JPH054552B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a pilot valve mechanism incorporated in an electric signal-pneumatic converter, an electric signal-pneumatic positioner, or a pneumatic-pneumatic positioner, etc., which are suitably employed in the instrumentation field. [Background of the Invention] This type of pilot valve mechanism can be broadly classified into a bleed type and a non-bleed type. A bleed type pilot valve mechanism has a structure that allows the air given from the supply side to escape into the atmosphere, whereas a non-bleed type pilot valve mechanism has an exhaust pressure port, but mainly directs the air from the supply side to the output side as it is. is configured to do so. Typical examples of a bleed type pilot valve mechanism and a non-bleed type pilot valve mechanism are shown in FIGS. 1 and 2, respectively. That is, according to the bleed type pilot valve mechanism, a chamber 4 is defined in a part of the body 2, and this chamber 4
A diaphragm 6 is disposed at. Further, on the opposite side, a chamber 8 is defined in the body 2,
This chamber 8 is in communication with a supply port 10. A leaf spring 12 is disposed inside the chamber 8, and this leaf spring 12 presses the air supply valve 14 from below to above in the figure. In fact, the air supply valve 14 is fixed to one end of the rod 18 facing into the through hole 16 communicating the chambers 4 and 8, and the other end of the rod 18 is connected to the exhaust valve 2.
Connected to 0. In this case, the through hole 16 becomes a branched through hole 19 and communicates with the chamber 4. An exhaust valve 20 having a tapered valve portion is fixed to the diaphragm 6, and opens and closes the exhaust valve 20 by seating on a seating portion 22. A through hole 24 is defined in the through hole 16 for deriving the output pressure.
Furthermore, the chamber 4 is in communication with a through hole 26 for deriving exhaust pressure. Note that a nozzle 28 faces the chamber 4 via the diaphragm 6. In the above configuration, by changing the nozzle back pressure via the flapper 29 facing the nozzle 28, the diaphragm 6 is displaced in the vertical direction in the figure. That is, as the nozzle back pressure increases, the diaphragm 6 displaces the rod 18 downward. On the other hand, since the air supply valve 14 is pressed upward by the leaf spring 12, the balance between the diaphragm 6 and the leaf spring 12 causes the air supply valve 14 to
The supply pressure passing through the exhaust valve 20 and the seating part 22 are restricted when being led out to the output side through the through hole 24, and the exhaust pressure released to the atmospheric pressure side through the through hole 26 is restricted. This will be restricted by the distance between the two. In this way, the change in nozzle back pressure regulates the displacement operation of the exhaust valve 20 and the air supply valve 14, thereby making it possible to adjust the output pressure to a desired value. Next, the non-bleed type pilot valve mechanism will be explained. Supply port 32 and output port 34 on body 30
An air supply valve 36 is disposed between the supply port 32 and the output port 34. The air supply valve 36 is pressed upward in the figure by the coil spring 38 and is seated on the seating portion 40, thereby cutting off communication between the supply port 32 and the output port 34. The air supply valve 36 is integrally formed with an inner valve 42 via a rod, and this inner valve 42 engages with an exhaust valve 44. Body 30 defines a chamber 46 that is in communication with supply port 32 by a through hole 48 . A first diaphragm 50 having a relatively large pressure receiving area and a second diaphragm 52 having a small pressure receiving area are disposed inside the chamber 46, whereby the chamber 46 is connected to the small chambers 54, 5.
6 and 58. The first diaphragm 50 and the second diaphragm 52 are integrally connected by a connecting member 60, and the exhaust valve 44 is further formed in the connecting member 60. The small chamber 56 communicates with the atmosphere through a through hole 62, and the small chamber 58 communicates with the output port 34 through the through hole 64. In the figure, reference numeral 66 indicates a nozzle portion having a passage communicating with the chamber 46, and reference numeral 68 indicates a flapper. In the above configuration, by bending the flapper 68 and changing the nozzle back pressure of the nozzle portion 66, the first diaphragm 50 and the second diaphragm 52 are connected to the exhaust valve 44 via the connecting member 60. is displaced downward. As a result, the air supply valve 36 is displaced downward against the elastic force of the coil spring 38, and the pressurized air supplied from the supply port 32 is led out to the output port 34 side. This air pressure at the output port 34 is taken out through the through hole 64 as an output pressure signal. On the other hand, this output pressure is fed back to the small chamber 58 and counteracts the nozzle back pressure, so that the distance between the air supply valve 36 and the seating portion 40 is adjusted so that a desired output pressure of air can be obtained. Therefore, in general, with the bleed type pilot valve mechanism shown in Fig. 1, it is possible to obtain a relatively large gain of about 10 to 20 times, that is, the ratio of the change in output pressure to the change in nozzle back pressure. It is possible. However, structurally, as described above, the supplied pressurized air is always led out to the exhaust pressure side, that is, the atmosphere side, through the through hole 26, so that the amount of air consumed becomes extremely large. For example, when the supply pressure is 1.4Kg/ ^cm2 , the consumption is 20n/cm2.
It becomes very large, around min. On the other hand, according to the non-bleed type pilot valve mechanism shown in FIG. 2, the pressure gain is determined by the effective pressure receiving areas of the first diaphragm 50 and the second diaphragm 52. However, since there are certain restrictions on the size of the product, this type of structure can only provide a gain of about three times. However, as can be easily understood from the above structure, in a non-bleed type pilot valve mechanism, in an equilibrium state, output pressure air is not led out from the through hole 62 communicating with the atmosphere. In addition, it has become possible to significantly reduce air consumption to about 1/5 to 1/10 compared to the bleed type. Therefore, in view of the above configuration, the reality is that the bleed type pilot valve mechanism or the non-bleed type pilot valve mechanism is used depending on the purpose. However, recently, from the viewpoint of energy saving, non-bleed type pilot valve mechanisms are often adopted rather than bleed type, which consumes a large amount of air.
There is an increasing demand for increasing the gain as much as possible in this non-bleed type pilot valve mechanism. [Object of the Invention] The present invention has been made in view of the above, and includes a diaphragm chamber defined inside a body, and three diaphragms having different pressure-receiving areas mutually spaced apart by a predetermined distance and stacked in the diaphragm chamber. Nozzle back pressure is applied to a nozzle back pressure chamber defined between the first diaphragm and the body, and nozzle back pressure is applied to the output pressure chamber defined between the first diaphragm and the second diaphragm. A supply pressure is introduced into a supply pressure chamber defined between the second diaphragm and the third diaphragm, and a supply pressure is introduced between the third diaphragm and the body. The exhaust pressure chamber is configured to communicate with the atmosphere. This makes it possible to obtain a large pressure gain, and avoids overshoot, where the output pressure is too high relative to the set pressure, or undershoot, where the pressure is too low relative to the set pressure. However, it is an object of the present invention to provide a pilot valve mechanism that is quick in response and highly stable under any conditions of use. [Means for Achieving the Object] In order to achieve the above-mentioned object, the present invention provides a nozzle flapper mechanism provided inside a valve body, and a nozzle flapper mechanism provided in the valve body, between an input port and an output port defined in the valve body. an air supply valve disposed so as to be freely displaceable; a first diaphragm stacked in the valve body with a predetermined distance between them; a second diaphragm having a smaller pressure-receiving area than the first diaphragm; A third diaphragm having a smaller pressure-receiving area than the diaphragm is connected to the first to third diaphragms, is displaced in conjunction with the displacement of the first to third diaphragms, and has one end abutted against the air supply valve. a connecting member that allows the air supply valve to be opened and closed; a nozzle back pressure chamber defined by the first diaphragm that communicates with the input port and receives nozzle back pressure of the nozzle flapper mechanism; communicates with the input port; a supply pressure chamber defined between the second diaphragm and the third diaphragm; and an output pressure chamber communicating with the output port and defined between the first diaphragm and the second diaphragm. It is characterized by being prepared. [Embodiments] Next, preferred embodiments of the non-bleed pilot valve mechanism according to the present invention will be described in detail with reference to the accompanying drawings. In FIG. 3, reference numeral 70 indicates a non-bleed pilot valve mechanism according to the present invention. The pilot valve mechanism 70 actually includes a body 72 having an input port 74 and an output port 76 defined therein. An air supply valve 78 is provided in a passage communicating between the input port 74 and the output port 76.
will be placed. The air supply valve 78 engages with the seat 80 to block communication of pressurized air from the input port 74 to the output port 76. Air supply valve 7
A coil spring 82 is disposed at 8.
The coil spring 82 constantly presses the air supply valve 78 against the seat 80 by means of the support 84 . The air supply valve 78 is integrally constructed with an inner valve 88 via a rod 86. The inner valve 88 can engage with an exhaust valve described later. A diaphragm chamber 90 is defined approximately at the center of the body 72 . The diaphragm chamber 90 includes a first diaphragm 92 having a relatively large pressure receiving area from above in the figure, a second diaphragm 94 having a smaller pressure receiving area from the first diaphragm 92, and a second diaphragm 94 having a smaller pressure receiving area than the second diaphragm 94. A third diaphragm 96 is provided. As can be easily understood from the figure, the first diaphragm 92, the second diaphragm 94, and the third diaphragm 96 are integrally connected by a connecting member 98 and are spaced apart from each other by a predetermined distance. Therefore, the first diaphragm 92 and the second diaphragm 9
4. The diaphragm chamber 90 is divided by the third diaphragm 96 into a small chamber 102 as a nozzle back pressure chamber, a small chamber 104 as an output pressure chamber, a small chamber 106 as a supply pressure chamber, and a small chamber 107 as an exhaust pressure chamber. become. An exhaust valve 108 is integrally formed in the connecting member 98, and this exhaust valve 108
The tip thereof can freely engage with the inner valve 88. In fact, the exhaust valve 108 has a through hole 110 extending in its axial direction, and the inner valve 88 opens and closes the exhaust passage by facing the through hole 110. Exhaust valve 10
The through hole 110 of No. 8 has a through hole 112 perpendicular to the axis, and this through hole 112 is in communication with the small chamber 107. A through hole 114 is provided in the body 72 and communicates with the input port 74 . After the through hole 114 rises upward and bends, it is in communication with the small chamber 102. In addition, this through hole 114 is branched and the through hole 11
6, and is in communication with the small chamber 106. Furthermore, a through hole 118 is defined in the output port 76 defined in the body 72, and this through hole 118 faces the pressure sensor 120. Further, this through hole 118 branches to become a through hole 122, and this through hole 122 is in communication with the small chamber 104. In this case, small room 107
is in communication with the atmosphere through a through hole 124. A nozzle 130 is provided in the upper part of the diaphragm chamber 90, and this nozzle 130 has a narrow diameter through hole 132.
It is in communication with the small chamber 102 via. Therefore,
It can be easily understood that the small chamber 102 essentially constitutes a nozzle back pressure chamber. The nozzle 130 in this case faces the chamber 134,
Inside this chamber 134, a plate-shaped flapper 136 is arranged with its tip close to the nozzle 130. The flapper 136 is formed of a so-called electrostrictive element consisting of two piezoelectric ceramics 138, 138 provided with electrodes (not shown) and an intermediate electrode plate 140 sandwiched between these piezoelectric ceramics 138, 138. , respective piezoelectric ceramics 138, 13
A predetermined voltage is applied through lead wires 142, 142 formed at 8.
In fact, a controller 144 is connected to the flapper 136, and this controller 144 is also electrically connected to the pressure sensor 120. Note that the chamber 134 is in communication with the atmosphere through a through hole 145. FIG. 4 shows a block diagram of this pneumatic-electrical control system. First, the output side of the controller 144 is connected to the flapper 136 as described above. The first diaphragm 92 is pressurized by the output of the flapper 136, that is, by the change in nozzle back pressure. The air supply valve 78 and the exhaust valve 108 are displaced under the pressure receiving action of the first diaphragm 92 . This determines the output pressure from the output port 76. On the other hand, the output pressure signal from the output port 76 reaches the through hole 122 via the through hole 118, and then
Feedback is provided to the small room 104. For this reason,
As a result, a force corresponding to the area difference between the second diaphragm 94 and the third diaphragm 96 of the small chamber 106 receiving the supply pressure and a force corresponding to the area difference between the first diaphragm 92 and the second diaphragm 94 of the small chamber 104 receiving the output pressure are generated. Force is added and subtracted between the diaphragm 92 and the diaphragm 92 on which the force and nozzle back pressure act. In this case, the output pressure further reaches the pressure sensor 120 through the through hole 118, is converted into an electrical signal, and is added to the input signal. The non-bleed type pilot valve mechanism according to the present invention is basically constructed as described above, and its operation will be explained next. Therefore, first, air at a predetermined pressure is supplied to the input port 74 from an air pressure supply source (not shown). In this case, since the air supply valve 78 is pressed against the seating portion 80 by the elastic force of the coil spring 82, communication between the input port and the output port 76 is cut off. The pressurized air from this input port 74 reaches the small chamber 102 through the through hole 114 and also reaches the small chamber 106 through the through hole 116 . In such a state, an input signal is sent to controller 114. As a result, the flapper 136 is bent in accordance with the input voltage signal, and the tip of the flapper 136 is connected to the nozzle 130.
approach. As a result, the pressure led to the outside through the input port 74, the through hole 114, the small chamber 102, and the through hole 132 increases the nozzle back pressure and pressurizes and displaces the first diaphragm 92. As a result, the first diaphragm 92, the second diaphragm 94, and the third diaphragm 96 are displaced downward in the figure integrally with the exhaust valve 108 via the connecting member 98, and as a result, the air supply valve 78 is
Move away from 0. This allows input port 74
The pressurized air from will be directed to the output port 76. Incidentally, the air pressure signal derived from this output port 76 is introduced through the through hole 118 to the pressure sensor 120, which basically consists of a bridge circuit, and is converted into an electrical signal. The pressure sensor 120 then sends the electrical signal to the controller 144, and the difference from the input signal is taken inside the controller. Therefore, as a result, the voltage applied to the flapper 136 is the difference between the input signal introduced to the controller 144 and the feedback signal obtained from the pressure sensor 120, which is further amplified by an amplifier. By the way, the pressurized air obtained through the output port 76 and the through hole 118 is further applied to the small chamber 104 through the through hole 122. In this case, the first diaphragm 92 and the second diaphragm 94 are configured to have different pressure receiving areas. Therefore, if we consider a case where the nozzle back pressure acting on the upper side of the first diaphragm 92 increases, the balance of forces that have been balanced up to now will be disrupted, and the exhaust valve 1
08 downwards, and as a result, the input port opens and the output pressure increases. This increased output pressure is fed back to the small chamber 104 and acts on both the first diaphragm 92 and the second diaphragm 94, but since the first diaphragm 92 has a larger effective area, the difference in force between the two ends up being acts upward, and acts in the direction of closing the air supply valve against the downward force caused by the nozzle back pressure. Note that supply pressure is applied to the small chamber 106 and acts on the second diaphragm 94 and the third diaphragm 96, but since the second diaphragm 94 has a larger area, a force corresponding to the area difference always acts upward. , which acts as a kind of pneumatic spring. In this way, the input signal and the feedback signal are added, and when a pressure level corresponding to the difference signal is reached, the air supply valve 78 is closed and a new equilibrium state is obtained for the system. When the input signal is lower than the output pressure obtained from the output port 76, the exhaust valve 108 is displaced upward due to the opposite effect to the above, and passes from the output port 76 through the through hole 110 and the through hole 112. Since pressurized air flows from 124 to the atmospheric pressure side, this stabilizes the system. In this way,
An output pressure proportional to the input signal is always obtained. The above is an explanation of the basic operation. Therefore, in order to find the gain of the pilot valve mechanism configured as shown in FIG. 3, we will consider the force equilibrium state.
In this case, the effective pressure-receiving area of the first diaphragm 92 is _A1 , and the pressure-receiving area of the second diaphragm 94 is A1.
A ₂ and the pressure receiving area of the third diaphragm 96 is A ₃
Let the pressure receiving area of the air supply valve 78 be _A4 . The air pressure applied to the small chamber 102 is P _o , the pressure applied to the small chamber 104 is P ₀ , and the air pressure applied to the small chamber 104 is P 0 .
Let P _s be the pressure applied to 06. Therefore, P _o・A ₁ +P ₀・A ₂ +P _o・A ₃ =P ₀・A ₁ +P _s・A ₂ +P _s・A ₄ +F _s ……(1) Rearranging this equation (1), we get the following We obtain equation (2) of P ₀ =A ₁ /A ₁ −A ₂ ×P _o +A ₃ −(A ₂ +A ₄ ) /A ₁ −A ₂ ×P _s −F _s /A ₁ −A ₂ ...(2) Above (2) In the formula, each effective pressure receiving area A ₁ , A ₂ , A ₃ , A ₄ of the first diaphragm 92, the second diaphragm 94, the third diaphragm 96, and the air supply valve 78
Furthermore, since the supply pressure P _s is initially set and the elastic force F _s of the coil spring 82 is a constant term, the above equation (2) becomes the following equations (3) and (4). It is expressed as follows. P ₀ =A ₁ /A ₁ −A ₂ ×P _o +K _p −K _f ……(3) However, K _p =A ₃ −(A ₂ +A ₄ )/A ₁ −A ₂ ×P _S K _f = _Fs / _A1 - _A2 . Therefore, P ₀ =K ₁ ×P _o −K ₂ ...(4) However, K ₁ =A ₁ /A ₁ −A ₂ and K ₂ =K _p −K _f . K ₁ in this equation (4), that is, A ₁ /(A ₁ −
A ₂ ) is the gain of the pilot valve mechanism according to the present invention. The pilot valve gain K ₁ is A ₁ / (A ₁ −
As expressed by the formula A ₂ ), a value close to infinity is obtained by making the difference between the pressure receiving area A ₁ of the first diaphragm 92 and the pressure receiving area A ₂ of the second diaphragm 94 as close to 0 as possible. Is possible. Therefore, the pressure receiving area A ₂ of the second diaphragm 94
Table 1 shows the gains related to the calculation results obtained when the difference between the pressure receiving area A ₁ of the first diaphragm 92 and the pressure receiving area A 1 of the first diaphragm 92 is made as small as possible.

[Table] As can be easily understood from this table, A ₂ −A ₁
For example, if the effective pressure receiving area of the first diaphragm 92 and the second diaphragm 94 is selected to be 0.95, a pressure gain of 20 times will be obtained. That is, although it is a non-bleed type, a pressure gain equivalent to the gain of a bleed type pilot valve mechanism can be easily obtained. Moreover, as shown in FIG. 4, there is a first large feedback system that converts the pressure branched from the output side in response to an input signal into an electrical signal using a pressure sensor, and a diaphragm 92 and 94 that receives the pressure of the supply and exhaust valves. Two feedback systems are provided, each consisting of a pressure system that feeds back the amount of displacement of the diaphragm 92. Therefore, the output pressure is directly fed back to the diaphragm 92 by this second feedback system. Therefore, when there is an overshoot on the output pressure side, feedback is immediately transmitted as a pressure signal, which is different from replacing it with an electrical signal and then applying feedback.
Feedback is applied quickly, and the system is therefore extremely stable. In addition, since the pressure sensor 120 is configured to further apply feedback as an electrical signal to adjust the nozzle back pressure, even more accurate control can be achieved. In the above embodiment, among the three diaphragms, the first diaphragm 9 on which the nozzle back pressure acts is
The output pressure side is fed back to the opposite side of the diaphragm 2, and the supply pressure is applied between the other two diaphragms 94 and 96. However, by appropriately selecting the effective area of the three diaphragms arranged in a stacked manner, it is also possible to appropriately select the position where the output pressure side and the supply pressure side communicate. Furthermore, in this embodiment, a pressure sensor is incorporated in order to feedback the output pressure, but a displacement sensor may be used instead of this pressure sensor. This is shown in FIG. That is, the output from the output port 76 is branched and introduced into the diaphragm actuator 200. A shaft 202 is connected to the diaphragm body of the diaphragm actuator 200, and the diaphragm actuator 200 is constantly pressed upward by a coil spring 204. A pin 205 is implanted in the shaft 202, and a lever 208 having an elongated hole 206 is engaged with the pin 204. A cam 210 is fixed to the tip of the lever 208. cam 210
A roller 212 is rotatably engaged with the peripheral surface of.
The roller 212 is connected to a fulcrum 216 by a leaf spring 214.
A displacement sensor 218 constituted by a strain gauge is attached to the middle of the leaf spring 214. The output side of displacement sensor 218 is provided to controller 144 . In the figure, reference numeral 220 indicates a valve body that is opened and closed by displacement action on the shaft 202. In the above configuration, the change in the output pressure derived from the output port 76 causes the coil spring 20 to
For example, the diaphragm body of the diaphragm actuator 200 is pressurized against the elastic force of 4. Along with this, when the shaft 202 descends, the pin 205 swings the lever 208, changing the cam lift of the cam 210 relative to the roller 212. As a result, the leaf spring 214 is deflected, and the displacement sensor 218 replaces the displacement force with an electrical signal and sends it to the controller 144 as a feedback signal. This has the advantage of forming an electrical signal-pneumatic positioner, and is also applicable to pneumatic positioners. [Effects of the Invention] As described above, the present invention has both a feedback system consisting of only a pressure system and a feedback system consisting of an electric signal system, and has a configuration in which a feedback system is provided at a predetermined interval within the valve body. A first diaphragm, a second diaphragm, and a third diaphragm having different pressure-receiving areas are provided, which are spaced apart and stacked. Therefore, the gain on the output side relative to the input side can be selected to be extremely large, and since it is configured as a non-bleed type, the supply pressure air is not released to the atmosphere.
Air consumption is also extremely low. Furthermore, the feedback system as a whole is divided into two parts: a pressure system and an electrical system.
Since it is composed of two systems, the effect of more precise control can be obtained. Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design are possible without departing from the gist of the present invention. Of course.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal sectional view of a conventional bleed type pilot valve, Fig. 2 is a longitudinal sectional view of a conventional non-bleed type pilot valve, and Fig. 3 is a non-bleed type pilot valve according to the present invention. FIG. 4 is a diagram illustrating a longitudinal section of the pilot valve mechanism, FIG. 4 is a control block diagram with different feedbacks incorporated in FIG. 3, and FIG. 5 is a schematic diagram illustrating how feedback signals are obtained by using actuators. 70...Non-bleed type pilot valve mechanism, 7
2...Body, 74...Input port, 76...Output port, 78...Air supply valve, 88...Inner valve, 9
2, 94, 96... diaphragm, 108... exhaust valve, 130... nozzle, 120... pressure sensor, 136... flapper, 144... controller.

Claims (1)

[Scope of Claims] 1. A nozzle flapper mechanism provided inside a valve body; an air supply valve displaceably disposed between an input port and an output port defined in the valve body; and the valve. a first diaphragm stacked in a space separated by a predetermined distance within the main body; a second diaphragm having a smaller pressure receiving area than the first diaphragm; a third diaphragm having a smaller pressure receiving area than the second diaphragm; a connecting member that is connected to the first to third diaphragms, is displaced in conjunction with the displacement of the first to third diaphragms, and has one end abutting an air supply valve to enable the air supply valve to be opened and closed; a nozzle back pressure chamber defined by the first diaphragm that communicates with the port and receives nozzle back pressure of the nozzle flapper mechanism; and a nozzle back pressure chamber that communicates with the input port and is defined between the second diaphragm and the third diaphragm. A non-bleed pilot valve mechanism comprising: a boost pressure chamber that is connected to the output port; and an output pressure chamber that communicates with the output port and is defined between the first diaphragm and the second diaphragm. 2. In the pilot valve mechanism according to claim 1, an exhaust pressure chamber is defined between the third diaphragm and the valve body, and this exhaust pressure chamber communicates with the output port by opening the exhaust valve. A non-bleed pilot valve mechanism characterized by: