JP2009081286A - Thermoelectric conversion module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module which prevents the breakage of a thermoelectric conversion element caused by a thermal stress. <P>SOLUTION: The thermoelectric conversion module 200 includes a pair of electrodes 13 and 14, and one or more thermoelectric conversion elements disposed between the pair of electrodes 13 and 14. At least one of the thermoelectric conversion elements comprises two or more thermoelectric conversion element split pieces that are not fixed to each other at an interface but are stacked in a current channel direction. The height (L) and the width (W) of the thermoelectric conversion element split piece satisfy the relation represented by expression (1), where σ<SB>TE</SB>denotes rupture strength, α denotes linear expansion coefficient, E denotes elastic modulus, T<SB>H</SB>denotes the high-temperature side temperature of the thermoelectric conversion element split piece, T<SB>R</SB>denotes the initial temperature of the thermoelectric conversion element split piece, and T<SB>C</SB>denotes the low-temperature side temperature of the thermoelectric conversion element split piece. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a thermoelectric conversion module having a thermoelectric conversion element capable of relieving thermal stress due to a temperature difference.

Thermoelectric conversion is a phenomenon in which heat and electricity are converted into each other, and since heat and electricity are directly converted without the power of a motor or the like, the development of thermoelectric conversion elements using this phenomenon is In recent years, it has attracted attention from the viewpoint of energy saving.
A power generation element, which is a type of thermoelectric conversion element, uses the Seebeck effect, which generates an electromotive force when a temperature difference is applied to both ends of a solid. Heat generated from waste incinerators and power plants, such as waste heat and geothermal heat It plays the role of improving the energy utilization efficiency of the entire industry in that power can be extracted directly from energy.
In addition, the heating / cooling element, which is one type of other thermoelectric conversion elements, utilizes the Peltier effect that generates a temperature difference when a potential difference is applied to both ends of a solid, and can be heated or cooled without causing noise or vibration. Therefore, it is used for household electronic devices.

  For the thermoelectric conversion element, it is preferable to use a material having three of high conductivity, large thermoelectromotive force, and low thermal conductivity, that is, a material that conducts electricity well but does not transmit heat because of its use. From this point of view, a semiconductor having an intermediate property between a good conductor and an insulator is usually used for the thermoelectric conversion element.

Practically, p-type thermoelectric conversion elements and n-type thermoelectric conversion elements are alternately arranged and wired in series to increase the power generation output or heating / cooling output. FIG. 1 is a diagram schematically showing a layer structure of a general thermoelectric conversion module. As shown in FIG. 1, the thermoelectric conversion module 100 sandwiches p-type thermoelectric conversion elements 1 or n-type thermoelectric conversion elements 2 that are alternately arranged in a grid shape by a pair of electrodes 3, and further the sandwiched objects are electroded. 3 is sandwiched between the substrates 4 from both sides. At this time, by joining the electrodes 3 to the corresponding thermoelectric conversion elements, all the thermoelectric conversion elements are electrically wired in series, and a lead wire is drawn from the electrode 5 at the end and connected to a device that requires a power source or a power source. can do.
When used as a power generation device, an electromotive force is generated in each element by applying a temperature difference between the two substrates 4, and a current flows. When used as a heating / cooling device, a temperature difference is generated at both ends of each element by applying a potential difference to the electrodes 5 at the two ends. As a result, the temperature difference between the two substrates 4 acts on the heating or cooling. Is possible.
The power generation output or heating or cooling output can be increased by extending the electrode 5 at the end and connecting it to another thermoelectric conversion module.

  The temperature difference applied to each element as a power generating element is usually 50 to 800 ° C., and the temperature difference applied to each element as a heating / cooling element usually reaches 20 to 80 ° C. The destruction of the thermoelectric conversion element resulting from thermal expansion and contraction due to such a temperature difference is a fatal problem. In order to solve this problem, for example, in Patent Document 1, the thermoelectric conversion element is divided into a plurality of parts (more specifically, two on the high temperature side and the low temperature side), and the mating surface slides. By making it possible, the structure which absorbs the thermal expansion-contraction difference by a temperature difference is proposed.

Japanese Utility Model Publication No. 3-112955

  However, in Patent Document 1, the thermal stress due to the temperature difference applied to the thermoelectric conversion element is alleviated by the division, but the heat due to the temperature difference applied to the individual thermoelectric conversion element divided pieces itself obtained by dividing the thermoelectric conversion element. Stress is not considered. Therefore, even if the thermoelectric conversion element as a whole can absorb the thermal expansion / contraction difference, the individual thermoelectric conversion element divided pieces may be destroyed by thermal stress, and as a result, the thermoelectric conversion element cannot function.

  As described above, in order to prevent destruction of the thermoelectric conversion element due to thermal stress, further improvements have been required in the design of the thermoelectric conversion element itself. An object of the present invention is to alleviate thermal stress due to a temperature difference applied to each thermoelectric conversion element itself by defining the dimensions of the thermoelectric conversion element divided pieces.

  The thermoelectric conversion module of the present invention comprises a pair of electrodes and a thermoelectric conversion element provided between the pair of electrodes, and at least one of the thermoelectric conversion elements is an interface between two or more pieces of thermoelectric conversion elements. And the height (L) of the thermoelectric conversion element divided pieces and the width (W) of the thermoelectric conversion element divided pieces are expressed by the following formula ( The relationship 1) is satisfied.

(However, in the above formula (1), sigma _TE is breaking strength, alpha linear expansion coefficient, E is the elastic modulus, T _H is a high temperature-side temperature of the thermoelectric conversion elements divided pieces, T _R is the thermoelectric conversion elements divided piece initial temperature of, T _C denotes a lower side temperature of the thermoelectric conversion elements divided pieces.)

  The thermoelectric conversion module having such a configuration alleviates thermal stress due to a temperature difference applied to each segment of the thermoelectric conversion element itself by defining the dimensions of the thermoelectric conversion element as in the above formula (1). Thereby, destruction of the thermoelectric conversion element itself can be prevented.

  In the thermoelectric conversion module of the present invention, among the thermoelectric conversion element divided pieces included in the same thermoelectric conversion element, the width (W) of at least one of the thermoelectric conversion element divided pieces is the other thermoelectric conversion element divided piece. Is preferably smaller than the width (W).

  In the thermoelectric conversion module having such a configuration, as the width (W) of the thermoelectric conversion element segment is reduced, the height (L) of the thermoelectric conversion element segment is calculated from the above formula (1). As a result, the overall height of the thermoelectric conversion module can be reduced, so that the thermoelectric conversion module occupies while relaxing the thermal stress due to the temperature difference applied to each of the thermoelectric conversion element segment pieces itself. The volume can be reduced.

  According to the present invention, by defining the dimensions of the thermoelectric conversion elements as in the above formula (1), the thermal stress due to the temperature difference applied to each thermoelectric conversion element segment itself can be alleviated, and the thermoelectric conversion element is reduced. The destruction of the conversion element itself can be prevented.

  The thermoelectric conversion module of the present invention includes a pair of electrodes and a thermoelectric conversion element provided between the pair of electrodes, and at least one of the thermoelectric conversion elements is an interface between two or more pieces of thermoelectric conversion element segments. And the height (L) of the thermoelectric conversion element divided pieces and the width (W) of the thermoelectric conversion element divided pieces are expressed by the following formula ( The relationship 1) is satisfied.

(However, in the above formula (1), sigma _TE is breaking strength, alpha linear expansion coefficient, E is the elastic modulus, T _H is a high temperature-side temperature of the thermoelectric conversion elements divided pieces, T _R is the thermoelectric conversion elements divided piece initial temperature of, T _C denotes a lower side temperature of the thermoelectric conversion elements divided pieces.)

  Here, “height” refers to a length in a direction substantially parallel to the current flow path direction. Further, the “width” here means a length in a direction substantially perpendicular to the current flow path direction.

  “Initial temperature” as used herein refers to the temperature of the element before providing a temperature difference when the thermoelectric conversion element is used as a power generation element, and when the thermoelectric conversion element is used as a heating / cooling element. The temperature of the element before the temperature difference is generated by applying a voltage to both ends of the element is shown.

  In addition, the above-mentioned “the height (L) of the thermoelectric conversion element divided pieces and the width (W) of the thermoelectric conversion element divided pieces satisfy the relationship of the following formula (1)” means that the multi-divided pieces are stacked. Regarding the height and width of the whole thermoelectric conversion element, the height and width of all the thermoelectric conversion element divided pieces constituting the thermoelectric conversion element in which the multi-division pieces are stacked without satisfying the relationship of the above formula (1) are individually In other words, the relationship of the above formula (1) is satisfied.

  As the thermoelectric conversion element, a p-type thermoelectric conversion element and an n-type thermoelectric conversion element are practically used alternately.

The p-type thermoelectric conversion element here refers to a heating / cooling element using the Peltier effect that is cooled upstream of the current flowing through the element and heated downstream of the current. Moreover, in the electric power generation element using the Seebeck effect, it means that a current flows from the cooled low temperature side of the element toward the heated high temperature side.
Specifically, a bismuth tellurium-based material typified by a solid solution of bismuth telluride (Bi ₂ Te ₃ ) and antimony telluride (Sb ₂ Te ₃ ), a lead tellurium-based material typified by PbTe, a cobalt oxide Representative metal oxide materials, silicon germanium materials typified by Si _0.8 Ge _0.2 , skutterudide compound materials including alloys of cobalt and antimony, silicide compound materials that are metal silicides, Ba ₈ A clathrate compound-based material represented by Ga _18-x Ge _{28 + x} (0 ≦ x ≦ 2) can be given. Of these, the clathrate compound-based material is preferably used in that it does not contain a highly toxic metal such as lead, tellurium, and antimony and does not contain an expensive rare metal such as cobalt.

The n-type thermoelectric conversion element here refers to a heating / cooling element using the Peltier effect that is heated upstream of the current flowing through the element and cooled downstream of the current. Moreover, in the electric power generation element using the Seebeck effect, the current flows from the heated high temperature side of the element toward the cooled low temperature side.
Specifically, a bismuth tellurium-based material typified by a solid solution of bismuth telluride (Bi ₂ Te ₃ ) and bismuth selenide (Bi ₂ Se ₃ ), a lead tellurium-based material typified by PbTe, a cobalt oxide Representative metal oxide materials, silicon germanium materials typified by Si _0.8 Ge _0.2 , skutterudide compound materials including alloys of cobalt and antimony, silicide compound materials that are metal silicides, Ba ₈ A clathrate compound-based material represented by Ga _18-x Ge _{28 + x} (2 ≦ x ≦ 4) can be given. Of these, the clathrate compound-based material is preferably used in that it does not contain a highly toxic metal such as lead, tellurium, and antimony and does not contain an expensive rare metal such as cobalt.

An electrode here is what assists transfer of the electron between thermoelectric conversion elements by arranging a thermoelectric conversion element in series. As will be described later, since heat exchange between the substrate and the thermoelectric conversion element must not be hindered, it is required to have a low thermal resistance and a good conductor, such as copper, aluminum, nickel, gold, tungsten, and alloys thereof. Can be used. Among these, it is preferable to use copper which is particularly excellent as a good conductor.
In addition, a titanium-copper electrode in which titanium is mixed in the electrode can be used so that diffusion bonding with the thermoelectric conversion element can be performed.

The substrate here refers to a substrate that transfers heat to and from the thermoelectric conversion element through electrodes. Since it is required to have a small thermal resistance, an insulator, and excellent vibration resistance and impact resistance, the material is at least one of alumina, mullite, silicon carbide, aluminum nitride, and silicon nitride. A sintered body can be exemplified. In particular, it is preferable to use ceramics made of aluminum nitride or alumina.
Further, by using the substrate with metallized electrodes, the element and the substrate can be directly joined by soldering. A substrate with a metallized electrode is one in which a metallized electrode is thinly applied to a predetermined position of the substrate in advance. The thickness and material of the metallized electrode is preferably a copper electrode of 5 to 100 μm in view of conductivity and solderability.

The above “constituted by stacking two or more pieces of thermoelectric conversion element pieces in the direction of the current flow path without sticking at the interface” means that the interface between the divided pieces is not necessarily in the direction of the current flow path. It does not mean that it is vertical. FIG. 2 is a schematic cross-sectional view showing two pieces of thermoelectric conversion element division pieces and a current flow path direction. 2A and 2B show a current flow path direction 6, a thermoelectric conversion element segment piece 7 upstream of the current flow path direction, and a thermoelectric conversion element segment piece 8 downstream of the current flow path direction. As shown in FIG. 2 (a), the interface between the divided piece 7 and the divided piece 8 may be perpendicular to the direction 6, and as shown in FIG. Instead of being perpendicular to the direction 6, it may be slanted. However, as shown in FIG. 8 showing an example outside the present invention, the interface between the two thermoelectric conversion element segment pieces 9 is not parallel to the current flow path direction 6.
Further, the thermoelectric conversion element divided pieces are not joined to each other, and are brought into electrical conduction by being pressed against each other. At this time, the thermal stress applied to the thermoelectric conversion element divided pieces can be further alleviated by applying a material that does not interfere with electrical conduction, such as graphite, gold, and copper, at the interface between the thermoelectric conversion element divided pieces. Can do.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic cross-sectional view of a typical example of the thermoelectric conversion module of the present invention. The thermoelectric conversion module 200 of the present invention includes a p-type thermoelectric conversion element 15 and an n-type thermoelectric conversion element 16, a pair of electrodes 13 and 14 sandwiching and joining the element 15 or the element 16, and the electrodes 13 and 14 A pair of substrates 11 and 12 are sandwiched and joined. Further, the element 15 and the element 16 are stacked in the direction of the current flow path without the two pieces of the p-type thermoelectric conversion element divided pieces 15a and 15b and the n-type thermoelectric conversion element divided pieces 16a and 16b being fixed to each other. It is configured.
It is also possible to add another thermoelectric conversion element by extending the electrode 14, and in this case, the electrode 14, the p-type thermoelectric conversion element 15, the electrode 13, the n-type thermoelectric conversion The p-type thermoelectric conversion element 15 and the n-type thermoelectric conversion element 16 are arranged alternately and in series by the repeating unit in the order of the element 16 and the electrode 14.

Further, the p-type thermoelectric conversion element divided pieces 15a and 15b and the n-type thermoelectric conversion element divided pieces 16a and 16b have heights L _{1 to} L ₄ and widths W _{1 to} W ₂ as shown in the figure, respectively. is doing. Note that L ₁ + L ₂ = L ₃ + L ₄ , and the values of W ₁ and W ₂ are independent of each other.
Each set of lengths (L ₁ , W ₁ ), (L ₂ , W ₁ ), (L ₃ , W ₂ ), (L ₄ , W ₂ ) shown in FIG. The relationship between the length (L) in the height direction and the length (W) in the width direction shown in (1) is satisfied.

Equation (1) is “Analysis for Thermoelectric Conversion System Design” (by Yoshihiko Ogawa, Morikita Publishing, 1998) p. The description of 103-104 can be derived with reference. FIG. 4 is an explanatory view of the deformation of the rectangular structure due to the temperature difference.
As shown in FIG. 4, the height L, a structure 21 of the rectangular width W (depth shown) is assumed to be uniform temperature T _R at the beginning. Next, an upper portion of the structure 21 is cooled to a temperature T _C, and the lower part of the structure 21 by being heated to a temperature T _H, and became a structure 22 that is deformed. At this time, the changed surface becomes a part of a circular cross section having the radius _RH , but the angle θ formed at the center is sufficiently small.

4, the heated surface (hereinafter, hot side hereinafter) to a temperature T _H width W _H and width change .delta.W _H after heating is
W _H = W + δW _H Formula (2)
It is expressed. Moreover, the use of linear expansion coefficient indicating a rate of change in length in response to temperature change alpha, the relationship between the width variation .delta.W _H, width W, the temperature T _H and the initial temperature T _R, the equation (3) Can be described in
_{δW H = αW (T H -T} R) ··· (3)

4, a surface that is cooled to a temperature T _C (hereinafter, low-temperature side is referred to as) the width W _C and width change .delta.W _C after cooling of,
W _C = W−δW _C Formula (4)
It is expressed. Moreover, the use of the linear expansion coefficient α indicating the ratio of length to correspond to the temperature change varies, the relationship between the width variation .delta.W _C, the width W, the temperature T _C and the initial temperature T _R, the equation (5) Can be described in
δW _C = αW (T _R −T _C ) (5)

  Furthermore, from the assumption that the angle θ is sufficiently small, the following equation (6) is established. Expression (7) is obtained by the expression modification of Expression (6).

By using Expressions (2) to (5) and Expression (7), the height change ΔL _H shown in FIG. 4 can be expressed as Expression (8).

When the elastic modulus E is used, the relationship between the height change ΔL _H , the height L, and the fracture strength σ can be described as in Expression (9).
σ = E (ΔL _H / L) (9)
Therefore, the following formula (10) is obtained by substituting the formula (8) into the formula (9).

On the other hand, when the structures 21 and 22 are regarded as thermoelectric conversion element divided pieces before and after thermal deformation, assuming that the fracture strength of the thermoelectric conversion element divided pieces is σ _TE , the thermoelectric conversion element divided pieces are caused by their own thermal stress. In order not to be destroyed, “σ <σ _TE ” must be satisfied. Therefore, by using equation (10), equation (1) was obtained as shown below.

The fracture strength σ _TE can be obtained by a four-point bending test. The linear expansion coefficient α can be obtained by the TMA method using TMA8140 (Rigaku Corporation). The elastic modulus E can be obtained by a pulse method. The temperature difference between the upper temperature _{T H} and the initial temperature _{T R} of the thermoelectric conversion elements divided pieces _(T H _-T R), and the high temperature-side temperature _{T H} and the temperature difference between the cold side temperature _{T C (T} H _{-T C)} Can be obtained by direct measurement with a thermocouple.

  In FIG. 3, each of the p-type thermoelectric conversion element 15 and the n-type thermoelectric conversion element 16 is configured by stacking two thermoelectric conversion element divided pieces. One of them may be configured by stacking thermoelectric conversion element division pieces. Moreover, you may be comprised by stacking three or more thermoelectric conversion element division | segmentation pieces, Furthermore, the number of the thermoelectric conversion element division | segmentation pieces stacked by the said element 15 and the said element 16 may differ. In a general design, the heights of all the elements 15 and 16 (that is, the sum of the heights of the thermoelectric conversion element divided pieces constituting all the elements 15 or 16) are made equal. There is a need. If the height of one element is different from the height of the other elements, it becomes impossible to correctly hold all the elements by the substrate, and heat transfer between the substrate and each element becomes incomplete, As a result, the power generation output or the heating or cooling output is drastically reduced.

Furthermore, as shown in FIG. 5, when the interface between the thermoelectric conversion element divided pieces is slanted in the direction of the current flow path, only the shortest height L needs to be considered. The reason for this is that when the above formula (1) is taken into consideration, the condition of the formula (1) becomes most severe when L in the formula (1) is the smallest, and the minimum value of L is the formula (1). This is because any height L in the thermoelectric conversion element segment satisfies the formula (1). Therefore, in FIG. 5, the sets of lengths (L ₇ , W ₃ ), (L ₆ , W ₃ ), (L ₉ , W ₄ ), (L) for the thermoelectric conversion element segment pieces 15 a, 15 b, 16 a and 16 b ( L ₁₂ , W ₄ ) need only satisfy the relationship between the height (L) and the width (W) shown in the above formula (1), and the heights L ₅ , L ₈ , L ₁₀ , and L ₁₁ There is no need to consider.

FIG. 6 is a schematic cross-sectional view of a modification of the thermoelectric conversion module of the present invention. The thermoelectric conversion module 300 of the present invention includes a p-type thermoelectric conversion element 35 and an n-type thermoelectric conversion element 36, a pair of electrodes 33 and 34 that sandwich and join the element 35 or the element 36, and the electrodes 33 and 34. A pair of substrates 31 and 32 are sandwiched and joined. Furthermore, the element 36 is configured by stacking the n-type thermoelectric conversion element split pieces 36a and 36b in the direction of the current flow path without being fixed.
It is possible to add another thermoelectric conversion element by extending the electrode 34, and in this case, the electrode 34, the p-type thermoelectric conversion element 35, the electrode 33, the n-type thermoelectric conversion. The p-type thermoelectric conversion element 35 and the n-type thermoelectric conversion element 36 are arranged alternately and in series by the repeating unit in the order of the element 36 and the electrode 34.

Further, the p-type thermoelectric conversion element 35 and the n-type thermoelectric conversion elements divided pieces 36a and 36b has a height _L 13 _{~L 15} as shown in FIG, the width _W 5 to _W-7, respectively, W _6> is a _{W 7.} Note that L ₁₃ = L ₁₄ + L ₁₅ .
Furthermore, each length set (L ₁₃ , W ₅ ), (L ₁₄ , W ₆ ), (L ₁₅ , W ₇ ) of each of the divided pieces shown in FIG. Satisfies the relationship between length (L) and width (W).

When using a thermoelectric conversion element that is defined by the above formula (1) and is composed of two or more pieces of thermoelectric element divided pieces having the same width (W), the height (L) and width (W) Since the relationship is already defined by the above formula (1), it is difficult to freely change the height (L). However, as shown in FIG. 6, by the width W ₇ of the divided piece 36b included in the same said element 36, a construction is adopted smaller than the width W ₆ of the other of the split pieces 36a, wherein As the width W ₇ is reduced, the height L ₁₅ of the segment 36b can be reduced from the above equation (1), and the height of the element 36 can be reduced. In connection with it, the height of the whole thermoelectric conversion module can be made low.

The thermoelectric conversion module having such a configuration is provided to each thermoelectric conversion element divided piece itself by defining the height (L) and width (W) of the thermoelectric conversion element divided piece as shown in the above formula (1). The thermal stress due to the temperature difference can be alleviated, and the thermoelectric conversion element itself configured by stacking the thermoelectric conversion element segment pieces in the direction of the current flow path without sticking can be prevented.
Moreover, since the thermoelectric conversion module of such a structure can suppress the height (L) of the said thermoelectric conversion element division | segmentation piece small from said Formula (1) as the said width | variety (W) is made small. As a result, the overall height of the thermoelectric conversion module can be reduced, and the occupied volume of the thermoelectric conversion module can be kept small while alleviating the thermal stress due to the temperature difference applied to each of the thermoelectric conversion element segment pieces themselves. Can do.

  FIG. 7 shows a configuration of a p-type thermoelectric conversion element, an n-type thermoelectric conversion element, and electrodes, which are a part of the thermoelectric conversion modules of Examples 1 to 4 and the comparative example of the present invention. In the figure, the white quadrilateral is the p-type thermoelectric conversion element or the p-type thermoelectric conversion element divided piece, and the black quadrilateral paired with it is the n-type thermoelectric conversion element or the n-type thermoelectric conversion element divided piece. In addition, a vertically striped quadrilateral represents an electrode connecting the p-type thermoelectric conversion element and the n-type thermoelectric conversion element.

[Example 1]
Example 1 shown in FIG. 7A reflects a typical example (FIG. 3), and Ba ₈ Ga ₁₈ Ge _{28 is used for} a p-type thermoelectric conversion element, and Ba ₈ Ga ₁₆ is used for an n-type thermoelectric conversion element. Ge ₃₀ was used. The breaking strength σ _TE of Ba ₈ Ga ₁₈ Ge ₂₈ is 110 MPa, the linear expansion coefficient α is 14 × 10 ⁻⁶ , the elastic modulus E is 90 GPa, and the breaking strength σ _TE of Ba ₈ Ga ₁₆ Ge ₃₀ is 110 MPa, the linear expansion coefficient α. Is 14 × 10 ⁻⁶ , and the elastic modulus E is 90 GPa. Both the p-type thermoelectric conversion element and the n-type thermoelectric conversion element have a high temperature side temperature T _H of the first thermoelectric conversion element divided piece counted from the high temperature side surface. The low temperature side temperature T _C and the initial temperature T _R are ( _TH , T _C , T _R ) = (600 ° C., 530 ° C., 20 ° C.), and the second thermoelectric conversion element divided piece counting from the high temperature side Since the T _H , T _C , and T _R of ( _TH , T _C , T _R ) = (530 ° C., 100 ° C., 20 ° C.), the p-type thermoelectric conversion element and the n-type thermoelectric conversion element Both are the first thermoelectrics counted from the high temperature side The height L and the width W of the conversion element divided piece are (L, W) = (1.27 mm, 4.0 mm), and the height L and the width of the second thermoelectric conversion element division piece counted from the high temperature side surface. W is (L, W) = (3.2 mm, 4.0 mm).

[Example 2]
Example 2 shown in FIG. 7 (b) reflects the typical example (FIG. 3). However, each of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element is formed by stacking three thermoelectric conversion element divided pieces. It is configured. Similarly to the above, Ba ₈ Ga ₁₈ Ge _{28 was used for} the p-type thermoelectric conversion element, and Ba ₈ Ga ₁₆ Ge ₃₀ was used for the n-type thermoelectric conversion element. Both the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements, high-temperature side temperature T _H of counting from hot side first thermoelectric conversion element divided _piece, lower side temperature T _C, the initial temperature T _R is (T _H , T _C , T _R ) = (600 ° C., 530 ° C., 20 ° C.), and the T _H , T _C , and T _R of the second thermoelectric conversion element divided piece counted from the high temperature side are (T _{H, T C, T R)} = (530 ℃, 460 ℃, a 20 ° C.), the _{T H} of the third thermoelectric conversion elements divided pieces counted from hot side, wherein _{T C,} wherein _{T R} is ( Since T _H , T _C , T _R ) = (460 ° C., 100 ° C., 20 ° C.), the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are the first thermoelectric conversion elements counted from the high-temperature side. The height L and width W of the split pieces are (L, W) = (1.3 mm, 4.0 mm). The height L and width W of the second thermoelectric conversion element division piece are (L, W) = (1.3 mm, 4.0 mm), and the third thermoelectric conversion element division is counted from the high-temperature side. The height L and width W of the piece are (L, W) = (2.9 mm, 4.0 mm).

[Example 3]
Example 3 shown in FIG. 7C reflects a typical example, and as shown in FIG. 5, the interface between the thermoelectric conversion element divided pieces is not perpendicular to the current flow path direction but is slanted. Similarly to the above, Ba ₈ Ga ₁₈ Ge _{28 was used for} the p-type thermoelectric conversion element, and Ba ₈ Ga ₁₆ Ge ₃₀ was used for the n-type thermoelectric conversion element. Both the p-type thermoelectric conversion elements and the n-type thermoelectric conversion elements, high-temperature side temperature T _H of counting from hot side first thermoelectric conversion element divided _piece, lower side temperature T _C, the initial temperature T _R is (T _H , T _C , T _R ) = (600 ° C., 530 ° C., 20 ° C.), and the T _H , T _C , and T _R of the second thermoelectric conversion element divided piece counted from the high temperature side are (T _{Since H 1} , T _C , T _R ) = (530 ° C., 100 ° C., 20 ° C.), both the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are divided from the first thermoelectric conversion element counted from the high temperature side. The height L and width W to be considered of the piece are (L, W) = (1.3 mm, 4.0 mm), and the height to be considered of the second thermoelectric conversion element divided piece counted from the high temperature side surface. L and width W are (L, W) = (3.2 mm, 4.0 mm).

[Example 4]
Example 4 shown in FIG. 7 (d) reflects the modification (FIG. 6). The n-type thermoelectric conversion element is composed of two pieces of thermoelectric conversion element divided pieces, whereas the p-type thermoelectric element. The conversion element consists of only one piece of element. Further, similarly to the above p-type thermoelectric conversion elements in _Ba 8 _Ga 18 _{Ge 28,} n-type thermoelectric conversion element using the _Ba 8 _Ga 16 _{Ge 30.} The p-type thermoelectric conversion element has a high temperature side temperature T _H , a low temperature side temperature T _C , and an initial temperature T _R (T _H , T _C , T _R ) = (600 ° C., 100 ° C., 20 ° C.), and n-type The T _H , T _C , and initial temperature T _R of the first thermoelectric conversion element divided piece counting from the high temperature side constituting the thermoelectric conversion element are (T _H , T _C , T _R ) = (600 ° C., 530). ° C., a 20 ° C.), the _{T H} of counting from hot side the second thermoelectric conversion element divided pieces, the _{T C,} wherein _{T R} is _{(T H, T C, T} R) = (530 ℃, (100 ° C., 20 ° C.), the height L and width W of the p-type thermoelectric conversion element are (L, W) = (4.0 mm, 4.0 mm), which constitutes the n-type thermoelectric conversion element. The height L and width W of the first thermoelectric conversion element segment counted from the high temperature side are (L, W) = (1.27 mm, 4.0 mm). Ri, height L and width W of the second thermoelectric conversion element split pieces counted from the high temperature side is (L, W) = (2.7mm, 3.4mm).

[Comparative example]
In the comparative example shown in FIG. 7 (e), a p-type thermoelectric conversion element and an n-type thermoelectric conversion element each composed of only one piece were used as in the past. Further, similarly to the above p-type thermoelectric conversion elements in _Ba 8 _Ga 18 _{Ge 28,} n-type thermoelectric conversion element using the _Ba 8 _Ga 16 _{Ge 30.} In both the p-type thermoelectric conversion element and the n-type thermoelectric conversion element, the high temperature side temperature T _H , the low temperature side temperature T _C , and the initial temperature T _R are ( _TH , T _C , T _R ) = (600 ° C., 100 ° C., And the height L and the width W are (L, W) = (3.4 mm, 4.0 mm) for both the p-type thermoelectric conversion element and the n-type thermoelectric conversion element.

In all of Examples 1 to 4 and the comparative example, the following common conditions were used. That is, Ti ₂ Cu ₃ was used for the high temperature side electrode and joined to the thermoelectric conversion element by diffusion bonding. Copper was used for the low temperature side electrode, and the portion of the thermoelectric conversion element in contact with the low temperature side electrode was plated in the order of Au plating, Ni plating, and Au plating, and then joined to the low temperature side electrode by soldering. The thermoelectric conversion element segment pieces constituting the thermoelectric conversion element are not bonded to each other, pressed against each other, and further applied by applying copper, which is a material that is easy to slide on the interface between the thermoelectric conversion element segment pieces and does not hinder electrical conduction. Took a good continuity. Further, a thermoelectric conversion module was fabricated by sandwiching a pair of aluminum nitride from both sides of the electrode as a substrate.

It is the figure which showed typically the layer structure of the general thermoelectric conversion module. It is the cross-sectional schematic diagram which showed the 2 piece thermoelectric conversion element division | segmentation piece and the electric current flow path direction. It is a cross-sectional schematic diagram of the typical example of the thermoelectric conversion module of this invention. It is explanatory drawing about a deformation | transformation of the square structure by a temperature difference. It is the cross-sectional schematic diagram which showed the case where the interface of thermoelectric conversion element division | segmentation pieces is slanting in the direction of a current flow path. It is a cross-sectional schematic diagram of the modification of the thermoelectric conversion module of this invention. It is the figure which showed the structure of the p-type thermoelectric conversion element, n-type thermoelectric conversion element, and electrode which are some thermoelectric conversion modules of Examples 1-4 of this invention, and a comparative example. It is a figure which shows the example which deviates from this invention, and is a figure which shows that the interface of two thermoelectric conversion element division | segmentation pieces is parallel to a current flow path direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... p-type thermoelectric conversion element 2 ... n-type thermoelectric conversion element 3 ... Electrode 4 ... Board | substrate 5 ... End electrode 6 ... Current flow path direction 7 ... Thermoelectric conversion element division | segmentation piece 8 upstream of a current flow path direction ... Current flow path direction Downstream thermoelectric conversion element division piece 9 ... thermoelectric conversion element division piece 11, 12 ... substrate 13, 14 ... electrode 15 ... p-type thermoelectric conversion element 15a, 15b ... p-type thermoelectric conversion element division piece 16 ... n-type thermoelectric conversion element 16a , 16b ... n-type thermoelectric conversion element segment 21 ... rectangular structure 22 ... deformed structure 31, 32 ... substrate 33, 34 ... electrode 35 ... p-type thermoelectric conversion element 36 ... n-type thermoelectric conversion element 36a, 36b ... n-type thermoelectric conversion element segment 100 ... thermoelectric conversion module 200 ... thermoelectric conversion module 300 ... thermoelectric conversion module

Claims (2)

Comprising a pair of electrodes and a thermoelectric conversion element provided between the pair of electrodes;
At least one of the thermoelectric conversion elements is constituted by stacking two or more pieces of thermoelectric conversion element pieces in the direction of the current flow path without being fixed at the interface, and
The thermoelectric conversion module, wherein a height (L) of the thermoelectric conversion element divided piece and a width (W) of the thermoelectric conversion element divided piece satisfy the relationship of the following formula (1).

(However, in the above formula (1), sigma _TE is breaking strength, alpha linear expansion coefficient, E is the elastic modulus, T _H is a high temperature-side temperature of the thermoelectric conversion elements divided pieces, T _R is the thermoelectric conversion elements divided piece initial temperature of, T _C denotes a lower side temperature of the thermoelectric conversion elements divided pieces.)   Among the thermoelectric conversion element divided pieces included in the same thermoelectric conversion element, the width (W) of at least one of the thermoelectric conversion element divided pieces is larger than the width (W) of the other thermoelectric conversion element divided pieces. The thermoelectric conversion module according to claim 1, which is small.

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