JPH11274577A - Thermoelectric module - Google Patents

Abstract

(57) [Problem] To provide the maximum performance of both types of thermoelectric elements and to improve the structural characteristics even when there is a difference in electrical characteristics and thermal characteristics between a P-type thermoelectric element and an N-type thermoelectric element. No new performance degradation factors occur. SOLUTION: The upper and lower electrode surfaces of a P-type thermoelectric element 1p and an N-type thermoelectric element 1n are connected to an electrode 4, and a P-type thermoelectric element 1p and an N-type thermoelectric element 1n are interposed between substrates 3 and 3 vertically facing each other. Are arranged. The cross-sectional area ratio of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is set so that the product of the average value of the electric resistance value and the average value of the thermal conductivity of the P-type and N-type thermoelectric elements is close to the minimum. I am trying to become. By adjusting the difference between the electrical and thermal characteristics of the P-type thermoelectric element and the N-type thermoelectric element by the cross-sectional area, the length of both types of thermoelectric elements can be made the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric module in which a large number of thermoelectric elements are arranged.

[0002]

2. Description of the Related Art A thermoelectric module comprises a P-type thermoelectric element and an N-type thermoelectric element.
Formed at the same time by connecting the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element to the electrodes and connecting the P-type thermoelectric element between the vertically opposed substrates. A device provided with an N-type thermoelectric element is generally used.

Meanwhile, a thermoelectric element used in a thermoelectric module is obtained by mechanically processing a crystal material manufactured by a zone melt method, and a powder obtained by extruding or pressing a powder obtained by pulverizing the crystal material. Then 40
Some are obtained by sintering by applying heat of about 0 ° C. In the former case, there is no significant difference in the electrical and thermal properties of the P-type thermoelectric element and the N-type thermoelectric element, but in the latter case,
The electrical and thermal properties of the thermoelectric element are affected by the particle size of the pulverized powder. For example, as properties of the crystal material, the P-type thermoelectric material has physical properties of an electric resistivity of 0.95 to 0.73 Ωm, a thermal conductivity of 1.65 to 1.41 W / mK, and a Seebeck coefficient of 19.
In addition to the use of 7 to 183 V / mK, an N-type thermoelectric material has an electric resistivity of 1.05 × 0.77Ωm, a thermal conductivity of 1.72 to 1.52 W / mK, and a Seebeck coefficient of 208 to
In the case of using 182 V / mK, the performance of the P-type thermoelectric element is maximized when the particle size of the powder is about 0.1 mm (electrical resistivity is about 1.07 to 2.3 × 10 ⁻⁵ Ωm). ,
The thermal conductivity is about 0.75 to 1.2 W / mK, and the N-type thermoelectric element has the maximum performance when the thickness is about 0.1 mm (electrical resistivity is about 1.0 × 10 ⁻⁵ Ωm, and thermal conductivity is about 1. 2-1.30
W / mK).

Here, in the conventional thermoelectric module, the P-type thermoelectric element and the N-type thermoelectric element have the same shape, but as described above, the P-type thermoelectric element and the N-type
The current value (optimum current) that maximizes the performance of each thermoelectric element when there is a difference in electrical and thermal characteristics from the thermoelectric element.
Therefore, the performance of both types of thermoelectric elements cannot be maximized.

For this purpose, Japanese Patent Laid-Open Publication No. Hei 6-310765 discloses that the optimum currents of the two types of thermoelectric elements are made equal by making the lengths of the P-type thermoelectric elements and the N-type thermoelectric elements different. I have.

[0006]

However, when the lengths of the two types of thermoelectric elements are made different, the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element are connected to the electrodes, and the upper and lower substrates are opposed to each other. In the case of a structure in which a P-type thermoelectric element and an N-type thermoelectric element are interposed, a copper layer or the like is separately provided to fill the difference in length between the shorter thermoelectric element and the substrate. It must be provided, and the presence of such a copper layer or the like causes a decrease in module performance due to Joule heat or thermal resistance generated there.

[0007] The present invention has been made in view of such a point, and even when the P-type thermoelectric element and the N-type thermoelectric element have a difference in electrical characteristics and thermal characteristics, both types of thermoelectric elements can be used. Another object of the present invention is to provide a thermoelectric module capable of maximizing the performance of the thermoelectric module and not causing any additional structural deterioration.

[0008]

According to the present invention, there is provided a P-type thermoelectric element and an N-type thermoelectric element in which the upper and lower electrode surfaces are connected to electrodes, and the P-type thermoelectric element and the N-type thermoelectric element are disposed between vertically opposed substrates. In the thermoelectric module in which the thermoelectric elements are arranged, the cross-sectional area ratio of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is calculated by calculating the average of the electric resistance values of the P-type and N-type thermoelectric elements and the heat. It is characterized in that the product of the conductivity and the average value is near the minimum.

The electrical connection between the P-type thermoelectric element and the N-type thermoelectric element
By adjusting the difference in thermal characteristics by the cross-sectional area, the length of both types of thermoelectric elements can be made the same. When the thermoelectric element is manufactured by extruding a crystalline powder of thermoelectric material by a compacting process such as pressing, the cross-sectional area of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is determined by the P-type thermoelectric element. It is preferable to increase the size of the element and to set the cross-sectional area ratio of both elements to a range of 1.5 to 2.9.

At this time, if at least the thermoelectric element having a larger cross-sectional area has a circular shape cut in a plane parallel to the electrode surface, the thermoelectric element having a larger cross-sectional area is more likely to be subjected to thermal stress. Stress concentration is difficult. At least the thermoelectric element having a smaller cross-sectional area has a hollow shape, and the P-type thermoelectric element and the N-type thermoelectric element have substantially the same outer dimensions.
Again, stress concentration on one thermoelectric element can be avoided.

When the space between the cylindrical P-type thermoelectric element and the N-type thermoelectric element adjacent to each other is filled with an insulating material, the effect of improving the impact strength by the insulating material can be obtained. When both types of thermoelectric elements are arranged in an array in which the straight lines to the center of two thermoelectric elements electrically adjacent to the thermoelectric element form an angle of 132 to 158 °, the amount of insulating material can be reduced. In addition, the amount of heat leak from the insulating material can be reduced.

The insulating material may be one containing air bubbles, one having a through hole penetrating in a direction perpendicular to the electrode surface, or one having a length perpendicular to the electrode surface shorter than the length of the thermoelectric element. preferable. In the thermoelectric module in which the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element are connected to the electrodes, and the P-type thermoelectric element and the N-type thermoelectric element are arranged between the vertically opposed substrates, The element is manufactured by extruding a crystalline material powder of a thermoelectric material by a compacting process such as pressing, and the N-type element is longer than the length of the P-type thermoelectric element in a direction perpendicular to the electrode surface.
The length of the thermoelectric element may be increased, and the length ratio between the two may be in the range of 1.5 to 2.9.

[0013]

To describe an example of embodiment of the embodiment of the present invention, in FIG. 1, ceramic pair against vertically (e.g. as Al ₂ O ₃ and the TiAl) substrate 3,
A plurality of P-type thermoelectric elements 1p and N-type thermoelectric elements 1n are arranged between the three, and copper or aluminum or conductive adhesive is attached to the upper and lower electrode surfaces of these P-type thermoelectric elements 1p and N-type thermoelectric elements 1n. The electrode 4 made of a conductor such as an agent is joined,
P-type thermoelectric elements 1p and N-type thermoelectric elements 1n are connected alternately and in series.

Here, the P-type thermoelectric element 1p and the N-type thermoelectric element 1n have substantially the same length in the direction perpendicular to the electrode surface, but the cross-sectional area taken along a plane parallel to the electrode surface is apparent from FIG. Thus, the cross-sectional area AP of the P-type thermoelectric element 1p is larger than the cross-sectional area AN of the N-type thermoelectric element 1n.
Now, for example, as a P-type thermoelectric element, a Seebeck coefficient of 20
A device having 0 × 10 ⁻⁶ V / K, an electric resistivity of 2.3 × 10 ⁻⁵ Ωm, a thermal conductivity of 0.75 W / mK, and a Seebeck coefficient of 200 × 10 ⁻⁶ V / K as an N-type thermoelectric element are used. ,
Electric resistivity 1.0 × 10 ⁻⁵ Ωm, thermal conductivity 1.30 W /
In the case of using mK, if the cross-sectional area ratio AP / AN of both types of thermoelectric elements 1p and 1n is 1.5 to 2.9, the performance of each of the P-type thermoelectric element 1p and the N-type thermoelectric element 1n is maximized. It is possible to pull out. As is clear from FIG. 3, when the cross-sectional area ratio AP / AN of the two types of thermoelectric elements 1p and 1n is set to 2.1, it is almost 12 compared with the case where both thermoelectric elements 1p and 1n have the same shape. % Performance improvement.

The performance index shown on the vertical axis in FIG. 3 is an index indicating the performance of the thermoelectric module, which is proportional to the Seebeck coefficient of the thermoelectric element, and has an electric resistance (unit: Ω) and a thermal conductivity (unit: W). / K), it is possible to improve the performance of the module by determining the cross-sectional area ratio of the thermoelectric element so that electric resistance × thermal conductivity becomes a small value.

The cross-sectional shapes of the P-type thermoelectric element 1p and the N-type thermoelectric element 1n are not limited to the square shapes as shown in FIGS. In particular, it is preferable to use a thermoelectric element 1p having a larger cross-sectional area having a circular cross-sectional shape.
4 and 5 show the thermoelectric elements 1p and 1n having a circular cross section. If the cross-sectional shape of the thermoelectric elements 1p and 1n has a corner like a quadrangle, stress is concentrated on the corner when a heat cycle is applied, and cracks or the like occur in the thermoelectric element from there. This causes a reduction in the life of the thermoelectric module. When the two thermoelectric elements 1p and 1n have different cross-sectional areas, the thermoelectric element 1 having a larger cross-sectional area is used.
Particularly large thermal stress is applied to p. However, if the cross-sectional shape is circular, since there is no corner portion where stress is easily concentrated, it is possible to prevent cracks from occurring in the thermoelectric element during a heat cycle, and to improve the life of the thermoelectric module. .

As shown in FIGS. 6 and 7, at least the thermoelectric element (N-type thermoelectric element 1n) having a smaller cross-sectional area has a hollow shape, and the thermoelectric element (P-type thermoelectric element 1p) having a larger cross-sectional area has a hollow shape. P-type thermoelectric element 1p
And the N-type thermoelectric element 1n have different outer shapes, which can reduce the bias of thermal stress during a heat cycle, thereby preventing cracks and the like from being generated in the thermoelectric element and reducing the life of the thermoelectric module. Can be improved.

As shown in FIG. 8 and FIG. 9, a ceramic is provided in a space between the P-type thermoelectric element 1p and the N-type thermoelectric element 1n.
An insulating material 5 such as glass, epoxy, or phenol may be filled. The impact resistance of the thermoelectric module is increased by the insulating material 5. However, arranging the insulating material 5 causes a problem of the amount of heat leak from the insulating material 5, but the two P-type thermoelectric elements electrically adjacent to and electrically connected to the N-type thermoelectric element 1n. Regarding the arrangement of 1p and 1p, angles formed by lines L1 and L2 connecting these centers are 132 to 158.
When the angle is set to °, the cross-sectional area of the insulating material 5 can be reduced, so that the amount of heat leak of the insulating material 5 during a heat cycle can be reduced and the performance of the thermoelectric module can be improved. The cross-sectional area ratio AP / AN of the thermoelectric elements 1p and 1n
Is 1.5 °, 132 °, and the sectional area ratio AP / AN is 2.
In the case of 1, as shown in FIG.
When / AN is 2.9, 158 ° is optimal.

If a material containing closed cells such as nitrogen, fluorine and air is used as the insulating material 5, the thermal resistance of the insulating material 5 during a heat cycle can be increased. The amount of heat leak can be reduced, and the performance of the thermoelectric module can be improved.
A through hole may be provided in the insulating material 5 in a direction perpendicular to the electrode surfaces of the thermoelectric elements 1p and 1n. Drilling (mechanical processing) by laser irradiation or drilling, or embedding pins etc. in advance in the insulating material together with the thermoelectric element, and then providing a through hole by punching out only the pins, etc., the cross-sectional area of the insulating material , The amount of heat leakage of the insulating material during the heat cycle can be reduced, and the performance of the thermoelectric module can be improved.

The length (thickness) of the insulating material 5 is determined by the thermoelectric elements 1p,
It may be shorter than 1n. By removing the insulating material 5 by laser irradiation, mechanical processing, chemical etching, or the like, if a distance is provided between the upper surfaces of the thermoelectric elements 1p, 1n and the insulating material 5, the thermoelectric elements 1p, 1n and the electrodes 4
Insulation 5 caused by the temperature difference occurring at the junction with
In this case, the amount of heat leak can be reduced, and the performance of the thermoelectric module can be improved.

In FIG. 11 and subsequent figures, the P-type thermoelectric element 1p and the N-type thermoelectric element 1n have substantially the same cross-sectional area, and the length LP of the P-type thermoelectric element 1p and the length LN of the N-type thermoelectric element 1n. In the figure, the ratio LN / LP is set to be between 1.5 and 2.9. In the figure, reference numeral 6 denotes a conductive layer made of copper, aluminum, solder, or the like for adjusting the length. A thermoelectric element manufactured by extruding a powder obtained by pulverizing a crystal material by extrusion or pressing and then sintering by applying heat at about 400 ° C. has a P-type thermoelectric element having an electrical resistivity of approximately 23 ×.
10 ⁻⁵ Ωm and a thermal conductivity of 0.75 W / mK, and the N-type one has an electrical resistivity of approximately 1.0 × 10 ⁻⁵ Ωm and a thermal conductivity of 1.30 W / mK. By doing so, it is possible to maximize the performance of each of the P-type thermoelectric element 1p and the N-type thermoelectric element 1n. Further, since the P-type thermoelectric element 1p and the N-type thermoelectric element 1n have the same cross-sectional shape, the bias of the stress in one direction is small, and the life of the thermoelectric module is improved.

[0022]

As described above, in the present invention, the upper and lower electrode surfaces of the P-type thermoelectric element and the N-type thermoelectric element are connected to the electrodes, and the P-type thermoelectric element and the N-type thermoelectric element are disposed between the vertically opposed substrates. In the thermoelectric module in which the elements are arranged, the cross-sectional area ratio of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is calculated by calculating the average electric resistance value of the P-type and N-type thermoelectric elements and the heat conduction. Since the product of the average value and the average value is close to the minimum, even when the P and N-type thermoelectric elements having different electrical and thermal characteristics are modularized, the performance degradation caused by the different characteristics is prevented. It can be eliminated and the device performance can be maximized.

In the case where the thermoelectric element is manufactured by extruding a crystalline material powder of thermoelectric material by a compacting process such as pressing, the cross-sectional area of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is determined. The best result can be obtained in that the P-type thermoelectric element is made larger and the cross-sectional area ratio of both is set in the range of 1.5 to 2.9 to make full use of the element performance. When a shape cut at least in a plane parallel to the electrode surface of the thermoelectric element having a larger cross-sectional area is a circular shape, it is difficult to concentrate stress on the thermoelectric element having a larger cross-sectional area where thermal stress is more likely to be applied. In addition, the life of the thermoelectric module can be improved.

If the thermoelectric element having at least the smaller cross-sectional area is made hollow and the P-type thermoelectric element and the N-type thermoelectric element have substantially the same outer dimensions, stress concentration on one of the thermoelectric elements can be avoided. The life of the thermoelectric module can be improved. If the space between the cylindrical P-type thermoelectric element and the N-type thermoelectric element adjacent to each other is filled with an insulating material, the effect of improving the impact strength by the insulating material can be obtained, and furthermore, from the center of any thermoelectric element. If both types of thermoelectric elements are arranged in an array in which the straight lines to the center of two thermoelectric elements electrically adjacent to the thermoelectric element form an angle of 132 to 158 °, the amount of insulating material can be reduced. Therefore, the amount of heat leakage from the insulating material can be reduced, and the performance can be improved.

The insulating material may contain air bubbles, may have a through hole penetrating in a direction perpendicular to the electrode surface, or may have a length in the direction perpendicular to the electrode surface longer than the length of the thermoelectric element. If the length is short, the amount of heat leak can be reduced, so that the performance can be improved.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention, in which (a)
Is a perspective view, (b) is a perspective view with the substrate removed, and (c) is a perspective view with the electrodes removed.

FIG. 2 is a horizontal sectional view of the same.

FIG. 3 is a characteristic diagram of the above.

4A and 4B show another example, in which FIG. 4A is a plan view and FIG. 4B is a cross-sectional view.

FIG. 5A is a plan view showing the arrangement of electrodes in the above embodiment, and FIG. 5B is a horizontal sectional view of the thermoelectric element in the embodiment.

6A and 6B show still another example, in which FIG. 6A is a plan view and FIG. 6B is a sectional view.

FIG. 7A is a plan view showing an arrangement of electrodes in the above embodiment, and FIG. 7B is a horizontal sectional view of the thermoelectric element in the embodiment.

8A and 8B show another example, in which FIG. 8A is a plan view in a state where a substrate is removed, and FIG. 8B is a cross-sectional view in a state where a substrate is removed.

FIG. 9 is a horizontal sectional view of the same.

FIG. 10 is a characteristic diagram of the above.

FIG. 11 is a perspective view of an example of a different embodiment.

FIG. 12 is a sectional view of the above.

FIG. 13 is a characteristic diagram of the above.

[Explanation of symbols]

 1p P-type thermoelectric element 1n N-type thermoelectric element 3 Substrate 4 Electrode

Claims (9)

[Claims] 1. A thermoelectric module wherein upper and lower electrode surfaces of a P-type thermoelectric element and an N-type thermoelectric element are connected to electrodes, and a P-type thermoelectric element and an N-type thermoelectric element are disposed between vertically opposed substrates. , The cross-sectional area ratio of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is defined as the product of the average value of the electric resistance value and the average value of the thermal conductivity of the P-type and N-type thermoelectric elements. A thermoelectric module characterized by being located near. 2. A thermoelectric module wherein upper and lower electrode surfaces of a P-type thermoelectric element and an N-type thermoelectric element are connected to electrodes, and a P-type thermoelectric element and an N-type thermoelectric element are arranged between vertically opposed substrates. In the thermoelectric element, the thermoelectric element is manufactured by extruding a crystalline powder of thermoelectric material by a compacting process such as pressing, and the cross-sectional area of the P-type and N-type thermoelectric elements cut by a plane parallel to the electrode surface is P-type. A thermoelectric module characterized in that the thermoelectric element is larger and the cross-sectional area ratio between the two is in the range of 1.5 to 2.9. 3. The thermoelectric module according to claim 1, wherein at least the thermoelectric element having a larger cross-sectional area has a circular shape cut by a plane parallel to the electrode surface. 4. The thermoelectric element having at least a smaller cross-sectional area has a hollow shape, and the P-type thermoelectric element and the N-type thermoelectric element have substantially the same outer dimensions. The thermoelectric module according to any of the above items. 5. A space between a cylindrical P-type thermoelectric element and an N-type thermoelectric element which are adjacent to each other is filled with an insulating material, and is electrically adjacent to the thermoelectric element from the center of any thermoelectric element. 132 straight lines to the center of one thermoelectric element
The thermoelectric module according to any one of claims 1 to 4, wherein both types of thermoelectric elements are arranged in an array forming an angle of ~ 158 °. 6. The thermoelectric module according to claim 5, wherein the insulating material contains bubbles. 7. The thermoelectric module according to claim 5, wherein the insulating material has a through hole penetrating in a direction perpendicular to the electrode surface. 8. The thermoelectric module according to claim 5, wherein the length of the insulating material in a direction perpendicular to the electrode surface is shorter than the length of the thermoelectric element. 9. A thermoelectric module wherein upper and lower electrode surfaces of a P-type thermoelectric element and an N-type thermoelectric element are connected to electrodes, and a P-type thermoelectric element and an N-type thermoelectric element are arranged between vertically opposed substrates. In the thermoelectric element, the thermoelectric element is manufactured by extruding a crystalline powder of thermoelectric material by a compacting process such as pressing, and the length of the N-type thermoelectric element is longer than the length of the P-type thermoelectric element in the direction perpendicular to the electrode surface. And the length ratio of both is 1.5 to 2.
9. A thermoelectric module having a range of 9.