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United States Patent Application	20090266520
Kind Code	A1
YU; Junhyun	October 29, 2009

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Foreign Application Data

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Date	Code	Application Number
Apr 23, 2008	JP	2008-112688
Mar 31, 2009	JP	2009-084013

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Claims

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1. A phase conversion cooler comprising:a cooling head having a first side to contact an object to be cooled and contain a refrigerant therein;a first circular port for discharging the refrigerant out of the cooling head, the first circular port being provided to a second side not opposite to the first side of the cooling head;a second circular port for taking in the refrigerant, the second circular port being provide to a third side not opposite to the first side and the second side of the cooling head;a first pipe whose one end is connected to the first circular port, the first pipe being a part of a circular pipe;a condenser part connected to the other end of the first pipe and placed in a heat dissipation environment; anda second pipe whose one end is connected to the condenser part and the other end is connected to the second circular port, the second pipe being a part of the circular pipe,wherein the cooling head is formed by resin molding housing and a metal plate, and at least a part of the first side of the cooling head is formed with a metal plate.

2. The phase conversion cooler according to claim 1, wherein:in addition to the metal plate of the first side, at least one of sides other than the first side of the cooling head is provided with a metal plate.

3. The phase conversion cooler according to claim 2, wherein:the metal plate of the first side is contact with the other metal plate of at least one of sides other than the first side of the cooling head is in contact with each other.

4. The phase conversion cooler according to claim 2, wherein:the other metal plate of at least one of sides other than the first side of the cooling head is provided on an inner surface of the cooling head.

5. The phase conversion cooler according to claim 1, wherein:the first side of the resin mold housing of the cooling head comprises a resin-free portion closed with the metal plate.

6. The phase conversion cooler according to claim 1, wherein:the metal plate comprises a protrusion anchored into the resin molding housing.

7. The phase conversion cooler according to claim 1, wherein:the metal plate is provided to the resin molding housing of the cooling head by insert molding.

8. The phase conversion cooler according to claim 1, wherein:the second pipe has a portion inclined toward the side of the first pipe.

9. The phase conversion cooler according to claim 1, wherein:when the cooling head stands at that the first side of the cooling head is positioned as an under side of the cooling head, a height of the first circular port and that of the second circular port are different from each other in a vertical direction.

10. Mobile equipment provided with the phase conversion cooler constructed by any one of claims 1 to 9.

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Description

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CLAIM OF PRIORITY

[0001]The present application claims priority from Japanese patent application serial No. 2009-084013, filed on Mar. 31, 2009, which further claims priority from Japanese patent application serial No. 2008-112688, filed on Apr. 23, 2008, the contents of which are hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a small lightweight phase conversion type cooler with high cooling efficiency and mobile equipment.

[0004]2. Description of Related Art

[0005]A forced heat dissipation means is provided instead of natural heat dissipation, in high-level heat-generating parts among parts provided in a computer. For example, in an LSI (Large Scale Integrated circuit) such as a CPU (Central Processing Unit), since heat generation causes a serious problem in accordance with degree of integration and/or processing speed, a heat dissipation means is absolutely necessary.

[0006]A phase conversion cooler is known as a cooler used for the heat dissipation applicable to such electronic parts, as disclosed in Japanese laid-open publication Nos. 2004-85186, Hei 7-142886 and 2006-125718.

[0007]As shown in FIG. 7, a conventional phase conversion cooler 101 has a cooling head 102 having a first side (which is faced toward the rear side of the drawing in FIG. 7) in contact with a cooled object, a first circular port 103 provided to a second side 102b not opposite to the first side of the cooling head 102, a second circular port 104 provided to a third side 102c not opposite to the first side and the second side 102b of the cooling head 102, a first pipe 105 whose one end is connected to the first circular port 103 as an outlet port, a condenser part 106 connected to another end of the first pipe 105 and placed in a heat dissipation environment, and a second pipe 107 whose one end is connected to the condenser part 106 and another end is connected to the second circular port 104 as inlet port. The phase conversion cooler 101 has a refrigerant circular system for a refrigerant changeable in liquid phase/vapor phase.

[0008]The cooling head 202 is a metal container with high thermal conductivity having an approximately rectangular parallelepiped shape. The first side (the front surface on the rear side of the drawing) of the cooling head 102 is in contact with a heat radiating surface of an LSI as an object to be cooled.

[0009]The first pipe 105 connected to the first circular port 103 is extended by a sufficiently long length in a direction orthogonal to the second side 102b of the cooling head 102 and connected to the condenser part 106. In the status shown in the figure, as the second side 102b of the cooling head 102 is positioned as an upper side of the cooling head 102, the first pipe 105 is extended upward.

[0010]The condenser part 106 has a surface area widened by e.g. folding back a metal pipe with high thermal conductivity plural times. The condenser part 106 is placed in a heat dissipation environment sufficiently away from the cooled object. The heat dissipation environment means an environment appropriate to heat dissipation such as an environment easily exposed to atmosphere, an environment adjacent to a member with high thermal conductivity exposed to atmosphere or an environment around which any heat source or member with low heat-resistance does not exist.

[0011]The second pipe 107 connected to the second circular port 104 is extended by a comparatively short length part in a direction orthogonal to the third side 102c of the cooling head 102, then other part is bent toward the condenser part 106, then extended by a long length in parallel with the first pipe 105 and connected to the condenser part 106. In the status shown in the figure, as the third side 102c of the cooling head 102 is positioned as a vertical side of the cooling head 102, the second pipe 107 is laterally extended and then extended upward vertically.

[0012]The first pipe 105, the condenser part 106 and the second pipe 107 can be formed as one continuous pipe.

[0013]The phase conversion cooler 101 contains a refrigerant in its internal space formed from the cooling head 102 through the first pipe 105, the condenser part 106 and the second pipe 107, again to the cooling head 102.

[0014]In the phase conversion cooler 101, heat from the cooled object is thermal-conducted to the cooling head 102, and the refrigerant in the cooling head 102 is vaporized (boiled) into gas phase by the heat. The refrigerant in gas phase flows upward in the cooling head 102 into the first pipe 105 via the first circular port 103 and flow into the condenser part 106. The refrigerant in gas phase is heat-dissipated with the condenser part 106 then liquefied (condensed) into liquid phase. The refrigerant in liquid phase flows downward in the second pipe 107 from the condenser part 106 into the cooling head 102 via the second circular port 104. In this manner, in the conventional phase conversion cooler 101, the refrigerant absorbs the heat of the cooled object by vaporization, then the condenser part 106 dissipates the heat outside the system (atmosphere or the like), and then the refrigerant in liquid phase returns to the cooling head 102, i.e., the circulation of the refrigerant is repeated. This achieves continuous forced-cooling of the cooled object.

[0015]In the phase conversion cooler 101 which is smaller and simpler in comparison with a cooling fan to do air-cooling to a cooled object, a pump mechanism to do forced circulate of a refrigerant with a mechanical force is not required.

[0016]The percentage of the liquid phase in the entire phase conversion cooler (in the internal space from the cooling head 102 through the first pipe 105, the condenser part 106 and the second pipe 107, again to the cooling head 102) is 20 to 30% to total amount of the refrigerant by volume. In the cooling head 102, the refrigerant exists in appropriate percentages of liquid phase and gas phase.

[0017]The refrigerant in liquid phase is stored in a lower part of the cooling head 102, and a liquid surface (s) of the refrigerant is above the second circular port 104. The refrigerant in gas phase occupies space higher from the liquid surface (s). The first circular port 103 is positioned above the space. Accordingly, the volume of refrigerant in gas phase is increased by vaporization, the refrigerant in gas phase easily flows into the first pipe 105, and further, the refrigerant in gas phase flows only into the first pipe 105. Further, the refrigerant in liquid phase changed from gas phase to liquid phase with the condenser part 106 flows into the second pipe 107 in accordance with gravity and returns to the cooling head 102. In this arrangement, the refrigerant in gas phase flows upward from the cooling head 102 into the condenser part 106, then the refrigerant in liquid phase flows downward from the condenser part 106 into the cooling head 102, i.e., the circulation of the refrigerant is promoted smoothly.

[0018]The conventional phase conversion cooler 101 is provided to a desktop type personal computer or the like. However, a problem occurs when this phase conversion cooler 101 is provided in a portable device (mobile equipment) such as a cellular phone or a notebook-sized personal computer.

[0019]Since the housing of mobile equipment is smaller than that of fixed type equipment such as a desktop type personal computer and its inner space is small, a phase conversion cooler to be provided to such mobile equipment must be further downsized and thinned in comparison with the conventional phase conversion cooler.

[0020]In the conventional phase conversion cooler 101, for the purpose of improvement in thermal exchange efficiency with the cooled object, the cooling head 102 is entirely made of a metal material. Further, as the cooling head 102 serves as a refrigerant container, it is necessary for the cooling head 102 to have a hollow and airtight structure. The cooling head 102 is more particularly formed by so-called sheet metal processing of three-dimensionally assembling metal plates and sealing the jointed portions with welding.

[0021]In order to join the metal plates with high airtightness, it is necessary to prepare metal plates having a predetermined or relatively greater thickness. If using thin metal plates to be welded, the shape of the metal plates may be distorted or hole(s) may be formed. Accordingly, in the conventional phase conversion cooler, the metal plates of the cooling head have relatively great thickness. The thickness is more particularly about 1 mm. Generally, the limit of thickness of copper plates to welding is equal to or greater than 0.5 mm. Accordingly, the external dimensions of the cooling head 102 become greater. The limitation of the thickness of the metal plates disturbs the downsizing of the cooling head 102 and the ensuring of refrigerant container space.

[0022]Further, when the metal plates are three-dimensionally assembled, many joints are generated. To form the cooling head 102 in an approximately rectangular parallelepiped shape as shown in FIG. 7, six metal plates are assembled and twelve ridge lines are welded. Further, the circular ports 103 and 104 as refrigerant supply/discharge formed by holes bored in the metal plates, and metal plates to be formed into the first pipes 105 and the second pipes 107 are joined with the circulate ports 103 and 104, these portions are also weld-joined portions. In this manner, when the cooling head 102 is formed with metal plates, the number of weld joint positions is large and the process cost is increased.

[0023]Further, the conventional phase conversion cooler 101, where the metal plates are thick and the number of weld joint positions is large as described above, is heavy in weight. The heavy weight is a demerit for mobile equipment which must have an important commercial value, lightness.

[0024]Further, when the cooling head 102 is entirely metal member, the heat thermally conducted from the cooled object to the first side of the cooling head 102 is diffused to other sides of the cooling head 102 by thermal conduction. This heat diffusion contributes to cooling of the cooled object but is inconvenient from the viewpoint of phase conversion cooling. In this case, the heat transmitted from the cooled object to the refrigerant is reduced and the amount of vaporized refrigerant is reduced, and the efficiency of phase conversion cooling is lowered. Further, the heat diffused to the entire cooling head 102 by the thermal conduction is thermally conducted to the ambient atmosphere, thereby hot air is stored around the cooled object.

[0025]Further, the cooling head 102 may be formed by casting. However, as metals have high viscosity even in molten state, when the cooling head 102 is formed by casting, the thickness of the metal material of the cooling head 102 cannot be reduced. Accordingly, the above-described problems of the wall thickness, the heavy weight and the thermal conduction and the like cannot be solved by casting.

SUMMARY OF THE INVENTION

[0026]The present invention is to solve the above-described problems and provides a small and lightweight phase conversion cooler with high cooling efficiency.

[0027]According to one aspect of the present invention, provided is a phase conversion cooler comprising: a cooling head having a first side to contact an object to be cooled and contain a refrigerant therein; [0028]a first circular port for discharging the refrigerant out of the cooling head, the first circular port being provided to a second side not opposite to the first side of the cooling head; [0029]a second circular port for taking in the refrigerant, the second circular port being provide to a third side not opposite to the first side and the second side of the cooling head; [0030]a first pipe whose one end is connected to the first circular port, the first pipe being a part of a circular pipe; [0031]a condenser part connected to the other end of the first pipe and placed in a heat dissipation environment; and [0032]a second pipe whose one end is connected to the condenser part and the other end is connected to the second circular port, the second pipe being a part of the circular pipe, [0033]wherein the cooling head is formed by resin molding housing and a metal plate, and at least a part of the first side of the cooling head is formed with a metal plate.

[0034]Further, it may be arranged such that plural sides of the cooling head are provided with the metal plate.

[0035]Further, it may be arranged such that the metal plates in the plural sides of the cooling head are in contact with each other.

[0036]Further, it may be arranged such that the other metal plate of at least one of sides other than the first side of the cooling head is provided on an inner surface of the cooling head.

[0037]Further, it may be arranged such that the first side of the resin mold housing of the cooling head has a resin-free portion closed with the metal plate.

[0038]Further, it may be arranged such that the metal plate is provided to the resin molding housing of the cooling head by insert molding.

[0039]Further, it may be arranged such that the metal plate is provided to the resin molding housing of the cooling head by insert molding, and the metal plate has a protrusion anchored into the resin molding housing.

[0040]Further, it may be arranged such that the second pipe has a portion inclined toward the side of the first pipe.

[0041]Further, it may be arranged such that, when the cooling head stands at that the first side of the cooling head is positioned as an under side of the cooling head, a height of the first circular port and that of the second circular port are different from each other in a vertical direction.

[0042]Further, it may be arranged such that mobile equipment according to the present invention is provided with the above-described phase conversion cooler.

[0043](Advantages of the Invention)

[0044]The present invention is advantageous that the phase conversion cooler according to the present invention is small and lightweight and has high cooling efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045]FIG. 1A is a perspective view of a cooling head of a phase conversion cooler according to an embodiment of the present invention, showing a second, a third and a sixth sides;

[0046]FIG. 1B is a perspective view of the cooling head of the phase conversion cooler according to the embodiment of the present invention, showing a first, a fourth and a fifth sides;

[0047]FIG. 1C is a cross-sectional view of the cooling head of the phase conversion cooler according to the embodiment of the present invention, where the first side is positioned as an under surface;

[0048]FIG. 2A is a perspective view for explaining insert molding, showing assembled metal plates;

[0049]FIG. 2B is a perspective view for explaining the insert molding, showing the cooling head after resin injection molding;

[0050]FIG. 3A is a cross-sectional view of the phase conversion cooler in FIGS. 1A to 1C in an erect position;

[0051]FIG. 3B is a cross-sectional view of the phase conversion cooler in FIGS. 1A to 1C in a right-leaning position;

[0052]FIG. 3C is a cross-sectional view of the phase conversion cooler in FIGS. 1A to 1C in a left-leaning position;

[0053]FIG. 4 is a perspective view showing pipe connection in the phase conversion cooler in FIGS. 1A to 1C;

[0054]FIG. 5 is a perspective view of the phase conversion cooler according to the embodiment of the present invention in a horizontal position;

[0055]FIG. 6A is a perspective view of a cellular phone provided with the phase conversion cooler according to the present invention;

[0056]FIG. 6B is a sectional side view of the cellular phone; and

[0057]FIG. 7 is a cross-sectional view of the conventional phase conversion cooler in an erect position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058]Hereinbelow, a preferred embodiment of the present invention will now be described in detail in accordance with the accompanying drawings.

[0059]As shown in FIGS. 3A to 3C, a phase conversion cooler 1 according to the present invention has a cooling head 2 having a first side 2a (see FIGS. 1B and 1C and FIG. 5) to contact an object to be cooled, a first circular port 3 as an outlet port provided in a second side 2b not opposite to the first side 2a of the cooling head 2, a second circular port 4 as an inlet port provided in a third side 2c not opposite to the first side 2a and the second side 2b of the cooling head 2, a first pipe 5 whose one end is connected to the first circular port 3, a condenser part 6 connected to another end of the first pipe 5 and placed in a heat dissipation environment, and a second pipe 7 whose one end is connected to the condenser part 6 and another end is connected to the second circular port 4.

[0060]An internal space for refrigerant circulation is formed by the circulation system from the cooling head 2 through the first pipe 5, the condenser part 6 and the second pipe 7, again to the cooling head 2. The internal space contains a refrigerant such that the percentage of the liquid phase of the refrigerant in equal to or higher than 20%. In the phase conversion cooler 1, a liquid surface (s) of the refrigerant is positioned above the third side 2c when the cooling head 2 stands at that the third side 2c of the cooling head 2 is positioned as an under side of the cooling head 2 (see FIG. 3C). As a slope 8 inclined with respect to the first pipe 5 is particularly formed in the second pipe 7, the liquid surface (s) is kept above the third side 2c.

[0061]As shown in FIGS. 1A to 1C in detail, in the present invention, the cooling head 2 is a container having an approximately rectangular parallelepiped outer shape including approximately rectangular parallelepiped space inside by a resin molding housing. The resin molding housing of the cooling head 2 is mainly made of engineering plastic.

[0062]The first side 2a of the cooling head 2 is a heat receiving surface to contact a heat radiating surface of the cooled object (e.g., an LSI). In the present invention, at least the first side 2a as the heat receiving surface of the cooling head 2 is provided with a metal plate 9. In the present embodiment, in addition to the first side 2a, the second side 2b, the third side 2c, the fourth surface 2d opposite to the second side 2b and the fifth surface 2e opposite to the third side 2c of the cooling head 2 are provided with the metal plate 9. Holes facing the first circular port 3 and the second circular port 4 are bored in the metal plates 9 provided to the second side 2b and the third side 2c.

[0063]The metal plate 9 is a copper plate having a thickness of 0.1 mm. The metal plates 9 in the respective sides are provided in contact with each other, however, it is not necessary to weld the metal plates 9 to each other. The metal plates 9 are provided to the cooling head 2 by insert molding upon formation of the resin molding housing of the cooling head 2.

[0064]The metal plate 9 is formed by progressive pressing of sequentially pressing sheet metal parts by shape. The cooing head 2 is formed by setting the metal plates 9 processed as above in a die and injecting liquid resin into the die pressing the liquid resin as resin injection molding (insert molding). Note that the metal plate 9 is provided with protrusions 9a as shown in FIG. 2A. The protrusions 9a are anchored into the resin molding case (cooling head) 2, so that integration between the metal plates 9 and the resin can be improved, and dropout of the metal plates 9 from the resin can be prevented.

[0065]The metal plates 9 may be provided on inner surfaces or outer surfaces of respective sides of the cooling head 2. As shown in FIG. 1C, in the present embodiment, the metal plates 9 are provided on the inner surfaces of the cooling head 2 except for the first side 2a. Note that the first side 2a of the cooling head 2 has a resin-free portion like window and one of the metal plates 9 is provided to the first side 2a so as to close the resin-free portion. Accordingly, one of the metal plates 9 is to be in contact with the heat radiating surface of the cooled object. Note that it may also be arranged such that the metal plate 9 in the first side 2a is provided in the outer side or inner side of the cooling head 2 so as to close the window (resin-free portion) of the cooling head 2.

[0066]The first circular port 3 is formed with resin by integral molding with the cooling head 2. The first circular port 3 is a hollow cylindrical protrusion communicating the inside of the cooling head 2 with the outside. The first circular port 3 is formed in dimensions to be engaged with the first pipe 5.

[0067]As shown in FIG. 3A, the first pipe 5 connected to the first circular port 3 is extended by a sufficiently long length in a direction orthogonal with respect to the second side 2b of the cooling head 2 and connected to the condenser part 6. In the status shown in the figure, as the second side 2b of the cooling head 2 is positioned as an upper side of the cooling head 2, the first pipe 5 is extended upward.

[0068]The condenser part 6 has a surface area widened by e.g. folding back a metal pipe with high thermal conductivity plural times. The condenser part 6 is placed in a heat dissipation environment sufficiently away from the cooled object. The heat dissipation environment means an environment appropriate to heat dissipation such as an environment easily exposed to atmosphere, an environment adjacent to a member with high thermal conductivity exposed to atmosphere or an environment around which any heat source or member with low heat-resistance does not exist.

[0069]The second circular port 4 is formed with resin by integral molding with the cooling head 2. The second circular port 4 is a hollow cylindrical protrusion communicating the inside of the cooling head 2 with the outside. The second circular port 4 is formed in dimensions to be engaged with the second pipe 7.

[0070]Note that as shown in FIG. 4, the second circular port 4 may be connected to the second pipe 7 via a joint 10. Further, though not shown, the first circular port 3 may also be connected to the first pipe 5 via the joint 10.

[0071]As shown in FIG. 3A, the second pipe 7 is extended by a length shorter than that of the conventional second pipe in a direction orthogonal to the third side 2c of the cooling head 2, then bent toward the condenser part 6, then inclined and extended by a long length in a direction from about the second side 2b of the cooling head 2 to approach the first pipe 5, and connected to the condenser part 6. In the status shown in the figure, as the third side 2c of the cooling head 2 is positioned as a side surface of the cooling head 2, the second pipe 7 is laterally extended by a short length and then extended upward by a short length, and the slope 8 as a major part is extended diagonally.

[0072]In the conventional phase conversion cooler 101, welding is required to join the metal pipes as the first pipe 105 and the second pipe 107 to the circular ports 103 and 104. However, for the welding, the first pipe 105 and the second pipe 107 must have sufficient lengths from the second side 2b and the third side 2c. On the other hand, in the present invention, as the cooling head 2 is comprised of the resin molding housing, the first circular port 3 and the second circular port 4 can be formed as protrusions from the cooling head 2. As the second circular port 4 is formed in dimensions to be engaged with the second pipe 7 (or the joint 10), the second pipe 7 extended in the direction orthogonal to the third side 2c may have a length only for engagement with the second circular port 4. Accordingly, the length of the second pipe 7 extended in the direction orthogonal to the third side 2c can be shorter than that of the conventional second pipe 7. Therefore, in the present invention, the phase conversion cooler 1 can be further downsized.

[0073]Next, a cooling operation of the phase conversion cooler according to the present invention will be described using FIGS. 3A to 3C.

[0074]FIG. 3A shows a cellular phone provided with the phase conversion cooler 1 according to the present invention in an erect position. The erect position means a position of a cellular phone when a user talking on the cellular phone is in a standing position. In the phase conversion cooler 1, the second side 2b of the cooling head 2 is positioned as an upper side of the cooling head 2. At this time, the liquid surface (s) of the refrigerant is positioned above the second circular port 4.

[0075]In the phase conversion cooler 1, heat from the cooled object is thermally conducted to the cooling head 2, then the refrigerant in the cooling head 2 is vaporized (boiled) into gas phase by the heat. The refrigerant in gas phase flows upward in the cooling head 2 into the first pipe 5 via the first circular port 3 and flows into the condenser part 6. The refrigerant in gas phase is thermally dissipated with the condenser part 6 then liquefied (condensed) into liquid phase. The refrigerant in liquid phase flows downward in the second pipe 7 from the condenser part 6 into the cooling head 2 via the second circular port 4. In this manner, in the phase conversion cooler 1 according to the present invention, the refrigerant absorbs the heat of the cooled object by vaporization, then the condenser part 6 dissipates the heat outside the system (atmosphere or the like), and then the refrigerant in liquid phase returns to the cooling head 2, i.e., the circulation of the refrigerant is repeated. This achieves continuous forced-cooling of the cooled object.

[0076]When the user lies on his/her back and puts the cellular phone to his/her right ear, the cellular phone becomes in a right-leaning position. When the cellular phone is in the right-leaning position, in the phase conversion cooler 1, the first pipe 5 is extended horizontally in a position comparatively lower side of the cooling head 2, and the second pipe 7 is extended upward from the upper side of the cooling head 2, as shown in FIG. 3B. The second circular port 4 is positioned above the liquid surface (s), and the first circular port 3 is positioned below the liquid surface (s). At this time, a circulation route of the refrigerant becomes inverted to that in FIG. 3A, however, the repetition of smooth circulation of the refrigerant is not different from that in FIG. 3A.

[0077]As described above, when the cellular phone is in the position where the third side 2c of the cooling head 2 is positioned as the upper side of the cooling head 2, the liquid surface (s) of the refrigerant is positioned above the first circular port 3. As the refrigerant in gas phase exists in the cooling head 2, phase-conversion cooling can be performed on the cooled object via the heat receiving surface.

[0078]When the user lies on his/her back and puts the cellular phone to his/her left ear, the cellular phone becomes in a left-leaning position. When the cellular phone is in the left-leaning position, in the phase conversion cooler 1, the first pipe 5 is extended horizontally in a position comparatively upper side of the cooling head 2, and the second pipe 7 is extended downward from the under side of the cooling head 2, as shown in FIG. 3C. The second pipe 7 is extended downward by a short length and bent laterally, then extended laterally by a short length then inclined upward to the condenser part 6. As the slope 8 is provided, the length of the second pipe 7 can be short, and in addition, the length of the second pipe 7 positioned below the third side 2c of the cooling head 2 can be short. In this arrangement, as the length of the second pipe 7 filled with the refrigerant is shorter than that in the conventional art shown in FIG. 7, the liquid surface (s) is positioned above the third side 2c of the cooling head 2.

[0079]As described above, in the phase conversion cooler 1 according to the present invention, when the third side 2c of the cooling head 2 is positioned as an under side of the cooling head 2, the liquid surface (s) of the refrigerant is positioned above the third side 2c. Accordingly, as the refrigerant in gas phase exists in the cooling head 2, the phase conversion cooling can be performed on the cooled object via the heat receiving surface. Further, as the first circular port 3 is positioned above the liquid surface (s) and the second circular port 4 is positioned below the liquid surface s, the circulation of the refrigerant is smoothly repeated in the same refrigerant circulation route as that in FIG. 3A.

[0080]Next, the advantages of the phase conversion cooler according to the present invention will be described.

[0081]The advantages of the phase conversion according to the present invention are reduction in size and weight, facilitation of manufacture, and improvement in cooling efficiency.

[0082]First, the reduction in size and weight will be described. In the present invention, the cooling head 2 is formed by resin molding. Incidentally, in the case of the conventional cooling head 102, the cooling head 2 is formed by three-dimensionally assembling the metal plates and welding the joints. In such configuration of the conventional cooling head, downsizing cannot be realized without difficulty since the metal plates have a predetermined or greater thickness. However, in the present invention, as the cooling head 2 is formed by resin molding, the wall thickness of the cooling head 2 can be reduced, and as a result, the cooling head 2 can be downsized. Further, as resin is used in place of metal as a main material of the cooling head 2, weight reduction can be achieved. The thickness of the conventional metal plate is 1 mm, whereas the thickness of the metal plate 9 used in the present invention is equal to or less than 0.3 mm (in the above-described embodiment, 0.1 mm). Accordingly, the weight of the metal plate 9 causes no problem.

[0083]Further, as resin is used in place of metal as a main material of the cooling head 2, the processing cost can be reduced.

[0084]Next, the facilitation of manufacture will be described. In the present invention, the cooling head 2 is formed by resin molding. In the case of the conventional cooling head 102, when the cooling head 2 is formed by three-dimensionally assembling the metal plates and welding the joints, welding is required to weld all the ridge lines to attain airtightness and to join the metal pipes as the first pipe 105 and the second pipe 107 with the circular ports 103 and 104. In the present invention, as the cooling head 102 is formed by resin molding, all the welding processes are omitted. Further, as the cooling head 2 is formed by resin molding, the first circular port 3 and the second circular port 4 can be formed as protrusions from the cooling head 2, and joining of the first pipe 5 and the second pipe 7 (or the joint 10) can be facilitated.

[0085]Regarding the improvement in cooling efficiency, in the present invention, at least the first side 2a as a heat receiving surface of the cooling head 2 is provided with the metal plate 9. When the metal plate 9 is provided in the inner side of the cooling head 2, as the metal plate 9 becomes in contact with the refrigerant, thermal conduction from the cooling head 2 to the refrigerant is promoted. On the other hand, when the metal plate 9 is provided in the outer surface of the cooling head 2, as the metal plate 9 becomes in direct contact with the cooled object, the thermal conduction from the cooled object to the cooling head 2 is promoted. Further, as described in FIGS. 1A to 1C, when the metal plate 9 is provided in the inner surface or the outer surface of the cooling head 2 so as to cover the opening in the resin formed in the first side 2a of the cooling head 2, the thermal conduction from the cooled object to the cooling head 2 is promoted and thermal conduction from the cooling head 2 to the refrigerant is promoted. Further, in the present invention, as parts of the cooling head 2 without metal plate 9 are made of resin, the thermal conductivity is lower than that of metal. Accordingly, the heat of the metal plate 9 is not easily thermal-conducted to the entire cooling head 2 but mainly thermal-conducted to the refrigerant. Accordingly, most of the heat from the cooled object contributes to vaporization of the refrigerant, and temperature rise of the entire cooling head 2 and the ambient atmosphere by the thermal conduction can be avoided. In this manner, the present invention improves the efficiency of phase conversion cooling.

[0086]The position of the cellular phone during use is limited. As shown in FIGS. 3A to 3C, in any position the cellular phone provided with the phase conversion cooler 1 according to the present invention is used, in the phase conversion cooler 1, the refrigerant in gas phase exists in the cooling head 2. In any position, the refrigerant in gas phase is always in contact with the first side 2a of the cooling head 2. Accordingly, the thermal conduction to the refrigerant can be infallibly attained by providing the metal plate 9 in the first side 2a.

[0087]When the sides other than the first side 2a of the cooling head 2 are also provided with the metal plates 9, the metal plates 9 in the sides other than the first side 2a also contribute to thermal exchange with the refrigerant. In particular, as it is understood from FIGS. 3A to 3C, regarding the fourth surface 2d opposite to the second side 2b, the fifth surface 2e opposite to the third side 2c and the third side 2c, there are opportunities for contact between the refrigerant in liquid phase and entire surface area. Therefore it is preferable that these sides are provided with the metal plate 9.

[0088]Further, it is preferable that the metal plates 9 provided in the sides other than the first side 2a as a heat receiving surface are provided on the inner surfaces of the cooling head 2. This arrangement can suppress conduction of heat, conducted from the first side 2a to the sides other than the first side 2a, to the ambient atmosphere of the cooling head 2. Accordingly, storage of hot air around the cooled object can be suppressed, and most of the heat of the metal plates 9 can be thermal-conducted to the refrigerant. Accordingly, the efficiency of phase conversion cooling can be improved.

[0089]Further, as described in FIG. 1C, as the metal plates 9 in the respective sides are provided in contact with each other, heat can be easily conducted from the metal plate 9 provided in the first side 2a as a heat receiving surface to the metal plates 9 provided to the sides other than the first side 2a. In this arrangement, when the phase conversion cooler 1 is in the positions shown in FIGS. 3A to 3C, heat is easily conducted from the metal plate 9 in the first side 2a as a heat receiving surface to the other side-metal plates 9 whose inner surfaces entirely are in contact with the refrigerant in liquid phase. Accordingly, the thermal conduction from the cooling head 2 to the refrigerant can be promoted, and the efficiency of phase conversion cooling can be improved.

[0090]Next, other embodiments of the present invention will be described.

[0091]As shown in FIG. 5, the cooling head 2 of the phase conversion cooler 1 is mounted such that the first side 2a as a heat receiving surface is in contact with an LSI 41 as a cooled object.

[0092]The second circular port 4 is formed in the third side 2c of the cooling head 2 in a position close to the first side 2a. On the other hand, the first circular port 3 is formed in the second side 2b of the cooling head 2 in a position close to the sixth side 2f opposite to the first side 2a. That is, when the first side 2a of the cooling head 2 is positioned as an under side of the cooling head 2, the height of the first circular port 3 and that of the second circular port 4 are different in the vertical direction.

[0093]In this structure, as shown in FIG. 5, the phase conversion cooler 1 is in the position where the cooling head 2 is positioned on the LSI 41 and the first side 2a of the cooling head 2 is in contact with the LSI 41 (this position is a horizontal position). The second circular port 4 is positioned below the liquid surface (s), and the first circular port 3 is positioned above the liquid surface (s). Accordingly, in the present embodiment, in addition to the positions of the phase conversion cooler 1 shown in FIGS. 3A to 3C, even in the horizontal position, the circulation of the refrigerant can be smoothly repeated.

[0094]Further, as the entire first side 2a as a heat receiving surface is in contact with the refrigerant and provided with the metal plate 9, the efficiency of phase conversion cooling is high.

[0095]Next, an embodiment in which the phase conversion cooler 1 according to the present invention is provided in a cellular phone will be described.

[0096]As shown in FIGS. 6A and 6B, a cellular phone 51 is formed by rotatably connecting a key operation unit 52 and a display unit 53 via a hinge 54. The key operation unit 52 includes the LSI 41 packaged on a circuit board (not shown), and the cooling head 2 of the phase conversion cooler 1 is mounted on a heat radiating surface of the LSI 41. The display unit 53 includes the condenser part 6. The first pipe 5 and the second pipe 7 are arranged from the key operation unit 52 to the display unit 53.

[0097]As shown in FIGS. 6A and 6B, the cellular phone 51 is placed on a flatland or held in a user's hand and the key operation unit 52 is horizontally set, and the display unit 53 is opened at an opening angle of 120.degree. with respect to the key operation unit 52. At this time, as the cooling head 2 is in the horizontal position shown in FIG. 5, high cooling efficiency is attained in the phase conversion cooler 1.

[0098]When the cellular phone 51 is opened at an opening angle of 180.degree. and used for communication, the cellular phone 51 is in the erect position, the left-leaning position or the right-leaning position in accordance with the user's position. As described in FIGS. 3A to 3C, in the phase conversion cooler 1, phase conversion cooling can be sufficiently performed regardless of use position, and high cooling efficiency is attained.

[0099]Although the invention has been described with respect to the specific exemplary embodiments for complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.

[0100]It is noted that Applicant's intent is to encompass equivalents of all claim elements, even if amended later during prosecution.

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