JP5781900B2 - Positioner - Google Patents

Description

  The present invention relates to a positioner that converts an electric signal into a pneumatic signal to control the valve opening of a control valve.

  Conventionally, in a chemical plant or the like, a positioner is provided for a control valve used for the flow rate process, and the opening degree of the control valve is controlled by this positioner. The positioner calculates a deviation between the set opening degree sent from the host device and the actual opening degree fed back from the control valve, and generates a control signal as an electric signal corresponding to the deviation, An electropneumatic converter that converts the control signal generated by the control calculation unit into a pneumatic signal, and a pneumatic signal amplifier (pilot relay) that amplifies the pneumatic signal from the electropneumatic converter and supplies it as output air pressure to the control valve actuator (See, for example, Patent Document 1).

  In this positioner, an angle sensor is used as a displacement detector that detects the actual opening of the control valve as a displacement amount of the valve shaft, and this angle sensor rotates according to the displacement amount of the valve shaft via a feedback lever. It has a rotation axis. An electric signal corresponding to the rotation angle of the rotation shaft of the angle sensor is fed back to the control calculation unit as a signal indicating the actual opening.

  In such a positioner, the displacement detection unit (angle sensor), control calculation unit, electropneumatic conversion unit, etc., which are electrical components, are housed in the case, and are fixed to the yoke of the control valve via a bracket or the like. It is common to be done. However, since the control valve constitutes a vibration source that generates vibration along with the flow control, the positioner fixed to the control valve is also affected by the vibration, and the accuracy of the valve opening degree control deteriorates. There is a fear.

  Therefore, Patent Document 2 discloses a positioner that aims to solve such deterioration of controllability due to vibration of the positioner. In the positioner disclosed in Patent Document 2, the angle sensor that has been accommodated in the conventional explosion-proof case is taken out and separated, and the separated angle sensor is fixed to the yoke of the control valve via a bracket. The positioner body is installed away from the control valve that is not subjected to vibration of the control valve, and the angle sensor and the positioner body are connected by a cable.

Japanese Utility Model Publication No. 62-28118 Japanese Utility Model Publication No. 04-8801

  However, in the positioner shown in Patent Document 2, since the angle sensor is fixed to the yoke of the positioner, from the clearance of the rotation shaft of the angle sensor that rotates according to the amount of displacement of the valve shaft of the control valve, the angle sensor Rain water intrudes into the inside or moisture enters, causing corrosion damage to the electrical components of the angle sensor, or wear of the rotating shaft, and the wear powder enters the gap between the bearing and the rotating shaft is fixed. There was a problem of doing.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a positioner capable of preventing corrosion damage to the electrical components of the displacement detection unit and adhesion of the rotating shaft. There is to do.

  In order to achieve such an object, the present invention includes a displacement detection unit that detects a displacement amount of an operating shaft of a control valve that is operated by air pressure and outputs an electrical signal corresponding to the displacement amount, and an electrical signal from the displacement detection unit. The control calculation unit that calculates the deviation between the actual opening and the set opening of the control valve obtained from the signal and outputs a control signal corresponding to this deviation, and the electropneumatic that converts the control signal from the control calculation unit into a pneumatic signal In a positioner comprising a conversion unit and a pneumatic signal amplification unit that amplifies the pneumatic signal from the electropneumatic conversion unit and supplies it as an output pneumatic pressure to the operation device of the control valve, the displacement detection unit is fixedly installed on the control valve and controlled The calculation unit, electropneumatic conversion unit, and air pressure signal amplification unit are housed in the case and have a cable for guiding an electric signal from the displacement detection unit to the control calculation unit. The cable purges the detection unit in the displacement detection unit. Lead the air to Wherein the road is provided.

  According to this invention, air is guided into the detection unit of the displacement detection unit through the passage provided in the cable that guides the electric signal from the displacement detection unit to the control calculation unit, and the detection unit of the displacement detection unit is purged with air. As a result, even if rainwater, moisture, or the like enters the detection unit of the displacement detection unit, the rainwater, moisture, or the like that has entered is blown away, and the detection unit of the displacement detection unit is maintained in a state free of rainwater, moisture, or the like.

  In the present invention, the air guided to the displacement detection unit may be sent from a supply source different from the supply source of air to the positioner. However, if the supply source of air to the positioner is used, the supply source of air Need not be provided separately. If air is sent from the case of the positioner to the displacement detector, the air used in the positioner is effectively utilized.

  According to the present invention, since the cable for guiding the electrical signal from the displacement detection unit to the control calculation unit is provided with the passage for guiding the air for purging the inside of the detection unit of the displacement detection unit, the inside of the detection unit of the displacement detection unit is air purged. As a result, the inside of the detection unit of the displacement detection unit is kept free of rainwater, moisture, and the like, and it is possible to prevent corrosion damage to the electrical components of the displacement detection unit and sticking of the rotating shaft.

It is a block diagram which shows one Embodiment of the positioner which concerns on this invention. It is a front view which shows the connection condition with the control valve of this positioner. It is a top sectional view showing the attachment situation in the control valve of the angle sensor of this positioner. It is sectional drawing which shows an example of the cable which guides the electric signal from an angle sensor in the case of a positioner. It is sectional drawing which shows the other example of the cable which guides the electric signal from an angle sensor in the case of a positioner. It is sectional drawing of the lead-in part of the cable to an angle sensor. It is sectional drawing which shows the structure inside an angle sensor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a positioner according to the present invention. In the figure, reference numeral 100 denotes a positioner according to the present invention, and reference numeral 200 denotes a regulating valve whose valve opening degree is controlled by the positioner 100.

  The control valve 200 has an operating device 21 for driving a valve shaft (actuating shaft) 20, and a connecting pin 22 is provided on the valve shaft 20, and a long hole 23 a is slidable in the connecting pin 22. A feedback lever 23 is provided to be inserted. The feedback lever 23 rotates around the fulcrum P1 according to the vertical movement of the valve shaft 20, that is, according to the vertical movement of the connecting pin 22.

  The positioner 100 obtains a deviation between the set opening degree θsp sent from the host device (not shown) and the actual opening degree θpv fed back from the control valve 200, and an electric signal corresponding to the deviation is used as a control signal. The control calculation unit 1 to be generated, and the electropneumatic conversion unit 2 that receives the air pressure Ps supplied from the air pressure supply source 300 and converts the control signal generated by the control calculation unit 1 into an air pressure signal (nozzle back pressure) Pn; The air pressure signal amplifying unit (pilot relay) 3 that amplifies the air pressure signal Pn converted by the electropneumatic conversion unit 2 and outputs it as the output air pressure Pout to the controller 21 of the control valve 200, and the angle sensor (displacement detection unit) 4 I have.

  In this positioner 100, the angle sensor 4 is fixed to the yoke 24 (see FIG. 2) of the control valve 200 via the bracket 25, and the rotation shaft 41 (see FIG. 3) is connected to the feedback lever 23. As a result, the rotation shaft 41 of the angle sensor 4 rotates with the rotation of the feedback lever 23 around the fulcrum P1, and an electric signal corresponding to the amount of displacement of the valve shaft 20 becomes the actual opening θpv of the control valve 200. It is fed back to the control calculation unit 1. The feedback lever 23 has a pin pressing spring 26 that presses the connecting pin 22 against one side wall (in this example, the upper side wall) 23a1 extending in the longitudinal direction of the long hole 23a. It is attached to the wall surface.

  In the positioner 100, the control calculation unit 1, the electropneumatic conversion unit 2, and the air pressure signal amplification unit 3 are accommodated in a case 5. In this case 5, the control calculation unit 1 and the electropneumatic conversion unit 2 are further accommodated in a container (not shown) having an explosion-proof structure. Further, a cable 6 that guides an electrical signal from the angle sensor 4 to the control calculation unit 1 is provided between the case 5 and the angle sensor 4. The cable 6 has a configuration unique to the present embodiment. In addition to the lead wire group 61 that guides an electrical signal from the angle sensor 4 to the control calculation unit 1, the air pressure Ps to the electropneumatic conversion unit 2 is branched to form an angle. An air tube 62 that leads into the detection portion of the sensor 4 is provided.

  FIG. 4 shows a cross-sectional view of the cable 6. In this example, an air tube 62 is provided at the center of the cable 6, and a lead wire group 61 is provided around the air tube 62. As shown in FIG. 5, the cable 6 may have a dharma cross section, and the lead wire group 61 and the air tube 62 may be divided into two in one cable 6.

  FIG. 6 shows a cross-sectional view of the lead-in portion of the cable 6 to the angle sensor 4. The cable 6 is drawn through a bushing 8 into a case 7 in which the angle sensor 4 is accommodated. The bushing 8 is fastened to the case 7 by a nut 9. In the case 7, the lead wire group 61 drawn from the cable 6 is crimped and connected to the lead wire from the angle sensor 4 by the insulating sleeve 10. The end face of the air tube 62 drawn out from the cable 6 faces the accommodation space 7 a of the lead wire group 61 in the case 7, and air from the air tube 62 is blown into the accommodation space 7 a of the lead wire group 61.

  FIG. 7 is a cross-sectional view showing an internal configuration of the angle sensor 4. In the angle sensor 4, a rotating shaft 41 having a yoke 44 fixed to its lower end is inserted from below into a case 43 in which a cylindrical bearing cylinder 42 is housed and fixed, and the upper end of the rotating shaft 41 is inserted through the upper surface of the case 43. The opening 47 on the lower surface of the case 43 is closed by a lid 47 that protrudes from the hole 45 and is further attached with a magnetic sensor 46. Two permanent magnets 49 and 50 are accommodated in the yoke 44 fixed to the rotating shaft 41, and the magnetic sensor 46 is fixed to the upper surface of the support base 51.

  Note that 52 is a locking ring attached to the ring groove of the rotating shaft 41 protruding from the upper surface of the case 43, 53 is a ring inserted between the yoke 44 and the bearing cylinder 42, 54 and 55 are packings, 56 Is a flange, 57 is a cap, 58 is a bolt for connecting the feedback lever 23 to the rotary shaft 41, 59 is a substrate for taking out an electric signal from the magnetic sensor 46, and the lid 47 has a communication hole communicating with the internal space of the case 43. 47a is provided.

  In the angle sensor 4, the rotating shaft 41 rotates integrally with the yoke 44 with the inner peripheral surface 42 a of the bearing cylinder 42 as a bearing surface. As a result, the direction of the lines of magnetic force generated by the magnets 49 and 50 on the surface of the magnetic sensor 46 changes, the output resistance value of the magnetic sensor 46 changes, and an electrical signal corresponding to the rotation angle of the rotary shaft 41 is generated.

  In the positioner 100 configured as described above, the air pressure from the air pressure supply source 300 to the electropneumatic converter 2 is passed through the air tube 62 provided in the cable 6 that guides the electrical signal from the angle sensor 4 to the control arithmetic unit 1. Ps branches and is guided to the accommodation space 7a of the lead wire group 61 in the case 7 in which the angle sensor 4 is accommodated.

  As a result, air is blown from the end face of the air tube 62 into the housing space 7a of the lead wire group 61 in the case 7, and this blown air is guided to the internal space of the case 43 of the angle sensor 4 through the communication hole 47a. The inside of the detection part of the angle sensor 4 is purged with air.

  As a result, even if rainwater or moisture enters the detection unit of the angle sensor 4, the rainwater or moisture that has entered the blowout is blown away, and the detection unit of the angle sensor 4 is kept in a state free of rainwater or moisture. Corrosion damage of the electric parts of the sensor 4 and sticking of the rotating shaft 51 are prevented.

  In this embodiment, the air pressure Ps from the air pressure supply source 300 to the electropneumatic converter 2 is branched and guided to the angle sensor 4. However, the air pressure signal (nozzle back) from the electropneumatic converter 2 is used. Pressure) Pn may be branched and guided to the angle sensor 4, or the output air pressure Pout from the air pressure signal amplifier 3 may be branched and guided to the angle sensor 4. Although not shown, the air discharged from the positioner 100 to the outside may be guided to the angle sensor 4.

  Also, an air pressure supply source different from the air pressure supply source 300 to the positioner 100 is provided, and the air from this other air pressure supply source enters the middle of the cable 6 without passing through the positioner 100. The air that has entered the cable 6 may be sent to the angle sensor 4.

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

  DESCRIPTION OF SYMBOLS 1 ... Control calculating part, 2 ... Electropneumatic conversion part, 3 ... Air pressure signal amplification part (pilot relay), 4 ... Angle sensor (displacement detection part), 41 ... Rotating shaft, 47a ... Communication hole, 5 ... Case, 6 ... Cable, 61 ... Lead wire group, 62 ... Air tube, 20 ... Valve shaft (operating shaft), 21 ... Actuator, 23 ... Feedback lever, 100 ... Positioner, 200 ... Control valve, 300 ... Supply source of air pressure.

Claims (2)

A displacement detector that detects a displacement amount of an operating shaft of a control valve that operates by air pressure, and outputs an electric signal according to the displacement amount;
Obtaining a deviation between the actual opening and the set opening of the control valve obtained from the electrical signal from the displacement detector, and outputting a control signal according to the deviation;
An electropneumatic converter that converts a control signal from the control calculation unit into a pneumatic signal;
In a positioner comprising an air pressure signal amplifying unit that amplifies the air pressure signal from the electropneumatic conversion unit and supplies it as an output air pressure to the controller of the control valve;
The displacement detector is fixedly installed on the control valve,
The control calculation unit, the electropneumatic conversion unit and the air pressure signal amplification unit are housed in a case,
A cable for guiding an electrical signal from the displacement detection unit to the control calculation unit;
The cable is provided with a passage for guiding the air for purging the inside of the detection portion to the displacement detection portion. The positioner as claimed in claim 1,
The positioner characterized in that the air guided to the displacement detector is sent from within the case.

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