JP2009025099A - Thermal flow sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal flow sensor for performing flow detection of fluid under test using a heating resistor and a pair of temperature measuring resistors, in which sensitivity and accuracy in the flow detection are ensured, and flexibility in its installation position is increased. <P>SOLUTION: The thermal flow sensor 10 is formed as a card-shaped sensor comprising a rectangular resin film piece 12, a conductive film 14 formed by a predetermined wiring pattern on one surface 12a of the resin film piece 12, and a protective film 16 which partially covers the conductive film 14. As parts of the conductive film 14, the heating resistor 22, the pair of temperature measuring resistors 24, 26, and electrode pads 32A, 32B, 34A, 34B, 36A, 36B which expand in nearly a fan-shaped form from each of them are formed. In order to perform flow detection of the fluid under test flowing through a flow channel 2 formed within a laminated substrate unit 100, the thermal flow sensor 10 can be thereby placed within the laminated substrate unit 100 easily. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermal flow sensor configured to detect a flow rate of a fluid to be detected using a heating resistor and a pair of temperature measuring resistors.

  Conventionally, a thermal flow sensor is known as one type of flow sensor for measuring the flow rate of a fluid to be tested.

  For example, in “Patent Document 1” and “Patent Document 2”, a heating resistor disposed in a flow path of a test fluid and a pair of temperature measuring elements disposed in the flow path in the vicinity of the upstream side and in the vicinity of the downstream side thereof. A thermal flow sensor with a resistor is described. In this thermal flow sensor, the heating resistor and each resistance temperature detector are arranged so as to extend in a direction substantially orthogonal to the flow direction of the fluid to be detected. In this thermal flow sensor, the temperature of the fluid to be detected is detected by each of the pair of temperature measuring resistors while the fluid to be tested flowing through the flow path is heated by the heating resistor, and the detected temperature difference Based on the above, the flow rate of the fluid to be detected is detected.

  At that time, many thermal flow sensors have a configuration in which a heating resistor and a pair of temperature measuring resistors are formed on a silicon substrate, as described in the above-mentioned “Patent Document 1”. Yes. On the other hand, the thermal flow sensor described in the above-mentioned “Patent Document 2” has a configuration in which a heating resistor and a pair of temperature measuring resistors are formed on a resin film piece.

JP 2000-206134 A JP 2000-227352 A

  If a resin film piece with excellent heat insulation is used instead of a silicon substrate as in the thermal flow sensor described in the above-mentioned “Patent Document 2”, the heating resistor and the back surface of each resistance temperature detector are used. It is possible to sufficiently secure the sensitivity of flow rate detection without forming a heat insulation cavity. This makes it possible to reduce the thickness of the thermal flow sensor.

  However, in the thermal flow sensor described in “Patent Document 2”, plate-like lead wires are attached to both ends of the heating resistor and both ends of each resistance temperature detector. It is configured to connect the heating resistor and each resistance temperature detector to the external flow rate detection control circuit via each lead wire, so that the location where the thermal flow sensor can be installed is limited. There's a problem.

  The present invention has been made in view of such circumstances, and is a thermal flow sensor configured to detect a flow rate of a fluid under test using a heating resistor and a pair of temperature measuring resistors. An object of the present invention is to provide a thermal flow sensor that can sufficiently secure the sensitivity and accuracy of flow rate detection and can increase the degree of freedom of its installation location.

  In the present invention, the thermal flow sensor is configured as a card-like sensor using a resin film piece, and the above-described object is achieved by devising the configuration of the heating resistor and each resistance temperature detector. It is a thing.

That is, the thermal flow sensor according to the present invention is
A thermal type comprising: a heating resistor disposed in the flow path of the fluid to be tested; and a pair of temperature measuring resistors disposed in the flow path in the vicinity of the upstream side and the downstream side of the heating resistor. In the flow sensor,
The thermal flow sensor is configured as a card-like sensor comprising a resin film piece, a conductive film formed with a predetermined wiring pattern on one surface of the resin film piece, and a protective film partially covering the conductive film. Has been
The heating resistor and each temperature measuring resistor are formed as a part of the conductive film so as to extend in a direction substantially orthogonal to the flow direction of the fluid to be tested,
The protective film is formed so as to cover at least a portion facing the flow path on the one surface of the resin film piece,
As a part of the conductive film, a pair of electrode pads extending from the heating resistor and a pair of electrode pads extending from the temperature measuring resistors are formed,
Each of the electrode pads is formed so as to extend in a substantially fan shape from each of the heating resistor and the resistance temperature detectors.

  As long as the “thermal flow sensor” is configured as a card-like sensor, the specific shape and size are not particularly limited, and the thickness is not particularly limited. Absent.

  If the “heating resistor” and each of the “temperature measuring resistors” are formed so as to extend in a direction substantially orthogonal to the flow direction of the fluid to be detected, the specific paths thereof are not particularly limited. Instead, it may be formed so as to extend only in an I-shaped path, may be formed so as to extend in a U-shaped path, or may be formed so as to extend in a path that is folded back multiple times. Also good.

  The “substantially fan-shaped” means a shape whose width gradually increases as the distance from the heating resistor and each resistance temperature detector increases, and the degree of expansion is not particularly limited.

  As shown in the above configuration, the thermal flow sensor according to the present invention partially covers a resin film piece, a conductive film formed with a predetermined wiring pattern on one surface of the resin film piece, and the conductive film. Since it is configured as a card-like sensor composed of a protective film, it can be easily placed at various locations that require detection of the flow rate of the fluid to be detected.

  At that time, the heating resistor and each resistance temperature detector in this thermal flow sensor are formed as a part of the conductive film so as to extend in a direction substantially orthogonal to the flow direction of the fluid to be tested, As a part of the conductive film, a pair of electrode pads extending from the heating resistors and a pair of electrode pads extending from the respective resistance thermometers are formed. Since it forms so that it may spread from each of each resistance temperature sensor in the substantially fan shape, the following effects can be acquired.

  That is, in order to increase the sensitivity of flow rate detection, it is preferable to set the distance between the centers of the heating resistor and each resistance temperature detector in the flow direction as small as possible. In that respect, in the thermal type flow sensor according to the present invention, each electrode pad is formed so as to expand in a substantially fan shape from each of the heating resistor and each temperature measuring resistor, so that the heating resistor and each temperature measuring resistor. Even when the center-to-center distance in the flow direction with the body is set to a sufficiently small value, a portion that is electrically connected to the electrode of the external flow rate detection control circuit in each electrode pad can be formed with a certain large area.

  As a result, the thermal flow sensor according to the present invention can be easily electrically connected to an external flow rate detection control circuit even though it is configured as a card-like sensor. In addition, since each of these electrode pads is formed so as to expand in a substantially fan shape, the resistance values of portions other than the heating resistor and each of the resistance temperature detectors can be suppressed sufficiently low, thereby increasing the accuracy of flow rate detection. be able to.

  Further, in the thermal flow sensor according to the present invention, since the part facing the flow path on one side of the resin film piece is covered with a protective film, the fluid to be detected has a low boiling point such as methanol, for example, Even when the liquid is liable to occur, the flow rate can be detected with high accuracy.

  That is, if there is a large unevenness in the portion facing the flow path in the thermal flow sensor, bubbles generated from the liquid heated by the heating resistor adhere to the uneven portion. The liquid temperature cannot be detected accurately. In that respect, in the thermal flow sensor according to the present invention, the portion that comes into contact with the test fluid is the surface of the protective film, and the height of the unevenness on this surface is suppressed to the height of the film thickness of the conductive film at the maximum. And sufficient smoothness is ensured. Therefore, it is possible to prevent the occurrence of a situation in which bubbles are attached to the uneven portion of the surface of the protective film, thereby making it possible to accurately detect the flow rate.

  As described above, according to the present invention, in the thermal flow sensor configured to detect the flow rate of the fluid to be detected using the heating resistor and the pair of temperature measuring resistors, the sensitivity and accuracy of the flow rate detection are sufficient. In addition, the degree of freedom of the installation location can be increased.

  In the above configuration, if the heating resistor and each resistance temperature detector are formed so as to extend along a U-shaped path in a direction substantially orthogonal to the flow direction of the fluid to be tested, a pair extending from the heating resistor Since each electrode pad and each pair of electrode pads extending from each resistance temperature sensor are formed on the same side with respect to the flow path of the fluid to be detected, these heating resistor and each resistance temperature sensor Can be easily connected to an external flow rate detection control circuit.

  In this case, if the pair of electrode pads extending from the heating resistor and the pair of electrode pads extending from each temperature measuring resistor are all formed on the same side with respect to the flow path of the fluid to be tested, The electrical connection between each of the heating resistors and each of the resistance temperature detectors and the external flow rate detection control circuit can be made on the same side. Therefore, it is possible to facilitate the installation of the thermal flow sensor at a location where flow rate detection is required, thereby enhancing the versatility of the thermal flow sensor.

  On the other hand, in this case, the pair of electrode pads extending from the heating resistors and the pair of electrode pads extending from the resistance temperature detectors are positioned on opposite sides of the flow path of the test fluid. With the formed configuration, it is possible to prevent the pair of electrode pads extending from each resistance temperature detector and the pair of electrode pads extending from the heating resistor from being arranged close to each other. As a result, even if the temperature of the pair of electrode pads extending from the heating resistor rises, the thermal effect can be prevented from reaching the detection signal from each temperature measuring resistor. Thus, the accuracy of flow rate detection can be increased.

  In the above configuration, the reference resistor for detecting the temperature of the test fluid at the position away from the heating resistor and each resistance temperature detector on the one side of the resin film piece in the flow direction of the test fluid is the conductive film. If the sensor is configured to extend in a direction substantially perpendicular to the flow direction of the test fluid, a sensor for detecting the temperature of the test fluid is separately provided in the flow path of the test fluid. The need for placement can be eliminated. Further, by adopting such a configuration, the positional relationship between the reference resistor, the heating resistor, and the pair of temperature measuring resistors can be always maintained constant, and in this respect also, the flow rate detection can be performed with high accuracy. It can be carried out.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view showing a thermal flow sensor 10 according to an embodiment of the present invention, and FIG. 2 is a detailed view of a portion II in FIG. FIG. 3B is a cross-sectional view showing the multilayer substrate unit 100 in which the thermal flow sensor 10 is incorporated, and FIG. 3A is a cross-sectional view showing the state of incorporation. Further, FIG. 4 is a perspective view showing the thermal flow sensor 10 incorporated in the multilayer substrate unit 100.

  As shown in FIGS. 3B and 4, the thermal flow sensor 10 according to the present embodiment is used in a state where the thermal flow sensor 10 is arranged in the flow path 2 of the test fluid formed inside the multilayer substrate unit 100. It is like that.

  The multilayer substrate unit 100 is incorporated as a part of a fuel cell system (not shown) for small electronic equipment such as a notebook personal computer. In this case, in this fuel cell system, each flow path of methanol, air, and hydrogen and an electronic circuit for controlling the flow rate of each flow path are formed so as to be incorporated in the multilayer substrate.

  The multilayer substrate is formed by laminating a plurality of substrates (for example, about 10 substrates) including the first and second substrates 102 and 104, and the multilayer substrate unit 100 is incorporated as a part thereof. . A part of the flow path formed in the multilayer substrate is configured by the flow path 2 of the multilayer substrate unit 100.

  The flow path 2 of the multilayer substrate unit 100 is a flow path for supplying methanol from a fuel cartridge (not shown) in the fuel cell system, and has a rectangular cross section with a width of 2 mm and a height of 1 mm, and has a predetermined length. It extends so as to extend linearly. And this flow path 2 is the flow path formed in the board | substrate of another hierarchy through the through-hole (not shown) formed in the 1st board | substrate 102 or the 2nd board | substrate 104 in the both ends. To be connected to.

  Methanol flowing through the flow path 2 is fed at a flow rate of about 1 milliliter per minute. The thermal flow sensor 10 detects the flow rate of methanol flowing through the flow path 2 as a test fluid.

  3A and 3B show the multilayer substrate unit 100 in a cross-sectional position along a plane orthogonal to the flow path 2. 1, 2 and 4, the flow path 2 is indicated by a two-dot chain line, and the direction of methanol flow is indicated by a two-dot chain arrow.

  As shown in FIGS. 1 and 4, the thermal flow sensor 10 is disposed in the flow path 2 in the vicinity of the heating resistor 22 disposed in the flow path 2 and in the vicinity of the upstream side and the downstream side of the heating resistor 22. A pair of resistance temperature detectors 24 and 26, and a heating resistor 22 and a reference resistance body 28 arranged at a position away from the pair of resistance temperature detectors 24 and 26 on the upstream side in the flow direction are provided. ing.

  In the thermal flow sensor 10, the heating resistor 22 is heated to a temperature about 5 ° C. higher than the temperature of methanol flowing through the flow path 2. The temperature of methanol is detected. Based on the temperature difference detected by the two resistance temperature detectors 24 and 26, the flow rate is measured in a flow rate detection control circuit (not shown) of the fuel cell system. At that time, the reference resistor 28 accurately detects the temperature of methanol flowing through the flow path 2 on the upstream side of the heating resistor 22, and this detected temperature is used as a reference temperature for heating the heating resistor 22. It is like that.

  This thermal flow sensor 10 includes a rectangular resin film piece 12, a conductive film 14 formed in a predetermined wiring pattern on one surface 12 a of the resin film piece 12, and a protection that partially covers the conductive film 14. A card-like sensor composed of the film 16 is configured.

  The resin film piece 12 is a polyimide film having a long side length of 11 mm, a short side length of 5.5 mm, and a thickness of 0.2 mm, and the long side direction is directed to the methanol flow direction. It is designed to be used with At that time, the flow path 2 has a width of 2 mm described above at a position closer to the long side 12b2 on the far side than the center line between the long side 12b1 on the near side and the long side 12b2 on the far side in the resin film piece 12. It is to be formed with.

  The conductive film 14 is formed by sputtering a metal, and its film thickness is set to 0.1 μm.

  The heating resistor 22 and the resistance temperature detectors 24 and 26 are formed as a part of the conductive film 14 so as to extend in a direction perpendicular to the flow direction of methanol. The reference resistor 28 is also formed as a part of the conductive film 14 so as to extend in a direction perpendicular to the methanol flow direction.

  A pair of marks 30 is formed as a part of the conductive film 14 at a position in contact with the upstream short side 12 c 1 and a position in contact with the downstream short side 12 c 2 in the resin film piece 12. These pairs of marks 30 are formed at intervals of 2 mm so as to straddle the flow path 2, thereby indicating the position of the flow path 2.

  The protective film 16 is formed in a region that is slightly wider than the width of the flow path 2 (about 3 mm wide) and extends in a strip shape along the methanol flow direction (that is, a region indicated by a mesh line in the figure). Thus, the heating resistor 22, the pair of temperature measuring resistors 24, 26 and the reference resistor 28 are covered so that they are not in direct contact with methanol. The protective film 16 is formed by coating a fluorine-based resin, a polyimide resin, or the like that is electrically insulating and resistant to methanol, and has a thickness of 1 μm.

  As shown in FIG. 2, each of the heating resistor 22 and each of the resistance temperature detectors 24 and 26 is formed to extend along a U-shaped path in a direction orthogonal to the methanol flow direction.

  At this time, both the heating resistor 22 and the temperature measuring resistors 24 and 26 are formed within a range slightly narrower than the width of the flow path 2. Each of the heating resistor 22 and each of the resistance temperature detectors 24 and 26 has a pair of base end portions located on the front side (that is, the long side 12b1 side) and the other side (that is, the long side 12b2). Side).

  The heating resistor 22 and the resistance temperature detectors 24 and 26 are all formed with a width of 20 μm, and the center line interval between the forward path portion and the return path portion is set to 40 μm. Further, the center-to-center distance in the flow direction between the heating resistor 22 and the temperature measuring resistors 24 and 26 is set to 80 μm.

  Electrode pads 32 </ b> A and 32 </ b> B extending from the base end portion in a substantially fan shape are formed as part of the conductive film 14 at each base end portion of the heating resistor 22. In addition, electrode pads 34 </ b> A and 34 </ b> B extending from the base end portion in a substantially fan shape are formed as a part of the conductive film 14 at each base end portion of the upstream temperature measuring resistor 24. Furthermore, electrode pads 36 </ b> A and 36 </ b> B extending from the base end portion in a substantially fan shape are formed as part of the conductive film 14 at each base end portion of the downstream resistance temperature detector 26.

  Each of these electrode pads 32A, 32B, 34A, 34B, 36A, and 36B divides the 180 ° angular region located on the near side with respect to the straight line extending in the methanol flow direction into approximately six equal parts with a slight angular interval. Are formed at an expansion angle (specifically, an expansion angle of about 20 to 25 °).

  As shown in FIG. 1, the end portions of these electrode pads 32A, 32B, 34A, 34B, 36A, 36B (that is, portions not covered by the protective film 16) are bent in a direction perpendicular to the methanol flow direction. Thus, it extends to the long side 12b1 on the near side of the resin film piece 12. At that time, the end portions of these electrode pads 32A, 32B, 34A, 34B, 36A, and 36B are all formed at equal intervals in the methanol flow direction (specifically, a width of about 1 mm). Has been. Thus, a pair of electrode pads 32A and 32B extending from the heating resistor 22 is formed in a symmetrical shape with respect to the methanol flow direction, and a pair of electrode pads 34A extending from the temperature measuring resistor 24 on the upstream side. 34B and a pair of electrode pads 36A, 36B extending from the resistance temperature detector 26 on the downstream side are formed symmetrically with respect to the methanol flow direction.

  The reference resistor 28 is formed in the vicinity of the upstream short side 12c1 of the resin film piece 12. The reference resistor 28 is disposed at a position about 6 mm away from the heating resistor 22.

  The reference resistor 28 is also formed to extend along a U-shaped path in a direction orthogonal to the methanol flow direction, like each of the heating resistor 22 and each of the resistance temperature detectors 24 and 26.

  At this time, the reference resistor 28 is also formed within a range slightly narrower than the width of the flow path 2. The reference resistor 28 is also formed so that the pair of base end portions is located on the near side and folded back on the other side. The reference resistor 28 is also formed with a width of 20 μm, and the center line interval between the forward path part and the return path part is set to 40 μm.

  Electrode pads 38 </ b> A and 38 </ b> B extending in a substantially fan shape from the base end are also formed as part of the conductive film 14 at each base end of the reference resistor 28. However, each of the electrode pads 38A and 38B is formed so as to extend from the reference resistor 28 toward the downstream side because the reference resistor 28 is disposed in the vicinity of the short side 12c1 on the upstream side. At this time, the electrode pad 38A is formed in substantially the same shape as the electrode pad 32B extending from the heating resistor 22, and the electrode pad 38B is substantially similar in shape to the electrode pad 36B extending from the temperature measuring resistor 26. It is formed with.

  As shown in FIG. 3B, in the multilayer substrate unit 100, the thermal flow sensor 10 is disposed so as to be sandwiched between the first substrate 102 and the second substrate 104. In this state, one wall surface of the channel 2 having a rectangular cross section is formed over a predetermined length. At that time, both the first and second substrates 102 and 104 are configured as resin substrates. As a specific material of the resin substrate, for example, polyimide, polyetherimide, polyethersulfone, or the like can be used.

  As shown in FIG. 3A, the first substrate 102 is set to have a plate thickness of 1 mm, and a concave portion 102b having substantially the same size and the same depth as the thermal flow sensor 10 is provided on one surface 102a thereof. Is formed. That is, the recess 102b is a rectangular recess having a long side length of about 11 mm and a short side length of about 5.5 mm, and the depth is set to about 0.2 mm.

  The thermal flow sensor 10 is accommodated in the recess 102b of the first substrate 102 with the one surface 12a side of the resin film piece 12 exposed. At this time, the thermal flow sensor 10 is accommodated in the recess 102b without a substantial gap, and the one surface 12a of the resin film piece 12 is substantially flush with the one surface 102a of the first substrate 102.

  On the other hand, the 2nd board | substrate 104 is set to 2 mm in plate | board thickness, and it has a rectangular cross section with a width of 2 mm and a depth of 1 mm on one side 104a, and is linear over a predetermined length (for example, a length of about 20 to 40 mm). A concave groove 104b extending in a shape is formed. A conductive film 106 extending to the vicinity of the concave groove 104b is formed on one surface 104a of the second substrate 104 with a predetermined wiring pattern.

  The conductive film 106 constitutes a part of the flow rate detection control circuit of the fuel cell system, and the wiring pattern thereof is the electrode pads 32A, 32B, 34A, 34B, 36A of the thermal flow rate sensor 10. , 36B, 38A, and 38B, the pattern shape is set to be conductive. Through the conductive film 106, the heating resistor 22, the resistance temperature detectors 24 and 26, and the reference resistor 28 of the thermal flow sensor 10 are connected to other control circuits in the flow rate detection control circuit of the fuel cell system, respectively. It is electrically connected to a portion (for example, a bridge circuit).

  As shown in FIG. 3A, the multilayer substrate unit 100 is assembled with respect to the first substrate 102 after the thermal flow sensor 10 is accommodated in the recess 102 b of the first substrate 102. In the state where the concave groove 104b is arranged so that the concave groove 104b is orthogonal to the heating resistor 22 and the pair of temperature measuring resistors 24, 26 of the thermal flow sensor 10, the first surface 104a has a first surface 104a. This is performed by bonding to one side 102a of the substrate 102.

  At that time, a conductive adhesive (not shown) is applied to the contact portions between the electrode pads 32A, 32B, 34A, 34B, 36A, 36B, 38A, 38B and the conductive film 106 of the thermal flow sensor 10 respectively. Thus, conduction between the two is ensured, and in other portions, a normal adhesive (see FIG. 5) is provided between the one surface 102a of the first substrate 102 and the one surface 104a of the second substrate 104. (Not shown) is applied to ensure sufficient water-tightness (and air-tightness) around the channel 2.

  Note that a portion of the first substrate 102 or the second substrate 104 located at both ends of the recess 102b has a through hole (for connecting the channel 2 to a channel formed in another level of the substrate ( (Not shown) is formed.

  FIG. 5A is a cross-sectional view taken along the line Va-Va in FIG. FIG. 2B is a detailed view of a portion b of FIG. 1A, and FIG. 2C is a detailed view of a portion c of FIG.

  As shown in these drawings, the thermal flow sensor 10 has a heating resistor 22, a pair of temperature measuring resistors 24 and 26, and a reference resistor 28 on one surface 12a of the resin film piece 12 formed as a smooth surface. Are formed as a part of the conductive film 14, and these are covered with the protective film 16, so that the surface 16a of the protective film 16 facing the flow path 2 in the thermal flow sensor 10 is substantially smooth. It becomes.

  That is, in the scale of FIG. 5A, the cross-sectional shape along the methanol flow direction of the surface 16a of the protective film 16 is a straight line, and the cross-sectional shape is also shown in FIG. Is still in a straight line shape, and finally a slight unevenness is recognized in FIG. At that time, the unevenness of the surface 16a of the protective film 16 shown in FIG. 4C is due to the appearance of a step corresponding to the thickness of each of the heating resistor 22 and the resistance temperature detector 26 on the surface 16a of the protective film 16. However, since both the heating resistor 22 and the resistance temperature detector 26 are formed as a part of the conductive film 14 having a film thickness of 0.1 μm, the level difference is a slight height of 0.1 μm. . For this reason, even if bubbles are generated from the methanol heated by the heating resistor 22, there is no possibility that the bubbles will adhere to the uneven portions.

  As described above in detail, the thermal flow sensor 10 according to this embodiment includes a rectangular resin film piece 12 and a conductive film 14 formed in a predetermined wiring pattern on one surface 12a of the resin film piece 12, Since it is configured as a card-like sensor comprising a protective film 16 that partially covers the conductive film 14, in order to detect the flow rate of methanol flowing through the flow path 2 formed inside the multilayer substrate unit 100, It becomes easy to arrange the laminated substrate unit 100 inside.

  At that time, in the thermal flow sensor 10 according to the present embodiment, the heating resistor 22 and each of the resistance temperature detectors 24 and 26 are part of the conductive film 14 in a direction perpendicular to the methanol flow direction. Further, as a part of the conductive film 14, a pair of electrode pads 32 A and 32 B extending from the heating resistor 22 and a pair of electrode pads extending from the resistance temperature detectors 24 and 26 are formed as a part of the conductive film 14. 34A, 34B, 36A, and 36B are formed. These electrode pads 32A, 32B, 34A, 34B, 36A, and 36B are substantially fan-shaped from the heating resistor 22 and the resistance temperature detectors 24 and 26, respectively. Therefore, the following operational effects can be obtained.

  That is, in the thermal flow sensor 10 according to the present embodiment, the center distance in the flow direction between the heating resistor 22 and each of the temperature measuring resistors 24 and 26 is as high as 80 μm in order to increase the sensitivity of flow rate detection. Although set to a small value, each electrode pad 32A, 32B, 34A, 34B, 36A, 36B is formed so as to expand in a substantially fan shape from each of the heating resistor 22 and each of the temperature measuring resistors 24, 26. Therefore, a portion of each of the electrode pads 32A, 32B, 34A, 34B, 36A, and 36B that is electrically connected to the conductive film 106 formed on the one surface 104a of the second substrate 104 can be formed with a somewhat large area. .

  As a result, the thermal flow sensor 10 according to the present embodiment is configured as a card-like sensor, but with the conductive film 106 constituting a part of the flow rate detection control circuit of the fuel cell system. Electrical connection can be made easily. Moreover, each of these electrode pads 32A, 32B, 34A, 34B, 36A, 36B is formed so as to expand in a substantially fan shape, so that the resistance values of the portions other than the heating resistor 22 and the temperature measuring resistors 24, 26 are set. It can be kept sufficiently low, and the accuracy of flow rate detection can be increased in this respect as well.

  Further, in the thermal type flow sensor 10 according to the present embodiment, since the part facing the flow path 2 on one side 12a of the resin film piece 12 is all covered with the protective film 16, methanol having a low boiling point and easily generating bubbles. The flow rate can be accurately detected regardless of the fluid to be tested.

  That is, the portion in contact with methanol in the thermal flow sensor 10 according to the present embodiment is the surface 16a of the protective film 16, and the height of the unevenness of the surface 16a is at most 0.1 μm thick of the conductive film 14. Therefore, sufficient smoothness is ensured. Therefore, it is possible to prevent a situation in which bubbles generated from methanol are attached to the uneven portion of the surface 16a of the protective film 16, and thereby the flow rate can be accurately detected.

  As described above, according to the present embodiment, in the thermal flow sensor 10 configured to detect the flow rate of methanol using the heating resistor 22 and the pair of temperature measuring resistors 24 and 26, the sensitivity of the flow rate detection. In addition, it is possible to increase the degree of freedom of the installation location while ensuring sufficient accuracy.

  In that case, since the resin film piece 12 of the thermal flow sensor 10 according to the present embodiment is formed in a rectangular shape, the sensor body 10 can be easily manufactured, and the first substrate 102 can be manufactured. The recess 102b can be easily formed.

  In addition, the thermal flow sensor 10 according to the present embodiment is formed such that the heating resistor 22 and the resistance temperature detectors 24 and 26 each extend along a U-shaped path in a direction orthogonal to the methanol flow direction. Therefore, the pair of electrode pads 32A and 32B extending from the heating resistor 22 and the pair of electrode pads 34A, 34B, 36A and 36B extending from the resistance temperature detectors 24 and 26 are respectively connected to the methanol flow path 2. Are formed on the same side. Therefore, it is possible to facilitate electrical connection between each of the heating resistor 22 and each of the resistance temperature detectors 24 and 26 and the conductive film 106 constituting a part of the flow rate detection control circuit of the fuel cell system. .

  Moreover, the thermal flow sensor 10 according to the present embodiment includes a pair of electrode pads 32A and 32B extending from the heating resistor 22 and a pair of electrode pads 34A and 34B extending from the resistance temperature detectors 24 and 26, respectively. Since 36A and 36B are all formed on the same side with respect to the methanol flow path 2, it is possible to facilitate the installation of the thermal flow sensor 10 at a location where flow rate detection is required. The versatility of the flow sensor 10 can be enhanced.

  That is, the thermal flow sensor 10 according to the present embodiment is incorporated as a part of the multilayer substrate unit 100, but in a partial region of the one surface 104 a of the second substrate 104 in the multilayer substrate unit 100. The conductive film 106 constituting a part of the flow rate detection control circuit of the fuel cell system can be formed in a concentrated manner, whereby the configuration of the multilayer substrate unit 100 can be simplified.

  Further, in the thermal flow sensor 10 according to the present embodiment, the pair of electrode pads 34A and 34B and the pair of electrode pads 36A and 36B are formed symmetrically with respect to the flow direction of methanol, so that the upstream side The liquid temperature detection by the temperature measuring resistor 24 and the liquid temperature detection by the downstream temperature measuring resistor 26 can be performed under the same conditions, whereby the flow rate can be detected with higher accuracy.

  Furthermore, the thermal flow sensor 10 according to the present embodiment has a liquid flow sensor at a position away from the heating resistor 22 and the temperature measuring resistors 24 and 26 on the one surface 12a of the resin film piece 12 on the upstream side in the methanol flow direction. Since the reference resistor 28 for detecting the temperature is formed as a part of the conductive film 14 so as to extend in a direction orthogonal to the flow direction of methanol, a sensor for detecting the liquid temperature is separately provided. The necessity to arrange in the flow path 2 can be eliminated. Further, by adopting such a configuration, the positional relationship between the reference resistor 28, the heating resistor 22 and the pair of temperature measuring resistors 24 and 26 is always maintained constant. The flow rate can be accurately detected. In addition, since the reference resistor 28 is disposed at a position sufficiently separated from the heating resistor 22 by about 6 mm, the liquid temperature can be detected without being affected by the heat from the heating resistor 22 at all.

  In the present embodiment, when the flow rate is measured, the heating resistor 22 is not heated to a high temperature, but is heated to a temperature about 5 ° C. higher than the temperature of methanol flowing through the flow path 2. Even though the boiling point of methanol is as low as 65 ° C., it is possible to prevent boiling and alteration of the methanol.

  Furthermore, in the present embodiment, the thermal flow sensor 10 is accommodated in the recess 102b with almost no gap, and the one surface 12a of the resin film piece 12 is substantially the same as the one surface 102a of the first substrate 102. Since it is incorporated as a part of the multilayer substrate unit 100 in a unified state, the arrangement of the thermal flow sensor 10 does not cause a gap or a step in the wall surface of the flow path 2. As a result, the accuracy of flow rate detection can be sufficiently maintained. At this time, since the flow path 2 is formed by the first and second substrates 102 and 104 having excellent heat insulation, the accuracy of flow rate detection can be sufficiently maintained in this respect.

  In the thermal flow sensor 10 according to the present embodiment, the reference resistor 28 is disposed at a position about 6 mm away from the heating resistor 22. However, as in the present embodiment, the heating resistor 22 is disposed. If the reference resistor 28 is separated from the heating resistor 22 by about 2 mm or more, the heating temperature of the heating resistor 22 is about 5 mm higher than the temperature of methanol flowing through the flow path 2. It is possible to be hardly affected. However, if the reference resistor 28 is disposed at a position about 6 mm away from the heating resistor 22 as in the thermal flow sensor 10 according to the present embodiment, the thermal flow sensor 10 is connected to the flow rate sensor. It can be easily installed at locations where measurement conditions are greatly different, and the versatility can be sufficiently enhanced.

  Since the thickness of the resin film piece 12 of the thermal flow sensor 10 according to the present embodiment is set to 0.2 mm, it can be made sufficiently thin as a card-like sensor. Thus, even when a mounting machine is used when accommodating this in the recess 102b of the first substrate 102, the required rigidity can be ensured. However, the thickness of the resin film piece 12 can be further reduced, and can be increased to increase the rigidity. At that time, the thickness of the resin film piece 12 is preferably set to a value in the range of about 0.1 to 0.5 mm.

  In the present embodiment, since both the first and second substrates 102 and 104 are configured as resin substrates having excellent heat insulation properties, the heat insulation property of the methanol flow path 2 may be extremely high. Thus, the accuracy of flow rate detection by the thermal flow sensor 10 can be made extremely high.

  In the above embodiment, the thermal flow sensor 10 has been described as being disposed on the lower side of the flow path 2. However, the thermal flow sensor 10 is configured to be disposed on the upper side of the flow path 2 (that is, FIG. It is also possible to arrange the laminated substrate unit 100 shown in b) so as to be turned upside down, or to be arranged on the side of the flow path 2.

  Moreover, in the said embodiment, although the resin film piece 12 of the thermal type flow sensor 10 was demonstrated as what was formed in the rectangular shape, this resin film piece 12 is made into each rectangular corner part or one part corner part. It is also possible to have a shape in which chamfering or corner R is applied, and it is also possible to have a shape other than a rectangle.

  Furthermore, in the above embodiment, the heating resistor 22, the resistance temperature detectors 24 and 26, and the reference resistor 28 are all described as extending in a direction orthogonal to the methanol flow direction. However, even when formed so as to extend in a direction slightly deviated from the direction perpendicular to the flow direction of methanol, substantially the same effect as in the case of the above embodiment can be obtained.

  In the above embodiment, the first and second substrates 102 and 104 are described as being configured as resin substrates. However, one or both of the first and second substrates 102 and 104 may be used. For example, it may be configured as a metal substrate made of aluminum or stainless steel.

  Furthermore, in the above-described embodiment, the thermal flow sensor 10 is disposed in the methanol flow path 2 formed inside the multilayer substrate unit 100 that is incorporated as a part of the multilayer substrate in the fuel cell system. However, the thermal type flow sensor 10 is used to detect the flow rate of air or hydrogen flowing through the flow path 2 in the multilayer substrate unit 100 disposed in the other part of the multilayer substrate. It is also possible.

  Moreover, in the said embodiment, although demonstrated as what was used in the state in which the thermal type flow sensor 10 was integrated as a part of the multilayer substrate unit 100, this thermal type flow sensor 10 is used in an aspect other than this. It is also possible to do so. For example, in a state where a slot for inserting a card is formed on the inner surface of the pipe, and the thermal flow sensor 10 is inserted into this slot, thereby making electrical connection with an external flow rate detection control circuit. It is possible to detect the flow rate of the fluid to be tested flowing in the pipe.

  Next, a modification of the above embodiment will be described.

  First, a first modification of the above embodiment will be described.

  FIG. 6 is a plan view showing a thermal flow sensor 50 according to this modification, and FIG. 7 is a detailed view of a portion VII in FIG.

  As shown in these drawings, the thermal flow sensor 50 according to the present modification has the same basic configuration as that of the above embodiment, and is configured as a card-like sensor. However, in this thermal flow sensor 50, the arrangement of the heating resistor 22 and the pair of electrode pads 32A and 32B extending from the heating resistor 22 is different from that in the above embodiment, and accordingly, resin The size and other details of the film piece 12 are different from those in the above embodiment.

  That is, in the present modification as well, the heating resistor 22 and the resistance temperature detectors 24 and 26 are formed to extend along a U-shaped path in a direction orthogonal to the methanol flow direction. The resistor 22 and the resistance temperature detectors 24 and 26 are reversed. Specifically, each of the resistance temperature detectors 24 and 26 has a pair of proximal ends positioned on the near side and is formed so as to be folded back on the opposite side. The pair of base end portions are located on the opposite side, and are formed so as to be folded back on the near side. Accordingly, each pair of electrode pads 34A, 34B, 36A, 36B extending from the resistance temperature detectors 24, 26 is formed on the front side of the flow path 2, whereas the heating resistor 2 The extending pair of electrode pads 32 </ b> A and 32 </ b> B is formed on the other side of the flow path 2.

  The four electrode pads 34A, 34B, 36A, and 36B are spread angles obtained by dividing an angular region of 180 ° located on the near side with respect to a straight line extending in the methanol flow direction into approximately four equal parts with a slight angular interval ( Specifically, it is formed at an expansion angle of about 35 to 40 °. The end portions of these electrode pads 34A, 34B, 36A, 36B (that is, the portions not covered with the protective film 16) are bent in the direction orthogonal to the methanol flow direction so as to be on the front side of the resin film piece 12. It extends to the long side 12b1. At that time, the end portions of these electrode pads 34A, 34B, 36A, and 36B (that is, the portions not covered by the protective film 16) all have the same width (specifically, a width of about 1 mm) in the methanol flow direction. ) And at equal intervals. As a result, the pair of electrode pads 34A and 34B extending from the upstream resistance temperature detector 24 and the pair of electrode pads 36A and 36B extending from the downstream resistance temperature detector 26 are related to the methanol flow direction. It is formed in a symmetrical shape.

  On the other hand, the two electrode pads 32A and 32B have a spread angle (specifically, an angular region of 180 ° located on the other side of a straight line extending in the methanol flow direction divided into approximately two equal intervals with a slight angular interval. Is formed at an expansion angle of about 75 to 80 °. The ends of the electrode pads 32A and 32B extend to the long side 12b2 on the other side of the resin film piece 12 so as to bend in a direction perpendicular to the methanol flow direction. At this time, the end portions of the electrode pads 32A and 32B are formed with the same width (specifically, a width of about 1 mm) and at equal intervals in the methanol flow direction. As a result, a pair of electrode pads 32A and 32B extending from the heating resistor 22 are formed symmetrically with respect to the methanol flow direction.

  In this modification, the configuration of the reference resistor 28 is the same as that in the above embodiment, but the pair of electrode pads 38A and 38B extending from the reference resistor 28 is larger than that in the above embodiment. It is formed at an angle (specifically, an expansion angle of about 35 to 40 °).

  In the thermal flow sensor 50 according to the present modification, the long side of the resin film piece 12 is equivalent to the amount of the pair of electrode pads 32A and 32B extending from the heating resistor 22 formed on the other side of the flow path 2. The length of is shortened. Specifically, it is set to 8.5 mm. On the other hand, the length of the short side of this resin film piece 12 is the same as that of the said embodiment. However, the thermal flow sensor 50 according to this modification is configured such that the flow path 2 is located at the center of the resin film piece 12 in the short side direction. And the part exposed from the protective film 16 is ensured equally in the both sides of the flow path 2 at the single side | surface 12a of the resin film piece 12. FIG.

  Even when the configuration of this modification is employed, the degree of freedom of the installation location of the thermal flow sensor 50 can be increased while sufficiently ensuring the sensitivity and accuracy of flow rate detection.

  Further, by adopting the configuration of this modification, a pair of electrode pads 34A, 34B, 36A, 36B extending from the resistance temperature detectors 24, 26 and a pair of electrode pads 32A extending from the heating resistor 22 are used. , 32B can be prevented from being arranged close to each other. As a result, even if the temperature of the pair of electrode pads 32A and 32B extending from the heating resistor 22 increases, the thermal effect does not reach the detection signals from the temperature measuring resistors 24 and 26. As a result, the accuracy of flow rate detection can be increased.

  Furthermore, by adopting the configuration of this modification, the thermal flow sensor 50 can be configured more compactly, and the degree of freedom of the installation location can be further increased in terms of size.

  Further, in the thermal flow sensor 10 according to this modification, the electrode pads 32A, 32B, 34A, 34B, 36A, 36B, 38A, and 38B are formed with a larger spread angle than in the above embodiment. Therefore, the resistance values of portions other than the heating resistor 22, the resistance temperature detectors 24 and 26, and the reference resistor 28 can be further reduced, thereby further increasing the sensitivity of flow rate detection.

  Next, a second modification of the above embodiment will be described.

  FIG. 8 is a plan view showing a thermal flow sensor 60 according to this modification, and FIG. 9 is a detailed view of a part IX in FIG.

  As shown in these drawings, the thermal flow sensor 60 according to the present modification has the same basic configuration as that of the embodiment and the first modification, and is configured as a card-like sensor. However, the thermal flow sensor 60 includes an arrangement of a pair of electrode pads 32A and 32B extending from the heating resistor 22 and an arrangement of the reference resistor 28 and a pair of electrode pads 38A and 38B extending from the reference resistor 28. However, it differs from the case of the said 1st modification, and in connection with this, the structure of the size of the resin film piece 12 and other details differs from the case of the said 1st modification.

  In other words, in this modification, not only the heating resistor 22 but also the reference resistor 28 is opposite in direction to the resistance temperature detectors 24 and 26. Specifically, the reference resistor 28 and the pair of electrode pads 38A, 38B of the first modification are reversed to the far side and further displaced to the downstream side. Thereby, in the present modification, the length of the long side of the resin film piece 12 is further shorter than in the case of the first modification. Specifically, it is set to 5.5 mm.

  However, in order to realize this, in this modification, the distance of the reference resistor 28 from the heating resistor 22 is set to about 2.5 mm, which is a considerably shorter value than in the case of the above-described embodiment and the first modification. In addition, the pair of electrode pads 32A and 32B extending from the heating resistor 22 also extends toward the downstream side from the heating resistor 22 in the same manner as the pair of electrode pads 38A and 38B extending from the reference resistor 28. It is formed as follows.

  Moreover, in this modification, the length of the short side of the resin film piece 12 is a little shorter than the case of the said embodiment and the said 1st modification. Specifically, it is set to 5 mm.

  Even when the configuration of this modification is employed, the degree of freedom of the installation location of the thermal flow sensor 60 can be increased while sufficiently ensuring the sensitivity and accuracy of flow rate detection.

  In addition, by adopting the configuration of this modification, the thermal flow sensor 60 can be configured more compactly, and the degree of freedom of the installation location can be further increased in terms of size.

  In the thermal flow sensor 60 according to this modification, the distance of the reference resistor 28 from the heating resistor 22 is set to about 2.5 mm, which is considerably shorter than the case of the above embodiment and the first modification. However, as described above, if this distance is set to a value of 2 mm or more, it is possible to detect the liquid temperature without being substantially affected by the heat from the heating resistor 22.

  In addition, the numerical value shown as a specification in the said embodiment and each modification is only an example, and of course, you may set these to a different value suitably.

The top view which shows the thermal type flow sensor which concerns on one Embodiment of this invention. Detailed view of part II in Fig. 1 (A) is sectional drawing which shows the mode of incorporating the said thermal type flow sensor in the multilayer substrate unit, (b) is sectional drawing which shows the laminated substrate unit in which the said thermal type flow sensor was incorporated. The perspective view which shows the thermal type flow sensor integrated as a part of the said multilayer substrate unit (A) is a cross-sectional view taken along the line Va-Va in FIG. 1, (b) is a detailed view of part b of (a), and (c) is a detailed view of part c of (b). The top view which shows the thermal type flow sensor which concerns on the 1st modification of the said embodiment. Detail view of part VII in Fig. 6 The top view which shows the thermal type flow sensor which concerns on the 2nd modification of the said embodiment. Detailed view of part IX in Fig. 8

Explanation of symbols

2 Flow path 10, 50, 60 Thermal flow sensor 12 Resin film piece 12a, 102a, 104a Single side 12b1 Long side on the near side 12b2 Long side on the other side 12c1 Short side on the upstream side 12c2 Short side on the downstream side 14, 106 Film 16 Protective film 16a Surface 22 Heating resistor 24, 26 Resistance temperature detector 28 Reference resistor 30 Mark 32A, 32B, 34A, 34B, 36A, 36B, 38A, 38B Electrode pad 100 Multilayer substrate unit 102 First substrate 102b Concave part 104 Second substrate 104b Concave groove

Claims (4)

A thermal type comprising: a heating resistor disposed in the flow path of the fluid to be tested; and a pair of temperature measuring resistors disposed in the flow path in the vicinity of the upstream side and the downstream side of the heating resistor. In the flow sensor,
The thermal flow sensor is configured as a card-like sensor comprising a resin film piece, a conductive film formed with a predetermined wiring pattern on one surface of the resin film piece, and a protective film partially covering the conductive film. Has been
The heating resistor and each temperature measuring resistor are formed as a part of the conductive film so as to extend in a direction substantially orthogonal to the flow direction of the fluid to be tested,
The protective film is formed so as to cover at least a portion facing the flow path on the one surface of the resin film piece,
As a part of the conductive film, a pair of electrode pads extending from the heating resistor and a pair of electrode pads extending from the temperature measuring resistors are formed,
Each said electrode pad is formed so that it may spread from each of the said heating resistor and each said resistance temperature sensor in a substantially fan shape, The thermal type flow sensor characterized by the above-mentioned.   2. The heat according to claim 1, wherein the heating resistor and each of the temperature measuring resistors are formed so as to extend along a U-shaped path in a direction substantially orthogonal to a flow direction of the fluid to be tested. Type flow sensor.   A pair of electrode pads extending from the heating resistor and a pair of electrode pads extending from the resistance temperature detectors are formed so as to be located on opposite sides of the flow path. The thermal type flow sensor according to claim 2 characterized by things.   A reference resistor for detecting the temperature of the test fluid at a position away from the heating resistor and the resistance temperature detectors on the one side of the resin film piece on the upstream side in the flow direction of the test fluid, The thermal flow sensor according to any one of claims 1 to 3, wherein the thermal flow sensor is formed as a part of the conductive film so as to extend in a direction substantially orthogonal to the flow direction of the fluid to be detected.

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