JP2897154B2 - Electro-pneumatic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electropneumatic converter for converting an electric signal into air pressure.

[0002]

2. Description of the Related Art Conventionally, an electropneumatic converter as shown in FIG. 3 has been known as an electropneumatic converter for converting an electric signal into an air pressure and outputting it. In the figure, reference numeral 1 denotes a flapper that swings around P1 as a fulcrum, 2 denotes a nozzle arranged with the supply air outlet facing the flapper 1, 3 denotes a coil, 4 denotes a permanent magnet, 5-1 and 5- yoke 2 which is attached to the permanent magnet, 6 Reicho spring, 7 feedback bellows 8 biasing spring, 9 is a relay valve, the air pressure P _S where the air pressure supply source is supplied to the nozzle 2 ing. In the electropneumatic converter configured as described above,
The current (4 to 20 mA) corresponding to the input electric signal is applied to the coil 3
Is supplied to the flapper 1, a force acts on the flapper 1 due to the interaction between the magnetic field generated by the coil 3 and the magnetic field generated by the permanent magnet 4, and the flapper 1 swings in the nozzle direction or the counter-nozzle direction with P1 as a fulcrum. Thus, the distance between the nozzle 2 and the flapper 1 is changed, the back pressure P _N of the nozzles 2 is changed.
After the back pressure P _{N of the} nozzle 2 is amplified by the relay valve 9, it is supplied as an output air pressure P _out to an operating device 23 that drives the valve shaft of the automatic control valve 22. At this time, the output air pressure P
_out is also given to the feedback bellows 7 so that the force according to the input electric signal acting on the flapper 1 and the force of the feedback bellows 7 are balanced, and the output air pressure P _out proportional to the input electric signal is obtained.

[0003]

However, according to such a conventional electropneumatic converter, since a current corresponding to an input electric signal is always supplied to the coil 3, there is a problem that power consumption is severe. Was.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an electro-pneumatic converter with low power consumption.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an exciting method for generating first and second pulse-like exciting currents having different polarities at a period determined based on an input electric signal. Current generating means, a coil receiving supply of the first and second pulsed exciting currents generated by the exciting current generating means, a nozzle having a supply air outlet, and a permanent magnet attached to the permanent magnet A case in which a yoke having a magnetic flux passage gap and a part thereof is arranged in the passage gap of the yoke, and a part of the surface faces the nozzle outlet, and a first pulse-like current is supplied to the coil. Due to the residual magnetism left after being magnetized, a part thereof continues to be attracted to one end face side of the passage gap, and the nozzle outlet continues to be closed against the air pressure ejected therefrom, while the second port is connected to the coil. Pulsed current supplied In the case of a flapper made of a ferromagnetic material, a part is continuously attracted to the other end face side of the passing gap due to residual magnetism left by being magnetized to the opposite polarity to the above and opening the nozzle outlet. It has.

[0006]

Therefore, according to the present invention, the first coil
The flapper is magnetized by the supply of the pulse-like exciting current, and a part of the flapper is continuously attracted to one end face side of the passing gap by the remaining remanent magnetism, so that the ejection port of the nozzle reduces the ejection air pressure therefrom. Meanwhile, the flapper is kept closed by the flapper while the flapper is magnetized to the opposite polarity by the supply of the second pulse-like exciting current to the coil, and a part of the flapper is partially closed by the remaining remanent magnetism. The suction is continued toward the other end surface, and the nozzle outlet is kept open.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. FIG. 1 is a configuration diagram of an electropneumatic converter showing one embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a permanent magnet, 11-1
And 11-2, yokes attached to the N pole side and S pole side of the permanent magnet 10; 12, a facing gap between the yokes 11-1 and 11-2 (a gap for passing a magnetic flux created by the permanent magnet 10) 11;
-3 is a flapper having the tip 12-1 inserted therein, 13 is a nozzle arranged with a part of the flapper 12 facing the injection port 13-1 of the supply air, and 14 is a nozzle to the nozzle 13. A fixed throttle arranged in a passage for supply air, 1
5 is a volume tank which receives the back pressure P _N of the nozzle 12 as an input, 16 is a coil wound around the flapper 12, and 17 is an exciting circuit for supplying an exciting current I to the coil 16, and these are electro-pneumatic. A conversion unit has been constructed.
In this electro-pneumatic converter, the flapper 12 is made of a ferromagnetic material, and is provided so as to swing clockwise and counterclockwise around P2 as a fulcrum. Further, the nozzle 13, the air pressure P _S where the air pressure supply source is supplied.

Reference numeral 18 denotes an input electric signal (analog signal: 4 to
A / D converter for converting 20 mA) into a digital signal (0 to 100%) and outputting the converted signal. Reference numeral 19 denotes a current output air pressure P _out (analog signal: for example, 0.2
１．０1.0 kgf / cm ² ) to a digital signal (0-100
%) And outputs an A / D converter, 20 is an A / D converter.
Digital signal D _in output from D converter 18 and A / D
Difference Δ from digital signal D _out output from converter 19
D is a subtractor for calculating D, and 21 is a ΔD calculated by the subtractor 20.
To input a command corresponding to ΔD to the excitation circuit 17
U.

Next, while exchanging the function of the exciting circuit 17,
The operation of the electropneumatic converter will be described. Input electrical signal by the A / D converter 18 is converted into a digital signal D _in, given to the subtractor 20. The subtractor 20 calculates A /
The difference ΔD between the digital signal D _in from the D converter 18 and the digital signal D _out from the A / D converter 19 is calculated, and the calculated ΔD is provided to the CPU 21. CPU2
1 sends a command corresponding to the difference to the excitation circuit 17 based on ΔD given from the subtractor 20, that is, based on the difference between the target output air pressure P _out corresponding to the input electric signal and the current output air pressure P _out .

The excitation circuit 17 generates first and second pulse-like excitation currents I1 and I2 having different polarities in a cycle T according to ΔD based on a command from the CPU 21 (FIG. 2).
(A)), the exciting currents I1 and I2 are
Supply to 6. As a result, the flappers 12 are alternately magnetized with opposite polarities. That is, the flapper 12 is magnetized by the first exciting current I1, and its tip 12-1
Becomes the S polarity (see FIG. 2B), and the second exciting current I
2, the flapper 12 is magnetized in the opposite polarity to the above, and its tip 12-1 has N polarity.

The flapper 12 is magnetized and its tip 12
When -1 becomes the S polarity, the tip 12-1 becomes the gap 11-3.
Is sucked to the upper end surface 11-11 side of the flapper, whereby the flapper 12 rotates clockwise about P2 as a fulcrum. By the clockwise rotation of the flapper 12, the ejection port 13-1 of the nozzle 13 is closed by the flapper 12,
Back pressure P _N increases. Tip 12-1 of flapper 12
Because the flapper 12 is a ferromagnetic material and has a large coercive force, the residual magnetism continues to be attracted to the upper end surface 11-11 side of the gap 11-3 even after the excitation current I1 has disappeared. That is, the ejection port 13-1 of the nozzle 13 is connected to the exciting current I1.
Even after the disappearance of the flapper, the flapper 1
2 continue to be occluded.

On the other hand, when the flapper 12 is magnetized and its tip 12-1 has N polarity, the tip 12-1
-3 is sucked toward the lower end surface 11-21, whereby the flapper 12 rotates counterclockwise about P2 as a fulcrum. When the flapper 12 rotates counterclockwise, the nozzle 1
3 is opened, and the back pressure P _{N of the} nozzle 13 is released.
Descends. Since the flapper 12 is a ferromagnetic material and has a large coercive force, the tip portion 12-1 of the flapper 12 is attracted to the lower end surface 11-21 of the gap 11-3 by the residual magnetism even after the excitation current I2 is lost. to continue. That is, the ejection port 13-1 of the nozzle 13 is kept open even after the excitation current I2 has disappeared.

In this manner, the ejection port 13 of the nozzle 13
By -1 is closed and opening alternately with a period T corresponding to [Delta] D, the output air pressure from the volume tank 15 back pressure P _N of the nozzles 13 is raised, lowered been adjusted, at operation 23 side current output air pressure P _out is adjusted to the target output pressure P _out of meeting the input electrical signal.

Here, the excitation current I to the coil 16 may be supplied only to the hatched portion shown in FIG. 2A, so that the power consumption is greatly reduced as compared with the prior art.

Although the coil 16 is wound around the flapper 12 in the present embodiment, the coil 16 may be arranged close to the flapper 12 without being wound around the flapper 12. In the present embodiment, needless to say, the exciting current I
Is changed.

[0017]

As is apparent from the above description, according to the present invention, the flapper is magnetized by the supply of the first pulse-like exciting current to the coil, and a part of the flapper is formed by the remaining residual magnetism. Continues to be sucked to one end face side of the passing gap, and the nozzle outlet continues to be closed by the flapper against the air pressure ejected therefrom, while the second to the coil
By supplying the pulse-like exciting current, the flapper is magnetized in the opposite polarity to the above, and a part of the flapper continues to be attracted to the other end face side of the passing gap by the remaining residual magnetism, so that the nozzle ejection port is Since the coil is kept open and the supply of the exciting current to the coil is small, the power consumption is greatly reduced as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electropneumatic converter showing one embodiment of the present invention.

FIG. 2 is a time chart showing a state of supply of an exciting current I to a coil and a state of magnetization of a tip portion of a flapper.

FIG. 3 is a configuration diagram showing a conventional electropneumatic converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Permanent magnet 11-1, 11-2 Yoke 11-3 Opposition gap 12 Flapper 12-1 Tip part 13 Nozzle 14 Fixed throttle 15 Volume tank 16 Coil 17 Excitation circuit 18 A / D converter 19 A / D converter 20 Subtractor 21 CPU

Claims (1)

(57) [Claims] 1. Exciting current generating means for generating first and second pulsed exciting currents having different polarities at a period determined based on an input electric signal; and first and second generating means for generating the exciting current. A coil receiving a pulsed excitation current, a nozzle having a supply air outlet, a yoke attached to a permanent magnet and having a gap through which a magnetic flux created by the permanent magnet passes; A part is disposed, and a part of the part faces the ejection port of the nozzle, and the part is magnetized when the first pulse-shaped current is supplied to the coil, and the part is formed by residual magnetism. When the second pulse-shaped current is supplied to the coil while the suction opening of the nozzle continues to be sucked on one end surface side of the passage gap and closes the ejection port of the nozzle against the ejection air pressure from the nozzle. Contrary to the above And a flapper made of a ferromagnetic material that continues to be attracted to the other end face side of the passing gap by the residual magnetism left after being polarized to a polarity and keeps the nozzle opening of the nozzle open. Characterized electro-pneumatic converter.