Fluid control device, diagnostic program for fluid control device, and diagnostic method for fluid control device

Abstract

This system enables diagnosis of whether a malfunction in the fluid control device is due to fluid resistance, and quantitatively determines the correction amount for the correction coefficient used in flow rate calculation. [Solution] The fluid control device 100 includes a second flow rate calculation unit 431 that calculates the flow rate through the fluid resistance 33 based on the time change of the upstream pressure P1 or downstream pressure P2 when the fluid control valve 32 is closed, and a diagnostic parameter calculation unit 432 that calculates diagnostic parameters based on the first flow rate calculated by the first flow rate calculation unit 41 and the second flow rate calculated by the second flow rate calculation unit 431 when the fluid control valve 32 is closed.

Description

Technical Field

[0001] The present invention relates to a fluid control device, a diagnostic program for the fluid control device, and a diagnostic method for the fluid control device.

Background Art

[0002] Conventional fluid control devices include, for example, as shown in Patent Document 1, a fluid resistance provided in a flow path, a downstream valve provided on the downstream side of the fluid resistance, an upstream pressure sensor that detects the upstream pressure of the fluid resistance, and a downstream pressure sensor that detects the downstream pressure that is the pressure between the fluid resistance and the downstream valve.

[0003] In this type of fluid control device, a first flow rate flowing through the fluid resistance is calculated based on the upstream pressure and the downstream pressure, and a second flow rate flowing out from the downstream valve is calculated based on the first flow rate and a converted flow rate calculated from the time change amount of the downstream pressure. Then, a diagnostic unit provided in the fluid control device compares the first flow rate and the second flow rate in a state where the downstream valve is closed, and diagnoses the presence or absence of an abnormality in the fluid control device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, the abnormality of the fluid control device described above may be, for example, an abnormality of the fluid resistance, an abnormality of the fluid control valve, and / or an abnormality of the pressure sensor. However, in the fluid control device described above, although the diagnostic unit can diagnose the presence or absence of an abnormality in the fluid control device, it cannot diagnose which device in the fluid control device has the abnormality.

[0006] In particular, the above-mentioned fluid control device cannot diagnose whether a malfunction in the fluid control device is due to an abnormality in fluid resistance, and therefore cannot quantitatively calculate the abnormality in flow resistance. Furthermore, if there is an abnormality in fluid resistance, it is conceivable to change the correction coefficient used in flow rate calculation according to that abnormality in flow resistance, but since it is not possible to diagnose whether there is an abnormality in fluid resistance, it is not possible to change the correction coefficient according to the abnormality in flow resistance.

[0007] Therefore, the present invention has been made in view of the above-mentioned problems, and its main objective is to enable diagnosis of whether an abnormality in a fluid control device is due to an abnormality in fluid resistance, and to quantitatively calculate the abnormality in flow resistance. [Means for solving the problem]

[0008] In other words, the fluid control device according to the present invention is characterized by comprising: a fluid resistance provided in a flow path; an upstream pressure sensor for detecting the upstream pressure of the fluid resistance; a downstream pressure sensor for detecting the downstream pressure of the fluid resistance; a first flow rate calculation unit for calculating the flow rate through the fluid resistance based on the upstream pressure and the downstream pressure; a fluid control valve provided on the upstream side of the upstream pressure sensor or the downstream side of the downstream pressure sensor; a valve control unit for controlling the fluid control valve based on the first flow rate; a second flow rate calculation unit for calculating the flow rate through the fluid resistance based on the time change of the upstream pressure or the downstream pressure when the fluid control valve is closed; and a diagnostic parameter calculation unit for calculating diagnostic parameters based on the first flow rate calculation unit and the second flow rate calculation unit when the fluid control valve is closed.

[0009] With such a fluid control device, abnormalities in fluid resistance can be diagnosed using diagnostic parameters calculated based on two flow rates, a first flow rate and a second flow rate, which are calculated from the flow rate through the fluid resistance when the fluid control valve is closed. Furthermore, if the fluid resistance is abnormal, the abnormality in the fluid resistance can be quantitatively determined based on the diagnostic parameters, and the correction coefficient used in the flow rate calculation of the first flow rate calculation unit can be changed.

[0010] The system further includes a diagnostic unit that diagnoses abnormalities in the fluid resistance and / or modifies the correction coefficient in the flow rate calculation of the first flow rate calculation unit based on the diagnostic parameters. In this configuration, the diagnostic unit diagnoses abnormalities in fluid resistance based on diagnostic parameters. Therefore, the diagnostic unit can not only diagnose whether or not there are abnormalities in fluid resistance, but also diagnose the degree or type of abnormality in fluid resistance based on the diagnostic parameters. Furthermore, since the diagnostic unit changes the correction coefficient used in the flow rate calculation of the first flow rate calculation unit, even if the diagnostic parameters change compared to normal fluid resistance, the first flow rate calculation unit can accurately calculate the first flow rate based on the changed correction coefficient.

[0011] The diagnostic unit diagnoses an abnormality in the fluid resistance based on the value of the diagnostic parameter at the time the fluid control valve is closed or after a predetermined period has elapsed since the time it was closed, or changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit. With this configuration, the diagnostic unit can diagnose whether the abnormality in the fluid control device is due to an abnormality in fluid resistance or an abnormality in equipment other than fluid resistance, based on the value of the diagnostic parameter at the time the fluid control valve is closed or after a predetermined period has elapsed since the time it was closed.

[0012] The main types of fluid resistance abnormalities include fluid resistance clogging, where the fluid flows less easily than during calibration, and fluid resistance leakage, where the fluid flows excessively more easily than during calibration. Therefore, the diagnostic unit can distinguish between blockage and leak in the fluid resistance based on the values ​​of the diagnostic parameters. With this configuration, the diagnostic unit can determine the type of fluid resistance abnormality.

[0013] The diagnostic unit includes one that diagnoses abnormalities in fluid equipment other than fluid resistance based on the time-dependent changes in the diagnostic parameters. With this configuration, it is possible to determine whether the abnormality is in fluid equipment other than fluid resistance based on the changes in diagnostic parameters over time. Specifically, if the changes in the diagnostic parameters over time are within a predetermined range, the diagnostic unit can diagnose an abnormality in fluid resistance, and if the changes in the diagnostic parameters over time are outside the predetermined range, the diagnostic unit can diagnose an abnormality in the fluid control valve or each pressure sensor.

[0014] The diagnostic unit diagnoses abnormalities in the fluid control valve and / or the pressure sensors after diagnosing an abnormality in the fluid resistance and / or after changing the correction coefficient. With this configuration, the diagnostic unit can diagnose abnormalities in the fluid resistance as well as abnormalities in the fluid control valve and / or each pressure sensor, so it can diagnose which component of the fluid control device is malfunctioning.

[0015] The diagnostic parameter may be the ratio of the first flow rate to the second flow rate, or a value obtained using that ratio. With this configuration, it becomes possible not only to diagnose the presence or absence of abnormal fluid resistance, but also to determine the type and degree of such abnormality.

[0016] Furthermore, the diagnostic program for the fluid control device is a diagnostic program for a fluid control device comprising: a fluid resistance provided in a flow path; an upstream pressure sensor for detecting the upstream pressure of the fluid resistance; a downstream pressure sensor for detecting the downstream pressure of the fluid resistance; a first flow rate calculation unit for calculating a first flow rate flowing through the fluid resistance based on the upstream pressure and the downstream pressure; a fluid control valve provided on the upstream side of the upstream pressure sensor or the downstream side of the downstream pressure sensor; and a valve control unit for controlling the fluid control valve based on the first flow rate, wherein the computer is equipped with the following functions: a second flow rate calculation unit for calculating a second flow rate flowing through the fluid resistance based on the time change of the upstream pressure or the downstream pressure when the fluid control valve is closed; and a diagnostic parameter calculation unit for calculating diagnostic parameters based on the first flow rate calculated by the first flow rate calculation unit and the second flow rate calculated by the second flow rate calculation unit when the fluid control valve is closed.

[0017] Furthermore, the diagnostic method for a fluid control device according to the present invention comprises a fluid resistance provided in a flow path, an upstream pressure sensor for detecting the upstream pressure of the fluid resistance, a downstream pressure sensor for detecting the downstream pressure of the fluid resistance, a first flow rate calculation unit for calculating the flow rate through the fluid resistance based on the upstream pressure and the downstream pressure, a fluid control valve provided on the upstream side of the upstream pressure sensor or the downstream side of the downstream pressure sensor, and a valve control unit for controlling the fluid control valve based on the first flow rate, characterized in that the flow rate through the fluid resistance is calculated based on the time change of the upstream pressure or the downstream pressure when the fluid control valve is closed, and diagnostic parameters are calculated based on the first flow rate calculated by the first flow rate calculation unit and the second flow rate when the fluid control valve is closed. [Effects of the Invention]

[0018] According to the present invention configured as described above, it is possible to diagnose whether an abnormality in the fluid control device is an abnormality in fluid resistance, and the abnormality in flow resistance can be quantitatively calculated.

Brief Description of Drawings

[0019] [Figure 1] It is a schematic diagram showing a fluid control device according to an embodiment of the present invention. [Figure 2] It is a graph showing the change over time of diagnostic parameters of the same embodiment. [Figure 3] In the same embodiment, (a) a graph showing the valve leak pressure change model, the sensor shift pressure change model, and the change over time of the upstream pressure when there is an abnormality in the fluid control valve, and (b) a graph showing the valve leak pressure change model, the sensor shift pressure change model, and the change over time of the upstream pressure when there is an abnormality in the pressure sensor. [Figure 4] In the same embodiment, (a) a graph showing the change over time of the valve leak difference and the change over time of the sensor shift difference when there is an abnormality in the fluid control valve, and (b) a graph showing the change over time of the valve leak difference and the change over time of the sensor shift difference when there is an abnormality in the pressure sensor. [Figure 5] It is a flowchart showing a diagnostic method of the fluid control device in the same embodiment. [Figure 6] It is a graph obtained by Fourier-transforming the valve leak difference and the sensor leak difference when there is an abnormality in the pressure sensor in another embodiment. [Figure 7] In another embodiment, it is a graph obtained by applying a low-pass filter to the valve leak difference and a graph obtained by applying a low-pass filter to the sensor leak difference when there is an abnormality in the pressure sensor.

Modes for Carrying Out the Invention

[0020] An embodiment of the fluid control device according to the present invention will be described below with reference to the drawings. Note that, for the sake of clarity, some figures in the following drawings may be simplified or exaggerated for illustrative purposes. The same reference numerals are used for identical components, and their descriptions will be omitted as appropriate.

[0021] The fluid control device 100 in this embodiment is used, for example, in semiconductor manufacturing processes, and is installed in one or more gas supply lines to control the flow rate of process gas flowing through each gas supply line.

[0022] Specifically, the fluid control device 100 is a so-called differential pressure mass flow controller (differential pressure MFC), and as shown in Figure 1, it comprises a flow path block 2 in which a plurality of internal flow paths 2R are formed, a fluid control device 3 provided in the flow path block 2, and an arithmetic control device 4 that controls the fluid control device 3 and performs various calculations.

[0023] The flow path block 2 is provided with an inlet port 21 for introducing fluid into the internal flow path 2R and an outlet port 22 for discharging fluid from the internal flow path 2R. An upstream pipe (not shown) is connected to the inlet port 21, and an upstream pneumatic valve (not shown) is provided on the upstream pipe. A downstream pipe (not shown) is connected to the outlet port 22, and a downstream pneumatic valve (not shown) is provided on the downstream pipe.

[0024] The fluid control device 3 controls the fluid in the internal flow path 2R and includes a flow sensor 31 for measuring the flow rate of the fluid flowing through the internal flow path 2R, and a fluid control valve 32 provided upstream of the flow sensor 31.

[0025] The flow sensor 31 is a differential pressure type flow sensor and has an upstream pressure sensor 31a located upstream of the fluid resistance 33 in the internal flow path 2R, and a downstream pressure sensor 31b located downstream of the fluid resistance 33. The first flow rate calculation unit 41 of the calculation control device 4, which will be described later, calculates the flow rate flowing through the internal flow path 2R using the upstream pressure P1 of the fluid resistance 33 detected by the upstream pressure sensor 31a and the downstream pressure P2 of the fluid resistance 33 detected by the downstream pressure sensor 31b. The fluid resistance 33 can be, for example, a restrictor, orifice, nozzle, venturi tube, and / or capillary tube.

[0026] The fluid control valve 32 is located upstream of the flow sensor 31. Specifically, the fluid control valve 32 controls the flow rate by moving the valve body forward and backward relative to the valve seat using a piezo actuator. The valve opening of the fluid control valve 32 is feedback controlled by the valve control unit 42 of the calculation control device 4, which will be described later. In this embodiment, the fluid control valve 32 is located upstream of the upstream pressure sensor 31a, but it may also be located downstream of the downstream pressure sensor 31b.

[0027] The arithmetic control unit 4 is a so-called computer equipped with, for example, a CPU, memory, A / D / D / A converter, and input / output means. When a program stored in memory is executed, the various devices cooperate to perform at least the functions of a first flow rate calculation unit 41, a valve control unit 42, and a diagnostic mechanism 43, as shown in Figure 1. In this embodiment, the arithmetic control unit 4 is housed in a casing that houses the fluid control equipment 3, but the arithmetic control unit 4 may be provided outside the casing. Alternatively, only the diagnostic mechanism 43 may be provided outside the casing.

[0028] The following describes the various components that make up the arithmetic control unit 4.

[0029] The first flow rate calculation unit 41 calculates the flow rate (first flow rate Q1) through the fluid resistance based on the upstream pressure P1 and the downstream pressure P2. Specifically, the first flow rate calculation unit 41 calculates the differential pressure ΔP between the upstream pressure P1 and the downstream pressure P2, and calculates the first flow rate Q1 by multiplying this differential pressure ΔP by a predetermined coefficient. At this time, it is assumed that a predetermined fluid is flowing through the fluid resistance 33.

[0030] The valve control unit 42 controls the fluid control valve 32 based on the first flow rate Q1. In this embodiment, the valve control unit 42 controls the valve opening degree of the fluid control valve 32 based on the first flow rate Q1.

[0031] The diagnostic mechanism 43 diagnoses abnormalities in the fluid resistance 33, the fluid control valve 32, and / or the pressure sensors 31a and 31b while the fluid control valve 32 is closed.

[0032] Specifically, as shown in Figure 1, the diagnostic mechanism 43 includes a second flow rate calculation unit 431, a diagnostic parameter calculation unit 432, a diagnostic unit 433, a valve leak pressure change model creation unit 434, a valve leak difference calculation unit 435, a sensor shift pressure change model creation unit 436, and a sensor shift difference calculation unit 437.

[0033] In this embodiment, the diagnostic mechanism 43 diagnoses an abnormality in the fluid resistance 33 with the fluid control valve 32 closed, and then diagnoses an abnormality in the fluid control valve 32 and / or each pressure sensor 31a, 31b. Below, among the functional parts constituting the diagnostic mechanism 43, the functional part that diagnoses an abnormality in the fluid resistance 33 will be described first.

[0034] The second flow rate calculation unit 431 calculates the flow rate (second flow rate Q2) flowing through the fluid resistance based on the time change of the upstream pressure P1 when the fluid control valve 32 is closed. Specifically, the second flow rate Q2 is the flow rate obtained by differentiating the time derivative of the ideal gas law solved for the upstream pressure P1 when the fluid control valve 32 is closed. More specifically, the second flow rate Q2 is expressed as the product of the time derivative of the ideal gas law solved for the upstream pressure P1 and the internal volume. Here, the internal volume refers to the space in the internal flow path 2R from the valve seat surface of the fluid control valve 32 to the upstream end of the fluid resistance 33. Note that the time change of the upstream pressure P1 when calculating the second flow rate Q2 is not limited to the value obtained by differentiation, but can also include, for example, the difference in the upstream pressure P1 at two points in time after the fluid control valve 32 is closed.

[0035] The diagnostic parameter calculation unit 432 calculates diagnostic parameters based on the first flow rate Q1 calculated by the first flow rate calculation unit 41 and the second flow rate Q2 calculated by the second flow rate calculation unit 431 when the fluid control valve 32 is closed. The diagnostic parameters are values ​​obtained using the ratio of the first flow rate Q1 and the second flow rate Q2. Specifically, the diagnostic parameters are represented by the following equation 1. The state in which the fluid control valve 32 is closed refers to the state in which the fluid control valve 32 is closed from a state in which fluid is flowing in the internal flow path 2R. Note that when the fluid control valve 32 is closed, fluid has drained from the downstream side of the fluid control valve 32, and fluid has accumulated on the upstream side of the fluid control valve 32.

[0036]

number

[0037] Here, S is a diagnostic parameter, Q1 is the first flow rate, and Q2 is the second flow rate. Note that the internal volume, which is one of the parameters that make up the second flow rate Q2, must be determined before using the fluid control device 100. Therefore, the internal volume is measured during the manufacturing of the fluid control device 100 so that the diagnostic parameter becomes 0.

[0038] In this embodiment, the diagnostic parameter calculation unit 432 calculates diagnostic parameters over a predetermined period. Specifically, as shown in Figure 2, the diagnostic parameter calculation unit 432 calculates diagnostic parameters during the period from when the fluid control valve 32 is closed until the upstream pressure P1 falls and converges to a predetermined value.

[0039] The diagnostic unit 433 diagnoses abnormalities in the fluid resistance 33 based on diagnostic parameters and / or changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit 41. In this embodiment, the diagnostic unit 433 diagnoses abnormalities in the fluid resistance 33 and / or changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit 41 based on when the fluid control valve 32 is closed or the value of the diagnostic parameters for a predetermined period from when it is closed, or the change in the diagnostic parameters over time. Specifically, the diagnostic unit 433 calculates an approximate curve that approximates the change in the diagnostic parameters over time for a predetermined period, and diagnoses abnormalities in the fluid resistance 33 and / or changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit 41 based on the value of the diagnostic parameters and / or the approximate curve. Here, the value of the diagnostic parameter refers not only to the value of the diagnostic parameter itself when the fluid control valve 32 is closed or for a predetermined period from the time it is closed, but also to, for example, a value obtained by the average value of multiple points of the ratio between the first flow rate Q1 and the second flow rate Q2 after the time the fluid control valve 32 is closed, or the intercept value of the approximation curve of the diagnostic parameter.

[0040] More specifically, if the diagnostic parameters remain constant within a predetermined range including zero for a predetermined period, the diagnostic unit 433 diagnoses that the fluid resistance 33 is normal. As shown in Figure 2, if the diagnostic parameters are outside the predetermined range including zero for a predetermined period, and the slope of the approximation curve of the diagnostic parameters is within a predetermined range, the diagnostic unit 433 diagnoses that the fluid resistance 33 is abnormal. Note that "the slope of the approximation curve of the diagnostic parameters is within a predetermined range" means, for example, that the slope of the approximation curve is zero or substantially zero.

[0041] If the diagnostic unit 433 determines that there is an abnormality in the fluid resistance 33, and the value of the diagnostic parameter is positive for a predetermined period, the diagnostic unit 433 can determine that the abnormality in the fluid resistance 33 is a leak in the fluid resistance 33. If the value of the diagnostic parameter is negative for a predetermined period, the diagnostic unit 433 can determine that the abnormality in the fluid resistance 33 is a blockage in the fluid resistance 33.

[0042] Figure 2 shows the pressure changes, time changes of diagnostic parameters, and approximate curves for cases where there is an abnormality in the fluid resistance 33 (Case 1) and cases where there is an abnormality in a fluid control device 3 other than the fluid resistance (Case 2). As shown in Figure 2, after the fluid control valve 32 is closed, the pressure changes in Case 1 and Case 2 (dotted line in Figure 2) are almost identical. Therefore, it is not possible to diagnose which part of the fluid control device 100 is malfunctioning based solely on the pressure changes in Case 1 and Case 2.

[0043] Therefore, by calculating the diagnostic parameters and approximation curve, it is possible to diagnose whether the abnormalities in Case 1 and Case 2 are due to an abnormality in the fluid resistance 33 or an abnormality in a fluid control device 3 other than the fluid resistance 33. In Figure 2, the diagnostic parameters are shown as solid lines, and the approximation curve of the diagnostic parameters is shown as a dotted line. Specifically, in Case 1, the diagnostic parameters at the time the fluid control valve 32 is closed are outside a predetermined range including zero, and the slope of the approximation curve of the diagnostic parameters over a predetermined period is within a predetermined range. In this case, the abnormality in Case 1 can be diagnosed as an abnormality in the fluid resistance 33.

[0044] On the other hand, in Case 2, the diagnostic parameters at the time the fluid control valve 32 is closed are within a predetermined range including zero, and the slope of the approximation curve of the diagnostic parameters over a predetermined period is outside the predetermined range. In this case, the abnormality in Case 2 can be diagnosed as the fluid resistance 33 being normal, while the fluid control equipment 3 other than the fluid resistance 33 is abnormal.

[0045] Furthermore, if the diagnostic parameters at the time the fluid control valve 32 is closed are outside a predetermined range including zero, and the slope of the approximation curve of the diagnostic parameters over a predetermined period is outside a predetermined range, then in addition to an abnormality in the fluid resistance 33, an abnormality in the fluid control equipment 3 other than the fluid resistance 33 can be diagnosed. Also, if the diagnostic parameters at the time the fluid control valve 32 is closed are within a predetermined range including zero, and the slope of the approximation curve of the diagnostic parameters over a predetermined period is within a predetermined range, then both the fluid resistance 33 and the fluid control equipment 3 other than the fluid resistance 33 can be diagnosed as normal.

[0046] In this embodiment, if the diagnostic unit 433 diagnoses an abnormality in the fluid resistance 33, the diagnostic unit 433 can change the correction coefficient in the flow rate calculation of the first flow rate calculation unit 41. In this embodiment, the correction coefficient is changed by multiplying an initial correction coefficient, which represents the ratio of the flow rate of the reference instrument to the flow rate of the comparator, by a value obtained from the first flow rate Q1 and the second flow rate Q2. In this embodiment, the value obtained from the first flow rate Q1 and the second flow rate Q2 is the ratio of the first flow rate Q1 to the second flow rate Q2.

[0047] The method for calculating and changing the correction coefficient will be explained. First, in the initial state, such as when the fluid control device 100 is shipped, the initial correction coefficient is calculated by calculating the ratio between the flow rate calculated by the fluid control device 3 using a calibrated reference instrument and the flow rate calculated by the fluid control device 100.

[0048] Next, in the first diagnosis, the ratio of the first flow rate Q1 to the second flow rate Q2 is calculated, and the correction coefficient is changed by multiplying this ratio by the initial correction coefficient. Once the first diagnosis is complete, the first flow rate calculation unit 41 calculates the flow rate using the initial correction coefficient multiplied by the ratio of the first flow rate Q1 to the second flow rate Q2 as the correction coefficient.

[0049] Next, in the second diagnosis, the ratio of the first flow rate Q1 to the second flow rate Q2 is calculated, and the correction coefficient is changed by multiplying this ratio by the correction coefficient. As a result, the correction coefficient becomes the product of the initial correction coefficient, the ratio calculated in the first diagnosis, and the ratio calculated in the second diagnosis. Once the second diagnosis is completed, the first flow rate calculation unit 41 calculates the flow rate using the correction coefficient changed by the second diagnosis.

[0050] For the third and subsequent diagnoses, the ratio of the first flow rate Q1 to the second flow rate Q2 is calculated, similar to the second diagnosis. The correction coefficient is then changed by multiplying this ratio by the correction coefficient that was modified in the previous diagnosis.

[0051] Here, the ratio of the first flow rate Q1 and the second flow rate Q2 used when changing the correction coefficient may be changed according to the slope of the approximation curve of the diagnostic parameters. For example, if the slope of the approximation curve of the diagnostic parameters is outside a predetermined range, the ratio of the first flow rate Q1 and the second flow rate Q2 used when changing the correction coefficient may be the first flow rate Q1 and the second flow rate Q2 at the time the fluid control valve 32 is closed or after a predetermined period has elapsed since the time it was closed, or a value obtained by subtracting the value of the intercept of the approximation curve of the diagnostic parameters from 1. On the other hand, if the slope of the approximation curve of the diagnostic parameters is within a predetermined range, the ratio of the first flow rate Q1 and the second flow rate Q2 used when changing the correction coefficient may be the average value of multiple points of the ratio of the first flow rate Q1 and the second flow rate Q2 after the time the fluid control valve 32 is closed, or a value obtained by subtracting the value of the intercept of the approximation curve of the diagnostic parameters from 1.

[0052] Next, we will describe the components of the diagnostic mechanism 43 that diagnose abnormalities in the fluid control valve 32 and / or the pressure sensors 31a and 31b.

[0053] The valve leak pressure change model creation unit 434 creates a valve leak pressure change model that shows the pressure change due to valve leak in the fluid control valve 32. The valve leak pressure change model is a model that can diagnose an abnormality in the fluid control valve 32 if it matches the pressure detected by each pressure sensor 31a and 31b.

[0054] To create a valve leak pressure change model, the valve leak pressure change model creation unit 434 first acquires the upstream pressure P1 detected by the upstream pressure sensor 31a over a predetermined period, for example, from 0 to 3 seconds. Then, the valve leak pressure change model creation unit 434 creates a valve leak pressure change model by fitting the equation obtained by solving the differential equation represented by the following equation 2 (equation 3) to the upstream pressure P1 detected by the upstream pressure sensor 31a. Alternatively, the valve leak pressure change model creation unit 434 may also create the valve leak pressure change model by fitting it to the downstream pressure P2 detected by the downstream pressure sensor 31b.

[0055]

number

[0056] In Math 2, P is pressure, and k and c ov c is a predetermined coefficient. In the case of a valve leak, the rate of change of the upstream pressure P1 shifts compared to the normal state, so in Equation 2, the amount of the shift in the rate of change of that pressure is c. ov This model assumes that the downstream pressure P2 is 0, and the time evolution of the upstream pressure P1 is used as the model.

[0057]

number

[0058] In Math 3, P is pressure and t is time. Also, a, b, c ov This coefficient is obtained by fitting it to the upstream pressure P1 detected by the upstream pressure sensor 31a.

[0059] The valve leak difference calculation unit 435 calculates the valve leak difference, which is the difference between the valve leak pressure change model and the upstream pressure P1 detected by the upstream pressure sensor 31a. Alternatively, the valve leak difference calculation unit 435 may use the difference between the valve leak pressure change model and the downstream pressure P2 detected by the downstream pressure sensor 31b as the valve leak difference.

[0060] To calculate the valve leak difference, the valve leak difference calculation unit 435 first obtains a valve leak pressure change model from the valve leak pressure change model creation unit 434 and obtains the upstream pressure P1 from the upstream pressure sensor 31a. Then, the valve leak difference calculation unit 435 calculates the difference between the valve leak pressure change model and the upstream pressure P1 to obtain the valve leak difference.

[0061] The sensor shift pressure change model creation unit 436 creates a sensor shift pressure change model that shows the pressure change due to the sensor shift of the upstream pressure sensor 31a or the downstream pressure sensor 31b. The sensor shift pressure change model is a model that can diagnose an abnormality in each pressure sensor 31a and 31b if it matches the pressure detected by each pressure sensor 31a and 31b.

[0062] To create a sensor shift pressure change model, the sensor shift pressure change model creation unit 436 first acquires the upstream pressure P1 detected by the upstream pressure sensor 31a over a predetermined period, for example, from 0 to 3 seconds. Then, the sensor shift pressure change model creation unit 436 creates a sensor shift pressure change model by fitting the equation 5 obtained by solving the differential equation represented by the following equation 4 to the upstream pressure P1 detected by the upstream pressure sensor 31a. Alternatively, the sensor shift pressure change model creation unit 436 may create the sensor shift pressure change model by fitting it to the downstream pressure P2 detected by the downstream pressure sensor 31b.

[0063]

number

[0064] In equation 4, P is the pressure and k is a predetermined coefficient.

[0065]

number

[0066] In the case of sensor shift, only the overall upstream pressure P1 shifts, and the rate of change of the upstream pressure P1 is approximately the same as under normal conditions. Therefore, the sensor shift pressure change model is represented by Equation 4, and the amount of shift is represented by the integral constant B in Equation 5.

[0067] The sensor shift difference calculation unit 437 calculates the sensor shift difference, which is the difference between the sensor shift pressure change model and the upstream pressure P1 detected by the upstream pressure sensor 31a. The sensor shift difference allows for the diagnosis of abnormalities in the fluid control valve 32 in a shorter time than the sensor shift pressure change model. The sensor shift difference calculation unit 437 may also use the difference between the sensor shift pressure change model and the downstream pressure P2 detected by the downstream pressure sensor 31b as the sensor shift difference.

[0068] To calculate the sensor shift difference, the sensor shift difference calculation unit 437 first obtains a sensor shift pressure change model from the sensor shift pressure change model creation unit 436 and obtains the upstream pressure P1 from the upstream pressure sensor 31a. Then, the sensor shift difference calculation unit 437 calculates the difference between the sensor shift pressure change model and the upstream pressure P1 to obtain the sensor shift difference.

[0069] The diagnostic unit 433 diagnoses abnormalities in the fluid control valve 32 and / or in the pressure sensors 31a and 31b after diagnosing an abnormality in the fluid resistance 33 and / or after changing the correction coefficient.

[0070] Here, as shown in Figure 3(a), if the pressure change obtained from the valve leak pressure change model matches the time-dependent change in the upstream pressure P1 detected by the upstream pressure sensor 31a, the diagnostic unit 433 can diagnose an abnormality in the fluid control valve 32. Specifically, as shown in Figure 3(a), if the pressure change obtained from the valve leak pressure change model matches the time-dependent change in the upstream pressure P1 over a predetermined period, and the pressure change obtained from the sensor shift pressure change model deviates from the upstream pressure P1 over time, the diagnostic unit 433 can diagnose an abnormality in the fluid control valve 32.

[0071] On the other hand, as shown in Figure 3(b), if the pressure change obtained from the sensor shift pressure change model matches the time-dependent change in the upstream pressure P1 detected by the upstream pressure sensor 31a, the diagnostic unit 433 can diagnose an abnormality in each of the pressure sensors 31a and 31b. Specifically, as shown in Figure 3(b), if the pressure change obtained from the sensor shift pressure change model matches the time-dependent change in the upstream pressure P1 over a predetermined period, and the valve leak pressure change model deviates from the upstream pressure P1 over time, the diagnostic unit 433 can diagnose an abnormality in each of the pressure sensors 31a and 31b.

[0072] Incidentally, the diagnostic unit 433 can diagnose abnormalities in a shorter time by comparing the valve leak difference and the sensor shift difference than by comparing the pressure change obtained from the valve leak pressure change model and the pressure change obtained from the sensor shift pressure change model. Therefore, in this embodiment, after diagnosing an abnormality in the fluid resistance 33 and / or after changing the correction coefficient, the diagnostic unit 433 compares the valve leak difference and the sensor shift difference to diagnose an abnormality in the fluid control valve 32 and / or an abnormality in each pressure sensor 31a, 31b. Specifically, the diagnostic unit 433 diagnoses that an abnormality has occurred in the equipment corresponding to the smaller of the valve leak difference and the sensor shift difference.

[0073] More specifically, the diagnostic unit 433 acquires the valve leak difference and sensor shift difference over a predetermined period. Then, as shown in Figure 4(a), if the valve leak difference is smaller than the sensor shift difference, the diagnostic unit 433 diagnoses an abnormality in the fluid control valve 32. On the other hand, as shown in Figure 4(b), if the sensor shift difference is smaller than the valve leak difference, the diagnostic unit 433 diagnoses an abnormality in the upstream pressure sensor 31a.

[0074] Furthermore, if the diagnostic unit 433 diagnoses an abnormality in the upstream pressure sensor 31a, the diagnostic unit 433 determines the sensor shift amount of the upstream pressure sensor 31a from the sensor shift pressure change model. The sensor shift amount here refers to the amount that indicates the deviation of the upstream pressure sensor 31a from the time of calibration, and more specifically, it is the value of the steady-state term of the sensor shift pressure change model (the value represented by B in Equation 5).

[0075] The diagnostic unit 433 then outputs the sensor shift amount to the first flow rate calculation unit 41. The first flow rate calculation unit 41 adds the sensor shift amount to the differential pressure ΔP between the upstream pressure P1 and the downstream pressure P2 to calculate the first flow rate Q1.

[0076] <Diagnostic Method for Fluid Control Devices> Next, the diagnostic method for the fluid control device 100 of this embodiment will be described with reference to Figure 5.

[0077] First, with the fluid control valve 32 closed, the first flow rate calculation unit 41 calculates the first flow rate Q1, and the second flow rate calculation unit 431 calculates the second flow rate Q2. Then, the diagnostic parameter calculation unit 432 calculates diagnostic parameters based on the first flow rate Q1 and the second flow rate Q2 (S1). The diagnostic parameter calculation unit 432 calculates diagnostic parameters over a predetermined period of time.

[0078] Next, the diagnostic unit 433 diagnoses an abnormality in the fluid resistance 33 based on the diagnostic parameters (S2). Specifically, the diagnostic unit 433 calculates an approximate curve of the diagnostic parameters over a predetermined period and diagnoses whether or not there is an abnormality in the fluid resistance 33, and / or the type of abnormality in the fluid resistance 33, based on that approximate curve.

[0079] Next, if there is an abnormality in the fluid resistance 33, the diagnostic unit 433 changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit 41 based on the diagnostic parameters (S3). If there is no abnormality in the fluid resistance 33, the diagnostic unit 433 does not need to change the correction coefficient in the flow rate calculation of the first flow rate calculation unit 41. Also, for example, in cases such as replacement of the fluid resistance 33, the diagnostic unit 433 does not need to change the correction coefficient even if there is an abnormality in the fluid resistance 33.

[0080] Next, the diagnostic unit 433 diagnoses whether there is an abnormality in the fluid control valve 32 and / or each pressure sensor 31a, 31b based on the slope of the approximation curve of the diagnostic parameters over a predetermined period (S4). If the slope of the approximation curve of the diagnostic parameters is within the predetermined range, the diagnostic unit 433 terminates the diagnosis of the fluid control device 100. Alternatively, the next step may be taken regardless of whether the slope of the approximation curve is within the predetermined range.

[0081] On the other hand, if the slope of the approximation curve of the diagnostic parameters is outside a predetermined range, the diagnostic unit 433 diagnoses that there is an abnormality in the fluid control valve 32 and / or each pressure sensor 31a, 31b. Then, the valve leak pressure change model creation unit 434 acquires the upstream pressure P1 and creates a valve leak pressure change model, and the sensor shift pressure change model creation unit 436 acquires the upstream pressure P1 and creates a sensor shift pressure change model (S5).

[0082] Once a valve leak pressure change model is created, the valve leak difference calculation unit 435 calculates the valve leak difference based on the valve leak pressure change model and the upstream pressure P1. Also, once a sensor shift pressure change model is created, the sensor shift difference calculation unit 437 calculates the sensor shift difference based on the sensor shift pressure change model and the upstream pressure P1 (S6).

[0083] Next, the diagnostic unit 433 compares the valve leak difference and the sensor shift difference to diagnose whether there is a malfunction in the fluid control valve 32 or in each of the pressure sensors 31a and 31b (S7). Specifically, the diagnostic unit 433 compares the magnitude of the valve leak difference and the sensor shift difference to diagnose whether there is a malfunction in the fluid control valve 32 or in each of the pressure sensors 31a and 31b.

[0084] If the valve leak difference is smaller than the sensor shift difference, the diagnostic unit 433 diagnoses that there is an abnormality in the fluid control valve 32 (S8). Then, the diagnostic unit 433 terminates the diagnosis of the fluid control device 100.

[0085] On the other hand, if the sensor shift difference is smaller than the valve leak difference, the diagnostic unit 433 diagnoses that there is an abnormality in each of the pressure sensors 31a and 31b (S9).

[0086] If the diagnostic unit 433 diagnoses that there is an abnormality in each of the pressure sensors 31a and 31b, it determines the sensor shift amount of the upstream pressure sensor 31a from the sensor shift pressure change model and corrects the upstream pressure P1 output by the upstream pressure sensor 31a based on the sensor shift amount (S10). Then, the diagnostic unit 433 ends the diagnosis of the fluid control device 100.

[0087] <Effects of this embodiment> According to the fluid control device 100 in this embodiment, when the fluid control valve 32 is closed, an abnormality in the fluid resistance 33 can be diagnosed using diagnostic parameters calculated based on two flow rates, a first flow rate Q1 and a second flow rate Q2, that flow through the fluid resistance.

[0088] Furthermore, if the fluid resistance 33 is abnormal, the diagnostic unit 433 can change the correction coefficient used in the flow rate calculation of the first flow rate calculation unit 41 based on the diagnostic parameters.

[0089] In addition, the diagnostic unit 433 compares the valve leak difference and the sensor shift difference to diagnose whether the problem lies with the fluid control valve 32 or with each pressure sensor 31a, 31b. Therefore, the diagnostic unit 433 can diagnose whether the problem lies with the fluid resistance 33, the fluid control valve 32, or each pressure sensor 31a, 31b.

[0090] <Other Embodiments> However, the present invention is not limited to the embodiments described above.

[0091] In the above embodiment, the diagnostic unit 433 diagnosed whether there was an abnormality in the fluid resistance 33, an abnormality in the fluid control valve 32, or an abnormality in each of the pressure sensors 31a and 31b. However, the diagnostic unit 433 may only diagnose whether there is an abnormality in the fluid resistance 33 among the fluid control equipment 3.

[0092] In the above embodiment, the fluid control valve 32 was provided upstream of each pressure sensor 31a, 31b, and the diagnostic unit 433 made a diagnosis based on the pressure falloff after the fluid control valve 32 was closed, but it is not limited to this. For example, the fluid control valve 32 may be provided downstream of each pressure sensor 31a, 31b, and the diagnostic unit 433 may make a diagnosis based on the pressure riseoff after the fluid control valve 32 was closed.

[0093] In the above embodiment, the diagnostic unit 433 diagnosed an abnormality in the fluid resistance 33 based on diagnostic parameters, but the correction coefficient may be changed without diagnosing an abnormality in the fluid resistance 33.

[0094] To easily diagnose whether the problem lies with the fluid control valve or with each pressure sensor, the diagnostic unit 433 may perform a Fourier transform on the valve leak difference and the sensor shift difference, and then compare the Fourier-transformed valve leak difference and sensor shift difference to diagnose whether the problem lies with the fluid control valve 32 or with each pressure sensor 31a, 31b.

[0095] Specifically, the diagnostic unit 433 performs a Fourier transform on both the valve leak difference and the sensor shift difference. As a result, as shown in Figure 6, the larger difference has a peak at low frequencies, such as around 3 Hz, while the value of the smaller difference after the Fourier transform is closer to the reference value (e.g., 0) compared to the larger difference. Therefore, the difference between the valve leak difference and the sensor shift difference becomes larger, especially at low frequencies.

[0096] As an alternative method for easily diagnosing whether the problem lies with the fluid control valve or with each pressure sensor, the diagnostic unit 433 may compare the squared error of the valve leak difference and the squared error of the sensor shift difference to diagnose whether the problem lies with the fluid control valve 32 or with each pressure sensor 31a, 31b.

[0097] Specifically, the diagnostic unit 433 applies a low-pass filter to both the valve leak difference and the sensor shift difference to remove high-frequency noise, and then calculates the squared error. By applying the low-pass filter, as shown in Figure 7, the difference between the valve leak difference and the sensor shift difference becomes clear. When the squared error is calculated for these differences, the smaller difference becomes closer to the reference value (e.g., 0), while the larger difference moves further away from the reference value, resulting in a larger difference between the valve leak difference and the sensor shift difference.

[0098] In the above embodiment, the diagnostic parameter was a value obtained using the ratio of the first flow rate Q1 to the second flow rate Q2, but the diagnostic parameter may also be the ratio of the first flow rate Q1 to the second flow rate Q2. In this case, the diagnostic parameter and the correction coefficient will be the same value. Note that the ratio of the first flow rate Q1 to the second flow rate Q2 may have the first flow rate Q1 as the numerator and the second flow rate Q2 as the denominator, or the first flow rate Q1 as the denominator and the second flow rate Q2 as the numerator.

[0099] In the above embodiment, the diagnostic unit 433 may output abnormalities in the fluid resistance 33, abnormalities in the fluid control valve 32, and / or abnormalities in each of the pressure sensors 31a and 31b to a display unit such as a display.

[0100] In this embodiment, the fluid control device 100 was a differential pressure type MFC, but it is not limited to this, and may be a so-called thermal mass flow controller, a pressure control device, or other fluid control device.

[0101] In the above embodiment, the diagnostic mechanism 43 included a valve leak pressure change model creation unit 434, a valve leak difference calculation unit 435, a sensor shift pressure change model creation unit 436, and a sensor shift difference calculation unit 437. However, in order to diagnose whether the abnormality is in each pressure sensor or something else, the diagnostic mechanism 43 only needs to include at least the sensor shift pressure change model creation unit 436 and the sensor shift difference calculation unit 437. In addition, although the coefficients are calculated by fitting each model, the coefficients may be determined using a method other than fitting.

[0102] In this embodiment, the fluid resistance 33 is not limited to a restrictor, but may be an orifice, a venturi tube, and / or a capillary tube, for example. In this case, by applying each model according to the type of fluid resistance 33, it is possible to diagnose whether the problem is with the fluid control valve or with each pressure sensor.

[0103] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention. [Explanation of symbols]

[0104] 100... Fluid control device 2 ···Flow channel block 3. Fluid control equipment 31 ···Pressure sensor 31a...Upstream pressure sensor 31b... Downstream pressure sensor 32 ··· Fluid control valve 33...Fluid resistance 4 ···Calculation control unit 41...1st flow rate calculation section 42... Valve control unit 43. Diagnostic Mechanism 431...Second flow rate calculation section 432... Diagnostic parameter calculation unit 433...Diagnostic Department 434... Valve Leak Pressure Change Model Creation Section 435... Valve Leak Difference Calculation Unit 436... Sensor Shift Pressure Change Model Creation Section 437...Sensor shift difference calculation unit Q1...1st flow rate Q2...Second flow rate

Claims

1. Fluid resistance provided in the flow path, An upstream pressure sensor for detecting the upstream pressure of the fluid resistance, A downstream pressure sensor for detecting the downstream pressure of the fluid resistance, A first flow rate calculation unit calculates the flow rate through the fluid resistance based on the upstream pressure and the downstream pressure, A fluid control valve provided on the upstream side of the upstream pressure sensor or the downstream side of the downstream pressure sensor, A valve control unit controls the fluid control valve based on the first flow rate, A second flow rate calculation unit calculates the flow rate through the fluid resistance based on the time change of the upstream pressure or the downstream pressure when the fluid control valve is closed, A fluid control device comprising a diagnostic parameter calculation unit that calculates diagnostic parameters based on a first flow rate calculated by the first flow rate calculation unit and a second flow rate calculated by the second flow rate calculation unit when the fluid control valve is closed.

2. The fluid control device according to claim 1, further comprising a diagnostic unit that diagnoses an abnormality in the fluid resistance based on the diagnostic parameters and / or changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit.

3. The fluid control device according to claim 2, wherein the diagnostic unit diagnoses an abnormality in the fluid resistance or changes the correction coefficient in the flow rate calculation of the first flow rate calculation unit based on the value of the diagnostic parameter when the fluid control valve is closed or for a predetermined period of time from when it is closed.

4. The fluid control device according to claim 2 or 3, wherein the diagnostic unit determines whether the fluid resistance is clogged or leaking based on the value of the diagnostic parameter.

5. The fluid control device according to any one of claims 2 to 4, wherein the diagnostic unit diagnoses abnormalities in fluid equipment other than the fluid resistance based on the change in the diagnostic parameters over time.

6. The fluid control device according to any one of claims 2 to 5, wherein the diagnostic unit diagnoses an abnormality in the fluid resistance and / or changes the correction coefficient, and then diagnoses an abnormality in the fluid control valve and / or each of the pressure sensors.

7. The fluid control device according to any one of claims 1 to 6, wherein the diagnostic parameter is the ratio of the first flow rate to the second flow rate or a value obtained using the ratio.

8. A diagnostic program for a fluid control device comprising: a fluid resistance provided in a flow path; an upstream pressure sensor for detecting the upstream pressure of the fluid resistance; a downstream pressure sensor for detecting the downstream pressure of the fluid resistance; a first flow rate calculation unit for calculating the flow rate through the fluid resistance based on the upstream and downstream pressures; a fluid control valve provided upstream of the upstream pressure sensor or downstream of the downstream pressure sensor; and a valve control unit for controlling the fluid control valve based on the first flow rate, wherein A second flow rate calculation unit that calculates the flow rate through the fluid resistance based on the time change of the upstream pressure or the downstream pressure when the fluid control valve is closed, A diagnostic program for a fluid control device, which provides a computer with a function as a diagnostic parameter calculation unit that calculates diagnostic parameters based on a first flow rate calculated by the first flow rate calculation unit and a second flow rate calculated by the second flow rate calculation unit when the fluid control valve is closed.

9. A diagnostic method for a fluid control device comprising: a fluid resistance provided in a flow path; an upstream pressure sensor for detecting the upstream pressure of the fluid resistance; a downstream pressure sensor for detecting the downstream pressure of the fluid resistance; a first flow rate calculation unit for calculating the flow rate through the fluid resistance based on the upstream pressure and the downstream pressure; a fluid control valve provided on the upstream side of the upstream pressure sensor or the downstream side of the downstream pressure sensor; and a valve control unit for controlling the fluid control valve based on the first flow rate, wherein Based on the time change of the upstream pressure or the downstream pressure when the fluid control valve is closed, the flow rate through the fluid resistance is calculated. A diagnostic method for a fluid control device, comprising calculating diagnostic parameters based on a first flow rate calculated by the first flow rate calculation unit and a second flow rate while the fluid control valve is closed.

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