U.S. patent application number 14/136228 was filed with the patent office on 2014-04-17 for axial-flow fan.
This patent application is currently assigned to Sanyo Denki Co., Ltd.. The applicant listed for this patent is Sanyo Denki Co., Ltd.. Invention is credited to Tomoaki Ikeda, Katsumichi Ishihara, Masashi Miyazawa, Honami Oosawa.
Application Number | 20140105763 14/136228 |
Document ID | / |
Family ID | 38087735 |
Filed Date | 2014-04-17 |
United States Patent
Application |
20140105763 |
Kind Code |
A1 |
Ishihara; Katsumichi ; et
al. |
April 17, 2014 |
AXIAL-FLOW FAN
Abstract
An axial-flow fan according to the present disclosure can
increase the amount of the airflow and simultaneously reduce the
noise level. A plurality of stationary blades 11A to 11D are
curved, in a convex manner, toward a rotating direction of an
impeller. The plurality of stationary blades 11A to 11D are
generally inclined so that discharge-side edge portions 11d thereof
are located more forward than suction-side edge portions 11c
thereof in the rotating direction. An inclination angle .theta.4 of
each of the plurality of stationary blades 11A to 11D in the
vicinity of the external end portion 11a is larger than the
inclination angle .theta.3 in the vicinity of the internal end
portion 11b. The inclination angle is gradually changed from the
vicinity of the external end portion 11a toward the vicinity of the
internal end portion 11b.
Inventors: |
Ishihara; Katsumichi;
(Nagano, JP) ; Oosawa; Honami; (Nagano, JP)
; Miyazawa; Masashi; (Nagano, JP) ; Ikeda;
Tomoaki; (Nagano, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sanyo Denki Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Sanyo Denki Co., Ltd.
Tokyo
JP
|
Family ID: |
38087735 |
Appl. No.: |
14/136228 |
Filed: |
December 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11563982 |
Nov 28, 2006 |
|
|
|
14136228 |
|
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Current U.S.
Class: |
417/354 |
Current CPC
Class: |
F04D 25/0646 20130101;
F04D 29/544 20130101; H05K 7/20172 20130101; F04D 29/661 20130101;
F04D 25/0613 20130101 |
Class at
Publication: |
417/354 |
International
Class: |
F04D 25/06 20060101
F04D025/06; F04D 29/66 20060101 F04D029/66 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2005 |
JP |
2005-346880 |
Claims
1. An axial-flow fan comprising: a fan housing including an air
channel having an air discharge opening and an air suction opening,
an impeller having a plurality of blades and disposed inside the
fan housing, a rotor to which the impeller is fixed and which
rotates about a shaft, a stator disposed corresponding to the
rotor, a motor case including a bottom wall portion located at a
side of the air discharge opening and a peripheral wall portion
formed continuously with the bottom wall portion and extending
toward the air suction opening, the stator being fixed to the
bottom wall portion, the motor case located inside the air channel,
and a plurality of stationary blades disposed at intervals in a
rotating direction of the rotor and located inside the air
discharge opening of the air channel, each of the plurality of
stationary blades connecting the motor case and the fan housing,
each of the plurality of stationary blades having an external end
portion connected to an inner wall portion of the fan housing, an
internal end portion connected to the peripheral wall portion of
the motor case, a discharge-side edge portion formed between the
external end portion and the internal end portion and located at a
side of the air discharge opening, and a suction-side edge portion
formed between the external end portion and the internal end
portion and located at a side of the air suction opening, each of
the plurality of stationary blades being curved, in a convex
manner, toward the rotating direction of the rotor, all or most of
stationary blades in the plurality of stationary blades being
generally inclined so that the discharge-side edge portion of the
stationary blade is located more forward than the suction-side edge
portion thereof in the rotating direction, wherein a virtual plane
is defined along the air discharge opening and an orthogonal
virtual plane being orthogonal to the virtual plane is defined as
intersecting the discharge-side edge portion and the suction-side
edge portion such that the orthogonal virtual plane is orthogonal
to both the discharge-side edge portion and the suction-side edge
portion, and a virtual line is defined to pass through a first
intersection where the orthogonal virtual plane intersects the
discharge-side edge portion and a second intersection where the
orthogonal virtual plane intersects the suction-side edge portion,
wherein the discharge-side edge portion extends along and parallel
to the virtual plane, wherein an inclination angle is defined as an
angle between the virtual plane and the virtual line, wherein the
inclination angle for the stationary blades in the vicinity of the
external end portions is larger than the inclination angle the
stationary blades in the vicinity of the internal end portions, and
wherein the inclination angle gradually and continuously changes to
gradually become larger from the vicinity of the internal end
portion to the vicinity of the external end portion such that any
location on the stationary blade, from the vicinity of the external
end portion to the vicinity of the internal end portion, has a
larger inclination angle as compared to locations on the blade that
that are relatively closer to the vicinity of the internal end
portion.
2. The axial-flow fan according to claim 1, wherein the air channel
has a cross-sectional shape, as taken in a direction where an axial
line is a perpendicular line, which becomes larger toward the air
discharge opening in an area from where the impeller exists to
where the air discharge opening is located.
3. The axial-flow fan according to claim 2, wherein the inclination
angle in the vicinity of the external end portion is within a range
of 50.degree. to 60.degree., and the inclination angle in the
vicinity of the internal end portion is within a range of
45.degree. to 55.degree..
4. The axial-flow fan according to claim 1, wherein one stationary
blade among the plurality of stationary blades has a structure
which receives therein a plurality of lead wires for supplying
electric power to the stator, and the stationary blades other than
the one stationary blade are the most of the plurality of
stationary blades.
5. The axial-flow fan according to claim 1, wherein an outer
surface of the bottom wall portion of the motor case is located
closer to the air suction opening than the discharge-side edge
portions of all or most of the plurality of the stationary blades
are located.
6. The axial-flow fan according to claim 5, wherein the outer
surface of the bottom wall portion of the motor case is composed of
a flat bottom surface and an outer peripheral surface portion
continuous with the flat bottom surface, and the outer peripheral
surface portion is gradually curved from the bottom surface toward
an outer peripheral surface of the peripheral wall portion.
7. The axial-flow fan according to claim 4, wherein all or most of
the plurality of stationary blades each include an extended portion
extending on the bottom wall portion of the motor case, and the
extended portion has a guide surface for guiding a part of air
flowing along the stationary blades toward the bottom surface of
the bottom wall portion.
8. The axial-flow fan according to claim 7, wherein the extended
portion further has an extended guide surface formed continuously
with the guide surface and extending toward the rotating
direction.
9. The axial-flow fan according to claim 5, wherein all or most of
the plurality of stationary blades each include an extended portion
extending on the bottom wall portion of the motor case, and the
extended portion has a guide surface for guiding a part of air
flowing along the stationary blades toward the bottom surface of
the bottom wall portion.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an axial-flow fan used for
cooling an electric component or the like.
BACKGROUND OF THE INVENTION
[0002] FIG. 16 is a perspective view of an axial-flow fan equipped
with stationary blades shown in FIG. 1 of U.S. Design Pat. No.
D506,540 (Official Gazette). FIG. 17 is a rear view of a
conventional axial-flow fan shown in FIG. 5 of the same Official
Gazette. As shown in these figures, in conventional axial-flow fans
equipped with stationary blades, each of a plurality of stationary
blades 101 is curved, in a convex manner, toward one side in a
circumferential direction of a shaft. The plurality of stationary
blades 101 are generally inclined so that the suction-side edge
portions 101 are located at an opposite side to the suction-side
edge portions in the circumferential direction of the shaft. The
plurality of stationary blades are inclined at a substantially
constant angle.
[0003] However, it is impossible for the conventional axial-flow
fan to increase an amount of airflow and to simultaneously reduce
the noise level without modifying the structure thereof.
SUMMARY OF THE INVENTION
[0004] An object of the present invention is to provide an
axial-flow fan capable of increasing the amount of airflow and
simultaneously reducing the noise level.
[0005] Another object of the present invention is to provide an
axial-flow fan capable of entirely cooling an object to be cooled
even when the distance between an object to be cooled and an air
discharge opening of the axial-flow fan is short.
[0006] An axial-flow fan of the present invention comprises a fan
housing including an air channel having an air discharge opening
and an air suction opening, an impeller having a plurality of
blades and disposed inside the fan housing, a rotor to which the
impeller is fixed and which rotates about a shaft, a stator
disposed corresponding to the rotor, a motor case to which the
stator is fixed, and a plurality of stationary blades connecting
the motor case and the fan housing. The motor case includes a
bottom wall portion located at a side of the air discharge opening
and a peripheral wall portion formed continuously with the bottom
wall portion and extending toward the air suction opening. The
stator is fixed to the bottom wall portion. The plurality of
stationary blades are disposed at intervals in a rotating direction
of the rotor and located inside the air discharge opening of the
air channel. Each of the plurality of stationary blades has an
external end portion connected to an inner wall portion of the fan
housing, an internal end portion connected to the peripheral wall
portion of the motor case, a discharge-side edge portion formed
between the external end portion and the internal end portion and
located at a side of the air discharge opening, and a suction-side
edge portion formed between the external end portion and the
internal end portion and located at a side of the air suction
opening. Each of a plurality of stationary blades is curved, in a
convex manner, toward the rotating direction of the rotor. All or
most of stationary blades among the plurality of stationary blades
are generally inclined so that the discharge-side edge portions
thereof are located more forward than the suction-side edge
portions thereof in the rotating direction. When one of the
stationary blades is not utilized as means for receiving therein
lead wires to supply electric power to the motor, all of the
plurality of stationary blades have basically the same structure.
When one stationary blade among the stationary blades is utilized
as means for receiving therein the lead wires to supply electric
power to the motor, the plurality of stationary blades except for
the one stationary blade (i.e., most of stationary blades) have
basically the same structure.
[0007] In the axial-flow fan of the present invention, an
inclination angle for all or most of the plurality of stationary
blades in the vicinity of the external end portion is larger than
the inclination angle in the vicinity of the internal end portion,
and the inclination angle is gradually changed from the vicinity of
the external end portion toward the vicinity of the internal end
portion. Herein, the inclination angle is defined as an angle
formed by a virtual plane along the air discharge opening and a
virtual line which passes through a first intersection where an
orthogonal virtual plane, which is defined as being orthogonal to
the virtual plane and also orthogonal to the discharge-side edge
portion and the suction-side edge portion, intersects with the
discharge-side portion, and also passes through a second
intersection where the orthogonal virtual plane intersects with the
suction-side edge portion.
[0008] The flow rate of air discharged from the air discharge
opening of the axial-flow fan tends to become faster in an area
closer to the fan housing (in an outer side) while the flow rate
tends to become slower in an area closer to the motor case (in an
inner side). This tendency is the same when stationary blades of a
simple shape are used. According to the present invention, by
arranging all or most of the plurality of stationary blades as
described above, the flow rate of the airflow flowing in the
vicinity of the internal end portions of the stationary blades is
increased with respect to the flow rate of the airflow flowing in
the vicinity of the external end portions of the stationary blades.
The flow rate of the airflow is gradually increased from the
external end portion toward the internal end portion of the
stationary blades. As a result, the flow rate of the air discharged
from the air discharge opening is generally uniformized as much as
possible, thereby increasing an amount of the airflow and
simultaneously reducing the noise level.
[0009] In a small-size axial-flow fan, when the air channel has a
cross-sectional shape, as taken in a direction where an axial line
is a perpendicular line, which becomes larger toward the air
discharge opening in an area from where the impeller exists to
where the air discharge opening is located, the inclination angle
is preferably defined as follows; the inclination angle in the
vicinity of the external end portion may be within a range of
50.degree. to 60.degree., and the inclination angle in the vicinity
of the internal end portion may be within a range of 45.degree. to
55.degree.. It will be easily understood by those skilled in the
art that the preferred ranges of the respective inclination angles
vary depending on the shape and number of the rotating blades, the
shape and number of the stationary blades, the shape of the inner
wall portion of the fan housing (the shape of the air channel) and
the like.
[0010] One stationary blade among the plurality of stationary
blades may be formed to receive therein the plurality of the lead
wires for supplying electric power to the stator. In this case, the
plurality of stationary blades other than the one stationary blade
are the most of the plurality of stationary blades.
[0011] An outer surface of the bottom wall portion of the motor
case may be located closer to the air suction opening than the
discharge-side edge portions of all or most of the plurality of the
stationary blades are located. With this arrangement, a part of
airflow flowing along the stationary blade gets into an area near a
bottom surface of the motor case, and then blown out of the air
discharge opening. As a result, even when the distance between an
object to be cooled and the air discharge opening of the axial-flow
fan is short, the air discharged from the axial-flow fan can be
blown onto a part of the object to be cooled that is located
opposing to the motor case of the axial-flow fan, thereby entirely
cooling the object to be cooled.
[0012] The outer surface of the bottom wall portion of the motor
case is composed of a flat bottom surface and an outer peripheral
surface portion continuous with the flat bottom surface. It should
be noted that the flat bottom surface includes not only an entirely
flat surface but also a surface of which the major part is flat.
For example, a bearing for supporting the shaft may be disposed in
the central area of the bottom surface. In this case, the outer
peripheral surface portion is preferably shaped to be gradually
curved from the bottom surface toward the outer peripheral surface
of the peripheral wall portion. With this arrangement, the air
flowing along the stationary blades toward the motor case can
smoothly run onto the bottom surface of the motor case. As a
result, the amount of the air, which flows from the bottom surface
of the motor case toward the air discharge opening, can be
increased.
[0013] Preferably all or most of the plurality of stationary blades
each include an extended portion extending on the bottom wall
portion of the motor case, and the extended portion includes a
guide surface for guiding a part of air flowing along the
stationary blades toward the bottom surface of the bottom wall
portion. With such a guide surface, the air can actively be guided
onto the bottom wall portion along the guide surface.
[0014] Further, the extended portion preferably includes an
extended guide surface, which is formed continuously with the guide
surface and is extending toward the rotating direction. The
extended guide surface helps the airflow, which has run onto the
bottom wall portion of the motor case, get spirally out of the air
discharge opening smoothly.
[0015] According to the present invention, the amount of airflow
produced by the axial-flow fan can be increased more and
simultaneously the noise level can be reduced more than ever.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of an axial-flow fan according
to an embodiment of the present invention as viewed from the right
upper front side thereof, where lead wires are omitted.
[0017] FIG. 2 is a front view of the axial-flow fan of the
embodiment shown in FIG. 1.
[0018] FIG. 3 is a rear view of the axial-flow fan of the
embodiment shown in FIG. 1.
[0019] FIG. 4 is a right-side view of the axial-flow fan shown in
FIG. 2.
[0020] FIG. 5 is a cross-sectional view of the axial-flow fan as
taken along line 5-5 in FIG. 4 where an internal structure of a
motor is omitted.
[0021] FIG. 6 is a cross-sectional view of the axial-flow fan as
taken along line 6-6 in FIG. 4 where the internal structure of the
motor is omitted.
[0022] FIG. 7 is a cross-sectional view as taken along line 7-7 in
FIG. 2.
[0023] FIG. 8 illustrates cross-sectional shapes of a rotating
blade and a stationary blade in order to explain the respective
shapes of the rotating blade and the stationary blade.
[0024] FIG. 9A is a perspective view showing airflow paths in this
embodiment; and FIG. 9B is a perspective view showing airflow paths
in a conventional arrangement.
[0025] FIG. 10A is a fragmentary view of a stationary blade for
illustrating an inclination angle; FIG. 10B is a cross-sectional
view of the stationary blade as taken in the vicinity of an
internal end portion; and FIG. 10C is a cross-sectional view of the
stationary blade as taken in the vicinity of an external end
portion.
[0026] FIGS. 11A to 11C respectively show the structures and
inclination angles of test axial-flow fans prepared for verifying
the effects, which are obtained by defining inclination angles of
the stationary blades in the vicinity of the external end portions
thereof to be larger than those of the stationary blades in the
vicinity of the internal end portions, and changing the inclination
angle gradually from the vicinity of the external end portion
toward the vicinity of the internal end portion.
[0027] FIG. 12 is a graphical chart showing measurement results of
static pressure--airflow characteristics for the three fans shown
in FIGS. 11A to 11C (wherein the arrangements are the same except
for the shape of the stationary blades and the number of rotations
is kept constant).
[0028] FIG. 13 is a table showing the measurement results.
[0029] FIG. 14. is a graphical chart showing measurement results of
static pressure--airflow characteristics for three fans which
respectively use the stationary blades shown in FIGS. 11A to
11C.
[0030] FIG. 15 is a table showing the measurement results.
[0031] FIG. 16 is a perspective view of a conventional axial-flow
fan.
[0032] FIG. 17 is a rear view of the conventional axial-flow
fan.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] An embodiment of an axial-flow fan according to the present
invention will be hereinafter described in detail with reference to
the accompanying drawings. FIG. 1 is a perspective view of an
axial-flow fan 1 according to an embodiment of the present
invention as viewed from the right upper front side thereof, where
lead wires are omitted. FIG. 2 is a front view of the axial-flow
fan 1 of the embodiment shown in FIG. 1, and FIG. 3 is a rear view
thereof. FIG. 4 is a right-side view of the axial-flow fan 1 shown
in FIG. 2. FIG. 5 is a cross-sectional view of the axial-flow fan 1
as taken along line 5-5 in FIG. 4 where an internal structure of a
motor is omitted. FIG. 6 is a cross-sectional view of the
axial-flow fan 1 as taken along line 6-6 in FIG. 4 where the
internal structure of the motor is omitted. FIG. 7 is a
cross-sectional view of the axial-flow fan as taken along line 7-7
in FIG. 2.
[0034] Referring to these figures, the axial-flow fan 1 comprises a
fan housing 3 and an impeller 7 equipped with seven rotating blades
5, which is rotatably disposed inside the fan housing 3. As shown
in FIG. 7, the axial-flow fan 1 further comprises a motor 9 and
five stationary blades 11A to 11E. The motor 9 comprises a rotor 9A
and a stator 9B. The rotor 9A is mounted with the impeller 7. In
this embodiment, the rotor 9A includes a rotating shaft 8 and a
plurality of permanent magnets M which are fixed onto a peripheral
wall portion of a cup-shaped member 12 fixedly mounted onto the
rotating shaft 8. The stator 9B includes a stator core and
excitation windings wound around the stator core. The stator 9B is
fixed to a motor case 10. Inside the motor case 10, a circuit board
mounted with a circuit for supplying excitation current to the
excitation windings is fixedly installed. The motor case 10
includes a bottom wall portion 10A located at a side of an air
discharge opening 16 which will be described later, and a
peripheral wall portion 10B continuously formed with the bottom
wall portion 10A and extending toward an air suction opening 14
which will be described later. An outer surface of the bottom wall
portion 10A of the motor case 10 is composed of a flat bottom
surface 10C and an outer peripheral surface portion 10D continuous
with the flat bottom surface 10C. The outer peripheral surface
portion 10D is gradually curved from the bottom surface 10C toward
an outer peripheral surface of the peripheral wall portion 10B.
[0035] The fan housing 3 has a suction-side flange 13 of an annular
shape at one side in an extending direction of an axial line AL of
the rotating shaft 8 (refer to FIG. 7) and a discharge-side flange
15 of an annular shape at the other side in the extending direction
of the axial line. The fan housing 3 also includes a cylindrical
portion 17 between the flanges 13 and 15. An air channel 19, which
has the air suction opening 14 and the air discharge opening 16
respectively disposed at either end thereof, is an internal space
formed by the suction-side flange 13, the discharge-side flange 15
and the cylindrical portion 17. A tapered surface 21 is formed
inside the suction-side flange 13 as shown in FIG. 3 and FIG. 7.
The tapered surface 21 is curved so that the distance between the
axial line of the rotating shaft 8 and the tapered surface 21
gradually becomes larger toward the air suction opening 14. As a
result, a space 22, the cross sectional area of which becomes
larger toward the air suction opening 14, is formed inside the
suction-side flange 13. Also, a tapered surface 23 is formed inside
the discharge-side flange 15 as shown in FIG. 2 and FIG. 7. The
tapered surface 23 is curved so that the distance between the axial
line of the rotating shaft 8 and the tapered surface 23 gradually
becomes larger toward the air discharge opening 16. As a result, a
space 24, the cross sectional area of which becomes larger toward
the air discharge opening 16, is formed inside the discharge-side
flange 15. The suction-side flange 13 and the discharge-side flange
15 are respectively outlined in a substantially rectangular shape.
A through-hole allowing a screw to pass therethrough is formed each
in four corners of each of the flanges.
[0036] The impeller 7 includes a rotating blade fixing member 6 of
a cup-like shape. Seven rotating blades 5 are fixed onto a
peripheral wall portion of the rotating blade fixing member 6 as
shown in FIG. 7. The cup-shaped member 12 is fixed inside the
peripheral wall portion of the rotating blade fixing member 6, and
the plurality of permanent magnets M constituting a part of the
rotor of the motor 9 are fixed onto the peripheral wall of the
cup-shaped member 12.
[0037] FIG. 8 illustrates cross-sectional shapes of a rotating
blade 5 and a stationary blade 11C in order to explain the
respective shapes of the rotating blade 5 and the stationary blade
11A to 11D. In FIG. 8, an arrow of a solid line indicates a
rotating direction of the rotating blade 5, and arrows of broken
lines respectively indicate the airflow direction. FIG. 8 shows a
cross-sectional view of the stationary blade 11C as taken along
line 8-8 in FIG. 2. FIG. 8 also shows a cross-sectional view of the
rotating blade 5 as taken in the same manner as the cross-sectional
view of the stationary blade 11C. Each of the seven rotating blades
5 is curved in such a manner that a concave portion 5a is opened
toward a rotating direction of the impeller 7 as shown FIG. 8
(clockwise as viewed in FIG. 2; counterclockwise as viewed in FIG.
3). As shown in FIG. 8, the stationary blade 11C is curved in such
a manner that a concave portion is opened toward a direction
opposite to the rotating direction of the impeller 7 when viewed in
the cross-sectional view taken along line 8-8 in FIG. 2.
[0038] Five stationary blades 11A to 11E are disposed at intervals
in the rotating direction of the impeller 7 (rotor) and located
inside the air discharge opening 16 of the air channel 19 as shown
in FIG. 1 and FIG. 2. Each of the four stationary blades 11A to 11D
has an external end portion 11a connected to an inner wall portion
of the fan housing 3, an internal end portion 11b connected to the
peripheral wall portion 10B of the motor case 10, a discharge-side
edge portion 11c formed between the external end portion 11a and
the internal end portion 11b and located at a side of the air
discharge opening 16, and a suction-side edge portion 11d formed
between the external end portion 11a and the internal end portion
11b and located at a side of the air suction opening 14. In this
embodiment, one blade 11E of the stationary blades has a groove
portion 27 that receives therein a plurality of lead wires 25 for
supplying electric power to the excitation windings of the stator
9B. The groove portion 27 is opened toward the air discharge
opening 16. The discharge-side edge portion 11c of the one
stationary blade 11E is composed of two divided edges 11c1 and 11c2
respectively located at either side of the groove portion 27. The
two divided edges 11c1 and 11c2 are inclined in the vicinity of the
internal end portion 11b so that the flat bottom surface 10C of the
bottom wall portion 10A of the motor case 10 and the two divided
edges 11c1 and 11c2 are flush with each other. With this
arrangement, the lead wires 25 can be easily inserted into the
groove portion 27.
[0039] In this embodiment, as shown in FIGS. 1, 2 and 7, the outer
surface (bottom surface 10C) of the bottom wall portion 10A of the
motor case 10 is located closer to the air suction opening 14 than
the discharge-side edge portions 11c of the four stationary blades
11A to 11D are located. In other words, the discharge-side edge
portions 11c of the four stationary blades 11A to 11D are located
closer to the air discharge opening 16 than the outer surface
(bottom surface 10C) of the bottom wall portion 10A of the motor
case 10 is located. With this arrangement, a part of air flowing
along the stationary blades 11A to 11E runs into an area above the
bottom surface 10C of the motor case 10, and then the air is
discharged from the air discharge opening 16 as shown in FIG. 9(A),
in which airflow paths are indicated with arrows. As a result, even
when the distance between an object to be cooled and the air
discharge opening of the axial-flow fan 1 is short, the air flow
discharged from the axial-flow fan can be blown onto a part of the
object to be cooled that is located opposing to the motor case 10
of the axial-flow fan 1. Thus, the object to be cooled can entirely
be cooled. For the purpose of comparison, FIG. 9(B) shows airflow
paths when discharge-side edge portions 11c' of stationary blades
11A' to 11D' and the bottom surface of the bottom wall portion 10A
of the motor case 10 are flush with each other; i.e., the
discharge-side edge portions 11c and the bottom surface of the
bottom wall portion 10A of the motor case 10 are located at the
same height. A space S shown in FIG. 9(B) is an area where the air
does not flow.
[0040] As shown in FIGS. 1, 2 and 7, each of the four stationary
blades 11A to 11D is formed integrally with an extended portion 11e
that extends on the bottom wall portion 10A of the motor case 10.
Each of the extended portions 11e has a guide surface 11f for
guiding a part of the air flowing along the stationary blades 11A
and 11D toward the bottom surface 10C of the bottom wall portion
10A. The guide surface 11f extends along an outer peripheral
surface portion 10D which is curved from the outer surface of the
peripheral wall portion 10B of the motor case 10 toward the bottom
surface 10C of the bottom wall portion 10A, and then extends on the
bottom surface 10C. Such guide surface 11f allows the air to be
actively guided onto the bottom wall portion 10C therealong.
Further, the extended portion 11e also has an extended guide
surface 11g, which is formed continuous with the guide surface 10f
and extending toward the rotating direction of the impeller 7. The
extended guide surface 11g facilitates the air, which has flown
onto the bottom wall portion 10C of the motor case 10, to be
smoothly flown out spirally from the air discharge opening 16. By
providing the guide surface 11f and the extended guide surface 11g,
a larger amount of air flows onto the bottom surface 10C of the
motor case 10. Even when the guide surface 11f and the extended
guide surface 11g are not provided, since the bottom surface 10C is
located closer to the air suction opening than the discharge-side
edges of the stationary blades 11A to 11D are located, the airflow
is directed toward a central area of the motor case 10.
Accordingly, compared to a conventional structure shown in FIG.
9(B), a larger amount of the air is discharged from the central
area of the motor case 10.
[0041] A dimensional difference in height between the bottom
surface 10C of the bottom wall portion 10A of the motor case 10 and
the discharge-side edge portions 11c of the stationary blades 11A
to 11E is preferably 3 mm or more.
[0042] Now, how to determine the shape of the stationary blades 11A
to 11D will be hereinafter described, using the stationary blade
11A as an example with reference to FIG. 2. First of all, a first
virtual plane PS1 is defined to extend in a radial direction,
including thereon an inner end of the discharge-side edge portion
11c of the stationary blade 11A and a center line CL extending
through the center of the rotating shaft 8. Then, a second virtual
plane PS2 is defined to extend in a radial direction, including
thereon an outer end of the discharge-side edge portion 11c of the
stationary blade 11A and the center line CL. Further, a third
virtual plane PS3 is defined to extend in a radial direction,
including thereon an outer end of the suction-side edge portion 11d
of the stationary blade 11A and the center line CL. Then, the shape
of each stationary blade 11 is determined so that both of the
directions from the first virtual plane PS1 toward the second
virtual plane PS2 and from the second virtual plane PS2 toward the
third virtual plane PS3 are oriented toward a direction opposite to
the rotating direction of the impeller 7.
[0043] In this embodiment, the four stationary blades 11A to 11D
are arranged so that the inclination angle .theta.4 in the vicinity
of external end portion 11a is larger than the inclination angle
.theta.3 in the vicinity of the internal end portion 11b, and that
the inclination angle is gradually changed from the vicinity of the
external end portion 11a toward the vicinity of the internal end
portion 11b. That is, each of the stationary blades 11A to 11D is
shaped as if the external end portion 11a is fixed and then the
internal end portion 11b is twisted clockwise with respected to the
fixed external end portion 11a as the external end portion 11a is
viewed from the internal end portion 11b. In other words, each of
the stationary blades 11A to 11D is shaped as if the internal end
portion 11b is fixed and then the external end portion 11a is
twisted clockwise with respect to the fixed internal end portion
11b as the internal end portion 11b is viewed from the external end
portion 11a.
[0044] Here, the inclination angle will be described with reference
with FIG. 10. FIG. 10A is a fragmentary view of a stationary blade
for illustrating an inclination angle. FIG. 10B is a
cross-sectional view, in which the stationary blade 11D is cut off
in the vicinity of the internal end portion 11b, and FIG. 10C is a
cross-sectional view, in which the stationary blade 11D is cut off
in the vicinity of the external end portion 11a. First of all, a
virtual plane PS4 is defined to extend along the air discharge
opening 16. Then, orthogonal virtual planes PS5, PS6 are defined to
be respectively orthogonal to the virtual plane PS4 and
respectively orthogonal to the discharge-side edge portion 11c and
the suction-side edge portion 11d. Virtual line PL1 is defined to
pass through a first intersection CP1 where the orthogonal virtual
plane PS5 intersects with the discharge-side edge portion 11C, and
also to pass through a second intersection CP2 where the orthogonal
virtual plane PS5 intersects with the suction-side edge portion
11d. Virtual line PL2 is defined to pass through another first
intersection CP11 where the orthogonal virtual plane PS6 intersects
with the discharge-side edge portion 11C, and also to pass through
another second intersection CP12 where the orthogonal virtual plane
PS6 intersects with the suction-side edge portion 11d. Then, an
inclination angle is defined as an angle formed by the either of
the virtual lines (PL1, PL2) and the virtual plane PS4.
[0045] FIG. 10B shows an inclination angle .theta.3 which is
measured when the stationary blade 11D is cut off along the
orthogonal virtual plane PS5 in the vicinity of the internal end
portion 11b. FIG. 10C shows an inclination angle .theta.4 which is
measured when the stationary blade 11D is cut off along the
orthogonal virtual plane PS6 in the vicinity of the internal end
portion 11b. As described above, in this embodiment, the
inclination angle .theta.4 in the vicinity of the external end
portion 11a of each of the four stationary blades 11A to 11D is
larger than the inclination angle .theta.3 in the vicinity of the
internal end portion 11b, and the inclination angle is gradually
changed from the vicinity of the external end portion 11a toward
the vicinity of the internal end portion 11b. In this embodiment,
the angle of the inclination angle .theta.3 is preferably within a
range of 45.degree. to 55.degree., and the angle of the inclination
angle .theta.4 is within a range of 50.degree. to 60.degree..
[0046] The flow rate of the air discharged from the air discharge
opening 16 of the axial-flow fan 1 tends to become faster in an
area closer to the fan housing 3 (outer side) while the flow rate
tends to become slower in an area closer to the motor case 10
(inner side). That is the reason why the stationary blades 11A to
11D are shaped as described above. This tendency is the same when
stationary blades of a simpler shape are used. When the stationary
blades 11A to 11D are arranged as described above, the flow rate of
the air flowing in the vicinity of the internal end portions 11b of
the stationary blades 11A to 11D is increased relative to the flow
rate of the air flowing in the vicinity of the external end
portions 11a of the stationary blades 11A to 11D. The flow rate of
the air is gradually increased from the external end portions 11a
toward the internal end portions 11b of the stationary blade. Based
on the foregoing, it is understood that the flow rate of the air
discharged from the air discharge opening 16 is generally
uniformized as much as possible, thereby increasing an amount of
the airflow and simultaneously reducing the noise level. In this
embodiment, the rotating blade 5 has an inner side edge fixed to
the rotating blade fixing member 6 and an outer side edge located
more outside in the radial direction. An angle (inclination angle)
formed by the inner side edge of the rotating blade 5 and an
imaginary plane, which is defined to be parallel to the virtual
plane PS4 and extend along a bottom wall surface of the rotating
blade fixing member 6, is larger than an angle (inclination angle)
formed by the imaginary plane and the outer side edge of the
rotating blade 5. The difference of these inclination angles may be
appropriately determined depending on a desired flow rate.
[0047] FIGS. 11A to 11C respectively shows a structure and
inclination angles of test axial-flow fans prepared for verifying
the effects which are obtained by defining inclination angles
.theta.4 of the stationary blades in the vicinity of the external
end portions thereof to be larger than inclination angles .theta.3
of the stationary blades in the vicinity of the internal end
portions thereof, and changing the inclination angle gradually from
the vicinity of the external end portion toward the vicinity of the
internal end portion. Different from the fan of the above-described
embodiment, in these test fans, all the stationary blades 11 are of
the same shape without using one of the blades as supporting means
for the lead wires. In order to verify the effect of twisting the
stationary blades, different from the embodiment, the
discharge-side edge portions 11c of the stationary blades 11 are
arranged to be flush with the bottom wall portion 10C of the motor
case 10. Furthermore, each of the stationary blades 11 is not
formed with the extended portion. In the fan shown in FIG. 11A, the
inclination angles of the stationary blades are arranged to be
constant (57.degree.) from the internal end portion to the external
end portion. In the fan shown in FIG. 11B, as with the fan of the
embodiment, the inclination angle is arranged to be smaller)
(47.degree.) at the side of the internal end portion of the
stationary blade, the inclination angle is arranged to be larger
(57.degree.) at the side of the external end portion, and the
inclination angle is arranged to gradually become larger from the
internal end portion toward the external end portion. In the fan
shown in FIG. 11C, the inclination angle is arranged to be larger
at the side of the internal end portion of the stationary blades
(57.degree.), the inclination angle is arranged to be smaller
(47.degree.) at the side of the external end portion, and the
inclination angle is arranged to gradually become smaller from the
internal end portion toward the external end portion.
[0048] FIG. 12 is a graph chart showing measurement results of
static pressure--airflow characteristics for the three fans shown
in FIGS. 11A to 11C (wherein the arrangements are the same except
for the shape of the stationary blades and the number of rotations
is kept constant). As demonstrated in FIG. 12, in the
characteristics B obtained from the fan (shown in FIG. 11B), in
which the inclination angle at the side of the external end portion
is larger than the inclination angle at the side of the internal
end portion as with the embodiment of the preset invention, the
airflow is larger than those in the characteristics A and C
obtained from the other two fans (shown in FIGS. 11A and 11C) under
the same static pressure.
[0049] When the measurement shown in FIG. 12 was carried out, noise
was also measured simultaneously under the same conditions. A table
shown in FIG. 13 shows the measurement results. The table shown in
FIG. 13 demonstrates differences in sound pressure level with
respect to the sound pressure level Na of noise, which was
generated by the fan shown in FIG. 11A driven at a specific speed
(the inclination angle of the stationary blades was constant). In
the fan (shown in FIG. 11B) in which the inclination angle at the
side of the external end portion was arranged to be larger than
that of the inclination angle at the side of the internal end
portion as with the above-described embodiment, the sound pressure
level of the noise was decreased by 1 dB (A); while in the fan
(shown in FIG. 11C) in which the inclination angle at the side of
the external end portion was arranged to be smaller than that of
the inclination angle at the side of the internal end portion, the
sound pressure level was increased by 0.5 dB (A). The measurement
results demonstrate that, when the inclination angle at the side of
the external end portion is arranged to be larger than the
inclination angle at the side of the internal end portion as with
the embodiment of the present invention, the airflow can be
increased while simultaneously reducing the noise level.
[0050] It has been confirmed that the airflow is increased and the
noise level is reduced when the stationary blades of a shape shown
in FIG. 11B are used as stationary blades for an axial-flow fan
which has been disclosed in the applicant's prior application
identified by Japanese Patent Application No. 2004-278370. FIG. 14.
is a graphical chart showing measurement results of static
pressure--airflow characteristics for three fans which respectively
use the stationary blades shown in FIGS. 11A to 11C. A table shown
in FIG. 15 indicates changes in noise level, as measured as with
the table shown in FIG. 13.
[0051] In the above-described embodiment, one blade 11E of the
stationary blades is constructed to receive the lead wires 25. When
the lead wires are simply pulled out without adopting the
arrangement shown in this embodiment, the stationary blade 11E has
the same structure as other stationary blades 11A to 11D. All of
the stationary blades 11a to 11E may be twisted as described
before.
[0052] Further, the present invention is not limited to these
embodiments, but various variations and modifications may be made
without departing from the scope of the present invention.
* * * * *