JPH0245775Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention is used in process control to convert electrical detection signals detected by various detectors into pneumatic signals and output them to the pneumatic control operation unit. Improvement of an electro-pneumatic converter in which a bimorph is bonded to the flapper as an electrostrictive element, and the above detection electric signal is applied to this to convert the displacement of the flapper due to its curvature into nozzle back pressure. It is related to.

(B) Prior art Among the many electrostrictive elements, bimorph ceramic elements (hereinafter referred to as bimorph), which have been mainly used in pickups and the like, have a structure that lowers the mechanical impedance of the element itself. In comparison, it is much better. This bimorph is shown at one end (1) as shown in Figure 1.
Thin plate-shaped bimorphs 2 and 2' are attached to both sides of flapper 1 to which F) is fixed in each strain direction (tensile (+
F) and compression (-F)) are reversed, and DC voltage E _dc (+) is applied to flapper 1 and (-) to bimorphs 2 and 2' as shown in the figure, as shown by the dotted line. For example, apply a displacement d _f of about 2 μ per 1 V to the flapper tip IT in the direction of arrow a. This displacement d _f changes the back pressure of the nozzle (not shown) facing the flapper tip IT, and this change in nozzle back pressure is guided to the pilot relay where it is amplified.
Outputs a unified signal of 0.2 to 1.0Kg/ ^cm2 . By using the bimorph in this manner, the displacement of the flapper corresponding to the detection signal is converted into a pneumatic signal without requiring a complicated balance mechanism consisting of a combination of levers and links. A new type of electro-pneumatic converter with a nozzle flapper mechanism having a simplified structure and reduced size has already been devised and used in some cases. However, the above-mentioned bimorph has a property that when a voltage is constantly applied, the above-mentioned displacement amount (-D) of about 2 μ per 1 V gradually decreases, and therefore, process control that requires high reliability over a long period of time. The system's signal converters have drawbacks that prevent them from being used with confidence.

(c) Purpose This invention solves the above-mentioned drawbacks, improves the conventional electropneumatic transducer using an electrostrictive element such as a bimorph, and enables the electropneumatic transducer to be used without constantly applying an input voltage signal to the electrostrictive element. The object is to obtain a convenient electro-pneumatic converter that outputs a pneumatic signal corresponding to a signal.

(d) Configuration In order to achieve the above objectives, this invention has an electro-pneumatic converter configured as follows. That is, in the electropneumatic converter according to this invention, an electrostrictive element is bonded,
The tip of a nozzle, which is connected to an air supply source via an air piping, is placed opposite the free end side of the flapper whose one end is fixed, with a predetermined gap therebetween, and a voltage is applied between the flapper and the electrostrictive element. A pilot valve is provided for amplifying the change in nozzle back pressure caused by the bending of the free end of the flapper and displacing the nozzle in the direction of closing the nozzle, and outputting the amplified change to the output piping. In an electro-pneumatic converter that converts an input voltage signal into a pneumatic signal and outputs it to an output pipe, the output pipe is branched, and the pneumatic signal output to the output pipe is converted into a voltage signal by the branch pipe. Install a pneumatic converter,
and a comparison operational amplifier, the input voltage signal being input to one input terminal, the other input terminal being connected to the pneumatic converter, and the output terminal being connected to the flapper; converting a pneumatic pressure signal corresponding to the input voltage signal inputted to one input terminal into a voltage signal by the pneumatic converter and inputting the converted voltage signal to the other input terminal of the comparison operational amplifier; Accordingly, a pneumatic feedback circuit is provided which makes the deviation signal of the comparator operational amplifier zero and the voltage applied between the flapper and the electrostrictive element to zero, thereby returning the flapper to its original position and preventing it from being displaced. , the nozzle is integrally formed in the center of a metal diaphragm that displaces with a linear characteristic in response to changes in nozzle back pressure, and the nozzle is displaced by the nozzle back pressure to cause the nozzle back pressure to change against the flapper. The structure is characterized in that it is held with a corresponding gap.

(e) Examples Examples of this invention will be described below with reference to the drawings. FIG. 2 is a structural block diagram of an electro-pneumatic converter according to an embodiment of the present invention, in which bimorphs 2 and 2' having a thickness of, for example, about 0.2 mm are bonded to both sides of the flapper 1 with an adhesive. The configuration in which the end (1F) is fixed by the insulating base 3 and the (+) side of the DC voltage signal S _f is applied is the same as the conventional one as explained in FIG. 1. The nozzle mechanism 4 facing this flapper tip IT is one of the main parts of this invention, and the nozzle 5 has a thickness t of about 0.2 mm and a diameter D of 20 mm.
It is attached to the central opening of a metal diaphragm 6 of about mm. The diaphragm 6 is hermetically sealed around its periphery to a metal container 8 which together forms a nozzle back pressure chamber 7, and an air inflow hole 9 is provided in the center of the container 8.

An air pipe 10 is connected to the air inflow hole 9, and the air pipe 10 is connected to an air supply source (not shown). In addition, air piping 1
0, a throttle 11 is interposed as shown by the dotted line, and branch pipes 1 are connected to the air pipe 10 at positions before and after the throttle 11, respectively.
2, 13 are branched, and each branch pipe 12, 13
A pilot valve 14 is connected in parallel with the throttle 11. From the air supply source, pressurized air with an air pressure Pi of, for example, 1.4 kg/cm ² is supplied to the air pipe 10, and the nozzle back pressure Pn of the back pressure chamber 7 is
is controlled by the pilot valve 14, for example, from 0.4 to
The air pressure signal Sp is amplified to 1.0 kg/cm ² and is output from the pilot valve 14 to the output piping 15 and sent to an operating section such as a control valve (not shown). . The configurations from 9 to 15 above are the same as before, but another important part of this invention is from the output pipe 15 to the branch pipe 1.
6, and the voltage signal Sn which is the output from this pneumatic converter 17 is (-)
This is a static feedback circuit 18 formed by a comparison operational amplifier A input to the terminal. An input signal S _i such as temperature from a detection section (not shown) is input to the other (+) terminal of the amplifier A - voltage conversion circuit 1
9, it is converted into a voltage signal S _e and input. In the above configuration, when the input signal S _i is input now, the amplifier A amplifies the above S _e and, for example, DC3~
When the flapper applied voltage S _f of 6V is applied to the flappers 1 and 2.2', the flapper tip IT curves in the direction of closing the nozzle 5, as explained in FIG. As a result, the flapper-nozzle gap G becomes narrower, and the nozzle back pressure P _o becomes close to the atmospheric pressure.
This increased nozzle back pressure P o increases from P _op , and this increased nozzle back pressure P _o
The pressure is amplified by the pilot valve 14 and transmitted to the operating section as an output signal S _p . This output signal
At the same time, S _p is input to the amplifier A as a voltage signal S _o by the above-mentioned pneumatic feedback circuit 18, and is compared with the above-mentioned input voltage signal S _e , and is operated until the deviation Δe becomes zero. In this state of Δe=0, no voltage is applied to the bimorphs 2 and 2' and the above detection signal is
An output signal S _p corresponding to S _i is sent to the operating section. This will be explained with reference to FIG. 3 and the following drawings. Figure 3 shows the relative relationship between the flapper tip 1T and the nozzle 5, with the horizontal axis showing the displacement d _f of the flapper tip 1T shown in Figure 1 in μ units, and the vertical axis when the nozzle 5 is fixed as in the conventional device. nozzle back pressure
This is a diagram of the flap nozzle characteristic curve obtained as P _o ′, where flap 1 has bimorph curvature from 10μ.
The larger the displacement is to 15μ, the closer it gets to the nozzle 5, so the nozzle back pressure P _o ' changes from 0.4Kg/cm ² to 0.6
It shows that the amount increases to Kg/ ^cm2 . Next, FIG. 4 shows the elastic properties of the diaphragm 6, in which the nozzle 5 is provided, against pressure. The figure shows the nozzle back pressure P _o of the back pressure chamber 7 on the horizontal axis, and the diaphragm 6 on the vertical axis.
Since the diaphragm material, thickness, diameter, etc. mentioned above are appropriately selected and designed, linear characteristics are obtained as shown in the figure, and the nozzle back pressure is 0.4 to 0.6 kg/cm ² _. On the other hand, the displacement is correct at 10μ to 15μ. This is illustrated in Figure 5, where the nozzle back pressure P _o is 0.4Kg/cm ² and the figure is 0.6
In the figure when Kg/cm ² , the diaphragm 6 is displaced from the position 6' shown by the dotted line to the position 6 shown by the solid line,
It is shown that the nozzle also rises from 5' to 5 accordingly. On the other hand, Fratupa 1
initially or when the input signal changes, it momentarily shifts as shown in Figure 1, but as explained in Figure 2, the output air pressure signal S _p causes the applied voltage S _f to be canceled by the feedback voltage S _o . Since Δe=0, it has returned to its original position. In other words,
The flapper 1 approaches the nozzle 5 once, but when it returns due to the nozzle back pressure P _o generated,
It has the effect of lifting the nozzle 5 and stabilizing it in a position that maintains the flapper-nozzle gap G corresponding to the detection signal S _i . FIG. 6 is a diagram showing the conversion characteristics of the electro-pneumatic converter of this invention based on the overall operation of the flapper nozzle, where the horizontal axis represents the bimorph applied voltage S _f and the corresponding nozzle back pressure P _o , .
The vertical axis is the output air pressure signal S _p , and S _f starts from 3V.
In the range of 6V, S _p changes from a residual pressure of 0.2Kg/cm ² to 1.0
It shows that it responds almost linearly up to a pressure of Kg/cm ² , and as mentioned above, S _f is only momentarily applied to bimorphs 2 and 2', and then the state of Δe = 0 is maintained at all times. It will be kept.

The above are examples of this invention, but it goes without saying that this invention is not limited to the numerical values used in the illustrations and explanations. For example, the thickness and diameter of the metal diaphragm are just one example, and the relationship between the nozzle back pressure and its displacement can be designed in any way. Furthermore, a mechanism for adjusting the nozzle displacement d _n can also be added. Further, the electrostrictive element is not limited to a bimorph type, and may be bonded to only one side of the flapper.

(f) Effects Since this device is constructed as described above, it is possible to operate an electrostrictive element such as a bimorph at almost zero voltage, completely prevent drift due to continuous voltage application, and achieve high reliability over a long period of time. It has a great effect of keeping the nozzle displacement as mentioned above.
Since it is as small as 5μ, the metal diaphragm that supports it can be given sufficient rigidity, making it possible to provide a compact and convenient device with a simple structure that is robust and completely unaffected by external vibrations. It is something that has been learned.

[Brief explanation of the drawing]

Figure 1 is a side view for explaining the operation of the flapper of an electrostrictive element junction that has already been developed, and Figure 2 is a side view of the flapper of the electrostrictive element junction that has already been developed.
The configuration block diagram (nozzle and flapper) of the electro-pneumatic converter according to the embodiment of this invention using the flapper shown in the figure is a side view. Figure 4 is a graph showing the pressure characteristics of the metal diaphragm to which the nozzle of this device is attached. Figure 5 is a graph showing the relative relationship of the flapper nozzle of this device during operation. The back pressure is 0.4Kg/cm ² , and the figure shows 0.6Kg/cm ² . FIG. 6 is a graph showing the input/output conversion characteristics of this device. 1...Flatspa, IT...Flatspa tip, 2,
2'... Pair of electrostrictive elements, a... Displacement direction due to curvature of the electrostrictive element, 5... Nozzle, 6... Metal diaphragm for equipping the nozzle, 7... Nozzle back pressure chamber, 8... Above A metal container that forms a nozzle back pressure chamber together with the diaphragm 6, P _o ...nozzle back pressure,
G...Flapper-nozzle gap dimension, d _f ... Displacement amount of flapper tip IT, d _n ... Displacement amount of diaphragm 6, S _p ... Output air pressure signal, S _e ... Input voltage signal, 17... Pneumatic converter of pneumatic feedback circuit, A... Comparison amplifier, S _o ... Nozzle back pressure P _o
Corresponding voltage signal, 18... Static feedback circuit, Δe... Deviation output voltage of above A, S _f ... Electrostrictive element applied voltage.

Claims (1)

[Scope of utility model registration request] The tip of a nozzle, which is connected to an air supply source through an air pipe, is placed opposite to the free end side of the flapper to which the electrostrictive element is bonded and one end of which is fixed, with a predetermined gap between the flapper and the electric current. A pilot valve is provided which amplifies the change in nozzle back pressure caused by the application of a voltage between the strain elements, causing the free end side of the flapper to curve and displace the nozzle in the direction of closing, and outputs the amplified change to the output piping. , an electro-pneumatic converter that converts an input voltage signal input to the flapper side into a pneumatic pressure signal and outputs it to an output pipe, the output pipe is branched, and the pneumatic pressure signal output to the output pipe is connected to the branch pipe. A pneumatic converter for converting a signal into a voltage signal is provided, and one input terminal is connected to the input voltage signal, the other input terminal is connected to the pneumatic converter, and an output terminal is connected to the flapper. The pneumatic converter converts a pneumatic pressure signal corresponding to the input voltage signal input into one input terminal into a voltage signal into the other input terminal of the comparison operational amplifier. By inputting the converted voltage signal, the deviation signal of the comparison operational amplifier is made zero, the voltage applied between the flapper and the electrostrictive element is made zero, and the flapper is returned to its original position. In addition, the nozzle is integrally formed in the center of a metal diaphragm that is displaced linearly in response to changes in nozzle back pressure, and the nozzle is integrally formed in the center of a metal diaphragm that is displaced linearly in response to changes in nozzle back pressure. An electro-pneumatic converter characterized in that the nozzle is displaced and held with respect to the flapper with a gap corresponding to the nozzle back pressure.