JPH05108166A - Positioner - Google Patents

Abstract

PURPOSE:To facilitate the adjustment for attaching a positioner to an actuator. CONSTITUTION:A position perpendicular to a valve system 3 of a potentiometer 20 or the position perpendicular to the valve system of a feedback lever 25, and a rotational angle theta showing the opening degree of a valve 1 detected by the potentiometer 20 or the like is corrected based on the calculated quadrature position and converted into a linear opening degree. As a result, accurate feedback to a driving part 2 can be performed even when an error occurs in the case of attaching the positioner to a valve system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioner for adjusting the opening of a valve that controls the flow rate of fluid.

[0002]

2. Description of the Related Art Conventionally, as a first example of this type of positioner, there is a force balance type positioner as shown in FIG. In the figure, 1 is a valve, 2 is a drive unit for opening and closing the valve 1, 3 is a valve stem, 4 is a booster, 5
Is a nozzle, 6 is a torque motor, 7 is a flapper, and 8 is a feedback lever. That is, the air signal SUP indicating a constant amount of air supplied from the outside is injected to the flapper 7 via the nozzle 5 and is also supplied to the drive unit 2 via the booster 4, and this air pressure drives the drive unit. Reference numeral 2 controls the opening of the valve 1 via the valve stem 3.
Now, in order to set the opening of the valve 1 to a certain value, the set value R
Is input, the increase / decrease in the amount of air injected from the nozzle 5 is controlled by the position of the flapper 7 driven by the torque motor 6, and as a result, a relation opposite to the increase / decrease relation in the amount of air injected from the nozzle 5 is controlled. Drive 2 depending on the amount of air in
Is driven to control the opening of the valve 1. On the other hand, the opening degree of the valve 1 is feedback-controlled by the feedback lever 8 attached to the valve stem 2. That is,
The springs 9 and 10 are interlocked with the drive of the feedback lever 8.
The flapper 7 is held at an appropriate position by driving, and as a result, the amount of drive air supplied to the drive unit 2 is controlled to a constant value by holding the injection amount from the nozzle 5 at an appropriate value. ..

Next, FIG. 7 shows a second embodiment of the conventional positioner, in which the controlled opening of the valve 1 is detected and fed back by using a rotary potentiometer. That is, in the figure, 20 is a potentiometer, 21 is an A / D converter, 22 is a controller, and 23 is an electropneumatic converter that converts an electric signal into an air signal. When this positioner sends a set value R for setting the opening of the valve 1 to the controller 22, the controller 22 sends this as an electric signal to the electropneumatic conversion section 23. And
In the electropneumatic converter 23, the supplied air signal SUP
Of these, an air signal corresponding to this electric signal is sent to the drive unit 2 to control the opening degree of the valve 1. When the opening control of the valve 1 is performed in this manner, the potentiometer 20 detects the angle formed by the stroke displacement of the valve stem 3 caused by the opening control of the valve 1 and the installed potentiometer 20, that is, the rotation angle θ. , A / D converter to convert to an electric signal. The electric signal indicating the feedback amount output from the A / D converter 21 is sent to the controller 22, and as a result, the controller unit 22 controls the amount of drive air given to the drive unit 2 in a controlled manner.

[0004]

The conventional positioner is
For example, in the case of the first example shown in FIG. 6, if the attachment point A of the feedback lever 8 and the attachment point B of the positioner to the valve stem 3 are not attached with accurate precision, accurate feedback is not performed. was there. In addition, the second example also has a similar drawback, for example, as shown in FIG.
As shown in (c), when the angle θE corresponding to the mounting error occurs during the mounting adjustment of the potentiometer 20,
As shown in (b) of the figure, the feedback amount X deviates from the normal value, and accurate feedback is not performed.

Further, there is a problem in that some degree of linearity error occurs even if the mounting is performed accurately. That is, in FIG. 7, it is assumed that the value R as shown in the equation (1) is set in order to control the opening of the valve 1 and set its rotation angle to θ.

[Equation 1] In addition, the potentiometer 20 is the valve stem 3 here.
If the adjustment angle when mounted on the
an θs / θs. Then, the feedback amount X in this case can be expressed as in equation (2), where L is the linear distance between the valve stem 3 and the potentiometer 20.

[Equation 2] However, as shown in FIG. 8A, the feedback amount X changes in a curved line with respect to the linear change of the set value R, so that the formula (3) is provided between the set value R and the feedback amount X. There is a drawback that an error ERR as shown in (1) occurs and feedback cannot be performed accurately.

[Equation 3]

[0006]

In order to solve such a problem, the present invention provides a potentiometer mounted on a valve stem for transmitting a driving force from a driving unit to the valve, in which the valve is positioned at a right angle position with respect to the valve stem. It was set at the midpoint between the fully closed angle in the fully closed state and the fully opened angle when the valve was in the fully open state, and the rotation angle based on the detected valve opening was corrected based on the determined right angle position. After that, it is converted into a linear opening and fed back to the drive unit. In addition, the position of the potentiometer attached to the valve stem is controlled to a position other than the fully closed position when the valve is in the fully closed state and the fully open position when the valve is in the fully open state, and the position of the potentiometer at a right angle to the valve stem is controlled. Is calculated, and the detected rotation angle is corrected based on the calculated right angle position and then converted into a linear opening. Also, calculate the position perpendicular to the valve stem of the installed potentiometer from the difference between the fully open position when the valve is fully open and the fully closed position when the valve is fully closed, and the distance between the potentiometer and the valve stem. In addition, the detected rotation angle is corrected based on the calculated right angle position and then converted into a linear opening. In addition, the contact surface between the feedback pin provided on the valve stem and the feedback lever attached to the valve stem is formed by a resistance element, and the position of the feedback lever at a right angle to the valve stem is calculated based on the resistance value of this resistance element. The detected rotation angle is corrected based on the calculated right angle position and then converted into a linear opening.

[0007]

[Function] The right angle position of the potentiometer with respect to the valve stem or the right angle position of the feedback lever with respect to the valve stem is calculated, and the rotation angle indicating the opening degree of the valve detected by the potentiometer or the like is corrected based on the calculated right angle position. After that, it is converted to a linear opening. As a result, even if an error occurs in mounting the positioner on the valve stem, accurate feedback can be performed to the drive unit.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. In this positioner, when the set value R is sent to the controller 22 in order to set the opening degree of the valve 1 to a predetermined value, the controller 22 transmits this as an electric signal to the electropneumatic conversion section 23 and at the same time, the electropneumatic conversion section 23. In the above, in the supplied air signal SUP, an air signal corresponding to this electric signal is sent to the drive unit 2 to control the opening degree of the valve 1. The opening of the valve 1 controlled by the drive unit 2 is adjusted by the potentiometer 20 to the valve stem 3
Is detected as a rotation angle θ indicating the stroke displacement, and this is sent to the rotation angle / linear position conversion means 24 via the A / D converter 21. The rotation angle / linear position conversion means 24 first obtains a tentative feedback amount from the input rotation angle θ and the linear distance L between the potentiometer 20 and the valve stem 3, and the obtained feedback amount is relative to the rotation angle θ. Conversion is performed so as to change linearly, and the converted feedback amount X is converted by the controller 22.
Send to. As a result, in the controller 22,
Since a feedback amount that does not cause a linear shift from the input set value R is obtained, accurate feedback control can be performed.

Next, FIG. 2 is a block diagram showing a second embodiment of the present invention, in which the feedback amount X is calculated in consideration of the mounting error when mounting the positioner on the valve stem 3. It is a thing. That is, in FIG. 2, the reference angle is the position where the voltage division ratio of the potentiometer 20 is 50%, the fully closed angle indicating the fully closed state of the valve 1 is θZ, the fully closed position is XZ, and the fully open angle indicating the fully opened state of the valve 1 is θS. ,
The fully open position is XS, the angle difference between the reference angle and the right angle position is θE, the reference angle position is XE, and the stroke span of the valve stem 3 is V.
Assuming S and the distance between the potentiometer 20 and the valve stem 3 to be L, the rotation angle / linear position conversion means 24 performs conversion as shown in equation (4) to perform feedback amount X.
To calculate.

[Equation 4]

Here, the difference angle θE between the reference angle and the right angle position
Is an angle determined by the mounting of the positioner and the actuator, and an accurate feedback amount X cannot be calculated unless the mounting error, that is, the difference angle θE is obtained. In the present invention, the difference angle θE due to this mounting error is calculated by the following four methods, and the detected rotation angle θ is corrected by the calculated difference angle θE.
That is, in the first method, the difference angle θE between the reference angle and the right angle position is set to the midpoint between the fully closed angle θZ and the fully opened angle θS, as shown in the equation (5).

[Equation 5] In such a case, although a certain degree of error occurs, the processing in the rotation angle / linear position conversion means 24 becomes simple.

Next, in the second method, the difference angle θE between the reference angle and the right angle position is controlled to one point other than the fully closed position XZ and the fully opened position XS, and the difference angle θE is calculated from the opening position at that time. .. As one example thereof, as shown in FIG. 3, when the difference angle θE between the reference angle and the right angle position is controlled to the midpoint position XM, the expressions (6) to (11) are established. That is,

[Equation 6]

[Equation 7]

[Equation 8]

[Equation 9]

[Equation 10]

[Equation 11]

Here, the fully closed angle θZ, the fully opened angle θS and the stroke span VS are obtained at the time of adjustment, and the angle θM is obtained by setting the input to 50%, and the stroke VM at that time is measured. Thus, the difference angle θE between the reference angle and the right angle position is calculated by the equation (12). With this method, the processing in the rotation angle / linear position conversion means 24 becomes complicated, but an accurate value can be calculated.

[Equation 12]

As a second example, the difference angle θE between the reference angle and the right angle position is controlled to a certain point, for example, a set value R. In this case, the equation (8) is transformed into the equation (13), and the difference angle θE is calculated from the equation (13) and the equations (6), (7), and (9) to (12). It

[Equation 13]

As a third example, the reference angle is controlled to be the difference angle θE between the reference angle and the right angle position. In this case, in the above equations, each θM becomes “0”, and if the measurement position at this time is VE, equation (12) becomes (1
It can be transformed as shown in equation (4), and θE can be calculated from this.

[Equation 14]

Next, as a third method for calculating the difference angle θE between the reference angle and the right angle position, as shown in FIG. 4, the distance L between the valve stem 3 and the potentiometer 20 and the stroke span of the valve stem 3 are calculated. This is a method of obtaining from VS, and in this case, equations (15) to (17) are established. That is,

[Equation 15]

[Equation 16]

[Equation 17]

The difference angle θE obtained from these equations (15) to (17) is calculated from equation (18).

[Equation 18] A, B, and C in equation (18) are (19) and
It is a value represented by the equations (20) and (21).

[Formula 19]

[Equation 20]

[Equation 21]

In these equations (18) to (21), the distance L between the valve stem 3 and the potentiometer 20, the stroke span VS of the valve stem 3, the fully closed angle θZ, and the fully opened angle θS are known, respectively. The difference angle θE between the reference angle and the right angle position can be easily calculated.

Next, as a fourth method for calculating the difference angle θE between the reference angle and the right angle position, there is a method as shown in FIG. In this system, a resistance element 26 is provided in a feedback lever 25 attached to the valve stem 3, and a change in resistance value due to the operation of a feedback pin 28 is detected to obtain a difference angle θE. That is, the valve stroke is changed so that the valve 1 is changed from the fully closed state to the fully open state, and the feedback pin 28 is operated to operate the resistance element 26.
The angle θ at which the resistance value R _S is minimized is obtained by the difference angle θE between the reference angle and the perpendicular position. That is,

[Equation 22]

[0019]

As described above, according to the present invention, the right angle position of the potentiometer with respect to the valve stem or the right angle position of the feedback lever with respect to the valve stem is calculated, and the rotation angle indicating the opening degree of the valve detected by the potentiometer or the like is obtained. Was corrected based on the calculated right angle position and converted into a linear opening,
Even if an error occurs in mounting the positioner on the valve stem, accurate feedback can be provided to the drive unit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a positioner according to the present invention.

FIG. 2 is an explanatory view showing another embodiment of the positioner.

FIG. 3 is an explanatory diagram showing a method of calculating an angle θE based on an attachment error of the positioner.

FIG. 4 is an explanatory diagram showing a method of calculating an angle θE based on an attachment error of the positioner.

FIG. 5 is an explanatory diagram showing a method of calculating an angle θE based on an attachment error of the positioner.

FIG. 6 is a configuration diagram of a conventional positioner.

FIG. 7 is a block diagram of a conventional positioner.

FIG. 8 is a diagram showing characteristics of a conventional positioner.

[Explanation of symbols]

 1 Valve 2 Drive Unit 3 Valve Stem 20 Potentiometer 21 A / D Converter 22 Controller 23 Electro-Pneumatic Converter 24 Rotation Angle / Linear Position Converting Means 25 Feedback Lever 26 Resistance Element 28 Feedback Pin

Claims (4)

[Claims] 1. A potentiometer is attached to a valve stem that opens and closes a valve by transmitting the driving force of a drive unit, and the opening degree of the driven valve is detected by the potentiometer as a rotation angle and based on the detected rotation angle. In the positioner that feeds back to the drive unit, the position of the installed potentiometer at a right angle to the valve stem is defined as the fully closed angle when the valve is fully closed and the fully open angle when the valve is fully open. A positioner characterized in that the position is set to a midpoint, and the detected rotation angle is corrected based on the calculated right angle position and then converted into a linear opening. 2. A potentiometer is attached to a valve stem that opens and closes a valve by transmitting the driving force of a drive unit, and the opening of the driven valve is detected as a rotation angle by the potentiometer and based on the detected rotation angle. In a positioner that feeds back to the drive unit, the position of the potentiometer attached to the valve stem is set to a position other than a fully closed position when the valve is fully closed and a fully open position when the valve is fully open. While controlling and calculating the right angle position of the potentiometer with respect to the valve stem based on the opening position at that time, it is possible to correct the detected rotation angle based on the calculated right angle position and then convert it into a linear opening. A characteristic positioner. 3. A potentiometer is attached to a valve stem that opens and closes a valve by transmitting the driving force of a drive unit, and the opening degree of the driven valve is detected by the potentiometer as a rotation angle and based on the detected rotation angle. In the positioner that feeds back to the drive unit, the position of the mounted potentiometer at right angles to the valve stem is defined as the fully open position when the valve is in the fully open state and the fully closed position when the valve is in the fully closed state. A positioner which is calculated from the difference and the distance between the potentiometer and the valve stem, and is converted into a linear opening after correcting the detected rotation angle based on the calculated right angle position. 4. A feedback lever is attached to a valve stem that opens and closes a valve by transmitting the driving force of a drive unit, and the opening degree of the driven valve is detected as a rotation angle by the feedback lever and the detected rotation angle is set. In a positioner that performs feedback to the drive unit based on, a contact surface between a feedback pin provided on the valve stem and the feedback lever is formed by a resistance element, and the feedback lever of the feedback lever is formed based on a resistance value of the resistance element. A positioner that calculates a right angle position with respect to the valve stem, corrects the detected rotation angle based on the calculated right angle position, and then converts it into a linear opening.