JPS5815802B2 - flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate control device for supplying water to a water storage tank or pond (hereinafter simply referred to as a pond) via an electric valve and allowing an arbitrary amount of water to flow out from the pond.

FIG. 1 shows a control system of this type of conventional flow rate control device.

In this figure, 11 is a pond, 12 is a water level detector that detects the water level of the pond 11, 13 is a converter that converts the displacement of this water level detector 12 into an electric signal, 14 is a controller, 15 is a switching control device,
16 is an inflow motor operated valve operated by a constant speed motor 17.

FIG. 2 shows the valve opening-flow rate characteristics of sluice valves, butterfly valves, funnel valves, etc. currently in practical use as motor-operated valves 16.

When controlling the water level of the pond 11 at a constant level around an arbitrary point using the device shown in FIG. 14, and if the measured value is higher than the target value, a command to close the valve, and if it is lower than the target value, a command to open the valve is given to the reversible opening/closing device 14 of the valve operating motor 17 in constant speed operation, thereby controlling the flow rate. However, the amount of outflow from pond 11 is Q.

When the amount is small, the motor-operated valve 16 operates in the valve opening range of 0 to 10 as shown in FIG.

However, in this region, as is clear from the characteristics in Figure 2, the change in flow rate due to minute changes in the valve opening is extremely large, and therefore, the water level fluctuation ΔH in the pond 11 caused by opening and closing of the valve becomes too large. It is difficult to operate the water level control loop stably.

In view of this point, it is an object of the present invention to provide a flow rate control device by opening and closing an inflow valve, which can stably control the water level of a pond regardless of the degree of opening of the valve.

The present invention will be described below with reference to the drawings. In the present invention, as shown in one embodiment in FIG. It uses a converter 18 in which SIRISK positive and inverse converters are connected in reverse parallel, and is equipped with a gate-controlled phase control device 19 for making it a variable speed power supply.
A converter 20 converts the valve opening degree of valve opening 6 into an electric signal V, and this valve opening degree signal Vi is converted into a required waveform output V.

A function generator 21 is provided to convert the function generator 21 into
The output is manually inputted to the phase control device 19 as an operating speed command for the valve operation electric motor 17, and other parts are the same as those in FIG. 1, so a description thereof will be omitted.

The converter 20 used has the characteristics shown in FIG. 4, and the function generator 21 has the characteristics shown in FIG. 5.

In FIG. 5, the horizontal axis is the input voltage and the vertical axis is the output.

FIG. 3 is a diagram showing the relationship between the valve opening degree θ and the flow rate Qi.

That is, from FIG. 4, the output Vi of the converter 20 is proportional to the valve opening degree, and! , the output V of the function generator 21.

In other words, the operating speed of the valve operating motor 17 is determined by the converter 2.
Since the relationship shown in FIG. 5 exists for the output Vi of 0, the inflow valve 1
The valve opening degree and valve opening/closing speed of No. 6 have the characteristics shown in FIG.

From the characteristics shown in Fig. 6, the valve opening is small (outflow amount Q).

It can be seen that in the region where the valve opening degree is small, the valve opening and closing speed is slow, and therefore the flow rate change is small, and in the region where the valve opening is large, the valve opening and closing speed is fast, and therefore the flow rate change is large.

FIG. 7 shows the relationship between the time during valve operation and the flow rate, using the inflow valve opening degree or the initial flow rate as a parameter.

In FIG. 7, the horizontal axis represents the valve operation time taken from the start of valve opening/closing, and t'ro to tTN is the time required to fully open the valve.

The valley point on the vertical axis is Q. 〜QN represents the initial flow rate, and Qo
=O represents a state in which the valve is fully open.

The solid line portion pointing to the right with respect to the vertical axis represents the case where the valve is “open”, and the portion pointing leftward with a dotted line represents the case where the valve is “closed”.

As can be seen from this characteristic diagram, regardless of the initial flow rate, during valve operation, the change in flow rate with respect to time can be controlled stably and in a straight line with the same desirably the same sensitivity.

In this way, in the present invention, an inflow valve opening signal is obtained, and this opening signal is converted by a function generator to determine the operating speed of the valve operating motor, so that the flow rate change is small in a region where the valve opening is small. Since pressure is applied to control the valve opening, instability in control in a region where the valve opening is small can be resolved, and stable and uniform control can be achieved over the entire range from fully closed to fully open.

In the above embodiment, the case where the water level of the pond is stably controlled by opening and closing the inlet valve has been explained, but it is also possible to automatically control the flow rate of fluid using valves used for various purposes such as discharge valves, extraction valves, flow rate control valves, etc. In this case, the present invention can be applied to all systems in which the relationship between the valve opening degree and the flow rate has non-linearity as shown in FIG.

For example, in equipment that automatically controls the water level of a pump well or receiving well in a water treatment plant using an inlet valve, or automatically controls the amount of water delivered using a discharge valve, the amount of water supplied decreases considerably at night, and During the first phase water circulation period when construction is carried out in sections, the amount of water to be treated will be reduced to just a few minutes of its planned capacity, so it will be necessary to extremely restrict the inflow or discharge valves. As mentioned above, with conventional methods, automatic control is difficult, and for this reason, there are many cases of manual operation, and even though the water treatment plant is automated, a separate operator is required. There was a need to do so.

Further, an automatic fluid flow rate control device using a valve is required to be able to operate stably regardless of the target flow rate value, but in practice this condition has often not been satisfied.

In these cases, if the method of the present invention is applied, the operation of the mechanical equipment or plant can be almost completely automated.

Moreover, when performing valve control in a fluid pressure system, it is effective in suppressing the occurrence of merging and surging phenomena caused by an excessive rate of change in flow rate, and has the advantage of being able to be economically designed.

According to the present invention described above, it is possible to provide a flow rate control device by opening and closing an inflow valve that can stably control the water level of a pond regardless of the magnitude of the valve opening.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional flow rate control device by opening and closing an inflow valve, Fig. 2 is a valve opening-flow rate characteristic diagram of the electric inflow valve shown in Fig. 1,
FIG. 3a is a system diagram of an embodiment of the present invention, and the same figure is a
Figure 4 is a diagram explaining the relationship between the electric valve opening and the inflow amount, Figure 4 is a valve opening-output voltage characteristic diagram of the converter of the same example, and Figure 5 is the input voltage of the function generator of the same example. - Output voltage characteristic diagram, FIG. 6 is a valve opening degree-valve opening/closing strength characteristic diagram in the same embodiment, and FIG. 7 is a valve operating time-flow rate characteristic diagram in the same embodiment. 11...Pond, 12...Water level detector, 1
3...Water level-electrical signal converter, 14...
・Controller, 15...Opening/closing control device, 16...
...Electric valve, 17...Valve operation motor, 20.
...Valve opening - electrical signal converter, 21...
Function generator, 18...Reversible, variable voltage power supply, 1
9... Phase control device.

Claims (1)

[Claims] 1 Equipment that supplies water to a water storage tank or pond via an electric valve, and allows water to flow out from the pond at a desired rate.The valve operation electric motor is operated by the valve opening/closing signal from the water level gauge, and the water level in the pond is maintained at a constant water level around an arbitrary point. In the control device, a converter for obtaining a valve opening signal corresponding to the opening of the electric valve and a function generator whose output becomes significantly small in a region where the valve opening signal is small are provided, and the output of this function generator is used to control the valve opening. A flow control device that uses the speed command value of the operating motor to reduce the opening/closing speed of the electric valve in a region where the valve opening is small.