JPH1037901A - Electro/pneumatic converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve vibration-proofing performance in a converter which converts mechanical displacement of a nozzle flapper mechanism by changing inputted current into outputted air pressure. SOLUTION: This electro/pneumatic converter is provided with a stationary iron core coil 4 which generates a variable magnetic field corresponding to inputted current, a pair of yokes 2 which is arranged so that they may be a part of respective components of two magnetic passages by the variable magnetic field, a permanent magnet 10 which is arranged so that the magnetic passage by the variable magnetic field and the magnetic passage by a fixed magnetic field may be partly common, a movable piece 3 which is arranged in the magnetic field and displaces according to the magnitude of the variable magnetic field, and a nozzle flapper mechanism 3C which converts the mechanical displacement of the movable piece 3 into the back pressure of a nozzle 8. The movable piece 3 is a thin metallic flat spring where a flapper part 3C and a pair of supporting parts are formed and movable iron cores 6A, 6B of ferromagnetic material are bonded in the middle part, and has a cantilever structure whose supporting part is fixed at the yokes 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric / pneumatic converter for converting an input current into an output air pressure by converting a current into a mechanical displacement and converting the mechanical displacement into a pneumatic pressure by a nozzle / flapper mechanism. More particularly, it relates to an electric / pneumatic converter suitable for a valve positioner.

[0002]

2. Description of the Related Art A conventional electric / pneumatic converter is shown in FIG.
As shown in FIG. 3, a pair of soft magnetic materials yokes 31 and 32 which are arranged opposite to each other while maintaining a pair of gaps, a permanent magnet 41 magnetizing the pair of yokes with opposite polarities, and a regular interval between the pair of gaps. A movable piece 33 of a soft magnetic material fixedly inserted so as to be rotatable around a spring material 36, a counterweight 35 attached to one end of the movable piece 33,
Coil 3 arranged so as to surround movable piece 33
4 and a nozzle 37 which is disposed opposite to the other end of the movable piece 33 and is supplied with supply air pressure Ps via a throttle 38. 39 is a zero adjustment screw, 4
0 is a spring for zero adjustment.

In the conventional electric / pneumatic converter configured as described above, when an input current is applied to the coil 34, a magnetic field corresponding to the magnitude of the current is generated, and two magnetic paths having opposite magnetic field directions are formed. That is, the clockwise first magnetic path and the counterclockwise second magnetic path are formed as indicated by thin dotted lines in the figure. More specifically, the first magnetic path is formed by the yoke 31, the movable piece 33, and the gap therebetween, and at the same time, the yoke 32, the movable piece 33
And a gap between them forms a second magnetic path. The yoke 31, the movable piece 33, the yoke 32, and the gap between them are formed by a permanent magnet 41 with two magnetic paths both clockwise in the direction of the magnetic field, as indicated by thick dotted lines. For this reason, a difference is generated in the magnetic attraction force acting on the left and right sides of the movable piece 33 of the soft magnetic material, and the movable piece 33 rotates around the spring material 36 as a fulcrum, and the flapper portion of the movable piece 33 and the nozzle 37 The gap between changes. Nozzle 37
Is supplied with a constant supply air pressure Ps from an air pressure source. Therefore, when the gap between the nozzle 37 and the flapper portion of the movable piece 33 changes, the nozzle back pressure Pn, that is, the output air pressure changes correspondingly. Thus, the electrical / pneumatic converter of FIG. 6 functions to obtain an output pneumatic signal corresponding to the input current signal.

In the electric / pneumatic converter shown in FIG. 6, a movable piece 33 of a soft magnetic material having a counterweight 35 attached to one end thereof is connected to a yoke 31 by a spring material 36.
It is stuck to. Therefore, the combined body of the movable piece 33 and the counterweight 35 forms a vibration system as a pendulum. The natural frequency of the vibration system as a pendulum is determined by the length and the mass when conditions other than the length and the mass of the pendulum are fixed. In other words, the natural frequency in this case decreases as the pendulum length increases, and decreases as the mass increases. Since the movable piece 33 made of a soft magnetic material is a main member for forming a magnetic path, the movable piece 33 cannot be made too thin to increase the magnetic efficiency. In addition, the counterweight 35 must be of a weight that balances with the movable piece 33, so that it cannot be made too light. Further, a movable piece 33 having a flapper portion formed at one end and a counterweight 35 attached to the other end.
Since these ends extend outside the yokes 31, 32, their lengths cannot be shortened below the lengths of the yokes 31, 32. Therefore, the combination of the movable piece 33 and the counterweight 35 is necessarily of a considerable weight and length, and its natural frequency is quite low, and 50H
Cannot be more than z. Generally, various mechanical vibrations generated at the site where the electric / pneumatic converter is installed are 50
Hz or less. For this reason, the electric / pneumatic converter shown in FIG. 6 may cause resonance with the mechanical vibration, resulting in breakage of equipment and other inconveniences. In short, there is a disadvantage that the vibration resistance is low.

An electric / pneumatic converter shown in FIG. 7 was invented in order to solve the above-mentioned disadvantage of low vibration resistance, which is disclosed in Japanese Patent Application Laid-Open No. 4-119202. . In FIG. 7, a yoke 21 is a yoke having an E-shaped cross section, and has a bottom 21D and three legs 21A.
21B and 21C. The coil 16 is fitted on the leg 21B of the yoke 21, and permanent magnets 20A and 20B whose magnetic poles are opposite to each other are disposed on the tip surfaces of the legs 21A and 21C. Permanent magnet 2
A movable piece 22 is provided so as to face 0A and 20B. The movable piece 22 has substantially the same length as the bottom portion 21D of the yoke 21, and its longitudinal center portion is supported by a fulcrum spring 17 so as to be vertically swingable. Support spring 17
Has one end fixed to a bracket 23 attached to a yoke 21 and the other end attached to the upper surface of the movable piece 22 with a set screw 2.
4 fixed. A nozzle 18 is further provided at the tip of the leg 21A of the yoke 21 so as to be closely opposed to the lower surface of one end (the left end in the figure) of the movable piece 22. The nozzle 18 is supplied with a predetermined air pressure Ps from a supply air source via a throttle 25, a pipe 26, and an air passage 27. One end of the movable piece 22 functions as a flapper. A stopper 28 is provided at the distal end of the leg 21C of the yoke 21 so as to face the lower surface of the other end (the right end in the figure) of the movable piece 22. Further, the other end of the movable piece 22 is provided with a zero adjustment screw 29 and a zero adjustment spring 30 which constitute a zero adjustment mechanism.

In the conventional electric / pneumatic converter configured as described above, when an input current is applied to the coil 16, a magnetic field corresponding to the magnitude of the input current is generated, and two magnetic paths having opposite magnetic field directions are generated. That is, a clockwise first magnetic path and a counterclockwise second magnetic path are formed. More specifically, the first magnetic path is formed by the leg portion 21B of the yoke 21, the right portion of the movable piece 22, the permanent magnet 20B, the leg portion 21C and the bottom portion 21D of the yoke 21, and the gap therebetween. Legs 21
B, left part of movable piece 22, permanent magnet 20A, yoke 2
A second magnetic path is formed by the first leg 21A and the bottom 21D and the gap between them. By the way, the yoke 21 and the movable piece 2
2, a counterclockwise magnetic path is formed by the fixed magnetic field of the permanent magnets 20A and 20B. That is, the permanent magnet 20
A, leg 21A, bottom 21D and leg 21 of yoke 21
C, a permanent magnet 20B, a movable piece 22, and a magnetic path including a gap therebetween are formed. For this reason, the coil 16
And the magnetic field generated by the permanent magnets 20A and 20B reinforce each other in the same direction on the left side of the fulcrum of the movable piece 22, and decrease in the opposite direction on the right side. Therefore, the magnetic attraction force increases on the left side of the fulcrum of the movable piece 22 and weakens on the right side, so that a difference is generated between the left side and the right side, and the movable piece 22 rotates about the fulcrum spring 17 as a fulcrum. The gap between the nozzle 18 changes. Nozzle 1
8 is supplied with a constant supply air pressure Ps from an air pressure source, and when the gap between the nozzle 18 and the flapper portion of the movable piece 22 changes, the nozzle back pressure Pn, that is, the output air pressure The signal changes. Thus, the electrical / pneumatic converter of FIG. 7 generates an output pneumatic signal corresponding to the input current signal.

The electric / pneumatic converter shown in FIG. 7 has a symmetrical structure in which the fulcrum of the movable piece 22 having the flapper and the center of gravity of the apparatus main body are completely coincident with each other. Does not occur. Since the movable part in the apparatus of FIG. 7 is only the movable piece 22 made of a thin iron piece, the weight is less than half compared to the movable part in the apparatus of FIG. 6, that is, the combined body of the movable piece 33 and the counterweight 35. Has a higher natural frequency.
Further, a cross spring having a structure in which two leaf springs are combined is employed as the fulcrum spring 7, and bending works in the rotating direction to reduce rigidity, and rigidity is extremely increased in other directions. Due to these structural features, the electric / pneumatic converter of FIG. 7 has greatly improved vibration resistance compared to the device of FIG.

However, although the movable piece 22 in the electric / pneumatic converter shown in FIG. 7 is a thin iron piece, it is a main member for forming a magnetic path, so that it cannot be made too thin because magnetic efficiency needs to be increased. The movable piece 22 is located at the bottom 21 of the yoke 21.
The length must be approximately equal to D. For this reason, the movable part or movable piece 22 in the apparatus of FIG. 7 is different from the movable part or movable piece 33 and the counterweight 35 in the apparatus of FIG.
Although the weight is reduced to about half as compared with the combined body, there is a disadvantage that the length is only slightly shortened and the natural frequency cannot be too high. Further, in the electric / pneumatic converter shown in FIG. 7, since the fulcrum of the movable piece 22 is constituted by the cross spring and the mounting bracket 23, there is a disadvantage that the fulcrum structure is complicated and the mounting operation is troublesome.

[0009]

An object of the present invention is to substantially increase the natural frequency of a movable portion having a flapper formed thereon so that the movable portion on which the apparatus is installed is not affected by mechanical vibration. An object of the present invention is to provide a good electric / pneumatic converter, and to provide a simple structure for a fulcrum of a movable portion thereof and to facilitate an attaching operation. A second problem to be solved is to facilitate cleaning of the nozzle of the electric / pneumatic converter.

[0010]

According to the present invention, there is provided a coil with a fixed iron core for generating a variable magnetic field corresponding to an input current, and arranged so as to be part of respective components of two magnetic paths by the variable magnetic field. A pair of yokes, a permanent magnet disposed between the pair of yokes such that the magnetic path of the permanent magnet and the two magnetic paths of the variable magnetic field are partially common. And a nozzle and a flapper mechanism for converting a mechanical displacement of the movable piece into a nozzle back pressure. A thin metal leaf spring in which a flapper portion and a pair of support portions are formed and a movable iron core of a ferromagnetic material piece is bonded to both sides of the center portion thereof, and a predetermined gap is provided between a pair of yokes and inserted and arranged. And the support is By the fixed cantilever structure over click to achieve a reduction of the significant reduction and length of the weight of the movable part, thus greatly increasing the natural frequency.
In other words, an electric / pneumatic converter excellent in vibration resistance has been realized.

According to a second aspect of the present invention, there is provided a through-hole provided linearly penetrating through a yoke or a housing and having a nozzle fixing portion inserted at one open end, an air passage shunted from the through-hole. A device having a removable lid inserted with an air seal at the other open end of the through-hole, and a stopper for holding the lid on the yoke; The nozzle can be easily cleaned from outside.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric / pneumatic converter according to an embodiment of the present invention shown in FIG. 1 has a pair of soft magnetic yokes 1 and 2 having the same shape and dimensions. The yoke 1 has legs 1A and 1B at the center and lower part, and the yoke 2 has legs 2A and 2B at the center and lower part. When these yokes are arranged facing each other, the distance between the opposing legs 1A and 2A is 1
An interval having a constant width is formed between B and 2B. Also, recesses are formed between the center leg 1A and the lower leg 1B of the yoke 1 and between the center leg 2A and the lower leg 2B of the yoke 2, respectively. The coils 4 are housed and arranged in these recesses. The permanent magnet 10 is arranged so as to be in contact with the upper end of each of the yokes 1 and 2. As illustrated in FIG. 3, the fixed core 5 is a thick plate made of a ferromagnetic material having a rectangular core at one end and a support at the other end. The fixed iron core 5 has its core part located in the coil 4 and the ends of its support part are connected to the yokes 1 and 2.
Are fixed between the legs 1B and 2B. By arranging the fixed core as described above, the coil 4 is a coil with a fixed core.

As shown in FIG. 3, the movable piece 3 has a rectangular flapper portion 3C at one end and a pair of elongated support portions 3A at the other end.
And 3B are formed, and movable iron cores 6A and 6B made of a rectangular ferromagnetic material are adhered to both sides of the center of the metal leaf spring. The movable piece 3 is disposed between the pair of yokes 1 and 2 with its flapper portion 3C flush with the fixed core 5 and the ends of the movable cores 6A and 6B close to the ends of the fixed core. ing. Further, the movable piece 3 penetrates through the coil 4 with the pair of support portions 3A and 3B straddling the rectangular core portion of the fixed iron core 5 and its ends are formed by the legs 1B and 2B of the yokes 1 and 2. It is sandwiched between and fixed, and has a cantilever structure. The movable piece 3 has an elongated concave shape in FIG. 3, but may have a Y-shape. The movable piece 3 has a pair of support portions 3A and 3
Although B is fixed to the yokes 1 and 2 in FIG. 3, it may be fixed to the housing of the apparatus. The nozzle 8 to which the supply air pressure is supplied from a supply air pressure source (not shown) via a restrictor is fixed to the yoke 1 with its distal end disposed close to and opposed to the flapper section 3C. The nozzle 8 and the flapper section 3C of the movable piece 3 constitute a main part of a nozzle / flapper mechanism for converting displacement into air pressure. A stopper 9 having the same external shape as the nozzle 8 is disposed with its tip end facing the flapper portion 3C and opposed thereto, and is fixed to the yoke 2.

An end of the upper end of the fixed core 5 is
A and 6B are close to the distal ends of the lower end portions, and a gap serving as a magnetic path is formed therebetween. When the magnetic fluid 15 is applied to this gap as shown in FIG. 4, the fixed iron core 5 and the movable iron core 6A
And 6B are magnetically coupled to each other to improve magnetic efficiency. In this case, the magnetic fluid 15 does not hinder the displacement of the movable piece 3 at all. The magnetic fluid is a liquid in which ferromagnetic ultra-fine particles are stably dispersed in a high-concentration magnetite or the like in a liquid, and is composed of three components: a liquid serving as a medium, magnetic fine particles, and a surfactant. Have been. The surfactant is for preventing aggregation of the particles adsorbed on the surface of the magnetic particles and for maintaining a stable dispersion state. Also,
Since the movable iron cores 6A and 6B are disposed close to and opposed to the distal ends of the legs 1A and 1B of the yoke 1, respectively, the movable iron cores 6A and 6B are located between the distal ends of the legs 1A of the yoke 1 and the movable iron core 6A, and of the yoke 2. Air gaps serving as magnetic paths are also formed between the tip of the leg 2A and the movable core 6B.

In the electric / pneumatic converter of the present invention constructed as described above, the permanent magnet 10, the yoke 1, the movable iron cores 6A and 6B, the yoke 2
And a magnetic path Fc formed by a gap therebetween. The direction of the magnetic path Fc due to the fixed magnetic field is counterclockwise as shown by the thick dotted line in FIG. When an input current flows through the coil 4, a variable magnetic field corresponding to the magnitude of the input current is generated in the coil 4, and as shown by a dotted line in FIG. The first magnetic path Fa and the yoke 2 are part of the components of the magnetic path.
A magnetic path Fb is formed. That is, the yoke 1, the movable core 6A,
A clockwise first magnetic path Fa composed of the fixed core 5, the interposed member 14A and the gap therebetween, and the yoke 2, the movable core 6B, the fixed core 5, the interposed member 14B, and the gap therebetween. And a counterclockwise second magnetic path Fb. Therefore, the magnetic path Fc due to the fixed magnetic field and the two magnetic paths Fa and Fb due to the variable magnetic field are formed by the central leg 1A and the movable core 6A of the yoke 1, and the central leg 2A and the movable core 6B of the yoke 2. Is used as a common magnetic path component. Due to the formation of the magnetic path as described above, the magnetic field in the gap between the yoke 1 and the movable core 6A is strengthened because the magnetic path Fc by the fixed magnetic field and the first magnetic path Fa by the variable magnetic field are in the same direction. Further, due to the formation of the magnetic path as described above, the magnetic field in the gap between the yoke 2 and the movable iron core 6B is weakened because the magnetic path Fc due to the fixed magnetic field and the second magnetic path Fb due to the variable magnetic field are in the opposite direction. . Then the movable piece 3
The movable piece 3 is displaced leftward in the figure due to the difference between the magnetic attraction forces on the left side and right side of FIG. The mechanical displacement of the movable piece 3 corresponds to the strength of the variable magnetic field. In this way, the input current is converted to a mechanical displacement.

Next, how the mechanical displacement is converted into a pneumatic output by the nozzle / flapper mechanism will be described. As described above, the movable piece 3 is a thin metal leaf spring having a cantilever structure in which the flapper portion 3C is formed at the movable end. Therefore, the mechanical displacement of the movable piece 3 is the flapper 3C.
And changes the gap between the flapper section 3C and the tip of the nozzle 8, that is, the nozzle-flapper gap. 6 and 7, the supply air pressure Ps from a supply air pressure source (not shown) passes through a throttle,
It is supplied through an air passage 7. Therefore, when the nozzle-flapper gap changes, the nozzle back pressure Pn changes correspondingly. The nozzle back pressure Pn increases as the gap between the nozzle and the flapper decreases, and decreases as the gap increases. The degree of the increase or decrease depends on the size of the gap,
That is, it is proportional to the mechanical displacement of the movable piece 3. Then, the nozzle back pressure Pn is extracted as the pneumatic output of the electric / pneumatic converter. In this way, the input current is converted to a pneumatic output.

FIG. 5 is an enlarged cross-sectional view of the nozzle portion of FIG. 1. In the through hole 14 provided in the yoke 1, a fixing portion of the nozzle 8 is inserted into one opening end, and the other opening end. A lid 11 is fitted to the portion with an air seal 13 such as an O-ring. The set screw 12 holds the lid 11 at a predetermined position during normal operation, and is removed when cleaning the nozzle 8.

The electric / pneumatic converter may be mounted on an air damper. In this way, the vibration absorbing power can be further increased, and thus the vibration resistance can be further increased. Also,
If Teflon coating is applied to the tip of the nozzle 8 and the nozzle-facing surface of the flapper portion 3C, the adhesion of dirt to these portions can be greatly reduced.

[0019]

As described above, the present invention converts an electric current into a mechanical displacement and converts the mechanical displacement into a pneumatic pressure by a nozzle / flapper mechanism, thereby converting an input current into an output pneumatic pressure. In the converter,
The weight of the movable portion that is mechanically displaced by the action of the variable magnetic field due to the input current is greatly reduced. That is,
The movable portion 3 in the present invention is a thin metal leaf spring having a substantially concave shape or a substantially Y shape in which a flapper portion 3C and a pair of support portions 3A and 3B are formed. The cores 6A and 6B are adhered to each other, and the support portions 3A and 3B have a cantilever structure fixed to a fixed portion such as a yoke. Due to such a structure, the movable portion in the present invention has a weight reduced by half and a length reduced as compared with the conventional one. Therefore, in the present invention, the natural frequency of the movable part is significantly increased to 200 Hz or more, so that an electric / pneumatic converter excellent in vibration resistance is realized. Moreover, no special mounting means such as a bracket is required for fixing the movable portion to the yoke or the housing, and the mounting operation is simple.

In the present invention, since the nozzle 8 is disposed in the space formed by the pair of yokes and the permanent magnets 10, it is required that the nozzle 8 be easily cleaned. In response to this demand, as is apparent from FIG. 4, a through hole 14 linearly communicating with the nozzle 8 is provided in the yoke 1, and the through hole 14 is closed with a removable lid 11 provided with an air seal 13. Things. Therefore, it is possible to easily remove the nozzle 8 by removing the lid 11 at the time of cleaning and using air or needles for cleaning.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an electric / pneumatic converter according to one embodiment of the present invention.

FIG. 2 is an explanatory view of a magnetic path of the electric / pneumatic converter according to the embodiment of the present invention shown in FIG. 1;

FIG. 3 is a perspective view showing an example of a structure and an arrangement relationship of a movable part, a fixed iron core, a coil, and a yoke of the electric / pneumatic converter according to one embodiment of the present invention.

FIG. 4 shows a magnetic fluid provided in a gap between a movable iron core and a fixed iron core.

FIG. 5 is a schematic view of an enlarged nozzle portion of the electric / pneumatic converter of the present invention of FIG. 1;

FIG. 6 is a schematic diagram showing a configuration of a conventional example of an electric / pneumatic converter.

FIG. 7 is a schematic diagram showing a configuration of another example of the conventional electric / pneumatic converter.

[Explanation of symbols]

 Reference Signs List 1 yoke 1A leg 1B leg 2 yoke 2A leg 2B leg 3 movable piece 3A support 3B support 3C flapper 4 coil 5 fixed iron 6A movable iron 6B movable iron 7 air passage 8 nozzle 9 stopper 10 permanent magnet Lid 12 Stopper 13 Air seal 14 Through hole 15 Magnetic fluid Fa First magnetic path due to variable magnetic field of coil Fb Second magnetic path due to variable magnetic field of coil Fc Magnetic path due to fixed magnetic field of permanent magnet 16 Coil 17 Support spring 18 Nozzle 20A Permanent magnet 20B Permanent magnet 21 Yoke 21A Leg 21B Leg 21C Leg 21D Bottom 22 Movable piece 23 Bracket 24 Set screw 25 Throttle 26 Pipe 27 Air passage 28 Stopper 29 Zero adjustment screw 30 Zero adjustment spring 31 Yoke 32 Yoke 33 Movable piece 34 Coil 35 Counterway DOO 36 spring member 37 nozzle 38 aperture 39 zero-adjustment screw 40 zero-adjustment spring 41 permanent magnet

Claims (2)

[Claims] 1. A coil with a fixed iron core for generating a variable magnetic field corresponding to an input current, a pair of yokes arranged to be part of respective components of two magnetic paths by the variable magnetic field, and a permanent magnet A permanent magnet disposed between a pair of yokes such that the magnetic path of the fixed magnetic field and the two magnetic paths of the variable magnetic field are partially common to each other; In the electric / pneumatic converter including a movable piece that is displaced correspondingly and a nozzle / flapper mechanism that converts a mechanical displacement of the movable piece into a nozzle back pressure, the movable piece has a flapper portion and a pair of support portions. And a thin metal plate spring having a movable iron core of a ferromagnetic material piece adhered to both sides of a central portion thereof, wherein the thin metal leaf spring is inserted and arranged with a predetermined gap between a pair of yokes, and the support portion is attached to the yoke. Fixed cantilever Electric / pneumatic converter characterized by a movable piece having a beam structure 2. A through-hole, which is provided so as to penetrate the yoke linearly and has a fixed portion of the nozzle inserted at one opening end, an air passage shunted from the through-hole, and a through-hole of the through-hole. 2. A nozzle comprising a removable lid inserted with an air seal at the other open end and a stopper for holding the lid on a yoke.
Electrical / pneumatic converter as described