JP2000000029U - Thermoelectric watch - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the power generation output of a thermoelectric power generation wristwatch that uses the power generation output of a thermoelectric power generation element as an energy source, it is desirable to minimize the temperature difference generated between the case back and the case as much as possible. Provides a possible structure. The thermoelectric generator includes a metal case, a thermal insulator, a back cover, a module, and a thermoelectric generator in which a plurality of thermocouples are arranged. The thermoelectric generator has a hot junction in contact with the back cover. And the metal case 10 not including the thermal insulator 40 and the back cover 20 is disposed between the case 10 and the back cover 20 so that the cold junction 62 contacts the case 10.
The heat radiation layer 70 is provided only on the surface.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a thermoelectric wristwatch that holds a thermoelectric element inside and is driven by the generated energy, and particularly relates to a structure for expanding a temperature difference effective for improving power generation efficiency.

[0002]

[Prior art]

 The structure of a wristwatch using a thermoelectric element as an energy source will be described with reference to the cross-sectional view of FIG. A minute thermoelectric power generation element 60 is mounted in the wristwatch using the empty space.

As shown in FIG. 3, a thermoelectric generator 60 is mounted in a space between the watch module 50 and the back cover 20, and its hot junction 61 contacts the back cover 20, and its cold junction 62 is a metal. Is in thermal contact with the case 10 via a module cover 53 made of a metal.

The back cover 20 is warmed to near body temperature because it is in direct contact with the user's arm, but the case 10 is constantly cooled by the outside air, so that a temperature difference occurs between the two.

[0005] Therefore, a temperature difference also occurs between the hot junction 61 and the cold junction 62 of the thermoelectric generation element 60 that is in contact with both, and accordingly, an electromotive force is generated in the thermoelectric generation element 60, and the energy required by the timepiece is generated. Will be supplied.

It is needless to say that the material characteristics and the number of thermocouples of the thermocouple included in the thermoelectric generation element 60 are important as factors that influence the power generation amount of the thermoelectric generation element 60.

[0007] However, another point is that the given temperature difference is a very important factor. This will be described with reference to the graph of FIG. A BiTe alloy was used as the thermoelectric generator 60 material.

The graph of FIG. 4A shows current-voltage characteristics when the number of thermocouple pairs of the thermoelectric generator is changed to 1000, 2000, and 3000 pairs when the temperature difference is 1 ° C. FIG. 4B shows the current-voltage characteristics when the temperature difference is changed to 1 ° C., 2 ° C., and 3 ° C. when the number of thermocouple pairs is 1000.

As is clear from the graph of FIG. 4, when the number of thermocouples is increased, the voltage is increased in proportion to the number of thermocouples.

However, since the internal resistance also increases in proportion, the current value does not change. That is, the output is linearly proportional to the number of thermocouples.

Further, in this case, since the pair of shapes is not changed, the area of the entire device increases. In contrast, it can be seen that when the temperature difference is increased, both the voltage and the current are increased in proportion.

That is, the output is quadratic in proportion to the temperature difference, and it can be seen that a slight difference in temperature difference is very effective.

Then, what is the actual temperature difference? When the temperature is 25 ° C., the temperature difference between the back cover 20 and the case 10 is at most about 2 ° C.

This is because the case is warmed by heat conduction from the back cover, and cooling by the outside air cannot be made in time.

In order to suppress the heat conduction, a heat insulator 40 is interposed between the case 10 and the back cover 20 so as not to contact with each other as shown in FIG.

However, the resulting temperature difference is about 2 ° C. The temperature difference between the actual arm and the outside air is at least 10 ° C, and it cannot be said that it is fully utilized.

In order to further widen the temperature difference, not only suppressing the heat conduction from the back cover 20 but also actively cooling the case 10 is an important issue. For that purpose, it is necessary to increase the heat radiation efficiency of the case 10 itself. However, the case 10 has not been actively improved.

In general, as a means for dissipating heat to avoid a high temperature, a heat dissipating fin is often used on the surface. This is described in, for example, JP-A-53-69677, and the application of mechanically processed fins to thermoelectric wristwatches is also considered.

However, since the fins formed by machining have a plate-like structure on the order of millimeters, it is technically difficult to attach them to the case, and as a further problem, wristwatches are not only functional but also decorative. Since it is important as a value, it must be said that it is extremely difficult to install fins with large irregularities.

[0020]

[Problems to be solved by the invention]

 As described above, in a thermoelectric generation watch, the temperature difference between the case that generates electromotive force in the element and the back cover is important.

However, it is not considered that the conventional configuration still sufficiently uses the difference between the body temperature and the outside temperature efficiently.

[Purpose of the Invention] The purpose of the present invention is to solve the above problems and improve the timepiece case to reduce the temperature of the case positively, thereby increasing the temperature difference between the case and the back cover more than before. The purpose is to increase the power generation efficiency of the thermoelectric element and to provide a wristwatch that is sufficiently valuable both in appearance and as a decoration.

[0023]

[Means for Solving the Problems]

 In order to achieve the above object, the thermoelectric watch of the present invention adopts the following structure.

The thermoelectric generation wristwatch of the present invention includes a metal case, a thermal insulator, a back cover, a module, and a thermoelectric generation element in which a large number of thermocouples are arranged, and the thermoelectric generation element has a hot junction in contact with the back cover. It is placed between the case and the back cover so that the cold junction is in contact with the case, and the heat radiation layer is provided only on the surface of the metal case that does not include the thermal insulator and the back cover.

[0025]

[Embodiment of the invention]

 A thermoelectric wristwatch according to a preferred embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing a thermoelectric wristwatch of the present invention.

As shown in FIG. 1, the wristwatch of the present invention has a metal case 10, a back cover 20, and a glass 30 similarly to a general wristwatch.

Further, in order to suppress heat conduction between the case 10 and the back cover 20, a plastic thermal insulator 40 is mounted between the two.

A display hand 51, a dial 52, and a module 50 having a drive unit are mounted inside.

The module 50 is provided with a module cover 53, and a thermoelectric generator 60 is installed between the module cover 53 and the back cover 20.

The thermoelectric generator 60 has a large number of thermocouples (not shown) made of BiTe alloy. The thermocouple 61 is in contact with the back cover 20, and the cold junction 62 is in contact with the module cover 53. It has become.

Since the module cover 53 is made of metal and is in thermal contact with the case 10, the temperature of the module cover 53 is substantially the same as that of the case 10, and a temperature difference between the module cover 53 and the back cover 20 is maintained.

The thermoelectric generation element 60 needs to be in close contact with both in order to efficiently use this temperature difference. In the present invention, the module cover 53 is provided with a spring property, and the back cover 20 is fixed with the screw 21. By doing so, the thermoelectric generator 60 is tightly sandwiched between the module cover 53 and the back cover 20.

By the way, the case 10 is generally made of stainless steel, titanium, aluminum, or the like. In the present invention, the surface treatment of each material is performed to newly provide a heat radiation layer 70 so as to increase the heat radiation efficiency to the outside air. I do. The specific configuration is shown below.

The heat radiation layer 70 according to the first embodiment is a thin film having countless minute irregularities. Hereinafter, a method of forming the heat radiation layer 70 will be described.

The case 10 is set as a cathode in a vacuum chamber provided with an anode, a hot filament, and titanium as an evaporation source.

After the inside of the vacuum chamber is evacuated to vacuum, argon and nitrogen are introduced to generate plasma by thermal electrons, and titanium evaporated by an electron beam method is reacted with a plasma gas to form a film.

This method is the same as the so-called ion plating method in which metal is deposited in plasma.

When a film is formed at an optimum gas pressure and an optimum cathode voltage, the introduced nitrogen and oxygen and carbon generated from the adsorbed gas of the vacuum layer are combined with titanium to form a TiNOC film, and a glossy black film is formed on the surface of the case 10. It is formed.

Since this thin film has minute irregularities of 1 μm or less, the surface area is extremely increased microscopically, and the heat radiation efficiency is very good. Also, due to the unevenness, the color looks very close to black, which is good as a watch exterior.

In addition to the method using such a vacuum technique, a coating method by spraying can also form a thin film having countless minute irregularities.

Fine particles of metal or carbon having a particle size of 5 to 10 μm are kneaded in an adhesive organic solvent and sprayed on the case 10 by a spray method.

The thin film thus formed has minute irregularities due to the fine particles, and also has a very large surface area, which improves the efficiency of heat radiation to the outside air.

In addition, a thin film having minute projections can be formed by a plating method or the like.

The heat radiation layer 70 according to the second embodiment is a thin film made of a high heat conductive material. The method for forming the heat dissipation layer 70 will be described below.

After the case 10 is set in a vacuum chamber and the inside of the vacuum chamber is evacuated to a vacuum, methane and hydrogen gas are introduced. When a high-frequency voltage is applied using the case 10 as a cathode to generate plasma, methane is decomposed and adheres to the surface of the case 10 as a diamond-like thin film.

This is what is called a plasma CVD method. At this time, in some cases, an adhesion layer such as a silicon thin film may be formed in advance to improve the adhesion between the case 10 and the diamond-like thin film.

The diamond-like thin film has a very high thermal conductivity because its structure is very similar to diamond. Therefore, the heat radiation efficiency to the outside air is improved.

Further, the diamond-like thin film may contain diamond crystals by increasing the plasma energy or increasing the temperature.

At this time, the thermal conductivity is further improved, and fine projections appear on the surface of the thin film due to the crystal particles, and the effect of increasing the surface area is added, so that the heat radiation efficiency can be further improved.

This diamond-like thin film has essentially no reflection of visible light and has a very high-grade black color, and is valuable as a watch exterior.

The heat radiation layer 70 in the third embodiment is a surface-altered layer of the case itself having minute irregularities. The method of forming the heat radiation layer 70 will be described below. This is a method in which the surface itself of the case 10 is treated by a physical or chemical method to form irregularities, and the heat radiation layer 70 is provided.

A ceramic powder having a size of about 10 μm is sprayed on the case 10 by the force of compressed air. This is the so-called honing method.

The surface of the case 10 is mechanically roughened by the honing method, so that irregularities on the order of 10 μm also occur. Since the unevenness increases the surface area, the heat radiation efficiency is greatly improved.

Furthermore, the method of providing the case 10 with irregularities can also be realized by plasma etching or chemical etching using an etchant such as an acid.

Alternatively, when the case 10 is subjected to the electrolytic oxidation treatment, the film becomes porous and irregularities can be formed.

For example, when the case 10 is made of aluminum, a typical example is to form an alumite film by electrolytic oxidation treatment in an acid such as oxalic acid.

Further, a combination of the above-described various heat radiation layers 70 as the heat radiation layer 70 has a still greater effect. One of them is to form a diamond-like thin film on the surface of the case 10 having the unevenness formed by the honing method.

By such means, the surface of the case 10 has the two characteristics of increasing the surface area due to the unevenness and improving the thermal conductivity, and the heat radiation efficiency is further improved.

The effect of the heat radiation layer 70 formed by each method described in this embodiment will be described with reference to FIG.

Only the front surface of the case 10 made of stainless steel is subjected to surface treatment, a heat radiation layer 70 is provided, and the temperature of the back surface is measured. At the time of measurement, the back surface is heated by a heater having a temperature higher than room temperature.

FIG. 2 shows the temperature change on the back surface of the case 10 subjected to the surface treatment as a difference from the back surface temperature of the case 10 not subjected to the surface treatment.

As shown in the graph of FIG. 2, the temperature of the case 10 where no surface treatment is performed is finally about 35 ° C. Room temperature is about 25 ° C.

In the graph of FIG. 2, curve a shows the case where a diamond-like thin film is used for the heat dissipation layer 70, curve b shows the case where the heat dissipation layer 70 is a surface treatment by honing, and curve c shows the case where the heat dissipation layer 70 is used. The case where the honing treatment and the diamond thin film are combined is shown, the curve d shows the case where the heat radiation layer 70 is a black ion plating film, and the curve e shows the temperature change when the heat radiation layer 70 is a fine particle film. ing.

As can be seen from FIG. 2, it can be seen that the temperature of each of the cases 10 subjected to the surface treatment is lower than that of the untreated case 10, and that the heat radiation effect is improved. .

The temperature drop is from −0.7 ° C. to −1.9 ° C., and considering that the temperature difference between the back cover 20 and the case 10 of the conventional thermoelectric wristwatch is about 2 ° C. The heat radiation effect is very large, indicating that it is possible to increase the power generation output from 0.8 to 2.8 times the conventional value.

In the embodiment of the present invention, the thermoelectric generation element 60 is installed so as to be sandwiched between the back cover 20 and the module cover 53, but the hot junction 61 contacts the back cover 20 and the cold junction There is no problem if 62 is in another position as long as it is in thermal contact with case 10. For example, it is conceivable to install module 62 around module 50 and module cover 53 so as to directly contact case 10. .

At this time, in order to bring the thermoelectric generator 60 into close contact with the case 10 and the back cover 20, an elastic plastic may be used as the material of the thermal insulator 40, and its deformation may be used.

Further, in the embodiment of the present invention, a BiTe alloy is used as the thermoelectric generator 60. However, a single material such as Bi, Sb, Te, or Si, or a material such as FeSi alloy or CrSi alloy may be used. it can.

[0069]

[Effects of the Invention] As is clear from the above description, in the present invention, the case of the thermoelectric generation wristwatch is subjected to surface treatment, and a heat radiation layer having minute irregularities on the surface or made of a high heat conductive material is provided.

As a result, it is possible to lower the temperature of the case as compared with the conventional case, and to obtain a large temperature difference from the case back. As a result, the built-in thermoelectric power generation element can obtain a considerably higher power generation output than before. In other words, by adopting the structure of the present invention, it is possible to provide a thermoelectric power generation wristwatch that can perform more stable driving than before and has a longer operating life.

Further, since the heat radiation layer in the present invention is formed entirely of a thin film or is a surface alteration layer of the case itself, the appearance is not uncomfortable and the value of the watch as a decorative article is not lost. The structure of the present invention can be applied to increase the efficiency of other electronic devices that use thermoelectric elements as energy sources in the future.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a thermoelectric wristwatch according to an embodiment of the present invention.

FIG. 2 is a graph showing a temperature change in a case subjected to various surface treatments in the embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional thermoelectric wristwatch.

FIG. 4 is a diagram showing output characteristics when the number of thermocouples or a given temperature difference of a general thermoelectric power generation element is changed.

[Explanation of symbols]

10: Case 20: Back cover
40: Thermal insulator 50: Module 53: Module cover 60: Thermoelectric generator 61: Hot junction 62: Cold junction 70: Heat dissipation layer

Claims (2)

[Utility model registration claims] 1. A thermoelectric generator, comprising a metal case, a thermal insulator, a back cover, a module and a plurality of thermocouples, wherein the thermoelectric generator is disposed such that its hot junction is in contact with the back cover. A thermoelectric power generation wristwatch, wherein a heat dissipation layer is provided only on a surface of a metal case that does not include a thermal insulator and a back cover, and is provided between a case and a back cover so that a contact is in contact with the case. 2. The thermoelectric wristwatch according to claim 1, wherein the heat radiating layer is a thin film made of a material having high thermal conductivity.