U.S. patent application number 11/946561 was filed with the patent office on 2008-05-15 for cooling apparatus for electronic devices.
This patent application is currently assigned to NEC CORPORATION. Invention is credited to Sakae KITAJO, Kazuyuki MIKUBO, Atsushi OCHI, Yasuhiro SASAKI, Mitsuru YAMAMOTO.
Application Number | 20080110600 11/946561 |
Document ID | / |
Family ID | 31884434 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080110600 |
Kind Code |
A1 |
MIKUBO; Kazuyuki ; et
al. |
May 15, 2008 |
COOLING APPARATUS FOR ELECTRONIC DEVICES
Abstract
The present invention provides a cooling apparatus which is easy
to build and to fix it to electronic devices, superior in thermal
conduction and heat dissipation, and possible to make thin the
total configuration of the apparatus. The liquid cooling unit 9 and
the air cooling unit 12 are formed in a unit. A heat absorption
surface 19 of the liquid cooling unit 9 is contacted or bonded to
the heat generation component such as the CPU and the heat
generator, which have the largest power consumption and also
locally generate heat within a small area in the box 2. In the
liquid cooling unit 9, a liquid cooling pump 14 composed of an
electromagnetic pump is arranged for circulating the coolant in the
flow path 10. The heat generated by the heat generation components
such as CPU 6, heat generator 7, and the like is thermally diffused
with heat conduction into the whole liquid cooling unit 9 by
circulating the coolant with the liquid cooling pump 14.
Inventors: |
MIKUBO; Kazuyuki; (Tokyo,
JP) ; KITAJO; Sakae; (Tokyo, JP) ; SASAKI;
Yasuhiro; (Tokyo, JP) ; OCHI; Atsushi; (Tokyo,
JP) ; YAMAMOTO; Mitsuru; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
NEC CORPORATION
Tokyo
JP
|
Family ID: |
31884434 |
Appl. No.: |
11/946561 |
Filed: |
November 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10524770 |
Feb 15, 2005 |
|
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|
PCT/JP2003/010419 |
Aug 18, 2003 |
|
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11946561 |
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Current U.S.
Class: |
165/104.33 ;
257/E23.098; 257/E23.099 |
Current CPC
Class: |
H01L 23/473 20130101;
H01L 23/467 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; G06F 1/20 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/104.33 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 2002 |
JP |
2002-237256 |
Claims
1. A cooling apparatus for cooling a heat generator in electronic
devices comprises: a flow path, in which a coolant flows, embedded
in a base; a liquid cooling pump disposed above the base for
circulating the coolant; a liquid cooling unit embedded in the base
for connecting the flow path and the liquid cooling pump; and an
air cooling unit member disposed on the base, wherein the liquid
cooling pump and the liquid cooling unit are integrated in a single
unit of a metal materials.
2. A cooling apparatus for cooling a heat generator in electronic
devices comprises: an unit for liquid cooling having a flow path in
which a coolant flows and a liquid cooling pump for circulating the
coolant, both of which are embedded in a base; and an air cooling
unit member disposed on the base, wherein the liquid cooling pump
and the liquid cooling unit are integrated in a single unit of a
metal material.
3. A cooling apparatus according to claim 1, wherein the flow path
is formed by joining a base having a groove and the heat absorption
surface.
4. A cooling apparatus according to claim 2, wherein the flow path
is formed by joining a base having a groove and the heat absorption
surface.
5. A cooling apparatus according to claims 1, wherein an air
cooling unit includes an air cooling fin group for exhausting heat,
which is diffused by the liquid cooling unit, in atmosphere.
6. A cooling apparatus according to claims 2, wherein an air
cooling unit includes an air cooling fin group for exhausting heat,
which is diffused by the liquid cooling unit, in atmosphere.
7. A cooling apparatus according to claim 2, wherein the air
cooling unit comprises an air cooling fan for flowing air to the
air cooling fin group.
8. A cooling apparatus according to claim 1, wherein the apparatus
further comprises: an air cooling fan supplying air to a liquid
cooling pump and to the air cooling fin group; and an electric
control circuit driving the liquid cooling pump and the air cooling
fan, wherein, an input to the electric control circuit is DC
current.
9. An electronic device mounting a cooling apparatus according to
claim 1.
10. An electronic device mounting a cooling apparatus according to
claim 2.
11. A cooling apparatus according to claim 3, wherein the air
cooling fin group and the base are formed in a single unit.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a cooling apparatus for
electronic device, and, more particularly to the cooling apparatus
for electronic device suitable for cooling a heat generation
component such as a CPU and the like mounted on, for example, a
laptop computer.
[0002] All of patents, patent applications, patent publications,
scientific articles and the like, which will hereinafter be cited
or identified in the present application, will hereby be
incorporated by references in their entirety in order to describe
more fully the state of the art, to which the present invention
pertains.
DESCRIPTION OF THE RELATED ART
[0003] Recently, with an increase in processing volume and
processing speed, a heat generator having a large power consumption
such as a CPU and the like is mounted on electronic devices such
as, for example, a PC. An amount of heat generated by the heat
generator is increasing linearly. On the other hand, operation
temperatures of various electronic components used in the
electronic devices are limited in general in view of thermal
reliability and temperature dependence of the operation
characteristics. Therefore, it has been an urgent matter for these
electronic devices to establish technologies for effectively
exhausting heat, which is generated within the devices, out of the
devices.
[0004] Generally, in the electronic devices such as a PC and the
like, for example, a metallic heat-sink or, so called, a heat-pipe
has been attached to a CPU and the like for diffusing the heat to a
whole body of the electronic devices by thermal conduction, or an
electromagnetic cooling fan has been disposed on the body for
exhausting the heat to the outside of the electronic devices
thereof.
[0005] However, for example, in a laptop PC and the like which is
packaged in high-density with electronic components, a heat
discharging space within the electronic device is limited. Then,
regarding a CPU with power consumption over 30 W, it has been
difficult to sufficiently discharge the internal heat to the
outside of the device, although a conventional cooling fan or a
combination of the cooling fan and the heat pipe has a proper
cooling performance for the CPU with power consumption around 30
W.
[0006] A cooling fan having a large blowing performance has also
been essential, and in the case of the electromagnetic fan,
calmness of the fan has been lacked by noises generated by, for
example, a wind roar of rotating blades.
[0007] In addition, regarding a PC for a server, demands for
compactness and calmness has become strong with increase in the
penetration rate of the PC. Accordingly, the same issue with a
laptop PC in regard to the heat dissipation has been existed as
well.
[0008] Cooling apparatuses of conventional electronic devices
disclosed in the Japanese laid-on patent applications, No.
2002-94276 and No. 2002-94277 have been developed as methods to
solve the above issues.
[0009] FIG. 1 is a traverse cross sectional view showing an
arrangement of a conventional cooling apparatus for electronic
devices.
[0010] As shown in FIG. 1, the conventional cooling apparatus
comprises a heat-sink 101, a heat-discharge pipe 102 for thermal
conduction, and an enforced cooling member 104. The heat-sink 101
has a heat sinking part therein contacting with a high power
consumption device such as a CPU and the like. A liquid flow path
105 is formed in the heat-sink 101. The liquid flow path 105 is
connected to the enforced cooling unit 104 through the
heat-discharge pipe 102. The enforced cooling unit 104 acts as a
heat-discharge unit. The enforced cooling unit 104 comprises a
liquid circulation pump 106, an air cooling fan 103, and a housing
107 containing the liquid circulation pump 106 and the air cooling
fan 103 therein. All of these are unified via a gasket.
[0011] A heat generated by a device with high power consumption is
transferred to the heat-sink 101 which is contacted to the device,
and thereby increases a temperature of liquid in the liquid flow
path 105 within the heat-sink 101. The liquid in the liquid flow
path 105 is carried to the enforced cooling unit 104 through the
heat-discharge pipe 102 by a pressure generated by the liquid
circulation pump 106. In the enforced cooling unit 104, the liquid
which is raised the temperature in the liquid flow path 105 is
cooled by the air cooling fan 103, and thereby the temperature is
decreased. The liquid of which temperature is decreased returns to
the heat-sink 101 by circulation. On the other hand, an air within
the enforced cooling unit 104, which is raised its temperature
through cooling the liquid in the enforced cooling unit 104, is
exhausted outside of the housing unit 107 by the air cooling fan
103.
[0012] However, the conventional cooling apparatus comprises the
heat-sink 101, the enforced cooling unit 104 as a heat-discharge
unit, and a heat-discharge pipe 102 connecting the both. In
addition, the apparatus further comprises, for example, a pump
cover and a heat-sink cover. Then, assembly and fixing of the
apparatus to an electronic device body are complex. Furthermore,
since a setting position of the air cooling unit having a fan is
limited to the vicinity of the enforced cooling unit 104 in which
the liquid circulation pump 106 is set, the cooling performance has
been not sufficient.
[0013] In addition, since a conventional cooling apparatus is
equipped with the liquid circulation pump 106 for the enforced air
cooling, a pump unit has become large and complex compared with
that of pump itself, thereby the total configuration of the
apparatus has been thick.
[0014] Furthermore, since the conventional cooling apparatus is
built with a resin gasket, the coolant of the apparatus has been
lost bit by bit by leaking outside of the apparatus during long
use, and thereby the cooling performance has been degraded.
DISCLOSURE OF THE INVENTION
[0015] Under the status described in the above, a development of a
cooling apparatus for electronic devices, which is free from the
above issues, has been expected.
[0016] It is therefore an object of the present invention to
provide a cooling apparatus for electronic devices which is free
from the above issues.
[0017] It is another object of the present invention to provide a
cooling apparatus for electronic devices which is easy to build and
to fix it to electronic devices, superior in thermal conduction and
heat dissipation, and possible to make thin the total configuration
of the apparatus.
[0018] In an exemplary embodiment, cooling apparatus in an
electronic device includes a flow path, embedded in a base, in
which a coolant flows, a liquid cooling pump disposed above the
base, a liquid cooling unit embedded in the base for connecting the
flow path and the liquid cooling pump; and an air cooling unit
member disposed on the base, the liquid cooling pump and the liquid
cooling unit being integrated in a single unit.
[0019] The flow path may be formed by joining a base having a
groove and the heat absorption surface.
[0020] The flow path may be formed within at least one of a fin
among a plurality of fins composing the air cooling group.
[0021] The air cooling unit may comprise an air cooling fan for
flowing air to the air cooling fin group
[0022] The air cooling unit may comprise a first air channel
totally covering the air cooling fin group, wherein an air flow
generated by the air cooling fan is controlled by the first air
channel.
[0023] At least one air hole for supplying air to the air cooling
unit may be formed in the liquid cooling unit.
[0024] The air cooling fin group may be divided into a plurality of
groups, wherein the air hole supplying air to the air cooling fin
group is formed for each plurality of groups of the air cooling fin
group in the liquid cooling unit.
[0025] The air cooling unit may further comprise a second air
channel covering each plurality of groups of the air cooling fin
group, wherein an air flow generated by the air cooling fan is
controlled by the second air channel for not to thermally
interfering among the plurality of groups of the air cooling
unit.
[0026] The air cooling unit further may comprise an air cooling fan
in each second air channel.
[0027] The air cooling unit may comprise a first air channel
totally covering the air cooling fin group, a second air channel
covering each plurality of groups of the air cooling fin group, a
common air flow path formed by the first air channel, and a
plurality of individual air flow paths formed by the plurality of
second flow paths.
[0028] The air cooling unit may comprise an air cooling fan
arranged in the common air flow path, wherein an air flow is
generated in each individual air flow path by the air cooling
fan.
[0029] A cross section area of an aperture at a border between the
individual air flow path and the common air flow path may be formed
to become larger according the distance from the air cooling fan so
that a volume of air flow in the individual air flow path becomes
equal.
[0030] The air cooling unit may comprise a piezoelectric material
supported by a support member and an air blow plate, which is
bonded to the piezoelectric material, generating air flow through
vibration thereof by controlling voltage of the piezoelectric
materials.
[0031] A shape of the air blow plate may be formed to become wider
with leaving from the piezoelectric material.
[0032] The air blow plate may comprise a first part having a first
elastic constant located at closer side to the piezoelectric
material and a second part having a second elastic constant, which
is higher than the first elastic constant, located at more distant
side from the piezoelectric material.
[0033] The air blow plate may comprise a first part having a first
thickness located at closer side to the piezoelectric material and
a second part having a second thickness, which is thicker than the
first thickness, located at more distant side from the
piezoelectric material.
[0034] The air cooling unit is characterized in that a plurality of
piezoelectric fans are arranged along air flow, and the each
piezoelectric fan adjacently arranged to each other is driven by
shifting a vibration phase of the air blow plate of piezoelectric
fan by 1/2 cycle or 1/4.
[0035] The flow path may be a closed loop with a circulation
method, in a part of the closed loop, wherein a micro channel
structure having a smaller cross section area than a cross section
area of the flow path may be formed.
[0036] The micro channel structure may be formed by joining a base
arranging a plurality of narrow grooves and the heat absorption
surface.
[0037] The liquid cooling unit may comprise a piezoelectric pump
having a platy piezoelectric element as a driving source, wherein
the coolant is circulated by the piezoelectric pump.
[0038] The piezoelectric pump may comprise a stacked plate
structure having a check valve of plate vane structure for
controlling a flow direction of the coolant.
[0039] The piezoelectric pump may be built into the liquid cooling
unit, wherein the piezoelectric pump and the liquid cooling unit
are integrated in a unit with metal material.
[0040] The piezoelectric pump may comprise a plurality of pump
members for introducing and exhausting the coolant and a plurality
of piezoelectric pump driving members for driving the plurality of
pump members.
[0041] The plurality of piezoelectric pump driving members may
control timings of introduction and exhaust of the coolant of the
plurality of pump members in different timing to each other.
[0042] The piezoelectric pump driving member may conduct an exhaust
more than two times longer than an introduction of the pump
member.
[0043] The liquid cooling unit may comprise a piezoelectric pump
having a toric piezoelectric actuator as a driving source, wherein
the coolant is circulated by the piezoelectric pump.
[0044] The liquid cooling unit may comprise an evaporation-method
pump circulating the coolant with evaporation of the coolant by a
heat generator.
[0045] The evaporation-method pump may comprise a plurality of heat
generators, wherein a flow direction of the coolant is determined
by controlling heat generation timing of the plurality of heat
generators.
[0046] The cooling apparatus may further comprise an air cooling
fan supplying air to a liquid cooling pump for circulating the
coolant and to the air cooling fin group, and an electric control
circuit driving the liquid cooling pump and the air cooling fan,
wherein an input to the electric control circuit is DC current.
[0047] The electric control circuit may input information about a
temperature of the heat generator, wherein the liquid cooling pump
and the air cooling fan are driven so as to maintain at maximum
temperature within an upper limit of the heat generator.
[0048] In addition, the present invention provides an electronic
device mounting a cooling apparatus fabricated according to any one
of claims 1 to 32.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a traverse cross sectional view showing a
configuration of a conventional cooling apparatus for electronic
devices.
[0050] FIG. 2A is a cross sectional view showing a cooling
apparatus which is built in electronic devices in the preferred
embodiment of the present invention.
[0051] FIG. 2B is a perspective view looked from back side of a
cooling apparatus shown in FIG. 2A.
[0052] FIG. 2C is a cross sectional view cut at A-B line shown in
FIG. 2B.
[0053] FIGS. 3A and 3B are traverse cross sectional views showing a
configuration of a cooling apparatus shown in FIGS. 2A and 2B.
[0054] FIG. 4 is a traverse cross sectional view showing a
practical configuration of a cooling apparatus shown in FIGS. 2A
and 2B.
[0055] FIG. 5 is a traverse cross sectional view showing a
practical configuration of a cooling apparatus shown in FIGS. 2A
and 2B.
[0056] FIG. 6 is a traverse cross sectional view showing a
practical configuration of a cooling apparatus shown in FIGS. 2A,
2B, and 2C.
[0057] FIG. 7 is a top plane view looked from upper side at C-D
line cross section of a liquid cooling unit of a cooling apparatus
shown in FIG. 6.
[0058] FIG. 8 is a traverse cross sectional view showing a
configuration of an air cooling fin group flow path formed in an
air cooling fin group shown in FIG. 2.
[0059] FIG. 9A is a partial cross sectional view showing a first
example of structure at E-F cross section of an air cooling fin
group flow path shown in FIG. 8.
[0060] FIG. 9B is a partial cross sectional view showing a second
example of structure at E-F cross section of an air cooling fin
group flow path shown in FIG. 8.
[0061] FIG. 9C is a partial cross sectional view showing a third
example of structure at E-F cross section of an air cooling fin
group flow path shown in FIG. 8.
[0062] FIG. 9D is a partial cross sectional view showing a fourth
example of structure at E-F cross section of an air cooling fin
group flow path shown in FIG. 8.
[0063] FIG. 10A is a partial cross sectional view showing a
structure at A-A cross section of an air cooling fin group flow
path shown in FIG. 9A.
[0064] FIG. 10B is a partial cross sectional view showing a
structure at A-A cross section of an air cooling fin group flow
path shown in FIG. 9B.
[0065] FIG. 10C is a partial cross sectional view showing a
structure at A-A cross section of an air cooling fin group flow
path shown in FIG. 9C.
[0066] FIG. 10D is a partial cross sectional view showing a
structure at A-A cross section of an air cooling fin group flow
path shown in FIG. 9D.
[0067] FIG. 11 is a perspective view showing a configuration of a
piezoelectric fan for using as an air cooling fan of a cooling
apparatus for electronic devices of the present invention.
[0068] FIG. 12A is a plane view showing a first modification
example of air blow plate of the piezoelectric fan shown in FIG.
11.
[0069] FIG. 12B is a plane view showing a second modification
example of air blow plate of the piezoelectric fan shown in FIG.
11.
[0070] FIG. 13A is a plane view showing a third modification
example of air blow plate of the piezoelectric fan shown in FIG.
11.
[0071] FIG. 13B is a side view showing a fourth modification
example of air blow plate of the piezoelectric fan shown in FIG.
11.
[0072] FIG. 14 is a side view showing an example using a plurality
of piezoelectric fans as an air cooling fan of a cooling apparatus
for electronic devices of the present invention.
[0073] FIG. 15A is a perspective view showing a configuration of
modification example of piezoelectric fan for using as an air
cooling fan of a cooling apparatus for electronic devices of the
present invention.
[0074] FIG. 15B is a side view showing an example using a plurality
of piezoelectric fans shown in FIG. 15A.
[0075] FIG. 16 is a cross sectional view showing a stacked
piezoelectric pump for using as a liquid cooling pump of a cooling
apparatus for electronic devices of the present invention.
[0076] FIG. 17 is a configuration view showing a configuration of a
stacked piezoelectric pump shown in FIG. 16.
[0077] FIG. 18A is a cross sectional view showing a stacked
structure of a toric piezoelectric pump for using as a liquid
cooling pump of a cooling apparatus for electronic devices of the
present invention.
[0078] FIG. 18B is a G-H cross section view of a stacked structure
shown in FIG. 18A.
[0079] FIG. 18C is a bottom view of a stacked structure shown in
FIG. 18A.
[0080] FIG. 19 is a partial plane view showing an
evaporation-method pump for using as a liquid cooling pump of a
cooling apparatus for electronic devices of the present
invention.
[0081] FIG. 20A is a traverse cross sectional view showing an
evaporation status of evaporation-method pump at a time for using
as a liquid cooling pump of a cooling apparatus for electronic
devices of the present invention.
[0082] FIG. 20B is a traverse cross sectional view showing an
evaporation status of evaporation-method pump for using as a liquid
cooling pump of a cooling apparatus for electronic devices of the
present invention at the time 100 milli-second later from a state
shown in FIG. 20A.
PREFERRED EMBODIMENTS OF THE PRESENT INVENTION
[0083] Embodiments of the present invention will be explained in
detail by referring figures.
[0084] FIG. 2A is a cross sectional view showing a configuration of
a cooling apparatus fixed in electronic devices in the preferred
embodiment of the present invention. FIG. 2B is a perspective view
looked from backside of a cooling apparatus shown in FIG. 2A. FIG.
2C is a cross sectional view cut at A-B line shown in FIG. 2B
[0085] A note type personal computer (hereinafter, referred to as
note PC) is picked up for explanation as a typical electronic
device for mounting a cooling apparatus for electronic devices of
this embodiment. However, applications of the cooling apparatus for
electronic devices of the embodiment is not limited to the note PC,
but also applicable to an apparatus which generates heat by
operation. In the note PC, as shown in FIG. 2A, a CD-ROM 3, PC card
4, HDD 5, a CPU 6 which locally generates heat, and a heat
generator 7, for example, chip set and the like are mounted on a
mother board 8. The mother board is put in a box 2 of which an
outside thickness is 3 to 4 cm. That is, a plurality of electronic
components is mounted within a small space limited by the box 2.
Meanwhile, a keyboard 11 and, although not shown, a display such as
a LCD and the like are arranged on the outside of the body 2.
[0086] As shown in FIGS. 2A, 2B, and 2C, a cooling apparatus 1 for
electronic devices in this embodiment comprises a liquid cooling
unit 9 and an air cooling unit 12. The liquid cooling unit 9 and
the air cooling unit 12 are formed in a unit. Among electronic
components mounted in the box 2, a component which has the largest
power consumption and also locally generates heat within a small
area is a heat generation component such as the CPU 6 and the heat
generator 7. A heat absorption surface 19 of the liquid cooling
unit 9 is contacted or bonded to the heat generation component such
as the CPU and the heat generator. The heat absorption surface may
be formed, for example, with a cap. For explaining a flow path 10
within the liquid cooling unit 9, FIG. 2B shows a status that the
heat absorption surface (i.e., metal cap) 19 is taken off.
Practically, the surface is being bonded and sealed for forming a
cap at lower side of the cooling apparatus 1.
[0087] In the liquid cooling unit 9, the flow path 10 in which a
coolant such as water, an antifreeze liquid and the like flows, is
disposed along the heat absorption surface (i.e., metal cap) 19. As
shown in FIG. 2C, the flow path 10 is formed with a space confined
by bonding the heat absorption surface (i.e., metal cap) 19 to a
lower surface of a base 24, which is formed grooves thereon. The
flow path 10 is filled with the coolant. The base 24 and the heat
absorption surface (i.e., metal cap) 19 are made of metal having a
high conductivity, for example, Cu, Al. Heat generated by the CPU
6, the heat generator 7 and the like is transferred to the coolant
in the flow path 10 and the base 24 through the heat absorption
surface (i.e., metal cap) 19. The heat absorption surface (i.e.,
metal cap) 19 is bonded to the base 24 of the liquid cooling unit 9
using one of the methods of, for example, diffusion bonding (i.e.,
brazing), pressure welding, and bonding with O-ring. 9
[0088] In the liquid cooling unit 9, a liquid cooling pump 14 which
is composed of an electromagnetic pump is arranged for circulating
the coolant in the flow path 10. The heat generated by the heat
generation components such as CPU 6, heat generator 7, and the like
is thermally diffused with heat conduction into the whole liquid
cooling unit 9 by circulating the coolant with the liquid cooling
pump 14.
[0089] A plurality of air vents 15a.about.15e which pass through
the heat absorption surface (i.e., metal cap) 19 and the liquid
cooling unit 9, and reaches to the air cooling unit 12, are
disposed in the liquid cooling unit 9. The plurality of air vents
15a.about.15e are located at positions escaping from the flow path
10. Cooled air 23 is introduced into the box 2 through an air
introduction vent 17 which is disposed in the box 2, and supplied
to the air cooling unit 12 through the air vents 15a.about.15e
[0090] According to FIGS. 2A, 2B, and 2C, in the air cooling unit
12, air cooling fin groups 13a.about.13e made of high conductivity
material such as Cu and Al, an air cooling fan 16 for discharging
heat of the air cooling fin groups 13a.about.13e in atmosphere
around the fin groups, an air cooling fan cover (air channel 1) 20
for covering an upper surface of the air cooling fin groups
13a.about.13e to avoid decrease in the cooling performance by
dispersing the cooled air 23 from the air cooling unit 12 to the
vicinity, and fin covers (air channel 2) 22a.about.22e forming a
flow path of the cooled air 23 for each air cooling fin group
13a.about.13e for avoiding heat exchange between the air cooling
fin groups 13a.about.13e to each other. The air cooling fin groups
13a.about.13e of the air cooling unit 12 and the base 24 of the
liquid cooling unit 9 are formed in a unit with metal such as Cu
and Al, thereby the heat from the liquid cooling unit 9 is
effectively transferred to the air cooling unit 12.
[0091] The heat generated by the CPU 6, the heat generator 7, and
the like is thermally diffused into the whole liquid cooling unit 9
with thermal conduction of the coolant circulating in a closed unit
after transferred by thermal conduction to the coolant circulating
in the flow path 10 using a liquid cooling pump 14. The thermally
diffused heat is also transferred to the air cooling fin groups
13a.about.13e of the air cooling unit 12. The heat transferred to
the air cooling fin groups 13a.about.13e is further thermally
exhausted outside of the box 2 by a cooled air flow 23 generated by
the air cooling fan 16. That is, the cooled air 23 is dispersed
into the air cooling fin groups 13a.about.13e through the air vents
15a.about.15e set in the liquid cooling unit 9 after introduced in
the box 2 via an air introduction vent 17 disposed in the box 2. In
addition, the cooled air 23 for each air cooling fin groups
13a.about.13e does not thermally interfere to each other and is
thermally exhausted outside of the box 2 via an air exhaust vent 18
of the box 2 after passing through the air cooling fan 16.
[0092] For a desktop PC, which generally has a sufficient free
space in the electronic device body, it is possible to cool a CPU 6
with power consumption around 25 W by natural cooling condition
which has only the air cooling fin groups 13a.about.13e as the air
cooling unit 12. However, in the electronic devices mounting
electronic component with power consumption over 25 W within a
small space such as the box 2 of this embodiment, the heat
transferred to the air cooling fin groups 13a.about.13e is confined
within the box 2, thereby an air cooling fan is needed to exhaust
the heat outside of the box 2 for avoiding increase in temperature
in the box 2.
[0093] Next, a practical configuration of the air cooling unit 12
in the cooling apparatus 1 will be explained in detail referring to
FIG. 3 to FIG. 5. FIGS. 3, 4 and 5 are traverse sectional views
showing the practical configuration of the cooling apparatus in
FIG. 2A and FIG. 2B.
[0094] As an air cooling fan 16 shown in FIGS. 2A and 2B, a well
known DC fan 21 can be used as shown in FIGS. 3A and 3B The DC fan
21 may be arranged in a space between the liquid cooling unit 9 and
the air cooling fan cover (air channel 1) 20, if possible, as shown
in FIG. 3A If it is not possible to arrange the DC fan 21 in the
space between the liquid cooling unit 9 and the air cooling fan
cover (air channel 1) 20, an arrangement of the DC fan 21 on the
air cooling fan cover (air channel 1) 20 may be possible as an
alternative as shown in FIG. 3B.
[0095] Furthermore, as the air cooling fan 16 shown in FIGS. 2A and
2B, as shown in FIG. 4 as an alternative, it may be possible to
arrange internal air cooling fans 30a.about.30e in the vicinity of
cooled air outlet of fan covers (air channel 2) 22a.about.22e of
the air cooling unit 12. If an air flow of the cooled air 23 is
formed by the internal air cooling fans 30a.about.30e, an
arrangement of the air cooling fan cover (air channel 1) 20 is not
necessary since the fan covers (air channel 2) 22a.about.22e act as
the fan cover.
[0096] The air cooling fin groups 13a.about.13e of the air cooling
unit 12 are consist of a plurality of divided fin groups for
efficiently introducing the cooled air 23 flown into through a
plurality of air vents formed in the liquid cooling unit 9. That
is, each air cooling fin groups 13a.about.13e is supplied the
cooled air 23 through each air vents 15a.about.15e, respectively.
However, even through the air cooling fin groups 13a.about.13e are
consist of the plurality of divided fin groups, each air cooling
fin groups 13a.about.13e thermally interferes to each other by heat
generation of the CPU 6 and heat generator 7. Then, the plurality
of fan covers (air channel 2) 22a.about.22e are disposed
corresponding to each air cooling fin groups 13a.about.13e for
controlling an air flow of the cooled air 23 so that the cooled air
23 passing through each air cooling fin groups 13a.about.13e is not
supplied to the other air cooling fin groups 13a.about.13e.
[0097] For the air flow of the cooled air 23 controlled by the air
cooling fin groups 13a.about.13e and the fan covers (air channel 2)
22a.about.22e, the air cooling fan cover (air channel 1) 20 is
disposed, which totally covers the air cooling unit 12 for avoiding
dispersion of the cooled air 23 flowing in a common air flow path,
for more efficiently exhausting the heat outside of the box 2 That
is, the common air flow path is formed for the air flowing in the
air cooling fin groups 13a.about.13e by the air cooling fan cover
(air channel 1) 20, and also an individual air flow path, in which
air passing through each air cooling fin groups 13a.about.13e
flows, is formed by the fan covers (air channel 2)
22a.about.22e.
[0098] In addition, as shown in FIG. 5, if a gap between a fin
cover 22a of an air cooling fin group 13a and a DC fan is named as
a fin gap 40a, if a gap between the fin cover 22a and fin covers
22b.about.22d of the air cooling fin groups 13b.about.13d are named
as fin gaps 40b.about.40d, and if gaps between the fin cover
22b.about.22d and a fin cover 22e of an air cooling fin group 22e
is named as a fin gap 40e, the fin gaps 40b.about.40d are larger
than the fin gap 40a, and also, the fin gap 40e is larger than the
fin gaps 40b.about.40d. That is, the fin gaps 40a.about.40e and
apertures opened to the common air flow path become larger with
increasing a distance from the DC fan 21. That is, a volume of the
cooled air 23, which is supplied through a plurality of air vents
15a.about.15e and flows in the air cooling fin groups 13a.about.13e
existing in an individual air flow path formed by the fan covers
(air channel 2) 22a.about.22e, is controlled by controlling an area
of the aperture so that the volume of the cooled air 23 at each air
cooling fin groups 13a.about.13e becomes equal, thereby controlling
the pressure. Accordingly, a flow rate of the cooled air 23 passing
through in the air cooling fin groups 13a.about.13e can be
maintained constant.
[0099] A practical configuration of the liquid cooling unit 9 of
the cooling apparatus 1 will be explained in detail by referring to
FIG. 6 and FIG. 7.
[0100] FIG. 6 is a traverse sectional view showing a practical
configuration of the cooling apparatus shown in FIGS. 2A, 2B and
2C. FIG. 7 is a top plane cross sectional view looked from upper
side at C-D cross section of the liquid cooling unit of the cooling
apparatus shown in FIG. 6.
[0101] A liquid cooling pump 14 of the liquid cooling unit 9 shown
in FIGS. 2A, 2B and 2C may comprise a liquid driving pump 50 shown
in FIGS. 6 and 7, which is disposed in a flow path 10 integrated
with the air cooling fin groups 13a.about.13e. Using the liquid
driving pump 50 disposed in the flow path 10, a coolant can be
circulated within a small closed space without connecting the
coolant in the flow path 10 and the liquid driving pump 50 by, for
example, pipes.
[0102] As shown in FIG. 7, the flow path 10 comprises a loop flow
path 60, which is closed with a circulation method. The loop flow
path 60 is formed in a closed loop avoiding a plurality of air
vents 15a.about.15e disposed in the liquid cooling unit 9, and has
a thermal diffusing function to a whole cooling apparatus 1. In
addition, for quickly transferring heat generated by the CPU 6 and
the like, an area of the loop flow path 60 corresponding to the CPU
6 and the like is formed longer in width (i.e., up and bottom
direction in FIG. 7) compared with that of the CPU 6 and the
like.
[0103] As shown in FIG. 7, a micro channel 61 is disposed in the
area corresponding to the CPU 6, which has the largest heat
generation among the mounted electronic components. The micro
channel 61 is located in the vicinity of absorption surface (i.e.,
metal cap) 19, and consist of a plurality of fine grooves of 1 mm
or less in width, formed on a base 24. The micro channel 61 is
composed of a plurality of fine flow paths which have smaller cross
section than that of the loop flow path 60, thereby resulting in
increase in heat exchange ratio by increasing in the flow rate of
the micro channel 61. However, since the flow resistance is
increased in the micro channel 61, it should be limited to the area
around the CPU 6.
[0104] As a coolant in the loop flow path 60, a liquid, for
example, water which has a large heat capacity per volume, is
employed, thereby a heat dissipation performance can be increased
drastically compared with the case where air or the like is used.
In addition, by making the length of the loop flow path 60 longer
than the CPU 6 size, a contacting area with the coolant circulating
within the loop flow path 60 can be increased, thereby resulting in
efficient heat transfer. However, if the contacting area is
increased to more than necessary, a pressure loss due to the flow
resistance is increased. If the pressure loss is beyond the
capability of the liquid driving pump 50, the coolant does not
circulate and the heat dissipation performance is decreased.
Therefore, an optimum contacting area is employed considering the
heat dissipation performance, the pressure loss, and the capability
of the liquid driving pump 50
[0105] Next, an example of air cooling fin groups 13a.about.13e in
which an air cooling fin group flow path 70 is disposed will be
explained in detail by referring FIG. 8 and FIG. 9.
[0106] FIG. 8 is a traverse cross sectional view showing a
configuration of the air cooling fin group flow path disposed in
the air cooling fin group shown in FIG. 2. FIG. 9A is a partial
cross sectional view showing a first example of the configuration
cut at E-F line of the air cooling fin group flow path shown in
FIG. 8. FIG. 9B is a partial cross sectional view showing a second
example of the configuration cut at E-F line of the air cooling fin
group flow path shown in FIG. 8. FIG. 9C is a partial cross
sectional view showing a third example of the configuration cut at
E-F line of the air cooling fin group flow path shown in FIG. 8.
FIG. 9D is a partial cross sectional view showing a fourth example
of the configuration cut at E-F line of the air cooling fin group
flow path shown in FIG. 8. FIG. 10A is a partial cross sectional
view showing a configuration cut at A-A line of the air cooling fin
group flow path shown in FIG. 9A. FIG. 10B is a partial cross
sectional view showing a configuration cut at A-A line of the air
cooling fin group flow path shown in FIG. 9B. FIG. 10C is a partial
cross sectional view showing a configuration cut at A-A line of the
air cooling fin group flow path shown in FIG. 9C. FIG. 10D is a
partial cross sectional view showing a configuration cut at A-A
line of the air cooling fin group flow path shown in FIG. 9D.
[0107] As shown in FIG. 8, an air cooling fin group flow path 70 in
which a coolant flows is formed within at least one fin among a
plurality of fins of the air cooling fin groups 13a.about.13e. If
the air cooling fin group flow path 70 is formed within the air
cooling groups 13a and 13e as shown in FIG. 8, the thermal
discharging effect is increased because an encapsulated coolant
such as water and the like circulates in the air cooling fin group
13a and 13e of the air cooling unit 12 as well as in the liquid
cooling unit 9. The air cooling fin group flow path 70, as shown in
FIG. 9A, may be formed within a part of the air cooling fin group
13a. The air cooling fin group flow path 70, as shown in FIG. 9B,
may also be formed within all part of the air cooling fin group
13a. Furthermore, since the air cooling performance is increased
with the air cooling fin group flow path 70, as shown in FIGS. 9C
and 9D, the number of the air cooling fin group 13a may be
decreased.
[0108] In addition, the air cooling fin group flow path 70 may be
formed within a plate-like air cooling fin group 13a as shown a
A-A' cross section in FIG. 10. The air cooling fin group flow path
70 may also be formed such that the flow path 70 itself acts as a
air cooling fin group 13a as shown a A-A' cross section in FIG. 10B
and a A-A' cross section in FIG. 10C. Furthermore, when the air
cooling fin group flow path 70 is used as a air cooling fin group
13a, it is preferable to increase the air cooling performance by
disposing a radiator structure formed with a metal net within a
space of the air cooling fin group flow path 70 as shown a A-A'
cross section in FIG. 10D.
[0109] A configuration of a piezoelectric fan available to use for
an air cooling fan 16 will be explained in detail by referring to
FIGS. 11, 12A, 12B, 13A, 13B, 14, 15A and 15B.
[0110] FIG. 11 is a perspective view showing a configuration of the
piezoelectric fan for using as an air cooling fan of the cooling
apparatus for electronic devices of the present invention. FIG. 12A
is a top plane view showing a first modification of an air blowing
plate of the piezoelectric fan shown in FIG. 11. FIG. 12B is a top
plane view showing a second modification of the air blowing plate
of the piezoelectric fan shown in FIG. 11. FIG. 13A is a plane view
showing a third modification of the air blowing plate of the
piezoelectric fan shown in FIG. 11. FIG. 13B is a plane view
showing a fourth modification of the air blowing plate of the
piezoelectric fan shown in FIG. 11. FIG. 14 is a side view showing
an example using a plurality of piezoelectric fans as an air
cooling fan of the cooling apparatus for electronic devices of the
present invention. FIG. 15A is a perspective view showing a
configuration of a modification example of the piezoelectric fan
for using as an air cooling fan of the cooling apparatus for
electronic devices of the present invention. FIG. 15B is a side
view showing an example using a plurality of piezoelectric fans
shown in FIG. 15A.
[0111] A piezoelectric fan 200 may be used for an air cooling fan
16 of the cooling apparatus 1 for electronic devices of this
embodiment shown in FIG. 2A and FIG. 2B. Referring to FIG. 11, it
can be seen that the piezoelectric fan 200 is configured such that
an air blowing plate 202 is joined to one end of a piezoelectric
element 201, and the other end of the piezoelectric element 201 is
fixed to a support 203. The air blowing plate 202 vibrates up and
down by operating the piezoelectric element 201, resulting in air
blowing.
[0112] FIG. 12A is the first modification example of the air
blowing plate 202 having a trapezoidal plate, which width becomes
wider linearly with reaching to the end. FIG. 12B is the second
modification example of the air blowing plate 202 having a
trapezoidal plate, which width becomes larger non-linearly with
reaching to the end. When the first or the second modification
example of the air blowing plate 202 is employed to the
piezoelectric fan 200, an inclusion of air from a side area becomes
easy, thereby much air can be fed. Accordingly, a blowing volume of
the piezoelectric fan 200 can be increased in both cases.
[0113] The piezoelectric fan 200 may have a structure combining a
plurality of materials and thicknesses. In the third modification
example shown in FIG. 13A, the air blowing plate 202 is consist of
an air blowing plate 202a and an air blowing plate 202b which have
different elastic force, respectively. The elastic constant of the
air blowing plate 202b for air blowing, which has an open end, is
smaller than that of the air blowing plate 202a joined to the
piezoelectric element 201. In the fourth modification example shown
in FIG. 13B, a thin air blowing plate 204, which has a thinner air
blowing plate than that of the air blowing plate 202, is joined to
the air blowing plate 202. In the fourth modification example, the
thin air blowing plate 204 bends easier than the air blowing plate
202 since the thin air blowing plate 204 is thinner than the air
blowing plate 202. When the third or the fourth modification
example of the air blowing plate 202 is employed to the
piezoelectric fan 200, an air blowing volume of the piezoelectric
fan 200 can be increased in both cases.
[0114] It is possible to stabilize an air flow rate using a
plurality of piezoelectric fan 200 for the air cooling fan 16. For
example, according to a structure of the air cooling fan shown in
FIG. 14, the plurality of piezoelectric fan 200a.about.200e are
arranged with a constant interval along direction of air flow
having wall 205 at both side of the air flow. In addition, by
shifting a driving phase of the piezoelectric fans by 1/2 to each
other, the air flow rate more stable than that of a single
piezoelectric fan can be achieved.
[0115] According to a piezoelectric fan shown in FIG. 15, the air
blowing plate 202 is joined to the piezoelectric element 201. In
addition, the thin blowing plate 204 is attached to the side of the
blowing plate 202. FIG. 15B is a schematic view showing that a
plurality of piezoelectric fans having the structure of the air
cooling fan 204 shown in FIG. 15A is arranged along the air flow.
In this example, five piezoelectric fans 200a.about.200e are
arranged, and operated by shifting each phase of the piezoelectric
fans by 1/4. With this structure and arrangement, the air flow rate
can be stabilized.
[0116] Next, a configuration of a piezoelectric pump which is
applicable to a liquid cooling pump 14 shown in FIGS. 2A and 2B
will be explained in detail by referring FIGS. 16, 17, 18A, 18B,
and 18C.
[0117] FIG. 16 is a cross sectional view showing a configuration of
a stacked piezoelectric pump for using as a liquid cooling pump of
the cooling apparatus for electronic devices of the present
invention. FIG. 17 is a configuration view showing a configuration
of the stacked piezoelectric PUMP shown in FIG. 16. FIG. 18A is a
cross sectional view showing a stacked structure of a toric
piezoelectric pump for using as a liquid cooling pump of the
cooling apparatus for electronic devices of the present invention.
FIG. 18B is a cross sectional view of the stacked structure cut at
G-H line shown in FIG. 18A. FIG. 18C is a bottom view of the
stacked structure shown in FIG. 18A.
[0118] For achieving a cooling apparatus which has a low noise,
thin body, and high performance, and also stimulates circulation of
a hot liquid, a role of pump stimulating circulation of the coolant
is very important. In addition, regarding a small size electronic
device which requires portability, the portability is essential,
thereby a battery is used as well as commercial power sources such
as an AC-DC adaptor and the like as the electric energy supply
source. Since a storage capacity of electric energy of the battery
is limited, power consumption of the cooling apparatus must be
minimized. Heat generation by a pump driving source causes an
increase in temperature of the coolant, thereby resulting in
decrease of heat exchange performance. Therefore, it is necessary
to use the pump driving source which has a high converting
efficiency from electric energy to mechanical energy. A
piezoelectric actuator using a piezoelectric ceramics is known as a
device having a high converting efficiency from electric energy to
mechanical energy in general A polarized piezoelectric ceramics is
able to generate a bending vibration by operating it attaching on,
for example, a metal plate. Characteristics of the piezoelectric
actuator having the stacked plate structure are such that the
displacement is not so large, it can be thin, the power generation
is large, and high frequency operation is easy.
[0119] However, for the piezoelectric pump which is making use of
the bending motion of the piezoelectric actuator, a check valve is
required for guiding a flow in one direction. Then, a delay of flow
speed caused by the mass thereof and a generation of pressure loss
must be prevented. If a connection part of the piezoelectric pump
unit and a flow path is formed with an elastic material such as
resin and the like, the pressure loss may be generated. In
addition, the elastic material used at the connection part may be
degraded during long use. As a result, for example, leakage and
volatilization of the coolant from each part may be caused. In a
coolant circulation type of cooling apparatus, in which the coolant
is encapsulated, the check valve intermittently operates. Then, it
is difficult to obtain a constant flow rate. In addition, in the
closed circulation cooling apparatus, a countermeasure is necessary
for the pressure loss caused by foams generating in the coolant in
the flow path. An amount of heat of a heat generation source
changes with time. According to the change of the amount of heat,
physical properties, for example, viscosity and thermal expansion
of materials composing the cooling apparatus change by the
temperature change of the coolant circulating in the cooling
apparatus, thereby a change of flow rate is likely to happen by the
pressure fluctuation. If the check valve is arranged under the
pump, the thinning of the pump becomes difficult due to the check
valve. Accordingly, if a piezoelectric pump is employed to the
cooling apparatus 1 for electronic devices of the present
invention, issues described in the above must be solved.
[0120] As a stacked piezoelectric pump applied to the present
invention, as shown in FIG. 16, an unified bending-type
piezoelectric pump which has a stacked plate structure having two
pressure rooms may be used. The unified bending-type piezoelectric
pump introduces liquid through an inlet 162 and exhaust the liquid
through an outlet 163 by introducing the liquid to the pressure
rooms 122, 123 and exhausting the liquid from the pressure rooms
122, 123 with respective stretching motion of pressure plates 113,
114. In the pressure rooms 122, 123, introduction check valves 132,
133 for limiting flow direction of the liquid and exhaust check
valves 154, 155 are disposed respectively. In FIG. 16, the inlet
162 and the outlet 163 are arranged on both right side and left
side, respectively. However, the inlet 162 and the outlet 163 are
connected at a position distant from the pump. Arrows in FIG. 16
show flowing directions of the liquid. In addition, the unified
bending-type piezoelectric pump is incorporated in the liquid
cooling unit 9 in a similar manner to a liquid driving pump 50
shown in FIG. 6. Since the unified bending-type piezoelectric pump
and the liquid cooling unit 9 are integrated in a unit with metal
materials, for example, Al, Stainless Steel, and Cu, the pressure
loss is prevented.
[0121] A flowing speed of the liquid flown in through the inlet 162
is decelerated at a spare room 166 and reaches to the introduction
check valves 132, 133 through introduction holes 142, 143. At the
time, the introduction check valves 132, 133 are lifted up to the
direction of pressure rooms 122, 123, and the liquid reaches to the
pressure rooms 122, 123. In the pressure rooms 122, 123, a bending
vibration of a vibration plate 115 is generated by stretching
motion of piezoelectric plates 113, 114. Then, the liquid is
pressed, but does not flow back since the introduction holes 142,
143 are shut by coming down of the introduction check valves 132,
133. At the same time, since exhaust check valves 154, 155 come
down, the liquid is exhausted through the outlet 163 via exhaust
holes 144, 145. The introduction check valves 132, 133 and the
exhaust check valves 154, 155 are made thin, for example, by using
a plate vane structure, thereby they can rapidly operate without
preventing the liquid motion.
[0122] A practical fabrication method of the unified bending-type
piezoelectric pump will be explained in detail by referring to FIG.
17.
[0123] Piezoelectric plates 113, 114 are made of lead zirconate
titanate-based ceramics material. The piezoelectric ceramics
material is formed of 15 mm in length, 15 mm in width, and 0.1 mm
in thickness, and silver electrodes are formed on both main
surfaces with a calcined method. Meanwhile, for example, gold,
nickel, chromium, Cu, silver, palladium alloy, and platinum, which
are electrically conductive, may be used for the electrode. In
addition, for example, a sputtering, a plating, an evaporation, and
a chemical vapor deposition may be employed for the electrode
forming method. The piezoelectric plates 113, 114, which are formed
electrodes thereon having no effect on the performance, are bonded
to a vibration plate 115 with an acryl-based bonder or a
polyimide-based bonder. In this embodiment, the piezoelectric
plates 113, 114 have been prepared with machine work. However, if
xirconia ceramics or silicon is used for the vibration plate 115,
it is possible to integrate the piezoelectric ceramics in a unit
using a print-calcined method, or a sputtering method, or a sol-gel
method, or a chemical vapor deposition method.
[0124] As shown in FIG. 17, the vibration plate 115 made of Al
formed of 50 mm in length, 50 mm in width, and 0.05 mm in
thickness, a pressure room plate 121 made of Al formed of 50 mm in
length, 50 mm in width, and 0.2 mm in thickness, an upper check
valve plate 131 made of Al formed of 50 mm in length, 50 mm in
width, and 0.5 mm in thickness, a center check valve plate 141 made
of Al formed of 50 mm in length, 50 mm in width, and 0.2 mm in
thickness, a lower check valve plate 151 made of Al formed of 50 mm
in length, 50 mm in width, and 0.1 mm in thickness, an
introduction-exhaust plate 161 made of Al formed of 50 mm in
length, 50 mm in width, and 0.4 mm in thickness, an elastic plate
171 made of Al formed of 50 mm in length, 50 mm in width, and 0.1
mm in thickness, and a rigid plate 181 made of Al formed of 50 mm
in length, 50 mm in width, and 1 mm in thickness, are stacked in a
unit using a diffusion bonding technique. The total thickness is
2.55 mm, resulting in realization of a thin pump.
[0125] The piezoelectric plates 113, 114 are bonded to positions on
the vibration plate 115 corresponding to the pressure rooms 122,
123. Power sources 111, 112 are connected to the piezoelectric
plates 113, 114. In addition, the pressure rooms 122, 123 having a
size of 15 mm in width and 15 mm in length are formed on the
pressure room plate 121, the introduction check valves 132, 133 and
the exhaust holes 144, 145 are formed on the upper check valve
plate 131, the introduction holes 142, 143 and the exhaust holes
144, 145 are formed on the center check valve plate 141, the
exhaust check valves 154, 155 and the introduction holes 142, 143
are formed on the lower check valve plate 151, the inlet 162 and an
introduction flow path 164, and the outlet 163 and an exhaust flow
path 164, and the spare room 166, are formed on the
introduction-exhaust plate 161, and an elastic plate
disintermediate 182 is formed on the rigid plate 181. The
introduction holes 142, 143 and the exhaust holes 144, 145 are 5 mm
in diameter, the introduction check valves 132, 133 and the exhaust
check valves 154, 155 have a size of 10 mm in length and 6 mm in
width and their ends are arranged at positions sealing each
introduction hole and exhaust hole, respectively. The piezoelectric
plates 113, 114 are able to operate at low voltage if the structure
is formed by stacking the piezoelectric ceramics and the electrode
one after the other. Furthermore, if a bimorph structure is
employed by sandwiching the vibration plate 115 with the
piezoelectric plates 113, 114 at both upper and lower sides, the
introduction and exhaust pressure of the liquid can be
increased.
[0126] As shown in FIG. 17, two or more pressure rooms 122, 123 are
formed as a plurality of pump units. Using at least two pumps, when
one pump unit exhausts liquid, another pump unit introduces liquid,
and the pump unit introduced the liquid exhausts liquid this time,
and another pump unit exhausted the liquid introduces liquid. By
operating two pump units combining in the above manner, the liquid
flow rate can constantly be maintained.
[0127] As an example, the piezoelectric pump has been operated by
applying DC 50 V, AC amplitude 50 V, 10 kHz and half cycle electric
field to the piezoelectric plates 113, 114 for the liquid
introduction operation, and also by applying DC 50 V, AC amplitude
50 V having a reverse phase of the liquid introduction operation,
and 5 kHz for the liquid exhaust operation. The flow rate can be
stabilized by controlling two pumps to operate in opposite phase to
each other, that is, to operate alternately to each other. In
addition, through control of the power sources 111, 112, an
introduction time of the liquid is made longer more than two times
of that of the exhaust time. Due to the above, efficiency of the
exhaust is improved since a turbulent flow in the pump room caused
by the exhaust is stabilized. If the lower check valve plate 151,
the introduction-exhaust plate 161, the elastic plate 171, and the
rigid plate 181 are made of metal material and also are unified
with a coolant circulation unit, the connection part shown in the
conventional art is not necessary, and thereby the pressure loss
due to the connection part can be avoided. In addition, since resin
is not used for the connection part, the liquid is prevented from
leaking and evaporating due to a crack of the resin caused by long
use.
[0128] For the liquid cooling pump 14, as shown in FIGS. 18A, 18B,
and 18C, a piezoelectric pump disposed a toric piezoelectric
actuator may be used. The piezoelectric pump disposed the toric
piezoelectric actuator generates a traveling wave by sequentially
bending each piezoelectric plate by changing a phase for driving
the piezoelectric plate which forms the toric piezoelectric
actuator. With the above method, the liquid in the flow path is
circulated in one direction without using the check valve.
[0129] As shown in FIG. 18A, a flow path 192 is sealed with two
protection plates of an upper protection plate 191 and a lower
protection plate 193. As shown in FIG. 18B, a toric piezoelectric
actuator 194 is arranged at a bottom surface of the lower
protection plate 193, and joined each other along the toric part of
the flow path 192 shown in FIG. 18C. For example, by arranging each
part of the piezoelectric actuator 194 with an opposite polarity
one after the other, and also by applying an electric field to the
each part by shifting the phase, the piezoelectric actuator 194
generates up and down stretching motion similar to a traveling
wave, thereby the liquid staying in the flow path 192 generates a
circular movement along the toric flow path, thereby the
introduction and the exhaust of the liquid simultaneously take
place for the flow paths shown at left side in FIG. 18C, and
thereby resulting in one direction of the liquid flow. A pump,
which neglects the check valve by using the motion of the
piezoelectric actuator 194 and circulates liquid including foams
generating in the flow path 192, can be realized.
[0130] A configuration of an evaporation-method pump, which uses
boiling and evaporation of liquid and is applicable to the liquid
cooling pump, will be explained in detail referring to FIG. 19 and
FIG. 20.
[0131] FIG. 19 is a partial plane view showing a configuration of
the evaporation-method pump for the liquid cooling pump of the
cooling apparatus for electric devices of the present invention.
FIG. 20A is a traverse cross sectional view showing an aspect of
evaporation of the evaporation-method pump at a time for the liquid
cooling pump of the cooling apparatus for electric devices of the
present invention. FIG. 20B is a traverse cross sectional view
showing the aspect of evaporation of the evaporation-method pump,
which is used for the liquid cooling pump of the cooling apparatus
for electric devices of the present invention, at the time 100
milli-second later from the state of FIG. 20A
[0132] According to FIG. 19, in which an evaporation-method pump
for the liquid cooling pump 14 is shown, a subsidiary stream 302
branched from a main stream 301 of the liquid is formed, and a heat
generator 303 is arranged in the subsidiary stream 302. If a
temperature of the liquid contacting to the heat generator exceeds
the boiling temperature by temperature rise of the heat generator
with power supply to the heat generator 303, the liquid boils,
thereby a steam 305 is generated. As a result, a liquid flow is
generated. In front of the heat generator 303 in the subsidiary
stream 302, a check valve 304 is arranged for preventing from
flowing back of the liquid. Accordingly, the liquid is controlled
to flow in one direction. Generally, if a liquid is vaporized by
boiling, a volume of the vapor becomes substantially larger than
that of the liquid. Then, if a liquid in a closed flow path is
partially boiled with heating, the liquid is pushed out due to the
expansion of the vaporization. Implementing this process
continuously and by arranging a check valve structure at a part of
the flow path, a pumping function for liquid can be realized.
[0133] In FIGS. 20A and 20B, a configuration of evaporation-method
pump disposing a plurality of heat generators 303 is shown. Five
heat generators 303 are arranged side by side close to the liquid
in main stream 301. FIG. 20A shows an aspect of the evaporation at
a time, and steams are being generated from the top of each heat
generator. FIG. 20B shows an aspect of evaporation at the time 100
milli-second later from the state of FIG. 20A. If the timing of
evaporation of the heat generator is coordinated so that the liquid
flows in the desired direction, a liquid flow can be formed. That
is, the steams 305 evaporating in the aspect shown in FIG. 20B is
sifted to the left side compared with the steams 305 shown in FIG.
20A. Continuing this process, the liquid can be flown from the
right to the left as indicated with arrows in FIGS. 20A and
20B.
[0134] In the embodiments described in the above, for example, a DC
fan 21 and a piezoelectric fan 200 are employed as an air cooling
fan, and also an electromagnetic pump, a piezoelectric pump, and an
evaporation-method pump are employed as a liquid cooling pump.
However, a combination of them is optional.
[0135] A cooling apparatus 1 of the present invention can be
demonstrated its effectiveness by mounting it on any kind of
electronic devices. For example, since a note PC and the like have
substantially large power consumption and the body is small and
thin, the effect of the cooling apparatus of the present invention
is substantially large. For example, if the cooling apparatus of
the present invention with a size of 5 mm in thickness and about
100 mm.times.200 mm in length and width is employed, a CPU with
power consumption about 40 W can be cooled. Therefore, a note PC
mounting the cooling apparatus of the present invention can be made
small, thin, and low noise, thereby resulting in realization of an
attractive note PC for consumers. The cooling apparatus 1 is also
able to mount on other electronic devices, for example, a desktop
computer, a computer server, network devices, a plasma display, a
projector, and a home server, resulting in realization of small,
low noise and high cooling performance devices, as in the case of
note PC.
[0136] For demonstrating cooling performance of the cooling
apparatus of the present invention, by encapsulating at least 20 ml
of cooling water in the flow path 10 of the liquid cooling unit 9,
which has a contour size of 200 mm.times.100 mm, and 1 mm in
thickness, and by circulating the cooling water with flow rate of
10.about.20 ml/minutes, the maximum temperature of CPU having power
consumption of about 25 W has been demonstrated to be suppressed at
90 C or less without air cooling unit 12 by experiment.
Accordingly, the volume of the liquid cooling unit and the unit
itself can be made about 1/5 and thinner respectively, compared
with the conventional heat-pipe technique and the enforced air
cooling technique, which can cool the CPU with power consumption of
about 25 W.
[0137] In addition, in a configuration which combines the liquid
cooling unit 9 and the air cooling unit 12 of the present invention
having a contour size of 200 mm.times.100 mm, and 5 mm in
thickness, by encapsulating at least 20 ml of cooling water in the
flow path 10 of the liquid cooling unit 9 and circulating the
cooling water with flow rate of 10.about.20 ml/minute, and also by
generating a forced air convection of about 0.8 m/second with air
fans arranged in the air cooling unit 12 which has the fin group,
the air channel 1 and the air channel 2, the maximum temperature of
CPU having power consumption of about 40 W has been demonstrated to
be suppressed at 90 C or less by experiment. Accordingly, the
volume of the liquid cooling unit can be made about 1/10, and the
unit can also be made thin, compared with the conventional enforced
air cooling technique, which can cool a CPU with power consumption
of about 40 W.
[0138] Regarding noise of the present liquid cooling apparatus, by
employing the piezoelectric technique described in the above
embodiment as a driving source for both the internal air cooling
fan 30 which is arranged in the air cooling unit 12 of the cooling
apparatus 1 and the liquid driving pump 50 which is arranged in the
liquid cooling unit 9, the noise level in operation of the present
liquid cooling apparatus has been suppressed at 30 dB or less. In
the conventional enforced air cooling technique which cools the CPU
with power consumption of around 40 W, at least two DC fans 21 are
used, for example, in case of note PC. Its noise level reaches to
at around 40 dB. As seen from the above, the noise level in this
embodiment has been substantially improved. Accordingly, a note PC
which mounts the present cooling apparatus can be used at a public
space where noise generation is forbidden, for example, a library,
a hospital and the like.
[0139] Regarding a fabricating method of the liquid cooling unit 9
and the air cooling unit 12 of the cooling apparatus 1, metal
materials, for example, Cu, Al, and Stainless Steel are used, and
fabrication techniques, for example, a common die-cast technique, a
die technique, and a etching technique, which are similar
techniques for fabricating the conventional heat-sink are
applicable for fabricating the liquid cooling unit 9 and the air
cooling unit 12 in a unit.
[0140] As explained in the above, according to the present
embodiment, the liquid cooling unit 9 and the air cooling unit 12
are being stacked, a platy shape or a shape close to a platy shape
is available for each component, the each component can be built in
a unit with stacking, and thereby the whole shape can be made flat.
Furthermore, it is superior in thermal conduction and in heat
dissipation, available to make the total configuration thin, and
easy to build and to fix to electronic devices.
[0141] In addition, according to the present embodiment, by
integrating the liquid driving pump 50 with the liquid cooling unit
9, freedom of design is improved, thereby the total thickness can
be made thin, 10 mm or less, or 5 mm or less, and thereby freedom
for mounting it on electronic devices, especially on such as note
PC and the like can be improved.
[0142] According to the present embodiment, in the air cooling unit
12, by disposing a common air flow path for flowing air which
passed through an individual air flow path, as well as disposing an
air vent for introducing air which is not warmed by forming a
plurality of individual air flow paths, the heat absorbed from heat
generation components within a limited space can be effectively
exhausted outside of electronic devices.
[0143] According to the present embodiment, in the liquid cooling
unit 9 having a flow path 10 in which a coolant flows, by forming
an air cooling fin group flow path 70 within the air cooling fin,
and by forming a micro channel 61 for partially improving a flow
speed within a part of the flow path 10, an efficiency of heat
exchange with the cooling media is improved, thereby resulting in
increase in the cooling performance.
[0144] According to the present embodiment, by combining a liquid
circulation cooling unit which uses the liquid cooling pump 14 and
an enforced air cooling using the air cooling fan 16, a blowing
volume of the air cooling fan 16 is suppressed. Therefore, noise
generation by the air cooling fan 16 can be reduced.
[0145] An electromagnetic pump, a piezoelectric bimorph pump, a
bubble pump, and a pump combined with the air cooling pump are
applicable to the liquid cooling pump 14 or the liquid driving pump
50 of the present embodiment. Using these pumps, a liquid
circulation volume per unit time is increased, and also the
thickness and the volume of whole cooling apparatus can be
reduced.
[0146] Regarding a power supply from outside to an electric control
circuit for driving the liquid cooling pump 14 or the liquid
driving pump 50 and the air cooling fan 16 of the present
embodiment, DC current is preferable. By incorporating information
on temperatures of, for example, the CPU 6 and the heat generator 7
into the electric control circuit, the liquid cooling pump 14 or
the liquid driving pump 50 and the air cooling fan 16 are driven so
that the temperature of the heat generation component is maintained
at the maximum temperature within the upper limit. As a result, the
power consumption of the cooling apparatus 1 can be saved.
[0147] As a control circuit for the cooling apparatus 1, an
electric driving circuit for driving the liquid cooling pump 14 or
the liquid driving pump 50 and an electric driving circuit for
driving the air cooling fan 16 exist. A configuration in which an
input voltage of the electric driving circuit is set under a
predetermined voltage, or both voltages of the electric driving
circuits are unified, is effective to achieve simplification of the
control circuit, improvement of the efficiency, and increase in
accuracy in this case, thereby resulting in high performance of the
cooling apparatus in total.
[0148] It is obvious that the present invention may be embodied in
other specific forms without departing from the spirit or essential
characteristics thereof. In addition, the number, the position, and
the shape of the component consisting of the cooling apparatus are
not limited to the above embodiments, and they may be made in an
appropriate number, position, and shape suitable for embodying the
present invention. An element showing the same element in each
figure has the same sign.
[0149] The present invention has been explained by referring
several preferred configurations and embodiments. The
configurations and embodiments are to be considered in all respect
as illustrative and not restrictive. It is apparent to be easy to
employ a variety of modifications and changes for component and
technique equivalent to the present invention for a skilled people
after reading the specification. The scope of the present invention
being indicated by the appended claims rather than by the foregoing
description and all changes which come within the meaning and range
of equivalency of the claims are therefore intended to be embraced
therein.
POSSIBILITY FOR INDUSTRIAL APPLICATION
[0150] The cooling apparatus for electronic devices of the present
invention has a configuration stacking the liquid cooling unit and
the air cooling unit. The each component can adopt a platy shape or
a shape similar to platy shape. The each component can be built
into a unit by stacking. Since the whole shape of the apparatus can
be made as a platy shape, the apparatus is superior in thermal
conduction and in heat dissipation, and is easy to make thin the
total configuration and also easy to build and fix the apparatus in
the electronic devices.
[0151] In addition, according to the embodiment, the cooling
apparatus can take a configuration to integrate the liquid driving
pump with the liquid cooling unit. As a result, design freedom of
the cooling apparatus is improved, the total thickness can be
thinned to 10 mm or less, or 5 mm or less. Accordingly, freedom for
mounting the cooling apparatus on electronic devices, especially on
note PC can be improved.
[0152] Furthermore, according to the present embodiment, in the air
cooling unit, by forming a common air flow path for flowing air
which passed through an individual air flow path, as well as
forming an air vent for introducing air which is not warmed by
disposing a plurality of individual air flow paths, the heat
absorbed from heat generation components within a limited space can
be effectively exhausted outside of electronic devices.
[0153] According to the present embodiment, in the liquid cooling
unit having a flow path in which a coolant flows, by forming an air
cooling fin group flow path within the air cooling fin, and by
forming a micro channel for partially improving a flow speed within
a part of the flow path, an efficiency of heat exchange with the
cooling media is improved, thereby resulting in increase in the
cooling performance.
[0154] According to the present embodiment, by combining a liquid
circulation cooling unit which uses the liquid cooling pump and an
enforced air cooling using the air cooling fan, a blowing volume of
the air cooling fan is suppressed. As a result, noise generation by
the air cooling fan 16 can be reduced.
* * * * *