U.S. patent application number 12/046640 was filed with the patent office on 2008-09-18 for manufacturing method of fin unit.
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 | 20080223551 12/046640 |
Document ID | / |
Family ID | 39761477 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080223551 |
Kind Code |
A1 |
OTSUKI; Takaya ; et
al. |
September 18, 2008 |
MANUFACTURING METHOD OF FIN UNIT
Abstract
In a manufacturing method of a fin unit for a heat sink for
dissipating a heat from a heat source, the fin unit includes a
plurality of fins radially arranged about its center axis, and a
fin supporting portion connecting inner ends of the fins and
supporting the fins. First, metal is heated. The heated metal is
extruded and/or drawn through a die to obtain a metal body. One of
the die and the metal body obtained through the die is rotated
relative to the other about a center axis of a die hole of the die.
The metal body is then cut, thereby obtaining the fin unit.
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
Minami-ku
JP
|
Family ID: |
39761477 |
Appl. No.: |
12/046640 |
Filed: |
March 12, 2008 |
Current U.S.
Class: |
165/80.3 ;
165/185; 29/890.03 |
Current CPC
Class: |
Y10T 29/4935 20150115;
H01L 2924/0002 20130101; H01L 23/467 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/80.3 ;
29/890.03; 165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00; B21D 53/02 20060101 B21D053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 13, 2007 |
JP |
2007-063909 |
Claims
1. A manufacturing method of a fin unit for a heat sink for
dissipating heat from a heat source, the fin unit including a
plurality of fins arranged about a center axis and a fin supporting
portion connecting radially inner ends of the fins, the
manufacturing method comprising the steps of: a) heating a metal;
b) extruding and/or drawing the metal from a die having a die hole
to obtain a metal body, the die hole being shaped to correspond to
the fins and the fin supporting portion; c) rotating at least one
of the metal body and the die relative to the other about a center
axis of the die hole; d) cutting the metal body to obtain the fin
unit; wherein at least a portion of each of the steps b) and c) are
carried out simultaneously.
2. The manufacturing method according to claim 1, wherein in the
step c), the metal body is connected to a supporting member and the
die is fixed relative to the metal body, and the metal body is
rotated about the center axis of the die hole relative to the die
by rotating the supporting member about the center axis of the die
hole.
3. The manufacturing method according to claim 2, wherein the
supporting member is rotated by a first servo motor.
4. The manufacturing method according to claim 3, wherein the step
of extruding and/or drawing the metal from the die is performed via
a second servo motor.
5. The manufacturing method according to claim 4, wherein the first
servo motor and the second servo motor are controlled in
synchronization with each other to control a rate at which the
metal body is obtained from the die and a rotation speed of the
supporting member in accordance with a distance between a leading
end of the metal body and the die.
6. The manufacturing method according to claim 1, wherein a
rotation speed of the metal body is changed to change an
inclination angle of a portion of the metal body which corresponds
to an outer peripheral edge of each of the fins with respect to the
center axis of the die.
7. The manufacturing method according to claim 1, wherein the metal
is aluminum or aluminum alloy.
8. The manufacturing method according to claim 1, wherein the metal
body extends continuously substantially parallel to the center axis
of the die, and includes a plurality of fin units each of which has
the fins and the fin supporting portion and which are arranged
substantially parallel to the center axis of the die.
9. The manufacturing method according to claim 1, further
comprising the step of: e) finishing an inner peripheral surface of
the fin supporting portion which is hollow and obtained in step
c).
10. The manufacturing method according to claim 1, further
comprising the step of: f) performing a heat treatment on the metal
body or the fin unit.
11. A fin unit manufactured by the manufacturing method according
to claim 1.
12. The fin unit according to claim 11, wherein each of the fins
includes an inner portion connected to an outer peripheral surface
of the fin supporting portion, and a plurality of outer portions
extending radially outward from a radially outer end of the inner
portion; the inner portion is defined by a single thin plate-shaped
member, and each of the outer portions is defined by a single thin
plate-shaped member; and the outer portions overlap each other in a
circumferential direction of the fin unit.
13. The fin unit according to claim 11, wherein each of the fins
extends radially outward from the fin supporting portion and are
curved in a clockwise or counterclockwise direction when viewed
along the center axis.
14. A cooling device for cooling a heat source by dissipating heat
transferred from the heat source, comprising: a heat sink including
the fin unit according to claim 11; and a fan arranged on one axial
side of the fin unit; wherein the fan is arranged to deliver air to
the heat sink.
15. The cooling device according to claim 14, wherein a fan-side
portion of each of the fins of the fin unit is inclined with
respect to the center axis of the fin unit so as to be
approximately parallel to an airflow from the fan.
16. The cooling device according to claim 14, wherein an outer
peripheral edge of a fan-side portion of each of the fins is
inclined with respect to the center axis of the fin unit at an
angle in a range from approximately 10 degrees to approximately 50
degrees.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fin unit for a heat sink
which dissipates heat transferred from a heat source to the
outside. The present invention also relates to a method for
manufacturing the fin unit, and a cooling device including the fin
unit.
[0003] 2. Description of the Related Art
[0004] CPUs (Central Processing Units) incorporated in personal
computers or servers are used with cooling devices for cooling the
CPUs. The cooling device can prevent lowering of the performance of
the CPU and electronic components near the CPU. An exemplary CPU
cooling device is a heat sink. The heat sink includes a base
portion which is in contact with the CPU via thermal grease or the
like and has a central axis, and a plurality of fins radially
extending from the base portion and capable of dissipating heat
transferred from the CPU. The heat sink is often used together with
a fan for delivering air arranged on a different surface of the
base portion from a surface which is in direct or indirect contact
with the CPU.
[0005] The heat generated by CPUs has been increasing with
improvement of the performance of the CPUs. Thus, in the market, it
is demanded that the heat sink have an improved cooling performance
(heat dissipating performance). One solution is to arrange each fin
at an angle relative to the central axis of the heat sink. This
arrangement can increase the total surface area of the fins, i.e.,
an area which contributes to dissipation of the heat from the CPU
to the outside, and therefore improve the cooling performance of
the heat sink, without increasing the entire size of the heat sink
or the number of the fins.
[0006] However, in order to arrange each fin at an angle relative
to the central axis, two or more complicated additional steps,
e.g., cutting or drawing are usually required after the heat sink
is formed or molded. For this reason, manufacturing of the heat
sink having inclined fins takes a large amount of time and cost,
and therefore mass production of the heat sink is difficult.
SUMMARY OF THE INVENTION
[0007] In order to overcome the problems described above, preferred
embodiments of the present invention provide a manufacturing method
of a fin unit for use in a heat sink for dissipating heat from a
heat source. The fin unit preferably includes a plurality of fins
arranged about its center axis and a fin supporting portion
connecting radially inner ends of the fins and supporting fins. The
manufacturing method preferably includes: a) heating metal; b)
extruding and/or drawing the metal from a die having a die hole to
obtain a metal body, the die hole being shaped to correspond to the
fins and the fin supporting portion; c) rotating at least one of
the metal body and the die relative to the other about a center
axis of the die hole; and d) cutting the metal body to obtain the
fin unit. The steps b) and c) are preferably carried out in
parallel.
[0008] According to another preferred embodiment of the present
invention, a fin unit manufactured by the aforementioned
manufacturing method is provided. Each of the fins preferably
include an inner portion connected to an outer peripheral surface
of the fin supporting portion, and a plurality of outer portions
extending radially outward from a radially outer end of the inner
portion. The inner portion is preferably defined by a single thin
plate-shaped member. Each of the outer portions is preferably
defined by a single thin plate-shaped member. The outer portions
preferably overlap each other in a circumferential direction of the
fin unit.
[0009] According to still another preferred embodiment of the
present invention, a cooling device for cooling a heat source by
dissipating heat transferred from the heat source is provided. The
cooling device preferably includes a heat sink including the
aforementioned fin unit, and a fan arranged on one axial side of
the fin unit. The fan delivers air to the heat sink.
[0010] 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
[0011] FIG. 1 is a perspective view of a cooling device according
to a first preferred embodiment of the present invention.
[0012] FIG. 2 is a side view of the cooling device according to the
first preferred embodiment of the present invention.
[0013] FIG. 3 is a plan view of a heat sink of the cooling device
of the first preferred embodiment of the present invention.
[0014] FIG. 4 is a side view of the heat sink according to the
first preferred embodiment of the present invention.
[0015] FIG. 5 is a flowchart for manufacturing a fin unit according
to the first preferred embodiment of the present invention.
[0016] FIG. 6 is a perspective view of a die used in the heat sink
according to the first preferred embodiment of the present
invention.
[0017] FIG. 7 is a perspective view of the heat sink during
manufacture in the first preferred embodiment of the present
invention.
[0018] FIG. 8 is an enlarged view of an outer side surface of a
heat sink according to a second preferred embodiment of the present
invention.
[0019] FIG. 9 is an enlarged view of an outer side surface of the
heat sink according to the first preferred embodiment of the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] Referring to FIGS. 1 through 9, preferred embodiments of the
present invention will be described in detail. It should be noted
that in the explanation of the present invention, when positional
relationships among and orientations of the different components
are described as being up/down or left/right, ultimately positional
relationships and orientations that are in the drawings are
indicated; positional relationships among and orientations of the
components once having been assembled into an actual device are not
indicated. Additionally, in the following description, an axial
direction indicates a direction substantially parallel to a center
axis, and a radial direction indicates a direction substantially
perpendicular to the center axis.
First Preferred Embodiment
[0021] 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 side view of the cooling device 1. The cooling device 1 is a heat
sink fan, i.e., an assembly of a heat sink 2 and a fan 3 for
delivering air to the heat sink 2 in the present preferred
embodiment. The cooling device 1 is arranged adjacent to or near a
heat source, e.g., a CPU in an electronic device such as a personal
computer or a server, and dissipates heat transferred from the heat
source through the heat sink 2 to the outside, thereby cooling the
heat source.
[0022] Referring to FIGS. 1 and 2, the cooling device 1 preferably
includes the heat sink 2 having a central axis J1 for dissipating
the heat from the heat source to the outside, and the fan 3 for
delivering air to the heat sink 2 so as to cool the heat sink 2.
The fan 3 is preferably an axial fan having a rotation axis
(central axis) coaxially arranged on the central axis J1 of the
heat sink 2, and delivers air from one side in an axial direction
to the other side, i.e., a side opposite to the heat sink 2. Please
note that the axial direction is substantially parallel to the
central axis J1. The fan 3 is secured to the heat sink 2, for
example, with an attaching portion 4. A CPU 9 as an exemplary heat
source mounted on a circuit board such as a motherboard is in
contact with a surface of the heat sink 2 opposite to the fan 3 in
the axial direction, as shown in FIG. 2. The cooling device 1 is
preferably secured to the circuit board with at least one fixing
pin 5.
[0023] In the following description, 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 that
the central axis J1 be parallel to the direction of gravity. In
addition, a direction substantially perpendicular to the central
axis J1 is referred to as a radial direction.
[0024] FIGS. 3 and 4 are a plan view and a side view of the heat
sink 2. More specifically, FIGS. 3 and 4 show the heat sink 2 when
viewed along the axial direction and the radial direction,
respectively. Referring to FIGS. 3 and 4, the heat sink 2 includes
a plurality of fins 22 arranged about the central axis J1 and
extending away from the central axis J1, i.e., outward in the
radial direction. Each fin 22 is preferably in the form of a thin
plate, for example. The fins 22 are connected at their radially
inner ends to a fin supporting portion 23 which is preferably
hollow and approximately cylindrical. Inside the fin supporting
portion 23 is arranged a core 24 preferably in the form of an
approximately circular cylinder. As shown in FIG. 4, an axially
lower end portion of the core 24 projects downward from lower ends
of the fins 22 and a lower end of the fin supporting portion 23 in
the axial direction. A bottom surface of the core 24, i.e., an
axially lower surface of the lower end portion thereof is in
contact with the CPU 9 (see FIG. 2) with thermal grease or the like
arranged therebetween, for example.
[0025] As shown in FIGS. 3 and 4, a clip 25 which is preferably
made of metal is attached to the lower end portion of the core 24.
Exemplary materials of the clip 5 are stainless steel, aluminum,
and aluminum alloy. The clip 25 includes a clip body 251 and four
clip legs 252, for example. The clip body 251 has a through hole
having a diameter approximately the same as that of the lower end
portion of the core 24. After the lower end of the core 24 is
inserted into the through hole of the clip 25, the clip 25 is fixed
to the core 24 by crimping, for example. The four clip legs 252 are
arranged around the central axis J1 and extend from the clip body
251 away from the central axis J1. Each clip leg 252 has a through
hole 253 at its radially outer end portion, into which the fixing
pin 5 is inserted. The clip 25 supports the fixing pins 5 (see
FIGS. 1 and 2) via the through holes 253. As described above, the
fixing pins 5 are used for fixing the cooling device 1 onto the
circuit board or the like.
[0026] In the present preferred embodiment, the fins 22 and the fin
supporting portion 23 are preferably formed integrally with each
other from aluminum or aluminum alloy, for example. The core 24 is
preferably made of copper, for example. However, the materials of
the fins 22, the fin supporting portion 23, and the core 24 are not
limited to the above. It is preferable that these materials have a
high thermal conductivity.
[0027] In the following description, the fins 22 and the fin
supporting portion 23 are referred to as a "fin unit 21" as a
whole.
[0028] Referring to FIG. 3, when the fin unit 21 is viewed along
the central axis J1, an outer shape of the fin unit 21, which is
defined by the radially outer ends of the fins 22, is preferably
approximately circular in the present preferred embodiment.
Moreover, the fin unit 21 preferably includes flat portions 212 on
the outer side surface thereof. When the fin unit 21 is viewed
along the center axis J1, the flat portion 212 is a straight
portion on the outer contour of the fin unit 21. The flat portions
212 are arranged about the central axis J1 at approximately
90-degree intervals in the present preferred embodiment. That is,
two of the flat portions 212 are opposite to each other and the
other two are opposite to each other, as shown in FIG. 4. Among the
four flat portions 212, each of at least two flat portions 212
which are opposite to each other is provided with a groove 213
extending substantially perpendicular to the central axis J1. When
engagement portions 441 of the attaching portions 4 of the fan 3
and the grooves 213 engage with each other, as shown in FIGS. 1 and
2, the fan 3 and the heat sink 2 are fixed to each other.
[0029] Returning to FIG. 3, each fin 22 of the fin unit 21 extends
away from the central axis J1, i.e., outward in the radial
direction, such that a distance between circumferentially adjacent
fins 22 is different from or equal to each other as the fins 22
extend outward in the radial direction. Moreover, each fin 22 is
preferably curved in a clockwise direction when viewed along the
central axis J1. In other words, when the heat sink 2 is viewed
along the central axis J1, each fin 22 is located ahead of the
center of the line which connects its radially inner and outer ends
to each other.
[0030] Each fin 22 includes an inner portion 221 preferably defined
by a single thin plate and an outer portion 222 preferably defined
by two or more thin plates, for example. In the present preferred
embodiment, the outer portion 222 is defined by two thin plates.
The inner portion 221 is connected at its radially inner end to the
outer periphery of the fin supporting portion 23. The outer
portions 222 extend from the radially outer end of the inner
portion 221 outward in the radial direction, and are arranged in
such a manner that two thin plates of the outer portion 222
circumferentially overlap one another. In the present preferred
embodiment, the radially outer end of the inner portion 221 of each
fin 22 is located at approximately the center of that fin 22 in the
radial direction.
[0031] In the fin unit 21, each fin 22 has two opposing surfaces
223 and 224 which slant with respect to the axial direction, as
shown in FIG. 4. When the heat sink 2 is viewed along the axial
direction, a direction from a top edge (axially upper end) 225 of
each fin 22 toward a bottom edge (axially lower end) 226 thereof on
a radially outer edge thereof extends clockwise, as shown in FIG.
3. In other words, a plane normal to each of the surfaces 223 and
224 is not parallel to a plane substantially perpendicular to the
center axis J1 of the fin unit 21. In the circumferential
direction, the direction from the top edge 225 to the bottom edge
226 of each fin 22 is approximately parallel to an airflow
delivered from the fan 3.
[0032] On the outer side surface 211 of the fin unit 21, except for
the flat portion 212, an angle of the outer edge of each fin 22, as
shown in FIG. 4, with respect to the axial direction is preferably
in a range from approximately 10 degrees to approximately 50
degrees, more preferably from approximately 20 degrees to
approximately 40 degrees. In the present preferred embodiment, the
angle is approximately 25 degrees, for example.
[0033] As described above, the fin unit 21 of the present preferred
embodiment includes the aforementioned fins 22 and the fin
supporting portion 23. Thus, the surface area of the fins 22 (i.e.,
the area contributing to dissipation of the heat transferred from
the CPU 9 to the outside) can be increased without increasing the
entire size of the fin unit 21. Accordingly, the heat transferred
from the CPU 9 to the heat sink 2 can be more easily dissipated to
the outside and the cooling performance of the heat sink 2 can be
improved.
[0034] In addition, the aforementioned structure of the fin unit 21
can eliminate the necessity of providing excessively thin fins 22
in order to increase the number of the fins 22 and in turn increase
the total surface area of the fins 22. That is, the total surface
area of the fins 22 can be increased while the strength of each fin
22 is kept at a sufficient level. This results in a further
improvement in the cooling performance of the heat sink 2.
[0035] Moreover, it is not necessary to excessively increase the
number of the fins 22. Thus, a die or mold (i.e., a die 8 described
below) used for manufacturing the heat sink 2 does not need to have
an excessively high dimensional precision. This means that the time
and cost required for manufacturing the die or mold can be reduced.
Accordingly, the time and cost for mass-production of the heat sink
2 can be reduced.
[0036] In the present preferred embodiment, the angle between the
outer edge of each fin 22 and the center axis J1 preferably is
approximately 10 degrees or more (more preferably, approximately 20
degrees or more), as described above. Thus, the total surface area
of the fins 22 (i.e., the area contributing to dissipation of the
heat transferred to the CPU 9 to the outside) can be further
increased, thereby further improving the cooling performance of the
heat sink 2 and the cooling device 1. On the other hand, since the
angle between the outer edge of each fin 22 and the center axis J1
preferably is approximately 50 degrees or less (preferably,
approximately 40 degrees or less), the fins 22 can be arranged
approximately parallel to a direction of an airflow delivered by
the fan 3 in accordance with a possible angle of each of the blades
324 of the impeller 322. As a result, a pressure loss of the
airflow at the heat sink 2 can be reduced, enabling the airflow to
draw more heat away from the heat sink 2, thus further improving
the cooling performance of the cooling device 1.
[0037] Next, the fan 3 is described. The fan 3 arranged axially
above the heat sink 2 as shown in FIGS. 1 and 2 includes a stator
portion 31 and a rotor portion 32.
[0038] The stator portion 31 preferably includes a base portion
311, an armature (not shown), and a bearing unit (not shown). In
the present preferred embodiment, the base portion 311 is
approximately circular about the center axis J1, for example. In
this case, the diameter of the base portion 311 is substantially
the same as the diameter of the core 24 of the heat sink 2. The
base portion 311 is preferably fixed to the heat sink 2 via the
attaching portion 4. The armature is fixed to the base portion 311
to be opposite to the inner side surface of the rotor portion 32.
The armature is electrically connected to a circuit board having at
least one circuit which controls the rotation of the impeller 322
by controlling a current or signal supplied thereto from the
outside. When a current is supplied from an external power supply
(not shown) to the armature through at least one wire and the
circuit board, for example, a torque which rotates the rotor
portion 32 is generated between the armature and the rotor portion
32. The bearing unit supports the rotor portion 32 in a rotatable
manner. Exemplary bearing units are a ball bearing, a bearing
including a component made of sintered material impregnated with
lubricant, and a hydrodynamic pressure bearing.
[0039] The rotor portion 32 is arranged axially below the base
portion 311, i.e., on the heat-sink 2 side of the base portion 311.
The rotor portion 32 is supported in a rotatable manner relative to
the bearing unit of the stator portion 31. The rotor portion 32
includes the impeller 322 preferably made of resin or plastic, for
example, and a field-generating magnet. The impeller 322 includes a
hollow hub 323 and a plurality of blades 324 which are secured to
the outer side surface of the hub 323 and radially extend
therefrom. In the present preferred embodiment, the hub 323 is
approximately cylindrical and centered about the center axis J1, is
open at at least a lower end, and has substantially the same
diameter as that of the base portion 311.
[0040] The field-generating magnet is fixed to the inside of the
hub 323. In the present preferred embodiment, the field-generating
magnet is arranged in an approximately annular configuration about
the center axis J1, for example. The field-generating magnet is
arranged opposite to the armature of the stator portion 31. When a
current is supplied from an external power supply to the armature,
a torque is generated between the armature of the stator portion 31
and the field-generating magnet of the rotor portion 32, as
described above. The thus generated torque rotates the impeller 322
about the center axis J1 in a clockwise direction in FIG. 1 in the
present preferred embodiment. This rotation of the impeller 322
creates an airflow flowing from the blades 324 to the heat sink 2.
In the present preferred embodiment, the hub 323 and the blades 324
are preferably formed integrally with each other from resin or
plastic by injection molding, for example.
[0041] Injection molding is a method for producing a product by
melting a material of the product, e.g., resin or plastic, pouring
the molten material into a die or mold with a pressure applied to
the material, and then cooling and solidifying the material. This
method is suitable for mass-production because a product having a
complicated shape can be manufactured in one processing step. The
dimensional precision can be increased up to plus/minus about 0.1
mm to plus/minus about 0.05 mm by optimizing the structure of the
die or mold used for injection molding and the molding conditions.
The die or mold is typically defined by a fixed die (mold) piece
and a movable die (mold) piece. These die (mold) pieces are
combined with each other to define a single die (mold).
[0042] Returning to FIGS. 1 and 2, the attaching portion 4 of the
fan 3 preferably includes a frame 41, a plurality of supports 42, a
plurality of ribs 43, and a plurality of rotation limiting portions
44. In the present preferred embodiment, four supports 42, four
ribs 43, and four rotation limiting portions 44 are preferably
provided, for example.
[0043] The frame 41 is arranged to surround the outer periphery of
the impeller 322. The supports 42 extend axially upward from the
frame 41 and are arranged about the center axis J1 at regular
circumferential intervals. Each rib 43 is connected to the outer
periphery of the base portion 311 of the fan 3 at its one end and
extends outwardly in the radial direction substantially
perpendicular to the center axis J1. The other end of each rib 43
is connected to an associated one of the supports 42 so that the
ribs 43 support the fan 3. The rotation limiting portions 44 extend
axially from the frame 41 toward the center axis J1. An opposite
end portion of the rotation limiting portion 44 of the frame 41
faces an associated one of the four flat portions 212 (see FIG. 4)
of the outer side surface 211 of the fin unit 21. Referring to FIG.
1, each rotation limiting portion 44 is provided with an engagement
portion 441 at its axially lower end portion. The engagement
portion 441 is arranged to project inward in the radial direction
and to engage with the groove 213 in the associated flat portion
212. With this engagement, the circumferential movement of the
attaching portion 4 and the heat sink 2 relative to the other when
an impact or the like is applied from the outside can be
prevented.
[0044] Next, a preferred method of manufacturing the fin unit 21 of
the heat sink 2 is described. FIG. 5 illustrates an exemplary
manufacturing process of the fin unit 21. In this preferred
embodiment of the present invention, a plurality of fin units 21
are preferably manufactured while being connected to one another in
their axial direction, and are then separated from one another.
FIG. 6 is a perspective view of a die 8 preferably used for
manufacturing the fin unit 21. FIG. 7 shows the fin unit 21 during
manufacture. The die 8 used in this preferred embodiment has an
approximately flat plate in which a die hole 81 having a shape
corresponding to the fins 22, the fin supporting portion 23, and
the core 24 is provided.
[0045] First, a material of the fin unit 21 is softened by being
heated to a high temperature (Step S11). In this preferred
embodiment, an approximately circular cylinder of aluminum or
aluminum alloy is heated to approximately 500.degree. C. to soften
the aluminum or aluminum alloy (Step S11).
[0046] Then, Step S12 is preferably carried out as follows. As
shown in FIG. 7, the softened material 200 is placed in a container
80 for extrusion and is shaped into a hollow, approximately
cylindrical shape, for example. The thus shaped softened material
200 is pressed by a pressing device (not shown) driven by a servo
motor (not shown) against the die 8 having a shape shown in FIG. 6.
A space within the shaped material 200 corresponds to a space
inside the fin supporting unit 23 of the fin unit 21 shown in FIG.
3. The core 24 is then inserted into the space in the shaped
material 200. The space is coaxial with a center axis J2 of the die
hole 81 of the die 8 shown in FIG. 6.
[0047] The material 200 is pressed against the surface of the die 8
on one side in its axial direction parallel to the center axis J2
and is extruded through the die hole 81 from the surface of the
other side of the die 8. In the example of FIG. 7, the material 200
is pressed against the left surface of the die 8 and is extruded
from the right surface. In this manner, a metal body 201 is
obtained which extends continuously substantially parallel to the
center axis J2 of the die 8 and has portions defining a plurality
of fins 22 and a portion defining the fin supporting portion 23. A
space defined inside the fin supporting portion 23 has a center
axis coaxial with the center axis J2 of the die hole 81.
[0048] In the following description, the portions which define the
fins 22 and the portion which defines the fin supporting portion 23
are referred to as the fins 22 and the fin supporting portion 23,
respectively.
[0049] Then, a supporting member 82, which is preferably in the
shape of an approximately circular cylinder, for example, is
inserted into the space inside the fin supporting portion 23 of the
metal body 201, and connected to the metal body 201. The supporting
member 82 is then moved away from the die 8 along the center axis
J2 of the die 8 while being placed in the fin supporting portion 23
of the metal body 201, thereby drawing the metal body 201 from the
die hole 81. Please note that the supporting member 82 is arranged
with its center axis J3 substantially coincident with the center
axis J2 of the die hole 81.
[0050] While the softened metal material 200 is extruded and drawn
from the die 8 in the aforementioned manner, the supporting member
82 is rotated about its center axis J3. In this preferred
embodiment, when the supporting member 82, the die 8, and the
material 200 are viewed from the right in FIG. 7, i.e., they are
viewed from the downstream side in a direction in which the metal
body 201 is drawn, the supporting member 82 is rotated in a
counterclockwise direction. That is, the supporting member 82 is
moved from left to right in FIG. 7, while being rotated in the
counterclockwise direction when viewed from the right in FIG.
7.
[0051] Due to the rotation of the supporting member 82, the metal
body 201 exiting from the die 8 is rotated about the center axis J2
of the die hole 81 of the die 8 relative to the die hole 81. As a
result, a plurality of fins 22 are inclined with respect to the
center axis J2 of the die hole 81 (Step S12).
[0052] As described above, formation of the fins 22 and a process
for inclining the respective fins 22 with respect to the center
axis J2 are preferably carried out simultaneously in this preferred
embodiment. Thus, it is possible to easily manufacture the fin unit
21 having the fins 22 inclined with respect to the center axis J1
of the fin unit 21.
[0053] Moreover, the rotation of one of the metal body 201 and the
die 8 relative to the other is preferably achieved by rotating the
metal body 201 while the die 8 is fixed. Thus, a load applied to
the die 8 during this relative rotation can be reduced and control
of this relative rotation can be simplified. Accordingly, the fin
unit 21 of this preferred embodiment can be easily manufactured
without requiring a complicated process.
[0054] The supporting member 82 is connected to a servo motor which
operates at a controlled rotation speed in synchronization with the
servo motor for pressing the metal 200 against the die 8. The
reason for this is now described. A relationship between the
rotation speed of the supporting member 82 for supporting a portion
around a leading end of the metal body 201 and the rotation speed
of a portion of the metal body 201 near the die 8, i.e., a
relationship of the rotation speed between both axial ends of the
metal body 201 is changed depending on the axial distance between
the leading end of the metal body 201 and the die 8. Thus, it is
necessary to control the rotation speed of the metal body 201 at
both axial ends so that inclination of the fins 22 with respect to
the center axis J2 is substantially the same at both axial ends of
the metal body 201. For this reason, the rotation of the supporting
member 82 is performed by using the servo motor and the rotation
speed thereof is controlled. In this manner, it is possible to
control the rotation speed of the metal body 201 near the die 8
with high precision and therefore manufacture the fin unit 21 with
high precision. In addition, the fin unit 21 can be made with even
higher precision by controlling a rate at which the metal body 201
is drawn from the die 8 by using another servo motor synchronized
with the servo motor for rotating the supporting member 82.
[0055] Step S13 is now described. After the metal body 201 is
formed and shaped by extrusion and drawing in Steps S11 and S12,
the metal body 201 is cooled by, for example, air delivered by an
air-blowing apparatus. The thus cooled metal body 201 is subjected
to a heat treatment for improving the hardness and strength
thereof. In this preferred embodiment, the metal body 201 is heated
to approximately 185.degree. C.
[0056] In the following Step S14, the metal body 201 is cooled by
water, air delivered by an air-blowing apparatus, or the like.
Then, the metal body 201 is cut at a plurality of points in its
longitudinal direction (which is substantially parallel to the
center axis J2 of the die hole 81) in such a manner that a cut
plane thereof is substantially perpendicular to the longitudinal
direction. In this manner, a plurality of fin units 21 (see FIG. 3)
each having a plurality of fins 22 and the fin supporting portion
23 are easily and rapidly manufactured while being separated from
one another.
[0057] In the above-described method, the fin units 21 are cut
after the heat treatment of the heat body 201 in Steps S13 and S14.
However, the order of these steps is not limited to the above. The
heat treatment may be individually carried out for each of the fin
units 21 after they are separated from each other. Alternatively,
the heat treatment and separation of the fin units 21 may be
carried out at the same time.
[0058] In the following Step S15, the outer peripheral surface 211
of each fin unit 21 obtained in Step S14 is partially cut, thereby
forming flat portions 212 and grooves 213 (see FIG. 4). Then, the
inner side surface of the hollow fin supporting portion 23 of each
fin unit 21 is finished by CNC (computer numerical control)
machining which can provide a high precision of processing, e.g.,
broaching. The manufacturing process of the fin unit 21 preferably
ends with this step.
[0059] After the fin unit 21 is manufactured, the fin unit 21 is
heated again, and the core 24 is inserted into the fin supporting
portion 23 of the fin unit 21 and fixed thereto by shrink fitting,
for example. In this preferred embodiment, the fin unit 21 is
heated to approximately 300.degree. C. and the core 24 in the shape
of the approximately circular cylinder is inserted into and fitted
to the fin supporting portion 23. Thus, the heat sink 2 is
manufactured. Then, the clip 25 is secured to the lower end portion
of the core 24 of the heat sink 2, as shown in FIG. 4.
Additionally, the fan 3 is attached on the upper side of the heat
sink 2, as shown in FIGS. 1 and 2, thereby completing the cooling
device 1.
[0060] As described above, in Step S15 finishing is performed for
the inner side surface of the fin supporting portion 23 of the fin
unit 21 obtained by cutting the metal body 201. This finishing can
improve adhesion of the inner side surface of the fin supporting
portion 23 and the outer side surface of the core 24 to each other,
i.e., adhesion of the fin unit 21 and the core 24 to each other.
Consequently, thermal conductivity from the core 24 to the fin unit
21 is improved, resulting in the efficient transfer of heat from a
heat source such as the CPU 9 to the fin unit 21. Thus, the cooling
performance of the heat sink 2 can be further improved.
[0061] The fin unit 21 of this preferred embodiment is made of
aluminum or aluminum alloy. Aluminum and aluminum alloy are
excellent in thermal conductivity and workability, and easily
available. Therefore, when the heat sink 2 is made of aluminum or
aluminum alloy, heat resistance of the heat sink 2 can be reduced
and the cooling performance of the heat sink 2 is improved.
Moreover, the use of aluminum or aluminum alloy as the material of
the heat sink 2 enables easy manufacturing of the fin unit 21 and
reduces the manufacturing cost of the fin unit 21.
Second Preferred Embodiment
[0062] A fin unit of a heat sink according to a second preferred
embodiment of the present invention is now described. The fin unit
21a of the second preferred embodiment preferably has substantially
the same structure as the fin unit 21 shown in FIGS. 3 and 4. In
the following description, respective components of the fin unit
21a are labeled with the same reference signs as those for the
corresponding components of the fin unit 21. The fin unit 21a of
the present preferred embodiment is preferably manufactured in
substantially the same manner as the fin unit 21 of the first
preferred embodiment, except that while the metal body 201 is
extruded and drawn from the die 8 (see FIG. 7) and rotated, the
rotation speed of the metal body 201 is changed.
[0063] FIG. 8 shows the outer side surface 211 of the fin unit 21a
of the present preferred embodiment in an enlarged view. In this
description, the outer side surface of the fin unit means an
approximately cylindrical shape defined by the outer peripheral
edges of the fins 22 along the circumferential direction. FIG. 9
shows the outer side surface 211 of the fin unit 21 of the first
preferred embodiment in an enlarged view. In FIGS. 8 and 9, the
outer side surface 211 in a state before the flat portions 212 (see
FIGS. 1 to 4) are formed are shown for facilitating the
understanding of these drawings. Moreover, the number of the fins
22 shown in FIGS. 8 and 9 is different from the actual number.
Please note that the number of the fins 22 is not specifically
limited.
[0064] In the manufacturing method of the present preferred
embodiment, while a portion of the metal body 201 which corresponds
to a single fin unit 21a is extruded and drawn from the die 8, the
rotation speed of the supporting member 82 (FIG. 7) is gradually
changed such that in that portion of the metal body 201, an
inclination angle of each fin 22 with respect to the center axis J2
of the die 8 (see FIG. 6) is changed along the center axis J2. More
specifically, the inclination angle of each fin 22 with respect to
the center axis J2 is larger in a region near the supporting member
82 (the upper portion in FIG. 8) than in a region axially apart
from the supporting member 82 (the lower portion in FIG. 8). For
example, the inclination angle of each fin 22 with respect to the
center axis J2 of the die 8 at a radially outer edge of that fin 22
is larger than that at any portion inside the radially outer edge
of that fin 22.
[0065] In other words, while attention is focused on a portion of
the metal body 201 which corresponds to a single fin unit, each fin
22 is curved to be convex toward the supporting member 82 (i.e.,
upward in FIG. 8) on a plane obtained by connecting supporting
member 82 side ends of the fins 22 (i.e., upper ends in FIG. 8) and
opposite ends thereof to each other.
[0066] In the manufacturing method of the fin unit 21a of this
preferred embodiment, extrusion and drawing of the metal body 201
and rotation of the metal body 201 relative to the die hole 81 are
preferably carried out simultaneously as in the first preferred
embodiment. Thus, the fin unit 21a having the fins 22 respectively
inclined with respect to the center axis J1 of the fin unit 21a can
be easily manufactured.
[0067] Especially in this preferred embodiment, each fin 22 is
curved with respect to the center axis J2 due to the change in the
rotation speed of the metal body 201. That is, an angle formed by
the outer peripheral edge of each fin 22 and the center axis J2 is
varied. With this configuration of the fins 22, the surface area of
the fins 22 can be increased as compared with a case where the fins
22 are not curved but are straight, thus improving the cooling
performance of the heat sink. On the other hand, according to the
manufacturing method of the heat sink in the first preferred
embodiment, control of the rotation speed of the supporting member
82 (see FIG. 7) can be simplified. Thus, the manufacturing process
can be simplified.
[0068] Although the preferred embodiments of the present invention
are described above, the present invention is not limited thereto.
The present invention can be implemented by varying the
aforementioned preferred embodiments in various ways.
[0069] In the fin unit 21 of the first preferred embodiment, it is
not always necessary that each fin 22 is inclined with respect to
the center axis J1 to be approximately parallel to an airflow from
the fan 3 over the entire length thereof. The effect that the
airflow can enter between the fins 22 smoothly can be achieved by
inclining at least an axially upper portion of each fin 22 with
respect to the center axis J1 so that the portion is approximately
parallel to the airflow from the fan 3. Here, the axially upper
portion of each fin 22 is a fan 3 side portion of each fin 22 in
the axial direction. As a result, a pressure loss of the airflow
from the fan 3 at the heat sink 2 can be reduced, and the amount of
heat the airflow can receive from the heat sink 2 can be increased.
Thus, the cooling performance of the cooling device 1 is improved.
In this case, when the outer peripheral edge of the inclined
portion of each fin 22 is inclined with respect to the center axis
J1 of the fin unit 21 at an angle in a range from approximately
10.degree. to approximately 50.degree., more preferably
approximately 20.degree. to approximately 40.degree., the cooling
performance of the cooling device 1 can be further improved.
[0070] In the cooling device 1 of the first preferred embodiment,
it is not always necessary that the axis of rotation of the fan 3
is coincident with the center axis J1 of the fin unit 21. The axis
of rotation of the fan 3 may be spaced from the center axis J1, as
long as they are substantially parallel to each other.
[0071] The heat sink 2 may be provided with a recess on the axially
upper end surface of the core 24. The recess may have any shape,
for example, a tapered shape in which an inner diameter thereof is
reduced as it moves axially downward, a shape of a polygonal
column, a conical shape. In this case, it is possible to reduce the
weight of the core 24 while keeping the cooling performance of the
heat sink 2 at a level required by a customer, or even at a higher
level. Thus, the manufacturing cost of the heat sink 2 can be
reduced.
[0072] In the fin 22 of the first preferred embodiment, two or more
outer portions 222 are formed radially outside the radially outer
end of the inner portion 221 which is located around the center of
each fin 22 when the fin 22 is viewed along the center axis J1.
However, it is not always necessary that each fin 22 is divided
into a plurality of outer portions at the radially outer end of the
inner portion 221. In other words, each fin 22 may be defined by a
single plate along its entire length with no branching portion.
[0073] Moreover, the core 24 is preferably arranged inside the fin
supporting portion 23 in the first preferred embodiment. However,
the core 24 may be omitted. The core 24 may be omitted if the fin
supporting portion 23 is formed into an approximately cylindrical
shape which is not hollow. In this case, the lower end of the fin
supporting portion 23 is in contact with a heat source such as the
CPU 9.
[0074] In the manufacturing method of any of the above-described
preferred embodiments, it is not always necessary that the metal
material 200 is heated and softened. The metal material 200 may be
heated to a temperature lower than a temperature at which the
material 200 is softened.
[0075] In Step S12 of the aforementioned manufacturing method, the
metal material 200 is extruded from the die hole 81 of the die 8
and the extruded metal body 201 is drawn from the die hole 81 while
being supported by the supporting member 82. However, the present
invention is not limited thereto. Only one of the steps of
extruding and drawing of the metal material 200 may be
performed.
[0076] The rotation of the metal body 201 relative to the die hole
81 in Step S12 is not always achieved by rotating the metal body
201 relative to the fixed die 8. Alternatively, while the metal
body 201 is extruded and/or drawn from the die 8 without being
rotated, the die 8 maybe rotated about the center axis J2 thereof.
Alternatively, while the metal body 201 is extruded and/or drawn
from the die 8, both the metal body 201 and the die 8 may be
rotated.
[0077] In the manufacturing method of the aforementioned preferred
embodiments, a plurality of fin units 21 are preferably formed from
a single continuous block of material 200. However, the above
manufacturing method can be applied to a case where only one fin
unit 21 is formed from a single continuous block of material 200.
In this case, the fin unit is obtained by cutting both longitudinal
ends (both axial ends) of the metal body 201 obtained from the die
8, which is continuous in the axial direction.
[0078] It is not always necessary to use aluminum or aluminum alloy
as the material of the fin unit. Other metals or alloys which can
be processed by extrusion and/or drawing, e.g., copper and iron may
be used. Moreover, the material of the core 24 is not limited to
copper, as described above. The same material as the fin unit,
e.g., aluminum or aluminum alloy, may be used for the core 24. In
this case, the core 24 may be integral with the fin supporting
portion 23 when the fin unit is manufactured.
[0079] The heat sink of any of the above preferred embodiments is
not necessarily used together with the fan 3 attached thereon to
define the cooling device 1. The heat sink of any of the above
preferred embodiments may be attached to a heat source by itself so
as to dissipate heat transferred from the heat source.
[0080] 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.
* * * * *