JP6868465B2 - Temperature sensor - Google Patents

Description

The present invention relates to a film-type thermocouple temperature sensor having excellent flexibility.

特許文献２では、導電性粒子を含有する樹脂を用いた温度センサーが提案されている。その原理は以下の通りである。即ち、低温では樹脂中の導電性粒子は互いに接触しており、抵抗値は低いが、温度が上昇し、ある温度を超えると樹脂が熱膨張し、導電性粒子間に間隙が生じ抵抗値が増大する。このような特性は、温度の上昇と共に電気抵抗が増大するため「ＰＣＴ特性」（Ｐｏｓｉｔｉｖｅ Ｔｅｍｐｅｒａｔｕｒｅ Ｃｏｅｆｆｉｃｉｅｎｔ）という。 As a flexible type temperature sensor, a type that utilizes the temperature dependence of electrical resistance has been proposed. For example, Patent Document 1 uses a semiconductor thin film. The electrical resistance of a semiconductor decreases as the temperature rises, and its temperature dependence is expressed by the following equation. This type of temperature sensor is called a thermistor, and as the B value increases, the electrical resistance changes sensitively to temperature, so a material with a large B constant is required.

Patent Document 2 proposes a temperature sensor using a resin containing conductive particles. The principle is as follows. That is, at low temperatures, the conductive particles in the resin are in contact with each other and the resistance value is low, but the temperature rises, and when the temperature exceeds a certain temperature, the resin thermally expands, creating gaps between the conductive particles and increasing the resistance value. Increase. Such a characteristic is called a "PCT characteristic" (Positive Temperature Coefficient) because the electric resistance increases as the temperature rises.

Since the temperature sensor described in Patent Document 1 requires a sputtering device for forming a semiconductor film, there is a concern that the manufacturing cost will increase. Further, it is necessary to reduce the film thickness in order to suppress the occurrence of cracks due to bending, but when the resistance value becomes large due to the thinning, there is a problem that self-heating is generated by the current at the time of resistance measurement and the measurement accuracy is lowered. ..
On the other hand, the temperature sensor described in Patent Document 2 has a very narrow measurement temperature range of 10 ° C. or less. Further, since it is used near the melting point of the resin, there is a problem in durability.

Japanese Unexamined Patent Publication No. 2014-70953 WO2015-119205

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a temperature sensor capable of simultaneously measuring the temperature of a plurality of flat surfaces with high accuracy and a basic unit of the temperature sensor. To do.

In order to achieve the above object, the present inventor has been able to invent the following temperature sensor as a result of diligent studies. That is, the present invention is a temperature sensor having the following technical configurations.

[1] A basic unit of a temperature sensor that measures the temperature of a plurality of measurement points, which is provided by electrically joining an n-type thermoelectric conversion material thin film and a p-type thermoelectric conversion material thin film to a ribbon-shaped electrically insulating sheet. The n-type thermoelectric conversion material thin film end and the p-type thermoelectric conversion material thin film end of the ribbon-shaped thermoelectric element are electrically connected to the n-type electrode and the p-type electrode arranged on the high thermal conductivity sheet, respectively, and the n-type electrode and the p-type are connected. A basic unit of a temperature sensor characterized in that the temperature at the junction between an n-type thermoelectric conversion material thin film and a p-type thermoelectric conversion material thin film is measured by the potential difference between both electrodes.
[2] The basic unit of the temperature sensor according to the above [1], wherein the joint portion between the n-type thermoelectric conversion material thin film and the p-type thermoelectric conversion material thin film is bonded by a metal electrode.
[3] A temperature sensor characterized in that a plurality of basic units of the temperature sensor according to the above [1] or the above [2] are arranged on a high thermal conductive sheet.
[4] The temperature sensor according to the above [3], wherein a reference temperature sensor for measuring a reference temperature is installed on the surface of the high thermal conductivity sheet.
[5] A plurality of n-type electrodes and a plurality of p-type electrodes are arranged on the high thermal conductivity sheet, and the n-type thermoelectric conversion material thin film end and the p-type thermoelectric conversion material thin film end of the basic unit are n-type electrodes. The temperature sensor according to the above [3] or the above [4], wherein each of the n-type electrodes and the p-type electrodes is electrically connected so that the combination of the p-type electrodes and the p-type electrodes is different.
[6] A plurality of n-type electrodes and a plurality of p-type electrodes are arranged on the high thermal conductivity sheet so as to intersect in an insulated state, and the basic unit is placed on the intersecting n-type electrodes and p-type electrodes. The temperature sensor according to the above [5], wherein the terminal of the thin film of the n-type thermoelectric conversion material and the end of the thin film of the p-type thermoelectric conversion material are electrically connected.

The temperature sensor of the present invention is in close contact with an object having a curved shape (a pipe-shaped object, a human neck, an arm, etc.), and can simultaneously measure the temperature of the surface of these objects with high accuracy. .. In particular, it is useful for measuring the temperature distribution of an object having a curved surface shape.

It is sectional drawing of the ribbon-shaped thermoelectric element which provided the p-type thermoelectric conversion material thin film and the n-type thermoelectric conversion material thin film on the ribbon-shaped electrically insulating sheet. Both ends of the ribbon-shaped element shown in FIG. 1 are fixed by bridging two electrodes fixed to a high thermal conductive sheet, and electrodes are installed at the junction between the n-type thermoelectric conversion material thin film and the p-type thermoelectric conversion material thin film. , It is a cross-sectional view of the basic unit of the temperature sensor as the contact point with the object. It is a top view of the temperature sensor which arranged 3 × 3 basic units of the temperature sensor of FIG. 2 on one high thermal conductivity sheet. It is a figure explaining the specific method for measuring the temperature of each measurement point of the temperature sensor of FIG. An example of a method for manufacturing the ribbon-shaped thermoelectric element of FIG. 1 is shown. It is a figure which showed the state (top surface (a) and cross section (b)) immediately after film formation of a thin film thermoelectric conversion element, and the state (c) which was cut into a ribbon shape. It is a figure which shows the measuring method of the relationship between the temperature difference ΔT between both ends and the central part of the ribbon-shaped thermoelectric element of FIG. 1 and the thermoelectromotive force. It is a figure which shows the relationship between the temperature difference ΔT between both ends and the central part of the ribbon-shaped thermoelectric element of FIG. 1 and the thermoelectromotive force. It is a figure which shows the relationship between the output voltage of the temperature sensor of FIG. 2 and the measurement temperature.

The temperature sensor of the present invention is characterized in that a plurality of the basic units described in the above [1] are arranged on a high thermal conductive sheet. First, the basic unit of the temperature sensor of the present invention will be described.

The basic unit of the temperature sensor of the present invention is an n-type thermoelectric conversion material thin film of a ribbon-shaped thermoelectric element provided by electrically joining an n-type thermoelectric conversion material thin film and a p-type thermoelectric conversion material thin film to a ribbon-shaped electrically insulating sheet. The end and the end of the p-type thermoelectric conversion material thin film are electrically connected to the n-type electrode and the p-type electrode arranged on the high thermal conductivity sheet, respectively, and the n-type is caused by the potential difference between the n-type electrode and the p-type electrode. It is characterized by measuring the temperature of the joint between the thermoelectric conversion material thin film and the p-type thermoelectric conversion material thin film.

Hereinafter, it will be described more specifically with reference to the drawings.
FIG. 1 is a cross-sectional view of a ribbon-shaped thermoelectric element constituting a basic unit. In the ribbon-shaped thermoelectric element 10, an n-type thermoelectric conversion material thin film 1 and a p-type thermoelectric conversion material thin film 2 are formed on a ribbon-shaped electrically insulating sheet 4. They are provided in contact so as to be electrically joined. Further, it is more preferable that the n-type thermoelectric conversion material thin film 1 and the p-type thermoelectric conversion material thin film 2 are brought into contact with each other and bonded, and the bonded portion is bonded by the metal electrode 3.
The ribbon-shaped electrically insulating sheet 4 is preferably a flexible sheet.

The basic unit of the temperature sensor of the present invention measures the temperature of the joint between the n-type thermoelectric conversion material thin film and the p-type thermoelectric conversion material thin film.
Therefore, the boundary between the n-type and p-type thermoelectric conversion material thin films serves as a contact point with the object to be measured.
By providing the metal electrode 3 in the film bonding portion, electrical bonding can be ensured, contact resistance can be reduced, and thermal conductivity is good, which is also preferable for temperature measurement.

FIG. 2 is a cross-sectional view of the basic unit of the temperature sensor. The n-type electrode 22 and the p-type electrode 23 fixed to the high thermal conductivity sheet 25 are electrically connected to the n-type thermoelectric conversion material thin film 1 end and the p-type thermoelectric conversion material thin film 2 end of the ribbon-shaped thermoelectric element by the conductive adhesive 21, respectively. It is connected to.
It is preferable to provide an insulating layer 23 between the high thermal conductive sheet 25 and the n-type electrode 22 and the p-type electrode 23 in order to further ensure electrical insulation, but the high thermal conductive sheet 25 has good electrical insulation. If it is, the insulating layer 23 may not be provided.

As the ribbon-shaped electrically insulating sheet 4, a resin such as polyimide, polyethylene terephthalate, or silicone, which is a flexible material, or a ribbon-shaped sheet made of a material such as paper can be used.

The n-type and p-type thermoelectric conversion material thin films can be produced by a commonly used film forming process using n-type and p-type thermoelectric conversion materials.
The film forming process includes dry methods such as vacuum deposition, CVD, and sputtering, coating methods such as casting, spin coating, bar coating, and slit coating, printing methods such as inkjet and screen printing, and plating. A film forming process such as a method or an electrolytic deposition method can be used.

Known materials may be used for the n-type and p-type thermoelectric conversion materials. For example, for n-type thermoelectric conversion materials, Bi ₂ Te ₃ , CoSb ₃ , Mg ₂ Si, FeSi ₂ , SiGe and other compound semiconductors, semiconductors such as Si and Ge, and for p-type thermoelectric conversion materials, Bi ₂ Te ₃ , Compound semiconductors such as PbTe, CoSb ₃ , Mg ₂ Si, FeSi ₂ , SiGe, semiconductors such as Si and Ge, conductive polymers such as polyacetylene, polypyrrole, polythiophene, polyaniline, poly (p-phenylene vinylene), and carbon nanotubes. Materials such as carbon-based materials such as graphene can be used.

A metal thin film such as Ag, Au, Cu, or Pt can be used for the metal electrode 3, and the film forming method includes a dry method such as a vacuum vapor deposition method or a sputtering method, a coating method, a plating method, and electrolytic precipitation. Wet methods such as methods, coating methods such as casting method, spin coating method, bar coating method, slit coating method, and printing methods such as inkjet method and screen printing method using metal nanoparticles ink such as Ag, Au, and Cu. Can be used.

Metal thin films such as Ag, Au, Cu, and Pt can be used for the n-type electrode 22 and the p-type electrode 23, and the film forming method includes a dry method such as a vacuum vapor deposition method or a sputtering method, a coating method, and plating. Wet methods such as methods and electrolytic precipitation methods, as well as coating methods such as casting method, spin coating method, bar coating method, and slit coating method using metal nanoparticle inks such as Ag, Au, and Cu, inkjet method, and screen printing. A printing method such as a method or a method of adhering a metal foil processed into a desired shape can be used.

A commercially available conductive adhesive can be used as the conductive adhesive 21, but a type that cures at room temperature is desirable. Specific examples include Dotite (Fujikura Kasei) and TK Paste (Kaken Tech).

For the high thermal conductive sheet 25, a metal foil such as Cu or Al, a carbon material such as graphite, or various commercially available heat radiating sheets can be used.

As the insulating layer, a resin such as polyimide, polyethylene terephthalate, or silicone, a sheet made of a material such as paper, or the like can be used.

Next, the temperature measurement principle using the basic unit of this flexible temperature sensor will be described. When the joint portion between the n-type thermoelectric conversion material thin film 1 and the p-type thermoelectric conversion material thin film 2 or the electrode 3 provided at the joint portion is brought into contact with the temperature measurement object, the following equation (1) is obtained. In addition, an electromotive force V proportional to the temperature difference ΔT between the contact point and the n-type electrode (p-type electrode) is generated between the n-type electrode 22 and the p-type electrode p. The proportionality constant S at this time is equal to the sum of the absolute value of the Seebeck coefficient Sn of the n-type thermoelectric conversion material thin film and the absolute value of the Seebeck coefficient Sp of the p-type thermoelectric material thin film.
V = S × ΔT (S = | Sn | + | Sp |) (1)
T = V ÷ S + T ₀ (2)
Therefore, dividing V by S gives ΔT. When the reference temperature T ₀ is added to this, the temperature at the contact point is obtained (Equation (2)). Regarding T ₀ , since the temperatures of both the n-type electrode and the p-type electrode are fixed to the high thermal conductive sheet, they are substantially equal to the temperature of the surface of the high thermal conductive sheet. Temperature of the high thermal conductive sheet surface may also be substituted by a temperature, but measures the temperature of the direct high thermal conductive sheet surface temperature sensor, such as a commercially available thermocouple or thermistor, may be used as the reference temperature T _0.

Next, the temperature sensor of the present invention will be described.
The temperature sensor of the present invention is characterized in that a plurality of basic units of the temperature sensor according to the above [1] or the above [2] are arranged on a high thermal conductive sheet.
The high thermal conductive sheet is of the same type as the high thermal conductive sheet described in the basic unit, and the one exemplified above can be used. By using the high thermal conductivity sheet, the relative values of a plurality of installed temperature sensors can be measured.

Preferably, the temperature sensor of the present invention is characterized in that a reference temperature sensor for measuring a reference temperature is installed on the surface of the high thermal conductivity sheet.
As the reference temperature sensor, a commercially available thermistor, thermocouple, resistance temperature detector, IC temperature sensor, or the like can be used.
As an example of installing the reference temperature sensor, a temperature sensor for measuring the reference temperature may be adhered to the surface of the high thermal conductivity sheet. By doing so, the temperature of the surface of the high thermal conductive sheet 25 can be set as the reference temperature.
Even without a reference temperature sensor, the temperature sensor of the present invention can measure the relative temperature of a plurality of measurement points, and the ambient temperature when the temperature sensor such as the room temperature is measured is used as the reference temperature. This makes it possible to measure a plurality of temperatures. However, in order to measure a plurality of temperatures with higher accuracy, it is preferable to install a reference temperature sensor for measuring a reference temperature on the surface of the high thermal conductivity sheet.

More preferably, in the temperature sensor of the present invention, a plurality of n-type electrodes and a plurality of p-type electrodes are arranged on the high thermal conductivity sheet, and the n-type thermoelectric conversion material thin film end and the p-type thermoelectric of the basic unit are arranged. The end of the thin film of the conversion material is electrically connected to either the n-type electrode and the p-type electrode so that the combination of the n-type electrode and the p-type electrode is different.

Most preferably, the temperature sensor of the present invention is arranged on the high thermal conductive sheet so that a plurality of n-type electrodes and a plurality of p-type electrodes intersect in an insulated state, and the n-type electrodes intersecting with each other. It is characterized in that the n-type thermoelectric conversion material thin film end and the p-type thermoelectric conversion material thin film end of the basic unit are electrically connected to the p-type electrode.
By arranging the n-type electrode and the p-type electrode in this way, the apparatus can be further simplified.

Hereinafter, the most preferable embodiment will be described with reference to FIG.
FIG. 3 is a diagram showing a temperature sensor in which 3 × 3 basic units of the temperature sensor of FIG. 2 are arranged on the same high thermal conductivity sheet.
On the high thermal conductivity sheet 25, three n-type electrodes 22 (vertical direction) and p-type electrodes 23 (horizontal direction) are installed intersecting each other. The intersection of the n-type electrode 22 and the p-type electrode 23 is electrically insulated. The method of electrical insulation may be a normal electrical insulation method, but insulation can be achieved by providing an insulating layer 23 under each electrode. Then, the basic units are arranged in the vicinity of each intersection (9 in the figure), and both ends of the ribbon-shaped thermoelectric element 10 of the basic unit (n-type thermoelectric conversion material thin film end and p-type thermoelectric conversion material thin film end) are conductive. It is electrically connected to the nearby n-type electrode 22 and p-type electrode 23 by the adhesive 21.
A reference temperature sensor 26 is installed on the surface of the high thermal conductive sheet 25 opposite to the surface on which the basic unit of the temperature sensor is installed.

Next, a method of measuring the temperature in each basic unit will be described. FIG. 4 is a wiring diagram for connecting the n-type electrodes n1 to n3 and the p-type electrodes p1 to p3 of the temperature sensor 20 of FIG. 3 to the voltmeter 31. The temperature at the measurement points a to i at the center of the basic unit can be obtained by substituting the voltage between the electrodes shown in Table 1, the voltage-temperature difference conversion constant, and the reference temperature into the equation (2). Switches 32 and 33 are inserted between the voltmeter and the n-type electrode and between the voltmeter and the p-type electrode to measure the voltage between the desired electrodes, respectively.

[Example 1]
Embodiments of the present invention will be described with reference to the examples of FIGS. 3 and 5. FIG. 5A shows a thin film 1 of an n-type thermoelectric conversion material and a thin film 2 of a p-type thermoelectric conversion material formed on the surface of an electrically insulating sheet 4 (10 mm × 18 mm) in a strip shape with a width of 5 mm. is there. A polyimide film (thickness 50 μm) was used for the electrically insulating sheet 4. As the thermoelectric conversion material, bismuth antimony (BiSb) was formed into an n-type film by vacuum deposition, and a p-type conductive polymer PEDOT: PSS was formed into a film by a slit coating method. As a method for forming a thin film of a thermoelectric conversion material, a wet process such as inkjet or screen printing, or a dry process such as sputtering or CVD can be adopted. A metal electrode 3 was formed at the boundary between the thermoelectric conversion material thin films 1 and 2 in order to ensure electrical bonding and reduce contact resistance. For the metal electrode, a silver paste (Fujikura Kasei Dotite D-550) was formed with a slit coat.
When this is cut into a ribbon shape having a width of 3 mm, the ribbon-shaped thermoelectric element shown in FIG. 5 (c) can be obtained.

In FIG. 3, n-type electrodes 22 (vertical direction) and p-type electrodes (horizontal direction) are arranged in a grid pattern on a high thermal conductive sheet 25 (50 × 50 mm), and both ends of the ribbon-shaped thermoelectric element 10 are used as the respective electrodes. It is fixed. A copper foil (thickness 40 μm) was used for the high thermal conductivity sheet. A copper-polyimide laminated sheet (Nippon Steel Chemical ESPANEXMC12-25-00CEM, polyimide: 25 μm, Cu: 12 μm) was used for the n-type electrode and the p-type electrode. Further, a silver paste (Fujikura Kasei Dotite D-550) was used for electrically connecting and fixing the ribbon-shaped thermoelectric element to the n-type and p-type electrodes.

FIG. 7 shows the results of evaluating the thermoelectric conversion characteristics of the ribbon-shaped thermoelectric element of FIG. The measurement method is shown in FIG. Thermocouples 28 and 29 were adhered to the n-type electrode 22 and the metal electrode 3, respectively, and the back surface of the high thermal conductive sheet 24 was brought into contact with a hot plate for heating. By doing so, the ribbon-shaped thermoelectric element generates a thermoelectromotive force proportional to the temperature difference ΔT between the thermocouple 27 (high temperature side) and 28 (low temperature side). The proportionality constant was 0.0878 [mV / ° C] from the slope of the approximate straight line in FIG.

FIG. 8 shows the temperature actually measured by the temperature sensor of FIG. The value obtained by dividing the output voltage by the above proportionality constant 0.0878 was added to the reference temperature of 23 ° C. to convert it into a temperature.

According to the present invention, it is possible to measure the temperature distribution inside an object. Therefore, for example, if the temperature sensor is brought into contact with a heat generating portion in electronic devices, the temperature distribution can be constantly monitored even inside the housing. Similarly, if it is attached to the human body, it is possible to constantly monitor the body temperature distribution while wearing clothes. Further, if a flat device such as a touch panel is used, it is possible to detect the position touched by the finger. It is also expected to be applied to measure the temperature distribution of the palm and perform a medical examination. Furthermore, in the future, if this temperature sensor is incorporated into the skin of a humanoid robot, it is not a dream to realize a humanoid robot that can feel the temperature of the whole body like a human being.

1 n-type thermoelectric conversion material thin film 2 p-type thermoelectric conversion material thin film 3 metal electrode 4 electrically insulating sheet 10 ribbon-shaped thermoelectric element 20 temperature sensor 21 conductive in which 3 × 3 basic units of temperature sensors are arranged on a high thermal conductive sheet 25 Sex adhesive 22 n-type electrode
23 p-type electrode
24 Insulation layer 25 High thermal conductivity sheet 26 Reference temperature sensor 28 Thermocouple (for high temperature measurement)
29 Thermocouple (for temperature measurement of low temperature part)
31 Voltmeter 32 n-type electrode changeover switch 33 p-type electrode changeover switch

Claims (6)

It is a basic unit of a temperature sensor that measures the temperature of multiple measurement points, and is a ribbon-shaped thermoelectric that is provided by electrically joining an n-type thermoelectric conversion material thin film and a p-type thermoelectric conversion material thin film to a ribbon-shaped electrically insulating sheet. The n-type thermoelectric conversion material thin film end and the p-type thermoelectric conversion material thin film end of the element are electrically connected to the n-type electrode and the p-type electrode arranged on the high thermal conductivity sheet, respectively, and both the n-type electrode and the p-type electrode are connected. A basic unit of a temperature sensor characterized in that the temperature of a joint between an n-type thermoelectric conversion material thin film and a p-type thermoelectric conversion material thin film is measured by a potential difference between electrodes. The basic unit of a temperature sensor according to claim 1, wherein a joint portion between an n-type thermoelectric conversion material thin film and a p-type thermoelectric conversion material thin film is bonded by a metal electrode. A temperature sensor according to claim 1 or 2, wherein a plurality of basic units of the temperature sensor are arranged on a high thermal conductive sheet. The temperature sensor according to claim 3, wherein a reference temperature sensor for measuring a reference temperature is installed on the surface of the high thermal conductivity sheet. A plurality of n-type electrodes and a plurality of p-type electrodes are arranged on the high thermal conductivity sheet, and the n-type thermoelectric conversion material thin film end and the p-type thermoelectric conversion material thin film end of the basic unit are n-type electrodes and p-type. The temperature sensor according to claim 3 or 4, wherein the electrodes are electrically connected to either n-type electrode and any p-type electrode so that the combination of electrodes is different. A plurality of n-type electrodes and a plurality of p-type electrodes are arranged on the high thermal conductivity sheet so as to intersect in an insulated state, and the n-type thermoelectric of the basic unit is placed on the intersecting n-type electrodes and p-type electrodes. The temperature sensor according to claim 5, wherein the terminal of the thin film of the conversion material and the end of the thin film of the p-type thermoelectric conversion material are electrically connected.

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