JP2012141181A - Flow sensor - Google Patents

Abstract

A flow sensor having a wide detectable range is provided.
A flow sensor includes a first substrate 20a having a first recess 201a formed on one surface and a second substrate having a second recess 201b formed at a position facing the first recess 201a on one surface. 20b and an upstream temperature sensor 23 and a downstream side that are arranged between the first recess 201a and the second recess 201b and configured to measure a temperature difference between the heater 21 that heats the fluid and the fluid generated by the heater 21 A detection unit 21 including a temperature sensor 24, and the other surface of the first substrate 20a and the other surface of the second substrate 20b are joined to form a first recess 201a of the first substrate 20a. Among the portions where the second recesses 201b of the second substrate 20b are formed, one thermal conductivity is higher than the other.
[Selection] Figure 1

Description

  Some embodiments according to the present invention relate to a flow sensor including a substrate on which a detection unit for detecting a velocity of a fluid is formed.

  Conventionally, as a flow sensor of this type, a detection unit including a heating unit and a temperature measuring unit is provided on the upper surface, and in a thermal flow meter including a single substrate formed of glass or the like, a groove is provided and glass or the like is provided. It is known that the other groove formed is covered with the lower surface of one substrate to configure the groove as a flow path (see, for example, Patent Document 1).

JP 2009-276264 A

  However, in the thermal type flow meter described in Patent Document 1, glass is used as one substrate and the other substrate, and glass is a material having a relatively low thermal conductivity. ), The sensitivity to the flow rate may be saturated. As a result, there is a problem that detection is not possible when the flow velocity is high, and the detectable range (range ability) is narrow.

  Some aspects of the present invention have been made in view of the above-described problems, and an object thereof is to provide a flow sensor having a wide detectable range.

  The flow sensor according to the present invention includes a first substrate in which a first recess is formed on one surface, and a second substrate in which a second recess is formed at a position facing the first recess on one surface. A detection unit including a substrate, a heater that is disposed between the first recess and the second recess, and that is configured to measure a temperature difference between the fluid generated by the heater and a heater that heats the fluid. And the second surface of the first substrate and the second surface of the second substrate are joined together, and the portion of the first substrate in which the first recess is formed and the second substrate Among the portions where the second recesses are formed, one thermal conductivity is higher than the other thermal conductivity.

  According to such a configuration, the detection unit is disposed between the first recess and the second recess, and the other surface of the first substrate and the second surface of the substrate are joined to the second. Thereby, the detection unit is covered with the first recess and the second recess and is not exposed (exposed) to the outside. In addition, it is possible to prevent the fluid from eroding (invading) from between the first substrate and the second substrate. Furthermore, the first recess and the second recess can form a thin diaphragm as compared with the other portions of the first substrate and the second substrate. Furthermore, one of the portions of the first substrate where the first recess is formed and the portion of the second substrate where the second recess is formed has one thermal conductivity higher than the other. Thereby, compared with the case where the thermal conductivity of a 1st board | substrate and the thermal conductivity of a 2nd board | substrate are comparable as the conventional flow sensor, the part in which the 1st recessed part was formed, and a 2nd recessed part It is possible to increase the average thermal conductivity of the portion where the heat sink is formed, and heat from the heater included in the detection unit is easily conducted to the temperature measurement unit via the first concave portion and the second concave portion that cover the detection portion. Therefore, the thermal coupling between the heater and the temperature measuring unit can be enhanced. Thereby, even when the flow rate is high, the sensitivity to the flow rate is less likely to be saturated, and the detectable range (range ability) can be expanded.

  Preferably, the first substrate and the second substrate have corrosion resistance against a predetermined corrosive substance.

According to such a configuration, the first substrate and the second substrate have corrosion resistance against a predetermined corrosive substance. Thereby, for example, the corrosion resistance of the flow sensor against a predetermined corrosive substance such as a gas (gas) containing SOx, NOx, Cl ₂ , BCl ₃ , or a chemical solution (liquid) containing sulfuric acid or nitric acid can be improved. .

  Preferably, one of the first substrate and the second substrate is glass, and the other material is stainless steel or sapphire.

  According to such a configuration, one material of the first substrate and the second substrate is glass, and the other material is stainless steel or sapphire. Here, glass is a material having a thermal conductivity of about 1.1 [W / m · K] at room temperature, whereas stainless steel has a thermal conductivity of about 14 to 27 [W / m · K] at room temperature. Sapphire is a material having a thermal conductivity of about 46 [W / m · K] at room temperature. Thereby, in the case of the combination of glass and stainless steel, the average thermal conductivity is about 8.4 [W / m · K], and in the case of the combination of glass and sapphire, the average thermal conductivity is 23.4. Since it is about [W / m · K], the average thermal conductivity of the first concave portion and the second concave portion can be increased as compared with the case of a combination of glasses as in the conventional flow sensor. Thereby, a flow sensor with a wide detectable range (range ability) can be easily realized.

Also, glass, stainless steel, and sapphire, for example, SOx, NOx, Cl2, and BCl ₃ gas containing such (gas), corrosion resistance against corrosive materials such as chemical (liquid) containing sulfuric acid and nitric acid Material. Thereby, a flow sensor having high corrosion resistance with respect to a predetermined corrosive substance can be easily realized.

  Furthermore, glass, stainless steel, and sapphire are materials with high mechanical strength. Accordingly, it is possible to provide mechanical strength that can protect the detection unit when dust such as dust or dust contained in the fluid collides with the first recess and the second recess covering the detection unit.

  Moreover, the flow sensor according to the present invention includes a first substrate having a first recess on one surface, and a second substrate having a second recess at a position facing the first recess on one surface. A detector including a heater that is disposed between the first recess and the second recess and configured to measure a temperature difference between the fluid generated by the heater and the fluid that is generated by the heater; The other surface of the first substrate and the second surface of the second substrate are joined together, and the bottom surface of the first recess and the bottom surface of the second recess are made of a predetermined metal film. It is covered.

  According to such a configuration, the detection unit is disposed between the first recess and the second recess, and the other surface of the first substrate and the second surface of the substrate are joined to the second. Thereby, the detection unit is covered with the first recess and the second recess and is not exposed (exposed) to the outside. In addition, it is possible to prevent the fluid from eroding (invading) from between the first substrate and the second substrate. Furthermore, the first recess and the second recess can form a thin diaphragm as compared with the other portions of the first substrate and the second substrate. Furthermore, the bottom surface of the first recess and the bottom surface of the second recess are covered with a predetermined metal film. Here, since the predetermined metal is a material having a relatively high thermal conductivity, the heat from the heater included in the detection unit causes the detection unit to be compared with the case where the predetermined metal is not covered with the predetermined metal film. Since it becomes easy to conduct to the temperature measuring unit via the first recessed portion and the second recessed portion to be covered, the thermal coupling between the heater and the temperature measuring unit can be enhanced.

  Preferably, a first flow path through which the fluid flows is formed on one surface side of the first substrate, and a second flow path through which the fluid flows is formed on one surface side of the second substrate. A flow path forming member provided so as to be formed is further provided.

  According to this configuration, the first flow path through which the fluid flows is formed on one surface side of the first substrate, and the second fluid flows through the one surface side of the second substrate. A flow path is formed. Thereby, since the fluid flows through both the first flow path and the second flow path, compared with the case where the fluid flows through either one of the first flow path and the second flow path. The heat distribution by the heater is likely to change due to the fluid flow. Thereby, the sensitivity of a detection part can be raised with respect to the flow velocity. At this time, the detection unit is arranged in a suspended state between the first flow path and the second flow path. Accordingly, pressure is applied from the fluid to one surface side of the first substrate and one surface side of the second substrate, so that one surface side of the first substrate and one surface of the second substrate are The pressure difference (differential pressure) received from the fluid on both surfaces of the substrate is reduced, so that the stress generated in the first substrate and the second substrate can be reduced, and the noise of the detection signal due to the stress is reduced. be able to.

  Preferably, the flow path forming member has corrosion resistance against a predetermined corrosive substance.

According to such a configuration, the flow path forming member has corrosion resistance against a predetermined corrosive substance. Thus, since the portion exposed to the fluid in the flow sensor has a corrosion resistance, for example, SOx, NOx, Cl2, BCl ₃ gas containing such (gas) and, chemical solution containing sulfuric acid and nitric acid (liquid) It can be suitably used when the fluid contains a predetermined corrosive substance such as.

  Preferably, the temperature measuring unit has a plurality of temperature sensors respectively disposed upstream and downstream of the heater.

  According to such a configuration, the temperature measuring unit has the plurality of temperature sensors respectively disposed on the upstream side and the downstream side with respect to the heater. Thereby, the temperature of the fluid upstream of the heater and the temperature of the downstream fluid can be measured, respectively, and the temperature difference of the fluid generated by the heater can be easily measured.

  According to the present invention, the first concave portion and the second concave portion can form a diaphragm having a smaller thickness than other portions of the first substrate and the second substrate. Thereby, the responsiveness of a detection part can be improved. In addition, as compared with the case where the thermal conductivity of the first substrate and the thermal conductivity of the second substrate are comparable as in the conventional flow sensor, the portion where the first recess is formed and the second recess are The average thermal conductivity of the formed portion can be increased, and heat from the heater included in the detection unit can be easily conducted to the temperature measurement unit through the first and second recesses covering the detection unit. Therefore, the thermal coupling between the heater and the temperature measuring unit can be enhanced. Thereby, even when the flow rate is high, the sensitivity to the flow rate is less likely to be saturated, and the detectable range (range ability) can be expanded. In addition, since the predetermined metal is a material having a relatively high thermal conductivity, heat from the heater included in the detection unit covers the detection unit as compared with a case where the predetermined metal is not covered with the predetermined metal film. Since it becomes easy to conduct to a temperature measuring unit via the 1st crevice and the 2nd crevice, thermal coupling with a heater and a temperature measuring unit can be raised. This also makes it difficult to saturate the sensitivity to the flow rate even when the flow rate is high, and the detection range (range ability) can be expanded.

It is a side sectional view explaining an example of a flow sensor concerning the present invention. FIG. 2 is a bottom view of the upper flow path forming member shown in FIG. 1. It is a top view of the lower flow path forming member shown in FIG. It is a top view of the board | substrate shown in FIG. It is a side sectional view explaining an example of a manufacturing method of the substrate shown in FIG. It is a side sectional view explaining an example of a manufacturing method of the substrate shown in FIG. It is a side sectional view explaining an example of a manufacturing method of the substrate shown in FIG. It is a side sectional view explaining an example of a manufacturing method of the substrate shown in FIG. It is a side sectional view explaining an example of a manufacturing method of the substrate shown in FIG. It is a side sectional view explaining an example of a manufacturing method of the substrate shown in FIG. It is a graph explaining the relationship between the flow velocity and output in the board | substrate shown in FIG. It is a side sectional view explaining other examples of a flow sensor concerning the present invention. FIG. 13 is a side sectional view for explaining an installation example of the flow sensor shown in FIG. 12. It is a side sectional view explaining other examples of a flow sensor concerning the present invention. It is a sectional side view explaining the example of installation of the flow sensor shown in FIG. It is a side sectional view explaining other examples of a flow sensor concerning the present invention. It is a side sectional view explaining other examples of a flow sensor concerning the present invention. FIG. 18 is a side sectional view for explaining the substrate shown in FIG. 17. It is a side sectional view explaining other examples of a flow sensor concerning the present invention. It is a principal part expanded sectional view explaining the board | substrate shown in FIG.

  Embodiments of the present invention will be described below. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions and the like should be determined in light of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings. In the following description, the upper side of the drawing is referred to as “upper”, the lower side as “lower”, the left side as “left”, and the right side as “right”.

  1 to 11 show an example of a flow sensor according to the present invention. FIG. 1 is a side sectional view for explaining an example of a flow sensor according to the present invention. As shown in FIG. 1, the flow sensor 10 includes a substrate 20 including a first substrate 20 a and a second substrate 20 b, an upper flow path forming member 30 installed on the substrate 20, and a substrate 20 below the substrate 20. The lower flow path forming member 40 is provided. The upper flow path forming member 30 and the lower flow path forming member 40 in the present embodiment correspond to an example of “flow path forming member” in the flow sensor of the present invention.

  FIG. 2 is a bottom view of the upper flow path forming member 30 shown in FIG. As shown in FIG. 2, a rectangular recess 31 is provided on the lower surface of the upper flow path forming member 30. The recess 31 forms a second flow path 31a between the opposing surfaces of the substrate 20, that is, the upper surface of the second substrate 20b shown in FIG. The recess 31 is provided with an inflow port 32 and an outflow port 33 that communicate with the outside. As shown in FIG. 1, the inflow port 32 and the outflow port 33 penetrate from the bottom surface of the recess 31 to the upper surface of the upper flow path forming member 30, and the fluid flowing in from the inflow port 32 passes through the second flow path 31a. It flows out from the outlet 33 through. Further, notches 34 and 35 are formed at positions corresponding to electrode portions 26 and 27 of the substrate 20 described later, and when the upper flow path forming member 30 is installed on the substrate 20, the electrode portions 26 and 27 are formed. Is exposed.

  FIG. 3 is a top view of the lower flow path forming member 40 shown in FIG. As shown in FIG. 3, a rectangular recess 41 is provided on the upper surface of the lower flow path forming member 40. The recess 41 forms a first flow path 41a between opposing surfaces of the substrate 20, that is, the lower surface of the first substrate 20a shown in FIG.

Examples of the material of the upper flow path forming member 30 and the lower flow path forming member 40 include silicon (Si), silicon (Si) coated with silicon dioxide (SiO ₂ ), alumina ceramics, glass, sapphire, and stainless steel. Etc. The material of the upper flow path forming member 30 and the lower flow path forming member 40 includes a predetermined corrosive materials, e.g., SOx, NOx, Cl2, and BCl ₃ gas containing such (gas), sulfuric acid and nitric acid What has corrosion resistance with respect to a chemical | medical solution (liquid) etc. is preferable. Specifically, when the corrosive substance contains chlorine (Cl) such as Cl 2 and BCl ₃ , silicon (Si) does not have corrosion resistance to the corrosive substance (low corrosion resistance), and therefore, the upper flow It is not appropriate to use as a material for the path forming member 30 and the lower flow path forming member 40. On the other hand, when the corrosive substance is SOx, NOx, or the like that does not contain chlorine (Cl), silicon (Si) has corrosion resistance (high corrosion resistance) against the corrosive substance. It can be suitably used as a material for the lower flow path forming member 40. The upper flow path forming member 30 and the lower flow path forming member 40 may be made of the same material or different materials.

  FIG. 4 is a top view for explaining the substrate 20 shown in FIG. As illustrated in FIG. 4, the substrate 20 includes a detection unit 21 that is provided at the center of the substrate 20 and detects the fluid velocity. The detection unit 21 includes a heater (resistance element) 22 that heats the fluid, and a pair of resistance elements 23 and 24 that are configured to measure a temperature difference of the fluid generated by the heater 22. Thereby, the thermal flow sensor 10 that detects the velocity (flow velocity) of the fluid from the temperature difference of the fluid can be easily realized (configured). The resistance elements 23 and 24 in the present embodiment correspond to an example of a “temperature measuring unit” in the flow sensor of the present invention.

  The resistance elements 23 and 24 are provided on both sides of the heater 22 on the left side and the right side of the heater 20 with the heater 22 interposed therebetween. The substrate 20 is provided with an ambient temperature sensor (resistive element) 25 and a pair of electrodes 26a, 26b, 26c, 27a, 27b, and 27c provided on the upper side and the lower side of the substrate 20 in plan view. The electrode portions 26 and 27 are further included. The electrodes 26a, 26b, 26c, 27a, 27b, and 27c of the electrode portions 26 and 27 are electrically connected to the heater 22, the resistance elements 23 and 24, and the ambient temperature sensor 25 through wiring formed on the substrate 20. Has been.

  In the flow sensor 10 having such a configuration, for example, as indicated by a block arrow in FIG. 1, the resistance elements 23, 22, and 24 are arranged in order along the flow direction of the fluid to be measured, for example, gas. Placed in. In this case, the resistance element 23 functions as an upstream temperature sensor provided upstream of the heater 22 (left side in FIG. 1), and the resistance element 24 is downstream of the heater 22 (right side in FIG. 1). It functions as a provided downstream temperature sensor. As described above, the resistance element 23 is disposed on the upstream side of the heater 22 and the resistance element 23 is disposed on the downstream side, whereby the temperature of the upstream fluid and the temperature of the downstream fluid with respect to the heater 22 are respectively set. It is possible to measure, and the temperature difference of the fluid described later generated by the heater 22 can be easily measured.

  As will be described later, a portion of the substrate 20 where the detection unit 21 is provided forms a diaphragm having a small heat capacity. The ambient temperature sensor 25 measures the temperature of gas flowing through a pipe line (not shown) where the flow sensor 10 is installed. The heater 22 is exemplarily disposed at the center of the substrate 20 and is heated so as to be higher than the temperature measured by the ambient temperature sensor 25. The upstream temperature sensor 23 is used to detect a temperature upstream of the heater 22, and the downstream temperature sensor 24 is used to detect a temperature downstream of the heater 22.

  Here, when there is no flow in the pipe, the heat applied by the heater 21 is distributed symmetrically in the upstream direction and the downstream direction. Accordingly, the temperatures of the upstream temperature sensor 23 and the downstream temperature sensor 24 are equal, and the resistance values of the upstream temperature sensor 23 and the downstream temperature sensor 24 are equal. On the other hand, when the gas in the pipe line flows from upstream to downstream, the heat applied by the heater 22 is carried in the downstream direction. Therefore, the temperature of the downstream temperature sensor 24 is higher than the temperature of the upstream temperature sensor 23.

  Such a temperature difference causes a difference between the resistance value of the upstream temperature sensor 23 and the resistance value of the downstream temperature sensor 24. The difference between the resistance value of the downstream temperature sensor 24 and the resistance value of the upstream temperature sensor 23 has a correlation with the gas velocity and flow rate in the pipe. Therefore, based on the difference between the resistance value of the downstream temperature sensor 24 and the resistance value of the upstream temperature sensor 23, the speed (flow velocity) and flow rate of the fluid flowing through the pipeline can be calculated. Information on resistance values of the resistance elements 22, 23 and 24 can be taken out as electrical signals through the electrode portions 26 and 27 shown in FIG.

  As shown in FIG. 4, the substrate 20 is provided with a pair of through holes 28 and 29 formed on both the left and right sides of the detection unit 21 with the detection unit 21 interposed therebetween. As shown in FIG. 1, the through holes 28 and 29 penetrate from the upper surface to the lower surface of the substrate 20, and the through hole 28 is disposed upstream from the detection unit 21 (on the left side in FIG. 1). It functions as a side through hole, and the through hole 29 is arranged on the downstream side (right side in FIG. 1) with respect to the detection unit 21 and functions as a downstream through hole. Accordingly, as shown in FIG. 1, when the fluid flows through the second flow path 31 a, the fluid flows through the first flow path 41 a through the upstream through hole 28 and through the downstream through hole 29. It becomes possible to return to the 1st flow path 31a again.

  In this case, as indicated by an arrow in FIG. 1, the fluid flowing in from the inflow port 32 flows through the second flow path 31 a formed by the upper flow path forming member 30 and passes through the upstream through hole 28. The first flow path 41a formed by the lower flow path forming member 40 is circulated. Further, the fluid that has flowed through the second flow path 31 a flows out from the outflow port 32, and the fluid that has flowed through the first flow path 41 a flows out from the outflow port 32 through the downstream side through hole 29. Thus, the lower flow path forming member 40 forms the first flow path 41a through which the fluid flows on one surface (the lower surface in FIG. 1) side of the first substrate 20a, and the upper flow path forming member 30 is By forming the second flow path 31a through which the fluid flows on the one surface (upper surface in FIG. 1) side of the two substrates 20b, the fluid flows through both the first flow path 41a and the second flow path 31a. As compared with the case where the fluid flows through either the first flow path 41a or the second flow path 31a, the heat distribution by the heater 22 is easily changed by the flow of the fluid. At this time, the detection unit 21 is arranged in a suspended state between the first flow path 41a and the second flow path 31a.

  Next, an example of a method for manufacturing the substrate 20 will be described with reference to FIGS.

  5 to 10 are side sectional views for explaining an example of a method for manufacturing the substrate 20 shown in FIG. 5 to 8 and FIG. 10 are cross-sectional views taken along the line I-I shown in FIG. 4, and FIG. 9 is a cross-sectional view taken along the line II-II shown in FIG. First, as shown in FIG. 5, a plate-like wafer A is prepared as a member serving as a base of the first substrate 20 a shown in FIG. 1. The wafer A has a thickness of about 250 [μm], for example.

  Next, as shown in FIG. 6, a recess like a counterbore is formed in the center of the lower surface of the wafer A by machining using a drill or the like. Next, a metal such as platinum is attached to the surface (upper surface) opposite to the portion where the recess is formed by a method such as sputtering, CVD, or vacuum deposition, thereby forming each element constituting the detection unit 21 ( Patterning). Further, by the same method, the electrodes constituting the electrode portions 26 and 27 are formed (patterned) on both sides (right side and left side) sandwiching the detection portion 21, and the detection portion and the electrode portions 26 and 27 are connected. A wiring to be formed is formed (patterned).

  Next, a plate-like wafer B similar to the wafer A shown in FIG. 5 is prepared as a base member of the second substrate 20a shown in FIG. 1, and the upper surface of the wafer B as shown in FIG. A recess like a counterbore is formed in the center by machining using a drill or the like. Further, when the wafer A and the wafer B, which will be described later, are bonded, through holes are respectively formed in the wafer B at positions corresponding to the electrode portions 26 and 27 of the wafer A. Similarly, when the wafer A and the wafer B are bonded together, a recess having a predetermined depth such as a spot facing is formed in the wafer B at a position corresponding to the detection unit 21 and the wiring of the wafer A. Thereby, when the wafer A and the wafer B are bonded to each other, it is possible to prevent a bonding step due to a step caused by the detection unit 21 and the wiring provided on the wafer A.

  Next, as illustrated in FIG. 8, the lower surface of the wafer B illustrated in FIG. 7 is placed on the upper surface of the wafer A illustrated in FIG. 6, and the upper surface of the wafer A and the lower surface of the wafer B are bonded. As a result, the detection unit 21 provided on the upper surface of the wafer A is covered with the wafer A and the wafer B.

  As a bonding method, for example, diffusion bonding, surface activated bonding (normal temperature bonding) in which ion beams using an inert gas such as argon (Ar) are irradiated and activated and then bonded are joined, gold or silver For example, brazing, anodic bonding, and the like, which are performed after the brazing material is bonded to both surfaces.

  Note that the term “joining” in the present specification means a broad sense joining that joins things together, and is a concept including brazing. Moreover, it is preferable that the term “joining” means to exclude a method using an adhesive.

  Next, as shown in FIG. 9, through holes 28 and 29 penetrating from the upper surface of the wafer B to the lower surface of the wafer A are formed on both sides (right side and left side) sandwiching the detection unit 21 by machining using a drill or the like. Form.

  Finally, as shown in FIG. 10, the etching is indicated by the block arrows in FIG. 10 to control the thicknesses of the portions where the recesses of the wafer A and the recesses of the wafer B are formed. . Thereby, the substrate 20 including the first substrate 20a and the second substrate 20b is manufactured.

  In this substrate 20, as a result of etching, a first recess 201a is formed on one surface (the upper surface in FIG. 10) of the first substrate 20a, and the first surface on the one surface (the lower surface in FIG. 10) of the second substrate 20b. A second recess 201b is formed at a position facing the first recess 201a. Moreover, the detection part 21 is arrange | positioned between the 1st recessed part 201a and the 2nd recessed part 201b. Thereby, the detection part 21 is covered with the 1st recessed part 201a and the 2nd recessed part 201b, and is not exposed (exposed) with respect to the exterior. Further, since the other surface (upper surface in FIG. 10) of the first substrate 20a and the other surface (lower surface in FIG. 10) of the second substrate 20b are joined, the first substrate 20a and the second substrate 20b are joined together. It is possible to prevent the fluid from eroding (invading) from the middle.

  The 1st crevice 201a and the 2nd crevice 201b comprise diaphragm 201 with small heat capacity, and diaphragm 201 has thickness of about 10-100 [micrometers], for example. In this way, the first recess 201a is formed on one surface (upper surface in FIG. 10) of the first substrate 20a, and the position facing the first recess 201a on one surface (lower surface in FIG. 10) of the second substrate 20b. In addition, since the second recess 201b is formed, the first recess 201a and the second recess 201b form a diaphragm 201 that is thinner than the other portions of the first substrate 20a and the second substrate 20b. It becomes possible.

  FIG. 11 is a graph for explaining the relationship between the flow velocity and the output in the substrate 20 shown in FIG. In FIG. 11, the horizontal axis represents the average velocity (average flow velocity) [m / s] of the fluid, and the vertical axis represents the output [−] normalized by setting the output of the average flow velocity 1 [m / s] to “1”. (Dimensionless).

  Here, when the Pyrex (registered trademark) glass is used as the material of the first substrate and the second substrate as in the conventional flow sensor, for example, the thermal conductivity of the first substrate and the thermal conductivity of the second substrate are In the case of the same level, the output is saturated when the average flow velocity is about 10 [m / s], as plotted (drawn) with diamonds in FIG. 11. In the conventional flow sensor, the average flow velocity is 10 [m / s]. The above high flow rate range could not be detected.

  On the other hand, in the substrate 20 of the present invention, the thermal conductivity of the first substrate 20a is higher than the thermal conductivity of the second substrate 20b. That is, when, for example, Pyrex (registered trademark) glass is used as the material of the first substrate 20a and stainless steel is used as the material of the second substrate 20b, for example, plotting (drawing) with a square in FIG. The output does not saturate until the average flow rate is about 20 [m / s]. Further, when, for example, Pyrex (registered trademark) glass is used as the material of the first substrate 20a and sapphire is used as the material of the second substrate 20b, for example, the output is plotted in a triangle in FIG. Does not saturate until the average flow velocity is about 40 [m / s]. As described above, the thermal conductivity of the portion of the first substrate 20a where the first recess 201a is formed is higher than the thermal conductivity of the portion of the second substrate 20b where the second recess 201b is formed. Compared to the case where the thermal conductivity of the first substrate and the thermal conductivity of the second substrate are comparable, the average thermal conductivity of the first recess 201a and the second recess 201b covering the detection unit 21 is The heat by the heater 22 included in the detection unit 21 can be easily conducted to the upstream temperature sensor 23 and the downstream temperature sensor 24 through the first recess 201a and the second recess 201b covering the detection unit 21. Therefore, the thermal coupling between the heater 22, the upstream temperature sensor 23, and the downstream temperature sensor 24 can be enhanced.

  In addition, it is not limited to the case where the thermal conductivity of the 1st board | substrate 20a is higher than the thermal conductivity of the 2nd board | substrate 20b, Even if the thermal conductivity of the 2nd board | substrate 20b is higher than the thermal conductivity of the 1st board | substrate 20a. Good. For example, when using, for example, stainless steel as the material of the first substrate 20a and using, for example, Pyrex (registered trademark) glass as the material of the second substrate 20b, it is the same as plotted (drawn) with a square in FIG. It is known from experiments that the results can be obtained. Further, when using, for example, sapphire as the material of the first substrate 20a and using, for example, Pyrex (registered trademark) glass as the material of the second substrate 20b, the same as plotted (drawn) with triangles in FIG. Experiments have shown that results can be obtained.

  Further, in order to detect the range of the high flow velocity, not the overall thermal conductivity of the first substrate 20a and the second substrate 20b, in particular, the first concave portion 201a and the second concave portion 201b that cover the detection unit 21, that is, The thermal conductivity of the diaphragm 201 becomes a problem (important). Therefore, it is only necessary that one of the portions where the first recess 201a is formed and the portion where the second recess 201b is formed has a higher thermal conductivity than the other. Even in this case, it has been experimentally known that the same result as that shown in FIG. 11 can be obtained.

  Examples of the material of the first substrate 20a and the second substrate 20b include glass, inconel, stainless steel, sapphire, alumina, aluminum alloy, copper, and the like. The thermal conductivity of these materials is 1.1 [W / m · K] for glass, 11.5 to 14.8 [W / m · K] for glass, and 14 for stainless steel at a temperature of 300 [K]. 27 [W / m · K], Sapphire 46 [W / m · K], Alumina 36 [W / m · K], Aluminum Alloy 96-222 [W / m · K], Copper 398 [ W / m · K].

Moreover, it is preferable that the 1st board | substrate 20a and the 2nd board | substrate 20b are what has corrosion resistance with respect to a predetermined | prescribed corrosive substance, for example, glass, inconel, stainless steel, sapphire, alumina, etc. Thus, for example, SOx, NOx, Cl2, and BCl ₃ gas containing such (gas), for a given corrosive substances, such as chemical (liquid) containing sulfuric acid and nitric acid, enhances the corrosion resistance of the flow sensor 10 be able to. Further, since the first substrate 20a and the second substrate 20b are joined, it is possible to prevent a predetermined corrosive substance from eroding (invading) from between the first substrate 20a and the second substrate 20b. It becomes.

  In particular, it is more preferable that one of the first substrate 20a and the second substrate 20b is glass, and the other material is stainless steel or sapphire. Here, glass is a material having a thermal conductivity of about 1.1 [W / m · K] at room temperature, whereas stainless steel has a thermal conductivity of about 14 to 27 [W / m · K] at room temperature. Sapphire is a material having a thermal conductivity of about 46 [W / m · K] at room temperature. Thereby, in the case of the combination of glass and stainless steel, the average thermal conductivity is about 8.4 [W / m · K], and in the case of the combination of glass and sapphire, the average thermal conductivity is 23.4. Since it is about [W / m · K], the average thermal conductivity of the first substrate 20a and the second substrate 20b can be increased as compared with the case of combining glass as in the conventional flow sensor. .

Also, glass, stainless steel, and sapphire, for example, SOx, NOx, Cl2, and BCl ₃ gas containing such (gas), corrosion resistance against corrosive materials such as chemical (liquid) containing sulfuric acid and nitric acid Material. Thereby, a flow sensor having high corrosion resistance with respect to a predetermined corrosive substance can be easily realized.

  Furthermore, glass, stainless steel, and sapphire are materials with high mechanical strength. Accordingly, it is possible to provide mechanical strength that can protect the detection unit 21 when dust such as dust or dust contained in the fluid collides with the first recess 201a and the second recess 201b that cover the detection unit 21.

  12 is a side sectional view for explaining another example of the flow sensor according to the present invention, and FIG. 13 is a side sectional view for explaining an installation example of the flow sensor 10A shown in FIG. The flow sensor according to the present invention is not limited to the examples shown in FIGS. For example, as shown in FIG. 12, in the flow sensor 10A, the substrate 20 shown in FIG. 1 is arranged upside down, the upper flow path forming member 30 is installed on the first substrate 20a, and the second substrate 20b A lower flow path forming member 40 is installed below. The lower flow path forming member 40 is provided with an inlet 42 and an outlet 43 that communicate with the outside and the second flow path 31a.

  In this case, as shown in FIG. 13, the flow sensor 10 </ b> A is assembled and installed through an O (O) ring X in a main body Y in which a fluid flows in a predetermined direction (from left to right in FIG. 13). . Thereby, when the fluid flows through the second flow path 31a, the fluid flows through the first flow path 41a through the upstream through hole 28 shown in FIG. 11 and passes through the downstream through hole 29 shown in FIG. Thus, it is possible to return to the second flow path 31a again.

  14 is a side sectional view for explaining another example of the flow sensor according to the present invention, and FIG. 15 is a side sectional view for explaining an installation example of the flow sensor 10B shown in FIG. The flow path forming member only needs to be provided on one surface side of the first substrate 20a and one surface side of the second substrate 20b so as to form a flow path. It is not limited to forming. For example, as shown in FIG. 14, in the flow sensor 10B, the substrate 20 shown in FIG. 1 is arranged upside down, and the upper flow path forming member 30 is installed on the first substrate 20a.

  In this case, as shown in FIG. 15, the flow sensor 10B flows in a predetermined direction (from the left side to the right side in FIG. 15), and the flow sensor 10B is installed on the main body W with a part of the upper surface opened to cover the opening. The Thereby, the 2nd flow path 31a is formed between the main body B and one surface (lower surface in FIG. 15) of the 2nd board | substrate 20b shown in FIG.

  FIG. 16 is a side sectional view for explaining another example of the flow sensor according to the present invention. Further, the fluid is not limited to passing through the upstream side through hole 28 and the downstream side through hole 29. For example, as shown in FIG. 16, the flow sensor 10 </ b> C includes an inlet 32 at one end (left end in FIG. 16) of the recess 31 shown in FIG. 2 that forms the first flow path 31 a, and the other end of the recess 31. An outlet 33 is provided at the right end in FIG. Further, the inlet 42 is provided at one end (left end in FIG. 16) of the recess 41 shown in FIG. 3 forming the second flow path 31a, and the outlet 43 is provided at the other end (right end in FIG. 16) of the recess 41. It has been.

  In this case, the flow sensor 10C is arranged with the inlet 32 and the inlet 42 facing the direction in which the fluid flows as indicated by the block arrows in FIG. As a result, the fluid flows through the first flow path 31 a through the inlet 32 and the outlet 33, and flows through the second flow path 41 a through the inlet 42 and the outlet 43. Therefore, the substrate 20 may not have the upstream through hole 28 and the downstream through hole 29.

  17 is a side sectional view for explaining another example of the flow sensor according to the present invention, and FIG. 18 is a side sectional view for explaining the substrate 20A shown in FIG. 18 is a cross-sectional view taken along the line III-III shown in FIG. The substrate is not limited to the case where one conductivity is higher than the other conductivity among the portion where the first recess 201a covering the detection unit 21 and the portion where the second recess 201b is formed. For example, as shown in FIG. 17, the flow sensor 10D includes a substrate 20A.

  As shown in FIG. 18, the substrate 20A has a first recess 201a formed on one surface (the upper surface in FIG. 18) of the first substrate 20a, like the substrate 20 shown in FIG. A second recess 201b is formed at a position facing the first recess 201a on one surface (the lower surface in FIG. 18). The detection unit 21 is disposed between the first recess 201a and the second recess 201b, and the other surface (upper surface in FIG. 18) of the first substrate 20a and the other surface (lower surface in FIG. 18) of the second substrate 20b. Are joined. Moreover, the 1st recessed part 201a and the 2nd recessed part 201b comprise the diaphragm 201 with small heat capacity.

  Further, in the substrate 20A, the bottom surface of the first recess 201a and the bottom surface of the second recess 201b are covered with a predetermined metal film C. Here, since the predetermined metal is a material having a relatively high thermal conductivity, the average of the first concave portion 201a and the second concave portion 201b is compared with a case where the predetermined metal is not covered with the predetermined metal film C. The heat conductivity can be increased, and the heat from the heater 22 included in the detection unit 21 is transferred to the upstream temperature sensor 23 and the downstream temperature sensor 24 via the first recess 201a and the second recess 201b that cover the detection unit 21. Since it becomes easy to conduct, the thermal coupling between the heater 22 and the upstream temperature sensor 23 and the downstream temperature sensor 24 can be enhanced.

  Examples of the predetermined metal include platinum (Pt), gold (Au), aluminum (Al), copper (Cu), and nickel (Ni). These metals can be attached to the bottom surface of the first recess 201a and the bottom surface of the second recess 201b by a method such as a sputtering method, a CVD method, or a vacuum deposition method to form the film C.

  In addition, it becomes possible to set to a desired detectable range (range ability) by changing the kind of the predetermined metal used as the material of the film C, the thickness of the film C, and the like.

  FIG. 19 is a side sectional view for explaining another example of the flow sensor according to the present invention, and FIG. 20 is an enlarged sectional view of a main part for explaining the substrate shown in FIG. Further, as a substrate different from the substrate shown in FIGS. 1 to 18, for example, as shown in FIG. 19, the flow sensor 10E includes a substrate 20B.

  As shown in FIG. 20, the substrate 20B has a first recess 201a formed on one surface (the upper surface in FIG. 20) of the first substrate 20a, like the substrate 20 shown in FIG. A second recess 201b is formed at a position facing the first recess 201a on one surface (the lower surface in FIG. 20). The detector 21 is disposed between the first recess 201a and the second recess 201b, and the first recess 201a and the second recess 201b form a diaphragm 201 having a small heat capacity.

  Further, the substrate 20B has an arch-shaped curved surface with the position of the heater 22 as the apex (center) on the bottom surface of the first recess 201a and the bottom surface of the second recess 201b. As a result, the curved surface portion, that is, the portion where the heater 22, the upstream temperature sensor 23, and the downstream temperature sensor 24 are positioned is thicker than the other portions on the bottom surface of the first recess 201a and the bottom surface of the second recess 201b. Is getting thicker. This also facilitates conduction of heat from the heater 22 included in the detection unit 21 to the upstream temperature sensor 23 and the downstream temperature sensor 24 via the first recess 201a and the second recess 201b covering the detection unit 21. The thermal coupling between the heater 22, the upstream temperature sensor 23, and the downstream temperature sensor 24 can be enhanced.

  In addition, it is preferable that the thickness of the arch-shaped curved portion is not more than twice the thickness of the other portion of the bottom surface of the first recess 201a and the bottom surface of the second recess 201b. For example, when the thickness of the bottom surface of the first concave portion 201a and the other portion of the bottom surface of the second concave portion 201b is 100 [μm], the bottom surface of the first concave portion 201a is up to 50 [ μm], and the bottom surface of the second recess 201b is set to 50 [μm] at the maximum in the downward direction.

  Thus, according to the flow sensors 10, 10A, 10B, 10C, and 10E in the present embodiment, the detection unit 21 is disposed between the first recess 201a and the second recess 201b, and the other of the first substrate 20a. This surface (upper surface in FIGS. 10 and 18) and the other surface (lower surface in FIGS. 10 and 18) of the second substrate 20b are joined. Thereby, the detection part 21 is covered with the 1st recessed part 201a and the 2nd recessed part 201b, and is not exposed (exposed) with respect to the exterior. It is also possible to prevent the fluid from eroding (invading) from between the first substrate 20a and the second substrate 20b. Furthermore, the first concave portion 201a and the second concave portion 201b can form a diaphragm 201 that is thinner than the other portions of the first substrate 20a and the second substrate 20b. Thereby, the responsiveness of the detection part 21 can be improved. Furthermore, one of the portions of the first substrate 20a where the first recess 201a is formed and the portion of the second substrate 20b where the second recess 201b is formed has one thermal conductivity higher than the other. Thereby, compared with the case where the thermal conductivity of the first substrate and the thermal conductivity of the second substrate are comparable as in the conventional flow sensor, the portion where the first recess 201a is formed and the second recess 201b. The average thermal conductivity of the portion where the heat sink is formed can be increased, and the heat from the heater 22 included in the detection unit 21 is detected by the upstream temperature sensor via the first recess 201a and the second recess 201b covering the detection unit 21. 23 and the downstream temperature sensor 24 can be easily conducted, so that the thermal coupling between the heater 22 and the upstream temperature sensor 23 and the downstream temperature sensor 24 can be enhanced. Thereby, even when the flow rate is high, the sensitivity to the flow rate is less likely to be saturated, and the detectable range (range ability) can be expanded.

Further, according to the flow sensors 10, 10A, 10B, 10C, and 10E in the present embodiment, the first substrate 20a and the second substrate 20b have corrosion resistance against a predetermined corrosive substance. Thus, for example, SOx, NOx, Cl2, and BCl ₃ gas containing such (gas), for a given corrosive substances, such as chemical (liquid) containing sulfuric acid and nitric acid, flow sensor 10, 10A, 10B , 10C, 10E can be improved.

  Further, according to the flow sensors 10, 10A, 10B, 10C, and 10E in the present embodiment, one of the first substrate 20a and the second substrate 20b is glass, and the other material is stainless steel or sapphire. is there. Here, glass is a material having a thermal conductivity of about 1.1 [W / m · K] at room temperature, whereas stainless steel has a thermal conductivity of about 14 to 27 [W / m · K] at room temperature. Sapphire is a material having a thermal conductivity of about 46 [W / m · K] at room temperature. Thereby, in the case of the combination of glass and stainless steel, the average thermal conductivity is about 8.4 [W / m · K], and in the case of the combination of glass and sapphire, the average thermal conductivity is 23.4. Since it is about [W / m · K], the average thermal conductivity of the first substrate 20a and the second substrate 20b can be increased as compared with the case of combining glass as in the conventional flow sensor. . Thereby, the flow sensors 10, 10A, 10B, 10C, and 10E having a wide detectable range (range ability) can be easily realized.

Also, glass, stainless steel, and sapphire, for example, SOx, NOx, Cl2, and BCl ₃ gas containing such (gas), corrosion resistance against corrosive materials such as chemical (liquid) containing sulfuric acid and nitric acid Material. Thereby, the flow sensors 10, 10A, 10B, 10C, and 10E having high corrosion resistance against a predetermined corrosive substance can be easily realized.

  Furthermore, glass, stainless steel, and sapphire are materials with high mechanical strength. Accordingly, it is possible to provide mechanical strength that can protect the detection unit 21 when dust such as dust or dust contained in the fluid collides with the first recess 201a and the second recess 201b that cover the detection unit 21.

  Moreover, according to the flow sensor 10D in the present embodiment, the detection unit 21 is disposed between the first recess 201a and the second recess 201b. Thereby, the detection part 21 is covered with the 1st recessed part 201a and the 2nd recessed part 201b, and is not exposed (exposed) with respect to the exterior. Further, the first concave portion 201a and the second concave portion 201b can form a diaphragm 201 having a smaller thickness than other portions of the first substrate 20a and the second substrate 20b. Thereby, the responsiveness of the detection part 21 can be improved. Furthermore, the bottom surface of the first recess 201a and the bottom surface of the second recess 201b are covered with a predetermined metal film C. Here, since the predetermined metal is a material having a relatively high thermal conductivity, the average of the first concave portion 201a and the second concave portion 201b is compared with a case where the predetermined metal is not covered with the predetermined metal film C. The heat conductivity can be increased, and the heat from the heater 22 included in the detection unit 21 is transferred to the upstream temperature sensor 23 and the downstream temperature sensor 24 via the first recess 201a and the second recess 201b that cover the detection unit 21. Since it becomes easy to conduct, the thermal coupling between the heater 22 and the upstream temperature sensor 23 and the downstream temperature sensor 24 can be enhanced. Thereby, even when the flow rate is high, the sensitivity to the flow rate is less likely to be saturated, and the detectable range (range ability) can be expanded.

  Further, according to the flow sensors 10, 10A, 10B, 10C, 10D, and 10E in the present embodiment, one surface of the first substrate 20a (the bottom surface in FIGS. 1, 16, 17, and 19; A first flow path 41a through which a fluid flows is formed on the upper surface side in FIG. 14, and one surface of the second substrate 20b (the upper surface in FIGS. 1, 16, 17, and 19; in FIGS. 12, 15) A second flow path 31a through which fluid flows is formed on the lower surface side. Thereby, since the fluid flows through both the first flow path 41a and the second flow path 31a, compared with the case where the fluid flows through either the first flow path 41a or the second flow path 31a. The heat distribution by the heater 22 is likely to change due to the fluid flow. Thereby, the sensitivity of a detection part can be raised with respect to the flow velocity. At this time, the detection unit 21 is arranged in a suspended state between the first flow path 41a and the second flow path 31a. Thereby, one surface of the first substrate (the lower surface in FIGS. 1, 16, 17, and 19 and the upper surface in FIGS. 12 and 14) and one surface of the second substrate 20b (FIG. 1, FIG. 16, 17, and 19, pressure is applied from the fluid to the upper surface and the lower surface in FIGS. 12 and 15, so that one surface of the first substrate 20 a (FIGS. 1, 16, 17, and 19). On the lower surface, the upper surface in FIGS. 12 and 14 and the one surface of the second substrate 20b (the upper surface in FIGS. 1, 16, 17, and 19 and the lower surface in FIGS. 12 and 15), The pressure difference (differential pressure) received from the fluid is reduced, the stress generated in the first substrate 20a and the second substrate 20b can be reduced, and the noise of the detection signal due to the stress can be reduced. .

Further, according to the flow sensors 10, 10A, 10B, 10C, 10D, and 10E in the present embodiment, the upper flow path forming member 30 and the lower flow path forming member 40 have corrosion resistance against a predetermined corrosive substance. Thus, since a flow sensor 10, 10A, 10B, 10C, 10D, the portion exposed to the fluid at 10E corrosion resistance, e.g., SOx, NOx, Cl2, BCl ₃ gas containing such (gas) It can also be suitably used when the fluid contains a predetermined corrosive substance such as a chemical solution (liquid) containing sulfuric acid or nitric acid.

  Further, according to the flow sensors 10, 10 </ b> A, 10 </ b> B, 10 </ b> C, 10 </ b> D, and 10 </ b> E in the present embodiment, the upstream temperature sensor 23 and the temperature measuring unit disposed on the upstream side and the downstream side with respect to the heater 22 respectively. A downstream temperature sensor 24 is provided. Thereby, the temperature of the fluid upstream and the temperature of the fluid downstream of the heater 22 can be measured, respectively, and the temperature difference of the fluid generated by the heater 22 can be easily measured.

  Note that the configurations of the above-described embodiments may be combined or some components may be replaced. The configuration of the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention.

10, 10A, 10B, 10C, 10D, 10E ... Flow sensor 20 ... Substrate 20a ... First substrate 20b ... Second substrate 21 ... Detection unit 22 ... Heater (resistance element)
23 ... Upstream temperature sensor (resistive element)
24 ... downstream temperature sensor (resistive element)
28 ... Upstream side through hole 29 ... Downstream side through hole 30 ... Upper flow path forming member 31a ... Second flow path 40 ... Lower flow path forming member 41a ... First flow path 201a ... First recess 201b ... Second recess

Claims (7)

A first substrate having a first recess formed on one side;
A second substrate in which a second recess is formed at a position facing the first recess on one surface;
A detection unit that is disposed between the first recess and the second recess and includes a heater that heats the fluid and a temperature measurement unit configured to measure a temperature difference of the fluid generated by the heater; With
The other surface of the first substrate and the second surface of the second substrate are bonded to each other;
Of the portion of the first substrate where the first recess is formed and the portion of the second substrate where the second recess is formed, one thermal conductivity is higher than the other thermal conductivity. A flow sensor characterized by The flow sensor according to claim 1, wherein the first substrate and the second substrate have corrosion resistance against a predetermined corrosive substance. The flow sensor according to claim 1 or 2, wherein one of the first substrate and the second substrate is made of glass, and the other material is stainless steel or sapphire. A first substrate having a first recess on one side;
A second substrate having a second recess at a position facing the first recess on one surface;
A detection unit that is disposed between the first recess and the second recess and includes a heater that heats the fluid and a temperature measurement unit configured to measure a temperature difference of the fluid generated by the heater; With
The other surface of the first substrate and the second surface of the second substrate are bonded to each other;
The bottom surface of the first recess and the bottom surface of the second recess are covered with a predetermined metal film. A first flow path through which the fluid flows is formed on one surface side of the first substrate, and a second flow path through which the fluid flows is formed on one surface side of the second substrate. The flow sensor according to any one of claims 1 to 4, further comprising a flow path forming member provided on the surface. The flow sensor according to claim 5, wherein the flow path forming member has corrosion resistance against a predetermined corrosive substance. The flow sensor according to any one of claims 1 to 6, wherein the temperature measuring unit includes a plurality of temperature sensors respectively disposed upstream and downstream of the heater.

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