FLOW METER

Abstract

Flow meter (100, 100A), equipped with: a flow detector (1, 1A) arranged in a current path (4, 4A) for outputting a value relating to a temperature difference in the flow direction of a fluid, which changes depending on the flow rate of the fluid flowing through the current path (4, 4A), and for detecting the flow using the output value, and a cover element (7, 7A) designed to cover the flow detection device (1, 1A) in the flow path (4, 4A), wherein the flow path (4, 4A) is a secondary flow path branching off from a main flow path (3, 3A) through which the fluid flows, wherein the flow measuring device is arranged in the secondary flow path (4, 4A), wherein the cover element (7, 7A) comprises: an inlet hole (27, 22) provided upstream of a portion at which the flow detection (1, 1A) is arranged, and allowing the fluid to flow from the flow path (4, 4A) outside the cover element (7, 7A), the flow path (4, 4A) passing the cover element (7, 7A), into a portion located inside the cover element (7, 7A) and at which the flow detection (1, 1A) is arranged, and an outlet hole (28, 33) provided downstream of the flow detector (1, 1A) and allowing the fluid to flow from the portion located inside the cover element (7, 7A) and on which the flow detector (1, 1A) is arranged into the flow path (4, 4A) outside the cover element (7, 7A), the flow path (4, 4A) passing the cover element (7, 7A), wherein an outer surface (10, 10A) of the cover member (7, 7A) upstream of the portion at which the flow detector (1, 1A) is arranged has an inclined surface which is inclined towards the inlet of the inlet hole (27, 22).

Description

TECHNICAL FIELDThe present invention relates to a flowmeter.BACKGROUND ARTA technique configured to measure the flow rate of a fluid flowing in a flow path with a flow sensor is disclosed (e.g., JP 3 658 321 B 2, JP 2007-086 085 A, and JP 2012-141 181 A). JP 3 658 321 B2 discloses that the temperature distribution information of a current path through a thermopile is detected in a thermal flow sensor, and the flow rate of a fluid is calculated on the basis of the temperature distribution information. JP 2007-086 085 A discloses that a flow sensor and a rectifier are installed in a current path in an electronic gas meter. JP 2012-141 181 A discloses a thermal flow sensor formed with a substrate having a first substrate and a second substrate, and a portion installed on the substrate to form an upper current path. It is disclosed that a rectangular recess is provided on the lower surface of the upper flow path forming portion, the recess forms a second flow path with the upper surface of the second substrate, and the recess is provided with an inlet and an outlet leading to the outer region. Further prior art is formed by EP 2 163 864 A1 and US 2014 / 0069205 A1. EP 2 163 864 A1 discloses a flowmeter having an inlet port into which a measurement fluid flows, an outlet port from which a measurement fluid flows, and a flow path connecting the inlet port and the outlet port, the flow path being bent at a first bent portion, wherein: a first porous plate is disposed in the first bent portion of the flow path at an angle relative to the direction in which the flow path extends before and after the first bent portion, and a flow sensor for detecting the flow speed or the flow volume of a measurement fluid flowing in the flow path is disposed on the inner wall of the flow path on the side of the outflow port of the first bent portion.SUMMARY OF THE INVENTIONWhen the flow rate of a fluid flowing in a flow path is measured with a thermal flow sensor, the thermal flow sensor is arranged such that a sensor element that detects the temperature distribution of the flow path is exposed in the flow path. However, when the sensor element is arranged in this manner, the output of the sensor element that detects the temperature distribution may fluctuate due to the influence of contaminants such as dust or dirt mixed with the fluid flowing in the flow path. That is, the inventor has found that the accuracy of the flow measurement is lowered if the flow sensor is arranged in the above-explained manner.In view of the foregoing, it is an object of the present invention to provide a technique configured to suppress variations in output of a sensor element due to the influence of impurities flowing through a current path.This object is achieved by the subject matter of independent claim 1. Preferred embodiments of the invention are the subject of the dependent claims. The invention is defined by the claims, aspects of the invention being explained in the following:According to an aspect of the present invention, there is provided a flow meter including a flow detector disposed in a flow path for outputting a value related to a temperature difference in a flow direction of a fluid that changes depending on a flow rate of the fluid flowing through the flow path, and configured to detect the flow rate using the outputted value, and a cover member configured to cover the flow rate detection in the flow path, the cover member including: an inlet hole provided upstream of a portion where the flow rate detection is disposed, and allowing a fluid to flow from the flow path outside the cover member into a portion that is inside the cover member and where the flow rate detection is disposed, and an outlet hole provided downstream of the flow rate detection, and allowing a fluid to flow out from the portion inside the cover member and on which the flow detection is disposed into the flow path outside the cover member, wherein an outer surface of the cover member upstream of the portion on which the flow detection is disposed has an inclined surface inclined toward the inlet of the inlet hole.When the contaminants reach a location where the flow detection is disposed, it is conceivable that the information on the temperature difference in the flow direction of the fluid outputted from the flow detection fluctuates. However, after the formation, the contaminants flowing in the flow path are prevented from coming into the flow detection by providing the cover member. Therefore, the variation of the output from the flow rate detection is suppressed. Consequently, the decrease in the detection accuracy of the flow is suppressed. When the flow path is provided inside the cover member, the flow of the fluid is rectified in the vicinity of the location where the flow detection is disposed. That is, the sensitivity of the flowmeter is improved.Further, according to the present embodiment, since the fluid flows along the inclined surface of the outer surface of the cover member in the flow path, it is smoothly guided to the inlet of the inlet hole. Therefore, generation of a turbulent flow in the flow path is suppressed. Consequently, scattering of contaminants in the current path is suppressed, and thus the contaminants are prevented from reaching the portion where the flow detection is disposed. Therefore, the variation of the output of the flow rate detection is suppressed. Further, accumulation of the contaminants on the inclined surface is suppressed. Therefore, the accumulated contaminants are suppressed from being scattered by the turbulence etc. generated in the flow path and coming to the flow detection. Consequently, the variation in the output of the flow detection is suppressed. Therefore, the decrease in the detection accuracy of the flow is suppressed.The flow meter according to the one aspect is further provided with a rectifying element configured to rectify the flow direction of the fluid flowing in from the inlet hole toward the portion where the flow detection is disposed, wherein the rectifying element may be provided at the outlet of the inlet hole and may also have a plane along a direction from the outlet of the inlet hole to the portion where the flow detection is disposed.After the formation, the fluid flowing into the cover member from the inlet hole is rectified to be directed along the plane of the rectifier member toward the portion where the flow detection is disposed. Therefore, the sensitivity of the flow detection at low flow rate is more reliably improved.In the flow meter according to the one aspect, the inlet hole may be provided twice in a direction orthogonal to the flow direction of the fluid, and the rectifying element may be provided between the respective outlets of the two inlet holes.After the formation, a sudden change in the cross-sectional area of a space inside the cover member orthogonal to the flow direction of the fluid at the outlet of the inlet hole is suppressed. Therefore, generation of a turbulent flow in the vicinity of the inlet hole is suppressed. Consequently, scattering of contaminants in the flow path is suppressed, and thus the contaminants are prevented from mixing with the fluid and reaching the portion where the flow detection is disposed. Consequently, the variation in the output of the flow detection is suppressed. Therefore, the decrease in the detection accuracy of the flow is suppressed.In the flow meter according to the one aspect, the flow path has a recess on a side wall, and an upstream side of the recess has an inclined surface inclined toward the bottom of the recess, wherein the cover member may include a protrusion disposed in a portion of the flow path opposite to the bottom of the recess of the flow path and protruding from the disposed portion toward the bottom, and the inlet hole may include a hole passed through the protrusion.After formation, the fluid in the flow path flows along the inclined surface of the depression and thus smoothly passes through the depression. That is, the fluid is smoothly guided to the inlet of the inlet hole. Therefore, generation of a turbulent flow in the flow path is suppressed. Consequently, scattering of contaminants in the current path is suppressed, and thus the contaminants are prevented from reaching the portion where the flow detection is disposed. Therefore, the variation of the output of the flow rate detection is suppressed. Further, since the recess side has the inclined surface, accumulation of the contaminants on the side is suppressed. Therefore, the accumulated contaminants are suppressed from being scattered by the turbulence etc. generated in the flow path and coming to the flow detection. Consequently, the variation in the output of the flow detection is suppressed. Therefore, the decrease in the detection accuracy of the flow is suppressed.In the flowmeter according to the one aspect, the flow path is a bypass flow path branched from the main flow path through which the fluid flows, and the flowmeter may be disposed in the bypass flow path.After being formed, the fluid flowing in the main flow path passes through the inlet holes provided in the cover member via the sub flow path, and reaches the portion where the flow detection is disposed. That is, since the fluid flowing through the main flow path does not directly flow into the cover member, contaminants mixed with the fluid are prevented from reaching the portion where the flow detection is disposed. Therefore, the variation of the output from the flow rate detection is suppressed.In the flowmeter according to the one aspect, there is further provided a behavior detector disposed in a second current path different from the current path and configured to output a value related to the temperature of the second current path that changes depending on the behavior of the fluid flowing through the second current path and detect the behavior using the output value, wherein the cover member may further include a second hole that surrounds the behavior detector and exposes the behavior detector in the second current path.After formation, the behavior of the fluid can be detected in addition to the flow of the fluid.Therefore, even if the temperature difference in the direction of flow of the fluid depends on the behavior of the fluid, the detected behavior of the fluid can be used to correct the detected flow rate of the fluid. Therefore, it is possible to measure the flow rate with high accuracy. After the formation, when the flow rate detection and the behavior detection are mounted on the same substrate, the mixing of the contaminants from the substrate side for the flow rate detection and the behavior detection will be easily suppressed by providing the one cover member on the substrate. Since the behavior detection and the cover member do not overlap in the height direction after the formation, the portion where the behavior detection is disposed can be thinned.According to the present invention, it is possible to provide a technique for suppressing the variation in output of a sensor element due to the influence of impurities flowing through a current path.BRIEF EXPLANATION OF THE DRAWINGSFIGS. 1A and 1B show an overview of a flowmeter. FIG. 1A shows an example of a cross-sectional view of the flowmeter according to an embodiment. FIG. 1B shows an example of a cross-sectional view of a flowmeter according to a comparative example; FIGS. 2A to 2C schematically show the principle of flow measurement by a detection element. FIG. 2A is a view illustrating the direction in which the detection element is disposed. FIG. 2B schematically shows an example of the temperature distribution that arises when a micro-heater is activated without gas flowing. FIG. 2C schematically shows an example of the temperature distribution that arises when the micro-heater is activated with flowing gas; FIG. 3 shows an example of the simulation results of the number of dust particles coming into the vicinity of a thermopile; FIG. 4 shows an example of outputting the difference between the outputs of the two thermopiles with respect to the actual gas flow rate; FIG. 5 is an exploded perspective view illustrating an example of the measurement device according to a modified example; FIG. 6 is a view illustrating the orientation in which a behavior detection element is disposed; FIGS. 7A and 7B show an example of a flow pipe to which a cover is attached and the cover attached to the flow pipe. FIG. 7A is a top perspective view of the flow tube to which the cover is attached. FIG. 7B is a plan view in which the cover is attached to the flow pipe shown in FIG. 7A ; and FIGS. 8A and 8B show an overview of the cover. FIG. 8A shows an example of a perspective view of the cross section of the cover attached to the flow tube. FIG. 8B is a front view of the cross section in FIG. 8A.EMBODIMENT OF THE INVENTIONHereinafter, an embodiment according to an aspect of the present invention (hereinafter also referred to as "embodiment") will be explained with reference to the drawings. However, the embodiment explained below is only an example of the present invention in all respects. It is to be understood that various improvements and modifications may be made without departing from the scope of the present invention. That is, in the embodiment of the present invention, a concrete configuration according to the embodiment can be suitably incorporated.§ 1 Application ExampleUsing FIG. 1A, an example of a situation in which the present invention is applied will be explained. FIG. 1A shows an example of a cross-sectional view of a flowmeter 100 according to the embodiment. The flowmeter 100 according to the embodiment is provided with a sensing element 1 and a substrate 5 on which the sensing element 1 is mounted. The detection element 1 is provided with a micro-heater 40 and two thermopiles 41A, 41B, and detects a temperature difference in the flow direction of gas that correlates with the flow rate of the gas (details will be explained later). The detection element 1 is further disposed halfway of a bypass flow path 4 provided partly in a main flow path 3 of a flow pipe 2.The flowmeter 100 is provided with a cover 7 that covers the sensing element 1. Inside the cover 7, a space 8 capable of accommodating the detection element 1 is formed. On the lower surface 9 of the cover 7, there are provided an inlet hole 27 through which gas can flow from the bypass flow path 4 into the space 8, and an outlet hole 28 through which gas can flow from the interior of the space 8 into the bypass flow path 4.According to the flow meter 100 explained above, by providing the cover 7, dust or dirt, etc. flowing in the main flow path 3 or the sub flow path 4 are prevented from reaching a location where the detection element 1 is disposed. Therefore, the output of the thermopile 41A and the output of the thermopile 41B provided in the sensing element 1 are prevented from fluctuating due to dust, dirt, etc.§ 2 Embodiment Example[Hardware Configuration]FIGS. 1A and 1B show an overview of the flowmeter. FIG. 1A shows an example of a cross-sectional view of a flowmeter 100 according to the embodiment. FIG. 1B shows an example of a cross-sectional view of a flowmeter 200 according to a comparative example. The flowmeter 100 according to the embodiment is provided with a sensing element 1 and a substrate 5 on which the sensing element 1 is mounted. The detection element 1 is provided with a micro-heater 40 and two thermopiles 41A, 41B, and detects a temperature difference in the flow direction of gas that correlates with the flow rate of the gas (details will be explained later). The substrate 5 is disposed on a side wall forming the main flow path 3 of the flow tube 2 such that a mounting surface 6 on which the sensing element 1 is mounted faces the center of the flow tube 2. In the vicinity of the side wall, the bypass flow path 4 is also partially provided, which branches off from the main flow path 3 of the flow pipe 2. The detection element 1 is arranged on the half path of the bypass current path 4. Here, the flowmeter 100 is an example of the "flowmeter" of the present invention. The detection element 1 is also an example of the "flow detection" of the present invention. The bypass current path 4 is also an example of the "current path" and the "bypass current path" of the present invention.Here, the gas in FIGS. 1A and 1B flows from the left side to the right side in the main flow path 3 and the sub flow path 4 of the flow pipe 2. The proper direction also refers to the downstream direction. The downward direction further refers to the direction in which the sensing element 1 protrudes with respect to the substrate 5. The upward direction further refers to a direction opposite to the downward direction.The flowmeter 100 is further provided with a cover 7. The cross section of the cover 7 has a downwardly convex shape as shown in FIG. 1A. A left side 10 exposed in the bypass flow path 4 of the cover 7 has a downward-rightward slope. The right side 11 exposed in the bypass flow path 4 of the cover 7 has a downward-leftward slope. Inside the cover 7, a space 8 capable of accommodating the detection element 1 is further formed. The detection element 1 mounted on the mounting surface 6 is covered by such a cover 7 and is disposed in the space 8. The cover 7 is further provided with an inlet hole 27 that allows gas to flow from the bypass flow path 4 into the space 8. The inlet hole 27 is provided so as to penetrate a part of the left side 10 and a part of the bottom surface 9. The cover 7 is further provided with an exhaust hole 28 that allows gas to flow out from the inside of the space 8 into the bypass flow path 4. The outlet hole 28 is provided so as to penetrate a part of the right side 11 and a part of the bottom surface 9. Here, the cover 7 is an example of the "cover member" of the present invention. The inlet hole 27 provided in the cover 7 is an example of the "inlet hole" and the "hole passing through the boss" of the present invention. The outlet hole 28 provided in the cover 7 is also an example of the "outlet hole" of the present invention.The lower part of the bypass flow path 4 opposite to the lower surface 9 of the cover 7 further has a recess 12 recessed downward. The part that is to the left of the recess 12 and faces the left side 10 of the cover 7 further has a left side 13. The left side 13 has an inclined surface having the same inclination angle as the inclined surface provided on the left side 10 of the cover 7. Also, the part that is to the right of the recess 12 and faces the right side 11 of the cover 7 has a right side 14. The right side 14 has an inclined surface having the same inclination angle as the inclined surface provided on the right side 11 of the cover 7.On the other hand, the flowmeter 200 according to the comparative example in FIG. 1B is provided with the sensing element 1 and the substrate 5, like the flowmeter 100 according to the embodiment. The detection element 1 is arranged under the half path of the bypass current path 4. However, the flowmeter 200 is not provided with the cover 7.[Principle of Flow Measurement]The principle of flow measurement using the detection element 1 will be explained here. FIGS. 2A to 2C schematically show an example of the principle of flow measurement with the sensing element 1. FIG. 2A is a plan view of the sensing element 1. FIG. 2B is a cross-sectional view of the sensing element 1 mounted on the substrate 5, showing the temperature distribution that arises when the micro-heater 40 is activated without gas flowing. On the other hand, FIG. 2C is a cross-sectional view of the detection element 1 mounted on the substrate 5, showing the temperature distribution generated when the micro-heater 40 is activated with flowing gas. As shown in FIG. 2A, the thermopiles 41A, 41B are arranged in a row in the direction of gas flow via the micro-heater 40. Further, as shown in FIG. 2B, the sensing element 1 is provided with a thin film 42 formed on the substrate 5, and the micro-heater 40 and the thermopiles 41A, 41B are formed to be included in the thin film 42. A cavity 43 is provided on the substrate 5 below the thin film 42. Due to the provision of the cavity 43, a warm contact of the micro-heater 40 and the thermopiles 41A, 41B are on the cavity 43 and a cold contact of the thermopiles 41A, 41B is on the substrate 5.As shown in FIG. 2B, when gas does not flow in the space 8, heat from the micro-heater 40 diffuses symmetrically around the micro-heater 40. Therefore, no difference is generated between the output of the thermopile 41A and the output of the thermopile 41B. On the other hand, as shown in FIG. 2C, when the gas flows into the space 8, the heat from the micro-heater 40 does not diffuse symmetrically around the micro-heater 40 and further to the downstream thermopile 41B due to the influence of the gas flow. Therefore, a difference is generated between the output of the thermopile 41A and the output of the thermopile 41B. The difference in the above output varies depending on the flow rate of the gas. In other words, the flow rate of the gas is determined from the difference between the output of the thermopile 41A and the output of the thermopile 41B.The difference ΔV between the voltage output from the thermopile 41A and the voltage output from the thermopile 41B is represented in the following formula (1), for example. [Formula 1]Here, T h represents the temperature of the micro-heater 40, and T a represents the temperature in the vicinity of the detection element 1. Moreover, v f is the velocity of the gas flow, and A and b are constants.Next, the operation in which the gas flowing in the main flow path 3 reaches a location where the detection element 1 is disposed will be explained. The gas flowing in the main flow path 3 flows into a left part of the sub flow path 4, and then flows into the space 8 inside the cover 7 through the inlet hole 27 provided in the cover 7, Here, the left side 10 of the cover 7 is provided with a downward rightward descending inclination, so that the gas is smoothly guided to the inlet of the inlet hole 27. The gas flowing from the inlet hole 27 into the space 8 inside the cover 7 then passes through the part where the detection element 1 is disposed. The gas then flows from the space 8 into the bypass flow path 4 via the outlet hole 28, and since the outlet hole 28 is provided with an inclined surface on a part of the right side 11, the gas flowing out into the bypass flow path 4 via the outlet hole 28 is smoothly guided along the inclined surface to an outlet hole communicating with the main flow path 3. The gas then flows out of said outlet hole into the main flow path 3.FIG. 3 shows an example of the simulation results of the number of dusts coming from the mainstream path 3 to the vicinity of the thermopiles 41A, 41B in the cover 7. As shown in FIG. 3, the number of dusts coming into the vicinity of the thermopiles 41A, 41B in the cover 7 when the cover 7 is provided (the embodiment in FIG. 1A ) is reduced to about 1 / 6 as compared with the number of dusts coming into the vicinity of the thermopiles 41A, 41B in the cover 7 when the cover 7 is not provided (the comparative example in FIG. 1B ).FIG. 4 shows an example of outputting the difference between the outputs of the two thermopiles 41A, 41B with respect to the actual gas flow rate. As shown in FIG. 4, in comparison between the case where the cover 7 is present (the embodiment in FIG. 1A ) and the case where the cover 7 is not present (the comparative example in FIG. 1B ), the output of the difference between the output of the thermopile 41A and the output of the thermopile 41B is in a linear relationship to the flow concerned in the low flow area. It is also seen that, when the cover 7 is provided, the sensitivity of the detection element 1 at low flow rate is improved as compared with the case without the cover 7.[Effects and Effects]According to the above-mentioned flowmeter 100, as shown in FIG. 3, by providing the cover 7, dust, dirt, etc. flowing through the main flow path 3 or the sub flow path 4 are suppressed from being introduced to the location where the detection element 1 is disposed. Therefore, the variation of the output of the thermopile 41A and the output of the thermopile 41B provided in the detection element 1 is suppressed. Consequently, the decrease in the detection accuracy of the flow is suppressed. On the other hand, according to the flowmeter 200 in the comparative example, the cover 7 is not provided as shown in FIG. 1B. Therefore, as shown in FIG. 3, it is considered that dust, dirt, etc. are more easily taken to the place where the detection element 1 is disposed than the flowmeter 100 in the embodiment. Thus, it is assumed that the output of the thermopile provided in the flowmeter 200 fluctuates. That is, it is assumed that, according to the flowmeter 200 according to the comparative example, the accuracy of the flow rate detection decreases.Further, according to the flow meter 100 explained above, the left side 10 of the cover 7 and the left side 13 of the recess 12 of the bypass flow path 4 have an inclined surface, so that the accumulation of dust, dirt, etc. on the inclined surface is suppressed. The gas in the bypass path 4 is further smoothly guided to the inlet of the inlet hole 27 of the cover 7 along the left side 10 of the cover 7 with the inclined surface. Therefore, generation of a turbulent flow in the bypass flow path 4 is suppressed. That is, the accumulation of dust, dirt, etc. in the bypass flow path 4 is suppressed, and even when dust, dirt, etc. are accumulated, the scattering by turbulent flow is suppressed. Consequently, dust, dirt, etc. are suppressed from reaching the detection element 1.§ 3 Modified ExamplesAlthough the embodiments of the present invention are explained in detail above, the foregoing explanation is merely an example of the invention in all respects. It is to be understood that various improvements and modifications may be made without departing from the scope of the present invention. For example, the following changes are possible. Hereinafter, the same reference numeral is used for the same constituent elements as the embodiment, and the explanation for the same point as the embodiment has been omitted as appropriate. The following modified examples may be combined as appropriate.<3.1>FIG. 5 shows an example of an exploded perspective view of a meter 100A according to a modified example. The measurement apparatus 100A in the modified example is provided with a flow rate detection element 1A that is disposed in the same manner as the detection element 1 in the above embodiment and configured to detect the flow rate of the gas. Further, the measurement apparatus 100A is provided with a behavior detection element 1B configured to detect the behavior of the gas although it is of the same element type as the detection element 1 in the above embodiment. The flow detection element 1A is provided with a micro-heater 40A and thermopiles 41C, 41D. The behavior detection element 1B is provided with a micro-heater 40B and thermopiles 41E, 41F (explained later in FIG. 6 ). The flow detection element 1A and the behavior detection element 1B are mounted on a mounting surface 6A of a substrate 5A. The measurement device 100A is provided with a cover 7A that covers each detection element of the flow detection element 1A and the behavior detection element 1B. The flow detection element 1A and the behavior detection element 1B covered by the cover 7A are disposed in a bypass flow path (explained later) formed on the upper surface of the flow pipe 2A. Here, the measurement device 100A is an example of the "flowmeter" of the present invention. The flow detection element 1A is also an example of the "flow detection" of the present invention. The behavior detection element 1B is also an example of the "behavior detection" of the present invention. The cover 7A is also an example of the "cover member" of the present invention.FIG. 6 is a view illustrating the orientation in which the behavior detection element 1B is disposed. As shown in FIG. 6, the thermopiles 41E, 41F provided in the behavior detection element 1B are arranged in a row so as to span the micro-heater 40A, and the direction of the array is a direction orthogonal to the direction of the gas flow. When the micro-heater 40B of the behavior detection element 1B thus arranged is activated, the heat from the micro-heater 40B diffuses symmetrically in the direction in which the thermopile 41E and the thermopile 41F align around the micro-heater 40B. The degree of heat diffusion also depends on the behavior of the gas. In other words, the output value of the thermopile 41E or the thermopile 41F can be used for calculation of the gas. Here, the behavior of the gas is, for example, the thermal conductivity and the thermal conductivity. The calculation of the behavior of the gas may be further performed using the output from one of the thermopiles 41E and the thermopile 41F or using an average value of the output from the thermopile 41E and the output from the thermopile 41F.FIGS. 7A and 7B and FIGS. 8A and 8B show an overview of a flow pipe 2A to which the cover 7A is attached and the cover 7A provided in the measurement apparatus 100A. FIG. 7A is a perspective plan view of the flow tube 2A to which the cover 7A is attached. FIG. 7B is a plan view in which the cover 7A is attached to the flow pipe 2A shown in FIG. 7A. FIG. 8A is a perspective view of the cross section of the flow pipe 2A and the cover 7A attached to the flow pipe 2A. FIG. 8B is a front view of the cross section mainly in the vicinity of the cover 7A. The cover 7A is attached to the upper surface of the flow pipe 2A as shown in FIG. 7B as well as FIGS. 8A and 8B by ultrasonic welding, as shown in FIG. 7A. Further, the upper part 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 behavior detection element 1B are mounted.As shown in FIG. 7A, the flow pipe 2A is provided with bypass flow paths 4A, 4B branching from the main flow path of the flow pipe 2A. The bypass flow path 4A is provided with an inlet hole 16 that allows inflow of gas from the main flow path. The bypass flow path 4A is provided with a recess 12A in which the flow detection element 1A covered by the cover 7A is disposed. Further, a groove 29 is provided at the bottom of the recess 12A. The sub flow path 4A is further provided with an outlet hole 18 through which the gas can flow out into the main flow path. Here, the bypass current path 4A is an example of the "current path" and the "bypass current path" of the present invention. The bypass current path 4B is also an example of the "second current path" and the "bypass current path" of the present invention.On the other hand, in the bypass flow path 4B, an inlet hole 17 through which the gas can flow in from the main flow path 3A is provided. In the central part of the bypass flow path 4B, a recess 20 is provided in which the behavior detection element 1B covered by the cover 7A is disposed. The sub flow path 4B is further provided with an outlet hole 19 through which the gas can flow out into the main flow path 3A.As shown in FIGS. 7B and 8A, the cover 7A is provided with a recess 21 in which the flow detection element 1A is disposed. The outer shape of the cover 7A corresponding to the recess 21 rises downward, and the upstream outer surface and the downstream outer surface of the protrusion have an inclined surface (details will be explained later). The recess 21 in which the flow detection element 1A is accommodated is inside the recess 12A shown in FIG. 7A. That is, the flow detection element 1A is not exposed in the bypass flow path 4A. The cover 7A is further provided with a hole 24 in which the behavior detection element 1B is disposed. The behavior detection element 1B in the state of being disposed in the hole 24 is disposed inside the recess 20 shown in FIG. 7A. That is, the lower surface of the behavior detection element 1B is exposed in the bypass current path 4B.As shown in FIG. 7B, the recess 21 of the cover 7A is provided with two inlet holes 22 through which gas can flow in from the bypass flow path 4A. The depression 21 is further provided with two outlet holes 23 through which gas can flow from the depression 21 into the bypass flow path 4A. The inlet hole 22 and the outlet hole 23 are provided such that the inlet hole 22 is located upstream in the bypass flow path 4A and the outlet hole 23 is located downstream in the bypass flow path 4A. The two inlet holes 22 and the two outlet holes 23 are provided symmetrically with respect to the central axis along the gas flow direction in the depression 21. Between the respective outlets of the two inlet holes 22, there is provided a rectifying wall 25 which projects in the direction from the inlet hole 22 to the outlet hole 23. In the same manner, between the respective inlets of the two outlet holes 23, there is provided a rectifying wall 26 which projects in the direction from the outlet hole 23 toward the inlet hole 22. The surface of the rectifying wall 25 has a flat portion along the direction from the inlet hole 22 to the portion where the detection element 1A is disposed. In the same manner, the surface of the rectifying wall 26 has a flat portion along the direction from the outlet hole 23 to the portion where the detection element 1A is disposed. Therefore, the gas flowing in from each of the two inlet holes 22 flows along the plane of the rectifying walls 25, 26. Here, the inlet hole 22 is an example of the "inlet hole" and the "hole passing through the boss" of the present invention. The outlet hole 23 is also an example of the "outlet hole" of the present invention. The rectifying wall 25 is also an example of the "rectifying element" of the present invention.As shown in FIG. 8B, the left side 10A of the recess 21 of the cover 7A has a downward rightward slope as in the above embodiment. Also, the right side 11A of the recess 21 of the cover 7A has a downward-left slope.Further, as shown in FIG. 8B, the left side 13A of the groove 29 provided in the bypass flow path 4A has an inclined surface having the same inclination angle as the inclination angle of the inclined surface provided in the opposite left side 10A of the cover 7A. The right side 14A of the groove 29 further has an inclined surface having the same inclination angle as the inclination angle of the inclined surface provided in the opposite right side 11A of the cover 7A.Next, the operation in which the gas flowing in the main flow path 3A comes to the place where the flow detection element 1A and the behavior detection element 1B provided in the measurement device 100A are disposed will be explained. A part of the gas flowing in the main flow path 3A flows into the recess 12A of the sub flow path 4A via the inlet hole 16. The gas then flows through the space between the lower surface 9A of the cover 7A and the groove 29 of the bypass path 4A, and reaches the inlet of the inlet hole 22 provided in the cover 7A. Here, the left side 10A of the cover 7A and the left side 13A of the groove 29 are provided with a downward rightward descending inclination as shown in FIG. 8B, so that the gas is smoothly guided along the inclination toward the inlet of the inlet hole 22.The gas that reaches the inlets of the two inlet holes 22 flows from the respective outlets of the two inlet holes 22 into the recess 21 of the cover 7A. The gas then passes through the vicinity of the thermopiles 41C, 41D disposed inside the depression 21. Here, the thermopiles 41C, 41D are arranged in the row in the flow direction of the gas. The gas passing through the vicinity of the thermopiles 41C, 41D is further rectified by the rectifying wall 25 so as to be guided from the outlet of the inlet hole 22 to the portion where the detection element 1A is disposed. Therefore, a difference occurs between the output of the thermopile 41C and the output of the thermopile 41D provided in the flow detection element 1A, and the flow rate of the gas correlated with the above difference can be detected. Thereafter, the gas passing through the vicinity of the thermopiles 41C, 41D flows out into the bypass flow path 4A via the outlet hole 23. Here, the gas flowing out into the sub flow path 4 via the discharge hole 28 is smoothly guided to the discharge hole 18 communicating with the main flow path 3A along an inclined surface provided on the right side 11A of the cover 7A. The gas then flows out from the outlet hole 18 into the main flow path 3A.On the other hand, a part of the gas flowing through the main flow path 3A also flows into the recess 20 of the sub flow path 4B via the inlet hole 17. The gas flowing into the depression 20 passes through the vicinity of the thermopiles 41E, 41F disposed in the depression 20 in the exposed state. Therefore, the output values of the thermopiles 41E or 41F can be used to determine the behavior of the gas. The gas passing through the vicinity of the thermopiles 41E, 41F then flows out into the main flow path 3A via the outlet hole 18.[Effects and Effects]The above-described measurement device 100A achieves the same effect as the flow measurement device 100 in the embodiment. In addition, since the meter 100A is provided with rectifying walls 25, 26, the gas flowing from the respective outlets of the two inlet holes 22 into the inside of the cover 7A is rectified to be aligned along the plane of the rectifying wall 25 along the direction from the inlet holes 22 to the portion where the detection element 1A is disposed. Therefore, even when the flow rate of the gas flowing in the cover 7A is low, the sensitivity of the thermopiles 41C, 41D of the flow detection element 1A is improved.Further, according to the above-mentioned meter 100A, the rectifying wall 25 is provided between the respective outlets of the two inlet holes 22. Therefore, sudden change in the cross-sectional area of a recessed part of the recess 21 in a direction orthogonal to the flow direction of the gas (the direction from the outlet of the inlet hole 22 to the location where the flow detection element 1A is disposed) is suppressed. Therefore, generation of turbulent flow in the vicinity of the respective outlets of the two inlet holes 22 is suppressed. Consequently, the scattering of dust, dirt, etc. in the bypass flow path 4A is suppressed, so that dust, dirt, etc. are suppressed from being mixed with the gas and coming to the portion where the flow detection element 1A is disposed. This also suppresses the variation in the output of the thermopile 41C and the output of the thermopile 41D provided in the flow detection element 1A. Therefore, the decrease in the detection accuracy of the flow is suppressed.According to the above-explained measurement device 100A, besides the flow rate of the gas, the behavior of the gas can also be detected. Therefore, even if the temperature difference in the flow direction of the gas depends not only on the flow rate of the gas but also on the behavior of the gas, highly accurate flow measurement can be made by using the behavior of the gas detected by the behavior detection element 1B and correcting the flow rate of the gas detected by the flow detection element 1A. Further, according to the above-explained measurement apparatus 100A, the flow rate detection element 1A and the behavior detection element 1B are mounted on the substrate 5A, and the cover 7A is provided on the substrate 5A. Therefore, it is easily suppressed that contaminants are mixed into the flow detection element 1A and the behavior detection element 1B from the side on which the substrate 5A is disposed.Further, according to the above-mentioned measurement apparatus 100A, the flow rate of the gas branched into the bypass flow paths 4A, 4B can be individually controlled by width adjusting the respective bypass flow paths. Therefore, the flow rate of the gas flowing through the bypass flow path 4A corresponding to the detection range of the flow detection element 1A and the flow rate of the gas flowing through the bypass flow path 4B corresponding to the detection range of the behavior detection element 1B can be controlled. Therefore, the measurement device 100A can detect the flow rate and the behavior of the gas at an optimum flow rate corresponding to the own detection range of the respective detection elements. Consequently, the flow rate detection element 1A and the behavior detection element 1B can measure the flow rate and the behavior of the gas with high accuracy. Further, according to the above-explained measurement device 100A, the behavior detection element 1B and the cover 7A do not overlap in the height direction, so that the portion where the behavior detection element 1B is disposed can be thinned.< Modified Examples>The shape of the cover 7A covering the flow detection element 1A according to the modified example may be applied to the shape of the cover 7 according to the embodiment (the shape of the cover of the measurement device provided only with the flow detection element). Although the meter 100A is provided with the rectifying walls 25, 26 as an example of a rectifying element, the rectifying element is not limited to the shape of the rectifying walls 25, 26, and may take any shape as long as gas can be rectified from the outlet of the inlet hole 22 toward the flow detecting element 1A. Further, the shapes of the inlet hole 22 and the outlet hole 23 are not limited to the indication of the above embodiment and modified examples. For example, the location of the inlet hole 22 is not limited to the above modified examples, and may be provided at a location upstream of the location where the flow detection element 1A is disposed in the bypass flow path 4A, and for example, may be provided under the halfway of an inclined surface including the left side 10 of the cover 7A. Further, the location of the outlet hole 23 is not limited to the indication of the above modified examples, and may be provided at a location downstream of the location where the flow detection element 1A is disposed in the bypass flow path 4A. The number of the inlet holes 22 and the number of the outlet holes may be any. The relative positional relationship of the two inlet holes 22 can be changed. Also, the relative positional relationship of the two outflow holes 23 can be changed. The inclined surface including the left side 10 on the upstream side of the cover 7 may be further provided inclined toward the inlet hole 22 to correspond to the position of the inlet hole 22. The flow measuring device 100 explained above can also be provided in the main flow path 3.The above-disclosed embodiments and modified examples may be combined, respectively.In order that the features of the present invention can be compared with the configurations of the embodiments, the features of the present invention are denoted by reference numerals in the drawings.< 1>A flowmeter (100, 100A) provided with:a flow detection device (1, 1A) disposed in a flow path (4, 4A) for outputting a value related to a temperature difference in a flow direction of a fluid that changes depending on a flow rate of the fluid flowing through the flow path (4, 4A), and for detecting the flow rate using the output value; anda cover member (7, 7A) configured to cover the flow detector (1, 1A) in the flow path (4, 4A),wherein the cover member (7, 7A) comprises:an inlet hole (27, 22) provided upstream of a portion where the flow detector (1, 1A) is disposed, and allowing a fluid to flow from the flow path (4, 4A) outside the cover member (7, 7A) into a portion that is inside the cover member (7, 7A) and where the flow detector (1, 1A) is disposed, andan outlet hole (28, 23) provided downstream of the flow detector (1, 1A) and allowing a fluid to flow out from the portion that is inside the cover member (7, 7A) and at which the flow detector (1, 1A) is disposed into the flow path (4, 4A) outside the cover member (7, 7A),wherein an outer surface (10, 10A) of the cover member (7, 7A) upstream of the portion where the flow detector (1, 1A) is disposed has an inclined surface inclined toward the inlet of the inlet hole (27, 22).< 2>The flow meter (100A) according to Claim 1, further comprising a rectifying element (25) configured to rectify the flow direction of the fluid flowing in from the inlet hole (22) toward the portion where the flow detector (1A) is disposed, wherein the rectifying element (25) is provided at the outlet of the inlet hole (22) and has a plane along a direction from the outlet of the inlet hole (22) to the portion where the flow detector (1A) is disposed.< 3>The flow meter (100A) according to claim 2, wherein the inlet hole (22) is provided twice in a direction orthogonal to the flow direction of the fluid, and the rectifying element (25) is provided between the respective outlets of the two inlet holes (22).< 4>The flowmeter (100, 100A) according to any one of claims 1 to 3, wherein the flow path (4, 4A) has a recess (12, 12A) on a side wall, and an upstream side of the recess (12, 12A) has an inclined surface (13, 13A) inclined toward the bottom of the recess, wherein the cover member (7, 7A) has a protrusion that is disposed in a portion of the flow path (4, 4A) opposite to the bottom of the recess (12, 12A) of the flow path (4, 4A) and protrudes from the disposed portion toward the bottom, and the inlet hole (27, 22) includes a hole that is passed through the protrusion.< 5>The flowmeter according to any one of claims 1 to 4, wherein the flow path (4, 4A) is a bypass flow path branched from the main flow path (3, 3A) through which the fluid flows, the flowmeter being disposed in the bypass flow path (4, 4A).< 6>The flowmeter (100A) according to any one of claims 1 to 5, further comprising a behavior detector (1B) disposed in a second current path (4B) different from the current path (4A) and configured to output a value related to the temperature of the second current path (4B) that changes depending on the behavior of the fluid flowing through the second current path (4B), and detect the behavior using the output value, wherein the cover member (7A) further includes a second hole (24) that surrounds the behavior detector (1B) and exposes the behavior detector (1B) in the second current path (4B).

Claims

A flow meter (100, 100A) comprising: a flow detector (1, 1A) disposed in a flow path (4, 4A), for outputting a value related to a temperature difference in a flow direction of a fluid that changes depending on a flow rate of the fluid flowing through the flow path (4, 4A), and configured to detect the flow rate using the outputted value; and a cover member (7, 7A) configured to cover the flow detector (1, 1A) in the flow path (4, 4A), wherein the flow path (4, 4A) is a sub-flow path branched from a main flow path (3, 3A) through which the fluid flows, wherein the flow meter is disposed in the sub-flow path (4, 4A), wherein the cover member (7, 7A) has: an inlet hole (27, 22) provided upstream of a portion where the flow detector (1, 1A) is disposed and allowing the fluid to flow from the flow path (4, 4A) outside the cover member (7, 7A), the flow path (4, 4A) passing the cover member (7, 7A), into a portion which is inside the cover member (7, 7A) and where the flow detector (1, 1A) is disposed; and an outlet hole (28, 33) provided downstream of the flow detector (1, 1A) and allowing the fluid to flow from the portion which is inside the cover member (7, 7A) and where the flow detector (1, 1A) is disposed, in the flow path (4, 4A) outside the cover member (7, 7A), the flow path (4, 4A) passing the cover member (7, 7A), an outer surface (10, 10A) of the cover member (7, 7A) upstream of the portion where the flow detector (1, 1A) is disposed has an inclined surface inclined toward the inlet of the inlet hole (27, 22).The flow meter (100A) according to claim 1, further comprising a rectifying element (25) configured to rectify the flow direction of the fluid flowing in from the inlet hole (22) toward the portion where the flow detector (1A) is disposed, wherein the rectifying element (25) is provided at the outlet of the inlet hole (22) and has a plane along a direction from the outlet of the inlet hole (22) to the portion where the flow detector (1A) is disposed.The flowmeter (100A) according to claim 2, wherein the inlet hole (22) is provided twice in a direction orthogonal to the flow direction of the fluid, and the rectifying element (25) is provided between the respective outlets of the two inlet holes (22).The flowmeter (100, 100A) according to any one of claims 1 to 3, wherein the flow path (4, 4A) has a recess (12, 12A) on a side wall, and an upstream side of the recess (12, 12A) has an inclined surface (13, 13A) inclined toward the bottom of the recess, wherein the cover member (7, 7A) has a protrusion that is disposed in a portion of the flow path (4, 4A) opposite to the bottom of the recess (12, 12A) of the flow path (4, 4A) and protrudes from the disposed portion toward the bottom, and the inlet hole (27, 22) includes a hole that is passed through the protrusion.The flowmeter (100A) according to any one of claims 1 to 4, further comprising a behavior detector (1B) disposed in a second current path (4B) different from the current path (4A) and configured to output a value related to the temperature of the second current path (4B) that changes depending on the behavior of the fluid flowing through the second current path (4B), and detect the behavior using the output value, wherein the cover member (7A) further includes a second hole (24) that surrounds the behavior detector (1B) and exposes the behavior detector (1B) in the second current path (4B).

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