Control device for motorized valves

Abstract

A control device of an electric valve, which comprises a motor, a speed reduction mechanism, an output shaft of the speed reduction mechanism is connected with a valve rod of the valve through a torque sensor, an output end of the torque sensor is connected with an operational amplifier A1 through a first electronic switch K1, an output end of the torque sensor is connected with an operational amplifier A2 through a second electronic switch K2, the first electronic switch K1 and the second electronic switch K2 are alternately conducted, a primary of a transformer B2 is connected between output ends of the operational amplifier A1 and the operational amplifier A2, a secondary voltage of the transformer B2 is compared by a comparator A3 and a motor control signal is outputted after comparison, the beneficial effect of the present application is that, by detecting a change rate of the valve torque with time, errors caused by additional torque of medium pressure change of the valve and friction change of moving parts such as the valve rod and the nut of the valve can be eliminated, and zero drift problems of the torque sensor can also be eliminated; the valve is closed and sealed, and the valve is not excessively rotated to be damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to a control device of an electric valve. BACKGROUND

[0002] The opening and closing control device of an electric valve such as a gate valve or a stop valve comprises a torque transducer and a travel switch. The torque transducer is used to detect the torque of the valve. By means of the change of the torque of the valve, it is determined whether the valve is in the fully closed position. When the valve is in the fully closed position, the torque of the valve rises to a certain value, so that the motor stops rotating forward. The travel switch is used to detect whether the valve is in the fully open position. When the valve is in the fully open position, the travel switch operates, so that the motor stops rotating reversely.

[0003] Due to the change of the medium pressure in the valve and the change of the friction of the moving parts such as the valve rod and the nut of the valve, the torque of the valve changes. In addition, the zero drift problem occurs after the torque transducer is used for a period of time. At this time, the valve torque signal output by the torque transducer is not accurate when compared with the set value, which may cause the valve to be not tightly closed or the valve to be excessively rotated. SUMMARY

[0004] In view of the above problems, the present application provides a control device of an electric valve, which can automatically eliminate the influence of the change of the medium pressure in the valve and the change of the friction of the moving parts such as the valve rod and the nut of the valve on the valve torque signal, improve the accuracy of the valve torque detection, and make the valve tightly closed on the basis of not being excessively rotated.

[0005] The technical scheme of the present application is that the control device of the electric valve comprises a motor, a speed reduction mechanism, and an output shaft of the speed reduction mechanism connected with the valve rod of the valve through a torque transducer. The signal output end of the torque transducer is connected with the non-inverting input end of an operational amplifier A1 through a first electronic switch K1. The non-inverting input end of the operational amplifier A1 is connected with the ground through a capacitor C2. The inverting input end of the operational amplifier A1 is connected with the output end of the operational amplifier A1.

[0006] The signal output end of the torque transducer is connected with the non-inverting input end of an operational amplifier A2 through a second electronic switch K2. The non-inverting input end of the operational amplifier A2 is connected with the ground through a capacitor C3. The inverting input end of the operational amplifier A2 is connected with the output end of the operational amplifier A2.

[0007] The primary of transformer B2 is connected between the output of operational amplifier A1 and the output of operational amplifier A2, the secondary of transformer B2 is connected with the input of bridge rectifier QL2, the output of bridge rectifier QL2 is connected in parallel with capacitor C4, the positive pole of the output of bridge rectifier QL2 is connected with the inverting input of comparator A3, the non-inverting input of comparator A3 is connected with the slide arm of potentiometer W1, one end of potentiometer W1 is connected with power supply VDD through resistor R1, the other end of potentiometer W1 is grounded, and the output of comparator A3 outputs motor control signal.

[0008] The output of square wave oscillator is connected with the control end of first electronic switch K1, and the output of square wave oscillator is connected with the control end of second electronic switch K2 through inverter.

[0009] The present application has the advantages that, by detecting the change rate of torque signal with time, the error caused by additional torque due to the change of medium pressure in valve and the friction change of moving parts such as valve rod and nut can be eliminated, and the zero drift problem of torque transducer can also be eliminated; when the change rate reaches the set value, the motor stop signal is outputted, so that the valve is closed and sealed without damage caused by excessive rotation. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is the circuit schematic diagram of the present application.

[0011] Figure 2 It is the circuit schematic diagram of square wave oscillator. EMBODIMENT

[0012] The control device of electric valve comprises a motor, the main shaft of the motor is connected with the input shaft of a speed reduction mechanism, and the output shaft of the speed reduction mechanism is connected with the valve rod of the valve through a torque transducer.

[0013] The signal output end of torque transducer is connected with the non-inverting input of operational amplifier A1 through first electronic switch K1, the non-inverting input of operational amplifier A1 is grounded through capacitor C2, and the inverting input of operational amplifier A1 is connected with the output of operational amplifier A1; the function of capacitor C2 is to keep the voltage of non-inverting input of operational amplifier A1 unchanged when first electronic switch K1 is in off state.

[0014] The signal output end of torque transducer is connected with the non-inverting input of operational amplifier A2 through second electronic switch K2, the non-inverting input of operational amplifier A2 is grounded through capacitor C3, and the inverting input of operational amplifier A2 is connected with the output of operational amplifier A2.

[0015] The output terminal of the operational amplifier A1 is connected with the output terminal of the operational amplifier A2, the primary of the transformer B2 is connected between the output terminal of the operational amplifier A1 and the output terminal of the operational amplifier A2, the secondary of the transformer B2 is connected with the input terminal of the bridge rectifier QL2, the output terminal of the bridge rectifier QL2 is connected in parallel with the capacitor C4, the positive pole of the output terminal of the bridge rectifier QL2 is connected with the inverting input terminal of the comparator A3, the non-inverting input terminal of the comparator A3 is connected with the slide arm of the potentiometer W1, one end of the potentiometer W1 is connected with the power supply VDD through the resistor R1, the other end of the potentiometer W1 is grounded, and the output terminal of the comparator A3 outputs the motor control signal U0.

[0016] The output terminal of the square wave oscillator is connected with the control terminal v1 of the first electronic switch K1, and the output terminal of the square wave oscillator is connected with the input terminal of the inverter, and the output terminal of the inverter is connected with the control terminal v2 of the second electronic switch K2.

[0017] The square wave oscillator can be based on a time base integrated circuit or based on an operational amplifier, which includes the operational amplifier A4, the non-inverting input terminal of the operational amplifier A4 is connected with the power supply VDD through the resistor R3, the non-inverting input terminal of the operational amplifier A4 is grounded through the resistor R5, the non-inverting input terminal of the operational amplifier A4 is connected with the output terminal of the operational amplifier A4 through the resistor R6, the inverting input terminal of the operational amplifier A4 is grounded through the capacitor C3, and the inverting input terminal of the operational amplifier A4 is connected with the output terminal of the operational amplifier A4 through the variable resistor R4.

[0018] The inverter can be a NOT gate integrated circuit or based on a transistor, which includes the transistor T2, the resistor R7 and the resistor R8, the output terminal of the operational amplifier A4 is connected with the base of the transistor T2 through the resistor R7, the emitter of the transistor T2 is grounded, the collector of the transistor T2 is connected with the power supply VDD through the resistor R8, the output terminal of the operational amplifier A4 is connected with the control terminal v1 of the first electronic switch K1, and the collector of the transistor T2 is connected with the control terminal v2 of the second electronic switch K2.

[0019] The principle of the control device of the electric valve is that the first electronic switch K1 and the second electronic switch K2 are alternately turned on or turned off, so that the voltage output by the operational amplifier A1 and the voltage output by the operational amplifier A2 are alternately increased, the voltage difference between them corresponds to the change rate of the torque, and the polarity of the voltage difference is alternately changed, the voltage difference is output to the comparator A3 through the transformer B2 and the rectifier filter circuit, and compared with the set voltage (the voltage on the non-inverting input terminal of the comparator A3), when the voltage difference is equal to or greater than the set voltage, the output terminal of the comparator A3 outputs a low level, that is, a motor stop signal, and the stop signal passes through a relay or a power amplifier such as a thyristor to stop the forward rotation of the motor, that is, to stop the closing action of the valve.

[0020] By detecting the rate of change of torque, the influence of additional torque caused by the change of medium pressure in the valve and the frictional force change of the moving parts such as valve stem, nut, etc. of the valve can be eliminated; the expression of the voltage u1 outputted by the operational amplifier A1 is:

[0021] u1=uz1+uf;

[0022] The expression of the voltage u2 outputted by the operational amplifier A2 is:

[0023] u2=uz2+uf,

[0024] Where uz1 and uz2 correspond to the torque of the normal rotation of the valve, and uf corresponds to the additional torque and the drift voltage of the torque sensor;

[0025] The voltage difference between uz1 and uz2 is:

[0026] Δu= u1- u2= (uz1+uf)-(uz2+uf)= uz1- uz2;

[0027] In the closing process of the valve, uf can be eliminated by subtraction operation, and therefore Δu is only related to uz1 and uz2; the torque characteristic of the valve is that in the closing process of the valve, the torque of the valve basically rises linearly, and when approaching the full-closed position, the torque of the valve rises according to an exponential change rule;

[0028] Therefore, uz1 and uz2 are alternately rising, the polarity of Δu alternately changes, Δu is alternating current, and when the rate of change of uz1 and uz2 with time rises exponentially, the amplitude of Δu gradually rises.

[0029] The variable resistor R4 in the regulating square wave oscillator can change the oscillation frequency of the square wave oscillator, that is, the alternate conduction frequency of the first electronic switch K1 and the second electronic switch K2, and the alternate conduction frequency, that is, the period of alternate conduction can be determined according to the movement speed of the valve plate of the valve. The period of alternate conduction is 1 to 4 times the time required for the valve plate to move 0.01 millimeter, so that the rate of change of torque can be obtained in time.

[0030] When the motor is reversed, the valve is opened, and the opening position of the valve is controlled by a travel switch. When the valve is in the fully open position, the travel switch acts to stop the motor.

Claims

1. Control device for an electrically operated valve comprising an electric motor, a reduction gear, the output shaft of which is connected to the valve stem of the valve via a torque transducer, characterized in that The signal output end of the torque transducer is connected with the non-inverting input end of the operational amplifier A1 through the first electronic switch K1, the non-inverting input end of the operational amplifier A1 is grounded through the capacitor C2, and the inverting input end of the operational amplifier A1 is connected with the output end of the operational amplifier A1; The signal output end of the torque transducer is connected with the non-inverting input end of the operational amplifier A2 through the second electronic switch K2, the non-inverting input end of the operational amplifier A2 is grounded through the capacitor C3, and the inverting input end of the operational amplifier A2 is connected with the output end of the operational amplifier A2; The output end of the operational amplifier A1 is connected with the output end of the operational amplifier A2, and the primary of the transformer B2 is connected between the output end of the operational amplifier A1 and the output end of the operational amplifier A2, the secondary of the transformer B2 is connected with the input end of the bridge rectifier QL2, the output end of the bridge rectifier QL2 is connected in parallel with the capacitor C4, the positive electrode of the output end of the bridge rectifier QL2 is connected with the inverting input end of the comparator A3, the non-inverting input end of the comparator A3 is connected with the slide arm of the potentiometer W1, one end of the potentiometer W1 is connected with the power supply VDD through the resistor R1, the other end of the potentiometer W1 is grounded, and the output end of the comparator A3 outputs the motor control signal; The output end of the square wave oscillator is connected with the control end of the first electronic switch K1, and the output end of the square wave oscillator is connected with the control end of the second electronic switch K2 through the inverter.

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