JP2722035B2 - Electro-pneumatic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electropneumatic converter suitable for an electropneumatic positioner or the like.

[0002]

2. Description of the Related Art An electropneumatic converter of this type, which is conventionally used in a valve positioner or the like and converts an electric signal into a pneumatic signal and outputs the converted signal, is generally known as shown in FIGS. Have been. That is, FIG. 9 is a block diagram showing the operation principle of the valve positioner, and 1 is a CP.
An operation unit including U and the like, 2 is an electropneumatic converter, and 3 is a feedback sensor that detects an output (control amount) of the electropneumatic converter 2.

The electro-pneumatic converter 2 includes a permanent magnet 4 formed in a U-shape in plan view as shown in FIG.
A pair of upper and lower yokes 5 and 5, each of which is attached to both ends of the upper and lower surfaces with one end facing each other, a coil 6 disposed between the upper and lower yokes 5 and 5, and upper and lower yokes 5 and 5.
Is disposed with an appropriate gap between the opposing surfaces of the coil, penetrates the center of the coil 6, and has a lower end pivotally supported by one of the lower yokes 5 by a fulcrum spring 7. And the like, a counter weight 9 provided at the lower end of the flapper 8, a zero point adjusting spring 10 provided at one of the upper yokes 5, and the like.
A nozzle 11 is disposed at the upper end of the flapper 8 so as to be closely opposed to the nozzle 11. The nozzle 11 is supplied with a predetermined air pressure SUP from an air supply source.

In the valve positioner having such a configuration, when an input signal Io (4 to 20 mA) is input to the arithmetic section 1, the valve positioner is compared with the feedback signal I1 from the feedback sensor 3 and when the deviation is zero, No correction signal is sent to the electropneumatic converter 2. When the input signal Io changes in accordance with the set value and a deviation occurs from the electric signal I1 from the feedback sensor 3 in the arithmetic unit 1, a correction signal corresponding to the deviation is output to the electropneumatic converter 2.
This correction signal is input to the coil 6 and changes the strength of the magnetic field, so that the flapper 8 swings in the direction of the nozzle 11 or in the direction opposite to the nozzle. For this reason, the nozzle flapper distance d changes, and the back pressure PN of the nozzle 11 changes.
After the nozzle back pressure PN is amplified by a pilot relay (not shown) or the like, it is supplied as an output pressure Pout to an operating device that drives the valve shaft of the control valve, whereby the control valve is automatically opened and closed. Further, the output pressure Pout is detected by the feedback sensor 3 and input as a feedback signal to the arithmetic unit 1, so that the valve is stabilized when the deviation between Io and I1 becomes zero.

[0005]

Incidentally, in such a conventional electropneumatic converter 2, a coil spring (or leaf spring) 10 having one end connected to the flapper 8 is used as a zero point adjusting mechanism. , When performing zero adjustment,
There is a problem in that friction or displacement is inevitably generated at the attachment portion or contact portion between the flapper 8 and the spring 10, and hysteresis occurs in the output air pressure. Also, if the adjusting screw or the spring is loose due to vibration or the like, it causes a change in the operating point, resulting in a problem of poor stability.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems. An object of the present invention is to prevent the occurrence of hysteresis due to friction by adjusting the flapper in a non-contact manner. Another object of the present invention is to provide an electropneumatic converter capable of improving vibration resistance.

[0007]

Means for Solving the Problems The present invention has been made to achieve the above object, and a first invention is to dispose a coil and a permanent magnet on a yoke having an E-shaped cross section. A nozzle is provided on one end leg of the yoke, and a flapper is swingably disposed on the yoke via a bracket such that one end thereof is in close proximity to the nozzle, and a magnet is rotatably fitted to a part of the yoke. It is inserted.

According to a second aspect of the present invention, a coil and a permanent magnet are disposed on a yoke having an E-shaped cross section, a nozzle is provided on one end of the yoke, and a flapper is provided so that one end thereof is in close proximity to the nozzle. The yoke is swingably disposed via a bracket, a gap is provided in a part of the yoke, and a magnetic material is inserted into the gap so as to be movable in the longitudinal direction of the flapper.

According to a third aspect of the present invention, a coil and a permanent magnet are provided on a yoke having an E-shaped cross section, nozzles are provided at both ends of the yoke, and a flapper having both ends closely opposed to the nozzles is provided. A nozzle is swingably disposed on the yoke via a bracket, and one of the nozzles is movable in the longitudinal direction of the flapper in a recess formed around the yoke and communicated with a supply air pressure passage. It is provided and used for zero adjustment.

[0010]

In the first aspect of the invention, the magnet rotates to change the magnetic field on both sides of the yoke, and the change in the magnetic field gives a rotational moment to the flapper, thereby adjusting the zero point. In the second invention, the magnetic body moves to change the magnetic field on both sides of the yoke, and the change in the magnetic field gives a rotational moment to the flapper, thereby adjusting the zero point. In the third invention, one of the nozzles is movable and adjustable in the longitudinal direction of the flapper, and when moved toward the fulcrum side of the flapper, gives a small rotational moment to the flapper.
A large rotational moment is given when moving away from the fulcrum.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows a first embodiment of the electropneumatic converter according to the present invention.
It is sectional drawing which shows an Example. FIG. 2 is a plan view of the converter. In these figures, the electropneumatic converter 20 is a yoke 2
1 is provided. The yoke 21 has three legs 21A, 21B, and 21C integrally formed by forming an E-shaped cross section, and a permanent magnet 4 is provided on the central leg 21B.
For example, the coils 6A and 6B are fitted to the legs 21A and 21C on the left and right sides, respectively, with the N pole facing up and the S pole facing down. The coils 6A and 6B are excited so that the magnetic poles are opposite to each other. In this case, in the present embodiment, the left coil 6A is energized so that the upper side is an S pole and the lower side is an N pole, and the right coil 6B is energized so that the upper side is an N pole and the lower side is an S pole.

The flapper 8 is supported by a fulcrum spring 7 at a middle portion in the longitudinal direction above the yoke 21 so as to be swingable in a vertical direction, and is disposed substantially horizontally. The fulcrum spring 7 has a free end fixed to a bracket 23 attached to the yoke 21 and a base fixed to the upper surface of the flapper 8 by a set screw 24. A nozzle 11 is disposed on the upper surface of the leg portion 21A. The nozzle 11 is opposed to the lower surface on the left side from the fulcrum of the flapper 8 and an air pressure SUP of a predetermined pressure is supplied from a supply air source (not shown). The air is supplied from the supply passage 26 through the throttle 25. An air passage 27 connecting the nozzle 11 and the air supply passage 26 is formed inside the leg portion 21A. On the other hand, a stopper pin 28 is provided on the upper surface of the other leg 21 </ b> C so as to be closely opposed to the lower surface of the right end of the flapper 8.

A flapper 8 and a through hole 29 orthogonal to the long axis direction are formed in a lower portion of the yoke 21 between the legs 21B and 21C.
A magnet 30 as a zero adjustment mechanism is rotatably fitted in 9. The magnet 30 is magnetized in a direction perpendicular to the axial direction, so that the peripheral surface is magnetized to the N pole and the S pole,
The yoke 21 is configured to be rotated from the outside.

FIG. 3 is a diagram showing the operation principle of the electropneumatic converter 20. In the figure, reference numeral 34 denotes a fulcrum of the flapper 8, a solid line arrow 35 indicates the direction of the magnetic field generated by the coils 6 A and 6 B, and a dotted arrow line 36 indicates the direction of the magnetic field generated by the magnet 4. When a current flows through the coils 6A and 6B, a magnetic field in the same direction as the direction of the magnetic field of the permanent magnet 4 is generated on the left coil 6A side, and the magnetic field strength of the permanent magnet 4 is canceled on the right coil 6B side. A magnetic field is generated in the direction. For this reason, the force F for attracting the flapper 8 is increased on the left side, and the force F is weakened on the right side. Move closer to the nozzle 11. Accordingly, the nozzle flap distance (d) decreases and the nozzle back pressure increases, thereby generating a pneumatic signal proportional to the current signal.

FIG. 4 is a diagram showing the nozzle / flapper characteristics.
The straight line portion between the pressures PL and P0 is the range actually used. That is, the output is P0 to PL for a signal range of 4 mm to 20 mmA. Here, when the zero point adjustment of the electropneumatic converter 20 is performed, the magnet 3 inserted into the through hole 29 is used.
The direction of the magnetic pole may be changed by rotating 0 from the outside. That is, for example, as shown in FIG. 3, when the N pole is turned to the right and the S pole is turned to the left, the magnetic field of the permanent magnet 4 and the magnetic field of the magnet 30 cancel each other out on the right side of the yoke, so that the force F for attracting the flapper 8 is obtained. Is weakened, and the magnetic field of the magnet 30 is superimposed on the magnetic field of the permanent magnet 4 on the left side of the yoke, so that the force F for attracting the flapper 8 increases. Therefore, the flapper 8 generates a rotating torque in the counterclockwise direction, and reduces the nozzle flap distance d. Conversely, turning the north pole of the magnet 30 to the left and the south pole to the right can cause the flapper 8 to generate clockwise rotation torque. Therefore, the rotational torque is changed by the rotation of the magnet 30, and the nozzle / flap distance d is set to d =
The zero point can be adjusted by setting d0 and balancing the air pressure SUP and the flapper 8.

Thus, in such a zero-point adjusting mechanism, the intensity of the magnetic field is changed by the rotation of the magnet 30 to displace the flapper 8 in a non-contact manner to perform the zero-point adjustment. The stability and vibration resistance of the electropneumatic converter can be improved without the need for any adjusting screws or springs that cause generation and fluctuation of the operating point.

FIG. 5 is a sectional view showing a second embodiment of the present invention. In this embodiment, instead of the magnet 30 in the above-described embodiment, a magnetic body 41 is movably inserted and arranged in a horizontally long gap 40 provided below the inside of the yoke 21, and the magnetic body 41 is moved from the outside of the yoke. The zero point is adjusted by moving in the left-right direction. That is, when the magnetic body 41 is moved right and left, the magnetic gaps 43a and 43b formed on both sides of the magnetic body 41 change. Now, when the magnetic body 41 is moved to the left, the left magnetic gap 43a becomes smaller, and conversely, the right magnetic gap 43b becomes larger. As a result, the magnetic flux passing on the left side increases and the magnetic flux passing on the right side decreases, so that the flapper 8 can generate a rotating torque in the counterclockwise direction. Conversely, when the magnetic body 41 is moved to the right, the magnetic flux passing on the left side decreases and the magnetic flux passing on the right side increases, so that the flapper 8 can generate a clockwise rotation torque. Therefore, even in such a configuration, the zero point can be adjusted in the same manner as in the first embodiment.

FIG. 6 is a sectional view showing a third embodiment of the present invention. In this embodiment, the flapper 8
A through-hole 44 formed of a circular hole in a direction perpendicular to the longitudinal direction of the yoke is formed. A cylindrical magnetic body 45 having a flat portion 45a over the entire length is rotatably fitted into the through-hole 44, and from the outside of the yoke. The zero point adjustment is performed by rotating the magnetic body 45. That is, when the position of the magnetic gap 46 formed between the flat portion 45a and the inner peripheral surface of the through hole 44 is changed by the rotation of the magnetic body 45, the magnetic flux passing through the left and right sides of the yoke 21 changes. As in the first and second embodiments, the flapper 8 can generate a clockwise or counterclockwise rotation torque.
Thus, the zero point can be adjusted. In this embodiment, the coil 6 is fitted to the center leg 21B, and the permanent magnets 4A, 4B are attached to the legs 21A, 21C on both sides.
An example in which is disposed is shown.

FIG. 7 is a sectional view showing a fourth embodiment of the present invention.
FIG. 8 is a partially broken plan view. In this embodiment, a zero point adjusting nozzle 50 is used instead of the stopper pin 28 (see FIG. 1).
Are disposed on the distal end surfaces of the legs 21C of the yoke 21. The nozzle 50 is disposed movably in the left-right direction via an O-ring 52 in a concave portion 51 formed in the center of the lower surface of the permanent magnet 4B, and the reduced-diameter nozzle portion 50a is attached to the permanent magnet 4B. The flapper 8 protrudes upward and is closely opposed to the lower surface of the right end of the flapper 8. Also, as shown in FIG. 8, the nozzle 50 is screwed into a screw 53 that is disposed so as to be allowed to rotate only on the permanent magnet 4B. When the screw 53 is rotated, the nozzle 50 is moved and adjusted in the left-right direction. It is configured.
The supply air pressure SUP is also supplied to the nozzle 50 via the supply air pressure passage 56 formed in the leg 21C.

In such a configuration, when adjusting the zero point, the screw 53 may be rotated to move the nozzle 50 in the left-right direction. When the nozzle 50 moves, the distance from the rotation fulcrum 34 (see FIG. 3) of the flapper 8 to the nozzle 50 changes, and when the nozzle 50 is moved to the fulcrum side, the distance decreases. The rotation torque of the flapper 8 in the counterclockwise direction due to the supplied air pressure is reduced. Conversely, when the nozzle 50 is moved to the side opposite to the fulcrum, the distance increases, and the rotational torque of the flapper 8 in the counterclockwise direction increases. Therefore,
Even in such a configuration, the zero point can be adjusted as in the first to third embodiments.

[0021]

As described above, in the electropneumatic converter according to the present invention, since the flapper is displaced in a non-contact manner by utilizing a magnetic change or air pressure, the screw for directly displacing the flapper is provided. , No spring or the like is required, and as a result, there is no occurrence of hysteresis due to friction, and the zero point does not shift due to vibration, so that the stability and vibration resistance of the electropneumatic converter can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an electropneumatic converter according to the present invention.

FIG. 2 is a plan view of the converter.

FIG. 3 is a diagram illustrating an operation principle of the electropneumatic converter.

FIG. 4 is a diagram showing nozzle / flapper characteristics.

FIG. 5 is a sectional view showing a second embodiment of the present invention.

FIG. 6 is a sectional view showing a third embodiment of the present invention.

FIG. 7 is a sectional view showing a fourth embodiment of the present invention.

FIG. 8 is a partially broken plan view of a main part.

FIG. 9 is an operation principle diagram of the valve positioner.

FIGS. 10A and 10B are a cross-sectional view and a plan view showing a conventional example of an electropneumatic converter.

[Explanation of symbols]

 4, 4A, 4B Permanent magnet 5 Yoke 6, 6A, 6B Coil 8 Flapper 11 Nozzle 20 Electro-pneumatic converter 21 Yoke 21A-21C Leg 23 Bracket 27 Air supply passage 30 Through hole 31 Magnet 40 Air gap 41 Magnetic body 44 Penetration Hole 45 Magnetic body 46 Magnetic gap 50 Nozzle 52 Recess 56 Air supply passage

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-106402 (JP, A) JP-A-4-151002 (JP, A) Fully open 63-96301 (JP, U) Really open 1962 30001 (JP, U) Patent 2567971 (JP, B2) Patent 2573221 (JP, B2)

Claims (3)

(57) [Claims] 1. A coil and a permanent magnet are disposed on a yoke having an E-shaped cross section, a nozzle is provided on one end of the yoke, and a flapper is mounted on the yoke such that one end thereof is in close proximity to the nozzle. An electro-pneumatic converter characterized by being rotatably disposed through a magnet and rotatably fitted with a magnet in a part of the yoke. 2. A coil and a permanent magnet are disposed on a yoke having an E-shaped cross section, a nozzle is provided on one end of the yoke, and a flapper is mounted on the yoke such that one end thereof is in close proximity to the nozzle. An electro-pneumatic converter characterized by being provided so as to be swingable through a gap, providing a gap in a part of the yoke, and inserting a magnetic material into the gap so as to be movable in the longitudinal direction of the flapper. . 3. A coil and a permanent magnet are provided on a yoke having an E-shaped cross section, nozzles are provided on both ends of the yoke, and a flapper having both ends close to and opposed to each nozzle is provided with a bracket on the yoke. One nozzle is disposed so as to be movable in the longitudinal direction of the flapper in a recess formed around the yoke and communicated with the supply air pressure passage. An electro-pneumatic converter used for zero adjustment.