JPS60196819A - Flow rate intermittent control device to be driven by pulse - Google Patents

Abstract

PURPOSE:To improve the accuracy of the absolute value of a flow rate and the measuring accuracy of a controlled variable by using a quantitative pump to be driven by pulses and controlling discharge from the pump intermittently. CONSTITUTION:Current flowing from a power supply 19 into a driving coil 7 through a phototransistor 18 sucks a driving rod 6a, so that a diaphragm 6 is lifted up to a position 6b. Since a non-return valve 5 passing fluid only in the arrow W direction exists, an inlet valve 3 is opened and an outlet valve 4 is closed in accordance with the lift of the diaphragm 6 and a fixed quantity of an additive from an additive tank 10 is sucked into the body 2 of an electromagnetic quantitative pump 1. Since the quantity of the sucked additive is determined by the size of the body 2 and the diaphragm 6 and the stroke S of a diaphragm driving rod 6a, the adding quantity of the additive is also determined by determining the number of driving pulses to be applied to the pump 1. During the period that a necessary controlled variable is less than a fixed value, the succeeding control meter operating cycle, i.e. the succeeding density measurement, is executed when a comparatively long period has been passed after the end of addition, so that precise density measurement can be performed after mixture or reaction of an additive or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pulse-driven intermittent flow rate control device, and more particularly, to a pulse-driven intermittent flow control device that controls a pulse-driven metering pump intermittently according to the output of a regulator that generates a time-proportional on-off operation signal. The present invention relates to a pulse-driven intermittent flow rate control device that is operated.

BACKGROUND OF THE INVENTION There is an increasing need to precisely control concentrations in process control, water quality control, and the like. In particular, in pH control related to neutralization reaction by addition of acid or alkali, there is a difficult problem in that a slight excess or deficiency of an additive can cause the pH value to vary significantly compared to the control target value. To solve this problem, it has been proposed to precisely control the flow rate of the additive using a pulse-driven metering pump such as an electromagnetic metering pump.

However, with conventional flow control using electromagnetic metering pumps,
Although the flow rate expressed as the amount added per unit time is precisely controlled, the addition is performed by a drive pulse based on the measured value of the controlled amount immediately after the previous addition. Therefore, when controlling the flow rate using conventional electromagnetic metering pumps, etc., the control amount, such as concentration measurement, is measured before the additive has been sufficiently mixed and reacted, resulting in a decrease in measurement accuracy and the control amount exceeding the target value. It has the disadvantage of easily causing overshoot.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art by providing a pulse-driven intermittent flow rate control device that uses a pulse-driven metering pump and makes the discharge from the pump intermittent. It is in.

Structure of the Invention In order to achieve the above object, the pulse-driven intermittent flow rate control device according to the present invention includes a regulator that generates an operation signal with a pulse width proportional to the required operation amount for the flow rate, and a controller that generates pulses continuously at a constant cycle. A configuration is used that includes a pulse generator that controls the operation signal, a gate circuit that passes pulses from the pulse generator only for a time corresponding to the pulse width of the operation signal, and a metering pump that is driven by the pulses from the gate circuit.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1st
The figure shows an electromagnetic metering pump as an example of a pulse-driven metering pump used in the device of the present invention, but the present invention is not limited to the electromagnetic pump shown in the figure, but includes step motors, servo mechanisms, variable speed motors, etc. Even if a pump uses this mechanism, it is sufficient if the pump discharges a constant amount of acid with each drive pulse. An inlet valve 3 is attached to the suction port of the main body 2 of the electromagnetic metering pump l, and an outlet valve 4 is attached to the discharge port. A reverse valve 5 is attached to the outside of the inlet valve 3 and outlet valve 4 when viewed from the main body 2.

The body 2 has a rigid peripheral wall and a bottom wall and a top closed by a diaphragm 6.

A drive coil 7 is arranged around a drive rod 6a integrally connected to the diaphragm 6, and a control circuit 8 is connected to this drive coil 7. When the coil 7 is energized, the drive rod 6a is attracted until it comes into contact with the stopper 9, bending the diaphragm 6 to the position indicated by the dashed line 6b,
The volume of the main body 2 is increased by the amount of curvature. Therefore, the stroke S of the drive rod is from the deenergized position shown by the solid line in FIG. 1 to the position where it abuts the stopper 9. Further, by moving the stopper 9 as shown by the arrow X, the size of the stroke S can be adjusted.

The suction side of the electromagnetic metering pump l is connected to the additive tank lO via a pipe line.
The discharge side thereof is connected to the processing tank 11 via a pipe line. In the processing tank 11, a stirrer 12 stirs the added additive with the tank liquid, and a delivery pump 13 sends the tank liquid out of the tank as necessary.

FIG. 2 is an explanatory diagram of one embodiment of the electrical circuit in the apparatus of the present invention. It is connected to the input of the gate circuit 16. The light emitting diode 17 is energized by the output of the gate circuit 16, and the light from the first light emitting diode 17 makes the phototransistor 18 conductive, and current from the power source 19 flows through the coil 7.

The operation will be explained with reference to FIGS. 3A to 3E. The regulator 15 operates at a constant cycle To, generates an operation signal in an on-off format with a pulse width Tc, and makes the ratio (Tc/To) of the pulse width of the on signal to the cycle proportional to the magnitude of the operation amount. It shall be assumed that The pulse generator 14 has a pulse width t+(
7) Generate pulses continuously. Preferably, regulator 1
The period T of the pulse generator is selected so that a plurality of pulses from the pulse generator 14 reach the gate circuit 16 within one period of the operation signal No. 5.

The gate circuit 16 has a pulse generator 1 at its input, for example.
When the signal from 4 and the signal from regulator 15 are simultaneously present, the pulse generator 14 has the same period T and the same pulse width 1, as shown in FIG. 3C. generates a pulse of 0
The gate circuit 16 used in the present invention only needs to pass the pulse from the pulse generator 14 during the pulse width TC of the signal from the regulator 15, and does not necessarily need to be an AND circuit.

The signal from the gate circuit 16 passes through the light emitting diode 17 and returns to the ground circuit, but the light generated from the light emitting diode 17 at this time drives the phototransistor 18 inserted into the power supply circuit of the drive coil 7 of the electromagnetic metering pump l. Make conductive. Therefore, the current flowing from the power supply 19 to the drive coil 7 via the phototransistor 18 is transmitted to the drive rod 6a.
By suctioning the diaphragm 6, the diaphragm 6 is pulled up to the position indicated by the dashed line 6b. Due to the presence of the check valve 5 that allows fluid to flow only in the direction of the arrow W, the large mouth valve 3 opens and the outlet valve 4 closes in response to the above-mentioned pulling up of the diaphragm 6, and only a certain amount of the additive from the additive tank 1 ( ) is released. It is sucked into the main body 2 of the electromagnetic metering pump l.The amount of the sucked additive is determined by the dimensions of the main unit 2 and the diaphragm 6, and the stroke S of the diaphragm drive rod 6a. When the number of driving pulses to be generated is determined as shown in Fig. 3C,
The amount of additive added is also determined.

One feature of the present invention is that the flow rate Q corresponds to the amount of additive added, etc.
(FIG. 1) can be determined accurately as described above. In the electromagnetic metering pump l, it is also possible to adjust the discharge amount per time by the stroke length of the diaphragm drive rod 6a, but the stroke length can be adjusted by using a mechanical position that is difficult to obtain with high precision, that is, a stopper. 9 position adjustment is required.2 The present invention accurately adjusts the flow rate corresponding to the inflow amount of additives, etc. without using complicated mechanical position adjustment and only by electrical adjustment, and achieves high adjustment. Accurate flow rate and control can be performed.

In comparison with the conventional technology, conventional flow rate control using an electromagnetic metering pump etc., for example, monitors the deviation of the controlled amount in a controlled manner, and controls the operating pulse p at a pulse period that changes depending on the magnitude of the deviation as shown in Fig. 3F. All of these operating pulses p are continuously applied to an electromagnetic metering pump or the like. In this case, it is difficult to perform the high-precision flow rate adjustment of the present invention by adjusting the stroke number described below. Furthermore, the operation pulse p as shown in FIG. 3F with small pulse interval fluctuation is J! ! If the additive is added to the pump continuously, there is a high possibility that the additive is being added even when the concentration of the treated liquid is detected by the concentration meter, and even if addition is not continued, the time from the end of addition to the concentration detection is likely to be high. Since the time is too short, it is difficult to accurately detect the moisture content, and the flow rate must be controlled using measured values with low precision.

In contrast, in the present invention, 3T in FIG. 3C.

As shown in the pulseless periods such as 2T, 4T, etc.
As long as the required operation amount is below a certain value, the subsequent controller operation cycle, that is, the subsequent concentration measurement, will be performed after a considerable time has passed after the completion of addition. Concentration measurements can be made. Therefore, the flow rate control device of the present invention can perform precise flow rate control in accordance with a specific purpose of flow rate control. Furthermore, a situation in which a no-cycle period does not occur occurs when the amount of required operation is large, so it can be considered that there is no need for very high adjustment accuracy.

It is preferable that the period and pulse width of the pulse from the pulse generator 14 are not limited to T, , t, etc. in FIG. 3B, but are variable.
It is preferable to make it changeable like T2 and t2 in the figure. Third
FIG. shows the output of the gate circuit 16 when N.
Since the output of the gate circuit 16 in this case has a large pulse width, it can be used not only for the electromagnetic metering pump l but also for an electromagnetic valve (not shown) or the like.

As expected from the comparison of Figures 3A to 3E, control is achieved by synchronizing the output of the pulse generator 14 and the output of the regulator 15 or by providing a phase difference between the two outputs. It is also possible to change the aspect.

As described in detail, the pulse-driven intermittent flow rate control device according to the present invention is configured to intermittently drive a metering pump driven by a pulse signal, and therefore has the following effects.

(a) A metering pump with accurate discharge amount is used as the operating end device, and a non-discharge time is set according to the required operation amount after the end of discharge and before the start of measurement, which improves the accuracy of the absolute value of the flow rate and the control amount. At the same time, it is possible to improve the measurement accuracy of the flow rate and to improve the quality of control such as reducing overshoot with respect to the control target value, thereby significantly improving the accuracy of flow rate control related to manufacturing processes, etc. I can do that.

(b) Since the number of strokes corresponding to the discharge amount is controlled with high precision using pulse signals, by monitoring and recording the number of pulses, the flow rate and cumulative discharge amount of the fluid to be controlled can be monitored and recorded.

(c) Since the control signal circuit and the drive circuit for operating terminal devices such as pumps can be insulated using light emitting diodes, phototransistors, etc., highly accurate flow rate control can be performed using a small circuit with a small current.

(d) An electromagnetic metering pump can also be used when the regulator output is a so-called on-off signal.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the intermittent flow rate control device, FIG. 2 is a schematic sectional view of the electric circuit, and FIGS. 3A to 3F are time charts of the electric circuit. ■...Electromagnetic metering pump, 14...Pulse generator, 1
5...Adjuster, 16...Gate circuit, Q...Flow rate, Tc...Pulse width proportional to the manipulated variable, T,, T2
...Pulse period of the pulse generator. Patent Applicant Okura Electric Co., Ltd. Patent Attorney Agent Patent Attorney Tsugube Ichito Figure 1 Figure 2

Claims (1)

[Claims] A regulator that generates an operation signal with a pulse width proportional to the required operation amount for the flow rate, a pulse generator that continuously generates pulses at a constant period, and a pulse from the pulse generator that is generated only for a time equal to the pulse width of the operation signal. A pulse-driven intermittent flow rate control device comprising a gate circuit 4 that passes through a gate circuit, and a metering pump driven by pulses from the gate circuit.