JPH04130504A - Flow rate controller - Google Patents

Abstract

PURPOSE:To prevent a valve from being clogged with dust by alternately and periodically increasing/decreasing opening degree of plural valves provided in series based on the measurement result with a flowmeter. CONSTITUTION:A valve part 2 consists of two valves 21 and 22 provided in series with respect to a pipe line 1 and the opening degree of these valves 21 and 22 are respectively controlled by a control circuit 4 and alternately increased/decreased at a prescribed time interval. Either one of these valves is always kept at a set opening degree (varies corresponding to a detection result of a sensor part 3) to obtain the value of a set flow rate and the opening degree of the other valve is kept at that enough larger than that of the former valve. Thus, even if the valve to be kept at the set opening degree is clogged with dust, the dust can pass through the valve because the opening degree of the valve is increased after a prescribed period of time and clogging of the valve can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a flow rate control device for controlling the flow rate of fluid flowing in a pipe.

``Prior Art J'' For example, there is a device that uses a thermal flowmeter to control the flow rate of fluid flowing in a pipe.A thermal flowmeter heats the fluid flowing in a pipe from the outside. The temperature difference of the fluid before and after the heating point is also measured, and the flow rate is determined from that temperature difference and the specific heat of the fluid. A valve is provided in the flowmeter, and the flow rate is feedback-controlled by adjusting the opening degree of the valve based on the measurement results of the thermal flowmeter.

``Problem to be Solved by the Invention'' By the way, in the above-mentioned flow control device that adjusts the valve opening based on the measurement results of a flowmeter, control becomes uncontrollable if the valve is clogged with dirt. It is. In particular, flow rate control devices that use thermal flowmeters are generally used in a small valve opening range, and even at maximum flow rate, the valve opening is only a few tens of micrometers. They are extremely small, and are therefore very susceptible to becoming clogged with dust, and there has been a demand for an improvement.

"Means for Solving the Problems" The present invention measures the flow rate of fluid flowing in a pipeline using a flowmeter, and adjusts the opening degree of a valve provided in the middle of the pipeline based on the measurement result. A flow rate control device configured to control a flow rate by providing a plurality of the valves in series, and adjusting the opening degrees of the valves alternately and periodically based on the meter of the flowmeter, respectively. It is characterized by being configured so that it can be increased or decreased.

"Operation" The flow rate control device of the present invention controls the flow rate by adjusting the opening degrees of a plurality of valves provided in series based on the measurement results by the flowmeter, and the opening degrees of these valves are alternately adjusted. And it is made to increase and decrease periodically. Then, the opening degree of one of the valves will always be the set opening degree to obtain the set flow rate.
In addition, by setting the opening degree of the other valve to be sufficiently larger than that, the flow rate of the fluid flowing through the pipe line is determined by the valve having the set opening degree and is maintained at the set value. Furthermore, even if dirt gets caught in the valve, the opening degree of the knob is increased after a predetermined period of time, so the dirt can easily pass through and the pipe line will not become clogged.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a diagram showing the overall schematic configuration of the flow rate control device of this embodiment, in which reference numeral I indicates a pipe through which the fluid to be controlled flows, 2 indicates a valve section provided in the middle of the pipe 1, and 3 indicates a pipe line through which the fluid to be controlled flows. A sensor section 4 consisting of a thermal flowmeter is a control circuit, and this control a circuit 4 compares the output signal from the sensor section 3 with a flow rate setting signal set from the outside, and controls the pipe line 1. The valve portion 2 is controlled by foot so that the flow rate of the flowing fluid is at a set value.

As shown in FIG. 2, the valve section 2 is composed of two valves 21 and 22 arranged in series with respect to the pipe line l, and the opening degrees of these valves 21 and 22 are controlled by the control circuit 4, respectively. It is controlled as shown in FIG. That is, the opening degrees of these valves 21 and 22 are alternately increased and decreased at predetermined time intervals, and when the opening degree of one valve 21 (22) is increased, the opening degree of the other valve 22 (21) is increased. The degree is set to be small. Then, the opening degree of one of the valves is always maintained at the set opening degree to obtain the set flow rate value (this changes every moment according to the detection result of the sensor unit 3), and the opening degree of the other valve is made to be sufficiently larger than that.

Further, as shown in FIG. 4, the sensor section 3 is composed of a heating element 32 attached to the outside of the conduit 1, and a pair of temperature sensors 33 and 34 attached before and after the heating element 32. It is something that That is, this sensor section 3 is a thermal flow meter itself, and uses a heating element 32 to heat the fluid flowing in the pipe 1, and uses temperature sensors 33 and 34 to measure the temperature of the fluid before and after heating, respectively. Difference Δ
The calculation unit 35 calculates the fluid flow rate (mass flow rate) Qs based on the following equation (1) from T and the value of the constant pressure specific heat cp of the fluid, and outputs the result to the control circuit 4. ing.

ΔT=−Cp−Qm (k is a constant)・−・・−(1
) In the flow rate control device having the above configuration, by setting the opening degree setting pattern of each valve 2122 as shown in FIG. This can effectively eliminate the problem of dust clogging the 22. In other words, always? The opening of one of these valves is maintained at the set opening to obtain the set flow rate value, and the set opening is sufficiently small compared to the opening of the other valve. The flow rate of the fluid flowing through path 1 is determined by the set opening degree of this valve,
Therefore, the flow rate will be maintained at the set value. Even if dirt gets caught in the valve, the opening degree of the valve is increased after a predetermined period of time, so the dirt can easily pass through, and the valve will not become clogged. Therefore, it is particularly suitable for use when the valve is used in a small opening range and is easily clogged with dust.

In addition, when the fluid to be controlled is pulsating, that is, when the flow rate increases and decreases periodically, the conventional flow rate t $
Although the J m device did not necessarily provide sufficient accuracy, the above-described flow rate control device can control the flow rate with high precision even when pulsation occurs.

This will be explained with reference to FIG.

When the flow rate of the fluid flowing through the pipe line 1 is pulsating as shown by the solid line on the upper side of Fig. 5, the opening degree of each valve 21, 22 is shown on the lower side of Fig. 5 in response to the period. Control as follows. In other words, when the flow rate is larger than the average value, the opening degree of the upstream valve 21 is used as the set opening degree for obtaining the flow rate set value, and the opening degree of the downstream valve 22 is increased, and conversely, When the flow rate is smaller than the average value, the opening degree of the valve 22 on the downstream side is set to the set opening degree, and the opening degree of the valve 21 on the upstream side is increased.

In this way, pulsation can be eliminated by setting the opening degree of each valve 21, 22 in accordance with the period of pulsation, and the flow rate after passing through valve section 2 is indicated by the broken line on the upper side of Fig. 5. As shown, it is maintained at approximately the average value. Therefore, the flow rate detection accuracy in the sensor section 3 is improved, and as a result, highly accurate attendant control becomes possible.

In the above embodiment, a thermal flowmeter is used in the sensor section, but it is also possible to use not only a thermal flowmeter but other types of flowmeters.

"Effects of the Invention J As explained in detail above, the flow rate control device of the present invention alternately and periodically increases or decreases the opening degree of a plurality of valves provided in series based on the measurement results by a flowmeter. Therefore, the opening degree increase/decrease pattern of these valves is such that the opening degree of one of the valves is always the set opening degree to obtain the set flow rate value, and the opening degree of the other valve is always the set opening degree to obtain the set flow rate value. By setting the value to be sufficiently larger than that, the flow rate of the fluid flowing through the pipe can be maintained at the set value, and the valve can be effectively prevented from being clogged with dust. Even if pulsation occurs, the pulsation can be eliminated and highly accurate control can be performed.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the flow rate control device according to the present invention.
The figure shows the configuration of the valve part, Figure 3 shows the valve opening setting pattern, Figure 4 shows the configuration of the sensor part, and Figure 5 shows the opening setting pattern to eliminate pulsation. be. ...Pipe line, 2...Valve part, ...
...Sensor part (flow meter), 4...Control circuit, 1
．． 22...Valve, 2...Heating element, 33.34...Temperature sensor, 5...Calculating section.

Claims (1)

[Claims] A flow rate control device that is configured to measure the flow rate of fluid flowing in a pipeline using a flowmeter and control the flow rate by adjusting the opening degree of a valve installed in the middle of the pipeline based on the measurement results. A flow control device characterized in that a plurality of the valves are arranged in series, and the opening degrees of the valves are alternately and periodically increased or decreased based on the measurement results of the flowmeter. .