Flow measurement device

Abstract

To eliminate impacts of dust adhesion in a flow-rate measurement device, to enable a more accurate measurement, and to improve a degree of freedom of a use environment.SOLUTION: A flow-rate measurement device (1) comprises: a heating unit (113) that heats a measurement target fluid; a plurality of temperature detection units (111 and 112) that are arranged across the heating unit in a flow direction of the measurement target fluid; a flow-rate calculation unit (133) that calculates a flow rate of the measurement target fluid from an output value of the temperature detection unit; and a detection unit (135) that detects an adhesion degree of dust or a water droplet in the temperature detection unit on the basis of a relationship between respective outputs of the plurality of temperature detection units.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a flow measurement device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been proposed a measuring device that includes a heater and a sensor, and that calculates the flow velocity or flow rate of a fluid by detecting a temperature distribution that changes due to the flow of the fluid with the sensor.

[0003] In addition, a flow measurement device has been proposed that has a flow detection unit for detecting the flow rate of the fluid to be measured flowing through the main flow path, a heating unit for heating the fluid to be measured and a temperature detection unit for detecting the temperature of the fluid to be measured, a characteristic value acquisition unit for acquiring a characteristic value of the fluid to be measured, and a flow correction unit that uses the characteristic value of the fluid to be measured acquired by the characteristic value acquisition unit to correct the flow rate of the fluid to be measured calculated based on the detection signal output from the flow detection unit, wherein the heating unit and the temperature detection unit are arranged side by side in a direction perpendicular to the flow direction of the fluid to be measured, and the characteristic value acquisition unit acquires the characteristic value from the difference in temperature of the fluid to be measured detected by the temperature detection unit before and after changing the temperature of the heating unit (see, for example, Patent Document 1).

[0004] In the conventional thermal flow measurement devices described above, dust and condensation may adhere to the sensor surface over time, affecting the temperature distribution detected by the sensor and causing changes in the flow measurement characteristics, which may result in a decrease in the accuracy of the flow measurement device or may limit the environment in which the flow measurement device itself can be used to measure clean gases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-129470 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology that can eliminate the effects of dust and / or water droplet adhesion in a flow measurement device, enable more accurate measurements, and increase the flexibility of the usage environment. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a flow rate measurement device for detecting a flow rate of a measurement target fluid flowing through a main flow path, comprising: a heating unit that heats the fluid to be measured; a plurality of temperature detecting units disposed on either side of the heating unit in the flow direction of the fluid to be measured, and configured to detect the temperature of the fluid to be measured; a flow rate calculation unit that calculates a flow rate of the fluid to be measured from output values ​​of the plurality of temperature detection units; a detection unit that detects the degree of adhesion of dust or water droplets to the temperature detection unit based on a relationship between the outputs of the plurality of temperature detection units; The flow rate measuring device is characterized by comprising:

[0008] According to the present invention, it is possible to detect the degree of adhesion of dust or water droplets due to condensation to the temperature detection unit without adding a new sensor or the like.

[0009] In the present invention, a temperature sensor for measuring the ambient temperature of the flow rate measuring device may be further provided. The detection unit may detect the degree of adhesion of dust or water droplets to the temperature detection unit based on the relationship between the outputs of the plurality of temperature detection units and the ambient temperature measured by the temperature sensor.

[0010] Here, it is known that the relationship between the outputs of the plurality of temperature detection units is affected by the degree of adhesion of dust and water droplets due to condensation as well as the ambient temperature. Therefore, by measuring the ambient temperature of the flow measurement device with a temperature sensor and having the detection unit detect the degree of adhesion of dust or water droplets to the temperature detection unit based on the relationship between the outputs of the plurality of temperature detection units and the ambient temperature measured by the temperature sensor, it is possible to detect the degree of adhesion of dust more accurately.

[0011] The present invention also provides the above-mentioned flow rate measuring device, a display unit that displays the flow rate measured by the flow rate measuring device; an integrated control unit that controls the flow rate measuring device and the display unit; The flow measurement unit may include:

[0012] This will enable the easy and efficient manufacture of gas meters that are highly accurate and have a high degree of freedom in the environment in which they are used.

[0013] The present invention also provides the above-mentioned flow rate measuring device, a display unit that displays the flow rate measured by the flow rate measuring device; an integrated control unit that controls the flow rate measuring device and the display unit; a power supply unit that supplies power to the flow rate measuring device, the display unit, and the integrated control unit; a housing capable of accommodating the flow rate measuring device, a display unit, and an integrated control unit; an operation unit that allows settings related to the operation of the flow rate measuring device to be made from outside the housing; The gas meter may be provided with:

[0014] This makes it possible to provide a gas meter with higher accuracy and greater flexibility in the environment in which it can be used. [Effects of the Invention]

[0015] According to the present invention, in a flow rate measurement device, it is possible to eliminate the influence of dust and condensation on estimation, and to increase the degree of freedom in the usage environment. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an exploded perspective view showing an example of a flow rate measuring device according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing an example of a flow rate measuring device according to a first embodiment of the present invention. [Figure 3] FIG. 2 is a plan view showing a sub-flow path portion in the first embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view showing an example of a sensor element according to the first embodiment of the present invention. [Figure 5] FIG. 2 is a cross-sectional view for explaining the mechanism of the sensor element in the first embodiment of the present invention. [Figure 6] 1 is a plan view showing a schematic configuration of a flow rate detection unit according to a first embodiment of the present invention. [Figure 7] 1 is a plan view showing a schematic configuration of a physical property value detecting unit in Example 1 of the present invention. [Figure 8] FIG. 2 is a block diagram showing the functional configuration of a circuit board according to the first embodiment of the present invention. [Figure 9] 10A and 10B are diagrams showing the influence of dust on the relationship between the outputs of two temperature detection units. [Figure 10] FIG. 10 is a diagram showing the influence of the ambient temperature on the relationship between the outputs of two temperature detection units. [Figure 11] 10 is a flowchart of a dust variation correction routine according to the first embodiment of the present invention. [Figure 12] FIG. 10 is a block diagram showing a functional configuration of a gas meter according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Application example] Application examples of the present invention will be described below with reference to the drawings. The present invention is applied, for example, to a thermal flow rate measuring device 1 as shown in FIG. 1. As shown in FIG. 2, the flow rate measuring device 1 divides a fluid flowing through a main flow path section 2, directs a portion of the divided flow to a flow rate detecting section 11, and measures the flow rate at the flow rate detecting section 11, which has a high correlation with the flow rate of the fluid in the main flow path section 2. As shown in FIG. 4, the sensor element used in the flow rate detecting section 11 has a configuration in which two thermopiles 102 are arranged on either side of a microheater (heating section) 101. The measurement principle utilizes the correlation between the difference in the temperature detection values ​​detected by the two thermopiles 102 and the flow rate of the fluid passing over them, as shown in FIG. 5.

[0018] As shown in the functional block diagram 8 of the flow rate measuring device 1, the output of the flow rate detecting unit 11 is transmitted to a control unit 13 realized by a CPU (Central Processing Unit) disposed on the circuit board 5. The detected value is transmitted to the detection value acquisition unit 131, and the flow rate is calculated as a final output in the flow rate calculation unit 133. In the thermal flow rate measurement device as described above, the flow rate value output from the flow rate calculation unit 133 may be affected by deposits (in this application example, dust) on the surfaces of the temperature detection units 111 and 112 of the flow rate detection unit 11.

[0019] In contrast, in the present invention, as shown in FIG. 8, dust detection unit 135 detects the degree of dust adhesion based on the relationship between the outputs of temperature detection unit 111 and temperature detection unit 112. Then, correction value determination unit 136 determines a correction value for the output value of flow rate calculation unit 133 based on the outputs of temperature detection unit 111 and temperature detection unit 112. Then, dust correction unit 137 corrects the output value of flow rate calculation unit 133. This is based on the fact that, as shown in FIG. 9, there is a correlation between the relationship between the outputs of temperature detection units 111 and 112 and the degree of dust adhesion. More specifically, the relationship between the difference Ta-Tb between the output values ​​of temperature detection units 111 and 112 and the correction value for the output of flow rate calculation unit 133 is stored in the form of a data table, and correction value determination unit 136 reads the correction value from the data table, and dust correction unit 137 corrects the output of flow rate calculation unit 133. This eliminates the effect of dust on the output of flow rate measurement device 1, enabling more accurate measurement. Furthermore, it is possible to increase the degree of freedom in the environment in which the flow rate measuring device 1 is used.

[0020] The relationship between the outputs of temperature detection units 111 and 112 may be affected by the ambient temperature in addition to the degree of dust adhesion. Therefore, in the present invention, an independent temperature sensor for measuring the ambient temperature may be provided, and the measurement value of the temperature sensor may be used to eliminate the influence of the ambient temperature on the relationship between the outputs of temperature detection units 111 and 112.

[0021] The present invention may be applied to the thermal type flow measuring device 1 as described above, or may be applied to a gas meter 150 as shown in Fig. 12 that is equipped with the flow measuring device 1. In addition to the flow measuring device 1, the gas meter 150 is equipped with a display unit 151, a power supply unit 152, an operation unit 153, a vibration detection unit 154, a cutoff unit 155, a gas meter control unit 156, a gas meter storage unit 157, and a gas meter communication unit 158.

[0022] Furthermore, the present invention may be applied to a flow measurement device unit 150a in FIG. 12 in which the flow measurement device 1, display unit 151, power supply unit 152, vibration detection unit 154, gas meter control unit 156, gas meter memory unit 157, and gas meter communication unit 158 ​​are unitized to facilitate assembly when manufacturing the gas meter 150.

[0023] Example 1 The following describes in more detail flow measurement devices according to embodiments of the present invention with reference to the drawings. While the following embodiments will be described using the case of detecting dust adhesion as an example, the same applies to the case of detecting water droplets due to condensation. Therefore, the description of the case of detecting water droplets due to condensation will be omitted.

[0024] <Device configuration> Fig. 1 is an exploded perspective view showing an example of a flow rate measuring device 1 according to this 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 into, for example, a gas meter, combustion equipment, an internal combustion engine such as an automobile, a fuel cell, other industrial equipment such as medical equipment, and embedded equipment, and measures the amount of fluid passing through a flow path. Note that the dashed arrows in Figs. 1 and 2 illustrate the direction of fluid flow.

[0025] As shown in FIG. 1 , the flow measurement 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 FIGS. 1 and 2 , the flow measurement device 1 according to this embodiment includes a sub-flow path section 3 branching off from the main flow path section 2. The sub-flow path section 3 is provided 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 configured by 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 property of the fluid, and the flow rate detected by the flow rate detection section 11 is corrected based on the physical property of the fluid; however, the flow measurement device 1 does not necessarily have to include the physical property detection section 12.

[0026] The main flow path section 2 is a tubular member through which a flow path for the fluid to be measured (hereinafter also referred to as the main flow path) penetrates in the longitudinal direction. As shown in FIG. 2 , the inner circumferential surface of the main flow path section 2 has an inlet (first inlet) 34A formed upstream of the direction of fluid flow and an outlet (first outlet) 35A formed downstream of the direction of fluid flow. For example, the axial length of the main flow path section 2 is approximately 50 mm, the diameter of the inner circumferential surface (the inner diameter of the main flow path section 2) is approximately 20 mm, and the outer diameter of the main flow path section 2 is approximately 24 mm, but the dimensions of the main flow path section 2 are not limited to these. In addition, the main flow path section 2 has an orifice 21 between the inlet 34A and the outlet 35A. The orifice 21 is a resistor whose inner diameter is smaller than those of the areas before and after it in the main flow path section 2. The amount of fluid flowing into the sub-flow path section 3 can be adjusted by adjusting the size of the orifice 21.

[0027] 1 and 2, a sub-channel section 3, which is a section that contains sub-channels branched off from the main channel, is provided vertically above the main channel section 2. The sub-channels in the sub-channel section 3 include 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.

[0028] The inflow channel 34 is a channel for allowing the fluid flowing through the main channel section 2 to flow in and for diverting the fluid to the physical property detection channel 32 and the flow rate detection channel 33. The inflow channel 34 is formed in a direction perpendicular to the flow direction of the fluid in the main channel section 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 section 2 is further diverted via the inflow channel 34 to the physical property detection channel 32 and the flow rate detection channel 33. An amount of fluid corresponding to the amount of fluid flowing through the main channel section 2 flows into the physical property detection channel 32 and the flow rate detection channel 33. Therefore, the flow rate detection unit 11 can detect a value corresponding to the amount of fluid flowing through the main channel section 2.

[0029] 1, the physical property detection flow path 32 is formed vertically above the main flow path section 2, extends in a direction parallel to the main flow path section 2, and is a flow path with a substantially U-shaped cross section as viewed from above. The physical property detection flow path 32 has a physical property detection unit 12 therein for detecting the physical property of the fluid to be measured. One end of the physical property detection channel 32 is connected to an inlet 34A via an inflow channel 34, and the other end is connected to an outlet 35A via an outflow channel 35.

[0030] The flow rate detection flow path 33 is also a flow path that extends in a direction parallel to the fluid flow direction in the main flow path section 2 and has a substantially U-shaped cross section when viewed from above. A flow rate detection unit 11 for detecting the flow rate of the fluid is disposed inside the flow rate detection flow path 33. One end of the flow rate detection flow path 33 communicates with an inlet 34A via an inflow flow path 34, and the other end communicates with an outlet 35A via an outflow flow path 35. The physical property value detection unit 12 and the flow rate detection unit 11 are each mounted on a circuit board 5. The circuit board 5 covers the tops of the physical property detection flow path 32 and the flow rate detection flow path 33, which are open at the top, and is disposed so that the physical property value detection unit 12 is located in the physical property detection flow path 32 and the flow rate detection unit 11 is located in the flow rate detection flow path 33.

[0031] The outflow channel 35 is a channel for causing the fluid to be measured, which has passed through the physical property detection channel 32 and the flow rate detection channel 33, to flow out into the main channel section 2. The outflow 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 outflow channel 35.

[0032] In this embodiment, as described above, the measurement target fluid flowing in through a single inlet 34A is diverted to the physical property detection flow path 32 and the flow rate detection flow path 33. This allows the flow rate detection unit 11 and the physical property detection unit 12 to detect the physical property values ​​and flow rate of the measurement target fluid based on fluids with approximately the same conditions, such as temperature and density. In the flow measurement device 1, after fitting the seal 4 into the sub-flow path unit 3, the circuit board 5 is placed thereon, and the circuit board 5 is further fixed to the sub-flow path unit 3 with the cover 6, thereby ensuring airtightness inside the sub-flow path unit 3.

[0033] Fig. 3 is a plan view of the sub-channel section 3 shown in Fig. 1. As shown in Fig. 3, the physical property detection channel 32 and the flow rate detection channel 33 are disposed symmetrically with respect to a line (not shown) connecting the inflow channel 34 and the outflow channel 35. Arrows P and Q schematically represent the ratio of the flow rates of the fluids 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 diverted fluid is in the ratio P to Q.

[0034] The amount of fluid actually flowing through the physical property detection flow path 32 and the flow rate detection flow path 33 varies depending on the flow rate of the fluid flowing through the main flow path section 2, but in normal use, the size of the sub flow path section 3 relative to the main flow path section 2, the size of the orifice 21, and the widths of the physical property detection flow path 32 and the flow rate detection flow path 33 are set so that the amount of fluid flowing through the physical property detection flow path 32 will be a value within the detection range of the physical property detection section 12, and the amount of fluid flowing through the flow rate detection flow path 33 will be a value within the detection range of the flow rate detection section 11. Note that the widths of the physical property detection flow path 32 and the flow rate detection flow path 33 are merely examples and are not limited to the example shown in FIG.

[0035] In this way, in the flow measurement device 1, it is possible to individually control the flow rates of the fluids branched into the physical property detection flow path 32 and the flow rate detection flow path 33 by adjusting the width of each. Therefore, it is possible to control the flow rate of the fluid flowing through the physical property detection flow path 32 in accordance with the detection range of the physical property detection unit 12, and to control the flow rate of the fluid flowing through the flow rate detection flow path 33 in accordance with the detection range of the flow rate detection unit 11.

[0036] The physical property detection flow path 32 and the flow rate detection flow path 33 are not limited to a configuration formed in a substantially U-shape when viewed from above. The channel 33 may have any other shape as long as it is set to a width (cross-sectional area) that allows the flow rate of the fluid passing through the physical property detection channel 32 and the flow rate detection channel 33 to be controlled.

[0037] Furthermore, although the shapes of the spaces in which the physical property value detection unit 12 and the flow rate detection unit 11 are arranged in the physical property detection flow path 32 and the flow rate detection flow path 33 are approximately square in top view, the present invention is not limited to this. The shapes of the physical property value detection flow path 32 and the flow rate detection flow path 33 may be determined depending on the shapes of the physical property value detection unit 12 and the flow rate detection unit 11 to be arranged, as long as they allow the physical property value detection unit 12 or the flow rate detection unit 11 to be arranged.

[0038] Therefore, for example, when the size of the physical property detection unit 12 is smaller than the width of the physical property detection flow path 32, the width of the space in the physical property detection flow path 32 where the physical property detection unit 12 is disposed may be made to match the width of other parts of the physical property detection flow path 32. That is, in this case, the part extending in the longitudinal direction of the physical property detection flow path 32 has a shape with a substantially constant width. The same applies to the flow rate detection flow path 33.

[0039] As described above, the amount of fluid flowing through the physical property detection flow path 32 and the flow rate detection flow path 33 is smaller than the amount of fluid flowing through the main flow path section 2, but each of them changes depending on the amount of fluid flowing through the main flow path section 2. If the flow rate detection unit 11 and the physical property detection unit 12 were to be disposed in the main flow path section 2, it would be necessary to increase the size of the flow rate detection unit 11 and the physical property detection unit 12 depending on the amount of fluid flowing through the main flow path section 2. However, in this embodiment, by providing a sub-flow path section 3 branching off from the main flow path section 2, it is possible to measure the flow rate of the fluid using the small-scale flow rate detection unit 11 and the physical property detection unit 12.

[0040] In this embodiment, the cross-sectional area of ​​the physical property detection flow path 32 is smaller than the cross-sectional area of ​​the flow rate detection flow path 33, and as indicated by the size of the arrows P and Q in Fig. 3, the amount of fluid flowing through the physical property detection flow path 32 is smaller than the amount of fluid flowing through the flow rate detection flow path 33. In this way, by making the amount of fluid flowing through the physical property detection unit 12 smaller than the amount of fluid flowing through the flow rate detection unit 11, it is possible to reduce errors caused by the influence of the flow rate when the physical property detection unit 12 detects the physical property values ​​and temperature of the fluid.

[0041] FIG. 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. FIG. 5 is a cross-sectional view for explaining the mechanism of the sensor element. The sensor element 100 includes a microheater (also referred to as a heating unit) 101 and two thermopiles (also referred to as temperature detection units) 102 arranged symmetrically across the microheater 101. That is, the microheater 101 and the two thermopiles 102 are arranged side by side in a predetermined direction. As shown in FIG. 5, insulating thin films 103 are formed above and below these, and the microheater 101, thermopile 102, and insulating thin film 103 are provided on a silicon base 104. Furthermore, a cavity 105 formed by etching or the like is provided in the silicon base 104 below the microheater 101 and thermopile 102.

[0042] The microheater 101 is a resistor made of, for example, polysilicon. In FIG. 5, the dashed ellipse schematically shows the temperature distribution when the microheater 101 generates heat. Note that 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 FIG. 5(a). On the other hand, when a fluid flows in the direction indicated by the dashed arrow in FIG. 5(b), the surrounding air moves, causing the temperature downstream of the microheater 101 to be higher than the temperature upstream. The sensor element 100 utilizes this uneven distribution of heater heat to output a value indicating the flow rate.

[0043] The output voltage ΔV of the sensor element is expressed by, for example, the following equation (1).

number

[0044] The circuit board 5 of the flow measurement device 1 also 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 detection unit 11. Also, 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.

[0045] <Flow rate detector and physical property detector> Fig. 6 is a plan view showing a schematic configuration of the flow rate detecting unit 11 shown in Fig. 1, and Fig. 7 is a plan view showing a schematic configuration of the physical property detecting unit 12 shown in Fig. 1. As shown in Fig. 6, the flow rate detecting unit 11 includes a first thermopile (also referred to as a temperature detecting unit) 111 and a second thermopile (also referred to as a temperature detecting unit) 112 that detect the temperature of the fluid to be measured, and a microheater (also referred to as a heating unit) 113 that heats the fluid to be measured. The heating unit 113, the temperature detecting unit 111, and the temperature detecting unit 112 are arranged side by side within the flow rate detecting unit 11 along the arrow P that indicates the flow direction of the fluid to be measured. The heating unit 113, the temperature detecting unit 111, and the temperature detecting unit 112 are each substantially rectangular in plan view, and the longitudinal direction of each is perpendicular to the arrow P that indicates the flow direction of the fluid to be measured.

[0046] Temperature detection unit 111 and temperature detection unit 112 are arranged upstream of heating unit 113 and temperature detection unit 111 is arranged downstream of heating unit 113, and detect temperatures at positions symmetrical with respect to heating unit 113.

[0047] In the flow measurement device 1, the physical property value detection unit 12 and the flow rate detection unit 11 use sensor elements 100 having substantially the same structure, and the sensor elements 100 are arranged at angles relative to the fluid flow direction that differ by 90 degrees in a plan view of the sensor elements 100. This allows sensor elements 100 with the same structure to be used for the physical property value detection unit 12 and the flow rate detection unit 11, thereby reducing the manufacturing cost of the flow measurement device 1.

[0048] 7, the physical property value detecting unit 12 includes a first thermopile (also referred to as a temperature detecting unit) 121 and a second thermopile (also referred to as a temperature detecting unit) 122 that detect the temperature of the fluid to be measured, and a microheater (also referred to as a heating unit) 123 that heats the fluid to be measured. The heating unit 123, the temperature detecting unit 121, and the temperature detecting unit 122 are arranged side by side in a direction perpendicular to the flow direction Q of the fluid to be measured within the physical property value detecting unit 12. The heating unit 123, the temperature detecting unit 121, and the temperature detecting unit 122 each have a substantially rectangular shape in a plan view, and the longitudinal direction of each is aligned with the flow direction Q of the fluid to be measured. The temperature detecting unit 121 and the temperature detecting unit 122 are arranged symmetrically with respect to the heating unit 123, and detect temperatures at symmetrical positions on both sides of the heating unit 123. Therefore, the measured values ​​of the temperature detection unit 121 and the temperature detection unit 122 are almost the same, and the average value may be adopted, or either one of the values ​​may be adopted.

[0049] Here, because the temperature distribution is biased downstream due to the flow of the fluid, the change in temperature distribution in the direction perpendicular to the flow direction is smaller than the change in temperature distribution in the direction of the fluid flow. Therefore, 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, it is possible to reduce changes in the output characteristics of the temperature detection unit 121 and the temperature detection unit 122 due to changes in temperature distribution. Therefore, the effect of changes in temperature distribution due to the flow of the fluid can be reduced, and the detection accuracy of the physical property value detection unit 12 can be improved.

[0050] Furthermore, because 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 in 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 units 121 and 122 can be reduced. Similarly, when measuring fluid temperature, errors in the measurement value caused by flow velocity can be reduced. The fluid temperature may be calculated by subtracting the temperature increase due to heating by the heating unit 123 from the temperatures detected by the temperature detection units 121 and 122, or may be detected without heating by the heating unit 123. The physical property detection unit 12 can reduce the influence of changes in temperature distribution due to the flow of the fluid to be measured, thereby improving the detection accuracy of the physical property values ​​and fluid temperature.

[0051] Furthermore, because the longitudinal direction of the temperature detecting units 121 and 122 is arranged along the flow direction of the fluid to be measured, the temperature detecting units 121 and 122 can detect temperatures over a wide range along 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 detecting units 121 and 122 can be reduced. Therefore, the influence of changes in temperature distribution due to the flow of the fluid to be measured can be reduced, and the detection accuracy of the physical property detecting unit 12 can be improved.

[0052] <Functional configuration> 8 is a block diagram showing an example of the functional configuration of the flow measurement device 1. The flow measurement device 1 includes a flow rate detection unit 11, a physical property value detection unit 12, a control unit 13, and a communication unit 15. 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. Note that the heating unit 113 shown in FIG. 6 and the heating unit 123 shown in FIG. 7 are not shown. The control unit 13 includes a detection value acquisition unit 131, a characteristic value calculation unit 132, a flow rate calculation unit 133, a dust detection unit 135, a correction value determination unit 136, and a dust correction unit 137.

[0053] The flow rate detecting unit 11 outputs a signal corresponding to the temperature detected by the temperature detecting unit 111 and a signal corresponding to the temperature detected by the temperature detecting unit 112 to the detection value acquiring unit 131 of the control unit 13. The physical property detecting unit 12 outputs a signal corresponding to the temperature detected by the temperature detecting unit 121 to the characteristic value calculating unit 132. Note that the physical property detecting unit 12 may calculate an average value of the signals corresponding to the temperatures detected by the temperature detecting units 121 and 122 and output the average value to the characteristic value calculating unit 132. Alternatively, the signal corresponding to the temperature may be acquired using either the temperature detecting unit 121 or the temperature detecting unit 122.

[0054] The detection value acquisition unit 131 acquires the temperature detection values ​​output by the temperature detection units 111 and 112 in the flow rate detection unit 11 at predetermined measurement intervals, and outputs the difference between the temperature detection values ​​of the temperature detection units 121 and 122. The characteristic value calculation unit 132 calculates a characteristic value based on the detection value of at least one of the temperature detection units 121 and 122 of the physical property value detection unit 12. The characteristic value calculation unit 132 calculates the temperature of the microheater of the physical property value detection unit 12. The characteristic value may be calculated by changing the temperature of the fluid to be measured, which is detected by the temperature detection unit 121 or the temperature detection unit 122 before and after the change, and multiplying the difference in temperature by a predetermined coefficient.

[0055] The flow rate calculation unit 133 calculates the flow rate of the fluid based on the difference between the detection values ​​of the temperature detection unit 111 and the temperature detection unit 112 output by the detection value acquisition unit 131. At this time, the flow rate calculation unit 133 may correct the flow rate using the characteristic value calculated by the physical property value detection unit 12. The communication unit 15 transmits information processed by the control unit 13 to the outside wirelessly or via a wired connection, and receives commands and setting values ​​from the outside wirelessly or via a wired connection and transmits them to the control unit 13.

[0056] In the above-described flow measurement device 1, the temperature detection units 111 and 112 of the flow rate detection unit 11 are constantly in contact with the fluid to be measured. Therefore, dust may adhere to the surfaces of the temperature detection units 111 and 112 over time. In such cases, the thermal conductivity between the fluid and the temperature detection units 111 and 112 may change, thereby changing the relationship between the output values ​​of the temperature detection units 111 and 112. In contrast, in this embodiment, the dust detection unit 135 detects the degree of dust adhesion to the temperature detection units 111 and 112. The correction value determination unit 136 determines a correction value for correcting the output value of the flow rate calculation unit 133. The dust correction unit 137 corrects the output value of the flow rate calculation unit 133 using the correction value determined by the correction value determination unit 136. The operations of the dust detection unit 135, the correction value determination unit 136, and the dust correction unit 137 are described in detail below.

[0057] FIG. 9 shows the effect of dust on the relationship between the output value of temperature detection unit 111 and the output value of temperature detection unit 112. In FIG. 9, the horizontal axis of the graph represents the output value Ta of temperature detection unit 111, and the vertical axis represents the output value Tb of temperature detection unit 112. The dashed line in FIG. 9 indicates the relationship between Ta and Tb before the dust test at an ambient temperature of 25°C. The solid line indicates the relationship between Ta and Tb before the dust test at an ambient temperature of 25°C. As described above, dust adhering to temperature detection unit 111 and temperature detection unit 112 changes the relationship between the output of temperature detection unit 111 and the output value of temperature detection unit 112. Note that, for example, if water droplets due to condensation adhere to temperature detection unit 111 and temperature detection unit 112, the thermal conductivity between the fluid and temperature detection unit 111 and temperature detection unit 112 similarly changes, and the relationship between the output values ​​of temperature detection unit 111 and temperature detection unit 112 changes in the same way.

[0058] 10, the relationship between the output value Ta of the temperature detection unit 111 and the output value Tb of the temperature detection unit 112 also changes depending on the ambient temperature. In response to this, the flow rate measurement device 1 in this embodiment has a temperature sensor 16 capable of detecting the ambient temperature, in addition to the temperature detection units 111 and 112. The relationship between the output value Ta of the temperature detection unit 111 and the output value Tb of the temperature detection unit 112 is corrected based on the detection value of the temperature sensor 16. This makes it possible to more accurately detect changes in the relationship between the output value Ta of the temperature detection unit 111 and the output value Tb of the temperature detection unit 112 due to the adhesion of dust.

[0059] In this embodiment, the above-described characteristics are utilized to detect the degree of dust adhesion to temperature detection units 111 and 112. More specifically, a data table is provided that stores combinations of output values ​​Ta of temperature detection unit 111, output values ​​Tb of temperature detection unit 112, ambient temperature, and degree of dust adhesion, and the degree of dust adhesion corresponding to the measured values ​​of output values ​​Ta of temperature detection unit 111, output values ​​Tb of temperature detection unit 112, and ambient temperature is read from the data table, thereby detecting the degree of dust adhesion.

[0060] It is known that there is a certain relationship between the degree of dust adhesion to the temperature detection units 111 and 112 and the correction value for correcting Ta-Tb, which is the difference between the output of the temperature detection units 111 and 112. Therefore, in this embodiment, By storing the relationship between the amount of dust and the correction value in advance as a data table, it becomes possible to correct the change in the output value of the flow rate calculation unit 133 due to the adhesion of dust.

[0061] 11 shows a flowchart of the dust variation correction routine in this embodiment. This flowchart is stored in a storage device (not shown) provided in the control unit 13. When this routine is executed, the degree of dust adhesion is detected in S101. More specifically, as described above, the degree of dust adhesion is detected by reading out the actually obtained output value Ta of the temperature detection unit 111, output value Tb of the temperature detection unit 112, and ambient temperature measurement values ​​from a data table storing combinations of the output value Ta of the temperature detection unit 111, output value Tb of the temperature detection unit 112, ambient temperature, and degree of dust adhesion. When the processing of S101 is completed, the process proceeds to S102.

[0062] In S102, the correction amount is determined from the level of dust adhesion detected in S101. More specifically, as described above, the correction value FV1D is determined by reading the correction value corresponding to the level of dust adhesion detected in S101 from a table that stores the relationship between the level of dust adhesion and the correction value. After the processing of S102 is completed, the process proceeds to S103.

[0063] In S103, the output value of the flow rate calculation unit 133 is corrected by the calculation FV1'=FV1+FV1D. When the process of S103 ends, this routine is temporarily ended.

[0064] As described above, in the flow measurement device 1 according to this embodiment, the degree of dust adhesion can be detected from a pre-stored data table and the output values ​​of the temperature detection units 111 and 112. It is also possible to calculate a flow rate corrected for the influence of dust adhesion, thereby improving the accuracy of the flow measurement device 1. Note that, in this embodiment, an example has been described in which, after detecting the degree of dust adhesion, a correction value is determined and the calculated flow rate of the fluid to be measured is corrected, but the present invention does not necessarily assume correction. After detecting the degree of dust adhesion, it is possible to simply output the detection result (i.e., a signal corresponding to the degree of dust adhesion), or to perform a predetermined warning process.

[0065] Example 2 Next, as Example 2, a gas meter and a flow measurement device unit in which the flow measurement device according to Example 1 is incorporated will be described. This example is an example in which the flow measurement device 1 according to Example 1 is incorporated into a gas meter for measuring gas usage. FIG. 16 is a block diagram showing an example of the functional configuration of a gas meter 150 in which the flow measurement device 1 is incorporated. In addition to the flow measurement 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 cutoff 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, except for the operation unit 153, these components are housed in a housing 150b.

[0066] Here, the display unit 151 is a display that displays the amount of gas used based on the flow rate measured and output by the flow measurement device 1, as well as the date, whether or not a shutoff process has been performed (described later), and the like, and may be a liquid crystal display panel or the like. The power supply unit 152 is a part that supplies power to the flow measurement device 1 and other components of the gas meter 150, and may be composed of a battery such as an alkaline battery. The operation unit 153 is provided outside the gas meter 150, and is a part that is operated by a gas contractor or a meter reader, etc. For example, it may be possible to perform operations such as resetting the gas meter 150, adjusting the time, switching the items to be displayed and output, and canceling the shutoff state (described later).

[0067] The vibration detection unit 154 includes, for example, an acceleration sensor (not shown) and detects vibrations of the gas meter 150 itself. The cutoff unit 155 has an actuator such as a solenoid and a valve that closes the main flow path unit 2, and when the vibration detection unit 154 detects vibrations equal to or greater than a threshold, The gas meter control unit 156 determines that an earthquake has occurred and shuts off the gas passing through the main flow path unit 2. The gas meter control unit 156 is electrically connected to the flow measurement device 1, the display unit 151, the power supply unit 152, the operation unit 153, the vibration detection unit 154, the shutoff unit 155, the gas meter storage unit 157, and the gas meter communication unit 158, and controls each unit. For example, it receives input information from the operation unit 153 and transmits commands according to the input information to each unit. Furthermore, if the vibration detection unit 154 detects an acceleration signal equal to or greater than a threshold, it transmits a shutoff signal to the shutoff unit 155. The gas meter storage unit 157 is a unit that stores outputs from the flow measurement device 1 and the vibration detection unit 154 in chronological order for a predetermined period of time, and may be composed of a memory element such as an SRAM or a 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 a wired connection, and receives commands and setting values ​​from the outside and transmits them to the gas meter control unit 156. In addition, by communicating with the communication unit 15 of the flow measurement device 1, information to be processed by the control unit 13 of the flow measurement device 1 may be received, and control signals and setting values ​​for the flow measurement device 1 may also be transmitted.

[0068] Of the components of the gas meter 150, for example, the flow measurement device 1, the display unit 151, the power supply unit 152, the vibration detection unit 154, the gas meter control unit 156, the gas meter storage unit 157, and the gas meter communication unit 158 ​​may be unitized, and the operation unit 153 and the cutoff unit 155 may be electrically connected to this flow measurement device unit 150a and incorporated into the housing 150b, thereby making it possible to configure the gas meter 150. In this way, the gas meter 150 can be manufactured more efficiently.

[0069] In the present embodiment, the configurations of the gas meter 150 and the flow measurement device unit 150a are merely examples and may be modified depending on the function of the gas meter 150 and manufacturing conditions. Furthermore, the flow measurement device according to the present invention is not limited to the configurations shown in the above embodiments. For example, the flow measurement device 1 in the above embodiments is assumed to include a physical property value detection unit 12 and to correct the output value of the flow rate calculation unit 133 based on the physical property value of the fluid. However, the present invention may be applied to a flow measurement device that does not include this physical property value detection unit 12. Furthermore, the flow measurement device 1 in the above embodiments is a multi-passage type having sub-passages. However, the present invention may also be applied to a single-passage type flow measurement device that directly measures the flow rate of the fluid flowing through the main pass. The configurations of the above embodiments may be combined as much as possible without departing from the objectives and technical spirit of the present invention. Furthermore, in the above embodiments, the present invention has been described in terms of detecting the degree of dust adhesion, but the present invention may also be applied to detecting the degree of water droplet adhesion due to condensation.

[0070] In the following, the constituent elements of the present invention will be described with reference to the reference numerals in the drawings in order to make it possible to compare the constituent elements of the present invention with the configurations of the embodiments. <Invention 1> A flow rate measuring device (1) for detecting a flow rate of a fluid to be measured flowing through a main flow path (2), a heating unit (113) for heating the fluid to be measured; a plurality of temperature detection units (111, 112) disposed on either side of the heating unit in the flow direction of the fluid to be measured, and configured to detect the temperature of the fluid to be measured; a flow rate calculation unit (133) that calculates the flow rate of the fluid to be measured from the output values ​​of the plurality of temperature detection units; a detection unit (135) that detects the degree of adhesion of dust or water droplets to the temperature detection unit based on the relationship between the outputs of the plurality of temperature detection units; A flow rate measuring device comprising: [Explanation of symbols]

[0071] 1:Flow rate measuring device 11: Flow rate detection unit 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 section 131: Detection value acquisition unit 132: characteristic value calculation unit 133:Flow rate calculation section 135: Dust detection unit 136: Correction value determination unit 137: Dust correction section 15: Communications Department 150: Gas meter 150a: Flow measuring device unit

Claims

[Claim 1] A flow rate measuring device for detecting a flow rate of a measurement target fluid flowing through a main flow path, a heating unit that heats the fluid to be measured; a plurality of temperature detecting units disposed on either side of the heating unit in the flow direction of the fluid to be measured, and configured to detect the temperature of the fluid to be measured; a flow rate calculation unit that calculates a flow rate of the fluid to be measured from output values ​​of the plurality of temperature detection units; a detection unit that detects the degree of adhesion of dust or water droplets to the temperature detection unit based on a change in the relationship between the outputs of the plurality of temperature detection units; Equipped with a temperature sensor for measuring an ambient temperature of the flow rate measuring device; A flow measuring device characterized in that the detection unit detects the degree of adhesion of dust or water droplets to the temperature detection unit based on changes in the relationship between the outputs of each of the multiple temperature detection units and the ambient temperature measured by the temperature sensor.

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