Thermoelectric conversion module, thermoelectric conversion device, power generation method, and heat transmission method

Abstract

A thermoelectric conversion module (18) comprises a substrate (40) and a plurality of thermoelectric conversion bodies (42) that are arranged on the substrate (40). The thermoelectric conversion bodies (42) have an N-type thermoelectric conversion element (44) that, as seen in cross-section, has a first cross-sectional area, a P-type thermoelectric conversion element (46) that, as seen in cross-section, has a second cross-sectional area that is smaller than the first cross-sectional area, and an electrode (48) that electrically connects one end of the N-type thermoelectric conversion element (44) and one end of the P-type thermoelectric conversion element (46). At least one of the following conditions is met: (1) τ1α>τ1β; (2) τ2α>τ2β.

Description

Thermoelectric conversion module, thermoelectric conversion device, power generation method, and heat transfer method

[0001] The present disclosure relates to a thermoelectric conversion module, a thermoelectric conversion device, a power generation method, and a heat transfer method.

[0002] A thermoelectric conversion module used for thermoelectric power generation utilizing the Seebeck effect or thermoelectric cooling utilizing the Peltier effect is known. This thermoelectric conversion module includes an N-type thermoelectric conversion element, a P-type thermoelectric conversion element, and an electrode that electrically connects one end of the N-type thermoelectric conversion element to one end of the P-type thermoelectric conversion element.

[0003] The efficiency of energy conversion between heat and electricity in thermoelectric power generation and thermoelectric cooling (hereinafter referred to as "thermoelectric conversion efficiency") is determined by the figure of merit of the material used to form the N-type thermoelectric conversion element and the P-type thermoelectric conversion element. In other words, the higher the figure of merit, the higher the thermoelectric conversion efficiency. Patent Document 1 and Non-Patent Document 1 disclose that Mg, which exhibits a high figure of merit, is used as a material for N-type thermoelectric conversion elements. ３ Sb ２ A technique using a compound based on the compound has been disclosed.

[0004] Japanese Patent No. 6127281 Japanese Patent Application Laid-Open No. 2013-012571

[0005] H. Tamaki et al., Advanced Materials 28, 10182, (2016).R. Shu et al., Adv. Funct, Mater. 29, 1807235 (2019).G. Li et al., J. Mater. Chem. A, 5, 9050 (2017).G. Li et al., Phys. Rev. Lett. 119, 085501 (2017).

[0006] The present disclosure provides a thermoelectric conversion module, a thermoelectric conversion device, a power generation method, and a heat transfer method that can improve strength while increasing thermoelectric conversion efficiency.

[0007] A thermoelectric conversion module according to one aspect of the present disclosure includes a substrate having a main surface and a plurality of thermoelectric conversion bodies arranged on the main surface of the substrate, each of the plurality of thermoelectric conversion bodies including a first thermoelectric conversion element having a first cross-sectional area in a cross-sectional view taken along a plane substantially parallel to the main surface, a second thermoelectric conversion element having a second cross-sectional area in the cross-sectional view that is smaller than the first cross-sectional area, and an electrode electrically connecting one end of the first thermoelectric conversion element to one end of the second thermoelectric conversion element; １α >τ １β Condition (1) and τ ２α >τ ２β and in the condition (1), the τ １α is the compressive strain ε １ is a compressive stress applied to the first thermoelectric conversion element to generate τ １β is the compressive strain ε １ is a compressive stress applied to the second thermoelectric conversion element to generate the τ ２α is the shear strain ε ２ is a shear stress applied to the first thermoelectric conversion element to generate τ ２β is the shear strain ε ２ is a shear stress applied to the second thermoelectric conversion element to generate a shear stress.

[0008] These general or specific aspects may be realized by an apparatus or a method, or by any combination of an apparatus and a method.

[0009] According to a thermoelectric conversion module according to an aspect of the present disclosure, it is possible to improve the strength while increasing the thermoelectric conversion efficiency.

[0010] 1 is a perspective view showing a thermoelectric conversion device according to an embodiment; FIG. 2 is a cross-sectional view of a main part of a thermoelectric conversion device according to an embodiment; FIG. 3 is a perspective view showing a thermoelectric conversion module according to an embodiment; FIG. 4 is a plan view showing a thermoelectric conversion module according to an embodiment, with one of the substrates omitted; FIG. 5 is a cross-sectional view of a thermoelectric conversion module according to an embodiment; FIG. 6 is a diagram for explaining compressive stress acting on a thermoelectric conversion module according to an embodiment; FIG. 7 is a diagram for explaining shear stress acting on a thermoelectric conversion module according to an embodiment; FIG. 8 is a graph showing the relationship between strain and stress in a thermoelectric conversion module according to an embodiment; FIG. 9 is a plan view showing a thermoelectric conversion module according to a first modified example of an embodiment, with one of the substrates omitted; FIG. 10 is a plan view showing a thermoelectric conversion module according to a second modified example of an embodiment, with one of the substrates omitted; FIG. 11 is a plan view showing a thermoelectric conversion module according to a third modified example of an embodiment, with one of the substrates omitted; FIG. 12 is a plan view showing a thermoelectric conversion module according to a fourth modified example of an embodiment, with one of the substrates omitted.

[0011] (Findings that Form the Basis of the Present Disclosure) The present inventors have found that the following problems arise with the technology described in the "Background Art" section.

[0012] Thermoelectric power generation is a technology that converts thermal energy into electrical energy by utilizing the Seebeck effect, i.e., the thermoelectric power that occurs between the two ends of an object in proportion to the temperature difference when a temperature difference occurs between the two ends. Thermoelectric cooling is a technology that utilizes the Peltier effect, i.e., the phenomenon of heat transfer by electrons carried by electric current. Thermoelectric power generation has been put to practical use, for example, as a power source for remote locations and space, while thermoelectric cooling has been put to practical use, for example, as an element for precise temperature control of electronic devices, optical devices, etc.

[0013] The efficiency of energy conversion between heat and electricity in thermoelectric power generation and thermoelectric cooling is determined by the figure of merit ZT of the material used. The higher the figure of merit ZT, the higher the energy conversion efficiency, and a high figure of merit ZT is achieved in a semiconductor into which electrically conductive carriers are injected.

[0014] Thermoelectric conversion modules of a type having a π-type structure are known. In this type of thermoelectric conversion module, P-type and N-type thermoelectric conversion elements having Seebeck coefficients S of different signs are electrically connected in series and arranged in parallel with respect to heat flow. This achieves efficient thermoelectric conversion. For a practical thermoelectric conversion module having a π-type structure, durability against stress caused by pressure or thermal stress associated with temperature differences is important; that is, it is important to increase the strength of the entire thermoelectric conversion module. Therefore, in addition to sufficient mechanical strength of the P-type and N-type thermoelectric conversion elements, the arrangement of the P-type and N-type thermoelectric conversion elements and the N-type thermoelectric conversion material on the substrate is also important.

[0015] As a thermoelectric conversion material system that exhibits a high figure of merit, Bi ２ Te ３ system (Sb ２ Te ３ Chalcogenide compounds, such as GeTe-based compounds, are known. Chalcogenide compounds contain rare elements such as Te (tellurium) and Se (selenium), and are brittle materials that require careful handling.

[0016] As a thermoelectric conversion material system that exhibits a high figure of merit and uses a small amount of rare metals, N-type Mg as disclosed in Patent Document 1 and Non-Patent Document 1 is used. ３ Sb ２ Compounds based on this compound are known.

[0017] However, Mg is used as a material for N-type thermoelectric conversion elements. ３ Sb ２ When a P-type compound is used, the strength of the thermoelectric conversion module may be reduced depending on the material of the P-type thermoelectric conversion element.

[0018] The present inventors have ３ Sb ２The researchers focused on the fact that a thermoelectric module constructed by pairing an N-type thermoelectric element made of a chalcogenide-based compound with a P-type thermoelectric element made of a chalcogenide-based compound can be used as a thermoelectric power generation module or Peltier cooling module with a high figure of merit. They also discovered that the cross-sectional area of ​​the N-type thermoelectric element can be made larger than that of the P-type thermoelectric element. This is expected to reduce the amount of rare metals used and improve durability for the entire thermoelectric module.

[0019] Patent Document 2 discloses a thermoelectric conversion module using N-type and P-type thermoelectric conversion elements with different cross-sectional areas. More specifically, Patent Document 2 discloses a thermoelectric conversion module in which the cross-sectional areas of the N-type and P-type thermoelectric conversion elements are different from each other as a configuration for suppressing a decrease in output of the thermoelectric conversion module due to an increase in connection resistance. ３ Sb ２ There is no disclosure or suggestion of forming the layer from a compound based on a fluorine-containing compound or a chalcogenide compound.

[0020] Furthermore, the inventors have conducted extensive research and have newly discovered that the strength of the entire thermoelectric conversion module can be increased by arranging the N-type thermoelectric conversion elements and the P-type thermoelectric conversion elements so that they have approximately the same length and face each other in a cross-sectional view. Patent Document 2 does not disclose or suggest an arrangement for increasing the strength of the entire thermoelectric conversion module.

[0021] Based on this new finding, the present inventors have completed the thermoelectric conversion module according to the present disclosure.

[0022] A thermoelectric conversion module according to a first aspect of the present disclosure includes a substrate having a main surface and a plurality of thermoelectric conversion bodies arranged on the main surface of the substrate, each of the plurality of thermoelectric conversion bodies including a first thermoelectric conversion element having a first cross-sectional area in a cross-sectional view taken along a plane substantially parallel to the main surface, a second thermoelectric conversion element having a second cross-sectional area smaller than the first cross-sectional area in the cross-sectional view, and an electrode electrically connecting one end of the first thermoelectric conversion element and one end of the second thermoelectric conversion element; １α >τ １β Condition (1) and τ ２α >τ ２β and in the condition (1), the τ １α is the compressive strain ε １ is a compressive stress applied to the first thermoelectric conversion element to generate τ １β is the compressive strain ε １ is a compressive stress applied to the second thermoelectric conversion element to generate the τ ２α is the shear strain ε ２ is a shear stress applied to the first thermoelectric conversion element to generate τ ２β is the shear strain ε ２ is a shear stress applied to the second thermoelectric conversion element to generate a shear stress.

[0023] According to this aspect, a thermoelectric conversion module that is resistant to compressive stress and / or shear stress can be realized.

[0024] In addition, in the thermoelectric conversion module according to the second aspect of the present disclosure, in the first aspect, the first thermoelectric conversion element may be an N-type thermoelectric conversion element, and the second thermoelectric conversion element may be a P-type thermoelectric conversion element.

[0025] A thermoelectric conversion module according to a third aspect of the present disclosure includes a substrate having a main surface and a plurality of thermoelectric conversion bodies arranged on the main surface of the substrate, each of the plurality of thermoelectric conversion bodies having an N-type thermoelectric conversion element formed in a substantially rectangular shape and having a first cross-sectional area in a cross-sectional view taken along a plane substantially parallel to the main surface, a P-type thermoelectric conversion element formed in a substantially rectangular shape in the cross-sectional view and having a second cross-sectional area smaller than the first cross-sectional area, and an electrode electrically connecting one end of the N-type thermoelectric conversion element to one end of the P-type thermoelectric conversion element, wherein the N-type thermoelectric conversion element contains Mg, and a specific thermoelectric conversion body among the plurality of thermoelectric conversion bodies is arranged such that a first side of the N-type thermoelectric conversion element and a second side having substantially the same length as the first side of the P-type thermoelectric conversion element face each other in the cross-sectional view.

[0026] According to this aspect, the N-type thermoelectric conversion element contains Mg, which can increase the figure of merit and strength of the N-type thermoelectric conversion element. By making the first cross-sectional area of ​​the N-type thermoelectric conversion element, which has such a relatively high figure of merit and strength, larger than the second cross-sectional area of ​​the P-type thermoelectric conversion element, it is possible to improve the strength of the thermoelectric conversion module while increasing the thermoelectric conversion efficiency.

[0027] In addition, in the thermoelectric conversion module according to the fourth aspect of the present disclosure, in any one of the first to third aspects, the first cross-sectional area may be configured to be 1.5 to 4 times the cross-sectional area of ​​the second cross-sectional area.

[0028] According to this aspect, it is possible to effectively improve the strength of the thermoelectric conversion module while effectively increasing the thermoelectric conversion efficiency.

[0029] Furthermore, in the thermoelectric conversion module according to the fifth aspect of the present disclosure, in the third aspect, the specific thermoelectric conversion element may be arranged in at least a peripheral region of the substrate, and the peripheral region may be configured to be a region corresponding to the N-type thermoelectric conversion elements and the P-type thermoelectric conversion elements arranged along the periphery of the substrate, among the plurality of N-type thermoelectric conversion elements and the plurality of P-type thermoelectric conversion elements arranged on the main surface of the substrate.

[0030] According to this aspect, when the thermoelectric conversion module is used in a thermoelectric conversion device, the peripheral region of the substrate is prone to be subjected to pressure, vibration, etc. By disposing the specific thermoelectric conversion elements in the peripheral region of such a substrate, the strength of the thermoelectric conversion module can be effectively improved.

[0031] Furthermore, in the thermoelectric conversion module according to the sixth aspect of the present disclosure, in the fifth aspect, two or more of the specific thermoelectric conversion elements may be configured to be electrically connected in series in a first direction and arranged adjacent to each other in a second direction perpendicular to the first direction.

[0032] According to this aspect, a plurality of N-type thermoelectric conversion elements and a plurality of P-type thermoelectric conversion elements can be arranged at high density.

[0033] Furthermore, in the thermoelectric conversion module according to the seventh aspect of the present disclosure, in the second or fifth aspect, the substrate may be polygonal having a plurality of vertices, and the N-type thermoelectric conversion elements may be arranged at positions on the main surface of the substrate closest to each of the plurality of vertices.

[0034] According to this aspect, when the thermoelectric conversion module is used in a thermoelectric conversion device, pressure, vibration, etc. are likely to act near each of the multiple vertices of the substrate. By arranging N-type thermoelectric conversion elements near each of the multiple vertices of such a substrate, the strength of the thermoelectric conversion module can be effectively improved.

[0035] Furthermore, in the thermoelectric conversion module according to the eighth aspect of the present disclosure, in the second or fifth aspect, the length of the long side of each of the plurality of N-type thermoelectric conversion elements may be configured to be at least twice the length of any one side of each of the plurality of P-type thermoelectric conversion elements in the cross-sectional view.

[0036] According to this aspect, a plurality of N-type thermoelectric conversion elements and a plurality of P-type thermoelectric conversion elements can be arranged at high density.

[0037] Furthermore, in the thermoelectric conversion module according to the ninth aspect of the present disclosure, in the fifth or sixth aspect, the number of the N-type thermoelectric conversion elements arranged in the peripheral region may be configured to be greater than the number of the P-type thermoelectric conversion elements arranged in the peripheral region.

[0038] According to this aspect, the strength of the peripheral region of the substrate of the thermoelectric conversion module can be effectively improved.

[0039] In addition, in the thermoelectric conversion module according to the tenth aspect of the present disclosure, in the second aspect, the compressive fracture stress τ of the N-type thermoelectric conversion element １ｎ，ｍａｘ is the compressive fracture stress τ of the P-type thermoelectric conversion element １ｐ，ｍａｘ or the shear fracture stress τ of the N-type thermoelectric conversion element is greater than ２ｎ，ｍａｘ is the shear fracture stress τ of the P-type thermoelectric conversion element ２ｐ，ｍａｘ It may be configured to be larger than

[0040] According to this aspect, the strength of the N-type thermoelectric conversion element against compressive stress and / or shear stress can be increased compared to the P-type thermoelectric conversion element.

[0041] In addition, in the thermoelectric conversion module according to the eleventh aspect of the present disclosure, in the second aspect, 2≦σ ｐ / σ ｎ ≦4, and in the condition (3), the σ ｎ is the electrical conductivity of the N-type thermoelectric conversion element at room temperature, and σ ｐ is the electrical conductivity of the P-type thermoelectric conversion element at room temperature.

[0042] According to this aspect, by appropriately changing the compositions of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, the carrier concentration and carrier mobility of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element can be controlled, thereby changing the electrical conductivity of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element. As a result, the imbalance in electrical characteristics between the N-type thermoelectric conversion element and the P-type thermoelectric conversion element, which is caused by making the first cross-sectional area of ​​the N-type thermoelectric conversion element larger than the second cross-sectional area of ​​the P-type thermoelectric conversion element, can be eliminated, and thermoelectric power generation efficiency can be effectively improved.２ Te ３ In the case of Mg-based compounds, the carrier concentration, carrier mobility, and electrical conductivity can be changed by adjusting the mutual ratio of Bi, Sb, Te, and Se, and the amount of additives such as Cu, Sn, and I. ３ Sb ２ In the case of Bi-based compounds, the carrier concentration, carrier mobility, and electrical conductivity can be changed by adjusting the mutual ratio of Mg, Sb, and Bi, and the amount of additives such as Mn, Zn, Li, Na, K, Sc, Y, La, B, Al, Ge, Sn, Pb, Se, and Te.

[0043] In addition, in a thermoelectric conversion module according to a twelfth aspect of the present disclosure, in the eleventh aspect, the σ ｐ is 400 S / cm≦σ ｐ It may be configured to satisfy the condition expressed as ≦4000 S / cm.

[0044] According to this aspect, by appropriately changing the composition of the P-type thermoelectric conversion element, the carrier concentration of the P-type thermoelectric conversion element can be controlled to increase, thereby changing the electrical conductivity of the P-type thermoelectric conversion element.

[0045] In addition, in the thermoelectric conversion module according to a thirteenth aspect of the present disclosure, in the eleventh or twelfth aspect, the σ ｎ is 100 S / cm≦σ ｎ It may be configured to satisfy the condition expressed as ≦1000 S / cm.

[0046] According to this aspect, by appropriately changing the composition of the N-type thermoelectric conversion element, the carrier concentration of the N-type thermoelectric conversion element can be controlled to be suppressed, thereby changing the electrical conductivity of the N-type thermoelectric conversion element.

[0047] In addition, in the thermoelectric conversion module according to the fourteenth aspect of the present disclosure, in any one of the second to thirteenth aspects, the P-type thermoelectric conversion element may be configured to be formed from a chalcogenide-based compound.

[0048] According to this aspect, the figure of merit of the P-type thermoelectric conversion element can be increased, thereby effectively increasing the thermoelectric conversion efficiency.

[0049] In addition, in the thermoelectric conversion module according to a fifteenth aspect of the present disclosure, in the fourteenth aspect, the P-type thermoelectric conversion element is (Bi, Sb) ２ (Se, Te) ３ based compounds, or (Ge, Sn, Pb) ａ (Sb, Bi) ｂ (Mg, Mn, Ti, In, Cr, Ag, Zn) ｃ It may be configured to be formed of an (S, Se, Te) based compound.

[0050] According to this aspect, the figure of merit of the P-type thermoelectric conversion element can be increased, thereby effectively increasing the thermoelectric conversion efficiency.

[0051] In addition, in the thermoelectric conversion module according to the sixteenth aspect of the present disclosure, in any one of the second to fifteenth aspects, the N-type thermoelectric conversion element may further be configured to contain at least one of Sb and Bi.

[0052] According to this aspect, the figure of merit and strength of the N-type thermoelectric conversion element can be increased, thereby improving the strength of the thermoelectric conversion module while increasing the thermoelectric conversion efficiency.

[0053] In addition, in the thermoelectric conversion module according to the seventeenth aspect of the present disclosure, in the sixteenth aspect, the N-type thermoelectric conversion element is made of Mg ３ (Sb, Bi) ２ The compound may be formed from a compound of the formula (I).

[0054] According to this aspect, the figure of merit and strength of the N-type thermoelectric conversion element can be increased, thereby improving the strength of the thermoelectric conversion module while increasing the thermoelectric conversion efficiency.

[0055] Furthermore, a thermoelectric conversion device according to an eighteenth aspect of the present disclosure includes a first fluid flow path section through which a first fluid flows, a second fluid flow path section through which a second fluid flows, and a thermoelectric conversion module according to any one of the first to seventeenth aspects, which converts thermal energy resulting from the temperature difference between the first fluid and the second fluid into electric power.

[0056] According to this aspect, by using any one of the thermoelectric conversion modules described above, it is possible to improve the strength of the entire thermoelectric conversion device while increasing the thermoelectric conversion efficiency.

[0057] Furthermore, a power generation method according to a 19th aspect of the present disclosure includes applying a temperature difference to a thermoelectric conversion module according to any one of the first to 17th aspects, and extracting electric power associated with thermoelectromotive force generated in each of a plurality of thermoelectric converters of the thermoelectric conversion module due to the temperature difference.

[0058] According to this aspect, by using any one of the thermoelectric conversion modules described above, thermoelectric power generation can be performed effectively.

[0059] Furthermore, a heat transfer method according to a twentieth aspect of the present disclosure includes passing an electric current through a thermoelectric conversion module according to any one of the first to seventeenth aspects, and transporting heat by the electric current.

[0060] According to this aspect, by using any one of the thermoelectric conversion modules described above, precise temperature control can be performed by heating or cooling.

[0061] These general or specific aspects may be realized by an apparatus or a method, or by any combination of an apparatus and a method.

[0062] Hereinafter, embodiments will be described with reference to the drawings.

[0063] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step sequences shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components. Furthermore, the drawings are not necessarily strict illustrations. In each drawing, substantially identical components are designated by the same reference numerals, and redundant descriptions are omitted or simplified.

[0064] (Embodiment) [1. Overview of Thermoelectric Conversion Device] First, an overview of a thermoelectric conversion device 2 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing a thermoelectric conversion device 2 according to an embodiment. Fig. 2 is a cross-sectional view of a main part of the thermoelectric conversion device 2 according to an embodiment.

[0065] 1 and 2, the front-rear direction of the thermoelectric converter 2 is the X-axis direction, the left-right direction of the thermoelectric converter 2 is the Y-axis direction, and the up-down direction of the thermoelectric converter 2 is the Z-axis direction.

[0066] The thermoelectric converter 2 is, for example, a thermoelectric conversion unit that generates electricity by utilizing the thermal energy of exhaust gas discharged from an engine mounted on a vehicle.

[0067] As shown in Figures 1 and 2, the thermoelectric conversion device 2 includes a pair of low-temperature fluid flow path sections 4, 6 (an example of a first fluid flow path section), a pair of side restraint sections 8, 10, a high-temperature fluid flow path section 12 (an example of a second fluid flow path section), a high-temperature fluid inlet section 14, a high-temperature fluid outlet section 16, and a pair of thermoelectric conversion modules 18, 20.

[0068] The pair of cryogenic fluid flow path sections 4, 6 are arranged facing each other with a gap therebetween in the vertical direction (Z-axis direction).

[0069] The upper cryogenic fluid flow path section 4 includes a housing 22 having a flat, hollow, rectangular parallelepiped shape and a tubular cryogenic fluid inlet 24 and a tubular cryogenic fluid outlet 26 that protrude from the side of the housing 22 to the outside. The housing 22 is made of, for example, stainless steel. As shown in FIG. 2 , a cryogenic fluid flow path 28 is formed inside the housing 22, through which a cryogenic fluid (an example of a first fluid) flows. The cryogenic fluid is, for example, cold water or cold air having a lower temperature than the high-temperature fluid (described below). The cryogenic fluid inlet 24 and the cryogenic fluid outlet 26 are spaced apart in the front-to-rear direction (X-axis direction) and communicate with the cryogenic fluid flow path 28 of the housing 22. The cryogenic fluid flows into the cryogenic fluid flow path 28 of the housing 22 through the cryogenic fluid inlet 24, flows through the cryogenic fluid flow path 28, and is then discharged to the outside through the cryogenic fluid outlet 26.

[0070] The lower cryogenic fluid flow path section 6 includes a housing 30 in the shape of a flat, hollow, rectangular parallelepiped, and a tubular cryogenic fluid inlet 32 ​​and a tubular cryogenic fluid outlet 34 that protrude from the side of the housing 30 to the outside. The housing 30 is made of, for example, stainless steel. As shown in FIG. 2 , a cryogenic fluid flow path 36 through which the cryogenic fluid flows is formed inside the housing 30. The cryogenic fluid inlet 32 ​​and the cryogenic fluid outlet 34 are spaced apart in the front-to-rear direction and communicate with the cryogenic fluid flow path 36 of the housing 30. The cryogenic fluid flows into the cryogenic fluid flow path 36 of the housing 30 through the cryogenic fluid inlet 32, flows through the cryogenic fluid flow path 36, and is then discharged to the outside through the cryogenic fluid outlet 34.

[0071] 1, the pair of side restraint portions 8, 10 are arranged facing each other with a gap in the left-right direction (Y-axis direction). That is, the pair of side restraint portions 8, 10 are arranged so as to cover, from the left-right sides, a high-temperature fluid channel portion 12 (described later) arranged between the pair of low-temperature fluid channel portions 4, 6. Each of the pair of side restraint portions 8, 10 is formed in the shape of a rectangular flat plate.

[0072] As shown in FIG. 2 , the high-temperature fluid channel section 12 is disposed between the pair of low-temperature fluid channel sections 4, 6. Specifically, the high-temperature fluid channel section 12 is defined by a space surrounded by the pair of low-temperature fluid channel sections 4, 6 and the pair of side restraint sections 8, 10. The high-temperature fluid channel section 12 functions as a high-temperature fluid channel through which a high-temperature fluid (an example of a second fluid) flows. The high-temperature fluid is a fluid with a higher temperature than the low-temperature fluid, such as exhaust gas emitted from an engine mounted on a vehicle. Although not shown, the high-temperature fluid channel section 12 is provided with a plurality of heat transfer fins for transferring heat from the high-temperature fluid to each of the pair of thermoelectric conversion modules 18, 20.

[0073] The high-temperature fluid inlet section 14 and the high-temperature fluid outlet section 16 are arranged opposite each other with a gap in the front-rear direction. That is, the high-temperature fluid inlet section 14 and the high-temperature fluid outlet section 16 are arranged so as to cover the high-temperature fluid passage section 12, which is arranged between the pair of low-temperature fluid passage sections 4, 6, from the sides in the front-rear direction. The high-temperature fluid inlet section 14 and the high-temperature fluid outlet section 16 are formed in a tubular shape and communicate with the high-temperature fluid passage section 12. The high-temperature fluid flows into the high-temperature fluid passage section 12 through the high-temperature fluid inlet section 14, flows through the high-temperature fluid passage section 12 in the front-rear direction (from the negative side to the positive side of the X-axis), and is then discharged to the outside through the high-temperature fluid outlet section 16.

[0074] 2, the pair of thermoelectric conversion modules 18, 20 are respectively disposed between the high-temperature fluid channel section 12 and the pair of low-temperature fluid channel sections 4, 6. That is, the pair of thermoelectric conversion modules 18, 20 are disposed facing each other with a gap therebetween in the vertical direction.

[0075] The upper thermoelectric conversion module 18 is formed in the shape of a rectangular flat plate overall, and is arranged so as to be sandwiched from above and below between the high-temperature fluid channel section 12 and the upper low-temperature fluid channel section 4. That is, the upper thermoelectric conversion module 18 is in contact with the lower surface (the surface on the high-temperature fluid channel section 12 side) of the housing 22 of the upper low-temperature fluid channel section 4, and is also in contact with the heat transfer fins and the like of the high-temperature fluid channel section 12. As a result, the upper thermoelectric conversion module 18 performs thermoelectric power generation by converting thermal energy resulting from the temperature difference between the high-temperature fluid flowing in the high-temperature fluid channel section 12 and the low-temperature fluid flowing in the upper low-temperature fluid channel section 4 into electric power due to the Seebeck effect.

[0076] The lower thermoelectric conversion module 20 is formed in a rectangular flat plate shape overall, and is arranged so as to be sandwiched from above and below between the high-temperature fluid channel section 12 and the lower low-temperature fluid channel section 6. That is, the lower thermoelectric conversion module 20 is in contact with the upper surface (the surface on the high-temperature fluid channel section 12 side) of the housing 30 of the lower low-temperature fluid channel section 6, and is also in contact with the heat transfer fins and the like of the high-temperature fluid channel section 12. As a result, the lower thermoelectric conversion module 20 performs thermoelectric power generation by converting thermal energy resulting from the temperature difference between the high-temperature fluid flowing in the high-temperature fluid channel section 12 and the low-temperature fluid flowing in the lower low-temperature fluid channel section 6 into electric power due to the Seebeck effect.

[0077] 2 to 5, the configuration of the thermoelectric conversion module 18 will be described. Note that since the pair of thermoelectric conversion modules 18, 20 each have the same configuration, only the configuration of the thermoelectric conversion module 18 will be described below.

[0078] Fig. 3 is a perspective view showing the thermoelectric conversion module 18 according to the embodiment. Fig. 4 is a plan view showing the thermoelectric conversion module 18 according to the embodiment, with one of the substrates 38 omitted. Fig. 5 is a cross-sectional view of the thermoelectric conversion module 18 according to the embodiment.

[0079] 3 to 5, the horizontal direction of the thermoelectric conversion module 18 is the X-axis direction, the vertical direction of the thermoelectric conversion module 18 is the Y-axis direction, and the thickness direction of the thermoelectric conversion module 18 is the Z-axis direction.

[0080] 3, the thermoelectric conversion module 18 includes a pair of substrates 38, 40 and a plurality of thermoelectric converters 42. The thermoelectric conversion module 18 has a π-type structure. By applying a temperature difference to the thermoelectric conversion module 18, it is possible to extract electric power associated with the thermoelectromotive force generated in each of the plurality of thermoelectric converters 42 of the thermoelectric conversion module 18 by the temperature difference.

[0081] Each of the pair of substrates 38, 40 is formed in a rectangular, flat plate shape (an example of a polygonal shape having multiple vertices) and is made of, for example, a ceramic substrate. The pair of substrates 38, 40 are arranged to face each other in the thickness direction (Z-axis direction) of the thermoelectric conversion module 18. As shown in FIG. 2 , one substrate 38 is in contact with the underside of the housing 22 of the upper cryogenic fluid path section 4, and the other substrate 40 is in contact with the high-temperature fluid path section 12. At this time, in order to reduce the thermal contact resistance between the one substrate 38 and the housing 22 of the upper cryogenic fluid path section 4, the one substrate 38 is brought into close contact with the housing 22 of the upper cryogenic fluid path section 4 while applying pressure. Furthermore, in order to reduce the thermal contact resistance between the other substrate 40 and the high-temperature fluid path section 12, the other substrate 40 is brought into close contact with the high-temperature fluid path section 12 while applying pressure. Note that for convenience of explanation, one of the substrates 38 is partially cut away in FIG. 3 .

[0082] The plurality of thermoelectric converters 42 are disposed between the pair of substrates 38, 40. Specifically, the plurality of thermoelectric converters 42 are disposed on the opposing main surfaces 38a, 40a of the pair of substrates 38, 40. Each of the plurality of thermoelectric converters 42 has an N-type thermoelectric converter element 44 (an example of a first thermoelectric converter element), a P-type thermoelectric converter element 46 (an example of a second thermoelectric converter element), and an electrode 48. The N-type thermoelectric converter element 44 and the P-type thermoelectric converter element 46 have Seebeck coefficients with different signs.

[0083] The N-type thermoelectric conversion element 44 is a thermoelectric conversion element in which the carrier is an electron, and contains Mg (magnesium) and at least one of Sb (antimony) and Bi (bismuth). Specifically, the N-type thermoelectric conversion element 44 contains Mg ３ (Sb, Bi) ２ In this embodiment, the N-type thermoelectric conversion element 44 is made of, for example, Mg ３ Sb ２ In this specification, the notation (A, B, ...) in the chemical formula of a compound means at least one of "A", "B", .... For example, Mg ３ (Sb, Bi) ２ The compound is Mg３ Sb ２ compounds or Mg ３ Bi ２ This refers to compounds such as

[0084] The P-type thermoelectric conversion element 46 is a thermoelectric conversion element in which the carriers are holes, and is formed of a chalcogenide compound. Specifically, the P-type thermoelectric conversion element 46 is made of (Bi, Sb) ２ (Se, Te) ３ based compounds, or (Ge, Sn, Pb) ａ (Sb, Bi) ｂ (Mg, Mn, Ti, In, Cr, Ag, Zn) ｃ In this embodiment, the P-type thermoelectric conversion element 46 is made of, for example, Bi. ２ Te ３ The SiO2 layer is formed of a GeTe-based compound or a GeTe-based compound.

[0085] The electrode 48 is formed in a rectangular flat plate shape, and electrically connects one end of the N-type thermoelectric conversion element 44 and one end of the P-type thermoelectric conversion element 46 .

[0086] 4, the two thermoelectric converters 42 are electrically connected in series in the Y-axis direction (an example of a first direction) and are arranged adjacent to each other in the X-axis direction (an example of a second direction orthogonal to the first direction). That is, the two thermoelectric converters are arranged in multiple rows (four rows in this embodiment) in the X-axis direction. Note that, although the two thermoelectric converters 42 are electrically connected in series in the Y-axis direction in this embodiment, the present invention is not limited to this, and three or more thermoelectric converters 42 may be electrically connected in series in the Y-axis direction.

[0087] For example, in each of the two thermoelectric converters 42 located in the leftmost column in Fig. 4 , one end of the N-type thermoelectric converter element 44 and one end of the P-type thermoelectric converter element 46 are electrically connected by an electrode 48 arranged on one of the substrates 38. For convenience of explanation, one of the substrates 38 is not shown in Fig. 4. Of the two thermoelectric converters 42 located in the leftmost column in Fig. 4 , the other end of the P-type thermoelectric converter element 46 of the lower thermoelectric converter 42 in Fig. 4 and the other end of the N-type thermoelectric converter element 44 of the upper thermoelectric converter 42 in Fig. 4 are electrically connected by an electrode 48 arranged on the other of the substrate 40.

[0088] In addition, the other end of the P-type thermoelectric element 46 of the thermoelectric converter 42 located at the top of the leftmost column in FIG. 4 is electrically connected to the other end of the N-type thermoelectric element 44 of the thermoelectric converter 42 located at the top of the second-leftmost column by an electrode 48 disposed on the other substrate 40. This electrode 48 is formed, for example, in a hexagonal flat plate shape. By forming the electrode 48 electrically connecting the two thermoelectric converters 42 in this manner in a hexagonal shape, abnormal heat generation due to current concentration can be suppressed compared to when the electrode 48 is formed in a rectangular shape. Similarly, as shown by the dashed dotted lines in FIG. 4 , the N-type thermoelectric element 44, the P-type thermoelectric element 46, the N-type thermoelectric element 44, the P-type thermoelectric element 46, ..., the N-type thermoelectric element 44, the P-type thermoelectric element 46 are arranged in a serpentine pattern in this order and electrically connected in series.

[0089] Of the plurality of N-type thermoelectric conversion elements 44 and the plurality of P-type thermoelectric conversion elements 46 connected in series, the other ends of the N-type thermoelectric conversion elements 44 and the P-type thermoelectric conversion elements 46 arranged at both ends are electrically connected to extraction electrodes 50 and 52, respectively. As shown in Fig. 3, wiring 54 and 56 are electrically connected to these extraction electrodes 50 and 52, respectively. For convenience of explanation, the wiring 54 and 56 are not shown in Figs. 4 and 5.

[0090] In the cross-sectional view shown in FIG. 5 taken along a plane substantially parallel to the main surface 40 a of the substrate 40 (or the main surface 38 a of the substrate 38), the N-type thermoelectric conversion element 44 is formed in a rectangular shape (an example of a substantially rectangular shape) and has a first cross-sectional area A ｎ The P-type thermoelectric conversion element 46 is formed in a square shape (an example of a substantially rectangular shape) and has a first cross-sectional area A ｎ a second smaller cross-sectional area A ｐ The first cross-sectional area A ｎ is the second cross-sectional area A ｐ It is preferable that the cross-sectional area is 1.5 times or more and 4 times or less.

[0091] 5, the thermoelectric converter 42 is arranged such that one side 44a (an example of a first side) of the N-type thermoelectric conversion element 44 and one side 46a (an example of a second side) of the P-type thermoelectric conversion element 46 face each other. Here, the one side 44a of the N-type thermoelectric conversion element 44 and the one side 46a of the P-type thermoelectric conversion element 46 have substantially the same length L. In this specification, a thermoelectric converter 42 in which the one side 44a of the N-type thermoelectric conversion element 44 and the one side 46a of the P-type thermoelectric conversion element 46 have substantially the same length and are arranged to face each other is referred to as a "specific thermoelectric converter."

[0092] The thermoelectric converter 42 is disposed in at least the peripheral region of the substrate 40 (or the substrate 38). Here, the peripheral region is a region corresponding to the N-type thermoelectric converter elements 44 and the P-type thermoelectric converter elements 46 disposed along the peripheral edge of the substrate 40 (or the substrate 38) among the plurality of N-type thermoelectric converter elements 44 and the plurality of P-type thermoelectric converter elements 46 disposed on the main surface 40a of the substrate 40 (or on the main surface 38a of the substrate 38).

[0093] The strength of the thermoelectric conversion module 18 will be described below with reference to Fig. 6 to Fig. 8. Fig. 6 is a diagram illustrating compressive stress acting on the thermoelectric conversion module 18 according to the embodiment. Fig. 7 is a diagram illustrating shear stress acting on the thermoelectric conversion module 18 according to the embodiment. Fig. 8 is a graph showing the relationship between strain and stress in the thermoelectric conversion module 18 according to the embodiment.

[0094] As described above, in the thermoelectric conversion module 18 according to the embodiment, the first cross-sectional area A ｎ is the second cross-sectional area A of the P-type thermoelectric conversion element 46 ｐ As shown in FIG. 6, the compressive strain ε １ In order to generate a compressive stress τ １ｍｏｄｕｌｅ is expressed as the following equation 1.

[0095] τ １ｍｏｄｕｌｅ = {A ｐ ×f １ｐ (ε １ ) + A ｎ ×f １ｎ (ε １ ) / (A ｐ +A ｎ ) (Formula 1)

[0096] In the above formula 1, f １ｐ , f １ｎ are functions that represent the compressive stress-compressive strain relationship for the P-type thermoelectric conversion elements 46 and the N-type thermoelectric conversion elements 44. Here, the following equations 2 and 3 hold for the P-type thermoelectric conversion elements 46 and the N-type thermoelectric conversion elements 44, respectively.

[0097] τ １ｐ = f １ｐ (ε １ｐ ) (Formula 2) τ １ｎ = f １ｎ (ε １ｎ ) (Formula 3)

[0098] In the above formula 2, τ １ｐ (τ １α (an example of which) is a compressive strain ε １ｐ is the compressive stress applied to the P-type thermoelectric conversion element 46 to generate τ. １ｎ (τ １β (an example of which) is a compressive strain ε １ｎ is the compressive stress applied to the N-type thermoelectric conversion element 44 to generate the

[0099] As shown in FIG. 6, a compressive stress τ１ｍｏｄｕｌｅ When the applied voltage is ε , if the deformation from the substrates 38 and 40 to the electrode 48 and the junctions between the electrode 48 and the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44 is negligibly small, １ = ε １ｐ = ε １ｎ As a result, the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44 are subjected to the same compressive strain ε １ occurs, so ε １ｐ = ε １ｎ Under the condition τ １ｐ <τ １ｎ If so, the first cross-sectional area A ｎ is the second cross-sectional area A ｐ The larger the compressive strain ε of the thermoelectric conversion module 18 is compared with １ The compressive stress τ required to generate １ｍｏｄｕｌｅ becomes larger, and the strength of the entire thermoelectric conversion module 18 is improved.

[0100] As shown in FIG. 7, the shear strain ε ２ In order to generate the shear stress τ ２ｍｏｄｕｌｅ is expressed as the following equation 4.

[0101] τ ２ｍｏｄｕｌｅ = {A ｐ ×f ２ｐ (ε ２ ) + A ｎ ×f ２ｎ (ε ２ ) / (A ｐ +A ｎ ) (Formula 4)

[0102] In the above formula 4, f ２ｐ , f ２ｎ are functions that represent the shear stress-shear strain relationship for the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44. Here, the following equations 5 and 6 hold for the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44, respectively.

[0103] τ ２ｐ = f ２ｐ (ε ２ｐ ) (Equation 5) τ ２ｎ = f ２ｎ(ε ２ｎ ) (Formula 6)

[0104] In the above equation 5, τ ２ｐ (τ ２α (an example of which) applies shear strain ε ２ｐ is the shear stress applied to the P-type thermoelectric conversion element 46 to generate τ. ２ｎ (τ ２β (an example of which) applies shear strain ε ２ｎ is the shear stress applied to the N-type thermoelectric conversion element 44 to generate

[0105] As shown in FIG. 7, a shear stress τ ２ｍｏｄｕｌｅ When the deformation from the substrates 38, 40 to the joint is negligibly small when ε is applied, ２ = ε ２ｐ = ε ２ｎ As a result, the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44 have the same shear strain ε ２ occurs, so ε ２ｐ = ε ２ｎ Under the condition τ ２ｐ <τ ２ｎ If so, the first cross-sectional area A ｎ is the second cross-sectional area A ｐ The shear strain ε of the thermoelectric conversion module 18 increases as compared with ２ The shear stress τ required to generate ２ｍｏｄｕｌｅ becomes larger, and the strength of the entire thermoelectric conversion module 18 is improved.

[0106] In the thermoelectric conversion module 18 according to the embodiment, when the N-type thermoelectric conversion elements 44 are superior to the P-type thermoelectric conversion elements 46 in both the breaking strength and the slope of the stress-strain curve (elastic modulus), the first cross-sectional area A ｎ is the second cross-sectional area A of the P-type thermoelectric conversion element 46 ｐBy adopting a structure in which the stress / strain is greater than τ, the thermoelectric conversion module 18 has excellent properties in terms of fracture strength. The stress / strain direction may be superior in either the compression direction or the shear direction. If the N-type thermoelectric conversion elements 44 are superior to the P-type thermoelectric conversion elements 46 in the compression direction, a thermoelectric conversion module 18 that is strong against compressive stress is realized. On the other hand, if the N-type thermoelectric conversion elements 44 are superior to the P-type thermoelectric conversion elements 46 in the shear direction, a thermoelectric conversion module 18 that is strong against shear stress is realized. That is, τ １ｎ >τ １ｐ The condition expressed by and τ ２ｎ >τ ２ｐ It is sufficient that at least one of the conditions expressed by the following is satisfied.

[0107] 8 schematically shows typical behavior of the stress-strain curves, i.e., the relationship between stress τ and strain ε, of the thermoelectric conversion module 18, the N-type thermoelectric conversion elements 44, and the P-type thermoelectric conversion elements 46 according to the embodiment. Fig. 8 shows the stress applied when strain is applied to the thermoelectric conversion module 18, the N-type thermoelectric conversion elements 44, and the P-type thermoelectric conversion elements 46, and the thermoelectric conversion module 18, the N-type thermoelectric conversion elements 44, and the P-type thermoelectric conversion elements 46 are destroyed (broken) at the stress or strain values ​​indicated by black circles.

[0108] As shown by the solid line in the lower graph in FIG. ２ Te ３ The stress-strain curve of the P-type thermoelectric conversion element 46 (chalcogenide-based element) formed of a chalcogenide compound, typically a Mg-based or GeTe-based compound, is linear, and the P-type thermoelectric conversion element 46 is destroyed at low stress or strain values. On the other hand, as shown by the upper solid line in the graph of FIG. ３ Sb ２ N-type thermoelectric conversion element 44 (Mg ３ Sb ２ The stress-strain curve of the N-type thermoelectric conversion element 44 is slightly curved, and it breaks at a high stress or strain value, so it has excellent toughness and ductility among thermoelectric conversion elements. １ｎ，ｍａｘis the compressive fracture stress τ that is the compressive stress at which the P-type thermoelectric conversion element 46 is broken. １ｐ，ｍａｘ In addition, the shear fracture stress τ ２ｎ，ｍａｘ is the shear fracture stress τ, which is the shear stress at which the P-type thermoelectric conversion element 46 is broken. ２ｐ，ｍａｘ is larger than τ １ｎ，ｍａｘ >τ １ｐ，ｍａｘ The condition expressed by and τ ２ｎ，ｍａｘ >τ ２ｐ，ｍａｘ It is sufficient that at least one of the conditions expressed by the following is satisfied. In addition, Non-Patent Document 2 states that Mg is a property correlated with the breaking strength. ３ Sb ２ The fracture toughness value of the Bi system element is ２ Te ３ It is disclosed that the material exhibits an excellent fracture toughness value, approximately three times that of the conventional element.

[0109] The two dashed lines in FIG. 8 represent the stress-strain curve of the thermoelectric conversion module 18 predicted based on the above formula (1) under two cross-sectional area ratio conditions (A ｐ : A ｎ = 1:2, A ｐ : A ｎ In the case where the N-type thermoelectric conversion element 44 is superior to the P-type thermoelectric conversion element 46 in terms of the slope df / dε of the stress-strain curve, which is called the shear modulus and the transverse modulus, the first cross-sectional area A ｎ By increasing the ratio, the maximum stress required to generate strain leading to fracture increases, that is, the strength of the thermoelectric conversion module 18 is improved.

[0110] Non-patent documents 3 and 4 describe Mg ３ Sb ２ and Bi ２ Te ３ These documents disclose the results of simulations based on the first-principles calculation method for the stress-strain curve of Mg ３ Sb ２ The transverse elastic modulus of Bi is 12 GPa. ２ Te ３It is disclosed that the transverse elastic modulus of the first cross-sectional area A is about 4 to 6 GPa. ｎ Increasing the ratio of the cross-sectional area A ｎ / A ｐ By selecting a value of 2 or more, the longitudinal elastic modulus of the thermoelectric conversion module 18 is ３ Sb ２ It reaches a strength of about 9 to 10 GPa, which is comparable to that of the simple substance Mg ３ Sb ２ First cross-sectional area A of the system compound ｎ The strength improvement effect of increasing the ratio of Bi ２ Te ３ This can be obtained when not only GeTe-based compounds but also general chalcogenide compounds such as GeTe-based compounds are used as the material for the P-type thermoelectric conversion element 46 .

[0111] In addition, chalcogenide materials use rare elements such as Se (selenium) and Te (tellurium) as their main components, so the cross-sectional area ratio A ｎ / A ｐ Increasing the value of β leads to suppression of the use of rare elements, and therefore the thermoelectric conversion module 18 according to the embodiment is also advantageous in terms of improving environmental friendliness.

[0112] Next, the thermoelectric conversion characteristics of the thermoelectric conversion module 18 will be described. When a thermoelectric conversion module 18 combining N-type thermoelectric conversion elements 44 and P-type thermoelectric conversion elements 46 with different cross-sectional areas is used for thermoelectric power generation or thermoelectric cooling, the optimal drive current conditions usually differ between the N-type thermoelectric conversion elements 44 and the P-type thermoelectric conversion elements 46, resulting in a decrease in the thermoelectric conversion performance of the thermoelectric conversion module 18. To avoid this problem, it is effective to increase the carrier concentration of the P-type thermoelectric conversion elements 46 and suppress the carrier concentration of the N-type thermoelectric conversion elements 44.

[0113] The Seebeck coefficients of the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44 in the operating temperature range of the thermoelectric conversion module 18 are respectively S ｐ , S ｎ , and each electrical conductivity is σ ｐ , σ ｎ, and the thermal conductivity of each is κ ｐ , κ ｎ When the cross-sectional area ratio A is set to 1 / 2, the thermal power generation efficiency or the cooling coefficient of performance (COP) is maximized. ｎ / A ｐ is expressed by the following equation 7.

[0114]

[0115] In addition, the cross-sectional area ratio A that maximizes the power generation density or heat absorption density per unit area ｎ / A ｐ is expressed as in the following equation 8.

[0116] A ｎ / A ｐ = σ ｐ |S ｐ | / σ ｎ |S ｎ | (Formula 8)

[0117] The above formulas 7 and 8 are both σ ｎ / σ ｐ is a decreasing function of σ ｐ , σ ｎ is proportional to the carrier concentration, the carrier concentration ratio N ｎ / N ｐ By reducing the temperature, the thermoelectric conversion characteristics of the thermoelectric conversion module 18 can be maximized.

[0118] As an example, the P-type thermoelectric conversion element 46 is made of Bi. ０．５ Sb １．５ Te ３ (S ｐ = 180 μV / K, σ ｐ =1000S / cm, κ ｐ = 1.5 W / mK), and Mg as the N-type thermoelectric conversion element 44 ３．２ SbBi ０．９９８ Te ０．００２ (S ｎ =-220μV / K, σ ｎ = 400 S / cm, κ ｎ = 0.9 W / mK). At this time, the cross-sectional area ratio A that maximizes the power generation efficiency and the cooling coefficient of performance is ｎ / A ｐis 2.04, and the cross-sectional area ratio A that maximizes the power generation density and heat absorption density is ｎ / A ｐ is 2.05. By manufacturing a thermoelectric conversion module 18 having such a cross-sectional area ratio, it is possible to maximize the characteristics and improve the strength at the same time. In addition, by reducing the amount of Te in the N-type thermoelectric conversion elements 44, σ ｎ or Bi ０．５ Sb １．５ Te ３ By doping Cu (copper) or Sn (tin), the cross-sectional area ratio A ｎ / A ｐ can be made even larger.

[0119] The electrical conductivity of the N-type thermoelectric conversion element 44 at room temperature is σ ｎ , the electrical conductivity of the P-type thermoelectric conversion element 46 at room temperature is σ ｐ Then, 2≦σ ｐ / σ ｎ It is preferable that the condition expressed as ≦4 is satisfied. ｐ is 400 S / cm≦σ ｐ It is preferable that the condition expressed as ≦4000 S / cm is satisfied, and σ ｎ is 100 S / cm≦σ ｎ It is preferable to satisfy the condition expressed as ≦1000 S / cm.

[0120] [3. Effects] As described above, in this embodiment, in the cross-sectional view shown in FIG. ３ Sb ２ The first cross-sectional area A of the N-type thermoelectric conversion element 44 formed of the compound ｎ is the second cross-sectional area A of the P-type thermoelectric conversion element 46 formed of, for example, a chalcogenide compound. ｐ Furthermore, one side 44a of the N-type thermoelectric conversion element 44 and one side 46a of the P-type thermoelectric conversion element 46 have approximately the same length L and are arranged to face each other.

[0121] This makes it possible to increase the thermoelectric conversion efficiency while improving the strength of the thermoelectric conversion module 18. As a result, even if the thermoelectric conversion module 18 is subjected to an impact, vibration, or the like, damage to the thermoelectric conversion module 18 can be suppressed.

[0122] [4. Modified Examples of Thermoelectric Conversion Module] [4-1. Modified Example 1] The configuration of a thermoelectric conversion module 18A according to Modified Example 1 of the embodiment will be described with reference to FIG. 9. FIG. 9 is a plan view showing a thermoelectric conversion module 18A according to Modified Example 1 of the embodiment, with one of the substrates 38 omitted. In this modified example, the same components as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted. For convenience of explanation, the electrodes 48 are not shown in FIG. 9.

[0123] 9 , in a thermoelectric conversion module 18A according to the first modification, the shapes of the N-type thermoelectric conversion elements 44A and the P-type thermoelectric conversion elements 46A of a thermoelectric converter 42A are different from the shapes of the N-type thermoelectric conversion elements 44 and the P-type thermoelectric conversion elements 46 of the thermoelectric converter 42 described above. Specifically, in a cross-sectional view taken along a plane substantially parallel to the main surface 40a of the substrate 40, the N-type thermoelectric conversion elements 44A are formed in a square shape (an example of a substantially rectangular shape), and the P-type thermoelectric conversion elements 46A are formed in a rectangular shape (an example of a substantially rectangular shape).

[0124] In this modification, the same effects as those of the above embodiment can be obtained.

[0125] [4-2. Modification 2] The configuration of a thermoelectric conversion module 18B according to Modification 2 of the embodiment will be described with reference to Fig. 10. Fig. 10 is a plan view showing a thermoelectric conversion module 18B according to Modification 2 of the embodiment, with one of the substrates 38 omitted. In this modification, the same components as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted. For convenience of explanation, the electrodes 48 are not shown in Fig. 10.

[0126] 10 , in a thermoelectric conversion module 18B according to Modification 2, the arrangement of the multiple thermoelectric conversion elements 42 differs from that of the above embodiment. Specifically, as indicated by the dashed dotted lines in FIG. 10 , N-type thermoelectric conversion elements 44, P-type thermoelectric conversion elements 46, N-type thermoelectric conversion elements 44, P-type thermoelectric conversion elements 46, ..., P-type thermoelectric conversion elements 46, N-type thermoelectric conversion elements 44 are arranged in a zigzag pattern in this order and are electrically connected in series. This allows the multiple N-type thermoelectric conversion elements 44 and the multiple P-type thermoelectric conversion elements 46 to be arranged at high density.

[0127] Furthermore, in a cross-sectional view taken along a plane substantially parallel to the main surface 40a of the substrate 40, the length L1 of the long side of each of the plurality of N-type thermoelectric conversion elements 44 is at least twice the length L2 of one side of each of the plurality of P-type thermoelectric conversion elements 46. In this case, a gap may be formed between two adjacent P-type thermoelectric conversion elements 46 in the long side direction of the N-type thermoelectric conversion elements 44. This allows the plurality of N-type thermoelectric conversion elements 44 and the plurality of P-type thermoelectric conversion elements 46 to be arranged with high density.

[0128] Furthermore, the number of N-type thermoelectric conversion elements 44 arranged in the peripheral region of the substrate 40 is greater than the number of P-type thermoelectric conversion elements 46 arranged in the peripheral region of the substrate 40. This effectively improves the strength of the peripheral region of the substrate 40 of the thermoelectric conversion module 18B.

[0129] [4-3. Modification 3] The configuration of a thermoelectric conversion module 18C according to Modification 3 of the embodiment will be described with reference to Fig. 11. Fig. 11 is a plan view showing a thermoelectric conversion module 18C according to Modification 3 of the embodiment, with one of the substrates 38 omitted. In this modification, the same components as those in the above embodiment and Modification 1 are designated by the same reference numerals, and their description will be omitted. For convenience of explanation, the electrodes 48 are not shown in Fig. 11.

[0130] 11 , in a thermoelectric conversion module 18C according to Modification 3, the arrangement of the N-type thermoelectric conversion elements 44A differs from that of the above embodiment. Specifically, as in Modification 2, as indicated by the dashed dotted line in FIG. 11 , the N-type thermoelectric conversion elements 44A, P-type thermoelectric conversion elements 46A, N-type thermoelectric conversion elements 44A, P-type thermoelectric conversion elements 46A, ..., P-type thermoelectric conversion elements 46A, N-type thermoelectric conversion elements 44A are arranged in a zigzag pattern in this order and are electrically connected in series.

[0131] The N-type thermoelectric conversion elements 44A are disposed at positions closest to each of the four vertices 40b on the main surface 40a of the substrate 40. That is, the four N-type thermoelectric conversion elements 44A are disposed at the four corners (or in the vicinity thereof) of the main surface 40a of the substrate 40, respectively.

[0132] In practice, stress often concentrates at the four corners of the substrate 40 in the thermoelectric conversion module 18C, so by preferentially arranging the N-type thermoelectric conversion elements 44A in positions where distortion is likely to occur, it is possible to improve the strength of the thermoelectric conversion module 18C at the four corners of the substrate 40. In this case, the modulus of elasticity of the N-type thermoelectric conversion elements 44A may be lower than the modulus of elasticity of the P-type thermoelectric conversion elements 46A, and the strength of the thermoelectric conversion module 18C can be improved as long as the N-type thermoelectric conversion elements 44A are superior only in terms of breaking strength.

[0133] [4-4. Modification 4] The configuration of a thermoelectric conversion module 18D according to Modification 4 of the embodiment will be described with reference to Fig. 12. Fig. 12 is a plan view showing a thermoelectric conversion module 18D according to Modification 4 of the embodiment, with one of the substrates 38 omitted. In this modification, the same components as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted. For convenience of explanation, the electrodes 48 are not shown in Fig. 12.

[0134] As shown in Figure 12, in the thermoelectric conversion module 18D according to the fourth modification, similarly to the third modification, as shown by the dotted line in Figure 12, the N-type thermoelectric conversion elements 44, the P-type thermoelectric conversion elements 46, the N-type thermoelectric conversion elements 44, the P-type thermoelectric conversion elements 46, ..., the P-type thermoelectric conversion elements 46, the N-type thermoelectric conversion elements 44 are arranged in a zigzag pattern in this order and are electrically connected in series.

[0135] Furthermore, the N-type thermoelectric conversion elements 44 are disposed at positions closest to each of the four vertices 40b on the main surface 40a of the substrate 40. That is, the four N-type thermoelectric conversion elements 44 are disposed at (or in the vicinity of) the four corners of the main surface 40a of the substrate 40. As a result, the same effects as those of the third modification can be obtained in this modification as well.

[0136] (Other Embodiments) While the thermoelectric conversion module according to one or more aspects of the present disclosure has been described above based on the embodiments and modifications, the present disclosure is not limited to these embodiments and modifications. As long as the modifications do not deviate from the spirit of the present disclosure, various modifications that would occur to a person skilled in the art may also be included within the scope of one or more aspects of the present disclosure.

[0137] In the above embodiments and variants, the high-temperature fluid is exhaust gas and the low-temperature fluid is cold water or cold air, but this is not limited to this, and each of the high-temperature fluid and the low-temperature fluid may be any liquid or gas.

[0138] In the above-described embodiment and modifications, the thermoelectric conversion module 18 (18A, 18B, 18C, 18D, 20) is used for thermoelectric power generation utilizing the Seebeck effect. However, the present invention is not limited to this, and the thermoelectric conversion module 18 may be used for thermoelectric cooling (or thermoelectric heating) utilizing the Peltier effect. In this case, by passing a current through the thermoelectric conversion module 18 (18A, 18B, 18C, 18D, 20), heat can be transported by the current. This allows precise temperature control by heating or cooling.

[0139] The thermoelectric conversion module according to the present disclosure can be used, for example, in generators that generate electricity by utilizing the thermal energy of exhaust gases emitted from automobiles, factories, etc., or for temperature control of precision equipment such as electronic devices and optical devices.

[0140] 2 Thermoelectric conversion device 4, 6 Low-temperature fluid flow path section 8, 10 Side restraint section 12 High-temperature fluid flow path section 14 High-temperature fluid inlet section 16 High-temperature fluid outlet section 18, 18A, 18B, 18C, 18D, 20 Thermoelectric conversion module 22, 30 Housing 24, 32 Low-temperature fluid inlet section 26, 34 Low-temperature fluid outlet section 28, 36 Low-temperature fluid flow path 38, 40 Substrate 38a, 40a Main surface 40b Vertex 42, 42A Thermoelectric conversion body 44, 44A N-type thermoelectric conversion element 44a, 46a One side 46, 46A P-type thermoelectric conversion element 48 Electrode 50, 52 Lead-out electrode 54, 56 Wiring

Claims

1. A thermoelectric conversion module, comprising: A main surface; a plurality of thermoelectric converters disposed on the main surface; Each of the plurality of thermoelectric converters is a first thermoelectric conversion element having a first cross-sectional area in a cross-sectional view taken along a plane substantially parallel to the main surface; a second thermoelectric conversion element having a second cross-sectional area smaller than the first cross-sectional area in the cross-sectional view; an electrode electrically connecting one end of the first thermoelectric conversion element and one end of the second thermoelectric conversion element; τ １α >τ １β Condition (1) and τ ２α >τ ２β At least one of the conditions (2) is satisfied, In the above condition (1), The τ １α is a compressive strain ε １ a compressive stress applied to the first thermoelectric conversion element to generate The τ １β is the compressive strain ε １ a compressive stress applied to the second thermoelectric conversion element to generate In the above condition (2), The τ ２α is the shear strain ε ２ is a shear stress applied to the first thermoelectric conversion element to generate The τ ２β is the shear strain ε ２ is a shear stress applied to the second thermoelectric conversion element to generate Thermoelectric conversion module.

2. the first thermoelectric conversion element is an N-type thermoelectric conversion element, The second thermoelectric conversion element is a P-type thermoelectric conversion element. The thermoelectric conversion module according to claim 1 .

3. The first cross-sectional area is 1.5 to 4 times the second cross-sectional area. The thermoelectric conversion module according to claim 1 .

4. A specific thermoelectric converter among the plurality of thermoelectric converters is arranged such that, in the cross-sectional view, a first side of the N-type thermoelectric converter element and a second side having approximately the same length as the first side of the P-type thermoelectric converter element face each other, the specific thermoelectric converter is disposed in at least a peripheral region of a substrate having the main surface, The peripheral region is a region corresponding to the N-type thermoelectric conversion elements and the P-type thermoelectric conversion elements that are arranged along the peripheral edge of the substrate, among the plurality of N-type thermoelectric conversion elements and the plurality of P-type thermoelectric conversion elements that are arranged on the main surface of the substrate. The thermoelectric conversion module according to claim 2 .

5. The two or more specific thermoelectric conversion elements are electrically connected in series in a first direction and are arranged adjacent to each other in a second direction perpendicular to the first direction. The thermoelectric conversion module according to claim 4 .

6. the substrate having the main surface has a polygonal shape having a plurality of vertices; The N-type thermoelectric conversion elements are disposed at positions on the main surface of the substrate closest to each of the plurality of vertices. The thermoelectric conversion module according to claim 2 .

7. In the cross-sectional view, the length of a long side of each of the plurality of N-type thermoelectric conversion elements is at least twice as long as the length of any one side of each of the plurality of P-type thermoelectric conversion elements. The thermoelectric conversion module according to claim 2 .

8. The number of the N-type thermoelectric conversion elements arranged in the peripheral region is greater than the number of the P-type thermoelectric conversion elements arranged in the peripheral region. The thermoelectric conversion module according to claim 4 .

9. The compressive fracture stress τ of the N-type thermoelectric conversion element １ｎ，ｍａｘ is the compressive fracture stress τ of the P-type thermoelectric conversion element １ｐ，ｍａｘ or the shear fracture stress τ of the N-type thermoelectric conversion element is greater than ２ｎ，ｍａｘ is the shear fracture stress τ of the P-type thermoelectric conversion element ２ｐ，ｍａｘ Greater than The thermoelectric conversion module according to claim 2 .

10. 2≦σ ｐ / σ ｎ Satisfying condition (3) represented as ≦4, In the condition (3), The σ ｎ is the electrical conductivity of the N-type thermoelectric conversion element at room temperature, The σ ｐ is the electrical conductivity of the P-type thermoelectric conversion element at room temperature The thermoelectric conversion module according to claim 2 .

11. The σ ｐ is 400 S / cm ≦ σ ｐ Satisfy the condition expressed as ≦4000 S / cm The thermoelectric conversion module according to claim 10 .

12. The σ ｎ is 100 S / cm ≦ σ ｎ Satisfy the condition expressed as ≦1000 S / cm The thermoelectric conversion module according to claim 10 or 11.

13. The P-type thermoelectric conversion element is formed of a chalcogenide compound. The thermoelectric conversion module according to claim 2 .

14. The P-type thermoelectric conversion element is (Bi, Sb) ２ (Se, Te) ３ Compounds based on Ge, Sn, Pb ａ (Sb, Bi) ｂ (Mg, Mn, Ti, In, Cr, Ag, Zn) ｃ It is made of (S, Se, Te) compounds. The thermoelectric conversion module according to claim 13 .

15. The N-type thermoelectric conversion element further contains Mg. The thermoelectric conversion module according to claim 2 .

16. The N-type thermoelectric conversion element is made of Mg ３ (Sb, Bi) ２ It is formed of compounds based on The thermoelectric conversion module according to claim 15 .

17. a first fluid flow path portion through which a first fluid flows; a second fluid flow path portion through which a second fluid flows; and a thermoelectric conversion module according to claim 1, which converts thermal energy due to a temperature difference between the first fluid and the second fluid into electric power. Thermoelectric conversion device.

18. A main surface, a plurality of thermoelectric converters disposed on the main surface; Each of the plurality of thermoelectric converters is an N-type thermoelectric conversion element having a first cross-sectional area in a cross-sectional view taken along a plane substantially parallel to the main surface; A P-type thermoelectric conversion element having a second cross-sectional area smaller than the first cross-sectional area in the cross-sectional view; an electrode electrically connecting one end of the N-type thermoelectric conversion element and one end of the P-type thermoelectric conversion element; σ p satisfies the condition expressed by 400 S / cm≦σ p ≦4000 S / cm, σ n satisfies the condition expressed by 100 S / cm≦σ n ≦1000 S / cm, The σ n is the electrical conductivity of the N-type thermoelectric conversion element at room temperature, The σ p is the electrical conductivity of the P-type thermoelectric conversion element at room temperature. Thermoelectric conversion module.

19. Applying a temperature difference to the thermoelectric conversion module according to claim 1; and extracting electric power associated with a thermoelectromotive force generated in each of the plurality of thermoelectric converters of the thermoelectric conversion module due to the temperature difference. Power generation method.

20. A method for producing a thermoelectric conversion module comprising: transporting heat by said electric current. Heat transfer method.