Electronic apparatus having a heat-radiating unit for radiating heat of heat-generating components

[0001] This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-147805, filed May 26, 2003, the entire contents of which are incorporated herein by reference.

[0002] 1. Field

[0003] The present invention relates to an electronic apparatus having heat-generating components such as a semiconductor package and a chip set. Particularly, the invention relates to a structure that cools heat-generating components.

[0004] 2. Description of the Related Art

[0005] A CPU is incorporated in, for example, notebook-type portable computers. The heat that the CPU generates while operating increases as its data-processing speed rises or as it performs more and more functions. The higher the temperature of the CPU, the less efficiently it operates. To cool the CPU, so-called “cooling system of liquid cooling type” have been developed in recent years. The cooling system uses a liquid coolant having a larger thermal conductivity constant than air.

[0006] Jpn. Pat. Appln. KOKAI Publication No. 7-142886 discloses a cooling system of liquid cooling type, configured for use in portable computers that comprises a main unit and a display unit. The cooling system comprises a heat-receiving header, heat-radiating header, and two tubes. The heat-receiving header is provided in the main unit and thermally connected to the CPU incorporated in the main unit. The heat-radiating header is provided in the display unit or in the main unit along with the heat-receiving header. If the heat-radiating header is provided in the display unit, the heat-radiating header lies adjacent to the display device incorporated in the display unit. Both tubes extend from the main unit to the display unit to circulate the liquid coolant between the heat-receiving header and the heat-radiating header.

[0007] In this cooling system, the liquid coolant absorbs the heat of the CPU in the heat-receiving header. In other words, the liquid coolant is heated in the heat-receiving header. The heated liquid coolant is supplied to the heat-radiating header via the first tube. As the coolant passes through the heat-radiating header, it releases the heat of the CPU. That is, the liquid coolant is cooled in the heat-radiating header. The cooled coolant is supplied back to the heat-receiving header via the second tube and absorbs the heat of the CPU. As the liquid coolant circulates, heat is transferred from the CPU to the heat-radiating header, which radiates the heat. Thus, the heat is released from the display unit or the main unit.

[0008] If the heat-radiating header that radiates the heat of the CPU is provided in the display unit, the heat-radiating header is adjacent to the display device incorporated in the display unit. The heat emanating from the heat-radiating header inevitably heats the display device. Consequently, the temperature of the display device may rise above the maximum use temperature. If this happens, the images that display device displays will be degraded in quality.

[0009] The heat-radiating header may be provided in the main unit. If this is the case, the heat emanating from the heat-radiating header accumulates in the main unit. When the temperature in the main unit rises, the circuit components and the disk drive, which are provided in the main unit, will be heated to high temperatures. The temperature of the circuit components, for example, may rise above their maximum thermal threshold. If this occurs, the circuit components may be degraded in performance or may undergo thermal breakdown.

[0010] U.S. Pat. No. 6,519,147 discloses a liquid-cooling system for use in portable computers having a body part and a display part. The cooling system comprises a heat-receiving head and a tube. The heat-receiving head is incorporated in the body part of the computer and connected to heat-generating components such as a CPU and a chip set. The tube is filled with liquid coolant and connected to the heat-receiving head. The tube extending between the body part and the display part.

[0011] The display part has a liquid crystal display panel and a housing containing the panel. The tube extends into the housing and lies in the gap between the liquid crystal display panel and the back of the housing. The tube meanders on the back of the housing, thus contacting the housing.

[0012] In this liquid-cooling system, the liquid coolant is heated as heat exchange is performed in the heat-receiving head. The liquid coolant heated flows in the tube toward the display part. As the liquid coolant flows through the tube, it transmits the heat of the heat-generating components to the housing. Therefore, the heat diffuses in the housing and is radiated from the entire back of the housing.

[0013] In the cooling systems, the liquid coolant heated in the heat-receiving header is led into the tube, raising the surface temperature of the tube. The tube is made of material having high heat-radiating property because it transmits the heat of the liquid coolant to the housing. The liquid crystal panel is liable to the heat emanating from the tube. When the panel is heated to high temperatures, the liquid crystal molecules cannot be oriented as is desired. In consequence, the images that the liquid crystal panel displays will be degraded in quality.

[0029] An embodiment of this invention will be described, with reference to FIGS. 1 to 14.

[0030] FIGS. 1-7 illustrate a portable computer 1, or an electronic apparatus according to the present invention. The portable computer 1 comprises a main unit 2 and a display unit 3. The main unit 2 has a first housing 4 that is shaped like a flat box. The first housing 4 supports a keyboard 5. The front half of the upper surface of the first housing 4 is a palm rest 6, on which the user of the computer 1 may place his or her palms while operating the keyboard 5.

[0031] The rear edge of the first housing 4 has a coupling seat 7. The coupling seat 7 extends in the widthwise direction of the first housing 4 and protrudes upwards to a level higher than the upper surface of the first housing 4 and the keyboard 5. Three hollow projections 8a, 8b and 8c are formed integral with the coupling seat 7. The first hollow projection 8a projects upwards from one end of the seat 7. The second hollow projection 8b projects upwards from the other end of the seat 7. The third hollow projection 8c projects upwards from the middle part of the seat 7 and is located between the first and second hollow projections 8a and 8b.

[0032] As illustrated in FIGS. 1, 6 and 8, the first housing 4 contains a printed circuit board 10. The printed circuit board 10 has a CPU 11 on its upper surface. The CPU 11, which is a heat-generating component deployed within a BGA-type semiconductor package for example. Located in the rear part of the first housing 4, the CPU 11 has a base substrate 12 and an IC chip 13. The IC chip 13 is mounted on the center part of the base substrate 12. In general, the amount of heat produced by the CPU 11 is correlated to its operational speed. Therefore, the IC chip 13 should be cooled to maintain operational stability.

[0033] The display unit 3 is an independent component, separated from the main unit 2. The display unit 3 comprises a display device (e.g., liquid crystal display panel) 14 and a second housing 15. The liquid crystal display panel 14, or any other type of display device, has a screen 14a that displays images. The second housing 15 is shaped like a flat box and has almost the same size as the first housing 4. The second housing 15 contains the liquid crystal display panel 14. It has a rectangular opening 16 in its front. Through the opening 16, the screen 14a of the liquid crystal display panel 14 is exposed outside the second housing 15.

[0034] As FIGS. 2 and 6 depicts, the second housing 15 has a back plate 17. The back plate 17 is provided on the back of the liquid crystal display panel 14. As FIG. 8 shows, the back plate 17 has a pair of hollow parts 17a and 17b. Both hollow parts 17a and 17b lie at a level higher than the midpoint of the second housing 15. They are spaced apart in the widthwise direction of the second housing 15 and project toward the back of the second housing 15.

[0035] As is illustrated in FIGS. 4 to 8, the portable computer 1 has a support unit 20. The support unit 20 has a third housing 21. The third housing 21 is shaped like a flat box, comprising a top wall 21a, a bottom wall 21b, left and right side walls 21c and 21d, and a pair of end walls 21e and 21f. The top wall 21a and the bottom wall 21b are opposite of each other. The side walls 21c and 21d and the end walls 21e and 21f connect the four edges of the top wall 21a to the corresponding edges of the bottom wall 21b. Therefore, at least one edge forming end wall 21e of support 20 is coupled to display unit 3 while another edge forming end wall 21f is coupled to main unit 2, such as the coupling seat 7 of main unit for example. The third housing 21 has a smaller width than the first and second housings 4 and 15.

[0036] As seen from FIGS. 7 and 8, one horizontal edge of the third housing 21 has three recesses 22a, 22b and 22c. The first and second recesses 22a and 22b are spaced apart in the widthwise direction of the third housing 21 and aligned with the first and second hollow projections 8a and 8b, respectively. The first and second hollow projections 8a and 8b protrude into the first and second recesses 22a and 22b. The third recess 22c lies between the first and second recesses 22a and 22b, aligned with the third hollow projection 8c. The third hollow projection 8c protrudes into the third recess 22c.

[0037] A pair of first hinges 23a and 23b couple the horizontal edge of the third housing 21 to the coupling seat 7 of the first housing 4. One of the first hinges, 23a, extends between the first hollow projection 8a of the seat 7 and the third housing 21. The other first hinge 23b extends between the second hollow projection 8b of the seat 7 and the third housing 21. The first hinges 23a and 23b have a common horizontal axis X1 that extends in the widthwise direction of the first housing 4. The horizontal edge of the third housing 21 can rotate around the axis X1 with respect to the coupling seat 7 of the first housing 4.

[0038] As FIG. 8 shows, the other horizontal edge of the third housing 21 has two recesses 25a and 25b. These recesses 25a and 25b are spaced in the widthwise direction of the third housing 21 and aligned with the hollow projections 17a and 17b of the second housing 15. The hollow projections 17a and 17b protrude into the recesses 25a and 25b.

[0039] A pair of second hinges 26a and 26b couple the other horizontal edge of the third housing 21 to the back plate 17 of the second housing 15. One of the second hinges, 26a, extends between the hollow projection 17a of the second housing 15 and the third housing 21. The other second hinge 26b extends between the hollow projection 17b of the second housing 15 and the third housing 21. The second hinges 26a and 26b have a common horizontal axis X2 that extends in the widthwise direction of the third housing 21. The other horizontal edge of the third housing 21 can rotate around the axis X2 with respect to the back plate 17 of the second housing 15.

[0040] That is, the third housing 21 can rotate between a position where it overlaps the back plate 17 of the second housing 15 and a position where it is remote from the back plate 17. The third housing 21 can be held at these positions, owing to the braking forces of the second hinges 26a and 26b.

[0041] Thus, the support unit 20 couples the display unit 3 to the main unit 20 allowing the display unit 3 to rotate independently of the support unit 20. More specifically, the display unit 3 can rotate between the first and second positions, while overlapping the support unit 20. FIG. 7 shows the display unit 3 rotated to the first position. As seen from FIG. 7, the display unit 3 lies on the main unit 2, covering the keyboard 5 and palm rest 6 from above, as long as it remains at the first position. FIG. 1 shows the display unit 3 rotated to the second position. At the second position, the display unit 3 stands upright at the rear edge of the main unit 2, exposing the keyboard 5, palm rest 6 and screen 14a.

[0042] The user of the computer 1 may rotate the display unit 3 upwards to any position between the first and second position. In this case, the back plate 17 of the second housing 15 moves away from the support unit 20. As a result, the display unit 3 moves to a third position as is illustrated in FIG. 6. At the third position, the display unit 3 stands up, more forwards a little than at the second position. Thus, the display unit 3 can be moved in a generally lateral direction over the main unit 2 by changing the angle at which the support unit 20 stands. The support unit generally remains in a raised orientation at the back of the display unit 3 when in the second or third positions. Once the display unit 3 has reached the third position, the housing of the support unit 20, i.e., third housing 21, gradually inclines upwards as it moves forward from the rear edge of the first housing 4.

[0043] As is depicted in FIGS. 4 and 8, the portable computer 1 incorporates a cooling unit 30 that is designed to cool the CPU 11 with liquid coolant.

[0044] The cooling unit 30 comprises a rotary pump 31, a heat-radiating portion 32, and a circulation path 33.

[0045] The rotary pump 31 functions as heat-receiving portion as well, to receiving the heat that the CPU 11 generates while operating. The pump 31 is provided in the first housing 4 and mounted on the upper surface of the printed circuit board 10. As FIG. 10 shows, the rotary pump 31 comprises an impeller 34, a pump housing 35 and a flat motor 36. The flat motor 36 starts driving the impeller 34 when the power switch on the portable computer 1 is turned on or when the temperature of the CPU 11 rises to a preset thermal threshold value.

[0046] The pump housing 35 contains the impeller 34. The pump housing 35 is shaped like a flat box and larger than the CPU 11. It is made of material excelling in thermal conductivity, such as aluminum alloy. The pump housing 35 has a bottom wall 37a, a top wall 37b, and four side walls 37c. The walls 37a, 37b and 37c define a pump chamber 38, in which the impeller 34 is located. The lower surface of the bottom wall 37a of the pump housing 35 is flat, serving as heat-receiving surface 42. The heat-receiving surface 42 is large, covering the CPU 11 from above.

[0047] As illustrated in FIG. 9, the pump housing 35 has an inlet port 39 and an outlet port 40 The ports 39 and 40 open to the pump chamber 38 and protrude from one of the side walls 37c toward the back of the first housing 4.

[0048] The pump housing 35 has four legs 43. The legs 43 are provided at the four corners of the pump housing 34 and project downwards from the heat-receiving surface 42. Screws 44 fasten the legs 43 to the upper surface of the printed circuit board 10. Since the legs 43 are so fastened to the board 10, the pump housing 35 overlaps the CPU 11 and the center part of the heat-receiving surface 42 is thermally coupled to the IC chip 13 of the CPU 11.

[0049] The third housing 21 of the support unit 20 contains the heat-radiating portion 32 of the cooling unit 30. As FIGS. 8, 11 and 12 shows, the heat-radiating portion 32 comprises an electric fan 50, first to third heat-radiating blocks 51a, 51b and 51c, and a tube 52.

[0050] The electric fan 50 has a fan case 53 and a centrifugal impeller 54. The fan case 53 is made of material with a high thermal conductivity constant, such as aluminum alloy. The fan case 53 comprises a rectangular main part 55 and a cover 56. The main part 55 has a side wall 58 and a pair of bosses 59a and 59b. The side wall 58 rises from one edge of the main part 55. The bosses 59a and 59b are provided at the opposite edge of the main part 55. The cover 56 is secured to the side wall 58 and bosses 59a and 59b and extends between the top of the side wall 58 and the tops of bosses 59a and 59b.

[0051] The main part 55 supports the impeller 54, which is interposed between the main part 55 and the cover 56. A flat motor (not shown) starts driving the impeller 54 when the power switch on the portable computer 1 is turned on or when the temperature of the CPU 11 rises to a preset thermal threshold value.

[0052] The fan case 53 has two suction ports 61a and 61b and first to third discharge ports 62a, 62b and 62c. The suction ports 61a and 61b are made, each in the cover 56 and the main part 55. They oppose each other, across the impeller 54.

[0053] As seen from FIG. 8, the first discharge port 62a lies between one boss 59a, on the one hand, and the side wall 58 of the main part 55, on the other. The second discharge port 62b lies between the bosses 59a and 59b. The third discharge port 62c lies between the one boss 59b, on the one hand, and side wall 58 of the main part 55, on the other. Stated in another way, the first discharge port 62a and the third discharge port 62c are positioned on opposite sides of the impeller 54, and the second discharge port 62b faces the side wall 58 across the impeller 54.

[0054] Made in three sides of the fan case 53, the first to third discharge ports 62a, 62b and 62c surround the periphery of the impeller 54. Hence, the discharge ports 62a, 62b and 62c opens in three directions, each extending in three lines that meet at the axis 01 of rotation of the impeller 54. Thus, the ports 62a, 62b and 62c define an elongate opening that extends around the axis 01 through a larger angle of rotation than in the conventional cooling systems.

[0055] When the impeller 54 is driven, air flows into the fan case 53 through the suction ports 61a and 61b. In the fan case 53, the air flows to the center part of the impeller 54 and further flows from the periphery of the impeller 54. Finally, the air is expelled from the fan case 53 through the first to third discharge ports 62a, 62b and 62c. Therefore, the cooling air is applied in three directions from the fan case 53 of the electric fan 50.

[0056] FIG. 13 illustrates a relation between the size of the opening of a discharge port and the amount and pressure in and at which cooling air is applied through discharge port, said opening extending around the axis of rotation of an impeller. As line A shows, the pressure at which the cooling air is applied through the discharge port remains unchanged, regardless of the size of the opening of the port. As line B indicates, the amount in which the cooling air is applied through the discharge port increases in proportion to the size of the opening of the port.

[0057] As specified above and shown in FIG. 8, the electric fan 50 has three discharge ports 62a, 62b and 62c, which are made in the three sides of the fan case 53. Hence, the fan 50 can apply cooling air through the ports 62a, 62b and 62c in a sufficient amount. For instance, cooling air may be applied in a sufficient amount and at a sufficient pressure when the ports 62a to 62c define an elongate opening extending around the axis 01 of rotation of the impeller 54 through an angle equal to or greater than 190°.

[0058] As shown in FIGS. 8 and 12, screws fasten the fan case 53 of the electric fan 50 to the bottom wall 21b of the third housing 21. The top wall 21a and bottom wall 21b of the third housing 21 have intake ports 63a and 63b, respectively. The intake ports 63a and 63b oppose the suction ports 61a and 61b of the fan case 53 and have a larger opening than the suction ports 61aand 61b. Two mesh guards 64 cover the intake ports 63a and 63b, respectively, to prevent foreign matter, such as clips, from entering the intake ports 63a and 63b.

[0059] As illustrated in detail in FIG. 8, the first and third discharge ports 62a and 62c of the fan case 53 oppose the side walls 21c and 21d of the third housing 21, respectively. The second discharge port 62b of the fan case 53 opposes the end wall 21e of the third housing 21. The side walls 21c and 21d of the third housing 21 have a plurality of exhaust ports 65. The exhaust ports 65 are arranged in a row, each spaced apart from another, and located at the back of the display unit 3.

[0060] The first to third heat-radiating blocks 51a, 51b and 51c are provided, respectively, in the first to third discharge ports 62a, 62b and 62c of the fan case 53. The blocks 51a, 51b and 51c have heat-radiating fins 67 each. The fins 67 are shaped like a flat plate. The fins 67 are made of metal that excels in thermal conductivity, such as aluminum alloy. The heat-radiating fins 67 are arranged are spaced apart, extending parallel to one another. The fins 67 are secured to the rims of the first to third discharge ports 62a, 62b and 62c of the fan case 53. The heat-radiating fins 67 of the first to third heat-radiating blocks 51a, 51b and 51c oppose the exhaust ports 65 of the third housing 21.

[0061] The first to third heat-radiating blocks 51a, 51b and 51c are arranged, surrounding the impeller 54 of the electric fan 50 at three sides of the fan case 53. The cooling air discharged through the first to third discharge ports 62a, 62b and 62c flows, passing through the gaps between the heat-radiating fins 67 of the first to third heat-radiating blocks 51a, 51b and 51c.

[0062] The tube 52 of the heat-radiating portion 32 is made of metal that excels in thermal conductivity, such as aluminum alloy. As seen from FIGS. 8 and 11, the tube 52 extends through the center parts of the heat-radiating fins 67 of the first to third heat-radiating blocks 51a, 51b and 51c and is thermally connected to the heat-radiating fins 67. The tube 52 has a coolant inlet port 68 and a coolant outlet port 69. The ports 68 and 69 are located near the junction between the first housing 4 and the third housing 21.

[0063] As FIGS. 8-12 depict, the circulation path 33 of the cooling unit 30 have two connection tubes 71a and 71b. The first connection tube 71a connects the outlet port 40 of the rotary pump 31 and the coolant inlet port 68 of the heat-radiating portion 32. The first connection tube 71a first extends from the rotary pump 31 to the third hollow projection 8c of the first housing 4, then passes through the junction between the projection 8c and the third housing 21, and further extends into the coolant inlet port 68 of the heat-radiating portion 32.

[0064] The second connection tube 71b connects the inlet port 39 of the rotary pump 31 and the coolant outlet port 69 of the heat-radiating portion 32. The second connection tube 71b first extends from the rotary pump 31 to the third hollow projection 8c of the first housing 4, then passes through the junction between the projection 8c and the third housing 21, and finally extends into the coolant outlet port 69 of the heat-radiating portion 32.

[0065] The first and second connection tubes 71a and 71b are flexible, both made of rubber or synthetic resin. Therefore, they can deform to absorb the twisting of the circulation path 33, which takes place when the positional relation between the rotary pump 31 and the heat-radiating portion 32 changes as the third housing 21 is rotated.

[0066] The liquid coolant fills the pump chamber 38 of the rotary pump 31, the tube 52 of the heat-radiating portion 32, and the circulation path 33. The liquid coolant is, for example, an antifreeze liquid prepared by adding ethylene glycol solution and, if necessary, corrosion inhibitor to water. The liquid coolant absorbs heat from the IC chip 13 as it flows in the pump chamber 38 of the rotary pump 31. Thus, the liquid coolant acts as a medium that transfers the heat of the IC chip 13 to the heat-radiating portion 32 in the present embodiment.

[0067] As illustrated in FIGS. 8 and 11, the tube 52 of the heat-radiating portion 32 is composed of an upstream tube 73a and a downstream tube 73b. The upstream tube 73a comprises the coolant inlet port 68 at one end and an outlet port 74 at the other end. The upstream tube 73a is bent in the form of L, passing through the heat-radiating fins 67 of the first heat-radiating block 51a and through the heat-radiating fins 67 of the second heat-radiating block 51b. The downstream tube 73b comprises the coolant outlet port 69 at one end and an inlet port 75 at the other end. The downstream tube 73b extends substantially straight, passing through the heat-radiating fins 67 of the third heat-radiating block 51c.

[0068] A reserve tank 80 is provided between the upstream tube 73a and the downstream tube 73b, to temporarily contain the liquid coolant. The reserve tank 80 is incorporated in the third housing 21 and located between the second heat-radiating block 51b of the heat-radiating portion 32 and the end wall 21f of the third housing 21. According to one embodiment, the tank 80 is rectangular shaped like a flat box, generally extending in the widthwise direction of the third housing 21. The reserve tank 80 is secured to the bottom wall 21b of the third housing 21 or the heat-radiating portion 32.

[0069] The outlet port 74 of the upstream tube 73a and the inlet port 75 of the downstream tube 73b open to the interior of the reserve tank 80. Thus, the liquid coolant contained in the reserve tank 80 can flow into the inlet port 75 of the downstream tube 73b. The inlet port 75 of the downstream tube 73b is positioned at the center part of the reserve tank 80. Hence, as shown in FIG. 14, the inlet port 75 of the downstream tube 73b is located near the intersection P of two diagonals G1 and G2, each connecting the opposite corners of the tank 80. The inlet port 75 therefore lies below the surface level L of the liquid coolant stored in the reserve tank 80 and remains immersed in the liquid coolant.

[0070] As FIG. 8 shows, the liquid crystal display panel 14 provided in the second housing 15 is electrically connected by a cable 83 to the printed circuit board 10 incorporated in the first housing 4. The cable 83 extends from the liquid crystal display panel 14, passes through the junction between the hollow projection 17a of the second housing 15 and the recess 25a of the third housing 21, and extends into the third housing 21. In the third housing 21, the cable 83 passes between the first heat-radiating block 51a and side wall 21c and extends into the first housing 4 through the junction between the first recess 22a of the third housing 21 and the first hollow projection 8a of the first housing 4.

[0071] In summary, as shown in FIGS. 8-12, IC chip 13 of the CPU 11 generates heat while the portable computer 1 is being used. The heat that the IC chip 13 generates is transmitted to the pump housing 35 because the IC chip 13 is thermally connected to the heat-receiving surface 42 of the pump housing 35. The pump housing 35 has the pump chamber 38, which is filled with the liquid coolant. The liquid coolant absorbs most of the heat provided to the pump housing 35 from the IC chip 13.

[0072] When the impeller 34 of the rotary pump 31 rotates, the liquid coolant is forced from the pump chamber 38 through the outlet port 40. The coolant flows into the heat-radiating portion 32 through the first connection tube 71a. Thus, the liquid coolant circulates between the pump chamber 38 and the heat-radiating portion 32.

[0073] More specifically, the liquid coolant heated by virtue of the heat exchange in the pump chamber 38 is supplied to the upstream tube 73a of the heat-radiating portion 32. The liquid coolant flows through the upstream tube 73a. The coolant heated further flows from the outlet port 74 of the upstream tube 73a into the reserve tank 80. The liquid coolant flowing through the upstream tube 73a may contain bubbles. In this case, the bubbles are removed from the coolant in the reserve tank 80. The liquid coolant that is temporarily stored in the reserve tank 80 is drawn into the inlet port 75 of the downstream tube 73b. The liquid coolant then flows from the downstream tube 73b into the second connection tube 71b.

[0074] The upstream tube 73a and downstream tube 73b, in which the liquid coolant flows, are thermally connected to the heat-radiating fins 67 of the first to third heat-radiating blocks 51a, 51b and 51c. The heat of the IC chip 13, absorbed in the liquid coolant, is therefore transmitted to the heat-radiating fins 67 as the liquid coolant flows through the upstream tube 73a and downstream tube 73b.

[0075] The first to third heat-radiating blocks 51a, 51b and 51c are located at the three discharge ports 62a, 62b and 62c of the electric fan 50, respectively, and surround the impeller 54 at three sides of the fan case 53. When the impeller 54 rotates, the cooling air discharged via the discharge ports 62a, 62b and 62c passes between the heat-radiating fins 67. The cooling air is then applied to the first and second tubes 73a and 73b. As a result, the cooling air takes away the heat transmitted from the IC chip 13 to the heat-radiating fins 67 and the first and second tubes 73a and 73b.

[0076] The liquid coolant is cooled because of the heat exchange performed in the heat-radiating portion 32. The coolant thus cooled flows back into the pump chamber 38 of the rotary pump 31 through the second connection tube 71b. The coolant repeats absorption of the heat of the IC chip 13. It is then supplied to the heat-radiating portion 32. Thus, the liquid coolant transfers the heat of the IC chip 13 to the heat-radiating portion 32. The heat is released outside the portable computer 1, from the heat-radiating portion 32.

[0077] As shown in FIGS. 4 and 5, for this embodiment of the portable computer 1, the heat-radiating portion 32 is provided in the support unit 20 coupling the display unit 3 to the main unit 2. Namely, the heat-radiating portion 32 is remote from the main unit 2 and the display unit 3. Therefore, the heat released from the heat-radiating portion 32 does not accumulate in either the first housing 4 of the main unit 2 or the second housing 15 of the display unit 2. This controls the increase in the temperature in the first housing 4 and second housing 15.

[0078] Hence, the printed circuit board 10 and liquid crystal display panel 14, which are provided in the first and second housing 4 and 15, respectively, experience minor thermal influences. The printed circuit board 10 can be prevented from being deformed, and the liquid crystal display panel 14 is prevented from being degraded in performance.

[0079] Further, no space needs to be provided in either the first housing 4 or the second housing 15 to accommodate for the cooling unit 30. This helps to render the first and second housing 4 and 15 thin and small.

[0080] With the configuration described above, the third housing 21 having the heat-radiating portion 32 gradually inclines as it is moved forward from the rear edge of the first housing 4 after the display unit 3 has been rotated to the third position. As a result, the back plate 17 of the second housing 15 moves away from the bottom wall 21b of the third housing 21, opening the intake port 63b (FIG. 12) made in the bottom plate 21b. Both intake ports 63a and 63b of the third housing 21 are thereby exposed. Air can therefore flow into the electric fan 50 through the intake ports 63a and 63b.

[0081] This increases the amount of air supplied through the discharge ports 62a, 62b and 62c of the electric fan 50 (FIG. 8). The first to third heat-radiating blocks 51a, 51b and 51c can therefore be cooled with the cooling air at high efficiency.

[0082] In addition, according to this embodiment of the invention, the third housing 21 of the support unit 20 solely supports the display unit 2. Thus, a greater part of the third housing 21 provides a space for accommodating the cooling unit 30. Therefore, the electric fan 50 can be a large one that excels in air-supplying ability, and first to third heat-radiating blocks 51a, 51b and 51c can be large enough to increase the heat-radiating area of each fin 67 (FIG. 8). This can enhance the efficiency of cooling the CPU 11 and ultimately achieves more reliable cooling of the CPU 11.

[0083] The present invention is not limited to the embodiment described above. Various changes and modifications can be made, without departing from the scope and spirit of the invention. For example, a heat-receiving portion may be provided, independently of the rotary pump, though the rotary pump 31 functions as heat-receiving portion as well in the above-described embodiment.

[0084] Furthermore, the medium for transferring heat is not limited to a liquid that circulates between the heat-receiving portion and the heat-radiating portion. Moreover, at least one heat pipe, for example, may transfer the heat of the heat-generating component directly to the heat-radiating portion.

[0085] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.