JP2016094951A - Electropneumatic converter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate influence of an outer magnetic field without applying any magnetic shield against an electromagnetic coil and without arranging a correcting coil.SOLUTION: There is provided a coil 13 for detecting a composite magnetic field so as to detect an orientation and an intensity of composite magnetic field of a magnetic field (controlling magnetic field) φS generated by an electromagnetic coil 7 and a component φG in parallel with the controlling magnetic field φS of an outer magnetic field acted on the electromagnetic coil 7. A calculation part 1A is provided with a control output correction function F2 so as to correct a control output (coil driving current) Is in such a way that an orientation and an intensity of the composite magnetic field detected by the coil 13 for detecting the composite magnetic field may become the same as an orientation and an intensity of the magnetic field (an object magnetic field) corresponding to a target value to be generated by the electromagnetic coil 7.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an air pressure conversion device that converts an electric signal into an air pressure signal.

[Conventional example 1: Electro-pneumatic converter]
Conventionally, as this type of electropneumatic converter, an electropneumatic converter 100 configured as shown in FIG. 9 is known (see, for example, Patent Document 1). FIG. 9 is a block diagram showing a main part of the electropneumatic converter 100. Reference numeral 1 denotes a calculation unit including a CPU, 2 denotes an electropneumatic conversion unit, and 3 denotes a nozzle back pressure P _N from the electropneumatic conversion unit 2. Is a pilot relay for amplifying the output air pressure Pout, and 4 is a feedback sensor for detecting the output air pressure Pout.

In the electropneumatic converter 100, the electropneumatic converter 2 includes a permanent magnet 5 formed in a U shape in plan view as shown in FIG. 10 and one end portion opposed to both upper and lower end portions of the permanent magnet 5. Each of the attached yokes 6, the electromagnetic coils 7 disposed between the upper and lower yokes 6, and an appropriate gap between the yokes 6 are disposed to penetrate the center of the electromagnetic coil 7, and the lower ends thereof A flapper (iron piece) 9 is pivotally supported by one of the lower yokes 6 by a fulcrum spring 8 and a counterweight 10 provided at the lower end of the flapper 9. The nozzle 11 is disposed in close proximity to each other. The nozzle 11 is supplied with air of a predetermined pressure P _S from an air pressure supply source via a throttle 12.

  In the electropneumatic converter 100 configured as described above, when an input electrical signal (current signal including target value information) Iin (4 to 20 mA) is input, a current signal fed back from the feedback sensor 4 (feedback signal). ) If and the difference between the input electric signal Iin and the feedback signal If is input to the arithmetic unit 1.

  The calculation unit 1 includes a control output generation function F1, and inputs a difference ΔI between the input electric signal Iin and the feedback signal If (a difference between the current signal including target value information and the current signal fed back), A command for making the input signal difference ΔI zero is generated as a current signal Is corresponding to the target value, and the current signal Is corresponding to the generated target value is output to the electropneumatic converter 2 as a control output Is. In the electropneumatic converter 2, the electromagnetic coil 7 converts the control output Is from the calculator 1 into a magnetic force, and swings the flapper 9 in the nozzle direction or the counter-nozzle direction.

As a result, the separation distance x between the nozzle 11 and the flapper 9 changes, that is, the separation distance x of the nozzle flapper mechanism (air pressure conversion unit) composed of the nozzle 11 and the flapper 9 changes, and the back pressure of the nozzle 11 (nozzle) Back pressure) _PN changes. The nozzle back pressure P _N is amplified by the pilot relay 3 and then supplied as an output air pressure Pout to an operating device that drives the valve shaft of the control valve 300, whereby the valve opening degree of the control valve 300 is controlled.

  The output air pressure Pout is detected by the feedback sensor 4 and returned to the input side of the calculation unit 1 as a feedback signal If. For this reason, the valve opening degree of the control valve 300 is stabilized when the deviation between the input electric signal Iin and the feedback signal If becomes zero.

[Conventional example 2: Electro-pneumatic positioner]
An electropneumatic positioner 200 configured as shown in FIG. 12 is also known as an electropneumatic conversion device (see, for example, Patent Document 2). FIG. 12 is a block diagram showing the main part of the electropneumatic positioner 200, in which 21 is an input signal processing unit, 22 is an arithmetic unit provided with a CPU, 23 is an electropneumatic conversion unit, and 24 is from the electropneumatic conversion unit 23. The air signal amplifying unit 25 amplifies the nozzle back pressure P _N and supplies it to the control valve 300 as the output air pressure Pout, 25 detects the lift position of the control valve 300 as the valve opening, and the current according to the detected valve opening It is a valve opening degree detection part which returns a signal to the input side of the calculating part 22 as the feedback signal If.

In the electropneumatic positioner 200 configured as described above, an input electric signal (current signal including target value information) Iin (4 to 20 mA) is sent to the input signal processing unit 21. The calculation unit 22 includes a control output generation function F1, and the difference between the input electric signal Iin from the input signal processing unit 21 and the feedback signal If from the valve opening degree detection unit 25 (a current signal including target value information) A difference (ΔD from the current signal fed back) ΔI is input, and a command to make the input signal difference ΔI zero is generated as a current signal Is corresponding to the target value (set value). The corresponding current signal Is is output to the electropneumatic converter 23 as a control output Is. Similar to the electropneumatic conversion unit 2 shown in FIG. 10, the electropneumatic conversion unit 23 includes an electromagnetic coil and a nozzle flapper mechanism (pneumatic pressure conversion unit), converts the control output Is from the calculation unit 22 into a magnetic force, converting the converted force to the nozzle back pressure P _N.

The nozzle back pressure P _N converted by the electropneumatic conversion unit 23 is amplified by the air signal amplification unit 24 and then supplied as an output air pressure Pout to an operating device that drives the valve shaft of the control valve 300. A valve opening of 300 is controlled.

  Further, the valve opening degree of the control valve 300 is detected by the valve opening degree detection unit 25 and returned to the input side of the calculation unit 22 as a feedback signal If. For this reason, the valve opening degree of the control valve 300 is stabilized when the deviation between the input electric signal Iin and the feedback signal If becomes zero.

JP 7-110003 A Japanese Patent Laid-Open No. 11-51703

  However, such an electropneumatic conversion device has a problem that it is affected by fluctuations in the external magnetic field because the electromagnetic coil is used to convert the control output from the calculation unit into magnetic force.

  That is, taking the electropneumatic converter 100 shown in FIG. 9 as an example, as shown in FIG. 10, the electromagnetic coil 7 is used to convert the control output Is from the calculation unit 1 into a magnetic force. For this reason, an external magnetic field acts on the magnetic field generated by the electromagnetic coil 7 and is affected by the fluctuation of the acting external magnetic field.

  FIG. 11 illustrates the relationship between the magnetic field generated by the electromagnetic coil 7 and the external magnetic field acting on the electromagnetic coil 7. In the figure, φS is a magnetic field (control magnetic field) generated by the electromagnetic coil 7, and φG is a component in a direction parallel to the control magnetic field φS of the external magnetic field acting on the electromagnetic coil 7.

  In this example, the calculation unit 1 includes a CPU 1-1 and a coil drive circuit 1-2. In response to the instruction from the CPU 1-1, the coil drive circuit 1-2 causes the control output Is to flow through the electromagnetic coil 7 as a current (coil drive current) Is corresponding to the target value.

  In this example, a magnetic field parallel to the control magnetic field φS and opposite to the control magnetic field φS generated by the electromagnetic coil 7 acts as a component φG in a direction parallel to the control magnetic field φS of the external magnetic field. For this reason, the strength of the control magnetic field φS is substantially reduced, and the magnetic force acting on the flapper 9 is reduced.

The external magnetic field acting on the control magnetic field φS generated by the electromagnetic coil 7 (component φG in the direction parallel to the external magnetic field control magnetic field φS) varies depending on the environment in which the electropneumatic transducer 100 is placed. When the external magnetic field that acts on the control magnetic field φS generated by fluctuates, the magnetic force that acts on the flapper 9 also fluctuates. For this reason, the nozzle back pressure _PN fluctuates, and the control of the valve opening of the control valve 300 becomes unstable.

  Also in the electropneumatic positioner 200 shown in FIG. 12, the electromagnetic coil is used in the electropneumatic converter 23, so that the same problem as the electropneumatic converter 100 occurs. In the electropneumatic converter 100 and the electropneumatic positioner 200, the output air pressure Pout and the valve opening of the control valve 300 are observed. However, since the magnetic field is not observed, it cannot be handled by itself. Also, if a nonconformity occurs on site, it takes time to identify the cause.

  Although it is conceivable to shield the electromagnetic coil, it is difficult to completely eliminate the influence of the external magnetic field. In addition, an electropneumatic converter such as an electropneumatic converter or an electropneumatic positioner that controls the valve opening of the control valve is required to be downsized in addition to an explosion-proof structure. That is, it is difficult to reduce the size of the periphery of the electromagnetic coil, the assembly structure is complicated, and the cost is increased. Further, in the intrinsically safe explosion-proof structure, the electromagnetic coil that is the energizing part must be separated from the housing by a certain amount or more.

  In addition, it is conceivable to provide a correction coil for canceling the influence of the external magnetic field, that is, it is possible to cancel the external magnetic field by passing a current through the correction coil. In addition, a circuit for detecting an external magnetic field, a circuit for driving a correction coil, and the like are also required, and the configuration becomes complicated.

  The present invention has been made to solve such problems, and the object of the present invention is to eliminate the influence of an external magnetic field without magnetically shielding an electromagnetic coil and without providing a correction coil. It is an object of the present invention to provide an electropneumatic conversion device that can do this.

  In order to achieve such an object, the present invention provides a calculation unit that outputs a current signal according to a target value as a control output, an electromagnetic coil that converts the control output from the calculation unit into a magnetic force, and the electromagnetic coil includes: In an electropneumatic converter having an air pressure conversion unit that converts the converted magnetic force into air pressure, the magnetic field generated by the electromagnetic coil is used as a control magnetic field, and the control magnetic field and an external magnetic field acting on the electromagnetic coil are controlled. It has a synthetic magnetic field detector that detects the direction and strength of the synthetic magnetic field with the component in the direction parallel to the magnetic field, and the arithmetic unit generates the electromagnetic coil with the direction and strength of the synthetic magnetic field detected by the synthetic magnetic field detector. A control output correction unit that corrects the control output so as to be the same as the direction and strength of the magnetic field according to the target value to be obtained is provided.

  According to this invention, the direction and strength of the combined magnetic field of “the magnetic field generated by the electromagnetic coil (control magnetic field)” and “the component in the direction parallel to the control magnetic field of the external magnetic field acting on the electromagnetic coil”. Is detected by the synthetic magnetic field detector. The calculation unit outputs a control output to the electromagnetic coil so that the direction and strength of the synthetic magnetic field detected by the synthetic magnetic field detection unit are the same as the direction and strength of the magnetic field according to the target value to be generated by the electromagnetic coil. Correct. That is, in the present invention, the influence of the external magnetic field is eliminated only by detecting the direction and strength of the combined magnetic field and correcting the control output to the electromagnetic coil based on the detected combined magnetic field.

  In the present invention, the calculation unit inputs a difference between a current signal including target value information and a current signal fed back and inputs a command for setting the difference between the input signals to zero as a current signal corresponding to the target value. And a current signal corresponding to the generated target value is output as a control output. In this case, the feedback current signal may be a current signal corresponding to the air pressure converted by the air pressure conversion unit, and the valve opening degree of the control valve to which the air pressure converted by the air pressure conversion unit is given as an operation output It may be a current signal according to.

  According to the present invention, the direction and strength of the combined magnetic field of “the magnetic field generated by the electromagnetic coil (control magnetic field)” and “the component in the direction parallel to the control magnetic field of the external magnetic field acting on the electromagnetic coil”. And the control output to the electromagnetic coil is corrected so that the direction and strength of the detected composite magnetic field are the same as the direction and strength of the magnetic field according to the target value to be generated by the electromagnetic coil. Since the electromagnetic coil is not magnetically shielded and no correction coil is provided, the direction and strength of the combined magnetic field can be detected, and the control output to the electromagnetic coil based on the detected combined magnetic field. It is possible to eliminate the influence of the external magnetic field only by correction.

It is a block diagram which shows the principal part of one Embodiment (electropneumatic converter) of the electropneumatic converter which concerns on this invention. It is a longitudinal cross-sectional view which shows the structure of the electropneumatic conversion part in this electropneumatic converter. It is a figure which shows the principal part of the calculating part in this electropneumatic converter. It is a flowchart which shows the processing operation which CPU of the calculating part in this electropneumatic converter performs. It is a figure which shows a mode that the magnetic field for control (phi) S which the coil for electropneumatic conversion in this electropneumatic converter produces | generates is correct | amended. It is a block diagram which shows the principal part of other embodiment (electropneumatic positioner) of the electropneumatic converter which concerns on this invention. It is a longitudinal cross-sectional view which shows the structure of the electropneumatic conversion part in this electropneumatic positioner. It is a figure which shows the principal part of the calculating part in this electropneumatic positioner. It is a block diagram which shows the principal part of the conventional electropneumatic converter. It is a longitudinal cross-sectional view which shows the structure of the electropneumatic conversion part in the conventional electropneumatic converter. It is a figure which shows the principal part of the calculating part in the conventional electropneumatic converter. It is a block diagram which shows the principal part of the conventional electropneumatic positioner.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment 1: Electropneumatic converter]
FIG. 1 is a block diagram showing a main part of an embodiment of an electropneumatic converter according to the present invention. FIG. 1 shows a block diagram of a main part of an electropneumatic converter as the first embodiment.

  1, the same reference numerals as those in FIG. 9 denote the same or equivalent components as those described with reference to FIG. 9, and the description thereof will be omitted. This electropneumatic converter 100 is different from the conventional electropneumatic converter 100 shown in FIG. 9 in the function of the calculation unit 1 and the configuration of the electropneumatic conversion unit 2.

  Hereinafter, the conventional electropneumatic converter 100 is referred to as an electropneumatic converter 100B, and the electropneumatic converter 100 according to the present embodiment is referred to as an electropneumatic converter 100A. 2 is an arithmetic unit 1B and an electropneumatic converter 2B, and the arithmetic unit 1 and the electropneumatic converter 2 in the electropneumatic converter 100A of this embodiment are an arithmetic unit 1A and an electropneumatic converter 2A.

  In the present embodiment, as shown in FIG. 2, the electropneumatic conversion unit 2A is provided below the electromagnetic coil 7 provided between the upper and lower yokes 6 so as to detect the combined magnetic field coaxially and in parallel with the electromagnetic coil 7. A coil 13 is provided. The combined magnetic field detection coil 13 includes a magnetic field (control magnetic field) generated by an electromagnetic coil (hereinafter referred to as an electropneumatic conversion coil) 7 and a control magnetic field for an external magnetic field acting on the electropneumatic conversion coil 7. The direction and strength of the combined magnetic field with the component in the direction parallel to the direction is detected.

  In the present embodiment, in addition to the control output generation function F1, the calculation unit 1A receives the direction and strength of the synthesized magnetic field detected by the synthesized magnetic field detection coil 13, and the direction and strength of the synthesized magnetic field. Is a control output correction function for correcting the control output Is to the electropneumatic converter 2A so that the direction and strength of the magnetic field (target magnetic field) corresponding to the target value to be generated by the electropneumatic conversion coil 7 is the same. F2 is provided. The control output correction function F2 corresponds to the control output correction unit referred to in the present invention, and the control output generation function F1 corresponds to the control output generation unit.

  FIG. 3 shows a main part of the calculation unit 1A. The arithmetic unit 1A includes a CPU 1-1, a coil driving circuit 1-2, an amplifier 1-3, an A / D converter 1-4, and a memory 1-5.

  In the arithmetic unit 1A, the coil drive circuit 1-2 receives an instruction from the CPU 1-1 and causes the control output Is to flow through the electropneumatic conversion coil 7 as a current (coil drive current) Is corresponding to the target value.

  In the arithmetic unit 1A, the amplifier 1-3 and the A / D converter 1-4 are provided as a processing circuit between the synthetic magnetic field detection coil 13 and the CPU 1-1, and the synthetic magnetic field detection coil 13 detects the synthesis. Of the magnetic field (the magnetic field generated by the electropneumatic conversion coil 7 (control magnetic field) φS and the combined magnetic field of the component φG in a direction parallel to the control magnetic field φS of the external magnetic field acting on the electropneumatic conversion coil 7). The direction and strength are given to the CPU 1-1.

  In the arithmetic unit 1A, the control output generation function F1 and the control output correction function F2 are realized as processing operations of the CPU 1-1 according to a program stored in the memory 1-5.

  Hereinafter, with reference to the flowchart shown in FIG. 4, the processing operation unique to the present embodiment executed by the CPU 1-1 in the arithmetic unit 1A will be described.

  In the arithmetic unit 1A, the CPU 1-1 inputs a difference (difference between a current signal including target value information and a current signal fed back) ΔI between the input electric signal Iin and the feedback signal If, and this input signal A command for setting the difference ΔI to zero is generated as a current signal (control output) Is corresponding to the target value.

  That is, the CPU 1-1 inputs a target value (step S101), obtains a control output Is that can obtain a magnetic field (target magnetic field) corresponding to the target value (step S102), and obtains the obtained control output Is. The current (coil drive current) Is corresponding to the target value is passed through the electropneumatic conversion coil 7 (step S103). As a result, the electropneumatic conversion coil 7 generates the control magnetic field φS.

  On the other hand, the combined magnetic field detection coil 13 includes a control magnetic field φS generated by the electropneumatic conversion coil 7 and a component φG in a direction parallel to the control magnetic field φS of the external magnetic field acting on the electropneumatic conversion coil 7. Detect the direction and strength of the synthetic magnetic field. The direction and strength of the combined magnetic field detected by the combined magnetic field detection coil 13 is given to the CPU 1-1 through a processing circuit including the amplifier 1-3 and the A / D converter 1-4.

  The CPU 1-1 takes in the direction and strength of the synthesized magnetic field detected by the synthesized magnetic field detection coil 13 (step S104), and the direction and strength of the taken synthesized magnetic field and the target that the electropneumatic conversion coil 7 should generate. The direction and strength of the magnetic field (target magnetic field) corresponding to the value are compared (step S105). The magnetic field (target magnetic field) corresponding to the target value to be generated by the electropneumatic conversion coil 7 at this time is stored in the memory 1-5 as a value obtained from an arithmetic expression or a table.

  Here, if the direction and strength of the captured synthetic magnetic field do not match the direction and strength of the target magnetic field (NO in step S105), the CPU 1-1 determines the direction and strength of the captured synthetic magnetic field as the target. A control output Is that is the same as the direction and strength of the magnetic field is obtained (step S106), that is, the current control output Is instructed to the coil drive circuit 1-2 is corrected, and the corrected control output Is is the target. A current (coil drive current) Is corresponding to the value is passed through the electropneumatic conversion coil 7 (step S107).

  As a result, as shown in FIG. 5, the control magnetic field φS generated by the electropneumatic conversion coil 7 is corrected. The CPU 1-1 proceeds to steps S104, S105, S106, and S107 until the direction and strength of the combined magnetic field detected by the combined magnetic field detection coil 13 matches the direction and strength of the target magnetic field (YES in step S105). Repeat the processing operation. That is, the correction of the control magnetic field φS generated by the electropneumatic conversion coil 7 is repeated.

  The CPU 1-1 repeats the processing operations of steps S104, S105, and S107 even after the direction and strength of the combined magnetic field detected by the combined magnetic field detection coil 13 matches the direction and strength of the target magnetic field. As a result, the direction and strength of the synthesized magnetic field detected by the synthesized magnetic field detection coil 13 do not match the direction and strength of the target magnetic field due to fluctuations in the external magnetic field (NO in step S105). In the same manner as described above, the control magnetic field φS generated by the electropneumatic conversion coil 7 is corrected (steps S106 and S107), and the direction and strength of the composite magnetic field detected by the composite magnetic field detection coil 13 is the target magnetic field. Can be matched to the direction and strength.

  In this way, in the present embodiment, the combined magnetic field detected by the combined magnetic field detection coil 13 (the control magnetic field φS generated by the electropneumatic conversion coil 7 and the external acting on the electropneumatic conversion coil 7). The direction and the strength of the magnetic field for controlling the magnetic field φS and the component φG in the direction parallel to the magnetic field are always matched to the direction and strength of the target magnetic field without shielding the electropneumatic conversion coil 7. In addition, the influence of the external magnetic field can be eliminated without providing a correction coil.

  The processing operation shown in FIG. 4 is performed every time a target value is input to the calculation unit 1, that is, the difference between the input electric signal Iin and the feedback signal If (current signal including target value information and current fed back). This is executed each time a difference from the signal is inputted as ≠ 0.

[Embodiment 2: Electropneumatic positioner]
FIG. 6 is a block diagram showing a main part of another embodiment of the electropneumatic converter according to the present invention. FIG. 6 shows a block diagram of a main part of an electropneumatic positioner as a second embodiment.

  6, the same reference numerals as those in FIG. 12 denote the same or equivalent components as those described with reference to FIG. 12, and the description thereof will be omitted. The electropneumatic positioner 200 is different from the conventional electropneumatic positioner 200 shown in FIG. 12 in the function of the calculation unit 22 and the configuration of the electropneumatic conversion unit 23.

  Hereinafter, the conventional electro-pneumatic positioner 200 is referred to as an electro-pneumatic positioner 200B, the electro-pneumatic positioner 200 according to the present embodiment is referred to as an electro-pneumatic positioner 200A, and the calculation unit 22 and the electro-pneumatic conversion unit 23 in the conventional electro-pneumatic positioner 200B are referred to as a calculation unit 22B. The calculation unit 22 and the electropneumatic conversion unit 23 in the electropneumatic conversion unit 23B and the electropneumatic positioner 200A of the present embodiment are referred to as a calculation unit 22A and an electropneumatic conversion unit 23A.

  Also in this embodiment, the electropneumatic conversion unit 23A includes the synthetic magnetic field detection coil 13 as in the electropneumatic conversion unit 2A shown in FIG. 2 (see FIG. 7). In addition to the control output correction function F1, the calculation unit 22A receives the direction and strength of the synthesized magnetic field detected by the synthesized magnetic field detection coil 13, and the direction and strength of the synthesized magnetic field is the electropneumatic conversion coil. 7 includes a control output correction function F2 that corrects the control output Is to the electropneumatic converter 23A so that the direction and strength of the magnetic field (target magnetic field) corresponding to the target value to be generated is the same.

  The configuration of the calculation unit 22A is the same as the configuration of the calculation unit 1A shown in FIG. 3 (see FIG. 8). In this calculation unit 22A, the CPU 22-1 is fed back with the difference between the input electric signal Iin from the input signal processing unit 21 and the feedback signal If from the valve opening degree detection unit 25 (a current signal including target value information). A difference (ΔI from the current signal) ΔI is input, and a command for making the input signal difference ΔI zero is generated as a current signal (control output) Is corresponding to the target value. Only in this respect, the processing operation of the CPU 22-1 in the calculation unit 22A is the same as the processing operation of the CPU 1-1 in the calculation unit 1A.

  In the first and second embodiments described above, the coil is used to detect the synthetic magnetic field. However, the coil is not limited to the coil as long as the direction and strength of the synthetic magnetic field can be detected. In addition, a processing circuit including an amplifier and an A / D converter is provided for a coil for detecting a synthetic magnetic field. This is a general sensor output processing circuit. The configuration can also be applied.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Operation part, 1-1 ... CPU, 1-2 ... Coil drive circuit, 1-3 ... Amplifier, 1-4 ... A / D converter, 1-5 ... Memory, 2 ... Electropneumatic conversion part, 3 ... Pilot relay, 4 ... feedback sensor, 7 ... electromagnetic coil (electro-pneumatic conversion coil), 9 ... flapper, 11 ... nozzle, 13 ... synthetic magnetic field detection coil, 21 ... input signal processing unit, 22 ... calculation unit, 22- DESCRIPTION OF SYMBOLS 1 ... CPU, 22-2 ... Coil drive circuit, 22-3 ... Amplifier, 22-4 ... A / D converter, 22-5 ... Memory, 23 ... Electropneumatic conversion part, 24 ... Air signal amplification part, 25 ... Valve opening detector, 100 ... electro-pneumatic converter, 200 ... electro-pneumatic positioner, 300 ... control valve.

Claims (4)

A calculation unit that outputs a current signal according to a target value as a control output, an electromagnetic coil that converts the control output from the calculation unit into a magnetic force, and a pneumatic conversion unit that converts the magnetic force converted by the electromagnetic coil into air pressure In the electropneumatic converter provided,
The magnetic field generated by the electromagnetic coil is used as a control magnetic field, and the direction and strength of the combined magnetic field of this control magnetic field and a component of the external magnetic field acting on the electromagnetic coil in a direction parallel to the control magnetic field is detected. A synthetic magnetic field detector
The computing unit is
Control output correction for correcting the control output so that the direction and strength of the synthetic magnetic field detected by the synthetic magnetic field detection unit is the same as the direction and strength of the magnetic field corresponding to the target value to be generated by the electromagnetic coil An electropneumatic conversion device comprising: a unit. In the electropneumatic conversion device according to claim 1,
The computing unit is
The difference between the current signal including target value information and the current signal fed back is input, and a command for setting the difference between the input signals to zero is generated as a current signal corresponding to the target value. An electropneumatic conversion device comprising: a control output generation unit that outputs a current signal according to a value as the control output. In the electropneumatic conversion device according to claim 2,
The feedback current signal is
An electropneumatic conversion device, characterized in that it is a current signal corresponding to the air pressure converted by the air pressure conversion unit. In the electropneumatic conversion device according to claim 2,
The feedback current signal is
The electropneumatic conversion device, wherein the air pressure converted by the air pressure conversion unit is a current signal corresponding to a valve opening degree of a control valve provided as an operation output.

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