JPH0648002B2 - Electric Pneumatic Positioner - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electropneumatic positioner that opens and closes a valve by generating an output air pressure signal according to an input current signal, and more particularly to improving responsiveness.

(Prior Art) FIG. 3 is a block diagram of a conventionally known electro-pneumatic positioner. In the figure, 1 is a torque motor that generates a suction force according to the output signal of a controller, 2 is a lever that moves according to the suction force of the torque motor 1, and 3 is a nozzle provided opposite the lever 2. A nozzle flapper mechanism using the lever 2 as a flap is configured. 4 is a bilot relay that amplifies the back pressure of the nozzle 3, and 5 is the air pressure supplied to the nozzle 3 (for example, 1.4 k
A throttle for introducing g / cm ² ) and a valve 6 for operating the position of the valve body by the output air pressure signal of the pilot relay 4. 7 is a valve stem that is fixed to the valve 6 and transmits the displacement to the valve body; 8 is a clamp that fixes the clamp pin 9 to the valve stem 7; 10 is a lever that converts the displacement of the clamp pin 9 into rotation of the shaft 11; A lever fixed to the shaft 11 moves the lever 14 via a screw mechanism 13. Reference numeral 15 is a feedback spring that returns the movement of the lever 14 to the lever 2. Here, from the clamp 8 to the feedback spring 15, the feedback element 16 for returning the displacement of the valve 6 to the lever 2.
(See FIG. 4).

Reference numeral 17 is a yoke that constitutes the magnetic circuit of the torque motor 1,
The lever 2 is inserted in the substantially C-shaped space. 18
Is a spring that connects the lever 2 and the yoke 17, supports the lever 2, and applies a restoring force to the lever 2 with respect to the feedback spring 15.

The operation of the apparatus thus configured will be described with reference to FIGS. 3 and 4. FIG. 4 is a configuration block diagram of the apparatus shown in FIG. When the output current of the controller increases, the lever 2 moves in the arrow A direction by the torque motor 1. Then, since the nozzle 3 is blocked, the nozzle back pressure increases, and the pilot relay 4 operates to output the total supply air pressure. Then, the valve stem 7 moves in the arrow B direction, so that the shaft 11 rotates in the arrow C direction via the lever 10. Then, the lever 12 moves the lever 14 in the direction of the arrow D, and the feedback spring 15 is moved to the arrow E.
Stretch in the direction. Then, since the lever 2 balances and reaches the equilibrium state, the position of the valve stem 7 becomes directly proportional to the current signal of the controller.

(Problems to be Solved by the Invention) In the electro-pneumatic positioner configured as described above, it is desired that even valves having different diameters have a quick response and good controllability. However, the large valve and the small valve have the following problems because the amount of air required to drive the valve is different.

That is, in order to control a large valve, it is desirable that the pilot relay has a large supply / exhaust flow rate, and the response is fast and the loop gain can be large enough to cause no steady-state deviation and no problem in terms of performance. can get.

However, if this is applied to the small valve as it is, the supply / exhaust flow rate of the pilot relay is too large, so that it is necessary to reduce the loop gain in order to prevent oscillation. Then, the loop gain is small, which causes a problem that the steady-state deviation becomes large.

Similarly, if the control characteristics of the small valve are applied to the large valve as they are, the problem arises that the response becomes slow because the supply / exhaust amount of the pilot relay is small.

The present invention has solved the above-mentioned problems, and an object of the present invention is to provide an electropneumatic positioner that has a fast response, a small steady-state deviation, and no oscillation regardless of whether it is a large valve or a small valve.

(Means for Solving the Problem) In the present invention which achieves such an object, a torque motor 1 that generates a torque signal corresponding to an operation signal, and a nozzle flapper 3 that includes a flapper that is displaced according to the torque of the torque motor. The electro-pneumatic positioner including the pilot relay 4 for amplifying the air pressure signal from the nozzle flapper and outputting the amplified signal to the valve 6 has the following configuration.

That is, a displacement detector 20 that detects a displacement corresponding to the movement of the valve body of the valve, a voltage converter 31 that inputs a signal from the outside and converts it into a voltage signal, an output signal of this voltage converter, and The deviation from the output signal of the displacement detector is supplied to the proportional device in the case of the large valve, and is switched to the integrator in the case of the small valve to be supplied to the integrator, and the signal sent from the switching device is predetermined. An integrator 32 that integrates with a time constant Ti,
A proportional device 37 for proportionally calculating a signal sent from the switching means with a predetermined gain, and a proportional differentiator 34 for performing a proportional differential operation on the signal from the displacement detector with a predetermined time constant Td,
It is characterized by including an amplifier 33 that amplifies a deviation between the output signal of the integrator or the proportional device and the output signal of the proportional differentiator and outputs the operation signal of the torque motor.

(Operation) The nozzle flapper and pilot relay are air systems,
Generates force to drive the valve. The displacement detector and the control circuit are electric systems, and are connected to the air system by a torque motor. Here, the control circuit constitutes a feedback control loop including a proportional differentiator and an amplifier by switching between the integrator and the proportional device by the switching means depending on whether it is a large valve or a small valve. When the integrator is selected, the proportional differentiator magnifies and detects even a slight movement of the valve, so that the braking performance is improved and it is suitable for a small valve. If a proportional device is selected, the response is proportionally improved when an integrator is used, which is suitable for a large valve.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, and FIG. 2 is a configuration block diagram of the apparatus of FIG. The first
In FIGS. 2 and 3, components having the same functions as those in FIGS. 3 and 4 are designated by the same reference numerals and the description thereof will be omitted.

In the figure, 20 is a non-contact displacement meter such as an eddy current type, an optical type, or a capacitance type, which is used up to a displacement detector for detecting the displacement of the valve 6, but the output signal is obtained as an electric signal. A contact displacement meter can be used if it exists. 30 is a control circuit for controlling the attraction force of the torque motor 1 by the signal of the displacement detector 20, 31 is a current signal of the controller (for example, 4
-20 mA) to voltage signal current-voltage converter, 3
An integrator 2 integrates the signal of the current-voltage converter 31 and has a time constant Ti. Reference numeral 33 designates an amplifier that outputs a current for driving the torque motor 1 according to the output of the integrator 32.
Reference numeral 4 is a proportional differentiator for inputting the output signal of the displacement detector 20 and performing proportional: differential calculation (differential calculation time constant Td) on this signal. Reference numeral 35 is an integrator 32 for the signal processed by the proportional differentiator 34.
In the feedback path that is added to the signal processed in
The added signal is processed by the amplifier 33. 36
Is a feedback path for adding the output signal of the displacement detector 20 to the signal processed by the current-voltage converter 31, and the added signal is processed by the integrator 32.

The switching means 38 supplies the deviation between the output signal of the current-voltage converter 31 and the output signal of the displacement detector 20 to the proportional device in the case of a large valve and to the integrator in the case of a small valve. Then, for example, it is set by manual operation. The proportional device 37 performs a proportional operation on the signal sent from the switching means 38 with a predetermined gain Kc2, and is alternatively used for feedback control together with the integrator 32.

The operation of the apparatus thus configured will be described with reference to FIGS. 1 and 2. The current signal of the controller activates the torque motor 1 via the control circuit 30. Then, the lever 2 receives a force in the direction of arrow A by the torque, and operates to close the nozzle 3. Then, the valve 6 is displaced via the pilot relay 4, and the displacement detector 20 detects this displacement. The displacement and speed of the valve 6 are detected by the proportional differentiator 34 and the feedback path 35, so that the response becomes faster. Further, since the feedback path 36 and the proportional unit 37 or the integrator 32 which is switched by the switching unit 38 according to whether the valve 6 is large or small are controlled so that the valve 6 is at the target position, the steady-state deviation is generated. It reaches zero and reaches an equilibrium state.

When the valve 6 is small, the switching means 38 selects the integrator 32. The pilot relay 4 easily oscillates when the supply / exhaust amount of the pilot relay 4 is large, but since the proportional differentiator 34 also detects and feeds back even a slight movement of the valve 6, the braking performance improves and oscillation does not occur. On the other hand, when the valve 6 is large, the switching means 38 selects the proportionalizer 37. The steady-state deviation becomes zero when the integrator 32 is used, but even when the proportionalizer 37 is used, the steady-state deviation becomes small because the loop gain is large and can be ignored. Proportioner 3
The response of 7 is faster and preferable compared to the case where the integrator 32 is selected.

In other words, small valves focus on steady deviation and oscillation prevention rather than responsiveness, and large valves focus on faster response, so the control characteristics of the electropneumatic positioner should be switched according to the type of valve. Is there.

(Effect of the Invention) As described above, according to the present invention, the proportional loop 37 or the integrator 32 is selected by the switching means 38 according to whether the valve 6 is large or small, and the feedback loop is changed. . Therefore, the small valve reduces the steady-state deviation and prevents oscillation, and the large valve has a faster response compared to the case of driving a large valve using a conventional electro-pneumatic positioner, and it is a universal valve regardless of the type. There is an effect that an electro-pneumatic positioner that can be used for

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram of the illustrated apparatus. FIG. 3 is a block diagram of the conventional device, and FIG. 4 is a block diagram of the device of FIG. 1 ... Torque motor, 3 ... Nozzle, 4 ... Pilot relay, 20 ... Displacement converter, 30 ... Control circuit, 32
...... Integrator, 34 …… Proportional differentiator, 35,36 …… Feedback path.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 54-151780 (JP, A) JP 60-73103 (JP, A) JP 60-136602 (JP, A) Actually published 55- 105602 (JP, U) JP-B-43-14797 (JP, B1)

Claims (1)

[Claims] 1. A torque motor (1) for generating a torque signal according to an operation signal, a nozzle flapper (3) including a flapper displaced according to the torque of the torque motor, and an air pressure signal from the nozzle flapper are amplified. In an electropneumatic positioner equipped with a pilot relay (4) for outputting to a valve (6), a displacement detector (20) for detecting a displacement corresponding to the movement of the valve body of the valve and a signal from the outside are inputted. A voltage converter (31) for converting into a voltage signal by means of a voltage converter, and a deviation between the output signal of this voltage converter and the output signal of the displacement detector is supplied to a proportional device in the case of a large valve and in the case of a small valve. Switching means (38) for switching and supplying to the integrator
And the signal sent from the switching means is set to a predetermined time constant (Ti).
Integrator (32) for integrating with, a proportional device (37) for proportionally calculating a signal sent from the switching means with a predetermined gain, and a signal from the displacement detector with a predetermined time constant (Td) A proportional differentiator (34) that performs a differential operation, and an amplifier (33) that amplifies the deviation between the output signal of the integrator or the proportional differentiator and the output signal of the proportional differentiator to output the operation signal of the torque motor. And an electro-pneumatic positioner comprising: