Liquid cooling jacket

In a liquid cooling jacket, to improve the heat transfer coefficient, extensibility and assembling, the liquid cooling jacket comprises a base bonded to a heating element; a post standing perpendicularly to the base; a plurality of radiating fins attached to the post and arranged so as to be parallel to the base; a partition filling up intervals between the plurality of radiating fins at a predetermined width; and a case which surrounds the post and the radiating fins and is bonded to the base, and to which an inlet and an outlet for coolant are attached at positions where flow of the coolant is divided by the partition. The plurality of radiating fins may be arranged at intervals each of which is narrow in comparison with a thickness of each of the plurality of radiating fins. Therefore, because the coolant flow within the liquid cooling jacket ensures a plurality of passages, the passage resistance is low. In addition, by setting the size of each of the inlet and outlet for the coolant to be substantially equal to the height of the arranged radiating fins, the flow rates on the radiating fins can be even.

CROSS REFERENCE TO RELATED APPLICATION

This application relates to and claims priority from Japanese Patent Application No. 2003-349701, filed on Oct. 8, 2003, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid cooling jacket attached to a heating element in a liquid cooling system used for cooling an electronic device.

2. Description of the Related Art

Conventionally, a liquid cooling jacket used for cooling an electronic device must efficiently transmit heat from a heating element to coolant.

For this reason, as an example, a conventional liquid cooling jacket has therein a meandering passage, as illustrated inFIG. 18. In this example, the passage1302within the jacket1301meanders so that the flow1303of coolant is in contact with the jacket1301as long as possible. This is a method in which the contact area between the coolant and the inner surface of the jacket wall is increased by increasing the length of the passage within the jacket1301as much as possible to efficiently transmit heat from a heating element to the coolant.

In another example, as illustrated inFIG. 19, the flow1401of coolant is divided into a plurality of streams1403ato1403f. This is a method in which provision of a plurality of passage paths decreases the passage resistance and increases the contact area between the coolant and radiating fins1402to efficiently transmit heat (for example, see JP-A-2000-340727).

In addition, because convenience of piping is superior if the inlet and outlet of coolant are in a row, a conventional liquid cooling jacket has the inlet and outlet of coolant arranged in a row. As illustrated inFIG. 20, this is a method in which a partition1502is provided at the center of the arrangement of radiating fins1501to turn back the flow1401of coolant and thereby the inlet and outlet are arranged in a row (for example, see JP-A-2002-170915).

However, the meandering passage as illustrated inFIG. 18has a problem that the passage resistance increases as the length of the passage increases, and thus the pressure loss increases.

The passage in which the flow of coolant is divided into a plurality of steams, as illustrated inFIG. 19, has a problem that it is difficult to make the coolant flow evenly among the radiating fins. More specifically, because any liquid flow has straight motility, there is a problem that the coolant is hard to flow to the radiating fin near the inlet. Thus, as illustrated inFIG. 19, unevenness occurs in the flow rates of the streams1403ato1403f. As a result, the heat transfer coefficient decreases so that heat from the heating element cannot be efficiently transmitted to the coolant.

The structure as illustrated inFIG. 20also has a problem that unevenness occurs in the liquid streams1503ato1503cbetween the radiating fins. More specifically, the flow rate of the stream1503bnear the inlet or outlet is the highest and the other flow rates of the streams1503aand1503care lower. As a result, the heat transfer coefficient decreases so that heat from the heating element cannot be efficiently transmitted to the coolant.

In addition, any prior art as described above has a problem that improvement of coefficient of thermal conductivity is difficult even if the jacket size is increased in order to ensure more contact area, because the distance from the centered heating element increases. More specifically, conventionally, as illustrated inFIG. 21, a base301horizontally spreads heat to transmit the heat to each radiating fin302. However, the base thickness t1has a limit by the influence of weight and height. Actually, the thickness is about 7 mm at the maximum. Therefore, the spread303of heat is limited to the periphery of the heating element103and heat cannot be transmitted to the end radiating fins302a. That is, as the jacket size increases, the cooling effect of the end radiating fins decreases.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid cooling jacket good in heat transfer coefficient and superior in extensibility and assembling.

A liquid cooling jacket according to the present invention comprises a base bonded to a heating element; a post standing perpendicularly to the base; a plurality of radiating fins attached to the post and arranged so as to be parallel to the base; a partition filling up intervals between the plurality of radiating fins at a predetermined width; and a case which surrounds the post and the radiating fins and is bonded to the base, and to which an inlet and an outlet for coolant are attached at positions where flow of the coolant is divided by the partition. The plurality of radiating fins may be arranged at intervals each of which is narrow in comparison with a thickness of each of the plurality of radiating fins.(1) According to the present invention, because the coolant flow within the liquid cooling jacket ensures a plurality of passages, the passage resistance is low. In addition, by setting the size of each of the inlet and outlet for the coolant to be substantially equal to the height of the arranged radiating fins, the flow rates between the radiating fins can be even.(2) According to the present invention, because the post for transmitting heat to each radiating fin is thick and the height of the post can be at a small distance from the base in contact with the heating element, the coefficient of thermal conductivity is high.(3) According to the present invention, because the route of the coolant is turned back by the partition provided between the radiating fins, the inlet and outlet for the coolant can be arranged in a row and thus convenience on piping is superior.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments according to the present invention will be described in detail with reference to drawings. Through all drawings for explaining the embodiments, the same components are denoted as a rule by the same reference numerals, respectively, to omit the repetitious description.

With reference toFIG. 1, the structure of an electronic device to which a liquid cooling jacket according to the present invention is applied will be described.FIG. 1is a perspective view of the electronic device to which the liquid cooling jacket according to the present invention is applied. As an example of the electronic device,FIG. 1illustrates a desktop type personal computer.

InFIG. 1, a mother board102is near the bottom face within a casing101. On the mother board102mounted are a CPU103as a heating element, a chip set104, and a memory105. An HDD106, an FDD107, and a CD-ROM drive108are installed as external storage devices within the casing101. A liquid cooling jacket131according to the present invention is attached to the CPU103.

This liquid cooling jacket131is made of metal superior in heat transfer, such as copper or aluminum.

The contact surface with the CPU103is bonded under pressure with thermal compound or highly heat-conductive silicone rubber being interposed, thereby a structure is realized in which heat generated in the CPU103is efficiently transmitted to the liquid cooling jacket131. Coolant is made to flow within the liquid cooling jacket131by a pump132to realize a structure for transmitting heat to the coolant.

A heat sink135as a radiator unit is disposed outside the rear face of the casing101. The heat sink135is made up of a base135aand fins135b. The coolant flows within the base135ato realize a structure for transmitting the heat of the coolant to the whole of the base135a. In addition, the base135ahas a mechanism for keeping a constant liquid quantity. That is, the base135aalso functions as a reserve tank for the coolant.

The fins135bare arranged so as to face the rear face of the casing. That is, the wind from a fan113blows on the fins135b.

The fan113attached to the rear face of the casing101is disposed so as to be opposite to the heat sink135and the wind from the fan113blows directly to the fins135b. More specifically, the fan113is an axial fan whose suction side is near the inside of the casing101and whose discharge side is near the heat sink135. A power supply109is adjacent to the fan113.

Tubes133and metallic pipes134connect the liquid cooling jacket131and the heat sink135to each other. The tubes133and the metallic pipes134allow the coolant to flow therein and thus they form a heat transmission path between the liquid cooling jacket131and the heat sink135.

The whole piping is mainly made of the metallic pipes134and the rubber tubes133are partially used. Because the tubes133can be bent, maintenance such as replacement of the CPU103is easy. That is, the liquid cooling jacket131can be detached from the CPU103without detaching the fan113and the heat sink135. In addition, by using the metallic pipes134for the part of the piping other than the tubes133, moisture permeation is suppressed.

The flowing route of the coolant is from the pump132through the liquid cooling jacket131and the heat sink135to the pump132. Thus, in the direction of the coolant flow by the pump132, the pump132sucks the coolant after passing through the heat sink135and discharges the coolant to the liquid cooling jacket131. Therefore, the cooled coolant flows in the pump132and thereby the pump132is prevented from being heated.

Next, with reference toFIGS. 2 to 7, the structure of the liquid cooling jacket according to the present invention will be described.FIG. 2is an exploded view of the liquid cooling jacket according to the present invention.FIG. 3is an explanatory view for explaining heat conduction to radiating fins of the liquid cooling jacket according to the present invention.FIG. 4is an explanatory view for explaining an example in which a heat pipe is used as a post of the liquid cooling jacket according to the present invention.FIG. 5is an explanatory view for explaining the flow of the coolant of the liquid cooling jacket according to the present invention.FIG. 6is an explanatory view for explaining a shape for decreasing the diameter of an inlet or outlet of the liquid cooling jacket according to the present invention.FIG. 7is an explanatory view for explaining another shape for decreasing the diameter of the inlet or outlet of the liquid cooling jacket according to the present invention.

First, components of the liquid cooling jacket will be described. As illustrated inFIG. 2, the liquid cooling jacket is made up of a base201bonded to the heating element103, a post202standing vertically to the base201, radiating fins203attached to the post202so as to be parallel to the base201, a partition204filling up the intervals between the radiating fins at a predetermined width, and a case205that surrounds the post202and the radiating fins203, is bonded to the base201, and is provided with an inlet206and an outlet207for the coolant.

The base201is in contact with the heating element with high flatness. The base201has a function of keeping the post202vertical and a function of ensuring watertightness with the case205. For efficiently transmitting heat to the post202, a material high in heat conductivity, such as copper, may be used. The base201may be formed integrally with the post202. Otherwise, a structure may be adopted in which the post202penetrates the base201to be in direct contact with the heating element103. In this case, because the heat conductivity of the base201is not important, a cheap material can be used.

The post202vertically transmits heat from the heating element103and further transmits the heat to the radiating fins203. In the related art, as described before, the base201horizontally spreads heat, as shown in the heat spread303inFIG. 21, to transmit heat to each radiating fin302. However, the base thickness has a limit by the influence of weight and height. Actually, the thickness is about 7 mm at the maximum and thus the thermal resistance is high. Therefore, the heat spread303is limited to an area in the vicinity of the heating element103and heat cannot be transmitted to the end flat plates302a.

Contrastingly, in this embodiment, as illustrated inFIG. 3, heat conduction to each radiating fin203is born by the post202. This post202is columnar and thick as a diameter r1of about 30 mm, and thus the thermal resistance is low. Further, even at the top portion of the post202, sufficient cooling can be performed because the height of the post202is approximately equal to the height of the inlet206and outlet207for the coolant. For example, in case that the inlet206and outlet207each have an inner diameter of 7 φ mm and an outer diameter of 9 φ mm, the post202may have a height of about 10 mm. Because the distance from the heating element103is small, heat401from the heating element103can be sufficiently transmitted.

To further improve the cooling ability, as illustrated inFIG. 4, a heat pipe209may be used as the post202. If the post202has a function of the heat pipe209, a structure other than that illustrated inFIG. 4is also possible.

The radiating fins203are attached to the post202in a positional relation of being parallel to the base201. The radiating fins203each have a shape concentric with the post202. The radiating fins203have a function of transmitting heat from the post202to the coolant. To further improve the heat transmissibility to the coolant, the surface of each radiating fin203may have protrusions, openings, or the like.

In this embodiment, the post202is columnar and the radiating fins203are concentric with the post202. However, the shapes of the post202and radiating fins203are not limited to these. Other shapes may be adopted.

The radiating fins203of this embodiment must be designed differently from fins for air cooling. More specifically, air and liquid widely differs from each other in heat capacity. For example, the heat capacity of water is 89 times of that of air. That is, because the coolant as liquid is superior to air in ability of taking heat off, the fins can be small-sized in comparison with those for air cooling.

However, a noteworthy fact of fins for liquid cooling is that the temperature of each fin end is immediately lowered because heat is taken off by the coolant if the heat conductive ability of the fins is low. As a result, the temperature of each fin end remains low and heat is hard to be transmitted to the fin end. This decreases the cooling ability. That is, the fins for liquid cooling require high heat conductive ability.

More specifically, generally in case of radiating fins for air cooling, in many cases, each interval between the radiating fins is wide in comparison with the thickness of each radiating fin because a large amount of air is required for discharging heat. However, inversely in case of liquid cooling of this embodiment, each radiating fin is preferably thick to increase the heat conductive ability of the fin itself. In case of this embodiment, for water cooling, each interval between the radiating fins is narrow in comparison with the thickness of each radiating fin, for example, the thickness of each radiating fin203is 2 mm and each interval between the fins is 1 mm.

As illustrated inFIG. 2, the radiating fins are provided with a partition204filling up the intervals between the radiating fins at a predetermined width. This partition204is for forming a passage for the coolant208as illustrated inFIG. 2. Because the liquid flow is thereby turned back, the inlet206and the outlet207can be arranged parallel to each other. This can improve convenience on piping. If the liquid flow need not be turned back, the partition204may be omitted so that the inlet206and the outlet207are disposed in opposition to each other.

The inlet206and the outlet207have a function of making the coolant flow evenly among the intervals between the radiating fins. In this embodiment, as illustrated inFIG. 5, the size of each of the inlet206and outlet207is substantially equal to the height of the radiating fins203. Thus, from the coolant208having entered the jacket, the coolant flows208aflowing in the intervals between the radiating fins203can be even.

Here, if the diameter of the inlet206or outlet207is intended to be decreased for reasons of, e.g., the tube connected to the jacket, as illustrated inFIG. 6, the shape of the inlet206or outlet207may be tapered after the insertion portion of the tube133. Otherwise, as illustrated inFIG. 7, the inlet206or outlet207may be disposed at an angle with the radiation fins203and the passage between the inlet206or outlet207and the radiation fins203is connected by an inclined wall.

Next, with reference toFIGS. 8 to 10, an example of the liquid cooling jacket according to the present invention in consideration of assembling will be described.FIGS. 8 and 9are explanatory views for explaining the structure of the liquid cooling jacket according to the present invention in consideration of assembling.FIG. 10is an explanatory view for explaining the shape of the partition of the liquid cooling jacket according to the present invention.

As illustrated inFIG. 8, the base201, the post202, and the radiating fins203are integrally formed by rotary lathe processing. On the circumference of the edge of the base201has been formed a threaded portion701by being subjected to threading processing. On the other hand, the case205also has been subjected to the corresponding threading processing.

In the case205, as illustrated inFIG. 9, a groove801in which the partition204is fitted is provided between the inlet206and outlet207for the coolant.

The partition204has the shape as illustrated inFIG. 10, which has grooves901to be fitted on the respective radiating fins203. The partition204can slide as shown by arrows802inFIG. 9in a state of being fitted on the radiating fins203.

The coefficient of thermal expansion of the partition204may be set at a value different from that of the coefficient of thermal expansion of the radiating fins. This measure makes it possible that the partition groove901is processed such that the partition204and the radiating fins203can be easily moved upon assembling, and the partition groove is narrowed by heat of the coolant so that the partition204and the radiating fins203can be completely brought into close contact with each other upon actual cooling.

An assembling procedure of the liquid cooling jacket of this embodiment will be described. First, the partition204is fitted in the radiating fins203. Next, the case205is put on the base201such that the partition204is fitted in the groove801at this time. Afterward, it suffices that the case205is rotated to be screwed in the base201. At this time, by making the threaded portion701tapered, watertightness can be easily realized.

Next, with reference toFIGS. 11 to 17, other structures of liquid cooling jackets of this embodiment will be described.

FIG. 11is a view illustrating an example in which liquid cooling jackets according to the present invention are put in layers to further improve the performance.FIG. 12is a view illustrating an example in which an air-cooling heat sink and a fan are put in layers on a liquid cooling jacket according to the present invention to further improve the performance.FIG. 13is a view illustrating an example in which the performance is intended to be further improved by an air-cooling heat sink formed integrally with a liquid cooling jacket according to the present invention.FIGS. 14 and 15are views illustrating examples in each of which the arrangement of the inlet and outlet of a liquid cooling jacket according to the present invention is changed.FIGS. 16 and 17are views illustrating examples in each of which a spiral radiating fin is used in a liquid cooling jacket according to the present invention.

In liquid cooling jackets of this embodiment, because heat from the heating element is vertically conducted, as illustrated inFIG. 11, the heat transfer coefficient can be further improved by putting a liquid cooling jacket on another liquid cooling jacket. More specifically, the post202having received heat from the heating element103is in contact with a top plate1001of the case205and thus the former is thermally connected to the latter. Therefore, the heat from the heating element103is transmitted to the post202of the upper jacket as shown by an arrow1002. Thus, because the heat from the heating element103is transmitted to the coolant by a plurality of jackets, the heat transfer coefficient is further improved.

In addition, by thermally connecting the post202to the top plate1001of the case205, as illustrated inFIG. 12, the cooling ability can be intended to be further improved by attaching an air-cooling heat sink1101and a fan1102.

Further, as illustrated inFIG. 13, the post202may penetrate the top plate1001to be formed integrally with an air-cooling heat sink1201.

In addition, as for the directions of the inlet206and outlet207of the liquid cooling jacket, as illustrated inFIGS. 14 and 15, the direction of one or both of the inlet and outlet can be changed.

In addition, by using a spiral radiating fin, the coolant can be turned without using the partition204.

In this measure, as illustrated inFIGS. 16 and 17, by using a spiral radiating fin1801, the coolant having entered from the inlet206is made to spirally flow and discharged from the upper outlet207. In case of this embodiment, the position of the outlet207suffices if it is in the upper portion of the case205. For example, the outlet207may be at a position denoted by a reference numeral207′ shown inFIG. 16, or may be on the top face of the case205as illustrated inFIG. 17.

As described above, in this embodiment, the liquid cooling jacket comprises a base201bonded to a heating element103, a post202standing vertically to the base201, a plurality of radiating fins203attached to the post202and arranged so as to be parallel to the base201, a partition204filling up the intervals between the plurality of radiating fins203at a predetermined width, and a case205which surrounds the post202and the radiating fins203and is bonded to the base201and to which an inlet206and an outlet207are attached at positions symmetrical in relation to the partition204. The plurality of radiating fins203are arranged at the intervals each of which is narrow in comparison with the thickness of each radiating fin203. Therefore, because the coolant flow within the liquid cooling jacket ensures a plurality of passages, the passage resistance is low. In addition, by setting the size of each of the inlet and outlet for the coolant to be substantially equal to the height of the arranged radiating fins203, the flow rates on the radiating fins203can be even.

In addition, because the post202for transmitting heat to each radiating fin203is thick and the height of the post202can be at a small distance from the base201in contact with the heating element103, the coefficient of thermal conductivity is high.

In addition, because the route of the coolant is turned back by the partition204provided between the radiating fins203, the inlet and outlet for the coolant can be arranged in a row and thus convenience on piping is superior.

It should be further understood by those skilled in the art that the foregoing description has been made on embodiments of the invention and that various changes and modifications may be made in the invention without departing from the spirit of the invention and the scope of the appended claims.