WO2019064819A1

WO2019064819A1 - Flow rate measurement device

Info

Publication number: WO2019064819A1
Application number: PCT/JP2018/026185
Authority: WO
Inventors: 克行山本; 憲一半田
Original assignee: オムロン株式会社
Priority date: 2017-09-29
Filing date: 2018-07-11
Publication date: 2019-04-04
Also published as: JP2019066276A; JP7104502B2

Abstract

Provided is a flow rate measurement device wherein measurement precision is maintained and power consumption is reduced, while suppressing an increase in pressure loss. The flow rate measurement device comprises: a flow rate detection unit that detects a value corresponding to the flow rate of a fluid to be measured flowing through a main flow path at a prescribed measurement timing; a flow rate calculation unit that calculates the flow rate of the fluid to be measured on the basis of the value corresponding to the flow rate detected by the flow rate detection unit; and a measurement interval changing unit that, if any periodic change in the flow rate is detected on the basis of the flow rate calculated by the flow rate calculation unit, changes the measurement timing on the basis of the detected period of the change.

Description

Flow measurement device

The present invention relates to a flow rate measuring device.

Heretofore, there has been proposed a measuring device which includes a heater and a sensor and calculates the flow velocity or flow rate of the fluid by the sensor detecting a temperature distribution changing with the flow of the fluid.

For example, a member having a minimal cross-section flow path having a smaller cross section than the cross section of the flow path at a position where the flow rate sensor is provided on the wall surface of the flow path where the fluid to be measured flows Has been proposed (for example, Patent Document 1). According to the present technology, by providing the perforated plate, the influence of the pulsation can be reduced.

WO 2004/090476

In a flow rate measuring device using a sensor, the measurement accuracy of the flow rate can be improved by shortening the sampling interval of the sensor. However, shortening the sampling interval increases the number of measurements per hour and also increases the power consumption of the sensor.

Also, depending on the application of the sensor, such as, for example, a gas meter, the pressure drop allowed for the sensor may be limited. That is, if the pressure loss increases, for example, there is a risk that the fluid can not be supplied to the device connected to the end of the pipe. In such applications, it has been difficult to reduce the effects of minor fluctuations in the flow rate solely by structural measures such as providing a perforated plate in the flow path.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the power consumption while maintaining the measurement accuracy while suppressing the increase in pressure loss in the flow rate measuring device.

The flow rate measurement device according to the present invention is based on a flow rate detection unit that detects a value corresponding to the flow rate of the measurement target fluid flowing through the main flow path at a determined measurement timing, and a value corresponding to the flow rate detected by the flow rate detection unit. Change the measurement timing based on the period of the detected change when the periodic change of the flow is detected based on the flow calculated by the flow calculating unit and the flow calculating unit that calculates the flow of the fluid to be measured And a measurement interval changing unit.

When a periodic change in the flow rate is detected, by changing the measurement timing based on the measured period, for example, when pulsation or fluctuation occurs in the flow rate of the fluid to be measured, based on the periodic change Measurement timing can be changed. Therefore, power consumption can be reduced by reducing the number of measurements per time while determining the timing of measurement so as not to cause a deviation in the flow rate. In addition, since such processing can be performed by software, no structural measures are necessary and there is no risk of pressure loss.

Further, the measurement interval change unit may detect a change in the value of the flow rate calculated by the flow rate calculation unit, and may detect a periodic change using the change. Specifically, any measurement value can be used as a reference for detecting periodicity from the value of flow rate. That is, periodic changes can be detected based on the regularity of timing when any value is measured.

In addition, the measurement interval changing unit may change the measurement timing to intermittently detect a value according to the flow rate based on the detected change cycle. If a value corresponding to the flow rate is intermittently detected based on the cycle of the detected change, even if the flow rate fluctuates within one cycle, sampling can be performed without bias, and the measured flow rate Accuracy can be maintained.

In addition, each of the detection of values according to the flow rate performed intermittently may be started at intervals of integral multiples of the cycle of the detected change. In this way, sampling can be performed without bias on the basis of the cycle of change in flow rate, and the accuracy of the measured flow rate can be maintained.

The contents described in the means for solving the problems can be combined as much as possible without departing from the problems and technical ideas of the present invention. Further, the contents of the flow rate measuring device shown in the means for solving the problems can be provided as a program to be executed by an arithmetic device such as a method or processor or a medium for storing the program.

In the flow rate measuring device, while suppressing the increase in pressure loss, it is possible to maintain the measurement accuracy and reduce the power consumption.

It is an exploded perspective view showing an example of a flow rate measuring device. It is a sectional view showing an example of a flow rate measuring device. It is a top view which shows a sub flow path part. It is a perspective view showing an example of a sensor element. It is sectional drawing for demonstrating the structure of a sensor element. It is a top view which shows schematic structure of a flow volume detection part. It is a top view which shows schematic structure of a physical-property value detection part. It is a block diagram which shows the function structure of a circuit board. It is a processing flow figure showing an example of flow rate measurement processing. It is a figure showing typically the time change of the flow rate per unit time in case a pulsation arises in change of a flow rate. It is a figure which shows typically the relationship between the temperature of the micro heater of a sensor element, and measurement timing. It is a graph which shows sensor sensitivity ratio on a vertical axis | shaft, and thermal conductivity on a horizontal axis. It is a graph which shows sensor sensitivity ratio on the vertical axis, and shows ΔT on the horizontal axis. It is a figure which shows the modification of a sub flow path part. It is a figure which shows the modification of a sub flow path part. It is a figure which shows the modification of a sub flow path part. It is a figure which shows the modification of a sub flow path part. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a figure which shows the modification of a flow rate measuring apparatus. It is a block diagram showing functional composition of a modification including a circuit board and a host device. It is a figure which shows the modification of a sensor element.

Hereinafter, a flow rate measuring device according to an embodiment of the present invention will be described using the drawings. The embodiment described below is an example of a flow rate measuring device, and the flow rate measuring device according to the present invention is not limited to the following configuration.

<Device configuration>
FIG. 1 is an exploded perspective view showing an example of a flow rate measuring device 1 according to the present embodiment. FIG. 2 is a cross-sectional view showing an example of the flow rate measuring device 1. The flow rate measuring device 1 is incorporated in, for example, a gas meter, a combustion device, an internal combustion engine such as a car, a fuel cell, other industrial devices such as a medical device, and a built-in device to measure the amount of fluid passing through the flow path. The dashed arrows in FIG. 1 and FIG. 2 illustrate the flow direction of the fluid.

Further, as shown in FIG. 1, the flow rate measuring device 1 according to the present embodiment includes the main flow passage portion 2, the sub flow passage portion 3, the seal 4, the circuit board 5, and the cover 6. As shown in FIGS. 1 and 2, in the present embodiment, the flow rate measuring device 1 has a sub flow passage portion 3 branched from the main flow passage portion 2. Further, the flow rate measuring device 1 includes the flow rate detecting unit 11 and the physical property value detecting unit 12 in the sub flow passage unit 3. The flow rate detection unit 11 and the physical property value detection unit 12 are thermal flow sensors including a heating unit formed by a microheater and a temperature detection unit formed by a thermopile. In the present embodiment, the physical property value detection unit 12 is used to detect the temperature of the fluid. Further, in the present embodiment, the calculated flow rate is corrected based on the physical property value, but the flow rate measuring device 1 may not include the physical property value detection unit 12.

The main flow passage portion 2 is a tubular member in which a flow passage of a fluid to be measured (hereinafter also referred to as a main flow passage) penetrates in the longitudinal direction. As shown in FIG. 2, an inlet (first inlet) 34A is formed on the upstream side with respect to the flow direction of the fluid to be measured on the inner circumferential surface of the main flow passage 2 and the outlet (downstream) A first outlet 35A is formed. For example, the axial length of the main flow passage 2 is about 50 mm, the diameter of the inner circumferential surface (inner diameter of the main flow passage 2) is about 20 mm, and the outer diameter of the main flow passage 2 is about 24 mm, It is not limited to such an example. Further, in the main flow passage portion 2, an orifice 21 is provided between the inlet 34A and the outlet 35A. The orifice 21 is a resistor whose inner diameter is smaller in the main flow passage 2 than in the front and rear thereof, and the amount of fluid flowing into the sub flow passage 3 can be adjusted by the size of the orifice 21.

In FIG. 1 and FIG. 2, the sub flow passage portion 3, which is a portion including the sub flow passage branched from the main flow passage, is provided vertically above the main flow passage portion 2. Further, the sub-flow path in the sub-flow path portion 3 includes the inflow flow path 34, the physical property value detection flow path 32, the flow rate detection flow path 33, and the outflow flow path 35. The inflow channel 34 communicates with the inflow port 34 A branching from the main flow channel 2, the outflow channel 35 communicates with the flow outlet 35 A merging with the main flow channel 2, and the sub flow channel 3 A part of the fluid flowing through the main flow passage 2 branches and flows.

The inflow channel 34 is a flow channel for allowing the fluid to be measured flowing in the main channel portion 2 to flow into the physical property value detection channel 32 and the flow rate detection channel 33. The inflow channel 34 is formed along the direction perpendicular to the flow direction of the fluid in the main channel portion 2, one end communicates with the inflow port 34A, and the other end is the physical property value detection channel 32 and the flow rate detection It communicates with the flow path 33. A part of the fluid to be measured flowing through the main flow channel 2 is further divided into the physical property value detection flow channel 32 and the flow rate detection flow channel 33 via the inflow flow channel 34. The amount of fluid corresponding to the amount of fluid flowing through the main flow passage 2 flows into the physical property value detection flow passage 32 and the flow rate detection flow passage 33. Therefore, for example, the flow rate detection unit 11 can detect a value corresponding to the amount of fluid flowing through the main flow passage unit 2.

As shown in FIG. 1, the physical property value detection flow path 32 is formed vertically above the main flow path portion 2 and extends in a direction parallel to the main flow path portion 2, and the cross section viewed from the upper side is substantially U-shaped. Flow path. The physical property value detection channel 12 for detecting the physical property value of the fluid to be measured is disposed inside the physical property value detection channel 32. One end of the physical property value detection flow path 32 communicates with the inflow port 34A via the inflow flow path 34, and the other end communicates with the outflow port 35A via the outflow flow path 35.

The flow rate detection flow path 33 is also a flow path extending in a direction parallel to the flow direction of the fluid in the main flow path portion 2 and having a substantially U-shaped cross section viewed from the upper side. In the flow rate detection flow path 33, a flow rate detection unit 11 for detecting the flow rate of the fluid to be measured is disposed inside. Further, one end of the flow rate detection flow path 33 is in communication with the inflow port 34 A via the inflow flow path 34, and the other end is in communication with the outflow port 35 A via the outflow flow path 35. The physical property detection unit 12 and the flow rate detection unit 11 are mounted on the circuit board 5 respectively. The circuit board 5 covers the upper part of the physical property value detection flow path 32 and the flow rate detection flow path 33 with the upper part opened, and the physical property value detection unit 12 is positioned in the physical property value detection flow path 32. The flow rate detection unit 11 is disposed in the flow path 33.

The outflow flow channel 35 is a flow channel for causing the measurement target fluid that has passed through the physical property value detection flow channel 32 and the flow rate detection flow channel 33 to flow out to the main flow channel portion 2. The outflow channel 35 is formed along a direction perpendicular to the main channel portion 2, one end communicates with the outlet 35A, and the other end is connected to the physical property value detection channel 32 and the flow rate detection channel 33. It is in communication. The fluid to be measured that has passed through the physical property value detection flow path 32 and the flow rate detection flow path 33 flows out to the main flow path portion 2 through the outflow flow path 35.

As described above, the physical property detection unit 12 and the flow rate detection unit 11 are configured to divide the measurement target fluid introduced from one inflow port 34A into the physical property value detection flow path 32 and the flow rate detection flow path 33, Physical property values and flow rates can be detected based on the fluid to be measured, which has almost the same conditions such as temperature and density.

In the flow rate measuring apparatus 1, after the seal 4 is fitted in the sub flow path portion 3, the circuit board 5 is disposed, and the circuit board 5 is fixed to the sub flow path portion 3 by the cover 6. The airtightness inside the road 3 is secured.

FIG. 3 is a plan view of the sub flow passage 3 shown in FIG. As shown in FIG. 3, one end of the physical property value detection flow channel 32 communicates with the inflow flow channel 34, and the other end communicates with the outflow flow channel 35. Similarly, one end of the flow rate detection flow path 33 communicates with the inflow flow path 34, and the other end communicates with the outflow flow path 35.

Further, arrows P and Q schematically represent the ratio of the flow rate of the fluid to be measured divided into the physical property value detection flow path 32 and the flow rate detection flow path 33. In the present embodiment, the cross-sectional areas of the physical property value detection flow path 32 and the flow rate detection flow path 33 are determined such that the amount of fluid divided is P to Q.

The amount of fluid actually flowing through the physical property value detection flow path 32 and the flow rate detection flow path 33 fluctuates according to the flow rate of the fluid to be measured flowing through the main flow path portion 2. The amount of fluid flowing through the flow channel 32 is a value within the detection range of the physical property value detection unit 12, and the amount of fluid flowing through the flow rate detection channel 33 is a value within the detection range of the flow detection unit 11, The size of the sub flow path portion 3 with respect to the main flow path portion 2, the size of the orifice 21, and the widths of the physical property value detection flow path 32 and the flow rate detection flow path 33 are respectively set. The widths of the physical property value detection flow path 32 and the flow rate detection flow path 33 are examples, and the present invention is not limited to the example shown in FIG.

As described above, in the flow rate measuring device 1, it is possible to individually control the flow rates of the fluid to be measured divided into the physical property value detection flow path 32 and the flow rate detection flow path 33 by adjusting the respective widths. is there. Therefore, the flow rate of the fluid to be measured flowing through the physical property value detection flow path 32 is controlled according to the detection range of the physical property value detection unit 12, and the flow rate detection flow path 33 flows according to the detection range of the flow rate detection unit 11. The flow rate of the fluid to be measured can be controlled.

The physical property value detection flow path 32 and the flow rate detection flow path 33 are not limited to the configuration formed in a substantially U-shape in top view. That is, the physical property value detection flow path 32 and the flow rate detection flow path 33 have a width (cross sectional area) in which the flow rate of the fluid to be measured passing through the physical property value detection flow path 32 and the flow rate detection flow path 33 can be controlled. If set, other shapes may be adopted.

Further, in the physical property value detection flow path 32 and the flow rate detection flow path 33, the shape of the space in which the physical property value detection unit 12 and the flow rate detection unit 11 are arranged is substantially square in top view It is not limited. The shapes of the physical property value detection flow path 32 and the flow rate detection flow path 33 may be any shape as long as the physical property value detection unit 12 or the flow rate detection unit 11 can be disposed. It can be determined according to the shape or the like.

Therefore, for example, when the size of the physical property value detection unit 12 is smaller than the width of the physical property value detection flow path 32, the width of the physical property value detection flow path 32 is made equal to the width of the physical property value detection section 12. It is also good. That is, in this case, the portion extending in the longitudinal direction of the physical property value detection channel 32 has a substantially constant width. The same applies to the flow rate detection flow path 33.

As described above, the amount of fluid flowing through the physical property value detection flow passage 32 and the flow rate detection flow passage 33 is smaller than the amount of fluid flowing through the main flow passage portion 2, but the amount of fluid flowing through the main flow passage portion 2 It changes according to. In the case where the flow rate measuring device 1 is disposed in the main flow path portion 2, it is necessary to increase the scale of the flow rate detection portion 11 and the physical property value detection portion 12 according to the amount of fluid flowing through the main flow path portion 2. In the embodiment, by providing the sub flow passage 3 branched from the main flow passage 2, the flow rate of the fluid can be measured by the flow detection unit 11 with small scale and the physical property detection unit 12 with a small scale.

Further, the cross sectional area of the physical property value detection flow path 32 is smaller than the cross sectional area of the flow rate detection flow path 33, and as represented by the sizes of arrows P and Q in FIG. The amount of fluid flowing through the flow passage 33 is smaller than the amount of fluid flowing through the flow rate detection channel 33. Thus, when the amount of fluid flowing through the physical property value detection unit 12 is smaller than the amount of fluid flowing through the flow rate detection unit 11, the physical property value detection unit 12 detects the physical property value or temperature of the fluid. An error due to the influence of the flow rate can be reduced.

FIG. 4 is a perspective view showing an example of a sensor element used in the flow rate detection unit and the physical property value detection unit. FIG. 5 is a cross-sectional view for explaining the mechanism of the sensor element. The sensor element 100 includes a microheater (heating unit) 101 and thermopiles (temperature detection units) 102 provided symmetrically with the microheater 101 interposed therebetween. That is, the micro-heaters 101 and the thermopile 102 are arranged in line in a predetermined direction. As shown in FIG. 5, the insulating thin film 103 is formed on the upper and lower sides of these, and the micro heater 101, the thermopile 102 and the insulating thin film 103 are provided on the silicon base 104. Further, a cavity (cavity) 105 formed by etching or the like is provided in the microheater 101 and the silicon base 104 below the thermopile 102. The micro heater 101 is, for example, a resistor formed of polysilicon. In FIG. 5, a broken line ellipse schematically shows a temperature distribution when the micro heater 101 generates heat. The thicker the broken line, the higher the temperature. When there is no air flow, the temperature distribution around the micro heater 101 becomes substantially even as shown in the upper part (1) of FIG. On the other hand, for example, when the air flows in the direction indicated by the broken line arrow in the lower part (2) of FIG. 5, the surrounding air moves, so the temperature is higher on the leeward side than the windward side of the micro heater 101 . The sensor element outputs a value indicating the flow rate by utilizing such a bias of the heater heat distribution. The output voltage ΔV of the sensor element is expressed, for example, by the following equation (1).

Th is the temperature of the microheater 101 (temperature at the end of the thermopile 102 on the side of the microheater 101), and Ta is the lower temperature of the temperature of the end of the thermopile 102 far from the microheater 101 (FIG. 5) In the upper stage (1), it is the temperature of the left end of the thermopile 102 on the left or the temperature of the right end of the thermopile 102 on the right, and in the lower stage (2) of Fig. 5, the temperature of the left end of the thermopile 102 on the upstream side) Vf is an average value of flow velocity, and A and b are predetermined constants.

The circuit board 5 of the flow rate measuring device 1 includes a control unit (not shown) realized by an IC (Integrated Circuit) or the like, and calculates the flow rate based on the output of the flow rate detecting unit 11. Alternatively, a predetermined characteristic value may be calculated based on the output of the physical property value detection unit 12, and the flow rate may be corrected using the characteristic value.

<Flow rate detector and physical property value detector>
FIG. 6 is a plan view showing a schematic configuration of the flow rate detection unit 11 shown in FIG. 1, and FIG. 7 is a plan view showing a schematic configuration of the physical property value detection unit 12 shown in FIG. In the flow rate measuring device 1, the physical property value detection flow path 32 and the flow rate detection flow path 33 have different widths, and the physical property value detection unit 12 of the physical property value detection flow path 32 is disposed. The width of the flow path is narrower than the width of the flow path in which the flow rate detection unit 11 of the flow rate detection flow path 33 is disposed. Thus, in the flow rate measuring device 1, the flow rates of the fluid to be measured divided into the physical property value detection flow path 32 and the flow rate detection flow path 33 are individually controlled.

As shown in FIG. 6, the flow rate detection unit 11 detects the temperature of the fluid to be measured, the first thermopile (temperature detection unit) 111 and the second thermopile (temperature detection unit) 112, and the micro heater heating the fluid to be measured (Also referred to as "heating unit") 113. The heating unit 113, the temperature detection unit 111, and the temperature detection unit 112 are arranged in the flow rate detection unit 11 along the flow direction P of the fluid to be measured. The shapes of the heating unit 113, the temperature detection unit 111, and the temperature detection unit 112 are substantially rectangular in plan view, respectively, and their longitudinal directions are orthogonal to the flow direction P of the fluid to be measured.

In the temperature detection unit 111 and the temperature detection unit 112, the temperature detection unit 112 is disposed on the upstream side of the heating unit 113, and the temperature detection unit 111 is disposed on the downstream side. To detect.

In the flow rate measuring device 1, the sensor element 100 having substantially the same structure is used for the physical property value detection unit 12 and the flow rate detection unit 11, and the arrangement angle with respect to the flow direction of the fluid to be measured Above, they are placed 90 degrees apart. Thereby, the sensor of the same structure can be functioned as the physical property value detection part 12 or the flow volume detection part 11, and the manufacturing cost of the flow volume measurement apparatus 1 can be reduced.

On the other hand, as shown in FIG. 7, the physical property detection unit 12 detects the temperature of the fluid to be measured, the first thermopile (also referred to as "temperature detection unit") 121 and the second thermopile (also referred to as "temperature detection unit") And a micro heater (also referred to as a "heating unit") 123 for heating the fluid to be measured. The heating unit 123, the temperature detection unit 121, and the temperature detection unit 122 are arranged in the physical property detection unit 12 in a direction orthogonal to the flow direction Q of the fluid to be measured. The shapes of the heating unit 123, the temperature detection unit 121, and the temperature detection unit 122 are substantially rectangular in plan view, respectively, and the longitudinal direction of each is along the flow direction Q of the fluid to be measured. Further, the temperature detection unit 121 and the temperature detection unit 122 are disposed symmetrically on both sides of the heating unit 123, and detect temperatures at symmetrical positions on both sides of the heating unit 123. Therefore, the measurement values of the temperature detection unit 121 and the temperature detection unit 122 are substantially the same, and an average value may be adopted, or any one value may be adopted.

Here, since the temperature distribution is biased to the downstream side by the flow of the fluid to be measured, the change in the temperature distribution in the direction orthogonal to the flow direction is smaller than the change in the temperature distribution in the flow direction of the fluid to be measured. Therefore, by arranging the temperature detection unit 121, the heating unit 123, and the temperature detection unit 122 in this order in the direction orthogonal to the flow direction of the fluid to be measured, the temperature detection unit 121 based on the change in temperature distribution is obtained. And, the change of the output characteristic of the temperature detection unit 122 can be reduced. Therefore, the detection accuracy of the physical property value detection unit 12 can be improved by reducing the influence of the change in temperature distribution due to the flow of the fluid to be measured.

In addition, since the longitudinal direction of the heating unit 123 is disposed along the flow direction of the measurement target fluid, the heating unit 123 can heat the measurement target fluid over a wide range of the flow direction of the measurement target fluid. . Therefore, even if the temperature distribution is biased downstream due to the flow of the fluid to be measured, it is possible to reduce the change in the output characteristics of the temperature detection unit 121 and the temperature detection unit 122. Similarly, in the case of measuring the fluid temperature, it is possible to reduce the error in the measurement value caused by the flow velocity. The fluid temperature may be determined by subtracting the temperature increase due to heating by the heating unit 123 from the temperatures detected by the temperature detection unit 121 and the temperature detection unit 122, or the heating unit 123 does not perform heating. It may be detected in the state. According to the physical property value detection unit 12, it is possible to suppress the influence of the change of the temperature distribution due to the flow of the fluid to be measured, and to improve the detection accuracy of the physical property value and the fluid temperature.

Furthermore, since the longitudinal direction of the temperature detection unit 121 and the temperature detection unit 122 is disposed along the flow direction of the fluid to be measured, the temperature detection unit 121 and the temperature detection unit 122 can widely cover the flow direction of the fluid to be measured Temperature can be detected. Therefore, even if the temperature distribution is biased downstream due to the flow of the fluid to be measured, it is possible to reduce the change in the output characteristics of the temperature detection unit 121 and the temperature detection unit 122. Therefore, the detection accuracy of the physical property value detection unit 12 can be improved by reducing the influence of the change in temperature distribution due to the flow of the fluid to be measured.

<Functional configuration>
FIG. 8 is a block diagram showing an example of a functional configuration of the circuit board 5 provided in the flow rate measuring device 1. The flow rate measuring device 1 includes a flow rate detecting unit 11, a physical property value detecting unit 12, and a control unit 13. The flow rate detection unit 11 includes a temperature detection unit 111 and a temperature detection unit 112. The physical property value detection unit 12 includes a temperature detection unit 121 and a temperature detection unit 122. The heating unit 113 shown in FIG. 6 and the heating unit 123 shown in FIG. 7 are not shown. Further, the control unit 13 includes a detection value acquisition unit 131, a characteristic value calculation unit 132, a flow rate calculation unit 133, and a measurement parameter change unit 134.

The flow rate detection unit 11 detects a value indicating the flow rate of the fluid to be measured based on the temperature detection signals output from the temperature detection unit 111 and the temperature detection unit 112. For example, the flow rate detection unit 11 calculates the difference between the temperature detection signal output from the temperature detection unit 111 and the temperature detection signal output from the temperature detection unit 112, and indicates the flow rate of the fluid to be measured based on the difference. Ask for Then, the flow rate detection unit 11 outputs a value indicating the flow rate to the control unit 13.

The physical property value detection unit 12 outputs the temperature detection signal output from the temperature detection unit 121 to the characteristic value calculation unit 132. The physical property detection unit 12 may obtain an average value of the temperature detection signals output from the temperature detection unit 121 and the temperature detection unit 122, and output the average value to the characteristic value calculation unit 132. In addition, the temperature detection signal may be acquired using one of the temperature detection unit 121 and the temperature detection unit 122.

The detection value acquisition unit 131 acquires a detection value corresponding to the flow rate of the fluid output by the flow rate detection unit 11 at a predetermined measurement interval. The characteristic value calculation unit 132 calculates the characteristic value based on the detection value of at least one of the temperature detection unit 121 and the temperature detection unit 122 of the physical property value detection unit 12. The characteristic value calculation unit 132 changes the temperature of the micro heater of the physical property value detection unit 12 and calculates the characteristic value by multiplying the difference of the temperature of the fluid to be measured detected by the thermopile before and after the change by a predetermined coefficient. You may do so. Further, the flow rate calculation unit 133 calculates the flow rate based on the detection value acquired by the detection value acquisition unit 131. At this time, the flow rate calculation unit 133 may correct the flow rate by further using the characteristic value calculated by the physical property value detection unit 12. Further, the measurement parameter changing unit 134 changes the setting to a measurement parameter such as a measurement interval calculated based on the measurement result. For example, based on the flow rate calculated by the flow rate calculation unit 133, the measurement parameter change unit 134 changes the interval at which the detection value acquisition unit 131 obtains the detection value.

<Flow measurement process>
FIG. 9 is a process flow diagram showing an example of the flow rate measurement process. In the present embodiment, for example, measurement parameters such as a measurement interval (sampling interval) of the flow rate detection unit 11 are periodically corrected. That is, the measurement parameter changing unit 134 of the circuit board 5 determines whether it is time to detect the frequency (FIG. 9: S1). In this step, when the predetermined period has elapsed since the previous correction, the measurement parameter changing unit 134 determines that it is the timing to detect the frequency.

When it is determined that it is the timing to detect the frequency (S1: YES), the measurement parameter changing unit 134 causes the detection value acquisition unit 131 to acquire the detection value by high-speed sampling at a shorter measurement interval than usual (S2) . In this step, the measurement interval is shortened in order to detect changes in flow rate in more detail. That is, the detection value acquisition unit 131 acquires detection values corresponding to the flow rate of the fluid to be measured based on the temperature detection signals of the temperature detection unit 111 and the temperature detection unit 112 at short measurement intervals. Specifically, the flow rate detection unit 11 outputs the temperature detection signal output from the temperature detection unit 111 and the temperature detection signal output from the temperature detection unit 112. Further, the detection value acquisition unit 131 calculates the difference between the two temperature detection signals. Also, the flow rate calculation unit 133 calculates the flow rate based on the detected value. The flow rate calculation unit 133 may correct the flow rate based on the characteristic value.

Further, the measurement parameter changing unit 134 calculates the frequency or the period of the change of the flow rate based on the calculated flow rate (S2). In this step, regularity such as periodicity is detected from the change in the calculated flow rate, and the number of repetitions per unit time or the time taken for the repetition is determined.

FIG. 10 is a diagram schematically showing temporal change in flow rate per unit time when pulsation occurs in change in flow rate. In the graph of FIG. 10, the vertical axis represents the flow rate per hour (L / h), and the horizontal axis represents time (s). Further, in the example of FIG. 10, as indicated by a solid curve, pulsation occurs in the flow rate at a frequency of about 20 Hz. Such pulsations and fluctuations may occur, for example, due to the structure of piping in which the flow rate measuring device is installed. The circles in FIG. 10 indicate sampling timings.

In S2, for example, based on a judgment criterion such as whether a value below a predetermined value regularly appears for a flow rate at a certain point in time, or at least one of a local maximum and a local minimum regularly appears, etc. The periodicity of the change in flow rate is detected to determine the frequency. In cyclicity detection, is approximately the same value as the flow rate value calculated at a certain time point calculated periodically based on the flow rate value calculated based on the detection value obtained by the above-mentioned high-speed sampling to decide. Further, the maximum value or the minimum value may be detected and used for the determination using the latest predetermined number of flow rate values. For example, it may be determined whether the period in which the calculated flow rate value is increasing and the period in which the calculated flow value is decreasing are periodically repeated. For example, the frequency can be determined by detecting the value of the flow rate at a certain point initially detected and the increase or decrease of the flow rate over time. That is, as shown in the section where the both ends are arrows in FIG. 10, the same value as a certain flow calculated in the section where the flow tends to increase is similarly repeatedly calculated in the section where the flow tends to increase The frequency can be counted by determining that one period is between the values. At this time, even if the value is calculated in the section in which the flow rate tends to decrease, it can be determined that the period is not a break. Similarly, the local maximum value or the local minimum value may be detected, and the frequency may be counted by determining the period between the local maximum value or the local minimum value as one cycle. In this case, for example, a peak value with a slope of zero representing an increase or decrease in the flow rate appearing after a section where the flow rate tends to increase is judged as a maximum value or a slope appears after a section where the flow rate tends to decrease The peak value of is judged as the minimum value. Further, not only the waveform as shown in FIG. 10, but also a complicated waveform shape may appear periodically. Therefore, if the error with respect to the flow rate measured at a certain point appears between the maximum values above the predetermined threshold or between the minimum values below the predetermined threshold a predetermined number of times, the periodicity is It may be determined that there is. At this time, for example, a moving average of the calculated flow rate may be used. In summary, the measurement parameter changing unit 134 detects the periodicity using the change in the value of the flow rate.

Thereafter, it is determined whether or not the measurement cycle (or frequency) when the process (S1 to S3) for detecting the frequency last time is performed and the measurement cycle (or frequency) when the process for detecting the current frequency is performed do not match To do (S4). In this step, it is determined whether or not the cycle has changed when the periodicity is detected in the previous or current time.

If it is determined in S4 that the measurement parameter does not match the previous measurement cycle (S4: YES), the measurement parameter changing unit 134 changes the measurement parameter (measurement interval etc.) based on the periodicity (S5). It is assumed that the measurement is performed at predetermined intervals, for example, every several cycles, with a period of one cycle. That is, in this step, the measurement parameter changing unit 134 sets, for example, an interval of an integral multiple of the detected period to the start point of each measurement performed intermittently. Also, the duration of measurement is set so as to continue the measurement of the flow rate for a period of one cycle. The period may be continued not for one cycle but for an integral multiple of the cycle. In addition, the measurement interval in each period may be performed at a speed lower than that of sampling performed at high speed to detect periodicity in S2, for example. The measurement interval in each period may be set short, for example, when the rate of change of the flow rate changes significantly in a short period of time.

Then, after S5, if it is determined that it is not the timing to correct the measurement interval in S1 (S1: NO), or if it is determined in S4 that it matches the previous measurement cycle (S4: NO), The detection value acquisition unit 131 and the flow rate calculation unit 133 measure the flow rate with the set measurement parameter (measurement interval etc.) (S6). In this step, measurement is started at the measurement interval set in S5. In addition, measurement is performed continuously at the predetermined sampling rate and the measurement period set in S5. That is, measurement is intermittently performed based on the cycle of change in flow rate to be measured, and the flow rate in the period in which measurement is not performed is complemented on the basis of the flow rate in the preceding and subsequent periods to obtain the entire flow rate.

The flow rate measuring device 1 repeats the flow rate measuring process as described above.

<Effect>
According to the flow rate measuring device 1, when pulsation or fluctuation occurs in the fluid to be measured, power consumption can be reduced while maintaining the accuracy of the measurement. That is, since the measurement interval is set based on the change period of the flow rate, it is possible to suppress the bias of the sampling target and maintain the measurement accuracy. In addition, by performing measurement intermittently based on the cycle of change in flow rate, power consumption can be suppressed more than when sampling is continued.

FIG. 11 is a view schematically showing the relationship between the temperature of the micro heater 101 of the sensor element 100 shown in FIG. 4 and the like and the measurement timing. In the graph of FIG. 11, the vertical axis represents the temperature of the micro heater 101, and the horizontal axis represents the passage of time. The flow rate measuring apparatus 1 uses the sensor element 100 including the micro heater 101, and heats the micro heater 101 based on the control of the detection value acquisition unit 131 of the control unit 13 when measuring the flow rate. Therefore, by reducing the number of times of measurement, the consumption of power due to the heating of the micro heater 101 can be suppressed.

(Correction based on the characteristic value)
The flow rate measuring device 1 may correct the value of the flow rate based on the characteristic value. By further performing the correction based on the characteristic value, the value of the flow rate can be appropriately corrected for various fluids to be measured, but this correction is not necessarily required. Next, correction based on characteristic values of physical properties will be described. In the correction based on the characteristic value, a sensor sensitivity ratio is determined. The sensor sensitivity ratio is a ratio of a sensor output value in the case of flowing a predetermined gas to a sensor output value in the case of flowing the gas serving as a reference, and is a characteristic value representing a thermal diffusivity. The sensor sensitivity ratio α is obtained by the following equation (2).
α = β × ΔT (2) where β is a predetermined coefficient. Further, ΔT is a difference between detection values output by the temperature detection unit 121 and the temperature detection unit 122 before and after the temperature change of the heating unit 123.

Thereafter, the flow rate calculation unit 133 calculates the corrected flow rate using the following equation (3).
Output after correction = output of flow rate calculation unit × α (3)

In the present embodiment, the thermal diffusivity of the fluid to be measured can be detected by using the amount of change in temperature (ΔT) detected by the heat pile when the temperature of the heater is changed. The flow rate output by the thermal flow sensor has a correlation with the thermal diffusivity, and the flow rate correction process according to the present embodiment enables appropriate correction for any gas. Therefore, the measurement accuracy of the flow rate can be improved with respect to the measurement target fluid having different thermal diffusivities.

FIG. 12 is a graph showing the sensor sensitivity ratio on the vertical axis and the thermal conductivity on the horizontal axis. Here, as shown in FIG. 12, for example, when there are a plurality of gas groups having different physical property values other than the thermal conductivity, such as mixed gases having different compositions, it is necessary to obtain the thermal conductivity as the physical property value. It is unclear which sensor sensitivity ratio should be used for correction. That is, in the method of performing correction using one set of the heating temperature of the microheater and the detection temperature of the thermopile, correction is performed based on two or more reference gases belonging to a predetermined gas group, but for a plurality of gas groups It was not possible to make corrections properly.

FIG. 13 is a graph showing the sensor sensitivity ratio on the vertical axis and ΔT on the horizontal axis. The sensor sensitivity ratio and ΔT are approximated to a straight line even for the gas shown in FIG. 12 in which the sensor sensitivity ratio and the thermal conductivity are not approximated to a straight line. Therefore, in the present embodiment, the correction can be performed also on the gas group whose thermal diffusivity is unknown.

As described above, the detection of the fluid temperature and the detection of the physical property value by the physical property value detection unit 12 can improve the temperature compensation accuracy without increasing the number of parts. In addition, if the sensor element 100 having the same structure is used in common as the physical property value detection unit 12 and the flow rate detection unit 11, the types of parts can be reduced and the manufacturing cost of the flow measurement device 1 can be reduced.

<Modification of sub-channel portion>
14A to 14D show deformation of the physical property value detection flow path 32 and the flow rate detection flow path 33 formed between the inflow flow path 34 and the outflow flow path 35 on the upper surface of the sub flow path portion 3. It is a top view which shows an example. For example, as shown in FIG. 14A, the physical property value detection flow path 32 may be formed in a straight line, and the flow rate detection flow path 33 may be formed in a substantially U-shape.

Further, as shown in FIGS. 14B to 14D, the direction in which the fluid to be measured flows into the flow rate detection channel 33 is orthogonal to the direction in which the fluid to be measured flows into the physical property value detection channel 32. The physical property value detection flow path 32 may be formed as described above. That is, the flow direction of the fluid to be measured, and the predetermined direction in which the temperature detection unit 121, the heating unit 123, and the temperature detection unit 122 are arranged on the physical property value detection unit 12 disposed in the physical property value detection channel 32; Arranged vertically. The sensor element 100 of the physical property value detection unit 12 and the sensor element 100 of the flow rate detection unit 11 are arranged in a direction rotated 90 degrees in plan view with respect to the flow direction of the fluid to be measured. Therefore, as shown in FIGS. 14B to 14D, in the case where the flow direction of the fluid to be measured is orthogonalized, the arrangement direction of the sensor element 100 of the physical property value detection unit 12 and the sensor element 100 of the flow rate detection unit 11 may be matched it can. Therefore, in the manufacturing process of the flow rate measuring device 1, the process of mounting the physical property value detecting unit 12 and the flow rate detecting unit 11 on the circuit board 5 can be simplified.

<Modification 1 of flow rate measuring device>
Another modification of the flow rate measuring device according to the present invention will be described based on FIGS. 15A to 15C. In addition, regarding the member corresponding to the embodiment described above, the corresponding reference numeral is attached and the description thereof is omitted. In the flow rate measuring device according to the present modification, the flow rate detecting unit is disposed in the main flow path.

FIG. 15A is a perspective view showing a flow rate measuring device 1a according to the present modification. FIG. 15B is a cross-sectional view showing the flow rate measuring device 1a shown in FIG. 15A. FIG. 15C is a top view showing the sub flow passage 3a shown in FIG. 15A.

As shown in FIGS. 15A to 15C, in the flow rate measuring device 1a, an opening 37A is formed between the inlet 34A and the outlet 35A on the inner peripheral surface of the main flow passage 2a. A flow path 37a for detecting a flow rate in which the flow rate detector 11 is disposed is formed in the sub flow path 3a, and the flow path 37a for detecting flow rate communicates with the opening 37A. Therefore, the fluid to be measured flowing through the main flow passage 2a flows into the flow rate detection flow passage 37a via the opening 37A, and the flow rate detection unit 11 detects the flow rate. By controlling and adjusting the size of the opening 37A, it is possible to control the flow rate of the measurement target fluid flowing from the main flow passage 2a into the flow rate detection flow passage 37a.

The sub-passage portion 3a is composed of the inflow channel 34, the physical property value detection channel 32, and the outflow channel 35, and the physical property value detection channel 32 extends in the longitudinal direction. The flow path has a physical property value detection flow path 32 in which a physical property value detection unit 12 for detecting the physical property value of the fluid to be measured is disposed.

Thus, in the flow rate measurement device 1a, the physical property value detection unit 12 is disposed in the sub flow passage 3a, and the flow rate detection unit 11 is disposed in the main flow passage 2a. For this reason, even with the flow rate measuring device 1a, it is possible to control the flow rate according to the detection range of the physical property value detection unit 12. Therefore, the temperature and physical property value of the fluid to be measured can be detected with high accuracy also in this modification. In the present modification, the flow rate detection unit 11 and the physical property value detection unit 12 may be arranged in reverse. Even with such a configuration, since the value corresponding to the temperature of the fluid is directly detected, the influence of the difference between the fluid temperature and the ambient temperature can be reduced.

<Modification 2 of flow rate measuring device>
Another modification of the flow rate measuring device according to the present invention will be described based on FIGS. 16A and 16B. In addition, regarding the member corresponding to the embodiment, the corresponding reference numeral is attached and the description thereof is omitted. The flow rate measuring device according to the present modification differs from the above-described flow rate measuring device in that it has two independent sub flow paths.

FIG. 16A is a perspective view showing a flow rate measuring device 1b according to the present embodiment, and FIG. 16B is a top view showing the sub flow passage portion 3 shown in FIG. 16A. As shown in FIGS. 16A and 16B, in the flow rate measuring device 1b, the sub flow passage 3b is formed with two sub flow passages on the inside and the upper surface thereof.

The first sub-passage is composed of the inflow channel 34b, the physical property value detection channel 32b, and the outflow channel 35b, and the physical property value detection channel 32b extends in the longitudinal direction. A physical property value detection unit 12 for detecting physical property values of the fluid to be measured is disposed in the extending flow path.

The second sub-passage portion is composed of the inflow passage 34B, the flow rate detection passage 33B, and the outflow passage 35B, and the flow rate detection passage 33B extends in the longitudinal direction. A flow rate detection unit 11 for detecting the flow rate of the fluid to be measured is disposed in the flow path.

As described above, in the flow rate measuring device 1 b, the sub flow path portion 3 b has two independent sub flow paths, and the physical property value detection portion 12 is disposed in the first sub flow path portion. Are disposed in the second sub flow passage. For this reason, according to the flow rate measuring device 1b, it is possible to individually control the flow rates according to the detection ranges of the physical property value detecting unit 12 and the flow rate detecting unit 11. Therefore, the temperature and physical property value of the fluid to be measured can be detected with high accuracy also in this modification.

<Modification 3 of flow rate measuring device>
Another modified example of the flow rate measuring device according to the present invention will be described based on FIGS. 17A to 17C. In addition, regarding the member corresponding to the embodiment, the corresponding reference numeral is attached and the description thereof is omitted. The flow rate measuring device according to the present modification differs from the flow rate measuring device described above in that the physical property value detecting flow path is formed in the flow rate detecting flow path.

FIG. 17A is a perspective view showing a flow rate measuring device 1c according to the present embodiment. FIG. 17B is a perspective view showing the sub flow passage portion 3c shown in FIG. 17A. FIG. 17C is a top view showing the sub flow passage portion 3c shown in FIG. 17A.

As shown in FIGS. 17A to 17C, in the flow rate measuring device 1c, the sub flow path portion 3c includes the inflow path 34, the physical property value detection flow path 32c, the flow rate detection flow path 33c, and the outflow And a flow path 35.

In the sub flow path portion 3c, the physical property value detection flow path 32c is formed in the flow rate detection flow path 33c, and the flow rate detection unit 11 is disposed upstream with respect to the flow direction of the fluid to be measured. The physical property value detection unit 12 is disposed on the side. Here, the physical property value detection flow path 32 c is separated from the flow rate detection flow path 33 c by the flow rate control member 40 for controlling the flow rate of the fluid to be measured, and the physical property value detection unit 12 is a flow rate control member 40. It is located inside.

The flow rate control member 40 is a member for controlling the flow rate of the fluid to be measured which passes through the physical property value detection unit 12 of the physical property value detection flow path 32c, and is composed of a first side wall 40a and a second side wall 40b. It is done. Each of the first side wall portion 40a and the second side wall portion 40b is a substantially U-shaped plate-like member, and is disposed with a predetermined interval in a state where the respective end portions are opposed to each other. Therefore, by controlling the distance between the first side wall 40a and the second side wall 40b, the flow rate of the fluid to be measured passing through the flow rate control member 40, that is, the physical property value detection flow path 32c, is adjusted. Can.

As described above, in the flow rate measuring device 1c, the sub flow path portion 3c includes the flow rate control member 40, and the physical property value detection flow path 32c is provided inside the flow rate control member 40. It is possible to provide the physical property value detection flow path 32c at any position of the above. Further, by providing the flow rate control member 40, the flow rate of the fluid to be measured passing through the physical property value detection flow path 32c can be easily controlled.

As described above, even if the physical property value detection flow path 32 c is formed in the flow rate detection flow path 33 c and configured, the flow rates according to the detection ranges of the physical property value detection unit 12 and the flow rate detection unit 11 are individually It is possible to control. Therefore, the temperature and physical property value of the fluid to be measured can be detected with high accuracy also in this modification.

<Modification 4 of flow rate measuring device>
Another modification of the flow rate measuring device according to the present invention will be described based on FIGS. 18A to 18C. In addition, regarding the member corresponding to the embodiment, the corresponding reference numeral is attached and the description thereof is omitted. The flow rate measuring apparatus according to the present modification differs from the flow rate measuring apparatus described above in that the physical property value detecting unit 12 is not provided, and the flow rate detecting unit 11 is provided in the main flow path.

FIG. 18A is a perspective view showing a flow rate measuring device 1d according to the present modification. FIG. 18B is a cross-sectional view cut along a plane passing through the center of the cross section of the flow rate measurement device 1 d and the center of the flow rate detection unit 11. FIG. 18C is a cross-sectional view of the main flow path cut along a plane perpendicular to the fluid flow direction.

As shown in FIGS. 18A to 18C, in the flow rate measurement device 1d, a flow rate detection flow path 33d, which is an opening capable of accommodating the flow rate detection unit 11, is provided on the side surface of the main flow passage portion 2. Further, the circuit board 5 (shown in FIG. 18B) is connected from the outside of the main flow passage portion 2 so as to cover the flow rate detection flow path 32d. At this time, the flow rate detection unit 11 mounted on the circuit board 5 is disposed in the flow rate detection flow path 33 d. The flow rate detection flow path 33 d according to the present modification is not divided from the main flow path portion 2, and the flow rate detection portion 11 is provided in the main flow path portion 2.

Even with the flow rate detection unit 11 in such a flow rate measurement device 1d, it is possible to detect a value according to the amount of fluid flowing in the main flow passage portion 2. Furthermore, the physical property value detection unit 12 may also be provided in the main flow channel section 2, but even if the physical property value detection unit 12 is not provided as in this modification, pulsation or fluctuation occurs in the fluid to be measured. If so, power consumption can be reduced while maintaining measurement accuracy.

<Modification 5 of flow rate measuring device>
Another modification of the flow rate measuring device according to the present invention will be described based on FIGS. 19A and 19B. In addition, regarding the member corresponding to embodiment, the corresponding code | symbol is attached | subjected and the description is abbreviate | omitted. The flow rate measuring apparatus according to the present modification does not include the physical property value detecting unit 12 and the flow rate detecting unit 11 is provided in the flow rate detecting flow passage branched from the main flow passage 2. It is different from the measuring device.

FIG. 19A is a perspective view showing a flow rate measuring device 1e according to the present modification. FIG. 19B is a cross-sectional view showing the flow rate measuring device 1 e shown in FIG. 19A.

As shown in FIGS. 19A and 19B, in the flow rate measuring device 1e, the sub-flow path unit 3e includes the inflow path 34, the flow rate detection path 33e, and the outflow flow path 35. . In the sub flow passage portion 3e, a flow rate detection flow passage 33c branched from the main flow passage portion 2 is formed, and the flow rate detection unit 11 is disposed in the flow rate detection flow passage 33c.

<Modification 6 of flow rate measuring device>
The change of the measurement parameter may be controlled by a device other than the control unit 13 included in the circuit board 5. FIG. 20 is a functional block diagram showing an example in which a host device 9 different from the circuit board 5 is provided with the measurement parameter changing unit 134, such as a gas meter for installing the flow rate measuring device 1, for example. Also in FIG. 20, the members corresponding to those of the embodiment are denoted by the corresponding reference numerals, and the description thereof will be omitted.

In this modification, the circuit board 5 and the host device 9 are connected by signal lines or wirelessly. The measurement parameter changing unit 134 is realized by a processor such as a microcontroller included in the host device 9 and performs the same processing as that of the embodiment. In addition, in this modification, the host apparatus 9 shall be called the "flow measuring device" which concerns on this invention. Even with such a configuration, when pulsation or fluctuation occurs in the fluid to be measured, the power consumption can be reduced while maintaining the accuracy of the measurement.

<Modification of sensor element>
FIG. 21 is a top view showing a schematic configuration of a modification of the physical property value detection unit 12 shown in FIG. As illustrated in FIG. 19, for example, the temperature detection unit 122 may be omitted, and the physical property detection unit 12 a may be configured by the heating unit 123 and the temperature detection unit 121. That is, even if the heating unit 123 and the temperature detection unit 121 are arranged in a direction perpendicular to the flow direction of the fluid to be measured, the temperature detection unit 121 can detect the fluid temperature and the physical property value of the fluid. .

The configurations of the embodiments and the modifications as described above can be combined as much as possible without departing from the problems and technical ideas of the present invention. Further, the flow rate measuring method executed by the flow rate measuring device 1 may be provided as a program to be executed by an arithmetic device such as a processor or a medium storing the program.

1: Flow rate measuring device 11: Flow rate detection unit 111: Temperature detection unit 112: Temperature detection unit 113: Heating unit 12: Physical property value detection unit 121: Temperature detection unit 122: Temperature detection unit 123: Heating unit 13: Control unit 131: Detected value acquisition unit 132: Characteristic value calculation unit 133: Flow calculation unit 134: Measurement parameter change unit 2: Main flow passage 21: Orifice 3: Secondary flow passage 32: Physical property value detection flow channel 33: Flow flow detection flow channel 34: Inflow flow path 35: Outflow flow path 40: Flow control member 4: Seal 5: Circuit board 6: Cover 100: Sensor element 101: Micro heater 102: Thermopile 103: Insulating thin film 104: Silicon base 105: Cavity

Claims

A flow rate detection unit that detects a value corresponding to the flow rate of the measurement target fluid flowing through the main flow path at a predetermined measurement timing;
A flow rate calculation unit that calculates the flow rate of the fluid to be measured based on the value corresponding to the flow rate detected by the flow rate detection unit;
A measurement interval change unit that changes the measurement timing based on the detected periodical change when the periodical change of the flowrate is detected based on the flow rate calculated by the flow rate calculator;
Flow measurement device comprising:
The flow rate measuring apparatus according to claim 1, wherein the measurement interval changing unit detects a change in the value of the flow rate calculated by the flow rate calculating unit, and detects the periodic change using a change in the value of the flow rate.
The flow rate measuring device according to claim 1 or 2, wherein the measurement interval changing unit changes the measurement timing to intermittently detect a value according to the flow rate based on a cycle of the detected change.
The flow rate measuring device according to claim 3, wherein each of the detection of the value according to the flow rate performed intermittently is started at an interval of an integral multiple of a cycle of the detected change.