Flow measurement device

Abstract

The present invention provides a flow measurement device that suppresses output changes of a sensor element caused by the influence of impurities flowing in a flow path. The flow measurement device of the present invention comprises: a flow detection unit configured in the flow path to output a value related to the temperature difference in the flow direction of the fluid that changes according to the flow rate of the fluid flowing in the flow path, and to detect the flow rate using the output value; and a covering member that covers the flow detection unit in the flow path. The covering member comprises: an inflow hole that is arranged on the upstream side of the portion where the flow detection unit is arranged, allowing the fluid to flow from the flow path outside the covering member to the portion inside the covering member where the flow detection unit is arranged; an outflow hole that is arranged on the downstream side of the flow detection unit, allowing the fluid to flow out from the portion inside the covering member where the flow detection unit is arranged to the flow path outside the covering member, and the outer side surface of the covering member on the upstream side of the portion where the flow detection unit is arranged has an inclined surface that is inclined toward the inlet direction of the inflow hole.

Description

Technical Field

[0001] The invention relates to a flow measuring device. Background Art

[0002] A technology for measuring the flow rate of a fluid flowing in a flow path using a flow sensor is disclosed (e.g., Patent Documents 1 to 3). Patent Document 1 discloses the use of a thermopile provided in a thermal flow sensor to detect temperature distribution information of a flow path, and calculates the flow rate of the fluid based on the temperature distribution information. Patent Document 2 discloses the provision of a flow sensor and a rectifier on a flow path in an electronic gas flow meter. Patent Document 3 discloses a thermal flow sensor, which includes a substrate including a first substrate and a second substrate, and an upper flow path forming component provided on the substrate. In addition, a rectangular recess is provided on the bottom of the upper flow path forming component, and the recess forms a second flow path between the recess and the top of the second substrate. In addition, an inlet and an outlet leading to the outside are provided in the recess.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 3658321

[0006] Patent Document 2: Japanese Patent Application Publication No. 2007-086085

[0007] Patent Document 3: Japanese Patent Application Publication No. 2012-141181

[0008] When a thermal flow sensor is used to measure the flow rate of a fluid flowing in a flow path, the flow sensor is configured in such a way that a sensor element for detecting the temperature distribution of the flow path is exposed in the flow path. However, if the sensor element is configured in this way, the output of the sensor element for detecting the temperature distribution may change due to the influence of impurities such as dust or dirt mixed in the fluid flowing in the flow path. That is, the inventors of the present invention have found that the accuracy of flow measurement decreases when the flow sensor is configured as described above. Summary of the invention

[0009] The present invention has been made in view of such actual circumstances, and an object of the present invention is to provide a technology for suppressing output fluctuations of a sensor element caused by the influence of impurities flowing in a flow path.

[0010] In order to solve the above-mentioned problems, the present invention adopts the following structure.

[0011] That is, a flow measurement device according to one aspect of the present invention comprises: a flow detection unit, which is arranged in a flow path, outputs a value related to a temperature difference in a flow direction of the fluid that changes according to the flow rate of the fluid flowing in the flow path, and detects the flow rate using the output value; a covering member, which covers the flow detection unit in the flow path, the covering member having: an inflow hole, which is arranged on the upstream side of a portion where the flow detection unit is arranged, and enables fluid to flow from the flow path outside the covering member to the portion inside the covering member where the flow detection unit is arranged; an outflow hole, which is arranged on the downstream side of the flow detection unit, and enables fluid to flow out from the portion inside the covering member where the flow detection unit is arranged to the flow path outside the covering member, and the outer side surface of the covering member on the upstream side of the portion where the flow detection unit is arranged has an inclined surface inclined toward the inlet direction of the inflow hole.

[0012] When impurities reach the place where the flow detection unit is configured, it can be considered that the information related to the temperature difference in the flow direction of the fluid output by the flow detection unit changes. However, according to this structure, by having a covering member, it is possible to suppress the impurities flowing in the flow path from reaching the flow detection unit. Therefore, the change in the output from the flow detection unit is suppressed. Therefore, the decrease in the detection accuracy of the flow rate is suppressed. In addition, when a flow path is provided inside the covering member, the flow of the fluid near the place where the flow detection unit is configured is rectified. In other words, the sensitivity of the flow measurement device is improved.

[0013] In addition, according to this structure, since the fluid flows in the flow path along the inclined surface on the outside of the covering member, it is smoothly guided to the entrance of the inflow hole. Therefore, the generation of turbulence in the flow path is suppressed. Therefore, since the impurities are suppressed from spreading in the flow path, the impurities are suppressed from reaching the portion where the flow detection unit is configured. Therefore, the change in the output from the flow detection unit is suppressed. In addition, the accumulation of impurities on the inclined surface is suppressed. Therefore, the accumulated impurities are suppressed from spreading due to the turbulence generated in the flow path and reaching the flow detection unit. Therefore, the change in the output from the flow detection unit is suppressed. Therefore, the decrease in the accuracy of flow detection is suppressed.

[0014] In the flow measurement device of the above-mentioned aspect, it can also be that there is also a rectifying component, which rectifyes the flow direction of the fluid flowing in from the inlet toward the direction of the part where the flow detection part is configured, and the rectifying component is arranged at the outlet of the inlet and has a plane along the direction from the outlet of the inlet toward the part where the flow detection part is configured.

[0015] According to this configuration, the fluid flowing into the covering member from the inflow hole is rectified along the plane of the rectifying member toward the portion where the flow rate detection unit is arranged. Therefore, when the flow rate is low, the sensitivity of the flow rate detection unit is more reliably improved.

[0016] In the flow measurement device according to the first aspect, two inflow holes may be provided in a direction perpendicular to the fluid flow direction, and the rectifying member may be provided between respective outlets of the two inflow holes.

[0017] According to this structure, at the outlet of the inflow hole, the cross-sectional area of ​​the space inside the covering component is suppressed from changing sharply in the direction orthogonal to the fluid flow direction. Therefore, the generation of turbulence near the outlet of the inflow hole is suppressed. Therefore, since the impurities are suppressed from being dispersed in the flow path, the impurities are suppressed from being mixed into the fluid and reaching the part where the flow detection part is arranged. Therefore, the change of the output from the flow detection part is suppressed. Therefore, the decrease of the flow detection accuracy is suppressed.

[0018] In the flow measuring device of the above-mentioned aspect, the flow path may also have a recessed portion on the side wall, and the side surface on the upstream side of the recessed portion may have an inclined surface inclined toward the bottom surface of the recessed portion, the covering component may have a portion of the flow path arranged opposite to the bottom surface of the recessed portion of the flow path, and a convex portion protruding from the arranged portion toward the bottom surface, and the inflow hole may include a hole passing through the convex portion.

[0019] According to this structure, since the fluid flows in the flow path along the inclined surface of the recess, it can smoothly pass through the recess. That is, the fluid is smoothly guided to the entrance of the inflow hole. Therefore, the generation of turbulence in the flow path is suppressed. Therefore, since the impurities are suppressed from spreading in the flow path, the impurities are suppressed from reaching the portion where the flow detection unit is configured. Therefore, the change in the output from the flow detection unit is suppressed. In addition, since the side surface of the recess has an inclined surface, the accumulation of impurities on the side surface is suppressed. Therefore, the situation where the accumulated impurities are dispersed due to the turbulence generated in the flow path and reach the flow detection unit is suppressed. Therefore, the change in the output from the flow detection unit is suppressed. Therefore, the decrease in the accuracy of flow detection is suppressed.

[0020] In the flow measurement device according to the above aspect, the flow path may be a sub-flow path branched from a main flow path in which the fluid flows, and the flow path may be arranged in the sub-flow path.

[0021] According to this structure, the fluid flowing through the main flow path passes through the secondary flow path and then reaches the portion where the flow detection unit is arranged through the inflow hole provided on the covering member. In other words, since the fluid flowing through the main flow path does not directly flow into the inside of the covering member, impurities mixed in the fluid are suppressed from reaching the portion where the flow detection unit is arranged. Therefore, the change of the output from the flow detection unit is suppressed.

[0022] In the flow measurement device of the above-mentioned aspect, it is also possible to further include a characteristic detection unit, which is arranged in a second flow path different from the flow path, outputs a value related to the temperature of the second flow path that changes according to the characteristics of the fluid flowing in the second flow path, and uses the output value to detect the characteristic, and the covering component also has a second hole that surrounds the characteristic detection unit and makes the characteristic detection unit exposed in the second flow path.

[0023] According to this structure, in addition to the flow rate of the fluid, the characteristics of the fluid can also be detected. Therefore, even when the temperature difference in the flow direction of the fluid depends on the characteristics of the fluid, the detected characteristics of the fluid can be used to correct the detected flow rate of the fluid. Therefore, high-precision flow measurement can be performed. In addition, according to this structure, in the case where the flow detection part and the characteristic detection part are installed on the same substrate, by providing this one covering part on the substrate, it is possible to simply suppress the situation where impurities are mixed from the side of the substrate to the flow detection part and the characteristic detection part. In addition, according to this structure, since the characteristic detection part and the covering part do not overlap in the height direction, the part where the characteristic detection part is configured can be made thinner.

[0024] According to the present invention, it is possible to provide a technique for suppressing output fluctuations of a sensor element due to the influence of impurities flowing in a flow path. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an overview of the flow measurement device. Figure 1 (A) shows an example of a cross-sectional view of a flow measurement device according to an embodiment, Figure 1 (B) shows an example of a cross-sectional view of a flow measurement device of a comparative example.

[0026] Figure 2 It schematically illustrates the flow measurement principle based on the detection element. Figure 2 (A) is a diagram illustrating the configuration direction of the detection element. Figure 2 (B) schematically illustrates the temperature distribution generated when the microheater is started without gas flowing. Figure 2 (C) schematically illustrates the temperature distribution generated when the microheater is started under the state of gas flowing.

[0027] Figure 3 2 is a simulation result showing the amount of dust that reaches the vicinity of the thermopile.

[0028] Figure 4 is an output illustrating the difference between the outputs of the two thermopiles relative to the actual flow rate of the gas;

[0029] Figure 5It is an exploded perspective view illustrating a measurement device according to a modified example.

[0030] Figure 6 It is a diagram for explaining the arrangement direction of the characteristic detection element.

[0031] Figure 7 exemplifies a flow tube with a cover installed and a cover installed on the flow tube. Figure 7 (A) shows a top perspective view of a flow tube with a cover installed. Figure 7 (B) indicates that the cover is installed on Figure 7 (A) is a top view of the flow tube shown.

[0032] Figure 8 This is an example of the outline of the cover. Figure 8 (A) is a perspective view illustrating a cross section of a cover mounted on a flow tube, Figure 8 (B) is viewed from the front Figure 8 (A) is a cross-sectional view of the .

[0033] Description of reference numerals:

[0034] 1: Detection element

[0035] 1A: Flow detection element

[0036] 1B: Characteristic detection element

[0037] 2.2A: Flow tube

[0038] 3. 3A: Mainstream Road

[0039] 4, 4A, 4B: Auxiliary flow path

[0040] 5. 5A: Substrate

[0041] 6.6A: Mounting surface

[0042] 7, 7A: Cover

[0043] 8: Space

[0044] 9, 9A: Lower surface

[0045] 10, 10A: Left side

[0046] 11, 11A: Right side

[0047] 12, 12A: concave part

[0048] 13, 13A: Left side

[0049] 14, 14A: Right side

[0050] 16: Inflow hole

[0051] 17: Inflow hole

[0052] 18: Outflow hole

[0053] 19: Outflow hole

[0054] 20: concave part

[0055] 21: Concave

[0056] 22: Inflow hole

[0057] 23: Outflow hole

[0058] 24: Hole

[0059] 25, 26: Rectification wall

[0060] 27: Inflow hole

[0061] 28: Outflow hole

[0062] 29: Slot

[0063] 40, 40A, 40B: Micro heater

[0064] 41A, 41B, 41C, 41D, 41E, 43F: Thermopile

[0065] 42: Film

[0066] 43: Cavity

[0067] 100: Flow measurement device

[0068] 100A: Measuring device

[0069] 200: Flow measurement device DETAILED DESCRIPTION

[0070] Hereinafter, an embodiment of one aspect of the present invention (hereinafter also referred to as "the present embodiment") is described with reference to the accompanying drawings. However, the present embodiment described below is merely an example of the present invention in all aspects. Of course, various improvements and modifications may be made without departing from the scope of the present invention. That is, in the implementation of the present invention, a specific structure corresponding to the embodiment may also be appropriately adopted.

[0071] 1 Application example

[0072] use Figure 1 (A) is used to illustrate an example of a scenario to which the present invention is applicable. Figure 1(A) shows an example of a cross-sectional view of the flow measurement device 100 of the present embodiment. The flow measurement device 100 of the present embodiment includes a detection element 1 and a substrate 5 on which the detection element 1 is mounted. The detection element 1 has a microheater 40 and two thermopiles 41A and 41B, and detects a temperature difference in the flow direction of the gas associated with the gas flow rate (described in detail later). In addition, the detection element 1 is arranged in the middle of the secondary flow path 4 partially provided on the main flow path 3 of the flow tube 2.

[0073] In addition, the flow measurement device 100 includes a cover 7 that covers the detection element 1. A space 8 that can accommodate the detection element 1 is formed inside the cover 7. In addition, the lower surface 9 of the cover 7 is provided with an inflow hole 27 through which gas can flow from the secondary flow path 4 into the space 8, and an outflow hole 28 through which gas can flow from the space 8 into the secondary flow path 4.

[0074] According to the flow measurement device 100 as described above, by providing the cover 7, it is possible to prevent dust or dirt flowing through the main flow path 3 or the secondary flow path 4 from reaching the position where the detection element 1 is arranged. Therefore, the output of the thermopile 41A and the output of the thermopile 41B provided in the detection element 1 are prevented from being changed by dust or dirt.

[0075] 2. Example of configuration

[0076] [Hardware Configuration]

[0077] Figure 1 This section shows an overview of flow rate measurement equipment. Figure 1 (A) shows an example of a cross-sectional view of the flow measurement device 100 according to this embodiment. Figure 1 (B) shows an example of a cross-sectional view of a flow measurement device 200 of a comparative example. The flow measurement device 100 of the present embodiment includes a detection element 1 and a substrate 5 on which the detection element 1 is mounted. The detection element 1 has a microheater 40 and two thermopiles 41A and 41B, and detects a temperature difference in the flow direction of the gas associated with the gas flow rate (described in detail later). The substrate 5 is disposed on a side wall of the main flow path 3 forming the flow tube 2 so that the mounting surface 6 on which the detection element 1 is mounted faces the center of the flow tube 2. In addition, near the side wall, a secondary flow path 4 is partially disposed by branching off from the main flow path 3 of the flow tube 2. Then, the detection element 1 is arranged in the middle of the secondary flow path 4. Here, the flow measurement device 100 is an example of a "flow measurement device" of the present invention. In addition, the detection element 1 is an example of a "flow detection unit" of the present invention. In addition, the secondary flow path 4 is an example of a "flow path" and a "secondary flow path" of the present invention.

[0078] Here, in Figure 1 (A) and Figure 1In (B), the gas flows from the left side to the right side in the main flow path 3 and the secondary flow path 4 of the flow tube 2. In addition, in the following description, the left direction refers to the upstream direction. In addition, the right direction refers to the downstream direction. In addition, the downward direction refers to the direction in which the detection element 1 protrudes relative to the substrate 5. In addition, the upward direction refers to the direction opposite to the downward direction.

[0079] In addition, the flow measurement device 100 includes a cover 7. The cross section of the cover 7 is as follows: Figure 1 (A) shows a shape that is convex downward. In addition, the left side surface 10 of the cover 7 exposed in the auxiliary flow path 4 has an inclined surface inclined in the lower right direction. In addition, the right side surface 11 of the cover 7 exposed in the auxiliary flow path 4 has an inclined surface inclined in the lower left direction. In addition, a space 8 capable of accommodating the detection element 1 is formed inside the cover 7. The detection element 1 mounted on the mounting surface 6 is arranged in the space 8 covered by such a cover 7. In addition, the cover 7 is provided with an inflow hole 27 through which gas can flow from the auxiliary flow path 4 into the space 8. The inflow hole 27 is provided in a manner that penetrates a portion of the left side surface 10 and a portion of the lower surface 9. In addition, the cover 7 is provided with an outflow hole 28 that allows gas to flow out from the space 8 to the auxiliary flow path 4. The outflow hole 28 is provided in a manner that penetrates a portion of the right side surface 11 and a portion of the lower surface 9. Here, the cover 7 is an example of a "covering member" of the present invention. In addition, the inflow hole 27 provided in the cover 7 is an example of an "inflow hole" and a "hole penetrating a convex portion" of the present invention. In addition, the outflow hole 28 provided in the cover 7 is an example of the "outflow hole" of the present invention.

[0080] In addition, the lower portion of the secondary flow path 4 opposite to the lower surface 9 of the cover 7 has a recessed portion 12 that is recessed downward. And, on the left side of the recessed portion 12, the portion opposite to the left side surface 10 of the cover 7 has a left side surface 13. The left side surface 13 has an inclined surface with the same inclination angle as the inclined surface provided on the left side surface 10 of the cover 7. Similarly, on the right side of the recessed portion 12, the portion opposite to the right side 11 of the cover 7 has a right side surface 14. The right side surface 14 has an inclined surface with the same inclination angle as the inclined surface provided on the right side surface 11 of the cover 7.

[0081] on the other hand, Figure 1 The flow measurement device 200 of the comparative example shown in (B) includes the detection element 1 and the substrate 5 similarly to the flow measurement device 100 of the present embodiment. The detection element 1 is disposed in the middle of the secondary flow path 4. However, the flow measurement device 200 does not include the cover 7.

[0082] [Flow measurement principle]

[0083] Here, the principle of flow rate measurement using detection element 1 will be described. Figure 2 The flow measurement principle of the detection element 1 is schematically illustrated. Figure 2 (A) shows a top view of the detection element 1 . Figure 2(B) is a cross-sectional view of the detection element 1 mounted on the substrate 5, and is a diagram showing the temperature distribution generated when the microheater 40 is started without gas flow. On the other hand, Figure 2 (C) is a cross-sectional view of the detection element 1 mounted on the substrate 5, and is a diagram showing the temperature distribution generated when the micro heater 40 is started in a gas flow state. Figure 2 As shown in (A), the thermopiles 41A and 41B are arranged to span the microheater 40 in the direction of gas flow. Figure 2 As shown in (B), the detection element 1 includes a thin film 42 formed on a substrate 5, and the microheater 40 and the thermopiles 41A and 41B are formed in a manner contained in the thin film 42. A cavity 43 is provided on the substrate 5 below the thin film 42. Due to the presence of this cavity 43, the warm junction of the microheater 40 and the thermopiles 41A and 41B is located on the cavity 43, and the cold junction of the thermopiles 41A and 41B is located on the substrate 5. And, an output corresponding to the difference between the temperature at the warm junction and the temperature at the cold junction is performed from each thermopiles 41A and 41B.

[0084] like Figure 2 As shown in (B), when there is no gas flow in the space 8, the heat from the microheater 40 diffuses symmetrically around the microheater 40. Therefore, there is no difference between the output of the thermopile 41A and the output of the thermopile 41B. Figure 2 As shown in (C), when the gas flows in the space 8, the heat from the microheater 40 is affected by the gas flow, and does not expand symmetrically with the microheater 40 as the center, and further diffuses to the downstream thermopile 41B side. Therefore, the output of the thermopile 41A is different from the output of the thermopile 41B. In addition, the difference in the output changes according to the flow rate of the gas. In other words, the flow rate of the gas is obtained based on the difference between the output of the thermopile 41A and the output of the thermopile 41B.

[0085] Incidentally, the difference ΔV between the voltage output from the thermopile 41A and the voltage output from the thermopile 41B is expressed, for example, as in the following formula (1).

[0086]

[0087] Here, T h represents the temperature of the micro heater 40, T a represents the temperature around the detection element 1. In addition, V f is the flow rate of the gas, A and b are constants.

[0088] Next, the process from when the gas flowing in the main flow path 3 reaches the position where the detection element 1 is arranged is described. The gas flowing in the main flow path 3 flows into the left part of the secondary flow path 4. Thereafter, the gas flows into the space 8 inside the cover 7 through the inflow hole 27 provided on the cover 7. Here, since an inclined surface inclined toward the lower right direction is provided on the left side surface 10 of the cover 7, the gas is smoothly guided to the entrance of the inflow hole 27. Then, the gas flowing into the space 8 inside the cover 7 from the inflow hole 27 passes through the portion where the detection element 1 is arranged. Then, the gas flows out from the space 8 to the secondary flow path 4 through the outflow hole 28. Here, since the outflow hole 28 is provided on a portion of the right side surface 11 having an inclined surface, the gas flowing out to the secondary flow path 4 through the outflow hole 28 is smoothly guided along the inclined surface to the outflow hole connected to the main flow path 3. Then, the gas flows out from the outflow hole to the main flow path 3.

[0089] Figure 3 The simulation result of the number of dust particles reaching the vicinity of the thermopiles 41A and 41B in the cover 7 from the main flow path 3 is shown. Figure 3 As shown, when the cover 7 is provided ( Figure 1 The number of dust particles reaching the vicinity of the thermopiles 41A and 41B in the cover 7 is the same as that in the case where the cover 7 is not provided ( Figure 1 Compared with the comparison example (B), the number of dust particles is reduced to about 1 / 6.

[0090] Figure 4 The output of the difference between the output of the thermopile 41A and the output of the thermopile 41B with respect to the actual flow rate of the gas is illustrated. Figure 4 As shown, compared with the case where the cover 7 is not provided ( Figure 1 Compared with the comparative example (B), when the cover 7 is provided ( Figure 1 In the present embodiment (A), the difference between the output of the thermopile 41A and the output of the thermopile 41B is linearly related to the flow rate in the low flow rate region. In addition, when the cover 7 is provided, the sensitivity of the detection element 1 is improved at low flow rates compared to when the cover 7 is not provided.

[0091] [Function and Effect]

[0092] According to the flow measurement device 100 as described above, Figure 3 As shown in FIG. 1 , by providing the cover 7, it is possible to prevent dust or dirt flowing through the main flow path 3 or the secondary flow path 4 from reaching the position where the detection element 1 is arranged. Therefore, the output of the thermopile 41A and the output of the thermopile 41B provided in the detection element 1 are prevented from changing. Therefore, the decrease in the detection accuracy of the flow rate is prevented. On the other hand, according to the flow measurement device 200 of the comparative example, as shown in FIG. Figure 1 As shown in (B), the cover 7 is not provided. Figure 3As shown, dust or dirt easily reaches the place where the detection element 1 is arranged compared with the flow measurement device 100 of this embodiment. Therefore, it is considered that the output of the thermopile provided in the flow measurement device 200 changes. That is, according to the flow measurement device 200 of the comparative example, it is considered that the detection accuracy of the flow rate is reduced.

[0093] In addition, according to the flow measurement device 100 as described above, since the left side surface 10 of the cover 7 and the left side surface 13 of the recess 12 of the secondary flow path 4 have an inclined surface, it is possible to suppress the accumulation of dust or dirt on the inclined surface. In addition, the gas of the secondary flow path 4 is smoothly guided to the entrance of the inflow hole 27 of the cover 7 along the left side surface 10 of the cover 7 having the inclined surface. Therefore, the generation of turbulence in the secondary flow path 4 is suppressed. That is, the accumulation of dust or dirt on the secondary flow path 4 is suppressed, and even if dust or dirt accumulates, the dispersion caused by turbulence is suppressed. Therefore, the situation where dust or dirt reaches the detection element 1 is suppressed.

[0094] 3 Modifications

[0095] The embodiments of the present invention are described in detail above, but the above description is only an example of the present invention in any aspect. Of course, various improvements and modifications can be made without departing from the scope of the present invention. For example, the following changes can be made. In addition, the following uses the same symbols for the same components as the above embodiment, and the description is appropriately omitted for the same points as the above embodiment. The following modifications can be appropriately combined. (3.1)

[0097] Figure 5 An exploded perspective view of a measuring device 100A in a modified example is illustrated. The measuring device 100A in the modified example is configured in the same manner as the detection element 1 in the above-mentioned embodiment, and is provided with a flow detection element 1A that detects the flow rate of a gas. In addition, the measuring device 100A is also provided with an element of the same type as the detection element 1 in the above-mentioned embodiment, but is a characteristic detection element 1B for detecting the characteristics of a gas. The flow detection element 1A includes a microheater 40A and thermopiles 41C and 41D. The characteristic detection element 1B includes a microheater 40B and thermopiles 41E and 41F (in Figure 6). And, these flow detection elements 1A and characteristic detection elements 1B are mounted on the mounting surface 6A of the substrate 5A. In addition, the measuring device 100A includes a cover 7A, which covers each detection element of the flow detection element 1A and the characteristic detection element 1B. The flow detection element 1A and the characteristic detection element 1B covered by the cover 7A are arranged on a secondary flow path (described later) formed on the upper surface of the flow tube 2A. Here, the measuring device 100A is an example of a "flow measurement device" of the present invention. In addition, the flow detection element 1A is an example of a "flow detection unit" of the present invention. In addition, the characteristic detection element 1B is an example of a "characteristic detection unit" of the present invention. In addition, the cover 7A is an example of a "covering component" of the present invention.

[0098] Figure 6 1B is a diagram illustrating the arrangement direction of the characteristic detection element 1B. Figure 6 As shown, the thermopile 41E and the thermopile 41F of the characteristic detection element 1B are arranged in a manner spanning the microheater 40A, but the arrangement direction is a direction orthogonal to the gas flow direction. When the microheater 40B of the characteristic detection element 1B configured in this way is started, the heat from the microheater 40B is symmetrically diffused in the direction in which the thermopile 41E and the thermopile 41F are arranged with the microheater 40B as the center. The degree of heat diffusion depends on the characteristics of the gas. In other words, the characteristics of the gas can be calculated using the output value from the thermopile 41E or the thermopile 41F. Here, the characteristics of the gas are, for example, thermal conductivity and thermal diffusivity. In addition, the calculation of the gas characteristics can be performed by using the output from any one of the thermopile 41E and the thermopile 41F, or by using the average value of the output of the thermopile 41E and the output of the thermopile 41F.

[0099] Figure 7 and Figure 8 The schematic diagram of the flow tube 2A to which the cover 7A is attached and the schematic diagram of the cover 7A included in the measuring device 100A are illustrated. Figure 7 (A) shows a top perspective view of the flow tube 2A with the cover 7A installed. Figure 7 (B) indicates that the cover 7A is installed on Figure 7 A top view of the flow tube 2A shown in (A). Figure 8 (A) is a perspective view of a cross section of the flow tube 2A and the cover 7A mounted on the flow tube 2A. Figure 8 (B) is a diagram showing the cross section near the cover 7A, particularly as viewed from the front. Figure 7 (B) and Figure 8 The cover 7A shown is mounted on the Figure 7The upper portion of the cover 7A is open, and the opening is covered by the mounting surface 6A of the substrate 5A on which the flow detection element 1A and the characteristic detection element 1B are mounted.

[0100] like Figure 7 As shown in (A), the flow tube 2A is provided with secondary flow paths 4A and 4B branching from the main flow path of the flow tube 2A. The secondary flow path 4A is provided with an inflow hole 16 capable of flowing gas from the main flow path. In addition, the secondary flow path 4A is provided with a recess 12A, and the recess 12A is provided with a flow detection element 1A in a state covered by a cover 7A. In addition, a groove 29 is provided at the bottom of the recess 12A. In addition, the secondary flow path 4A is provided with an outflow hole 18 capable of flowing gas out to the main flow path. Here, the secondary flow path 4A is an example of the "flow path" and the "secondary flow path" of the present invention. In addition, the secondary flow path 4B is an example of the "second flow path" and the "secondary flow path" of the present invention.

[0101] On the other hand, the secondary flow path 4B is provided with an inflow hole 17 through which gas can flow in from the main flow path 3A. Then, a recess 20 is provided in the central portion of the secondary flow path 4B, and the characteristic detection element 1B covered by the cover 7A is arranged in the recess 20. In addition, the secondary flow path 4B is provided with an outflow hole 19 through which gas can flow out to the main flow path 3A.

[0102] In addition, if Figure 7 (B) and Figure 8 As shown in (A), the cover 7A is provided with a recessed portion 21 in which the flow detection element 1A is disposed. In addition, the outer shape of the cover 7A corresponding to the recessed portion 21 is a downwardly convex shape, and the outer side surfaces on the upstream side and the downstream side of the convex portion have inclined surfaces (described in detail later). Then, the recessed portion 21 for accommodating the flow detection element 1A is disposed in Figure 7 The inside of the recess 12A shown in (A) of FIG. 1 is shown. That is, the flow detection element 1A is not exposed in the secondary flow path 4A. In addition, the cover 7A is provided with a hole 24 in which the characteristic detection element 1B is arranged. Then, the characteristic detection element 1B arranged in the hole 24 is arranged in Figure 7 That is, the bottom surface of the characteristic detection element 1B is exposed in the auxiliary flow path 4B.

[0103] In addition, if Figure 7As shown in (B), two inflow holes 22 capable of flowing gas from the secondary flow path 4A are provided in the recess 21 of the cover 7A. In addition, two outflow holes 23 capable of flowing gas from the recess 21 to the secondary flow path 4A are provided in the recess 21. The inflow hole 22 and the outflow hole 23 are arranged so that the inflow hole 22 becomes the upstream side of the secondary flow path 4A, and the outflow hole 23 becomes the downstream side of the secondary flow path 4A. In addition, the two inflow holes 22 and the two outflow holes 23 are symmetrically arranged in the recess 21 with respect to the central axis along the gas flow direction. And, between the respective outlets of the two inflow holes 22, a rectifying wall 25 protruding from the inflow hole 22 to the direction of the outflow hole 23 is provided. Similarly, between the respective entrances of the two outflow holes 23, a rectifying wall 26 protruding from the outflow hole 23 to the direction of the inflow hole 22 is provided. And, the surface of the rectifying wall 25 has a planar portion along the direction from the inflow hole 22 toward the portion where the detection element 1A is arranged. Similarly, the surface of the rectifying wall 26 has a planar portion along the direction from the outflow hole 23 toward the portion where the detection element 1A is arranged. Therefore, the gas flowing in from each of the two inflow holes 22 flows along the plane of the rectifying walls 25 and 26. That is, the gas is rectified from the outlet of the inflow hole 22 toward the portion where the detection element 1A is arranged. Here, the inflow hole 22 is an example of the "inflow hole" and the "hole through the convex portion" of the present invention. In addition, the outflow hole 23 is an example of the "outflow hole" of the present invention. In addition, the rectifying wall 25 is an example of the "rectifying component" of the present invention.

[0104] In addition, if Figure 8 As shown in (B), the left side surface 10A of the recessed portion 21 of the cover 7A has a slope inclined toward the lower right direction similar to the above-mentioned embodiment. Similarly, the right side surface 11A of the recessed portion 21 of the cover 7A has a slope inclined toward the lower left direction.

[0105] In addition, if Figure 8 As shown in (B), the left side surface 13A of the groove 29 provided in the secondary flow path 4A has an inclined surface with the same inclination angle as the inclined surface provided on the left side surface 10A of the opposite cover 7. In addition, the right side surface 14A of the groove 29 has an inclined surface with the same inclination angle as the inclined surface provided on the right side surface 11A of the opposite cover 7A.

[0106] Next, the process of the gas flowing in the main flow path 3A reaching the positions where the flow detection element 1A and the characteristic detection element 1B of the measuring device 100A are arranged will be described. A part of the gas flowing in the main flow path 3A flows into the recess 12A of the secondary flow path 4A through the inflow hole 16. After that, the gas flows between the lower surface 9A of the cover 7A and the groove 29 of the secondary flow path 4A, and reaches the entrance of the inflow hole 22 provided in the cover 7A. Here, as shown in FIG. Figure 8As shown in FIG. 2(B) , the left side surface 10A of the cover 7A and the left side surface 13A of the groove 29 are provided with inclined surfaces inclined toward the lower right direction, so that the gas is smoothly guided to the inlet of the inflow hole 22 along the inclined surfaces.

[0107] The gas reaching the inlet of the two inlet holes 22 flows into the recess 21 of the cover 7A from each outlet of the two inlet holes 22. Then, it passes through the vicinity of the thermopiles 41C and 41D arranged inside the recess 21. Here, the thermopiles 41C and the thermopiles 41D are arranged in the direction of gas flow. In addition, the gas passing through the vicinity of the thermopiles 41C and 41D is rectified from the outlet of the inlet hole 22 to the portion where the detection element 1A is arranged through the rectifying wall 25. Therefore, the output of the thermopiles 41C and 41D provided by the flow detection element 1A produces a difference, and the flow rate of the gas related to the difference can be detected. Then, the gas passing through the vicinity of the thermopiles 41C and 41D flows out to the secondary flow path 4 through the outflow hole 23. Here, the gas flowing out to the secondary flow path 4 through the outflow hole 28 is smoothly guided to the outflow hole 18 connected to the main flow path 3A along the inclined surface provided on the right side 11A of the cover 7A. Then, the gas flows out from the outflow hole 18 to the main flow path 3A.

[0108] On the other hand, part of the gas flowing in the main flow path 3A also flows into the recessed portion 20 of the secondary flow path 4B through the inflow hole 17. The gas flowing into the recessed portion 20 passes through the vicinity of the thermopiles 41E and 41F arranged in the recessed portion 20 in an exposed state. Therefore, the characteristics of the gas can be detected using the output value from the thermopiles 41E or the thermopiles 41F. Then, the gas passing through the vicinity of the thermopiles 41E and 41F flows out to the main flow path 3A through the outflow hole 18.

[0109] [Function and Effect]

[0110] According to the measuring device 100A as described above, the same effect as that of the flow measuring device 100 of the present embodiment is achieved. In addition, since the measuring device 100A includes the rectifying walls 25 and 26, the gas flowing into the inside of the cover 7A from the outlets of the two inflow holes 22 is rectified along the plane of the rectifying wall 25, which is along the direction from the inflow hole 22 toward the part where the detection element 1A is arranged. Therefore, even when the flow rate of the gas flowing inside the cover 7A is low, the sensitivity of the thermopiles 41C and 41D of the flow detection element 1A is improved.

[0111] In addition, according to the measuring device 100A as described above, a rectifying wall 25 is provided between the respective outlets of the two inflow holes 22. Therefore, a situation in which the cross-sectional area of ​​the space of the recessed portion of the recess 21 changes sharply in a direction orthogonal to the gas flow direction (the direction from the outlet of the inflow hole 22 toward the place where the flow detection element 1A is arranged) is suppressed. Therefore, the generation of turbulence near the respective outlets of the two inflow holes 22 is suppressed. Therefore, since dust or dirt is suppressed from spreading in the secondary flow path 4A, the situation in which dust or dirt is mixed in the gas and reaches the part where the flow detection element 1A is arranged is suppressed. As a result, the output of the thermopile 41C and the output of the thermopile 41D of the flow detection element 1A are also suppressed. Therefore, the decrease in the accuracy of flow detection is suppressed.

[0112] In addition, according to the measuring device 100A as described above, in addition to the flow rate of the gas, the characteristics of the gas can also be detected. Therefore, even in the case where the temperature difference in the flow direction of the gas depends not only on the flow rate of the gas but also on the characteristics of the gas, the characteristics of the gas detected by the characteristic detection element 1B can be used to correct the flow rate of the gas detected by the flow detection element 1A, thereby enabling high-precision flow measurement. In addition, according to the measuring device 100A as described above, the flow detection element 1A and the characteristic detection element 1B are mounted on the substrate 5A, and a cover 7A is provided on the substrate 5A. Therefore, it is possible to simply suppress the mixing of impurities from the side of the configuration substrate 5A into the flow detection element 1A and the characteristic detection element 1B.

[0113] In addition, according to the measuring device 100A as described above, the flow rate of the gas diverted to the secondary flow path 4A and the secondary flow path 4B can be controlled separately by adjusting the width of each secondary flow path. Therefore, the flow rate of the gas flowing in the secondary flow path 4A can be controlled according to the detection range of the flow detection element 1A, and the flow rate of the gas flowing in the secondary flow path 4B can be controlled according to the detection range of the characteristic detection element 1B. Therefore, the measuring device 100A can detect the flow rate and characteristics of the gas at the optimal flow rate according to the inherent detection range of each detection element. Therefore, the flow detection element 1A and the characteristic detection element 1B can measure the flow rate and characteristics of the gas with high precision. Furthermore, according to the measuring device 100A as described above, the characteristic detection element 1B and the cover 7A do not overlap in the height direction, so the part where the characteristic detection element 1B is configured can be made thinner.

[0114] (Other Modifications)

[0115] The shape of the cover 7A covering the flow detection element 1A involved in the modification can also be applied to the shape of the cover 7 of the present embodiment (the shape of the cover of the measuring device having only the flow detection element). In addition, the measuring device 100A is provided with the rectifying walls 25 and 26 as an example of a rectifying component, but the rectifying component is not limited to the form of the rectifying walls 25 and 26, as long as it is a form that can rectify the gas from the outlet of the inflow hole 22 toward the flow detection element 1A. In addition, the form of the inflow hole 22 and the outflow hole 23 is not limited to the form described in the above-mentioned embodiment and the modification. For example, the position of the inflow hole 22 is not limited to the description of the above-mentioned modification, as long as it is set at a position upstream of the position where the flow detection element 1A is arranged in the secondary flow path 4A, for example, it can also be set in the middle of the inclined surface of the left side 10 of the cover 7A. In addition, the position of the outflow hole 23 is not limited to the description of the above-mentioned modification, and it can also be set at a position downstream of the position where the flow detection element 1A is arranged in the secondary flow path 4A. In addition, the number of inflow holes 22 and the number of outflow holes can be several. In addition, the relative position relationship of the two inflow holes 22 can be changed. Similarly, the relative positional relationship between the two outflow holes 23 can be changed. In addition, the inclined surface of the left side surface 10 on the upstream side of the cover 7 can also be arranged in a manner that corresponds to the position of the inflow hole 22 and is inclined toward the direction of the inflow hole 22. In addition, the flow measurement device 100 can also be arranged on the main flow path 3.

[0116] The embodiments and modifications disclosed above can be combined respectively.

[0117] In order to compare the components of the present invention with the components of the embodiments, the components of the present invention are described below with the reference numerals in the drawings.

[0118] <Additional Note 1>

[0119] A flow measurement device (100A) comprising:

[0120] A flow rate detection unit (1, 1A) is arranged in a flow path (4, 4A), outputs a value related to a temperature difference in a flow direction of the fluid that changes according to the flow rate of the fluid flowing in the flow path (4, 4A), and detects the flow rate using the output value.

[0121] a covering member (7, 7A) covering the flow detection section (1, 1A) in the flow path (4, 4A),

[0122] The covering member (7, 7A) has:

[0123] an inflow hole (27, 22) disposed on the upstream side of the portion where the flow detection portion (1, 1A) is disposed, and capable of allowing fluid to flow from the flow path (4, 4A) outside the covering member (7, 7A) into the portion inside the covering member (7, 7A) where the flow detection portion (1, 1A) is disposed;

[0124] an outflow hole (28, 23) disposed on the downstream side of the flow detection section (1, 1A) and capable of allowing the fluid to flow out from the portion of the covering member (7, 7A) where the flow detection section (1, 1A) is disposed to the flow path (4, 4A) outside the covering member (7, 7A),

[0125] The outer side surface (10, 10A) of the covering member (7, 7A) on the upstream side of the portion where the flow rate detection unit (1, 1A) is arranged has an inclined surface inclined toward the inlet direction of the inlet hole (27, 22).

[0126] <Note 2>

[0127] The flow measurement device (100A) as described in Supplementary Note 1 further comprises a rectifying member 25 for rectifying the flow direction of the fluid flowing in from the inflow hole (22) toward the portion where the flow detection unit (1A) is arranged.

[0128] The rectifying member 25 is provided at the outlet of the inflow hole (22) and has a flat surface along a direction from the outlet of the inflow hole (22) toward a portion where the flow rate detection unit (1A) is arranged.

[0129] <Addendum 3>

[0130] As described in Supplementary Note 2, the flow measurement device (100A) has two inflow holes (22) arranged in a direction orthogonal to the fluid flow direction.

[0131] The rectifying member 25 is disposed between respective outlets of the two inflow holes (22).

[0132] <Addendum 4>

[0133] The flow measurement device (100, 100A) according to any one of Appendixes 1 to 3, wherein the flow path (4, 4A) has a recess (12, 12A) on the side wall, and the side surface on the upstream side of the recess (12, 12A) has an inclined surface (13, 13A) inclined toward the bottom surface of the recess,

[0134] The covering member (7, 7A) has a portion of the flow path (4, 4A) disposed opposite to the bottom surface of the recessed portion (12, 12A) of the flow path (4, 4A), and a convex portion protruding from the disposed portion toward the bottom surface.

[0135] The inflow hole (27, 22) includes a hole penetrating the convex portion.

[0136] <Addendum 5>

[0137] The flow measurement device according to any one of Supplementary Notes 1 to 4, wherein the flow path (4, 4A) is a secondary flow path branched from a primary flow path (3, 3A) of the fluid flow,

[0138] The secondary flow path (4, 4A) is arranged therein.

[0139] <Addendum 6>

[0140] The flow measurement device (100A) as described in any one of Appendixes 1 to 5 further comprises a characteristic detection unit (1B) which is arranged in a second flow path (4B) different from the flow path (4A), outputs a value related to the temperature of the second flow path (4B) which changes according to the characteristics of the fluid flowing in the second flow path (4B), and detects the characteristic using the output value,

[0141] The covering member (7A) further includes a second hole (24), the second hole (24) surrounding the characteristic detection member (1B) so that the characteristic detection member (1B) is exposed in the second flow path (4B).

Claims

1. A flow measurement device, characterized in that: have: a flow rate detection unit disposed in the flow path, outputting a value related to a temperature difference in a flow direction of the fluid that changes according to the flow rate of the fluid flowing in the flow path, and detecting the flow rate using the output value; a covering member that covers the flow detection portion in the flow path, The covering member has: an inflow hole provided at an upstream side of the portion where the flow rate detection portion is arranged, and capable of allowing a fluid to flow from the flow path outside the covering member to the portion inside the covering member where the flow rate detection portion is arranged; an outflow hole provided on the downstream side of the flow detection section, capable of allowing the fluid to flow out from the portion inside the covering member where the flow detection section is arranged to the flow path outside the covering member, The outer side surface of the covering member on the upstream side of the portion where the flow rate detection unit is arranged has an inclined surface inclined toward the inlet direction of the inlet hole, The flow path has a concave portion on a side wall, and the side surface on the upstream side of the concave portion has an inclined surface inclined toward the bottom surface of the concave portion. The covering member has a convex portion, which is arranged at a portion of the flow path facing the bottom surface of the concave portion of the flow path and protrudes from the arranged portion toward the bottom surface. The inflow hole includes a hole penetrating the convex portion.

2. The flow measurement device according to claim 1, characterized in that: The flow path is a sub-flow path branched from a main flow path in which a fluid flows, and is arranged in the sub-flow path.

3. The flow measurement device according to claim 1, characterized in that: further comprising a characteristic detection unit disposed in a second flow path different from the flow path, outputting a value related to the temperature of the second flow path that changes according to the characteristic of the fluid flowing in the second flow path, and detecting the characteristic using the output value, The covering member further includes a second hole that surrounds the characteristic detection portion and allows the characteristic detection portion to be exposed in the second flow path.

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