JPH041398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a pulse pneumatic transducer used for process control and the like.

(b) Prior art As shown in Fig. 1, a conventional pulse pneumatic converter receives an UP pulse signal sent from a voltage pulse converter (not shown) in the control room or
The DOWN pulse signal is amplified by the pulse motor drive circuit 1 and applied to the pulse motor 2, and the pulse motor 2 is moved in steps to displace the nozzle flapper 8 via the gears 3, 4, 5, 6 and the spring 7. There is one in which the gap of the nozzle 9 is controlled and the output air pressure is derived from the booster relay 10 in accordance with the input pulse signal. In addition, this pulse pneumatic pressure converter detects the position of the pulse motor 2 with a potentiometer 12 via gears 4 and 11, and feeds back an answer signal to the control room side via a resistance-electrical signal converter 13. There is. This type of pulse pneumatic converter uses a pulse motor and gears to convert input pulse signals into pneumatic pressure, so when operated continuously at high speeds, the mechanical parts are subject to severe wear and tear, shortening their lifespan. It was hot. In addition, since the answer back signal is obtained by detecting the position of the pulse motor 2 with the potentiometer 12, even if there is a malfunction in the pneumatic system, the effect will not appear immediately on the answer back signal, thus reducing reliability. There was a problem.

(c) Purpose An object of the present invention is to eliminate the drawbacks of the conventional pulse pneumatic converter described above and to provide a pulse pneumatic converter that has a long life and is highly reliable.

(d) Configuration In order to achieve the above object, the pulse air pressure converter of the present invention includes a counter that receives an input pulse signal and integrates it, a D/A converter that converts the integrated output of this counter into an analog signal, and a supply air pressure converter. a pilot valve that receives and derives an output air pressure; a pneumatic converter that converts the output air pressure from the pilot valve into an electrical signal; and a comparator that receives and compares the output of the D/A converter and the output of the pneumatic converter. , a nozzle flapper system consisting of a nozzle and a nozzle flapper whose nozzle back pressure is controlled according to the comparator output, and an answerback signal circuit which feeds back the output of the pneumatic converter.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a block diagram of a pulse air pressure converter showing one embodiment of the present invention. In the same figure, 21
is a voltage pulse converter installed on the control room A side, which outputs an UP pulse signal or
Outputs DOWN pulse signal. 22 is the UP pulse signal line, 23 is the DOWN pulse signal line,
24 is a common line, and these signal lines constitute a pulse signal transmission path 25.
Through this pulse signal transmission path 25, a pulse signal is transmitted from the control room A to the pulse air pressure converter B side at the site. 26 is an up/down counter that receives the UP pulse signal and the DOWN pulse signal and adds up the sum. The output of this up-down counter 26 is applied to a D/A converter 28 via a bit signal output line 27. The output of the D/A converter 28 is connected to the plus (+) input terminal of a comparator 29.
The output of the nozzle flapper 30 depends on the output.
is supplied to the nozzle flapper system 31 so as to displace the . Although the nozzle flap system 31 is schematically shown here as a nozzle flap 31, a fulcrum 33, and a nozzle 34, various nozzle flap systems may be used as appropriate, such as those using bimorph for the flap, and those using electromagnetic force to move the flap. do it.

A pilot valve 34 receives the supplied air pressure and outputs an output air pressure according to the back pressure of the nozzle 33. The output air pressure derived from this pilot valve 34 is transferred to a pneumatic converter 3 formed by a piezoelectric sensor or the like.
5 and is converted into an electrical signal (current Io). This current Io is transmitted as an answerback signal by the answerback signal transmission line 36.
Feedback is provided to the power supply 37 in the control room A. Furthermore, this current Io is
The voltage flowing through the resistor 38 and generated at the resistor 38 is connected to be applied to the negative (-) input terminal of the comparator 29.

In the pulse air pressure converter configured as described above, when an UP pulse signal or a DOWN pulse signal is applied from the voltage pulse converter 21 via the pulse transmission line 25, the up/down counter 26
integrates these pulse signals and converts the integrated result into an analog signal by the D/A converter 28 and outputs it. Therefore, if the input voltage is large and many UP pulses are transmitted through the pulse transmission line 25, the integrated value of the up-down counter 26 will also be large, and the analog output value of the D/A converter 28 will be large, causing the opposite effect. When the input signal becomes small, the analog output value of the D/A converter 28 also becomes small.

The analog output value of the D/A converter 28 is compared by a comparator 29 with a voltage proportional to the output air pressure from a resistor 38. As the output air pressure at that point is small and the input voltage becomes large, the output signal of the comparator 28 becomes large, which causes the nozzle flapper 30 of the nozzle flapper system 31 to be largely displaced, and the nozzle 33
This narrows the gap between the nozzle and the nozzle, increasing the nozzle back pressure and increasing the output air pressure. When the output air pressure increases, the pneumatic converter 35 converts the increase in the output air pressure into an increase in the current Io. That is, the pneumatic converter 35 operates as an impedance conversion element.
When the current Io increases, the voltage across the resistor 38 increases, so the output of the comparator 29 becomes smaller, and the degree to which the nozzle flapper 30 is displaced becomes smaller, and the gap between the nozzle flapper 30 and the nozzle 33 gradually increases to derive the output air pressure corresponding to the input voltage. balance with. The output air pressure at this time is output from the pneumatic converter 35 as an answer back signal of the current Io.
Feedback is sent to the control room A side via the answer back transmission line 36.

In this pulse pneumatic converter, if there is an abnormality in the pneumatic system, for example when the output air pressure becomes extremely low, the answer back signal will become small and this signal will be indicated as the valve opening in the control room, so the abnormality will occur immediately. can be noticed.

In addition, in the pulse pneumatic converter of the above embodiment, a DC power source is used as the power source 37, but this
As shown in the figure, power may be supplied to the pulse pneumatic converter B from an AC power source 39 in the control room A, and converted to a DC voltage by an AC/DC converter 40.

(f) Effects According to the pulse air pressure converter of the present invention, since the only moving part is the nozzle flapper system, there is almost no mechanical wear and tear, so that a long life can be obtained. Furthermore, since an electrical signal proportional to the output air pressure is used as the answer back signal, if an abnormality occurs in the air pressure system, it can be dealt with immediately, resulting in excellent reliability.

[Brief explanation of drawings]

Figure 1 is a block diagram showing a conventional pulse air pressure converter, Figure 2 is a block diagram of a pulse air pressure converter showing an embodiment of the present invention, and Figure 3 is a diagram of the power supply used in the pulse air pressure converter. FIG. 7 is a block diagram showing another example. 26: Up-down counter, 28: D/A converter, 29: Comparator, 30: Nozzle flapper, 31: Nozzle flapper system, 33: Nozzle, 34: Pilot valve, 35: Pneumatic converter, 3
6: Answer back signal transmission line, 38: Resistor for current detection.

Claims (1)

[Claims] 1. A counter that receives an input pulse signal and integrates it, a D/A converter that converts the integrated output of this counter into an analog signal, a pilot valve that receives the supply air pressure and derives the output air pressure, and a a pneumatic converter that converts into an electrical signal; a comparator that receives and compares the output of the D/A converter and the output of the pneumatic converter;
A pulse pneumatic pressure converter comprising a nozzle flapper system consisting of a nozzle and a nozzle flapper whose nozzle back pressure is controlled according to the comparator output, and an answerback signal circuit which feeds back the output of the pneumatic converter.