thermoelectric conversion module

Abstract

To provide a thermoelectric conversion module with which, while having flexibility and high deformability, yet it is possible to obtain a high power generation amount.SOLUTION: Provided is a thermoelectric conversion module in a sheet form, in which a thermoelectric element is disposed stretching between a pair of principal planes that is given a temperature difference. Metal wiring is alternately laid to a first principal plane and a second principal plane so that a p-type thermoelectric element piece and an n-type thermoelectric element piece disposed stretching between the two principal planes are electrically connected alternately to each other. The metal wiring on at least the second principal plane is made to be a meandering wiring, and the distance between the p-type and n-type thermoelectric element pieces at both ends of the wiring is made to be variable, the p-type and n-type thermoelectric element pieces being penetratingly inserted into a sheet body composed of a flexible rubber that includes air bubbles, with at least the side faces encapsulated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sheet-like thermoelectric conversion module in which thermoelectric elements are arranged across a pair of main surfaces across which a temperature difference can be applied. [Background technology]

[0002] A sheet-like thermoelectric conversion module is known in which a plurality of thermoelectric elements utilizing the Seebeck effect are arranged across a pair of main surfaces that are provided at an interface having a temperature difference and that are exposed to this temperature difference. Such thermoelectric conversion elements are widely used in the form of small semiconductor thermoelectric elements formed in the shape of rectangular parallelepiped chips, each of which is made up of a pair of p-type and n-type semiconductor pieces. A large number of such small semiconductor thermoelectric elements can be electrically connected together with appropriate wiring to extract a predetermined amount of power.

[0003] For example, Patent Document 1 discloses a thermoelectric conversion module having a cooling surface on one side and a heating surface on the other side. This thermoelectric conversion module includes multiple thermoelectric elements using the Seebeck effect, a pair of flexible substrates that sandwich the thermoelectric elements and form a cooling surface and a heating surface, multiple inter-element electrodes provided on opposing surfaces of the flexible substrates and electrically connecting the thermoelectric elements, and lead wires electrically connected to the end electrodes that connect end elements located at the ends of the electrical arrangement. By providing the thermoelectric elements on the flexible substrate, the flexible substrate is given deformability, allowing it to be attached to fit the shape of a heating member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-171230 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the sheet of a sheet-type thermoelectric conversion module is made thin to improve flexibility and deformability, a sufficient temperature difference between the pair of main surfaces cannot be obtained, resulting in a decrease in power generation. Furthermore, when considering attachment to curved surfaces of various shapes or surfaces that undergo dynamic deformation, it is necessary to provide not only flexibility but also stretchability, and shape stability is also required, so that the module returns to its original shape when the load is removed after deformation.

[0006] The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a thermoelectric conversion module that has flexibility, including flexibility and stretchability, high deformability, excellent shape stability, and can generate a high amount of power. [Means for solving the problem]

[0007] The present invention is a sheet-like thermoelectric conversion module in which thermoelectric elements are arranged across a pair of main surfaces across which a temperature difference can be applied, and in which metal wiring is provided alternately on the first main surface side and the second main surface side so as to electrically connect p-type thermoelectric element pieces and n-type thermoelectric element pieces provided across a first main surface and a second main surface of the main surfaces alternately, and at least the metal wiring on the second main surface side is a serpentine wiring so that the distance between the p-type thermoelectric element pieces and the n-type thermoelectric element pieces connected to both ends thereof can be changed, and the p-type thermoelectric element pieces and the n-type thermoelectric element pieces are inserted into a sheet made of a rubber elastic material containing bubbles, and at least the side surfaces of the sheet are sealed.

[0008] According to these features, the sheet body made of a rubber elastic material and the serpentine wiring have flexibility, including flexibility and stretchability, and high deformability, while the rubber elastic material containing air bubbles provides excellent shape stability, and a sufficient temperature difference can be obtained between the pair of main surfaces, resulting in a high amount of power generation.

[0009] In the above invention, the rubber elastic body may be an elastomer sponge having open cells that connect the cells to the surface. The elastic modulus of the elastomer sponge may be in the range of 1 to 100 kPa. According to this feature, a high amount of power can be generated while having flexibility and high deformability.

[0010] In the above invention, a support substrate may be provided along one of the main surfaces below the thermoelectric element and the metal wiring. The support substrate may be made of polyimide. This feature provides flexibility, high deformability, and excellent shape stability. That is why.

[0011] The invention described above may be characterized in that it includes a chip-shaped element in which the metal wiring on the first main surface side and the p-type thermoelectric element component and the n-type thermoelectric element component on both sides thereof are sealed and integrated together. This characteristic makes it possible to obtain a high amount of power generation while having flexibility and high deformability.

[0012] In the above invention, the thermal conductivity of the elastomer sponge may be in the range of 0.01 to 0.1 W / m K. The electrical conductivity of the metal wiring may be 1.0×10 4 ~1.0×10 8 The p-type thermoelectric element piece may have a Seebeck coefficient in the range of 1 to 1000 μV / K. The n-type thermoelectric element piece may have a Seebeck coefficient in the range of -1000 to -1 μV / K. These characteristics allow for a higher amount of power generation while maintaining flexibility and high deformability.

[0013] In the above-described invention, the sheet body may be sandwiched between a pair of surface sheet bodies made of a rubber elastic material having a higher thermal conductivity than the sheet body, thereby achieving a high amount of power generation while maintaining flexibility and high deformability. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a photograph showing the appearance of a thermoelectric conversion module as an example according to the present invention. [Figure 2] 1A and 1B are a top view and a side view, respectively, of a sheet body of a thermoelectric conversion module, which is transparently displayed. [Figure 3] FIG. 2 is a top view of a main part of the thermoelectric conversion module when a sheet body is displayed in a transparent manner. [Figure 4] FIG. 2 is a cross-sectional view of a main part of a thermoelectric power generation module. [Figure 5] 10 is a photograph showing a state in which a thermoelectric power generation module is deformed by hand. [Figure 6] 1 is a photograph showing the appearance of a test specimen for a stretch durability test. [Figure 7] 1 is a table showing the measurement results of the elastic modulus and thermal conductivity of the sheet body used for each test specimen. [Figure 8] 1A is a graph showing the results of a stretch durability test, and FIG. 1B is a graph showing the resistance change rate indicating breakage in the same test. [Figure 9] This is a photograph of the exterior of a test specimen used in power generation performance tests. [Figure 10] 1 is a graph showing the relationship between heat source temperature and open-circuit voltage. [Figure 11] 10 is a graph showing the amount of power generated in a test specimen having a flexible rubber sponge sealing structure. DETAILED DESCRIPTION OF THE INVENTION

[0015] A thermoelectric conversion module according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG.

[0016] 1 and 2, the thermoelectric conversion module 10 includes a plurality of thermoelectric elements 1 arranged along the main surface of a sheet body 2, with each thermoelectric element 1 being inserted through the sheet body 2. The thermoelectric elements 1 are electrically connected to each other by metal wiring 3, and connected to terminal electrodes 4 for extracting electric power to the outside. Here, an example is shown in which the number of thermoelectric elements 1 is 30, and all of them are connected in series in an arrangement of 5 columns and 6 rows.

[0017] Each thermoelectric element 1 is arranged in a fixed orientation so as to generate electromotive force due to the temperature difference between the front and back sides of the sheet body 2. As described above, the thermoelectric elements 1 are inserted into the sheet body 2, and at least their sides are enclosed in the sheet body 2. As a result, by creating a temperature difference between the high-temperature side and the low-temperature side of a pair of main surfaces of the sheet body 2, the thermoelectric elements 1 arranged across both main surfaces generate electricity, and a sheet-like thermoelectric conversion module 10 can be obtained.

[0018] The sheet body 2 is made of a rubber elastic material containing air bubbles, which provides excellent thermal insulation between the two main surfaces, as well as bendability (flexibility) in the direction of bending the main surfaces and stretchability in the direction along the main surfaces. In particular, the sheet body 2 preferably has open cells, which connect the interiors of the cells to the surface. By using open cells, the Young's modulus of the thermoelectric conversion module 10 can be reduced compared to when a sheet body with closed cells is used. In other words, by using open cells, stretchability and bendability can be further improved, which is preferable. For example, an elastomer sponge such as a flexible silicone rubber sponge can be suitably used as the sheet body 2.

[0019] The elastic modulus of the sheet body 2 is preferably selected from the range of 1 to 100 kPa. In particular, if the elastic modulus of the sheet body 2 is low, excessive stress is not applied to the internal wiring 3 when the thermoelectric conversion module 10 is deformed, and inhibition of deformation of the wiring 3 can be suppressed. In other words, a low elastic modulus of the sheet body 2 is preferable because it increases the deformability of the thermoelectric conversion module and also contributes to an improvement in the lifespan.

[0020] The thermal conductivity of the sheet member 2 is preferably selected from the range of 0.01 to 0.1 W / m K. In particular, by keeping the thermal conductivity low, it is possible to maintain a large temperature difference between the two main surfaces of the thermoelectric conversion module, thereby increasing the amount of power generation.

[0021] As shown in FIG. 3, the wiring 3 is a serpentine wiring made of a metal thin film that can change the distance between the thermoelectric elements 1. Such serpentine wiring allows the positions of the thermoelectric elements to easily follow the expansion and bending of the thermoelectric conversion module 10. Copper, which has a relatively low electrical resistance and is inexpensive, is preferably used as the material for the wiring 3. By using copper foil for the wiring 3, the width of the wiring 3 can be increased, and the electrical resistance of the wiring can be reduced while maintaining high deformability against bending. In other words, the internal resistance of the thermoelectric conversion module 10 can be reduced, and the amount of power generation can be increased. The electrical conductivity of the wiring 3 is 1.0×10 4 ~1.0×10 8 It is also preferable that the conductivity is selected from within the range of S / m. In particular, the higher the conductivity, the lower the internal resistance of the thermoelectric conversion module 10 can be, which is preferable.

[0022] Referring also to FIG. 4, the thermoelectric element 1 can be, for example, a chip-shaped element with a π-type structure, in which two types of thermoelectric element pieces, a p-type semiconductor piece 11p and an n-type semiconductor piece 11n, are sealed with a sealing material 15 and their low-temperature sides are connected and integrated. In the case of semiconductors, a Bi-Te-based thermoelectric material is preferably used, as it achieves high thermoelectric conversion efficiency. The sealing material 15 can be an insulating material such as epoxy resin. The p-type semiconductor piece 11p and the n-type semiconductor piece 11n are arranged so as to be separated on the left and right by the sealing material 15, and their low-temperature sides (upper side in the drawing) are connected to each other by a low-temperature electrode 14 made of copper. The low-temperature electrode 14 made of copper is connected to a high-temperature electrode 12 made of, for example, Ni, attached to the upper surfaces of the p-type semiconductor piece 11p and the n-type semiconductor piece 11n via low-melting-point solder 13. On the other hand, on the high temperature side (bottom side of the paper), wiring 3 is connected to high temperature side electrodes 12 attached to the undersides of the p-type semiconductor piece 11p and the n-type semiconductor piece 11n via low melting point solder 13, and they are separated from each other by sealing material 15.

[0023] The p-type semiconductor pieces and n-type semiconductor pieces may not be encapsulated in a chip-type element but may be individually arranged. For example, the p-type semiconductor pieces and n-type semiconductor pieces may be arranged across both the high-temperature and low-temperature main surfaces, and the p-type semiconductor pieces and n-type semiconductor pieces may be electrically connected alternately. In this case, such connections are made by metal wiring alternately provided on both main surfaces. The metal wiring on at least one of the two main surfaces is made into a meandering wiring. In other words, a thermoelectric conversion module is made using p-type semiconductor pieces and n-type semiconductor pieces, and the distance between the p-type semiconductor pieces and the n-type semiconductor pieces connected to both ends of the meandering wiring is made variable. This also makes it possible to obtain a thermoelectric conversion module similar to that using the above-mentioned chip-type element. The electrical wiring on both main surfaces may be made into a meandering wiring, and the distance between all of the p-type semiconductor pieces and the n-type semiconductor pieces may be made variable.

[0024] It is also preferable that the Seebeck coefficient of each of the p-type semiconductor piece 11p and the n-type semiconductor piece 11n is selected from the range of 1 to 1000 μV / K. In both cases, a large Seebeck coefficient is preferable because it allows for a larger amount of power generation.

[0025] Furthermore, the wiring 3 and thermoelectric element 1 are provided with a support substrate 17 adhered to their lower portions by an adhesive layer 16. The support substrate 17 is arranged along the high-temperature side of the main surface of the sheet member 2, and preferably has flexibility and shape stability. Polyimide can be suitably used as such a support substrate 17. The two-layer structure of the support substrate 17 made of polyimide and the wiring 3 made of copper foil can provide the thermoelectric conversion module 10 with flexibility, high deformability, and excellent shape stability. The support substrate 17 also contributes to the shape stability of the thermoelectric conversion module 10 during its fabrication.

[0026] The thermoelectric elements 1 and wiring 3 are disposed inside the sheet 2 while being entirely covered with an insulating film 18. Considering the possibility that the thermoelectric elements 1 and wiring 3 may come into contact beyond the bubbles when the sheet 2 having open cells is bent excessively, the insulating film 18 can prevent short circuits due to such contact. Furthermore, using a paraxylylene-based polymer as the insulating film 18 is preferable as it also functions as a protective film against the humidity of the outside air.

[0027] The thermoelectric conversion module 10 further includes a pair of surface sheet bodies 2a and 2b, which sandwich the entire module. The surface sheet bodies 2a and 2b are preferably made of a rubber elastic material with higher thermal conductivity than the sheet body 2, and by increasing the thermal conductivity in the direction along the main surface, a high temperature difference can be maintained between the high-temperature side and the low-temperature side of the thermoelectric element 1. From the viewpoint of this thermal conductivity, it is preferable that the surface sheet bodies 2a and 2b do not contain air bubbles. For example, the surface sheet bodies 2a and 2b are preferably made of a silicone elastomer mixed with a material with high thermal conductivity, such as silver flakes, and formed into a sheet shape, which further increases the thermal conductivity.

[0028] [Manufacturing test] Next, the results of a test conducted to evaluate the performance of the actually manufactured thermoelectric conversion module 10 will be described with reference to FIGS.

[0029] As shown in Figure 5, a thermoelectric conversion module 10 was actually manufactured and a deformation test was conducted. The thermoelectric conversion module 10 had the same structure as that shown in the previous drawings, and a flexible silicone rubber sponge with open cells was used as the sheet body 2. The wiring 3 was made of copper foil, the support substrate 17 was made of polyimide, and the insulating film 18 was made of paraxylylene-based polymer. A chip-type thermoelectric element made of a Bi-Te-based semiconductor was used as the thermoelectric element 1. Silicone rubber was used for the surface sheet bodies 2a and 2b, and no other materials were mixed in.

[0030] A thermoelectric conversion module 10 having a roughly rectangular flat plate shape was bent as shown in FIG. 1(a), pulled as shown in FIG. 1(b), and randomly rolled and folded as shown in FIG. 1(c). After each deformation was applied with fingers, the force that applied the deformation was removed. Then, as shown in FIG. 1(d), the thermoelectric conversion module 10 returned to its original roughly rectangular flat plate shape. In other words, it was found that the thermoelectric conversion module 10 has excellent shape stability while possessing flexibility, including flexibility and stretchability, and high deformability.

[0031] Next, three types of test specimens were fabricated by changing the material of the thermoelectric conversion module sheet, and comparative tests were conducted. The three types of test specimens were: Test specimen Ta, in which the sheet material was hard silicone rubber; Test specimen Tb, in which the sheet material was soft silicone rubber; and Test specimen Tc, in which the sheet material was soft silicone rubber sponge, a rubber elastic body containing air bubbles. The other materials were the same as those used in the deformation test described above.

[0032] First, specimens Ta to Tc for the expansion and contraction durability test were prepared, each having three thermoelectric elements as shown in Fig. 6. The symbols Ta to Tc are also commonly used for the specimens for the power generation performance test (see Fig. 9) described later.

[0033] As shown in Figure 7, the elastic modulus and thermal conductivity of each sheet used for specimens Ta to Tc were measured. The results showed that the hard silicone rubber used for specimen Ta had a higher elastic modulus of 1.32 MPa than the other two, while the soft silicone rubber sponge used for specimen Tc had the lowest. This means that specimen Tc is estimated to have the greatest deformability for a given stress. The hard silicone rubber used for specimen Ta and the soft silicone rubber used for specimen Tb had high thermal conductivities of 0.16 and 0.20 W / m K, respectively, while the soft silicone rubber sponge used for specimen Tc had a low thermal conductivity of 0.08 W / m K. This suggests that a thermoelectric conversion module using soft silicone rubber sponge can maintain a high temperature difference between the high-temperature and low-temperature sides, resulting in high power generation.

[0034] Figure 8(a) shows the results of the stretch durability test using specimens Ta (made of hard silicone rubber), Tb (made of flexible silicone rubber), and Tc (made of flexible silicone rubber sponge). In the stretch durability test, the specimens were attached to a tensile testing machine and repeatedly subjected to tensile deformation to achieve a predetermined elongation while measuring the internal resistance of the specimen as a thermoelectric conversion module using the four-terminal method. The number of repetitions required for failure was recorded. The rate of change in internal resistance was monitored during the test, and failure was determined when the rate of change in internal resistance exceeded 100%. In other words, failure was determined as electrical insulation failure. For example, Figure 8(b) shows the rate of change in internal resistance at plot point P. In this example, for specimen Ta, made of hard silicone rubber, the rate of change in internal resistance suddenly increased to 100% at 78 cycles (number of repetitions) when the elongation rate was set to 20%. This indicates failure.

[0035] In the stretch durability test, specimen Ta, which used hard silicone rubber, showed the lowest durability, while specimen Tc, which used soft silicone rubber sponge, showed the highest durability. For specimen Tc, the maximum elongation was 125%, and the number of repetitions until breakage at an elongation of 50% was 1,025. The maximum elongation was defined as the elongation until breakage after a single tensile deformation.

[0036] Figure 9 shows the appearance of test specimens Ta to Tc used for the power generation performance test. Each test specimen had 30 thermoelectric elements arranged in 5 columns and 6 rows. The high-temperature side of each test specimen was placed in close contact with the hot plate, which served as the heat source, and the low-temperature side was placed so that it was exposed to the room air, creating a temperature difference. The surface temperature of the hot plate was measured as the heat source temperature, and the open-circuit voltage of each specimen was measured. Each test specimen was also placed on the hot plate, and the power generation amount was measured while measuring the temperatures of its top and bottom surfaces.

[0037] As shown in Figure 10, the open-circuit voltage was highest for specimen Tc, which used soft silicone rubber sponge, at heat source temperatures between 60 and 100°C, while specimens Ta, which used hard silicone rubber, and Tb, which used soft silicone rubber, had similar values. This is thought to be because a temperature difference corresponding to the difference in thermal conductivity (see Figure 7) occurred between the high-temperature side and the low-temperature side. In other words, a high thermal conductivity reduced the temperature difference and reduced the open-circuit voltage, while a low thermal conductivity increased the temperature difference and increased the open-circuit voltage.

[0038] Figure 11 shows the power generation capacity of the test specimen Tc, which uses a flexible silicone rubber sponge. It was confirmed that the power generation capacity can be increased by increasing the temperature difference between the high-temperature side (bottom surface) and the low-temperature side (top surface). In this case, a maximum power generation capacity of 32.2 μW was obtained at a temperature difference of 8.6°C.

[0039] As described above, it was found that the test specimen Tc made of the soft silicone rubber sponge has flexibility, including flexibility and stretchability, and high deformability, while also being able to generate a high amount of power.

[0040] Although the embodiments of the present invention and modifications based thereon have been described above, the present invention is not necessarily limited thereto, and a person skilled in the art will be able to find various alternative embodiments and modifications without departing from the spirit of the present invention or the scope of the appended claims. [Explanation of symbols]

[0041] 1 Thermoelectric element 2 Sheet body 3 Wiring 10 Thermoelectric conversion module

Claims

1. A sheet-like thermoelectric conversion module in which thermoelectric elements are arranged across a pair of main surfaces that can be given a temperature difference, metal wiring is provided alternately on the first main surface side and the second main surface side so as to electrically connect alternately p-type thermoelectric element components and n-type thermoelectric element components provided across a first main surface and a second main surface of the main surfaces, The metal wiring on at least the second main surface side is formed as a meandering wiring, and the distance between the p-type thermoelectric element component and the n-type thermoelectric element component connected to both ends of the meandering wiring is variable; the p-type thermoelectric element pieces and the n-type thermoelectric element pieces are inserted into a sheet made of a rubber elastic material containing bubbles, and at least the side surfaces of the sheet are sealed; The thermoelectric conversion module is characterized in that the rubber elastic body is an elastomer sponge having open cells that connect the cells to the surface.

2. 2. The thermoelectric conversion module according to claim 1, wherein the modulus of elasticity of the elastomer sponge is within a range of 1 to 100 kPa.

3. 2. The thermoelectric conversion module according to claim 1, wherein a support substrate is provided on the metal wiring along one of the main surfaces.

4. 4. The thermoelectric conversion module according to claim 3, wherein the support substrate is made of polyimide.

5. 2. The thermoelectric conversion module according to claim 1, further comprising a chip-shaped element in which the metal wiring on the first main surface side and the p-type thermoelectric element piece and the n-type thermoelectric element piece on both sides thereof are sealed and integrated.

6. 2. The thermoelectric conversion module according to claim 1, wherein the thermal conductivity of the elastomer sponge is within a range of 0.01 to 0.1 W / m·K.

7. The conductivity of the metal wiring is 1.0×10 ４ ~1.0 x 10 ８ 2. The thermoelectric conversion module according to claim 1, wherein the electrical conductivity is in the range of S / m.

8. 2. The thermoelectric conversion module according to claim 1, wherein the Seebeck coefficient of the p-type thermoelectric element piece is in the range of 1 to 1000 μV / K.

9. 2. The thermoelectric conversion module according to claim 1, wherein the Seebeck coefficient of the n-type thermoelectric element piece is within a range of −1000 to −1 μV / K.

10. 10. The thermoelectric conversion module according to claim 1, wherein the thermoelectric conversion module is sandwiched between a pair of surface layer sheets made of a rubber elastic material having a higher thermal conductivity than the sheet body.

Images