U.S. patent application number 12/668581 was filed with the patent office on 2010-07-29 for counter-rotating axial-flow fan.
This patent application is currently assigned to SANYO DENKI CO., LTD.. Invention is credited to Katsumichi Ishihara, Toshiyuki Nakamura, Atsushi Yanagisawa.
Application Number | 20100189544 12/668581 |
Document ID | / |
Family ID | 40228585 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100189544 |
Kind Code |
A1 |
Nakamura; Toshiyuki ; et
al. |
July 29, 2010 |
COUNTER-ROTATING AXIAL-FLOW FAN
Abstract
A counter rotating axial flow fan that reduces vibration
generation over a wide rotational speed range. A disk-shaped
cushioning member is disposed between a circular plate portion of a
first support frame main body half portion and a circular plate
portion of a second support frame main body half portion. The
cushioning member is compressed, with hook portions forming a
plurality of engaging portions and hole portions forming a
plurality of engaged portions completely engaged with each
other.
Inventors: |
Nakamura; Toshiyuki;
(Nagano, JP) ; Yanagisawa; Atsushi; (Nagano,
JP) ; Ishihara; Katsumichi; (Nagano, JP) |
Correspondence
Address: |
RANKIN, HILL & CLARK LLP
38210 GLENN AVENUE
WILLOUGHBY
OH
44094-7808
US
|
Assignee: |
SANYO DENKI CO., LTD.
Tokyo
JP
|
Family ID: |
40228585 |
Appl. No.: |
12/668581 |
Filed: |
July 8, 2008 |
PCT Filed: |
July 8, 2008 |
PCT NO: |
PCT/JP2008/062312 |
371 Date: |
January 11, 2010 |
Current U.S.
Class: |
415/68 |
Current CPC
Class: |
F04D 29/668 20130101;
F04D 29/646 20130101; F04D 19/007 20130101 |
Class at
Publication: |
415/68 |
International
Class: |
F04D 25/16 20060101
F04D025/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2007 |
JP |
2007-183756 |
Claims
1. A counter-rotating axial flow fan comprising: a housing
including a housing main body having defined therein an air channel
having a suction port at one end in an axial direction and a
discharge port at the other end in the axial direction, and a motor
support frame disposed at a center portion of the air channel; a
first impeller disposed in a first space defined in the housing
between the motor support frame and the suction port and including
a plurality of blades; a first motor including a first rotary shaft
to which the first impeller is fixed to rotate the first impeller
in a first rotational direction in the first space; a second
impeller disposed in a second space defined in the housing between
the motor support frame and the discharge port and including a
plurality of blades; and a second motor including a second rotary
shaft to which the second impeller is fixed to rotate the second
impeller in a second rotational direction opposite the first
rotational direction in the second space, the motor support frame
including a support frame main body located at the center portion
of the air channel and a plurality of webs disposed between the
support frame main body and the housing main body at predetermined
intervals in a circumferential direction of the rotary shafts to
couple the support frame main body and the housing main body, the
housing including a first split housing unit and a second split
housing unit coupled to each other by a mechanical coupling
structure, the first split housing unit including a first housing
main body half portion including a first cylindrical air channel
half portion having the suction port at one end and having defined
therein a main portion of the first space, and a first support
frame half portion which is one of two pieces obtained by splitting
the motor support frame along a split plane extending in a radial
direction perpendicular to the axial direction, the second split
housing unit including a second housing main body half portion
including a second cylindrical air channel half portion having the
discharge port at one end and having defined therein a main portion
of the second space, and a second support frame half portion which
is the other of the two pieces obtained by splitting the motor
support frame along the split plane, the coupling structure
including a plurality of engaging portions integrally formed with
the first housing main body half portion of the first split housing
unit and disposed at intervals in the circumferential direction,
and a plurality of engaged portions integrally formed with the
second housing main body half portion of the second split housing
unit and disposed at intervals in the circumferential direction to
be engaged with the plurality of engaging portions, the coupling
structure and the first and second split housing units being
configured such that an opposed surface of the first support frame
half portion and an opposed surface of the second support frame
half portion entirely contact each other when the plurality of
engaging portions and the plurality of engaged portions are
completely engaged with each other, the first support frame half
portion including a first support frame main body half portion to
which the first motor is fixed and a plurality of first web half
portions, and the second support frame half portion including a
second support frame main body half portion to which the second
motor is fixed and a plurality of second web half portions, wherein
a soft cushioning member with a plurality of independent air
bubbles dispersed therein is disposed between the first support
frame main body half portion and the second support frame main body
half portion, the cushioning member being compressed when the
plurality of engaging portions and the plurality of engaged
portions are completely engaged with each other.
2. A counter-rotating axial flow fan comprising: a housing
including a housing main body having defined therein an air channel
having a suction port at one end in an axial direction and a
discharge port at the other end in the axial direction, and a motor
support frame disposed at a center portion of the air channel; a
first impeller disposed in a first space defined in the housing
between the motor support frame and the suction port and including
a plurality of blades; a first motor including a first rotary shaft
to which the first impeller is fixed to rotate the first impeller
in a first rotational direction in the first space; a second
impeller disposed in a second space defined in the housing between
the motor support frame and the discharge port and including a
plurality of blades; and a second motor including a second rotary
shaft to which the second impeller is fixed to rotate the second
impeller in a second rotational direction opposite the first
rotational direction in the second space, the motor support frame
including a support frame main body located at the center portion
of the air channel and a plurality of webs disposed between the
support frame main body and the housing main body at predetermined
intervals in a circumferential direction of the rotary shafts to
couple the support frame main body and the housing main body, the
housing including a first split housing unit and a second split
housing unit coupled to each other by a mechanical coupling
structure, the first split housing unit including a first housing
main body half portion including a first cylindrical air channel
half portion having the suction port at one end and having defined
therein a main portion of the first space, and a first support
frame half portion which is one of two pieces obtained by splitting
the motor support frame along a split plane extending in a radial
direction perpendicular to the axial direction, the second split
housing unit including a second housing main body half portion
including a second cylindrical air channel half portion having the
discharge port at one end and having defined therein a main portion
of the second space, and a second support frame half portion which
is the other of the two pieces obtained by splitting the motor
support frame along the split plane, the coupling structure
including a plurality of engaging portions integrally formed with
the first housing main body half portion of the first split housing
unit and disposed at intervals in the circumferential direction,
and a plurality of engaged portions integrally formed with the
second housing main body half portion of the second split housing
unit and disposed at intervals in the circumferential direction to
be engaged with the plurality of engaging portions, and the
coupling structure and the first and second split housing units
being configured such that opposed surfaces of the first and second
support frame half portions entirely contact each other when the
plurality of engaging portions and the plurality of engaged
portions are completely engaged with each other, wherein a soft
cushioning member with a plurality of independent air bubbles
dispersed therein is disposed between the first support frame half
portion and the second support frame half portion, the cushioning
member being compressed when the plurality of engaging portions and
the plurality of engaged portions are completely engaged with each
other.
3. The counter-rotating axial flow fan according to claim 2,
wherein the first support frame half portion includes a first
support frame main body half portion to which the first motor is
fixed, the second support frame half portion includes a second
support frame main body half portion to which the second motor is
fixed, and the cushioning member is disposed between the first
support frame main body half portion and the second support frame
main body half portion.
4. The counter-rotating axial flow fan according to claim 1,
wherein the first and second split housing units are formed from a
synthetic resin material.
5. The counter-rotating axial flow fan according to claim 1,
wherein the first and second split housing units are formed from
aluminum.
6. The counter-rotating axial flow fan according to claim 1,
wherein the cushioning member is an acrylic foam sheet with a
thickness of not less than 0.4 mm and not more than 0.8 mm.
7. The counter-rotating axial flow fan according to claim 2,
wherein the first and second split housing units are formed from a
synthetic resin material.
8. The counter-rotating axial flow fan according to claim 2,
wherein the first and second split housing units are formed from
aluminum.
9. The counter-rotating axial flow fan according to claim 2,
wherein the cushioning member is an acrylic foam sheet with a
thickness of not less than 0.4 mm and not more than 0.8 mm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a counter-rotating axial
flow fan for use to cool the inside of an electric device and the
like.
BACKGROUND ART
[0002] Japanese Unexamined Patent Application Publication No.
2004-278370 (Patent Document 1) and U.S. Pat. No. 7,156,611 (Patent
Document 2) each disclose a counter-rotating axial flow fan
including a housing including a housing main body having defined
therein an air channel having a suction port at one end in an axial
direction and a discharge port at the other end in the axial
direction, and a motor support frame disposed at a center portion
of the air channel. In the counter-rotating axial flow fan, a first
impeller rotated by a first motor is disposed in a first space in
the housing between the motor support frame and the suction port.
Also, a second impeller rotated by a second motor is disposed in a
second space in the housing between the motor support frame and the
discharge port. The first impeller rotates in the opposite
direction to the second impeller. In the counter-rotating axial
flow fan, the housing includes a first split housing unit and a
second split housing unit coupled to each other by a coupling
structure. The first split housing unit includes a first housing
main body half portion including a first cylindrical air channel
half portion having defined therein a main portion of the first
space, and a first support frame half portion which is one of two
pieces obtained by splitting the motor support frame along an
imaginary reference split plane extending in a radial direction
perpendicular to the axial direction. The second split housing unit
includes a second housing main body half portion including a second
cylindrical air channel half portion having defined therein a main
portion of the second space, and a second support frame half
portion which is the other of the two pieces obtained by splitting
the motor support frame along the imaginary reference split
plane.
[0003] [Patent Document 1] Japanese Unexamined Patent Application
Publication No. 2004-278370
[0004] [Patent Document 2] U.S. Pat. No. 7,156,611
SUMMARY OF INVENTION
Technical Problem
[0005] In the counter-rotating axial flow fan according to the
related art, however, vibration increases in a plurality of
rotational speed ranges (resonance ranges) as the rotational speeds
of the first and second motors are increased. If the
counter-rotating axial flow fan is used within any of such
rotational speed ranges with increased vibration, the
counter-rotating axial flow fan may produce significant vibration,
which may result in significant noise.
[0006] An object of the present invention is to provide a
counter-rotating axial flow fan in which vibration generation may
be reduced more than ever in a wide rotational speed range.
Solution to Problem
[0007] The present invention provides a counter-rotating axial flow
fan including a housing, a first impeller, a first motor, a second
impeller, and a second motor. The housing includes a housing main
body having defined therein an air channel having a suction port at
one end in an axial direction and a discharge port at the other end
in the axial direction, and a motor support frame disposed at a
center portion of the air channel. The first impeller is disposed
in a first space defined in the housing between the motor support
frame and the suction port, and includes a plurality of blades. The
first motor includes a first rotary shaft to which the first
impeller is fixed to rotate the first impeller in a first
rotational direction in the first space. The second impeller is
disposed in a second space defined in the housing between the motor
support frame and the discharge port, and includes a plurality of
blades. The second motor includes a second rotary shaft to which
the second impeller is fixed to rotate the second impeller in a
second rotational direction opposite the first rotational direction
in the second space.
[0008] The motor support frame includes a support frame main body
located at the center portion of the air channel and a plurality of
webs disposed between the support frame main body and the housing
main body at predetermined intervals in a circumferential direction
of the rotary shafts to couple the support frame main body and the
housing main body.
[0009] The housing includes a first split housing unit and a second
split housing unit coupled to each other by a mechanical coupling
structure. The first split housing unit includes a first housing
main body half portion including a first cylindrical air channel
half portion having the suction port at one end and having defined
therein a main portion of the first space, and a first support
frame half portion which is one of two pieces obtained by splitting
the motor support frame along a split plane extending in a radial
direction perpendicular to the axial direction. The second split
housing unit includes a second housing main body half portion
including a second cylindrical air channel half portion having the
discharge port at one end and having defined therein a main portion
of the second space, and a second support frame half portion which
is the other of the two pieces obtained by splitting the motor
support frame along the split plane.
[0010] The coupling structure adopted in the present invention
includes a plurality of engaging portions integrally formed with
the first housing main body half portion and disposed at intervals
in the circumferential direction, and a plurality of engaged
portions integrally formed with the second housing main body half
portion and disposed at intervals in the circumferential direction
to be engaged with the plurality of engaging portions. The coupling
structure and the first and second split housing units are
configured such that an opposed surface of the first support frame
half portion and an opposed surface of the second support frame
half portion entirely contact each other when the plurality of
engaging portions and the plurality of engaged portions are
completely engaged with each other. The phrase "opposed surfaces
entirely contact each other" as used herein means that opposed
surfaces contact each other through a large number of point
contacts as seen from a microscopic point of view.
[0011] In the present invention, in particular, a soft cushioning
member is disposed between the first support frame half portion and
the second support frame half portion, the cushioning member being
compressed when the plurality of engaging portions and the
plurality of engaged portions are completely engaged with each
other. A plurality of independent air bubbles are dispersed in the
soft cushioning member adopted in the present invention. The
independent air bubbles may include not only individual air bubbles
but also large independent air bubbles formed by incorporating a
plurality of air bubbles. When such a cushioning member is used, it
is possible to generally suppress an increase in vibration over a
wide rotational speed range from a low rotational speed range to a
high rotational speed range. Specific preferred embodiments of the
soft cushioning member with a plurality of independent air bubbles
dispersed therein include an acrylic foam sheet. If an acrylic foam
sheet is used as the soft cushioning member, the thickness of the
acrylic foam sheet is preferably not less than 0.4 mm and not more
than 0.8 mm. If the thickness of the acrylic foam sheet is less
than 0.4 mm, the thickness of the cushioning member itself is too
small to provide a sufficient vibration absorption effect. If the
thickness of the acrylic foam sheet is more than 0.8 mm, it is
necessary to separately provide a gap in which the acrylic foam
sheet is to be disposed between the first support frame half
portion and the second support frame half portion. However,
providing such a gap is not preferred because it changes the
resonance frequencies of vibration and thus complicates measures
taken against the vibration.
[0012] The specific soft cushioning member used in the present
invention also serves a function of reducing vibration produced
between the first support frame half portion and the second support
frame half portion. As a result, according to the present
invention, it is possible to generally suppress an increase in
vibration over a wide rotational speed range from a low rotational
speed range to a high rotational speed range compared to the
related art.
[0013] The soft cushioning member may be entirely disposed between
the first support frame half portion and the second support frame
half portion.
[0014] The first and second split housing units may be formed from
a synthetic resin material, or may be formed from a metal material
such as aluminum.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is an exploded cross-sectional view of a half portion
of a counter-rotating axial flow fan according to an embodiment of
the present invention.
[0016] FIG. 2 is an exploded perspective view of the
counter-rotating axial flow fan according to the embodiment of the
present invention.
[0017] FIGS. 3A and 3B are graphs showing the results of vibration
measurements performed to verify the effect of the present
invention.
[0018] FIGS. 4A and 4B are graphs showing the results of vibration
measurements performed to verify the effect of the present
invention.
[0019] FIG. 5 is a graph showing the detailed results of vibration
measurements performed to verify the effect of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0020] An embodiment of the present invention will be described in
detail below with reference to the drawings. FIG. 1 is an exploded
cross-sectional view of a half portion of a counter-rotating axial
flow fan according to an embodiment of the present invention. FIG.
2 is an exploded perspective view of the counter-rotating axial
flow fan. As shown in the drawings, the counter-rotating axial flow
fan according to the embodiment includes a housing 1, a first motor
3, a first impeller 5, a second motor 7, and a second impeller 9.
The first impeller 5 is disposed in a first space S1 defined in the
housing 1 between a motor support frame (23, 53) to be discussed
later and a suction port 11a, and includes a plurality of blades 6.
The first motor 3 includes a first rotary shaft 4 to which the
first impeller 5 is fixed to rotate the first impeller 5 in a first
rotational direction in the first space S1. The second impeller 9
is disposed in a second space S2 defined in the housing 1 between
the motor support frame (23, 53) and the discharge port 13b, and
includes a plurality of blades 10. The second motor 7 includes a
second rotary shaft 8 to which the second impeller 9 is fixed to
rotate the second impeller 9 in a second rotational direction
opposite the first rotational direction in the second space S2.
[0021] The housing 1 is configured by assembling a first split
housing unit 11 and a second split housing unit 13 via a coupling
structure. The first split housing unit 11 is formed from a
synthetic resin material or a metal material such as aluminum. As
shown in FIG. 1, the first split housing unit 11 includes a first
housing main body half portion 15 and a first support frame half
portion 17 integrally formed with each other. The first housing
main body half portion 15 includes first and second flange portions
19 and 20 and a first cylindrical air channel half portion 21. The
first flange portion 19 includes first to fourth corners 19a to 19d
arranged in a circumferential direction of the rotary shaft 4
(hereinafter simply referred to as "circumferential direction")
arranged on a common axis A of the first and second motors 3 and 7.
The first flange portion 19 includes the suction port 11a at one
end in the direction of the common axis A. Four hole portions 19e
are respectively formed at the four corners of the first flange
portion 19 (the first to fourth corners 19a to 19d) to serve as
engaged portions for use in forming a coupling structure with the
second split housing unit 13. The details of the shape of the hole
portions 19e and the details of the engagement relationship between
the hole portions 19e and the hook portions 49 forming engaging
portions to be discussed later are the same as the relationship
between hole portions and hook portions forming a coupling
structure disclosed in Japanese Unexamined Patent Application
Publication No. 2004-278370 (U.S. Pat. No. 7,156,611), and
therefore are not described herein. The second flange portion 20 is
formed with through holes 20a through which mounting members for
mounting the counter-rotating axial flow fan to an electric device
are to be inserted. The first and second flange portions 19 and 20
are integrally formed with both ends of the first cylindrical air
channel half portion 21. The first cylindrical air channel half
portion 21 extends in an axial direction of the rotary shafts 4 and
8 (hereinafter simply referred to as "axial direction") arranged on
the common axis A.
[0022] The first support frame half portion 17 includes a first
support frame main body half portion 23 to which the first motor 3
is fixed and three first web half portions 25. The first support
frame main body half portion 23 includes a circular plate portion
23b having a cylindrical boss portion 23a at a center portion
thereof, and a peripheral wall portion 23c extending in the axial
direction from the outer peripheral portion of the circular plate
portion 23b. A first metallic bearing holder 27 made of brass is
fixedly fitted in the boss portion 23a. A base plate 29 of a stator
of the first motor 3 is disposed to block a space surrounded by the
circular plate portion 23b and the peripheral wall portion 23c. A
stator core 33 including a plurality of winding portions 31 is
fitted with the bearing holder 27.
[0023] The three first web half portions 25 are disposed between
the peripheral wall portion 23c of the first support frame main
body half portion 23 and an inner peripheral surface of the first
housing main body half portion 15 at predetermined intervals in the
circumferential direction to couple the first support frame main
body half portion 23 and the first housing main body half portion
15.
[0024] A cup-shaped member 35 made of a magnetically permeable
material is fixed to one end of the rotary shaft 4 to support the
impeller 5 including the plurality of blades 6. A plurality of
permanent magnets 37 are fixed to the inner peripheral portion of
the cup-shaped member 35.
[0025] The second split housing unit 13 is also formed from a
synthetic resin material or a metal material such as aluminum. As
shown in FIG. 1, the second split housing unit 13 includes a second
housing main body half portion 39 and a second support frame half
portion 41 integrally formed with each other. The second housing
main body half portion 39 includes first and second flange portions
43 and 45 and a second cylindrical air channel half portion 47. The
first flange portion 43 includes four corners, namely first to
fourth corners 43a to 43d, arranged in a circumferential direction
of the rotary shaft 8 (hereinafter simply referred to as
"circumferential direction") arranged on the common axis A of the
first and second motors 3 and 7. Four hook portions 49 and four
projections 51 are respectively integrally formed with the four
corners of the first flange portion 43 (the first to fourth corners
43a to 43d) to serve as engaging portions for use in forming a
coupling structure with the first split housing unit 11. The
details of the engagement relationship of the hook portions 49 and
the projections 51 with the hole portions 19e are the same as the
relationship between hole portions and hook portions forming a
coupling structure disclosed in Japanese Unexamined Patent
Application Publication No. 2004-278370. As disclosed in Japanese
Unexamined Patent Application Publication No. 2004-278370 (U.S.
Pat. No. 7,156,611), the hook portions 49 are partly fitted in the
hole portions 19e, and the second split housing unit 13 is rotated
by a predetermined angle about the common axis A. Then, the
projections 51 are fitted in fitting recesses (not shown) formed in
an end surface of the first flange portion 19 of the first split
housing unit 11. As a result, the second split housing unit 13 is
prevented from rotating. Also, engagement between the hook portions
49 and edge portions around the hole portions 19e prevents the
second split housing unit 13 from separating from the first split
housing unit 11 in the axial direction. The second flange portion
45 is formed with through holes 45a through which mounting members
for mounting the counter-rotating axial flow fan to an electric
device are to be inserted. The first and second flange portions 43
and 45 are integrally formed with both ends of the second
cylindrical air channel half portion 47. The second cylindrical air
channel half portion 47 extends in the axial direction (the axial
direction of the rotary shafts 4 and 8 arranged on the common axis
A).
[0026] The second support frame half portion 41 includes a second
support frame main body half portion 53 to which the second motor 7
is fixed and three second web half portions 55. The second support
frame main body half portion 53 includes a circular plate portion
53b having a cylindrical boss portion 53a at a center portion
thereof, and a peripheral wall portion 53c extending in the axial
direction from the outer peripheral portion of the circular plate
portion 53b. A second metallic bearing holder 57 made of brass is
fixedly fitted in the boss portion 53a. A base plate 59 of a stator
of the second motor 7 is disposed to block a space surrounded by
the circular plate portion 53b and the peripheral wall portion 53c.
A stator core 63 including a plurality of winding portions 61 is
fitted with the bearing holder 57.
[0027] The three second web half portions 55 are disposed between
the peripheral wall portion 53c of the second support frame main
body half portion 53 and an inner peripheral surface of the second
housing main body half portion 39 at predetermined intervals in the
circumferential direction to couple the second support frame main
body half portion 53 and the second housing main body half portion
39. Of the three web half portions 55, one web half portion has a
groove 55A formed for receiving lead wires.
[0028] A cup-shaped member 65 made of a magnetically permeable
material is fixed to one end of the rotary shaft 8 to support the
impeller 9 including the plurality of blades 10. A plurality of
permanent magnets 67 are fixed to the inner peripheral portion of
the cup-shaped member 65.
[0029] In the embodiment, the first and second support frame half
portions 17 and 41 are assembled to form the motor support frame
(23, 53). In other words, the first and second support frame half
portions 17 and 41 are formed by splitting the motor support frame
(23, 53) into two pieces along a split plane extending in a radial
direction perpendicular to the axial direction in which the common
axis A extends. With this configuration of the embodiment, the
coupling structure and the first and second split housing units 11
and 13 are configured such that an opposed surface of the first
support frame half portion 17 and an opposed surface of the second
support frame half portion 41 entirely contact each other when the
four engaging portions (the four hook portions 49) and the four
engaged portions (the four hole portions 19e) are completely
engaged with each other.
[0030] In the embodiment, a soft disk-like cushioning member 71
with a plurality of independent air bubbles dispersed therein is
disposed between the first support frame half portion 17 and the
second support frame half portion 41, specifically between the
circular plate portion 23b of the first support frame main body
half portion 23 and the circular plate portion 53b of the second
support frame main body half portion 53. As the soft cushioning
member 71, preferably, an acrylic foam sheet may be used. The
cushioning member 71 is disposed as it is compressed with the four
hook portions 49 forming the plurality of engaging portions and the
four hole portions 19e forming the plurality of engaged portions
completely engaged with each other. When the cushioning member 71
with a plurality of independent air bubbles dispersed therein is
compressed, the cushioning member 71 produces a restoring force
substantially evenly from its entirety to return from a compressed
state to an original state. The restoring force acts in a direction
to release the engagement between the plurality of engaging
portions (the four hook portions 49) and the plurality of engaged
portions. As a result, the coupling force between the plurality of
engaging portions (the four hook portions 49) and the plurality of
engaged portions (the edge portions around the four hole portions
19e) is strengthened, which prevents generation of a large gap
between the first and second split housing units 11 and 13 which
will cause vibration therebetween, and to reduce vibration that is
actually produced. The cushioning member 71 also serves a function
of absorbing vibration produced between the first support frame
half portion 17 and the second support frame half portion 41 to
reduce such vibration. As a result, according to the present
invention, it is possible to generally suppress an increase in
vibration within a wide rotational speed range compared to the
related art.
[0031] In the above embodiment, the soft cushioning member 71 is
disposed only between the circular plate portion 23b of the first
support frame main body half portion 23 and the circular plate
portion 53b of the second support frame main body half portion 53
to obtain favorable results. However, an enhanced vibration
suppression effect is obtained by disposing a soft cushioning
member also between the first web half portions 25 and the second
web half portions 55.
[0032] Vibration measurement tests were performed as described
below to verify the effect of the present invention. FIGS. 3 to 5
are each a graph showing the results of vibration measurement
tests. In the vibration measurement tests, the vibration
acceleration (m/s.sup.2) at a measurement location M1 (a portion of
the first flange portion 43 of the second split housing unit 13) in
the circumferential direction and the vibration acceleration
(m/s.sup.2) at a measurement location M2 (near a through hole 20a
of the second flange portion 20 of the first split housing unit 11)
at the discharge port in the axial direction were measured, and the
obtained vibration accelerations (m/s.sup.2) were synthesized and
plotted on a graph. FIG. 3A is a graph showing the results of
measuring the relationship between the rotational speed (the
rotational speed of the second motor rotating at high speeds) and
the vibration acceleration of vibration produced when the present
invention is applied to a counter-rotating axial flow fan available
from the applicant (Sanyo Denki Co., Ltd.) under the product number
9CRA0412P5J03, and when the present invention is not applied
thereto. In FIG. 3A, X indicates changes in vibration acceleration
of a counter-rotating axial flow fan provided with a soft
cushioning member 71 (Embodiment 1), and Y indicates changes in
vibration acceleration of a counter-rotating axial flow fan
provided with no cushioning member 71 (Comparative Example 1). As
the soft cushioning member, a cushioning member commercially
available from Sumitomo 3M Limited under the product name Y-4615
was used. From the measurement results, it is found that generation
of vibration was suppressed in a wide rotational speed range from a
low rotational speed range to a high rotational speed range by
using the cushioning member.
[0033] FIG. 3B is a graph showing the results of measuring the
relationship between the rotational speed (the rotational speed of
the second motor rotating at high speeds) and the vibration
acceleration of vibration produced when the present invention is
applied to another type of counter-rotating axial flow fan also
available from the applicant (Sanyo Denki Co., Ltd.) but under a
different product number 9CRA0412P4J03 and of different dimensions
from the counter-rotating axial flow fan used in FIG. 3A, and when
the present invention is not applied thereto. In FIG. 3B, X
indicates changes in vibration acceleration of a counter-rotating
axial flow fan provided with a cushioning member 71 (Embodiment 2),
and Y indicates changes in vibration acceleration of a
counter-rotating axial flow fan provided with no cushioning member
71 (Comparative Example 2). The soft cushioning member used was the
same as that used in FIG. 3A. Also from the measurement results of
these embodiments, it is found that generation of large vibration
was significantly suppressed in a wide rotational speed range from
a low rotational speed range to a high rotational speed range by
using the cushioning member.
[0034] FIG. 4A is a graph showing the results of measuring the
relationship between the rotational speed (the rotational speed of
the second motor rotating at high speeds) and the vibration
acceleration of vibration produced when the present invention is
applied to a counter-rotating axial flow fan produced by and
available from a manufacturer other than the applicant, and when
the present invention is not applied thereto. In FIG. 4A, X
indicates changes in vibration acceleration of a counter-rotating
axial flow fan provided with a cushioning member 71 (Embodiment 3),
and Y indicates changes in vibration acceleration of a
counter-rotating axial flow fan provided with no cushioning member
71 (Comparative Example 3). The cushioning member used was the same
as that used in FIG. 3A. From the measurement results, it is found
that generation of vibration was generally suppressed through the
entire rotational speed range by using the cushioning member.
[0035] Like FIG. 4A, FIG. 4B is a graph showing the results of
measuring the relationship between the rotational speed (the
rotational speed of the second motor rotating at high speeds) and
the vibration acceleration of vibration produced when the present
invention is applied to another type of counter-rotating axial flow
fan produced by and available from a manufacturer other than the
applicant, and when the present invention is not applied thereto.
In FIG. 4B, X indicates changes in vibration acceleration of a
counter-rotating axial flow fan provided with a cushioning member
71 (Embodiment 4), and Y indicates changes in vibration
acceleration of a counter-rotating axial flow fan provided with no
cushioning member 71 (Comparative Example 4). The cushioning member
used was the same as that used in FIG. 3A. From the measurement
results, it is found that generation of vibration was generally
suppressed through the entire rotational speed range by using the
cushioning member.
[0036] As a result of the above vibration measurements (FIGS. 3 and
4), it was found that favorable results were obtained by using an
acrylic-foam cushioning member with independent air bubbles.
Further, a preferable thickness range of the acrylic-foam
cushioning member was confirmed and it was verified whether or not
materials other than the acrylic foam were suitable for use as the
cushioning member. FIG. 5 is a graph showing the results of
measuring the relationship between the rotational speed (the
rotational speed of the second motor rotating at high speeds) and
the vibration acceleration of vibration produced by the same
counter-rotating axial flow fan as in FIG. 3 under the same
measurement conditions as in FIG. 3, where the thickness of the
acrylic foam sheet was changed, a cushioning member made of a
material other than the acrylic foam was used, no cushioning member
was used, and a gap was positively provided in place of a
cushioning member.
[0037] In FIG. 5, the "dotted line" indicates changes in vibration
acceleration of a counter-rotating axial flow fan provided with the
soft cushioning member 71 formed by an acrylic foam sheet having a
thickness of 0.4 mm (Embodiment 5). The "broken line" indicates
changes in vibration acceleration of a counter-rotating axial flow
fan provided with the cushioning member 71 formed by an acrylic
foam sheet having a thickness of 0.8 mm (Embodiment 6). The "thick
solid line" indicates changes in vibration acceleration of a
counter-rotating axial flow fan provided with no cushioning member
71 (Comparative Example 5). The "thick broken line" indicates
changes in vibration acceleration of a counter-rotating axial flow
fan provided with a gap of 0.2 mm positively provided between the
first support frame main body half portion 23 and the second
support frame main body half portion 53 (Comparative Example 6).
The normal "solid line" indicates changes in vibration acceleration
of a counter-rotating axial flow fan provided with a cushioning
member formed by an aluminum sheet having a thickness of 0.46 mm
(Comparative Example 7). The "dash and dot line" indicates changes
in vibration acceleration of a counter-rotating axial flow fan
provided with a cushioning member formed by a plastic sheet having
a thickness of 0.5 mm (Comparative Example 8).
[0038] The measurement results are described below. When no
cushioning member was used (Comparative Example 5), a plurality of
resonance points (peaks) appeared in the vibration acceleration. In
particular, a very high peak was exhibited in the vibration
acceleration in a high rotational speed range around 14000 [rpm].
When an aluminum sheet was used as the cushioning member
(Comparative Example 7) and when a plastic sheet was used as the
cushioning member (Comparative Example 8), the plurality of
resonance points (peaks) in the vibration acceleration in a high
rotational speed range were slightly decreased. However, the
resonance point (peak) in the vibration acceleration around 14000
[rpm] remained relatively high, although it was not as high as when
no cushioning member 71 was used (Comparative Example 5).
[0039] In contrast, when an acrylic foam sheet having a thickness
of 0.4 mm was used as the cushioning member 71 (Embodiment 5), the
plurality of peaks in the vibration acceleration in a high
rotational speed range were decreased, and in addition, the peak in
the vibration acceleration around 14000 [rpm] was reduced by 40%
with respect to when no cushioning member 71 was used (Comparative
Example 5), and reduced by 30% with respect to when an aluminum
sheet and a plastic sheet were used as the cushioning member 71
(Comparative Examples 7 and 8). Also, when an acrylic foam sheet
having a thickness of 0.8 mm was used as the cushioning member 71
(Embodiment 6), the plurality of peaks in the vibration
acceleration in a high rotational speed range were decreased, and
in addition, the peak in the vibration acceleration around 14000
[rpm] was reduced by 60% with respect to when no cushioning member
71 was used (Comparative Example 5) , and reduced by 50% with
respect to when an aluminum sheet and a plastic sheet were used as
the cushioning member 71 (Comparative Examples 7 and 8). When an
acrylic foam sheet having a thickness of 0.8 mm was used
(Embodiment 6), the peak in the vibration acceleration around 14000
[rpm] was reduced by 30% with respect to when an acrylic foam sheet
having a thickness of 0.4 mm was used (Embodiment 5).
[0040] When a gap of 0.2 mm was provided without using a cushioning
member (Comparative Example 6), a peak higher than the highest peak
that appeared when no cushioning member 71 was used (Comparative
Example 5) was exhibited in the vibration acceleration around 12000
[rpm] although no high peak was exhibited in the vibration
acceleration around 14000 [rpm]. Moreover, the number of peaks in
the vibration acceleration that were relatively high was increased
compared to when no cushioning member 71 was used (Comparative
Example 5). Consequently, it is found that generation of vibration
cannot be reduced in a wide rotational speed range from a low
rotational speed range to a high rotational speed range by simply
providing a gap with no cushioning member disposed therein,
although vibration can be suppressed in a high rotational speed
range by transferring high peaks in the vibration acceleration to a
lower rotational speed range (by causing a shift phenomenon).
[0041] As can be seen from the above results, it is possible to not
only suppress significant vibration that is produced in a high
rotational speed range but also generally suppress an increase in
vibration over a wide rotational speed range by setting the
thickness of the acrylic foam sheet used as the cushioning member
71 in a range from 0.4 mm to 0.8 mm. If the thickness of the
acrylic foam sheet is less than 0.4 mm, it is expected that the
thickness of the cushioning member itself is too small to provide a
necessary and sufficient vibration absorption effect. If the
thickness of the acrylic foam sheet is more than 0.8 mm, it is
necessary to separately provide a gap in which the thick acrylic
foam sheet is to be disposed between the first support frame half
portion and the second support frame half portion. It is not
preferable to positively provide a gap because the effect of the
shift phenomenon, as discussed earlier when a gap of 0.2 mm was
provided, appears.
[0042] In the above embodiment, the cushioning member 71 is
disposed only between the circular plate portion 23b of the first
support frame main body half portion 23 and the circular plate
portion 53b of the second support frame main body half portion 53.
However, it is a matter of course that the cushioning member 71 may
also be disposed between the first web half portions 25 and the
second web half portions 55.
INDUSTRIAL APPLICABILITY
[0043] According to the present invention, a soft cushioning member
with a plurality of independent air bubbles dispersed therein is
disposed between a first support frame half portion and a second
support frame half portion, the cushioning member being compressed
when a plurality of engaging portions and a plurality of engaged
portions are completely engaged with each other. Therefore, it is
possible to generally suppress an increase in vibration over a wide
rotational speed range compared to the related art.
* * * * *