HEAT SINK

The present disclosure is related to providing a heat sink that can exhibit an excellent cooling property for even a heating element generating a high amount of heat and being mounted to a narrowed space. The heat sink includes a plurality of heat pipes to be thermally connected to a heating element, and a heat dissipation section thermally connected to the plurality of heat pipes, in which in the plurality of heat pipes, at least evaporation sections to be thermally connected to the heating element have flattened portions whose cross sectional shape in a direction orthogonal to a heat transfer direction of the plurality of heat pipes is flattened, and surfaces in the flattened portions in a thickness direction are arranged facing the heating element.

BACKGROUND

Technical Field

The present disclosure is related to a heat sink configured to cool a heating element set as a cooling target by transferring heat of the heating element to a heat dissipation section by using a heat transfer function of a heat pipe.

BACKGROUND

Along with an enhancement of functions of an electronic device in recent years, a large number of parts including a heating element such as an electronic part have been mounted inside the electronic device at a higher density than ever. In addition, along with the enhancement of the functions of the electronic device, an amount of heat generated by the heating element such as the electronic part has increased more than ever. As a unit configured to cool the heating element such as the electronic part, a heat sink is used in some cases. To reliably and also efficiently cool even a heating element generating a high amount of heat, a heat sink where a plurality of heat pipes are thermally connected to the heating element is used in some cases.

As the heat sink where the plurality of heat pipes are thermally connected to the heating element, for example, a heat sink exists where a large number of flat plate-like heat dissipation fins protruding to outer peripheral surfaces of a plurality of tubular heat pipes are disposed (Japanese Patent Laid-Open No. 2003-110072). The heat sink of Japanese Patent Laid-Open No. 2003-110072 is a heat sink formed in a manner that heat of the heating element is transferred to the heat dissipation fins by the plurality of tubular heat pipes, and the heat is to be dissipated from the heat dissipation fins.

In a heat sink where the heat of the heating element is transferred from a heat reception section to the heat dissipation fins by the plurality of heat pipes such as the heat sink of Japanese Patent Laid-Open No. 2003-110072, to exhibit a cooling property for even a heating element generating a high amount of heat, it is necessary to form a heat pipe group where a large number of heat pipes are arranged in parallel, and thermally connect the heat pipe group to the heating element. On the other hand, to thermally connect the heat pipe group formed by the large number of heat pipes to the heating element, it is necessary to secure a large space for housing the heat pipe group inside the electronic device. However, since a large number of parts are mounted inside the electronic device at the higher density than ever, the heating element may also be mounted into an even narrowed space in some cases.

Because of a constraint of the space inside the electronic device as described above, the number of installed heat pipes forming the heat pipe group may be restricted in some cases. When the number of installed heat pipes is restricted, the cooling property for the heating element generating a high amount of heat may not be sufficiently applied to the heat sink in some cases.

SUMMARY

The present disclosure is related to providing a heat sink that can exhibit an excellent cooling property for even a heating element generating a high amount of heat and being mounted into a narrowed space.

A gist of the configuration of the present disclosure is as follows.

[1] A heat sink including a plurality of heat pipes to be thermally connected to a heating element, and a heat dissipation section thermally connected to the plurality of heat pipes, in which in the plurality of heat pipes, at least evaporation sections to be thermally connected to the heating element have flattened portions whose cross sectional shape in a direction orthogonal to a heat transfer direction of the plurality of heat pipes is flattened, and surfaces in the flattened portions in a thickness direction are arranged facing the heating element.

[2] The heat sink as described in [1], in which the evaporation section of the heat pipe is located in one end portion of the heat pipe, and a condensation section of the heat pipe to be thermally connected to the heat dissipation section is located in another end portion of the heat pipe.

[3] The heat sink as described in [1], in which the evaporation section of the heat pipe is located in a central portion of the heat pipe, and the condensation section of the heat pipe to be thermally connected to the heat dissipation section is located in both end portions of the heat pipe.

[4] The heat sink as described in any one of [1] to [3], in which the evaporation sections of the plurality of heat pipes are arranged in parallel along an extending direction of the heating element.

[5] The heat sink as described in any one of [1] to [4], in which the evaporation section of the heat pipe is thermally connected to a heat reception plate, and the heat reception plate is to be thermally connected to the heating element.

[6] The heat sink as described in any one of [1] to [5], in which the flattened portion extends from the evaporation section to the condensation section.

[7] The heat sink as described in any one of [1] to [6], in which the heat pipe includes a first wick structure corresponding to fine grooves formed on an inner surface of a container, and a second wick structure having protrusion portions protruding from the inner surface of the container in flat segments forming a main surface of the flattened portion.

[8] The heat sink as described in [7], in which the heat pipe further includes a third wick structure disposed in a layered manner on an inner surface of the flattened portion in the thickness direction.

In accordance with a mode of the heat sink of the present disclosure, since at least the evaporation section in the heat pipe has the flattened portion whose cross sectional shape in the direction orthogonal to the heat transfer direction of the heat pipe is flattened and the surface in the flattened portion in a thickness direction is arranged facing the heating element, an increased number of heat pipes can be thermally connected to the heating element set as the cooling target without increasing an installment space of the heat reception section of the heat sink. In addition, in accordance with a mode of the heat sink of the present disclosure, an increased number of heat pipes can be thermally connected to the heat dissipation section of the heat sink. Therefore, in accordance with a mode of the heat sink of the present disclosure, a heat dissipation efficiency of the heat dissipation section improves, and the excellent cooling property can be exhibited for the heating element even having the high heat value mounted into the narrowed space.

In accordance with a mode of the heat sink of the present disclosure, since the one end portions or central portions of the plurality of heat pipes are arranged in parallel along the extending direction of the heating element, the plurality of heat pipes can be reliably and also easily thermally connected to the heating element.

In accordance with a mode of the heat sink of the present disclosure, since the one end portion or central portion of the heat pipe is thermally connected to the heat reception plate, a thermal connectivity between the heat pipe and the heating element improves. In addition, the heat reception plate also has an action as a heat equalizing plate configured to equalize thermal loads to the respective heat pipes arranged in parallel, and can more reliably exhibit heat transfer properties of the respective heat pipes.

In accordance with a mode of the heat sink of the present disclosure, since the heat pipe includes the first wick structure corresponding to the fine grooves formed on the inner surface of the container and the second wick structure having the protrusion portions protruding from the inner surface of the container in the flat segments forming the main surface of the flattened portion, a liquid working fluid can be smoothly recirculated to the flattened portion. Thus, even the heat pipe having the flattened portion in the evaporation section can exhibit the excellent heat transfer property.

In accordance with a mode of the heat sink of the present disclosure, since the heat pipe further includes the third wick structure disposed in the layered manner on the inner surface of the flattened section in the thickness direction, the liquid working fluid can be more smoothly recirculated to the flattened portion. Thus, even the heat pipe having the flattened portion in the evaporation section can exhibit the more excellent heat transfer property.

DETAILED DESCRIPTION

Hereafter, a heat sink according to a first embodiment of the present disclosure will be described with reference to the drawings.FIG. 1is a perspective view of the heat sink according to the first embodiment of the present disclosure.FIG. 2is a plan view of the heat sink according to the first embodiment of the present disclosure.FIG. 3is a side view of one end portion of the heat sink according to the first embodiment of the present disclosure.FIG. 4is a plan view of a heat sink according to a second embodiment of the present disclosure.FIG. 5is a side view of the heat sink according to the second embodiment of the present disclosure.FIG. 6is an explanatory view of a cross section A-A inFIG. 4of the heat sink according to the second embodiment of the present disclosure.FIG. 7is an explanatory view of a wick structure disposed in heat pipes provided to the heat sink according to the present disclosure.

As illustrated inFIGS. 1 to 3, a heat sink1according to the first embodiment includes a plurality of heat pipes11thermally connected to a heating element101set as a cooling target of the heat sink1, and a heat dissipation section40. The plurality of heat pipes11are commonly thermally connected to the heat dissipation section40. The heat dissipation section40has a plurality of heat dissipation fins41. The heat pipe11is a heat transfer member having an internal space sealed and subjected to decompression treatment. A working fluid (not illustrated) is sealed in the internal space of the heat pipe11.

In each of the plurality of heat pipes11, one end portion12is thermally connected to the heating element101, and another end portion13is thermally connected to the heat dissipation section40. Therefore, in each of the plurality of heat pipes11, the one end portion12functions as an evaporation section, and the other end portion13functions as a condensation section. In each of the plurality of heat pipes11, a longitudinal direction linking the one end portion12to the other end portion13corresponds to a heat transfer direction. In the heat sink1, a heat pipe group is formed in the plurality (four, inFIGS. 1 to 3) of heat pipes11. In the heat pipe group, the respective heat pipes11are arranged in parallel in a side view. In the heat sink1, the respective heat pipes11are arranged in parallel on a line in a side view. In addition, the evaporation sections of the plurality of heat pipes11are arranged in parallel along an extending direction of the heating element101.

In each of the plurality of heat pipes11, a cross sectional shape of the heat pipe11in a short direction, that is, a cross sectional shape in a direction orthogonal to the heat transfer direction of the heat pipe11is a flattened shape obtained by subjecting a circular shape to flattening process. That is, the heat pipe11has a flattened portion60whose cross sectional shape in the direction orthogonal to the heat transfer direction is flattened. In the heat sink of the present disclosure, in terms of space saving in a thermal connection portion with the heating element, it is sufficient when at least a part of the evaporation section in the heat pipe has the flattened portion, but in the heat pipe11, the flattened portion60extends from the evaporation section corresponding to the one end portion12to the condensation section corresponding to the other end portion13.

The flattened portion60includes mutually facing flat segments61forming a main surface, and mutually facing surfaces62linking the facing flat segments61in a thickness direction. The mutually facing flat segments61form a longitudinal direction of the flattened portion60, and the mutually facing surfaces62in the thickness direction form the short direction of the flattened portion60. In the flattened portion60, one of the surfaces62in the thickness direction is arranged on a side of the heating element101. In addition, the facing flat segments61adopt a mode of being erected. That is, the flattened portion60in the longitudinal direction adopts the mode of being erected. From the aforementioned description, the surfaces62in the thickness direction form a width direction of the heat pipe group.

Therefore, in the heat sink1, an increased number of the heat pipes11can be thermally connected to the heating element101without increasing an installment space of a heat reception section of the heat sink1as compared with a heat pipe where a shape of the heat pipe in the short direction is circular.

As illustrated inFIG. 3, in the heat pipe11, the one end portion12is thermally connected to a first surface31of a heat reception plate30. The plurality of heat pipes11are all installed on the same surface of the heat reception plate30. The heating element101is thermally connected to a second surface32corresponding to a surface on the opposite side of the first surface31of the heat reception plate30. Therefore, each of the plurality of heat pipes11is thermally connected to the heating element101via the heat reception plate30. It is noted that in the heat sink1, a cover member110is attached to cover the heat reception plate30and an upper surface of the one end portion12of the heat pipe11.

As illustrated inFIG. 7, a wick structure51configured to cause the liquid working fluid (not illustrated) to recirculate from the other end portion13to the one end portion12is disposed inside a container50of each of the heat pipes11. The wick structure51is a structure having capillarity. A type and a shape of the wick structure51are not particularly limited. In the heat pipe11, the wick structure51includes a first wick structure52corresponding to a plurality of fine grooves, a second wick structure53having a protrusion portion protruding from the inner surface of the container50in the flat segments61forming the main surface of the flattened portion60on an inner surface of the heat pipe11, and a third wick structure54disposed in a layered manner on the surfaces62of the flattened portion60in the thickness direction on an inner surface of the container50of the heat pipe11.

The first wick structure52is the plurality of fine grooves extending in the heat transfer direction on the inner surface of the container50. In addition, the first wick structure52is formed in the entirety of the container50in a circumference direction. From the aforementioned description, the first wick structure52is formed in the entirety of the inner surface of the container50.

The second wick structure53includes two protrusion portions protruding in a convex manner from the inner surface of the container50. The second wick structure53is disposed on the first wick structure52. In addition, the second wick structure53also protrudes relative to the third wick structure54disposed in a layered manner. That is, the second wick structure53has a wall thickness larger than that of the third wick structure54. In addition, the two protrusion portions described above are arranged facing each other. The second wick structure53having the protrusion portions is excellent in recirculation property of the liquid working fluid as compared with the wick structures having no protrusion portions (the first wick structure52and the third wick structure54in the heat pipe11). Therefore, since the liquid working fluid can be smoothly recirculated to the evaporation section corresponding to the flattened portion60, even the heat pipe11having the flattened portion60in the evaporation section can exhibit the excellent heat transfer property. An area where the second wick structure53is disposed is not particularly limited, and can be selected depending on a use condition or the like of the heat sink1, but in the heat sink1, the second wick structure53extends from the one end portion12to the other end portion13of the heat pipe11.

A type of the second wick structure53is a sintered body of metallic powder, a mesh formed of a metallic line, a metallic braided body, or the like, and is not particular limited, but in the heat pipe11, a sintered body of metallic powder such as copper or a copper alloy is used.

The third wick structure54is formed at a substantially uniform thickness in a layered manner along the surfaces62of the flattened portion60in the thickness direction. In addition, the third wick structure54is formed to be continuous to the second wick structure53in a cross section in the direction orthogonal to the heat transfer direction of the heat pipe11. The third wick structure54is disposed on the first wick structure52. An area where the third wick structure54is disposed is not particularly limited, and can be selected depending on the use condition or the like of the heat sink1, but in the heat sink1, the third wick structure54extends from the one end portion12to the other end portion13of the heat pipe11. It is noted that on the surfaces62of the flattened portion60in the thickness direction, since the capillarity of the first wick structure52contributes to the recirculation of the liquid working fluid to the evaporation section, a configuration may also be adopted where the third wick structure54is not disposed depending on the use condition or the like of the heat sink1.

A type of the third wick structure54is a sintered body of metallic powder, a mesh formed of a metallic line, a metallic braided body, or the like, and is not particularly limited, but in the heat pipe11, a sintered body of metallic powder such as copper or a copper alloy is used.

As illustrated inFIGS. 1 to 3, the one end portions12of the heat pipes11are arranged in parallel along the extending direction of the heating element101. In addition, the one end portions12of the plurality of heat pipes11are arranged in parallel substantially on the same plane.

As illustrated inFIG. 2, a shape of the one end portion12of each of the plurality of heat pipes11in a plan view is substantially linear, and a shape of a central portion14located between the one end portion12and the other end portion13in a plan view is also substantially linear. Therefore, in the plurality of heat pipes11, substantially linear parts in a plan view are arranged side by side from the one end portion12to the central portion14.

In the heat sink1, with regard to the heat pipe11, a bent portion15is formed in the other end portion13thermally connected to the heat dissipation section40. Therefore, each of the plurality of heat pipes11is substantially L-shaped in a plan view. In addition, the bent portion15of the heat pipe11located on a right side is bent in a right direction, and the bent portion15of the heat pipe11on a left side is bent in a left direction. In other words, bending directions of the bent portions15are opposite to each other with regard to the heat pipe11located on the left side and the heat pipe11located on the right side.

Each of the plurality of heat pipes11adopts a mode where the other end portion13extends in a substantially parallel direction to the longitudinal direction of the heat dissipation section40by the bent portion15. In the heat dissipation section40, the plurality of heat dissipation fins41are arranged in parallel such that a main surface (planar portion) of the heat dissipation fins41is arranged in a substantially parallel direction to the extending direction of the one end portion12of the heat pipe11. The heat dissipation fins41are a thin flat plate-like member. In the heat sink1, the other end portion13of the heat pipe11extending in the parallel direction to the longitudinal direction of the heat dissipation section40reaches an end portion of the heat dissipation section40in the longitudinal direction.

As illustrated inFIG. 1, an external shape of the heat dissipation section40is substantially cuboid. The heat dissipation section40adopts a structure where a first heat dissipation fin group42whose external shape is substantially cuboid, and a second heat dissipation fin group43whose external shape is substantially cuboid while being adjacent to the first heat dissipation fin group42are laminated. Both the first heat dissipation fin group42and the second heat dissipation fin group43adopt a structure where the plurality of heat dissipation fins41attached on a flat plate-like supporting body45are arranged in parallel in the substantially parallel direction to the longitudinal direction of the heat dissipation section40.

The other end portion13of the heat pipe11is inserted between the first heat dissipation fin group42and the second heat dissipation fin group43. When the other end portion13is arranged between the first heat dissipation fin group42and the second heat dissipation fin group43, the heat dissipation section40is thermally connected to the heat pipe11.

A material of the container50used in the heat pipe11is not particularly limited, and for example, copper, a copper alloy, aluminum, an aluminum alloy, stainless steel, and the like can be exemplified. In addition, the working fluid to be sealed in the container50can be appropriately selected according to compatibility with the material of the container50, and for example, water, fluorocarbons, cyclopentane, ethylene glycol, a mixture of these, and the like can be exemplified. In addition, a material of the heat dissipation fins41is not particularly limited, and for example, a metal such as copper and a copper alloy can be exemplified.

Next, a use method example of the heat sink1according to the first embodiment will be described. As illustrated inFIG. 3, the heat pipe group of the heat sink1is installed such that the plurality of heat pipes11are arranged immediately above and in the vicinity of the heating element101on a plane on a side of the heat reception plate30of the heating element101. The heat radiated from the heating element101is transmitted to the heat reception plate30. The heat transmitted to the heat reception plate30is transmitted from the heat reception plate30to the one end portion12of the heat pipe11. The heat transmitted to the one end portion12of the heat pipe11is transferred from the one end portion12of the heat pipe11to the other end portion13of the heat pipe11by a heat transfer action of the heat pipe11. The heat transferred to the other end portion13of the heat pipe11is transmitted to the heat dissipation section40having the plurality of heat dissipation fins41. When the heat transmitted to the heat dissipation section40is dissipated from the heat dissipation section40to an external environment, it is possible to cool the heating element101.

At this time, the heat pipe11includes the flattened portion60whose cross sectional shape in the orthogonal direction to the heat transfer direction of the heat pipe11is flattened, and the surfaces62of the flattened portion60in the thickness direction are arranged facing the heating element101, so that an increased number of the heat pipes11can be thermally connected to the heating element101set as the cooling target without increasing the installment space of the heat reception section of the heat sink1. In addition, in the heat sink1, in response to a state where an increased number of the heat pipes11can be thermally connected to the heating element101, an increased number of the heat pipes11can be thermally connected to the heat dissipation section40of the heat sink1, and a heat dissipation efficiency of the heat dissipation section40improves. Therefore, the heat sink1can exhibit the excellent cooling property for a heating element101even having a high heat value and being mounted to the narrowed space.

In addition, in the heat sink1, since the evaporation sections of the plurality of heat pipes11(in the heat sink1, the one end portions12) are arranged in parallel along the extending direction of the heating element101, it is possible to reliably and also easily thermally connect the plurality of heat pipes11to the heating element101.

In addition, in the heat sink1, since the evaporation section of the heat pipe11(in the heat sink1, the one end portion12) is thermally connected to the heat reception plate30, the thermal connectivity between the heat pipe11and the heating element101improves. In addition, since the heat reception plate30also has an action as a heat equalizing plate configured to equalize thermal loads to the heat pipes11arranged in parallel, it is possible to more reliably exhibit the heat transfer property of the heat pipe11.

Next, a heat sink according to a second embodiment of the present disclosure will be described with reference to the drawings. It is noted that with regard to the heat sink according to the second embodiment, since a main configuration is the same as that of the heat sink according to the first embodiment, the same components as those of the heat sink according to the first embodiment will be described by using the same reference signs.

In the heat sink1according to the first embodiment, the one end portion12of the first heat pipe11is thermally connected to the heat reception plate30, but instead of this, as illustrated inFIGS. 4 and 5, the heat sink2according to the second embodiment adopts a mode where the heat pipe11from the one end portion12to the other end portion13extends from one end33to another end34of the heat reception plate30. In addition, as illustrated inFIGS. 5 and 6, the heat pipe11is thermally connected to the first surface31of the heat reception plate30.

The heat dissipation fins41are elected on the first surface31of the heat reception plate30. In a heat sink2, the heat dissipation fins41are elected on the first surface31of the heat reception plate30in a vertical direction. Edge portions of the heat dissipation fins41are attached on the first surface31of the heat reception plate30. In addition, as the heat dissipation section40, the plurality of heat dissipation fins41are arranged in parallel at a predetermined interval from the one end33to the other end34of the heat reception plate30.

The heating element101is to be thermally connected to a central portion35of the heat reception plate30(that is, parts other than the one end33and the other end34of the heat reception plate30). Therefore, the central portion14of the heat pipe11(that is, parts other than the one end portion12and the other end portion13) is thermally connected to the heating element101to function as the evaporation section. In addition, both end portions (the one end portion12and the other end portion13) of the heat pipe11are thermally connected to the heat dissipation section40to function as the condensation section.

It is noted that with regard to the heat sink2, slight bending is formed in the heat pipe11such that the heat pipe11approaches the central portion in the orthogonal direction to the longitudinal direction of the heat pipe11in the central portion35of the heat reception plate30. According to the mode described above, it is possible to improve the thermal connectivity between the heat pipe group and the heating element101.

Also in the heat sink2where the heating element101is thermally connected to the central portion14of the heat pipe11, the heat pipe11includes the flattened portion60whose cross sectional shape in the orthogonal direction to the heat transfer direction of the heat pipe11is flattened, and the surfaces62of the flattened portion60in the thickness direction are arranged facing the heating element101. Thus, an increased number of the heat pipes11can be thermally connected to the heating element101without increasing the installment space of the heat reception section of the heat sink2. In addition, also in the heat sink2, in response to a state where an increased number of the heat pipes11can be thermally connected to the heating element101, an increased number of the heat pipes11can be thermally connected to the heat dissipation section40of the heat sink2, and the heat dissipation efficiency of the heat dissipation section40improves. Therefore, the heat sink2can also exhibit the excellent cooling property for the heating element101even having the high heat value and being mounted in the narrowed space.

Next, other embodiments of the present disclosure will be described. In the heat sink according to the first embodiment described above, the bent portion is formed in the other end portion of the heat pipe, and the heat pipe is substantially L-shaped in a plan view, but the shape of the heat pipe in a plan view is not particularly limited, and may be substantially linear, for example. In this case, the heat dissipation fins may be arranged in parallel such that the main surface (planar portion) of the heat dissipation fins is arranged in substantially orthogonal direction to the extending direction of one end portion of the heat pipe group.

The heat reception plate is disposed in the heat sink according to the first and second embodiments described above, but a configuration may be adopted where the heat reception plate is not disposed depending on a use situation of the heat sink. In addition, in the heat sink according to the first and second embodiments described above, the heat dissipation section is formed of the plurality of heat dissipation fins, but the mode of the heat dissipation section serving as a heat exchange unit is not particularly limited, and for example, a water cooling jacket and the like may also be used.

The heat sink of the present disclosure can be used in an extensive field, but for example, can be used in a field where a high performance electronic part is used such as a server used in a data center or the like since an excellent cooling performance can be exhibited for the heating element even having the high heat value and being mounted into the narrowed space.