JP2012042384A - Temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a temperature sensor capable of having a long wire length without making curvature radius of lead wires small.SOLUTION: The temperature sensor 100 includes thermo sensitive element 10 for outputting electrical signals corresponding to the temperature of a heat source and the lead wires 31, 32 for outputting the electrical signals. The lead wires 31, 32 are wired to wind around a prescribed point.

Description

  The present invention relates to a temperature sensor for non-contact measurement of the temperature of a heat source.

  As a temperature sensor for non-contact measurement of the temperature of the heat source, a method of detecting the amount of infrared heat radiated from the heat source is known. This type of temperature sensor includes an infrared absorption film that efficiently absorbs infrared rays from a heat source, and a temperature-sensitive element detects an increase in temperature of the infrared absorption film due to infrared reception. The temperature sensing element has a temperature characteristic in which an electrical characteristic changes corresponding to the temperature, and the temperature of the heat source can be estimated based on an electric signal output from the temperature sensing element. As such a temperature sensitive element, a thermistor having a resistance temperature characteristic in which a resistance value changes according to temperature, a thermocouple that generates a thermoelectromotive force according to temperature, or the like is known. Further, as an infrared absorbing film, a polymer film such as polyimide having a characteristic of absorbing a far-infrared wavelength band is known.

  The electrical signal output from the temperature sensing element is supplied to the detection circuit through the lead wiring wired on the infrared absorption film. Since the thermal conductivity (400 W / mK) of the lead wiring is extremely higher than the thermal conductivity (0.2 to 0.4 W / mK) of the infrared absorption film, the amount of heat flowing from the infrared absorption film to the temperature sensitive element is one. This part is pointed out as one of the factors that cause a decrease in the sensitivity of the temperature sensing element because it hardly flows into the temperature of the temperature sensing element and flows out through the lead wiring. In view of such circumstances, as a wiring pattern for suppressing heat from flowing out of the lead wire from the temperature sensing element, for example, as disclosed in Utility Model Registration No. 2506241, a meander shape is disclosed. The wiring pattern is known. Since the meander-like wiring pattern is bent while being repeatedly folded, the substantial wiring length can be increased and the thermal resistance can be increased.

Utility Model Registration No. 2506241

  However, if the area of the infrared absorption film is small, meander-shaped lead wirings must be packed in a limited space, so that the bending radius of curvature becomes extremely small, which may limit circuit design. Further, it is not preferable to repeatedly bend the lead wiring with a small radius of curvature, because the lead wiring may be peeled off or cracked due to the stress acting on the folded portion. In particular, when the thermal resistance of the lead wiring is increased in order to suppress the heat outflow from the temperature sensitive element, the lead wiring is thinned and thinned, so that it tends to become brittle against stress.

  Therefore, an object of the present invention is to propose a temperature sensor that can increase the wiring length without reducing the radius of curvature of the lead wiring.

  In order to solve the above-described problems, a temperature sensor according to the present invention includes a temperature-sensitive element that outputs an electrical signal corresponding to the temperature of a heat source, and a lead wiring for outputting the electrical signal. It is wired so as to wind around a predetermined point. According to such a wiring structure, since the lead wiring can be wound along the periphery of the region where the lead wiring is wired, even if the area of the lead wiring is small, the wiring length of the lead wiring is small. Can be long.

  The temperature sensor may further include an infrared absorption film that generates heat by absorbing infrared rays radiated from a heat source. The temperature sensing element can output an electric signal corresponding to the temperature of the heat source by detecting the amount of heat of the infrared absorption film. Further, since the lead wiring can be wound along the peripheral edge of the infrared absorption film, the wiring length of the lead wiring can be increased even if the area of the infrared absorption film is small. Assuming that heat other than heat conduction by the lead wiring escapes from the temperature sensitive element, the lead wiring crosses in the direction of heat escape, so that it is possible to provide a configuration in which heat is more difficult to escape.

  The temperature sensor according to the present invention may further include a heat collecting member for collecting the amount of heat distributed in the infrared absorption film in the temperature sensitive element. The amount of heat distributed in the infrared absorbing film is transferred to the temperature sensitive element quickly through the heat collecting member, so that the temperature of the heat source can be measured accurately and with good responsiveness.

  According to the temperature sensor of the present invention, the wiring length can be increased without reducing the curvature radius of the lead wiring.

3 is an explanatory diagram of a temperature sensor according to Embodiment 1. FIG. It is explanatory drawing of the temperature sensor concerning Example 2. FIG. It is explanatory drawing of the temperature sensor concerning a comparative example. 6 is a circuit configuration diagram of a temperature sensor according to Embodiment 4. FIG. 6 is a cross-sectional view of a temperature sensor according to Embodiment 4. FIG. 6 is a partial plan view of a temperature sensor according to Embodiment 4. FIG. FIG. 10 is an explanatory diagram of a temperature sensor according to a fourth embodiment. 6 is a partial cross-sectional view of a temperature sensor according to Embodiment 4. FIG. 6 is a partial cross-sectional view of a temperature sensor according to Embodiment 4. FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. The same members are denoted by the same reference numerals, and redundant description is omitted. The drawings are schematic, and the ratio of dimensions between members, the shape of the members, and the like may be different from the actual sensor structure within a range where the effects of the present invention can be obtained.

  FIG. 1 is an explanatory diagram of a temperature sensor 100 according to the first embodiment. The temperature sensor 100 absorbs infrared rays radiated from the heat source and generates heat, and the temperature sensing element 10 outputs an electric signal corresponding to the temperature of the heat source by detecting the amount of heat of the infrared absorption film 20. And lead wires 31 and 32 for outputting an electric signal from the temperature sensing element 10. The material of the infrared absorption film 20 may be any material that efficiently absorbs radiation infrared rays from a heat source and generates heat. For example, a material having an absorption spectrum for light in a wavelength band of 4 μm to 10 μm called far infrared rays. desirable. As such a material, a resin made of a polymer material such as fluorine, silicone, polyester, polyimide, polyethylene, polycarbonate, PPS (polyphenylene sulfide) is preferable. The temperature sensing element 10 is a sensor element (for example, a thermistor, a thermopile, a metal thermometer having a resistance temperature characteristic, etc.) whose electrical characteristics change according to temperature. The temperature sensing element 10 includes electrodes 11 and 12 connected to lead wires 31 and 32, respectively. A change in electrical characteristics corresponding to the temperature change of the temperature sensing element 10 is read as an electrical signal corresponding to the temperature of the heat source. The wires 31 and 32 are taken out to the outside. For example, when the temperature sensitive element 10 is a thermistor having resistance temperature characteristics, the temperature change of the temperature sensitive element 10 appears as a resistance value change. By causing a predetermined current to flow through the temperature sensing element 10 in advance, a change in resistance value of the temperature sensing element 10 is detected as a voltage change. The output voltage of the temperature sensing element 10 is signal-processed as an electrical signal corresponding to the temperature of the heat source.

  The lead wires 31 and 32 are wired so as to be wound around a predetermined point. Although the position of the predetermined point is not particularly limited, for example, an arbitrary position where the temperature sensing element 10 is disposed is preferable, and the center position of the temperature sensing element 10 is more preferable. According to such a wiring structure, since the lead wirings 31 and 32 can be wound along the peripheral edge of the infrared absorption film 20, even if the area of the infrared absorption film 20 is small, the wiring of the lead wirings 31 and 32 is possible. The length can be increased. Further, by winding the lead wires 31 and 32 so as to wind around a predetermined point, the curvature radius of the bent portion 50 of the lead wires 31 and 32 can be increased, so that the lead wires 31 and 32 are bent sharply. There is no need, and peeling of the lead wires 31 and 32, cracking, and the like can be effectively suppressed. For example, when the shape of the infrared absorption film 20 is rectangular, the bending angle of the bent portion 50 of the lead wirings 31 and 32 can be suppressed to about 90 °.

  FIG. 2 is an explanatory diagram of a temperature sensor 200 according to the second embodiment. As shown in the figure, the temperature sensor 200 is different from the first embodiment in that a heat collecting member 40 is provided, and the first and second embodiments have a common sensor structure. The heat collecting member 40 is a member for capturing the amount of heat distributed in various places of the infrared absorption film 20 and collecting the heat in the temperature sensing element 10. The heat collecting member 40 captures heat over a wide range not only from the region in the vicinity of the temperature sensing element 10 but also from the region away from the temperature sensing element 10, so that the electrodes 11, 12 can collect heat efficiently in the temperature sensing element 10. Are formed radially in the plane of the infrared absorption film 20. The heat collecting member 40 is not a member related to transmission of an electric signal but a member related only to heat conduction, and thus terminates in the plane of the infrared absorption film 20 without being connected to an external component. For this reason, heat does not flow out from the heat collecting member 40, and heat flows in one direction from the end of the heat collecting member 40 toward the temperature sensing element 10. The heat collecting member 40 radiates while repeatedly branching from the electrodes 11 and 12 toward the outer peripheral end of the infrared absorbing film 20 in order to uniformly capture the amount of heat stored in various places of the infrared absorbing film 20. It is preferable that it is formed. With such a configuration, the amount of heat distributed in the infrared absorption film 20 is scattered in an island shape between the branches of the heat collecting member 40, and the temperature gradient between the infrared absorption film 20 and the temperature sensing element 10. Thus, a heat flow can be generated toward the temperature sensing element 10. In addition, by forming the heat collecting member 40 radially, the heat collecting range 50 in which heat can be captured can be expanded to the entire infrared absorbing film 20, and the heat collecting efficiency can be increased. In addition, since the heat transfer path from the connection portion between the heat collecting member 40 and the electrodes 11 and 12 to each point of the infrared absorption film 20 can be shortened, the amount of heat distributed in the infrared absorption film 20 can be sensed through the heat transfer path with low thermal resistance. Heat can be quickly collected to the temperature element 10. Thereby, the temperature sensing element 10 can react with high responsiveness to the temperature change of the heat source.

  Since the amount of heat flowing through the heat collecting member 40 increases as it approaches the temperature sensing element 10, it is preferable that the heat collecting member 40 be thickened and the thermal resistance be lowered as the temperature sensing element 10 is approached. Thereby, the heat collecting member 40 becomes thinner as it approaches the end, and the thermal resistance becomes higher. Therefore, the heat flow toward the end can be suppressed and the heat flow to the temperature sensing element 10 can be promoted. . Further, even when the amount of heat distributed to each point of the infrared absorption film 20 is small, heat is collected via the low-resistance heat collecting member 40 and flows into the temperature sensing element 10. Decrease can be suppressed and sensitivity characteristics can be enhanced.

  At the time when the infrared rays from the heat source start to be radiated to the infrared absorption film 20, the temperature difference between the temperature sensing element 10 and the infrared absorption film 20 is large, and the temperature gradient from both the heat collecting member 40 to the temperature sensing element 10. Heat flows in. Then, as the temperature of the temperature sensitive element 10 rises, the temperature gradient becomes smaller, so that the heat flow into the temperature sensitive element 10 decreases. On the other hand, a part of the heat collected in the temperature sensing element 10 is radiated through the lead wires 31 and 32 and the ambient atmosphere, and the temperature of the temperature sensing element 10 is lowered. The heat inflow continues. Then, when the amount of heat flowing into the temperature sensing element 10 and the amount of heat flowing out of the temperature sensing element 10 are balanced, a thermal equilibrium state is established, and the temperature of the temperature sensing element 10 becomes constant.

  The material of the heat collection member 40 should just be a material which has a thermal resistance smaller than the thermal resistance of the infrared rays absorption film 20, and is excellent in thermal conductivity. For example, the material of the heat collecting member 40 may be the same as or different from the material of the lead wires 31 and 32. When the material of the heat collecting member 40 is the same as the material of the lead wires 31 and 32, there is an advantage that the heat collecting member 40 and the lead wires 31 and 32 can be formed in the same film forming process. For example, a copper foil is formed on the infrared absorbing film 20 and patterned into a predetermined shape using a known printing technique, thereby forming the heat collecting member 40 and the lead wires 31 and 32 having conductivity at once. be able to. When the material of the heat collecting member 40 is different from the material of the lead wires 31 and 32, for example, a material having a high thermal conductivity other than metal (such as a carbon graphite film) may be used as the material of the heat collecting member 40. .

  The lead wirings 31 and 32 are wired so as to be wound around a predetermined point (more specifically, around the heat collecting member 40). According to such a wiring structure, since the lead wirings 31 and 32 can be wound along the peripheral edge of the infrared absorption film 20, the lead is formed while sufficiently securing the area of the formation region 41 of the heat collecting member 40. The wiring length of the wirings 31 and 32 can be increased. On the other hand, in the temperature sensor 300 according to the comparative example shown in FIG. 3, since the lead wires 31 and 32 are bent in a meander shape, the heat collecting member 40 depends on the area occupied by the formation regions 71 and 72 of the lead wires 31 and 32. Therefore, it is difficult to increase the area of the heat collecting member 40. In addition, the bending angle of the bent portion 70 of the lead wirings 31 and 32 is limited due to restrictions in circuit design, so it is difficult to increase the wiring length in a limited space. Comparing Example 2 and the comparative example, the area of the heat collecting member 40 forming region 41 according to Example 2 is about 1.5 times the area of the heat collecting member 40 forming region 42 according to the comparative example. In addition, the wiring length of the lead wirings 31 and 32 according to the second embodiment is about 1.5 times the wiring length of the lead wirings 31 and 32 according to the comparative example. As described above, according to the second embodiment, it is possible to achieve both improvement in heat collection efficiency by increasing the area of the heat collection member 40 and suppression of heat outflow due to increase in the thermal resistance of the lead wires 31 and 32.

  In the comparative example, if the radius of curvature of the bent portion 70 is increased in order to reduce the stress acting on the bent portion 70 of the lead wirings 31 and 32, the number of turns of the lead wirings 31 and 32 is reduced. The wiring length is shortened. On the other hand, in Example 2, even if the bending angle of the bent portion 60 is increased in order to reduce the stress acting on the bent portion 60 of the lead wirings 31 and 32, the wiring length is hardly shortened. As described above, according to the second embodiment, by increasing the radius of curvature of the bent portion 60, it is possible to increase the wiring length of the lead wires 31 and 32 while reducing the stress acting on the bent portion 60. In the second embodiment, when the four corners of the infrared absorption film 20 are rounded, the length of the lead wirings 31 and 32 is increased even if the bent portion 60 is gently (curved radius) along the roundness. In the comparative example, when the four corners of the infrared absorption film 20 are rounded, the bent portion 70 is loosened so that the lead wires 31 and 32 and the four corners of the infrared absorption film 20 do not come into contact with each other. In addition, since the bent portion 60 is widened, the number of turns is reduced, and the wiring length of the lead wires 31 and 32 is shortened.

  FIG. 4 is a circuit configuration diagram of a temperature sensor 400 according to the third embodiment. The infrared temperature sensor 400 includes a half bridge circuit composed of a temperature sensing element 10A and a fixed resistance element 13A connected in series, and a half bridge circuit composed of a temperature compensation temperature sensor 10B and a fixed resistance element 13B connected in series. And have a full bridge circuit connected in parallel. A power source 14 is connected between the connection point of the two fixed resistance elements 13A and 13B and the connection point of the two temperature sensing elements 10A and 10B, and is configured so that a current flows through the full bridge circuit. Yes. The infrared sensing temperature sensing element 10A is a sensor element for sensing the amount of infrared radiation emitted from the heat source, and the temperature compensating temperature sensing element 10B is a sensor element for sensing the amount of heat from the external environment. . The amount of heat received by the infrared sensing temperature sensing element 10A is not limited to the amount of infrared radiation radiated from the heat source, but also receives the amount of heat from the external environment, so the temperature compensation temperature sensing element 10B detects the amount of heat from the external environment. Thus, the amount of infrared heat radiated from the heat source (that is, the temperature of the heat source) can be estimated. For this reason, the infrared detecting temperature sensing element 10A is arranged so as to receive infrared rays emitted from the heat source, while the temperature compensating temperature sensing element 10B does not receive infrared rays emitted from the heat source (in other words, For example, so that only the amount of heat from the external environment can be detected).

  An output terminal 15 is connected to a connection point between the infrared sensing temperature sensing element 10A and the fixed resistance element 13A, and an output terminal 16 is connected to a connection point between the temperature compensation temperature sensing element 10B and the fixed resistance element 13B. Yes. When the resistance temperature characteristics of the temperature sensing element 10A for infrared detection and the temperature sensing element 10B for temperature compensation are adjusted to be substantially the same, and the resistance values of the fixed resistance elements 13A and 13B are adjusted to be substantially the same, the infrared temperature sensor 400 receives the heat from the heat source. In the state where infrared rays are not irradiated, the voltage between the output terminals 15 and 16 becomes zero. On the other hand, in the state where the infrared temperature sensor 400 is irradiated with infrared rays from a heat source, the infrared detecting temperature sensing element 10A and the temperature compensation feeling. An unbalanced voltage is output between the output terminal electrodes 15 and 16 due to the difference in resistance value of each of the temperature elements 10B. By preparing map data that associates the unbalanced voltage with the temperature of the heat source in advance, the temperature of the heat source can be estimated from the unbalanced voltage.

  FIG. 5 is a cross-sectional view of the temperature sensor 400, and FIG. 6 is a partial plan view of the temperature sensor 400. As shown in FIG. 6, the infrared sensing temperature sensing element 10A includes electrodes 11A and 12A connected to the lead wires 31A and 32A on the infrared absorbing film 20A, respectively, and the temperature change of the infrared sensing temperature sensing element 10A. The change in the electrical characteristics corresponding to is taken out from the lead wires 31A and 32A as an electrical signal corresponding to the amount of heat generated from the heat source and the external environment. Similarly, the temperature compensation temperature sensing element 10B includes electrodes 11B and 12B connected to the lead wirings 31B and 32B, respectively, on the infrared absorption film 20B, so that the electric current corresponding to the temperature change of the temperature compensation temperature sensing element 10B can be obtained. The change in characteristics is taken out from the lead wires 31B and 32B as an electrical signal corresponding to the amount of heat generated from the external environment. The lead wirings 31 </ b> A, 32 </ b> A, 31 </ b> B, and 32 </ b> B are connected to the electric wire 411 through the solder 412. The infrared absorption films 20A and 20B are preferably separated so as not to conduct heat mutually. As shown in FIG. 5, the infrared absorption films 20 </ b> A and 20 </ b> B are interposed between the cover 402 and the bottom plate 401 via spacers 403. The cover 402 includes a light guide unit 420 that shields infrared rays from the heat source from entering the temperature-compensating temperature sensitive element 10B and guides the infrared rays from the heat source to the infrared absorption film 20A. The electric wire 411 is bonded to the bottom plate 401 with an adhesive 413.

  As a structure for improving the sensitivity of the temperature sensor 400, it is conceivable to increase the opening area of the light guide unit 420. However, only the temperature distribution of the infrared absorption film 20A in the vicinity of the temperature sensitive element 10A changes the temperature of the temperature sensitive element 10A. 7, the area (light receiving area) of the infrared absorption film 20 </ b> A may be smaller than the opening area of the light guide unit 420 as shown in FIG. 7. As a structure for making the area of the infrared absorption film 20A smaller than the opening area of the light guide section 420, for example, as shown in FIG. 8, an aperture 421 is provided on the infrared receiving surface to reduce the area of the infrared absorption film 20A. As shown in FIG. 9, a structure in which the inner wall of the light guide 420 is tapered to reduce the area of the infrared absorption film 20 </ b> A can be considered. In such a structure, since the area of the infrared absorption film 20A becomes small, it is preferable that the wiring patterns of the lead wirings 31A and 31B are designed to be the same wiring patterns as those in the first or second embodiment. Note that θ1 shown in FIG. 8 and θ2 shown in FIG. 9 each indicate an infrared incident angle range. The infrared absorbing film 20A may be provided with a heat collecting member as in the second embodiment. In addition, either the infrared absorption film or the infrared reflection film may be formed on the inner wall of the light guide unit 420.

  The temperature sensor according to the present invention can be used for non-contact measurement of the temperature of the heat source.

DESCRIPTION OF SYMBOLS 10 ... Temperature sensing element 11, 12 ... Electrode 20 ... Infrared absorption film 31, 32 ... Lead wiring 40 ... Heat collecting member 100, 200, 300, 400 ... Temperature sensor

Claims (3)

A temperature sensing element that outputs an electrical signal corresponding to the temperature of the heat source;
A lead wiring for outputting the electrical signal,
The temperature sensor, wherein the lead wiring is wired so as to wind around a predetermined point. The temperature sensor according to claim 1,
An infrared absorption film that absorbs infrared rays radiated from the heat source and generates heat;
The temperature sensor is a temperature sensor that detects heat generation of the infrared absorption film and outputs an electrical signal corresponding to the temperature of the heat source. The temperature sensor according to claim 2,
A temperature sensor further comprising a heat collecting member for collecting heat quantity distributed in the infrared absorption film on the temperature sensitive element.

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