U.S. patent application number 11/104805 was filed with the patent office on 2005-11-03 for pump, cooling system, and electronic apparatus.
Invention is credited to Sayano, Akio, Tomioka, Kentaro.
Application Number | 20050241809 11/104805 |
Document ID | / |
Family ID | 35185897 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241809 |
Kind Code |
A1 |
Tomioka, Kentaro ; et
al. |
November 3, 2005 |
Pump, cooling system, and electronic apparatus
Abstract
A cooling pump includes a rotor including a rotation axis, a
disc fixed with the rotation axis, an impeller fixed with the disc
for pressurizing a liquid coolant, and a plurality of permanent
magnets arrayed to be fixed with the disc in a ring shape; a case
including a pump chamber holding the rotor rotatably, the pump
chamber having an inlet and an outlet for the liquid coolant,
wherein a part of the bottom wall forming the pump chamber is a
heat-receiving portion; a cover including a recess, the cover
sealing the case, i.e., pump housing, liquid-tightly; and a
circular stator disposed in the recess, the stator generating a
rotating magnetic field with a plurality of electromagnets to
provide the rotor with torque around the rotation axis, wherein a
hydrophilic surface is disposed on the inner surface of the pump
chamber.
Inventors: |
Tomioka, Kentaro;
(Sayama-Shi, JP) ; Sayano, Akio; (Yokohama-Shi,
JP) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
35185897 |
Appl. No.: |
11/104805 |
Filed: |
April 13, 2005 |
Current U.S.
Class: |
165/104.33 ;
257/E23.098; 417/423.14; 417/DIG.1 |
Current CPC
Class: |
H01L 2924/0002 20130101;
G06F 1/203 20130101; H01L 23/473 20130101; F04D 29/026 20130101;
F05D 2300/51 20130101; H01L 2924/00 20130101; F05D 2300/21
20130101; F05D 2300/211 20130101; H01L 2924/3011 20130101; G06F
2200/201 20130101; H01L 2924/0002 20130101; F04D 29/426
20130101 |
Class at
Publication: |
165/104.33 ;
417/DIG.001; 417/423.14 |
International
Class: |
F28D 015/00; F04B
017/00; F25B 007/00; F04B 035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2004 |
JP |
P2004-134426 |
Claims
What is claimed is:
1. A pump comprising: a housing including a pump chamber; an
impeller disposed in the pump chamber; and a stator for rotating
the impeller, wherein an inner surface of the pump chamber includes
a hydrophilic surface.
2. The pump according to claim 1, wherein the hydrophilic surface
is a film mainly composed of a silicon oxide.
3. The pump according to claim 1, wherein the hydrophilic surface
is a film mainly composed of a titanium oxide.
4. The pump according to claim 1, wherein the hydrophilic surface
comprises a rough face.
5. The pump according to claim 1, wherein the pump housing
comprises a metal case and a resin cover to be combined with the
metal case, and the hydrophilic surface is provided on the inner
surface of the metal case.
6. The pump according to claim 5, wherein the metal case comprises
an outlet tube for discharging the liquid coolant and an inlet tube
for sucking the liquid coolant, and the hydrophilic surface is
provided on the inner surfaces of the outlet tube and the inlet
tube.
7. The pump according to claim 6, wherein the metal case comprises
the pump chamber and a reserve chamber, and the hydrophilic surface
is provided on the inner surface of the reserve chamber.
8. An electronic apparatus comprising: a casing; a substrate
disposed in the casing; a heat generating unit mounted on the
substrate; and a cooling system thermally connected to the heat
generating unit, the cooling system including a radiator for
dissipating the heat from the heat generating unit, a circulation
path for circulating a liquid coolant to the radiator, and a pump
for forcibly circulating the liquid coolant through the circulation
path, the pump including a housing including a pump chamber, an
impeller disposed in the pump chamber, and a stator for rotating
the impeller, wherein an inner surface of the pump chamber includes
a hydrophilic surface.
9. The electronic apparatus according to claim 8, wherein the
hydrophilic surface is a film mainly composed of a silicon
oxide.
10. The electronic apparatus according to claim 8, wherein the
hydrophilic surface is a film mainly composed of a titanium
oxide.
11. The electronic apparatus according to claim 8, wherein the
hydrophilic surface comprises a rough face.
12. The electronic apparatus according to claim 8, wherein the
housing comprises a metal case and a resin cover to be combined
with the metal case, and the hydrophilic surface is provided on the
inner surface of the metal case.
13. The electronic apparatus according to claim 12, wherein the
metal case comprises an outlet tube for discharging the liquid
coolant to the circulation path and an inlet tube for sucking the
liquid coolant from the circulation path, and the hydrophilic
surface is provided on the inner surfaces of the outlet tube and
the inlet tube.
14. The electronic apparatus according to claim 13, wherein the
metal case comprises the pump chamber and a reserve chamber, and
the hydrophilic surface is provided on the inner surface of the
reserve chamber.
15. A cooling system thermally connected to a heat generating unit,
the cooling system comprising: a radiator for dissipating the heat
from the heat generating unit; a circulation path for circulating a
liquid coolant to the radiator; and a pump for forcibly circulating
the liquid coolant through the circulation path, the pump including
a housing including a pump chamber, an impeller disposed in the
pump chamber, and a stator for rotating the impeller, wherein an
inner surface of the pump chamber includes a hydrophilic
surface.
16. The cooling system according to claim 15, wherein the
hydrophilic surface is a film mainly composed of a silicon
oxide.
17. The cooling system according to claim 15, wherein the
hydrophilic surface is a film mainly composed of a titanium
oxide.
18. The cooling system according to claim 15, wherein the
hydrophilic surface comprises a rough face.
19. The cooling system according to claim 15, wherein the housing
comprises a metal case and a resin cover to be combined with the
metal case, and the hydrophilic surface is provided on the inner
surface of the metal case.
20. The cooling system according to claim 19, wherein the metal
case comprises an outlet tube for discharging the liquid coolant to
the circulation path and an inlet tube for sucking the liquid
coolant from the circulation path, and the hydrophilic surface is
provided on the inner surfaces of the outlet tube and the inlet
tube.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of Japanese
Patent Application No. 2004-134426, filed Apr. 28, 2004, the entire
contents of which are incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to a pump, a cooling system,
and electronic apparatus, and in particular, to a pump used in a
liquid cooling system for cooling a heat generating unit, the
cooling system, and electronic apparatus including the same.
[0004] 2. Description of the Related Art
[0005] Recently, the data processing speed of electronic apparatus
such as a personal computer has been significantly improved. In
order to achieve this, the clock frequency for processing a central
processing unit (CPU) or peripheral semiconductor devices has also
become significantly higher than that in the known devices.
[0006] Accordingly, the heating value from the CPU and other
semiconductor devices has also been increased. In a known method, a
heat sink is thermally connected to a heat generating unit such as
a CPU and the heat sink is air-cooled. However, some recent
semiconductor devices cannot be cooled by such a method.
[0007] Meanwhile, a technology to apply a liquid cooling system to
compact electronic apparatus such as a personal computer has been
developed. The liquid cooling system can achieve higher cooling
efficiency because a liquid having a specific heat higher than that
of air is used as a coolant.
[0008] For example, Japanese Patent Nos. 3,431,024 and 3,452,059
disclose cooling systems including a closed circulation path for
circulating a coolant, a radiator that dissipates the heat from the
coolant, and a contact heat exchange pump. The pump is used for
pressuring the coolant in order that the coolant circulates in the
closed circulation path and is thermally brought into contact with
a heating semiconductor. Thus, the heating semiconductor is cooled
by heat exchange of the coolant. In addition, Jpn Pat. Publication
No. 2003-172286 discloses a technology to reduce the thickness of
the contact heat exchange pump.
[0009] In such a liquid cooling method, it is important to increase
the thermal conductivity from a heat-receiving face for receiving
the heat from a heat generating unit to a face being in contact
with a flow path of a liquid coolant. Jpn Pat. Publication No.
2003-68317 discloses a technology relating to a surface treatment
of a cooling flow path for cooling a separator of a fuel cell.
According to this technology, the surface of the cooling flow path
is roughened so as to increase the heat transfer area. As a result,
the thermal conductivity is increased. Although the above patent
document also describes the application of a hydrophilic coating
material, the hydrophilic coating material is applied in order to
prevent the freezing of the coolant. Therefore, the application of
the hydrophilic coating material does not directly affect the
improvement in the cooling efficiency.
[0010] In order to cool a heat generating unit such as a CPU at a
high cooling efficiency by circulating a coolant, it is extremely
important to increase the flow rate of the coolant to increase the
flow volume of the coolant per unit of time.
[0011] In particular, in a pump for circulating a coolant by
pressurizing, the increase in the flow rate of the coolant to
increase the flow volume significantly improves the cooling
efficiency.
[0012] For example, in the above-cited Jpn Pat. Publication No.
2003-172286 disclosing a contact heat exchange pump having a very
small thickness, a surface treatment on the inner surface of the
pump chamber is not described.
[0013] However, when the pump has an inner surface formed by, for
example, pressing, injection molding, or die casting, a
satisfactory heat transfer performance from a pump housing, which
is a heat receiver, to a coolant is not necessarily achieved.
[0014] According to the surface treatment technology of a flow path
disclosed in the above-cited Jpn Pat. Publication No. 2003-68317,
the rough face has the maximum arithmetic mean roughness (Ra) of
3.5 .mu.m. Furthermore, the technical field of the above patent
document relates to a fuel cell, which is different from the
technical field of the present invention. The present invention
relates to the cooling of a heating semiconductor such as a CPU. A
sufficient cooling performance cannot be expected with the
above-cited technology.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0016] FIG. 1 is a first view showing the appearance of electronic
apparatus according to an embodiment of the present invention;
[0017] FIG. 2 is a second view showing the appearance of the
electronic apparatus according to the embodiment of the present
invention;
[0018] FIG. 3 is a cross-sectional view showing an example of a
mounting state of a cooling pump according to the present
invention;
[0019] FIG. 4 is a view showing the structure of a cooling system
provided in electronic apparatus according to an embodiment of the
present invention;
[0020] FIG. 5 is a view showing the structure of a radiator of the
cooling system;
[0021] FIG. 6 is a first view showing the structure of a cooling
pump according to an embodiment of the present invention;
[0022] FIG. 7 is a second view showing the structure of the cooling
pump according to the embodiment of the present invention;
[0023] FIG. 8 is a cross-sectional view showing the structure of
the cooling pump according to the present invention; and
[0024] FIG. 9A, FIG. 9B, and the graph disposed thereunder show an
advantage of a surface-treated portion provided on the cooling pump
according to the present invention.
DETAILED DESCRIPTION
[0025] Embodiments of a cooling pump (pump), a cooling system, and
electronic apparatus according to the present invention will now be
described with reference to the attached drawings.
[0026] FIGS. 1 and 2 are views showing the appearance of a personal
computer 1 that is an embodiment of electronic apparatus according
to the present invention.
[0027] The personal computer 1 includes a main unit 2 and a panel
unit 3.
[0028] The main unit 2 of the personal computer 1 includes a main
unit casing 4 having a thin box-shape. The main unit casing 4
includes a bottom wall 4a, a top wall 4b, a front wall 4c, side
walls 4d disposed at the right and the left, and a back wall
4e.
[0029] A plurality of outlets 6 for releasing cooling air is
provided at the back wall 4e.
[0030] The top wall 4b of the main unit casing 4 holds a keyboard
5.
[0031] The panel unit 3 includes a panel unit casing 8 and a
display unit 9. The display unit 9 is held with the panel unit
casing 8 and includes a display panel 9a. The display panel 9a is
exposed from an opening 10 disposed at the front face of the panel
unit casing 8.
[0032] The panel unit casing 8 is supported so as to be opened or
closed freely with a hinge provided at the back end of the main
unit casing 4.
[0033] FIG. 1 shows the appearance when the panel unit 3 is opened,
whereas FIG. 2 shows the appearance when the panel unit 3 is
closed.
[0034] FIG. 3 is a cross-sectional view of a printed circuit board
12 provided in the main unit casing 4, a semiconductor device such
as a CPU 13 that is a heat generating unit mounted on the printed
circuit board 12, and a cooling pump 17 that is thermally connected
to the CPU 13.
[0035] The printed circuit board 12 is disposed, for example, in
the direction parallel to the bottom wall 4a of the main unit
casing 4. The CPU 13 is mounted on a surface, for example, the top
surface, of the printed circuit board 12.
[0036] The CPU 13 includes a base substrate 14 and an IC chip 15
provided at the center of the top surface of the base substrate 14.
In order to maintain the operation of the CPU 13, it is essential
to cool the IC chip 15 efficiently.
[0037] The outer surface of a bottom wall 25 of the cooling pump 17
forms a heat-receiving face 26. The heat-receiving face 26 is
thermally connected to the surface of the IC chip 15 with, for
example, heat-transfer grease or a heat-transfer sheet
therebetween.
[0038] FIG. 4 shows an example of the structure of a cooling system
16 provided in the main unit 2 of the personal computer 1.
[0039] The cooling system 16 includes the cooling pump 17, a
radiator 18, a circulation path 19, and an electric fan 20.
[0040] The cooling pump 17 is disposed so as to cover the CPU 13
mounted on the printed circuit board 12. Four corners of the
cooling pump 17 are pierced with screws 47. The screws 47 further
pierce the printed circuit board 12 to screw with four bosses 46
fixed on the bottom wall 4a of the main unit casing 4.
[0041] Thus, the cooling pump 17 is fixed with the printed circuit
board 12 and the bottom wall 4a of the main unit casing 4 and is
thermally connected to the CPU 13.
[0042] The cooling pump 17 includes an inlet tube 32 for sucking a
liquid coolant and an outlet tube 33 for discharging the liquid
coolant. The cooling pump 17, the inlet tube 32, and the outlet
tube 33 are formed as a single component.
[0043] The radiator 18 includes a first passage 50, a second
passage 51, and a third passage 52 through which the liquid coolant
flows.
[0044] FIG. 5 is a perspective view showing the structure of the
radiator 18 in detail. Referring to FIG. 5, the first passage 50
and the second passage 51 include pipes 53 and 54 having a flat
cross-section, respectively. The pipes 53 and 54 are disposed such
that the longitudinal direction of each cross-section is parallel
to the bottom wall 4a of the main unit casing 4.
[0045] The pipe 53 has a circular cross-section at the upstream end
of the first passage 50 to form a coolant inlet 56 through which
the liquid coolant is entered. On the other hand, the pipe 53 has
the flat cross-section at the downstream end of the first passage
50. The downstream end of the first passage 50 is connected to the
upstream end of the third passage 52.
[0046] The pipe 54 has a circular cross-section at the downstream
end of the second passage 51 to form a coolant outlet 57 through
which the liquid coolant is discharged. On the other hand, the pipe
54 has the flat cross-section at the upstream end of the second
passage 51. The upstream end of the second passage 51 is connected
to the downstream end of the third passage 52.
[0047] A plurality of cooling fins 63 are provided between a back
face 53a of the pipe 53 and a back face 54a the pipe 54. The
cooling fins 63 are fixed on the back faces 53a and 54a by, for
example, soldering. Thus, the cooling fins 63 are thermally
connected to the pipes 53 and 54.
[0048] Spaces between the cooling fins 63 form a plurality of
cooling air passages 62.
[0049] As shown in FIG. 4, the circulation path 19 includes an
upstream tube portion 70 and a downstream tube portion 71.
[0050] One end of the upstream tube portion 70 is connected to the
outlet tube 33 of the cooling pump 17 and another end of the
upstream tube portion 70 is connected to the coolant inlet 56 of
the first passage 50.
[0051] On the other hand, one end of the downstream tube portion 71
is connected to the inlet tube 32 of the cooling pump 17 and
another end of the downstream tube portion 71 is connected to the
coolant outlet 57 of the second passage 51.
[0052] The electric fan 20 sends cooling air to the radiator
18.
[0053] The electric fan 20 includes a fan casing 73 and an impeller
74 of the fan provided in the fan casing 73.
[0054] The fan casing 73 includes a cooling air outlet 75 that
discharges the cooling air and a duct 76 that guides the discharged
cooling air to the radiator 18.
[0055] The structure of the cooling pump 17 will now be described
in detail.
[0056] FIGS. 6 and 7 are views showing the structure of the cooling
pump 17 according to an embodiment of the present invention.
[0057] The cooling pump 17 includes a pump housing 21 serving as a
heat-receiving portion. The pump housing 21 includes a case 22 and
a cover 23.
[0058] The case 22 is composed of a metal having a high thermal
conductivity, for example, copper or aluminum. The cover 23 is
composed of a resin. The case 22 and the cover 23 are combined with
an O-ring 22a disposed therebetween. The case 22 includes a recess
24 opening in the upward direction in FIG. 7. The bottom wall 25 of
the recess 24 faces the CPU 13. The under surface of the bottom
wall 25 forms the heat-receiving face 26 that is thermally
connected to the CPU 13.
[0059] The recess 24 is separated with a partition wall 27 to form
a pump chamber 28 and a reserve chamber 29. The reserve chamber 29
stores the liquid coolant.
[0060] The partition wall 27 includes an inlet 30 and an outlet 31.
The inlet 30 is connected to the inlet tube 32 through which the
liquid coolant is sucked in the pump chamber 28. The outlet 31 is
connected to the outlet tube 33 through which the liquid coolant is
discharged from the pump chamber 28.
[0061] A rotor 39 is provided in the pump chamber 28.
[0062] The rotor 39 has a disc shape and includes a rotation axis
36 fixed at the center thereof. One end of the rotation axis 36 is
rotatably supported at the center of the pump chamber 28 and
another end of the rotation axis 36 is rotatably supported at the
center of the cover 23.
[0063] The rotor 39 includes an impeller 35 that pressurizes the
liquid coolant. A plurality of permanent magnets is embedded in an
annular side wall 41 of the rotor 39. The impeller 35 and the
plurality of permanent magnets are rotated around the rotation axis
36 as a single united component.
[0064] The cover 23 liquid-tightly seals the pump chamber 28
including the rotor 39, and the reserve chamber 29.
[0065] A stator 38 is disposed in a recess 23a formed on the upper
surface of the cover 23 in FIG. 7. The stator 38 includes a
plurality of electromagnets 40.
[0066] A predetermined current is applied to the plurality of
electromagnets 40. As a result, the stator 38 generates a rotating
magnetic field. A repulsive force caused by this rotating magnetic
field of the stator 38 and a magnetic field of the permanent
magnets provided in the rotor 39 generates torque to rotate the
rotor 39. Consequently, the impeller 35 provided on the rotor 39
pressurizes to circulate the liquid coolant.
[0067] A control circuit board 42 is also disposed in the cover 23.
The control circuit board 42 controls the current applied to the
electromagnets 40.
[0068] A lid 44 covers and protects the stator 38 and the control
circuit board 42. The lid 44 is fixed on the pump housing 21 with
screws 43.
[0069] FIG. 8 is a schematic cross-sectional view of the cooling
pump 17.
[0070] The case 22 and the cover 23 form the pump chamber 28. In
order to increase the flow rate of the liquid coolant and to
improve the cooling performance, a surface-treated portion 60 for
improving hydrophilicity is provided on the inner surface of the
pump chamber 28.
[0071] In a first embodiment of the hydrophilic surface 60 for
improving hydrophilicity, a silicon oxide film, for example, a
silicon dioxide (SiO.sub.2) film is formed on the inner surface of
the pump chamber 28 (i.e., a bottom face 25a facing the
heat-receiving face 26 and a side face 25b continuous to the a
bottom face 25a), an inner surface 32a of the inlet tube 32, and an
inner surface 33a of the outlet tube 33. In order to form the
silicon dioxide (SiO.sub.2) film, for example, the case 22 is
immersed in a solution of silicon dioxide (SiO.sub.2) and is then
dried.
[0072] In terms of the cooling performance, the thickness of the
silicon dioxide (SiO.sub.2) film is, for example, 0.1 to 0.6
.mu.m.
[0073] In a second embodiment of the hydrophilic surface 60 for
improving hydrophilicity, a titanium oxide film, for example, a
titanium dioxide (TiO.sub.2) film is formed on the inner surface of
the pump chamber 28, the inner surface 32a of the inlet tube 32,
and the inner surface 33a of the outlet tube 33. In order to form
the titanium dioxide (TiO.sub.2) film, for example, the case 22 is
immersed in a solution of titanium dioxide (TiO.sub.2) and is then
dried, as in the first embodiment.
[0074] In terms of the cooling performance, the thickness of the
titanium dioxide (TiO.sub.2) film is, for example, 0.1 to 0.6
.mu.m.
[0075] In a third embodiment of the hydrophilic surface 60 for
improving hydrophilicity, a treatment forming a rough face is
performed on the inner surface of the pump chamber 28, the inner
surface 32a of the inlet tube 32, and the inner surface 33a of the
outlet tube 33. In terms of the cooling performance, for example,
the inner surface has an arithmetic mean roughness (Ra) of 0.5 to
100 .mu.m.
[0076] A method for forming the rough face is not particularly
limited. For example, the rough face can be formed by honing.
[0077] FIG. 9A, FIG. 9B, and the graph disposed thereunder
qualitatively explain an advantage of the hydrophilic surface 60
for improving hydrophilicity provided on the inner surface of the
cooling pump 17.
[0078] FIG. 9A shows the case wherein the hydrophilic surface 60
for improving hydrophilicity is not provided. When a surface has a
low hydrophilicity, for example, a water droplet does not spread
out on the surface. In such a case, the liquid coolant flowing in
the pump chamber 28 receives a resistance from the inner surface of
the pump chamber 28. As a result, the flow rate and the flow volume
of the liquid coolant are restricted.
[0079] In contrast, FIG. 9B shows the case wherein the hydrophilic
surface 60 according to the present invention for improving
hydrophilicity is provided on the inner surface of the pump chamber
28. When a surface has a high hydrophilicity, for example, a water
droplet can spread out on the surface. In such a case, the
resistance of the inner surface of the pump chamber 28 is
decreased. As a result, the flow rate and the flow volume of the
liquid coolant can be increased, compared with the case wherein the
hydrophilic surface 60 for improving hydrophilicity is not
provided.
[0080] As shown in the graph disposed under FIGS. 9A and 9B, the
quantity of heat removed from the heat-receiving face 26 generally
has a positive correlation with the flow rate or the flow volume of
fluid flowing on the heat-receiving face or a face thermally
connected to the heat-receiving face. Therefore, when the
hydrophilic surface 60 for improving hydrophilicity is provided on
the inner surface of the pump chamber 28, the quantity of heat
removed from the heat-receiving face 26 is increased to improve the
cooling performance.
[0081] The operation of the cooling system 16 including the cooling
pump 17 according to the present invention will now be described
with reference to FIGS. 4 and 8.
[0082] The CPU 13, which is a heat generating unit, is thermally
connected to the heat-receiving face 26 of the case 22 shown in
FIG. 8 with heat-transfer grease or a heat-transfer sheet (not
shown) disposed therebetween.
[0083] The heat generated from the CPU 13 is conducted from the
heat-receiving face 26 to the inner surface of the pump chamber 28
on which the hydrophilic surface 60 is provided through the bottom
wall 25 of the case 22.
[0084] A cooled liquid coolant flows in the pump chamber 28 from
the inlet tube 32 through the inlet 30. The heat from the CPU 13
conducted to the inner surface of the pump chamber 28 is conducted
to the cooled liquid coolant. As a result, the liquid coolant
receives the heat.
[0085] Meanwhile, in the pump chamber 28, the rotor 39 is rotated
by receiving torque due to the rotating magnetic field generated
from the stator 38. The liquid coolant that has received the heat
is pressurized by the rotation of the impeller 35 provided on the
rotor 39. The liquid coolant is discharged from the outlet tube 33
through the outlet 31.
[0086] The hydrophilic surface 60 for improving hydrophilicity is
provided on the inner surface of the pump chamber 28. Therefore,
the liquid coolant circulating in the pump chamber 28 receives less
resistance, compared with the case wherein the hydrophilic surface
60 is not provided.
[0087] As a result, the flow rate of the liquid coolant circulating
in the pump chamber 28 is increased and the flow volume of the
liquid coolant per unit of time is also increased.
[0088] The increase in the flow rate or the flow volume of the
liquid coolant circulating in the pump chamber 28 increases the
quantity of heat removed from the CPU to improve the cooling
performance.
[0089] Furthermore, when the hydrophilic surface 60 in the pump
chamber 28 is a rough face described in the third embodiment, the
heat-receiving area on the inner surface of the pump chamber 28 is
increased. Thus, the cooling performance can be further
improved.
[0090] As shown in FIG. 4, the liquid coolant that has received the
heat is pressurized with the cooling pump 17 and is then discharged
from the outlet tube 33. Subsequently, the liquid coolant passes
through the upstream tube portion 70 of the circulation path 19 and
flows into the radiator 18.
[0091] In the radiator 18, the liquid coolant circulates in the
first passage 50, the third passage 52, and the second passage 51.
During this circulation, the heat from the liquid coolant is
transferred to the first passage 50, the second passage 51, and the
cooling fins 63, which are thermally connected to the first passage
50 and the second passage 51.
[0092] The cooling air generated by the rotation of the impeller 74
of the electric fan 20 blows on the first passage 50, the second
passage 51, and the cooling fins 63 to remove the heat from these
components. The cooling air is then released from the plurality of
outlets 6 provided at the back wall 4e of the main unit casing
4.
[0093] As described above, the liquid coolant that has received the
heat is cooled during circulating in the radiator 18. The cooled
liquid coolant passes through the downstream tube portion 71 of the
circulation path 19 and then returns to the pump chamber 28 through
the inlet tube 32 of the cooling pump 17.
[0094] Repeating this cycle allows the heat generated from the CPU
13 to be released to the outside of the main unit casing 4
continuously with the cooling air generated from the electric fan
20.
[0095] The present invention is not limited to the above
embodiments. The present invention may be embodied by modifying the
components without departing from the spirit and the scope of the
present invention. For example, the hydrophilic surface 60 may be
provided on the entire inner surface of the recess 24 including the
reserve chamber 29. This structure can further improve the
heat-receiving efficiency of the cooling pump 17 as a whole. In the
above embodiments, the pump includes the heat-receiving portion
that is thermally connected to the CPU. Alternatively, the
heat-receiving portion that is thermally connected to the CPU and
the pump may be separate components, and the pump may be disposed
at a halfway position of the circulation path.
* * * * *