JPH0425523Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pilot type electro-pneumatic proportional valve that is driven by a pilot valve that outputs a fluid pressure determined by the amount of current applied to a solenoid.

[Prior Art] The inventors of the present invention first developed a direct-acting electro-pneumatic proportional valve in which a valve member is directly driven by a proportional solenoid in which the attraction force between iron cores is proportional to the amount of current supplied to the solenoid. (For an example, see Japanese Patent Application No. 179613/1983).

The previously proposed direct-acting electro-pneumatic proportional valve can make the maximum output pressure of the output port equal to the primary pressure _P1 of the supply port, but in the pilot-type electro-pneumatic proportional valve, the pilot fluid pressure can be made equal to the primary pressure. Even if it is equal to P ₁ , the maximum output pressure of the output port is equal to Assuming that is As, it becomes P ₁ −fk/As, so there is a problem that the maximum output pressure of the output port is smaller than the primary pressure P ₁ .

In order to solve this problem, it is conceivable to install a spring in the pilot chamber that opposes the above-mentioned return spring to relatively reduce the biasing force of the return spring acting on the valve member. If a spring is installed in the valve, a new problem arises in that due to manufacturing errors in the spring, the stopping position of the valve member becomes unstable when the proportional solenoid is de-energized, in other words when pilot fluid is not being supplied to the main valve. occurs.

[Problems to be solved by the invention] The invention uses the first set spring provided in the pilot chamber of the main valve to bring the maximum output pressure of the output port as close as possible to the primary pressure, and also to The problem to be solved is to reliably displace the valve member to a predetermined position when the valve member is not energized by means of the provided centering bush.

[Means for Solving the Problems] The present invention provides a valve main body having a supply port, first and second output ports, and first and second discharge ports in both directions around a neutral position. a valve member that communicates flow paths between one of the supply port and the output port and between the other output port and the discharge port through displacement, and a pilot chamber at one end of the valve member;
A pilot type valve comprising a main valve having a feedback chamber communicating with a first output port at the other end of the valve member, and a pilot valve for supplying and discharging pilot fluid to and from the pilot chamber, wherein the valve member is connected to the pilot chamber. a centering bush that is disposed in the feedback chamber and has a locking portion that locks with the valve body on the valve member side and is movable in the direction of displacement of the valve member; A second set spring is provided for biasing the centering bush to a centering position where the locking portion is locked to the valve body, and the biasing force of the second set spring is made larger than the biasing force of the first set spring; The valve member is configured to communicate the flow path between the supply port and the second output port and between the first output port and the first discharge port when the valve member is in contact with the centering bush at the centering position. The pilot valve is configured to be driven by a proportional solenoid in which the suction force acting between the iron cores is proportional to the amount of current applied to the solenoid, and to output a fluid pressure determined by the amount of current applied to the solenoid. Therefore, the above problem is solved.

[Operation] When the proportional solenoid is de-energized, pilot fluid is not output from the pilot valve, so the centering bush is moved to the centering position where the locking part locks on the valve body by the biasing force of the second set spring. The valve member is brought into contact with the centering bushing in the centering position by the biasing force of the first set spring, and thereby the supply port and the second output port and the first output port and the first discharge port of the valve body are connected. The flow paths between the ports are in communication.

In this case, since the biasing force of the first set spring is smaller than the biasing force of the second set spring,
The centering bush and valve member remain in the position described above.

When the proportional solenoid is energized, pilot fluid having a fluid pressure determined by the amount of energization to the solenoid is supplied from the pilot valve to the pilot chamber of the main valve, and the operating force of the pilot fluid pressure acting on the valve member and the first set are Due to the sum of the biasing force of the spring, the valve member is displaced toward the feedback chamber together with the centering bush against the biasing force of the second set spring, so that the flow path between the second output port and the second discharge port is closed. The flow path between the supply port and the first output port communicates with each other, and the pressure fluid from the supply port flows out to the first output port and also flows into the feedback chamber.

As the fluid pressure in the first output port increases, the fluid pressure in the feedback chamber increases, and the sum of the acting force of the fluid pressure in the feedback chamber and the biasing force of the second set spring is the operating force of the pilot fluid pressure and the first set spring. When the biasing force of the set spring becomes equal to the sum of the biasing forces of the set spring, the valve member is displaced to the neutral position, so the secondary pressure of the first output port is changed from the pilot fluid pressure determined by the amount of current to the proportional solenoid to the second and first
The value becomes smaller by the pressure based on the difference in the biasing forces of the set springs.

Therefore, the maximum output pressure of the first port can be brought as close as possible to the primary pressure.

When the power to the proportional solenoid is cut off, the pilot fluid is discharged to the outside, so that the valve member is connected to the supply port, the second output port, and the second set spring by the sum of the fluid pressure in the feedback chamber and the biasing force of the second set spring. The centering bush, which is displaced to a position where the flow path between the first output port and the first discharge port communicates with each other, and is displaced together with the valve member, stops at the centering position where the locking portion locks with the valve body.

Due to the displacement of the valve member, the fluid in the feedback chamber is discharged to the outside through the first output port and the first discharge port, so the fluid pressure in the feedback chamber decreases, and the acting force due to the feedback fluid pressure is reduced to the first output port. When the biasing force of the first set spring becomes smaller, the valve member comes into contact with the centering bush at the centering position, and the flow paths between the supply port and the second output port and between the first output port and the first discharge port are communicated. Return to original position.

Therefore, even if springs are installed at both ends of the valve member, when the proportional solenoid is de-energized,
The valve member can be reliably displaced to a predetermined position.

[Example] Figures 1 and 2 show an example of the present invention,
This electro-pneumatic proportional valve includes a main valve 1 and a pilot valve 2, and the main valve 1 is mounted on a sub-plate 3 via a feedback plate which will be described later.

The valve body 5 of the main valve 1 has a pressure fluid supply port P, first and second output ports A and B, and first and second discharge ports EA and EB. A sleeve 6 with an opening communicating with each port is installed inside the sleeve 6, and a flow path between the supply port P and the output ports A and B, and between the output ports A and B and the discharge ports EA and EB is provided inside the sleeve 6. A spool 7 for switching the flow path is slidably inserted.

The spool 7 has a flow path between the supply port P and the second output port B, a flow path between the first output port A and the first discharge port EA, and a second discharge port EB.
While the flow path between ports P and A and the flow path between ports B and EB are communicating and the flow path between ports P and A is communicating and port EA is being closed, the flow path between ports P and B and between ports A and EA is A position where the flow paths are both constricted and communicating, and a position where ports P and EB are closed and ports A and EA are connected.
There is a position where only the flow path between ports P and EA is closed and communicates in a throttled state, and a position where ports P and EA are closed and only the flow path between ports B and EB communicates in a throttled state (second
(see figure).

A spring seat 8 having a through hole in the center is fixed to one side of the sleeve 6 in the valve body 5 by an adapter plate 9, and a pilot chamber 10 is formed between the spool 7 and the adapter plate 9. A first set spring 11 is compressed in the pilot chamber 10. A spring seat 13 is fixed to the other side of the sleeve 6 by an end plate 14, and a centering bush 15 is disposed within the spring seat 13 so as to be displaceable in the axial direction of the spool. A locking portion 15a that is sequentially reduced in diameter and locks to the sleeve 6, and a contact portion 15b that the spool 7 contacts are formed.
The centering bush 15 and the spring seat 13
A second set spring 16 having a larger urging force than the first set spring 11 is compressed between the two, and a feedback chamber 17 formed between the spool 7 and the spring seat 13 is provided in the feedback plate 18. A feedback passage 19 communicates with the first output port A.

On the other hand, the pilot valve 2 attached to the adapter plate 9 is configured as an electromagnetic valve having a proportional solenoid 21 that outputs a driving force proportional to the amount of energization, and the pilot body 22 of the pilot valve is connected to the supply port P. a communicating input port 23;
It is provided with an output port 24 and a feedback port 25 that communicate with the pilot chamber 10, and a discharge port 26 that communicates with the outside through a passage (not shown). A pilot spool 27 which is switched to communicate with the outlet 26 is slidably provided. Above spool 2
7 is a main body 22 in which a feedback port 25 is opened;
A return spring 29 compressed within the pilot feedback chamber 28 is biased to abut against a movable core (not shown) of the proportional solenoid 21.

Note that the spool 7 of the above embodiment has a through hole 7a having a throttle formed in the axial direction, and the pilot chamber 10 and the feedback chamber 17 are communicated with each other through the through hole, thereby suppressing the oscillation of the spool 7. It is prevented.

The pilot valve 2 has a proportional solenoid 21 when the input port 23 is closed and the output port 24 and the discharge port 26 are in communication (see the left half of FIG. 1).
When the coil is energized, an attractive force proportional to the amount of current flowing through the coil acts between the iron cores, and when the attractive force becomes transiently larger than the biasing force of the return spring 29, the pilot spool 27 moves to the input port 2.
3 and the output port 24 communicate with each other, and the discharge port 26 is switched to the closed position (see the right half of Fig. 1), so that pilot fluid is supplied to the pilot chamber 10 of the main valve, and the pilot fluid is also supplied through the feedback port 25. It is also supplied to the feedback chamber 28.
As a result, the fluid pressure in the feedback chamber 28 increases, and when the sum of the fluid pressure in the feedback chamber 28 and the biasing force of the return spring 29 becomes greater than the suction force of the proportional solenoid 21, the spool 27
closes the input port 23 and opens the output port 24 and the discharge port 26.
Since the input port 23 and the output port 24 are switched to a position where they communicate with each other, the fluid pressure in the feedback chamber 28 decreases, and the input port 23 and the output port 24 communicate with each other.

In this way, when the suction force of the proportional solenoid 21, which is proportional to the amount of energization, becomes equal to the sum of the fluid pressure in the pilot feedback chamber 28 and the biasing force of the return spring 29, the pilot spool 2
7 stops at the position where the output port 24 is closed, so
The pilot valve 2 outputs a pilot fluid pressure proportional to the amount of current applied to the proportional solenoid 21 to the pilot chamber 10 of the main valve 1.

Next, the operation of the above embodiment will be explained with reference to FIG.

When the proportional solenoid 21 is de-energized, communication between the input port 23 and the output port 24 of the pilot valve 2 is cut off, so that no pilot fluid is output. In this state, the centering bush 15 provided in the feedback chamber 17 of the main valve 1 is in the centering position where the locking portion 15a locks on the sleeve 6 due to the biasing force of the second set spring 16, and the spool 7 , is centered by contacting the contact portion 15b of the centering bush 15 by the biasing force of the first set spring 11 provided in the pilot chamber 10, and the first set spring 11
Since the biasing force of the second set spring 16 is smaller than the biasing force of the second set spring 16, the spool 7 stops at this position, and in this state, the ports P and B and A and EA are connected to each other.
Both are connected in a constricted state (see Fig. 2A).

When the coil of the proportional solenoid 21 is energized, as described above, the pilot fluid having a fluid pressure proportional to the amount of energization to the coil is supplied from the pilot valve 2 to the pilot chamber 10, and the operating force of the pilot fluid pressure is transiently increased. F and first set spring 11
When the sum of the biasing forces fs becomes larger than the biasing force fk of the second set spring 16, the spool 7 is displaced to a position where ports P and A and B and EB communicate with each other (see FIG. 2B). In this case, when the operating force F of the pilot fluid pressure becomes larger than the difference fk - fs between the biasing forces between the second and first set springs, the spool 7 is displaced. will improve.

When the spool 7 is displaced to the state shown in FIG. When the force becomes larger than the operating force, the spool 7 is displaced in the opposite direction and the ports P, B and A
and EA communicate with each other (see Fig. 2 C), and the reaction force of the feedback chamber 17 decreases, so the spool 7 is reversed and the first output port A and the first discharge port EA communicate in a throttled state (see Fig. 2C). 2D), the rate of decrease in pressure in the feedback chamber 17 is reduced.

In this way, the pilot fluid pressure operating force F
The sum of the biasing force fs of the first set spring 11 is the acting force Fa of the fluid pressure in the feedback chamber 17 and the second set spring 11.
When the biasing force fk of the set spring 16 becomes equal to the sum, the supply port P and the first discharge port EA are cut off, and only the second output port B and the second discharge port EB are displaced to a position where they communicate in a constricted state (the first Figure 2 E
), thereby setting the output pressure of the first output port A. In this case, the feedback room 17
The reaction force of the first and second set springs 11,
16 biasing force difference fk-fs, set spring 1
This can be reduced by reducing the spring constants 1 and 16 and the displacement χ of the spool 7 shown in FIG. 2E.

Figure 3 shows an example of the relationship between the voltage applied to the proportional solenoid 21 and the fluid pressure at output ports A and B when the primary pressure P ₁ is 9.0 kg/cm ² . When the voltage reaches about 0.8V, communication between the supply port P and the second output port B is cut off, and when the applied voltage slightly exceeds 4V, the output pressure at the second output port A reaches the maximum of 8.5Kg/cm ² . The dotted line in Figure 3 is
This is the maximum output pressure of the first output port A when the spool is not centered.

[Effects of the invention] The present invention provides a first settling spring in the pilot chamber at one end of the valve member of the main valve, which biases the valve member toward the feedback chamber. Since the sum of the biasing forces of the set spring, the acting force of the fluid pressure in the feedback chamber, and the sum of the biasing forces of the second set spring are opposed, the maximum set pressure of the first output port in the pilot type electro-pneumatic proportional valve is can be brought as close to the primary pressure as possible.

Further, the feedback chamber includes a displaceable centering bush having a locking portion that locks onto the valve body on the valve member side, and the centering bush is attached to a centering position where the locking portion locks onto the valve body. a second set spring having a larger biasing force than the first set spring for biasing the first set spring;
When fluid pressure is not supplied to the pilot chamber, the valve member is brought into contact with the centering bushing in the centering position to center the valve member, and the supply port and the second output port and the first output port and the first discharge port are connected. Since the flow passages between the valve members are communicated with each other, the valve member can be reliably displaced to a predetermined position when not energized, even though springs are provided at both ends of the valve member.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a main part of an embodiment of the present invention, FIGS. 2A to 2E are explanatory diagrams of operating states, and FIG. 3 is a diagram showing the relationship between applied voltage and set output pressure. 1... Main valve, 2... Pilot valve, 5... Valve body, 7... Spool, 10... Pilot chamber, 1
1...First set spring, 15...Centering bush, 15a...Locking portion, 16...Second set spring, 17...Feedback chamber, 21...Proportional solenoid, P...Supply port, A ,B...output port, EA,EB...exhaust port.

Claims (1)

[Claims for Utility Model Registration] In a valve body having a supply port, first and second output ports, and first and second discharge ports, supply by displacement in both directions centering on a neutral position. A valve member that communicates the flow path between the port and one of the output ports and between the other output port and the discharge port, a pilot chamber at one end of the valve member, and a feedback chamber that communicates with the first output port at the other end of the valve member. and a pilot valve for supplying and discharging pilot fluid to and from the pilot chamber, wherein the pilot chamber is provided with a first set spring that biases the valve member toward the feedback chamber, The feedback chamber includes a centering bush which has a locking part that locks onto the valve body on the valve member side and is movable in the displacement direction of the valve member; A second set spring is provided to press the valve to the centering position where the valve member stops, and the biasing force of the second set spring is made larger than the biasing force of the first set spring, so that the valve member is brought into contact with the centering bush at the centering position. In this state, the supply port and the second output port and the first output port and the first discharge port are configured to communicate with each other, and the pilot valve is configured such that the suction force acting between the iron cores is connected to the solenoid. A pilot type electro-pneumatic proportional valve, characterized in that it is driven by a proportional solenoid that is proportional to the amount of current applied to the solenoid, and outputs a fluid pressure determined by the amount of current applied to the solenoid.