JP2007155502A - Detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detector having improved accuracy for detecting the thermophysical values of a medium. <P>SOLUTION: The detector has a heater 300 for producing heat by power supply and a support part 500 for supporting the heater 300, and detects the thermophysical values of the medium by the heat exchange between the heater 300 and the medium. This detector has a crosslinked structure wherein the heater 300 is arranged to a cavity part 600 provided to the support part 500 and detection is performed during a period reaching a thermal equilibrium state after the start of power supply. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a detector that detects a thermal property value such as thermal conductivity of a medium such as a gas or a liquid, and more particularly to a detector that functions as an electric heater.

  Patent Document 1 “Method for Manufacturing Electric Heater” discloses a linear heater in which the heater portion is only an electrothermal material in FIG. 5 (b), but disclosed heat conduction to gas around the heater. Since it is not a thing, conduction efficiency is not considered.

  The “electric heater” of Patent Document 2 discloses a method for reducing heat dissipation from the heater to the electrode portion, and the effect is shown in FIG. However, in the relationship between the temperature difference and the detected amount, no consideration is given to bringing the temperature of the electrode portion close to the heater temperature.

  Patent document 3 “Atmosphere sensor structure” discloses widening the interval between heater patterns in order to achieve uniform thermal temperature distribution (paragraph 0018). However, since the heater and the thin film insulator 12 having different thermal properties are integrated, no consideration is given to efficiently detecting only the heat conduction between the heater and the atmosphere.

  Patent Document 4 describes a flow rate detecting element and a flow rate sensor that adjust the interval between heating resistors to reduce the amount of heat conduction to the support (paragraph 0025). However, the efficiency of heat conduction of the heating resistor itself is not considered.

The “heat exchanger” of Patent Document 5 discloses the technical contents showing the relationship between the fin pitch and the like of the heat exchanger and the thermal conductivity. is required.
Japanese Patent Publication No. 2-13739 Japanese Patent Publication No. 6-32267 Japanese Patent No. 3086314 JP 11-201792 A Japanese Examined Patent Publication No. 5-77959

The structure of a conventional detector is shown in FIG. In this detector, an electric insulating layer 200 (SiO ₂ ) is laminated on a substrate 100 (Si), and a pattern of a heater 300 made of an electrically conductive material (Pt), electrodes P1 and P2, and connection leads 400 is arranged. Further, the electrical insulating layer 200 is stacked, and the electrical insulating layer 200 in contact with the heater 300 is removed by etching. Then, the substrate 300 is etched to form a cavity 600, and the heater 300 is formed in the cavity 600. It is a structure that crosslinks. The support portion 500 has a function of supporting the heater 300 that is cross-linked. Electrical wiring is appropriately connected to the electrodes P1 and P2 of the detector of FIG. 15 by means of integrated circuit packaging means such as bonding wires, and is incorporated into the constant temperature control drive circuit shown in FIG. 16 through the electrodes P1 and P2 and connection leads 400. Electric power is applied to the heater 300 so that the heater 300 reaches a desired temperature by the constant temperature setting resistor of FIG. Depending on the temperature gradient between the heater 300 and the medium such as gas / liquid in the surrounding space 700 and the thermal conductivity of the medium such as gas / liquid in the surrounding space 700 until the heater 300 reaches a desired temperature, In order to conduct heat to a medium such as gas or liquid in the space 700, the temperature of the heater 300 itself rises transiently until reaching a thermal equilibrium state with a temperature gradient with the surrounding space 700. The temperature change that rises transiently is reflected in the output voltage detected by the electrode P2. Therefore, the amount of heat conduction to the heat conducting medium can be detected by measuring the transition of the output voltage, that is, the transition of the power consumption of the heater 300. By connecting a device equipped with the constant temperature control driving circuit shown in FIG. 16 to the electrodes P 1 and P 2, the temperature gradient between the heater 300 and a medium such as gas or liquid in the surrounding space 700 at the desired temperature of the heater 300. Accordingly, the amount of heat conduction can be measured by this apparatus as a transition of power consumption. As a result, the thermal conductivity of the medium such as gas or liquid in the surrounding space 700 is obtained, or if it is calibrated in advance with a medium having a predetermined thermal conductivity, the medium and others can be compared with the measured values. The mixing ratio (concentration) with the medium can be obtained.

The heat generated from the heater 300 not only conducts heat to the surrounding medium but also conducts heat to the support portion 500 of the heater 300. In order to increase the accuracy of the detection value, it is preferable to reduce the area of the support portion 500 that contacts as much as possible. Therefore, a structure in which a cavity portion 600 is provided is employed. Furthermore, in order to efficiently reflect the amount of heat generated by the heater 300 in the detected amount without excess or deficiency, it is desirable to make the temperature of the heater 300 as high as possible and the temperature of the medium as low as possible. As indicated by Newton's law of cooling, the rate at which the temperature T of the object changes within a unit time is proportional to the temperature difference between the current temperature T of the object and the surrounding surrounding the object, so that the temperature difference is This is due to the heat conduction principle that the larger the value, the greater the amount of heat conduction.

  However, in the case of the heater 300 arranged with double lines as shown in FIG. 15, the concern is that the temperature rise of the surrounding medium due to the influence of the adjacent heaters 300 (interval D1) arranged with double lines affects the accuracy of the detected value. Is done. Therefore, if the voltage is continuously applied, the temperature of the surrounding medium may be rapidly increased by the heater 300 over time. In this respect, if heaters arranged in a straight line with respect to the cavity portion 600 are used, there is no adjacent heater, so the temperature rise of the surrounding medium due to the influence of adjacent heaters arranged in multiple lines is eliminated. However, the structure in which the heaters are arranged in a straight line makes it difficult to detect with high accuracy because the value of the output voltage to be detected is too small. Further, in order to increase the value of the output voltage, if the heater is a straight line, the heater must be made thin and long. In addition, since the durability of the heater itself is usually hindered, a covering means for reinforcing the heater itself has been used in view of the ease of manufacturing the detector. However, since the portion of the covering means that reinforces the heater itself has a heat capacity, detecting the amount of heat conduction to the heater and the surrounding medium consumes extra conduction time and amount of conduction. A structure that does not use covering means such as the heater 300 has been adopted.

  In the conventional structure shown in FIG. 15, when the heater interval D1 is as narrow as 4 μm as shown in (b), as shown in (c), the heater surface position S1 and the heater vicinity position S2 (2 μm apart from S1) 17) is measured from the energization start time, the result is shown in the graph of FIG. At the position S1, a thermal equilibrium state of 200 ° C. is reached at 11 msec, the temperature gradually increases due to heat conduction at the position S2, and the temperature difference between S1 and S2 decreases from 140 ° C. at 11 msec to 110 ° C. at 30 msec. Then, as shown in the graph of FIG. 18, when the heater adjacent interval D1 is 4 μm, the output voltage Vout after 11 msec has decreased to 7.8V. This is because the heater gap is too small, so the temperature difference is small, and the influence of the adjacent heater is large.

  On the other hand, the detection must be performed at predetermined time intervals, but the temperature of the surrounding medium must not be increased by the heat generated from the heater 300. A heater in which the temperature of the surrounding medium rises due to the heat of the heater 300, so that the temperature difference between the heater 300 and the surrounding medium becomes small, the amount of heat conduction from the heater 300 decreases, and the detection amount decreases. The thermal effect on the surrounding medium by 300 must be taken into account.

  In addition, when the medium itself is at a high temperature, the temperature difference between the heater 300 and the surrounding medium is naturally small, and the thermal conductivity is small. Since the output voltage detected at this time shows non-linearity with respect to the temperature change of the medium, it takes time to calibrate and correct the temperature for temperature compensation with high accuracy, or use a complicated compensation circuit. There must be. In order to eliminate such a situation, it is natural to consider the arrangement, shape, energization, and detection method of the heater so that the temperature of the surrounding medium is not increased by the heater, but it is particularly necessary to consider the detection timing. is there.

  Accordingly, an object of the present invention is to provide a detector capable of improving the accuracy of detection of a thermophysical property value of a medium in consideration of the above circumstances.

  An aspect of the present invention that achieves the above object includes a first heat generating means that generates heat by energization, and a support means that supports the first heat generating means, by heat exchange between the first heat generating means and the medium. In the detector for detecting the thermophysical value of the medium, the detector has a bridging structure in which the first heat generating unit is arranged in a cavity provided in the supporting unit, and after the start of energization until the thermal equilibrium state is reached. The detection is performed.

  Here, there are two or more first heat generating means, and an interval between adjacent first heat generating means is set to be twice or more of a diffusion length of heat generated by the first heat generating means.

  Also, there is a second heat generating means that generates heat by energization and adjusts the temperature of the support means, and the timing of heat generation by the first heat generating means is substantially the same as the timing of heat generation by the second heat generating means. It is characterized by doing.

  Further, in order to energize the first heat generating means, there is provided a connecting means for connecting the first heat generating means and the electrode, and a covering means for covering the connecting means.

  Further, the first heat generating means has a three-dimensional shape, and has a temperature sensing means for detecting the amount of heat of the medium.

  The detector of the present invention can increase the amount of detection and improve the measurement accuracy by simple means considering the detection timing. Due to the simple means, the voltage required for energization is minimized, and the overload to the heat generating means is reduced and the stability of reproducibility is improved. Further, since the detection is performed in a short time, the transient fluctuation in the surrounding medium can be grasped in detail.

  Hereinafter, the best mode for carrying out the present invention will be described. In the description, reference is made to the drawings submitted at the same time as this specification.

The structure of the detector of this embodiment is shown in FIG. In this detector, an electric insulating layer 200 (SiO ₂ ) is laminated on a substrate 100 (Si), and a pattern of a heater 300 made of an electrically conductive material (Pt), electrodes P1 and P2, and connection leads 400 is shown in FIG. In this way, a microfabrication process is performed in which the electrical insulating layer 200 is further stacked, and the electrical insulating layer 200 in contact with the heater 300 is removed by etching, and then the substrate 100 is etched to form the cavity 600. As a result, the heater 300 is cross-linked to the cavity 600. The support portion 500 has a function of supporting the heater 300 that is cross-linked. The principle of measuring the thermal conductivity of the medium is as described above. A device equipped with the constant temperature control drive circuit shown in FIG. 16 is connected to the electrodes P1 and P2, and the transition of power consumption is measured by this device.

  When the material of the heater 300 is Pt, the heater has a thickness of 0.1 to 1 μm and a width of 1 to 5 μm in consideration of the detection amount and the yield of microfabrication. In this case, the smaller the cross-sectional area of the heater 300, the better the efficiency of heat generated inside to heat conduction to the outside. This is because if the cross-sectional area of the heater 300 is large, the heat inside the heater 300 is not easily transmitted to the outside, and the internal heat is lost.

  The heater 300 arranged along a straight line on the cavity 600 has a length of 1 to 5 mm. The longer the heater 300, the larger the amount of heat conduction and the larger the detected amount, but if it is too long, the material, thickness, width, temperature In consideration of the above, if it exceeds approximately 1.5 mm, a support portion may be provided at an intermediate position to prevent strength and deformation.

In addition, the heater support portion 500 is an electric insulating film other than the electrothermal material used as the heater 300 to prevent strength and deformation (a film covering the electric insulating layer 200, and uses SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ . .) Is often supported by a bridge or a diaphragm. However, since heat dissipation to the support portion 500 of the heater 300 is not heat dissipation to the surrounding medium, it is preferable to reduce the support portion 500 as much as possible. Therefore, it is more preferable to use only the electrothermal material as much as possible without supporting the electrothermal material with a bridge or a diaphragm. The outer shape of the substrate 100 is 0.2 to 0.4 mm in thickness, 0.5 to 1 mm in width, and 1.5 to 6 mm in length. The longer the heater 300 is, the longer the outer shape of the substrate 100 is.

  In order to obtain information on the thermophysical properties of the surrounding medium as a detector, the temperature of the heater 300 is set to an appropriate value of 50 to 500 ° C. by constant resistance control by the constant temperature drive control circuit of FIG. The heat supply amount due to the heat conduction is obtained as an increase amount of an electric signal such as power consumption to the constant temperature setting resistor (constant resistance value). In a medium with a dry air of 25 ° C., the time for reaching the heater thermal equilibrium state from 25 ° C. to 50 to 500 ° C. is 0.1 to 50 msec corresponding to the temperature for reaching the heater thermal equilibrium state.

  As an example, in a medium of dry air at 25 ° C., a heater 300 having a material of Pt, a thickness of 0.5 μm, a width of 3 μm, and a length of 1 mm is used, and the outer shape of the substrate 100 is 0.3 mm in thickness, 0.7 mm in width, The heater 300 was controlled at a constant temperature of 200 ° C. by a constant temperature drive control circuit of FIG. The results are shown in the graphs of FIGS.

  First, as shown in FIG. 2, the time for reaching the heater thermal equilibrium from room temperature 25 ° C. to 200 ° C. is 10 msec. Next, when the temperatures of the heater surface position S1 and the heater vicinity position S2 (2 μm away from S1) in FIG. 1C are measured from the energization start time, a thermal equilibrium state of 200 ° C. is reached at position S1 in 10 msec. At position S2, the temperature gradually increases due to heat conduction, and the temperature difference between S1 and S2 is 150 ° C. at 10 msec and decreases to 125 ° C. at 30 msec. Then, as shown in the graph of FIG. 3, when the output voltage Vout of 10 msec is 4.0 V, it becomes 3.8 V at 30 msec, which is reduced by about 5%.

  After reaching the thermal equilibrium state, the temperature of the heater 300 does not rise, but the temperature of the surrounding medium rises, so the temperature difference becomes smaller, the amount of heat conduction decreases, and the detection amount decreases. Therefore, the amount of heat conduction can be increased by detecting by the time when the thermal equilibrium state is reached, and the detected amount can be increased.

  Here, as shown in FIG. 4, if a stop time is provided so as to decrease the temperature at the position S2 and driving is performed and detection is performed at the “detection timing” in the figure, the measurement can be continuously performed with high repeatability. In addition, by installing a plurality of the detectors of FIG. 1 and driving them at different timings, it is possible to perform a measurement with a short detection intermittent time while maintaining a pause time in which the temperature can be lowered if the respective detections are combined. is there.

  Further, for example, when the medium is a mixed medium of dry air and hydrogen, as shown in FIG. 5, when the temperature is seen by the temperature dependency of the output voltage Vout, the detection timing is 30 msec as compared with the detection timing of 10 msec. Thus, the higher the temperature of the mixed medium, the smaller the change in output voltage. That is, it can be seen that at the detection timing 30 msec, the temperature of the mixed medium is not in a first-order proportional relationship than at 10 msec. Therefore, it can be seen that by detecting the output voltage to be detected by the time when the thermal equilibrium state is reached, the linearity to the high temperature region of the medium is improved and the measurement range can be expanded. For example, in the measurement of the concentration of hydrogen leaking into the air in the fuel cell system, the temperature range is -20 to 60 ° C, and in the measurement of the water vapor concentration with respect to hydrogen in the fuel cell, the temperature is 0 to 100 ° C. Thus, measurement can be performed with high accuracy under a wide range and high temperature conditions.

  From the above description, the detector of this embodiment has a large detection amount and improved measurement accuracy by a simple means considering the detection timing. Moreover, useless voltage application is eliminated by detecting with the minimum necessary power application. As a result, the overload to the heater can be reduced and stable reproducibility can be obtained. Moreover, the transient fluctuations of the surrounding medium could be grasped in detail by detecting in a short time. Moreover, it was possible to measure intermittently with good repeatability by driving and detecting the temperature to decrease. Further, the temperature dependency is improved by improving the temperature dependence, and the labor for acquiring the temperature calibration is simplified, and no compensation circuit is required. And the use of a detector is expanded by extending a measurement range.

  Another structure of the detector of this embodiment is shown in FIG. Since the basic structure is the same as that of FIG. 1, the description thereof is omitted. The difference is that the heater 300, the electrodes P1, P2, and the connection lead 400 pattern connecting the heaters 300 are arranged in a U-shape, and the portion where the pattern is folded is supported by the support portion 500. It is a point. As a result, two heaters 300 are disposed in the cavity 600. This is especially true if the degree of integration is improved by utilizing semiconductor microfabrication technology so that small-sized detectors can be mass-produced. For this reason, it is necessary to provide a detection region as large as possible in a very small chip, that is, it is necessary to arrange a double-line heater.

  Each heater 300 disposed on the cavity 600 has a length of 0.2 to 0.8 mm, and the heater interval D2 is 10 to 20 μm. The outer shape of the substrate 100 is 0.2 to 0.4 mm in thickness, 0.5 to 1 mm in width, and 0.5 to 1.5 mm in length. The time for reaching the thermal equilibrium state by the heater 300 from room temperature 25 ° C. to 50 to 500 ° C. is 0.1 to 50 msec corresponding to the temperature at which the heater thermal equilibrium state is reached.

  The method for obtaining information on the thermophysical properties of the medium around the detector is the same in that the constant temperature drive control circuit of FIG. 16 is used. However, since the heater 300 is a double line, the resistance value of the heater increases and the output voltage increases. Keep in mind.

  As an example, in a medium of dry air at 25 ° C., the material is Pt, the thickness is 0.5 μm, the width is 3 μm, the length is 1 mm, the heater adjacent distance D2 is 15 μm, the outer shape of the substrate 100 is 0.3 mm in thickness, and 0.7 mm in width. The heater 300 was controlled at a constant temperature of 200 ° C. by a constant temperature drive control circuit of FIG. The results are shown in the graphs of FIGS.

  First, as shown in FIG. 7, the time for the heater 300 to reach thermal equilibrium from 25 ° C. to 200 ° C. is 11 msec. Next, when the temperatures of the heater surface position S1 and the heater vicinity position S2 (2 μm away from S1) in FIG. 6C are measured from the energization start time, a thermal equilibrium state of 200 ° C. is reached at position S1 in 11 msec. At position S2, the temperature gradually increases due to heat conduction, and the temperature difference between S1 and S2 decreases to 150 ° C. at 11 msec and to 125 ° C. at 30 msec. This value is substantially the same as the elapsed time-temperature difference characteristic of the detector when there is no adjacent heater (FIG. 2), and it can be determined that the influence of the adjacent heater is small.

  Further, when the heater interval D1 is as narrow as 4 μm as in the prior art (FIG. 15), as shown in FIG. 17, the temperature difference between the positions S1 and S2 was 140 ° C. (11 msec) to 110 ° C. (30 msec). The detector having the structure shown in FIG. 6 maintains a state where the temperature difference is large. Further, when the transition of the output voltage Vout in FIG. 8 is compared, when the heater adjacent interval D2 is 15 μm, it is 7.9 V (11 msec), and the heater adjacent interval D1 is 7.8 V, which is reduced by about 2%. End up. Therefore, it is better to make the heater adjacent interval wider than 4 μm.

  The condition is that the temperature of the medium at the central position between adjacent heaters should not be increased by the heat conduction from the heater, considering the relationship between the temperature of the heater surface and the temperature of the medium in FIG. In other words, the heat conduction distance from the heater surface when the heater is maintained at a constant temperature is the heat diffusion length of the heater (= heat conduction speed × time), and considering the influence from adjacent heaters, the adjacent distance is the diffusion length. Two times or more are necessary. The diffusion length depends on the temperature difference, time, and thermal conductivity of the medium. Furthermore, it can be seen that the shorter the energization time, the shorter the distance between adjacent heaters. That is, the timing at which the temperature difference becomes the largest in a period where the temperature from the heater is not increased at the diffusion length to the medium is from the start of energization that reaches the maximum temperature of the heater until the thermal equilibrium state is reached.

  As an example, assuming a detector that measures the amount of water vapor in the atmosphere, the thermal diffusion length is 6 μm with a thermal conductivity of 26.1 mW / mK at 25 ° C., a temperature gradient of 150 K, and a time of 11 msec. Even if the amount of heat of the heater heating time to reach is included, the heater interval may be 10 to 20 μm or more. The heater adjacent interval of 15 μm can be said to be a substantially optimal interval when measuring the amount of water vapor in a normal living atmosphere near room temperature.

  Further, when viewing the graph of FIG. 8, the output voltage Vout when the heater adjacent interval D2 is 15 μm is 7.9 V at 11 msec and 7.5 V at 30 msec, which is reduced by about 5%. After reaching the thermal equilibrium state, the temperature of the heater does not rise, but the temperature of the surrounding medium rises, so the temperature difference becomes smaller, the amount of heat conduction decreases, and the detection amount decreases. Therefore, in addition to the above-mentioned heater adjacent interval being required to be twice or more the diffusion length, the amount of heat conduction can be increased by detecting by the time when the thermal equilibrium state is reached, and the detected amount can be increased.

  Thus, for example, when measuring the amount of water vapor in a normal living atmosphere near room temperature, the heater adjacent interval is 15 μm, and if the heater heating time is 11 msec and detected by 11 msec, it can be said that the condition is almost optimal. Furthermore, as described with reference to FIG. 4, if a pause time is provided so that the temperature at the position S <b> 2 is lowered and driven and detected, the measurement can be repeated intermittently with high accuracy, and other heaters are installed. If they are driven alternately, measurement with a shorter time interval can be performed.

  In FIG. 6, the double-line heater is shown as two heaters. However, as shown in FIG. In this case, the stability of the heater 300 is maintained by providing two hollow portions 600 at the top and bottom and supporting the intermediate position of the heater 300 by the support portion 500.

  From the above description, the detector shown in FIG. 6 has a large detection amount and improved measurement accuracy by simple means considering the detection timing. Moreover, useless voltage application is eliminated by detecting with the minimum necessary power application. As a result, the overload to the heater can be reduced and stable reproducibility can be obtained. Moreover, the transient fluctuations of the surrounding medium could be grasped in detail by detecting in a short time. Moreover, it was possible to measure intermittently with good repeatability by driving and detecting the temperature to decrease. In addition, the amount of detection increased as the amount of heat conduction increased, and the measurement accuracy improved. Moreover, the accuracy of the substrate has further reduced the size of the substrate, so that it can be mounted at a minute location. Further, the temperature dependency is improved by improving the temperature dependence, and the labor for acquiring the temperature calibration is simplified, and no compensation circuit is required. And the use of a detector is expanded by extending a measurement range.

  Another structure of the detector of this embodiment is shown in FIG. The basic structure is the same as that shown in FIG. The difference is that when the cavity portion 600 is provided, the support portion 500 is provided between them, that is, a part where the electrical insulating layer 200 is etched is omitted, and the electrodes P3 and P4, the support portion heater are omitted. The point is that 800 patterns are arranged. As a result, the pattern of the heater 300, the electrodes P1 and P2, and the connection lead 400 arranged on a straight line is supported by the support portion 500 at the center position. When a voltage is applied to the electrode P3 to generate heat in the support portion heater 800, this heat functions to adjust the temperature of the support portion 500. Then, the output voltage is detected by the voltage P4, and the transition of the power consumption in the support portion heater 800 is measured.

  Since heat dissipation from the heater 300 to the support portion 500 is not heat dissipation to the surrounding medium, it is better to reduce the area of the support portion 500 as much as possible. In addition, when the thermal conductivity of the heater 300 is not negligible compared to the thermal conductivity of the medium in the surrounding space 700, the support unit 500 is also brought close to the temperature of the heater 300 to reduce the heat flow from the heater 300 to the support unit 500. There is a need. In addition, when the temperature of the support unit 500 rises, heat conduction to the medium around the support unit 500 occurs, and the detected amount becomes an obstacle, so it is necessary to reduce the heat conduction from the support unit 500 to the medium. .

  When the material of the heater 300 is a metal material such as Pt, the thermal conductivity is much larger than that of a medium such as a gas in the surrounding space 700, so that the amount of heat conduction to the support portion 500 is conducted to a medium such as a surrounding gas. It tends to be bigger than it does. Therefore, if the temperature in the vicinity of the connection lead 400 connected to the support unit 500 and the electrodes P1 and P2 is close to that of the heater 300, since the temperature difference with the heater 300 is small, the amount of heat conduction is small and the detection amount is small. The patterns of the electrodes P3 and P4 and the support heater 800 that indirectly heat them are also provided.

  When detecting the heat conduction amount of the medium, the heating timing by the heater 300 and the timing for side-heating the support portion 500 may be basically made substantially the same. However, since the support portion 500 has a larger heat capacity than the heater 300 bridged to the cavity portion 600, it takes time to reach thermal equilibrium from the heater 300 in order to heat it at the same timing. Increasing the value is more effective (see the graph of FIG. 12).

However, when the temperature of the support part 500 rises, heat conduction to the medium around the support part 500 occurs. The vicinity of the connection lead 400 connected to the support unit 500 and the electrodes P1 and P2 has different thermophysical properties from the surrounding medium, and becomes an obstacle when measuring only the state of the surrounding medium. Therefore, it is necessary to exclude the influence. is there. For this purpose, the connection lead 400 may be made wider or thicker or shorter than the heater 300 to reduce the resistance value of the connection lead 400 and reduce the detection amount of the connection lead. Further, by applying a coating such as SiO ₂ having a higher thermal insulation than the heater 300 to the connection lead 400, the influence can be reduced by further reducing the heat conduction to the surrounding medium. Furthermore, the effect is enhanced by coating a polymer organic material film such as a resin material that has a better thermal insulation than a coating of SiO ₂ or the like with a high thermal insulation property or a porous Al ₂ O ₃ film. .

  FIG. 13 is a modification of FIG. 11 and shows a pattern in which the detector heater of FIG. 1 is provided with a support heater 800 and electrodes P3 and P4. The efficiency is selectively increased only in the region where the temperature difference is large, and the heat conduction information of the material of the substrate 100 can be removed to obtain information on the surrounding medium by being limited only to the heat conduction of the surrounding medium.

  From the above description, in addition to the effects described above, the temperature of the surrounding medium is further reduced by bringing the temperature near the connection lead 400 closer to the temperature of the heater 300 and reducing the amount of heat conduction to the surrounding medium near the connection lead 400. Only conduction information could be measured, and high-precision measurement was possible.

  FIG. 14 illustrates a configuration of a heat conduction type flow sensor in which the heater 300 used in the above-described detector has a three-dimensional shape. The above-described detector is a method for measuring the amount of heat released when heat is generated, corresponding to power consumption. However, when the medium for measuring the amount of heat conduction flows at a constant speed, the invention of the invention related to the above-described detector. It is better to use a method in which the temperature sensing unit 900 measures the amount of heat that is transmitted through the medium and conducted using specific matters. The temperature sensing unit 900 has a coil-like shape and is disposed on the concentric axes at both ends of the heater 300. At this time, the arrangement, shape and energization method of the heater 300 are devised so that the temperature of the surrounding medium does not rise.

  That is, the heater 300 is de-energized before the time of reaching the thermal equilibrium state, and when the heaters 300 are arranged in multiple lines, the interval between adjacent heaters 300 is set to be at least twice the thermal diffusion length of one heater. . Although not shown in FIG. 14, the support heater 800 may be used to heat the vicinity of the connection lead 400 of the support 500 and add a heat insulating material.

  With such a configuration, in addition to the effects described above, there is no waste in heat conduction to the fluid, so that a minute flow rate and a high-temperature fluid flow rate can be measured with high accuracy with a smaller electric power.

  The above-described embodiment is the best for carrying out the present invention, but the present invention is not limited to this. Therefore, various modifications can be made without departing from the scope of the present invention.

  Other than the base gas present in the base gas by detecting hydrogen leaking into the air, such as an absolute humidity sensor that measures the amount of water vapor in the air, a flammable gas leak detector and a hydrogen gas leak point detector for fuel cells Gas concentration sensor for measuring the gas concentration of gas, thermal conductivity gas analysis sensor for gas with a thermal conductivity different from the thermal conductivity of the base gas used in the gas chromatograph of the thermal conductivity detector system, thermal flow sensor for gas, Development of products such as thermal flow sensors for liquids and dew condensation sensors is desired.

  The heater temperature may be set to an appropriate value of 50 to 500 ° C. Depending on the thermal conductivity of the medium, the temperature of the medium, and the value to be measured, a gas or liquid thermal flow sensor is 50 to 150 ° C., an absolute humidity sensor is 150 to 400 ° C., and a gas concentration sensor is used. If it exists, it can be used by switching the temperature in the range of 200 to 500 ° C., and in the case of a gas analysis sensor in the range of 50 to 500 ° C.

The structure of the detector of this form is illustrated. (A) is a front view, (b) (c) is BB sectional drawing. In particular, (c) illustrates the heater surface position S1 and the heater vicinity position S2. It is a graph showing the time change of the temperature in position S1 and position S2 of the detector of FIG. It is a graph showing the time change of the output voltage from the heater 300 of the detector of FIG. It is a graph showing the time change of the temperature in the position S1 by the intermittent drive, and the position S2. It is a graph showing the temperature dependence of the output voltage with respect to the hydrogen concentration contained in the air. The other structure of the detector of this form is illustrated. (A) is a front view, (b) (c) is CC sectional drawing. In particular, (c) illustrates the heater surface position S1 and the heater vicinity position S2. It is a graph showing the time change of the temperature in position S1 and position S2 of the detector of FIG. It is a graph showing the time change of the output voltage from the heater 300 of the detector of FIG. It is a graph showing the relationship between the distance from the heater surface, and a temperature difference. The other structure of the detector of this form is illustrated. The other structure of the detector of this form is illustrated. (A) is a front view, (b) is DD sectional drawing. (C) is EE sectional drawing. It is the graph showing the drive timing and detection timing of the heater 300 and a support part heater. The other structure of the detector of this form is illustrated. The configuration of a heat conduction type flow sensor having a three-dimensional heater 300 is illustrated. 1 illustrates the structure of a conventional detector. (A) is a front view, (b) (c) is AA sectional drawing. In particular, (c) illustrates the heater surface position S1 and the heater vicinity position S2. It is a circuit diagram of the constant temperature control drive circuit incorporating the detector of the past and this form. It is a graph showing the time change of the temperature in position S1 and position S2 of the conventional detector. It is a graph showing the time change of the output voltage from the heater 300 of the conventional detector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Board | substrate 200 Electrical insulation layer 300 Heater 400 Connection lead 500 Support part 600 Cavity part 700 Ambient space 800 Support part heater 900 Temperature sensing part P1 electrode P2 electrode P3 electrode P4 electrode

Claims (5)

A first heat generating means for generating heat by energization;
Supporting means for supporting the first heat generating means;
In the detector for detecting the thermal property value of the medium by heat exchange between the first heat generating means and the medium,
A detector having a bridging structure in which the first heat generating means is disposed in a hollow portion provided in the support means, and performing detection before the thermal equilibrium state is reached after the start of energization. Having two or more first heat generating means;
2. The detector according to claim 1, wherein an interval between adjacent first heat generating means is set to be twice or more of a diffusion length of heat generated by the first heat generating means. A second heat generating means for generating heat by energization and adjusting the temperature of the support means;
3. The detector according to claim 1, wherein the timing of heat generation by the first heat generation unit is substantially the same as the timing of heat generation by the second heat generation unit. Connection means for connecting the first heat generating means and the electrode to energize the first heat generating means;
The detector according to claim 1, further comprising a covering unit that covers the connection unit. The first heating means has a three-dimensional shape;
The detector according to any one of claims 1 to 4, further comprising a temperature sensing means for detecting the amount of heat of the medium.

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