JP6940442B2 - Thermal flow sensor device and flow rate correction method - Google Patents

Description

The present invention relates to a thermal flow sensor device that calculates a flow rate of a measuring fluid based on a sensor output signal obtained from a temperature sensor that measures the temperature of the measuring fluid.

A thermal flow sensor for measuring the flow rate of a fluid has been put into practical use (see, for example, Patent Document 1). In the thermal flow sensor, the flow rate of the measured fluid can be measured (estimated) by grasping the flow rate-output signal characteristic of the assumed measurement fluid (for example, water) in advance. Therefore, when a fluid other than the measurement fluid whose characteristics are known in advance is to be measured, the flow rate value obtained from the flow rate-output signal characteristic is corrected by a correction coefficient.

In the current method of using a thermal flow sensor, the thermophysical properties of the fluid and the sensitivity when the same type of fluid is flowed in the past are confirmed, and the correction coefficient is set by estimation. This setting work is practically a manual work of the operator even in the case where the procedure is standardized to some extent. Therefore, it takes time and effort, and at the same time, variations that depend on the ability and subjectivity of the operator are likely to occur, and improvement is required.

Japanese Unexamined Patent Publication No. 2017-09348

The present invention has been made to solve the above problems, and an object of the present invention is to provide a thermal flow sensor device and a flow rate correction method capable of reducing the trouble of setting the correction coefficient and the variation of the correction coefficient. do.

The thermal flow sensor device of the present invention is a thermal flow sensor arranged in a flow path through which a measuring fluid flows and is configured to output a sensor output signal obtained from a temperature sensor that measures the temperature of the measuring fluid. And, the information of the theoretical curve that approximates the relationship between the opening degree of the valve arranged at the position of the flow path on the upstream side or the downstream side of the thermal flow sensor and the flow rate of the measurement fluid is stored in advance. Flow rate-output signal reference characteristic information configured to store in advance information about the relationship between the valve opening-flow rate characteristic information storage unit configured in and the flow rate in the reference measurement fluid and the sensor output signal. A flow rate derivation configured to convert the sensor output signal output from the thermal flow sensor into a flow rate value based on the storage unit and the information stored in the flow rate-output signal reference characteristic information storage unit. And the flow rate correction unit configured to correct the flow rate by multiplying the flow rate output value of this flow rate derivation unit by the correction coefficient, and the calculation / setting start of the correction coefficient of the theoretical flow rate obtained from the theoretical curve. When calculating and setting the magnification information storage unit configured to store the specified value of the increase amount of the magnification with respect to the initial value of the theoretical flow rate for each unit time and the closing price of this magnification in advance, and the correction coefficient. With reference to the information of the valve opening-flow rate characteristic information storage unit and the magnification information storage unit, the valve opening is specified so that the increase amount of the theoretical flow rate for each unit time of the magnification becomes the specified value. A valve opening instruction unit configured to transmit an opening degree instruction signal to a control device that controls the valve, a flow rate output initial value of the flow rate derivation unit at the start of calculation / setting of the correction coefficient, and the valve. An output signal acquisition unit configured to acquire the flow rate output value of the flow rate derivation unit after the time when the opening instruction signal for changing the opening degree is transmitted, and the flow rate output value with respect to the flow rate output initial value. Based on the information of the required time measuring unit configured to measure the first required time until the magnification reaches the closing price, the valve opening-flow rate characteristic information storage unit, and the magnification information storage unit. The second required time until the ratio of the theoretical flow rate to the initial value of the theoretical flow rate reaches the closing price is calculated, and the ratio of the first required time to the second required time is calculated as the correction coefficient. It is characterized by including a correction coefficient calculation unit configured to be set in the flow rate correction unit.

Further, one configuration example of the thermal flow sensor device of the present invention includes an execution management unit configured to control and manage to execute the calculation / setting process of the correction coefficient at a predetermined timing, and the correction. The degree of deviation between the history information presentation unit configured to present the history information of the correction coefficient from the past to the present calculated by the coefficient calculation unit and the normal value of the correction coefficient calculated by the correction coefficient calculation unit is It is characterized by further including an alarm output unit configured to output an alarm when the amount exceeds a specified amount.

Further, in the flow rate correction method of the present invention, the measurement fluid is circulated by referring to the flow rate-output signal reference characteristic information storage unit that stores information about the relationship between the flow rate in the reference measurement fluid and the sensor output signal in advance. The first step of converting the sensor output signal of the thermal flow sensor arranged in the flow path into the flow rate output value, the second step of multiplying the flow rate output value by the correction coefficient to correct the flow rate, and the above-mentioned A theory that approximates the relationship between the opening of a valve arranged at the flow path on the upstream side or downstream side of the thermal flow sensor and the flow rate of the measured fluid when calculating and setting the correction coefficient. While referring to the valve opening-flow rate characteristic information storage unit that stores curve information in advance, the unit time of the magnification of the theoretical flow rate obtained from the theoretical curve with respect to the initial value of the theoretical flow rate at the start of calculation and setting of the correction coefficient. With reference to the magnification information storage unit that stores the specified value of the increase amount for each and the closing price of this magnification in advance, the valve opening degree so that the increase amount of the theoretical flow rate for each unit time of the magnification becomes the specified value. A third step of transmitting an opening degree instruction signal for designating the valve to the control device controlling the valve, and a fourth step of acquiring the initial value of the flow rate output value at the start of calculation / setting of the correction coefficient. , The fifth step of acquiring the flow rate output value after the time when the opening instruction signal for changing the valve opening is transmitted, and the multiplication factor of the flow rate output value with respect to the initial value of the flow rate output value become the closing price. Based on the sixth step of measuring the first required time until reaching, and the information of the valve opening-flow rate characteristic information storage unit and the magnification information storage unit, the theoretical flow rate with respect to the theoretical flow rate initial value It is characterized by including a seventh step of calculating a second required time until the magnification reaches the closing price and calculating the ratio of the first required time to the second required time as the correction coefficient. Is to be.

Further, one configuration example of the flow rate correction method of the present invention was calculated by an eighth step instructing the calculation / setting process of the correction coefficient to be executed at a predetermined timing and the seventh step. An alarm is output when the degree of deviation between the 9th step of presenting the history information of the correction coefficient from the past to the present and the normal value of the correction coefficient calculated by the 7th step exceeds the specified amount. It is characterized by further including the tenth step to be performed.

According to the present invention, the correction coefficient can be determined by providing the valve opening-flow rate characteristic information storage unit, the magnification information storage unit, the valve opening instruction unit, the output signal acquisition unit, the required time measurement unit, and the correction coefficient calculation unit. It is possible to reduce the trouble of setting and the variation of the correction coefficient. Therefore, even an operator who does not have specialized knowledge of flow rate measurement can set an appropriate correction coefficient according to the measurement fluid.

Further, in the present invention, by providing the execution management unit, the history information presentation unit, and the alarm output unit, the correction coefficient calculated and set by the correction coefficient calculation unit can be monitored, and the state change (abnormality) of the measurement fluid can be monitored. Occurrence, etc.) can be expected to be detected.

FIG. 1 is a diagram showing the relationship between the true flow rate and the flow rate output of the thermal flow sensor when various fluids are circulated through the thermal flow sensor after the measurement fluid is set to be water. FIG. 2 is a block diagram showing a configuration of a thermal flow sensor device according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view of the mass flow controller. FIG. 4 is a plan view and a cross-sectional view showing the structure of the flow sensor chip of the thermal flow sensor. FIG. 5 is a block diagram showing a configuration of an electric circuit of a thermal flow sensor. FIG. 6 is a diagram showing an example of the relationship between the opening degree of the valve and the flow rate of the fluid. FIG. 7 is a diagram showing the relationship between the true flow rate and the sensor output signal when various fluids are circulated in the flow path. FIG. 8 is a diagram showing the relationship between the true flow rate of various fluids and the sensor output signal when the characteristics of water in FIG. 7 are used as a reference. FIG. 9 is a flowchart illustrating the operation of the valve opening degree indicating unit of the thermal flow sensor device according to the first embodiment of the present invention. FIG. 10 is a flowchart illustrating the operations of the output signal acquisition unit, the required time measurement unit, and the correction coefficient calculation unit of the thermal flow sensor device according to the first embodiment of the present invention. FIG. 11 is a flowchart illustrating the operation of the flow rate derivation unit and the flow rate correction unit of the thermal flow sensor device according to the first embodiment of the present invention. FIG. 12 is a block diagram showing a configuration of a thermal flow sensor device according to a second embodiment of the present invention. FIG. 13 is a flowchart illustrating the operation of the valve opening degree indicating unit and the execution management unit of the thermal flow sensor device according to the second embodiment of the present invention. FIG. 14 shows the operations of the output signal acquisition unit, the required time measurement unit, the correction coefficient calculation unit, the execution management unit, the history information presentation unit, and the alarm output unit of the thermal flow sensor device according to the second embodiment of the present invention. It is a flowchart to explain. FIG. 15 is a diagram showing an example of presenting history information of correction coefficients in the second embodiment of the present invention. FIG. 16 is a block diagram showing a configuration example of a computer that realizes the thermal flow sensor device according to the first and second embodiments of the present invention.

[Principle 1 of the invention]
The inventor uses, for example, _{the true flow rate-thermal flow sensor flow rate output characteristics when water (H 2} O) is used as the reference measurement fluid (that is, when water is calibrated as the measurement fluid) and fluids other than water. Comparing the true flow rate and the flow rate output characteristics when the fluid is circulated through the same flow sensor, as shown in FIG. 1, the flow rate output of the thermal flow sensor and the true flow rate are roughly proportional to each other in any fluid. I found out that.

In the example of FIG. 1, the types of fluids are water, isopropyl alcohol concentration, isopropyl alcohol high concentration, Florinate (registered trademark), hydrogen peroxide low concentration, hydrogen peroxide concentration, hydrogen peroxide high concentration, sulfuric acid low concentration. , Low concentration in sulfuric acid, high concentration in sulfuric acid, high concentration in sulfuric acid, and the temperature of each fluid was 25 ° C.

In addition, the inventor has determined that the fluid supply pressure is constant (when a valve that controls the flow rate of the fluid based on the flow rate value measured by the thermal flow sensor is arranged upstream or downstream of the thermal flow sensor. If the fluctuation is small), it can be considered that the relationship between the valve opening and the flow rate (constant magnification) can be roughly grasped in advance.

Then, the valve opening is changed so that the theoretical flow rate changes at a constant rate of change, and the theoretical required time until the magnification of the theoretical flow rate with respect to the initial value of the theoretical flow rate reaches the closing price and the flow rate output value with respect to the initial value of the flow rate output. I came up with the idea that the correction coefficient of the thermal flow sensor according to the measurement fluid can be calculated based on the ratio of the magnification to the time required to reach the closing price. Thereby, in the present invention, it is possible to reduce the trouble of setting the correction coefficient and reduce the variation.

[Principle 2 of the invention]
It can be expected to detect a state change (abnormality occurrence, etc.) of the measurement fluid by periodically executing a procedure for calculating the correction coefficient, transmitting it to, for example, a higher-level device and monitoring it.

[First Example]
Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing a configuration of a thermal flow sensor device according to a first embodiment of the present invention. This embodiment is an example corresponding to the principle 1 of the above invention. In the example of FIG. 2, an example of a mass flow controller including a thermal flow sensor device will be described, but the present invention can be applied to other than the mass flow controller. In the case of the mass flow controller, the valve is arranged downstream of the thermal flow sensor, but the valve may be arranged upstream of the thermal flow sensor.

The thermal flow sensor device 1 stores in advance information on a theoretical curve that approximates the relationship between the thermal flow sensor 2 and the valve opening degree and the flow rate of the measured fluid when the supply pressure is constant. Valve opening degree-flow rate characteristic When calculating and setting the information storage unit 3, the flow rate-output signal reference characteristic information storage unit 4 that stores information about the relationship between the flow rate in the reference measurement fluid and the sensor output signal in advance, and the correction coefficient. An opening instruction signal that specifies the valve opening so that the increase in the theoretical flow rate obtained from the theoretical curve for each unit time of the magnification with respect to the initial value of the theoretical flow rate at the start of calculation and setting of the correction coefficient becomes the specified value. The valve opening instruction unit 5 transmitted to the control device that controls the valve, the flow rate output initial value of the thermal flow sensor 2 at the start of calculation / setting of the correction coefficient, and the opening instruction signal for changing the valve opening are transmitted. The output signal acquisition unit 6 that acquires the flow rate output value of the thermal flow sensor 2 after that time, and the first until the ratio of the flow rate output value of the thermal flow sensor 2 to the initial value of the flow rate output reaches the closing price. The required time measuring unit 7 that measures the required time, the specified value of the increase amount of the theoretical flow rate obtained from the theoretical curve for each unit time with respect to the initial value of the theoretical flow rate at the start of calculation and setting of the correction coefficient, and this magnification. The magnification of the theoretical flow rate with respect to the initial value of the theoretical flow rate reaches the closing price based on the information of the magnification information storage unit 8 that stores the closing price of The correction coefficient calculation unit 9 that calculates the second required time up to and calculates the ratio of the first required time to the second required time as the correction coefficient, and the correction coefficient to the flow rate output value of the thermal flow sensor 2. It is provided with a flow rate correction unit 10 for correcting the flow rate by multiplying by.

The flow rate control device 19 of FIG. 1 is provided in the mass flow controller together with the valve. FIG. 3 is a cross-sectional view showing the structure of the mass flow controller. In FIG. 3, 11 is the main body block of the mass flow controller, 12 is the sensor package, 13 is the head portion of the sensor package 12, 14 is the flow sensor chip mounted on the head portion 13, 15 is the valve, and 16 is the inside of the main body block 11. 17 is an opening on the inlet side of the flow path 16, and 18 is an opening on the exit side of the flow path 16.

The fluid flows into the flow path 16 from the opening 17, passes through the valve 15, and is discharged from the opening 18. The thermal flow sensor 2 measures the flow rate of the fluid flowing through the flow path 16.
The flow rate control device 19 of the mass flow controller performs flow rate control based on the flow rate of the fluid measured by the thermal flow sensor device 1. Specifically, the flow rate control device 19 drives the valve 15 so that the measured flow rate and the set value match.

FIG. 4A is a plan view showing the structure of the flow sensor chip 14 of the thermal flow sensor 2, and FIG. 4B is a sectional view taken along line AA of the flow sensor chip 14 of FIG. 4A. In FIGS. 4A and 4B, 130 is a base silicon chip, 131 is a thin-walled diaphragm formed by providing a space 132 on the upper surface of the silicon chip 130, and 133 is a diaphragm made of, for example, silicon nitride. A heater made of a metal thin film formed on the diaphragm 131, 134 is a temperature sensor made of a metal thin film heat-sensitive resistor formed on the upstream side of the heater 133 on the diaphragm 131, and 135 is a downstream of the heater 133 on the diaphragm 131. A temperature sensor made of a metal thin film heat-sensitive resistor formed on the side, 136 is an ambient temperature sensor made of a metal thin film heat-sensitive resistor, and 137 is a slit penetrating the diaphragm 131.

The heater 133 and the temperature sensors 134 to 136 are covered with, for example, a thin film insulating layer 138 made of silicon nitride. The ambient temperature sensor 136 is arranged in a place where the temperature of the fluid can be detected without being affected by the heat from the heater 133. The flow sensor chip 14 is mounted on the head portion 13 of the sensor package 12 with the surface shown in FIG. 4A facing down, and is mounted on the main body block 11 so as to be exposed to the measurement fluid.

The structure of the thermal flow sensor 2 and its principle as described above are disclosed in, for example, Patent Document 1. FIG. 5 is a block diagram showing a configuration of an electric circuit of the thermal flow sensor 2. The heater drive unit 20 includes a bridge circuit 21, a transistor Q1, a differential amplifier A1, fixed resistors R3, R4, R5, R6, and a capacitor C1. The bridge circuit 21 is a circuit for driving the heater 133, and includes the heater 133, an ambient temperature sensor 136, and a pair of fixed resistors R1 and R2. The power supply voltage + V is supplied from a predetermined power supply (not shown) and applied to the bridge circuit 21 via the transistor Q1.

The differential amplifier A1 detects the bridge output voltage of the bridge circuit 21 according to the change in the resistance value between the heater 133 and the ambient temperature sensor 136, and feeds back the transistor Q1 so that the bridge output voltage becomes zero (0). Controlled to adjust the heater drive voltage applied to the bridge circuit 21. As a result, the heater drive unit 20 controls so that the heat generation temperature of the heater 133 is always higher than the ambient temperature by a constant temperature.

On the other hand, the flow rate measuring unit 22 includes a bridge circuit 23, a differential amplifier A2, a fixed resistor Rf, and a flow rate deriving unit 24. The bridge circuit 23 includes a pair of temperature sensors 134 and 135 and a pair of fixed resistors Rx and Ry. The power supply voltage + V is supplied from a predetermined power supply (not shown) and applied to the bridge circuit 23.

The differential amplifier A2 outputs the potential of the difference between the output voltages V4 and V5 of the bridge circuit 23 as a sensor output signal (temperature difference signal) Vt corresponding to the temperature difference measured by the temperature sensors 134 and 135. In this way, the change in resistance value due to heat of the pair of temperature sensors 134 and 135 is converted into the sensor output signal Vt.

The flow rate deriving unit 24 receives the sensor output signal Vt output from the differential amplifier A2 based on the relationship between the flow rate PV stored in advance in the flow rate-output signal reference characteristic information storage unit 4 and the sensor output signal Vt, which will be described later. Is converted into the value of the flow rate PV of the measurement fluid.

Next, the characteristic configuration of the thermal flow sensor device 1 of this embodiment will be described. The valve opening-flow rate characteristic information storage unit 3 stores in advance information about the relationship between the opening of the valve 15 and the flow rate PV of the fluid passing through the valve 15 when the supply pressure of the fluid is constant. .. For example, Japanese Patent No. 5931668 shows that when the opening degree of the valve 15 is changed linearly with time, the flow rate volume of the fluid flowing through the flow path is smaller toward the higher opening side.

As described above, it is known that the opening MV of the valve 15 and the flow rate PV have a non-linear relationship, and the amount of change in the flow rate PV decreases with respect to the amount of change in the opening MV on the higher opening side. There is. The outline of the relationship between the opening MV and the flow rate PV is shown in FIG. In the example of FIG. 6, for convenience, the opening MV of the valve 15 and the flow rate PV are normalized to values of 0 to 100%. Since the characteristic shown in FIG. 6 is a non-linear convergence phenomenon, it can be expressed by the exponential function of the following equation.
PV = K {1.0-exp (-MV / A)} ... (1)

In this way, the function that approximates the relationship between the opening MV of the valve 15 and the flow rate PV includes a constant term (1.0), a term related to the opening MV, and a gain representing the magnitude of the flow rate PV with respect to the opening MV. Defined by the coefficient K with respect to. A in equation (1) is a coefficient that gives a non-linear convergence state. The curves cur1 to cur4 in FIG. 6 are all premised on a constant supply pressure of the fluid, and as an example, all the curves have A = 30.0. In this case, equation (1) becomes equation (2).
PV = K {1.0-exp (-MV / 30.0)} ... (2)

In the case of the curve cur1, K = 104.0. Then, in FIG. 6, for example, the flow rate PV of the opening MV = 50% with respect to the flow rate PV of the opening MV = 20% of the valve 15 becomes 1.667 times in any of the curves cur1 to cur4. Since the same relationship can be said for other valve openings, it is possible to determine the valve opening instruction so that the theoretical flow rate changes at a specified rate of change by referring to this characteristic.

The valve opening-flow rate characteristic information storage unit 3 may store an equation of a theoretical curve (function) that approximates the relationship between the opening MV of the valve 15 and the flow rate PV, or the opening obtained from the function. The value of the theoretical flow rate PV for each MV may be stored. In order to identify the function, for example, the flow rate test of the mass flow controller may be performed in advance to check the values of the coefficient A and the gain K.

The flow rate-output signal reference characteristic information storage unit 4 stores in advance information about the relationship between the flow rate of the reference measuring fluid (for example, water) and the sensor output signal of the thermal flow sensor 2. FIG. 7 is a diagram showing the relationship between the true flow rate and the sensor output signal Vt when various fluids are circulated in the flow path 16. In the example of FIG. 7, the types of fluids are water, isopropyl alcohol concentration, isopropyl alcohol high concentration, Florinate (registered trademark), hydrogen peroxide low concentration, hydrogen peroxide concentration, hydrogen peroxide high concentration, sulfuric acid low concentration. , Low concentration in sulfuric acid, high concentration in sulfuric acid, high concentration in sulfuric acid, and the temperature of each fluid was 25 ° C. The sensor output signal Vt is normalized to a value of 0 to 100%.

If water is used as a reference, only the characteristics of water are investigated in advance, and the relationship between the true flow rate when the measurement fluid is water and the sensor output signal Vt is stored in the flow rate-output signal reference characteristic information storage unit 4. Just leave it. FIG. 7 is a characteristic diagram depicting the sensor output signal Vt when the true flow rate of water reaches 30 mL / min as 100%.

As described above, the relationship between the true flow rate and the flow rate output of the thermal flow sensor 2 (the output of the flow rate derivation unit 24) when water is used as the reference measurement fluid is as shown in FIG. As shown in FIG. 1, in any of the fluids, the flow rate output of the thermal flow sensor 2 and the true flow rate show a characteristic of being substantially proportional to each other. Therefore, the proportional coefficient of this characteristic is the correction coefficient obtained in this embodiment. Involved.

FIG. 8 shows the true flow rates of various fluids and the sensor output signal Vt when the characteristics of water in FIG. 7 are used as a reference (when the sensor output signal Vt at each flow rate when the measurement fluid is water is 100%). It is a figure which shows the relationship of. According to FIG. 8, it can be seen that a certain degree of flow rate measurement accuracy can be ensured by correcting with a substantially constant correction coefficient based on the characteristics of water in most flow rate regions.

FIG. 9 is a flowchart explaining the operation of the valve opening degree indicating unit 5, and FIG. 10 is a flowchart explaining the operations of the output signal acquisition unit 6, the required time measuring unit 7, and the correction coefficient calculating unit 9.
When the valve opening degree indicating unit 5 automatically sets the correction coefficient, the valve opening degree indicating unit 5 sends an opening degree instruction signal to the flow rate control device 19 so that the opening degree MV of the valve 15 becomes a predetermined initial value (for example, MV = 20%). (FIG. 9, step S100).

When the flow rate control device 19 receives the opening degree instruction signal from the valve opening degree instruction unit 5, the flow rate control device 19 preferentially performs the process corresponding to the opening degree instruction signal. That is, the flow rate control device 19 temporarily stops the above flow rate control, and controls the valve 15 so that the opening degree MV becomes the opening degree MV specified by the opening degree instruction signal. Then, the flow rate control device 19 returns to the flow rate control after a lapse of a certain period of time after receiving the last opening degree instruction signal. This fixed time is set to a time sufficient for, for example, the output signal acquisition unit 6 described later to finish acquiring the flow rate output value.

The output signal acquisition unit 6 acquires the flow rate output initial value PV1 output from the flow rate derivation unit 24 of the thermal flow sensor 2 when the opening degree of the valve 15 is the initial value MV = 20% (FIG. 10 step S200). .. In order to wait for the flow rate fluctuation when the opening degree of the valve 15 changes to MV = 20% to settle down, the output signal acquisition unit 6 waits after a predetermined waiting time elapses after the opening degree indicating signal is transmitted. It is desirable to acquire the initial flow rate output value PV1 of the thermal flow sensor 2.

After the output signal acquisition unit 6 acquires the flow rate output initial value PV1, the valve opening degree indicating unit 5 refers to the information of the valve opening degree-flow rate characteristic information storage unit 3 and the magnification information storage unit 8, and the opening degree MV-flow rate. On the theoretical curve (function) of PV, the temporal transition of the opening MV is obtained from the theoretical curve so that the amount of increase of the magnification Ra with respect to the initial value of the theoretical flow rate for each unit time becomes the specified value ΔR. The opening degree instruction signal is sequentially transmitted to the flow rate control device 19 so that the opening degree of the valve 15 changes according to the transition (step S101 in FIG. 9).

The valve opening degree indicating unit 5 corresponds to the initial value MV = 20% of the opening degree on the theoretical curve when, for example, MV = 20% is predetermined as the initial value of the opening degree MV when the correction coefficient is set. The theoretical flow rate initial value PVref is obtained. In the magnification information storage unit 8, the final value Rref of the theoretical flow rate PV magnification Ra = PV / PVref with respect to the theoretical flow rate initial value PVref is stored in advance, and the specified numerical value ΔR of the increase amount for each unit time (1 second) of the magnification Ra. (For example, 0.05) is stored in advance.

On the theoretical curve, the valve opening indicating unit 5 increases the amount of increase in the ratio Ra (the initial value of Ra is 1) of the theoretical flow rate PV with respect to the theoretical flow rate initial value PVref every second to a specified value ΔR (for example, 0.05). That is, the opening degree of the valve 15 is gradually increased so that the magnification Ra changes such as 1.05 times, 1.10 times, 1.15 times, and so on. In this way, the valve opening degree indicating unit 5 adjusts the opening degree of the valve 15 on the theoretical curve until the magnification Ra of the theoretical flow rate PV with respect to the theoretical flow rate initial value PVref reaches the closing price Rref (YES in step S102 of FIG. 9). The transmission process (step S101) of the opening degree instruction signal to be changed is repeated.

The output signal acquisition unit 6 acquires the flow rate output value PV2 output from the flow rate derivation unit 24 of the thermal flow sensor 2 after the time when the opening degree instruction signal for changing the opening degree of the valve 15 is first transmitted ( FIG. 10 Step S201).
The required time measuring unit 7 measures the elapsed time t from the time when the opening degree instruction signal for changing the opening degree of the valve 15 is first transmitted (step S202 in FIG. 10).

The output signal acquisition unit 6 and the required time measurement unit 7 step up until the magnification Rb = PV2 / PV1 of the flow rate output value PV2 with respect to the flow rate output initial value PV1 reaches the above closing price Rref (YES in step S203 of FIG. 10). The processes of S201 and S202 are repeated.
The cycle for changing the opening degree of the valve 15 (transmission cycle of the opening degree instruction signal) may be in units of 1 second, but since it is necessary for the required time measuring unit 7 to measure the time in units of less than 1 second, the step The processing cycle of S201 and S202 needs to be less than 1 second.

The correction coefficient calculation unit 9 obtains the required time t (first required time) until the magnification Rb of the flow rate output value PV2 with respect to the flow rate output initial value PV1 reaches the closing price Rref and the magnification Rb reaches the closing price Rref. When (YES in step S203), the theoretical flow rate initial value on the theoretical curve is based on the information stored in the valve opening-flow rate characteristic information storage unit 3 and the information stored in the magnification information storage unit 8. The theoretical required time tref (second required time) until the multiple Ra of the theoretical flow rate PV with respect to PVref reaches the closing price Rref is calculated (FIG. 10 step S204).

For example, if the closing price Rref of the magnification Ra is 1.65 times and the specified value ΔR of the increase amount for each unit time (1 second) of the magnification Ra is 0.05, the theoretical flow rate initial value PVref when MV = 20% is obtained. On the other hand, the theoretical required time tref until the theoretical flow rate PV on the theoretical curve finally becomes 1.65 times is 13 seconds. Further, if the closing price Rref of the magnification Ra is 1.25 times, the theoretical required time treff until the theoretical flow rate PV becomes 1.25 times the theoretical flow rate initial value PVref is 5 seconds.

Then, the correction coefficient calculation unit 9 calculates the ratio t / tref of the required time t to the calculated theoretical required time tref as the correction coefficient C, and sets this correction coefficient C in the flow rate correction unit 10 (step S205 in FIG. 10). ..

For example, on the theoretical curve, when the theoretical required time treff until the magnification Ra of the theoretical flow rate PV with respect to the theoretical flow rate initial value PVref reaches the closing price Rref = 1.25 times is 5 seconds, the flow rate output with respect to the initial flow rate output value PV1. Assuming that the time required for the magnification Rb of the value PV2 to reach the closing price Rref = 1.25 times is 6.535 seconds, the correction coefficient C is t / tref = 6.535 / 5 = 1.307 (130). It is calculated as 0.7%). According to FIG. 8, this value is a numerical value of the correction coefficient C automatically obtained when the sulfuric acid high concentration (or a fluid having a thermal conductivity equivalent to this) is the measurement fluid.

FIG. 11 is a flowchart illustrating the operation of the flow rate derivation unit 24 and the flow rate correction unit 10 of the thermal flow sensor 2.
The flow rate derivation unit 24 uses the flow rate PV of the sensor output signal Vt output from the differential amplifier A2 based on the relationship between the flow rate PV stored in the flow rate-output signal reference characteristic information storage unit 4 and the sensor output signal Vt. Is converted to the value of (FIG. 11, step S300).

The flow rate correction unit 10 corrects the flow rate PV by multiplying the value of the flow rate PV output from the flow rate extraction unit 24 of the thermal flow sensor 2 by the correction coefficient C (FIG. 11, step S301). The initial value (value when the measurement fluid is water) of the correction coefficient C before being set by the correction coefficient calculation unit 9 is 1.
The flow rate derivation unit 24 and the flow rate correction unit 10 perform the processes of steps S300 and S301 at regular time intervals during the flow rate control (flow rate measurement).

In this way, in this embodiment, it is possible to reduce the trouble of setting the correction coefficient C and the variation in the correction coefficient C. In this embodiment, if the valve opening instruction is managed so that the increase amount of the magnification Ra of the theoretical flow rate PV with respect to the theoretical flow rate initial value PVref on the theoretical curve becomes the specified value ΔR every second, the valve opening degree is set. -Even if a slight error occurs in the characteristics stored in the flow rate characteristic information storage unit 3, it is possible to appropriately correct the valve opening degree instruction.

The timing for starting the process described with reference to FIG. 10 may be when an operator gives an instruction to start setting, or when a predetermined timing is reached as in the second embodiment described later. ..

[Second Example]
Next, a second embodiment of the present invention will be described. FIG. 12 is a block diagram showing the configuration of the thermal flow sensor device according to the second embodiment of the present invention, and the same configurations as those in FIG. 2 are designated by the same reference numerals. This embodiment is an example corresponding to the principle 2 of the above invention.

The thermal flow sensor device 1a of the present embodiment includes a thermal flow sensor 2, a valve opening degree-flow rate characteristic information storage unit 3, a flow rate-output signal reference characteristic characteristic information storage unit 4, and a valve opening degree indicating unit 5. , The output signal acquisition unit 6, the required time measurement unit 7, the magnification information storage unit 8, the correction coefficient calculation unit 9, and the flow rate correction unit 10 perform the calculation / setting process of the correction coefficient at a predetermined timing. Calculated by the execution management unit 30 that controls and manages to execute, the history information presentation unit 31 that presents the history information of the correction coefficient C from the past to the present calculated by the correction coefficient calculation unit 9, and the correction coefficient calculation unit 9. It is provided with an alarm output unit 32 that outputs an alarm when the degree of deviation of the corrected correction coefficient C from the normal value exceeds a specified amount.

FIG. 13 is a flowchart illustrating the operation of the valve opening degree indicating unit 5 and the execution management unit 30 of this embodiment, and FIG. 14 shows the output signal acquisition unit 6, the required time measurement unit 7, the correction coefficient calculation unit 9, and the execution management unit 30. It is a flowchart explaining the operation of the history information presentation unit 31 and the alarm output unit 32.
The execution management unit 30 sets the valve opening degree indicating unit 5 and the output signal so as to start the correction coefficient calculation / setting process when the predetermined timing is reached (YES in step S400 in FIG. 13 and step S500 in FIG. 14). An instruction is given to the acquisition unit 6, the required time measurement unit 7, and the correction coefficient calculation unit 9 (step S401 in FIG. 13 and step S501 in FIG. 14).

The operation of the valve opening degree indicating unit 5 (steps S402 to S404 in FIG. 13) is as described in steps S100 to S102.
The operations of the output signal acquisition unit 6, the required time measurement unit 7, and the correction coefficient calculation unit 9 (steps S502 to S507 in FIG. 14) are as described in steps S200 to S205.
The history information presentation unit 31 stores the correction coefficient C from the past to the present calculated by the correction coefficient calculation unit 9, and presents the history information of the correction coefficient C from the past to the present (step S508 in FIG. 14). ..

FIG. 15 is a diagram showing an example of presenting history information of the correction coefficient C. In the example of FIG. 15, a graph is displayed on the screen 310 displayed by the history information presentation unit 31 with the number of times the correction coefficient C is calculated and set as the horizontal axis and the correction coefficient C as the vertical axis. Further, the history information presenting unit 31 displays on the screen 310 a line L1 indicating + 5% and a line L2 indicating −5% of the correction coefficient C calculated and set at the earliest.

The alarm output unit 32 has a degree of deviation from the latest normal value of the correction coefficient C calculated by the correction coefficient calculation unit 9 (usually the correction coefficient C calculated and stored at the initial stage of use of the thermal flow sensor device). When the amount exceeds the specified amount (YES in step S509 of FIG. 14), an alarm is output (step S510 of FIG. 14).

For example, the alarm output unit 32 outputs an alarm when the latest correction coefficient C deviates from the normal value by ± 5% or more. As an alarm output method, for example, there are methods such as displaying the content for notifying the occurrence of the alarm and transmitting the information for notifying the occurrence of the alarm to the outside.

In this way, in this embodiment, it can be expected to detect a state change (abnormality occurrence, etc.) of the measurement fluid by monitoring the correction coefficient C calculated and set by the correction coefficient calculation unit 9.

As described above, in the first and second embodiments, an example of a mass flow controller including a thermal flow sensor device is described, but the present invention can be applied to other than the mass flow controller. Further, the valve may be arranged either upstream or downstream of the thermal flow sensor 2.

Of the thermal flow sensor devices of the first and second embodiments, at least the valve opening-flow characteristic information storage unit 3, the flow rate-output signal reference characteristic information storage unit 4, the valve opening indication unit 5, and the output signal acquisition unit 6 and the required time measurement unit 7, the magnification information storage unit 8, the correction coefficient calculation unit 9, the flow rate correction unit 10, the execution management unit 30, the history information presentation unit 31, the alarm output unit 32, and the flow rate derivation unit 24 are CPUs. It can be realized by a computer equipped with a Central Processing Unit), a storage device and an interface, and a program that controls these hardware resources.

A configuration example of this computer is shown in FIG. The computer includes a CPU 200, a storage device 201, and an interface device (hereinafter, abbreviated as I / F) 202. The flow rate measuring unit 22 of the thermal flow sensor 2 and the flow rate control device 19 are connected to the I / F 202. In such a computer, a program for realizing the flow rate correction method of the present invention is stored in the storage device 201. The CPU 200 executes the processes described in the first and second embodiments according to the program stored in the storage device 201. Further, as is well known, the flow rate control device 19 can also be realized by a computer and a program.

The present invention can be applied to a thermal flow sensor.

1,1a ... Thermal flow sensor device, 2 ... Thermal flow sensor, 3 ... Valve opening-flow characteristic information storage unit, 4 ... Flow rate-output signal reference characteristic information storage unit, 5 ... Valve opening indication unit, 6 ... output signal acquisition unit, 7 ... required time measurement unit, 8 ... magnification information storage unit, 9 ... correction coefficient calculation unit, 10 ... flow rate correction unit, 11 ... main body block, 12 ... sensor package, 13 ... head unit, 14 ... Flow sensor chip, 15 ... valve, 16 ... flow path, 17, 18 ... opening, 19 ... flow control device, 20 ... heater drive unit, 21, 23 ... bridge circuit, 22 ... flow measurement unit, 24 ... flow lead unit, 30 ... Execution management unit, 31 ... History information presentation unit, 32 ... Alarm output unit, 130 ... Silicon chip, 131 ... Diaphragm, 133 ... Heater, 134, 135 ... Temperature sensor, 136 ... Ambient temperature sensor, 137 ... Slit.

Claims (4)

A thermal flow sensor that is arranged in the flow path through which the measuring fluid flows and is configured to output a sensor output signal obtained from a temperature sensor that measures the temperature of the measuring fluid.
It is configured to store in advance the information of the theoretical curve that approximates the relationship between the opening degree of the valve arranged at the location of the flow path on the upstream side or the downstream side of the thermal flow sensor and the flow rate of the measurement fluid. Valve opening-flow rate characteristic information storage unit,
A flow rate-output signal reference characteristic information storage unit configured to store information about the relationship between the flow rate in the reference measurement fluid and the sensor output signal in advance.
A flow rate deriving unit configured to convert the sensor output signal output from the thermal flow sensor into a flow rate value based on the information stored in the flow rate-output signal reference characteristic information storage unit.
A flow rate correction unit configured to correct the flow rate by multiplying the flow rate output value of this flow rate derivation unit by a correction coefficient,
It is configured to store in advance the specified value of the increase amount of the theoretical flow rate obtained from the theoretical curve for each unit time with respect to the initial value of the theoretical flow rate at the start of calculation and setting of the correction coefficient, and the closing price of this magnification. Magnification information storage unit and
When calculating and setting the correction coefficient, the valve opening-flow rate characteristic information storage unit and the information of the magnification information storage unit are referred to, and the amount of increase in the theoretical flow rate for each unit time of the magnification is the specified value. A valve opening instruction unit configured to transmit an opening instruction signal for designating a valve opening so as to be transmitted to a control device that controls the valve.
The initial value of the flow rate output of the flow rate derivation unit at the start of calculation / setting of the correction coefficient and the flow rate output value of the flow rate derivation unit after the time when the opening instruction signal for changing the valve opening degree is transmitted are acquired. The output signal acquisition unit configured as
A required time measuring unit configured to measure the first required time until the magnification of the flow rate output value with respect to the initial flow rate output value reaches the closing price.
Based on the information of the valve opening-flow rate characteristic information storage unit and the magnification information storage unit, the second required time until the magnification of the theoretical flow rate with respect to the theoretical flow rate initial value reaches the closing price is calculated. A thermal flow including a correction coefficient calculation unit configured to calculate the ratio of the first required time to the second required time as the correction coefficient and set it in the flow rate correction unit. Sensor device. In the thermal flow sensor device according to claim 1,
An execution management unit configured to control and manage the calculation / setting process of the correction coefficient at a predetermined timing, and an execution management unit.
A history information presentation unit configured to present history information of correction coefficients from the past to the present calculated by the correction coefficient calculation unit, and a history information presentation unit.
It is further provided with an alarm output unit configured to output an alarm when the degree of deviation of the correction coefficient calculated by the correction coefficient calculation unit from the normal value exceeds a specified amount. Thermal flow sensor device. Flow rate-output signal that stores information about the relationship between the flow rate of the reference measurement fluid and the sensor output signal in advance Refers to the reference characteristic information storage unit, and the thermal flow arranged in the flow path through which the measurement fluid flows. The first step of converting the sensor output signal of the sensor into a fluid output value,
The second step of correcting the flow rate by multiplying the flow rate output value by the correction coefficient,
When calculating and setting the correction coefficient, the relationship between the opening degree of the valve arranged at the location of the flow path on the upstream side or the downstream side of the thermal flow sensor and the flow rate of the measured fluid was approximated. A unit of magnification of the theoretical flow rate obtained from the theoretical curve with respect to the initial value of the theoretical flow rate at the start of calculation and setting of the correction coefficient while referring to the valve opening-flow rate characteristic information storage unit that stores the information of the theoretical curve in advance. With reference to the magnification information storage unit that stores the specified value of the increase amount for each hour and the closing price of this magnification in advance, the valve is opened so that the increase amount of the theoretical flow rate for each unit time of the magnification becomes the specified value. A third step of transmitting an opening instruction signal for specifying the degree to the control device that controls the valve, and
The fourth step of acquiring the initial value of the flow rate output value at the start of calculation / setting of the correction coefficient, and
A fifth step of acquiring the flow rate output value after the time when the opening instruction signal for changing the valve opening is transmitted, and
A sixth step of measuring the first required time until the magnification of the flow rate output value with respect to the initial value of the flow rate output value reaches the closing price, and
Based on the information of the valve opening degree-flow rate characteristic information storage unit and the magnification information storage unit, the second required time until the magnification of the theoretical flow rate with respect to the theoretical flow rate initial value reaches the closing price is calculated. A flow rate correction method comprising a seventh step of calculating the ratio of the first required time to the second required time as the correction coefficient. In the flow rate correction method according to claim 3,
The eighth step of instructing the calculation / setting process of the correction coefficient to be executed at a predetermined timing, and
The ninth step of presenting the history information of the correction coefficient from the past to the present calculated by the seventh step, and
A flow rate correction method further including a tenth step of outputting an alarm when the degree of deviation of the correction coefficient calculated by the seventh step from the normal value exceeds a predetermined amount.

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