JPH04185901A - Positioner - Google Patents

Abstract

PURPOSE:To eliminate a flame arrester to reduce cost and simplify a pneumatic circuit by providing coils inside a device case at the inner end of a yoke for an electropneumatic converter provided through the wall of the device case, and also providing a magnet and a nozzle flapper mechanism outside the device case at the outer end of the yoke. CONSTITUTION:A device case 15 forming an explosion-proof container is formed, a yoke 40 is provided through the wall of it, coils 42A and 42B are provided inside the device case 5 at the inner end of the yoke 40, and a nozzle flapper mechanism 9 comprising a magnet 41, a flapper 11, and a nozzle 12 is provided outside the device case at the outer end of the yoke. Thus it is not required to lead a pneumatic circuit into the device case 15 and a flame arrester is not required, resulting in reduction of the number of parts and cost, and simplification of the pneumatic circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a positioner suitable for application to an electropneumatic positioner for a control valve.

[Prior Art] Electricity/displacement conversion mechanisms conventionally used in electro-pneumatic instruments, such as electro-pneumatic converters, electro-pneumatic positioners for control valves, etc., are not fully compliant with explosion-proof standards when used in an explosive gas atmosphere. It is mandatory to have explosion-proof performance. Therefore, a structure is generally adopted in which the entire electricity/displacement conversion mechanism is housed in an explosion-proof case formed from a special pressure-resistant container.

Fig. 3 shows a conventional example of an electropneumatic positioner for a control valve that employs such a pressure-resistant and explosion-proof structure.To briefly explain this, the positioner 1 controls the displacement of the operating shaft 3 of the control valve 2 using a potentiometer, etc. The electric signal I is detected by the displacement detection unit 4 of
1, the electrical signal 11 is fed back to the mm calculation section 5, this feedback signal is compared with the input signal IO to the positioner 1, and the difference is sent to the electro-pneumatic converter 6, thereby converting the instrument signal The structure is such that the relationship between the valve shaft position and the valve shaft position is always accurately controlled against disturbances.

The control calculation unit 5 includes an input detection unit, a CPU, and the like. The electro-pneumatic converter 6 is an input signal converter. The nozzle flapper mechanism 9 is configured to include a coil 7 to which is supplied a magnetic field, a magnet 8 that is movable by the magnetic force of the coil 7, and a nozzle flapper mechanism 9 that converts the displacement of the magnet 8 into an air pressure signal. Nozzle flapper I
! #19 is the flapper 1 that swings around the fulcrum 10.
1. A nozzle 12 is provided close to and facing one end of the flapper 11 and receives a supply air pressure SUP from an air supply source, and the nozzle back pressure of this nozzle 12 is amplified by a pilot relay 13 to produce an output air pressure P.

It is configured to be outputted to the drive device 14 of the regulating valve 2 as ut.

Reference numeral 15 denotes a pressure-resistant and explosion-proof equipment case, the interior of which forms an explosion-proof chamber 16, which includes the displacement detection section 4, an electro-pneumatic converter 6, a nozzle flapper mechanism 9, a span adjustment switch 17, a span adjustment screw 18, and a zero adjustment switch. 19, a zero am screw 20, a terminal board 21, etc. are stored therein. A case 22 houses the pilot relay 13, and is attached to one side wall of the equipment case 15, between which frame arresters 23 and 24 for nozzle back pressure and exhaust are provided.

These 7-frame arresters 23 and 24 are constructed by arranging a plurality of metal cylinders 25 with different diameters approximately coaxially, and have a predetermined gap (explosion-proof gap) so that the gap between the cylinders conforms to explosion-proof standards. ) d (for example, 0.1 ■■), and the length of the circle Fi25 gives the depth of the gap d of 1 (for example, 10 dragons).

The flame arresters 23 and 24 are housed in storage holes 26A and 26B formed in the equipment case 15, respectively, and piping 27 forming an air circuit is connected to the openings at both ends of the storage hole 26A. Therefore, they are each closed by a lid body 28.

In addition, 29 is a pressure gauge, 30 is a pressure reducing valve, 31 is a throttle, and 32
is a selector switch that switches between manual and automatic mode.

In such a configuration, the input signal o to the valve positioner 1 varies, for example, in the range of 4 mA to 20 mA, and when the input signal is 4 mA, the control valve 2 is held in the fully closed state, and the input signal o is 20 mA.
It shall be kept fully open when A lever 33 that rotates in conjunction with the operating shaft 3 when the control valve 2 is in a fully closed state.
is stopped at the position rotated downward by the maximum angle. In this state, the electric signal 1 of the displacement detection section 4 is equal to the input signal 1.degree., and is A/D converted and input to the control calculation section 5 as a feedback signal. Since the input signal io input to the control calculation section 5 and the feedback signal 1 have the same value, the difference current between them is zero, and no correction signal is sent to the electro-pneumatic converter 6.

Input signal engineer. changes in accordance with the set value, and when a deviation occurs in the control calculation unit 5 from the feedback signal □ from the displacement detection unit 4, a corresponding correction signal is output to the electro-pneumatic 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 the output air pressure of the pilot relay 13 increases and becomes Pout, causing the drive device 14 to operate.

As a result, the operating shaft 3 moves upward and controls the control valve 2.
Further, the movement of the actuating shaft 3 is transmitted as a force that rotationally displaces the lever 33 in the counterclockwise direction in FIG. When the lever 33 rotates, the current value of the electric signal □, which is input as a feedback signal from the displacement detection tJ4 to the control calculation unit 5, gradually increases, and the input signal I according to the set value. The difference between the current value and the current value decreases, and the valve opening becomes stable when this difference current becomes zero. The operation of returning the valve from the open state to the fully closed state is the opposite of the above.

[Problems to be Solved by the Invention] Incidentally, in such a conventional explosion-proof electro-pneumatic positioner 1 for a regulating valve, in order to integrally connect the nozzle flapper mechanism 9 with the electro-pneumatic converter 6, it is necessary to Since the air circuit 27 was placed inside the equipment case 15, it was necessary to lead the air circuit 27 into the equipment case 15. Therefore, there are two
This requires two flame arresters 23 and 24, which increases the number of parts and increases costs, as well as complicating the air circuit.

Therefore, the present invention was made in view of the above-mentioned conventional problems, and its purpose is to reduce costs and simplify the air circuit without requiring a flame arrester. The purpose is to provide a positioner.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an electro-pneumatic converter disposed within an equipment case forming an explosion-proof container, and a yoke of the electro-pneumatic converter is connected to the equipment case. The yoke is provided through the wall of the case, a coil is attached to the inner end of the yoke located inside the equipment case, and a magnet and a nozzle flapper mechanism are provided to the outer end protruding outside the equipment case.

[Function] In the present invention, the yoke of the electro-pneumatic converter is provided by penetrating the wall surface of the equipment case, so that the outer end protruding outside the case provides a mounting part for the nozzle flapper mechanism and the magnet, and the inner end forms the mounting part of the coil.

[Example] Hereinafter, the present invention will be described in detail based on an example 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 diagram showing the operating principle of an electro-pneumatic converter. Components in the figure that are the same as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In these figures, the pneumatic converter 6 has an E-shaped cross-section and consists of three legs 40A, 40B, and 40C, and a connecting part 40D that connects one end of these legs. Naru York 4
It is equipped with 0. The yoke 40 is provided by insert molding or the like at the same time as the equipment case 15 that forms the explosion-proof container and is provided through the wall surface of the case 15, so that the tips of the legs 40A, 40B, and 40C are attached to the equipment case 15. The connecting portion 40D and the base end portions of the legs 40A, 40B, and 40C are located within the device case 15. A magnet 41 is fixed to the distal end surface of the center leg 40B with the north pole facing upward and the south pole facing downward, and coils 42A and 42B are fixed to the inner ends of the legs 40A and 40C on both sides, respectively. It is fitted.

A flapper 11 is disposed above each of the legs 40A, 40B, and 40C so as to face the distal end surfaces of these legs and the magnet 41. The flapper 11 has a length substantially equal to that of the yoke 40, and its longitudinal center portion is supported by a fulcrum spring 43 so as to be swingable in the vertical direction. The fulcrum spring 43 has one end fixed to a bracket 44 disposed with its base fixed to the outer wall of the equipment case 15, and the other end fixed to the upper surface of the flapper 11 with screws. Further, nozzles 12 are arranged at one end of the flapper 11 so as to be close to each other and face each other. Therefore, the nozzle flapper mechanism 9 is provided outside the equipment case 15, thereby making it unnecessary to introduce an air circuit into the equipment case 15 and install a flame arrester that satisfies explosion-proof standards.

In FIG. 2, reference numeral 50 indicates the fulcrum of the flapper 11, a solid line arrow line 51 indicates the magnetic field produced by the coils 42A and 42B, and a dotted line arrow line 52 indicates the direction of the magnetic field produced by the magnet 41. When current is passed through the coils 42A and 42B, On the left side coil 42A, a magnetic field is generated in the same direction as the magnetic field of the magnet 41, and on the other hand, on the right side coil 42B (l), a magnetic field is generated in a direction that cancels the strength of the magnetic field of the magnet 41. In this case, the force F that attracts flapper 11 is stronger, and the force is weaker on the right side, so flapper 1
1, a counterclockwise rotating torque proportional to the supplied current is generated around the fulcrum 50, and the flapper 11 is moved closer to the nozzle 12. Therefore, the nozzle gap decreases and the nozzle backpressure increases, thereby producing an air pressure signal proportional to the current signal.

Note that the other configurations are the same as the conventional structure shown in FIG.

According to the positioner 1 having such a configuration, the nozzle flapper mechanism 9 can be installed outside the equipment case 15, so an air circuit can be provided inside the equipment case 15, and a flame arrester can be built into the case wall. There is no need for this, and the number of parts can be reduced and the air circuit can be simplified.

[Effects of the Invention] As explained above, in the positioner according to the present invention, the yoke of the electro-pneumatic converter is provided to penetrate the equipment case forming the explosion-proof container, and the gIJli! Only the electrical part is installed in the
Since the nozzle flapper mechanism is provided at the outer end, there is no need to guide the air circuit into the equipment case, eliminating the need for a flame arrester, making it possible to reduce the number of parts, simplify the air circuit, and reduce costs.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the positioner according to the present invention, Fig. 2 is a diagram showing the operating principle of an electro-pneumatic converter, and Fig. 3 is a conventional example of an explosion-proof pneumatic positioner for a regulating valve. FIG. 6... Electro-pneumatic converter, 7-... Coil, 8...- Magnet, 9... Nozzle flapper mechanism, 11... Flapper, 12... Nozzle, 13-... Pilot relay,
15... Equipment case, 23.24... Flame arrester, 40... Yoke, 41... Magnet, 42
A, 42B...Coil, 50.-One fulcrum. Patent issuer Yamatake Honeywell Co., Ltd.

Claims (1)

[Claims] An electro-pneumatic converter is disposed within an equipment case forming an explosion-proof container, a yoke of the electro-pneumatic converter is provided to penetrate a wall surface of the equipment case, and an inner end of the yoke is located inside the equipment case. A positioner characterized in that a coil is attached to the part, and a magnet and a nozzle flapper mechanism are provided on the outer end that protrudes outside the device case.