JPH0450441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical signal-to-pneumatic conversion unit that converts an electrical signal into fluid pressure, particularly into pneumatic pressure.
More specifically, in an electrical signal to pneumatic conversion unit using a nozzle flapper, the electrical signal to pneumatic conversion unit is configured so that the ratio of the output pneumatic pressure to the nozzle back pressure, that is, the pressure gain can be extremely large. Regarding.

Conventionally, torque motors have been incorporated into devices widely used to convert electrical signals to pneumatic pressure. That is, according to this torque motor, a current is supplied to the coil that constitutes the motor, a rotational force corresponding to this current is obtained to displace the flapper, and this changes the nozzle back pressure to displace the diaphragm. The output air pressure is controlled by opening and closing the fluid passage through a valve body attached to this diaphragm.

According to such conventional technology, a relatively large torque motor must be built into the main body of the electrical signal-to-pneumatic converter, which inevitably increases the size of the device as a whole. Moreover,
The moving coil of the torque motor incorporated in this manner is supported by a thin leaf spring so that it can respond to even weak signals. Therefore, even if a minute signal is triggered, the leaf springs act together to change the nozzle back pressure, which causes the output pressure to fluctuate, creating the disadvantage that precise electrical signal-pneumatic pressure conversion cannot be achieved. ing. In other words, the disadvantage is that it is weak against mechanical vibration. In addition, in conventional devices, the gain of the output air pressure with respect to the nozzle back pressure is low, and in addition, it is easily affected by the tension of the diaphragm, so there is a drawback that high-precision electrical signal-air pressure conversion cannot be performed. It has been pointed out. Furthermore, due to the structure, the exhaust flow rate cannot be increased, so when the pressure on the load side suddenly increases significantly, the exhaust gas cannot follow the increase.

The present invention has been made to overcome such inconveniences, and the flapper is composed of an electrostrictive element, and the nozzle back pressure acts on one of the two diaphragms arranged in parallel. and on the other hand, configured to apply output air pressure between the two diaphragms,
The structure is such that atmospheric pressure acts on the other diaphragm side, and the difference in effective area of each diaphragm is minimized, thereby achieving a large gain in output air pressure with respect to nozzle back pressure. The object of the present invention is to provide an electrical signal-to-pneumatic conversion unit that can be lightweight.

In order to achieve the above object, the present invention includes a nozzle flapper mechanism that changes nozzle back pressure according to the amount of displacement of the flapper, and an air supply port that connects a supply port and an output port by a diaphragm that responds to the nozzle back pressure. In the electrical signal-pneumatic pressure conversion unit including a non-bleed type pilot valve section that controls the output air pressure by controlling the opening and closing of a provided inner valve, the flapper is composed of an electrostrictive element that is displaced in response to changes in the electrical signal. , the diaphragm is composed of two diaphragms with different sizes and areas, one diaphragm faces the nozzle hole, and the passage for introducing the output air pressure faces between the two diaphragms, and the other diaphragm faces the passage for introducing the output air pressure. A passage for introducing atmospheric pressure is faced, a passage for introducing the output air pressure is branched and communicated with a pressure sensor installed inside the unit main body, and the output of the pressure sensor is used to control the electrostrictive element. Features.

In the electrical signal-to-air pressure conversion unit configured as described above, the nozzle back pressure changes by displacing the flapper made of an electrostrictive element toward the nozzle, and under the action of this nozzle back pressure, one diaphragm is displaced.

By the displacement of the diaphragm, a passage for introducing the supply air pressure and a passage for introducing the output air pressure are opened, and a part of the supply air pressure becomes the output air pressure and is placed between the passage for introducing the output air pressure and the two diaphragms. and the pressure sensor.

When this output air pressure reaches an air pressure corresponding to the nozzle back pressure, the passage for introducing the supply air pressure and the passage for introducing the output air pressure are closed under the action of the other diaphragm that is displaced by the output air pressure. .

At this time, the output air pressure read by the pressure sensor is used to control the electrostrictive element, so the output air pressure can be controlled with high accuracy.

Furthermore, since the output air pressure is supplied between the two diaphragms, it is possible to obtain a large gain in the output air pressure with respect to the nozzle back pressure.

Next, preferred embodiments of the electrical signal-pneumatic conversion unit according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates the main body of the electrical signal-to-pneumatic conversion unit according to the present invention, and this main body 10 has a nozzle flapper mechanism 12 provided in the upper part of the interior thereof, and a pilot valve part 14 provided in the lower part of the interior thereof. include.

The nozzle flapper mechanism 12 includes a nozzle 18 of a predetermined diameter that communicates with a nozzle back pressure chamber 16 of a pilot valve section 14 (described later) via a passage 17, and a plate whose base end is locked to the conversion unit main body 10 by a screw 20. It consists of a flapper 22 shaped like the above. Said flapper 2
2 is formed of a so-called electrostrictive element consisting of two piezoelectric ceramics 24, 24 provided with electrodes (not shown) and an intermediate electrode plate 26 sandwiched between these piezoelectric ceramics 24, 24. , lead wires 28, 2 connected to the piezoelectric ceramics 24, 24, respectively.
The configuration is such that a predetermined voltage is applied via the terminal 8.

On the other hand, the pilot valve section 14 includes two diaphragms 30 and 32 arranged in parallel in the vertical direction, and an exhaust valve 3 interlocked with these diaphragms 30 and 32.
4 and an inner valve 36. The exhaust valve 34 is
substantially a diaphragm disk 33 that holds the diaphragms 30, 32 apart for a predetermined distance;
It consists of a cylindrical body formed at the lower end of the inner valve 36, and as will be described later, a part of the inner valve 36 can be seated on this cylindrical body. Note that the inner valve 36 has a first valve part 35 and a second valve part 37.

A supply port 38 is defined on one side of the conversion unit main body 10, and passages 40a, 40b, 40c, 40d, and 40e communicate with each other and extend from the middle of the supply port 38 to the nozzle back pressure chamber 16. ing. At this time, a fixed orifice 44 is provided in the passage 40d located downstream of the supply port 38.
is intervened. Furthermore, an atmospheric pressure chamber 48 is defined below the diaphragm 32 and is configured to communicate with the atmosphere via a passage (exhaust port) 50. In the figure, reference numeral 52 indicates an output port, and from the middle of this output port 52, a passage 53 connects to the upper diaphragm 30 and the lower diaphragm 32, which has a slightly smaller effective area that responds to pressure fluctuations than the upper diaphragm 30. It is configured such that it communicates with the feedback chamber 46 thus defined, and a portion of the output air pressure is introduced through the passage 53.

In this case, the inner valve 36 is arranged so as to close the air supply port 54 connecting the supply port 38 and the output port 52 when the three pressures, that is, nozzle back pressure, feedback pressure, and atmospheric pressure, are balanced. At that time, the second valve part 37 constituting the inner valve 36 engages with a valve seat 60 formed on the exhaust valve 34, and closes the exhaust passage 58 leading to the atmospheric pressure chamber 48 via the valve seat 60. is configured to do so. Therefore, it is easily understood that this pilot valve section 14 is a non-bleed type in which exhaust is not performed during equilibrium.

Furthermore, an O-ring 64 is interposed in the passage 62 in which the exhaust valve 34 slides. On the other hand, a circular hole 66 is defined in the main body 10, and a pressure sensor 68 is fitted into this hole 66. In fact, the hole 66
A passage 53a branched from the passage 53 extends and communicates with the passage 53 to supply the output pressure signal of the output port 52 to the pressure sensor 68. Although not shown, the pressure sensor 68 includes a semiconductor diaphragm therein, and this semiconductor diaphragm achieves the function of converting the output pressure signal into a voltage signal.

That is, as shown in FIG. 2, when the output pressure from the pilot valve section 14 is detected as an electrical signal by the pressure sensor 68, this detection signal is
The signal is fed back to the controller 72 via the amplifier circuit 70, and the controller 72 compares the detection signal with the input signal. The voltage signal related to the deviation after the comparison is amplified by the amplifier circuit 74 and applied to the flapper 22 according to the deviation, and as a result, the nozzle back pressure in the nozzle back pressure chamber 16 changes. The change in nozzle back pressure is caused by diaphragm 3.
produces a displacement of 0.

On the other hand, the output pressure from the pilot valve section 14 is also applied to the feedback chamber 46 via the passage 53. That is, the pressure that tends to lower diaphragm 30 due to changes in nozzle back pressure, for example, will oppose the feedback pressure applied to feedback chamber 46. Therefore, the change in the nozzle back pressure is added to the feedback pressure acting as a negative element, and the exhaust valve 34 is displaced by the substantial difference. As a result, the output pressure from the output port 52 constitutes a feedback system for the diaphragm 30, and a minor loop for this feedback is formed in the pilot valve section 14.

In other words, even if an input signal is applied to the nozzle flapper mechanism 12 with a sudden change and the output side is about to change suddenly, the branched pressure from the output port 52 will not be fed back through the passage 53. Because of the supply to chamber 46, rapid changes in diaphragm 30 in response to the input signal will be prevented within a short period of time. Therefore, stable output can be obtained.

In FIG. 1, reference numeral 76 indicates a spring that normally biases the inner valve 36 in the valve-closing direction.

Next, the operation and effects of this embodiment configured as described above will be explained.

First, according to the findings of the present inventors, it is possible to obtain a large pressure gain with respect to the nozzle back pressure in the following manner. That is, in the embodiment described above, the following equation holds true depending on the balance of forces acting on the diaphragm disk 33.

P _N・A _N +P _O A _O = P _O (A _N −A _S )…… ∵ P _N・A _N = P _O (A _N −A _S −A _O ) Generally,
Since A _O >>A _S , ∵P _O /P _N =A _N /A _N −A _OHere , P _N is the pressure acting on the diaphragm disk 33, that is, the nozzle back pressure, and on the other hand,
P _O indicates output air pressure. A _N is the effective area of the diaphragm 30, A _O is the effective area of the diaphragm 32, and A _S is the effective area of the diaphragm 30.
No feedback pressure is applied to the This is the so-called non-pressure receiving area (see Figure 1). Therefore,
In order to increase the pressure gain P _O /P _N , A _N and
The area difference between A and _O should be selected to be small. for example,
If A _N =5 and A _O =4, P _O /P _N =5/5-4, and a gain of five times is obtained.

Therefore, when the voltage applied to the flapper 22 made of an electrostrictive element increases while the system is in equilibrium as shown in FIG. 1, the free end of the flapper 22 is displaced in the direction of closing the nozzle 18. This results in
Since the amount of air ejected from the nozzle 18 decreases, the pressure in the nozzle back pressure chamber 16 (nozzle back pressure) increases, and this pressure acts on the upper surface of the upper diaphragm 30. That is, it acts as pressure to lower the upper diaphragm 30.

As a result, the equilibrium state of the system is disrupted, and the upper diaphragm 30 and the lower diaphragm 32 are integrally displaced downward, and as a result of this downward movement, the exhaust valve 34 integrally constructed therewith and the exhaust valve 34
The inner valve 36, which is interlocked with this, comes down. Therefore, the air supply port 54 is opened, and part of the supply pressure from the supply port 38 becomes the output pressure, and the output port 54 becomes the output pressure.
2. This output air is supplied to the load side (not shown) and performs the intended function.

At this time, in this embodiment, as described above, the passage 62 in which the exhaust valve 34 slides is hermetically sealed by the O-ring 64, and the lower diaphragm 32
The lower side of the tank is constantly exposed to the atmosphere through a passage 50. Therefore, the output pressure is not fed back to the lower side of the lower diaphragm 32.
On the other hand, a part of the output air pressure is generated by the two diaphragms 3.
Feedback is provided via a passage 53 to an intermediate point between 0 and 32. Therefore, as mentioned above, if the effective area difference between the two diaphragms 30 and 32 is selected to be small, the pressure gain of nozzle back pressure versus output pressure can be made very large, and the nozzle back pressure can be reduced to a small value. Even a change in the output pressure will result in a significant change in the output pressure.

As described above, the output pressure is fed back to the input side as an electrical signal by the pressure sensor 68 via the passage 53a. Therefore, when the output pressure matches the input signal, the inner valve 36 also returns to its original state, closing both the air supply port 54 and the valve seat 60 to obtain a new equilibrium state.

In the above embodiments, the nozzle flapper mechanism 12 and the pilot valve part 14 are integrated into the unit body 10, but the nozzle flapper mechanism 12 and the pilot valve part 14 are Needless to say, they can be constructed in a separate manner.

Next, FIG. 3 shows another embodiment of the electrical signal-to-pneumatic conversion unit according to the present invention, and in this embodiment, the same reference numerals as in the embodiment of FIG. 1 indicate the same components. do.

Therefore, in this embodiment, as can be easily understood from the figure, an exhaust hole 80 is formed below the inner valve 36 for exhausting air. Therefore, the inner valve 36 constituting the pilot valve section 14 has an inverted configuration compared to the configuration of the above embodiment, and the air supply valve 82 having the exhaust hole 80 is located in the hole 84 formed in the main body 10. It slides inside and is normally pressed upward by a coil spring 86. In addition, in the figure, reference numeral 88 indicates a rubber gasket,
Further, reference numeral 90 indicates a valve seat.

In such a configuration, when the pressure inside the nozzle back pressure chamber 16 changes, the diaphragms 30 and 32 descend to press the inner valve 36. As a result, the air supply valve 82 is pressed against the coil spring 86, and the rubber gasket 88 separates from the sharp valve seat 90 of the main body. Fluctuations in the output pressure obtained in this manner are detected by the pressure sensor 68 via the passage 53a and fed back to the controller 72, as in the previous embodiment. On the other hand, when the output side pressure increases, the pressure is applied to the feedback chamber 46 and pushes up the diaphragm disk 33, so that the valve part 37 is also pushed up in conjunction with this, and bleeding can be caused from the exhaust hole 80.

As explained above, according to the present invention, the pressure gain can be increased by guiding the output pressure to the middle of the two diaphragms in the pilot valve section, and even a small amount of displacement of the electrostrictive element can cause a large It becomes possible to obtain a change in output pressure. Furthermore, there is an advantage that a highly accurate conversion unit can be provided by reducing the effects of hysteresis characteristics and nonlinearity of the electrostrictive element. Furthermore, since the amount of displacement of the electrostrictive element is small, it is also effective in terms of durability of the electrostrictive element itself.

In addition, since the pilot valve part is constructed as a non-bleed type, there is an advantage that air consumption is small even when used at high pressure. In the embodiment shown in Fig. 1, the exhaust is carried out from the passage to the atmosphere through a chamber under the small area of the diaphragm, but as in the embodiment shown in Fig. 3, the exhaust is carried out from the lower side of the inner valve. It is also possible to In addition, in the configuration example shown in Figure 1, the output pressure is fed back to the middle of the two diaphragms, and the lower side of the smaller diaphragm is at atmospheric pressure, but by reversing this relationship, the pressure between the two diaphragms is It is also possible to set the intermediate pressure to atmospheric pressure and feed back the output pressure to the lower side of a small area diaphragm. In addition, as shown in Figure 3, supply pressure is applied between the two diaphragms.
It is also possible to configure the output pressure to be fed back to the lower side of a diaphragm having a small area, and exhaust the air from below. It also has the advantage of increasing the gain and improving the stability of the output.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the above embodiments, and the present invention unit is used as a pilot relay to control the displacement of a control valve. Of course, various improvements and changes in design are possible without departing from the gist of the present invention, such as suitably applying it as a pneumatic positioner.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an electric signal to pneumatic pressure conversion unit according to the present invention, FIG. 2 is a longitudinal cross-sectional view of a control system used in the unit of the present invention, and FIG. It is an explanatory diagram. 10...Unit body, 12...Nozzle flapper mechanism, 14...Pilot valve section, 16...Nozzle back pressure chamber, 18...Nozzle, 20...Screw, 22
...Flatspa, 24...Piezoelectric ceramic, 26...
...Intermediate electrode plate, 28...Lead wire, 30, 32...
... diaphragm, 33 ... diaphragm disk, 34 ... exhaust valve, 35 ... valve section, 36 ... inner valve, 37 ... valve section, 38 ... supply port, 46 ...
...Feedback room, 48...Atmospheric pressure room, 52...
...Output port, 54...Air supply port, 58...Exhaust passage, 60...Valve seat, 64...O ring, 66...
hole, 68... pressure sensor, 70... amplifier circuit,
72...Controller, 74...Amplification circuit, 76
... Spring, 80 ... Exhaust hole, 82 ... Air supply valve, 84 ... Hole, 86 ... Coil spring,
88...Rubber padskin, 90...Valve seat.

Claims (1)

[Scope of Claims] 1. A nozzle flapper mechanism that changes nozzle back pressure according to the amount of displacement of the flapper, and an inner valve provided at an air supply port that connects a supply port and an output port with a diaphragm that responds to the nozzle back pressure. In an electrical signal-to-air pressure conversion unit that includes a non-bleed type pilot valve that controls the output air pressure by opening and closing, the flapper is composed of an electrostrictive element that is displaced in response to changes in the electrical signal, and has two diaphragms. It consists of diaphragms of different sizes, with the nozzle hole of one diaphragm facing out, and
A passage for introducing the output air pressure is provided between the two diaphragms, and a passage for introducing the atmospheric pressure is made to face the other diaphragm, and the passage for introducing the output air pressure is branched and the pressure installed inside the unit body is made to face. An electrical signal-pneumatic conversion unit, characterized in that it communicates with a sensor and uses the output of the pressure sensor to control the electrostrictive element. 2. The unit according to claim 1, wherein the inner valve connected to the diaphragm engages with the exhaust hole, and opening the exhaust hole causes the output side pressure fluid to bleed. conversion unit.