JPH10299940A - Regulating valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform zero and span adjustment easily and in a short time without requiring operating of a valve stem by air supply and without requiring any measuring instrument. SOLUTION: A valve opening setting mechanism 50 is established in a feedback mechanism 15 of an electro-pneumatic positioner 5. This valve opening setting mechanism 50 consisting of a feedback lever 43 and a feedback pin 44, is used also as a feedback mechanism. An opening 45 of the feedback lever 43 which is formed into a sector shape, is fully closed at zero adjustment and the feedback pin 44 comes to contact with the lower edge of the opening 45 and this pin position is obtained as a minimum open position. A span adjustment, a state of the valve itself remains unchanged and the feedback lever 43 is turned and the feedback pin 44 comes to contact with the upper edge of the opening 45 and this pin position is obtained as a maximum opening position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control valve which is driven by a pneumatic signal from an electropneumatic positioner and controls opening and closing of a valve.

[0002]

2. Description of the Related Art Generally, a control valve of this type used for process control includes an actuator driven by an electropneumatic positioner. The electropneumatic positioner has an electropneumatic converter for converting an input electric signal (for example, 4 mA to 20 mA) into pneumatic pressure, and controls the valve opening of the control valve by operating the operating device with the converted pneumatic pressure. The electropneumatic positioner adjusts the valve opening so that the difference between the set opening signal sent from the control unit and the actual opening of the valve obtained from the feedback mechanism becomes zero (Japanese Patent Laid-Open No. 4-185901). Gazette).

In such a control valve, in order for the electropneumatic positioner to accurately grasp the valve opening from the feedback mechanism, the actual operating range (angle) of the valve is determined by an angle sensor directly connected to the feedback mechanism. Must be detected in advance and stored in the control unit. That is, the minimum opening position LRV serving as a reference when controlling the valve opening of the control valve.
(Zero point position) and maximum opening position URV (span point position)
Must be set in advance (zero, span adjustment).

For this reason, conventionally, this setting has been performed by actually supplying air. Specifically, the movement of the valve stem is read by a measuring instrument such as a dial gauge or a potentiometer, and adjusted to the nominal stroke (rated stroke).
Next, the control valve is switched to the manual state, the pressure reducing valve is operated, and the valve stem is adjusted to a predetermined position. As this position, for example, a position where the feedback lever of the feedback mechanism becomes horizontal is selected. This position is usually selected as a position at which the valve opening of the control valve becomes 50%, and is also an advantageous position for facilitating subsequent calculations. The valve stem is moved from this position to the minimum opening position to bring the valve to the fully closed state. The rotation angle of the feedback lever at this time is detected by an angle sensor.
Further, the horizontal distance from the center of the angle sensor to the valve stem is obtained, and the minimum opening position L from the horizontal position is calculated by calculation.
The RV is obtained and stored in the control unit (zero adjustment). Next, move the valve stem to the maximum opening position to set the valve to 100%
F. The state is set to S (full scale). At this time, the rotation angle of the feedback lever from the horizontal position is detected by an angle sensor, the maximum opening position URV is obtained by calculation, and stored in the control unit (span adjustment). The angle sensor is provided such that the center coincides with the rotation center of the feedback lever.

[0005]

As described above, in the conventional control valve, the valve stem is operated by actually supplying air, and the stroke at that time is measured by a measuring instrument such as a dial gauge. Zero and span adjustments were being made. Therefore, it is necessary to adjust the valve stem to the nominal stroke and set the measuring instrument.
There was a problem that adjustment took time. In addition, since air for adjusting the zero and span is required in addition to the air for driving the positioner, there is also a problem that the air consumption increases.

The present invention has been made to solve the above-mentioned conventional problems, and has as its object to eliminate the need for a measuring instrument such as a dial gauge and to eliminate the work of adjusting a valve stem to a nominal stroke. Accordingly, it is an object of the present invention to provide a control valve capable of performing zero and span adjustment easily and in a short time. Another object of the present invention is to provide a control valve which does not need to operate a valve stem by air supply and can reduce air consumption.

In order to achieve the above object, a first invention (an invention according to claim 1) includes an operating device operated by air pressure from a positioner, and the actual opening of the valve is transmitted to the positioner by a feedback mechanism. A valve opening setting mechanism that sets a minimum opening position and a maximum opening position that serve as references for controlling the valve opening in a control valve that is controlled such that the actual opening of the valve matches the set opening. It is characterized by having. Therefore, zero adjustment and span adjustment can be performed without supplying air to move the valve stem.

A second invention (invention according to claim 2) is characterized in that, in the first invention, a valve opening setting mechanism is provided in a feedback mechanism of a positioner. Therefore, various control valves can be accommodated only by changing the feedback mechanism.

According to a third invention (an invention according to a third aspect), in the second invention, the valve opening setting mechanism is movably inserted into the feedback lever having a fan-shaped opening and into the opening. At the time of normal operation, a feedback pin fixed to one side edge of the opening is provided. Therefore, the valve opening setting mechanism also serves as a feedback mechanism.

A fourth invention (an invention according to a fourth invention) is characterized in that, in the first invention, a valve opening setting mechanism is provided at a connecting portion between a drive shaft of an operating device and a valve stem. . Therefore, the connecting portion can be used effectively.

A fifth invention (an invention according to a fifth aspect) is the invention according to the fourth invention, wherein the valve opening setting mechanism is provided with two blocks capable of adjusting the movement of the valve opening in the axial direction of the valve stem. The first and second connecting pins are provided respectively, a feedback lever is connected to the first connecting pin at the time of zero adjustment and a normal operation, and the feedback lever is connected to the second connecting pin at the time of span adjustment. It is characterized by being connected. Therefore, it is possible to cope with different valve stem strokes.

According to a sixth aspect of the present invention, in the fourth aspect, the valve opening setting mechanism includes a rotating lever, and the rotating lever is connected to the valve at the minimum opening position and the maximum opening position. The rotation lever is connected to a feedback lever via a feedback pin. Therefore, it is not necessary to pull out the feedback pin at the time of adjustment.

In a seventh aspect (an invention according to a seventh aspect), in the fourth aspect, the valve opening setting mechanism includes a first mounting hole for setting a minimum opening position, and a maximum opening degree. A second mounting hole for setting a position, a feedback lever is connected to the first mounting hole via a feedback pin during zero adjustment and during normal operation, and the second mounting hole is used during span adjustment. And a feedback lever connected to the feedback lever via the feedback pin. Therefore, the structure is simple.

An eighth invention (an invention according to an eighth aspect) is the invention according to the fourth invention, wherein the valve opening setting mechanism comprises a first pin which can be moved forward and backward to set a minimum opening position, and a maximum opening position. The first pin protrudes forward from the second pin at the time of zero adjustment and at the time of normal operation, and a feedback lever is connected at the time of zero adjustment and at the time of normal operation. A second pin is projected forward of the first pin to connect the feedback lever. Therefore, the structure is simple, and the first pin also serves as the feedback pin of the feedback mechanism.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a sectional view showing an embodiment of a control valve according to the present invention, FIG. 2 shows a valve opening setting mechanism, (a) at the time of zero adjustment, (b) at the time of span adjustment, and (c). It is a figure showing the state at the time of normal operation. In the present embodiment, the actuator 4 is of a positive operation type (a type in which a valve stem is lowered by supplying air pressure to close a valve).
1 shows an example in which the present invention is applied to a control valve 1 using a diaphragm 22 as a drive type of a valve stem 11.

The control valve 1 includes a valve body 2 which is flange-connected in the middle of a pipe, and the operation device 4 which is installed on the upper part of the valve body 2 via a yoke 3. A conventionally well-known electropneumatic positioner 5 for driving the operation device 4 is attached.

The valve body 2 includes a main body 7 the inside of which is partitioned by a partition wall 6, an upper cover 9 fixed to an opening on the upper surface of the main body 7 via a guide ring 8, and an upper cover 9 and the guide ring. A valve stem (valve shaft) 11 slidably penetrating through the inner wall 8 and integrally provided with a plug 10 at the inner end, and a seat ring 12 provided on the partition wall 6 corresponding to the plug 10 Etc. are provided. The valve stem 11 penetrates through the upper lid 9 via a gland packing 13, and an outer end is connected to a drive shaft 14 of the operation device 4 via a connector (connecting portion) 15, and a feedback of the positioner 5 is provided. It is connected to the mechanism 16.

The operating device 4 includes a pressure vessel 20 composed of an upper case 20a and a lower case 20b which are formed vertically and are integrally connected. The pressure vessel 20 is mounted on the yoke 3. Fixed with a plurality of bolts 21,
The upper and lower two chambers 23a,
23b. The upper chamber 23a is provided with an output air pressure Pout (1.4 to 1.4) serving as a control signal from the positioner 5.
2.8 kg / cm ² ) through the pipe 25 and the upper case 20 a
A pneumatic chamber is formed by being supplied from the pneumatic supply port 26 provided in. On the other hand, the lower chamber 23b is open to the atmosphere, and forms a spring chamber by accommodating a plurality of compression coil springs 27 which oppose the output air pressure Pout and urge the diaphragm 22 upward.

The diaphragm 22 has an outer peripheral edge held by a joint surface between the upper case 20a and the lower case 20b, and a plate-shaped diaphragm plate 28 is provided at the center of the upper surface. On the other hand, on the lower surface side, a diaphragm plate 29 and a lower limit stopper 30 having a U-shaped cross section for setting the lower limit of the drive shaft 14 are provided.

The drive shaft 14 slidably penetrates a sleeve 31 provided in the lower case 20b, and an upper end thereof penetrates the lower limit stopper 30, the diaphragm plate 29, the diaphragm 22, and the diaphragm plate 28,
By being fixed to the diaphragm plate 28 by the nut 32, they are integrally fastened and fixed together. On the other hand, the lower end of the drive shaft 14 protruding below the lower case 2b is connected to the valve stem 11 via the connector 15.

The positioner 5 includes an electropneumatic converter (not shown) for converting an electric signal input from the controller into an air pressure signal by a nozzle / flapper mechanism, and amplifies the nozzle back pressure of the nozzle / flapper mechanism by a pilot relay. The air pressure is output to the operation device 4 as an output air pressure Pout. Also,
The displacement of the valve stem 11 on the control valve 1 side operated by the output air pressure Pout obtained in this manner is fed back to the electropneumatic conversion section by the feedback mechanism 16. Feedback mechanism 16
Is composed of a feedback lever 43 projecting from the housing of the positioner 5 and rotatable in the vertical direction, a feedback pin 44 connecting the feedback lever 43 and the connector 15, and the like. The feedback pin 44 projects from the connector 15 and is inserted into the opening 45 of the feedback lever 43.

A pointer 47 is attached to the connector 15 corresponding to the opening display plate 46 attached to the yoke 3.

The control valve 1 and the electropneumatic positioner 5 are well known in the prior art. However, in the present invention, the valve opening setting mechanism 50 is further provided on the control valve 1 in order to facilitate zero and span adjustment. Is provided. The valve opening setting mechanism 50 is constituted by the feedback lever 43 and the feedback pin 44, and is used as the feedback mechanism 16 of the positioner during normal operation. However, the opening 45 of the feedback lever 43 is formed in a fan shape having a central angle θ as shown in FIG. 2 instead of the conventional rectangular shape, and the feedback pin 44 is provided inside thereof with respect to the axial direction of the valve stem 11. Movably inserted,
During normal operation, as shown in FIG. 2C, this is different from the conventional feedback lever in that it is fixed to the lower edge of the opening 45 by an appropriate fixing member 52 such as a spring. The central angle θ of the opening 45 is set to an angle at which the maximum stroke of the feedback pin 44 corresponds to the nominal stroke of the valve.

FIG. 1 shows a state in which the drive shaft 14 is at the upper limit position and holds the valve in a fully open state in the control valve 1 having such a configuration. From this state, the pneumatic chamber 23
When the required output air pressure Pout is introduced into the air pressure supply port 26 through the air pressure supply port 26, the pressure in the air pressure chamber 23a increases, so that the diaphragm 22 descends against the compression coil spring 27,
As a result, the valve stem 11 is lowered integrally with the drive shaft 14, and the valve is closed in accordance with the output air pressure Pout to control the flow rate, and the opening of the valve is displayed by the opening display plate 46 and the pointer 47. Further, the actual operation amount (actual opening) of the control valve 1 operated by the output air pressure Pout is fed back to the electropneumatic positioner 5 via a feedback mechanism 16,
Control is performed so as to coincide with the set opening according to the input signal input to the electropneumatic positioner 5. The valve stem 1
When 1 is lowered by the maximum stroke, the lower limit stopper 30 contacts the inner surface of the lower case 23b, and the plug 10 is seated on the seat ring 12 to hold the valve in the fully closed state.

Here, in the present invention, since the valve opening setting mechanism 50 is provided, the zero adjustment and the span adjustment can be easily performed. That is, at the time of zero adjustment, the valve opening is set to the minimum opening (fully closed state), and the feedback pin 44 abuts on the lower edge of the opening 45 as shown in FIG. It is stored as the opening position LRV (reference position).

Next, at the time of span adjustment, the valve itself is maintained at the time of zero adjustment, and the feedback lever 43 is rotated downward as shown in FIG. The upper part 45 is brought into contact with the upper edge.
The rotation angle of the feedback lever 43 from the reference position is -θ, which is stored as + θ.

After the zero and span adjustments are made, the feedback lever 43 is rotated to bring the feedback pin 44 into contact with the lower edge of the opening 45 as shown in FIG. By fixing to the lever 43, it is used as a feedback mechanism.

In such a valve opening setting mechanism 50, it is not necessary to supply air pressure to the operating device 4 to operate the valve stem 11, and the stroke of the valve stem 11 is measured by a measuring instrument such as a dial gauge. No need,
The minimum opening position LRV and the maximum opening position URV can be set in a short time, and zero and span adjustment are easy. Further, since the valve opening setting mechanism 50 also serves as the feedback mechanism 16, the structure is simple and the number of parts does not increase.

FIG. 3 is a perspective view showing another embodiment of the valve opening degree setting mechanism. In the present embodiment, the valve opening setting mechanism 60 is provided at the connection between the valve stem 11 and the drive shaft 14. The valve opening setting mechanism 60 includes two blocks 6
1 and 62, and first and second connecting pins 63 and 64 projecting from the blocks 61 and 62, respectively.
The blocks 61 and 62 are connected so as to be adjustable in the axial direction of the valve stem 11. The blocks 61 and 62 function as the connector 15 by being attached to the valve stem 11 and the drive shaft 14. The first connecting pin 63 functions as a feedback pin by being slidably inserted into the elongated hole 65 of the feedback lever 43 during normal operation. Distance X between first and second connecting pins 63 and 64
Corresponds to the nominal stroke of the valve stem 11 and can be freely varied by moving the blocks 61 and 62 closer and farther apart. The feedback lever 43 is of a conventional type, and the long hole 65 is formed in a rectangular hole having a width slightly larger than the diameter of the pin 63.

In such a configuration, at the time of zero adjustment, the first connecting pin 63 is inserted into the elongated hole 65 of the feedback lever 43 to hold the feedback lever 43 horizontally. From this state, the valve stem 11 is lowered to set the valve opening to the minimum opening (fully closed state), and the position of the first connecting pin 63 at this time is set to the minimum opening position LRV. The angle (α) from the horizontal position at the minimum opening position LRV is obtained by an angle sensor provided in the electropneumatic positioner 5. Further, a horizontal distance L from the center of the angle sensor to the valve stem 11 is obtained, and a calculation process is performed to obtain a minimum opening position LRV (X) from the horizontal position (X = L · tan).
α).

Next, at the time of span adjustment, the first connection pin 63 is pulled out of the long hole 65 while the valve itself is kept at the time of zero adjustment, and the feedback lever 43 is turned upward to rotate the second connection pin 64. Is inserted into the elongated hole 65, and the position of the second connecting pin 64 at this time is defined as the maximum opening position LRV.
The angle from the horizontal position at the maximum opening position URV is obtained by an angle sensor, and the same processing as described above is performed to obtain the maximum opening position LRV (X) from the horizontal position.
Ask for.

In such a configuration, the connecting portion between the valve stem 11 and the drive shaft 14 can be effectively used, and the distance X between the connecting pins 63 and 64 can be changed. Can be applied to control valves having different strokes.

FIGS. 4A and 4B show still another embodiment of the valve opening setting mechanism, wherein FIG. 4A is a front view at the time of zero adjustment and normal operation, FIG. 4B is a side view, and FIG. Is a front view, and (d) is a side view. In the present embodiment, the valve opening setting mechanism 70 is provided at the connection between the valve stem 11 and the drive shaft 14 as in the above-described embodiment. The valve opening setting mechanism 70 includes a rotating lever 72 attached to the front surface of the connector 15 with a screw 71, and first and second locking levers 72 for locking the rotating lever 72 at the minimum opening position and the maximum opening position of the valve. The second stoppers 73 and 74,
A feedback pin 44 protrudes from the rotation lever 72, and this pin 44 is connected to the slot 6 of the feedback lever 43.
3 is slidably engaged.

In such a configuration, at the time of zero adjustment, the rotary lever 72 is brought into contact with the first stopper 73 as shown in FIG.
The position of the feedback pin 44 at this time is defined as the minimum opening position LRV. On the other hand, when the span is adjusted, the valve itself is kept as it is, and the rotating lever 72 is rotated clockwise as shown in FIG. The state is set to S, and the position of the feedback pin 44 at this time is defined as the maximum opening position URV. In addition, the minimum opening position LRV and the maximum opening position URV detect the rotation angle of the feedback lever 43 by the angle sensor similarly to the embodiment shown in FIG. If the horizontal distance is measured, it can be easily obtained by calculation.

In such a valve opening setting mechanism 70, the connector 15 for connecting the valve stem 11 and the drive shaft 14 can be effectively used, and the feedback pin 44 is connected to the slot 63 at the time of zero / span adjustment. The adjustment work is easy because it does not need to be pulled out.

FIGS. 5A and 5B show still another embodiment of the valve opening setting mechanism, wherein FIG. 5A is a front view at the time of zero adjustment and normal operation, FIG. () Is a front view at the time of span adjustment, and (d) is a partially cutaway side view. In the present embodiment, the valve opening setting mechanism 80 is provided with a first mounting hole 81 provided in the connector 15 for setting the minimum opening position LRV, and a maximum opening position UR.
And a second mounting hole 82 for setting V. The feedback pin 44 is mounted on the first mounting hole 81 during zero adjustment and during normal operation, and is removed from the first mounting hole 81 during span adjustment. The second mounting hole 82 is attached. The interval between the first and second mounting holes 81 and 82 is
It is set equal to the nominal stroke of the valve. The method of obtaining the minimum opening position LRV and the maximum opening position URV is the same as in the above-described embodiment. The first and second mounting holes 8
Numerals 1 and 82 are formed by screw holes, and the feedback pins 44 are screwed in and fixed by nuts 83.

In such a configuration, the first and second mounting holes 81 and 82 formed of screw holes only need to be formed in the connector 15, so that the structure is simple.

FIGS. 6A and 6B show still another embodiment of the valve opening setting mechanism, wherein FIG. 6A is a front view at the time of zero adjustment and normal operation, FIG. 6B is a partially cutaway side view, and FIG. () Is a front view at the time of span adjustment, and (d) is a partially cutaway side view. In the present embodiment, the valve opening setting mechanism 90 is constituted by a retractable first pin 91 for setting a minimum opening position and a retractable second pin 92 for setting a maximum opening position. The pins 91 and 92 are screwed into screw holes 93 and 94 formed on the front surface of the connector 15 so as to be spaced apart from each other in the axial direction of the valve stem 11. The distance between the screw holes 93 and 94 is set equal to the nominal stroke of the valve. In addition, the protrusion dimensions of the pins 91 and 92 from the connector 15 are different, and the first pin 91 is connected to the second pin 92 during normal operation as shown in FIG.
By projecting further forward and being inserted into the elongated hole 63 of the feedback lever 43, it functions as a feedback pin. Also, during the zero adjustment, the first
The feedback lever 43 is connected to the pin 91.
On the other hand, at the time of span adjustment, the second pin 92 projects forward from the first pin 91 and is connected to the feedback lever 43 as shown in FIG. The method of obtaining the minimum opening position LRV and the maximum opening position URV is shown in FIG.
Is exactly the same as the embodiment shown in FIG.

Even in such a configuration, the structure is simple.
The first pin 91 can be used as a feedback pin of a feedback mechanism.

In the above-described embodiment, an example is shown in which the present invention is applied to the positive-acting control valve 1 having the drive-type operating device 4 using the diaphragm 22, but the present invention is not limited to this. However, the present invention can also be applied to a reverse-acting control valve that opens the valve by raising the valve stem 11 by supplying the output air pressure Pout. In that case, the positional relationship between the minimum opening position and the maximum opening position is only reversed. Further, the control valve 1 is not limited to a plug type, and may be various types of valves such as a cage type.

[0041]

As described above, according to the control valve of the present invention, since the valve opening setting mechanism is provided, the valve is closed when zero adjustment is performed, the minimum opening position is obtained, and when the span adjustment is performed, The maximum opening position may be obtained by rotating the feedback lever with the valve itself kept in the closed state. Therefore, there is no need to supply air to operate the valve, and the amount of air consumption can be reduced. Further, since there is no need to use a measuring instrument, zero and span adjustment can be performed easily and in a short time. . Further, since the exclusion degree setting mechanism also serves as the feedback mechanism, the structure is simple and the number of parts can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a control valve according to the present invention.

FIGS. 2A and 2B are diagrams illustrating a valve opening setting mechanism, wherein FIG. 2A illustrates a state during zero adjustment, FIG. 2B illustrates a state during span adjustment, and FIG.

FIG. 3 is a perspective view showing another embodiment of the valve opening degree setting mechanism.

FIGS. 4A and 4B show still another embodiment of the valve opening setting mechanism, wherein FIG. 4A is a front view at the time of zero adjustment and normal operation, FIG. 4B is a side view, and FIG. FIG. 3D is a side view.

5A and 5B show still another embodiment of the valve opening degree setting mechanism, wherein FIG. 5A is a front view at the time of zero adjustment and at the time of normal operation, FIG. 5B is a partially cutaway side view, and FIG. FIG. 3D is a front view at the time of span adjustment, and FIG.

6A and 6B show still another embodiment of the valve opening degree setting mechanism, wherein FIG. 6A is a front view at the time of zero adjustment and normal operation, FIG. 6B is a partially cutaway side view, and FIG. FIG. 3D is a front view at the time of span adjustment, and FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Control valve, 4 ... Operation device, 5 ... Positioner, 7 ... Valve body, 10 ... Plug, 11 ... Valve stem, 14 ... Drive shaft, 15 ... Connector, 16 ... Feedback mechanism, 20
... pressure vessel, 22 ... diaphragm, 43 ... feedback lever, 44 ... feedback pin, 45 ... opening,
50, 60 ... valve opening degree setting mechanism, 61, 62 ... block,
63: first connecting pin, 64: second connecting pin, 70:
Valve opening setting mechanism, 72: rotating lever, 73, 74: stopper, 80: valve opening setting mechanism, 81: first mounting hole, 8
2: second mounting hole, 90: valve opening setting mechanism, 91: first
Pins, 92... Second pins.

Claims (8)

[Claims] An operating device that operates by air pressure from a positioner is provided, and the actual opening of the valve is transmitted to the positioner by a feedback mechanism so that the actual opening of the valve is controlled to match the set opening. A control valve, comprising: a valve opening setting mechanism for setting a minimum opening position and a maximum opening position, which are references when controlling the valve opening. 2. The control valve according to claim 1, wherein the valve opening setting mechanism is provided in a feedback mechanism of the positioner. 3. The control valve according to claim 2, wherein the valve opening setting mechanism is provided with a feedback lever having a fan-shaped opening, and is movably inserted into the opening to be on one side of the opening during normal operation. A control valve comprising a feedback pin fixed to an edge. 4. The control valve according to claim 1, wherein the valve opening setting mechanism is provided at a connection between the drive shaft of the operation device and the valve stem. 5. The control valve according to claim 4, wherein the valve opening setting mechanism is provided with two blocks that can be moved and adjusted in the axial direction of the valve stem, and first and second blocks respectively provided in these blocks. A control valve comprising a connecting pin, wherein a feedback lever is connected to the first connecting pin during zero adjustment and normal operation, and the feedback lever is connected to the second connecting pin during span adjustment. 6. The control valve according to claim 4, wherein the valve opening setting mechanism includes a rotation lever, and a stopper for locking the rotation lever at a minimum opening position and a maximum opening position of the valve. And a feedback lever connected to the rotating lever via a feedback pin. 7. The control valve according to claim 4, wherein the valve opening setting mechanism includes a first opening position setting mechanism for setting a minimum opening position.
And a second mounting hole for setting the maximum opening position. A feedback lever is connected to the first mounting hole via a feedback pin at the time of zero adjustment and at the time of normal operation. A control valve, wherein the feedback lever is connected to the second mounting hole via a feedback lever during adjustment. 8. The control valve according to claim 4, wherein the valve opening setting mechanism is provided with a first movable pin for setting a minimum opening position and a second movable retractable pin for setting a maximum opening position.
And the first pin during zero adjustment and during normal operation.
And a feedback lever is connected by projecting the first pin forward from the second pin, and the feedback lever is connected by projecting the second pin forward from the first pin during span adjustment. Control valve.