JPH0481643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pilot relay used in pneumatic instruments, positioners for control valves, and the like.

[Conventional technology]

In pneumatically operated control instruments and transducers, displacement is converted into pressure and amplified by the nozzle flapper mechanism, which is the first stage amplification element, and a pilot valve is used to amplify this pressure to an even greater pressure. be done. This type of pilot valve is roughly divided into bleed type and non-bleed type depending on whether the air is consumed continuously or discontinuously inside the pilot valve in the operating state. Gain is equal to the ratio of the effective areas of the two diaphragms. Figure 6 shows a conventional example of a non-bleed type pilot valve.
To explain this based on the same figure, 1 has 2 internal parts.
A housing partitioned into four chambers 5, 6, 7, 8 by two diaphragms 2, 3 and a partition wall 4, with chamber 5 connected to an air supply source (not shown) via an air supply passage 9. and a nozzle (not shown) to form an air supply chamber.
The lower part of the chamber 6 is formed to have a smaller diameter than the upper part, and the lower end small diameter part 10A of the piston valve 10, which also serves as a surface plate, is slidably inserted into this small diameter part via an O-ring 11, so that the two chambers, i.e. It is defined into an upper exhaust chamber 6A and a lower output chamber 6B. The air supply chamber 5 and the output chamber 6B communicate with each other through a communication hole 12 provided in the partition wall 4.

Reference numeral 13 designates a pilot valve that passes through the communication hole 12 so as to move forward and backward. This valve 13 is biased by a spring 14 in the closing direction, that is, upward in the figure, so that the lower valve body 13A provided at the lower end The upper valve element 13B, which is seated on the valve seat of the partition wall 4 and closes the communication hole 12, and which is provided at the upper end, is the piston valve 10.
Exhaust passage 15 formed in the lower end small diameter portion 10A of
The passage 15 is closed by being seated at the opening at the lower end of the passage 15. The exhaust passage 15 includes a blind hole 15A formed in the center of the lower end surface of the piston valve 10, and a lower end small diameter portion 1.
The blind hole 15 is formed through the circumferential surface of 0A in the radial direction.
A and a horizontal hole 15B that communicates with the exhaust chamber 6A, thereby allowing the exhaust chamber 6A and the output chamber 6B to communicate with each other. The exhaust chamber 6A communicates with the outside of the housing 1 through a vent hole 16, and is connected to the output chamber 6B.
is communicated with, for example, a valve operator (not shown) by an output air hole 17.

The chamber 7 forms a bias chamber, and the bias hole 1
A bias pressure P _B is given by 8. The chamber 8 forms a back pressure chamber by introducing the nozzle back pressure P _N through the nozzle back pressure hole 19 . The upper end of the piston valve 10 is held in common by the diaphragms 2 and 3, and the bias pressure is
It is urged upward by P _B.

The diaphragms 2 and 3 are connected to the housing 1
The diameter of the outer diameter support portions 2a, 3a supported by
R ₁ , R ₃ and the diameters R ₂ , R ₄ of the inner diameter support portions 2b, 3b supported by the piston valve 10 are different from each other, and the upper diaphragm partitions the bias chamber 7 and the back pressure chamber 8. 2 has a larger diameter (R ₁ >
R ₃ , R ₂ > R ₄ ).

When a pilot relay with such a configuration is used as a direct-acting type in which the output increases as the input increases, the downward force exerted by the nozzle back pressure P _N on the diaphragm 2 in the equilibrium state shown in the figure,
The upward forces acting on the diaphragm 3 due to the output pressure P _O are equal. At this time, the poppet valve 13 closes both the communication hole 12 and the lower end opening of the exhaust passage 15. When the nozzle back pressure P _N increases in this state, the equilibrium state of the forces acting on the diaphragms 2 and 3 is broken, so the diaphragm 2 is displaced downward and pushes the piston valve 10 downward. Therefore, the poppet valve 13 also descends against the spring 14 to open the communication hole 12. Therefore, the supply air pressure P _S flows into the output chamber 6B through the communication hole 12 and increases the pressure in the output chamber 6B until the vertical forces acting on the diaphragms 2 and 3 become equal. The pressure is supplied as output pressure P _O through the output air hole 17 to the operating device.

On the other hand, when the nozzle back pressure P _N decreases from this state, the piston valve 10 returns to its upward position due to the bias pressure P _B , and the poppet valve 13 rises due to the elastic force of the spring 14 . At this time, the upper valve body 13B of the poppet valve 13 is separated from the lower end opening of the exhaust passage 15, and the exhaust chamber 6A and the output chamber 6B are communicated via the passage 15, so that the pressure inside the output chamber 6B is
P _E is discharged to the outside of the housing 1 through the exhaust passage 15, the exhaust chamber 6A, and the vent hole 16 until an equilibrium state is reached.

In addition, when such a pilot relay is used as a reverse action type in which the output decreases as the input increases, the bias chamber 7 may be changed to a back pressure chamber, and the back pressure chamber 8 may be changed to a bias chamber.

[Problem to be solved by the invention]

By the way, in the conventional pilot valve as described above, when a large gain pilot relay with a large ratio of the effective areas of the two diaphragms 2 and 3 is used to configure a high gain pneumatic instrument, hunting (output (a phenomenon in which the pressure constantly changes up and down) occurs. In other words, when the ratio of the effective areas of diaphragms 2 and 3 is large, the nozzle back pressure
As P _N increases, the piston valve 10 is largely displaced,
Poppet valve 13 is opened rapidly. As a result, the supply air pressure P _S suddenly flows from the air supply chamber 5 through the communication hole 12 into the output chamber 6B, making the operations of the piston valve 10 and the poppet valve 13 unstable.
This causes hunting.

Therefore, in the past, a chamber with a fixed capacity was provided in the middle of the nozzle back pressure hole 19 to prevent the occurrence of hunting, but in such a configuration, the hunting 1 itself became large due to the fixed capacity, and the cost increased. There was a problem with the price being high.

Therefore, the present invention solves the above-mentioned problems and provides a pilot system that prevents the rapid operation of the valve by increasing the air damper effect of the bias chamber when the nozzle back pressure increases, thereby preventing hunting from occurring. The purpose is to provide a relay.

[Means to solve the problem]

The present invention has been made to achieve the above object, and a first aspect of the present invention is to provide a housing with a
A back pressure chamber and a bias chamber are provided which are defined by two diaphragms provided on both sides of the outer support portion, and nozzle back pressure is supplied to the back pressure chamber as input pressure, and the diaphragm is increased by this input pressure. A pilot relay that advances or retreats a valve means by displacement, thereby amplifying and outputting the input pressure,
Bias hole closing means is provided between the bias hole communicating with the bias chamber and the piston valve held by both of the diaphragms, which is closed by the operation of the piston valve and absorbs displacement of the diaphragm. It was established.

The second invention provides a back pressure chamber and a bias chamber defined by two diaphragms with a difference in both the inner and outer diameter support parts in the housing, and uses the nozzle back pressure as the input pressure. In a pilot relay that supplies back pressure to a back pressure chamber and moves the valve means forward and backward by displacement of the diaphragm due to this input pressure, thereby amplifying and outputting the input pressure, the piston valve supported by both the diaphragms is A flapper with a flexible ball is provided, and thereby the bias hole communicating with the bias chamber is controlled to open and close in accordance with the operation of the piston valve.

[Effect]

When the piston valve operates as the nozzle back pressure increases, the bias hole closing means in the first invention closes the bias hole, while the ball-equipped flapper closes the bias hole in the second invention. Therefore,
The internal pressure of the bias chamber increases as the volume of the bias chamber decreases, and it acts as an air damper.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

1A and 1B are enlarged views of section A in FIG. 2 showing an embodiment of the pilot relay according to the present invention, at equilibrium and when nozzle back pressure increases, and FIG. 2 is a sectional view of the same relay. Components and portions in the figure that are the same as those in FIG. 6 are designated by the same reference numerals, and their explanations will be omitted. In these figures, the present embodiment has a bias hole closing means 20 that is opened and closed in response to the operation of the piston 10 and absorbs the displacement of the diaphragm 2 between the bias hole 18 communicating with the bias chamber and the piston valve 10. The other structure is the same as the conventional structure shown in FIG. The bias hole closing means 20 includes a nozzle-shaped valve seat 2 provided with an open end of the bias hole 18.
1, and a flexible flapper 23 with a ball 22 provided on the lower surface of the distal end corresponding to the valve seat 21 and a proximal end fixed to the piston valve 10.

In such a configuration, when the nozzle back pressure P _N and the supply air pressure P _S are balanced and no amplification effect is performed, the bias pressure P _B is equal to the nozzle back pressure P _N
(P _B >P _N ), the ball 22 is spaced above the valve seat 21 and communicates with the bias chamber 7 and the bias hole 18, as shown in FIG. 1a.

Next, when the nozzle back pressure P _N becomes higher than the bias pressure P _B , the diaphragm 2 is displaced downward and the piston valve 10 and the poppet valve 13 are forced into the spring 14.
The ball 22 closes the valve seat 21 as shown in FIG. 1b. Then, the volume of the bias chamber 7 gradually decreases as the piston valve 10 descends, so that the internal pressure of the bias chamber 7 gradually increases and brakes the piston valve 10. That is, the lower the piston valve 10 is, the more the bias pressure trapped in the bias chamber 7 increases due to the decrease in volume, increasing the damping effect on the piston valve 10, and as a result, the piston valve 10 rapidly lowers. Without poppet valve 13
Since it operates slowly, stability is good and hunting can be prevented. In this case, the flapper 23 has flexibility and the piston valve 1
0, in other words, to absorb the displacement of the diaphragm 2, the valve seat 21 may be damaged or the ball 22
It doesn't overwhelm you.

On the other hand, from this state, the nozzle back pressure P _N decreases,
When the piston valve 10 rises, the internal pressure in the bias chamber 7 decreases, causing an overshoot, but due to feedback, the bias chamber 7 has the same effect as the increase in nozzle back pressure P _N when the piston valve 10 falls. will be fulfilled. Therefore, even at this time, the poppet valve 13 does not operate suddenly, and hunting can be prevented from occurring, and the nozzle back pressure hole 1
This eliminates the need for a fixed capacitor provided at 9.

FIGS. 3a and 3b are sectional views showing another embodiment of the bias hole closing means at equilibrium and when the nozzle back pressure increases. In this embodiment, a band-shaped body 25 made of a flexible material such as rubber is bent into a substantially square shape, one end of which is fixed to the lower surface of the peripheral edge of the piston valve 10, and the other end is attached to the opening end surface of the bias hole 18. The valve seat 21 is fixed to the other end thereof.
A bias hole 18 and a valve seat 2 are provided at the other end of the band-shaped body 25.
A small hole 26 is formed to communicate with the center hole of the piston valve 1, and in the equilibrium state shown in FIG.
0 is located above, and the strip body 25 is separated from the upper surface of the valve seat 21, so that the bias pressure P _B is applied to the small hole 26,
It flows into the bias chamber 7 through the valve seat 21. On the other hand, when the nozzle back pressure P _N increases and the piston valve 10 descends, the strip 25 deforms as shown in FIG. .

Therefore, this embodiment also provides the same effects as the above embodiments.

FIG. 4 is a sectional view showing still another embodiment of the bias hole closing means. In this embodiment, a flexible tube 3 made of rubber or the like is provided at the open end of the bias hole 18.
0, and an extension 31 that extends above the tube 30 and functions as a flapper is integrally provided on a part of the outer periphery of the piston valve 10, and these constitute a bias hole closing means 32. . In this case, as shown in FIG. 5, a flapper 33 may be provided on the lower surface of the peripheral edge of the piston valve 10, similar to the embodiment shown in FIG. Since the tube 30 is flexible, the flapper 33 does not need to be flexible and may be a rigid body.

In addition, in the above embodiments, the bias hole closing means for forming the nozzle flapper was explained.
The present invention is not limited to this, but a bellows is provided in place of the valve seat 21 or tube 30 described above, and the displacement of the piston valve 10, in other words, the diaphragm 2, is absorbed by the expansion and contraction of this bellows. Of course, it is possible. Furthermore, if the flappers 23 and 33 are flexible, the valve seat 21 or the tube 30 is not necessarily necessary, and it is possible to directly control the opening and closing of the bias hole 18.

〔Effect of the invention〕

As explained above, the pilot relay according to the present invention is provided with a bias hole closing means between the bias hole and the piston valve that controls opening and closing of the bias hole according to the operation of the piston valve, so that the nozzle back pressure increases. When the diaphragm is displaced and the bias hole closing means closes the bias hole, the internal pressure of the bias chamber increases and the air damping effect is enhanced.
Brake the sudden operation of the piston valve. Therefore, the poppet valve does not open suddenly and hunting can be prevented, and there is no need to provide a fixed capacity in the nozzle back pressure hole, making it possible to provide a small, stable, high-gain pilot relay.

[Brief explanation of drawings]

1A and 1B are enlarged views of part A in FIG. 2 showing an embodiment of the pilot relay according to the present invention, at equilibrium and when the nozzle back pressure increases; FIG. 2 is a sectional view of the same relay;
3a and 3b, 4 and 5 are sectional views showing other embodiments of the bias hole closing means, and FIG. 6 is a sectional view of a conventional pilot relay. 1... Housing, 2, 3... Diaphragm,
4... Partition wall, 5... Air supply hole, 6... Output chamber,
7... Bias chamber, 8... Back pressure chamber, 10... Piston valve, 13... Poppet valve, 18... Bias hole, 20... Bias hole closing means, 21... Valve seat, 22... Ball, 23...Fratsupa, 25...
...Band, 30...Tube, 33...Flapper, P _N ...Nozzle back pressure, P _B ...Bias pressure.

Claims (1)

[Scope of Claims] 1. A back pressure chamber and a bias chamber defined by two diaphragms having a difference in both the inner and outer diameter support parts are provided in the housing, and the nozzle back pressure is used as the input pressure. A pilot relay that supplies a back pressure to a back pressure chamber and moves the valve means forward or backward by displacement of the diaphragm due to the input pressure, thereby amplifying and outputting the input pressure, a bias hole communicating with the bias chamber; A pilot relay characterized in that a bias hole closing means is provided between a piston valve held by both diaphragms and is closed in response to the operation of the piston valve and absorbs displacement of the diaphragm. 2 A back pressure chamber and a bias chamber defined by two diaphragms with a difference between the inner and outer diameter support parts are provided in the housing, and the nozzle back pressure is supplied to the back pressure chamber as input pressure. The pilot relay moves the valve means forward or backward by displacement of the diaphragm due to the input pressure, thereby amplifying the input pressure and outputting the pilot relay, which is provided with a bias hole communicating with the bias chamber and supported by the diaphragm. A pilot relay characterized in that a piston valve is provided with a flexible flapper with a ball, and the opening and closing of the bias hole is controlled by the flapper with a ball.