JPH0725306U - Positioner - Google Patents

Abstract

(57) [Abstract] [Purpose] The zero point shift due to magnetic imbalance caused by being left unused for a long period of time can be performed easily without opening the case of the electro-pneumatic conversion section and with an extremely simple structure. Be able to undo. [Structure] A pneumatic actuator 55 is arranged to face the nozzle 15 with the flapper 9 in between. Immediately before use, the automatic / manual switching mechanism 8 is switched to the manual M, and in this state, the supply air pressure Psup is guided to the pneumatic actuator 55 via the flow path 56 branched from the supply air pressure path 25. Then, the actuator 55 extends and the flapper 9
The nozzle side end of is pressed to swing the flapper 9. When the flapper 9 is reciprocated several times between 0% and 100% by repeating such swinging operation by turning the switching valve 57 ON and OFF a plurality of times, the left and right magnetic hysteresis of the flapper 9 becomes equal. The zero shift due to magnetic hysteresis can be corrected.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a positioner suitable for application to, for example, an electropneumatic converter, an electropneumatic positioner used in a drive control unit of a pneumatic control valve, or the like.

[0002]

[Prior art]

 FIG. 3 is a diagram showing a conventional example of a valve positioner used for drive control of a control valve. This valve positioner applies an electric input signal Io to the nozzle flapper mechanism 3 as a mechanical displacement amount in the electropneumatic converter 2, and the supply air pressure Psup and the nozzle flapper gap supplied to the nozzle flapper mechanism 3 cause the nozzle to move. The back pressure PN is amplified by the pilot relay 4 into the positioner output pressure Pout, and the control valve 5 is drive-controlled by this output pressure Pout, and the valve displacement is electropneumatically converted through a lever connected to the valve shaft or the like. It is configured to feed back to the vessel 2.

An automatic / manual switching mechanism 8 is interposed in the flow path 7 connecting the nozzle 15 constituting the nozzle flapper mechanism 3 and the pilot relay 4, and when this is switched from automatic A to manual M, The control valve 5 can be controlled to open and close by manual operation.

Here, the specific configuration and operating principle of the electro-pneumatic converter 2 described above will be briefly described with reference to FIGS. 4 to 6. In these figures, 9 is a flapper made of a magnetic material and 11 is this flapper. 9 is a fulcrum that supports swinging displacement, and 12 is a yoke having coils 13a and 13b, a permanent magnet 14, and a nozzle 15, and has a substantially E-shaped cross section, and has three legs 12a, It has 12b and 12c. Note that the arrow a shown by the broken line in FIG. 5 indicates the direction of the magnetic field by the permanent magnet 14 in which the flapper 9 side is the N pole and the opposite side is the S pole, and the arrow b shown by the solid line is as shown by the N pole and the S pole. The direction of the magnetic field by the coils 13a and 13b obtained in FIG. Here, the polarities of the coils 13a and 13b are set to be opposite to each other.

When a current flows through the coils 13a and 13b, a magnetic field in the same direction as the magnetic field of the permanent magnet 14 is generated on the left leg 12a side of the yoke 12, and conversely on the right leg 12b side. A magnetic field is generated in a direction that cancels the strength of the magnetic field of the permanent magnet 14. For this reason, the force F attracting the flapper 9 on the left side increases, and the force F on the right side weakens on the contrary. Therefore, a counterclockwise rotation torque T centered on the fulcrum 11 is generated in the flapper 9 in proportion to the supply current Io. Therefore, the flapper 9 is brought closer to the nozzle 15 opposite to the tip of the left leg 12a of the yoke 12, and the nozzle gap, that is, the nozzle flapper gap is reduced, and the supply air pressure ( Nozzle back pressure PN associated with Psup) increases, so that an air pressure signal proportional to the current signal I0 can be generated as the output pressure Pout.

Further, the flapper 9 described above is provided with a pair of springs 16 and 17 as elastic members at both ends thereof between the flapper 9 and a base 18 as a fixed portion, and a predetermined pulling force is applied thereto. . The spring 16 on the left side is a biasing spring means for urging the flapper 9 so as to approach the nozzle 15. Further, the right spring 17 constitutes a zero adjusting mechanism 20 for setting the initial position of the flapper 9 by attaching means 19 for adjusting the urging force thereof.

In FIG. 4, reference numeral 21 is a stopper provided at the tip of the right leg 12 b of the yoke 12 in correspondence with the nozzle 15, and 22 is a fulcrum spring constituting a fulcrum 11 for supporting the flapper 9. The cross spring 23 is a bracket for mounting the cross spring.

In such electro-pneumatic converter 2, the supply air pressure path 25 having the throttle 24 supplies the supply air pressure Psup to the nozzle 15, and the nozzle back pressure PN on the downstream side of the throttle 24 changes the output pressure. It is output as Pout.

In the valve positioner as described above, which is attached to the control valve 5 installed in the field such as an oil refinery, mechanically operates the flapper 9 based on an electric input signal. An electro-pneumatic conversion unit including a control calculation unit for displacement and an electro-pneumatic converter 2 including a nozzle flapper mechanism 3 is housed in a case 26 having a flameproof structure.

[0010]

[Problems to be solved by the device]

 By the way, in the electro-pneumatic converter 2 as described above, when the input current I0 is given a predetermined value from 4 mA to 20 mA through the arithmetic unit to the coils 13a and 13b, the flapper 9 is driven through the fulcrum 11 to generate a required value. And swings in the direction of 0% F. S, 50% F.I. S, 100% F.I. The positions such as S will be appropriately displaced. That is, in a state where the flapper 9 is not used (a state in which there is neither supply air pressure nor input current), the flapper 9 is rotated clockwise by FIG. S position, 50% F.S. with a minimum input current of 4 mA. S, 100% F.S. with a maximum input current of 20 mA. It is displaced to the S position. In such an electropneumatic converter 2, the magnetic balance at each displacement position by the flapper 9 and the coils 13a, 13b and the permanent magnet 14 depends on the magnetic flux density, magnetic field strength, residual magnetic flux density, coercive force, hysteresis, etc. Examining the obtained magnetic hysteresis curve characteristics, the flapper 9 has a substantially horizontal 50% F.S. It has been confirmed that at the position of S, the gaps of the left and right magnetic circuits become equal and the magnetic balance is achieved.

On the other hand, when the supply air pressure Psup is not supplied to the nozzle 15 and the input signal IO to the coils 13a and 13b is not used, the flapper 9 keeps the 0% F. It is in the S position. However, in this state, the magnetic balance in the flapper 9 is lost and the magnetic hysteresis is large. Therefore, if left in this state for a long time, there is a problem that zero shift occurs.

When such a zero point shift occurs, the zero point adjustment must be readjusted. For this zero point adjustment, the case 26 is opened and the biasing force of the spring 17 is adjusted while observing the output pressure gauge. It is necessary to adjust by 19 and furthermore, an arbitrary electric signal (for example, 0%, 50%, 100%) is given to the coils 13a and 13b, and the output pressure at that position is adjusted to a normal value. However, there is a problem that the operation is troublesome and complicated. Therefore, it is desired to take some measures to prevent such a zero shift.

Particularly, in the conventional electro-pneumatic positioner and the like, the electro-pneumatic converter 2 described above is housed in the case 26 having a pressure-proof explosion-proof structure, so that the case 26 is installed in the explosion-proof area equipped with this type of positioner. I can't open it, and I can't adjust the zero point. There is also a problem in that workability is not preferable because the zero point adjustment cannot be performed outside the explosion-proof area unless the case 26 is opened.

The present invention has been made in view of such circumstances, and the case of the electropneumatic conversion unit can be opened for zero point shift due to magnetic imbalance caused by being left unused for a long period of time. The aim is to obtain a positioner that can be easily replaced by a simple structure that does not exist.

[0015]

[Means for Solving the Problems]

 To achieve the above object, a positioner according to the present invention comprises a coil, a permanent magnet, a nozzle flapper mechanism and an electropneumatic converter provided with a zero adjustment mechanism for the nozzle flapper mechanism, a nozzle back pressure of the nozzle flapper mechanism and an auto / automatic converter. In a positioner equipped with a pilot relay that is connected via a manual switching mechanism, a pneumatic actuator that faces the nozzle is placed across the flapper of the nozzle flapper mechanism described above, and it is branched from the supply air pressure path of the pilot relay. The flow path is connected to the pneumatic actuator via a switching valve.

[0016]

[Action]

 According to the present invention, when the pneumatic actuator is driven to forcibly move the flapper so that both ends of the flapper are alternately moved toward and away from the permanent magnet, magnetic hysteresis caused by leaving for a long time can be removed. it can.

[0017]

【Example】

 FIG. 1 is a sectional view showing an embodiment of a positioner according to the present invention. This embodiment shows a case where the invention is applied to a flameproof explosion-proof electropneumatic positioner. In addition, the same reference numerals are given to the portions corresponding to those in FIGS.

In the figure, inside the pressure and explosion-proof case 26, a yoke 12, a fulcrum 11, a coil 13, a permanent magnet 14, a nozzle flapper mechanism 3, and a zero adjustment mechanism 20 of the nozzle flapper mechanism 3 are provided. A container 2 is provided. The electro-pneumatic converter 2, the nozzle flapper mechanism 3 and the zero adjustment mechanism 20 are the same as those of the conventional structure described above.

The pilot relay 4 for amplifying and outputting the nozzle back pressure PN is a conventionally known one and has the following configuration. Here, in FIG. 1, the pilot relay 4 is shown as belonging to the bleed type, which is a model in which a part of the supply air pressure Psup is constantly discharged to the atmosphere during normal operation.

Briefly describing the schematic configuration of the pilot relay 4, a supply air pressure chamber 32, an output chamber 33, an atmosphere communication chamber 34, a bias chamber 35, and an input chamber 36 are provided in the body 31, and each of these chambers is provided. Among them, the supply air pressure chamber 32 and the output chamber 33 are communicated with each other by a through hole 37 formed in the inner partition wall, and the atmosphere communication chamber 34 and the bias chamber 35 and the bias chamber 35 and the input chamber 36 are connected to each other. It is partitioned by diaphragms 38 and 39.

Reference numeral 40 denotes a piston which is supported by the central portions of the upper and lower diaphragms 38 and 39 and whose lower end faces the atmosphere communication chamber 34 and the output chamber 33. The piston 40 is provided at the lower end side of the piston 40. Is fitted with an O-ring 41, thereby airtightly defining the atmosphere communication chamber 34 and the output chamber 33.

Further, the other end of the communication passage 42 that opens to the atmosphere communication chamber 34 is opened at the lower end of the piston 40, and the opening is arranged so as to penetrate the output chamber 33 and the through hole 37. It is adapted to be opened and closed by an upper valve body 43a of the poppet valve 43. On the other hand, the through hole 37 is configured to be opened / closed by the lower end side valve body 43b of the poppet valve 43. The poppet valve body 43 is biased by a bias spring 44 in a direction to close the through hole 37 and the communication passage 42. In such a configuration, the output pressure Pout fed to the valve drive portion of the control valve 5 through the pipe 45 from the output chamber 33 is different from that of each chamber depending on the input air pressure (nozzle back pressure PN) to the input chamber 36. It is controlled by the movement of the piston 40, which is moved by the pressure difference, and the poppet valve 43.

In the figure, 49 is a pipe for supplying Psup to the supply air pressure chamber 32, and 51 is a supply air pressure introduction flow path for introducing the supply air pressure to the bias chamber 35 facing the input chamber 36 via the upper diaphragm 39. The operation of the upper diaphragm 39, which is moved by the nozzle back pressure PN, is controlled by the pressure introduced into the bias chamber 35, and the required output pressure P is set by the piston 40 and the poppet valve 43. is what you get out. Reference numeral 53 is a pressure reducing valve arranged in the supply air pressure passage 25, by which the supply air pressure Psup is adjusted to a predetermined pressure.

Now, in the present invention, in the positioner having the above-described configuration, the pneumatic actuator 55 facing the nozzle 15 with the flapper 9 interposed is provided, and the pneumatic actuator 55 is branched from the supply air pressure passage 25 of the pilot relay 4. It is characterized in that the flow path 56 is connected via a switching valve 57. In the present embodiment, a bellows 58 is used as the pneumatic actuator 55, and the bellows 58 is expanded and contracted by the supply air pressure Psup, and the flapper 9 is pressed when expanded. However, the invention is not limited to this and is shown in FIG. As described above, the piston 59 constitutes the pneumatic actuator 55, the outer end of the piston 59 is opposed to the flapper 9, and the supply air pressure Psup causes the piston 59 to move against the spring 60 to swing the flapper 9. You may do it.

Thus, according to the positioner having such a configuration, the zero point shift due to the magnetic hysteresis due to being left for a long time can be restored from the outside of the case 26 by a simple operation. That is, when the automatic / manual switching mechanism 8 is switched to the manual M immediately before use and the supply air pressure Psup is guided to the bellows 58 through the flow path 56 branched from the supply air pressure path 25 in this state, the bellows 58 expands. And presses the end of the flapper 9 on the nozzle side. Therefore, the flapper 9 swings around the fulcrum 11. When such a swinging operation is repeated a plurality of times by turning the switching valve 57 on and off to make the flapper 9 reciprocate several times between 0% and 100%, the magnetic hysteresis on the left and right of the flapper 9 becomes equal. Therefore, the zero shift due to the magnetic hysteresis can be corrected. Then, after the correction of the zero point shift, the auto / manual switching mechanism 8 may be switched to the auto A.

Further, in the present invention, even in a positioner installed at a site where a pressure and explosion proof structure is required, zero adjustment can be performed very easily outside the pressure and explosion proof case 26. Zero adjustment can be performed very easily and reliably even in an explosion-proof area.

[0027]

[Effect of device]

 As described above, according to the positioner of the present invention, the pneumatic actuator is provided so as to face the flapper, and the actuator is configured to forcibly oscillate the flapper. It is possible to easily correct the zero shift caused by, and even if it is in the explosion-proof area, it can be done from outside the explosion-proof case, and its practical effect is very large.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a positioner according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the pneumatic actuator.

FIG. 3 is a cross-sectional view of a main part showing a conventional example of a positioner.

FIG. 4 is a cross-sectional view showing an example of a conventional electropneumatic converter.

FIG. 5 is a diagram showing an operating principle of an electropneumatic converter.

FIG. 6 is a schematic diagram for explaining an operation relationship between nozzles and flappers.

[Explanation of symbols] 2 Electro-pneumatic converter 3 Nozzle flapper mechanism 4 Pilot relay 5 Control valve 8 Auto / manual switching mechanism 9 Flapper 11 Support point 12 Yoke 13 Coil 14 Permanent magnet 15 Nozzle 20 Zero adjustment mechanism 25 Supply air pressure path 55 Pneumatic actuator 56 Flow path 57 Switching valve 58 Bellows 59 Piston Psup Supply air pressure Pout Output pressure PN Nozzle back pressure

Claims (1)

[Scope of utility model registration request] 1. A pilot connected to an electropneumatic converter having a yoke, a coil, a permanent magnet, a nozzle flapper mechanism and a zero adjustment mechanism for the nozzle flapper mechanism, and a nozzle back pressure of the nozzle flapper mechanism and an automatic / manual switching mechanism. In a positioner including a relay, an air pressure actuator is disposed in the vicinity of a nozzle with a flapper of the nozzle flapper mechanism interposed therebetween, and a flow path branched from a supply air pressure path of the pilot relay is connected to the air pressure actuator via a switching valve. Positioner characterized by being connected to.