JPS6298076A - Motor-driven valve actuator - Google Patents

Abstract

PURPOSE:To simplify the arrangement of a motor-driven adjusting valve, by stopping the supply of electrical current to a motor when the supply current to the motor exceeds a predetermined value. CONSTITUTION:A current detector 6 detects supply current to a motor 4 for driving an motor-driven adjusting valve 1. A comparator 7 compares the detected value Ix of the supply current to the motor 4 detected by the current detector 6 with a set current value Is, and if Ix>Is, it delivers a signal to a timer 8 which is turn delivers a signal to a hold circuit 9 when the signal from the comparator 7 continues exceeding a predetermined time. The hold circuit 9 holds the signal from the timer 8 for a predetermined time, and then delivers the signal to a drive device 3 which stops the supply of current to the motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in an electric valve operator comprising a closed loop control system.

<Prior art> In a closed-loop control system that controls the opening of an electric control valve, the electric valve is driven according to the deviation between the opening setting value and the actual opening detection value, so as to reduce the deviation to zero. Control takes place.

On the other hand, in the past, in addition to the above-mentioned closed-loop control system, when the control valve is fully open or fully open, it is detected by the position of the valve body or by a mint switch, and the power supply to the motor is stopped, and the control valve is closed-loop. This prevents overcurrent from flowing to the motor for a long time when the motor is fully opened or fully opened due to some abnormality in the control system.

<Problems to be solved by the invention> As mentioned above, in the past, for the purpose of protecting the motor, it was necessary to detect whether the control valve was fully open or fully closed, and a misotosinch was required, which complicated the configuration and increased costs. There was a problem with rising.

Additionally, in the past, when the valve body caught a foreign object and stopped at an opening other than the set opening, there was no way to immediately detect that the valve body had stopped, so an overcurrent could flow through the motor for a long time. As a result, the motor was damaged.

<Means for Solving the Problems> The present invention provides an electric valve operator comprising a closed loop control system having a control device for controlling the opening degree of the electric valve and a drive device for driving the electric valve. Current detection means for detecting the supply current of the motor to be driven; comparison means for comparing the current value detected by the current detection means with a set current value; and timer means for performing a timing operation according to the output of the comparison means. and a signal holding means for holding the output of the timer means at a constant value and giving it to the driving device, and resetting to stop the supply of current to the motor when the current supplied to the motor exceeds a certain value.

<Example> Hereinafter, one embodiment of the present invention will be described based on the drawings.

The opening degree of the electric control valve 1 is controlled by a closed loop control system having a control device 2 and a drive device 3.

The control device 2 sets the opening degree of the electric control valve 1 to the set value according to the deviation 2 between the opening degree setting value r of the electric control valve l and the opening degree feedback value X, which is the detected value of the actual opening degree. A control signal C is given to the drive device 3 as shown in FIG.

The drive device 3 supplies current to the motor 4 of the electric control valve 1 in accordance with this control signal C, and drives the electric control valve 1.

The current generator 6 detects the current supplied to the motor 4 that drives the electric control valve 1 . The comparator 7 compares the detected value 1x of the supply current of the motor 4 detected by the current detector 6 with a predetermined current setting value Is, and determines that I x > I s
A signal is given to timer 8 when . The timer 8 performs a timing operation in response to the signal from the comparator 7, and provides a signal to the hold circuit 9 when the signal from the comparator 7 continues for a certain period of time and times out. When the signal from the comparator 7 does not continue for more than a certain period of time, the timer circuit 8 stops the timekeeping operation as soon as the signal from the comparator 7 disappears, and does not provide a signal to the hold circuit 9. The hold circuit 9 holds the signal from the timer 8 constant and supplies the held signal to the drive device 3. At this time, the drive device 3 stops supplying current to the motor 4.

The hold circuit 9 is further given a deviation 2 between the opening degree setting value r and the opening degree feedback value X, and when the polarity of this deviation 2 changes, the hold circuit 9 is reset.

Now, when the opening set value "is set to fully open, the electric control valve 1 is driven in the closing direction, and the valve body has stopped in the fully closed state, the control signal C is output due to some abnormality in the control device 2. If this continues, the drive device 3 further supplies current to the motor 4 in response to the control signal C. In this case, the valve body 5 of the electric control valve 1 is in the fully closed position and the drive is blocked. Therefore, the current flowing through the motor 4 is about to increase rapidly. At this time, the detected value lx of the supply current of the motor 4 detected by the current detector 6 becomes larger than the current setting value Is, and the timer 8 starts the timing operation. start, and
When the state of Jx>Is continues and the timer 8 times up, the hold circuit 9 gives a signal to the drive device 3, and the drive device 3 stops supplying current to the motor 4.

Next, when the opening setting value "is changed to the opening direction, the polarity of deviation 2 changes, the hold circuit 9 is reset,
The drive device 3 resumes supplying current to the motor 4, and the electric control valve 1 is driven in the opening direction. Even if an overcurrent attempts to flow to the motor 4 due to some abnormality in the control device 2 when the motor is fully opened, the same operation as described above will cause the motor 4 to
The supply of current to is immediately stopped.

The above-mentioned operation is performed not only when the electric control valve 1 is fully open or fully open, but also when the electric control valve 1 stops at an opening degree different from the opening degree setting value r, for example, due to the valve body 5 getting caught in a foreign object. As a result, the load on the motor 4 increases rapidly and lx>Is, and the drive device 3 stops supplying current to the motor 4. Furthermore, when the valve body 5 stops due to a foreign object being caught, but the foreign object is removed in a short time due to the action of fluid, etc., the load on the motor 4 decreases at the same time, so lx<Is, and the hold circuit 9 is transferred from the timer 8 to the hold circuit 9. No signal is given and the drive device 3 does not stop supplying current to the motor 4.

Therefore, the electric control valve 1 does not stop frequently due to fluid containing foreign matter.

<Effects of the Invention> As explained above, in the present invention, the current supplied to the motor that drives the electric control valve is detected, and when this current becomes thicker than a set value, the supply of current to the motor is stopped. This eliminates the need for conventional limit and foot switches to detect fully open and fully closed, simplifying the configuration of the electric control valve and reducing costs.Furthermore, the valve body can stop due to foreign matter getting caught in it. Since the supply of current to the motor can be immediately stopped even when the electric valve operator of the present invention , it can be stopped with the valve body pushed in.

[Brief explanation of drawings]

The drawing is a block diagram showing the basic configuration of an embodiment of the present invention. 1...-Electric control valve 2--Control device 3-Drive device 4--Motor 6--Current detector 7-Comparator 8--Timer 9--Hold circuit

Claims (2)

[Claims] (1) In a motorized valve operator consisting of a closed loop control system having a control device that controls the opening degree of the motorized valve and a drive device that drives the motorized valve, current detection detects the supply current of the motor that drives the motorized valve. a comparison means for comparing the current value detected by the current detection means with a set current value; a timer means for performing a timing operation according to the output of the comparison means; and a timer means for keeping the output of the timer means constant. and a signal holding means for applying a signal to the drive device, the electric valve operating device being characterized in that it stops supplying current to the motor when the current supplied to the motor exceeds a certain value. (2) The electric valve operating device according to claim 1, wherein the signal holding means is reset when the polarity of the deviation between the opening degree setting value and the opening degree feedback value of the electric valve changes.