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

Abstract

A thermoelectric conversion module (18) is provided with a substrate (40) and a plurality of thermoelectric conversion bodies (42) disposed on the substrate (40). The thermoelectric conversion body (42) has: an N-type thermoelectric conversion element (44) having a first cross-sectional area in a cross-sectional view; a P-type thermoelectric conversion element (46) having a second cross-sectional area smaller than the first cross-sectional area in a cross-sectional view; 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). The following formula is satisfied: tau 1 [alpha] gt; condition (1) is represented by [tau] 1 [beta] and [tau] 2 [alpha] gt; and tau 2 [beta] represents at least one of conditions (2).

Description

Technical Field

[0001] The invention relates to a thermoelectric conversion module, a thermoelectric conversion device, a power generation method and a heat conduction method. Background Art

[0002] A thermoelectric conversion module used in thermoelectric power generation using the Seebeck effect or thermoelectric cooling using the Peltier effect is known. The thermoelectric conversion module includes an N-type thermoelectric conversion element, a P-type thermoelectric conversion element, and an electrode electrically connecting one end of the N-type thermoelectric conversion element to one end of the P-type thermoelectric conversion element.

[0003] The energy conversion efficiency between heat and electricity in thermoelectric power generation and thermoelectric cooling (hereinafter referred to as "thermoelectric conversion efficiency") is determined by the performance index of the material used to form the N-type thermoelectric conversion element and the P-type thermoelectric conversion element. That is, the higher the performance index, the higher the thermoelectric conversion efficiency. Patent Document 1 and Non-Patent Document 1 disclose a technology using a Mg3Sb2-based compound representing a high performance index as a material for an N-type thermoelectric conversion element.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6127281

[0007] Patent Document 2: Japanese Patent Application Publication No. 2013-012571

[0008] Non-patent literature

[0009] Non-patent literature 1: H. Tamaki et al., AdvA n ced Materials28,10182,(2016).

[0010] Non-patent document 2: R. Shu et al., Adv. Funct, Mater. 29, 1807235 (2019).

[0011] Non-patent document 3: G. Li et al., J. Mater. Chem. A, 5, 9050 (2017).

[0012] Non-patent document 4: G. Li et al., Phys. Rev. Lett. 119, 085501 (2017). Summary of the invention

[0013] Problems to be solved by the invention

[0014] The present disclosure provides a thermoelectric conversion module, a thermoelectric conversion device, a power generation method, and a heat conduction method capable of improving thermoelectric conversion efficiency and improving strength.

[0015] Means for solving problems

[0016] A thermoelectric conversion module according to one embodiment of the present disclosure comprises: a substrate having a main surface; and a plurality of thermoelectric converters arranged on the main surface of the substrate, each of the plurality of thermoelectric converters comprising: a first thermoelectric conversion element having a first cross-sectional area when a plane substantially parallel to the main surface is cross-sectionally viewed; a second thermoelectric conversion element having a second cross-sectional area smaller than the first cross-sectional area when the cross-sectional view is viewed; and an electrode electrically connecting one end of the first thermoelectric conversion element to one end of the second thermoelectric conversion element, wherein the thermoelectric conversion module satisfies the condition defined by τ 1α >τ 1β The condition (1) and the 2α >τ 2β At least one of the conditions (2) represented by the above, in the above condition (1), the above τ 1α is the compressive stress applied to the first thermoelectric conversion element in order to generate compressive strain ε1 in the thermoelectric conversion module, and τ 1β is the compressive stress applied to the second thermoelectric conversion element in order to generate the compressive strain ε1 in the thermoelectric conversion module. In the condition (2), τ 2α is the shear stress applied to the first thermoelectric conversion element in order to generate a shear strain ε2 in the thermoelectric conversion module, and the τ 2β This is the shear stress applied to the second thermoelectric conversion element in order to generate the shear strain ε2 in the thermoelectric conversion module.

[0017] In addition, these general or specific aspects may be implemented by a device or a method, or by any combination of a device and a method.

[0018] Effects of the Invention

[0019] According to the thermoelectric conversion module of one embodiment of the present disclosure, it is possible to improve thermoelectric conversion efficiency and strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a perspective view showing a thermoelectric conversion device according to an embodiment.

[0021] Figure 2 It is a cross-sectional view of a main part of the thermoelectric converter according to the embodiment.

[0022] Figure 3 It is a perspective view showing a thermoelectric conversion module according to the embodiment.

[0023] Figure 4 This is a plan view showing a thermoelectric conversion module according to the embodiment in a state where one substrate is omitted.

[0024] Figure 5 It is a cross-sectional view of a thermoelectric conversion module according to an embodiment.

[0025] Figure 6 It is a diagram for explaining the compressive stress acting on the thermoelectric conversion module according to the embodiment.

[0026] Figure 7 This is a diagram for explaining the shear stress acting on the thermoelectric conversion module according to the embodiment.

[0027] Figure 8 This is a graph showing the relationship between strain and stress in the thermoelectric conversion module according to the embodiment.

[0028] Fig. 9 This is a plan view showing a thermoelectric conversion module according to Modification 1 of the embodiment in a state where one substrate is omitted.

[0029] Fig.10 This is a plan view showing a thermoelectric conversion module according to Modification 2 of the embodiment in a state where one substrate is omitted.

[0030] Fig.11 It is a plan view showing a thermoelectric conversion module according to Modification 3 of the embodiment in a state where one substrate is omitted.

[0031] Fig.12 It is a plan view showing a thermoelectric conversion module according to Modification 4 of the embodiment in a state where one substrate is omitted. DETAILED DESCRIPTION

[0032] (Insights that form the basis of this disclosure)

[0033] The present inventors have discovered that the following problems occur with respect to the technology described in the “Background Art” column.

[0034] Thermoelectric power generation is a technology that converts thermal energy into electrical energy by utilizing the Seebeck effect, i.e., the thermoelectric potential generated between the two ends of an object in proportion to the temperature difference when a temperature difference occurs between the two ends of the object. In addition, thermoelectric cooling is a technology that utilizes the Peltier effect, i.e., the phenomenon of heat transfer using electrons transported by an electric current. Thermoelectric power generation is used, for example, as a power source for remote areas and space, and thermoelectric cooling is used, for example, as an element for precise temperature control of electronic devices or optical devices.

[0035] The energy conversion efficiency between heat and electricity in thermoelectric power generation and thermoelectric cooling is determined by the performance index ZT of the material used. The higher the performance index ZT, the higher the energy conversion efficiency. In semiconductors injected with conductive carriers, high performance index ZT is achieved.

[0036] As a thermoelectric conversion module, a type having a π-type structure is known. In this type of thermoelectric conversion module, a P-type thermoelectric conversion element and an N-type thermoelectric conversion element having Seebeck coefficients S of different signs are electrically connected in series and arranged in parallel with respect to heat flow. Thus, efficient thermoelectric conversion is achieved. In a thermoelectric conversion module having a practical π-type structure, durability against thermal stress caused by stress or temperature difference due to pressurization is important, that is, it is important to improve the overall strength of the thermoelectric conversion module. Therefore, in addition to sufficient mechanical strength of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, the configuration of the P-type thermoelectric conversion element and the N-type thermoelectric conversion material on the substrate is also important.

[0037] As thermoelectric conversion material systems that show high performance index, chalcogenide compounds represented by Bi2Te3 (Sb2Te3) or GeTe compounds are known. Chalcogenide compounds use Te (tellurium) and Se (selenium), which are rare elements, and are brittle materials, so they need to be handled with care.

[0038] As a thermoelectric conversion material system that shows a high performance index and uses a small amount of rare metal, N-type Mg3Sb2-based compounds disclosed in Patent Document 1 and Non-Patent Document 1 are known.

[0039] However, when a Mg 3 Sb 2 -based compound is used as a material for an N-type thermoelectric conversion element, there arises a problem in that the strength of the thermoelectric conversion module is reduced depending on the material of the P-type thermoelectric conversion element.

[0040] The inventors of the present invention have focused on the fact that a thermoelectric conversion module can be used as a thermoelectric power generation module or a Peltier cooling module having a high performance index by forming a thermoelectric conversion module in pairs with an N-type thermoelectric conversion element formed of a Mg3Sb2-based compound and a P-type thermoelectric conversion element formed of a chalcogenide-based compound. In addition, it has been found that the cross-sectional area of ​​the N-type thermoelectric conversion element is larger than the cross-sectional area of ​​the P-type thermoelectric conversion element. As a result, it is expected that the use of rare metals will be reduced and the durability will be improved as a whole thermoelectric conversion module.

[0041] In addition, a thermoelectric conversion module using an N-type thermoelectric conversion element and a P-type thermoelectric conversion element having different cross-sectional areas is disclosed in Patent Document 2. More specifically, in Patent Document 2, as a structure for suppressing a decrease in the output of the thermoelectric conversion module caused by an increase in connection resistance, a thermoelectric conversion module having a cross-sectional area of ​​an N-type thermoelectric conversion element and a cross-sectional area of ​​a P-type thermoelectric conversion element is disclosed, but there is no disclosure or suggestion regarding the formation of an N-type thermoelectric conversion element and a P-type thermoelectric conversion element from a Mg3Sb2-based compound and a chalcogenide-based compound.

[0042] Furthermore, the inventors have repeatedly conducted in-depth research and have newly discovered that when viewed in cross section, by configuring one side of an N-type thermoelectric conversion element and one side of a P-type thermoelectric conversion element to be approximately the same length and facing each other, the overall strength of the thermoelectric conversion module can be improved. Regarding the configuration method for improving the overall strength of the thermoelectric conversion module, there is no disclosure or suggestion in Patent Document 2.

[0043] Based on this new knowledge, the present inventors completed the thermoelectric conversion module according to the present disclosure.

[0044] The thermoelectric conversion module of the first embodiment of the present disclosure comprises: a substrate having a main surface; and a plurality of thermoelectric converters arranged on the main surface of the substrate, each of the plurality of thermoelectric converters comprising: a first thermoelectric conversion element having a first cross-sectional area when a plane substantially parallel to the main surface is cross-sectionally viewed; a second thermoelectric conversion element having a second cross-sectional area smaller than the first cross-sectional area when the cross-sectional view is viewed; and an electrode electrically connecting one end of the first thermoelectric conversion element to one end of the second thermoelectric conversion element, wherein the thermoelectric conversion module satisfies τ 1α >τ 1β The condition (1) expressed by τ 2α >τ 2β At least one of the conditions (2) represented by the above, in the above condition (1), the above τ 1α is the compressive stress applied to the first thermoelectric conversion element in order to generate compressive strain ε1 in the thermoelectric conversion module, and τ 1β is the compressive stress applied to the second thermoelectric conversion element in order to generate the compressive strain ε1 in the thermoelectric conversion module. In the condition (2), τ 2α is the shear stress applied to the first thermoelectric conversion element in order to generate a shear strain ε2 in the thermoelectric conversion module, and the τ 2β This is the shear stress applied to the second thermoelectric conversion element in order to generate the shear strain ε2 in the thermoelectric conversion module.

[0045] According to this aspect, a thermoelectric conversion module that is strong against compressive stress and / or shear stress can be realized.

[0046] In the thermoelectric conversion module of 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.

[0047] In addition, a third embodiment of a thermoelectric conversion module of the present invention comprises: a substrate having a main surface; and a plurality of thermoelectric converters arranged on the main surface of the substrate, each of the plurality of thermoelectric converters comprising: an N-type thermoelectric conversion element, which is formed into a substantially rectangular shape and has a first cross-sectional area when a plane substantially parallel to the main surface is cross-sectionally viewed; a P-type thermoelectric conversion element, which is formed into a substantially rectangular shape when cross-sectionally viewed and has a second cross-sectional area smaller than the first cross-sectional area; and an electrode, which electrically connects one end of the N-type thermoelectric conversion element to one end of the P-type thermoelectric conversion element, the N-type thermoelectric conversion element containing Mg, and a specific thermoelectric converter among the plurality of thermoelectric converters is arranged in such a manner that a first side of the N-type thermoelectric conversion element and a second side of the P-type thermoelectric conversion element having a length substantially the same as that of the first side are opposite to each other when cross-sectionally viewed.

[0048] According to this method, the N-type thermoelectric conversion element contains Mg, so the performance index and strength of the N-type thermoelectric conversion element can be improved. By making the first cross-sectional area of ​​the N-type thermoelectric conversion element having such a high performance index and strength larger than the second cross-sectional area of ​​the P-type thermoelectric conversion element, the thermoelectric conversion efficiency can be improved, and the strength of the thermoelectric conversion module can be improved.

[0049] In a thermoelectric conversion module according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the first cross-sectional area may be 1.5 to 4 times the second cross-sectional area.

[0050] According to this aspect, the thermoelectric conversion efficiency can be effectively improved, and the strength of the thermoelectric conversion module can be effectively improved.

[0051] In addition, in the fifth embodiment of the thermoelectric conversion module of the present disclosure, it can also be constructed that, in the third embodiment, the specific thermoelectric converter is arranged in at least an edge area of ​​the substrate, and the edge area is an area corresponding to the N-type thermoelectric conversion elements and the P-type thermoelectric conversion elements arranged along the edge of the substrate among the multiple N-type thermoelectric conversion elements and the multiple P-type thermoelectric conversion elements arranged on the main surface of the substrate.

[0052] According to this aspect, when the thermoelectric conversion module is used in a thermoelectric conversion device, pressure, vibration, etc. are likely to act on the edge region of the substrate. By arranging a specific thermoelectric converter in such an edge region of the substrate, the strength of the thermoelectric conversion module can be effectively improved.

[0053] In a sixth aspect of the thermoelectric conversion module of the present disclosure, in the fifth aspect, two or more of the specific thermoelectric converters may be electrically connected in series in a first direction and arranged adjacent to each other in a second direction orthogonal to the first direction.

[0054] 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 a high density.

[0055] In addition, in the seventh aspect of the thermoelectric conversion module of the present disclosure, it can also be configured that, in the second aspect or the fifth aspect, the substrate is a polygon with multiple vertices, and the N-type thermoelectric conversion element is arranged at a position closest to each of the multiple vertices on the main surface of the substrate.

[0056] According to this method, when the thermoelectric conversion module is used in a thermoelectric conversion device, pressure, vibration, etc. are easily applied to the vicinity of each of the multiple vertices of the substrate. By configuring 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.

[0057] In addition, in the eighth aspect of the thermoelectric conversion module of the present disclosure, it can also be configured that, in the second aspect or the fifth aspect, when viewed in cross section, the length of the long side of each of the multiple N-type thermoelectric conversion elements is more than twice the length of any side of each of the multiple P-type thermoelectric conversion elements.

[0058] 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 a high density.

[0059] In the thermoelectric conversion module of the ninth aspect of the present disclosure, in the fifth aspect or the sixth aspect, the number of the N-type thermoelectric conversion elements arranged in the edge region may be greater than the number of the P-type thermoelectric conversion elements arranged in the edge region.

[0060] According to this aspect, the strength of the edge region of the substrate of the thermoelectric conversion module can be effectively improved.

[0061] In addition, in the thermoelectric conversion module according to the tenth aspect of the present disclosure, it is also possible to configure that, in the second aspect, the compressive fracture stress τ of the N-type thermoelectric conversion element is 1n,max Greater than the compressive failure stress τ of the P-type thermoelectric conversion element 1p,max, or, the shear failure stress τ of the N-type thermoelectric conversion element 2n,max Greater than the shear failure stress τ of the P-type thermoelectric conversion element 2p,max .

[0062] According to this aspect, the strength of the N-type thermoelectric conversion element against the compressive stress and / or shear stress can be further improved compared to the P-type thermoelectric conversion element.

[0063] In addition, in the thermoelectric conversion module of the eleventh aspect of the present disclosure, it is also possible to configure such that, in the second aspect, 2≤σ p / σ n ≤4 represents condition (3), in which σ n is the 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.

[0064] According to this method, by appropriately changing the compositions of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, the carrier concentrations and carrier mobilities of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element can be controlled, and the conductivity of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element can be changed. As a result, the imbalance of the electrical characteristics between the N-type thermoelectric conversion element and the P-type thermoelectric conversion element 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 the thermal power generation efficiency can be effectively improved. It should be noted that in the case of Bi2Te3-based compounds, the carrier concentration, carrier mobility and conductivity are changed by adjusting the mutual ratio of Bi, Sb, Te, Se, and the amount of additives such as Cu, Sn, and I. In addition, in the case of Mg3Sb2-based compounds, the carrier concentration, carrier mobility and conductivity change by adjusting the mutual ratios of Mg, Sb, and Bi, and the amounts of additives such as Mn, Zn, Li, Na, K, Sc, Y, La, B, Al, Ge, Sn, Pb, Se, and Te.

[0065] In addition, in the thermoelectric conversion module of the twelfth aspect of the present disclosure, it is also possible to configure that, in the eleventh aspect, the σ p Satisfy 400S / cm≤σ p Conditions indicated by ≤4000S / cm.

[0066] According to this aspect, by appropriately changing the composition of the P-type thermoelectric conversion element, the conductivity of the P-type thermoelectric conversion element can be changed by controlling the carrier concentration of the P-type thermoelectric conversion element to increase.

[0067] In addition, in the thermoelectric conversion module of the thirteenth aspect of the present disclosure, it is also possible to configure that, in the eleventh aspect or the twelfth aspect, the σ n Satisfy 100S / cm≤σ n Conditions indicated by ≤1000S / cm.

[0068] According to this aspect, by appropriately changing the composition of the N-type thermoelectric conversion element, the conductivity of the N-type thermoelectric conversion element can be changed by controlling the carrier concentration of the N-type thermoelectric conversion element to be suppressed.

[0069] Furthermore, in the thermoelectric conversion module according to the fourteenth aspect of the present disclosure, in any one of the second aspect to the thirteenth aspect, the P-type thermoelectric conversion element may be formed of a chalcogenide-based compound.

[0070] According to this aspect, the performance index of the P-type thermoelectric conversion element can be improved, thereby effectively improving the thermoelectric conversion efficiency.

[0071] In addition, in the thermoelectric conversion module of the fifteenth aspect of the present disclosure, it can also be configured that in the fourteenth aspect, the P-type thermoelectric conversion element is composed of a (Bi, Sb)2(Se, Te)3 series compound or a (Ge, Sn, Pb) a (Sb,Bi) b (Mg, Mn, Ti, In, Cr, Ag, Zn) c (S,Se,Te) series compounds are formed.

[0072] According to this aspect, the performance index of the P-type thermoelectric conversion element can be improved, thereby effectively improving the thermoelectric conversion efficiency.

[0073] Furthermore, in the thermoelectric conversion module of the sixteenth aspect of the present disclosure, in any one of the second aspect to the fifteenth aspect, the N-type thermoelectric conversion element may further contain at least one of Sb and Bi.

[0074] According to this aspect, the performance index and strength of the N-type thermoelectric conversion element can be improved. Thus, the thermoelectric conversion efficiency can be improved, and the strength of the thermoelectric conversion module can be improved.

[0075] In addition, in the thermoelectric conversion module of the seventeenth aspect of the present disclosure, in the sixteenth aspect, the N-type thermoelectric conversion element may be formed of a Mg3(Sb,Bi)2-based compound.

[0076] According to this aspect, the performance index and strength of the N-type thermoelectric conversion element can be improved. Thus, the thermoelectric conversion efficiency can be improved, and the strength of the thermoelectric conversion module can be improved.

[0077] In addition, the eighteenth embodiment of the thermoelectric conversion device of the present disclosure comprises: a first fluid flow path portion for flowing a first fluid; a second fluid flow path portion for flowing a second fluid; and a thermoelectric conversion module of any one of the first to seventeenth embodiments, which converts thermal energy generated by the temperature difference between the first fluid and the second fluid into electricity.

[0078] According to this aspect, by using any of the above-mentioned thermoelectric conversion modules, it is possible to improve the thermoelectric conversion efficiency and enhance the strength of the entire thermoelectric conversion device.

[0079] In addition, a nineteenth aspect of the present disclosure includes: providing a temperature difference to the thermoelectric conversion module according to any one of the first to seventeenth 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.

[0080] According to this aspect, by using any of the above-mentioned thermoelectric conversion modules, thermoelectric power generation can be efficiently performed.

[0081] Furthermore, a heat transfer method according to a twentieth aspect of the present disclosure includes: flowing an electric current through the thermoelectric conversion module according to any one of the first aspect to the seventeenth aspect; and transferring heat using the electric current.

[0082] According to this aspect, by using any of the above-mentioned thermoelectric conversion modules, precise temperature control by heating or cooling can be performed.

[0083] In addition, these general or specific aspects may be implemented by a device or a method, or by any combination of a device and a method.

[0084] Hereinafter, embodiments will be described with reference to the drawings.

[0085] In addition, the embodiments described below all represent general or specific examples. The numerical values, shapes, materials, constituent elements, configuration positions of constituent elements, connection methods, steps, order of steps, etc. shown in the following embodiments are examples and do not limit the subject matter of the claims. In addition, among the constituent elements in the following embodiments, constituent elements not recorded in the independent claims representing the highest concept are described as arbitrary constituent elements. In addition, the figures are not necessarily strictly illustrated. In each figure, the same figure mark is marked for substantially the same structure, and repeated descriptions are omitted or simplified.

[0086] (Implementation Method)

[0087] [1. Overview of Thermoelectric Conversion Device]

[0088] First, refer to Figure 1 and Figure 2, an overview of the thermoelectric conversion device 2 according to the embodiment will be described. Figure 1 It is a perspective view showing a thermoelectric conversion device 2 according to the embodiment. Figure 2 It is a cross-sectional view of a main part of the thermoelectric converter 2 according to the embodiment.

[0089] In addition, Figure 1 and Figure 2 In the diagram, the front-rear direction of the thermoelectric converter 2 is defined as the X-axis direction, the left-right direction of the thermoelectric converter 2 is defined as the Y-axis direction, and the up-down direction of the thermoelectric converter 2 is defined as the Z-axis direction.

[0090] The thermoelectric conversion device 2 is, for example, a thermoelectric conversion unit for generating electricity using thermal energy of exhaust gas exhausted from an engine mounted on a vehicle.

[0091] like Figure 1 and Figure 2 As shown, the thermoelectric conversion device 2 includes a pair of low-temperature fluid flow path portions 4, 6 (an example of a first fluid flow path portion), a pair of side restraint portions 8, 10, a high-temperature fluid flow path portion 12 (an example of a second fluid flow path portion), a high-temperature fluid inlet portion 14, a high-temperature fluid discharge portion 16 and a pair of thermoelectric conversion modules 18, 20.

[0092] The pair of low-temperature fluid flow path portions 4 and 6 are arranged to face each other with a gap therebetween in the up-down direction (Z-axis direction).

[0093] The upper low-temperature fluid flow path portion 4 has a flat hollow rectangular parallelepiped housing 22 and a tubular low-temperature fluid inlet portion 24 and a low-temperature fluid outlet portion 26 protruding from the side of the housing 22. The housing 22 is formed of, for example, stainless steel. Figure 2 As shown, a low-temperature fluid flow path 28 for a low-temperature fluid (an example of a first fluid) to flow is formed inside the shell 22. The low-temperature fluid is, for example, cold water or cold air having a lower temperature than the high-temperature fluid (described later). The low-temperature fluid inlet 24 and the low-temperature fluid outlet 26 are arranged at intervals in the front-to-back direction (X-axis direction) and are connected to the low-temperature fluid flow path 28 of the shell 22. The low-temperature fluid flows into the low-temperature fluid flow path 28 of the shell 22 through the low-temperature fluid inlet 24, flows in the low-temperature fluid flow path 28, and is discharged to the outside through the low-temperature fluid outlet 26.

[0094] The lower low-temperature fluid flow path portion 6 has a flat hollow rectangular parallelepiped housing 30, a tubular low-temperature fluid inlet portion 32 and a low-temperature fluid outlet portion 34 protruding from the side of the housing 30. The housing 30 is formed of, for example, stainless steel. Figure 2As shown, a low-temperature fluid flow path 36 for the low-temperature fluid to flow is formed inside the housing 30. The low-temperature fluid inlet 32 ​​and the low-temperature fluid outlet 34 are arranged at intervals in the front-to-back direction and are connected to the low-temperature fluid flow path 36 of the housing 30. The low-temperature fluid flows into the low-temperature fluid flow path 36 of the housing 30 through the low-temperature fluid inlet 32, flows in the low-temperature fluid flow path 36, and is discharged to the outside through the low-temperature fluid outlet 34.

[0095] like Figure 1 As shown, a pair of side restraints 8, 10 are arranged opposite to each other with a gap in the left-right direction (Y-axis direction). That is, the pair of side restraints 8, 10 are arranged in a manner to cover the high-temperature fluid flow path portion 12 (described later) arranged between the pair of low-temperature fluid flow path portions 4, 6 from the side in the left-right direction. The pair of side restraints 8, 10 are each formed in a rectangular flat plate shape.

[0096] like Figure 2 As shown, the high-temperature fluid flow path portion 12 is arranged between a pair of low-temperature fluid flow path portions 4 and 6. Specifically, the high-temperature fluid flow path portion 12 is defined by a space surrounded by a pair of low-temperature fluid flow path portions 4 and 6 and a pair of side restraint portions 8 and 10. The high-temperature fluid flow path portion 12 functions as a high-temperature fluid flow path for a high-temperature fluid (an example of a second fluid) to flow. The high-temperature fluid is a fluid having a higher temperature than the low-temperature fluid, such as exhaust gas discharged from an engine mounted on a vehicle. In addition, although not shown in the figure, a plurality of heat-conducting fins for transferring the heat of the high-temperature fluid to a pair of thermoelectric conversion modules 18 and 20 are arranged in the high-temperature fluid flow path portion 12.

[0097] The high-temperature fluid inlet 14 and the high-temperature fluid discharge 16 are arranged opposite to each other with a gap in the front-to-back direction. That is, the high-temperature fluid inlet 14 and the high-temperature fluid discharge 16 are arranged in a manner to cover the high-temperature fluid flow path portion 12 arranged between a pair of low-temperature fluid flow path portions 4 and 6 from the side in the front-to-back direction. The high-temperature fluid inlet 14 and the high-temperature fluid discharge 16 are formed in a tubular shape and are connected to the high-temperature fluid flow path portion 12. The high-temperature fluid flows into the high-temperature fluid flow path portion 12 through the high-temperature fluid inlet 14, flows in the high-temperature fluid flow path portion 12 along the front-to-back direction (from the negative side to the positive side of the X-axis), and is discharged to the outside through the high-temperature fluid discharge 16.

[0098] like Figure 2 As shown, the pair of thermoelectric conversion modules 18, 20 are respectively arranged between the high temperature fluid flow path portion 12 and the pair of low temperature fluid flow paths 4, 6. That is, the pair of thermoelectric conversion modules 18, 20 are arranged to face each other at a distance in the vertical direction.

[0099] The upper thermoelectric conversion module 18 is formed as a rectangular flat plate as a whole, and is configured to be clamped from top to bottom by the high-temperature fluid flow path section 12 and the upper low-temperature fluid flow path section 4. That is, the upper thermoelectric conversion module 18 is in contact with the lower surface (the surface on the high-temperature fluid flow path section 12 side) of the shell 22 of the upper low-temperature fluid flow path section 4, and is in contact with the heat transfer fins and the like of the high-temperature fluid flow path section 12. Thus, the upper thermoelectric conversion module 18 performs thermoelectric power generation by converting the thermal energy caused by the temperature difference between the high-temperature fluid flowing in the high-temperature fluid flow path section 12 and the low-temperature fluid flowing in the upper low-temperature fluid flow path section 4 into electricity through the Seebeck effect.

[0100] The lower thermoelectric conversion module 20 is formed as a rectangular flat plate as a whole, and is configured to be clamped from top to bottom by the high-temperature fluid flow path section 12 and the lower low-temperature fluid flow path section 6. That is, the lower thermoelectric conversion module 20 is in contact with the upper surface (the surface on the high-temperature fluid flow path section 12 side) of the shell 30 of the lower low-temperature fluid flow path section 6, and is in contact with the heat transfer fins and the like of the high-temperature fluid flow path section 12. Thus, the lower thermoelectric conversion module 20 performs thermoelectric power generation by converting the thermal energy caused by the temperature difference between the high-temperature fluid flowing in the high-temperature fluid flow path section 12 and the low-temperature fluid flowing in the lower low-temperature fluid flow path section 6 into electricity through the Seebeck effect.

[0101] [2. Structure of the thermoelectric conversion module]

[0102] Reference Figure 2 to Figure 5 The structure of the thermoelectric conversion module 18 will be described. In addition, since the pair of thermoelectric conversion modules 18 and 20 have the same structure, only the structure of the thermoelectric conversion module 18 will be described below.

[0103] Figure 3 It is a perspective view showing a thermoelectric conversion module 18 according to the embodiment. Figure 4 1 is a plan view showing a thermoelectric conversion module 18 according to the embodiment in a state where one substrate 38 is omitted. Figure 5 2 is a cross-sectional view of a thermoelectric conversion module 18 according to the embodiment.

[0104] In addition, Figure 3 to Figure 5 In the diagram, the lateral direction of the thermoelectric conversion module 18 is defined as the X-axis direction, the longitudinal direction of the thermoelectric conversion module 18 is defined as the Y-axis direction, and the thickness direction of the thermoelectric conversion module 18 is defined as the Z-axis direction.

[0105] like Figure 3 As shown, the thermoelectric conversion module 18 includes a pair of substrates 38, 40 and a plurality of thermoelectric converters 42. In addition, the thermoelectric conversion module 18 has a π-type structure. By applying a temperature difference to the thermoelectric conversion module 18, the power accompanying the thermoelectromotive force generated in each of the plurality of thermoelectric converters 42 of the thermoelectric conversion module 18 can be extracted by utilizing the temperature difference.

[0106] The pair of substrates 38 and 40 are each formed into a rectangular (an example of a polygonal shape having a plurality of vertices) flat plate shape, and are formed of, for example, a ceramic substrate. The pair of substrates 38 and 40 are arranged so as to face each other in the thickness direction (Z-axis direction) of the thermoelectric conversion module 18. Figure 2 As shown, one substrate 38 is in contact with the lower surface of the shell 22 of the upper low-temperature fluid flow path portion 4, and the other substrate 40 is in contact with the high-temperature fluid flow path portion 12. At this time, in order to reduce the contact thermal resistance between one substrate 38 and the shell 22 of the upper low-temperature fluid flow path portion 4, one substrate 38 is pressed against the shell 22 of the upper low-temperature fluid flow path portion 4 while applying pressure. In addition, in order to reduce the thermal contact resistance between the other substrate 40 and the high-temperature fluid flow path portion 12, the other substrate 40 is pressed against the high-temperature fluid flow path portion 12 while applying pressure. In addition, for the sake of convenience of explanation, in Figure 3 In the figure, a part of the substrate 38 is cut away.

[0107] The plurality of thermoelectric converters 42 are arranged between the pair of substrates 38 and 40. Specifically, the plurality of thermoelectric converters 42 are arranged on the main surfaces 38a and 40a of the pair of substrates 38 and 40 that are opposite to each other. The plurality of thermoelectric converters 42 each include 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. In addition, the N-type thermoelectric converter element 44 and the P-type thermoelectric converter element 46 have Seebeck coefficients of different signs.

[0108] The N-type thermoelectric conversion element 44 is a thermoelectric conversion element whose carriers are electrons, and contains at least one of Mg (magnesium), Sb (antimony), and Bi (bismuth). Specifically, the N-type thermoelectric conversion element 44 is formed by a Mg3 (Sb, Bi) 2 series compound representing a high performance index. In the present embodiment, the N-type thermoelectric conversion element 44 is formed, for example, by a Mg3Sb2 series compound. It should be noted that in this specification, the expression (A, B, ···) in the chemical formula of the compound refers to at least one of "A", "B", ... For example, a Mg3 (Sb, Bi) 2 series compound refers to a Mg3Sb2 series compound or a Mg3Bi2 series compound, etc.

[0109] The P-type thermoelectric conversion element 46 is a thermoelectric conversion element whose carriers are holes, and is formed of a chalcogenide compound. Specifically, the P-type thermoelectric conversion element 46 is formed of a (Bi, Sb)2(Se, Te)3 compound or a (Ge, Sn, Pb) a (Sb,Bi) b (Mg, Mn, Ti, In, Cr, Ag, Zn) cIn the present embodiment, the P-type thermoelectric conversion element 46 is formed of, for example, a Bi2Te3 compound or a GeTe compound.

[0110] Electrode 48 is formed in a rectangular flat plate shape, and electrically connects one end of N-type thermoelectric conversion element 44 and one end of P-type thermoelectric conversion element 46 .

[0111] like Figure 4 As shown, the two thermoelectric converters 42 are electrically connected in series in the Y-axis direction (an example of the first direction), and are arranged adjacent to each other in the X-axis direction (an example of the second direction orthogonal to the first direction). That is, the two thermoelectric converters are arranged in multiple rows (4 rows in this embodiment) in the X-axis direction. In addition, in this embodiment, the two thermoelectric converters 42 are electrically connected in series in the Y-axis direction, but this is not limited to this, and three or more thermoelectric converters 42 may also be electrically connected in series in the Y-axis direction.

[0112] For example, in Figure 4 In each of the two thermoelectric converters 42 located in the leftmost column, one end of the N-type thermoelectric conversion element 44 and one end of the P-type thermoelectric conversion element 46 are electrically connected via an electrode 48 disposed on one substrate 38 side. Figure 4 A substrate 38 is omitted in the figure. Figure 4 In the two thermoelectric converters 42 located in the leftmost column, Figure 4 The other end of the P-type thermoelectric conversion element 46 of the thermoelectric conversion body 42 at the lower middle side is Figure 4 The other end of the N-type thermoelectric conversion element 44 of the thermoelectric conversion body 42 on the middle upper side is electrically connected via an electrode 48 disposed on the other substrate 40 side.

[0113] In addition, Figure 4 The other end of the P-type thermoelectric conversion element 46 of the thermoelectric converter 42 located on the upper side of the leftmost column and the other end of the N-type thermoelectric conversion element 44 of the thermoelectric converter 42 located on the upper side of the second column from the leftmost are electrically connected via an electrode 48 disposed on the other side of the substrate 40. The electrode 48 is formed, for example, in the shape of a hexagonal flat plate. By forming the electrode 48 that electrically connects the two thermoelectric converters 42 into a hexagonal shape in this way, abnormal heating caused by current concentration can be suppressed compared to the case where the electrode 48 is formed into a rectangular shape. Similarly, as follows, Figure 4 As shown by the single-dot chain line in , N-type thermoelectric conversion element 44, P-type thermoelectric conversion element 46, N-type thermoelectric conversion element 44, P-type thermoelectric conversion element 46, ..., N-type thermoelectric conversion element 44, P-type thermoelectric conversion element 46 are arranged in a serpentine shape in sequence and are electrically connected in series.

[0114] In addition, the other ends of the N-type thermoelectric conversion elements 44 and the P-type thermoelectric conversion elements 46 respectively arranged at both ends among the plurality of N-type thermoelectric conversion elements 44 and the plurality of P-type thermoelectric conversion elements 46 connected in series are electrically connected to the lead-out electrodes 50 and 52, respectively. Figure 3 As shown in FIG. 1 , wirings 54 and 56 are electrically connected to the lead electrodes 50 and 52, respectively. Figure 4 as well as Figure 5 In the figure, the wirings 54 and 56 are omitted.

[0115] In the case of performing a surface roughness test on a plane substantially parallel to the main surface 40a of the substrate 40 (or the main surface 38a of the substrate 38), Figure 5 In the cross-sectional view shown in FIG. 1 , 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 cross-sectional area A n The second smallest cross-sectional area A p In addition, the first cross-sectional area A is preferably n Relative to the second cross-sectional area A p 1.5 times or more and 4 times or less of the cross-sectional area.

[0116] Moreover, in Figure 5 In the cross-section shown, the thermoelectric converter 42 is arranged in a manner that one side 44a (an example of the first side) of the N-type thermoelectric converter element 44 and one side 46a (an example of the second side) of the P-type thermoelectric converter element 46 are opposite to each other. Here, one side 44a of the N-type thermoelectric converter element 44 and one side 46a of the P-type thermoelectric converter element 46 have substantially the same length L. In addition, in this specification, the thermoelectric converter 42 in which one side 44a of the N-type thermoelectric converter element 44 and one side 46a of the P-type thermoelectric converter element 46 have substantially the same length and are arranged opposite to each other is referred to as a "specific thermoelectric converter".

[0117] The thermoelectric converter 42 is arranged at least in the edge region of the substrate 40 (or the substrate 38). Here, the edge region is a region corresponding to the N-type thermoelectric conversion elements 44 and the P-type thermoelectric conversion elements 46 arranged along the edge of the substrate 40 (or the substrate 38) among the plurality of N-type thermoelectric conversion elements 44 and the plurality of P-type thermoelectric conversion elements 46 arranged on the main surface 40a of the substrate 40 (or the main surface 38a of the substrate 38).

[0118] Below, refer to Figure 6 to Figure 8 The strength of the thermoelectric conversion module 18 will be described. Figure 6 It is a diagram for explaining the compressive stress acting on the thermoelectric conversion module 18 according to the embodiment. Figure 7 This is a diagram for explaining the shear stress acting on the thermoelectric conversion module 18 according to the embodiment. Figure 8 Graph showing the relationship between strain and stress in the thermoelectric conversion module 18 according to the embodiment.

[0119] As described above, in the thermoelectric conversion module 18 of the embodiment, the first cross-sectional area A of the N-type thermoelectric conversion element 44 is n is larger than the second cross-sectional area A of the P-type thermoelectric conversion element 46 p .like Figure 6 As shown, in order to generate compressive strain ε1 in such a thermoelectric conversion module 18, the compressive stress τ applied to the thermoelectric conversion module 18 is 1module It is represented as the following formula 1.

[0120] τ 1module ={A p ×f 1p (ε1)+A n ×f 1n (ε1)} / (A p +A n )(Formula 1)

[0121] In the above formula 1, f 1p 、f 1n are functions representing the relationship between compressive stress and compressive strain for P-type thermoelectric conversion element 46 and N-type thermoelectric conversion element 44. Here, for P-type thermoelectric conversion element 46 and N-type thermoelectric conversion element 44, the following equations 2 and 3 are respectively established.

[0122] τ 1p =f 1p (ε 1p )(Formula 2)

[0123] τ 1n =f 1n (ε 1n )(Formula 3)

[0124] In the above formula 2, τ 1p (τ 1α is to cause the thermoelectric conversion module 18 to generate a compressive strain ε 1p The compressive stress applied to the P-type thermoelectric conversion element 46. In the above formula 3, τ 1n (τ 1β is to cause the thermoelectric conversion module 18 to generate a compressive strain ε 1n On the other hand, compressive stress is applied to the N-type thermoelectric conversion element 44 .

[0125] like Figure 6 As shown, when compressive stress τ is applied to the thermoelectric conversion module 18 1moduleWhen the deformation from the substrates 38 and 40 to the electrode 48 and the joints between the electrode 48 and the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44 is small enough to be ignored, ε1=ε 1p =ε 1n As a result, the same compressive strain ε1 is generated in the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44, so 1p =ε 1n Under the condition of τ 1p <τ 1n In the case of n and the second cross-sectional area A p The larger the ratio, the greater the compressive stress τ required to generate the compressive strain ε1 of the thermoelectric conversion module 18. 1module The larger the value, the higher the strength of the thermoelectric conversion module 18 as a whole.

[0126] In addition, if Figure 7 As shown, in order to generate shear strain ε2 in such a thermoelectric conversion module 18, the shear stress τ applied to the thermoelectric conversion module 18 is 2module It is represented as the following formula 4.

[0127] τ 2module ={A p ×f 2p (ε2)+A n ×f 2n (ε2)} / (A p +A n )(Formula 4)

[0128] In the above formula 4, f 2p 、f 2n are functions representing the relationship between shear stress and shear strain for P-type thermoelectric conversion element 46 and N-type thermoelectric conversion element 44. Here, for P-type thermoelectric conversion element 46 and N-type thermoelectric conversion element 44, the following equations 5 and 6 hold respectively.

[0129] τ 2p =f 2p (ε 2p )(Formula 5)

[0130] τ 2n =f 2n (ε 2n )(Formula 6)

[0131] In the above formula 5, τ 2p (τ 2α is to cause the thermoelectric conversion module 18 to generate a shear strain ε 2p The shear stress applied to the P-type thermoelectric conversion element 46. In the above formula 6, τ2n (τ 2β is to cause the thermoelectric conversion module 18 to generate a shear strain ε 2n The shear stress is applied to the N-type thermoelectric conversion element 44 .

[0132] like Figure 7 As shown, when a shear stress τ is applied to the thermoelectric conversion module 18 2module When the deformation from the substrates 38, 40 to the joint is small enough to be ignored, ε2 = ε 2p =ε 2n As a result, the same shear strain ε2 is generated in the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44, so 2p =ε 2n Under the condition of τ 2p <τ 2n In the case of n and the second cross-sectional area A p The larger the ratio is, the greater the shear stress τ required to generate the shear strain ε2 of the thermoelectric conversion module 18. 2module The larger the value, the higher the strength of the thermoelectric conversion module 18 as a whole.

[0133] In the thermoelectric conversion module 18 of the embodiment, when the N-type thermoelectric conversion element 44 is superior to the P-type thermoelectric conversion element 46 in both the fracture strength and the slope of the stress-strain curve (elastic modulus), by using the first cross-sectional area A of the N-type thermoelectric conversion element 44 n is larger than the second cross-sectional area A of the P-type thermoelectric conversion element 46 p The structure has excellent characteristics in terms of fracture strength. It is sufficient as long as it is excellent in either the compression direction or the shear direction as the direction in which stress / strain is applied. If the N-type thermoelectric conversion element 44 is superior to the P-type thermoelectric conversion element 46 in the compression direction, a thermoelectric conversion module 18 that is strong against compression stress is realized. On the other hand, if the N-type thermoelectric conversion element 44 is superior to the P-type thermoelectric conversion element 46 in the shear direction, a thermoelectric conversion module 18 that is strong against shear stress is realized. That is, the condition determined by τ is satisfied. 1n >τ 1p The conditions expressed by τ 2n >τ 2p At least one of the conditions shown will suffice.

[0134] Figure 8 The stress-strain curves of the thermoelectric conversion module 18, the N-type thermoelectric conversion element 44, and the P-type thermoelectric conversion element 46 of the embodiment, that is, typical behaviors of the relationship between stress τ and strain ε are schematically shown. Figure 8, the stress applied when strain is applied to the thermoelectric conversion module 18, the N-type thermoelectric conversion element 44, and the P-type thermoelectric conversion element 46 is shown. At the stress value or strain value represented by the black circle, the thermoelectric conversion module 18, the N-type thermoelectric conversion element 44, and the P-type thermoelectric conversion element 46 are destroyed (broken).

[0135] like Figure 8 As shown in the solid line graph in the lower middle part, the stress-strain curve of the P-type thermoelectric conversion element 46 (chalcogenide-based element) formed of chalcogenide compounds represented by the Bi2Te3 system and GeTe system is linear, and the P-type thermoelectric conversion element 46 is destroyed at a low stress value or strain value. Figure 8 As shown in the solid line graph in the middle upper side, the stress-strain curve of the N-type thermoelectric conversion element 44 (Mg3Sb2-based element) formed of the Mg3Sb2-based compound is slightly curved, and it is broken at a high stress value or strain value, so it has excellent toughness and ductility among thermoelectric conversion elements. That is, the compressive failure stress τ, which is the compressive stress at which the N-type thermoelectric conversion element 44 is broken, is 1n,max The compressive failure stress τ is greater than the compressive stress at which the P-type thermoelectric conversion element 46 is destroyed. 1p,max In addition, the shear failure stress τ, which is the shear stress at which the N-type thermoelectric conversion element 44 is destroyed, is 2n,max The shear failure stress τ is greater than the shear failure stress at which the P-type thermoelectric conversion element 46 is destroyed. 2p,max Here, it is satisfied by τ 1n,max >τ 1p,max The conditions and τ 2n,max >τ 2p,max At least one of the conditions indicated can be satisfied. In addition, in Non-Patent Document 2, as a property correlated with fracture strength, it is disclosed that the fracture toughness value of Mg3Sb2-based elements shows an excellent value of about 3 times the fracture toughness value of Bi2Te3-based elements.

[0136] in addition, Figure 8 The two dashed curves in the figure are based on two cross-sectional area ratio conditions (A p : A n =1:2, A p : A n =2:1) ​​to illustrate the stress-strain curve of the thermoelectric conversion module 18 predicted based on the above formula (1). Regarding the slope df / dε of the stress-strain curve, which is called the shear elastic modulus and the transverse elastic modulus, when the N-type thermoelectric conversion element 44 is superior to the P-type thermoelectric conversion element 46, by increasing the first cross-sectional area A of the N-type thermoelectric conversion element 44, the stress-strain curve of the thermoelectric conversion module 18 is calculated. nThe ratio of , the maximum stress required to produce strain until fracture increases, that is, the strength of the thermoelectric conversion module 18 is improved.

[0137] Non-patent documents 3 and 4 disclose simulation results based on the first principle calculation method of the stress-strain curve of Mg3Sb2 and Bi2Te3. These documents disclose that the transverse elastic modulus of Mg3Sb2 is 12 GPa and the transverse elastic modulus of Bi2Te3 is about 4 to 6 GPa. That is, by increasing the first cross-sectional area A n In particular, by selecting two or more cross-sectional area ratios A n / A p The value of the longitudinal elastic coefficient of the thermoelectric conversion module 18 is about 9 to 10 GPa, which is comparable to that of the single body of Mg3Sb2. n The strength improvement effect brought about by the ratio of can be obtained when not only Bi2Te3-based compounds but also general chalcogenide compounds such as GeTe-based compounds are used as the material of the P-type thermoelectric conversion element 46.

[0138] In addition, the chalcogenide material uses Se (selenium) and Te (tellurium) which are rare elements as main components, so the cross-sectional area ratio A n / A p The increase in the value of leads to the suppression of the use of rare elements. Therefore, the thermoelectric conversion module 18 of the embodiment is also advantageous in terms of improving environmental compatibility.

[0139] Next, the thermoelectric conversion characteristics of the thermoelectric conversion module 18 are described. When the thermoelectric conversion module 18, which combines the N-type thermoelectric conversion element 44 and the P-type thermoelectric conversion element 46 having different cross-sectional areas, is used for thermoelectric power generation or thermoelectric cooling, the optimal driving current conditions are usually different between the N-type thermoelectric conversion element 44 and the P-type thermoelectric conversion element 46, so the thermoelectric conversion performance of the thermoelectric conversion module 18 is reduced. In order to avoid this problem, it is effective to increase the carrier concentration of the P-type thermoelectric conversion element 46 and suppress the carrier concentration of the N-type thermoelectric conversion element 44.

[0140] The Seebeck coefficients of the P-type thermoelectric conversion element 46 and the N-type thermoelectric conversion element 44 within the operating temperature range of the thermoelectric conversion module 18 are respectively represented by S p , S n , let each conductivity be σ p , σ n , let each thermal conductivity be κ p , κ nWhen the thermal power generation efficiency or the cooling performance coefficient (Coefficient of performance; COP) is maximized, the cross-sectional area ratio A n / A p It is represented by the following formula 7.

[0141] [Number 1]

[0142]

[0143] In addition, the cross-sectional area ratio A that maximizes the power generation density or heat absorption density per unit area is n / A p It is expressed as the following formula 8.

[0144] A n / A p =σ p |S p | / σ n |S n |(Formula 8)

[0145] The above formulas 7 and 8 are for σ n / σ p The reduction function of p , σ n The ratio of the carrier concentration of the N-type thermoelectric conversion element 44 to the carrier concentration of the P-type thermoelectric conversion element 46 is proportional to the carrier concentration of the N-type thermoelectric conversion element 44. n / N p By reducing it, the thermoelectric conversion characteristics of the thermoelectric conversion module 18 can be maximized.

[0146] As an example, Bi is used as the P-type thermoelectric conversion element 46. 0.5 Sb 1.5 Te3(S p =180μV / K,σ p =1000S / cm,κ p = 1.5 W / mK), Mg is used as the N-type thermoelectric conversion element 44 3.2 Sb 0.998 Te 0.002 (S n =-220μV / K,σ n =400S / cm, κ n =0.9W / mK). At this time, the cross-sectional area ratio A that maximizes the power generation efficiency and the cooling performance coefficient is n / A p The cross-sectional area ratio A that maximizes the power generation density and heat absorption density is 2.04. n / A pis 2.05. By manufacturing the thermoelectric conversion module 18 having such a cross-sectional area ratio, it is possible to simultaneously achieve maximization of characteristics and improvement of strength. In addition, by reducing the amount of Te in the N-type thermoelectric conversion element 44, σ n , or in Bi 0.5 Sb 1.5 Doping Cu (copper) and Sn (tin) in Te3 can further increase the cross-sectional area ratio A n / A p .

[0147] In addition, when the conductivity of the N-type thermoelectric conversion element 44 at room temperature is σ n , the conductivity of the P-type thermoelectric conversion element 46 at room temperature is σ p When 2≤σ p / σ n ≤4 represents the condition. In addition, σ p Preferably, 400S / cm≤σ p ≤4000S / cm indicates the condition, σ n Preferably, 100S / cm≤σ n Conditions indicated by ≤1000S / cm.

[0148] [3. Effect]

[0149] As described above, in this embodiment, Figure 5 In the cross-sectional view shown, for example, the first cross-sectional area A of the N-type thermoelectric conversion element 44 formed of a Mg3Sb2-based compound is n For example, the second cross-sectional area A of the P-type thermoelectric conversion element 46 formed of a chalcogenide-based compound is p In addition, one side 44a of the N-type thermoelectric conversion element 44 and one side 46a of the P-type thermoelectric conversion element 46 have substantially the same length L, and are arranged to face each other.

[0150] This can improve the thermoelectric conversion efficiency and the strength of the thermoelectric conversion module 18. As a result, even when an impact, vibration, etc. are applied to the thermoelectric conversion module 18, it is possible to suppress the thermoelectric conversion module 18 from being damaged.

[0151] [4. Modification of Thermoelectric Conversion Module]

[0152] [4-1. Modification 1]

[0153] Reference Fig. 9 , the structure of the thermoelectric conversion module 18A according to the first modification of the embodiment will be described. Fig. 9FIG. 1 is a top view of a thermoelectric conversion module 18A of a first modification of the embodiment in which one substrate 38 is omitted. In this modification, the same reference numerals are used for the same structures as those in the above-mentioned embodiment, and their description is omitted. Fig. 9 The electrode 48 is omitted in the figure.

[0154] like Fig. 9 As shown, in the thermoelectric conversion module 18A of the modified example 1, the shapes of the N-type thermoelectric conversion element 44A and the P-type thermoelectric conversion element 46A of the thermoelectric converter 42A are different from the shapes of the N-type thermoelectric conversion element 44 and the P-type thermoelectric conversion element 46 of the thermoelectric converter 42 described above. Specifically, when a plane substantially parallel to the main surface 40a of the substrate 40 is cross-sectionally viewed, the N-type thermoelectric conversion element 44A is formed into a square shape (an example of a substantially rectangular shape), and the P-type thermoelectric conversion element 46A is formed into a rectangular shape (an example of a substantially rectangular shape).

[0155] In this modification, the same effects as those of the above-described embodiment can be obtained.

[0156] [4-2. Modification 2]

[0157] Reference Fig.10 , the structure of a thermoelectric conversion module 18B according to a second variation of the embodiment will be described. Fig.10 FIG. 1 is a top view of a thermoelectric conversion module 18B of a second modification of the embodiment in which one substrate 38 is omitted. In this modification, the same reference numerals are used for the same structures as those in the above-mentioned embodiment, and their description is omitted. Fig.10 The electrode 48 is omitted in the figure.

[0158] like Fig.10 As shown in FIG. 1 , in the thermoelectric conversion module 18B of the second modification, the arrangement of the plurality of thermoelectric converters 42 is different from that of the above-mentioned embodiment. Fig.10 As shown by the single-dot chain line in , the N-type thermoelectric conversion element 44, the P-type thermoelectric conversion element 46, the N-type thermoelectric conversion element 44, the P-type thermoelectric conversion element 46, ..., the P-type thermoelectric conversion element 46, and the N-type thermoelectric conversion element 44 are sequentially arranged in a zigzag shape and electrically connected in series. Thus, a plurality of N-type thermoelectric conversion elements 44 and a plurality of P-type thermoelectric conversion elements 46 can be arranged at a high density.

[0159] In addition, when a plane substantially parallel to the main surface 40a of the substrate 40 is cut, the length L1 of the long side of each of the plurality of N-type thermoelectric conversion elements 44 is more than twice the length L2 of each side 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 element 44. Thus, the plurality of N-type thermoelectric conversion elements 44 and the plurality of P-type thermoelectric conversion elements 46 can be arranged at a high density.

[0160] The number of N-type thermoelectric conversion elements 44 arranged in the edge region of substrate 40 is greater than the number of P-type thermoelectric conversion elements 46 arranged in the edge region of substrate 40. This can effectively improve the strength of the edge region of substrate 40 of thermoelectric conversion module 18B.

[0161] [4-3. Modification 3]

[0162] Reference Fig.11 , the structure of a thermoelectric conversion module 18C according to a third variation of the embodiment will be described. Fig.11 FIG. 1 is a top view of a thermoelectric conversion module 18C of a third modification of the embodiment in which one substrate 38 is omitted. In this modification, the same reference numerals are used for the same components as those in the above embodiment and the above modification 1, and their description is omitted. Fig.11 The electrode 48 is omitted in the figure.

[0163] like Fig.11 As shown, in the thermoelectric conversion module 18C of the modification example 3, the configuration of the N-type thermoelectric conversion element 44A is different from that of the above-mentioned embodiment. Specifically, as in the above-mentioned modification example 2, Fig.11 As shown by the single-dot chain line in , N-type thermoelectric conversion element 44A, P-type thermoelectric conversion element 46A, N-type thermoelectric conversion element 44A, P-type thermoelectric conversion element 46A, ..., P-type thermoelectric conversion element 46A, N-type thermoelectric conversion element 44A are arranged in a zigzag pattern in sequence and are electrically connected in series.

[0164] N-type thermoelectric conversion element 44A is arranged at a position closest to each of four vertices 40b on main surface 40a of substrate 40. That is, four N-type thermoelectric conversion elements 44A are arranged at four corners of main surface 40a of substrate 40 (or in the vicinity thereof).

[0165] In the thermoelectric conversion module 18C, stress is practically concentrated on the four corners of the substrate 40, so by preferentially arranging the N-type thermoelectric conversion element 44A at the position where strain is likely to occur, the strength of the four corners of the substrate 40 of the thermoelectric conversion module 18C can be improved. In this case, the elastic modulus of the N-type thermoelectric conversion element 44A may be lower than the elastic modulus of the P-type thermoelectric conversion element 46A, and as long as only the fracture strength is excellent, the strength of the thermoelectric conversion module 18C can be improved.

[0166] [4-4. Modification 4]

[0167] Reference Fig.12 , the structure of a thermoelectric conversion module 18D according to a fourth modification of the embodiment will be described. Fig.12 FIG. 1 is a top view of a thermoelectric conversion module 18D of a fourth modification of the embodiment in which one substrate 38 is omitted. In this modification, the same reference numerals are used for the same components as those in the above-mentioned embodiment, and their description is omitted. Fig.12 The electrode 48 is omitted in the figure.

[0168] like Fig.12 As shown, in the thermoelectric conversion module 18D of the modification example 4, similarly to the modification example 3, Fig.12 As shown by the single-dot chain line in , the N-type thermoelectric conversion element 44, the P-type thermoelectric conversion element 46, the N-type thermoelectric conversion element 44, the P-type thermoelectric conversion element 46, ..., the P-type thermoelectric conversion element 46, the N-type thermoelectric conversion element 44 are arranged in a zigzag pattern in sequence and are electrically connected in series.

[0169] In addition, the N-type thermoelectric conversion element 44 is arranged at the position 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 respectively arranged at the four corners (or their vicinity) of the main surface 40a of the substrate 40. Therefore, in this modification, the same effect as the above-mentioned modification 3 can be obtained.

[0170] (Other embodiments)

[0171] The above is a description of one or more thermoelectric conversion modules of the present disclosure based on the embodiments and various variations, but the present disclosure is not limited to these embodiments and various variations. As long as it does not deviate from the main purpose of the present disclosure, the various variations that a person skilled in the art can think of in the present disclosure may also be included in the scope of one or more embodiments of the present disclosure.

[0172] In the above-mentioned embodiment and each modification, the high temperature fluid is exhaust gas and the low temperature fluid is cold water or cold air, but the present invention is not limited thereto. The high temperature fluid and the low temperature fluid may be any liquid or gas (gas).

[0173] In addition, in the above-mentioned embodiment and each modification, the thermoelectric conversion module 18 (18A, 18B, 18C, 18D, 20) is used for thermoelectric power generation using the Seebeck effect, but it is not limited to this, and it can also be used for thermoelectric cooling (or thermoelectric heating) using the Peltier effect. In this case, by passing current through the thermoelectric conversion module 18 (18A, 18B, 18C, 18D, 20), heat can be transported using the current. As a result, precise temperature control based on heating or cooling can be performed.

[0174] [Industrial Availability]

[0175] The thermoelectric conversion module of the present disclosure can be used, for example, for a generator that generates electricity using heat energy of exhaust gas discharged from automobiles, factories, etc., or for temperature control of precision equipment such as electronic devices and optical devices.

[0176] Explanation of symbols

[0177] 2Thermoelectric conversion device

[0178] 4.6 Low-temperature fluid flow path section

[0179] 8, 10 side restraints

[0180] 12High-temperature fluid flow path section

[0181] 14High temperature fluid inlet

[0182] 16 High temperature fluid discharge part

[0183] 18, 18A, 18B, 18C, 18D, 20 Thermoelectric conversion module

[0184] 22, 30 shell

[0185] 24, 32 low temperature fluid inlet

[0186] 26, 34 low temperature fluid discharge part

[0187] 28, 36 low temperature fluid flow path

[0188] 38, 40 substrate

[0189] 38a, 40a main surface

[0190] 40b Vertex

[0191] 42, 42A thermoelectric converter

[0192] 44, 44AN thermoelectric conversion element

[0193] 44a, 46a side

[0194] 46, 46AP thermoelectric conversion element

[0195] 48 electrodes

[0196] 50, 52 lead-out electrodes

[0197] 54, 56 wiring

Claims

1. A thermoelectric conversion module, comprising: a substrate having a main surface; and A plurality of thermoelectric converters are arranged on the main surface of the substrate. Each of the plurality of thermoelectric converters has: The first thermoelectric conversion element has a first cross-sectional area when viewed in section 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, The thermoelectric conversion module satisfies τ 1α >τ 1β The condition (1) expressed by τ 2α >τ 2β At least one of the conditions (2) indicated, In the condition (1), the τ 1α is a compressive stress applied to the first thermoelectric conversion element in order to generate a compressive strain ε1 in the thermoelectric conversion module, The τ 1β is a compressive stress applied to the second thermoelectric conversion element in order to generate the compressive strain ε1 in the thermoelectric conversion module, In the condition (2), the τ 2α is a shear stress applied to the first thermoelectric conversion element in order to generate a shear strain ε2 in the thermoelectric conversion module, The τ 2β This is the shear stress applied to the second thermoelectric conversion element in order to generate the shear strain ε2 in the thermoelectric conversion module.

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

3. A thermoelectric conversion module, comprising: a substrate having a main surface; and A plurality of thermoelectric converters are arranged on the main surface of the substrate. Each of the plurality of thermoelectric converters has: The N-type thermoelectric conversion element is formed into a substantially rectangular shape when viewed in section along a plane substantially parallel to the main surface, and has a first cross-sectional area; 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, The N-type thermoelectric conversion element contains Mg, A specific thermoelectric converter among the plurality of thermoelectric converters is arranged such that a first side of the N-type thermoelectric converter element and a second side of the P-type thermoelectric converter element having substantially the same length as the first side face each other in the cross-sectional view.

4. The thermoelectric conversion module according to any one of claims 1 to 3, The first cross-sectional area is 1.5 times or more and 4 times or less of the second cross-sectional area.

5. The thermoelectric conversion module according to claim 3, The specific thermoelectric converter is arranged at least in an edge region of the substrate. The edge region is a region corresponding to the N-type thermoelectric conversion elements and the P-type thermoelectric conversion elements arranged along the edge of the substrate among the plurality of the N-type thermoelectric conversion elements and the plurality of the P-type thermoelectric conversion elements arranged on the main surface of the substrate.

6. The thermoelectric conversion module according to claim 5, The two or more specific thermoelectric converters are arranged so as to be electrically connected in series in a first direction and to be adjacent to each other in a second direction orthogonal to the first direction.

7. The thermoelectric conversion module according to claim 2 or 5, The substrate is in a polygonal shape with multiple vertices. The N-type thermoelectric conversion element is arranged at a position closest to each of the plurality of vertices on the main surface of the substrate.

8. The thermoelectric conversion module according to claim 2 or 5, In the cross-sectional view, the length of the long side of each of the plurality of N-type thermoelectric conversion elements is at least twice the length of any side of each of the plurality of P-type thermoelectric conversion elements.

9. The thermoelectric conversion module according to claim 5, The number of the N-type thermoelectric conversion elements arranged in the edge region is greater than the number of the P-type thermoelectric conversion elements arranged in the edge region.

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

11. The thermoelectric conversion module according to claim 2, Satisfies 2≤σ p / σ n ≤4 represents the condition (3), In the condition (3), The σ n is the 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.

12. The thermoelectric conversion module according to claim 11, The σ p Satisfy 400S / cm≤σ p Conditions indicated by ≤4000S / cm.

13. The thermoelectric conversion module according to claim 11 or 12, The σ n Satisfy 100S / cm≤σ n The condition is expressed as ≤1000S / cm.

14. The thermoelectric conversion module according to claim 2 or 3, The P-type thermoelectric conversion element is formed of a chalcogenide compound.

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

16. The thermoelectric conversion module according to claim 3, The N-type thermoelectric conversion element further contains at least one of Sb and Bi.

17. The thermoelectric conversion module according to claim 16, The N-type thermoelectric conversion element is formed of a Mg3(Sb,Bi)2-based compound.

18. A thermoelectric conversion device comprising: A first fluid flow path portion for the flow of a first fluid; A second fluid flow path portion for the second fluid to flow; and The thermoelectric conversion module according to any one of claims 1 to 3 converts heat energy generated by the temperature difference between the first fluid and the second fluid into electric power.

19. A method for generating electricity, comprising: Providing a temperature difference to the thermoelectric conversion module according to any one of claims 1 to 3; as well as Electric power associated with thermoelectromotive force generated in each of the plurality of thermoelectric converters of the thermoelectric conversion module due to the temperature difference is extracted.

20. A heat conduction method, comprising: causing an electric current to flow in the thermoelectric conversion module according to any one of claims 1 to 3; as well as Heat is transported via the current.

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