JP2003258323A - Thermoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To overcome a problem that an epoxy resin having big thermal conductivity of 0.3 W/m°C, which is filled into an thermoelectric device comprising a p-type thermoelectric semiconductor and an n-type thermoelectric semiconductor so as to enhance mechanical strength thereof, reduces thermoelectric performance of the thermoelectric device. <P>SOLUTION: An insulator comprising a porous polyurethane resin, styrene resin or the like containing micro bubbles is filled between a p-type thermoelectric semiconductor and an n-type thermoelectric semiconductor that constitute a thermoelectric device, thus a thermoelectric device being provided that maintains mechanical strength equal to that of a thermoelectric device having an epoxy resin filled therein and also has thermoelectric performance equal to that of a thermoelectric device not having an epoxy resin filled therein. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a thermoelectric element used in a thermoelectric power generator utilizing the Seebeck effect or a thermoelectric element used in a thermoelectric cooling device utilizing the Peltier effect, and particularly, the elements are arranged with a predetermined interval. Further, the present invention relates to a thermoelectric element in which at least a pair of p-type thermoelectric semiconductor and n-type thermoelectric semiconductor are electrically connected in series by a wiring electrode, and an insulator is filled in a gap between the thermoelectric semiconductors.

[0002]

2. Description of the Related Art Thermoelectric elements are mainly composed of a plurality of p-type thermoelectric semiconductors and n-type thermoelectric semiconductors, and have a function of directly converting thermal energy into electric energy and electric energy into thermal energy. When a temperature difference is applied across the thermoelectric element, a voltage is generated by the Seebeck effect. A thermoelectric generator is one that takes out this voltage as electric energy. Such a thermoelectric power generator makes it possible to directly convert energy from heat energy into electric energy, and has attracted attention as one of effective ways of utilizing heat energy as represented by waste heat utilization.

On the other hand, when a direct current is passed through this thermoelectric element,
Due to the Peltier effect, a phenomenon occurs in which one end absorbs heat and the other end dissipates heat (heat). Therefore, if an appropriate heat source is brought into contact with the heat absorbing side of the thermoelectric element in a good heat conduction state, it can be used as a thermoelectric cooling device for cooling the heat source. Also, by adjusting the current flowing through the thermoelectric element,
It can be used not only as a cooling device but also as a temperature control device for maintaining a constant temperature.

Unlike other types of cooling devices, thermoelectric cooling devices using thermoelectric elements do not include mechanical parts such as compressors and can be miniaturized, so that they are heat sources such as portable refrigerators, integrated circuits and laser light sources. It is used as a local thermoelectric cooling device or temperature control device.

In particular, a thermoelectric element used as a thermoelectric cooling device is sometimes called a Peltier device because of its effect, but there is no structural difference between thermoelectric elements used in a thermoelectric power generator and a thermoelectric cooling device. Therefore, both will be collectively referred to as "thermoelectric elements" in the description of the present invention. The Seebeck effect and the Peltier effect are effects that represent the performance of the thermoelectric element itself (superior or inferior of the thermoelectric element), and the performance of these effects will be referred to as "thermoelectric performance" below.

In a general thermoelectric element, a column-shaped p-type thermoelectric semiconductor and an n-type thermoelectric semiconductor having substantially the same length are paired at both ends to form a thermocouple.
Type thermoelectric semiconductors and n-type thermoelectric semiconductors are arranged alternately and regularly, and the thermocouples are electrically connected in series.

However, this general thermoelectric element is
There is nothing between the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor, and it is air, and since the thermoelectric semiconductor is a brittle material, it has low mechanical strength and the thermoelectric element is easily broken due to the influence of external force. there were.

To solve this problem, for example, Japanese Patent Laid-Open No. 63-20880 (Seiko Denshi Kogyo Co., Ltd.)
There is a structure disclosed in.

The characteristic structure of the above publication is that an electrically insulating material such as an epoxy resin is filled between the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor. With this structure, the mechanical strength is increased by filling the epoxy resin which is the insulator, and the disadvantage that the thermoelectric element is easily broken due to the influence of external force is improved.

[0010]

However, since the thermoelectric element of the prior art of the above publication is filled with epoxy resin as an insulator, its mechanical strength is higher than that of a general thermoelectric element. On the other hand, heat is transmitted through the epoxy resin, which is an insulator. Therefore, the amount of heat transmitted through the thermoelectric semiconductor is reduced by that amount, and heat energy loss occurs,
There was a fatal problem that the thermoelectric performance deteriorated.

[0011] Therefore, an object of the present invention is to solve the above problems, to maintain the mechanical strength equivalent to the thermoelectric element of the prior art, and to have the thermoelectric performance equivalent to the general thermoelectric element. To obtain a thermoelectric element.

[0012]

In order to achieve the above object, the present invention basically adopts the technical constitution as described below.

That is, the first means for solving the above problems in the present invention is to electrically connect at least a pair of p-type thermoelectric semiconductors and n-type thermoelectric semiconductors, which are arranged at a predetermined interval, with wiring electrodes. In the thermoelectric element in which the gaps between the thermoelectric semiconductors are connected in series and the gap is filled with the insulator, the insulator is an insulating resin containing bubbles. A second means is that the insulating resin is made of a polymer material such as urethane resin and styrene resin. Further, a third means is that the side surface of the thermoelectric element is covered with the insulating resin.

[Operation] In the thermoelectric element of the present invention, since the insulator is filled between the thermoelectric semiconductors, it maintains the same mechanical strength as the thermoelectric element of the prior art, and the urethane-based material contains bubbles in the insulator. Due to the use of a polymer material such as resin or styrene resin, the thermal conductivity of the insulator is reduced to the same level as air, and the loss of thermal energy is reduced. It can have the same thermoelectric performance as the device.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An optimum embodiment of the structure of a thermoelectric element of the present invention will be described below with reference to the drawings.

The structure and performance of the thermoelectric element according to the embodiment of the present invention will be described with reference to FIGS. However, in FIG. 3 and FIG. 4, in order to make the explanation of the internal structure of the thermoelectric element easier to understand, the heat conduction plate 1 of the thermoelectric element block 10 is shown.
8, the insulating layer 19 and the thermoelectric element block side surface 20 are omitted.

FIG. 1 is a sectional view showing the overall structure of the thermoelectric element of the present invention. Thermoelectric elements are roughly classified into a thermoelectric element block 10 and an upper surface 15 of the thermoelectric element block 10.
And a heat conducting plate 18 disposed on the lower surface 16 and an insulating layer 19 provided between the heat conducting plate 18 and the thermoelectric element block 10.

FIG. 2 is an enlarged sectional view of an essential part for explaining the constitution of the thermoelectric semiconductor and the insulator, and FIG. 3 is a plan view showing the constitution of the thermoelectric semiconductor and the insulator. In the thermoelectric element block 10 shown in FIG. 3, a plurality of columnar p-type thermoelectric semiconductors 11 and n-type thermoelectric semiconductors 12 form a pair and are regularly arranged at regular intervals, as shown in FIG. Then, a porous urethane resin or styrene resin containing microscopic bubbles 21 is filled so as to fill the gap between the p-type thermoelectric semiconductor 11 and the n-type thermoelectric semiconductor 12. Further, the insulator 14 covers the outer peripheral portion of the thermoelectric element block 10 to form the thermoelectric element block side surface 20.

A p-type thermoelectric semiconductor 11 and an n-type thermoelectric semiconductor 12
The presence of the insulator 14 between the two allows the thermoelectric semiconductors to be insulated from each other similarly to the structure of the epoxy resin disclosed in Japanese Patent Laid-Open No. Sho 63-20880 (Seiko Denshi Kogyo Co., Ltd.). It is possible to provide a structure in which a thermoelectric semiconductor having a brittle property is fixed and reinforced and mechanical strength is maintained while ensuring the above.

As the thermoelectric material, an alloy made of BiTeSb is used for the p-type thermoelectric semiconductor 11, and an alloy made of BiTe is used for the n-type thermoelectric semiconductor 12. However, the thermoelectric material is not limited to this.

Here, the upper surface 15 of the thermoelectric element block 10
FIG. 4 shows a perspective view seen from above, and FIG. 5 shows a perspective view seen from the direction of the lower surface 16. As shown in the perspective views of FIGS. 3 and 4, wiring electrodes 13 are provided on the upper surface 15 and the lower surface 16 of the thermoelectric element block 10, respectively, and a pair of p-type thermoelectric semiconductors 11 and n.
The mold thermoelectric semiconductor 12 is provided so as to be connected in series. The wiring electrode 13 is made of copper (C
u) Use a membrane. This copper film is formed on the thermoelectric element block 10 by vacuum vapor deposition, electrolytic plating, or the like.

The lead electrode 17 of the thermoelectric element is for connecting a lead wire for introducing a current from the outside, and a thin copper plate or the like is placed at both ends of the thermoelectric element block 10 with a conductive paste or solder. The thermoelectric semiconductor 11 and the n-type thermoelectric semiconductor 12 are connected.

On the upper surface 15 of the thermoelectric element block 10, the wiring electrodes 13 alternately connect adjacent p-type thermoelectric semiconductors 11 and n-type thermoelectric semiconductors 12 as shown in FIG. As shown in FIG. 5, the p-type thermoelectric semiconductor 11 and the n-type thermoelectric semiconductor 12 adjacent to each other in an oblique direction are connected to electrically connect a plurality of thermoelectric semiconductors in series.

That is, the pair of p-type thermoelectric semiconductors 11 and n-type thermoelectric semiconductors 12 become a plurality of continuous thermocouples by the wiring electrodes 13, and the wiring electrodes 13 formed on the upper surface 15 or the lower surface 16 of the thermoelectric element block 10. Has a configuration in which a cold junction or a hot junction of a thermocouple is planarly formed on each of the upper surface 15 and the lower surface 16 of the thermoelectron block 10.

Further, an insulating layer 19 is arranged on the upper surface 15 and the lower surface 16 of the thermoelectric element block 10 not shown in FIGS.
The heat conduction plate 18 is arranged on the insulating layer 19 (see FIG. 1). In the present invention, the insulating layer 19 is made of a highly heat-conductive resin adhesive or ceramic adhesive containing fine particles of alumina, boron nitride, aluminum nitride or the like. This is to reduce the thermal resistance between the upper surface 15 and the lower surface 16 and the heat conducting plate 18 as much as possible to improve the heat conductivity as much as possible.

For the heat conducting plate 18, it is desirable to use ceramics having high heat conductivity having insulating properties such as alumina and aluminum nitride as described above. The reason why the heat conductive plate 18 having an insulating property is used is that when the insulating layer 19 is thin, the heat conductive plate 18 may come into contact with the wiring electrode 13 to short-circuit the wiring electrode 13 and prevent the occurrence of short circuit. This is because However, if the insulating layer 19 has a thickness that can prevent short-circuiting of the wiring electrodes 13 and has sufficient insulating properties, a metal material such as copper (Cu) or aluminum (Al) is used as the heat conducting plate 18. It can also be used.

In addition, the insulating layer 19 and the heat conducting plate 18
In place of the above, by forming an insulating film such as aluminum nitride or diamond-like carbon on the upper surface 15 and the lower surface 16 of the thermoelectric element block 10 by vacuum vapor deposition or the like, the roles of both the insulating layer 19 and the heat conductive plate 18 are fulfilled. It may have a structure.

By the way, the prior art of JP-A-63-2
The thermal conductivity of the epoxy resin as an insulator disclosed in Japanese Patent No. 0880 (Seiko Denshi Kogyo Co., Ltd.) is about 0.3 W / m ° C.

Since thermoelectric performance is an energy conversion phenomenon between heat energy and electric energy generated inside the thermoelectric material, it is generally ideal in the performance of the thermoelectric element that heat flow occurs only in the thermoelectric material of the thermoelectric element. Therefore, if there is a substance that carries heat in addition to the thermoelectric material, the amount of heat carried by the thermoelectric material is reduced accordingly, and the energy conversion efficiency becomes poor. Therefore, the epoxy resin has a sufficient insulating function, but has a large thermal conductivity, so that the heat generated in the thermoelectric element propagates through the epoxy resin and the thermoelectric performance is deteriorated.

A characteristic structure of the present invention is that a porous urethane resin or styrene resin containing microscopic bubbles 21 is used as the insulator 14. Generally, the presence of a solid medium such as resin in the heat conduction path,
A lot of heat is conducted, and when the resin contains micro bubbles, the heat conduction is suppressed due to the bubbles. Due to such a heat conduction mechanism, the resin containing bubbles can have a low heat conductivity.

The thermal conductivity of the porous urethane resin or styrene resin containing the microscopic bubbles 21 is 0.02.
It is 5 to 0.03 W / mK, which is close to the thermal conductivity of 0.020 W / mK of gas such as air or nitrogen. Therefore, the thermoelectric element of the present invention can obtain the same level of thermoelectric performance as a general thermoelectric element that is not filled with an insulator.

The size of the micro bubbles 21 and the bubbles 21
The amount of can be controlled by the weight of the foaming agent contained in the resin. As the foaming agent, it is possible to use an inorganic foaming agent such as sodium carbonate or an organic foaming agent such as azobisformaldehyde, but since the inorganic system contains metal ions, the insulating property is improved and the thermal conductivity is improved. An organic foaming agent is preferable in order to reduce the rate.

Azobisformaldehyde is used as the organic foaming agent. Nitrogen gas is basically generated to form bubbles 21 in the heating step after the target resin is filled between the pair of thermocouples. It will be. When 1 mol of azobisformaldehyde is used, 22.4 liters of nitrogen gas or the like is generated, so that the amount of generated gas, that is, the size and amount of the bubbles 21 can be controlled by controlling the number of moles contained.

For example, to form a bubble 21 having a diameter of 2 nm, 1.88 × 10 ⁻³⁴ mol or 2.
18 × 10 ⁻³² g of azobisformaldehyde is dispersed in polyurethane resin or polystyrene resin and thermally decomposed. Using this principle, a certain amount of bubbles 2 in the resin
1 can be formed.

More preferably, by mixing an appropriate foaming agent together with the above foaming agent, the generated gas is trapped in the resin uniformly and stably by the foaming agent to form uniform micro bubbles 21. be able to.

The density of the bubbles 21 of the insulator 14 is related to the mechanical strength and the thermoelectric performance. When the bubbles 21 are rough, the thermal conductivity is low because the thermal conductivity is small, but the mechanical strength is somewhat. Get lower. Further, when the bubbles 21 are dense, the thermal conductivity is high and the thermoelectric performance is somewhat low, but the mechanical strength is high. That is, by controlling the density of the bubbles 21 of the insulator 14, thermoelectric elements can be obtained according to various purposes of use.

In the thermoelectric element of the present invention, the insulator 14 is filled between the thermoelectric semiconductors 11 and 12, and the outer peripheral portion is also covered. The insulator 14 is a micro bubble 21.
However, the bubbles 21 exist in an almost isolated state, and no connection of the bubbles 21 is observed.
Furthermore, the upper surface 15 and the lower surface 16 of the thermoelectric element block 10 are covered with an insulating layer 19.

Therefore, the thermoelectric semiconductors 11 and 12 of the thermoelectric element block 10 and the thermoelectric semiconductors 11 and 12 and the wiring electrode 1
The electrical contact between the electrode 3 and the extraction electrode 17 is blocked from the outside, and liquid such as moisture can be prevented from entering from the outside, so that the corrosion resistance is also improved.

Thus, by using the resin containing the bubbles 21 as the insulator 14, while utilizing the advantage of high mechanical strength as in the thermoelectric element using the epoxy resin of the prior art, it is fatal in the prior art. It was possible to obtain the thermoelectric performance equivalent to that of a general thermoelectric element by preventing the deterioration of the thermoelectric performance which was a target.

When the currents flowing through the two extraction electrodes 17 are gradually increased, the temperature difference between the upper surface 15 and the lower surface 16 of the thermoelectric element block 10 gradually increases (Peltier effect), and a certain current flows. It will be the maximum. The temperature difference at this time is called the maximum temperature difference. Whether or not the thermoelectric performance of this thermoelectric element is high, that is, whether the Seebeck effect and the Peltier effect are excellent, can be judged by the magnitude of the maximum temperature difference. That is, the larger the maximum temperature difference is, the higher the thermoelectric performance is, and the thermoelectric element is excellent.
Examples to which the present invention is specifically applied will be specifically described below, but the present invention is not limited to the following examples.

Example 1 In the structure of the thermoelectric element described in the above embodiment (see FIG. 1), the p-type thermoelectric semiconductor (BiTeSb) and the n-type thermoelectric semiconductor (BiTe) are 100 μm in length and 100 μm in width. A urethane having a rod shape of 100 μm and a height of 1 mm, a space width between the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor is 50 μm, and the space portion contains the bubbles formed by the method described in the above embodiment. A system resin (heat conductivity: 0.025 W / mK) is filled. The thermal conductivity of this urethane resin was measured using a thermal conductivity measuring device (TCA Point2 manufactured by Amco).
A sample of 200 × 200 × 20 mm was prepared and performed. The size of both the upper surface and the lower surface of the thermoelectric element block is 5
It is a square of mm, and the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor are wired in series using copper (Cu) which is a wiring electrode. Thermoelectric element block 10 having these material configurations
When the lower surface of the thermoelectric element block 10 was set to 25 ° C. and an electric current was passed through it, the temperature of the upper surface of the thermoelectric element block 10 decreased and the electric current was 0.0
At 39 A, the maximum temperature difference between the upper and lower surfaces of the thermoelectric element block 10 was 74.4 ° C.

(Example 2) In the same manner as in Example 1, a styrene resin containing bubbles as an insulator in the space between the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor of the thermoelectric element block (heat conductivity: 0.030 W / mK) and the maximum temperature difference between the upper and lower surfaces of the thermoelectric element block was measured by the same method as in Example 1. The result was 7 when the current value was 0.039A.
It was 4.2 ° C. The thermal conductivity of the styrene resin was measured by the same method as in Example 1.

Comparative Example 1 In the same manner as in Example 1, an epoxy resin (thermal conductivity: thermal conductivity: was used as an insulator in the space between the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor of the thermoelectric element block.
0.30 W / mK) and the maximum temperature difference between the upper and lower surfaces of the thermoelectric element block was measured by the same method as in Example 1, and it was 63.8 ° C. when the current value was 0.041 A.
The thermal conductivity of the epoxy resin was measured by the same method as in Example 1.

In Example 1 and Example 2 of the present invention, the maximum temperature difference is 74 ° C. or more, whereas in Comparative Example 1 of the prior art, the maximum temperature difference is slightly less than 64 ° C. It was confirmed that the thermoelectric performance of the thermoelectric element was high.

[0045]

According to the present invention, between the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor of the thermoelectric element, an insulator made of a porous urethane resin or styrene resin containing micro bubbles is filled. As a result, it was possible to obtain a thermoelectric element having thermoelectric performance equivalent to that of a general thermoelectric element while maintaining mechanical strength equivalent to that of the thermoelectric element of the related art.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a thermoelectric element according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part near an insulator according to the embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a thermoelectric element according to an embodiment of the present invention.

FIG. 4 is a perspective view for explaining the configuration of the thermoelectric element block according to the embodiment of the present invention when viewed from one direction.

FIG. 5 is a perspective view for explaining the configuration of the thermoelectric element block according to the embodiment of the present invention when viewed from the other direction.

[Explanation of symbols]

10 Thermoelectric element block 11 p-type thermoelectric semiconductor 12 n-type thermoelectric semiconductor 13 wiring electrodes 14 Insulator 15 Upper surface 16 Lower surface 17 Extraction electrode 18 heat conduction plate 19 Insulation layer 20 Thermoelectric element block side 21 bubbles

Claims (3)

[Claims] 1. At least a pair of a p-type thermoelectric semiconductor and an n-type thermoelectric semiconductor, which are arranged at a predetermined interval, are electrically connected in series by a wiring electrode, and the gap between the thermoelectric semiconductors is filled with an insulator. In the thermoelectric element, the thermoelectric element is characterized in that the insulator is an insulating resin containing bubbles. 2. The thermoelectric element according to claim 1, wherein the insulating resin is made of a polymer material such as urethane resin and styrene resin. 3. The thermoelectric element according to claim 1, wherein a side surface of the thermoelectric element is covered with the insulating resin.