US20080202730A1

US20080202730A1 - Liquid cooling system

Info

Publication number: US20080202730A1
Application number: US12/032,459
Authority: US
Inventors: Hitoshi Onishi; Jiro Nakajima
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 2007-02-23
Filing date: 2008-02-15
Publication date: 2008-08-28
Also published as: TW200841163A; JP2008210007A

Abstract

Embodiments of the present disclosure may include a liquid cooling system in which an inlet hole and an outlet hole that are located at both ends of a circulating flow passage opened onto a heat-radiating sheet having the circulating flow passage between a pair of heat-conductive metal plates that are superimposed on each other, a pump having a discharge port and a suction port that communicate with the inlet hole and the outlet hole installed on the heat-radiating sheet, a heat-generating element set on the heat-radiating sheet via a heat spreader, and used as a heat-receiving area, and the circulating flow passage having a heat-absorbing flow passage located in a lower face of the heat spreader and a heat-radiating flow passage located in the heat-radiating area other than the heat spreader and having a sufficiently larger length than the flow passage length of the heat-absorbing flow passage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of Japanese Patent Application No. 2007-043879 filed on Feb. 23, 2007, which is hereby incorporated by reference.

BACKGROUND

1. Field of the Disclosure
The present disclosure relates to a thin liquid cooling (water cooling) system, and particularly, to a liquid cooling system that is suitable to be used for a notebook computer.
2. Description of the Related Art
The present applicant is developing a liquid cooling system that cools a heat-generating source (CPU) of a notebook computer. In a notebook computer in which the storage space for components is limited, as can also be seen in Japanese Unexamined Patent Application Publication Nos. 2000-323880, 2004-6563, 2004-95891, and the like, a liquid cooling system that is thin as a whole and has a high unit property is needed.
However, a conventional liquid cooling system needs tubes in order to connect elements to one another because a pump, a heat-absorbing unit, a heat-radiating unit, and the like are provided independently. Therefore, it lacks in integrity (unit property), and has a problem in assembling performance. Further, there is a room for improvement in that the heat-generating source (CPU) is cooled effectively and heat is distributed (a locally hot portion is eliminated).

SUMMARY

Embodiments of the present disclosure may provide a liquid cooling system that does not need tubes throughout the system, and may have excellent unit property that all elements are provided on a heat-radiating sheet. Further, embodiments of the present disclosure may provide a liquid cooling system capable of efficiently distributing heat in the heat-radiating sheet, and making it hard for a local hot portion to be created.
A liquid cooling system according to the present disclosure may include: a heat-radiating sheet having a pair of heat-conductive metal plates that are superimposed on each other, and having a circulating flow passage between the pair of heat-conductive metal plates; an inlet hole and an outlet hole opened to the surface of the heat-radiating sheet and located at both ends of the circulating flow passage; a pump having a discharge port and a suction port that communicate with the inlet hole and the outlet hole, and installed on the heat-radiating sheet; a heat-receiving area and a heat-radiating area set on the heat-radiating sheet; and a heat-generating element installed on the heat-receiving area via a heat spreader made of a heat-conductive material. The circulating flow passage may have a heat-absorbing flow passage located in a lower face of the heat spreader of the heat-receiving area, and a heat-radiating flow passage located in the heat-radiating area and having a sufficiently larger length than the flow passage length of the heat-absorbing flow passage.
Specifically, the flow passage length of the heat-radiating flow passage may be 10 or more times the flow passage length of the heat-absorbing flow passage.
Preferably, the heat-absorbing flow passage may be provided with a main heat-absorbing flow passage located directly below the heat-generating element, and at least one heat-absorbing U-shaped flow passage adjacent to the main heat-absorbing flow passage. In one embodiment, the heat-radiating flow passage from the heat-absorbing U-shaped flow passage to the heat-radiating area may have a heat-radiating reciprocating flow passage that reciprocates multiple-times in the heat-radiating area before returning again to the heat-absorbing area.
The main heat-absorbing flow passage may be one in an inlet and an outlet, and may be branched into a plurality of flow passages directly below a heat-generating source.
In one embodiment of the main heat-absorbing flow passage, the main heat-absorbing flow passage may be connected to an outermost peripheral heat-radiating flow passage that returns to the outlet hole through the outermost periphery of the heat-radiating sheet after passing through the main heat-absorbing flow passage.
The area of a heat-radiating sheet may specifically be 10 or more times the area of the heat spreader.
The inlet hole and outlet hole of the circulating flow passage may be formed as tubular projections in the heat-radiating sheet, and the discharge port and suction port of the pump may be formed as a discharge port that communicates with the tubular projection serving as the inlet hole, and a suction port that communicates with the tubular projection serving as the outlet hole.
If a piezoelectric pump is used as the pump, the liquid cooling system may be made small and thin.
A spacer block may also be interposed between the pump and the heat-radiating sheet, and the spacer block may be formed with a liquid injection hole extending to the circulating flow passage.
The liquid cooling system of the present disclosure may be used to cool a CPU of a notebook computer. In this embodiment, the whole liquid cooling system may be received inside a main body having a keyboard. It may be advantageous in heat-radiating performance that the heat-radiating sheet of the liquid cooling system is provided along the surface of the keyboard.
The liquid cooling system of the present disclosure may have a high unit property because the pump, the heat spreader, and the heat-generating source are all mounted on the heat-radiating sheet. Further, since the circulating flow passage in the heat-radiating sheet includes the heat-absorbing flow passage located below the heat spreader (heat-absorbing area), and the heat-radiating flow passage located in the heat-radiating area, and the flow passage length of the heat-radiating flow passage is sufficiently larger than the flow passage length of the heat-absorbing flow passage, effective heat radiation and comparatively equal heat distribution may be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a plan view showing a liquid cooling system according to an embodiment of the present disclosure as applied to a cooling system of a notebook computer;

FIG. 2 depicts a partially enlarged plan view of the embodiment shown in FIG. 1;

FIG. 3 depicts a right side view of the embodiment shown in FIG. 2;

FIG. 4 depicts a sectional view taken along the line IV-IV of the embodiment shown in FIG. 3;

FIG. 5 depicts an expanded perspective view of a portion of the embodiment shown in FIG. 2;

FIG. 6 depicts a plan view of a piezoelectric pump in the liquid cooling system of the embodiment shown in FIG. 1;

FIG. 7 depicts a sectional view taken along the line VII-VII line of the embodiment shown in FIG. 6.

FIG. 8 depicts a sectional view showing a state in which the liquid cooling system of the embodiment shown in FIG. 1 is assembled into a notebook computer;

FIG. 9 depicts a sectional view corresponding the embodiment shown in FIG. 4, illustrating an additional configuration of the flow passage of the heat-radiating sheet, according to another embodiment of the present disclosure;

FIG. 10 depicts a sectional view showing the additional configuration of the flow passage, according to another embodiment of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 depicts a liquid cooling system 100 according to the present disclosure. As shown in FIG. 8, the liquid cooling system 100 may be received in a main body 103 having a keyboard 102 of a notebook computer 101, and may be used to cool a CPU 104 as a heat-generating source. The liquid cooling system 100 of this embodiment may be provided completely independently of an LCD (display) 105 that may be opened and closed with respect to the main body 103.
As also shown in FIGS. 2 to 4, the liquid cooling system 100 may have a heat-radiating sheet 10, a piezoelectric pump 20 placed on the heat-radiating sheet 10, and a heat spreader 40 made of a heat-conductive metallic material, and the CPU 104 may be placed on the heat spreader 40. A cover 41 may be located on the CPU 104 (the CPU 104 may be sandwiched between the heat spreader 40 and the cover 41), and a spacer 42 may be located between the heat-radiating sheet 10 and the piezoelectric pump 20. In addition, although the piezoelectric pump 20, the heat spreader 40, and the CPU 104 are provided at the back (back of the keyboard 102) of the heat-radiating sheet 10, FIGS. 1, 2, and 5 depict a liquid cooling system 100 as seen from the back for convenience of illustration.
The heat-radiating sheet 10 may be composed of a pair of heat-conductive metal plates (brazing sheet) 10U and 10L that are superimposed on each other, and the one brazing sheet 10L may be formed with a flow-passage recess 11 a that constitutes a circulating flow passage 11. The depth of the flow-passage recess 11 a may be, for example, around 0.2 mm. A brazing sheet may be formed by bonding brazing materials to the surface and back of a sheet core made of a metallic material (generally aluminum alloy). The flow-passage recess 11 a may be formed by press working. By making a pair of brazing sheets abut on each other and heating them under pressure, brazing materials may be melted and bonded to each other. Generally, although the brazing plate 10U (10L) may have a thickness of about 0.4 mm, the material, thickness, and others of the heat-radiating sheet 10 (brazing sheet) may not matter.
The whole shape of the circulating flow passage 11 of the heat-radiating sheet 10 is depicted in FIG. 1. The circulating flow passage 11 may circulate between an inlet 11 b and an outlet 11 c (refer to FIGS. 2 and 5), and an inlet projection (inlet hole) 12 and an outlet projection (outlet hole) 13 that communicate with the inlet 11 b and the outlet 11 c that are both ends of the flow-passage recess 11 a may be formed so as to project from the brazing sheet 10U. The inlet projection 12 and the outlet projection 13 may communicate with (e.g., fit into) a discharge port (hole) 34 and a suction port (hole) 35 of the piezoelectric pump 20, respectively, via the spacer 42. More specifically, as shown in FIG. 7, the spacer 42 may be formed with relay holes 42 a and 42 b, the inlet projection 12 and the outlet projection 13 of the heat-radiating sheet 10 (brazing sheet 10U) may fit into the relay holes 42 a and 42 b, respectively, and annular projections 42 a′ and 42 b′ that are made to project coaxially with the relay holes 42 a and 42 b may fit into the discharge port 34 and suction port 35 of the piezoelectric pump 20.
Further, the spacer 42 may be formed with a liquid injection plug 42c that communicates with a liquid injection hole 14 formed in the brazing sheet 10U. The spacer 42 may be omitted by providing the liquid injection plug 42c in other portions. In other words, the inlet projection 12 and the outlet projection 13 of the heat-radiating sheet 10 may directly fit on the discharge port 34 and the suction port 35 of the piezoelectric pump 20. The liquid-tight structure of these fitting portions is not shown. The fitting portions between the annular projections 42 a′ and 42 b′ and the discharge port 34 and suction port 35 of the piezoelectric pump 20 may be connected via O rings. In this case, more reliable sealing performance may be obtained.
Although the configuration of the pump (piezoelectric pump) 20 does not matter in the present disclosure, the piezoelectric pump 20 of the embodiment will be described with reference to FIGS. 6 and 7. The piezoelectric pump 20 may have a lower housing 21 and an upper housing 22 sequentially from below.
The discharge port 34 and the suction port 35 may be bored in the lower housing 21 so as to be orthogonal to a plate thickness plane of the housing and parallel to each other. A piezoelectric vibrator (diaphragm) 28 may be liquid-tightly sandwiched and supported between the upper housing 21 and the lower housing 22 via the O ring 29, and a pump chamber P may be formed between the piezoelectric vibrator 28 and the lower housing 21. An atmospheric chamber A may be formed between the piezoelectric vibrator 28 and the upper housing 22.
The piezoelectric vibrator 28 may be a unimorph vibrator having a central shim 28 a, and a piezoelectric body 28 b may be stacked on one (upper face of FIG. 7) of the surface and back of the shim 28 a. The shim 28 a may face the pump chamber P and contacts liquid. The shim 28 a may be made of a conductive metallic thin plate material, for example, a metallic thin plate having a thickness of about 50 to 300 μm and formed of stainless steel, a 42 alloy, etc. The piezoelectric body 28 b may be made of, for example, PZT (Pb(Zr, Ti)O₃) having a thickness of about 300 μm, and may be subjected to polarizing treatment in the direction of the surface and back thereof.
The discharge port 34 and suction port 35 of the lower housing 21 may be respectively provided with check valves (umbrella) 32 and 33. The check valve 32 may be a suction-side check valve that allows flow of fluid from the inlet port 35 to the pump chamber P, and may not allow flow of the fluid in a direction reverse thereto, and the check valve 33 may be a discharge-side check valve that allows flow of the fluid from the pump chamber P to the outlet port 34, and may not allow flow of the fluid in a direction reverse thereto.
The check valves 32 and 33 may have the same form, and may be constructed by mounting umbrellas 32 b and 33 b made of an elastic material on perforated substrates 32 a and 33 a bonded and fixed to flow passages.
In the piezoelectric pump 20, if the piezoelectric vibrator 28 elastically deforms (e.g., vibrates) normally and/or reversely, the suction-side check valve 32 may be opened and the discharge-side check valve 33 may be closed, in a stroke where the volume of the pump chamber P increases. Therefore, liquid may flow into the pump chamber P from the suction port 35 (outlet projection 13 of the heat-radiating sheet 10). On the other hand, in a stroke where the volume of the pump chamber P reduces, the discharge-side check valve 33 may be opened and the suction-side check valve 32 may be closed. Therefore, the liquid may flow out of the pump chamber P into the discharge port 34 (inlet projection 12 of the heat-radiating sheet 10). Accordingly, a pumping action may be obtained by making the piezoelectric vibrator 28 continuously elastically deform (e.g., vibrate) normally and/or reversely, and liquid may flow into the outlet 11 c from the inlet 11 b of the circulating flow passage 11 of the heat-radiating sheet 10. In addition, in one embodiment, FIG. 7 shows that the piezoelectric pump 20 may be disposed on the heat-radiating sheet 10 for the purpose description. However, in another embodiment, with the heat-radiating sheet 10 facing upward, the piezoelectric pump 20 may be installed at the back of the heat-radiating sheet, e.g., at the face of the heat-radiating sheet 10 opposite to the keyboard 102 of the personal computer 101.
In the surface of the heat-radiating sheet 10, a portion where the heat spreader 40 (cover 41) may be installed is a heat-receiving area, and an area excluding the heat spreader 40 (cover 41) and the spacer 42 (piezoelectric pump 20) may be a heat-radiating area. The whole area of the heat-radiating sheet 10 may be set to 10 or more times (about 17 times in this embodiment) the area of the heat spreader 40. Further, the total flow passage length of the circulating flow passage 11 in a heat-absorbing flow passage located in the lower face of the heat spreader 40 may be set to be sufficiently larger (10 or more times (about 20 times in this embodiment)) than the total flow passage length of the circulating flow passage 11 in a heat-radiating flow passage located in the heat-radiating area.
In the liquid cooling system 100 having the above-mentioned configuration, the heat spreader 40 (CPU 104) and the pump 20 may be mounted on the heat-radiating sheet 10. Thus, all circulating flow passages may be formed without using a flexible tube.
The flow in the circulating flow passage 11 of this embodiment that returns to the suction port 35 (the outlet projection 13 or outlet 11 c) out of the discharge port 34 (the inlet projection 12, the inlet 11 b) of the piezoelectric pump 20 may be as follows when being sequentially traced by reference numerals 1 f to 38 f given to the inside of the circulating flow passage 11 as depicted in FIG. 1. After the circulating flow passage 11 that goes straight along heat-radiating straight flow passages 1 f and 2 f from the inlet 11 b is folded back in a U-shape in a heat-radiating U-shaped flow passage 3 f, and goes straight along a heat-radiating straight flow passage 4 f, the circulating flow passage may go into the lower face of the heat spreader 40 (heat-absorbing area), and may be folded back in a heat-absorbing U-shaped flow passage 5 f. When passing through the heat-absorbing U-shaped flow passage 5 f, the heat of the heat spreader 40 (CPU 104) may be primarily absorbed by the liquid passing through the flow passage.
After the circulating flow passage 11 comes out of the lower face of the heat spreader 40, the circulating flow passage may go straight along the heat-radiating straight flow passage 6f, may then be folded back in a heat-radiating U-shaped flow passage 7 f, and may then be folded back in a heat-radiating U-shaped flow passage 9 f without going into the flow passage directly below the heat spreader 40. Next, after the circulating flow passage goes straight along a heat-radiating straight flow passage 10 f, the circulating flow passage may go round largely outward in heat-radiating right- angled flow passages 11 f and 12 f, may then be folded back in a heat-radiating straight flow passage 13 f, and may then be folded back in a heat-radiating U-shaped flow passage 14 f. In this example, the circulating flow passage may still reciprocate in the heat-radiating area without going into the flow passage directly below the heat spreader 40. Moreover, after the circulating flow passage goes straight along a heat-radiating straight flow passage 15 f, is folded back in a heat-radiating U-shaped flow passage 16 f, and goes straight along a heat-radiating straight flow passage 17 f, the circulating flow passage may lead to the heat-absorbing area directly below the heat spreader 40. As described above, the heat-radiating flow passage that has led to the heat-radiating area from the heat-absorbing U-shaped flow passage 5f may reciprocate multiple times in the heat-radiating area before it returns again to the heat spreader 40 (heat-absorbing area), and during this time, the liquid that has absorbed heat and risen in temperature by the heat spreader 40 (CPU 104) may be sufficiently cooled.
The circulating flow passage 11 that has led to the heat-absorbing area may go out to the heat-radiating area after it is folded back in the heat-absorbing U-shaped flow passage 18 f and absorbs heat. After the circulating flow passage goes out to the heat-radiating area, the circulating flow passage may go straight along the heat-radiating straight flow passage 19 f, may be folded back in a heat-radiating U-shaped flow passage 20 f, may go straight along a heat-radiating straight flow passage 21 f, may be folded back in a heat-radiating U-shaped flow passage 22 f, may go straight along a heat-radiating straight flow passage 23 f, and may be folded back in a heat-radiating U-shaped flow passage 24 f, and may go straight along a heat-radiating straight flow passage 25 f. During this time, the circulating flow passage rarely goes into the heat-absorbing area directly below the heat spreader 40. That is, the heat-radiating flow passage that has led to the heat-radiating area from the heat-absorbing U-shaped flow passage 18 f may reciprocate multiple times in the heat-radiating area before it returns again to the heat spreader 40 (heat-absorbing area). Similarly, the liquid that has absorbed head and has risen in temperature by the heat spreader 40 (CPU 104) may be sufficiently cooled by a plurality of times of reciprocation in the heat-radiating area.
The circulating flow passage 11 that goes straight along a heat-radiating straight flow passage 25f may go again into the flow passage under the heat spreader 40 in a heat-absorbing inlet 26 f. The flow passage that leads to a heat-absorbing outlet 28 f via a branching flow passage 27 f from the heat-absorbing inlet 26 f may be a main heat-absorbing flow passage located directly below the CPU 104 on the heat spreader 40. This main heat-absorbing flow passage may be located between the heat-absorbing U-shaped flow passages 5 f and 18 f. The branching flow passage 27 f may be a flow passage that branches (e.g., widens the total flow passage area) one flow passage in the heat-absorbing inlet 26 f and the heat-absorbing outlet 28 f into a plurality of flow passages directly below the CPU 104, may reduce liquid velocity below the CPU 104, and may effectively absorb the generated heat of the CPU 104.
The circulating flow passage 11 that comes out of the flow passage directly below the heat spreader 40 (CPU 104) may lead to an outer peripheral flow passage 34f from an outer peripheral flow passage 29 f passing through the outermost periphery of the heat-radiating sheet 10. Effective cooling may be attained as the liquid that has passed through the flow passage directly below the CPU 104 and has risen to a highest temperature passes through the outermost periphery of the heat-radiating sheet 10, e.g., a portion having a larger temperature difference with respect to the outside air. After the circulating flow passage is folded back inward in a heat-radiating U-shaped flow passage 34 f, the circulating flow passage may go straight along a heat-radiating straight flow passage 35 f, may be folded back in a heat-radiating U-shaped flow passage 36 f, may go straight along heat-radiating straight flow passages 37 f and 38 f, and may return to the suction port 35 (outlet projection 13 or outlet 11 c).
FIGS. 9 and 10 depict other examples in which the circulating flow passage 11 of the heat-radiating sheet 10 may be formed. FIG. 9 depicts an embodiment where flow-passage recesses 11 a may be respectively formed in facing surfaces between the brazing sheets 10U and 10L by stamping, and FIG. 10 depicts an embodiment where a flow-passage recess 11 a may be similarly formed only in one brazing sheet 10L.
The aspect of the circulating flow passage 11 shown in the above-mentioned embodiment is exemplary, and may therefore be changed, altered, or varied. The positions of the heat spreader 40 and pump 20 on the heat-radiating sheet 10 may also be changed, altered, or varied.

Claims

1. A liquid cooling system comprising:

a heat-radiating sheet having a pair of heat-conductive metal plates that are superimposed on each other, and having a circulating flow passage between the pair of heat-conductive metal plates;

an inlet hole and an outlet hole opened to the surface of the heat-radiating sheet and located at both ends of the circulating flow passage;

a pump having a discharge port and a suction port that communicate with the inlet hole and the outlet hole, and installed on the heat-radiating sheet;

a heat-receiving area and a heat-radiating area set on the heat-radiating sheet; and

a heat-generating element installed on the heat-receiving area via a heat spreader made of a heat-conductive material,

wherein the circulating flow passage has a heat-absorbing flow passage located in a lower face of the heat spreader of the heat-receiving area, and a heat-radiating flow passage located in the heat-radiating area and having a sufficiently larger length than the flow passage length of the heat-absorbing flow passage.

2. The liquid cooling system of claim 1, wherein the flow passage length of the heat-radiating flow passage is 10 or more times the flow passage length of the heat-absorbing flow passage.

3. The liquid cooling system of claim 1, wherein the heat-absorbing flow passage has a main heat-absorbing flow passage located directly below the heat-generating element, and at least one heat-absorbing U-shaped flow passage adjacent to the main heat-absorbing flow passage.

4. The liquid cooling system of claim 3, wherein the heat-radiating flow passage from the heat-absorbing U-shaped flow passage to the heat-radiating area has a heat-radiating reciprocating flow passage that reciprocates multiple-times in the heat-radiating area before returning again to the heat-absorbing area.

5. The liquid cooling system of claim 3, wherein the main heat-absorbing flow passage is one in an inlet and an outlet, and is branched into a plurality of flow passages directly below a heat-generating source.

6. The liquid cooling system of claim 3, wherein the main heat-absorbing flow passage is connected to an outermost peripheral heat-radiating flow passage that returns to the outlet hole through the outermost periphery of the heat-radiating sheet after passing through the main heat-absorbing flow passage.

7. The liquid cooling system of claim 1, wherein the area of the heat-radiating sheet is 10 or more times the area of the heat spreader.

8. The liquid cooling system of claim 1, wherein the inlet hole and outlet hole of the circulating flow passage are formed as tubular projections in the heat-radiating sheet, and the discharge port and suction port of the pump are formed as a discharge port that communicates with the tubular projection serving as the inlet hole, and a suction port that communicates with the tubular projection serving as the outlet hole.

9. The liquid cooling system of claim 1, wherein the pump is a piezoelectric pump.

10. The liquid cooling system of claim 1, wherein a spacer block is interposed between the pump and the heat-radiating sheet, and the spacer block is formed with a liquid injection hole extending to the circulating flow passage.

11. The liquid cooling system of claim 1, wherein the heat-generating source is a CPU of a notebook computer, and the whole liquid cooling system is received inside a main body having a keyboard.

12. The liquid cooling system of claim 11, wherein the heat-radiating sheet of the liquid cooling system is provided along the surface of the keyboard.