JP2010230601A - Sensing unit and thermal flow sensor mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extremely inexpensive thermal flow sensor of a simple structure for responding to various applications considering fluid temperature, viscosity, flammability, chemical stability or the like in measuring flow (mainly flow rate and the flow velocity) of fluid to be measured of liquid or gas. <P>SOLUTION: The sensing unit of the thermal flow sensor including a substrate having a heater and temperature sensor different according to application, and a flow channel of an internal shape according to the application constituting the thermal type flow sensor are separately prepared. A structure without leakage of fluid where the sensing unit and the flow channel are selected, combined and attached according to the application is formed. In this structure, the electrical terminals from the heater and temperature sensor are electrically interconnected via the substrate from the outside of the flow channel. In this structure, the heater and temperature sensor directly come into contact with the fluid, and the response speed and sensitivity are increased. An electric circuit measuring unit having a control circuit, arithmetic circuit, or the like is attached as necessary. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sensing unit that is a part of a thermal flow sensor that measures the flow rate, flow rate, and the like of a fluid that is a gas or a liquid, and a thermal flow sensor equipped with the sensing unit. A thermal flow sensor is provided.

  Conventionally, the present inventor has invented an “electric heater” (Patent Document 1) in which a resistor, such as a platinum thin film, is formed on a thin film that has been suspended in the air and is used as a heater. It is applied as a micro heater. Furthermore, the present inventor invented a “heating diode temperature measuring device, an infrared temperature measuring device using the same, a flow rate measuring device, and a method for manufacturing a flow rate sensing unit” (Patent Document 2). Since the semiconductor diode can also be used as a temperature sensor, it has been proposed to use it as a heater / temperature sensor. After that, the present applicants have found that “temperature detection method, temperature sensor and infrared sensor using the same” (Patent Document 3) and “calibration method such as current detection type thermocouple, current detection type thermocouple, infrared sensor and infrared ray”. Invented the “detector” (Patent Document 4) and measured the short-circuit current based on the thermoelectromotive force of the thermocouple, rather than measuring the temperature difference by measuring the open circuit voltage using a pair of thermocouples. Theoretically, it was shown that the sensitivity was higher than that of the thermopile, and was named a current detection type thermocouple. In addition, a thermocouple heater that can be used not only as a temperature difference sensor but also as a heater has been invented (Japanese Patent Application No. 2007-248520).

In general, a thin film that is formed on a substrate but floats in the air (thin film that is thermally separated from the substrate). When the heated thin film is stopped, the ambient temperature Tc is determined by Newton's law of cooling. Heat is radiated and cooled in proportion to the temperature difference (T-Tc) between the temperature of a certain substrate (ambient temperature before heating) and the temperature T of the heated thin film, and finally becomes equal to the temperature of the substrate. Thus, the temperature change of the temperature sensor when the temperature of the heated object conducts heat to the surrounding medium and the temperature rises or falls in relation to the current thermal conductivity of the surrounding medium. In a thermal conductivity sensor used to measure and measure the physical quantity to be measured of the surrounding medium, such as flow velocity, degree of vacuum, impurity concentration, enthalpy change, etc., the ambient temperature Tc is higher than the absolute temperature sensor. The temperature difference from the temperature T of the heated thin film is important. Thus, in order to measure the temperature difference, a small temperature difference sensor that outputs only the temperature difference is preferable because it can be measured with almost no influence of changes in the ambient temperature.

The inventor previously invented a gas flow sensor and an impurity concentration sensor using a current detection type thermocouple which is a temperature difference sensor (Japanese Patent Application No. 2007-305099). However, in this case, since the sensor has a micro valve, the manufacturing variation is not necessarily good, and the manufacturing cost is high. As a flow sensor, an inexpensive sensor having a slightly simpler structure has been desired.

In addition, conventionally, a groove-shaped channel formed on a substrate is bridged, and a thin film bridge (a thin film bridge floating in the air) thermally separated from this substrate is formed symmetrically along three grooves, There was a gas flow sensor in which a platinum thin film was formed, using the thin film bridge in the center as a heater and the thin film bridges on both sides as temperature sensors (USP4478077). This is because, when there is no gas flow along the flow path, the temperatures of the thin film bridges on both sides that are symmetrical about the central heater are equal, but if there is a gas flow, the upstream thin film bridge has a cold gas flow. As it flows, it cools, and on the downstream side, it receives heat from the central heater thin film bridge and rises in temperature. In this way, the gas flow causes a temperature difference between the thin film bridges on both sides of the heater, and this is a method for measuring the gas flow using this. However, since a resistance temperature sensor such as a platinum thin film is an absolute temperature sensor, the resistance itself corresponds to the absolute temperature. Therefore, in order to measure the temperature difference, it is necessary to prepare two absolute temperature sensors, and to calculate the difference between these outputs, and to reflect the ambient temperature change as it is. It was unsuitable.

In the conventional thermal type flow sensor, since an absolute temperature sensor such as a platinum heater is used in many cases, it is difficult to compensate the ambient temperature. In addition, a casing including a special dedicated flow path has to be an expensive flow sensor.

JP 55-111931 PR (Patent No. 1398241) JP 2006-250736 A JP-A-2005-221238 JP 2008-107307 A

  The present invention has been made to satisfy the above-mentioned demands, and in measuring the flow (mainly flow rate and flow velocity) of a fluid to be measured such as liquid or gas, fluid temperature, viscosity, flammability, chemical stability. It is an object of the present invention to provide a thermal flow sensor having a very inexpensive and simple structure that can be used in various applications in consideration of the above.

  In order to achieve the above object, a sensing unit according to claim 1 of the present invention is a component of a thermal type flow sensor for measuring a fluid flow, and includes a substrate having at least a heater and a temperature sensor. This sensing unit is configured independently of the flow path that constitutes the thermal flow sensor, and has a structure that is sealed so that the fluid to be measured does not leak and can be attached to the flow path. After being attached to the flow path, the electrical terminals from the heater and the temperature sensor can be electrically connected from the outside of the flow path via the substrate, and the heater and the temperature sensor are The structure is such that it is in direct contact with the fluid.

The flow path of the thermal flow sensor does not necessarily develop a special dedicated flow path, but becomes inexpensive by using a commercial standard flow path, for example, a standard stainless steel pipe as the flow path. Sensing provided with a substrate having a flow path having a structure in which a hole is formed in a stainless steel pipe as a flow path, and at least a heater and a temperature sensor (temperature difference sensor) which are at least a basic configuration of a thermal flow sensor. Providing a thermal flow sensor with an extremely low cost and simple structure that can be used for various applications by preparing separate units and combining them so that a single thermal flow sensor can be configured. It is.

The electrical terminals of the sensing unit as a part of the thermal type flow sensor that measures the flow of fluid, for example, have a structure like a hermetic seal, and the flow path is a hole made by hollowing out a standard stainless steel pipe as described above. Insert the part of the board with the heater and temperature sensor of the sensing unit into the hole that is hollowed in the flow path, and the periphery of the sensing unit exactly overlaps the outer shape of the stainless steel pipe of the flow path and is joined Make the structure as follows. Because of this extremely simple structure, it is inexpensive and highly accurate, and allows the selection of flow path dimensions and shape types according to various applications. Therefore, it is possible to provide a thermal type flow sensor that can meet various applications.

The sensing unit according to claim 2 of the present invention is a case where the temperature sensor is a temperature difference sensor. This makes it possible to provide a stable and highly accurate thermal flow sensor that is simple and does not depend on the ambient temperature.

The sensing unit according to claim 3 of the present invention is a case where the temperature difference sensor is a current detection type thermocouple. Since the current detection type thermocouple is only required to be a pair of thermocouples, it is possible to provide an extremely small and highly sensitive thermal type flow sensor.

When the temperature difference sensor is a thermocouple, the n-type high-concentration SOI layer of the silicon (Si) SOI substrate is used as one conductor of the thermocouple, and the silicon (Si) thermal oxide insulating layer (SiO ₂ film) is sandwiched between them. Thus, a pair of thermocouples can be formed using a nickel (Ni) thin film or the like as the other conductor, and can be formed on a cantilever, a diaphragm, or a crosslinked structure. In this case, a thermocouple formed in the same manner can be used as the heater, and a diode, a metal thin film, or an SOI layer resistor can be used as the heater. These can be easily formed by semiconductor microfabrication technology and MEMS technology.

Also, a thermoelectric material such as BiTe (Sb) can be formed as a thermocouple material by sputtering or vacuum deposition, and a thin film thermocouple can be formed on a diaphragm or cantilever such as a plastic or glass thin film.

Moreover, a metal thin film (for example, Au thin film) as the other thermocouple conductor is sputtered on a metal thin film (for example, Ni thin film) as one conductor of a thermocouple made of a thermocouple material via an insulating layer. It is also possible to create a thermocouple with high sensitivity and high speed response by reducing the heat capacity by forming it in the shape of floating in the air, especially for measuring the flow velocity of fluids with large mass such as liquids. In the current detection type thermocouple, the smaller the internal resistance, the larger the output, so that the resistance of the lead wire should be reduced if the resistance is negligible. Therefore, a thin film thermocouple is also suitable, and in practice, a combination of materials having a large figure of merit Z of the thermoelectric material is optimal for such a thermocouple.

The sensing unit according to claim 4 of the present invention is a case where the heater and the temperature sensor are used in combination. Even when a pair of thermocouples is used as the temperature sensor, since the thermocouple is a resistor, it generates heat when a current is passed and can be used as a heater. By using the thermocouple as a heater and a temperature sensor in this way, once the current is made to flow and operate as a heater, this time, in order to measure the temperature change during cooling, a current detection type thermocouple is used. As a pair, a temperature difference with respect to the substrate can be measured. In addition to providing a very compact sensing unit, it is possible to provide a thermal flow sensor equipped with the sensing unit.

The thermal flow sensor according to claim 5 of the present invention is configured so that the above-mentioned sensing unit is joined to the flow path constituting the thermal flow sensor so that the flow of the fluid flowing through the flow path can be measured. It is a feature.

As described above, for example, the flow path constituting the thermal type flow sensor also uses a part of a commercial standard stainless steel pipe to form a hollowed hole, in which the sensing unit joint is also made of stainless steel. As a part of the pipe, the inner diameter of the pipe and the outer shape of the stainless steel pipe of the flow path are selected so as to match each other, so that the pipe can be joined perfectly. At this time, for example, using a stable adhesive that does not emit gas, the flow path and the stainless steel pipe portion of the sensing unit can be adhered and attached (attached) so that the fluid to be measured does not leak. At this time, the electrical terminal of the sensing unit faces the outside of the flow path of the thermal type flow sensor, supplies power to the heater and temperature sensor of the sensing unit, and exchanges signals from the heater and temperature sensor. And be able to control them.

The sensing unit of the thermal type flow sensor may be arranged in various types such as the size and shape of the mounting part so that it can be attached to the channel having a predetermined shape that varies depending on the application of the thermal type flow sensor. It is also possible to fix the shape of the hole of the sensor unit and specify the shape of the joint of the sensing unit so as to match it.

The thermal type flow sensor according to claim 6 of the present invention is a case where it can be connected to the pipe of the fluid to be measured. For example, if the pipe into which the fluid to be measured flows in / out at the location where the thermal flow sensor is attached is a stainless steel pipe with a predetermined external dimension, prepare a stainless steel pipe with the same shape for the flow path of the thermal flow sensor. If a hole is made in this and used as a flow path, a thermal type flow sensor can be easily attached to the external piping by using a simple and inexpensive joint, which is convenient.

Further, a predetermined joint may be attached to the end of the flow path of the thermal type flow sensor, and a thermal type flow sensor including this can be obtained.

The thermal type flow sensor according to claim 7 of the present invention is a case where a measurement unit having an electric circuit necessary for measuring the flow of the fluid to be measured is mounted at least on the electrical terminal.

The heater and temperature sensor provided on the substrate of the sensing unit of the thermal flow sensor require power supply and signal exchange, and are performed through electrical terminals of the sensing unit. For this purpose, an electric circuit (including an electronic circuit) is necessary, and a power supply, an amplifier, a memory, an arithmetic circuit, a control circuit for temperature and measurement, a display circuit, and the like are required. A unit including at least a part of such an electric circuit is connected to the above-described electrical terminal for measurement and control. Here, this is called a measurement unit.

This measurement unit has an output display function, a function that allows wireless transmission and reception with the outside, and if necessary, controls and measures according to a predetermined program, An external power supply can be introduced, and a battery can be installed.

Since the sensing unit of the present invention plays a role as a part of the thermal type flow sensor, it can be exchanged and can be prepared independently from a flow path suitable for various fluids. Thus, there is an advantage that an inexpensive thermal flow sensor can be provided.

The sensing unit of the present invention can also be combined with a separately prepared flow path which is a part of the thermal flow sensor, but this flow path can also use a commercial standard pipe or the like. There is an advantage that an inexpensive thermal type flow sensor can be provided.

Since the sensing unit of the present invention can be used in combination with a heater and a temperature sensor provided therein, there is an advantage that an extremely compact thermal type flow sensor can be provided.

In the thermal type flow sensor of the present invention, a measurement unit having an electrical circuit necessary for measuring the flow of the fluid to be measured separately attached to the sensing unit and the flow path is attached to the electrical terminal of the sensing unit. Therefore, a measurement unit suitable for various measurement purposes can be prepared and combined with various sensing units and flow paths. Therefore, even if there are few kinds of parts, there is an advantage that a combination of them makes it possible to select a flow sensor suitable for many fluids and their measurement regions.

1 is a schematic plan view showing an embodiment of a substrate 1 of a sensing unit 10 which is a part of a thermal flow sensor of the present invention. (Example 1) It is the cross-sectional schematic which shows the structure of one Example of the sensing unit 10 which is one of the components of the thermal type flow sensor of this invention. (Example 1) It is a cross-sectional schematic diagram which shows one Example of the thermal type flow sensor of this invention. (Example 2) FIG. 4 is a schematic perspective view of an embodiment of the thermal type flow sensor of the present invention shown in FIG. 3. (Example 2) It is a cross-sectional schematic diagram which shows another Example of the thermal type flow sensor of this invention. (Example 3) It is the plane schematic which shows another Example of the board | substrate 1 of the sensing unit 10 which is a component of the thermal type flow sensor of this invention. Example 4 FIG. 7 is a schematic cross-sectional view taken along line X-X ′ in FIG. 6. Example 4 It is the plane schematic which shows another Example of the board | substrate 1 of the sensing unit 10 which is a component of the thermal type flow sensor of this invention. (Example 5) FIG. 9 is a schematic cross-sectional view taken along line X-X ′ in FIG. 8. (Example 5)

  Hereinafter, the sensing unit of the thermal flow sensor of the present invention can be formed of a silicon (Si) substrate using mature semiconductor integration technology and MEMS technology. The outline will be described based on an embodiment with reference to the drawings, centering on the case of manufacturing using this silicon (Si) substrate.

  FIG. 1 is a schematic plan view showing an embodiment of a substrate 1 of a sensing unit 10 which is a component of a thermal type flow sensor of the present invention. The substrate 1 is manufactured by an SOI substrate, and a cantilever 15 for sensing is formed by using an n-type SOI layer 11 of the SOI substrate. A high concentration n-type diffusion region 21 is formed by diffusing phosphorus, which is an n-type impurity, in the SOI layer 11 of the substrate 1. Since this region has a very low resistivity, it is convenient to use it as the thermocouple conductor A151. In the present embodiment, three cantilevers 15 using the SOI layer 11 are formed side by side, and the thermocouple 150 as the temperature difference sensor 120 is formed while all are temperature sensors 20. The central cantilever 15 can be used also as the heater 25. These thermocouples 150 use a high-concentration n-type diffusion region 21 as a thermocouple conductor A151, a silicon oxide film 50 as an insulating film, and a thermocouple conductor B152 as a metal film such as a nickel (Ni) thin film. This is an example using. The thermocouple conductor A 151 and the thermocouple conductor B 152 are electrically joined to form a thermocouple 150 using an ohmic contact 160 at the tip of the cantilever 15. Externally, the thermocouple conductor B electrode pads 72b and 73b of the thermocouple 150 and the thermocouple conductor A common electrode pad 70 are connected to an electrical terminal 370 (see FIG. 2). Since the center thermocouple 150 can also be used as the heater 25, the insulation groove 60 is formed in the SOI layer 11 of the substrate 1 and the current when operating as the heater 25 is specially formed. Consideration is given so as not to adversely affect a part of the thermocouple 150 formed in the cantilever 15 on both sides. Here, a case is shown in which the absolute temperature sensor 200 is formed of a pn junction diode so that the absolute temperature of the substrate 1 can be measured. Since the n-type SOI layer 11 is used to form the pn junction diode, the p-type diffusion region 22 can be easily formed by impurity thermal diffusion.

Three cantilevers 15 using the SOI layer 11 are formed side by side, all of the temperature sensors 20 are thermocouples 150, and the central cantilever 15 measures the flow of the fluid to be measured when used as the heater 25. It seems. When there is no flow, the cantilevers 15 on both sides, which are arranged at almost equal intervals from the central heater 25, have the same temperature rise due to heat conduction through the fluid from the heater 25. However, if there is a flow in one direction, the upstream cantilever 15 is cooled, but the downstream cantilever 15 receives heat from the heater 25 and rises in temperature. Since the temperature difference between the upstream side and the downstream side is related to the flow velocity (King's law), the fluid flow can be measured by the calibration curve and the thermocouple 150 mounted on the cantilever 15 on both sides. Of course, by using the thermocouple 150 of the central cantilever 15 as a heater / temperature difference sensor, the flow of the fluid can be measured as described later by using only this one.

In order to form the cantilever 15 serving as sensing using the SOI layer 11 described above, the cantilever 15 can be easily manufactured by a MEMS technique using a semiconductor microfabrication technique.

In the above example, the three cantilevers 15 having the thermocouples 150 that are the temperature difference sensors 120 are arranged side by side, and the central cantilever 15 is operated as the heater 25. Only one cantilever 15 of 15 is formed, and the thermocouple 150 there is used as the heater 25 and the temperature difference sensor 120. By doing in this way, since the more compact sensing unit 10 can be provided, a thermal type flow sensor becomes further compact. In this case, in order to operate the thermocouple 150 as the heater 25, for example, a temperature rise of about 10 ° C. is sufficient, and power supply of about 10 mW is sufficient. After that, the role as the heater 25 is stopped, the thermocouple 150 is used as the temperature difference sensor 120, and the current detection type thermocouple (measures the short-circuit current due to the thermoelectromotive force using the virtual short circuit of the OP amplifier). The output after a predetermined time elapses due to the cooling process of 15 is measured. When the flow of the fluid to be measured is fast, the cooling is fast and the output is small. However, when the flow is slow, it is difficult to cool, so the output of the OP amplifier remains large. The flow rate or flow rate is calculated from the difference between these outputs using a calibration curve.

FIG. 2 is a schematic cross-sectional view showing the structure of an embodiment of the sensing unit 10 which is one of the components of the thermal type flow sensor of the present invention. Here, a substrate support plate 350 is attached to a sensing unit support portion 360 using a part of a stainless steel pipe, and the substrate 1 described in FIG. Yes. A gap adjusting plate 320 that can adjust the gap 390 using the pin 390 is attached through the gap 301. Further, when the sensing unit 10 is attached to the flow path 300 (see FIG. 3), the electrical terminal 370 is disposed on the opposite side to the flow path 300 so as to be outside, and a sealing material such as a hermetic seal is provided. The sensing unit support 360 is attached so that fluid does not leak at 380. In the present embodiment, the O-ring 330 is used to show that the airtightness is maintained when the sensing unit 10 is attached to the flow path 300 (see FIG. 3).

FIG. 3 is a schematic cross-sectional view showing an embodiment of the thermal type flow sensor of the present invention. Here, the sensing unit 10 of the thermal type flow sensor of the present invention shown in FIG. 2 of the first embodiment is attached to the pipe-shaped flow path 300 by using the O-ring 330 so as to keep airtightness. The cross-sectional schematic of the case is shown. Of course, the O-ring 330 may be attached to the flow path 300 using an adhesive without using the O-ring 330. By using the flow restricting plate 310, the substrate support plate 350 and the gap adjusting plate 320 can be fixed so as not to move easily. The gap adjusting plate 320 may determine the thickness of the flow restricting plate 310 in advance according to the desired flow rate of the flow. The fluid to be measured mainly passes through the gap 301 in the flow path.

FIG. 4 is a schematic perspective view of an embodiment of the thermal type flow sensor of the present invention shown in FIG. 3, and shows a case where the flow restricting plate 310 is removed for easy understanding. Through the hole 45 formed in the flow path 300, the substrate 1 provided in the sensing unit 10, the substrate support plate 350 that fixes the substrate 1, the gap adjustment plate 320, and the like are inserted into the flow path 300. The inner diameter of the sensing unit support 360 is selected to be exactly the same as the outer shape of the pipe-shaped flow path 300, and here, it is sealed using an O-ring 330 so as to be removable. The sensing unit 10 and the flow path 300 are fixed with a metal band or the like so as not to be detached, but are omitted in this figure in order to avoid complexity. In addition, you may mutually join with an adhesive agent etc. In addition, the measurement unit 400 can be attached to the electrical terminal 370 jumping out.

FIG. 5: has shown the cross-sectional schematic which shows another Example of the thermal type flow sensor of this invention. Here, as a thermal type flow sensor, a pipe 600 in which joints 600 are attached to both ends of the pipe-shaped flow path 300 of the thermal type flow sensor of the present invention shown in the above-described embodiment 2 and the fluid to be measured flows in and out flows. This is a case where a pipe-like flow path 300 having the same outer diameter as 500 pipes is employed and can be directly connected to the pipe 300. Further, a state in which a measurement unit 400 including an electric circuit capable of exchanging signals and power with at least the heater 25 and the temperature sensor 20 is attached to the electrical terminal 370 of the sensing unit 10 is shown.

FIG. 6 is a schematic plan view showing another embodiment of the substrate 1 of the sensing unit 10 which is a part of the thermal type flow sensor of the present invention. In this example, a thin film made of a material having a low thermal conductivity and an electrical insulating property such as a plastic or glass thin film is formed on the base substrate 12 as a crosslinked structure thin film 16. This is a case where a thermocouple conductor A151 such as a BiTe (Sb) system and a thermocouple conductor B152 are overlapped at the center to form a junction 165 of the thermocouple 150. Here, this is a case where the temperature sensor 20 and the heater 25 are combined so that the thermocouple 150 which is the thin film temperature difference sensor 120 operates as the heater 25 while being the temperature sensor 20. Note that a part of the base substrate 12 is removed by etching to form a cavity 40 so that a bridge structure floating in the air is obtained. FIG. 7 is a schematic cross-sectional view taken along line X-X ′ in FIG. 6 described above.

FIG. 8 is a schematic plan view showing another embodiment of the substrate 1 of the sensing unit 10 which is a component of the thermal type flow sensor of the present invention. The difference from FIG. 6 of the above-described fourth embodiment is that the thermocouple conductor A151 and the thermocouple conductor B152 are formed directly on the substrate 1 by sputtering deposition or the like without forming the bridged structure thin film 16, respectively. In this case, a part of the lower portion of the substrate 1 is removed, and the cavity 40 is formed so as to have a bridge structure composed of only the thermocouple conductor A151 and the thermocouple conductor B152. In such a case, a metal thin film that is malleable and hardly broken is suitable as the material of the thermocouple conductor A151 and the thermocouple conductor B152. In particular, when the fluid to be measured is a liquid, the thermocouple 150 using such a metal thin film is suitable. Here, the example in which the cross-linked thin film 16 is eliminated has been described. However, even if the thermocouple is a metal thin film, the cross-linked thin film 16 having heat and electricity insulation may be formed even if the thermocouple is particularly thin. Good and sometimes better. FIG. 9 is a schematic cross-sectional view taken along line X-X ′ of FIG.

In the above, an example in which the lower portion of the substrate 1 is etched away to form the cavity 40 is shown. However, after a sacrificial layer is formed on the substrate 1 and a material for forming a thermocouple is formed thereon, After patterning in a predetermined shape, the sacrificial layer is etched away to form a cavity 40 in which the temperature sensor 20 such as the thermocouple 150 and the thin film of the heater 25 can be thermally separated from the substrate 1. .

The sensing unit and the thermal flow sensor as parts of the thermal flow sensor of the present invention are not limited to the present embodiment, and naturally, various modifications can be made while the gist, operation and effect of the present invention are the same. There can be.

The sensing unit and the thermal flow sensor as components of the thermal flow sensor of the present invention have a simple structure, and furthermore, components such as the sensing unit, the flow path, and the measurement unit are selected and combined according to the purpose of use. An inexpensive thermal flow sensor that meets your needs can be provided.

DESCRIPTION OF SYMBOLS 1 Substrate 10 Sensing unit 11 SOI layer 12 Base substrate 15 Cantilever 16 Bridged structure thin film 20 Temperature sensor 21 n-type diffusion region 22 p-type diffusion region 25 heater 40 cavity 45 hole 50 silicon oxide film 60 insulating groove 70 for thermocouple conductor A Common electrode pads 71a, 71b Heater electrode pad 72a Thermocouple conductor A electrode pad 72b Thermocouple conductor B electrode pad 73b Thermocouple conductor B electrode pad 74a, 74b Temperature difference sensor electrode pad 80 Pipe 90 Pipe 120 Temperature difference Sensor 150 Thermocouple 151 Thermocouple conductor A
152 Thermocouple conductor B
160 Ohmic contact 165 Junction 200 Absolute temperature sensor 300 Flow path 301 Gap 310 Flow restriction plate 320 Gap adjustment plate 330 O-ring 350 Substrate support plate 360 Sensing unit support 370 Electrical terminal 380 Sealing material 390 Pin 400 Measurement unit 500 Wiring 600 joints

Claims (7)

The sensing unit of the thermal type flow sensor for measuring the flow of the fluid has at least a substrate including a heater and a temperature sensor, and the sensing unit is configured independently of the flow path constituting the thermal type flow sensor. A structure that is sealed so that the fluid to be measured does not leak and can be attached to the flow path; after being attached to the flow path, the electrical terminals from the heater and the temperature sensor are connected to the flow path; A sensing unit having a structure in which electrical connection can be made from the outside of the flow path via a substrate, and the heater and the temperature sensor are in direct contact with the fluid. The sensing unit according to claim 1, wherein the temperature sensor is a temperature difference sensor. The sensing unit according to claim 2, wherein the temperature difference sensor is a current detection type thermocouple. The sensing unit according to claim 1, wherein both the heater and the temperature sensor are used. A thermal flow sensor, wherein the sensing unit according to any one of claims 1 to 4 is joined to the flow path so that the flow of fluid flowing through the flow path can be measured. 6. The thermal flow sensor according to claim 5, wherein the flow path is a commercial standard pipe and can be connected to a pipe of a fluid to be measured. The thermal type flow sensor according to any one of claims 5 and 6, wherein at least a measurement unit having an electric circuit necessary for measuring a flow of a fluid to be measured is attached to the electrical terminal.

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