Patent Publication Number: US-2012033382-A1

Title: Heat sink, liquid cooling unit, and electronic apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority of Japan Patent Application Number 2010-176132, filed on Aug. 5, 2010. 
     FIELD 
     The present invention relates to a heat sink for absorbing heat which is generated by an electronic module and a liquid cooling unit and an electronic apparatus which are provided with a heat sink. 
     BACKGROUND 
     Notebook personal computers and other electronic apparatuses have printed circuit boards installed therein. On the printed circuit boards, for example, LSI chips and other electronic modules are mounted. In order to absorb heat which is generated by these electronic modules, a liquid cooling unit provided with a heat sink is disposed on the printed circuit board. 
     As related art, Japanese Laid-Open Patent Publication No. 2002-261480 is known. 
     When using fins to raise a cooling efficiency of a heat sink, the heat which is propagated to the fins is absorbed by a coolant which flows along the wall surfaces of the fins. However, due to frictional resistance which occurs between the wall surfaces of the fins and the coolant, the flow velocity of the coolant which flows along the wall surfaces of the fins falls. Contrary to this, coolant which flows over a position away from the wall surfaces of the fins, to a certain extent, is not influenced much at all, by the frictional resistance which occurs between the wall surfaces of the fins and the coolant. For this reason, the flow velocity of the coolant which flows over a position away from the wall surfaces of the fins, to a certain extent, becomes faster than the flow velocity of the coolant which flows along the wall surfaces of the fins. 
     In this way, inside a heat sink provided with fins, a plurality of flows of coolant having different flow velocities are formed, therefore the cooling efficiency of the heat sink cannot be sufficiently raised. 
     SUMMARY 
     Accordingly, it is an object of the embodiment to provide a heat sink which improves the cooling efficiency over that of the related art. 
     According to a first aspect of the invention, there is provided a heat sink for absorbing heat which is generated by an electronic module by using a coolant which flows through its internal portion, comprising a housing which is provided with, in its internal portion, a first surface which is located in the vicinity of the electronic module and a second surface which faces the first surface and comprising fins which extend from the first surface toward the second surface, wherein a projecting portion which projects from the second surface toward the first surface is formed at the second surface between the top edges of the fins on the second surface side and the second surface. Further, according to a second aspect of the invention, there is provided a liquid cooling unit which is provided with the above heat sink. Further, according to a third aspect of the invention, there is provided an electronic apparatus which is provided with the above heat sink. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an example of a notebook PC of a first embodiment according to the invention. 
         FIG. 2  is a perspective view illustrating an example of the structure of an internal portion of a housing body of the first embodiment disclosed in the present specification. 
         FIG. 3  is a plan view illustrating an example of a liquid cooling unit of the first embodiment disclosed in the present specification. 
         FIG. 4  is a plan view illustrating an example of the structure of the internal portion of a heat sink of the first embodiment disclosed in the present specification. 
         FIG. 5A  is a cross-sectional view taken along a line A-A in  FIG. 3 , and  FIG. 5B  is a cross-sectional view taken along a line B-B in  FIG. 3 . 
         FIG. 6  is a cross-sectional view taken along a line C-C in  FIG. 3 . 
         FIG. 7A  is a plan view illustrating an example of the structure of the internal portion of a heat sink of a second embodiment disclosed in the present specification, and  FIG. 7B  is a cross-sectional view taken along a line D-D in  FIG. 7A . 
         FIG. 8  is a cross-sectional view taken along a line E-E in  FIG. 7A . 
         FIG. 9  is a cross-sectional view illustrating an example of a heat sink of a third embodiment disclosed in the present specification. 
         FIG. 10  is a plan view illustrating an example of the structure of the internal portion of a heat sink of a fourth embodiment disclosed in the present specification. 
         FIG. 11  is a cross-sectional view as seen from an arrow F-F direction in  FIG. 10 . 
         FIG. 12  is a cross-sectional view illustrating an example of a heat sink of a fifth embodiment. 
         FIGS. 13A ,  13 B, and  13 C are diagrams illustrating various modifications of a projecting portion. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     According to the heat sink of each embodiment, the cooling efficiency can be improved to more than that of the related art. 
     (1) First Embodiment 
     First, with reference to  FIG. 1 , a notebook personal computer (notebook PC)  10  will be explained as an example of the electronic apparatus according to the first embodiment.  FIG. 1  is a perspective view illustrating an example of the notebook PC  10  of the first embodiment. As shown in  FIG. 1 , the notebook PC  10  is provided with a housing body  20  and a display use housing  30 . The display use housing  30  is coupled with the housing body  20  so that opening/closing is possible. 
     The housing body  20  is provided with a base  22  and a cover  24 . The cover  24  can be attached/detached to/from the base  22 . Further, on the surface of the cover  24 , a keyboard  26 , a pointing device  28 , and other input devices are disposed. The display use housing  30  is provided with a liquid crystal panel module  32 . The liquid crystal panel module  32  displays text, graphics, etc. 
     Next, with reference to  FIG. 2 , the structure of the internal portion of the housing body  20  will be explained.  FIG. 2  is a perspective view showing an example of the structure of the internal portion of the housing body  20  of the first embodiment. As shown in  FIG. 2 , the housing body  20  of the first embodiment is provided with a printed circuit board unit  40 , a DVD (digital versatile disk) drive device  46 , a hard disk drive device  48 , a card unit  50 , and a liquid cooling unit  100 . 
     The printed circuit board unit  40  is provided with a printed circuit board  42  and an electronic module  44 . The electronic module  44  is mounted on the surface of the printed circuit board  42 . The electronic module  44  is for example an LSI circuit (large scale integrated circuit). On the electronic module  44  such as an LSI circuit, for example, a central processing unit chip is mounted. The central processing unit chip executes processing based on the operating system and application software. When the central processing unit chip executes the processing, the electronic module  44  such as an LSI circuit generate heat. In order to absorb the heat generated by the electronic module  44 , a liquid cooling unit  100  is attached to the printed circuit board unit  40 . The detailed configuration of the liquid cooling unit  100  will be explained later. 
     The DVD drive device  46  reads data from a DVD and writes data to the DVD. The hard disk drive device  48  stores, for example, the operating system and application software explained above. Further, the card unit  50  is mounted on the printed circuit board  42 . Into the card unit  50 , for example, a memory card or LAN (Local Area Network) card is inserted. 
     Here, with reference to  FIG. 3 , the liquid cooling unit  100  of the first embodiment will be explained.  FIG. 3  is a plan view showing an example of the liquid cooling unit  100  of the first embodiment. As shown in  FIG. 3 , the liquid cooling unit  100  of the first embodiment is provided with a heat exchanger  110 , fan unit  120 , tank  130 , pump  140 , and heat sink  150 . Members configuring the liquid cooling unit  100  are connected by hoses  102  and metal pipes  104  to form a circulation route. By the coolant which flows along the circulation route, the heat generated by the electronic module  44  is discharged to the outside of the notebook PC  10 . As the coolant, use is made of, for example, a propylene glycol-based antifreeze. 
     The heat exchanger  110  takes the heat from the coolant which flows into the heat exchanger  110 . The heat exchanger  110  is disposed in the vicinity of an exhaust port  52  (see  FIG. 2 ) formed at the side surface of the housing body  20 . Further, a fan unit  120  is disposed in the vicinity of the heat exchanger  110 . The fan unit  120  generates an air flow from the heat exchanger  100  toward the exhaust port  52 . For this reason, the heat taken from the coolant by the liquid cooling unit  100  is discharged through the exhaust port  52  to the outside of the notebook PC  10 . 
     The fan unit  120  is provided with a fan housing  122  and a fan  126 . On the bottom plate and top plate of the fan housing  122 , an air intake opening  124  is formed. The internal space of the fan housing  122  and the outside space of the fan housing  122  are connected through the air intake opening  124 . 
     The tank  130  is disposed downstream of the heat exchanger  110 . The tank  130  stores the coolant stripped of heat by the heat exchanger  110 . The pump  140  is disposed downstream of the tank  130 . The pump  140  discharges the coolant stored in the tank  130  to generate the flow of the coolant which flows along the circulation route. The pump  140  is, for example, a piezoelectric pump. 
     The heat sink  150  is disposed downstream of the pump  140 . As shown in  FIG. 2 , the heat sink  150  is disposed above the electronic module  144  which generates heat. The heat sink  150  absorbs the heat generated by the electronic module  44 . The detailed configuration of the heat sink  150  will be explained later. The heat exchanger  110  explained above is located downstream of the heat sink  150 . In the liquid cooling unit  100 , a circulation route is formed as explained above. 
     Next, the structure of the heat sink  150  of the first embodiment will be explained in detail with reference to  FIG. 4  to  FIG. 6 .  FIG. 4  is a plan view showing an example of the structure of the internal portion of the heat sink  150 . Specifically,  FIG. 4  is a plan view showing an example of the heat sink  150  when the top surface  154  of the housing  152  ( FIG. 6 ) which will be explained later is removed.  FIG. 5A  is a cross-sectional view taken along a line A-A in  FIG. 3 , and  FIG. 5B  is a cross-sectional view taken along a line B-B in  FIG. 3 .  FIG. 6  is a cross-sectional view taken along a line C-C in  FIG. 3 . 
     As shown in  FIG. 4 , the heat sink  150  is provided with a housing  152  and fins  160 . In the example shown in  FIG. 4 , the heat sink  150  is provided with nine fins  160 . Further, in the housing  152 , an inflow port  156  and an outflow port  158  are formed. To the inflow port  156  and outflow port  158  are connected to the metal pipes  104 . The coolant, which passes through the inflow port  156  and flows into the internal portion of the housing  152 , passes through the outflow port  158  and flows out to an external portion of the housing  152 . 
     As shown in  FIG. 6 , the housing  152  includes a bottom surface (first surface)  153  and a top surface (second surface)  154 . The bottom surface  153  contacts the electronic module  44 . Further, inside the housing  152 , the fins  160  are extended from the bottom surface  153  toward the top surface  154 . The fins  160  are formed by a metal material having a high heat conductivity, for example, aluminum. For this reason, the heat generated by the electronic module  44  is propagated to the bottom surface  153  of the housing  152  with fins  160  and is absorbed by the coolant. 
     Here, as shown in  FIG. 5A , the fins  160  of the first embodiment contact the bottom surface  153 , but do not contact the top surface  154 . For this reason, between the top edges of the fins  160  and the top surface  154  of the housing  152 , there is a region where there are no fins  160 . 
     Further, as shown in  FIG. 5B  and  FIG. 6 , between the top edges of the fins  160  and the top surface  154  of the housing  152 , a projecting portion  162  projecting from the top surface  154  toward the bottom surface  153  is formed at the top surface  154  of the housing  152 . The projecting portion  162  is formed by, for example, pushing down the top surface  154  of the housing  152 . Note that, in the example shown in  FIG. 5B  and  FIG. 6 , the top edges of the fins  160  do not contact the projecting portion  162 , but the top edges of the fins  160  may contact the projecting portion  162  as well. 
     In the heat sink  150  of the first embodiment, since, between the top edges of the fins  160  and the top surface  154  of the housing  152 , there is a region where there are no fins  160 , a flow velocity v 1  of the coolant which flows among the fins  160  is different from the flow velocity v 2  of the coolant which flows between the top edges of the fins  160  and the top surface  154  of the housing  152 . Specifically, the coolant which flows among the fins  160  is influenced by the frictional resistance created between the wall surfaces of the fins  160  and the coolant, so the flow velocity v 1  becomes smaller than the flow velocity v 2 . 
     Further, in the heat sink  150  of the first embodiment, since a projecting portion  162  projecting from the top surface  154  toward the bottom surface  153  is formed at the top surface  154  of the housing  152 , the coolant which flows between the top edges of the fins  160  and the top surface  154  of the housing  152  strikes the projecting portion  162  and flows into the spaces among the fins. As a result, on the downstream side from the projecting portion  162 , the velocity of the coolant, which flows among the fins  160 , rises. 
     Further, on the upstream side from the projecting portion  162 , the temperature of the coolant, which flows between the top edges of the fins  160  and the top surface  154  of the housing  152 , is lower than the temperature of the coolant, which flows among the fins  160 . For this reason, the coolant, which flows between the top edges of the fins  160  and the top surface  154  of the housing  152 , strikes the projecting portion  162  and flows into the spaces among the fins  160 , whereby the temperature of the coolant which flows among the fins  160  can be lowered on the downstream side from the projecting portion  162 . As explained above, according to the heat sink  150  of the first embodiment, the cooling efficiency can be improved over that of the related art. 
     (2) Second Embodiment 
     Next, a second embodiment according to the invention will be explained. The second embodiment differs in the configuration of the heat sink  150  from that of the first embodiment explained before. The rest of the configuration is similar to that of the first embodiment, so an explanation will be omitted. Below, the configuration of the heat sink  150  of the second embodiment will be explained with reference to  FIGS. 7A and 7B  and  FIG. 8 .  FIG. 7A  is a plan view showing an example of the heat sink  150  when removing the top surface  154  of the housing  152 , and  FIG. 7B  is a cross-sectional view taken along a line D-D in  FIG. 7A . Further,  FIG. 8  is a cross-sectional view taken along a line E-E in  FIG. 7A . 
     As shown in  FIGS. 7A and 7B  and  FIG. 8 , the heat sink  150  of the second embodiment is different from the first embodiment explained above in the point that a partition plate  164  is provided. The rest of the configuration is similar to that of the first embodiment. As shown in  FIGS. 7A and 7B , the partition plate  164  contacts the top edges of the fins  160  and is arranged parallel to the bottom surface  153  of the housing  152 . In the same way as the fins  160 , the partition plate  164  is formed by a thermally conductive metal material. The partition plate  164  may be formed by the same material as that of the fins  160  or may be formed by a different material. 
     Further, in the example shown in  FIGS. 7A and 7B , the partition plate  164  is arranged so as to contact the top edges of all fins  160 . However, it may be arranged so as to contact only the top edges of a portion of the fins  160 . Further, in the example shown in  FIG. 8 , the partition plate  164  is arranged on the upstream side from the projecting portion  162 . However, the partition plate  164  may be arranged on the downstream side from the projecting portion  162  as well. 
     The heat sink  150  of the second embodiment is provided with the partition plate  164  at the top edges of the fins  160 , therefore the heat generated by the electronic module  44  is propagated, through the bottom surface  153  of the housing  152  and the fins  160 , to the partition plate  164 . For this reason, a heat dissipation area of the portion to which the heat generated by the electronic module  44  is propagated increases, so the cooling efficiency can be improved more than the first embodiment. 
     (3) Third Embodiment 
     Next, a third embodiment according to the invention will be explained. The third embodiment is different in the configuration of the heat sink  150  from the second embodiment explained before. Below, the configuration of the heat sink  150  of the third embodiment will be explained with reference to  FIG. 9 .  FIG. 9  is a cross-sectional view showing an example of the heat sink  150  of the third embodiment. As shown in  FIG. 9 , this differs from the second embodiment in the point that the shape of the upstream side edges (portions indicated by T in  FIG. 9 ) of the fins  160  of the heat sink  150  of the third embodiment is a tapered shape. The rest of the configuration is similar to that of the second embodiment, so the explanation will be omitted. 
     As shown in  FIG. 9 , since the upstream side edges of the fins  160  of the third embodiment are a tapered shape, the coolant which flows into the internal portion of the housing  152  from the inflow port  156  can easily flow between the top edges of the fins  160  and the top surface  154  of the housing  152  along the tapered shapes. As a result, the flow velocity of the coolant which flows between the top edges of the fins  160  and the top surface  154  of the housing  152  becomes larger. Due to striking the projecting portion  162 , on the downstream side from the projecting portion  162 , the velocity of the coolant which flows among the fins  160  rises. In this way, in the heat sink  150  of the embodiment based on the present invention as well, the cooling efficiency can be improved. 
     Note that, in the example shown in  FIG. 9 , an explanation was given for the case where a partition plate  164  was disposed at the top edges of the fins  160 . However, the third embodiment can be applied even in a case where there is no partition plate  164 . 
     (4) Fourth Embodiment 
     Next, a fourth embodiment according to the invention will be explained. The fourth embodiment differs from the first embodiment in the configuration of the heat sink  150 . The rest of the configuration is similar to that of the first embodiment, therefore the explanation will be omitted. Below, the configuration of the heat sink  150  of the fourth embodiment will be explained with reference to  FIG. 10  and  FIG. 11 .  FIG. 10  is a plan view showing an example of the heat sink  150  when the top surface  154  of the housing  152  is removed. Further,  FIG. 11  is a cross-sectional view as seen from an F-F arrow direction in  FIG. 10 . 
     As shown in  FIG. 10  and  FIG. 11 , the heat sink  150  of the fourth embodiment differs from the first embodiment explained above in the point that a convex portion  166  is formed at the bottom surface of the housing  152 . The rest of the configuration is similar to that of the first embodiment. As shown in  FIG. 10 , the convex portion  166  is formed among a plurality of fins  160 . Further, as shown in  FIG. 11 , the convex portion  166  is preferably formed in the vicinity of the projecting portion  162  which is formed at the top surface  154  of the housing  152 . 
     The convex portion  166  is formed together with the fins  160  at the bottom surface  153  of the housing  152  by for example die casting. Further, when the fins  160  are provided with concave portions which fit with the convex portion  166  formed at the bottom surface  153  of the housing  152 , the convex portion  166  may be formed at the bottom surface  153  of the housing  152  by die casting, then the fins  160  attached to the convex portion  166 . 
     Since the convex portion  166  is formed at the bottom surface  153  of the housing  152  of the heat sink  150  of the fourth embodiment, the coolant, which flows among the fins  160  on the upstream side from the convex portion  166  and rises in temperature, strikes the convex portion  166  so can easily flow to between the top edges of the fins  160  and the top surface  154  of the housing  152  on the downstream side from the convex portion  166 . Further, the flow among the fins  160  can be disturbed and stirred. In this way, in the heat sink  150  of the fourth embodiment as well, the cooling efficiency can be improved. 
     (5) Fifth Embodiment 
     Next, a fifth embodiment according to the invention will be explained. The fifth embodiment differs from the first embodiment explained before in the configuration of the heat sink  150 . The rest of the configuration is similar to that of the first embodiment, therefore the explanation will be omitted. Below, the configuration of the heat sink  150  of the fifth embodiment will be explained with reference to  FIG. 12 .  FIG. 12  is a cross-sectional view showing an example of the structure of the internal portion of the heat sink  150  of the fifth embodiment. 
     As shown in  FIG. 12 , the heat sink  150  of the fifth embodiment differs from the first embodiment explained above in the point that recess portions  168  are formed at the top edges of the fins  160 . The rest of the configuration is similar to that of the first embodiment. In the example shown in  FIG. 12 , the recess portions  168  are formed in the vicinity of the projecting portion  162 . Note that, the number of the recess portions  168  formed in one fin  160  is not particularly limited. A plurality of recess portions  168  may be formed in one fin  160  as well. Further, the positions of formation of the recess portions  168  in the fins  160  may be different in each fin  160 . 
     Since the recess portions  168  are formed in the fins  160  of the fifth embodiment, the coolant, which flows among the fins  160 , passes through the recess portions  168  and easily flows to between adjacent fins  160 . Further, in the fifth embodiment, since the recess portions  168  are formed in the top edges of the fins  160 , the coolant which flows between the top edges of the fins  160  and the top surface  154  of the housing  152  easily passes through the recess portions  168  and flows into the spaces among the fins  160 . In this way, in the heat sink  150  of the fifth embodiment as well, the cooling efficiency can be improved. 
     Modifications 
     In the embodiments explained above, the example was given of forming the projecting portion  162  by pushing down a portion of the top surface  154  of the housing  152 , but the shape of the projecting portion  162  is not limited to this. Here, with reference to  FIGS. 13A to 13C , modifications of the projecting portion  162  will be explained. In  FIGS. 13A ,  13 B, and  13 C, the top surface  154  of the housing  152  and the projecting portion  162  are shown, but the other portions are omitted. As shown in  FIGS. 13A ,  13 B, and  13 C, the projecting portion  162  may be one added to the top surface  154  of the housing  152 , as well. 
     Further, so far as the shape is such that the coolant, which flows between the top edges of the fins  160  and the top surface  154  of the housing  152 , strikes the projecting portion  162  and easily flows into the spaces among the fins  160 , the shape of the projecting portion  162  is not limited to the shape of the embodiments explained above. For example, the projecting portion  162  may be given a trapezoidal shape as shown in  FIG. 13A , a semi-circular shape as shown in  FIG. 13B , or a triangular shape as shown in  FIG. 13C , as well. 
     A detailed explanation was given above on the heat sink, liquid cooling unit, and electronic apparatus of the present invention, but the present invention is not limited to the above-described embodiments. Further, the embodiments explained above may be suitably combined. Further, it should be understood by those skilled in the art that various modifications and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention.