U.S. patent application number 12/162895 was filed with the patent office on 2012-01-05 for axial flow fan.
Invention is credited to Kyung Seok Cho, Woo June Kim, Se Young Park.
Application Number | 20120003097 12/162895 |
Document ID | / |
Family ID | 38600424 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120003097 |
Kind Code |
A1 |
Cho; Kyung Seok ; et
al. |
January 5, 2012 |
AXIAL FLOW FAN
Abstract
An axial flow fan has structural stability, decreased
deformation, decreased blade unbalance and low noise level because
the blade distribution angle has an optimum clearance angle and
uneven rate.
Inventors: |
Cho; Kyung Seok; (Daejeon,
KR) ; Park; Se Young; (Daejeon, KR) ; Kim; Woo
June; (Daejeon, KR) |
Family ID: |
38600424 |
Appl. No.: |
12/162895 |
Filed: |
January 15, 2007 |
PCT Filed: |
January 15, 2007 |
PCT NO: |
PCT/KR2007/000234 |
371 Date: |
September 20, 2011 |
Current U.S.
Class: |
416/189 |
Current CPC
Class: |
F04D 29/384 20130101;
F04D 29/386 20130101; F04D 29/328 20130101; F04D 29/666
20130101 |
Class at
Publication: |
416/189 |
International
Class: |
F01D 5/22 20060101
F01D005/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2006 |
KR |
10-2006-0010535 |
Jan 5, 2007 |
KR |
10-2007-0001552 |
Claims
1. An axial flow fan comprising a hub, a plurality of blades
arranged radially in a circumference of the hub and having a
sweeping angle of which direction changes alternately in an area
between a root and a tip of the blade, and a fan band for
connecting integrally the tips of the each blade, wherein, a
distribution angle A1 of the blade is an angle between two lines
which pass through the center of the hub and the middle of each
root of the blade, respectively, where the adjacent two blades and
the hub contact each other, and an angle of an equiangular
distribution angle is 360/n, where n is the number of blades is n,
the blades are arranged so that the clearance angle is in a range
of 4.degree. to 9.degree., while satisfying the equation:
distribution angle of the blade=equiangular distribution
angle.+-.the clearance angle.
2. The axial flow fan according to claim 1, wherein the clearance
angle is in the range of 6.degree. to 7.degree..
3. The axial flow fan according to claim 2, wherein, an angle
between two lines which pass through the center of the hub and the
middle of each root of the blade, respectively, where the adjacent
two blades and the hub come into contact, is a hub-side
distribution angle of the blade, and an angle between two lines
which pass through the center of the hub and the middle of each tip
of the two blades, respectively is a tip-side distribution angle of
the blade, the hub-side distribution angle of the blade and the
tip-side distribution angle of the blade are same.
4. The axial flow fan according to claim 3, wherein the blade has a
sweeping angle which changes gradually as it goes from the tip of
the blade having a forward angle to the root of the blade having a
backward angle and connected to the hub and a plurality of flow
dispersing areas between the forward angle area of a side of the
tip of the blade and the backward angle area of a side of the root
of the blade, in which the direction of the sweeping angle is
alternately reversed.
5. The axial flow fan according to claim 4, wherein the blade has a
leading edge extending from the tip of the blade to the root of the
blade, and the direction of the sweeping angle of the leading edge
changes gradually from a maximum backward angle at the root of the
blade to a maximum forward angle at the tip of the blade, wherein
the direction of the sweeping angle is reversed from the backward
angle at a side of the root of the blade to a forward angle, then
reversed to a backward angle and reversed again to a forward angle
so as to be connected to a forward angle at a side of the tip of
the blade.
6. The axial flow fan according to claim 4, wherein the blade has a
trailing edge extending from the tip of the blade to the root of
the blade, and a changing pattern of a sweeping angle of the
trailing edge is the same as that of the leading edge.
7. The axial flow fan according to claim 1, wherein, an angle
between two lines which pass through the center of the hub and the
middle of each root of the blade, respectively, where the adjacent
two blades and the hub come into contact, is a hub-side
distribution angle of the blade, and an angle between two lines
which pass through the center of the hub and the middle of each tip
of the two blades, respectively is a tip-side distribution angle of
the blade, the hub-side distribution angle of the blade and the
tip-side distribution angle of the blade are same.
Description
RELATED APPLICATIONS
[0001] The present application is based on, and claims priority
from, KR Application Number 10-2006-0010535, filed Feb. 3, 2006; KR
Application Number 10-2007-0001552, filed Jan. 5, 2007; and PCT
Application Number PCT/KR2007/000234, filed Jan. 15, 2007, the
disclosures of which are hereby incorporated by reference herein in
their entireties.
TECHNICAL FIELD
[0002] The present invention relates to an axial flow fan, and more
particularly, to an axial flow fan capable of promoting structural
stability so as to decrease deformation and unbalance of a blade
and accomplishing low noise level.
BACKGROUND ART
[0003] As shown in FIG. 1, an axial flow fan 10, which is used for
cooling heat exchange medium passing an inside of a heat exchanger
such as a radiator, a condenser and so on of a vehicle, is provided
with a hub 20 coupled to a shaft 52 of a driving source 50 such as
a motor, a plurality of blades 30 arranged radially at an outer
circumference of the hub 20, and a fan band 40 for connecting tips
of the blades 30 so as to prevent the blades from being deformed.
The axial flow fan 10 is therefore rotated by rotational force
transferred from the driving source 50 to the hub 20 and blows air
in an axial direction by the blades 30.
[0004] A shroud 60 fixed to the heat exchanger is used to guide
efficiently the air blown by the axial flow fan 10. The shroud 60
is formed so as to have a blowhole which is sized so that the axial
flow fan 10 can be rotatably inserted therein, and support the
motor 50 which is a driving source.
[0005] In the blade 30 of a conventional axial flow fan 10, as
shown in FIG. 2, a leading edge LE which is an edge at a side of a
rotational direction and a trailing edge TE which is an edge at an
opposite side of the rotational direction have a backward sweeping
angle inclined toward an opposite direction of the rotation as it
goes from a root 32 of the blade connecting the blade 30 to the hub
20 to a center portion of the blade 30 and a forward sweeping angle
inclined toward the rotational direction as it goes to a tip 34 of
the blade connecting the blade to the fan band 40. Such change of
the sweep angle is an important factor in performance of the axial
flow fan, however it is known to be difficult to obtain
satisfactory blowing efficiency and noise reduction effect. In
consideration of above mentioned matter, improved axial flow fans
have been proposed in Korean Patent Application Laid Open Nos.
2002-94183 and 2002-94184 by the present inventor.
[0006] As shown in FIG. 3 and FIG. 4, the former axial flow fan 10a
has a waveform structured blade 30a, in which the sweeping angles
of the leading edge LE and the trailing edge TE change alternately
from a backward to a forward and from the forward to the backward
as it goes from a root 32a of the blade toward a tip 34a of the
blade. Further, a chord length CL is gradually increased as it goes
from the root 32a of the blade toward the tip 34a of the blade. A
reference symbol a denotes an angle of the blade 30 in relation to
a horizontal line H. Reference symbols 20a and 40a denote the hub
and the fan bend respectively.
[0007] As shown in FIG. 5 and FIG. 6, the latter axial flow fan 10b
has a waveform structured blade 30b as same as the former, and a
chord length CL (see FIG. 4) is also gradually increased as it goes
from the root 32b of the blade toward the tip 34b of the blade 34b.
Further, the root 32b of the blade has maximum backward sweeping
angle and the tip 34b of the blade has maximum forward sweeping
angle. Reference symbols 20b and 40b denote the hub and the fan
band respectively.
[0008] According to the axial flow fans 10a and 10b having the
above mentioned waveform structured blades 30a and 30b
respectively, an area between inflection points P1 and P2 located
on a mid-chord line, which runs along middle points between the
leading edge LE and the trailing edge TE, works as an area for
dispersing air flow and thus prevent the air flow from being
concentrated, thereby capable of increasing blowing efficiency and
reducing noise compared to the axial flow fan shown in FIG. 1 and
FIG. 2.
[0009] As shown in FIG. 7, in example, in the axial flow fan having
the blade with above mentioned waveform structure, when assuming
that an angle between two lines L1 and L2 which pass through a
center C of the hub 20b and middles C1 and C2 of each root 32b of
the blade, respectively, where the adjacent two blades 30b and the
hub 20b come into contact, is a distribution angle A1 of the blade
and a number of the blade is n, an equiangular distribution angle
is defined as a case that the distribution angle becomes 360/n.
[0010] In addition, the distribution angle A1 of the blade can be
moved by a predetermined angle in a rotational direction (+) or an
opposite direction of the rotation (-) of the axial flow fan in the
equiangular distribution angle, and at this time a range in which
the angle can be increased or decreased is referred as a clearance
angle B. In other words, it can be expressed by an equation: the
distribution angle A1 of the blade=an equiangular distribution
angle X the clearance angle B.
[0011] Meanwhile, U.S. Pat. No. 5,000,660 discloses an axial flow
fan with a blade of an uneven structure in which curvatures from a
root of the blade to a tip of the blade are different at least
between two blades, and the axial flow fan is suggested for the
purpose of increasing rigidity of a portion of the root of the
blade and reducing noise in a portion of the tip of the blade.
However, in the conventional axial flow fans with above described
waveform structure, there are problems that unbalance is occurred
when the axial flow fans rotate and satisfactory noise reduction
effect can not be achieved if the clearance angle B is set to be
excessively large.
DISCLOSURE
Technical Problem
[0012] An object of the present invention is to provide an axial
flow fan capable of promoting structural stability so as to
decrease deformation and unbalance of a blade and accomplishing low
noise level by determining a distribution angle of the blade with
an optimum clearance angle and thereby determining uneven rate of
the blade.
Technical Solution
[0013] An axial flow fan according to a preferred embodiment of the
present invention includes a hub; a plurality of blades arranged
radially in a circumference of the hub and having a sweeping angle
of which direction changes alternately in an area between a root
and a tip of the blade; and a fan band for connecting integrally
the tips of the each blade; wherein when assuming that an angle
between two lines which pass through a center of the hub and the
middle of each root of the blade, respectively, where the adjacent
two blades and the hub come into contact, is a distribution angle
A1 of the blade, and an angle of an equiangular distribution angle
is 360/n in the case that a number of the blades is n, the blades
are arranged so that the clearance angle is in a range of 4.degree.
to 9.degree., while satisfying an equation: distribution angle (A1)
of the blade=equiangular distribution angle.+-.clearance angle.
[0014] According to a preferred embodiment of the present
invention, it is preferable that the clearance angle is in the
range of 6.degree. to 7.degree. In addition, it is preferable that
when assuming that an angle between two lines which pass through a
center of the hub and middles of each root of the blade,
respectively, where the adjacent two blades and the hub come into
contact is, a hub-side distribution angle of the blade, and an
angle between two lines which pass through a center of the hub and
middles of each tip of the two blades, respectively is a tip-side
distribution angle of the blade, the hub-side distribution angle of
blade and the tip-side distribution angle of blade are same.
[0015] In addition, the blade has the sweeping angle which changes
gradually as it goes from the tip of the blade having a forward
angle to the root of the blade having a backward angle and
connected to the hub and a plurality of flow dispersing areas
between the forward angle area of a side of the tip of the blade
and the backward angle area of a side of the root of the blade, in
which a direction of the sweeping angle is alternately
reversed.
[0016] At this time, it is preferable that the blade has a leading
edge extending from the tip of the blade to the root of the blade,
and a direction of a sweeping angle of the leading edge changes
gradually from a maximum backward angle at the root of the blade to
a maximum forward angle at the tip of the blade, wherein the
direction of the sweeping angle is reversed from the backward angle
at a side of the root of the blade to a forward angle, then
reversed to a backward angle and reversed again to a forward angle
so as to be connected to a forward angle at a side of the tip of
the blade. Further, it is preferable that the blade has a trailing
edge extending from the tip of the blade to the root of the blade,
and a changing pattern of a sweeping angle of the trailing edge is
as same as that of the leading edge.
BRIEF DESCRIPTION OF DRAWINGS
[0017] The above and other objects, features and advantages of the
present invention will become apparent from the following
description of preferred embodiments given in conjunction with the
accompanying drawings, in which:
[0018] FIG. 1 is an exploded perspective view illustrating an
example of a conventional axial flow fan and shroud assembly.
[0019] FIG. 2 is a partial front view illustrating the conventional
axial flow fan.
[0020] FIG. 3 is a front view illustrating another example of a
conventional axial flow fan.
[0021] FIG. 4 is a sectional view of a blade for defining a
chord.
[0022] FIG. 5 is a perspective view illustrating yet another
example of a conventional axial flow fan.
[0023] FIG. 6 is a partial front view illustrating the axial flow
fan shown in FIG. 5.
[0024] FIG. 7 is a partial front view for explaining distribution
angle of a blade in the axial flow fan shown in FIG. 5.
[0025] FIG. 8 is a front view of a preferred embodiment of an axial
flow fan according to the present invention.
[0026] FIG. 9 is a partial front view for explaining a structure of
a blade in the axial flow fan shown in FIG. 8.
[0027] FIG. 10 to FIG. 15 are graphs comparatively showing noise
levels according to frequency in relation to the axial flow fan
according to the fan of FIGS. 8 and 9 and the conventional axial
flow fan.
[0028] FIG. 16 is a graph showing variation pattern in overall
noise according to variation of a clearance angle.
LISTING OF THE MAIN ELEMENTS OF THE DRAWINGS
[0029] 110: hub [0030] 120: blade [0031] 122: root of the blade
[0032] 124: tip of the blade [0033] 130: fan band [0034] A1:
distribution angle of the blade [0035] C: center of the hub [0036]
C1, C2: middle of the root of the blade which is in contact with
the hub [0037] L1, L2: line crossing a center of the hub and the
middle of the root of the blade [0038] D: flow dispersing area
[0039] S1, S2: flow concentrating part [0040] r.sub.11, r.sub.12,
r.sub.13: first, second and third inflection points
DETAILED DESCRIPTION OF THE DRAWINGS
[0041] Hereinafter, the preferred embodiments of the present
invention are described in detail with reference to accompanying
drawings.
[0042] FIG. 8 is an illustration of an axial flow fan according to
a preferred embodiment of the present invention. The axial flow fan
100 includes a hub 110; a plurality of blades 120 radially arranged
at a circumference of the hub 110 and having a sweeping angle of
which direction changes alternately in an area between a root 122
of the blade and a tip 124 of the blade; and a fan band 130 for
connecting integrally the tips 124 of the each blade 120. In the
present embodiment, the illustrated axial flow fan 100 has 9 blades
120.
[0043] In accordance with an aspect of the present invention, when
assuming that an angle between two lines L1 and L2 which pass
through a center C of the hub 110 and middles C1 and C2 of each
root 122 of the blade, respectively, where the adjacent two blades
120 and the hub 110 come into contact, is a distribution angle A1
of the blade, a range of an angle by which the distribution angle
A1 of the blade is movable in a rotational direction (+) or an
opposite direction of rotation (-) of the axial flow fan 100 is a
clearance angle, and a number of the blade is n, an equiangular
distribution, representing an interval by which the blades are
arranged, can be defined by 360/n.
[0044] In other words, the blades 120 can be exemplary arranged in
interval of 40.degree., an actual angular distribution of the blade
120 can be moved in the rotational direction (+) or the opposite
direction of rotation (-) of the axial flow fan 100 by a
predetermined angle in the range of the clearance angle. The
distribution angle A1 of the blade 120 can be expressed by an
equation: a distribution angle A1 of the blade=an equiangular
distribution angle.+-.a clearance angle, and the clearance angle is
preferably in a range of 4.degree. to 9.degree. and more preferably
in a range of 6.degree. to 7.degree..
[0045] Further, when assuming that an angle A1r between two lines
L1 and L2 which pass through center C of the hub 110 and the middle
C1 and C2 of each root 122 of the blade, respectively, where the
adjacent two blades 120 and the hub 110 come into contact is a
hub-side distribution angle of the blade and an angle A1t between
two lines L3 and L4 which pass through center C of the hub 110 and
the middle C3 and C4 of each tip 124 of the two blades 120,
respectively is a tip-side distribution angle of the blade, it is
preferable that the hub-side distribution angle A1r of blade and
the tip-side distribution angle A1t of blade are same.
[0046] FIG. 9 is a partial front view for explaining a structure of
the blade in the axial flow fan of the present invention shown in
FIG. 8. In the blade of FIG. 9 are shown a leading edge LE, a
trailing edge TE and a mid-chord line ML defined as a line which
runs radially along middle points between the leading edge LE and
the trailing edge TE. As shown, in the axial flow fan according to
the present invention, the leading edge LE of the blade 120 has a
sweeping angle of which direction is gradually changes from the
maximum backward sweeping angle at the root 122 of the blade to the
maximum forward sweeping angle at the tip 124 of the blade in a
full section between the root 122 of the blade and the tip 124 of
the blade. Further, the leading edge LE has a flow dispersing area
D, which is a small section starting from a first inflection point
r.sub.11, at which the direction of the sweeping angle is changes
from backward to forward, passing through a second inflection point
r.sub.12, at which the direction of the sweeping angle is changes
again from forward to backward, and reaching to a third inflection
point r.sub.13, at which the direction of the sweeping angle is
changes again from backward to forward.
[0047] In other words, the leading edge LE of the blade 120 is
formed such that the direction of the sweeping angle gradually
changes from backward at a side of root 122 of the blade in an
order of forward, backward and forward, and finally to forward at a
side of the tip 124 of the blade between a backward area of the
side of the root 122 of the blade 120 and a forward area of the
side of the tip 124 of the blade 120.
[0048] Further, as shown, the trailing edge TE of the blade 120 is
also formed as same pattern as the leading edge LE, that is, such
that the direction of the sweeping angle gradually changes from
backward at a side of root 122 of the blade in an order of forward,
backward and forward, and finally to forward at a side of the tip
124 of the blade between the backward area of the side of the root
122 of the blade 120 and the forward area of the side of the tip
124 of the blade 120.
[0049] As described above, the flow dispersing area D forms two
flow concentrating parts S1 and S2 at which flows are concentrated
to a side of the trailing edge TE and thus acts to lessen greatly
concentration of the flow, thereby increasing a blowing efficiency
relative to power consumption and greatly reducing noise
generation.
[0050] FIG. 10 to FIG. 15 are graphs comparatively showing noise
levels throughout frequencies in the case that the clearance angle
is 4.degree. to 9.degree. according to the present invention. As
shown in FIG. 10 to FIG. 15, test to the axial flow fans according
to the present invention (the first and second embodiments) and the
conventional axial flow fan under the condition of same voltage
showed that the axial flow fans according to the present are much
lower in noise level than the conventional one. The axial flow fans
according to the present invention has much air flow rate in a low
rpm and test to the axial flow fans according to the present
invention and the conventional axial flow fan under the condition
of same air flow rate showed that the axial flow fans according to
the present are much lower in noise level, rpm and voltage than the
conventional one.
[0051] In the graphs of FIG. 10 to FIG. 15, noise level of even fan
is denoted with black solid line and noise levels of each uneven
fan are denoted with gray dotted lines. In FIG. 10 to FIG. 15, it
may be clearly noted that a value of noise peak of the uneven fan
is much lower than that of the even fan.
[0052] Table 1 lists data of variation in overall noise according
to the clearance angle and FIG. 16 graphically shows the data of
table 1.
TABLE-US-00001 TABLE 1 Clearance Angle (.degree.) Overall Noise
(dB) 0 67.9 1 67.7 2 67.6 3 67.8 4 67.0 5 66.6 6 66.3 7 66.6 8 66.5
9 66.7 10 67.2 11 67.3 12 67.5 13 67.4 14 67.9
[0053] In the above table 1 and FIG. 16, the case that the
clearance angle is 0.degree. means the case of the even fan, i.e.
the case that blades are exactly arranged in an equiangular
distribution (distribution angle of blade=equiangular distribution
angle). FIG. 16 shows clearly a tendency, in which the noise is
very high in the case that the distribution angle of blade is the
equiangular distribution angle, that is, the clearance angle is
0.degree., and the noise is gradually reduced with increase of the
clearance angle while the noise is increased again if the clearance
angle passes over a specific value. As shown, it will be known that
the noise is clearly reduced in the case that the clearance angle
is 4.degree. to 9.degree. than in the case of the even fan,
particularly noise reduction effect is maximized in the case that
the clearance angle is 6.degree. to 7.degree..
INDUSTRIAL APPLICABILITY
[0054] With the above described axial flow fan according to the
present invention, it is capable of promoting silence operation of
an apparatus which employs an axial flow fan as noise can be
greatly reduced compared to the conventional axial flow fan by
determining the distribution angle of the blade 120 with an optimum
clearance angle. Further, blowing efficiency and noise reduction
effect can be much increased by adjusting the clearance angle as
well as forming the flow dispersing area on the blade.
[0055] In addition, as the axial flow fan according to the present
invention can generate much air flow rate even in low rpm compared
to the conventional one, it is capable of promoting structural
stability and thus increasing durability of the axial fan.
* * * * *