JP2587321B2 - Positioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a positioner suitable for application to an electropneumatic position for a control valve and the like.

[Prior Art] Conventional electro-pneumatic instruments, for example, electro-pneumatic converters, electric / displacement conversion mechanisms used for electro-pneumatic positioners for control valves, etc., are used according to explosion-proof standards when used in an explosive gas atmosphere. It is required to have sufficient explosion-proof performance. For this reason, a structure is generally adopted in which the entire electric / displacement conversion mechanism is housed in an explosion-proof case formed of a special pressure-resistant container. FIG. 3 shows a conventional example of an electropneumatic positioner for a control valve adopting such a pressure-resistant explosion-proof structure. The positioner 1 is a device for measuring the amount of displacement of an operating shaft 3 of a control valve 2 by a potentiometer or the like. Is converted into an electric signal I ₁ by the displacement detecting section 4 of the controller ₁ , the electric signal I ₁ is fed back to the control operation section 5, the feedback signal is compared with the input signal I ₀ to the positioner 1, and the difference is detected by electro-pneumatic. Converter 6
, The relationship between the meter signal and the valve shaft position is always controlled accurately against disturbance.

The control operation unit 5 has an input detection unit, a CPU, and the like. The electropneumatic converter 6 includes a coil 7 to which an input signal I ₀ is supplied, a magnet 8 movable by a magnetic acting force of the coil 7, and a nozzle flapper mechanism 9 for converting a displacement of the magnet 8 into a pneumatic signal. . The nozzle flapper mechanism 9 includes a flapper 11 that swings about a fulcrum 10 and a nozzle 12 that is provided in close proximity to one end of the flapper 11 and that is supplied with a supply air pressure SUP from an air supply source. The pressure is amplified by the pilot relay 13 and output to the drive device 14 of the regulating valve 2 as the output air pressure Pout.

Reference numeral 15 denotes an explosion-proof equipment case, in which an explosion-proof chamber 16 is formed, and the displacement detector 4, the electropneumatic converter 6, the nozzle flapper mechanism 9, the span adjustment switch 17, and the span adjustment screw
18, a zero adjustment switch 19, a zero adjustment screw 20, a terminal board 21 and the like are housed. Reference numeral 22 denotes a case for accommodating the pilot relay 13, which is attached to one side wall of the device case 15, and between which a flame arrester for nozzle back pressure and an exhaust frame arrestor are provided.
23 and 24 are provided. These flame arresters 2
Reference numerals 3 and 24 denote a plurality of metal cylinders 25 having different diameters arranged substantially coaxially, and a predetermined gap (explosion-proof gap) d (for example, 0) so that the gap between the cylinders conforms to the explosion-proof standard. , 1m
m) is the depth l of the cylinder 25 (for example, 10 mm)
Is given. And such a flame arrester 2
3 and 24 are respectively housed in storage holes 26A and 26B formed in the device case 15, and the openings at both ends of the storage hole 26A are closed by lids 28 because pipes 27 forming an air circuit are connected thereto. Have been.

In addition, 29 is a pressure gauge, 30 is a pressure reducing valve, 31 is a throttle, and 32 is a changeover switch for switching between manual and automatic.

In such a configuration, the input signal I ₀ to the valve positioner 1 is varied in the range of 20mA, for example, from 4mA, when 4mA, holds the control valve 2 is fully closed, when 20mA, is maintained fully opened state Shall be. In the fully closed state of the control valve 2,
The lever 33 which rotates in conjunction with the operating shaft 3 is stopped at a position where it is rotated downward by a maximum angle. Electrical signal I ₁ of the displacement detector 4 in this state is equal to the input signal I _0, is inputted to the control arithmetic unit 5 as the A / D-converted feedback signal. Since the input signal I ₀ and the feedback signal I ₁ input to the control calculation unit 5 have the same value, the difference current is zero,
No correction signal is sent to the electropneumatic converter 6. When the input signal ₀ changes according to the set value and the control calculation unit 5 deviates from the feedback signal I ₁ from the displacement detection unit 4, a correction signal corresponding to the deviation is output to the electropneumatic converter 6. Therefore, the magnet 8 is displaced to swing the flapper 11 counterclockwise, thereby reducing the nozzle gap.
When the nozzle gap decreases, the nozzle back pressure increases, so that the output air pressure of the pilot relay 13 increases to Pout, and the driving device 14 is operated. As a result, the operating shaft 3 moves upward to open the control valve 2. The movement of the operating shaft 3 is transmitted as a force for rotating and displacing the lever 33 counterclockwise in FIG. When the lever 33 is rotated, the current value of the electric signal I ₁ to be input as a feedback signal from the displacement detecting section 4 to the control operation unit 5 is gradually increased, the current value of the input signal I ₀ corresponding to the set value The difference between the two decreases, and the valve opening is stabilized when the difference current becomes zero. The operation of returning from the valve open state to the fully closed state is an operation opposite to the above.

[Problems to be Solved by the Invention] In such a conventional electropneumatic positioner 1 for an explosion-proof type regulating valve, since the nozzle flapper mechanism 9 is integrally connected to the electropneumatic converter 6, the explosion-proof type device case 15 Therefore, it was necessary to guide the air circuit 27 into the case 15. Therefore, two flame arresters 23 and 24 for nozzle back pressure and exhaust are required, which increases the number of parts and causes a cost increase, and also complicates the air circuit.

Accordingly, the present invention has been made in view of the above-described conventional problems, and has as its object to eliminate the need for a frame arrestor, and to achieve cost reduction and simplification of an air circuit. To provide a positioner.

Means for Solving the Problems In order to achieve the above object, the present invention provides a positioner provided with an electro-pneumatic converter including a yoke, a coil, a magnet, and a nozzle flapper mechanism. Place in the equipment case,
The tip of the yoke is projected outside the device case, and the magnet is fixed to the projected end,
The nozzle flapper mechanism is disposed to face the nozzle flapper mechanism.

[Operation] In the present invention, the yoke of the electropneumatic converter is provided so as to penetrate the wall surface of the device case, so that the outer end protruding outside the case provides a nozzle flapper mechanism and a magnet attachment portion, and the inner end. Form a mounting portion for the coil.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of a positioner according to the present invention, and FIG. 2 is a view showing the operation principle of an electropneumatic converter.
In the drawing, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. In these figures, the electropneumatic converter 6 is formed of three legs 40A, 40B, and 40C having an E-shaped cross section, and a connecting portion 40D that connects one end of each of the legs. A yoke 40 is provided. The yoke 40 is formed simultaneously with the formation of the equipment case 15 for forming the explosion-proof container by insert molding or the like.
By being provided through 15 walls, each leg 40
The tips of A, 40B, and 40C protrude outside the device case 15 and are located in the case 22, and the connecting portion 40D and the legs 40A, 40
The base ends of B and 40C are located in the equipment case 15. A magnet 41 is fixed to the tip of the center leg 40B with the N pole facing up and the S pole facing down.
The coils 42A and 42B are fitted respectively to the inner ends of the.

A flapper 11 is provided above each of the legs 40A, 40B, and 40C.
The distal ends of these legs and the magnet 41 are arranged to face each other. Flapper 11 has a length of yoke 40
The central portion in the longitudinal direction is supported by a fulcrum spring 43 so as to be vertically swingable. The fulcrum spring 43 has one end fixed to a bracket 44 provided with its base fixed to the outer wall of the device case 15 and the other end connected to the flapper 11.
It is screwed and fixed to the upper surface. And flapper 11
The nozzle 12 is arranged at one end of the nozzle so as to be closely opposed.
Therefore, the nozzle flapper mechanism 9 is provided outside the equipment case 15, thereby eliminating the need for introducing an air circuit into the equipment case 15 and installing a frame arrester that satisfies the explosion-proof standard.

In FIG. 2, reference numeral 50 denotes a fulcrum of the flapper 11, a solid line arrow 51 indicates the magnetic field generated by the coils 42A and 42B, and a dotted arrow line 52 indicates the direction of the magnetic field generated by the magnet 41. Coil 42
When a current flows through A and 42B, a magnetic field in the same direction as the direction of the magnetic field generated by the magnet 41 is generated on the left coil 42A side, and a magnetic field in a direction that cancels the magnetic field strength of the magnet 41 on the right coil 42B side. Occurs. For this reason, the force F for attracting the flapper 11 is increased on the left side, and the force is weakened on the right side. Move closer to 12. Accordingly, the nozzle gap is reduced and the nozzle back pressure is increased, thereby generating an air pressure signal proportional to the current signal.

The other structure is the same as the conventional structure shown in FIG.

Thus, according to the positioner 1 having such a configuration, since the nozzle flapper mechanism 9 can be installed outside the equipment case 15, an air circuit is provided in the equipment case 15, or a frame arrestor is incorporated into the case wall. There is no need, and the number of parts can be reduced and the air circuit can be simplified.

[Effect of the Invention] As described above, in the positioner according to the present invention, the yoke of the electropneumatic converter is provided so as to penetrate the equipment case forming the explosion-proof container, only the electric part is provided at the inner end, and the outer end is provided. Since the nozzle flapper mechanism is provided in the section, there is no need to guide the air circuit into the equipment case, the need for a frame arrestor is eliminated, the number of parts can be reduced, and the air circuit can be simplified and the cost can be reduced.

[Brief description of the drawings]

1 is a sectional view showing an embodiment of a positioner according to the present invention, FIG. 2 is a view showing the operation principle of an electropneumatic converter, and FIG. 3 is a conventional example of an explosion-proof pneumatic positioner for a regulating valve. It is sectional drawing. 6 ... Electro-pneumatic converter, 7 ... Coil, 8 ... Magnet,
9: Nozzle flapper mechanism, 11: Flapper, 12: Nozzle, 13: Pilot relay, 15: Equipment case, 2
3, 24 ... frame arrester, 40 ... yoke, 41 ... magnet, 42A, 42B ... coil, 50 ... fulcrum.

Claims (1)

(57) [Claims] 1. A positioner provided with an electropneumatic converter comprising a yoke, a coil, a magnet, and a nozzle flapper mechanism, wherein the yoke is disposed in an equipment case forming an explosion-proof container together with a coil, and a tip end of the yoke is connected to the equipment. A positioner characterized by projecting outside the case, fixing the magnet to the projecting end, and arranging the nozzle flapper mechanism so as to face the case.