KR20180050610A - Liquid flow rate control system - Google Patents

Abstract

The present disclosure relates to a flow control system and, more particularly, to a flow control system with a high degree of precision while being made at low production costs. According to one aspect of the present disclosure, the flow control system comprises: a flow adjusting unit, which adjusts the opening of a diaphragm to control the flow, wherein the diaphragm is initially provided in a state that the diaphragm is opened by a predetermined degree; an on/off valve arranged at the bottom of the flow adjusting unit; a flowmeter measuring the flow introduced to the flow adjusting unit; and a control unit controlling the opening and closing of the on/off valve and the degree of the opening of the diaphragm in the flow adjusting unit by comparing the actual flow measured by the flowmeter to a target flow, wherein the control unit starts a control operation in a state that the on/off valve is switched off.

Description

[0001] LIQUID FLOW RATE CONTROL SYSTEM [0002]

The present disclosure relates to a flow control system, and more particularly, to a flow control system capable of flow control with high precision while having a low manufacturing cost.

Herein, the background art relating to the present disclosure is provided, and these are not necessarily meant to be known arts.

A flow control system is a system provided for the delivery (or supply) of a desired flow rate and a change in flow rate, and generally includes a flow meter, a flow control valve and control means for controlling the operation thereof.

The operation of the flow control system is performed by a method in which the control means controls the opening of the flow control valve by comparing the flow rate sensed by the flow meter with the target flow rate.

Flow control systems are widely used in industries such as automobiles, semiconductors, plants, chemicals, and biotechnology, and the precision of flow control required by the industry is steadily increasing.

For this reason, various researches have been continuously carried out on each of the flowmeter, the flow control valve, and the control means constituting the flow control system. However, as the precision increases, the system price increases, which causes a heavy burden on the whole industry.

Particularly, as a flow control valve in the flow control system, an electric valve using a step motor is used, which has a very good precision, but is very expensive and is the biggest cause of system price increase.

In addition, since the motorized valve using the step motor does not have a separate flow rate correction function, there is a problem that hysteresis of the output flow rate occurs when the input end pressure fluctuates.

Such flow hunting can cause damage, such as inducing an unintended alarm of the flow monitoring equipment, or stopping the process.

Therefore, development of a technique for preventing flow hunting is required.

On the other hand, the flow control system has an example in which an ON / OFF valve is used.

However, in the case of control by the ON / OFF valve, it takes a longer time to control the valve by opening the valve according to the target flow rate in the closed state at the beginning of the flow control.

Therefore, in the initial flow control, there is a problem that a flow amount smaller than the target flow amount is discharged and reaches the target flow amount after a certain time, thereby affecting the process.

On the other hand, in various industrial fields, there is a demand for a flow control system for flow control when the target flow rate varies with time, and the demand for precise flow control of such flow control system is increasing.

It is an object of the present disclosure to provide a flow control system capable of preventing hunting of output flow rate due to fluctuation of input pressure.

The present disclosure aims at providing a flow control system capable of minimizing a difference between an actual flow rate and a target flow rate at the beginning of flow control.

It is an object of the present disclosure to provide a flow control system capable of minimizing a difference between a target flow rate and an actual flow rate that varies with time.

SUMMARY OF THE INVENTION Herein, a general summary of the present disclosure is provided, which should not be construed as limiting the scope of the present disclosure. of its features).

According to one aspect of the present disclosure, there is provided a flow rate regulator for regulating the flow rate by regulating the degree of opening of the diaphragm, wherein the initial diaphragm is pre- A flow rate regulator; An ON / OFF valve disposed downstream of the flow rate regulator; A flow meter for measuring a flow rate flowing into the flow rate regulator; And control means for controlling the opening degree of the diaphragm of the flow rate control unit and opening / closing of the ON / OFF valve by comparing the actual flow rate measured by the flow meter with a target flow rate, wherein the ON / And control means for starting the control.

In the flow rate control system according to an aspect of the present disclosure, the flow rate regulator may be provided such that the diaphragm is pre-opened by a predetermined amount by the control means.

In the flow rate control system according to one aspect of the present disclosure, the degree of preliminary opening of the diaphragm may be provided by the control means being adjusted based on the target flow rate.

According to this, since the flow hunting is prevented by the ON / OFF valve, the diaphragm is pre-opened before the start of the flow control, or is pre-opened by the control means, Can be minimized.

In the flow rate control system according to an aspect of the present disclosure, the flow rate regulator may include: a constant-pressure regulator whose opening degree is controlled by a pressure of fluid supplied to the diaphragm; And an electropneumatic regulator for regulating the pressure of the fluid supplied to the constant-pressure regulator.

Furthermore, in the flow rate control system according to an aspect of the present disclosure, the control means may be provided by pre-applying a positive current based on the target flow rate to the electropneumatic regulator to pre-open the diaphragm.

Further, in the flow rate control system according to an aspect of the present disclosure, the amount of the electric current pre-applied to the electropneumatic regulator may be a current corresponding to 80 to 90% of the current magnitude to be applied for the target flow rate have.

Further, in the flow rate control system according to an aspect of the present disclosure, the flow rate control system may further include an upper control unit that receives the target flow rate information from the outside and applies the flow rate information to the control unit.

On the other hand, in the flow rate control system according to an aspect of the present disclosure, the target flow rate information includes a first set flow rate Q1, a second set flow rate Q2 different from the first set flow rate, Q2) and the time interval (T) required to change from the first set flow rate (Q1) to the second set flow rate (Q2) And controlling the flow rate regulator by comparing the flow rate measured by the flow meter with the control flow rate Qa that varies according to the set time interval Ta computed based on the measured time interval Ta.

This makes it possible to control the difference between the target flow rate and the actual flow rate that varies with time to be minimized.

Here, the control flow rate Qa is varied by the variable flow rate Qs set for each set time interval Ta with the first set flow rate Q1 as an initial value, and after the elapse of the time interval T, 2 set flow rate Q2.

The set variable flow rate Qs is calculated by calculating a flow rate variation amount Qc = Q2-Q1 and a control flow rate variation time Tc = T / Ta; And calculating the set variable flow rate (Qs) by dividing the flow rate variation amount by the control flow rate variation time (Qc / Tc).

In the flow rate control system according to an aspect of the present disclosure, the target flow rate information includes at least three set flow rates (Q1, Q2, Qn; an integer of n? 3) and at least two or more times Wherein the control means is operable to determine a control flow rate (Tm) that varies according to the set time interval Ta computed based on each of the at least two time intervals and the two set flow rates associated therewith Qa) and the flow rate measured by the flow meter to control the flow rate regulator.

Accordingly, even when the rate of change of the target flow rate varies with time, the difference between the target flow rate and the actual flow rate can be minimized and controlled.

According to the flow rate control system according to an aspect of the present disclosure, since the diaphragm is pre-opened prior to the start of the flow rate control or is pre-opened by the control means, flow hunting is prevented, The difference between the flow rate and the target flow rate can be minimized.

According to the flow rate control system according to an aspect of the present disclosure, it is possible to control so that the difference between the target flow rate and the actual flow rate that varies with time is minimized.

According to the flow rate control system according to one aspect of the present disclosure, even when the rate of change of the target flow rate varies with time, the difference between the target flow rate and the actual flow rate can be minimized and controlled.

The flow control system according to an aspect of the present disclosure has an advantage that flow control with high precision can be performed while employing a constant pressure regulator instead of a motor valve using an expensive step motor. In addition, the manufacturing cost is reduced.

1 is a conceptual illustration of a flow control system in accordance with an embodiment of the present disclosure;
FIG. 2 is a view showing a configuration of a flow control system according to FIG. 1;
Figure 3 conceptually illustrates a flow control system according to another embodiment of the present disclosure;
FIG. 4 is a diagram showing the results of flow control by the flow control system of FIG. 3. FIG.

The present disclosure will now be described in detail with reference to the accompanying drawings.

However, the present invention is not limited to these embodiments. For example, the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit and scope of the present invention. It should be understood that the embodiments described herein are to be understood as the embodiments disclosed herein.

The terms used in this specification and claims are to be understood by the inventor as a concept selected for the convenience of explanation and should not be construed in a linguistic sense in understanding the meaning thereof but should be appropriately interpreted in accordance with the technical idea of the present disclosure will be.

In addition, the flow control system according to the present disclosure is not limited in its field of application and can be employed throughout the entire industry such as automobile, semiconductor, plant, chemical, and biotechnology fields. For example, in the case of the semiconductor industry, A step of applying or depositing a film to form a film on a wafer requiring injection of a chemical liquid necessary for the process, an exposure step of transferring a pattern of the photomask to the photoresist film applied on the wafer, an etching process of removing the film formed on the wafer , And a cleaning process for cleaning the surface of the wafer.

FIG. 1 is a conceptual view of a flow control system according to an embodiment of the present disclosure, and FIG. 2 is a diagram showing a configuration of a flow control system according to FIG.

1 and 2, the flow rate control system 100 according to the present embodiment includes a flow rate regulator 101, an ON / OFF valve 113, a flow meter 130, and a control means 140 .

In addition, the control unit 140 receives information necessary for the control operation of the control unit 140 from the outside and provides the information to the control unit 140. The upper control unit 150 processes the information input from the outside and provides the processed information to the control unit 140. [ May be further included.

The flow rate regulator 101 adjusts the flow rate by adjusting the opening degree of the diaphragm (not shown).

Here, the diaphragm is pre-opened by an initially set amount.

In the present embodiment, the flow rate regulator 101 regulates the pressure of the fluid supplied to the constant-pressure regulator 110 and the constant-pressure regulator 110 whose opening degree is regulated by the pressure of the fluid to which the diaphragm is fed And may be provided as a pneumatic regulator 120.

The ON / OFF valve 113 is disposed downstream of the flow rate regulator 101 and functions to selectively block the flow from the flow rate regulator 101 to the outside.

The flowmeter 130 measures the flow rate of the fluid flowing into the flow rate regulator 101.

The control means 140 compares the actual flow rate measured by the flow meter 130 with the target flow rate as a control reference and controls the opening degree of the diaphragm of the flow rate regulator 101 and the opening and closing of the ON / OFF valve .

Here, the control means 140 is provided to start the control when the ON / OFF valve 113 is OFF.

The flow regulator 110 adjusts the flow rate according to the opening and closing rate of the diaphragm (not shown) so that the opening and closing rate of the diaphragm (not shown) is controlled by the pressure of the air supplied from the pneumatic regulator 120 Respectively.

The flowmeter 130 is provided upstream of the constant-pressure regulator 110 in the flow direction to measure the flow rate. The type of the flowmeter 130 is not limited, but the ultrasonic flowmeter 130 minimizes the error in measuring the flow rate by the flowmeter It is preferable because it has an advantage that it can be performed.

The electro-pneumatic regulator 120 supplies air to the positive pressure regulator 110 to open and close the diaphragm provided in the positive pressure regulator 110. The air pressure regulator 120 regulates the pressure of air supplied to open the diaphragm, .

Here, the supplied air pressure is adjusted based on the difference between the target flow amount input from the outside through the upper control unit 150, which will be described later, and the flow rate sensed by the flow meter 130.

On the other hand, the electropneumatic regulator 120 preferably has heat exchange means for preventing the temperature of the air from rising to maintain the density of the air constant. This can be provided as a cooling tube that passes through the inside of the electropneumatic regulator 120 and performs heat exchange by contact with air.

The control means 140 controls the difference between the flow rate information sensed by the flow meter 130 and the target flow rate within an error range by feedback control.

Specifically, the controller receives the target flow amount input from the upper control unit 150, receives the flow rate information from the flow meter 130, compares sizes of the flow rate information, and then, based on the difference, ). ≪ / RTI >

The electropneumatic regulator 120 which receives the electrical signal regulates the opening degree of the diaphragm by supplying air having a pressure proportional to the magnitude of the electrical signal to the positive pressure regulator 110.

In the present embodiment, the diaphragm is pre-opened by an initially set amount or controlled by the control means 140 in a pre-opened state, so that the degree of opening of the diaphragm by the electropneumatic regulator 120 As the air pressure increases, the degree of opening decreases, and as the air pressure decreases, the degree of opening increases.

Thereby, the flow rate is changed, and the difference between the flow rate information input from the flow meter 130 and the target flow rate is corrected within the error range by repeating the above control operation by comparing the changed flow rate measured by the flow meter 130 and the target flow rate again Respectively.

On the other hand, in the present embodiment, the ON / OFF valve 113 causes the initial discharge flow rate to quickly reach the target flow rate.

Specifically, the target flow rate is supplied through the flow control system 200 by switching the ON / OFF valve 113 to the ON state after the flow rate discharged through the initial static pressure regulator 210 approaches the target flow rate do.

However, in this case, a considerable time (about 3 seconds) is required to bring the flow rate discharged through the initial static pressure regulator 210 to the target flow rate close to the target flow rate, and a configuration for improving the flow rate is required.

To this end, in the present embodiment, as described above, when the ON / OFF valve 113 is in the OFF state, the diaphragm is pre-opened to a predetermined amount or controlled by the control means 140 .

The diaphragm may be controlled such that a current corresponding to 80 to 90% of the current magnitude to be applied for discharge of the target flow rate is applied to the electropneumatic regulator 220 in the OFF state of the ON / OFF valve 113, Pre-Ready Open is made by the set amount.

According to this, since the constant-pressure regulator is pre-openedly opened by an amount that is set when the ON / OFF valve is in the OFF state, the flow rate discharged at the initial stage of discharge can quickly reach the target flow rate. According to the experiment of the present inventor, it was confirmed that a flow rate discharge with a difference of 1% or less with the target flow rate was achieved within about 1.5 seconds.

On the other hand, in the present embodiment, it is preferable that the electrical signal applied to the electropneumatic regulator 120 by the control means 140 is provided as an analog current signal of 4 to 20 mA.

The control by the current signal has the advantage of being less influenced by external noise than the control by the voltage signal.

On the other hand, the current control signal of 4 to 20 mA has an advantage in compatibility with the analog control standard.

The upper control unit 150 receives the target flow amount from the outside (for example, a process facility operator), and applies the flow rate to the control unit 140. In addition to the target flow rate, the upper control unit 150 receives various setting values for operating the process facility and controls the entire process facility. The information transfer between the upper control unit 150 and the control unit 140 is performed by communication.

According to the flow control system 100 according to the embodiment of the present invention described above, the valve for controlling the flow rate is provided as a low-cost constant-pressure regulator instead of an expensive motor valve, and the flow rate control through the constant- And it is possible to prevent sudden pressure fluctuation at the outlet side by the ON / OFF valve 113, thereby preventing flow hunting.

Also, since the diaphragm is pre-opened before the start of the flow control or is pre-opened by the control means, the difference between the actual output flow rate and the target flow rate at the initial stage of the flow control can be minimized.

FIG. 3 is a conceptual view of a flow control system according to another embodiment of the present disclosure, and FIG. 4 is a diagram showing a result of flow control by the flow control system of FIG.

Referring to Figs. 3 and 4, the flow control system 200 according to the present embodiment is the same as the above-described embodiment and configuration. However, there is a difference in the control operation by the control means 140, and because of such difference, it becomes possible to control the flow rate when the target flow rate varies with time.

Therefore, the description of the flow rate regulator 201, the ON / OFF valve 213, and the flow meter 230 is omitted in the foregoing description, and the control operation by the control means 240 will be described in detail below.

The control means 240 controls the opening degree of the flow rate control unit 201 by comparing the flow rate measured by the flow rate meter 230 with the control flow rate Qa, The flow rate is controlled so as to coincide with the control flow rate (Qa) within the error range.

In addition, the control means 240 performs feedback control of the flow rate passing through the flow rate regulator 201 while varying the control flow rate Qa by the variable flow rate Qs set per the set time interval Ta.

The upper control unit 250 receives various data for the entire system including the flow control system (e.g., the etching system) from the outside (e.g., the system operator), transfers the data to each control configuration (e.g., the lower control system) The second set flow rate Q2 is set at a first set flow rate Q1 different from the first set flow rate Q1 and a second set flow rate Q2 different from the first set flow rate. To the control unit 240. The control unit 240 receives the time interval T from the control unit 240,

In the conventional flow rate control system, the upper control unit has provided information on a constant set flow rate to the control means over time. In order to control the fluctuating flow rate over time, information of the set flow rate varied at regular time intervals is supplied to the control means The development cost for changing the system program of the high-level control unit is much required. In particular, repeated commands and data transmission / reception between the high-level control unit and the control unit cause a delay of the control time.

According to the embodiment of the present disclosure, it is sufficient that the upper control section 250 initially provides the information on the first and second set flow rates Q1 and Q2 and the time interval T as the target flow rate information, The controller 240 changes the control flow rate Qa by using the variable flow rate Qs set for the set time interval Ta so that the command and data are sent and received between the upper control unit 250 and the control unit 240 The time delay of the control can be prevented. As a result, accurate control of the flow rate that varies with time becomes possible.

In the present embodiment, the control means 240 calculates the control flow rate Qa from the first set flow rate Q1, the second set flow rate Q2 and the time interval T received from the upper control section 250 The control flow rate Qa after the elapse of the time interval T varies by the variable flow rate Qs set at the set time interval Ta with the first set flow rate Q1 as the initial value and the second set flow rate Q2 Respectively.

Specifically, the set variable flow rate Qs is calculated by: 1) calculating the flow rate variation amount Qc = Q2-Q1 and the control flow rate change number Tc = T / Ta; Qc is divided by the control flow rate change number Tc to calculate the variable flow rate Qs set by (Qc / Tc).

Here, it is preferable that the control fluctuation period Ta is 200 ms.

According to this, it is possible to prevent the control time delay due to an increase in the amount of data to be transmitted / received when the control fluctuation period Ta becomes short, while minimizing the flow error caused by the long control fluctuation period Ta.

Since the flow rate variation Qc can have a value (when the flow rate increases with time) or a negative value (when the flow rate decreases with time), the flow rate control by the control means 240 is time It is possible to precisely control the control flow rate to be linearly increased or decreased without delay.

Referring to FIG. 4, it is confirmed that the flow rate variation is linearly reduced from 800 mL / min, which is the first set flow rate Q1, to 500 mL / min, which is the second set flow rate Q2, for the time interval T Can

In the present embodiment, the target flow rate information includes at least three set flow rates (Q1, Q2, Qn; n is an integer of 3) and at least two time intervals (T1, n-1).

At this time, the control means 240 determines whether or not the control flow rate Qa, which is changed according to the set time interval Ta calculated based on at least two time intervals and two related set flow rates, And controlling the flow rate regulator 201 by comparing the flow rate of the fluid. Here, the control procedure for each individual time interval Tm is the same as that described above.

Accordingly, even when the rate of change of the target flow rate varies with time, the difference between the target flow rate and the actual flow rate can be minimized and controlled.

Claims (1)

A flow control unit for controlling the flow rate of the diaphragm by adjusting an opening degree of the diaphragm;
An ON / OFF valve disposed downstream of the flow rate regulator;
A flow meter for measuring a flow rate flowing into the flow rate regulator; And
And control means for controlling the opening degree of the diaphragm of the flow rate regulator and the opening and closing of the ON / OFF valve by comparing the actual flow rate measured by the flow meter with the target flow rate, And the control means starts the flow control system.

Images