool 2 is guided to the OUT side and moves to the right.

Thus, the inlet port 12 is opened and pressure oil flows to the outlet port 17, that is, from the IN side to the OUT side.
At this time, at the same time, the feedback pin 4 is activated by the opening degree X of the control spool, and the feedback spring 5 is
, a force Kx proportional to the opening x is generated on the left end face of the three-way servo valve, which is balanced with the force f of the force motor pushing rightward (f =
Kx), the control spool 2 is pushed back in the opposite direction and the control spool is positioned in this balance position. In this way, the opening degree x of the control spool 2 is obtained that is proportional to the force of the force motor, and the flow rate from the inlet port 12 to the outlet port 17 is controlled in proportion to the magnitude of the input current.

In this second illustrated state, for example, the outlet port 17,
The cylinder (not shown) connected to OUT reaches the end of its stroke, and a relief valve (not shown) placed in front of the IN port of the main valve causes the valve to OUT.
When controlling the side pressure to reduce the pressure on the side, the pressure at the IN port of this valve, and thus the inlet port 12, becomes lower than the pressure at the OUT side outlet port 17. however
The pressure oil in the OUT side outlet port 17 passes through the throttle 23 and is transmitted to the check valve 30, but the check valve 30 prevents the pressure oil from going beyond that, so the valve OUT side outlet port 17 is in the second oil chamber 15A. The pressure oil will not work. IN port i.e. inlet port 1
2 pressure drop occurs in the first oil chamber 1 of the control spool 2.
5B, the control spool 2 attempts to move in the direction of closing the opening, but the second oil chamber 15A is maintained in a state where no pressure oil enters or exits.
Due to the slight movement of the control spool 2, the pressure inside the oil chamber 15A becomes zero. That is, even when the pressure drops, the pressure inside the first oil chamber 15B acting on the control spool 2 is higher than the pressure inside the second oil chamber 15A, and therefore the control spool 2 maintains an opening proportional to the input current. As a result, the pressure oil on the OUT side escapes to IN OUT via the inlet port 12.

(Effects of the invention) As explained above, according to the invention, by simply inserting the small check valve 30 into the pilot oil passage 16, no other additional valve device is required.
Even if the pressure at the outlet port is higher than the pressure at the inlet port, the closing operation of the control spool 2 can be prevented,
Therefore, the electro-hydraulic flow control valve is capable of obtaining a desired opening degree of the control spool and sending a controlled flow rate from the inlet port to the outlet port regardless of the differential pressure before and after the constriction part.

[Brief explanation of the drawing]

Figure 1 is a hydraulic circuit diagram of an embodiment of the present invention in which the valve is in a neutral position, and Figure 2 shows the hydraulic pressure in which the valve in Figure 1 is in a position where the control spool is moved to the right by the input current of the force motor. It is a circuit diagram. DESCRIPTION OF SYMBOLS 1... Pressure compensator, 2... Control spool, 3... Spool, 4... Feedback pin, 5... Feedback spring, 9... Rod, 12... Inlet port, 14... Second Port, 15A...second oil chamber, 15B...first oil chamber, 17...outlet port, 18...throttle section, 19
...Three-way servo valve, 24...Force motor,
25... Spring, 28... First port, 2
9...Third port, 30...Check valve.

Claims (1)

[Scope of utility model registration request] It consists of a pressure compensator, a constriction, a three-way servo valve and a force motor arranged sequentially in line with the constriction; the constriction includes a control spool having two lands and a connection, a first and a second oil chamber, an inlet port and an outlet port, a communication oil passage between the first oil chamber and the inlet port, and a spring that presses a control spool in the second oil chamber to bias the inlet port in a direction. the pressure compensator is placed in front of the inlet port of the throttle section and is connected to the inlet port and the outlet port, respectively, to keep the differential pressure between the two ports constant; The directional servo valve includes a spool having three lands and a connecting part, a first port communicating with an inlet port of the throttle part via the throttle, and a second port communicating with a second oil chamber of the throttle part.
a zero-lap three-way servo valve having a third port in communication with an outlet port of the throttle section through the throttle, and a feedback spring in contact with one end of a spool; The control spool of the throttling section and the feedback spring of the three-way servo valve are connected by a feedback pin for control. An electro-hydraulic flow control valve in which axial movement of the spool is returned to the spool of the three-way servo valve via a feedback pin and a feedback spring; A flow from the throttle to the third port is provided between the throttle and the third port of an oil passage that communicates with the third port of the directional servo valve via the throttle. An electro-hydraulic flow control valve characterized by providing non-returning through a check valve.