Flow rate control device

Abstract

To provide a flow rate control device having a function for performing stable flow rate control even for instantaneous supply pressure fluctuations.SOLUTION: A period for which a deviation, which is a difference between a flow rate set value and a flow rate measurement value, is within a predetermine level is defined as a steady period, and the other periods are defined set as a change period. In this case, when a flow rate measurement signal output from a flow rate sensor unit 3 during the steady period changes in an increasing direction or a decreasing direction by a certain level or more due to an external factor received by the flow rate sensor unit 3, a new opening control signal after a change of the current opening control signal of a flow rate control valve unit 4 is obtained by adding to, the current opening control signal of the flow rate control valve unit 4, the result of dividing the product, which is obtained by multiplying an appropriately determined non-zero coefficient by the deviation (i.e., the difference between the flow rate set value and the flow rate measurement value), by a value obtained by multiplying an appropriately determined non-zero coefficient by the absolute value of the differentiated deviation and then adding a non-zero real number to that product.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a flow control device that controls the flow rate of fluids such as gases and liquids, and in particular to a flow control device that has a function of performing stable flow control even against external factors such as fluctuations in supply pressure. Recent gas panels have adopted a design in which the same type of gas is branched into multiple lines. This causes crosstalk between flow control devices that control the gas flow rate and instantaneous fluctuations in supply pressure due to regulator characteristics. The present invention relates to a flow control device that has a function of performing stable flow control even against external factors such as instantaneous supply pressure fluctuations. [Background technology]

[0002] For example, when various gases used in the manufacture of semiconductors are supplied to semiconductor manufacturing equipment, flow control devices are provided in the supply flow paths to regulate the flow rates of the respective gases. Conventionally, a pressure regulator was connected in series to each flow control device to prevent extreme fluctuations in the pressure in the flow paths of each flow control device, making flow control easier.

[0003] The flow control method in the flow control device is basically PID control, but for example, as shown in Patent Document 1, a method is known in which feedback control is performed by switching PID coefficients between a transient response state and a stable state.

[0004] Specifically, the one shown in Patent Document 1 uses a value obtained by substituting the flow rate set value into a predetermined function as a gain value to be multiplied by the deviation in the proportional calculation, and for example, the predetermined function used in a stable state calculates a smaller value when the substituted flow rate set value becomes smaller. In other words, the conventional mass flow controller shown in Patent Document 1 only changes the proportional coefficient, integral coefficient, and differential coefficient in the stable state in proportion to only the flow rate set value.

[0005] Also, Patent Document 2 describes "a method for correcting a parasitic flow rate of a fluid in a mass flow controller, comprising: acquiring a pressure measurement signal generated by a pressure sensor; acquiring a flow rate sensor signal generated by a flow rate sensor; generating an estimated parasitic flow rate signal using the pressure measurement signal; accelerating the flow rate sensor signal to generate an accelerated flow rate sensor signal having a bandwidth equivalent to that of the estimated parasitic flow rate signal; and generating a correction flow rate signal for controlling the mass flow controller using the accelerated flow rate sensor signal and the estimated parasitic flow rate signal." The method described in Patent Document 2 simply corrects the parasitic flow rate and does not have a function for performing stable flow rate control against instantaneous supply pressure fluctuations, etc.

[0006] Patent Document 3 also describes a method for controlling the mass flow rate of a fluid using a mass flow controller, comprising: receiving a pressure measurement value of the fluid generated by a pressure sensor; pausing a feedback control loop that controls a valve of the mass flow controller based on a difference between a measured flow rate and a set value of the flow rate in response to a rate of change of the pressure of the fluid satisfying a threshold condition; calculating a valve position of the valve based on the pressure measurement value when the feedback control loop is paused and characteristic data representing a response characteristic between the flow rate, pressure, and valve position in the mass flow controller; and re-operating the feedback control loop if the measured flow rate is not saturated after a certain period of time has elapsed or after the threshold condition is satisfied again; determining a difference between the measured flow rate and a set value of the flow rate when the feedback control loop is first resumed; and adjusting the characteristic data based on the difference to improve the accuracy of the calculation of the valve position when the feedback control loop is paused again. The method described in Patent Document 3 is a method for controlling the flow rate of a fluid using a multi-mode control algorithm, but the system is complicated.

[0007] Furthermore, Patent Document 4 describes a mass flow controller that includes: a flow sensor unit that measures the flow rate of a fluid flowing in a flow path and outputs a flow rate measurement signal indicating the measured value; a flow rate control valve provided upstream or downstream of the flow rate sensor unit; and a calculation unit that calculates a control value for the flow rate control valve, wherein during a change period during which a primary pressure measurement value, which is a measurement value of the pressure of the fluid upstream of the mass flow controller, has changed by a predetermined amount or more, and during a stable period which is the rest of the period, the calculation unit calculates a stable control value by performing a predetermined calculation process on the deviation between the flow rate measurement value indicated by the flow rate measurement signal and a flow rate set value, which is a target value, during the change period, and calculates a change control value by performing a predetermined calculation process on the primary pressure measurement value and the amount of change in the primary pressure measurement value. The mass flow controller described in Patent Document 4 switches control between stable periods and changing periods, and when the primary pressure changes suddenly, it performs control based on the primary pressure measurement value and the amount of change in the primary pressure measurement value. Therefore, although it can be used in systems where crosstalk occurs, it cannot be said to have the function of performing stable flow rate control against instantaneous supply pressure fluctuations, etc.

[0008] Patent Document 5 also describes a mass flow controller that includes a flow sensor unit that measures the flow rate of a fluid flowing through a flow path and outputs a flow rate measurement signal indicating the measured value, a flow control valve provided upstream or downstream of the flow sensor unit, a calculation unit that performs PID calculation on the deviation between the flow rate measurement value indicated by the flow rate measurement signal and a flow rate set value that is a target value to calculate a feedback control value for the flow rate control valve, and an opening control signal output unit that generates an opening control signal based on the feedback control value and outputs it to the flow rate control valve, wherein the calculation unit changes the proportional coefficient, integral coefficient, and differential coefficient used in the PID calculation in a stable state based on at least one of the primary pressure or the flow rate set value and the amount of change in the primary pressure over time. The mass flow controller described in Patent Document 5 is characterized in that the calculation unit that calculates the feedback control value changes the proportional coefficient, integral coefficient, and differential coefficient used in the PID calculation in a stable state based on at least one of the primary pressure or the flow rate set value and the amount of change in the primary pressure over time. In paragraphs 0030 to 0035, it is stated that when the amount of change over time in the primary pressure is positive (when the primary pressure is rising), the control value calculation unit 72 changes the PID coefficients as follows: P′=P×Fu(set) I′=I×Fu(set) D′=D×Fu(set) The above Fu(set) is a set coefficient function that is a function specific to the flow rate set value, but in order to simplify the calculation process, a broken line function with different proportional constants for 0-50% and 50-100% is used. Next, the control value calculation unit 72 changes the P'I'D' coefficient based on the primary pressure as follows. P″=P′×Gu(set) I″=I′×Gu(set) D″=D′×Gu(set) The above-mentioned Gu(set) is a pressure coefficient function that is a function specific to the primary pressure, but in order to simplify the calculation process, a proportional function that is proportional to the input primary pressure is used. As described above, in order to specifically implement the invention described in Patent Document 5, it is necessary to change P, I, D to P", I", D" based on the flow rate set value and the primary pressure, and use the P", I", D" to perform PID calculations on the deviation to calculate the feedback control value. As a result of using the broken line function and proportional function, it is difficult to improve accuracy.

[0009] Patent Document 6 also describes a mass flow controller that includes a flow sensor unit that measures the flow rate of a fluid flowing through a flow path and outputs a flow rate measurement signal indicating the measured value, a flow control valve provided upstream or downstream of the flow sensor unit, a control unit that calculates and outputs an opening control signal for the flow rate control valve from a predetermined calculation formula that includes at least the flow rate measurement value indicated by the flow rate measurement signal and a target flow rate set value as parameters, and a pressure sensor unit that detects the pressure of the fluid upstream or downstream of the flow sensor unit and outputs a pressure detection signal indicating the pressure value, and the control unit makes the calculation formula different between a change period, which is a predetermined period from the time when the flow rate set value is changed by a predetermined amount or more, and a stable period, which is a period other than the change period, and further includes the pressure value as a parameter of the calculation formula at least in the stable period. Paragraph 0009 of the patent describes that, "The main object of the present invention is to provide a mass flow controller that can suppress flow rate fluctuations even when pressure fluctuations occur due to crosstalk, etc., without sacrificing the speed of following changes in the flow rate set value." However, it is not clear how the equation for calculating the opening control signal for the flow control valve should be made different between the changing period and the stable period in order to solve the above problem.

[0010] Furthermore, Patent Document 7 describes a mass flow controller comprising: a flow sensor unit that measures the flow rate of a fluid flowing in a flow path and outputs a flow rate measurement signal indicating the measured value; a flow control valve provided upstream or downstream of the flow sensor unit; a calculation unit that performs PID calculation on the deviation between the flow rate measurement value indicated by the flow rate measurement signal and a flow rate set value that is a target value to calculate a feedback control value for the flow rate control valve; and an opening control signal output unit that generates an opening control signal based on the feedback control value and outputs the opening control signal to the flow rate control valve, wherein the calculation unit is configured to change the proportional coefficient, integral coefficient, and derivative coefficient used in the PID calculation in a stable state based on at least two of the primary side pressure, the amount of change over time in the primary side pressure, or the flow rate set value, and the calculation unit changes the proportional coefficient, integral coefficient, and derivative coefficient by varying a function specific to the flow rate set value or a function specific to the primary side pressure depending on whether the amount of change over time in the primary side pressure is positive or negative. The mass flow controller described in Patent Document 7 is characterized in that a calculation unit for calculating a feedback control value is configured to change the proportional coefficient, integral coefficient, and differential coefficient used in PID calculation in a stable state based on at least two of the primary pressure, the amount of change in the primary pressure over time, or the flow rate set value, and the calculation unit changes the proportional coefficient, integral coefficient, and differential coefficient by varying a function specific to the flow rate set value or a function specific to the primary pressure depending on whether the amount of change in the primary pressure over time is positive or negative. In order to specifically implement the invention described in Patent Document 7, as in Patent Document 5, it is necessary to change P, I, and D to P", I", and D", based on the flow rate set value and the primary pressure, and use the P", I", and D" to perform PID calculation on the deviation to calculate the feedback control value, and as a result of using the broken line function or proportional function, it is difficult to improve accuracy.

[0011] Patent Document 8 describes a method for a flow controller including a flow sensor coupled to a fluid flow path having an inlet side and an outlet side, the flow sensor adapted to provide a sensor output signal indicative of a sensed fluid flow through the flow path, the method including measuring a pressure of a fluid in the flow path, the pressure corresponding to a pressure transient in the flow path, the method further including providing a pressure signal corresponding to the measured pressure, forming a false flow signal emulating a response of the flow sensor due to the pressure transient, and adjusting the sensor output signal based on the false flow signal, the forming of the false flow signal including delaying the pressure signal such that the pressure signal is substantially aligned in time with the sensor output signal. The method described in Patent Document 8 can improve the control accuracy of the flow controller to some extent, but does not provide a function for stable flow control against instantaneous supply pressure fluctuations, etc. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2007-34550 A [Patent Document 2] Special Publication No. 2022-546662 [Patent Document 3] Patent No. 6112119 specification [Patent Document 4] Patent No. 5091821 Specification [Patent Document 5] Patent No. 5090559 specification [Patent Document 6] Patent No. 4658200 Specification [Patent Document 7] Patent No. 4763031 specification [Patent Document 8] Patent No. 4528617 specification Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made in consideration of the problems associated with the prior art, and its purpose is to provide a flow control device that has the function of performing stable flow control even in the face of external factors such as momentary supply pressure fluctuations. [Means for solving the problem]

[0014] As a result of extensive research by the present inventors to solve the above problems, the flow rate control device of the present invention employs the following means. That is, a flow sensor unit that measures the flow rate of a fluid flowing through a flow path and outputs a flow rate measurement signal indicative of the measured flow rate; a flow control valve section provided on the upstream side or downstream side of the flow sensor section; a control unit that calculates and outputs an opening control signal for the flow control valve unit from a calculation formula that includes a flow measurement value indicated by the flow measurement signal and a flow setting value that is a target value as parameters, If a period during which the deviation between the flow rate set value and the flow rate measured value is within a certain range is defined as a steady period, and the other period is defined as a changing period, When the flow measurement signal output by the flow sensor unit during the steady period changes by a certain amount or more in the upward or downward direction due to an external factor that the flow sensor unit receives, The new opening control signal after the current opening control signal of the flow control valve section has changed is obtained by adding to the current opening control signal of the flow control valve section a value obtained by multiplying a coefficient determined appropriately except for zero by a deviation that is the difference between the flow set value and the flow measured value, and dividing the value obtained by multiplying the absolute value of the derivative of the deviation that is the difference between the flow set value and the flow measured value by a coefficient determined appropriately except for zero and adding a real number excluding zero to the value obtained by multiplying the absolute value of the derivative of the deviation that is the difference between the flow set value and the flow measured value by a coefficient determined appropriately except for zero. Effect of the Invention

[0015] In a steady state (a state in which the measured flow rate is kept constant), the feedback control function works, so it is thought that the flow control valve opens or closes with a delay in response to pressure changes. However, in reality, it has been found that when there is a pressure change, the flow control valve opens or closes immediately, and moves more than necessary. When the flow control valve opens or closes more than necessary, the deviation, which is the difference between the flow rate set value and the measured flow rate, becomes large. If the deviation is divided by a constant greater than 1 to reduce this deviation, the deviation will become smaller, but this method makes the deviation even smaller, even though it is already small and does not need to be corrected. Therefore, a method of reducing the deviation only when the deviation is large is preferable. The flow control device of the present invention follows this concept. The appropriately determined coefficient excluding zero is a coefficient that is appropriately determined so as to optimize the effect of suppressing the influence of external factors on the opening control signal of the flow control valve unit and the flow measurement value, using the deviation that is the difference between the flow set value and the flow measurement value, time, an appropriately determined coefficient excluding zero, and a real number excluding zero, and a new opening control signal after the current opening control signal of the flow control valve unit changes is obtained by multiplying the current opening control signal of the flow control valve unit by the appropriately determined coefficient excluding zero and the deviation that is the difference between the flow set value and the flow measurement value, and dividing the result by the absolute value of the differential of the deviation that is the difference between the flow set value and the flow measurement value, multiplied by the appropriately determined coefficient excluding zero, and adding a real number excluding zero to the result. This makes it possible to perform stable flow control even against external factors such as instantaneous supply pressure fluctuations without the opening control signal of the flow control valve unit becoming excessive. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is an overall schematic diagram of one embodiment of a flow rate control device of the present invention. [Diagram 2] FIG. 2 is a block diagram showing the functions of the control unit in the embodiment. [Diagram 3]FIG. 3 is a schematic diagram of an experimental setup for confirming the effect of the flow rate control device of the present invention. [Figure 4] FIG. 4 is a diagram for comparing the effects of the control method of the flow control valve in the flow control device of the present invention with other control methods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Specific embodiments of the present invention will be described below, however, the present invention is not limited to the following embodiments, and various modifications and alterations are possible without departing from the technical scope of the present invention.

[0018] As shown in the overall schematic diagram of FIG. 1, the flow control device 1 of this embodiment includes an internal flow path 2, a flow sensor unit 3 that measures the flow rate of a fluid F flowing within the internal flow path 2, a flow control valve unit 4 provided downstream of the flow sensor unit 3, and a control unit 5, and is used, for example, in a gas supply system in a semiconductor manufacturing process.

[0019] The internal flow path 2 has an inlet port P1 on the upstream side and an outlet port P2 on the downstream side, and a fluid supply source is connected to the inlet port P1, and a chamber for manufacturing semiconductors is connected to the outlet port P2 via a pipe not shown. The flow sensor unit 3 includes, for example, a pair of heat-sensitive sensors, and the instantaneous flow rate of the fluid F is detected as an electric signal by the heat-sensitive sensors at a predetermined time interval, for example, every few milliseconds, and the electric signal is amplified by an internal electric circuit and output as a flow measurement signal having a value according to the detected flow rate. The flow control valve unit 4 controls the flow rate of the fluid F by, for example, adjusting the valve opening to a valve opening according to the value of an opening control signal, which is an electric signal from the outside. The control unit 5 is composed of a digital electric circuit having a CPU, memory, A / D converter, etc. By storing a predetermined program in the memory and operating the CPU and peripheral memory according to the program, the control unit 5 has at least the functions of a signal receiving unit 6, a calculation unit 7, an opening control signal output unit 8, and a flow output unit 9, as shown in FIG. 2.

[0020] The signal receiving unit 6 receives a flow measurement signal transmitted from the flow sensor unit 3, and a flow setting signal input from a separately installed control device such as a computer, and stores these values ​​in a designated area in the memory.

[0021] The calculation unit 7 includes a deviation calculation unit 71 that acquires the flow rate measurement value indicated by the flow rate measurement signal and calculates a deviation between the flow rate measurement value and a target value, i.e., the flow rate set value indicated by the flow rate set signal, a control value calculation unit 72 that performs PID calculation on the deviation to calculate a feedback control value to the flow rate control valve unit 4, and a flow rate output calculation unit 73 that calculates a flow rate output based on the flow rate measurement signal transmitted from the flow rate sensor unit 3. In addition, the control value calculation unit 72 calculates a control value for controlling the opening of the flow rate control valve unit 4 based on the flow rate measurement signal transmitted from the flow rate sensor unit 3 and the deviation, which is the difference between the flow rate set value and the flow rate measurement value.

[0022] The opening control signal output unit 8 generates an opening control signal having a value based on the feedback control value, and outputs the opening control signal to the flow rate control valve unit 4 .

[0023] The flow rate output unit 9 performs a predetermined calculation on the flow rate output value, and outputs a flow rate output signal so that it can be used externally.

[0024] Next, an explanation will be given of the results of an experiment comparing the effects of the control method of the flow control valve section in the flow control device of the present invention with other control methods, using an experimental setup for confirming the effects of the flow control device of the present invention as shown in FIG.

[0025] In Fig. 3, 10 is a regulator, 11 is a pressure gauge, 12 is a flow control device of the present invention, 13 is a flow measurement device, 14 is a mass flow controller, and 15 is a needle valve. In the experimental equipment shown in Fig. 3, when a fluid F (N2 gas) is flowed in the direction indicated by the arrow, a feedback control value is calculated by performing a PID calculation on the deviation, which is the difference between the flow rate set value and the flow rate measurement value, using PID coefficients (proportional coefficient P, integral coefficient I, differential coefficient D) in the control unit 5 of the flow control device 12, and an opening control signal is generated based on the feedback control value during all of the change period and the steady period. The opening control signal is used to control the opening of the flow control valve unit 4 of the flow control device 12, and the regulator 10 is adjusted to greatly change the flow rate of the mass flow controller 14. As a result, as shown by the solid line 16 in Fig. 4, the change in the flow measurement signal of the flow measurement device 13 when the detection signal of the pressure (external factor received by the flow sensor unit 3 of the flow control device 12) detected by the pressure gauge 11 excessively changes in the upward direction is shown by the solid line 17 in Fig. 4. The vertical axis of Fig. 4 indicates the signal level, and the horizontal axis of Fig. 4 indicates the passage of time. The pressure at the plateau F of the pressure detection signal 16 is 10 psi, and the pressure at the protrusion P is 13 psi.

[0026] In the present invention, the steady state period refers to a period other than the change period (e.g., about 2 seconds) which is a predetermined period from the point in time when the flow rate setting value has changed by a predetermined amount or more per unit time, and the flow rate setting value hardly changes. The predetermined amount refers to about 0 to 10% in terms of a percentage of the full scale, and is preferably 0.3 to 5%. Furthermore, the predetermined period refers to about several seconds, specifically about 0 to 10 seconds, and is preferably 0.3 to 5 seconds.

[0027] 4, the maximum downward swing S1 of the flow measurement signal 17 was 63.2%, and the maximum upward swing S2 of the flow measurement signal 17 was 149.6%. Here, a swing of 100% refers to the case where the flow set value and the measured flow value match.

[0028] In the experimental equipment shown in FIG. 3, when the fluid F (N2 gas) is flowed in the direction shown by the arrow, in the change period, the control unit 5 of the flow control device 12 uses a PID coefficient to perform a PID calculation on the deviation, which is the difference between the flow set value and the flow measurement value, to calculate a feedback control value, generates an opening control signal based on the feedback control value, and controls the opening of the flow control valve unit 4 of the flow control device 12 using the opening control signal. In the steady period, the control value calculation unit 72 of the flow control device 12 controls the opening of the flow control valve unit 4 of the flow control device 12 using a value MV' calculated by the following formula (1), and adjusts the regulator 10 to greatly change the flow rate of the mass flow controller 14. As a result, as shown by the solid line 16 in FIG. 4, the change in the flow measurement signal of the flow measurement device 13 when the detection signal of the pressure (external factor received by the flow sensor unit 3 of the flow control device 12) detected by the pressure gauge 11 excessively changes in the upward direction is shown by the solid line 18 in FIG. 4. 4, the maximum upward swings S3 and S6 of the flow measurement signal 18 were 111.2%, and the maximum downward swings S4 and S5 of the flow measurement signal 18 were 88.8%. Here, a swing of 100% refers to the case where the flow set value and the measured flow value match. MV'=MV+k×ε / (η|dε / dt|+c) (1) MV' is a new position control signal after the current position control signal of the flow control valve has changed, MV is the current position control signal of the flow control valve, ε is the deviation which is the difference between the flow set value and the measured flow rate, t is time, k and η are coefficients which are determined as appropriate except for zero, and c is a real number which is determined as appropriate except for zero. The coefficients k and η which are determined as appropriate except for zero are coefficients which are determined as appropriate so as to optimize the effect of suppressing the influence of external factors on the position control signal of the flow control valve and the measured flow rate, with the flow set value as a parameter. In equation (1), if ε≠0 and dε / dt=0, the following equation (2) is obtained. MV'=MV+k×ε / c (2) In equation (1), if ε=0 (dε / dt is an arbitrary value), the following equation (3) is obtained. MV'=MV (3) As is clear from equations (1), (2), and (3), according to the present invention, stable flow rate control can be performed even against external factors such as momentary supply pressure fluctuations.

[0029] If the amount of change in the opening control signal of the flow control valve is ΔMV, then equation (1) can also be expressed as the following equation (4). △MV=k×ε / (η|dε / dt|+c) (4)

[0030] As clearly shown by solid lines 17 and 18 in Fig. 4, by controlling the opening of the flow control valve section with the flow control device of the present invention, the maximum upward and downward swings of the flow measurement signal are significantly reduced, and stable flow control can be performed even against instantaneous supply pressure fluctuations. In the above, a case was described in which the detection signal of the pressure (external factor received by the flow sensor section 3 of the flow control device 12) detected by the pressure gauge 11 excessively changes in the upward direction, but even if the pressure detection signal detected by the pressure gauge 11 excessively changes in the downward direction, the directions of change of the solid lines 16, 17, and 18 in Fig. 4 are simply reversed, and by controlling the opening of the flow control valve section with the flow control device of the present invention, stable flow control can be performed even against instantaneous supply pressure fluctuations.

[0031] Therefore, according to the flow control device of the present invention, since the control is switched between the steady period and the changing period, in the changing period when the flow set value changes, the actual flow rate can be made to follow the changed flow set value very quickly, and in the steady period when the flow set value hardly changes, even if a disturbance (external factor) such as a pressure fluctuation on the upstream side of the flow control device occurs, the overreaction to the disturbance can be suppressed and the actual flow rate can be stabilized. Note that the external factors that the flow sensor unit 3 is subjected to include supply pressure fluctuations and back pressure fluctuations. [Explanation of symbols]

[0032] 1 Flow control device 2 Internal flow path 3 Flow sensor section 4 Flow control valve section 5. Control section 6 Signal receiving section 7 Calculation section 8 Opening control signal output section 9 Flow rate output section 10. Regulator 11 Pressure gauge 12 Flow Control Device 13 Flow measurement device 14 Mass Flow Controller 15 Needle valve 71 Deviation calculation section 72 Control value calculation unit 73 Flow rate output calculation section

Claims

[Claim 1] a flow rate sensor unit that measures a flow rate of a fluid flowing through the flow path and outputs a flow rate measurement signal indicative of the measured flow rate; a flow control valve section provided on the upstream side or downstream side of the flow sensor section; a control unit that calculates and outputs an opening control signal for the flow control valve unit from a calculation formula that includes a flow measurement value indicated by the flow measurement signal and a flow setting value that is a target value as parameters, If a period during which the deviation between the flow rate set value and the flow rate measured value is within a certain range is defined as a steady period, and the other period is defined as a changing period, When the flow measurement signal output by the flow sensor unit during the steady period changes by a certain amount or more in the upward or downward direction due to an external factor that the flow sensor unit receives, A flow control device characterized in that a new opening control signal after a change in the current opening control signal of the flow control valve section is obtained by adding to the current opening control signal of the flow control valve section a result obtained by multiplying a coefficient determined appropriately except for zero by a deviation that is the difference between a flow set value and a flow measurement value, and dividing the result obtained by multiplying the absolute value of the derivative of the deviation that is the difference between a flow set value and a flow measurement value by a coefficient determined appropriately except for zero and adding a real number excluding zero to the result obtained.

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