JP2003124532A - Thermal stress relaxation material for thermoelectric transducing module and thermoelectric transducing unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal relaxation material which has heat conductivity higher than a conventional thermal stress relaxation material made of graphite and can have the thermal power generation efficiency improved and a thermoelectric transducing unit which uses it. SOLUTION: The thermal stress relaxation material 6 for the thermoelectric transducing module which is interposed at least either one of between the thermoelectric transducing module and a low-temperature side member or between the thermoelectric transducing module and a high-temperature side member is a sheet type formed by laminating multiple graphite materials 8a, which are arranged almost at right angles to sheet surfaces 6a and 6b. Further, the thermoelectric transducing unit is formed by fixing the thermal stress relaxation material 6 to at least either the low-temperature side or high-temperature side of the thermoelectric transducing module.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermal stress relaxation material for a thermoelectric conversion module and a thermoelectric conversion unit using the same.

[0002]

2. Description of the Related Art A thermoelectric conversion module is known in which an N-type semiconductor and a P-type semiconductor are used and are interposed between a high temperature source and a low temperature source, and heat energy is converted into electric energy by a temperature difference between the high temperature source and the low temperature source. Generally, the low temperature side member such as the low temperature side heat exchanger is brought into contact with the low temperature side surface of the thermoelectric conversion module, and the high temperature side member such as the high temperature side heat exchanger is brought into contact with the high temperature side surface of the thermoelectric conversion system. It is configured.

However, the thermoelectric conversion module, the low-temperature side member, and the high-temperature side member have different temperatures and different amounts of thermal expansion from each other, resulting in poor contact between contact surfaces and heat conduction caused thereby. There is a problem in that the thermoelectric conversion efficiency is deteriorated as a result.

In order to solve this problem, Japanese Patent No. 3056047 discloses a technique of interposing a thermal stress relaxation material made of graphite between the respective members.

[0005]

However, as shown in FIG. 11, the thermal stress relaxation material made of graphite used in the above-mentioned conventional thermoelectric conversion system has a structure in which foil-like graphite 101 is stacked in multiple layers and pressed into a sheet shape. Hardened,
Alternatively, it is a sheet-like one in which a stainless steel foil 102 for maintaining the shape is interposed between the foil-like graphite 101, and the direction A (foil stacking direction) A orthogonal to the sheet surfaces 103 and 104 is the sheet surface 103, As compared with the direction B parallel to 104, there is anisotropy in thermal conductivity that the thermal conductivity between the layers is low and the thermal conductivity is low.

Therefore, as described above, the thermal stress relaxation material 105 in which foil-like graphite is stacked in layers is arranged so that the sheet surfaces 103 and 104 contact the thermoelectric conversion module and both heat source sides. In the thermoelectric conversion system, the sheet surfaces 103 and 104 of the thermal stress relaxation material 105 are
Since it is thermoelectrically converted by heat transfer in the direction A orthogonal to
It has an inherent problem of poor thermoelectric conversion efficiency.

Therefore, the appearance of a thermal stress relaxation material for a thermoelectric conversion system which is graphite excellent in thermal stress relaxation and which can solve the above problems, and a thermoelectric conversion unit using the same have been awaited.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a thermoelectric conversion module and a low temperature side member, and a thermoelectric conversion module and a high temperature side member. In the thermal stress relaxation material made of graphite interposed in at least one of the spaces, the thermal stress relaxation material is a sheet shape formed by stacking multiple graphite materials, and the graphite material is arranged in a direction substantially orthogonal to the sheet surface. It is a thermal stress relaxation material for a thermoelectric conversion module, which is characterized by being formed as follows.

The thermal stress relaxation material of the present invention is provided on at least one of the thermoelectric conversion module and the low temperature side member and between the thermoelectric conversion module and the high temperature side member, and the sheet surface of the thermal stress relaxation material is the thermoelectric conversion material. By interposing them so as to face the module and the member, the direction of the graphite material in the thermal stress relaxation material and the direction of the joint (interlayer) between the graphite materials are such that the thermoelectric conversion module, the low temperature side member, and the high temperature side member are positioned. Match the direction you want to. Therefore, the surface of the thermal stress relaxation material in the direction of high thermal conductivity contacts the thermoelectric conversion module and the heat source. Therefore, thermoelectric power generation efficiency becomes high.

According to a second aspect of the present invention, in the first aspect of the present invention, the thermal stress relaxation material is formed by stacking graphite materials in multiple layers and slicing in a direction substantially parallel to the stacking direction. It is a thermal stress relaxation material for a thermoelectric conversion module characterized by the above.

According to a third aspect of the present invention, in the first aspect of the present invention, the thermal stress relaxation material is formed by laminating a large number of graphite fibers and then slicing in a direction substantially parallel to the laminating direction. It is a thermal stress relaxation material for a thermoelectric conversion module characterized by the above.

Also in the second and third inventions, a thermal stress relaxation material having a structure similar to that of the first invention is obtained, and exhibits the same action as that of the first invention.

According to a fourth aspect of the present invention, there is provided a thermoelectric conversion unit using the thermal stress relaxation material, wherein a sheet-shaped thermal stress relaxation is provided on at least one of the low temperature side and the high temperature side of the thermoelectric conversion module. A thermoelectrically relaxing material having a thermal stress relaxation material in the form of a sheet in which graphite materials are laminated in multiple layers, and the graphite material is arranged in a direction substantially orthogonal to the sheet surface. It is a conversion unit.

In the present invention, the thermal stress relaxation material exerts the above-mentioned action, and the heat conversion module and the thermal stress relaxation material become an integral unit, and the work of assembling these to the high temperature side member or the low temperature side member is performed. As compared with the case where the heat conversion module and the thermal stress relaxation material are separately assembled to the high temperature side member and the low temperature side member, respectively, the management can be facilitated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on the embodiments shown in FIGS.

FIG. 1 is a sectional view showing an embodiment of a heat conversion system using the thermal stress relaxation material of the present invention.

In FIG. 1, reference numeral 1 denotes a thermoelectric conversion module using an N-type semiconductor and a P-type semiconductor, which is a low temperature side member of the thermoelectric conversion module 1 and a low temperature side member (low temperature side heat exchanger). ) 3 and between the high temperature side surface of the thermoelectric conversion module 1 and the high temperature side member (high temperature side heat exchanger) 5 provided with the high temperature medium passage 4, the thermal stress relaxation material 6 made of graphite of the present invention intervenes. Has been done.

Then, only the low temperature side member 3 and the high temperature side member 5 are connected to each other by the connecting means 7 such as a bolt, and the thermoelectric conversion module 1 and the thermal stress relaxation material 6 can slide relative to each other. Further, the thermal stress relaxation material 6 and the low temperature side member 3 and the high temperature side member 5 are sandwiched so as to be slidable relative to each other. That is, they are supported in a floating manner without using fixing means such as an adhesive. The mutual connection structure between the low temperature side member 3 and the high temperature side member 5 is always
The low temperature side member 3 and the high temperature side member 5 are bolted so that no gap is created between the members 3 and 5 and the thermal stress relaxation material 6 and between the thermoelectric conversion module 1 and the thermal stress relaxation material 6. 7 is fixed so as not to move in the axial direction, while the low temperature side member 3
The bolt through hole 3a is made larger than the diameter of the bolt 7, and the low temperature side member 3 and the high temperature side member 5 are coupled so as to be relatively movable in the direction orthogonal to the bolt axis.

Since the graphite forming the thermal stress relaxation material 6 is electrically conductive, the low temperature side member 3, the high temperature side member 5 and the thermoelectric conversion module 1 are provided with an electric insulation means or are subjected to an electric insulation treatment. For example, the material of the low temperature side member 3 and the high temperature side member 5 may be aluminum nitride, anodized, or the thermoelectric conversion module may be provided with an electrically insulating substrate.

Next, a first embodiment of the thermal stress relaxation material of the present invention used as the thermal stress relaxation material 6 will be described with reference to FIGS.

First, as shown in FIG. 2, a plurality of foil-shaped graphite materials 8 are laminated in multiple layers and then pressed in the lamination direction C to prepare a multilayer graphite body 9. In addition, in order to maintain the shape of the multi-layer graphite body 9, a reinforcing material such as a stainless steel foil may be sandwiched between the layers of the foil-shaped graphite material 8. However, it is preferable not to use this reinforcing material, because this reinforcing material has a heat conduction resistance.

The multilayer graphite body 9 formed as described above has anisotropy in thermal conductivity. That is, in the laminating direction C of the foil-shaped graphite material 8, the joint portion (interlayer) 10 between the layers serves as heat conduction resistance, and the foil-shaped graphite material is a direction substantially orthogonal to the laminating direction C. 8 has a characteristic that the thermal conductivity is lower than that in the direction D parallel to 8.

Next, as shown in FIG. 3, the multilayer graphite body 9 is sliced in a direction C ', which is substantially parallel to the stacking direction C thereof, to a predetermined thickness t by a cutting means 11 such as a cutter, for use in a thermoelectric conversion module. The thermal stress relaxation material 6 is obtained. The sliced thickness is, for example, about 0.5 mm.

In the thermal stress relaxation material 6 obtained by slicing as described above, as shown in FIG. 4, the foil-shaped graphite material 8 is cut into strips, and the strip-shaped graphite material 8a is obtained. A large number of sheets are arranged side by side on one plane (this state is referred to as a sheet shape obtained by stacking multiple graphite materials), and the joint portion (interlayer) 10 of the strip-shaped graphite material 8a is formed in the sheet shape. The thermal stress relaxation material 6 is formed parallel to the direction E that is substantially orthogonal to the sheet surfaces (front and back surfaces) 6a and 6b. Therefore, as shown in FIG. 4, the sheet-like thermal stress relaxation material 6 is in a state in which the heat conduction direction (between the front and back direction E) is not divided by the interlayer 10, and in the front and back direction E, The decrease in thermal conductivity due to the interlayer 10 does not occur.

The sheet-shaped thermal stress relaxation material 6
Is the slice surface, that is, the sheet surface (front and back surfaces) 6
As shown in FIG. 1, a and 6b are in contact with the heat transfer surface of the low temperature side member 3, the heat transfer surface of the high temperature side member 5, the low temperature side surface of the thermoelectric conversion module 1, and the high temperature side surface of the thermoelectric conversion module 1. To use.

With such a use, the direction of high thermal conductivity coincides with the direction of heat conduction from the low temperature side member 3 and the high temperature side member 5 to the thermoelectric conversion module 1, so that the heat conduction becomes good and excellent. Thermoelectric conversion efficiency can be obtained.

In the above-mentioned embodiment, the multilayer graphite body 9 is used.
Was sliced, but the strip-shaped graphite material 8a as described above was formed in advance, and a large number of this graphite material 8a,
As shown in FIG. 4, the sheet-like thermal stress relaxation material 6 may be formed by lining up in parallel (stacking) and pressing.

Further, it is known that the thinner the thermal stress relaxation material 6, the smaller the thermal resistance and the better the thermal conductivity. Therefore, in the above-mentioned embodiment of the present invention,
If sliced or arranged extremely thinly, the parallel state of the graphite material may be broken, and it may be difficult to maintain the shape of the sheet. In this case, as shown in FIG. 5, a fixing outer frame 12 may be provided on the outer peripheral surface of the sheet-shaped thermal stress relaxation material 6. As a material of the fixing outer frame 12, a material having high heat resistance such as stainless steel is desirable.

As a method of providing the fixing outer frame 12, after the graphite material is sliced or arranged side by side to obtain the sheet-like thermal stress relaxation material 6 shown in FIG. 4, the fixing outer frame 12 is provided. 12 may be provided, and in the step before slicing, the side surface of the multilayer graphite body 9,
That is, the fixing outer frame 12 is previously provided on the entire peripheral side surface of the sliced surface, and then the multilayer graphite body 9 and the fixing outer frame 12 are integrally sliced as described above and fixed. You may make it form the thermal stress relaxation material with an outer frame.

6 to 9 show a second embodiment of the thermal stress relaxation material according to the present invention.

In the second embodiment, first, a large number of graphite fibers are laminated (collected) in a substantially parallel manner and pressed, and then the mixture is pressed as shown in FIG.
A multilayer graphite body 13 as shown in (a) is prepared, or, as shown in FIG. 6 (b), a small number of graphite fibers 14a are gathered in parallel to form a rectangular or rectangular rod-like graphite aggregate 14. Are laminated and pressed to prepare a multilayer graphite body 13 as shown in FIG. 6 (a).

Then, as shown in FIG. 7, the multilayer graphite body 13 is sliced by a cutting means 11 such as a cutter in a direction C'which is substantially parallel to the laminating direction C, as in the first embodiment. A sheet-shaped thermal stress relaxation material 6 for a thermoelectric conversion module is obtained.

Even in the case where such graphite fibers are laminated, the thermal conductivity in the fiber direction D is higher than that in the direction C orthogonal to the fiber direction. Therefore, in the sheet-like thermal stress relaxation material 6 sliced as described above, the fiber direction D of graphite is a direction (front and back direction) E substantially orthogonal to the sheet surfaces 6a and 6b, as shown in FIG. The thermal conductivity in the direction E becomes high.

The sheet-like thermal stress relaxation material 6
Is the slice surface, that is, the sheet surface (front and back surfaces) 6
a and 6b are the heat transfer surface of the low temperature side member 3 and the high temperature side member 5
The heat transfer surface, the low temperature side surface of the thermoelectric conversion module 1, and the high temperature side surface of the thermoelectric conversion module 1 are brought into contact with each other and used as shown in FIG. By using in this way, excellent thermoelectric conversion efficiency can be obtained as in the first embodiment.

In the second embodiment, the first
If the slice is extremely thin, as in the example, the arrangement of the graphite fibers may be broken, and it may be difficult to maintain the shape of the sheet. In this case, as shown in FIG. 9, the fixing outer frame 12 may be provided on the outer peripheral surface of the sheet-shaped thermal stress relaxation material 6. As a material of the fixing outer frame 12, a material having high heat resistance such as stainless steel is desirable. The fixing outer frame 12 may be provided after slicing, as in the first embodiment, or may be provided in advance in the multilayer graphite body 13 before slicing so that the multilayer graphite body 13 and the fixing outer frame are provided. 12 and 12 may be integrally sliced and provided.

FIG. 10 shows that the thermal stress relaxation material 6 of the first embodiment or the second embodiment is fixed to the low temperature side surface and the high temperature side surface of the thermoelectric conversion module 1 by sticking or the like, and the thermal stress relaxation material 6 and the thermoelectric relaxation material 6 The thermoelectric conversion unit 15 is integrated with the conversion module 1.

The thermal stress relaxation material 6 and the thermoelectric conversion module 1 may be integrated by bonding at least a part of the contact surface between the thermoelectric conversion module 1 and the thermal stress relaxation material 6 using a patch. It suffices to keep them at least until they are sandwiched (set) between the low temperature side member 3 and the high temperature side member 5. The material of the patch is not particularly limited, but one having good thermal conductivity is preferable.

Although the thermal stress relaxation material 6 is provided on both the low temperature side surface and the high temperature side surface of the thermoelectric conversion module 1 in the embodiment of FIG. 10, it may be provided on either one of the surfaces.

According to this thermoelectric conversion unit 15, the thermal stress relaxation material 6 exerts the above-mentioned action, and the thermal conversion module 1 and the thermal stress relaxation material 6 are integrated into one unit,
The work of assembling these into the high temperature side member 5 and the low temperature side member 3 can be performed more easily than in the case where the heat conversion module 1 and the thermal stress relaxation material 6 are separately assembled into the high temperature side member 5 and the low temperature side member 3, respectively. At the same time, management of parts becomes easy.

[0040]

As described above, according to the thermal stress relaxation material made of graphite of the present invention, the thermal conductivity is improved and the thermoelectric conversion efficiency is improved as compared with the conventional thermal stress relaxation material made of graphite. The thermoelectric power generation efficiency is improved.

According to the invention described in claim 4, the thermal stress relaxation material exerts the above-mentioned effect, and the work of assembling the thermal stress relaxation material and the heat conversion module to the high temperature side member or the low temperature side member is improved. At the same time, the management of parts becomes easy.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a thermoelectric conversion system using a thermal stress relaxation material of the present invention.

FIG. 2 is a perspective view showing a multilayer graphite body that is a raw material for manufacturing the thermal stress relaxation material of the first embodiment of the present invention.

FIG. 3 is a perspective view showing a state where the thermal stress relaxation material of the present invention is obtained by slicing the multilayer graphite body of FIG.

FIG. 4 is a perspective view showing a thermal stress relaxation material of the present invention obtained by slicing in FIG.

5 is a perspective view showing a state in which a fixing outer frame is provided on the thermal stress relaxation material of FIG.

FIG. 6 (a) is a perspective view showing a multilayer graphite body which is a raw material for manufacturing the thermal stress relaxation material of the second embodiment of the present invention,
(B) is a perspective view of the graphite aggregate which comprises a multilayer graphite body.

FIG. 7 is a perspective view showing a state where the thermal stress relaxation material of the present invention is obtained by slicing the multilayer graphite body of FIG. 6 (a).

8 is a perspective view showing a thermal stress relaxation material of the present invention obtained by slicing in FIG.

9 is a perspective view showing a state in which a fixing outer frame is provided on the thermal stress relaxation material of FIG.

FIG. 10 is a cross-sectional view showing a thermoelectric conversion unit in which the thermal stress relaxation material of the present invention is fixed to a thermoelectric conversion module.

FIG. 11 is a perspective view showing a conventional thermal stress relaxation material.

[Explanation of symbols]

1 Heat conversion module 3 Low temperature side member 5 High temperature side member 6 Thermal stress relaxation material 8 Foil-shaped graphite material 8a Graphite material 14 Graphite aggregate 14a Graphite fiber 15 Thermoelectric conversion unit

Claims (4)

[Claims] 1. A graphite thermal stress relaxation material interposed between at least one of a thermoelectric conversion module and a low temperature side member and between a thermoelectric conversion module and a high temperature side member, wherein the thermal stress relaxation material is a graphite material. A thermal stress relaxation material for a thermoelectric conversion module, which is in the form of a sheet in which a plurality of layers are laminated, and a graphite material is arranged in a direction substantially orthogonal to the sheet surface. 2. The heat for a thermoelectric conversion module according to claim 1, wherein the thermal stress relaxation material is formed by stacking graphite materials in multiple layers and then slicing them in a direction substantially parallel to the stacking direction. Stress relaxation material. 3. The heat for a thermoelectric conversion module according to claim 1, wherein the thermal stress relaxation material is formed by stacking a large number of graphite fibers and then slicing them in a direction substantially parallel to the stacking direction. Stress relaxation material. 4. A sheet-like thermal stress relaxation material is fixed to at least one of a low temperature side and a high temperature side of the thermoelectric conversion module, and the thermal stress relaxation material is a sheet formed by laminating graphite materials in multiple layers. The thermoelectric conversion unit is characterized in that the graphite material is arranged and formed in a direction substantially orthogonal to the sheet surface.