JP2012002417A - Heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pipe that still shows good cooling properties even if used in a relatively low operating temperature.SOLUTION: The heat pipe 100 includes: a container 1 comprising a sealed pipe and having a first end and a second end; a coil 3 disposed in the container 1; a wick 2 held between the container 1 and the coil 3; and a working fluid retained in the container 1. The heat pipe 100 is configured such that the working fluid evaporated at the first end condenses at the second end for heat transfer from the first end to the second end. The coil 3 comprises a copper alloy whose surface is covered with a copper layer, or the coil 3 comprises a copper alloy and has a surface layer with a copper concentration higher than the central portion thereof.

Description

  The present invention relates to a heat pipe, and more particularly to a heat pipe having a relatively low operating temperature.

  A conventional heat pipe has a structure in which water is enclosed in a copper pipe, and one end of the heat pipe is connected to a heat source and the other end is connected to a radiator. The heat transferred from the heat source to the heat pipe is transferred through the heat pipe by heat transport and heat diffusion, and is released from the radiator. In general, the operating temperature is about 50 to 100 ° C., and a structure in which a large number of thin wires are lined on the inner wall of a copper pipe and the inside thereof is pressed with a coil to improve the heat transport capability (for example, , See Patent Document 1).

JP-A-9-170888 (page 5, FIG. 1)

  However, in recent years, heat pipes are used for cooling laser diode elements and the like, and the use temperature (cooling part temperature) is lower than, for example, 40 ° C. or lower. For this reason, the vapor pressure of water vapor in the heat pipe is less than one-tenth of that used at high temperatures, and a relatively small amount of non-condensable gas (such as hydrogen) mixed in the heat pipe (at the operating temperature). The influence of the gas that cannot be liquefied) has become large, and deterioration of cooling characteristics has been a problem.

  Accordingly, an object of the present invention is to provide a heat pipe having good cooling characteristics even at a relatively low operating temperature.

  The present invention comprises a sealed pipe, a container having a first end and a second end, a coil disposed inside the container, a wick held between the container and the coil, A working pipe that is held at the first end, the working fluid evaporated at the first end condenses at the second end, and performs heat transfer from the first end to the second end, The coil is a heat pipe characterized in that the surface is made of a copper alloy covered with a copper coating layer.

  In the heat pipe according to the present invention, it is possible to suppress deterioration of heat dissipation characteristics due to generation of non-condensable gas in the heat pipe, and to provide a highly reliable heat pipe even at a relatively low operating temperature.

It is the schematic of the heat pipe concerning embodiment of this invention. It is sectional drawing of the heat pipe concerning embodiment of this invention. It is sectional drawing of the coil concerning embodiment of this invention. It is sectional drawing of the other coil concerning embodiment of this invention.

  FIG. 1 is a schematic view of a heat pipe according to an embodiment of the present invention, indicated as a whole by 100, partially showing a fracture surface. 2 is a cross-sectional view of FIG. 1 when viewed in the II direction.

  The heat pipe 100 includes a container 1 made of a sealed pipe. The container 1 is made of, for example, copper, preferably oxygen-free copper. Here, although the cylindrical container 1 was shown, shapes, such as a prism, may be sufficient. The container 1 may have a bent shape. In addition, a large number of grooves may be provided on the inner wall of the container 1.

  A wick 2 is arranged inside the container 1 along the inner wall. The wick 2 is made of, for example, copper or a copper alloy, preferably an oxygen-free copper fine wire, or a fine wire knitted in a mesh shape.

  A coil 3 is provided inside the wick 2, and the wick 2 is sandwiched and held between the inner wall of the container 1 and the coil 3. FIG. 3 is a cross-sectional view of the coil 3. The coil 3 includes a main body portion 13 made of, for example, spring phosphor bronze (JIS C5210) and a covering portion 14 formed on the surface thereof, for example, made of copper plating. As a material of the body portion 13 of the coil 3, copper is the main component, zinc, phosphorus-containing copper alloy, copper is the main component, tin, zinc, phosphorus-containing copper alloy, copper is the main component, tin, zinc, Other copper alloys such as phosphorus and iron containing copper alloys can also be used.

  Inside the coil 3, a hollow vapor passage 4 is formed, and the vaporized working fluid moves.

  In the manufacturing process of the heat pipe 100, after the wick 2 and the coil 3 are arranged inside the container 1, the gas (mainly air) inside the container 1 is exhausted to be in a vacuum state. Subsequently, a working fluid made of water, for example, is placed in the vacuum container 1 and the ends are sealed to form a sealed pipe. Thus, the heat pipe 100 is completed.

  The heat pipe 100 is used with a first end shown in FIG. 1 in contact with a heating element such as a semiconductor element and a second end in contact with a radiator such as a radiation fin. The working fluid heated at the first end evaporates and moves through the vapor passage 4 to the second end. At the second end, the working fluid is cooled and condensed to return to the liquid. Due to the latent heat transfer accompanying the evaporation and condensation, heat is transferred from the first end to the second end, and the first end is cooled. The working fluid returned to the liquid at the second end is circulated to the first end through the liquid passage 5 by the capillary action of the wick 2.

  Here, as described above, the heat pipe 100 discharges the internal gas (mainly air) in the manufacturing process and encloses the working fluid after being in a vacuum state. For this reason, even if it is a structure without the penetration | invasion of external air, when evacuating, some gas may remain, without being discharged | emitted. Further, the inner wall or the like of the container 1 may adsorb and hold the gas, and the gas may flow out with time. Further, the material constituting the heat pipe 100 and the working fluid may react chemically, and gas may continue to be generated.

  Such residual gas becomes a non-condensable gas, cannot be condensed in the heat pipe 100, and stays in the condensing part (second end part) to deteriorate the heat radiation characteristics. Usually, the first two non-condensable gases deteriorate the initial characteristics, but since there is almost no change with time, there is no big problem with respect to the lifetime. However, since the last non-condensable gas continues to be generated due to a chemical reaction, the heat dissipation characteristics deteriorate over time, and if the user does not correctly recognize it as aged deterioration, it will cause failure of electronic equipment etc. Cause.

  For such non-condensable gases, the first two are due to the initial residual gas and can be reduced by improving the manufacturing process. The last one is caused by the combination of the material of the heat pipe 100 and the working fluid, and can be reduced by selecting the material. For example, when water is used as the working fluid, it can be reduced by using oxygen-free copper as a material constituting the container 1 and the wick 2.

  Conventionally, the operating temperature of the heat pipe is about 50 to 100 ° C. as described above, and the vapor pressure of the working fluid is relatively high. Therefore, measures for reducing non-condensable gas as described above have been effective. However, in recent years, when a laser diode or the like is used as a heating element, the cooling temperature (the temperature at the first end) is, for example, about room temperature to about 40 ° C. For this reason, the vapor pressure of the working fluid is lowered, and the influence of the non-condensable gas becomes relatively large, and even a small amount of non-condensable gas which has not been a problem in the past has been a problem.

  For example, when water is used as the working fluid, the vapor pressure becomes 0.123 bar or higher when used in a high temperature environment of 50 ° C. or higher as in the prior art, but like cooling of an electro-optical conversion element (for example, a laser diode). When it has to be cooled to approximately room temperature (20 ° C.), the vapor pressure is about 0.023 bar. As a result, the non-condensable gas is 44 times larger than the volume under the atmospheric pressure, and the influence of the non-condensable gas is greater than when used at a relatively high temperature as in the prior art.

  That is, when water is used as the working fluid, the vapor pressure is logarithmically reduced with respect to the environmental temperature, so that the expansion rate of the non-condensable gas in the low temperature region is significantly increased. For this reason, when using a heat pipe at low temperature, the non-condensable gas stagnates and expands in the heat radiating section, thereby causing a problem that the heat exchange area in the heat radiating section of the heat pipe is reduced and the heat radiating characteristics are deteriorated.

  As described above, the present invention did not cause a problem when used at a relatively high temperature as in the prior art, but reduced the non-condensable gas which becomes a problem when used at a low temperature of about 40 ° C. Thus, the present invention provides a heat pipe having good heat dissipation characteristics even at low temperatures.

  In this embodiment, as shown in FIG. 3, the working fluid and the main body portion are formed by covering the main body portion 13 made of spring phosphor bronze (JIS C5210) with the covering portion 14 made of copper plating to form the coil 3. 13 direct contact is prevented. As a result, the generation of non-condensable gas (for example, hydrogen) due to the contact between phosphorus and zinc contained in phosphor bronze for springs and water is prevented, and the heat pipe heat dissipation characteristics change over time due to the generation of such non-condensable gas (deterioration). ) Can be prevented.

  FIG. 4 is a cross-sectional view of another coil 3 according to the embodiment of the present invention. The coil 3 of FIG. 4 is present on the coil surface by holding the coil 3 made of phosphor bronze for spring directly immersed in a liquid such as water in advance or by immersing it in a high temperature liquid to promote a chemical reaction. Phosphorus and zinc are removed by a chemical reaction, and the surface of the coil 3 is made a surface layer having a high copper content including the holes 9.

  In this way, phosphorus and zinc are removed from the surface of the coil 3 to form a surface layer having a high copper content, so that the non-condensable gas produced by the contact of phosphorus and zinc contained in the phosphor bronze for spring with water is obtained. Generation | occurrence | production can be prevented and the time-dependent change (deterioration) of the heat dissipation characteristic of a heat pipe by generation | occurrence | production of this noncondensable gas can be prevented.

  3 and 4, the molecules of phosphorus 7 and zinc 8 contained in the coil 3 are schematically represented as typical molecules. However, when the coil 3 contains tin or the like, the phosphor 7 It can be handled in the same manner as zinc 8 and zinc. Further, as the material of the coil 3, other copper alloys as described above may be used.

  Non-condensable gas caused by residual gas can be reduced by improving the manufacturing process. As a method for suppressing the non-condensable gas, the material of the coil 3 can be changed. However, as a material satisfying both mechanical characteristics and chemical characteristics (hydrogen gas generation), phosphor bronze for springs is used. Is most preferred.

  Alternatively, the coil 3 in which the main body 13 is previously covered with the covering portion 14 may be used, and the main body 13 may be covered with the covering portion 14 before the heat pipe is sealed.

  Furthermore, when the container 1 and the wick 2 are formed from copper containing zinc or the like, these surfaces may be coated with copper plating.

  1 container, 2 wicks, 3 coils, 4 vapor passages, 5 liquid passages, 7 phosphorus, 8 zinc, 9 holes, 13 body, 14 covering, 100 heat pipe.

Claims (7)

A container comprising a sealed pipe and having a first end and a second end;
A coil arranged inside the container;
A wick held between the container and the coil;
A working fluid held in a container,
The working fluid evaporated at the first end is condensed at the second end, and heat transfer is performed from the first end to the second end,
The coil is made of a copper alloy whose surface is covered with a copper coating layer.   The heat pipe according to claim 1, wherein the coating layer is a copper plating layer. A container comprising a sealed pipe and having a first end and a second end;
A coil arranged inside the container;
A wick held between the container and the coil;
A working fluid held in a container,
The working fluid evaporated at the first end is condensed at the second end, and heat transfer is performed from the first end to the second end,
The heat pipe characterized in that the coil is made of a copper alloy and includes a surface layer having a copper concentration higher than that of the central portion.   The heat pipe according to claim 3, wherein the copper alloy contains at least zinc and phosphorus, and the concentration thereof is lower in the surface layer than in the central portion.   The heat pipe according to any one of claims 1 to 4, wherein the copper alloy is made of phosphor bronze for a spring.   The heat pipe according to claim 1, wherein the temperature of the first end is cooled to 40 ° C. or less.   The heat pipe according to claim 1, wherein the working fluid is water.

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