Flow rate measuring device, gas meter equipped with a flow rate measuring device, and flow rate measuring device unit for a gas meter

Abstract

To provide a technique which allows a more precise measurement of a flow rate in a flow rate measuring device.SOLUTION: A flow rate measuring device (1) for detecting the flow rate of a measurement target fluid flowing in a main passage (2), includes: a heating unit (113) for heating a measurement target fluid; temperature detection units (111, 112) for detecting the temperature of the measurement target fluid; and a flow rate correction unit (133) for detecting a pulsation frequency on a pulsation of the periodically changing flow rate of the measurement target fluid flowing in the main flow passage on the basis of the detected value obtained by the temperature detection unit and correcting the flow rate of the measurement target fluid flowing in the main flow passage according to the detected pulsation frequency.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present invention relates to a flow rate measuring device, a gas meter provided with the flow rate measuring device, and a flow rate measuring device unit for a gas meter.

Background Art

[0002] Conventionally, a thermal flow rate measuring device has been proposed that includes a heater and a sensor, and the sensor detects a temperature distribution that changes due to the flow of a fluid, thereby calculating the flow velocity or flow rate of the fluid.

[0003] In a gas meter or the like provided with a thermal flow rate measuring device as described above, for example, the fluid to be measured flowing through a pipe or the like may become a pulsating flow due to the influence of ambient vibration or a driving device such as a pump. Here, regarding the measurement of pulsating flow, for example, in Patent Document 1, an ultrasonic gas meter that "performs flow rate measurement using the propagation time of ultrasonic waves, transmits the ultrasonic waves N times at a constant period, then provides a minute fluctuation period, and then repeats the operation of transmitting the ultrasonic waves N times at a constant period to measure the flow rate" has been proposed. Further, Patent Document 2 proposes a flow rate measurement method in which "the value of the flow rate or flow velocity of a fluid flowing from the upstream side to the downstream side is intermittently measured at a predetermined frequency for each measurement period a plurality of times, and in the flow rate measurement method of integrating the values obtained for each measurement period, the start phase of the measurement period is changed based on a predetermined regularity."

[0004] However, in a thermal flow rate measuring device that includes a heater and detects a temperature distribution that changes due to the flow of the fluid to be measured, it has been difficult to accurately measure the flow rate value because the frequency of the pulsating flow affects the temperature distribution formed by the heater.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a technology that enables more accurate flow measurement in a thermal flow measuring device, even when pulsation occurs. [Means for solving the problem]

[0007] The present invention, which solves the above problems, A flow rate measuring device for detecting the flow rate of a fluid to be measured flowing through a main channel, A heating unit that heats the fluid to be measured, A temperature detection unit for detecting the temperature of the fluid to be measured, Based on the temperature detection unit, a flow rate correction unit detects the pulsation frequency related to the periodic fluctuation of the flow rate of the fluid to be measured flowing through the main channel, and corrects the flow rate of the fluid to be measured flowing through the main channel according to the detected pulsation frequency. This is a flow rate measuring device characterized by having the following features.

[0008] According to this flow rate measuring device, even if pulsations occur in the fluid being measured, the detected pulsations Because it becomes possible to correct the flow rate of the fluid being measured flowing through the main channel based on frequency, more accurate flow rate measurement becomes possible.

[0009] Furthermore, in the present invention, the flow rate correction unit is The temperature detection unit may acquire detection values ​​at a periodic interval different from the fluctuation period related to the fluctuation of the flow rate of the fluid being measured flowing through the main channel, and at least the pulsation frequency may be detected based on the time difference between two detection values ​​that are the same from the time series of detection values ​​acquired at the different periodic intervals. This makes it possible to detect the pulsation frequency from the time width (time difference) between two points that show the same detection value from the time series of detection values ​​acquired at a periodic interval different from the fluctuation period of the pulsation of the fluid being measured. Within a limited detection period, it becomes possible to identify the pulsation frequency based on a small number of detection values.

[0010] Furthermore, in the present invention, the flow rate correction unit is If the number of detected values ​​acquired at the different periodic intervals does not meet the predetermined conditions, the periodic interval may be changed. This makes it possible to acquire detected values ​​at the periodic interval that is optimal for sampling the pulsation frequency.

[0011] Furthermore, in the present invention, the flow rate correction unit is When the fluctuation range in the time series of detected values ​​acquired at the aforementioned different periodic intervals is within a predetermined range, the periodic interval may be changed. This makes it possible to make the fluctuation period of the pulsation frequency and the periodic interval for sampling the detected values ​​asynchronous, thereby enabling responses to a wide range of changes in the pulsation frequency.

[0012] Furthermore, in the present invention, the flow rate correction unit is If there are no groups of detected values ​​that continuously increase or decrease in the time series of detected values ​​acquired at the aforementioned different periodic intervals, the periodic interval may be changed. This allows the periodic interval to be changed by identifying at least groups of detected values ​​that continuously increase or decrease, even when the length of the period for sampling detected values ​​is limited. Since it is possible to determine whether the periodic interval is synchronized with the fluctuation period of the pulsation frequency even with a small number of samples, the processing load can be reduced and power consumption can be suppressed.

[0013] In the present invention, the flow rate correction unit When there is a group of detected values that continuously increase or decrease in the time series of the detected values obtained at the different periodic intervals, the acquisition of the detected values using the periodic interval may be executed a predetermined number of times. Thereby, it becomes possible to obtain an averaged pulsation frequency based on the detected values for a predetermined number of samples sampled using a specific periodic interval, and it becomes possible to perform flow rate measurement with higher accuracy.

[0014] Further, the present invention includes the above-described flow rate measurement device, a display unit that displays the flow rate corrected by the flow rate correction unit, an integrated control unit that controls the flow rate measurement device and the display unit, and may be a flow rate measurement device unit including

[0015] In this way, it becomes possible to manufacture a gas meter that can output and display the flow rate of the fluid to be measured more easily or efficiently.

[0016] Further, the present invention includes the above-described flow rate measurement device, a display unit that displays the flow rate measured by the flow rate measurement device, an integrated control unit that controls the flow rate measurement device and the display unit, a power supply unit that supplies power to the flow rate measurement device, the display unit, and the integrated control unit, a housing that can accommodate the flow rate measurement device, the display unit, and the integrated control unit, an operation unit that can set the operation of the flow rate measurement device from the outside of the housing, and may be a gas meter including

[0017] According to this, it is possible to provide a gas meter capable of performing flow rate measurement with higher accuracy.

Advantages of the Invention

[0018] According to the present invention, in a thermal flow rate measurement device, even in a state where pulsation occurs, it becomes possible to perform flow rate measurement with higher accuracy.

Brief Description of the Drawings

[0019] [Figure 1] It is an exploded perspective view showing an example of a flow rate measuring device in Example 1 of the present invention. [Figure 2] It is a cross-sectional view showing an example of a flow rate measuring device in Example 1 of the present invention. [Figure 3] It is a plan view showing a secondary flow path portion in Example 1 of the present invention. [Figure 4] It is a perspective view showing an example of a sensor element in Example 1 of the present invention. [Figure 5] It is a cross-sectional view for explaining the mechanism of the sensor element in Example 1 of the present invention. [Figure 6] It is a plan view showing a schematic configuration of a flow rate detection unit in Example 1 of the present invention. [Figure 7] It is a plan view showing a schematic configuration of a physical property value detection unit in Example 1 of the present invention. [Figure 8] It is a block diagram showing a functional configuration of a circuit board in Example 1 of the present invention. [Figure 9] It is a graph showing the variation of the flow rate value when pulsation is applied in a state where the flow rate of the fluid is kept constant. [Figure 10] It is a diagram for explaining the temperature distribution in the flow rate detection device when pulsation occurs. [Figure 11] It is a graph showing the deviation amount of the sensor output value with respect to the pulsation frequency. [Figure 12] It is a diagram for explaining the sampling period for measuring the pulsation frequency in Example 1 of the present invention. [Figure 13] It is a diagram for explaining frequency identification by the zero-crossing method in Example 1 of the present invention. [Figure 14] It is a diagram for explaining the sampling of the flow rate value during the heating period in Example 1 of the present invention. [Figure 15] It is a flowchart of the flow rate measurement process in Example 1 of the present invention. [Figure 16]This is a flowchart of the flow rate measurement process in Embodiment 1 of the present invention. [Figure 17] This figure shows an example of the measurement results of pulsation frequency obtained by flow rate measurement processing in Example 1 of the present invention. [Figure 18] This is a block diagram showing the functional configuration of a gas meter in Embodiment 2 of the present invention. [Modes for carrying out the invention]

[0020] [Examples of application] The following describes examples of applications of the present invention with reference to the drawings. The present invention is applied, for example, to a thermal flow rate measuring device 1 as shown in Figure 1. As shown in Figure 2, the flow rate measuring device 1 divides the fluid flowing through the main flow channel 2, guides a portion of it to a flow rate detection unit 11, and measures the flow rate in the flow rate detection unit 11, which has a high correlation with the flow rate of the fluid in the main flow channel 2. The sensor element used in the flow rate detection unit 11 has a configuration in which two thermopiles (temperature detection units) 102 are arranged with a microheater (heating unit) 101 in between, as shown in Figure 4.

[0021] In terms of the measurement principle, when there is no fluid flow, the temperature distribution around the microheater 101 becomes almost uniform, as shown in Figure 5(a). On the other hand, for example, in Figure 5(b), the dashed arrow When the fluid flows in the direction indicated, the unheated fluid moves, so the temperature becomes higher downstream of the microheater 101 than upstream. This utilizes the correlation between the temperature difference ΔT detected by the two thermopiles (temperature detection units) 102 and the flow rate of the fluid passing over them, which is associated with the uneven distribution of heater heat.

[0022] Furthermore, as shown in the functional block diagram 8 of the flow rate measuring device 1, the output of the flow rate detection unit 11 is realized by the control unit 13, which is located on the circuit board 5. The detected values ​​are transmitted to the detection value acquisition unit 131, and after necessary corrections are made in the flow rate calculation unit 133, the final output flow rate is calculated.

[0023] However, in gas meters and the like equipped with thermal flow measuring devices, if the fluid being measured flowing through piping becomes a pulsating flow due to the influence of ambient vibrations or drive devices such as pumps, the frequency of the pulsating flow interferes with the true value of the flow rate, as shown in Figures 9 to 11, making it difficult to measure the flow rate accurately.

[0024] Therefore, in this invention, the frequency related to fluctuations in pulsating flow is identified, and the amount of deviation from the true value is corrected according to the identified pulsation frequency. As a result, even when pulsation occurs in the fluid being measured, it becomes possible to correct the flow rate of the fluid being measured flowing through the main channel based on the detected pulsation frequency, thereby enabling more accurate flow rate measurement. Furthermore, in this invention, the zero-crossing method is employed to identify the frequency related to fluctuations in pulsating flow. This makes it possible to efficiently sample flow rate data within the limited heating period of the heater. Moreover, in this invention, if the sampled data and the number of data points do not meet predetermined conditions, the sampling frequency of the data is changed and remeasurement is performed. Here, predetermined conditions include when the pulsation period and the sampling period are synchronized, or when a predetermined number of data points cannot be obtained. As a result, when data measurement that does not meet the predetermined conditions is performed, the sampling frequency can be changed in the direction of higher or lower frequencies and resampling can be repeated, making it possible to measure data with a period interval optimal for the pulsation frequency, thereby improving the frequency detection accuracy.

[0025] The present invention may be applied to the thermal flow rate measuring device 1 described above, or to a gas meter 150 equipped with the flow rate measuring device 1, as shown in Figure 18. In addition to the flow rate measuring device 1, the gas meter 150 includes a display unit 151, a power supply unit 152, an operation unit 153, a vibration detection unit 154, a shut-off unit 155, a gas meter control unit 156, a gas meter storage unit 157, and a gas meter communication unit 158.

[0026] Furthermore, the present invention may also be applied to a flow rate measuring device unit 150a, as shown in Figure 18, which integrates the flow rate measuring device 1, display unit 151, power supply unit 152, vibration detection unit 154, gas meter control unit 156, gas meter storage unit 157, and gas meter communication unit 158 ​​into a single unit, making it easy to incorporate when manufacturing the gas meter 150.

[0027] [Example 1] In the following section, a flow rate measuring device according to an embodiment of the present invention will be described in more detail with reference to the drawings.

[0028] <Device configuration> Figure 1 is an exploded perspective view showing an example of a flow rate measuring device 1 according to this embodiment. Figure 2 is a cross-sectional view showing an example of a flow rate measuring device 1. The flow rate measuring device 1 is incorporated into, for example, gas meters, combustion equipment, internal combustion engines in automobiles, fuel cells, and other industrial equipment such as medical devices, and embedded devices to measure the amount of fluid passing through the flow path. The dashed arrows in Figures 1 and 2 illustrate the direction of fluid flow.

[0029] Furthermore, as shown in Figure 1, the flow rate measuring device 1 according to this embodiment includes a main flow path section 2, a sub-flow path section 3, a seal 4, a circuit board 5, and a cover 6. As shown in Figures 1 and 2, in this embodiment, the flow rate measuring device 1 has a sub-flow path section 3 branched from the main flow path section 2. The sub-flow path section 3 is also equipped with a flow rate detection section 11 and a physical property detection section 12. The flow rate detection section 11 and the physical property detection section 12 are composed of thermal flow sensors including a heating section formed by a microheater and a temperature detection section formed by a thermopile. In this embodiment, the physical property detection section 12 is used to detect the physical properties of the fluid, and the flow rate detected by the flow rate detection section 11 is corrected based on the physical properties of the fluid. However, the flow rate measuring device 1 does not necessarily have to be equipped with a physical property detection section 12.

[0030] The main flow channel section 2 is a tubular member through which the fluid to be measured (hereinafter also referred to as the main flow channel) penetrates in the longitudinal direction. As shown in Figure 2, an inlet (first inlet) 34A is formed on the upstream side of the inner circumferential surface of the main flow channel section 2, and an outlet (first outlet) 35A is formed on the downstream side with respect to the fluid flow direction. For example, the axial length of the main flow channel section 2 is approximately 50 mm, the diameter of the inner circumferential surface (inner diameter of the main flow channel section 2) is approximately 20 mm, and the outer diameter of the main flow channel section 2 is approximately 24 mm, but the dimensions of the main flow channel section 2 are not limited to these. In addition, an orifice 21 is provided in the main flow channel section 2 between the inlet 34A and the outlet 35A. The orifice 21 is a resistor in the main flow channel section 2 with an inner diameter smaller than the areas before and after it, and the amount of fluid flowing into the sub-flow channel section 3 can be adjusted by the size of the orifice 21.

[0031] In Figures 1 and 2, the sub-channel section 3, which contains a sub-channel branched from the main channel, is located vertically above the main channel section 2. The sub-channel within the sub-channel section 3 includes an inflow channel 34, a physical property detection channel 32, a flow rate detection channel 33, and an outflow channel 35. A portion of the fluid flowing through the main channel section 2 branches off and flows into the sub-channel section 3.

[0032] The inflow channel 34 is a channel that allows fluid flowing through the main channel 2 to flow in and divert it to the physical property detection channel 32 and the flow rate detection channel 33. The inflow channel 34 is formed along a direction perpendicular to the fluid flow direction in the main channel 2, with one end communicating with the inlet 34A and the other end communicating with the physical property detection channel 32 and the flow rate detection channel 33. A portion of the fluid flowing through the main channel 2 is further diverted to the physical property detection channel 32 and the flow rate detection channel 33 via the inflow channel 34. The amount of fluid flowing into these physical property detection channels 32 and flow rate detection channels 33 corresponds to the amount of fluid flowing through the main channel 2. Therefore, the flow rate detection unit 11 can detect a value corresponding to the amount of fluid flowing through the main channel 2.

[0033] As shown in Figure 1, the physical property detection channel 32 is formed vertically above the main channel section 2 and extends in a direction parallel to the main channel section 2, with a roughly U-shaped cross-section when viewed from above. A physical property detection unit 12 for detecting the physical properties of the fluid to be measured is arranged inside the physical property detection channel 32. One end of the physical property detection channel 32 communicates with the inlet 34A via the inlet channel 34, and the other end communicates with the outlet 35A via the outlet channel 35.

[0034] The flow rate detection channel 33 is a channel that extends in a direction parallel to the fluid flow direction in the main channel section 2, and has a roughly U-shaped cross-section when viewed from above. A flow rate detection unit 11 for detecting the fluid flow rate is located inside the flow rate detection channel 33. One end of the flow rate detection channel 33 communicates with the inlet 34A via the inlet channel 34, and the other end communicates with the outlet 35A via the outlet channel 35. The physical property detection unit 12 and the flow rate detection unit 11 are each mounted on the circuit board 5. The circuit board 5 covers the upper parts of the physical property detection channel 32 and the flow rate detection channel 33, which have openings at the top, and is positioned such that the physical property detection unit 12 is located in the physical property detection channel 32 and the flow rate detection unit 11 is located in the flow rate detection channel 33.

[0035] The discharge channel 35 is a channel for discharging the fluid to be measured, which has passed through the physical property detection channel 32 and the flow rate detection channel 33, into the main channel section 2. The discharge channel 35 is formed along a direction perpendicular to the main channel section 2, with one end communicating with the outlet 35A and the other end communicating with the physical property detection channel 32 and the flow rate detection channel 33. The fluid to be measured, which has passed through the physical property detection channel 32 and the flow rate detection channel 33, flows out into the main channel section 2 via the discharge channel 35.

[0036] In this embodiment, as described above, the fluid to be measured, which is introduced from a single inlet 34A, is divided into a physical property detection channel 32 and a flow rate detection channel 33. As a result, the flow rate detection unit 11 and the physical property detection unit 12 can detect the physical properties and flow rate of the fluid to be measured based on fluids with approximately the same conditions such as temperature and density. In addition, the flow rate measuring device 1 ensures airtightness inside the sub-channel section 3 by fitting a seal 4 into the sub-channel section 3, then placing the circuit board 5, and further fixing the circuit board 5 to the sub-channel section 3 with a cover 6.

[0037] Figure 3 is a plan view of the sub-channel section 3 shown in Figure 1. As shown in Figure 3, the physical property detection channel 32 and the flow rate detection channel 33 are arranged symmetrically with respect to a line (not shown) connecting the central axis of the inflow channel 34 and the central axis of the outflow channel 35 in a plan view. Arrows P and Q schematically represent the ratio of the flow rates of the fluid diverted to the physical property detection channel 32 and the flow rate detection channel 33. In this embodiment, the cross-sectional areas of the physical property detection channel 32 and the flow rate detection channel 33 are determined so that the amount of fluid diverted is in the ratio of P to Q.

[0038] The actual amount of fluid flowing through the physical property detection channel 32 and the flow rate detection channel 33 varies according to the flow rate of the fluid flowing through the main channel 2. However, in a normal operating configuration, the size of the sub-channel 3 relative to the main channel 2, the size of the orifice 21, and the widths of the physical property detection channel 32 and the flow rate detection channel 33 are set such that the amount of fluid flowing through the physical property detection channel 32 falls within the detection range of the physical property detection unit 12, and the amount of fluid flowing through the flow rate detection channel 33 falls within the detection range of the flow rate detection unit 11.

[0039] Thus, the flow rate measuring device 1 makes it possible to individually control the flow rates of the fluids that are diverted to the physical property detection channel 32 and the flow rate detection channel 33 by adjusting the width of each channel. Therefore, the flow rate of the fluid flowing through the physical property detection channel 32 can be controlled according to the detection range of the physical property detection unit 12, and the flow rate of the fluid flowing through the flow rate detection channel 33 can be controlled according to the detection range of the flow rate detection unit 11.

[0040] The physical property detection channel 32 and the flow rate detection channel 33 are not limited to being formed in a substantially U-shape when viewed from above. In other words, the physical property detection channel 32 and the flow rate detection channel 33 may be of other shapes as long as the width (cross-sectional area) is set to a size that allows control of the flow rate of the fluid passing through the physical property detection channel 32 and the flow rate detection channel 33.

[0041] Furthermore, while the shape of the space in which the physical property detection unit 12 and the flow rate detection unit 11 are arranged in the physical property detection channel 32 and the flow rate detection channel 33 is approximately square when viewed from above, the present invention is not limited to this. The shape of the physical property detection channel 32 and the flow rate detection channel 33 only needs to be such that the physical property detection unit 12 or the flow rate detection unit 11 can be arranged, and can be determined according to the shape of the physical property detection unit 12 and the flow rate detection unit 11 in which they are arranged.

[0042] Therefore, for example, if the size of the physical property detection unit 12 is smaller than the width of the physical property detection channel 32, the width of the space in the physical property detection channel 32 where the physical property detection unit 12 is positioned... The width of the physical property detection channel 32 may be made to match the width of other parts of the channel 32. In this case, the portion of the physical property detection channel 32 that extends in the longitudinal direction will have a shape with a nearly constant width. The same applies to the flow rate detection channel 33.

[0043] As described above, the amount of fluid flowing through the physical property detection channel 32 and the flow rate detection channel 33 is less than the amount of fluid flowing through the main channel 2, but each changes in accordance with the amount of fluid flowing through the main channel 2. If the flow rate detection unit 11 and the physical property detection unit 12 were to be placed in the main channel 2, it would be necessary to increase the size of the flow rate detection unit 11 and the physical property detection unit 12 in accordance with the amount of fluid flowing through the main channel 2. However, in this embodiment, by providing a sub-channel 3 that branches off from the main channel 2, the fluid flow rate can be measured using a smaller flow rate detection unit 11 and a smaller physical property detection unit 12.

[0044] Furthermore, in this embodiment, the cross-sectional area of ​​the physical property detection channel 32 is smaller than the cross-sectional area of ​​the flow rate detection channel 33, and as shown by the sizes of arrows P and Q in Figure 3, the amount of fluid flowing through the physical property detection channel 32 is less than the amount of fluid flowing through the flow rate detection channel 33. In this way, by making the amount of fluid flowing through the physical property detection unit 12 less than the amount of fluid flowing through the flow rate detection unit 11, the error caused by the flow rate when the physical property detection unit 12 detects the physical properties and temperature of the fluid can be reduced.

[0045] Figure 4 is a perspective view showing an example of a sensor element used in the flow rate detection unit 11 and the physical property detection unit 12. Figure 5 is a cross-sectional view illustrating the mechanism of the sensor element. The sensor element 100 comprises a microheater (also called a heating unit) 101 and two thermopiles (also called temperature detection units) 102 arranged symmetrically on either side of the microheater 101. That is, the microheater 101 and the two thermopiles 102 are arranged to be aligned in a predetermined direction. An insulating thin film 103 is formed above and below them, as shown in Figure 5, and the microheater 101, thermopiles 102 and insulating thin film 103 are provided on a silicon base 104. A cavity 105 formed by etching or the like is provided in the silicon base 104 below the microheater 101 and thermopiles 102.

[0046] The microheater 101 is a resistor made of, for example, polysilicon. In Figure 5, the dashed ellipse schematically shows the temperature distribution when the microheater 101 generates heat. The thicker the dashed line, the higher the temperature. When there is no fluid flow, the temperature distribution around the microheater 101 is almost uniform, as shown in Figure 5(a). On the other hand, if a fluid flows in the direction indicated by the dashed arrow in Figure 5(b), for example, the fluid moves, so unheated fluid flows into the upstream side of the microheater 101, and the temperature is higher downstream than upstream. The sensor element 100 uses this uneven distribution of heater heat to output a value indicating the flow rate.

[0047] The output voltage ΔV of the sensor element can be expressed, for example, by equation (1) below. ΔV = A × (Th - Ta) × b √(Vf) ···(1) Note that Th is the temperature of the microheater 101 (the temperature of the end of the thermopile 102 on the microheater 101 side), Ta is the lower of the two temperatures of the ends of the thermopile 102 furthest from the microheater 101 (in Figure 5(a), this is the temperature of the left end of the left thermopile 102 or the right end of the right thermopile 102, and in Figure 5(b), it is the temperature of the left end of the left thermopile 102, which is the upstream end), Vf is the average value of the flow velocity, and A and b are predetermined constants.

[0048] Furthermore, the circuit board 5 of the flow rate measuring device 1 includes a control unit (not shown) implemented by an IC (Integrated Circuit), etc., which calculates the flow rate based on the output of the flow rate detection unit 11. The circuit board 5 may calculate predetermined characteristic values ​​based on the output of the physical property detection unit 12 and correct the flow rate using these characteristic values.

[0049] <Flow detection unit and physical property detection unit> Figure 6 is a plan view showing the schematic configuration of the flow detection unit 11 shown in Figure 1, and Figure 7 is a plan view showing the schematic configuration of the physical property detection unit 12 shown in Figure 1. As shown in Figure 6, the flow detection unit 11 includes a first thermopile (also called a temperature detection unit) 111 and a second thermopile (also called a temperature detection unit) 112 for detecting the temperature of the fluid to be measured, and a microheater (also called a heating unit) 113 for heating the fluid to be measured. The heating unit 113 and the temperature detection units 111 and 112 are arranged side by side within the flow detection unit 11 along the flow direction P of the fluid to be measured. Furthermore, the shapes of the heating unit 113, the temperature detection unit 111, and the temperature detection unit 112 are each approximately rectangular in plan view, and their respective longitudinal directions are perpendicular to the flow direction P of the fluid to be measured.

[0050] The temperature detection unit 111 and temperature detection unit 112 are positioned with the temperature detection unit 112 located upstream of the heating unit 113 and the temperature detection unit 111 located downstream, detecting the temperature at symmetrical positions on either side of the heating unit 113.

[0051] In the flow rate measuring device 1, the physical property detection unit 12 and the flow rate detection unit 11 use sensor elements 100 with substantially the same structure. The sensor elements 100 of the physical property detection unit 12 and the sensor elements 100 of the flow rate detection unit 11 are positioned at an angle of 90 degrees relative to the direction of fluid flow, in a plan view of the sensor elements 100. This allows the use of sensor elements 100 with the same structure in both the physical property detection unit 12 and the flow rate detection unit 11, thereby reducing the manufacturing cost of the flow rate measuring device 1.

[0052] On the other hand, as shown in Figure 7, the physical property detection unit 12 includes a first thermopile (also called a temperature detection unit) 121 and a second thermopile (also called a temperature detection unit) 122 for detecting the temperature of the fluid to be measured, and a microheater (also called a heating unit) 123 for heating the fluid to be measured. The heating unit 123 and the temperature detection units 121 and 122 are arranged side by side within the physical property detection unit 12 in a direction perpendicular to the flow direction Q of the fluid to be measured. Furthermore, the shapes of the heating unit 123, temperature detection unit 121, and temperature detection unit 122 are each approximately rectangular in plan view, and their respective longitudinal directions are aligned with the flow direction Q of the fluid to be measured. In addition, the temperature detection units 121 and 122 are arranged symmetrically on either side of the heating unit 123, and detect the temperature at symmetrical positions on both sides of the heating unit 123. Therefore, the measured values ​​from the temperature detection unit 121 and the temperature detection unit 122 are almost identical, and either the average value or one of the values ​​may be adopted.

[0053] Here, because the temperature distribution is biased downstream due to the fluid flow, the change in the temperature distribution in the direction perpendicular to the flow direction is smaller than the change in the temperature distribution in the direction of fluid flow. For this reason, by arranging the temperature detection unit 121, the heating unit 123, and the temperature detection unit 122 in this order in a direction perpendicular to the flow direction of the fluid to be measured, the change in the output characteristics of the temperature detection unit 121 and the temperature detection unit 122 due to changes in the temperature distribution can be reduced. Thus, the influence of changes in the temperature distribution due to fluid flow can be reduced, and the detection accuracy of the physical property detection unit 12 can be improved.

[0054] Furthermore, since the longitudinal direction of the heating unit 123 is aligned with the flow direction of the fluid to be measured, the heating unit 123 can heat the fluid to be measured over a wide range of the flow direction of the fluid to be measured. Therefore, even if the temperature distribution is biased downstream due to the flow of the fluid to be measured, changes in the output characteristics of the temperature detection unit 121 and the temperature detection unit 122 can be reduced. Similarly, when measuring fluid temperature, the error in the measured value caused by the flow velocity can be reduced. This can be reduced. The fluid temperature may be determined by subtracting the temperature rise due to heating by the heating unit 123 from the temperatures detected by the temperature detection unit 121 and temperature detection unit 122, or it may be detected when the heating unit 123 is not performing heating. The physical property detection unit 12 can suppress the influence of changes in temperature distribution due to the flow of the fluid being measured, and improve the detection accuracy of physical properties and fluid temperature.

[0055] Furthermore, since the longitudinal directions of the temperature detection units 121 and 122 are aligned with the flow direction of the fluid being measured, the temperature detection units 121 and 122 can detect temperature over a wide range of directions in the flow direction of the fluid being measured. Therefore, even if the temperature distribution is biased downstream due to the flow of the fluid being measured, changes in the output characteristics of the temperature detection units 121 and 122 can be reduced. Consequently, the influence of changes in the temperature distribution due to the flow of the fluid being measured can be reduced, and the detection accuracy of the physical property detection unit 12 can be improved.

[0056] <Functional Configuration> Figure 8 is a block diagram showing an example of the functional configuration of the flow rate measuring device 1. The flow rate measuring device 1 comprises a flow rate detection unit 11, a physical property detection unit 12, a control unit 13, a storage unit 14, and a communication unit 15. The flow rate detection unit 11 comprises a temperature detection unit 111 and a temperature detection unit 112. The physical property detection unit 12 comprises a temperature detection unit 121 and a temperature detection unit 122. Note that the heating unit 113 shown in Figure 6 and the heating unit 123 shown in Figure 7 are omitted from the illustration. The control unit 13 includes a detection value acquisition unit 131, a characteristic value calculation unit 132, and a flow rate calculation unit 133. The storage unit 14 includes a storage medium such as flash memory, RAM (Random Access Memory), or ROM (Read Only Memory), and holds a correction table 141.

[0057] The flow rate detection unit 11 calculates the difference between the signal corresponding to the temperature detected by the temperature detection unit 111 and the signal corresponding to the temperature detected by the temperature detection unit 112, and outputs it to the detection value acquisition unit 131 of the control unit 13. The physical property detection unit 12 outputs the signal corresponding to the temperature detected by the temperature detection unit 121 to the characteristic value calculation unit 132. Alternatively, the physical property detection unit 12 may calculate the average value of the signals corresponding to the temperature detected by the temperature detection unit 121 and the temperature detection unit 122 and output it to the characteristic value calculation unit 132. Alternatively, the temperature-corresponding signal may be acquired using either the temperature detection unit 121 or the temperature detection unit 122.

[0058] The detection value acquisition unit 131 acquires detection values ​​corresponding to the fluid flow rate output by the flow rate detection unit 11 at predetermined measurement intervals (sampling periods). The characteristic value calculation unit 132 calculates characteristic values ​​based on the detection values ​​of at least one of the temperature detection unit 121 and temperature detection unit 122 of the physical property detection unit 12. Alternatively, the characteristic value calculation unit 132 may change the temperature of the microheater of the physical property detection unit 12 and calculate the characteristic value by multiplying the difference in the temperature of the target fluid detected by the temperature detection unit 121 or temperature detection unit 122 before and after the change by a predetermined coefficient.

[0059] The flow rate calculation unit 133 calculates the flow rate based on the detected values ​​acquired by the detected value acquisition unit 131. At this time, the flow rate calculation unit 133 may also correct the flow rate using characteristic values ​​calculated by the physical property detection unit 12. The communication unit 15 transmits the information processed by the control unit 13 to the outside wirelessly or via wired connection, and receives commands and setting values ​​from the outside wirelessly or via wired connection and transmits them to the control unit 13. The setting values ​​received from the outside include data held in the correction table 141 of the storage unit 14. The correction table 141 stores, for example, a flow rate correction value corresponding to the calculated pulsating flow frequency (pulsation frequency), as will be described later.

[0060] By the way, in the conventional flow rate calculation unit 133, the volumetric flow rate (L / min) of the fluid is calculated based on the ΔV equation obtained by equation (1). If pulsation occurs in the piping, the flow rate of the fluid flowing through the main flow channel 2 shown in Figures 1 and 2 will change due to the influence of the pulsation.

[0061] Figure 9 illustrates the fluctuation of the sensor output value (flow rate) when pulsation is applied to the main flow channel 2 while the fluid flow rate through the main flow channel 2 is kept constant (2 [L / min]). In Figure 9, graph g1, shown by a solid line, illustrates the change in the sensor output value when no pulsation is applied. Similarly, graph g2, shown by a dashed line, illustrates the change in the sensor output value when pulsation with a period interval varying at a frequency of "5 Hz" is applied, and graph g3, shown by a thin dashed line, illustrates the change in the sensor output value when pulsation with a period interval varying at a frequency of "10 Hz" is applied. Furthermore, graph g4, shown by a dashed line, illustrates the change in the sensor output value when pulsation with a period interval varying at a frequency of "20 Hz" is applied. Note that in Figure 9, the vertical axis represents the flow rate value (L / min) output as the sensor output value, and the horizontal axis represents time (s).

[0062] As shown in graph g1 of Figure 9, when there is no pulsation, the flow rate measured by the flow rate measuring device 1 according to this embodiment remains relatively stable near the predetermined value of 2 (L / min). However, when pulsation is applied, as shown in graphs g2 to g4, the sensor output value of the flow rate measuring device 1 changes according to the frequency of the applied pulsation. Specifically, with a pulsation period of 5 Hz, the flow rate obtained as the sensor output value fluctuates between -6 (L / min) and 10 (L / min). Similarly, with a frequency of 10 Hz, it fluctuates between -1 (L / min) and 8 (L / min), and with a frequency of 20 Hz, it fluctuates between 3 (L / min) and 7 (L / min). The trend in the range of fluctuation in the sensor output value of the flow rate measuring device 1 is that it is relatively large when the frequency applied as pulsation is low, and relatively small when the frequency is high. Furthermore, if we take the maximum and minimum values ​​of the sensor output (flow rate) from graph g2 to graph g4 as the average, we can see that this average tends to shift to the positive side as the frequency increases. For example, the flow rate, which was an average of "2 (L / min)" at a frequency of "5 Hz", shifts to "3.5 (L / min)" at a frequency of "10 Hz", and becomes "5 (L / min)" at a frequency of "20 Hz".

[0063] Figure 10 illustrates the temperature distribution within the flow detection device when pulsation occurs. Figure 10 shows an example corresponding to the schematic diagram of the temperature distribution within the flow detection device described in Figure 5, and illustrates a side cross-sectional view of the flow measuring device 1 according to this embodiment, viewed along the flow direction. As shown in Figure 10, the left side of this figure represents the upstream side A5 through which the fluid flows in the main flow channel 2 shown in Figure 2, and the right side represents the downstream side A6 through which the fluid flows. In the flow measuring device 1 of the example shown, an upstream thermopile 102 is exemplified at the upstream side A5, a downstream thermopile 102 is exemplified at the downstream side A6, and a microheater 101 is exemplified between the upstream thermopile 102 and the downstream thermopile 102. In the upstream thermopile 102, the cold junction 102a of the thermopile is located in the direction of the upstream side A5, and the hot junction 102b is located in the direction of the downstream side A6. Similarly, in the downstream thermopile 102, the hot junction 102c of the thermopile is located in the upstream A5 direction, and the cold junction 102d is located in the downstream A6 direction.

[0064] Furthermore, in region A1, demarcated by a dashed line, the temperature distribution due to the microheater 101 when there is no wind and no pulsation is illustrated by the hatched elliptical region A1a. Similarly, in region A2, the temperature distribution due to the microheater 101 when there is no wind and pulsation is illustrated by the hatched elliptical regions A2a and A2b. In region A3, the temperature distribution due to the microheater 101 when there is wind and no pulsation is illustrated by the hatched elliptical region A3a. In region A4, the temperature distribution due to the microheater 101 when there is wind and pulsation is illustrated by the hatched elliptical regions A4a and A4b.

[0065] In the absence of wind and pulsation, the temperature distribution around the microheater 101 will be almost uniform, as shown in the elliptical region A1a of Figure 10. When there is no wind and pulsation is present, it is estimated that the temperature distribution will shift to the upstream side A5 and the downstream side A6 in accordance with the negative and positive pressure fluctuations caused by the pulsation, as shown in the elliptical regions A2a and A2b of region A2. That is, when the pressure fluctuation due to pulsation is negative, the temperature distribution that was uniformly formed near the microheater 101 will move to the upstream side A5, and when the pressure fluctuation is positive, the temperature distribution that was uniformly formed near the microheater 101 will move to the downstream side A6. For this reason, it is estimated that when there is negative pressure, the hot junction 102b located at the upstream side A5 of the upstream thermopile 102 will detect the fluctuation in the temperature distribution due to pulsation, and when there is positive pressure, the hot junction 102c located at the upstream side A5 of the downstream thermopile 102 will detect the fluctuation in the temperature distribution due to pulsation. As a result, it is estimated that the fluctuation range of the sensor output value of the flow rate measuring device 1 changes depending on the pulsation frequency.

[0066] Next, when there is fluid movement (wind) within the main flow channel 2, if there is no pulsation, the temperature distribution around the microheater 101 is estimated to be biased toward the direction of fluid movement, i.e., downstream A6, as shown in the elliptical region A3a of region A3. Furthermore, if pulsation occurs, when the pressure fluctuation due to pulsation is positive, the temperature distribution biased toward downstream A6 will shift further downstream, as shown in the elliptical region A4b. When the pressure fluctuation due to pulsation is negative, the temperature distribution biased toward downstream A6 will shift slightly upstream to A5, as shown in the elliptical region A4a, but will still be formed relatively near the downstream thermopile 102. This bias in the temperature distribution when there is fluid movement (wind) within the main flow channel 2 and pressure fluctuations due to pulsation is estimated to change in position depending on the fluctuation period (frequency) of the pulsation. In other words, it can be estimated that when the frequency of the pulsation is high, the temperature distribution tends to be biased further downstream.

[0067] Figure 11 shows the deviation of the sensor output value with respect to the pulsation frequency. In Figure 11, graph g5 illustrates the deviation from the true value when pulsation of a predetermined frequency is applied to a state without pulsating flow, as shown by the double dashed line. Here, the deviation from the true value can be determined, for example, by the average of the sensor output value (flow rate value) when pulsation is applied to the main flow channel 2 while keeping the flow rate of the fluid flowing through the main flow channel 2 in Figure 9 constant (2 [L / min]).

[0068] As shown in graph g5 of Figure 11, when the pulsation frequency is low, the deviation from the true value is relatively small. For example, when the pulsation frequency is 5 Hz, the deviation from the true value (2 L / min) is about 1 L / min, while when the frequency is 10 Hz it becomes about 2 L / min, and when the frequency is 20 Hz it increases to about 3 L / min.

[0069] In the flow rate measuring device 1 according to this embodiment, in order to suppress the flow rate measurement error that depends on the fluctuation period (frequency) of the pulsation described above, the frequency of the pulsation is determined based on the sensor output value sampled during the heating period of the microheater 101. Then, the flow rate measuring device corrects the amount of deviation of the sensor output value according to the determined pulsation frequency. According to the flow rate measuring device 1 according to this embodiment, even when the fluid to be measured flowing through a pipe or the like becomes a pulsating flow due to the influence of ambient vibrations or pumps, it becomes possible to measure the flow rate with higher accuracy.

[0070] Figure 12 illustrates the sampling period for measuring the pulsation frequency. Figure 12 shows an example graph illustrating the change in pulsating flow rate when pulsating flow occurs. The vertical axis in Figure 12 represents the normalized flow rate, and the horizontal axis represents the normalized period interval.

[0071] In Figure 12, (a) shows an example graph where the pulsation period and the sampling period are synchronized, and the flow rate near the zero value, which changes due to the pulsation, is always sampled. In (b), the pulsation period and the sampling period are synchronized, and the flow rate near the maximum value, which changes due to the pulsation, is always sampled. As shown in Figure 12(a), when the sampling period is synchronized with the pulsation period and the flow rate near the zero value, which changes due to the pulsation, is always sampled, the average value becomes "0", and it is unclear whether the pulsation period is synchronized with the sampling period or not. Also, as shown in Figure 12(b), even when the sampling period is synchronized with the pulsation period and the flow rate near the maximum value, which changes due to the pulsation, is always sampled, the average value becomes the "max value", so although the flow rate value is different from the true value (zero value), it is still unclear whether the pulsation frequency is synchronized with the sampling period or not.

[0072] Therefore, in order to identify the fluctuating frequency of the pulsating flow generated in the fluid being measured, the pulsation period and the sampling period must be asynchronous, as shown in Figure 12(c). Then, by calculating the average value of the flow rate measured with a sampling period asynchronous to the pulsation period, the result will ultimately converge to the true value (for example, a "zero value").

[0073] In thermal flow measuring devices, the sampling period for measuring the pulsation frequency is limited to the heating period (heater ON period) of the microheater 101. Therefore, in the flow measuring device 1 according to this embodiment, the zero-crossing method is adopted as the sampling method in order to improve the frequency accuracy of the pulsating flow measured within the limited sampling period.

[0074] Figure 13 is a diagram illustrating frequency determination by the zero-crossing method processed in this embodiment. As shown in graph g6 of Figure 13, for changes in flow rate where pulsation occurs, a reference measurement value is determined from among the sampled measurement points as shown in measurement point [1] (reference point). Here, the selection of the reference point is arbitrary. Then, a measurement point with the same value as the reference point measurement value [ When m is obtained, the frequency related to the pulsation is determined from the time difference between the reference point [1] and the measurement point [m]. This is how it should be done. By using this zero-crossing method, it becomes possible to identify the frequency of pulsating flow generated in the fluid being measured within a limited sampling period.

[0075] Figure 14 illustrates the sampling of flow rate values ​​during the heating period of the flow rate measuring device 1. In Figure 14, the change in flow rate value in a pulsating fluid is shown in graph g7, and the heating period of the heater in the flow rate measuring device 1 is shown in graph g8. The vertical axis represents flow rate value, and the horizontal axis represents time. As shown in Figure 14, in the zero-crossing method, the sampling interval for identifying the pulsation frequency is one of the parameters that affects the detection accuracy of that frequency. That is, as shown in Figures 12(a) and (b), a sampling period synchronized with a pulsation of unknown frequency cannot obtain the correct average flow rate value. Also, since the memory capacity built into the flow rate measuring device 1 is limited, the number of flow rate value samples that can be stored to identify the pulsation frequency is limited. In this embodiment, the acquisition interval for obtaining flow rate values ​​is changed little by little, and the number of periods of the pulsating flow of one or more cycles is identified with the number of data that can be stored in the pre-prepared memory capacity. As such a period, it is desirable to be able to acquire a number of samples of about 1.5 cycles with respect to the fluctuation period of the pulsating flow.

[0076] <Flow rate measurement process> Figure 15 is a flowchart illustrating an example of the flow rate measurement process in this flow rate measuring device. This flow is executed by sending commands from a processor (not shown), such as a CPU, located on the circuit board 5 of the flow rate measuring device 1, to the flow rate detection unit 11, the physical property detection unit 12, and the control unit 13. When this flow is executed, in step S101, the frequency of the pulsating flow is detected. Specific details regarding the detection of the pulsating flow frequency are illustrated in the flowchart of Figure 16.

[0077] In the flowchart showing the details of step S101 in Figure 16, first, in step S111, triggered by the timing when the heating unit 113 of the flow detection unit 11 is turned ON, the control unit 13 is instructed to set an initial value for the measurement interval (sampling period) for the detection value acquisition unit 131 to acquire detection values ​​corresponding to the fluid flow rate output by the flow detection unit 11, and the process proceeds to step S112. Here, the initial value of the sampling period is set by, for example, the heating period of the heating unit 113 and the number of data that can be stored in the pre-prepared memory capacity. However, the initial value of the sampling period can be arbitrarily set according to the configuration and performance of the flow measurement device 1, the physical properties of the fluid whose flow rate is to be measured, etc.

[0078] In step S112, multiple measurements are taken at the set initial measurement interval. Here, multiple measurements refer to a predetermined number of samples (multiple times) to determine the periodic interval conditions for measuring the frequency of the pulsating fluid (pulsation frequency) during the heating period. Once a predetermined number of detection values ​​corresponding to the fluid flow rate, output from the flow rate detection unit 11, have been acquired, the process proceeds to step S113. In step S113, when the start flag value for initiating the measurement of the pulsation frequency generated in the fluid to be measured is reset, the process proceeds to step S114.

[0079] In step S114, once the data (n items) stored in memory has been read, the process proceeds to step S115. In step S115, it is determined whether the start flag value is "1" or not (reset value). In step S115, if the start flag value is "1" (step S115, "Yes"), the process proceeds to step S116; otherwise (step S115, "No"), the process proceeds to step S117.

[0080] In step S116, it is determined whether the measurement data stored in memory meets the end condition for identifying the pulsation frequency using the zero-crossing method. That is, as shown in Figure 13, it is determined whether the sampled measurement data contains a reference point and other measurement points that show the same flow rate value as the reference point. In step S116, if the sampled measurement data contains a reference point and other measurement points that show the same flow rate value as the reference point, it is determined that the end condition is met (step S116, "Yes"), and the process proceeds to step S122. Otherwise, it is determined that the end condition is not met (step S116, "No"), and the process proceeds to step S119.

[0081] In step S117, as explained in Figure 13, it is determined whether the measurement data stored in memory matches the start conditions for measuring the pulsation frequency using the zero-crossing method. That is, as shown in Figures 12(a) and (b), if the measurement interval and the pulsation period match, roughly the same flow rate value will be measured continuously. Also, if the measurement interval and the pulsation period do not match and an appropriate measurement interval (a measurement interval that allows for the identification of the pulsation frequency using the zero-crossing method) is used, as shown in Figures 12(c) and 14, flow rate values ​​that increase or decrease continuously in the sampling order will be obtained. Therefore, in step S117, it is determined whether there are multiple flow rate values ​​among the multiple measured flow rate values ​​(measurement data) that increase or decrease continuously in the sampling order. It is desirable that the number of flow rate value data that increase or decrease continuously in the sampling order be three or more. In step S117, if the number of flow rate data points among the multiple measured flow rate values ​​that increase or decrease consecutively in the sampling order is a predetermined number (3 or more) (step S117, "Yes"), it is determined that the start condition is met and the process proceeds to step S118. Otherwise (step S117, "No"), the process proceeds to step S119.

[0082] In step S118, the measurement of the pulsation frequency generated in the fluid to be measured is initiated. When the start flag value is set, the process proceeds to step S119. In step S119, the number of data (n) is incremented, and the process proceeds to step S120. In step S120, it is determined whether the incremented number of data is the final data to be stored in memory. The number of data that can be stored in memory is predetermined. In step S120, if it is the final data to be stored (step S120, "Yes"), the process proceeds to step S121. Otherwise (step S120, "No"), the process returns to step S114.

[0083] In step S121, if the measurement interval for measuring the frequency of the pulsating fluid (pulsation frequency) is updated, the process proceeds to step S112. The step of updating the measurement interval can be set arbitrarily. The measurement interval is updated to either narrow (in the high-frequency direction) or widen (in the low-frequency direction). In step S112 after the update, the flow rate value is measured according to the measurement interval updated in the update step.

[0084] In step S122, when the wavenumber of the pulsation generated in the target fluid is incremented, the process proceeds to step S123. In step S123, it is determined whether or not measurements for a predetermined "N wavenumber" have been completed in order to identify the frequency of the pulsation using the zero-crossing method. Here, the "N wavenumber" for identifying the frequency of the pulsation generated in the target fluid can be set arbitrarily. However, as explained in Figure 14, it is desirable that measurements be taken for a wavenumber corresponding to at least 1.5 periods of the pulsation generated in the target fluid. In step S123, if measurements for N wavenumbers have been completed (step S123, "Yes"), the process proceeds to step S124. Otherwise (step S123, "No"), the process returns to step S112.

[0085] In step S124, the average frequency of pulsations in the fluid being measured is calculated based on the time difference between the reference point and other measurement points that show the same flow rate value as the reference point in the measured data. The average frequency of pulsations is calculated by averaging the time differences obtained from measurements for N waves. In step S124, the average frequency may be calculated on the condition that it is less than a preset maximum frequency for pulsations. Such a maximum frequency can be arbitrarily set, for example, according to the pipe diameter of the main flow channel 2 or the physical properties of the fluid being measured. Alternatively, the average frequency may be calculated on the condition that, for example, the ratio of the maximum and minimum values ​​of the frequencies calculated from the measurement data within a predetermined number of periods (for example, within 10 periods) is a predetermined multiple (for example, 1.2 times). This makes it possible to improve the detection accuracy of pulsations in the fluid being measured. After the completion of step S124, this routine is terminated and the process proceeds to step S102 shown in Figure 15.

[0086] Returning to Figure 15, in step S102, the process proceeds to step S103 after calculating the optimal flow rate sampling time for the fluid to be measured based on the average frequency calculated in step S124. The processor sets the calculated sampling time as the measurement interval for the detection value acquisition unit 131 to acquire detection values ​​corresponding to the fluid flow rate output by the flow rate detection unit 11. In step S103, detection values ​​corresponding to the flow rate are acquired at the set sampling time, and the average value of the flow rate of the fluid to be measured is calculated based on these detection values. Then, in step S104, flow rate correction is performed on the average value calculated in step S103 according to the pulsation frequency calculated in step S101. For example, as shown in Figure 11, the amount of deviation from the true value corresponding to the frequency of pulsation in the fluid to be measured is stored in the correction table 141 as a flow rate correction value. Then, the flow rate correction value corresponding to the pulsation frequency calculated in step S101 is obtained from the correction table 141, and the average value of the flow rate calculated in step S103 is corrected. Once the processing in step S104 is completed, this routine is terminated.

[0087] Figure 17 shows an example of the measurement results of pulsation frequency measured by the flow rate measurement process according to this embodiment. In measuring the pulsation frequency, pulsations with periods indicated by test frequencies (5.0 Hz, 10.0 Hz, 15.0 Hz, 20.0 Hz) were applied to the fluid to be measured. The measured pulsation frequency is exemplified as the "judgment frequency". In measuring the pulsation frequency, "N" in the flow shown in Figure 16 was set to "10", and the frequency was calculated as the average value of 10 measurements. As shown in the judgment frequencies in Figure 17, "5.07 Hz" was calculated for a test frequency of "5.0 Hz", "10.10 Hz" for "10.0 Hz", "15.03 Hz" for "15.0 Hz", and "20.53 Hz" for "20.0 Hz". The error [%] of the judgment frequency for each test frequency was "1.4%", "1.0%", "0.2%", and "2.7%", respectively, indicating generally good frequency accuracy.

[0088] As described above, in this embodiment, the frequency of flow rate fluctuations due to pulsations in the fluid is determined from the detected value corresponding to the fluid flow rate output from the flow rate detection unit 11. Specifically, if the measured data does not meet predetermined conditions, sampling is repeated multiple times while updating the sampling period interval when acquiring the detected value at predetermined update steps. Then, the zero-crossing method is applied to the measured data that meets the predetermined conditions to calculate the frequency of flow rate fluctuations due to pulsations. As a result, even with a thermal flow rate measuring device that has a limited heating period, it becomes possible to accurately detect the frequency of pulsations in the fluid being measured based on a small number of data samples.

[0089] Furthermore, if pulsation occurs in the fluid being measured, the amount of deviation from the true value of the flow rate changes in accordance with the fluctuation period (frequency) of the pulsation. This deviation is relatively small when the pulsation frequency is low and tends to increase as the frequency increases. In the flow rate measuring device 1 according to this embodiment, the amount of deviation from the true value corresponding to the pulsation frequency can be stored as a flow rate correction value in the correction table 141. Then, the amount of deviation corresponding to the detected pulsation frequency can be obtained from the correction table 141 and corrected for the measured flow rate value. According to this embodiment, a flow rate measuring device with higher accuracy can be provided even when pulsation occurs.

[0090] [Example 2] Next, as Example 2, a gas meter incorporating the flow rate measuring device according to Example 1 and a flow rate measuring device unit will be described. This example shows the flow rate measuring device 1 according to Example 1 incorporated into a gas meter for measuring gas usage. Figure 18 is a block diagram showing an example of the functional configuration of a gas meter 150 incorporating the flow rate measuring device 1. In addition to the flow rate measuring device 1, the gas meter 150 includes a display unit 151, a power supply unit 152, an operation unit 153, a vibration detection unit 154, a shut-off unit 155, a gas meter control unit 156 as an integrated control unit, a gas meter storage unit 157, and a gas meter communication unit 158. Note that, with the exception of the operation unit 153, these components are housed within the casing 150b.

[0091] Here, the display unit 151 is a display that shows the amount of gas used based on the flow rate (heat flow rate (J / min), volume flow rate (l / min), or both) measured and output by the flow rate measuring device 1, as well as the date, whether or not shut-off processing has been performed (described later), etc., and a liquid crystal display board or the like may be used. The power supply unit 152 is the part that supplies power to the flow rate measuring device 1 and the other components of the gas meter 150, and may be composed of a battery such as an alkaline battery. The operation unit 153 is located outside the gas meter 150 and is the part that is operated by the gas customer or meter reader, etc. For example, it may be possible to perform operations such as resetting the gas meter 150, adjusting the time, switching the flow rate to be displayed and output (heat flow rate, volume flow rate, or both), and releasing the shut-off state, which will be described later.

[0092] The vibration detection unit 154 includes, for example, an acceleration sensor (not shown) and detects vibrations of the gas meter 150 itself. The shut-off unit 155 has an actuator such as a solenoid and a valve that closes the main flow path 2. If the vibration detection unit 154 detects vibrations above a threshold, it determines that an earthquake has occurred and shuts off the gas flowing through the main flow path 2. The gas meter control unit 156 is electrically connected to the flow rate measuring device 1, display unit 151, power supply unit 152, operation unit 153, vibration detection unit 154, shut-off unit 155, gas meter storage unit 157, and gas meter communication unit 158, and controls each unit. For example, it receives input information from the operation unit 153 and transmits commands to each unit according to the input information. Also, if the vibration detection unit 154 detects an acceleration signal above a threshold, it transmits a shut-off signal to the shut-off unit 155. The gas meter storage unit 157 is a part that stores the outputs from the flow rate measuring device 1 and the vibration detection unit 154 in chronological order over a predetermined period, and may be composed of memory elements such as SRAM or DRAM. The gas meter communication unit 158 ​​can transmit each piece of information processed by the gas meter control unit 156 to the outside wirelessly or via wired connection, and receives commands and set values ​​from the outside and transmits them to the gas meter control unit 156. It may also communicate with the communication unit 15 of the flow rate measuring device 1 to receive information processed by the control unit 13 of the flow rate measuring device 1, and to transmit control signals and set values ​​to the flow rate measuring device 1.

[0093] Furthermore, the components of the gas meter 150 may be configured such that, for example, the flow rate measuring device 1, display unit 151, power supply unit 152, vibration detection unit 154, gas meter control unit 156, gas meter storage unit 157, and gas meter communication unit 158 ​​are unitized, and the operation unit 153 and shut-off unit 155 are electrically connected to this flow rate measuring device unit 150a and incorporated into the housing 150b, thereby enabling the gas meter 150 to be constructed. In this way, it is possible to manufacture the gas meter 150 more efficiently.

[0094] In this embodiment, the configurations of the gas meter 150 and the flow rate measuring device unit 150a are examples only and can be modified depending on the function of the gas meter 150 and manufacturing conditions. Furthermore, the flow rate measuring device according to the present invention is not limited to the configurations shown in the above embodiment. The configurations of the above embodiment can be combined as much as possible without departing from the problems to be addressed or the technical ideas of the present invention.

[0095] Furthermore, in the above embodiment, the flow rate measuring device 1 was described as performing a correction process corresponding to the pulsation frequency using the detected values ​​from the temperature detection units 111 and 112 of the flow rate detection unit 11. However, substantially the same process can be performed using the detected values ​​from the physical property detection unit 12. Note that the flow rate measuring device 1 may also include only one of the components of the flow rate detection unit 11 or the physical property detection unit 12.

[0096] For the purpose of comparing the constituent elements of the present invention with the configurations of the embodiments, the constituent elements of the present invention are listed below with reference numerals in the drawings. <Invention 1> A flow rate measuring device (1) for detecting the flow rate of the fluid to be measured flowing through the main channel (2), A heating section (113) that heats the fluid to be measured, A temperature detection unit (111, 112) for detecting the temperature of the fluid to be measured, Based on the temperature detection unit, a flow rate correction unit (133) detects the pulsation frequency related to the periodic fluctuation of the flow rate of the fluid to be measured flowing through the main channel, and corrects the flow rate of the fluid to be measured flowing through the main channel according to the detected pulsation frequency. A flow rate measuring device characterized by comprising the following features. <Invention 2> The flow rate correction unit (133) is, The temperature detection unit acquires detected values ​​at a period interval different from the fluctuation period related to the fluctuation of the flow rate of the fluid to be measured flowing through the main channel, and at least the time difference between two detected values ​​that are the same from the time series of detected values ​​acquired at the different period intervals. The flow rate measuring device according to Invention 1, characterized by detecting the pulsation frequency. <Invention 3> The flow rate correction unit (133) is, The flow rate measuring device according to Invention 2, characterized in that the periodic interval is changed when the quantity of detected values ​​acquired at the different periodic intervals does not satisfy a predetermined condition. <Invention 4> The flow rate correction unit (133) is, The flow rate measuring device according to invention 2 or 3, characterized in that the period interval is changed when the fluctuation range in the time series of detected values ​​acquired at different period intervals is within a predetermined range. <Invention 5> The flow rate correction unit (133) is, The flow rate measuring device according to Invention 4, characterized in that, when there is no group of detected values ​​that continuously increase or decrease in the time series of detected values ​​acquired at the aforementioned different periodic intervals, the periodic interval is changed. <Invention 6> The flow rate correction unit (133) is, The flow rate measuring device according to Invention 5, characterized in that when there is a group of detected values ​​that continuously increase or decrease in the time series of detected values ​​acquired at different periodic intervals, the acquisition of detected values ​​using the periodic interval is performed a predetermined number of times. <Invention 7> A flow rate measuring device (1) according to any one of inventions 1 to 6, A display unit (151) that displays the flow rate corrected by the flow rate correction unit, The integrated control unit (156) controls the flow rate measuring device and the display unit, A flow rate measuring device unit (150a) is provided. <Invention 8> A flow rate measuring device (1) according to any one of inventions 1 to 7, A display unit (151) that displays the flow rate measured by the flow rate measuring device, The integrated control unit (156) controls the flow rate measuring device and the display unit, The power supply unit (152) supplies power to the flow rate measuring device (1), the display unit (151), and the integrated control unit (156), A housing (150b) capable of housing the flow rate measuring device (1), display unit (151), and integrated control unit (156), The housing (150b) includes an operating unit (153) from which settings related to the operation of the flow rate measuring device can be made from the outside, A gas meter (150) equipped with [a specific feature]. [Explanation of symbols]

[0097] 1:Flow rate measuring device 11: Flow detection section 111: Temperature detection unit 112: Temperature detection unit 113: Heating section 12: Physical property detection unit 121: Temperature detection unit 122: Temperature detection unit 123: Heating section 13: Control Unit 131: Detected value acquisition unit 132: Characteristic Value Calculation Unit 133:Flow rate calculation section 14: Storage section 141: Correction Table 15: Communications Department 2:Main flow section 21: Orifice 3: Sub-channel section 32: Channel for detecting physical properties 33: Flow detection channel 34:Inflow channel 35:Outflow channel 4: Stickers 5: Circuit board 6: Cover 100: Sensor element 101: Microheater 102: Thermopile 103: Insulating thin film 104: Silicon base 105: Cavity 150: Gas meter 150a: Flow rate measuring device unit

Claims

1. A flow rate measuring device for detecting the flow rate of a fluid to be measured flowing through a channel, A heating unit for heating the fluid to be measured, A temperature detection unit for detecting the temperature of the fluid to be measured, The system includes a flow rate correction unit that detects a pulsation frequency related to the periodic fluctuation of the flow rate of the fluid to be measured flowing through the channel based on the value detected by the temperature detection unit, and corrects the flow rate of the fluid to be measured flowing through the channel according to the detected pulsation frequency. The flow rate correction unit is, The temperature detection unit acquires detection values ​​at arbitrary periodic intervals with respect to the flow rate of the fluid to be measured flowing through the aforementioned channel, and stores the acquired plurality of detection values ​​in the storage unit (14) in chronological order (S112), The processing routine can be repeatedly executed, which involves selecting a portion of the multiple detected values ​​stored in the storage unit (14) as the target of processing, reading out a predetermined number of the detected values ​​in chronological order (S114), determining the start condition to determine whether there is a group of a predetermined number or more consecutive detected values ​​where the fluctuation range of the predetermined number of detected values ​​in the chronological order exceeds a predetermined range (S117), increasing the number of read values ​​to the predetermined number of detected values ​​already read (S119), determining whether the increased number of read detected values ​​is the final stored data stored in the storage unit (14) (S120), and if it is not the final stored data, returning to the process of reading out the detected values ​​to be processed again (S114). The aforementioned flow rate correction unit is In the aforementioned processing routine, If the above start condition is met (S115), at least the termination condition is determined, which is whether or not the same detected value exists in the time series of detected values ​​acquired at the arbitrary periodic interval (S116), If the termination condition is met (S116), the process of detecting the pulsation frequency is performed based on the time difference between the same detected values. If the termination condition is not met (S116), the process returns to the processing routine after increasing the number of detected values ​​to be read for the processing (S119). The aforementioned flow rate correction unit is In the aforementioned processing routine, If the above start condition is not met (S115), the detected value to be processed is read. The processing routine continues from the process of increasing the number (S119), In the aforementioned processing routine, If the increased number of detected values ​​read indicates the final stored data in the storage unit (14) (S120), the periodic interval for acquiring the detected value by the temperature detection unit is changed (S121), the detected value is acquired (S112), and the processing routine is started. A flow rate measuring device characterized by the following features.

2. The flow rate measuring device according to claim 1, A display unit that displays the flow rate corrected by the flow rate correction unit, The flow rate measuring device and the integrated control unit that controls the display unit, A flow rate measuring unit equipped with the following features.

3. The flow rate measuring device according to claim 1, A display unit that displays the flow rate measured by the flow rate measuring device, The flow rate measuring device and the integrated control unit that controls the display unit, A power supply unit that supplies power to the flow rate measuring device, display unit, and integrated control unit, A housing capable of housing the flow rate measuring device, display unit, and integrated control unit, An operating unit that allows settings related to the operation of the flow rate measuring device to be made from outside the housing, A gas meter equipped with a gas meter.

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