JPH0481642B2 - - 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 air is consumed continuously or discontinuously inside the pilot valve in the operating state, and in the case of non-bleed type, its proportional gain is equal to the ratio of the effective areas of the two diaphragms. FIG. 6 shows a conventional example of a non-bleed type pilot valve. This will be explained based on the same figure. 1 has four chambers 5, 6, The housing is divided into 7 and 8, with chamber 5
is connected to an air supply source (not shown) via an air supply passage 9 and to a nozzle (not shown), thereby forming 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 and the output pressure in the equilibrium state shown in the figure. The upward forces acting on the diaphragm 3 due to 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 prevents the valve from opening rapidly 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 pilot 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 a back pressure chamber defined by two diaphragms with a difference in both the inner and outer support portions in the housing. and a bias chamber, supplying nozzle back pressure as input pressure to the back pressure chamber, moving the valve means forward or backward by displacement of the diaphragm due to this input pressure, and thereby amplifying and outputting the input pressure. In the relay,
The opening and closing of the bias hole communicating with the bias chamber is controlled according to the operation of a diaphragm that defines the back pressure chamber and the bias chamber.

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 input pressure to control the back pressure. A part of the diaphragm sealing surface of the housing on the back pressure chamber side in the pilot relay that moves the valve means forward and backward by the displacement of the diaphragm due to the input pressure, thereby amplifying and outputting the input pressure. A notch recess communicating with the back pressure chamber is provided, and a bias hole is opened in the bias chamber side diaphragm sealing surface of the housing so as to face the notch recess with the diaphragm in between.

[Effect]

In the first invention, when the piston valve is actuated as the nozzle back pressure increases, the diaphragm closes the bias hole. Therefore, the internal pressure of the bias chamber increases as the volume of the bias chamber decreases.

In the second aspect of the invention, the notch recess of the housing allows local deformation of the diaphragm due to the bias pressure during equilibrium, thereby allowing the bias chamber and the bias hole to communicate with each other.

〔Example〕

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

FIG. 1 is an enlarged view of part A in FIG. 3 showing an embodiment of the pilot relay according to the present invention at the time of equilibrium;
FIG. 2 is an enlarged view of part A when the nozzle back pressure increases, FIG. 3 is a cross-sectional view of the same relay, and FIG. 4 is a cross-sectional view taken along the line shown in FIG. 3. In the drawings, the same members and portions as those in the conventional structure shown in FIG. 6 are designated by the same reference numerals, and their explanations will be omitted. In these figures, the present embodiment has two diaphragm seal surfaces 20, 2 of the housing 1 that support the outer diameter support portion 2a of the diaphragm 2 from both sides, that is, the diaphragm seal surfaces 20, 2 on the back pressure chamber side and the bias chamber side.
1, a notch recess 22 communicating with the back pressure chamber 8 is formed in a part of the diaphragm sealing surface 20 on the back pressure chamber side, and one end of the bias hole 18 is formed in the diaphragm sealing surface 21 on the bias chamber side to sandwich the diaphragm 2. to open the notch so as to face the notch recess 22,
This opening 18a is characterized in that the opening and closing of the opening 18a is controlled by the diaphragm 2, and the other configuration is substantially the same as the conventional structure shown in FIG. 6.

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 portion of the diaphragm 2 corresponding to the bias hole 18 is locally deformed upward by the bias pressure P _B as shown in FIG. 7 and bias hole 18
The bias pressure P _B is caused to flow into the bias chamber 7.

Next, when the nozzle back pressure P _N becomes higher than the bias pressure P _B , the diaphragm 2 is displaced downward and pushes down the piston 10 and the poppet valve 13 against the spring 14, and the bias hole 18 is moved downward as shown in FIG. The opening 18a is closed. Then, the volume of the bias chamber 7 decreases as the piston valve 10 descends, so the internal pressure of the bias chamber 7 gradually increases and brakes the piston 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 cannot be lowered rapidly. First, since the poppet valve 13 is operated slowly, stability is good and hunting can be prevented.

On the other hand, when the nozzle back pressure P _N decreases from this state and the piston valve 10 rises, the internal pressure in the bias chamber 7 only decreases and does not increase, so an overshoot occurs, but the piston valve 10 descends due to feedback. The bias chamber 7 performs the same function as the increase in the nozzle back pressure P _N at this time, so that the poppet valve 13 does not operate suddenly at this time as well, and hunting can be prevented from occurring.

FIG. 5 is a diagram for explaining the decrease in the volume of the bias chamber 7 as the nozzle back pressure P _N increases. When the piston valve 10 is displaced, the diaphragm 2,
3 moves from the solid line position to the dashed line position (P ₂
→ _P5 , _P4 → _P6 ). Cross-sectional area before and after displacement P ₁ P ₂ P ₃
Comparing P ₄ , P ₁ P ₃ P ₅ P ₆ , the quadrilateral P ₁ P ₃ P ₅ P ₇ is common before and after the displacement, and the areas P ₁ P ₂ P ₄ P ₅ P ₇ and P ₃ P ₄ P ₆
The former is large and the latter is small. Therefore, the volume (cross-sectional area x effective diameter) of the bias chamber 7 decreases after the displacement. The diaphragms 2 and 3 are made of a soft elastic material, and by providing a constriction, it can be considered that the effective diameter is constant and does not change.

In addition, in the above embodiment, a notch recess 22 is formed in a part of the diaphragm sealing surface 20 on the back pressure chamber side of the housing 1.
was provided to ensure smooth and reliable upward displacement of the diaphragm 2 due to the bias pressure P _B during equilibrium, but the present invention is not limited to this.
0 inner diameter to bias chamber side diaphragm seal surface 2
The inner diameter may be larger than that of 1.

〔Effect of the invention〕

As explained above, the pilot relay according to the present invention is configured to control the opening and closing of the bias hole by the diaphragm, so as the nozzle back pressure increases, the diaphragm displaces and closes the bias hole and closes the piston valve. When activated, the internal pressure in the bias chamber increases, enhancing the air damping effect and damping the sudden operation of the piston valve. Therefore, the poppet valve does not open suddenly, the occurrence of hunting can be prevented, and a small, stable, high-gain pilot relay can be provided without requiring a fixed capacity.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of part A in FIG. 3 showing an embodiment of the pilot relay according to the present invention at the time of equilibrium;
Figure 2 is an enlarged view of part A when the nozzle back pressure increases, Figure 3 is a cross-sectional view of the same relay, Figure 4 is a cross-sectional view taken along the line shown in Figure 3, and Figure 5 shows the decrease in the volume of the bias chamber. FIG. 6, which is an explanatory diagram, is a sectional view of a conventional pilot relay. 1... Housing, 2, 3... Diaphragm,
4... Bulkhead, 5... Air supply chamber, 6... Output chamber,
7... Bias chamber, 8... Back pressure chamber, 10... Piston valve, 13... Poppet valve, 18... Bias hole, 20... Back pressure chamber side diaphragm seal surface, 2
1...Bias chamber side diaphragm seal surface, 22
...Notch recess, 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. In the pilot relay, the input pressure is supplied to a back pressure chamber, and the valve means is moved forward and backward by displacement of the diaphragm due to the input pressure, thereby amplifying and outputting the input pressure. A pilot relay characterized in that opening and closing are controlled according to the operation of a diaphragm that defines a pressure chamber and a bias chamber. 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. In the pilot relay, the valve means is moved forward and backward by the displacement of the diaphragm due to the input pressure, thereby amplifying and outputting the input pressure. A pilot relay characterized in that a notch recess communicating with the chamber is provided, and a bias hole is opened in the bias chamber side diaphragm sealing surface of the housing so as to face the notch recess with the diaphragm in between.