JP2000188429A - Thermo-electric conversion module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermo-electric conversion module which easily controls power generation output depending on temperature distribution of a heat source, has a curved plane to maintain good thermal contact even for the heat source having a large temperature difference between the high temperature end and low temperature end and minimizes loss of the power generation output. SOLUTION: At least two pairs or more of the p-type and n-type thermo-electric semiconductor elements (1) are alternately arranged in a line, and moreover the p-type and n-type thermo-electric semiconductor elements (1) arranged alternately are connected in series electrically with the electrodes (3) formed at the high temperature end and low temperature end. For example, a strain alleviating electrode (2) mainly composed of carbon is provided at least between the electrode (3) of the high temperature end and the thermo-electric semiconductor element (1), and the adjacent thermo-electric semiconductor elements are deposited via an electrically insulating layer (4) which is mainly composed of an oxide glass material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric conversion module for extracting a thermoelectromotive force from a heat source, and more particularly to a structure of a junction between p-type and n-type thermoelectric semiconductors constituting a thermoelectric conversion module.

[0002]

2. Description of the Related Art Conventionally, Seebeck effect, Peltier effect and Thomson effect have been known as thermoelectric phenomena.

The Seebeck effect means that in a thermoelectric conversion element pair having a junction in which p-type and n-type thermoelectric semiconductors are electrically joined, if the junction is heated to a high temperature and the other end of the thermoelectric semiconductor is cooled to a low temperature, This is a phenomenon in which a thermoelectromotive force is generated according to the difference.

[0004] The Peltier effect means that in a thermoelectric conversion element pair having a junction in which p-type and n-type thermoelectric semiconductors are electrically joined, when a current flows from one thermoelectric semiconductor to the other thermoelectric semiconductor, the junction is This is a phenomenon that absorbs heat and generates heat at the other end of the thermoelectric semiconductor.

[0005] The Thomson effect means that when one end of a p-type or n-type thermoelectric semiconductor is heated to a high temperature and the other end is cooled and a current flows along a temperature gradient, heat is absorbed inside the semiconductor depending on the direction of the current. Or a phenomenon that causes occurrence.

A thermoelectric conversion device utilizing such an effect has no moving parts, does not generate vibration, noise, wear, etc., has a simple structure, is highly reliable, has a long service life, and is easy to maintain. . Therefore, there is a possibility that these features can be utilized as a simple energy conversion device.

[0007] As described above, the thermoelectric converter has a p-type and an n-type.
A thermoelectric conversion element pair in which thermoelectric semiconductors of a mold type are electrically connected is provided. The junction of the element pair may directly join the p-type and n-type thermoelectric semiconductors, or may indirectly join the p-type and n-type thermoelectric semiconductors via electrodes. As a specific thermoelectric conversion device, a thermoelectric generation device that extracts an electromotive force depending on a temperature difference between a high-temperature end and a low-temperature end of a thermoelectric conversion element pair using the Seebeck effect,
There is a thermoelectric cooling device that cools one end by generating a temperature difference depending on voltages applied to a high-temperature end and a low-temperature end using the Peltier effect.

When the thermoelectric generator is actually used,
A predetermined potential difference or current is generated in a state where a plurality of thermoelectric semiconductors are electrically connected in series or in parallel. In this case, the thermoelectric generator is installed as closely as possible to the heat source, and the heat flow from the heat source is made to flow to the thermoelectric semiconductor as much as possible to increase the electric conversion efficiency. It is also desirable to pack the thermoelectric semiconductor as densely as possible.

In order to satisfy such conditions, a thermoelectric conversion module in which p-type and n-type thermoelectric semiconductor element pairs are electrically connected in advance by electrodes is often manufactured. In addition, an electrical insulating layer is often provided to hold a thermoelectric conversion module including a thermoelectric semiconductor element and an electrode in a desired structure. For example, FIG. 3 of JP-A-5-41543 illustrates a module for a thermoelectric cooling device utilizing the Peltier effect. This module has a structure in which a plurality of element pairs are arranged and sandwiched between two square heat exchange substrates made of an insulating material having good thermal conductivity such as alumina ceramics. The heat exchange board has an effect of improving not only the heat exchange performance but also the mechanical strength of the module. In the case of a cooling device such as this known example, the temperature difference generated at both ends of the module is a maximum of about 100 ° C., and the number of installations is one to several tens.

On the other hand, in the case of a thermoelectric generator, the temperature difference generated between both ends of the module reaches 600 ° C., and the number of installed modules may be hundreds to thousands. For this reason, in general, a power generation module is required to have not only durability against destruction due to a temperature difference between both ends of the module but also durability against destruction due to mechanical pressure or vibration during installation or use. From this viewpoint, considering that the temperature on the high temperature side is high, it is difficult to increase the amount of heat transferred to the module by bonding the heat exchanger and the module in the thermoelectric generator with a brazing material or an adhesive. It is often installed by crimping. Attempting to uniformly compress several hundred or more modules to improve heat transfer from the heat exchanger to the modules results in significant mechanical pressure on the modules.

In general, thermoelectric semiconductor materials have lower strength than ordinary metal materials. Moreover, in order to increase the power generation efficiency, the thermoelectric conversion module is usually designed so that a large temperature difference is generated between both ends (high-temperature end and low-temperature end). For this reason, special measures are required to avoid destruction of the thermoelectric semiconductors constituting the thermoelectric conversion module during manufacturing and use.

For example, US Pat. No. 4,611,089 discloses a thermoelectric conversion module in which thermoelectric semiconductor elements are arranged two-dimensionally, and a high-temperature end and a low-temperature end have a substantially square planar shape. In this thermoelectric conversion module, two thermoelectric semiconductor elements are formed by an insulating holder having a grid shape in the vertical and horizontal directions.
Dimensionally arranged and held. In this thermoelectric conversion module, the thermal stress generated by the temperature difference generated between the high-temperature end and the low-temperature end can be reduced by the insulating holder, which is suitable for avoiding the destruction of the weak thermoelectric semiconductor element. In addition, a module having square ends is characterized by high strength against mechanical pressure and vibration during installation as described above.

On the other hand, this thermoelectric conversion module has the following disadvantages. (1) When the temperature variation of the heat source is large, the variation of the temperature difference applied to each element pair in the thermoelectric conversion module becomes large. However, it is not possible to increase the thermoelectric conversion efficiency by changing the electric circuit from the outside in response to the variation in the temperature difference, so that the power generation output loss increases. (2) When a large number of modules are installed in a heat source, in a square module, the high temperature side expands due to thermal expansion due to a temperature difference between a high temperature end and a low temperature end, and the module warps. For this reason, it is difficult to make thermal contact with the heat source, and the power generation output loss increases. (3) The portion of the heat source on which the thermoelectric conversion module is set needs to be flat. However, exhaust pipes and heat exchangers through which high-temperature exhaust such as internal combustion engines and waste incinerators flow are curved,
Good thermal contact cannot be obtained with a square thermoelectric conversion module. (4) When a large number of thermoelectric conversion modules are provided in a heat source, it is necessary to provide a space between the square modules in order to route leads and the like. For this reason,
It is difficult to increase the installation density of modules, for example, it is difficult to produce a thermoelectric generator using exhaust heat of an automobile as a heat source.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat source which can easily control the power generation output in accordance with the temperature distribution of the heat source and which has a curved surface and a large temperature difference between a high temperature end and a low temperature end. Another object of the present invention is to provide a thermoelectric conversion module that can maintain good thermal contact and minimize power generation output loss. Another object of the present invention is to provide a thermoelectric conversion module that can be installed at a high density and that can manufacture a compact and small thermoelectric generator.

[0015]

According to the present invention, there is provided a thermoelectric conversion module in which at least two pairs of p-type and n-type thermoelectric semiconductors are alternately arranged in a line, and p-type and n-type thermoelectric semiconductors are alternately arranged. A line module in which thermoelectric semiconductors are electrically connected in series by electrodes formed at a high-temperature end and a low-temperature end.

In the thermoelectric conversion module of the present invention,
It is preferable to provide a strain relaxation electrode containing, for example, carbon as a main component, at least between the electrode at the high-temperature end and the thermoelectric semiconductor. Further, it is preferable that the thermoelectric semiconductors adjacent to each other be fixed via an electrical insulating layer mainly containing oxide glass.

Further, in the thermoelectric conversion module of the present invention, a gap may be formed between the electrical insulating layer (or the brazing material provided thereon) and at least the electrode at the high temperature end.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

Examples of the thermoelectric semiconductor that can be used in the present invention include intermetallic compounds such as Bi ₂ Te ₃ and PbTe, and Si—Ge semiconductors. Among these thermoelectric semiconductors, it is preferable to use a Si-Ge semiconductor. This is because the working temperature of the Bi-Te based semiconductor is about 250 ° C., whereas the Si—Ge based semiconductor is used at a high temperature (about 1000 ° C. in vacuum, about 500 ° C. in air).
° C) and has better power generation characteristics than Fe-Si based semiconductors. The relative density of the Si-Ge based semiconductor is preferably 93% or more. If the relative density of the Si-Ge based semiconductor is less than 93%, the strength is poor and the thermoelectric conversion module of the present invention is damaged during manufacture. However, if the relative density is 93% or more, the manufacture of the thermoelectric conversion module becomes possible. If the relative density of the Si-Ge based semiconductor is 98% or more, the breakage rate during module production further decreases.

In the thermoelectric conversion module of the present invention,
It is preferable to provide a strain relaxation electrode containing, for example, carbon as a main component, at least between the electrode at the high-temperature end and the thermoelectric semiconductor. The strain relaxation electrode may be provided between the electrode at the low temperature end and the thermoelectric semiconductor.

In the line-type module, anisotropic bonding occurs between the thermoelectric element and the electrode due to the difference in the coefficient of thermal expansion between the thermoelectric element and the electrode and the difference in the coefficient of thermal expansion between the brazing filler metal and the thermoelectric element when the electrodes are joined. Although a thermal stress is generated, the strain relaxation electrode has a function of relaxing the thermal stress and improving the strength of the joint with respect to heat resistance and thermal shock resistance. In addition, the module has a function of preventing destruction at a thermoelectric element portion or a thermoelectric element joint portion with respect to vibration or mechanical pressure during installation or use of the module. Furthermore, when joining the plate-shaped electrode using a joining material such as a brazing material or a solder material, the joining material and the thermoelectric element material may react at a high temperature, and the properties and strength of the joining portion may be reduced. The strain relaxation electrode functions as a diffusion barrier layer, and also functions as a surface treatment layer for improving the wettability of a brazing material or solder material.

As described above, the strain-relaxing electrode of the present invention has various functions. However, the major difference between the diffusion barrier layer and the surface treatment layer employed in the conventional electrode bonding technology of semiconductor devices is that the thermal stress and the surface treatment layer are different. This is an effect of reducing distortion due to mechanical pressure and vibration. To fully demonstrate this effect,
It is desirable that the material of the strain relaxation electrode has a low electric resistance, a high thermal conductivity, and a thermal expansion coefficient equivalent to that of the thermoelectric semiconductor.

The strain relaxation electrode inserted between the thermoelectric semiconductor and the electrode is preferably at least thermally and electrically equivalent to or better than the thermoelectric semiconductor. When the strain relaxation electrode has lower thermal and electrical conductivity than the thermoelectric semiconductor, the power generation performance is greatly reduced, which is not preferable.

It is desirable that the electrode material be a good conductor electrically and thermally, and such a material generally has a strong metallic property and therefore has a large coefficient of thermal expansion. For example, Cu and F
The thermal expansion coefficients of e are about 18 × 10 ⁻⁶ / ° C. and about 13 × 10 ⁻⁶ / ° C., respectively. However, if these electrode materials are directly fixed to the thermoelectric semiconductor, a line-type module cannot be manufactured due to thermal stress. Therefore, the coefficient of thermal expansion α _S of the strain relaxation electrode is preferably a value between the coefficient of thermal expansion α _C of the electrode material and the coefficient of thermal expansion α _T of the thermoelectric semiconductor (the unit of the coefficient of thermal expansion is × 10 ^−6). / ° C, for example α =
1 indicates 1 × 10 ⁻⁶ / ° C.). More specifically, the thermal expansion coefficients of these materials preferably satisfy the following relationship.

Α_T≤α_CIn the case of α_T/ 2 ≦ α_S≤α_C α_T/ 2 ≦ α_C≤α_TIn the case of α_T/ 2 ≦ α_S≤α_T α_C≤α_T/ 2, α_C≤α_S≤α_T The coefficient of thermal expansion of the strain relaxation electrode is the coefficient of thermal expansion of the thermoelectric semiconductor.
A value close to the number, α _{S =}α_TWithin ± 0.5
Is desirable. Furthermore, the coefficient of thermal expansion of the strain relief electrode is
90 to 110% of the coefficient of thermal expansion of electronic semiconductors
Desirably. Less than 90% or 110%
If the temperature exceeds the limit, the
Cracks may occur near the joint due to the accompanying thermal shock.
Strain relaxation electrode is easy to peel near interface with thermoelectric element
You.

Hereinafter, the coefficient of thermal expansion of a thermoelectric semiconductor, the coefficient of thermal expansion of a good conductor that can be used as an electrode material or a strain relaxation electrode, and a suitable combination of these materials will be described. The thermal expansion coefficients of typical thermoelectric semiconductors are approximately SiGe: 4 (× 10 ⁻⁶ / ° C., units are omitted below), and PbTe: 20. The thermal expansion coefficients of typical good conductors are, for example, C: 4, Mo:
5, Cu: 18, Fe: 13, Ni: 14, Ag: 19
It is. As a preferable combination of materials, there is an example in which when SiGe is used for a thermoelectric semiconductor, C is used as a strain relaxation electrode and Mo is used as an electrode. Further, when PbTe is used as the thermoelectric semiconductor, an example is given in which Fe is used as the strain relaxation electrode and Cu is used as the electrode, and the thermoelectric semiconductor is fixed by diffusion bonding.

The thickness of the strain relaxation electrode is desirably as thin as possible from the viewpoint of power generation characteristics, but is desirably thick from the viewpoint of reducing the probability of breakage. Specifically, it is desirable that the thickness be 10 μm or more from the viewpoint of reduction in the probability of breakage and 10 mm or less from the viewpoint of power generation efficiency. Furthermore, it is desirable to set it in the range of 100 to 1000 μm. If the thickness is less than 10 μm, cracks and peeling are likely to occur in the thermoelectric element portion and the joint portion between the electrode and the strain relaxation electrode due to installation pressure and vibration during use. If the thickness is larger than 10 mm, the thermal resistance of the strain relaxation electrode portion increases, so that the amount of heat transmitted from the high-temperature heat exchanger wall surface of the power generation device to the end of the thermoelectric element through the electrode and the strain relaxation electrode decreases. As a result, the temperature difference between both ends of the thermoelectric element decreases,
This is not preferable because the power generation output is significantly reduced.

The present invention is characterized in that a strain relaxation electrode is formed at an end of a thermoelectric element and an electrode is further formed at the end of the thermoelectric element. The joining structure between the strain relaxation electrode and the electrode is not particularly limited. It is sufficient for the electrodes to be able to electrically join adjacent thermoelectric elements. The electrodes may be joined using a brazing material or solder material on the strain relief electrodes, or sprayed or printed on the strain relief electrodes. To form the electrode layer directly.

From the viewpoint of reducing the probability of breakage, it is preferable to fix thermoelectric semiconductors adjacent to each other via an electrically insulating layer mainly composed of oxide glass. Examples of the oxide glass include SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and Zn.
_{O, PbO, A 2 -O (} A is an alkali metal), A-O
(A is an alkaline earth metal) as a main component. By appropriately mixing these components, characteristics such as the coefficient of thermal expansion, softening point, electrical insulation, and thermal conductivity can be appropriately controlled. In order to improve the characteristics of the module,
It is preferable to have high electrical insulation and low thermal conductivity. The coefficient of thermal expansion of the insulating layer is preferably close to the value of the thermoelectric semiconductor, and specifically, 50 to 150% of the coefficient of thermal expansion of the thermoelectric semiconductor.
It is preferred that Greater than 150% or 50
%, The thermoelectric semiconductor and the insulating layer may be broken. Part or all of the oxide glass as the insulating layer may be crystallized.

In the present invention, it is preferable to form a gap between the electrically insulating layer (or the brazing material provided thereon) and at least the electrode at the high temperature end. It is more preferable that the gap is formed also on the electrode side at the low temperature end. Providing the void means that the electrically insulating layer (or brazing material) and the electrode are not brought into close contact with each other. Here, when the electrical insulating layer and the electrode come into contact, the reaction between the two proceeds, or a stress is generated due to a difference in thermal expansion caused by a temperature change during manufacturing,
The electrode may be deformed. Similarly, when the electrical insulation layer and the brazing material come into contact with the electrode, a reaction proceeds between the electrical insulation layer and the brazing material or a stress is generated, and the influence extends to the Mo electrode. May occur. When such a phenomenon occurs, the manufacturing yield of the thermoelectric conversion module decreases. On the other hand, when the gap is formed as described above, the reaction between different kinds of materials and the generation of stress can be reduced, so that the production yield of the thermoelectric conversion module can be improved. Further, when the deformation of the electrode is reduced by forming the gap, the smoothness of the electrode is improved, so that the efficiency of heat conduction from the heat source to the electrode is improved, and the power generation performance of the thermoelectric conversion module and its stability are improved. Can be improved. Further, by forming the gap, the heat flow transmitted from the high-temperature side heat source to the module high-temperature end electrode can be prevented from flowing to the low-temperature end through the electric insulating layer,
A module having a small power generation output loss can be provided.

In the case where a strain relaxation electrode containing carbon as a main component is provided on the upper part of the thermoelectric element, the wettability with the electric insulating layer made of oxide glass is poor, and the insulating layer easily adheres only to the side surface of the thermoelectric element. Therefore, it is easy to form a gap between the insulating layer (or the brazing material provided thereon) and the electrode.

When the reaction between different kinds of materials does not proceed and no stress is generated due to the difference in thermal expansion, the electric insulating layer (or the brazing material provided thereon) and the electrode are manufactured and used at the time of manufacture and use. Is also allowed to contact. For example,
Even if there are voids at room temperature, the voids may be eliminated by heating during manufacturing or use (particularly at a high temperature end). However, if the electrode contacts the insulating layer (or the brazing material provided thereon) at the manufacturing temperature or the use temperature, the above-described effects may not be sufficiently obtained. Therefore, it is preferable that the above-mentioned voids exist during manufacturing and use. In addition, since it is difficult to finely adjust the gap, the gap does not necessarily need to be formed by all elements of the thermoelectric conversion module, but may be formed by some elements. Thus, even when a gap is formed in some of the elements, the effect of improving the manufacturing yield of the thermoelectric conversion module can be obtained.

The size of the air gap is determined in consideration of the thermal expansion difference, elastic modulus, and the like of each constituent material of the thermoelectric conversion module. Also, an insulating layer (or a brazing material provided thereon)
The size of the gap is preferably large in order to reliably prevent the contact between the electrode and the electrode, but the size of the gap is preferably small in consideration of the reinforcing effect of the insulating layer on the thermoelectric conversion module. Therefore, the size of the gap is 50 times the element height.
% Or less, more preferably 1 to 10% of the element height, and most preferably about the thickness of the strain relaxation electrode from the viewpoint of strength and ease of manufacture.

A more preferable shape of the thermoelectric conversion module of the present invention will be described. Here, (the longitudinal direction of the line-type module), thermoelectric semiconductor height H (temperature gradient direction) (direction perpendicular to the longitudinal direction of the line type module), L the element length element width W, module L _M Length.

In the present invention, W and L are both 2
Preferably, it is less than 0 mm. This is 3.5 × 2
This is because, when a carbon strain relaxation electrode is bonded to a 0-mm Si-Ge-based semiconductor and then a Mo electrode is brazed, there are some that are broken after brazing and some that are not broken. Further, it is preferable that L _M / W> 4. If this value is 4 or less, it is difficult to obtain the effect that the module can be installed at a high density due to the line shape.
It is preferable that the L _M / W <100. This value is 10
If it is 0 or more, it becomes difficult to manufacture the thermoelectric conversion module.

The line-shaped thermoelectric conversion module according to the present invention can be installed in a heat source and then externally changing the number or arrangement of the thermoelectric semiconductors electrically connected in series or in parallel to obtain a voltage taken out of the thermoelectric conversion module. And the current can be easily controlled. Further, the amount of current with respect to the electromotive force (voltage) can be easily controlled by the module shape and the number of modules. Therefore, as compared with a two-dimensional square module, the present invention can be efficiently applied to a heat source having a large temperature gradient or a large change in temperature distribution. In addition, the thermoelectric conversion module of the present invention can be easily installed, for example, by adjusting the longitudinal direction of the line type module to the longitudinal direction of the cylinder with respect to the cylindrical heat source, and can maintain good thermal contact.

The above control will be described more specifically. When a part of the heat energy of the exhaust gas is converted to electricity by a module installed on the most upstream side of the exhaust flow,
A power generation voltage proportional to the temperature difference generated between both ends of the module is generated, while the exhaust gas temperature is reduced accordingly. The module installed downstream of this module has a smaller temperature difference than the most upstream module, and the power generation voltage is also reduced. When the flow rate of the exhaust gas is small, or when the thermoelectric conversion efficiency of the module is large and the amount of heat taken from the exhaust gas is large, the exhaust gas is rapidly cooled toward the downstream of the exhaust flow, and the power generation voltage decreases. In this case, the control can be performed by increasing the number of modules electrically connected in series at a position downstream of the exhaust flow. In the case of automobile exhaust heat, the amount of exhaust heat changes rapidly with time. Even in this case, in order to always generate power at a constant voltage, the number of modules electrically connected in series or in parallel is changed according to signals such as the flow rate of exhaust gas and the temperature at both ends of the module. Voltage and current can be controlled. The line type module of the present invention includes:
By setting the long axis perpendicular to the direction of the exhaust gas flow, it is possible to minimize power generation loss and stably generate power at a desired voltage.

On the other hand, in the conventional square module, since the temperature distribution occurs in one module, the above-described control is difficult, and the power generation loss increases. In addition, even when the generated power is stored in the battery, a storage loss occurs because the generated voltage is not constant.

[0039]

Embodiments of the present invention will be described below with reference to the drawings.

In the following examples, the thermoelectric semiconductor material has a composition of 80 at% Si-20 at% Ge.
Ge semiconductor as a base material, SiGe as a p-type thermoelectric semiconductor
Mixed with boron at a concentration of 0.5 to 2.0 × 10 ²⁰ mol / m ³ , and SiGe is used as an n-type thermoelectric semiconductor.
Used was mixed with phosphorus at a concentration of 0.5 to 2.0 × 10 ²⁰ mol / m ³ . These thermoelectric semiconductors were produced by sintering raw material powder.

Sample 1 As shown in FIGS. 1A and 1B, 3.5 × 3.5
× 8 mm, p-type and n-type S having a relative density of 93 to 98%
Nine iGe thermoelectric semiconductor elements 1 are alternately arranged in a total of 18 (9 pairs) in a row, and thermoelectric semiconductor elements 1 adjacent to each other are electrically connected in series by electrodes 3 formed at a high-temperature end and a low-temperature end. Thus, a 1 × 18 line type module was manufactured.

FIG. 2 shows the structure of the joint. As shown in FIG. 2, a 0.5 mm-thick carbon strain relief electrode 2 was bonded to the high-temperature end of the thermoelectric semiconductor element 1 by a diffusion bonding method. Although not shown in FIG. 2, the low-temperature end of the thermoelectric semiconductor element is also 0.5 m
An m-thick carbon strain relaxation electrode was bonded by a diffusion bonding method. These thermoelectric semiconductor elements 1 were fusion-bonded with the oxide glass 4. Further, the Mo electrodes 3 were joined by the nickel-based solder 12 so as to connect the adjacent thermoelectric semiconductor elements 1 to each other.

Each of the ten manufactured modules was placed in contact with the heater block and the cooling plate via an insulating plate, and all the modules were electrically connected in series. The area occupied by the high-temperature end of the module was 85% of the total area required for installation of the module including the connection portion between the modules. Pressing pressure from cooling plate side 10kg /
Crimping was performed at cm ² to evaluate the power generation output. When the temperature difference between the high temperature end and the low temperature end was about 400 ° C., the maximum output was 6 W. The power generation output was measured by increasing the installation pressure to 100 kg / cm ² , but no change was observed in the output.

As described above, by using the line type module of the present invention, it is possible to reduce the space required for connection between modules and the like, increase the installation density of the modules, and install the modules in a heat source. Further, when power is generated due to a temperature difference between both ends of the module, warpage caused by thermal expansion of the module is small, so that stable power generation output can be obtained even when the installation pressure of the module is small. As a result, it is possible to prevent the module from being damaged by thermal stress due to the temperature change of the heat source, and it is possible to reduce the power generation loss of the entire thermoelectric generator because a high installation pressure is not required, thereby making the device compact. This has the effect of further facilitating assembly.

In this case, when the thermoelectric conversion module was manufactured (after glass fusion or brazing), the SiGe portion was damaged in three out of a total of 16 manufactured. The thirteen thermoelectric conversion modules that were not damaged could be used under the above-mentioned use conditions.

Sample 2 A 1 × 18 line module was prepared in the same manner as in Sample 1, except that p-type and n-type SiGe thermoelectric semiconductor elements having a relative density of 98% or more (98.4 to 99.6%) were used. Manufactured. The module manufacturing yield was 95%. All manufactured thermoelectric conversion modules could be used under the above use conditions. When the power generation output was measured in the same manner as in Sample 1, the maximum output per module was 0.6 W when the temperature difference was about 400 ° C.

As described above, by manufacturing a module using a thermoelectric semiconductor element having a relative density of 98% or more, the manufacturing yield can be improved.

Samples 3-5 As shown in FIGS. 3 (A) and (B), 3.5 × 3.5
× 4 mm p-type and n-type SiGe thermoelectric semiconductor element 1
Are alternately arranged two by two in a row (two pairs), and the thermoelectric semiconductor elements adjacent to each other are electrically connected in series by electrodes 3 formed at the high-temperature end and the low-temperature end to form a 1 × 4 line type. A module was manufactured. The relative density of the p-type and n-type thermoelectric semiconductors is 93 to 98%. Samples 3-5
Is as follows. The manufactured thermoelectric conversion module was used for one hour with the high-temperature end adhered to a heat source and the low-temperature end maintained at about room temperature.

Sample 3 Mo is applied to the high-temperature end of the thermoelectric semiconductor device 1 by nickel-based brazing.
An attempt was made to join the electrodes 3. However, when a nickel-based solder was used, SiGe melted at the time of joining, and a thermoelectric conversion module could not be manufactured.

As shown in FIG. 4, the Mo electrode 3 was joined to the high-temperature end of the thermoelectric semiconductor element 1 by means of a silver-based solder (BAg-8) 11. Although not shown in FIG. 4, a Mo electrode was joined to the low-temperature end of the thermoelectric semiconductor element 1 with a silver-based solder (BAg-8). Some modules could be joined, but cracks occurred at the interface between the SiGe thermoelectric semiconductor element and the electrodes when installed in the power generation output evaluation device, and the output could not be evaluated.

Specimen 4 As shown in FIG.
The carbon strain relaxation electrode 2 having a thickness of mm was formed. Although not shown in FIG. 5, a 0.5 mm-thick carbon strain relief electrode was also formed at the low-temperature end of the thermoelectric semiconductor element. In addition, the Mo electrode 3 was joined on the carbon strain relief electrode 2 with a nickel-based solder 12.

One end of each of the manufactured modules was placed in contact with the heater block and the cooling plate via an insulating plate, and the module was pressed at a pressing pressure of 20 kg / cm ² to evaluate the power generation pressure. Temperature difference between high temperature end and low temperature end is about 4
At 00 ° C., the maximum output was 0.1 W.

Note that a part of the manufactured thermoelectric conversion module has insufficient strength, and when it is attached to a heat source, the
In some cases, the semiconductor was damaged (one out of four manufactured parts was damaged). The SiGe semiconductor did not break during mounting 3
Each of the thermoelectric conversion modules was usable under the above use conditions.

Next, the thickness of the carbon strain relaxation electrode is set to 8 μm.
Except having changed to m, 0.1 mm, 1 mm or 12 mm, a 1 × 4 line type module having the same configuration as above was manufactured. The module using the 0.1 mm or 1 mm thick carbon strain relaxation electrode showed the same power generation output characteristics as the module using the 0.5 mm thick electrode. However, in some modules using the 8 μm-thick carbon strain-mitigating electrode, cracks occurred at the interface between the carbon strain-mitigating electrode and the SiGe thermoelectric semiconductor element, and some modules could not generate power.
In this module, it was observed that the brazing material reacted with the SiGe semiconductor component to form a reaction phase. On the other hand, the module using the 12 mm-thick carbon strain relaxation electrode was able to evaluate the power generation output,
The maximum output was significantly reduced to 0.06W. this is,
It is considered that the power generation output was reduced because the high-temperature end junction of the thermoelectric semiconductor element was not sufficiently heated because the carbon strain relaxation electrode was too thick. From these results, the thickness of the carbon strain relaxation electrode is preferably set to 0.01 to 10 mm.

As described above, by forming the line type module by installing the strain relaxation electrodes, the electrodes can be joined while suppressing an excessive reaction between the brazing material and the thermoelectric semiconductor element. Furthermore, even when handling or installing in a thermoelectric conversion device, the joint strength is sufficient without cracks occurring at the joints, and a sufficient temperature difference can be provided between both ends of the thermoelectric semiconductor element, thereby generating power. It has become possible to manufacture thermoelectric conversion modules with high output.

Specimen 5 As shown in FIG. 6, 0.5
The carbon strain relaxation electrode 2 having a thickness of mm was joined. Although not shown in FIG. 6, a 0.5 mm-thick carbon strain relaxation electrode was also formed at the low temperature end of the thermoelectric semiconductor element. The side surfaces of these thermoelectric semiconductor elements 1 were fusion-bonded with the oxide glass 4. In addition, a nickel-based solder 1 is
2, the Mo electrode 3 was joined.

By fusing the side surfaces of the thermoelectric semiconductor element together with the oxide glass as described above, it is possible to reduce the possibility that the thermoelectric semiconductor element is erroneously damaged at the time of handling such as assembling into a power generator or measuring the size of a module. effective.

Actually, none of the obtained thermoelectric conversion modules (total number of manufactured modules: 16) was damaged at the time of attachment to a heat source, and all could be used satisfactorily under the above use conditions.

Samples 6 and 7 In order to evaluate the mass productivity of the thermoelectric conversion module, 3.5
× 3.5 × 8 mm, p-type and n with relative density of 98% or more
9 types of SiGe thermoelectric semiconductor elements alternately in total of 18
A larger number of 1 × 18 line type modules connected in series (9 pairs) were manufactured than in the previous examples, and the incidence of brazing defects was examined.

Sample 6 The structure of the joint was the same as in FIG. That is, a 0.5 mm-thick carbon strain relaxation electrode 2 is provided at both ends of the thermoelectric semiconductor element 1.
Are bonded by a diffusion bonding method, and these thermoelectric semiconductor elements 1
Was fused and bonded with an oxide glass 4, and the Mo electrode 3 was further bonded with a nickel-based solder 12 so that adjacent thermoelectric semiconductor elements 1 were connected in series. At this time, no adjustment was made to provide a void at the end of the oxide glass 4.

When 241 thermoelectric conversion modules of Sample 6 were manufactured, the incidence of defective brazing was 13.3%. Further, when the brazed Mo electrode was observed, remarkable deformation occurred. This is because the oxide glass and the nickel-based solder are in contact with each other, and the influence of the stress generated due to the reaction between the two and / or the difference in thermal expansion caused by the temperature change during the production reaches the Mo electrode. It is believed that there is.

In the sample 2 using a SiGe thermoelectric semiconductor element having a relative density of 98% or more equivalent to that of the sample 6, 95
It is considered that the reason why the% production yield was obtained is simply that the number of products was small and brazing defects did not significantly appear. Also, in Sample 2, no adjustment was made to provide a gap on the upper surface of the oxide glass, but a substantial production gap may have resulted in a high manufacturing yield.

Sample 7 FIG. 7 shows the structure of the joint. As shown in FIG. 7, a 0.5 mm thick carbon strain relief electrode 2 was bonded to both ends of the thermoelectric semiconductor element 1 by a diffusion bonding method. Although not shown in FIG. 7, a 0.5 mm-thick carbon strain relaxation electrode was also bonded to the low-temperature end of the thermoelectric semiconductor element by a diffusion bonding method. These thermoelectric semiconductor elements 1 were fusion-bonded with the oxide glass 4.
At this time, the amount of the oxide glass 4 was adjusted and the side surfaces of the thermoelectric semiconductor elements 1 were fused together with the aim of forming a void having a thickness (0.5 mm) of the carbon strain relaxation electrode 2. As a result, a height difference of 0.5 to 0.1 mm was generated between the end face of the carbon strain relaxation electrode 2 and the end face of the oxide glass 4. Further, the Mo electrode 3 was joined by the nickel-based solder 12 so as to connect the adjacent thermoelectric semiconductor elements 1 to form the gap 5.

When 120 thermoelectric conversion modules of Sample 7 were produced, the occurrence rate of brazing defects was 4.7%. Compared with Sample 6, the effect of reducing the brazing incidence was 65% [(1-4.7 / 13.3) × 100]. When the Mo electrode was observed, it was found that the deformation was greatly reduced and the smoothness was improved.

Here, if the smoothness of the electrodes is poor, the efficiency of heat conduction from the heat source to the thermoelectric conversion module decreases, and the temperature at the high-temperature end decreases, so that the power generation efficiency also decreases. On the other hand, when the electrode has high smoothness as described above, efficient heat conduction from the heat source to the thermoelectric conversion module can be obtained,
Power generation performance and its stability can be improved. In addition, the amount of heat passing from the module high-temperature end electrode to the low-temperature end electrode through the electrical insulating layer portion other than the element portion among the heat amount flowing inside the module can be reduced, and the power generation performance can be improved.

When the power generation output was measured using the thermoelectric conversion module of Sample 7 in the same manner as in Sample 1, the temperature difference was about 4%.
In the case of 00 ° C, the maximum output per module is 0.
9W.

As described above, oxide glass (or brazing material)
Providing a gap between the electrode and the electrode is effective in improving both the production yield and the performance of the thermoelectric conversion module.

After the sides of the thermoelectric semiconductor elements are fused with oxide glass, the gap may be formed by a method such as machining (grinding) the upper surface of the oxide glass. .

FIGS. 8 to 1 show the shapes of the voids other than FIG.
This will be described with reference to FIG. In FIG. 8, a nickel-based solder 12 is placed only on the carbon strain-mitigating electrode 2 on the thermoelectric semiconductor element 1 and the Mo electrode 3 is bonded thereon, so that a gap 5 is formed between the oxide glass 4 and the Mo electrode 3. Is formed.
In FIGS. 9 and 10, a recess is provided at a position corresponding to the upper surface of the oxide glass 4 on the lower surface of the Mo electrode 3, so that a gap 5 is substantially formed between the oxide glass 4 and the Mo electrode 3. I have. In FIG. 11, the nickel-based solder 12 on the oxide glass 4 and Mo are utilized by utilizing the fluidity of the nickel-based solder 12.
A gap 5 is formed between the electrode 3 and the electrode 3. Further, FIG.
The space may be provided by combining the forms of FIG.

[0070]

As described above in detail, according to the thermoelectric conversion module of the present invention, it is easy to control the power generation output in accordance with the temperature distribution of the heat source, and it has a curved surface and the temperature difference between the high-temperature end and the low-temperature end. Good thermal contact can be maintained even with a large heat source, and loss of power generation output can be minimized. Further, since the installation density of the modules can be increased, a compact and small thermoelectric generator can be manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view and a side view of a thermoelectric conversion module according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the thermoelectric conversion modules of samples 1 and 2.

FIG. 3 is a plan view and a side view of the thermoelectric conversion module according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view of a thermoelectric conversion module of Sample 3.

FIG. 5 is a cross-sectional view of a thermoelectric conversion module of Sample 4.

FIG. 6 is a cross-sectional view of a thermoelectric conversion module of Sample 5.

FIG. 7 is a cross-sectional view of a thermoelectric conversion module provided with a gap in a sample 7.

FIG. 8 is a cross-sectional view of another thermoelectric conversion module provided with a gap.

FIG. 9 is a sectional view of another thermoelectric conversion module provided with a gap.

FIG. 10 is a sectional view of another thermoelectric conversion module provided with a gap.

FIG. 11 is a sectional view of another thermoelectric conversion module provided with a gap.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... SiGe thermoelectric semiconductor 2 ... Carbon strain relaxation electrode 3 ... Mo electrode 4 ... Oxide glass 5 ... Void

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Terakado 3-10-10 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Within Japan Hojo Co., Ltd. (72) Inventor Ryuji Kayamoto 3- 10-10 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Japan (72) Inventor Atsuo Matsumoto 3-10-10 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Within Japan-originated Co., Ltd. (72) Inventor Masahiro Ogusu 3-10 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture, Japan (72) Inventor Keiko Kushibiki 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside Nissan Motor Co., Ltd. (72) Inventor Masakazu Kobayashi 2 Takaracho, Kanagawa-ku, Yokohama City, Kanagawa Prefecture 2 Nissan Motor Co., Ltd. (72) Inventor Kazuhiko Shinohara Kanagawa, Japan Hama City, Kanagawa-ku, Takaracho Address 2 Nissan-car Co., Ltd.

Claims (8)

[Claims] At least two pairs of p-type and n-type thermoelectric semiconductors are alternately arranged in a row, and alternately arranged p-type and n-type thermoelectric semiconductors are formed at a high-temperature end and a low-temperature end. A thermoelectric conversion module, wherein the thermoelectric conversion module is electrically connected in series by electrodes. 2. The thermoelectric conversion module according to claim 1, wherein a strain relaxation electrode is provided at least between the electrode at the high-temperature end and the thermoelectric semiconductor. 3. The thermoelectric semiconductor according to claim 1, wherein adjacent thermoelectric semiconductors are fixed via an electrical insulating layer, and a gap is formed at least between the thermoelectric semiconductor and an electrode at a high-temperature end. Thermoelectric conversion module. 4. The thermoelectric conversion module according to claim 1, wherein the thermoelectric semiconductors adjacent to each other are fixed via an electrical insulating layer containing oxide glass as a main component. 5. The thermoelectric conversion module according to claim 1, wherein the thermoelectric semiconductor is mainly composed of a Si—Ge based semiconductor. 6. The thermoelectric conversion module according to claim 1, wherein a main component of the strain relaxation electrode is carbon. 7. The thermoelectric conversion module according to claim 1, wherein an electrode made of Mo and a strain relaxation electrode containing carbon as a main component are fixed by brazing. 8. The thermoelectric conversion module according to claim 1, wherein the thermoelectric semiconductor has a relative density of 93% or more.