JPH06119056A - Flow rate controller - Google Patents

Abstract

PURPOSE:To control a flow rate at abnormal time so as to prevent the occurrence of the suspension of water supply by converting the opening signal of a flow rate control valve based on a previously decided function curve and switching and outputting a converted flow rate signal. CONSTITUTION:Usually a set value from a high-order CPU is inputted to a flow controller 1. The opening of the flow rate control value 2 is controlled based on a deviation of the flow rate measured value of a flow meter 3 from the set value so as to reduce the difference between the flow rate measured value and the set value. On the other hand, an opening/flow rate conversion circuit 6 calculates the flow rate obtd. by converting the opening of the flow rate control valve 2 based on the previously decided function curve, and outputs it to a deviation detection circuit 7. When the flow rate controller 1 controls the flow rate control valve 2 in a close direction because the measured value larger than the set value is indicated on account of the abnormality of the flow meter, the converted flow rate value from the conversion circuit 6 decreases and the deviation exceeds a prescribed one in the deviation detecting circuit 7. At that time, an abnormal signal holding circuit 8 operates a switch 4, inputs the converted flow rate value to the flow rate controller 1, executes PID control with the set value and continuous the flow rate control at the time of abnormality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate control device used in water supply and sewerage facilities.

[0002]

2. Description of the Related Art Conventional flow rate control is given as a set value from another facility by a flow rate controller, and the flow rate value on the site side is measured by a flow meter so that the set value is obtained.
The PID control is executed in the controller with the set value and the flow rate value, and the flow rate control valve is operated to control the deviation so that the flow rate value becomes a predetermined value.

That is, the actual flow rate is measured so as to obtain a given flow rate set value, and the opening degree of the flow rate control valve is controlled so that there is no deviation between the measured flow rate value and the set flow rate value.

However, when the flow rate value of the controlled object, which is a basic item for performing the above control operation, becomes abnormal, closed loop processing as a control system causes inconvenience.

[0005] Here, when an output that seems to be held within the measurement span is output as an abnormality of the flow meter, if the value is larger than the set value, the flow controller outputs a closed output to the flow control valve. However, since the flow rate is abnormal, the output signal does not move and the flow rate control valve is fully closed. If it is fully closed, water supply will be cut off and it will become a social problem.

On the contrary to the above, when the flowmeter becomes abnormal at a value lower than the set value and the signal is held, the flow control valve goes to full opening, and unnecessary water is continuously sent. In other words, it will not be an effective use of water.

[0007]

The sensor (flow meter) for measuring the flow rate of the object to be controlled in this way uses a highly reliable sensor, but it may be abnormal. Therefore, an object of the present invention is to provide a flow rate control device that controls flow rate even when an abnormality occurs, and executes control that does not cause water cutoff or the like.

[0008]

According to the present invention, there is provided a flow meter for measuring a flow rate of a fluid and outputting a measured flow rate signal, and a flow rate control valve connected in series with the flow meter for regulating the flow rate of the fluid. An opening meter for detecting the opening of the flow control valve and outputting an opening signal, and an opening / flow conversion circuit for converting the opening signal based on a predetermined function curve and outputting the converted flow signal And a deviation detector that compares the measured flow rate signal with the converted flow rate signal and outputs a flow rate deviation signal, and outputs a flow meter abnormality signal when the flow rate deviation signal exceeds a preset set flow rate deviation value, Input an abnormal signal holding circuit that continuously holds the abnormal signal and the measured flow rate signal and the converted flow rate signal, and always select the measured flow rate signal.If there is a flow meter abnormal signal, select the converted flow rate signal to instruct. A switch that outputs a flow rate signal and the indicated flow rate No. and enter a predetermined flow rate set value, a flow control device comprising comprising a flow controller for controlling the opening of the flow control valve, a on the basis of these deviations.

[0009]

In the flow rate control device of the present invention, the flow rate of the fluid is measured, the measured flow rate signal is output, and the flow rate control valve is connected in series with the flow meter to control the flow rate of the fluid. The opening degree is detected and an opening degree signal is output, the opening degree signal is converted based on a predetermined function curve, the converted flow rate signal is output, the measured flow rate signal and the converted flow rate signal are compared, and a flow rate deviation signal is output. When the flow rate deviation signal exceeds the preset set flow rate deviation value, the flowmeter abnormality signal is output, the flowmeter abnormality signal is continuously retained, and the measured flow rate signal and the converted flow rate signal are input, Depending on the presence / absence of an abnormal signal, either the measured flow rate signal or the converted flow rate signal is output, the designated flow rate signal and a predetermined flow rate set value are input, and the opening of the flow rate control valve is controlled.

[0010]

EXAMPLE An example of the present invention will be described below. In FIG. 1, 3 is a flow meter that measures the flow rate of the fluid and outputs a measured flow rate signal, 2 is a flow rate control valve that is connected in series with the flow rate meter 3 to regulate the flow rate of the fluid, and 5a is the flow rate control valve 2 An opening meter that detects the opening of the valve and outputs an opening signal, 6 is an opening / flow rate conversion circuit that converts the opening signal based on a predetermined function curve, and outputs a converted flow rate signal, and 7 is an actual measurement A deviation detector that compares the flow rate signal with the converted flow rate signal and outputs a flow rate deviation signal, and 8 outputs a flow meter abnormality signal when the flow rate deviation signal exceeds a preset flow rate deviation value, and a flow meter abnormality An abnormal signal holding circuit 4 for continuously holding the signal, 4 is a switch for inputting the actually measured flow rate signal and the converted flow rate signal, and for outputting an instruction flow rate signal of either the actually measured flow rate signal or the converted flow rate signal depending on the presence or absence of the flow meter abnormality signal, 1 is the indicated flow rate signal and It is a flow rate controller that controls the opening of the flow rate control valve 2 by inputting the flow rate setting value. Even if the measured flow rate value becomes abnormal in the flow rate control, the opening / flow rate is converted by the conversion circuit 6. The flow rate control device has a function of switching to the converted flow rate value, continuing the current flow rate control, and notifying that the sensor is abnormal.

That is, on the upper CPU side, an opening / flow rate conversion circuit 6, which has a curve of the characteristics of the flow control valve and has data prepared as a function of the opening / flow rate, the actual measured flow rate,
A deviation detection circuit 7 that compares the calculated flow rate value from the opening / flow rate conversion circuit 6 and outputs a signal when the deviation exceeds a certain value, and an abnormal signal hold circuit 8 that receives the output signal and holds the abnormal signal Each circuit for performing

Further, the basic structure is provided with a switch 4 for giving a flow rate signal to the flow rate controller 1.

In the normal control mode, the set value from the host CPU enters the flow rate controller 1, and PID control is executed in the flow rate controller 1 while observing the deviation from the flow rate value measured by the flow meter 3 to adjust the flow rate. While controlling the opening degree of the valve 2, the difference from the flow rate measurement value of the flow meter 3 is reduced.

In the opening / flow rate conversion circuit 6, the flow rate value converted from the opening degree of the flow rate control valve 2 is calculated and output to the deviation detection circuit 7.

The actual measured flow rate value is also input to the deviation detection circuit 7, and the deviation detection circuit 7 compares the actually measured flow rate with the converted flow rate. Goes on going.

When the signal is held by a measurement value larger than the set value due to the abnormality of the flow meter, the flow controller 1 controls the flow control valve 2 in the closing direction and moves to lower the flow value. The converted flow rate value calculated by the opening / flow rate conversion circuit 6 is in the downward direction and exceeds the specified deviation in the deviation detection circuit 7.

With this deviation abnormality signal, the abnormality signal holding circuit 8 holds the signal and operates the external switch 4 to input the converted flow rate value to the flow rate controller 1 and PID between it and the set value.
The control is executed, and the flow rate control at the time of abnormality is continued with the converted flow rate value obtained from the flow rate control valve opening.

Similarly, even when the measured flow rate signal is held at a value smaller than the set value, the processing is performed in the same manner, and an abnormal situation such as water interruption can be avoided.

Further, this function can be utilized even during the maintenance of the sensor of the flow meter and the like, and the troublesome handling of human system can be saved.

[0020]

As described above, according to the present invention, the protection of the flow rate control can be carried out and the control stability is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a flow rate control device showing an embodiment of the present invention.

[Explanation of symbols]

 1 ... Flow controller 2 ... Flow control valve 3 ... Flow meter 4 ... Switcher 6 ... Opening / flow conversion circuit 7 ... Deviation detection circuit 8 ... Abnormal signal maintenance circuit

Claims (1)

[Claims] 1. A flow meter for measuring a flow rate of a fluid and outputting a measured flow rate signal, a flow rate control valve connected in series with the flow rate meter for controlling the flow rate of the fluid, and an opening of the flow rate control valve. Degree meter that detects the degree of opening and outputs an opening degree signal; an opening degree / flow rate conversion circuit that converts the opening degree signal based on a predetermined function curve and outputs a converted flow rate signal; A deviation detector that compares the converted flow rate signal with the converted flow rate signal and outputs a flow rate deviation signal; and outputs a flow meter abnormality signal when the flow rate deviation signal exceeds a preset set flow rate deviation value Input an abnormal signal holding circuit that continues to hold a signal and the measured flow rate signal and the converted flow rate signal, always select the measured flow rate, and select the converted flow rate signal when the flow meter abnormal signal is present. Switch that outputs the indicated flow rate signal And a flow rate controller for inputting the instructed flow rate signal and a predetermined flow rate set value and controlling the opening of the flow rate control valve based on these deviations.