JP2006132844A - Electronic cooling element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize a cooling characteristic by a simple constitution in a cooling element using an electron tunnel effect. <P>SOLUTION: This electronic cooling element using the electron tunnel effect emits electrons into a vacuum space from a negative electrode by applying a negative voltage to the negative electrode of two metal plates facing in proximity through the vacuum space, and applying a positive voltage to a positive electrode, and traps the emitted electrons on the positive electrode side. In this case, the ductility of the negative electrode and the positive electrode is made different to provide a compact cooling device obtaining the cooling characteristic remarkably stabilized in comparison with a conventional structure and showing the same degree of performance as a compressor type. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of an electronic cooling element using an electron tunnel effect.

  At present, compressors are generally used in refrigerators and freezers. However, due to an increase in environmental protection orientation, a defluorocarbon cooling mechanism such as a Stirling engine has been demanded. On the other hand, a Peltier device is generally used as a cooling mechanism for small electronic components such as lasers.

  Although compressors and Stirling engines have high cooling performance, there is a disadvantage that the cooling system becomes large from the point of operation principle. On the other hand, although the Peltier element is small, it has a demerit that the cooling performance is reduced to about half compared to a compressor.

  In order to solve the above disadvantages, there is a demand for the development of a device that is as small as a Peltier device and that has a cooling performance similar to that of a compressor. Cooling using the electron tunnel effect is one of the candidates for such devices. An element is mentioned.

  Hereinafter, the structure of the cooling element using the electron tunnel effect will be described with reference to US Pat. No. 5,722,242 of Patent Document 1. As shown in FIG. 7, the cooling element includes a cathode 91 and an anode 92, a power supply 93 for supplying a current by applying a negative voltage and a positive voltage to these electrodes, and both electrodes (cathode 91 and It comprises a low work function material 94 coated on the surface of the anode 92).

  The cathode 91 and the anode 92 are arranged to face each other by a spacer 96 disposed between both electrodes, and a vacuum space 95 having an interval of 0.1 to 1 μm is formed between both electrodes. The low work function material 94 is a material that emits tunnel electrons and thermoelectrons 97 at an operating temperature, and a material having a work function of about 0.6 eV is used. Examples of such work functions include cesium compounds (TaCs, MoCs, CCs, NiCs, etc.), and organic compounds containing alkali metals (alkalides, electrides, etc.).

  With the above configuration, tunnel electrons and thermal electrons 97 supplied with thermal energy by the electrode in contact with the low work function substance 94 are emitted from the surface of the low work function substance 94 into the vacuum space 95. When a voltage is applied as shown in FIG. 9 using the power supply 93, tunnel electrons and thermoelectrons 97 are emitted from the cathode 91, move through the vacuum space 95, and are taken into the anode 92. When tunnel electrons and thermoelectrons 97 are emitted from the cathode 91, the cathode 91 is cooled because the heat of the cathode 91 is taken away. On the other hand, the temperature of the anode 92 to which the tunnel electrons having kinetic energy and the thermoelectrons 97 are supplied rises when the heat energy is supplied. In this way, the anode 92 is heated at the same time as the cathode 91 is cooled.

  Moreover, about the cooling system using the said electronic cooling element, it describes in patent document 2 and patent document 3, for example.

  The thermoelectric heat pump device described in Patent Literature 2 includes a heat pump unit, an ammeter, a thermometer, a power source, and a control unit that controls these. The heat pump unit includes a cathode and an anode, and a low work function material disposed on the opposing surfaces of these electrodes. An ammeter and a power source are provided between the cathode and the anode. The ammeter is for measuring the current flowing between the cathode and the anode. The thermometer is for measuring the temperature of the cooling medium, and is provided on the cathode side. The control means is connected to each of the ammeter, the thermometer, and the power source. In the electronic cooling system of Patent Document 2, the temperature of the cathode and the amount of current flowing between the cathode and the anode are monitored by the control means, and the voltage amount of the power supply is adjusted so as to maximize the cooling efficiency. It is.

  The thermoelectronic device described in Patent Document 3 includes a casing, a heat exchange mechanism installed in the casing, and a primary side passage (indoor air flow path) and a secondary side separated by the heat exchange mechanism. It consists of two passages, a passage (outside air flow path). The heat exchange mechanism has a thermoelectric element in which a space between the cathode and the anode is maintained in a vacuum state, and is disposed on both or one of the facing surfaces of the cathode and the anode. It has nanostructures made of conductive materials such as

In the Example described in the said patent document 3, it describes that switching of cooling / heating is possible by switching the voltage applied to the said thermoelectric element. For example, when the primary side passage of the thermoelectric element is a cathode and the secondary side passage is an anode, the indoor air in the primary side passage is cooled by the thermoelectric element, so that the thermoelectric element functions as a cooler. . On the other hand, when the primary side passage is an anode and the secondary side passage is a cathode, the indoor air is heated by the electronic cooling element, so that the heat exchanger functions as a heater.
US Pat. No. 5,722,242 (published March 3, 1998) JP 2002-333230 A (published on November 22, 2002) JP 2003-258326 A (published September 12, 2003) International Publication No. 99/13562 (published March 18, 1999) APPLIED PHYSICS LETTERS, Vol.78, No.17, p.2572 (2001)

  However, when the elements described in Patent Documents 1 to 3 are actually used, the space between the cathode and the anode is evacuated and the vacuum space is reduced in order to realize a cooling capacity comparable to that of a conventional compressor. The distance needs to be very narrow.

  Hereinafter, with reference to Non-Patent Document 1, the cooling function index (COP) of the electronic cooling element when the work function of the low work function material on the electron emission side is 0.6 eV and the vacuum space distance d is changed is estimated. The results are shown in FIG. This estimate is made assuming that the initial internal temperature is 52 ° C. and the internal temperature is cooled to 7 ° C.

  FIG. 8 shows the cooling performance index (COP) of the compressor when the interior is cooled from 52 ° C. to 7 ° C. by the compressor, that is, when the temperature difference between the initial interior temperature and the intended interior temperature is the same. = 1.0) is indicated by a broken line. As shown in the figure, in order to realize the cooling performance equivalent to that of a compressor by the electronic cooling element, it is necessary to keep the distance of the vacuum space between the anode and the cathode constituting the electronic cooling element at 5 nm or less. is there.

  The cooling performance index (COP) also depends on the work function of the electrode material, and tends to be higher as the work function of the low work function material on the electron emission side is lower. However, since a general low work function substance has a very high activity on the material surface, it has a high reactivity with moisture and oxygen in the atmosphere, and it is very difficult to maintain its characteristics. Therefore, when a material having a work function of about 0.6 eV as described above is used as a low work function substance on the electron emission side, it is indispensable to maintain a high degree of vacuum in the vacuum space portion of the electronic cooling element. is there.

  However, in the structure of the conventional cooling element shown in FIG. 7, when the vacuum space distance d of the vacuum space 95 between the cathode 91 and the anode 92 is 5 nm or less, it is greatly affected by the external atmospheric pressure. The problem of electrode deformation occurs.

  Further, when the conventional cooling element shown in FIG. 7 is operated, since the cathode 91 side is cooled and the anode 92 side is heated, deflection due to thermal stress occurs in each electrode, so that it is as narrow as 5 nm or less. It is very difficult to always maintain the width of the vacuum space 95.

  As described above, in the electronic cooling element using the electron tunnel effect, the vacuum space distance of the vacuum space 95 between the cathode 91 and the anode 92 is set to 5 nm or less in order to obtain stable cooling characteristics. is there. However, the vacuum space 95 is deformed due to the deformation of the electrodes (cathode 91 and anode 92) due to atmospheric pressure and the influence of the electrode deflection due to temperature. For this reason, the above conditions cannot be maintained, and as a result, there arises a problem that the cooling characteristics of the cooling element are remarkably deteriorated.

  With respect to the above problem, Patent Document 4 proposes a method of controlling a vacuum space with a mechanical piezoelectric motor or an electromagnetic actuator. In this document, as shown in FIG. 9, in addition to the cathode 111 and the anode 112 and the power source 117 in the vacuum space 114, the space gap 113 which is the distance between the cathode 111 and the anode 112 is detected (sensing). ) Sensing means 116, and an actuator 115 that drives the cathode 111 based on the detection result of the sensing means 116. However, such a configuration requires a means for feeding back the detection result of the sensing means 116 to the actuator, so that there is a problem that the cooling system becomes complicated.

  The present invention has been made in view of the above-described problems, and its purpose is to suppress a change in the inter-electrode distance that occurs when a cooling element is operated by a simple structure. An object of the present invention is to provide an electronic cooling element that can exhibit cooling characteristics.

  The inventors of the present invention have studied to solve the above problems, and as a result, by using the following new means, even if the electrode is bent due to the change in temperature, the cathode plate, the positive voltage, and the anode It has been found that the vacuum gap between the plates can be maintained at a distance of, for example, 5 nm or less.

  That is, in order to solve the above-described problem, the electronic cooling element of the present invention includes a cathode plate that applies a negative voltage and an anode plate that applies a positive voltage, and performs cooling by the electron tunnel effect. In the above, the cathode plate and the anode plate are characterized by having different deformability with temperature change.

  With the above configuration, even if the electrode plate is bent due to heat generation or heat absorption in the cathode plate and the cathode plate of the electronic cooling element (hereinafter referred to as “electrode plate” unless they are distinguished from each other), The distance (vacuum gap) can be maintained at, for example, 5 nm or less. For this reason, even when the temperature of the electrode changes by performing cooling by the electron tunnel effect, the electronic cooling element having the above configuration can obtain stable cooling characteristics. In addition, it is possible to minimize the influence of heat loss generated in the electronic cooling element due to the change in the vacuum gap.

  That is, in the present invention, by making the deformability of the cathode plate and the anode plate different, even when the electrode plate is bent due to a change in temperature, the vacuum space between the cathode plate and the anode plate is increased. For example, since it can be controlled within a preferable range of 5 nm or less, the electron tunnel effect can be stably exhibited.

  In the present invention, “different deformability” means that the change in shape when the temperature is changed under the same conditions, in other words, the change in shape when the temperature is changed under different conditions is substantially the same. Say. When the electron cooling element of the present invention is cooled by the electron tunnel effect, different temperature changes occur between the cathode plate and the anode plate. When the different temperature changes occur, the cathode plate and the anode plate The vacuum space between the electrode plates can be controlled by making the deformability of the cathode plate and the anode plate different so that substantially the same shape change occurs on the facing surface. Thereby, the expression of a stable electron tunnel effect can be maintained.

The shape change can be specified by a “deflection amount” that is a displacement amount from an initial state of the opposing surfaces of the cathode plate and the anode plate when a direction from the cathode plate to the anode plate is defined as a positive direction. . In the electronic cooling element of the present invention, the difference in the amount of deflection between the cathode plate and the anode plate at the temperature reached by each electrode when cooling is preferably 5 nm or less. Further, in order to maintain a vacuum gap of 5 nm, a spacer may be provided between the electrodes using SiO ₂ or the like. However, in order to reduce the load on the spacer, the difference in deflection is more preferably 3.0 nm or less. preferable. For example, if the temperature of the cathode plate is 7 ° C. and the temperature of the anode plate is 52 ° C. when the electronic cooling element is cooled, the deflection amount of the cathode plate and the deflection amount of the anode plate at these temperatures. Is preferably within the above range, and more preferably the deflection amount is substantially the same.

  The cathode plate and the anode plate of the electronic cooling element of the present invention are provided with a dish-like portion that forms a hollow structure portion on the opposite surface to the opposed surfaces, and the pressure in the hollow structure portion is outside the electronic cooling device. It is preferable that the pressure is set to be lower than that.

  As described above, a hollow structure is formed on the opposite surface of the cathode plate and the anode plate, and the pressure of the vacuum space is made lower than the atmospheric pressure outside the electronic cooling element. As a result, it is possible to prevent the influence of atmospheric pressure on the opposing surfaces of the cathode plate and the anode plate that exhibit the electron tunnel effect. That is, the hollow structure portion is formed by the dish-like portion provided on the side opposite to the facing surface, and the interior thereof is maintained at a predetermined pressure, whereby the vacuum space between the cathode plate and the anode plate and the atmospheric pressure Deflection between the cathode plate and the anode plate due to the difference can be buffered by the hollow structure portion.

  By setting the pressure in the hollow structure portion lower than the pressure outside the electronic cooling element, it is possible to buffer the influence from the outside, but the pressure in the vacuum space between the cathode plate and the anode plate ( The degree of vacuum is preferably set substantially the same. The pressure in the hollow structure part is preferably 100 Pa or less, which is preferable as the pressure of the vacuum space, for example.

  In addition, the hollow structure portion may be formed so as to cover the entire surface opposite to the region where electrons are emitted and the region where the emitted electrons are trapped (captured) on the opposing surfaces of the cathode plate and the anode plate. preferable. Thereby, the influence of the atmospheric pressure on the entire facing surface can be removed.

  Ar can be preferably used as the vacuum sealed gas sealed between the cathode plate and the anode plate and in the hollow structure portion.

  In the electronic cooling element of the present invention, the cathode plate and the anode plate may be made of the same material and have different thicknesses.

  With the above configuration, the deformability of the cathode plate and the anode plate can be made different, so that the vacuum gap can be maintained even when a deflection occurs due to the temperature change of these electrodes. For this reason, for example, it is possible to control the vacuum gap to 5 nm or less, and it is possible to realize an electronic cooling element that stably exhibits the electron tunnel effect.

  In addition, the ratio between the thickness of the cathode plate and the thickness of the anode plate is such that, when cooling is performed by the electron tunnel effect, the difference in shape change due to the temperature difference between the cathode plate and the anode plate is reduced. It is preferable that they are set as follows.

  With the above-described configuration, the vacuum gap between the cathode plate and the anode plate can be maintained, so that an electronic cooling element that stably exhibits the electron tunnel effect can be realized. By setting the ratio between the thickness of the cathode plate and the thickness of the anode plate as described above, that is, by increasing the thickness of the anode plate in proportion to the increase in the thickness of the cathode, The shape of the vacuum space (vacuum gap) can be maintained.

  In the electronic cooling element of the present invention, the cathode plate and the anode plate may be made of different materials and have the same thickness.

  With the above configuration, even when the cathode plate and the anode plate are bent due to temperature changes, the electron tunnel effect can be stably generated in the vacuum space (vacuum gap) between the cathode plate and the anode plate. Can be maintained at such a distance. That is, when the cathode plate and the anode plate have the same thickness, by making the materials different from each other, the deformability of the two can be made different. For example, the vacuum gap can be maintained at 5 nm or less. Therefore, the electron tunnel effect of the electronic cooling element can be stably expressed.

Examples of the combination of the different materials include a combination of Cu or In as the material of the cathode plate and Au as the material of the anode plate. By the above combination, it is possible to reduce the difference in deflection between the cathode plate and the anode plate due to the temperature change due to cooling. The electronic cooling element of the present invention is at least one of the cathode plate and the anode plate. However, it is a laminated structure of the first material and the second material, and the first material and the second material may have different deformability. Thus, the deformability can be easily adjusted by forming the cathode plate and / or anode plate in a laminated structure. For this reason, even when a deflection occurs in the cathode plate and the anode plate due to a temperature change, the vacuum gap between them can be controlled to a desired range. Moreover, as said laminated structure, it shall consist of a combination of Cu and Fe, for example.

  In the electronic cooling element of the present invention, it is preferable to form a planarizing layer having a surface roughness of 2.5 nm or less on the opposing surfaces (counter electrode surfaces) of the cathode plate and the anode plate. As a result, even when deflection occurs in the cathode plate and the anode plate due to temperature change, it is possible to more reliably realize control of the electrode gap to 5 nm or less, so that the electron tunnel effect can be expressed more stably. Become.

  Further, in the electronic cooling element of the present invention, a cooling effect comparable to that of a compressor can be obtained by forming a low work function material on the flattening layer formed on the opposing surfaces of the cathode plate and the anode plate. Is possible.

  As described above, in the electronic cooling element of the present invention, since the cathode plate and the anode plate have different deformability due to temperature change, even when electrode deflection occurs due to temperature change, the electron tunnel There is an effect that it is possible to control the distance of the vacuum space between the electrodes that exert the effect to, for example, 5 nm or less.

  In the electronic cooling element of the present invention, the cathode plate and the anode plate each include a dish-like portion that forms a hollow structure portion on a surface opposite to the facing surface, and the pressure in the hollow structure portion is reduced to an electron. Since the pressure is set lower than the pressure outside the cooling element, it is possible to prevent the influence of atmospheric pressure on the cathode plate and the anode plate that develop the electron tunnel effect.

[Embodiment 1]
A first embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 shows the present invention using an electron tunnel effect in which the same material is used for a cathode plate and an anode plate, and the deformability of the cathode plate and the anode plate is made different by making the thicknesses of the two different. It is a block diagram which shows the outline of embodiment of an electronic cooling element.

  First, the schematic structure of the electronic cooling element of the present embodiment will be described with reference to FIG. Of the reference numerals assigned to the members in the figure, 11 is a cathode plate-like portion (cathode plate), 21 is an anode plate-like portion (anode plate), 13 is a planarizing material, 14 is a vacuum space, 15 is Spacer, 16 is a vacuum seal, 12 is a cathode plate-like portion, 22 is an anode plate-like portion, 17 is a cathode plate-like portion 11 and cathode plate-like portion 12, and the anode plate-like portion 21 and The hollow structure part 17 formed in the anode by the anode dish-like part 22 is shown. Reference numeral 10 denotes a cathode composed of the cathode plate portion 11 and the cathode dish portion 12, and 20 denotes an anode composed of the anode plate portion 21 and the anode dish portion 22.

  As the material for the cathode plate-like portion 11, the anode plate-like portion 21, the cathode plate-like portion 12, and the anode plate-like portion 22, materials having high thermal conductivity such as Cu and W are desirably used. More specifically, a material having a thermal conductivity in the range of 100 to 450 W / (m · K) is preferably used.

  As shown in FIG. 1, the cathode 10 and the anode 20 are provided with a hollow structure portion 17. The hollow structure portion 17 is provided to buffer stress on the cathode plate portion 11 and the anode plate portion 21 due to external force (atmospheric pressure). The hollow structure portion 17 is formed on the cathode 10 and the anode 20, respectively, on the opposite side of the region of the cathode plate-like portion 11 that emits electrons and the region of the anode plate-like portion 21 that traps (captures) the emitted electrons. It is formed so as to cover the entire surface. For this reason, since the influence on the cathode plate-like portion 11 and the anode plate-like portion 21 due to external force can be buffered by the hollow structure portion 17, the shape of the vacuum space 14 can be maintained.

  Here, in order to buffer the influence of the atmospheric pressure on the shape of the vacuum space 14 by the hollow structure portion 17, the inside of the hollow structure portion 17 is maintained at a pressure that can cancel the influence of the atmospheric pressure. Need to be. That is, no voltage is applied to the electronic cooling element (electronic cooling device), the cathode 10 and the anode 20 are at room temperature (the electronic cooling element is not operating), and the voltage is applied to the electronic cooling element. In any state where the temperature difference between the cathode 10 and the anode 20 is generated (the state where the electronic cooling element is operating), the hollow structure portion 17 has a pressure at which the above function can be exhibited. It is said that.

  By making the internal pressure less than atmospheric pressure, the hollow structure portion 17 can exhibit the above function, but the pressure in the hollow structure portion 17 should be substantially the same as the pressure in the vacuum space 14. preferable. Specifically, as described later, since the pressure (degree of vacuum) in the vacuum space 14 is preferably 100 Pa or less, the pressure in the hollow structure portion 17 is also preferably 100 Pa or less.

  Moreover, as shown in FIG. 1, the planarizing material 13 is formed in layers over substantially the entire surface of the cathode plate-like portion 11 and the anode plate-like portion 21 that face each other. The planarizing material 13 is formed in order to keep the shape of the vacuum space 14 between the planarizing materials 13 constant. Specific examples of the planarizing material 13 include Si and Ta. The surface roughness of the planarizing material 13 can be set as appropriate according to the width of the vacuum space 14. For example, when the width of the vacuum space 14 is 5 nm, the surface roughness of the planarizing material 13 is 2. .5 nm or less. Here, the surface roughness means the same as the surface roughness and means an average value of the size of the unevenness on the surface of the planarizing material 13.

In order to stably maintain the width of the vacuum space 14 of the electronic cooling element, that is, the narrow gap between the planarizing materials 13, spacers 15 are inserted between the planarizing materials 13. In order to maintain a narrow gap between the planarizing materials 13, it can be said that providing the physical stabilizing means such as the spacer 15 is the best countermeasure. As the spacer 15, an insulator such as SiO ₂ or alumina, or a material having high electrical conductivity and low thermal conductivity such as fullerene can be used.

  In the electronic cooling element of the present embodiment, as shown in FIG. 1, a vacuum seal 16 is provided between the cathode 10 and the anode 20 in order to maintain the degree of vacuum in the vacuum space 14. The material of the vacuum seal 16 is preferably an insulator having a relatively low thermal conductivity, and for example, low melting glass can be used.

  In the electronic cooling element of the present embodiment, since the circular plates are used as the cathode plate-like portion 11 and the anode plate-like portion 21, the electronic cooling element of the present embodiment has a circular shape.

  When a negative potential is applied to the cathode 10 and the positive potential to the anode 20 of the electron cooling element having the above-described configuration, electrons move from the cathode plate-like portion 11 to the planarizing material 13 and pass through the vacuum space 14 to pass through the anode plate. The state portion 21 is reached. At that time, since heat is transferred by tunnel electrons or thermoelectrons passing through the vacuum space 14, the cathode plate-like portion 11 is cooled and the anode plate-like portion 21 is heated.

  FIG. 2 shows an enlarged cross-sectional view of a portion indicated by A in the vacuum space 14 of FIG. The schematic structure of the vacuum space 14 will be described with reference to FIG. In this figure, the same members as those in FIG. 1 are denoted by the same reference numerals, 13 is a planarizing material, 15 is a spacer, 23 is a low work function material, and 14 is a vacuum space. Thus, the layer of the low work function material 23 is formed on the surface of the planarizing material 13 in a region not in contact with the spacer 15. Since the low work function material 23 is a very thin film having a thickness of 5 nm or less, contact with the spacer 15 may cause a crack in the film of the low work function material 23 or peeling of the film. . For this reason, in the electronic cooling element of the present embodiment, the low work function material 23 is not formed at the contact portion between the planarizing material 13 and the spacer 15.

  Examples of the low work function material 23 include cesium compounds (TaCs, MoCs, CCs, NiCs, etc.), organic compounds containing alkali metals (alkalides, electrides, etc.), calcium compounds (WCa, CaB6, etc.), carbon nanotubes, and alkali metals. Inorganic compounds (alkalide, electride, etc.) are included. Further, the low work function material 23 may be a material in which electrons are injected into the above-described material.

  The degree of vacuum (pressure) of the vacuum space 14 necessary for maintaining the cooling characteristics of the electronic cooling element having the above configuration will be described. By transporting tunnel electrons or thermoelectrons from the cathode plate portion 11 to the anode plate portion 21 by the electron tunnel effect, the cathode plate portion 11 side is cooled and the anode plate portion 21 side is heated. As described above, when the pressure in the vacuum space 14 increases, the number of gas molecules existing in the vacuum space 14 increases. For this reason, since gas molecules move in addition to the thermoelectrons from the cathode plate-like portion 11 on the cooling side to the anode plate-like portion 21 on the heating side, the cooling characteristics of the electronic cooling element are impaired. The problem occurs.

  FIG. 3 is a graph showing the relationship between the degree of vacuum in the vacuum space 14 and the cooling amount of the electronic cooling element. The figure shows the relationship between the decrease in the degree of vacuum in the vacuum space 14 (increase in pressure) and the cooling amount when the initial value of the pressure in the vacuum space 14 is 10 Pa. From the content of the figure, when the pressure in the vacuum space 14 becomes 100 Pa, which is 10 times the initial value, the amount of decrease in the cooling amount is only 6% compared to the initial value (10 Pa: about 3.9 W). It turns out that it is. On the other hand, when the pressure in the vacuum space 14 is 1000 Pa, which is 100 times the initial value, the cooling amount is reduced by 61% compared to the initial value. Since the reduction amount with respect to the initial value of the cooling amount needs to be suppressed within 10% at most, according to FIG. 3, in order to satisfy such a condition (suppress the reduction amount within 10%), the inside of the vacuum space 14 It can be seen that the degree of vacuum should be 100 Pa or less.

[Examples and Comparative Examples]
(About the influence of the thickness of the cathode plate-like part 11 and the anode plate-like part 21)
As for the electronic cooling element having the structure shown in FIG. 1 described above, the cathode plate-like portion 11 and the anode plate-like portion 21 have different thicknesses, and the cathode plate-like portion 11 and the anode plate-like portion. The present invention will be described in more detail with reference to a comparative example having the same thickness as 21. However, the present invention is not limited to these.

  In the present example and the comparative example, the following equation (1) was obtained when the amount of heat moving in the vacuum space was obtained.

q = Λ × p × S × ΔT (1)
q: amount of heat transferred from the high temperature side to the low temperature side, Λ: gas free molecular conductivity (0.67 m / s · K), p: degree of vacuum between electrodes, S: vacuum partial contact electrode area, ΔT: high temperature part And the low temperature part (45 ° C. in this embodiment).

  The following examples and comparative examples assume the case where the internal temperature is lowered to 7 ° C. with respect to the indoor temperature of 27 ° C. Further, the volume of the indoor space that releases heat by the anode 20 is sufficiently larger than the volume of the internal space on the side cooled by the cathode 10, and the temperature change in the indoor space caused by the discharge of heat by the anode 20 can be ignored. It was supposed to be.

  As described above, in the electronic cooling element of the present embodiment, the end portions of the cathode plate-like portion 11 and the anode plate-like portion 21 are fixed by the vacuum seal 16. For this reason, the influence of the deflection | deviation by a thermal stress is suppressed in these edge parts. On the other hand, since the vicinity of the central part of the cathode plate-like portion 11 and the anode plate-like portion 21 is not fixed at all, it is greatly affected by deflection due to thermal stress. Therefore, in the following, the amount of deflection at the central part of the cathode plate-like portion 11 and the anode plate-like portion 21 which is considered to have the maximum deflection will be described as the amount of deflection.

  As shown in FIG. 1, a spacer 15 is provided near the center of the cathode plate portion 11 and the anode plate portion 21 with a planarizing material 13 interposed therebetween. Is not intended to prevent the cathode plate-like portion 11 and the anode plate-like portion 21 from being bent.

[Example 1]
In the electronic cooling element of this example, the cathode plate-like portion 11 and the anode plate-like portion 21 constituting the cathode 10 and the anode 20 are a circular Cu plate having a thickness of 1.0 mm and a circle having a thickness of 1.19 mm. A Cu plate was used. The cathode plate-like portion 11 and the anode plate-like portion 21 were the same circular Cu plates having a diameter of 11.5 mm except that the thicknesses were different. As the cathode dish-shaped part 12 and the anode dish-shaped part 22, the petri dish-shaped thing provided with the edge part in the circular Cu board whose diameter is 11.5 mm was used, respectively. Thus, in this embodiment, the shape of the vacuum space 14 formed in each of the cathode 10 and the anode 20 is the same.

As the planarizing material 13, a circular Si plate having a surface roughness of 2.5 nm or less and a thickness of 0.25 mm was used. In order to set the width of the vacuum space 14 to 5 nm, SiO ₂ was used as the spacer 15 and low melting glass was used as the vacuum seal 16.

[Comparative Example 1]
Except for the cathode plate-like portion 11 and the anode plate-like portion 21 being circular Cu plates having a thickness of 0.3 mm, the electronic cooling element of this comparative example was configured in the same manner as in Example 1 above.

[Discussion]
Table 1 shows the results of measuring the deflection amount of the electronic cooling elements of Example 1 and Comparative Example 1 described above. The table shows that the temperature of the cathode plate-like portion 11 is 7 ° C., the temperature of the anode plate-like portion 21 is 52 ° C., and the room temperature is lowered to 7 ° C. when the room temperature is 27 ° C. The deflection amount produced in the cathode plate-like portion 11 and the anode plate-like portion 21 of Example 1 and Comparative Example 1 is shown.

  In the electronic cooling element of Comparative Example 1 in which the cathode plate-like portion 11 and the anode plate-like portion 21 having the same thickness are formed by a circular Cu plate having the same structure, the maximum deflection amount of the cathode plate-like portion 11 is 10530 nm, the anode The maximum deflection amount of the plate-like portion 21 is 80530 nm. In the examples and comparative examples, the positive direction of the deflection is defined as the direction from the cathode plate portion 11 toward the anode plate portion 21, and therefore, in the cathode plate portion 11 and the anode plate portion 21, both It can be seen that there is a deflection in the same direction.

  Thus, in the electronic cooling element of Comparative Example 1 having the conventional structure in which the cathode plate-like portion 11 and the anode plate-like portion 21 have the same thickness (0.3 mm), the cathode plate-like portion 11, the anode plate-like portion 21, Therefore, it is impossible to maintain the width (vacuum space distance, vacuum gap) of the vacuum space 14 at 5 nm.

  On the other hand, Example 1 of the present invention has a structure in which the thickness of the cathode plate-like portion 11 is 1.0 mm, the thickness of the anode plate-like portion 21 is 1.19 mm, and the deformability of both is different. The maximum amount of deflection of the electrode-like portion 11 and the anode plate-like portion 21 is the same as 2890 nm. For this reason, it is possible to suppress the influence due to the difference in deflection amount between the cathode plate-like portion 11 and the anode plate-like portion 21 due to the temperature change, and to maintain the width of the vacuum space 14 at 5 nm.

  In the above examples and comparative examples, the following formula (2) was used as a formula for obtaining the deflection amount w (m). In this embodiment and the comparative example, the “deflection amount” means the cathode plate-like portion 11 or the anode plate-like portion 21 before the electronic cooling element is actuated and when the internal space is actuated to a desired temperature. The amount of change in the position along the direction of the deflection amount of the side surface (opposing surface) of the vacuum space 14.

w = 3 × P × a ⁴ × (1−ν ² ) / (16 × E × h ³ ) (2)
Here, E is the longitudinal elastic modulus or Young's modulus (GPa), a is the electrode radius (m), ν is the Poisson's ratio, and h is the electrode thickness (m) (the cathode plate-like portion 11 for obtaining the deflection amount and Value for anode plate portion 21).

  Moreover, P has shown the pressure (Pa) of the vacuum space 14, and is represented by following formula (3).

P = K × E × (T2-T1) × h ² (3)
K is the curvature coefficient (1 / ° C.) of the cathode plate-like portion 11 or anode plate-like portion 21, T ₁ is the temperature (° C.) of the cooling portion and the heat generating portion, and T ₂ is the room temperature (° C.).

  According to the above equation (2), the amount of deflection is inversely proportional to the cube of the electrode thickness h (m), so it may be sufficient to simply increase the thickness of the cathode plate portion 11 or the anode plate portion 21. Conceivable. However, for example, in order to make the vacuum space distance 5 nm or less while making the cathode plate-like portion 11 and the anode plate-like portion 21 the same thickness as in Comparative Example 1, the electrode thickness h is set to The thickness needs to be 2.5 mm, which is about 8 times the set thickness (0.3 mm). In this case, since the merit as a small cooling element of an electronic cooling element is lost, it is not practical.

(Optimal thickness ratio between cathode plate and anode plate)
The optimum thickness ratio between the cathode plate-like portion 11 and the anode plate-like portion 21 constituting the electronic cooling element varies depending on how many times these temperatures are set when cooling is performed. Therefore, in order to maintain the width of the vacuum space 14 when the temperature of the cathode plate-like portion 11 is 7 ° C. and the temperature of the anode plate-like portion 21 is three types (52 ° C., 39 ° C., 26 ° C.). The optimum optimum thickness of the anode plate portion 21 was determined. The temperatures of the cathode plate portion 11 and the anode plate portion 21 are measured in a non-contact manner using a radiation thermometer.

  In FIG. 4, the horizontal axis is defined as the thickness of the cathode plate-shaped portion 11 (cooling side), the vertical axis is defined as the thickness of the anode plate-shaped portion 21 (heat radiation side), and the temperatures of the anode plate-shaped portion 21 are the above three temperatures. In this case, it is a diagram showing a change in the optimum thickness of the anode plate portion 21 that is optimal for controlling the width of the vacuum space 14 (vacuum space distance) to 5 nm or less. As is apparent from the figure, the thickness of the cathode plate-like portion 11 and the optimum thickness of the anode plate-like portion 21 for maintaining the width of the vacuum space 14 are in a proportional relationship.

  It can also be seen that the optimum thickness of the anode plate portion 21 for maintaining the width of the vacuum space 14 at 5 nm or less is proportional to the temperature of the anode plate portion 21. That is, in any case where the thickness of the cathode plate-like portion 11 is 1, 2, 3, 4 and 5 nm, the optimum thickness when the temperature of the anode plate-like portion 21 is 39 ° C. and 56 ° C. is respectively When the temperature of the anode plate portion 21 is 26 ° C., it is 1.5 times and 2.0 times.

  On the contrary, even when the optimum thickness of the cathode plate portion 11 for maintaining the width of the vacuum space 14 is obtained while the temperature of the anode plate portion 21 is constant, the cathode plate portion 11 has the same thickness as described above. It has been confirmed that the optimum thickness is proportional to the thickness of the anode plate portion 21 and also to the temperature of the cathode plate portion 11.

  From the above results, the thickness of the cathode plate-like portion 11 and the anode plate-like portion 21 for maintaining the width of the vacuum space 14 is a factor related to the temperature of the cathode plate-like portion 11 and the anode plate-like portion 21. It turns out that it is prescribed.

[Embodiment 2]
A second embodiment of the present invention will be described in detail with reference to the drawings. In the present embodiment, a description will be given of an electronic cooling element in which the cathode plate and the anode plate have the same thickness and different materials are used to make the deformability of the two different. Note that members having the same functions as those described in the above embodiment are given the same member numbers, and description thereof is omitted in this embodiment.

  FIG. 5 is a cross-sectional view showing a schematic configuration of an electronic cooling element using the electron tunnel effect of the present embodiment. First, the schematic structure of the electronic cooling element of the present embodiment will be described with reference to FIG. Of the reference numerals attached to the members in FIG. 5, 31 is a cathode plate-like portion, 41 is an anode plate-like portion, 13 is a planarizing material, 14 is a vacuum space, 15 is a spacer, 16 is a vacuum seal, 17 Indicates hollow structures provided in the cathode 30 and the anode 40. Reference numeral 30 denotes a cathode composed of a cathode plate-like portion 31 and a cathode dish-like portion 32, and 40 denotes an anode composed of an anode plate-like portion 41 and an anode dish-like portion 42, respectively.

  The electronic cooling element according to the present embodiment is different from the above-described first embodiment in that the deformability of the cathode 30 and the anode 40 is made different from each other by using different materials. As a combination of materials of the cathode 30 and the anode 40, for example, Cu and Au, Cu and In, and the like can be given in this order.

  The case where the electron cooling element of the present embodiment is driven to perform cooling by the electron tunnel effect will be described below. As in the case of the first embodiment, the pressure of the hollow structure portion 17 provided in the cathode 30 and the anode 40 is in a state where no voltage is applied to the electronic cooling element, and the voltage starts to be applied to the electronic cooling element. In the initial state, the pressure is maintained at a level that can cancel the influence of vacuum or atmospheric pressure.

  Here, when a negative potential is applied to the cathode 30 of the electron cooling element and a positive potential is applied to the anode 40, the electrons move from the cathode plate-like portion 31 of the cathode 30 to the planarizing material 13, pass through the vacuum space 14, and the anode The plate-like portion 41 is reached. At that time, since heat is carried by tunnel electrons or thermoelectrons passing through the vacuum space 14, the cathode plate-like portion 31 is cooled and the anode plate-like portion 41 is heated. At that time, as described in the first embodiment, in the cathode plate-like portion 31 and the anode plate-like portion 32, the deflection due to the temperature change accompanying the cooling occurs.

[Example 2]
Except for using Cu as the material of the cathode 30, Au as the material of the anode 40, and setting the thickness of the cathode plate-like portion 31 and the anode plate-like portion 41 to 0.3 mm, Similarly, an electron whose thickness of the vacuum space 14 is controlled to 5 nm using Si having a thickness of 0.25 mm as the planarizing material 13, SiO ₂ having a thickness of 5 nm as the spacer 15, and low melting point glass as the vacuum sealant. A cooling element was produced.

  Table 2 shows Example 2 (cathode: Cu, anode: Au) in which the materials of the cathode plate-like portion 31 and the anode plate-like portion 62 are different, and a conventional configuration (when the cathode and anode are both Cu). About the comparative example 1, the result of the deflection amount measured by the method similar to Embodiment 1 is shown. As shown in the table, in Comparative Example 1 and Example 2 which are conventional configurations, the thickness of the cathode plate portion and the anode plate portion is 0.3 mm.

From the results shown in Table 2, the material of the anode 40 is not the same Cu (thermal expansion coefficient: 16.7E ⁻⁶ / ° C., Young's modulus: 110 GPa) as the cathode 30, but Au (thermal expansion coefficient) different from the cathode 30. : 14.1E ⁻⁶ / ° C., Young's modulus: 78.5 GPa), it can be seen that the difference in deflection between the cathode plate portion 31 and the anode plate portion 42 can be reduced to 2 nm. That is, when the cathode plate-like portion 31 and the anode plate-like portion 42 have the same thickness, in Example 1 of the conventional configuration in which these are formed of the same material (Cu), the difference in the deflection amount is 2000 nm. On the other hand, by forming these with different materials (Cu and Au), the difference in the amount of deflection can be reduced to 2 nm.

Accordingly, by forming the cathode plate-like portion 31 and the anode plate-like portion 42 from different materials as in the present embodiment, even when a deflection occurs due to a temperature change accompanying cooling, The width (vacuum space distance) can be maintained sufficiently. In addition, when In (thermal expansion coefficient: 24.8E- ⁶ / ° C., Young's modulus: 10.5 GPa) is used as the material of the anode 40 instead of Au, the same as in Example 2 using Au is used. It has been confirmed that the effect is obtained.

[Embodiment 3]
A third embodiment of the present invention will be described in detail with reference to the drawings. In the electronic cooling element of the present embodiment, at least one of the cathode plate and the anode plate has a laminated structure of a first material and a second material having different deformability from the first material. However, this is different from the first and second embodiments. In addition, about the member of the same function as the member demonstrated in said embodiment, the same member number is attached | subjected and description is abbreviate | omitted in this Embodiment.

  FIG. 6 is a cross-sectional view showing a schematic configuration of an electronic cooling element using the electron tunnel effect of the present embodiment. First, the schematic structure of the electronic cooling element of the present embodiment will be described with reference to FIG. Of the reference numerals assigned to the members in FIG. 6, 31 is a cathode plate-like portion, 51 is an anode plate-like portion comprising a first anode plate-like portion 51A and a second anode plate-like portion 51B, 13 Is a planarizing material, 14 is a vacuum space, 15 is a spacer, 16 is a vacuum seal, and 17 is a hollow structure provided in the cathode 30 and the anode 50. Reference numeral 50 denotes an anode 50 composed of an anode plate-like portion 51 and an anode dish-like portion 52.

  The anode plate-like portion 51A and the anode plate-like portion 51B constituting the anode plate-like portion 51 of the anode 50 are made of different materials. Specifically, Cu, Au, Si, In, W Metals such as can be combined. By setting the film thicknesses of the anode plate-like portion 51A and the anode plate-like portion 51B in accordance with the materials used, cooling is performed by changing the deformability of the anode plate-like portion 51 and the cathode plate-like portion 31. In this case, the amount of deflection when the temperature becomes different can be made substantially the same. For this reason, in the second embodiment, the cathode plate-like portion 31 and the anode plate-like portion 41 have the same thickness, and in this order, the same effect as when these materials are combined with Cu and Au or Cu and In. Can also be obtained in the electronic cooling element of the present embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. Further, embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

  It is a small electronic cooling element that exhibits high cooling characteristics, and can be applied to a cooling device of a defluorocarbon cooling mechanism.

FIG. 1 is a cross-sectional view showing a schematic configuration of an electronic cooling element using the electron tunnel effect of the present invention. FIG. 2 is an enlarged sectional view of the vacuum space portion of the electronic cooling element indicated by A in FIG. FIG. 3 is a graph showing the rate of decrease in the amount of cooling due to a decrease in the degree of vacuum at the vacuum gap portion in the electron cooling element using the electron tunnel effect. FIG. 4 is a diagram showing the temperature change of the anode thickness for maintaining the vacuum gap in the cooling element using the electron tunnel effect. FIG. 5 is a sectional view showing a schematic configuration of another embodiment of the electronic cooling element using the electron tunnel effect of the present invention. FIG. 6 is a cross-sectional view showing a schematic configuration of still another embodiment of the electronic cooling element using the electron tunnel effect of the present invention. FIG. 7 is a diagram showing a schematic configuration of a conventional cooling element using the electron tunnel effect. FIG. 8 is a diagram showing a change in COP (cooling performance index) value of a conventional heat pump apparatus using the electron tunnel effect. FIG. 9 is a diagram showing a schematic configuration of a cooling element using a conventional electron tunnel effect.

Explanation of symbols

10, 30 Cathode 20, 40, 50 Anode 11, 31 Cathode plate part (cathode plate)
12, 32 Cathode dish-shaped part (dish-shaped part)
21, 41, 51 Cathode plate part (anode plate)
22, 42, 52 Anode dish (dish)
17 Hollow structure

Claims (10)

In an electronic cooling element that has a cathode plate that applies a negative voltage and an anode plate that applies a positive voltage and performs cooling by the electron tunnel effect,
The electronic cooling element according to claim 1, wherein the cathode plate and the anode plate have different deformability with temperature change.   The cathode plate and the anode plate are provided with a dish-like portion that forms a hollow structure portion on a surface opposite to the facing surface, and the pressure in the hollow structure portion is set lower than the pressure outside the electronic cooling element. The electronic cooling element according to claim 1, wherein:   The electronic cooling element according to claim 2, wherein the pressure in the hollow structure portion is 100 Pa or less.   3. The electronic cooling element according to claim 2, wherein Ar is sealed as a vacuum sealed gas between the cathode plate and the anode plate and in the hollow structure portion.   The electronic cooling element according to claim 1 or 2, wherein the cathode plate and the anode plate are made of the same material and have different thicknesses.   When cooling by the electron tunnel effect, the ratio between the thickness of the cathode plate and the thickness of the anode plate is set so that the difference in the shape changes due to the temperature difference between the cathode plate and the anode plate is reduced. The electronic cooling element according to claim 5, wherein the electronic cooling element is provided.   The electronic cooling element according to claim 1, wherein the cathode plate and the anode plate are made of different materials and have the same thickness.   The electronic cooling element according to claim 7, wherein the material of the cathode plate is Cu or In, and the material of the anode plate is Au.   At least one of the cathode plate and the anode plate has a laminated structure of a first material and a second material, and the first material and the second material have different deformability. An electronic cooling element according to claim 1 or 2,   The electronic cooling element according to claim 9, wherein the laminated structure is a combination of Cu and Fe.

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