JPH07332306A - Zero adjustment mechanism of electro-pneumatic converter - Google Patents

Abstract

(57) [Summary] [Purpose] The rider's rattling can be reliably removed, and the strength of the rattling removal can be finely adjusted.
There is little variation in the operating force for rotating the feed screw shaft, improving operability. [Structure] One leg portion 19a of a rider 19 and an adjusting member 40 are screwed onto a feed screw shaft 31. The other leg portion 19b of the rider 19 is screwed into the male screw portion 46 provided on the outer peripheral surface of the adjusting member 40. The pitches of the feed screw shaft 31 and the male screw portion 46 are different. Therefore, when the adjusting member 40 is rotated,
The other leg portion 19b moves by the pitch difference and is elastically deformed to prevent the rider 19 and the adjusting member 40 from rattling. Moreover, the strength of the backlash removing force can be adjusted by this elastic deformation.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An electropneumatic converter of this type is used in an electropneumatic positioner or the like as shown in FIG.
It is configured so that 0 is converted into an air pressure signal to obtain a required output pressure Pout. Here, FIG. 2 is a block diagram showing the operating principle of the valve positioner, where 1 is an arithmetic unit having a CPU or the like to which the input signal I0 is input, 2 is an electropneumatic converter, and 3 is an electropneumatic converter 2. A feedback sensor for detecting the output pressure Pout outputs the output pressure Pout obtained according to the input signal I0 in the electropneumatic converter 2, and the output pressure Pout is detected by the feedback sensor 3 to generate an electric signal. It is fed back to the calculation unit ₁ by I ₁ , and is corrected when a deviation occurs.

The specific configuration and operating principle of the electropneumatic converter 2 described above will be briefly described with reference to FIGS. 3 and 4.
In these figures, 10 is a flapper made of a magnetic material,
Reference numeral 11 is a fulcrum that supports the flapper 10 so as to be capable of swinging displacement. 12 is a coil 13a, 13b, a permanent magnet 14,
Further, the yoke provided with the nozzle 15 is formed into a substantially E shape in a front view, so that the three leg portions 12a, 12b,
It has 12c. An arrow b shown by a solid line in FIG. 4 is, for example, a magnetic field direction of the permanent magnet 14 in which the flapper 10 side is an N pole and the opposite side is an S pole, and an arrow a shown by a broken line.
Is a coil 13 whose N and S poles are obtained as shown.
The direction of the magnetic field by a and 13b is shown. Here, the polarities of both coils 13a and 13b are set to be opposite.

Further, the flapper 10 described above has a pair of springs 16 and 17 as elastic members on both ends thereof.
Is provided between the base 18 and the base 18 as a fixed portion, and a predetermined tensile force is applied thereto. Left spring 16
Is a spring means for biasing the flapper 10 so as to be closer to the nozzle 15. On the other hand, the spring 17 on the right side constitutes a zero adjusting mechanism 20 for setting the initial position of the flapper 10 by being provided with means 19 for adjusting the urging force thereof.

In FIG. 3, reference numeral 21 is a stopper provided at the tip of the right leg 12b of the yoke 12 corresponding to the nozzle 15, and 22 is a cross as a fulcrum spring which constitutes a fulcrum 11 for supporting the flapper 10. The spring 23 is a mounting bracket.

In such an electropneumatic converter 2, the diaphragm 2
While the supply air pressure Psup having a constant pressure (for example, 1.2 to 1.4 Kg / cm ² ) is supplied to the nozzle 15 by the air flow path 25 having the number 4, the input signal I 0 (4 mA to 4 mA 20 mA) is the coil 1 of the electro-pneumatic converter 2.
3a, 13b, a magnetic field is generated in the same direction as the magnetic field by the permanent magnet 14 on the left leg 12a side of the yoke 12, and conversely on the right leg 12b side, the magnetic field strength of the permanent magnet 14 is increased. A magnetic field is generated in the direction that cancels the height. Therefore, the force F for attracting the flapper 10 is increased on the left side and is weakened on the right side, so that a counterclockwise rotation torque T about the fulcrum 11 is generated in the flapper 10 in the counterclockwise direction. Therefore, flapper 1
0 causes the nozzle gap to decrease by swinging counterclockwise about the fulcrum 11 to reduce the nozzle gap, that is, to increase the nozzle ejection resistance. As a result, the nozzle back pressure PN increases, this nozzle back pressure PN is amplified, and an electric signal proportional to the electric signal I0 is generated as the output pressure Pout.

In such electro-pneumatic converter 2, the magnetic balance at each displacement position by the flapper 10 and the coils 13a, 13b and the permanent magnet 14 is as follows: magnetic flux density, magnetic field strength, residual magnetic flux density, coercive force, Examining from the magnetic history curve characteristics obtained by hysteresis etc., the flapper 10
Is made substantially horizontal by the fulcrum 11 as shown by the solid line in FIG. It has been confirmed that at the position of S, the gaps of the left and right magnetic circuits become equal, and the magnetic circuits are magnetically balanced. On the other hand, the supply air pressure Psup is the nozzle 15
5 is not supplied to the coils 13a and 13b, and the input signal IO to the coils 13a and 13b is not used, the flapper 10 operates as shown in FIG.
At 0% F. It is in the S position. However, in this state, the magnetic balance of the flapper 10 and the like is lost and the magnetic hysteresis is large. Therefore, if left in this state for a long time, the problem of zero point shift is inevitable. It was a thing.
Therefore, when such a zero point shift occurs, it is necessary to readjust the zero point by the zero adjustment mechanism 20.

FIGS. 6A and 6B are a sectional view and an AA line sectional view showing an example of a conventional zero adjusting mechanism of this type. In the figure, this zero adjustment mechanism 20 is called a split nut system, and has a support base 30 that is formed in a U shape and is erected and fixed on the base 18, and a rotatable base whose both ends are supported by the support base 30. The feed screw shaft 31, a rider 19 as an adjusting means screwed to the feed screw shaft 31 and prevented from rotating by the long hole 32 of the support base 30, the rider 19 and the flapper 10 are connected, and the flapper 11 is connected to the flapper 11. The tension coil spring 17 is an elastic member that imparts clockwise habit, and a spring washer 33 that prevents the feed screw shaft 31 from rattling in the axial direction. The rider 19 is composed of a disc portion 19A having a protrusion 34 that is inserted into and engaged with the elongated hole 32, and a cylindrical portion 19B having an internal thread formed on the inner peripheral surface and a split groove 35 on the peripheral surface. When the shaft 31 is moved up and down by a rotating operation, the spring force of the tension coil spring 17 is changed, and thus the zero point shift is adjusted. The rider 19 has the feed screw shaft 3
It is possible to prevent the rattling by screwing the screw 1 to the screw 1 in a pressed state.

7 (a) and 7 (b) are a partially cutaway plan view and a sectional view showing another example of the conventional zero adjustment mechanism. This zero-adjustment mechanism 20 is called a tension nut system, and a plate-shaped rider 19 and an elastically deformable tension nut 36 are screwed onto the feed screw shaft 31, and the tension nut 36 is tightened. This is to prevent backlash.

[0010]

By the way, in the conventional zero-adjustment mechanism shown in FIGS. 6 and 7, it is difficult to set the strength of the rattling force to an optimum value structurally. On the other hand, if it is too weak, the rider 19 rattles. On the contrary, if it is too strong, there is a problem that a large operating force is required to rotate the feed screw shaft 31 and the operability deteriorates.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to surely prevent the rider from rattling and to increase the rattling force. Can be finely adjusted, and there is little variation in operating force for rotating the feed screw shaft,
An object of the present invention is to provide a zero adjustment mechanism of an electropneumatic converter having good operability.

[0012]

In order to achieve the above-mentioned object, the invention according to claim 1 is such that a rider is screwed onto a rotatable feed screw shaft whose both ends are supported by a support base, and the rider and flapper are connected to each other. In a zero-adjustment mechanism of an electropneumatic converter connected by elastic members, an adjusting member having threads formed on the inner and outer peripheral surfaces is screwed onto the feed screw shaft, and the rider is formed in a U-shape by an elastic thin plate. One of the legs is screwed into the feed screw shaft, and the other leg is screwed into the male screw portion of the adjusting member, and the pitches of the male screw portion of the adjusting member and the feed screw shaft are made different. And

[0013]

In the present invention, when the feed screw shaft is rotated, the rider and the adjusting member move in the same direction along the feed screw shaft to adjust the zero point shift. When the adjusting member is rotated, the adjusting member moves along the feed screw shaft. At this time, since the pitches of the feed screw shaft and the male screw portion of the adjusting member are different, the other leg portion of the rider screwed to the male screw portion is moved by the pitch difference and elastically deforms. Prevents the rattling of the adjustment member. Further, this changes the frictional force between the feed screw shaft and the rider, so that the strength of the rattling force for the rider is adjusted.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a sectional view showing an embodiment of a zero adjustment mechanism for an electropneumatic converter according to the present invention. The same components as those in FIGS. 6 and 7 are designated by the same reference numerals. In the figure, in the present embodiment, a feed screw shaft 31 is provided by a U-shaped support base 30 which is erected and fixed on the base 18.
Both ends of which are rotatably supported, the rider 19 and the adjusting member 40 are screwed onto the feed screw shaft 31, and
The adjusting member 40 is screwed to the rider 19 and the flapper 10.
(See FIG. 3) is a tension coil spring 17 as an elastic member.
It is configured to be connected to each other by.

The rider 19 is formed by bending a U-shaped metal plate or the like having elasticity to have a pair of legs 19a, 19 facing each other in parallel.
b and a connecting portion 19 for connecting the leg portions 19a and 19b
In addition, a spring mounting portion 42 having a small hole 41 into which one end of the tension coil spring 17 is locked is integrally provided in the connecting portion 19c. One leg 19a
Has a screw hole 43 into which the male screw 44 of the feed screw shaft 31 is screwed, and the distal end portion is slidably inserted into the long hole 32 provided in the support base 30 to rotate the rider 19. It forms a prevention part. The other leg portion 19b has a screw hole 47 into which a male screw portion 46 formed on the outer peripheral surface of the adjusting member 40 is screwed.

The adjusting member 40 is formed in a tubular shape,
The male screw portion 46 that is screwed into the screw hole 47 of the other leg portion 19b is formed on the outer peripheral surface, and the female screw 48 that the male screw 44 of the feed screw shaft 31 is screwed is formed on the inner peripheral surface. . A lock nut 49 is screwed onto the male screw portion 46. Then, the male screw portion 46 and the female screw portion 48
Are different in pitch, and the pitch of the male screw portion 46 is set smaller than the pitch of the female screw portion 48, for example. In addition,
As a matter of course, the pitch of the male screw 44 and the female screw portion 48 of the feed screw shaft 31 is equal.

Next, the zero point adjustment and the backlash removing force intensity adjustment by the zero adjustment mechanism having the above-mentioned structure will be described.
When the feed screw shaft 31 is rotated in, for example, the tightening direction (the direction of arrow 51 in FIG. 1), the rider 19 adjusts the adjustment member 4
With 0, it moves forward along the feed screw shaft 31 to extend the tension coil spring 17, and when it is rotated in the loosening direction (arrow 52 direction), it moves backward to compress the tension coil spring 17, By tension coil spring 17
The spring force of is changed, and the zero point of the flapper is adjusted. Then, the lock nut 49 is tightened to tighten the other leg portion 19b.
When pressed against, the rider 19 and the adjusting member 40 are restrained from each other in movement. That is, the rider 19 and the adjusting member 40
Is prevented from rattling with respect to the feed screw shaft 31.

When the adjusting member 40 is rotated while the lock nut 49 is loosened, the adjusting member 40 moves forward or backward along the feed screw shaft 31. At this time, since the male screw portion 46 of the adjusting member 40 has a pitch different from that of the male screw 44 of the feed screw shaft 31, the other leg portion 19b is moved forward or backward by the pitch difference per one rotation of the adjusting member 40 to be elastic. It is deformed and the distance to one leg 19a is changed. The legs 19b are elastically deformed so that both legs 1
When the distance between 9a and 19b changes, the feed screw shaft 31, the one leg portion 19a and the feed screw shaft 3 are caused by the elastic force.
The frictional force between 1 and the adjusting member 40 changes, thereby completely preventing the rider 19 and the adjusting member 40 from rattling, and the strength of the rattling removal, in other words, the operating force of the feed screw shaft 31. Is adjusted.

In this case, in the present invention, the other leg 1
Since 9b moves by the pitch difference between the screw 44 and the male screw portion 46, it is easier to finely adjust the strength of the rattling force as compared with the conventional tension nut type zero adjusting mechanism shown in FIG. That is, for example, the pitch of the feed screw shaft 31 is set to 2.
5. If the pitch of the male screw portion 46 is 2.4, the tension nut 36 is deformed by 2.5 mm per rotation in the tension nut method, whereas in the present invention, the other leg portion is rotated per rotation of the adjusting member 40. Since 19b is deformed by a pitch difference of 0.1 mm, finer adjustment is possible, and it is easy to set the operating force of the feed screw shaft 31 to an optimum value. The same applies even if the pitch of the feed screw shaft 31 is made smaller than the pitch of the male screw portion 46.

[0020]

As described above, according to the zero adjustment mechanism for an electropneumatic converter according to the present invention, an adjusting member having a screw formed on the inner and outer peripheral surfaces is screwed onto the feed screw shaft to elastically move the rider. Formed into a U-shape by a thin plate having one end, one leg of which is screwed into the feed screw shaft and the other leg of which is screwed into the male screw portion of the adjusting member, and the male screw portion of the adjusting member and the feed screw shaft. Since the pitch of the is different, when the adjusting member is rotated, the other leg moves and deforms by the difference in pitch between the screw of the feed screw shaft and the male screw of the adjusting member to change the distance between both legs, This prevents the rider from rattling with the adjusting member, and can finely adjust the strength of the rattling removal. Therefore, there is little variation in the strength of the backlash removing force, it is easy to set the operating force of the feed screw shaft to the optimum value, and the operability can be improved. Also, the structure is simple.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a zero adjustment mechanism of an electropneumatic converter according to the present invention.

FIG. 2 is a block diagram showing the operating principle of a valve positioner.

FIG. 3 is a cross-sectional view of essential parts showing a conventional example of an electropneumatic converter.

FIG. 4 is a diagram showing an operation principle of an electropneumatic converter.

FIG. 5 is a schematic diagram for explaining an operation relationship between nozzles and flappers.

6A and 6B are a sectional view and a sectional view taken along the line AA of a conventional split nut type zero adjustment mechanism.

7A and 7B are a partially cutaway plan view and a sectional view of a conventional tension nut type zero adjustment mechanism.

[Explanation of symbols]

10 ... Flapper, 12 ... Yoke, 13a, 13b ... Coil, 15 ... Nozzle, 17 ... Extension coil spring, 18 ... Base, 19 ... Rider, 19a ... One leg part, 19b ...
The other leg, 20 ... Zero adjustment mechanism, 30 ... Support base, 31 ...
Feed screw shaft, 40 ... Adjusting member, 44 ... Male screw, 46 ... Male screw portion, 48 ... Female screw, 49 ... Lock nut.

Claims (1)

[Claims] 1. A zero adjustment mechanism for an electropneumatic converter in which a rider is screwed onto a rotatable feed screw shaft whose both ends are supported by a support base, and the rider and flapper are connected by elastic members. A threaded adjusting member is screwed onto the feed screw shaft, and the rider is formed into a U shape by a thin plate having elasticity, one leg of which is attached to the feed screw shaft.
A zero adjustment mechanism for an electropneumatic converter, characterized in that the other leg is screwed into the male screw portion of the adjusting member respectively, and the pitch of the male screw portion of the adjusting member and the feed screw shaft are made different.