JPH0357321B2 - - Google Patents

Description

Detailed Description of the Invention <Field of Industrial Application> The present invention relates to a pneumatic signal output device that inputs an electrical signal and outputs a pneumatic signal according to the electrical signal. Accordingly, the present invention relates to a pneumatic signal output device that is applied when a load such as a valve is driven by a pneumatic signal.

<Prior Art> Conventionally, there is a device that uses a needle valve type servo valve as a device that outputs a pneumatic signal in response to an electric signal.

In such conventional devices, in order to obtain a pneumatic signal that accurately corresponds to an input signal, a highly accurate and expensive servo valve is required.

For example, as shown in Japanese Patent Publication No. 46-39967, an electric signal is amplified by a DC amplifier and the output is applied to a movable iron core type electromagnetic device.
Some devices are configured to convert the displacement of this movable core type electromagnetic device into a pneumatic signal by a nozzle flapper mechanism, and to feed back an electrical signal corresponding to the pneumatic pressure signal negatively to the input side of a DC amplifier.

<Problems to be Solved by the Invention> However, the conventional device having such a configuration requires a relatively large movable core type electromagnetic device, making the entire device large and complicated.

The present invention has been made in view of these points, and its object is to realize a device that has a simple configuration and can obtain an analog pneumatic signal that is accurately proportional to an input electrical signal.

<Means for Solving the Problems> The present invention for solving the problems described above includes: a pneumatic supply source; a tank connected to an output terminal; one end connected to the pneumatic supply source and the other end connected to the tank. An electrical signal is input to the first pneumatic switch, which has one end open and the other end connected to the tank, and the pulse width changes differentially depending on the magnitude of the electrical signal. and a pulse width signal output circuit that outputs two pulse width signals.

<Function> When the first pneumatic switch is turned on, it introduces air pressure from the pneumatic pressure source into the tank for only the time it is turned on.

The second pneumatic switch causes the air pressure introduced into the tank to be discharged to the outside for only the time that the second pneumatic switch is on.

The pulse width signal output circuit outputs two pulse width signals whose time widths differentially change in response to the input electrical signal, and one pulse width signal determines the on/off time of the first pneumatic switch. and controls the on/off time of the second pneumatic switch by the other pulse width signal.

The tank averages the fluctuations in the air pressure introduced through the first air pressure switch and the fluctuations in the air pressure discharged through the second air pressure switch, and outputs the averaged air pressure signal as an output signal.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a pulse width signal converter to which an input electric signal ei is applied and converts this signal into a pulse width signal, and 11 is a pulse width signal converter 1.
This is an inverter that inverts the pulse width signal from. The pulse width signal from the pulse width signal converter 1 and the pulse width signal from the inverter 11 have pulse widths (time widths) that vary differentially depending on the magnitude of the input electrical signal ei. It is becoming.

Here, the pulse widths of the pulse width signals differentially change depending on the input electrical signal ei, which means that the pulse width of the signal from the pulse width signal converter 1 changes as the input electrical signal ei becomes larger. The pulse width of the signal output from the inverter 11 increases accordingly, and as the input electrical signal ei becomes smaller, the pulse width of the signal output from the inverter 11 becomes smaller as the input electrical signal ei becomes larger. When the input electrical signal ei becomes smaller, the pulse width also becomes larger. In other words, when the pulse width of one signal becomes larger, the pulse width of the other signal becomes larger. It refers to a relationship that changes mutually so that it becomes smaller by the same amount.

2 is a first pneumatic switch that operates on/off in accordance with the pulse width signal from the pulse width signal converter 1, and 3 is a second pneumatic switch that operates on/off in response to the pulse width signal from the inverter 11. Here, a structure including diaphragms 21 and 31 that are displaced by air pressure is used.

4 is an air pressure supply source, 5 is an output terminal, and 6 is a tank connected to the output terminal 5.

In the first pneumatic switch 2, a pipe 22 corresponding to the input end of the switch is connected to the pneumatic supply source 4, and a pipe 23 corresponding to the output end is connected to the tank 6, so that the diaphragm 21 is displaced. This turns on and off between the tubes 22 and 23. A nozzle 25 is connected to one end of the pipe 24 through which switch control air pressure for displacing the diaphragm 21 is introduced, and this nozzle 25 is displaced in response to a pulse width signal from the pulse width signal converter 1. It is competing against Fratupa 26.

In the second pneumatic switch 3, a pipe 32 corresponding to the input end of the switch is open at one end, and a pipe 33 corresponding to the output end is connected to the tank 6. One end of the pipe 34 to which the switch control air pressure for displacing the diaphragm 31 is introduced,
A nozzle 35 is connected, and this nozzle 35
is opposed to the flapper 36 which is displaced in response to the pulse width signal from the inverter 11.

Note that air pressure from the air pressure supply source 4 is supplied to each nozzle 25, 35 via a restriction 27, 37.

FIG. 2 is a waveform diagram showing an example of a pulse width signal output from the pulse width signal converter 1.

The pulse width Td1 of this pulse width signal corresponds to the input electrical signal ei, and only during Td1, the flapper 26 is displaced in the direction of the arrow, and the back pressure of the nozzle 25 is lowered only during the pulse width Td1. 1 pneumatic switch 2 is opened.

In addition, the flapper 36 has a time width in FIG.
It is displaced in the direction of the arrow only during Td2, the back pressure of the nozzle 35 becomes low, and the second pneumatic switch 3 switches to Td.
It is open only between 2 and 3. As a result, the on-times of the first and second pneumatic switches 2 and 3 are controlled differentially depending on the magnitude of the input electrical signal ei.

That is, the pneumatic switch 2 receives the input electric signal ei
As the input electrical signal ei becomes larger, the on time becomes longer, and as the input electrical signal ei becomes smaller, the on time becomes shorter, whereas for the pneumatic switch 3, as the input electrical signal ei becomes larger, the on time becomes shorter, and as the input electrical signal ei becomes smaller, the on time becomes shorter. The on-times differ from each other so that the on-times become longer.

Note that the flappers 26 and 36 are composed of, for example, a pulse motor.

FIG. 3 is a simplified diagram showing the connections of the first and second pneumatic switches, the pneumatic supply source 4, and the tank 6, and FIG. 4 is an equivalent circuit equivalent to that of FIG. 3 using an electric circuit. It is.

In these figures, PS is the output pressure of the pneumatic supply source 4, and R1 and R2 are the pipes 22, 23, 32, 33.
, C is the capacity of tank 6, and the resistance R of each pipe is
Assuming that 1, R2 is sufficiently smaller than the tank capacity C, the output air pressure Po from the tank 6 is expressed by the following equation.

Po=PS・(K/C)・{(Td1−Td2)/TS} Where, K is a constant Therefore, the output air pressure Po corresponds exactly to the pulse width signal, that is, the input electrical signal ei. .

In this way, in the present invention, if the electric circuit is equivalent, the first air pressure switch controls the time for introducing air pressure into the tank, and the second air pressure switch controls the time for discharging air pressure from the tank. It controls the Furthermore, the tank averages the fluctuations in the air pressure introduced through the first air pressure switch and the fluctuations in the air pressure discharged through the second air pressure switch, and outputs the averaged air pressure signal as an output signal. It has the function of

FIG. 5 is a configuration explanatory diagram showing another embodiment of the apparatus according to the present invention.

In this embodiment, the output air pressure of tank 6 is
An air-to-electric conversion means 7 is provided which inputs Po, converts it into an electric signal ef, and feeds it back negatively to the input side of the pulse width signal converter 1.

As this air-to-electric conversion means, for example, a known means that combines a bellows and a displacement transducer can be used. In this example, DC solenoids are used as the flappers 26 and 36 that are displaced according to the pulse width signal, and these operate differentially with respect to the magnitude of the input electric signal ei.
The ON time of the second pneumatic switches 2 and 3 is controlled.

According to this embodiment, the pulse width signal converter 1
is the negative feedback signal ef from the air-electric conversion means 7,
It outputs a pulse width signal equal to the input electrical signal ei, and the output air pressure from the tank 6
Po corresponds more precisely to the input electrical signal ei.

FIG. 6 is a cross-sectional view showing another example of the structure of the flappers 26, 36 in FIG. 1 or 5. FIG. In this example, a piezoelectric bimorph formed by stacking piezoelectric ceramics 250 having electrodes 251 is used as a flapper.

In the above embodiments, the pulse width signal converter 1 may be a known analog circuit including an integrator and a comparator, a circuit using a microcomputer, or the like.

Further, in each of the above embodiments, the pneumatic switch includes a diaphragm that is displaced by back pressure from the nozzle flapper, but a solenoid valve or the like may be used instead.

<Effects of the Invention> As described in detail above, the present invention allows the introduction time of air pressure introduced into the tank and the discharge time of air pressure discharged from the tank to be differentially controlled depending on the magnitude of the input electrical signal. The output air pressure signal is obtained through a tank, and the tank has a smoothing effect on the pulsating air pressure signal. Therefore, according to the present invention, it is possible to obtain a pulsation-free pneumatic signal from the tank that accurately corresponds to the magnitude of the input electrical signal.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing an example of a pulse width signal output from a pulse width signal converter, and FIG. Figure 4 is a simplified diagram of the connections between the pneumatic switch, the pneumatic supply source, and the tank.
FIG. 5 is an explanatory diagram showing another embodiment of the device according to the present invention, and FIG. 6 is a sectional view showing another example of the configuration of the flapper. 1... Pulse width signal converter, 2, 3... First,
Second pneumatic switch, 4...Pneumatic pressure source, 6
……tank.

Claims (1)

[Scope of Claims] 1: a pneumatic pressure supply source; a tank connected to an output terminal; a first pneumatic switch having one end connected to the pneumatic pressure supply source and the other end connected to the tank; A second pneumatic switch, the other end of which is connected to the tank, inputs an electrical signal, and depending on the magnitude of this electrical signal, the pulse width of one signal increases while the pulse width of the other signal increases. and a pulse width signal output circuit that outputs two pulse width signals whose pulse widths are differentially changed from each other so that the pulse width becomes smaller, and one of the two pulse width signals controls the first pneumatic switch. controlling the on/off time and controlling the on/off time of the second pneumatic switch by the other of the two pulse width signals, such that the pneumatic pressure signal is obtained as an output signal from an output terminal connected to the tank; Signal output device.