JPH0660825B2 - Electro-pneumatic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an improvement of an electropneumatic converter.

<Prior Art> An example of the prior art will be described with reference to the configuration diagram of FIG. 6 and the block diagram of FIG.

Input terminals 1 and 1 ′ receive a current output Io from an operating means such as a controller as an input signal, and a torque motor 2 and an input current Io is applied to a coil 201. Reference numeral 3 is a lever driven by a torque motor, which is regulated to a reference position by springs 4 and 5, and one end 301 is driven in the direction of arrow A as a flapper by an input current. This flapper 30
The nozzle 6 is arranged to face 1 and the back pressure Pb thereof increases.

Reference numeral 7 denotes a throttle for the supply air source Ps, which supplies the air ejected from the nozzle. A pilot relay 8 amplifies the nozzle back pressure Pb and outputs an air pressure signal Po. This pneumatic signal
Po is guided to the feedback bellows 15.

One end of the feedback bellows 15 and the other end 302 of the lever 3 are fixed. Therefore, the force of the feedback bellows 15 in the B direction causes the other end 30 of the lever 3 to move.
2 is displaced in the B direction, and its force acts to pull back the displacement of the lever 3 in the A direction by the input current Io, and the system is balanced.

With such a force balance system, the pneumatic signal is controlled according to the input current Io.

FIG. 7 is a block diagram showing such a system.

<Problems to be Solved by the Invention> An electropneumatic converter based on such a force balance system requires a highly accurate torque motor that converts an input current into a force, and further converts an air pressure signal into a feedback signal by force. However, there is a drawback in that the structure is complicated and the cost is high because the connecting mechanism is mechanical and the structure is relatively large.

Further, there is a drawback that the response of the actuator controlling the flapper is delayed due to the response delay due to the capacity on the air pressure output side and the constants of the mechanical elements of the feedback mechanism, and the system tends to become unstable.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such problems and provide a compact, inexpensive and stable electric converter.

<Means for Solving Problems> A structural feature of the present invention is that, in an electropneumatic converter for outputting a pneumatic signal in response to an input current, the current signal is converted into a voltage signal or a digital signal. Input processing means, actuator means for controlling the pilot relay that outputs the preceding air pressure signal based on the difference between the output of this input processing means and the feedback signal, and the stem displacement that interlocks with the valve of the preceding pilot relay. Displacement-electrical signal converting means for converting into a signal and feeding back to the input side of the previous actuator means, and pressure-electricity for receiving the output of the previous pneumatic signal to obtain the previous feedback signal in the form of a voltage signal or a digital signal. It is equipped with a signal converting means.

<Operation> According to the present invention, the input current is converted into the voltage signal or the digital signal by the input processing means, the pilot relay is controlled based on the difference from the feedback signal given by the voltage signal or the digital signal, and the pneumatic signal is changed. Is output. The pneumatic signal output is converted into a voltage or digital signal feedback signal by the pressure-electric signal converting means to be balanced with the output of the input processing means, and the displacement of the stem interlocking with the valve of the pilot relay is converted into an electric signal to actuate the actuator. Is fed back to the input side of
Balance with actuator drive signal.

<Example> An example of the present invention will be described with reference to Figs. First
FIG. 2 and FIG. 2 show a configuration diagram and a block diagram of an embodiment for converting an input current into a voltage signal. The same elements as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 16 is an input processing means, which converts the input current Io into a voltage signal Vi. A differential amplifier 17 amplifies the difference between the voltage signal Vi and the feedback signal Vf. Feedback signal Vp related to the output of this amplifier and the stem displacement of the pilot relay
The piezoelectric actuator 18 for displacing the flapper 3 is driven by the difference voltage Vc. The configurations of the nozzle 6 and the pilot relay 8 are the same as the conventional configuration.

The air signal output Po of the pilot relay 8 is converted into a feedback signal Vf by the pressure-voltage signal converter 19. This transducer is composed of a vibrating force sensor means, and a pair of piezoelectric elements 193, 194 are arranged in a vibrating portion 192 formed by etching a cantilever 191 having one end fixed. The amplifier 197 and the two piezoelectric elements can form a closed loop to generate self-oscillation at the natural frequency of the vibrating section 192, and the pneumatic signal output is output to the other end of the cantilever through the bellows 196. By converting and inputting, a vibration output having a frequency related to the pneumatic signal output can be obtained. The signal processing circuit 195 has a function of converting an oscillation frequency into a voltage signal Vf.

The displacement-electrical signal converter 20 is a pressure-electrical signal converter having exactly the same configuration as 19 except that the other end of the cantilever is not a bellows but the stem displacement of the pilot relay is converted into a force via a spring. , Generating a voltage signal Vp related to the displacement of the stem 801 which is interlocked with the valve of the pilot relay 8,
It has a function of performing negative feedback to the output Vo of the differential amplifier 17. This feedback loop is intended to improve the stability of the system, and it is possible to eliminate instability factors caused by the capacity of the pneumatic signal output side, the constants of the constituent elements, and the like.

This displacement-to-electrical signal converter 20 can be realized with a device with lower accuracy than the device 19.

As a driving power source for the differential amplifier 17, the force-electrical signal converter 19, the displacement-electrical signal converter 20, etc., it is possible to use the constant voltage Eb obtained from the Zener diode 161 of the input processing means, Does not require power.

FIG. 2 is a block diagram showing the configuration of FIG. 1. The system is balanced by comparing the voltage signal Vi and the voltage feedback signal Vf, and the stem displacement of the pilot relay is fed back to the input side of the actuator. And the balance is realized by a double loop.

The means for realizing the displacement-electrical signal converter 20 can be applied by a magnetostrictive potentiometer, a displacement magnetoresistive converter, a device utilizing light or capacitance change, and the like. FIG. 3 shows an implementation example using a magnetostrictive potentiometer. Show.

The displacement signal of the stem 801 of the pilot relay 8 is the expansion mechanism 2
The coil 22 that is enlarged in 1 and is coupled to the magnetostrictive wire 23 in a non-contact manner is slid. Reference numeral 24 is a pulse generating means for supplying a pulse signal current from both ends of the magnetostrictive line, and 25 and 26 are pulse detecting means provided at both outer ends of the magnetostrictive line. The arithmetic circuit 27 processes the arrival time difference of the reflected pulse from the slider position. Then, the voltage signal Vp related to the displacement is obtained as a feedback signal.

The actuator means for driving the flapper 3 may be configured to be driven by a movable coil or a movable iron piece means in addition to the piezoelectric element as in the embodiment.

FIG. 4 shows an embodiment of a system balanced with a digital signal. The voltage signal Vi is converted into a digital signal Di by the analog / digital converter 28 and input to the microcomputer 30. On the other hand, the pressure-electric signal converter 19 'directly outputs the vibration frequency signal F related to the pressure, and the cycle counter 29 counts the clock to input it to the microcomputer 30 as a digital feedback signal Df corresponding to the vibration cycle. To be done.

The deviation of these digital signals Di and Df is arithmetically processed in this microcomputer 30, and the operation output Dm is transmitted as a digital signal. This operation output Dm is converted into a voltage signal Vo by the digital / analog converter 31, and subtracted from the feedback signal Vp related to the stem displacement of the pilot relay 8 to drive the actuator 18.
Entered in 17.

When the output of the pressure-electric signal converter and the displacement-electric signal converter are frequency outputs, it is easy to realize a balanced system with such digital signals, and by introducing a microcomputer, the input signal and pneumatic signal It is also easy to calculate the output relationship into a specific functional relationship.

The embodiment of FIG. 5 shows a configuration in which the system balance is realized by phase comparison of frequency signals. 32 is a voltage-frequency converter that converts the voltage signal Vi into a frequency signal ω ₁ , 33 is a phase comparison detector, which is a pressure-voltage converter related to the pneumatic signal output.
The frequency signal outputs ω ₂ and ω _{1 of} 19 'are compared, a signal φ related to the phase difference is calculated, and the voltage signal Vo is converted and output.

The difference between this output Vo and the feedback signal Vp related to the stem displacement of the pilot relay 8 is input to the differential amplifier 17.

As the phase comparison detector 33, a commercially available PLL-IC can be used.

This embodiment is also effective when the means for detecting the pneumatic signal output outputs a frequency signal.

<Effects of the Invention> As described above, according to the present invention, since the system is parallel by an electric signal regardless of the mechanical force balance as in the conventional electropneumatic converter, mechanical parts such as levers and bearings are parallel. In addition, since a high precision and large torque motor is not required, it is possible to realize an electropneumatic converter that is compact, inexpensive, easy to assemble, and has improved hysteresis characteristics and earthquake resistance.

Further, by adopting the double feedback, it is possible to realize a stable electropneumatic converter having good followability to the input signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram thereof, and FIG. 3 is a block diagram showing another embodiment of the main part of the present invention, FIG. 4, FIG. Is a block diagram showing another embodiment of the present invention, FIG. 6 is a block diagram showing an example of the prior art, and FIG.
The figure is a block diagram thereof. 1, 1 '... input terminal, 3 ... flapper, 8 ... pilot relay, 801 ... pilot relay stem, 16 ...
Input processing means, 17 differential amplifier, 18 actuator, 19 pressure-electric signal converter, 20 displacement-electric signal converter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Tanzawa 2-9-32 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Hokushin Electric Co., Ltd. (56) Reference JP-A-60-24415 (JP, A) JP Sho 60-112102 (JP, A)

Claims (1)

[Claims] 1. An electropneumatic converter for outputting a pneumatic signal corresponding to an input current, input processing means for converting the current signal into a voltage signal or a digital signal, and an output and feedback signal of the input processing means. An actuator means for controlling a pilot relay that outputs the air pressure signal based on the difference between the electric displacement and a stem-displacement that interlocks with the valve of the pilot relay and converts the stem displacement into an electric signal to feed back to the input side of the actuator means. An electropneumatic converter comprising signal conversion means and pressure-electric signal conversion means for receiving the output of the pneumatic signal and obtaining the feedback signal in the form of a voltage signal or a digital signal.