U.S. patent application number 12/046645 was filed with the patent office on 2008-09-18 for cooling device.
This patent application is currently assigned to NIDEC CORPORATION. Invention is credited to Tatsuya AKASE, Makoto FUJIHARA, Akira HIRAKAWA, Kazuhiro INOUCHI, Yoshinori INOUE, Takaya OTSUKI, Naoto YAMAOKA, Takamasa YAMASHITA.
Application Number | 20080223558 12/046645 |
Document ID | / |
Family ID | 39761481 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080223558 |
Kind Code |
A1 |
OTSUKI; Takaya ; et
al. |
September 18, 2008 |
COOLING DEVICE
Abstract
A cooling device includes a fan, a heat sink, and an attaching
portion arranged to attach the fan to the heat sink. The fan
includes an impeller rotating about a center axis, a motor arranged
to rotate the impeller, and a base portion supporting the motor.
The attaching portion includes a frame surrounding a portion of the
impeller opposed to the heat sink, a plurality of supports
projecting from the frame to a side opposite to the heat sink, and
a plurality of supporting ribs connecting the supports and the base
portion to each other, arranged about the center axis, and
extending from the base portion away from the center axis. Each
supporting rib has a first primary surface and a second primary
surface arranged opposite to the impeller. The first and second
primary surfaces are inclined with respect to a plane substantially
perpendicular to the center axis.
Inventors: |
OTSUKI; Takaya; (Kyoto,
JP) ; INOUCHI; Kazuhiro; (Kyoto, JP) ;
YAMASHITA; Takamasa; (Kyoto, JP) ; FUJIHARA;
Makoto; (Kyoto, JP) ; INOUE; Yoshinori;
(Kyoto, JP) ; YAMAOKA; Naoto; (Kyoto, JP) ;
AKASE; Tatsuya; (Kyoto, JP) ; HIRAKAWA; Akira;
(Kyoto, JP) |
Correspondence
Address: |
NIDEC CORPORATION;c/o KEATING & BENNETT, LLP
1800 Alexander Bell Drive, SUITE 200
Reston
VA
20191
US
|
Assignee: |
NIDEC CORPORATION
Kyoto
JP
|
Family ID: |
39761481 |
Appl. No.: |
12/046645 |
Filed: |
March 12, 2008 |
Current U.S.
Class: |
165/121 |
Current CPC
Class: |
H01L 23/4093 20130101;
F04D 29/582 20130101; H01L 2924/0002 20130101; H01L 23/467
20130101; F04D 29/646 20130101; H01L 2924/00 20130101; F04D 29/601
20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
165/121 |
International
Class: |
F28F 13/00 20060101
F28F013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2007 |
JP |
2007-061319 |
Claims
1-9. (canceled)
10. A cooling device comprising: a fan including an impeller
rotatable about a center axis of the fan, a motor arranged to
rotate the impeller, and a base portion arranged to support the
motor, the fan creating an air flow by rotation of the impeller; a
heat sink arranged at a location which receives the air flow from
the fan to be in contact with a heat source; and an attaching
portion arranged to fix the fan to the heat sink; wherein the
attaching portion includes: a frame surrounding at least a portion
of the impeller that is opposed to the heat sink; a plurality of
supports projecting from the frame to a side opposite to the heat
sink; and a plurality of supporting ribs arranged around the center
axis of the fan, which extend from the base portion away from the
center axis, and which connect to the supports; each of the
supporting ribs includes a first primary surface opposed to the
impeller and a second primary surface which is opposite to the
impeller, the first primary surface and the second primary surface
being inclined with respect to a plane substantially perpendicular
to the center axis; and in each of the first primary surface and
the second primary surface, a circumferential component extending
from a downstream-side end to an upstream-side end of the
supporting ribs in a rotation direction of the impeller is in a
direction opposite to the rotation direction of the impeller.
11. The cooling device according to claim 10, wherein a cross
section of each of the supporting ribs substantially perpendicular
to a longitudinal direction thereof is thinner on both sides of a
center in a circumferential direction than at the center.
12. The cooling device according to claim 10, wherein a normal
angle of at least one of the first primary surface and the second
primary surface near the downstream-side end thereof with respect
to the center axis is in a range from approximately 20.degree. to
approximately 40.degree., when being averaged in a radial direction
substantially perpendicular to the center axis.
13. The cooling device according to claim 10, wherein each of the
supporting ribs extends in a direction opposite to the rotation
direction of the impeller as it extends away from the center
axis.
14. The cooling device according to claim 13, wherein each of the
supporting ribs is curved so as to be convex along the rotation
direction of the impeller.
15. The cooling device according to claim 10, wherein an
upstream-side surface of each of the supports in the rotation
direction of the impeller is smooth and convex.
16. The cooling device according to claim 10, wherein an inner side
surface of the frame includes, at an end the inner side surface
opposite to the heat sink, an inclined surface which extends closer
to the center axis as it extends closer to the heat sink.
17. The cooling device according to claim 16, wherein the inclined
surface is approximately annular around the center axis.
18. The cooling device according to claim 10, wherein the heat sink
includes a plurality of heat-dissipating fins which are arranged
around the center axis and extend along the center axis.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a cooling device which
cools a heat source.
[0003] 2. Description of the Related Art
[0004] CPUs (Central Processing Units) incorporated in personal
computers or servers include cooling devices attached to the CPUs
for cooling the CPUs. An exemplary known cooling device is a device
in which a heat sink and a fan are combined with each other. In
this cooling device, the heat sink dissipates heat generated by the
CPU by a plurality of heat-dissipating fins that are radially
arranged, and the fan arranged on the opposite side of the heat
sink to the CPU delivers air to the heat sink.
[0005] For example, US 2005/0253467 A1 describes a cooling device
which includes an axial fan rotating about a rotation axis and a
heat sink arranged on an air-discharge side of the axial fan. The
heat sink includes a plurality of heat-dissipating fins arranged
radially about the rotation axis of the axial fan. A
motor-supporting member arranged to support a motor of the axial
fan is provided on an air-intake side of an impeller of the axial
fan, and is connected to an annular fan case, which covers only a
portion of the axial fan near the heat sink, via three webs which
are circumferentially spaced apart from each other on the
air-intake side of the axial fan.
[0006] U.S. Pat. No. 7,052,236 B2 describes a cooling device that
includes an axial fan and a housing covering the axial fan and that
sends air to a heat source. In this air-sending device, an inner
side surface of the housing is inclined with respect to a rotation
axis of the axial fan on an air-discharge side or an air-intake
side of the axial fan, so as to provide an air-flow guiding
portion. A plurality of stationary vanes which connect the air-flow
guiding portion and a base portion of a motor to each other are
radially arranged about the rotation axis of the axial fan. With
this configuration, the static pressure characteristics of the
axial fan are improved.
[0007] The cooling device having the axial fan and the heat sink
combined with each other, as described in US 2005/0253467 A1, must
improve its cooling performance in order to accommodate an increase
in heat generation caused by improvements in the CPU's performance.
Moreover, that cooling device must also have a smaller operating
sound in view of improvements in a working environment in which
personal computers and servers are used, for example. For these
reasons, in the performance evaluation of that cooling device, the
cooling performance when the operation sound is set to be equal to
or less than a predetermined limit level is compared. Therefore, if
the operating sound of the cooling device can be reduced without
reducing the number of revolutions of the axial fan, the number of
revolutions of the axial fan which causes the operating sound of
the limit level can be increased, thereby improving the cooling
performance of the cooling device. Alternatively, by increasing the
number of revolutions of the axial fan and reducing the cooling
performance of the heat sink itself, the manufacturing cost of the
heat sink can be reduced while maintaining the cooling performance
of the cooling device.
[0008] However, in the cooling device described in US 2005/0253467
A1, the webs arranged in an approximately rectangular column are
provided on the air-intake side of the impeller of the axial fan,
and therefore, a relatively large interference sound is generated
because of interference of an air flow created by rotation of the
impeller with the webs. For this reason, a reduction of the
operating sound of the cooling device is limited.
SUMMARY OF THE INVENTION
[0009] To overcome the problems described above, preferred
embodiments of the present invention provide a cooling device. The
cooling device includes a fan, a heat sink, and an attaching
portion which fixes the fan to the heat sink. The fan includes an
impeller rotating about a rotation axis, a motor arranged to rotate
the impeller, and a base portion supporting the motor, and creates
an air flow by the rotation of the impeller. The heat sink is
arranged at a location which receives the air flow from the fan, so
as to be in contact with a heat source. The attaching portion
includes a frame surrounding at least a portion of the impeller
which is opposed to the heat sink, and a plurality of supports
projecting from the frame toward a side of the frame opposite to
the heat sink. The attaching portion further includes a plurality
of supporting ribs which are arranged around a center axis, extend
from the base portion away from the center axis, and are connected
to the supports. Each supporting rib has a first primary surface
opposed to the impeller and a second primary surface on a side
opposite to the impeller. The first and second primary surfaces are
inclined with respect to a plane substantially perpendicular to the
center axis. In each of the first and second primary surfaces, a
circumferential component from a downstream-side end thereof to an
upstream-side end thereof in a rotation direction of the impeller
is opposite to the rotation direction.
[0010] A thickness of a cross-section of each supporting rib
substantially perpendicular to a longitudinal direction of the
supporting rib is preferably thinner on both sides of a center
thereof in a circumferential direction than at the center.
[0011] In at least one of the first and second primary surfaces, a
normal angle thereof near the downstream-side end is in a range
from approximately 20.degree. to approximately 40.degree., when
being averaged in a radial direction. Please note that the radial
direction is substantially perpendicular to the center axis J1.
[0012] Each supporting rib may extend in a direction opposite to
the rotation direction of the impeller as it extends away from the
center axis. Moreover, each supporting rib may be curved so that it
is convex along the rotation direction of the impeller.
[0013] An upstream-side surface of each support in the rotation
direction of the impeller is preferably smooth and convex.
[0014] An inner side surface of the frame may have, at an end
thereof opposite to the heat sink, an inclined surface which
extends close to the center axis as it extends close to the heat
sink. This inclined surface is preferably approximately annular
about the center axis.
[0015] The heat sink preferably includes a plurality of
heat-dissipating fins which are arranged around the center axis and
extend along the center axis.
[0016] Other features, elements, advantages and characteristics of
the present invention will become more apparent from the following
detailed description of preferred embodiments thereof with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a cooling device according
to a first preferred embodiment of the present invention.
[0018] FIG. 2 is a plan view of the cooling device according to the
first preferred embodiment of the present invention.
[0019] FIG. 3 is a plan view of a heat sink in the cooling device
of FIGS. 1 and 2.
[0020] FIG. 4 is a cross-sectional view of a supporting rib and a
blade of an impeller axially closest thereto in the cooling device
of FIGS. 1 and 2.
[0021] FIG. 5A is an enlarged view of a portion of the cooling
device of FIGS. 1 and 2 in the vicinity of a support of a
frame.
[0022] FIG. 5B is a cross-sectional view of the support.
[0023] FIG. 5C is a cross-sectional view of the frame.
[0024] FIG. 6 is a cross-sectional view of a supporting rib and a
blade of an impeller axially closest thereto, in a cooling device
according to a second preferred embodiment of the present
invention.
[0025] FIGS. 7A, 7B, 7C, and 7D show other exemplary shapes of the
supporting rib.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0026] Referring to FIGS. 1 through 7D, preferred embodiments of
the present invention will be described in detail. It should be
noted that in the explanation of preferred embodiments of the
present invention, when positional relationships among and
orientations of the different components are described as being
up/down or left/right, the positional relationships and
orientations shown in the drawings are indicated; positional
relationships among and orientations of the components once having
been assembled into an actual device are not indicated. Meanwhile,
in the following description, an axial direction indicates a
direction substantially parallel to a rotation axis, and a radial
direction indicates a direction substantially perpendicular to the
rotation axis.
FIRST PREFERRED EMBODIMENT
[0027] FIG. 1 is a perspective view of a cooling device 1 according
to a first preferred embodiment of the present invention. FIG. 2 is
a plan view of the cooling device 1.
[0028] The cooling device 1 of the present preferred embodiment is
a heat sink fan including a heat sink 2 and a fan 3. The cooling
device 1 is preferably attached to a heat source, e.g., a CPU
(Central Processing Unit) in a personal computer or other
electronic device, for example, and dissipates heat transferred
from the heat source through the heat sink 2, thereby cooling the
heat source.
[0029] As shown in FIGS. 1 and 2, the cooling device 1 includes the
heat sink 2 that dissipates the heat transferred from the heat
source, the fan 3 that delivers air to the heat sink 2 so as to
cool the heat sink 2, an attaching portion 4 that fixes the fan 3
to the heat sink 2, and a fixing pin 5 arranged to attach the
cooling device 1 to another device. In the present preferred
embodiment, the fan 3 is an axial fan which delivers air
approximately parallel to a center axis J1 by being rotated about
the center axis J1. The cooling device 1 is attached such that a
portion of the heat sink 2, which is located on a side opposite to
the fan 3 in an axial direction, is in contact with the CPU. In the
following description, for the sake of convenience, the fan 3 side
and the heat sink 2 side in the axial direction are referred to as
an upper side and a lower side, respectively. However, it is not
necessary for the center axis J1 to be in the same direction as
gravity.
[0030] FIG. 3 is a plan view of the heat sink 2. As shown in FIGS.
1 and 3, the heat sink 2 includes a plurality of heat-dissipating
fins 22 defined by thin plates which are radially arranged around
the center axis J1 of the fan 3 and extend along the center axis
J1, a cylindrical fin-supporting portion 23 which connects the
heat-dissipating fins 22 at inner radially portions thereof to each
other, and a core 24 defined by a circular cylinder (shown in FIG.
3 only) which is inserted into the fin-supporting portion 23. A
lower end portion of the core 24 (i.e., an opposite end portion to
the fan 3 (see FIG. 2)) projects downward from lower ends of the
heat-dissipating fins 22 and the fin-supporting portion 23, and a
lower end surface of the core 24 is in contact with the CPU.
[0031] In the present preferred embodiment, the heat-dissipating
fins 22 and the fin-supporting portion 23 shown in FIG. 3 are
preferably made of aluminum (Al) or aluminum alloy so as to be
integral with each other, while the core 24 is preferably made of
copper (Cu), for example. In the following description, the
combination of the heat-dissipating fins 22 and the fin-supporting
portion 23 are referred to as a "fin unit 21." Please note that the
material of the core 24 is not limited to copper. For example, the
core 24 may be made of aluminum or aluminum alloy. Moreover, the
core 24 may be made of the same material as that of the fin unit.
In this case, the core 24 may be integrally formed with the
fin-supporting portion 23 when the fin unit is formed.
[0032] As shown in FIG. 3, in the present preferred embodiment, an
outer side surface 211 of the fin unit 21 preferably is
approximately cylindrical about the center axis J1. Please note
that the outer side surface 211 of the fin unit 21 is preferably a
surface formed by circumferentially connecting outer radially edges
of the heat-dissipating fins 22. As shown in FIG. 1, two grooves
213 extending substantially perpendicularly to the center axis J1
are preferably provided on the outer side surface 211 of the fin
unit 21. By engagement of an engagement portion 441 of the
attaching portion 4 with the groove 213, the fan 3 is attached to
the heat sink 2.
[0033] As shown in FIG. 3, each heat-dissipating fin 22 of the fin
unit 21 extends outward from the fin-supporting portion 23 in a
radial direction, i.e., a direction away from the center axis J1,
and is curved. In the present preferred embodiment, each
heat-dissipating fin 22 preferably is convex toward a
counterclockwise direction in FIG. 3. Each heat-dissipating fin 22
includes an inner radial portion 221 connected to an outer side
surface of the fin-supporting portion 23 and a radially outer
portion 222 extending outward in the radial direction from a
radially outer end of the radially inner portion 221, i.e., from an
opposite end of the inner radial portion 221 to the fin-supporting
portion 23. In the present preferred embodiment, the inner radial
portion 221 is defined by a single thin plate, while the outer
radial portion 222 is defined by two thin plates one of which
circumferentially covers the other. The outer radial end of the
inner radial portion 221 is located approximately at the center of
the heat-dissipating fin 22 in the radial direction.
[0034] As shown in FIGS. 1 and 2, the fan 3 is arranged axially
above the heat sink 2 and includes a stator portion 31 having a
base portion 311 fixed to the heat sink 2 via the attaching portion
4, and a rotor portion 32 supported below the base portion 311
(i.e., on the heat sink 2 side of the fan 3) in a rotatable manner
relative to the stator portion 31. In the present preferred
embodiment, the base portion 311 of the stator portion 31 is
defined by an approximately circular plate centered on the center
axis J1. The diameter of the base portion 311 is approximately
equal to the diameter of the core 24 of the heat sink 2 (see FIG.
3), when the base portion 311 is viewed along the axial
direction.
[0035] The rotor portion 32 includes an impeller 322 which is made
of resin in the present preferred embodiment. The impeller 322
includes a hollow hub 323 and a plurality of blades 324 arranged on
an outer side surface of the hub 323 to extend outward in the
radial direction, as shown in FIG. 1. In the present preferred
embodiment, the hub 323 is approximately cylindrical about the
center axis J1 and opens upward in the axial direction. In the
present preferred embodiment, preferably seven blades 324, for
example, are fixed on the outer side surface of the hub 323. The
hub 323 and the blades 324 are preferably formed by injection
molding, for example. When the hub 323 is viewed along the axial
direction, the diameter thereof is approximately equal to the
diameter of the base portion 311. Inside the hub 323 an armature
and a field magnet which generate a torque about the center axis J1
and a bearing unit which supports the rotor portion 32 in a
rotatable manner relative to the stator portion 31 are
provided.
[0036] When the fan 3 is driven, the impeller 322 of the rotor
portion 32 is rotated about the center axis J1 in a clockwise
direction in FIG. 1 and sends air toward the heat sink 2. In other
words, an air flow from the base portion 311 of the stator portion
31 to the rotor portion 32 is created, and the heat sink 2 receives
the air flow from the fan 3.
[0037] The attaching portion 4 includes a frame 41 above the heat
sink 2 surrounding a lower portion of the impeller 322, i.e., a
portion of the impeller 322 which is opposed to the heat sink 2, as
shown in FIGS. 1 and 2. The frame 41 is approximately annular about
the center axis J1, for example. As shown in FIG. 1, the axial
height of the frame 41 is less than the axial height of the
impeller 322 of the fan 3 in the present preferred embodiment.
Thus, an axially upper portion of the impeller 322 (i.e., a portion
of the impeller 322 other than the aforementioned lower portion
thereof) is exposed axially above the frame 41.
[0038] The attaching portion 4 further includes a plurality of
supports 42 projecting from the frame 41 toward a side opposite to
the heat sink 2, i.e., upward, a plurality of supporting ribs 43
extending from the base portion 31 of the fan 3 outward in the
radial direction, i.e., away from the center axis J1, and a
plurality of rotation restricting portions 44 projecting downward
from the frame 41 along the outer side surface 211 of the fin unit
21. The rotation restricting portions 44 prevent rotation of the
attaching portion 4 relative to the heat sink 2 when the fan 3 is
attached to the heat sink 2. In the present preferred embodiment,
four rotation restricting portions 44 are provided. Two of the
rotation restricting portions 44 which are opposed to each other
are provided with engagement portions 441 which are to engage with
two grooves 213 on the outer side surface 211 of the fin unit 21,
respectively. Each rotation restricting portion 44 supports the
fixing pin 5.
[0039] In the cooling device 1, preferably four supports 42 and
four supporting ribs 43, for example, provided in the attaching
portion 4 are arranged around the center axis J1 at approximately
regular angular intervals in the circumferential direction, as
shown in FIG. 1. As shown in FIGS. 1 and 2, each supporting rib 43
is inclined so that it extends in an opposite direction (i.e., to a
counterclockwise direction in FIGS. 1 and 2) to the rotation
direction of the impeller 322 as it extends away from the center
axis J1. Moreover, each supporting rib 43 is curved so as to be
convex along the rotation direction of the impeller 322 (i.e., a
clockwise direction in FIGS. 1 and 2). In other words, a direction
from the supporting rib 43 to a straight line which connects a base
portion 311 side end of the supporting rib 43 and a support 42 side
end of the supporting rib 43 to each other extends in a direction
that is opposite to the rotation direction of the impeller 322.
[0040] FIG. 4 is a cross-sectional view of one supporting rib 43
and a blade 324 disposed closest thereto, taken along a cylindrical
plane centered on the center axis J1 near the center of the
supporting rib 43 in the radial direction. In FIG. 4, the rotation
direction of the impeller 322 is a direction from the right to the
left in FIG. 4. (This is the same in FIGS. 6, 7A, 7B, 7C, and 7D.)
The other supporting ribs 43 and the other blades 324 preferably
also have substantially the same shapes as those of the supporting
rib 43 and the blade 324 shown in FIG. 4, respectively.
[0041] The cross section of the supporting rib 43 shown in FIG. 4
(i.e., the cross section substantially perpendicular to the
longitudinal direction of the supporting rib 43 which extends from
the base portion 311 to the support 42 in FIG. 1) is thick at a
center in FIG. 4 (which corresponds to the center of the cross
section in the circumferential direction), and is thin on both
sides of the center, i.e., on the right and left of the center in
FIG. 4. The supporting rib 43 has a first primary surface 431
opposed to the impeller 322 of the fan 3 and a second primary
surface 432 which is on the opposite side of the supporting rib 43
from the first primary surface 431. The first primary surface 431
and the second primary surface 432 are not parallel to a plane that
is substantially perpendicular to the center axis J1, i.e., are
inclined or curved with respect to that plane. The first primary
surface 431 is located behind the second primary surface 432 (i.e.,
on the right of the second primary surface 432 in FIG. 4) in the
rotation direction of the impeller 322. In the present preferred
embodiment, in the cross section of the supporting rib 43 shown in
FIG. 4, the first primary surface 431 is approximately straight
while the second primary surface 432 is curved.
[0042] The first primary surface 431 has a leading
(downstream-side) end 433 and a trailing (upstream-side) end 434 in
the rotation direction. Those ends 433 and 434 are hereinafter
referred to as the downstream-side end 433 and the upstream-side
end 434 of the first primary surface 431 in the following
description. Similarly, the second primary surface 432 also has a
downstream-side end and an upstream-side end. In the present
preferred embodiment, the downstream-side end of the second primary
surface 432 is substantially coincident with the downstream-side
end 433 of the first primary surface 431, and is located ahead of
(on the downstream side of) the upstream-side end 434a of the
second primary surface 432 in the rotation direction. In other
words, in each of the first primary surface 431 and the second
primary surface 432 of the supporting rib 43, a circumferential
component from the downstream-side end 433 to the upstream-side end
434 or 434a is opposite to the rotation direction of the impeller
322.
[0043] A normal angle of the first primary surface 431 of each
supporting rib 43 at the downstream-side end 433 thereof with
respect to the center axis J1 (hereinafter, referred to as a normal
angle of the first primary surface 431) is preferably in a range
from approximately 20.degree. to approximately 40.degree., when
being averaged in the radial direction of that supporting rib 43.
"Normal angle" as used in the specification is defined as the angle
between the center axis J1 and a line extending in a direction that
is perpendicular to the first primary surface 431. In the present
preferred embodiment, that angle is approximately 30.degree.. Where
a downstream-side portion of each supporting rib 43 in the rotation
direction is chamfered in the cross section shown in FIG. 4, the
normal angle of the first primary surface 431 is a normal angle
thereof at an end of the chamfered portion which is adjacent to the
upstream-side end 434, i.e., at the boundary between the chamfered
portion and the first primary surface 431 with respect to the
center axis J1.
[0044] The shape of the blades 324 of the impeller 322 is
described. Each blade 324 has a primary surface 3241 opposed to the
supporting ribs 43, i.e., an upper primary surface 3241, and a
primary surface 3242 which is on the opposite side of the blade 324
from the supporting ribs 43, i.e., a lower primary surface 3242.
Hereinafter, the primary surfaces 3241 and 3242 are referred to as
a blade upper surface 3241 and a blade lower surface 3242,
respectively. As shown in FIG. 4, the blade upper surface 3241 and
the blade lower surface 3242 of each blade 324 are inclined in a
direction opposite to the inclination direction of the first
primary surface 431 and the second primary surface 432 of the
supporting rib 43. In other words, each blade 324 is inclined in a
direction opposite to the inclination direction of the supporting
rib 43.
[0045] A supporting rib 43 side end 3243 of the blade 324 is
located ahead of (i.e., on the downstream side of) the other end
3244 in the rotation direction of the impeller 3222. Thus, the
supporting rib 43 side end 3243 of the blade 324 and the other end
3244 thereof are respectively referred to as a blade leading edge
3243 and a blade trailing edge 3244 in the following description.
In the cooling device 1, when the impeller 322 is rotated, the
blade leading edge 3243 of each blade 324 passes below the upper
edges 434 and 434a of each supporting rib 43 prior to passing below
the lower edge 433 of that supporting rib 43.
[0046] In each blade 324, a normal angle of the blade upper surface
3241 at or near the blade leading edge 3243 of the blade upper
surface 3241 with respect to the center axis J1 (hereinafter,
referred to as a normal angle of the blade upper surface 3241) is
preferably in a range from approximately 20.degree. to
approximately 40.degree., when being averaged in the radial
direction. In the present preferred embodiment, the normal angle of
the blade upper surface 3241 is approximately 30.degree..
[0047] Next, the structure of the frame 41 is described. FIG. 5A is
an enlarged view of a portion around one of the supports 42 of the
attaching portion 4. FIG. 5B is a cross-sectional view of the
portion of the support 42 shown in FIG. 5A near the frame 41, taken
along a plane substantially perpendicular to the center axis J1.
FIG. 5C is a cross-sectional view of the frame 41 shown in FIG. 5,
taken along a plane including the center axis J1 and substantially
parallel to the center axis J1.
[0048] In the present preferred embodiment, an upstream-side
surface 421 of each support 42 in the rotation direction of the
impeller 322 is smooth and convex. For example, the upstream-side
surface 421 is round and chamfered, as shown in FIGS. 5A and 5B. An
inner side surface 411 of the frame 41 (i.e., a center axis J1 side
surface thereof) has an inclined surface 412 at an end thereof
opposite to the heat sink 2, i.e., at an end adjacent to the
supports 42 and the supporting ribs 43, as shown in FIG. 5C. The
inclined surface 412 is arranged such that it extends close to the
center axis J1 as it extends close to the heat sink 2. Where the
frame 41 is approximately annular about the center axis J1, the
inclined surface 412 is also approximately annular about the center
axis J1.
[0049] As described above, in the cooling device 1, each of the
first primary surface 431 and the second primary surface 432 of
each supporting rib 43 of the attaching portion 4 which fixes the
fan 3 to the heat sink 2, is inclined with respect to a plane
substantially perpendicular to the center axis J1. A
circumferential component from the downstream-side end 433 of each
supporting rib 43 to the upstream-side end 434 or 434a is in a
direction opposite to the rotation direction of the impeller 322.
Moreover, the first primary surface 431 and the second primary
surface 432 of each supporting rib 43 are inclined in a direction
opposite to the inclination direction of the blade upper surface
3241 and the blade lower surface 3242 of each blade 324 of the
impeller 322.
[0050] When the fan 3 is rotated, air taken in from the supporting
rib 43 side of the impeller 322 flows into the impeller 322 toward
the blade upper surfaces 3241 of the blades 324. Since the first
primary surface 431 and the second primary surface 432 of the
supporting rib 43 are inclined in a direction opposite to the
inclination direction of the blade upper surface 3241 of the blade
324 as described above, the first primary surface 431 and the
second primary surface 432 can be arranged approximately parallel
to the air flow flowing into the impeller 322, thereby reducing
interference between the supporting ribs 43 and the air flow and
reducing the operating sound of the cooling device 1 including the
interference sound generated at the supporting ribs 43.
[0051] Thus, the number of revolutions of the impeller 322 can be
increased without increasing the operation sound of the cooling
device 1, resulting in an increase in the volume of the air
supplied to the heat sink 2 from the fan 3. Consequently, the
cooling performance of the cooling device 1 is improved.
Alternatively, it is possible to reduce the cooling performance of
the heat sink 2 itself without reducing the cooling performance of
the cooling device 1. Therefore, the volume of the core 24 in the
heat sink 2 can be reduced, resulting in a weight reduction of the
cooling device 1 and a reduction of the manufacturing cost.
[0052] Since each supporting rib 43 preferably has a blade-shaped
cross section when cut along a plane substantially perpendicular to
the longitudinal direction thereof, interference of the air flow
flowing into the impeller 322 with the supporting ribs 43 is
further reduced, thus further reducing the operating sound of the
cooling device 1 caused by the supporting ribs 43. Moreover, the
interference of the air flow flowing into the impeller 322 with the
supporting ribs 43 can be further reduced by setting the average of
the normal angle of the first primary surface 431 in the radial
direction to be in a range from approximately 20.degree. to
approximately 40.degree.. Thus, the operating sound of the cooling
device 1 generated by the supporting ribs 43 is further
reduced.
[0053] If each supporting rib is provided approximately parallel to
the blade leading edge of one blade of the impeller when being
arranged circumferentially adjacent to that blade leading edge,
interference between the blade leading edge and the supporting rib
occurs over substantially the entire length of the supporting rib,
thus increasing the interference sound.
[0054] However, in the cooling device 1 of the present preferred
embodiment, the supporting ribs 43 are inclined so that they extend
toward the opposite direction to the rotation direction of the
impeller 322 as they extend away from the center axis J1.
Therefore, an angle formed by each supporting rib 43 and the blade
leading edge 3243 of the blade 324 of the impeller 322 when the
supporting rib 43 crosses the blade leading edge 3243 (i.e., an
angle which is assumed to be zero when the supporting rib 43 is
substantially parallel to the blade leading edge 3243, with the
intersection of the blade leading edge 3243 and the supporting rib
43 used as a reference) is increased. Thus, at every instant during
rotation of the impeller 322, instantaneous generation of a large
interference sound is prevented by reducing the intersection of the
supporting rib 43 and the blade leading edge 3243. Consequently,
the generation of a large interference sound caused by interference
between the supporting rib 43 and the blade leading edge 3243 over
substantially the entire length of the supporting rib 43 is
prevented, resulting in a further reduction of the operating sound
of the cooling device 1 caused by the supporting ribs 43.
[0055] Moreover, since each supporting rib 43 is preferably curved
to be convex along the rotation direction of the impeller 322, the
angle formed between each supporting rib 43 and the blade leading
edge 3243 of the blade 324 of the impeller 322 when the supporting
rib 43 and the blade leading edge 3243 cross each other is further
increased. Consequently, at every instant during the rotation of
the impeller 322, the instantaneous generation of a large
interference sound is prevented by reducing the intersection of the
supporting rib 43 and the blade leading edge 3243. Accordingly, the
operating sound of the cooling device 1 generated by the supporting
ribs 43 is further reduced.
[0056] As described above, the upper portion of the impeller 322 is
exposed above the frame 41 in the cooling device 1 of the present
preferred embodiment. Thus, when the fan 3 is driven, air can be
taken in from the surroundings of the impeller 322 (i.e., from
between three supports 42 arranged in the circumferential
direction). Therefore, the volume of air delivered to the heat sink
2 can be increased and the cooling performance of the cooling
device 1 can be further improved.
[0057] Air taken in from the surroundings of the impeller 322 flows
into the impeller 322 from between three supports 42 in a clockwise
direction in FIG. 1 which is along the rotation direction of the
impeller 322. Since the upstream-side surface 421 of each support
42 in the rotation direction of the impeller 322 is smooth and
convex in the attaching portion 4, as shown in FIGS. 5A and 5B,
interference of the air flow flowing from the surroundings of the
impeller 322 with the support 42 is reduced, thus reducing the
operating sound of the cooling device 1 including the interference
sound generated at the supports 42.
[0058] As shown in FIG. 5C, in the attaching portion 4, the
inclined surface 412 is provided at an end of the inner side
surface 411 of the frame 41 opposed to the heat sink 2. The
inclined surface 412 extends closer to the center axis J1 as it
extends closer to the heat sink 2. With this configuration,
interference of the air flow flowing from the surroundings of the
impeller 322 with the frame 41 is further reduced. Therefore, the
operating sound of the cooling device 1 including the interference
sound generated at the frame 41 is further reduced. Moreover, due
to an air-collecting effect of the frame 41, the volume of the air
delivered to the heat sink 2 is increased, thus further improving
the cooling performance of the cooling device 1.
[0059] In the cooling device 1 of the present preferred embodiment,
the heat sink 2 includes a plurality of heat-dissipating fins 22
defined by thin plates which are radially arranged around the
center axis J1 and extend along the center axis J1. Thus, it is
possible to increase the total surface area of the heat-dissipating
fins 22 without increasing the size of the fin unit 21, and/or
without excessively reducing the thickness of each heat-dissipating
fin in order to increase the number of the heat-dissipating fins,
thus ensuring that each of the heat-dissipating fins 22 is
sufficiently strong. Consequently, the cooling performance of the
heat sink 2 itself and the cooling performance of the cooling
device 1 are improved. Moreover, a portion of each heat-dissipating
fin 22 radially outside the center thereof is split into a
plurality of thin plates one of which covers the other in the
circumferential direction and which define the outer radial portion
222. Therefore, the total surface area of the heat-dissipating fins
22 is further increased, thus further improving the cooling
performance of the heat sink 2 and the cooling device 1.
SECOND PREFERRED EMBODIMENT
[0060] A cooling device according to a second preferred embodiment
of the present invention is now described. The cooling device of
the present preferred embodiment has substantially the same
structure as the cooling device 1 of the first preferred embodiment
shown in FIGS. 1 and 2, except for the cross-sectional shape of the
supporting rib. Thus, except for the supporting ribs, the
components of the present preferred embodiment are labeled with
same reference characters as those used in the first preferred
embodiment and the detailed description thereof is omitted.
[0061] FIG. 6 is a cross-sectional view corresponding to FIG. 4,
and illustrates a cross section of one supporting rib 43a and a
cross section of one of blades 324 of the impeller 322 which is
axially closest to that supporting rib 43a in the cooling device of
the present preferred embodiment, taken along a cylindrical plane
centered on the center axis J1 near the radial center of that
supporting rib 43a.
[0062] As shown in FIG. 6, the supporting rib 43a has a flat plate
shape having an approximately constant thickness. The first primary
surface 431 and the second primary surface 432 of the supporting
rib 43a define substantially straight lines in the cross section of
the supporting rib 43a which is substantially perpendicular to the
longitudinal direction thereof. In the supporting rib 43a, the
first primary surface 431 is inclined with respect to a plane
substantially perpendicular to the center axis J1 so that a
circumferential component from a downstream-side end 433 thereof to
an upstream-side end 434 thereof is in a direction opposite to the
rotation direction of the impeller 322, as in the first preferred
embodiment. Moreover, the second primary surface 432 is inclined
with respect to a plane substantially perpendicular to the center
axis J1 so that a circumferential component from a downstream-side
end 433a to an upstream-side end 434a is in a direction opposite to
the rotation direction of the impeller 322. The first primary
surface 431 is located behind the second primary surface 432 in the
rotation direction of the impeller 322.
[0063] Since the first primary surface 431 and the second primary
surface 432 of the supporting rib 43a are inclined in a direction
opposite to the blade upper surface 3241 of the blade 324 of the
impeller 322 as described above, interference of an air flow
flowing into the impeller 322 with the supporting ribs 43a is
reduced, thus reducing the operating sound of the cooling device
generated by the supporting ribs 43a, as in the first preferred
embodiment.
[0064] Moreover, in each supporting rib 43a, the average in the
radial direction of the normal angle of the first primary surface
431, i.e., the normal angle of the first primary surface 431
adjacent to the downstream-side end 433 with respect to the center
axis J1 is preferably in a range from approximately 20.degree. to
approximately 40.degree., as in the first preferred embodiment.
Thus, the interference of the air flow flowing into the impeller
322 with the supporting rib 43a is further reduced, and therefore,
the operating sound of the cooling device 1 generated by the
supporting ribs 43b is further reduced. In addition, the average in
the radial direction of the normal angle of the second primary
surface 432, i.e., the normal angle of the second primary surface
432 near the downstream-side end 433a with respect to the center
axis J1 is preferably in a range from approximately 20.degree. to
approximately 40.degree.. Thus, the operating sound of the cooling
device 1 generated by the supporting ribs 43a is further
reduced.
[0065] The cooling devices according to the preferred embodiments
of the present invention have been described above. However, the
cross-sectional shape of the supporting rib in the attaching
portion 4 of the cooling device is not limited to those shown in
FIGS. 4 and 6. For example, the supporting ribs may have
cross-sectional shapes as shown in FIGS. 7A, 7B, 7C, and 7D.
[0066] The cross section of the supporting rib 43b substantially
perpendicular to the longitudinal direction thereof, shown in FIG.
7A, has a blade shape in which the thickness thereof is relatively
thick at a center in the circumferential direction and is thinner
on both sides of the center in the circumferential direction, as in
the supporting rib 43 shown in FIG. 4. However, the supporting rib
43b is different from the supporting rib 43 shown in FIG. 4 in that
the downstream-side end 433 and the upstream-side end 434 of the
first primary surface 431 are spaced apart from the downstream-side
end 433a and the upstream-side end 434a of the second primary
surface 432, respectively.
[0067] The supporting rib 43c shown in FIG. 7B has a plate shape in
which the thickness is approximately constant. The first primary
surface 431 and the second primary surface 432 are curved in the
cross section of the supporting rib 43c that is substantially
perpendicular to the longitudinal direction thereof.
[0068] In the supporting rib 43d shown in FIG. 7C, in the cross
section that is substantially perpendicular to the longitudinal
direction of the supporting rib 43d, the first primary surface 431
is curved while the second primary surface 432 is approximately
linear.
[0069] The cross section of the supporting rib 43e substantially
perpendicular to the longitudinal direction thereof, shown in FIG.
7D, preferably has an approximately oval blade shape in which the
thickness is relatively large at a center in the circumferential
direction and is smaller on both sides of the center in the
circumferential direction.
[0070] Even if the supporting rib has any one of the
cross-sectional shapes shown in FIGS. 7A, 7B, 7C, and 7D, the first
primary surface 431 and the second primary surface 432 are inclined
with respect to a plane substantially perpendicular to the center
axis J1 in the cooling device of another preferred embodiment of
the present invention so that a circumferential component from the
downstream-side end 433 or 433a to the upstream-side end 434 or
434a is in a direction opposite to the rotation direction of the
impeller 322. With this configuration, the operating sound of the
cooling device generated by the supporting ribs is reduced, as in
the first and second preferred embodiments.
[0071] In the aforementioned first and second preferred
embodiments, both the first primary surface and the second primary
surface of the supporting rib preferably are inclined with respect
to a plane substantially perpendicular to the center axis. However,
it is not necessary that both the first primary surface and the
second primary surface are inclined. Instead, only one of the first
primary surface and the second primary surface may be inclined. The
interference of the air flow flowing into the impeller with the
supporting ribs can be reduced if at least one of the first primary
surface and the second primary surface of the supporting rib is
inclined. Thus, a reduction of the operating sound of the cooling
device, a weight reduction of the cooling device, and a reduction
of the manufacturing cost of the cooling device, which have been
described above, can be achieved.
[0072] Moreover, where only one of the first primary surface and
the second primary surface is inclined, the inclination angle of
the first primary surface or the second primary surface of the
supporting rib with respect to the center axis can be set to be in
a range from approximately 20.degree. to approximately
40.degree..
[0073] The number of the supporting ribs 43 in the attaching
portion 4 is not limited to four which is the number described in
the first and second preferred embodiments. Five or more supporting
ribs may be provided, for example. Moreover, the entire inner side
surface 411 of the frame 41 may be inclined with respect to the
center axis J1. In this case, the inner side surface 411 may have
an approximately annular inclined surface which extends closer to
the center axis J1 as it extends closer to the heat sink 2.
Furthermore, it is not necessary that the frame 41 surrounds the
entire circumference of the impeller 322. The frame 41 may have a
shape obtained by cutting out a portion of an annular shape, as
long as the frame 41 is arranged to surround the portion of the
impeller 322 which is opposed to the heat sink 2.
[0074] As described above, according to the cooling device of the
preferred embodiments of the present invention, the operating sound
generated by the supporting ribs, the operating sound generated by
the supports, and the operating sound generated by the frame are
reduced. Moreover, the cooling performance of the cooling device is
improved.
[0075] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *