U.S. patent application number 15/869583 was filed with the patent office on 2018-07-12 for serial axial flow fan.
The applicant listed for this patent is Nidec Corporation. Invention is credited to Shogo HAKOZAKI, Ryota YAMAGATA.
Application Number | 20180195526 15/869583 |
Document ID | / |
Family ID | 62782258 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180195526 |
Kind Code |
A1 |
HAKOZAKI; Shogo ; et
al. |
July 12, 2018 |
SERIAL AXIAL FLOW FAN
Abstract
A serial axial flow fan in which an end portion of a first axial
flow fan on an exhaust side, and an end portion of a second axial
flow fan on an intake side are connected to each other. At least
either of a plurality of first blades of a first impeller of the
first axial flow fan, and a plurality of second blades of a second
impeller of the second axial flow fan are provided with auxiliary
blade portions. Furthermore, Nin<Nout<Nrib is satisfied,
where a number of first blades is Nin, a number of second blades is
Nout, and a number of first support ribs and a number of second
support ribs are each Nrib.
Inventors: |
HAKOZAKI; Shogo; (Kyoto,
JP) ; YAMAGATA; Ryota; (Kyoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nidec Corporation |
Kyoto |
|
JP |
|
|
Family ID: |
62782258 |
Appl. No.: |
15/869583 |
Filed: |
January 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62445355 |
Jan 12, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 19/007 20130101;
F04D 29/384 20130101; F04D 29/181 20130101; F04D 29/52 20130101;
F04D 29/34 20130101; F04D 19/002 20130101; F04D 29/646 20130101;
F04D 29/325 20130101; F04D 29/666 20130101 |
International
Class: |
F04D 29/38 20060101
F04D029/38; F04D 29/34 20060101 F04D029/34; F04D 29/66 20060101
F04D029/66; F04D 19/00 20060101 F04D019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2018 |
JP |
2018-001030 |
Claims
1. A serial axial flow fan comprising: a first axial flow fan that
blows out air drawn in from an intake side to an exhaust side; a
second axial flow fan connected to the first axial flow fan along a
central axis of the first axial flow fan, the second axial flow fan
blowing out the air drawn in from an intake side to an exhaust
side, wherein an end portion of the first axial flow fan on the
exhaust side and an end portion of the second axial flow fan on the
intake side are connected to each other; the first axial flow fan
including a first impeller that rotates about the central axis, a
first motor portion that rotates the first impeller, a first
housing that includes a first cylindrical portion that surrounds an
outside of the first impeller in a radial direction, and a first
support rib that extends inwards from an inner surface of the first
cylindrical portion and that supports the first motor portion; the
first impeller including a plurality of first blades that extend
outwards in the radial direction and that are arranged in a
circumferential direction; the second axial flow fan including a
second impeller that rotates about the central axis, a second motor
portion that rotates the second impeller, a second housing that
includes a second cylindrical portion that surrounds an outside of
the second impeller in the radial direction, and a second support
rib that extends inwards from an inner surface of the second
cylindrical portion and that supports the second motor portion, a
number of the second support ribs being equal to a number of the
first support ribs; and the second impeller including a plurality
of second blades that extend outwards in the radial direction and
that are arranged in the circumferential direction; auxiliary blade
portions being included in at least either of the first blades and
the second blades; and Nin<Nout<Nrib being satisfied, where a
number of first blades is Nin, a number of second blades is Nout,
and a number of first support ribs and a number of second support
ribs are each Nrib.
2. The serial axial flow fan according to claim 1, wherein the
auxiliary blade portions are provided at outer edge portions of the
first blades in the radial direction.
3. The serial axial flow fan according to claim 2, wherein outsides
of the auxiliary blade portions in the radial direction are warped
towards the intake side.
4. The serial axial flow fan according to claim 1, wherein Nin,
Nout, and Nrib are a set of positive integers that do not have a
common divisor other than 1.
5. The serial axial flow fan according to claim 1, wherein Nin is
5.
6. The serial axial flow fan according to claim 1, wherein Nout is
7.
7. The serial axial flow fan according to claim 1, wherein the
first support rib is disposed on the exhaust side of the first
housing, wherein the second support rib is disposed on the intake
side of the second housing, and wherein a surface of the first
support rib that faces the exhaust side and a surface of the second
support rib that faces the intake side overlap each other in an
axial direction.
8. The serial axial flow fan according to claim 1, wherein Nrib is
11.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Patent Application No. 62/445,355 filed on Jan. 12, 2017 and
Japanese Patent Application No. 2018-001030 filed on Jan. 9, 2018.
The entire contents of these applications are hereby incorporated
herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present disclosure relates to a serial axial flow fan in
which axial flow fans are directly connected to each other.
2. Description of the Related Art
[0003] Hitherto, axial flow fans are used as cooling fans that cool
electronic components disposed inside casings. Static pressure and
air volume required in a cooling fan are on the rise due to an
increase in heat generating amounts of electronic components caused
by increase in performance, and due to an increase in the density
where the electronic components are disposed caused by
miniaturization of the casing. In order to increase the static
pressure and the air volume of the cooling fan, serially disposed
axial flow fans, such as the one described in Japanese Laid-open
Patent Application Publication No. 2007-303432 in which two (a
plurality of) axial flow fans are serially connected to each other
in an axial direction, are proposed.
[0004] Furthermore, a counter-rotating axial flow fan of patent
literature 2 includes a first impeller on a suction side, a second
impeller on a discharge side, and a stator blades disposed in a
static state at a position between the first impeller and the
second impeller. Furthermore, it is disclosed that the air volume
and the static pressure are the highest when the number of blades
of the first impeller is five, the number of stator blades is
three, and the number of second impellers is four.
[0005] In recent years, the amount of heat generated by electronic
components is increasing, and the density in which the electronic
components are disposed inside a casing is getting higher.
Furthermore, there are cases in which the air from the serially
disposed axial flow fan does not easily spread inside the casing
due to a formation of a portion where the gap between the
components are small, and due to another electronic component being
disposed behind an electronic component. The electronic components
may become insufficiently cooled due to hindrance in the spreading
of the airflow.
SUMMARY OF THE INVENTION
[0006] An object of the present disclosure is to provide a serial
axial flow fan that is capable of improving the static pressure and
the air volume with regards to the input shaft power, and that is
capable of reducing noise.
[0007] An exemplification of a serial axial flow fan according to
the present disclosure includes a first axial flow fan that blows
out air drawn in from an intake side to an exhaust side, a second
axial flow fan connected to the first axial flow fan along a
central axis of the first axial flow fan, the second axial flow fan
blowing out the air drawn in from an intake side to an exhaust
side, wherein an end portion of the first axial flow fan on the
exhaust side and an end portion of the second axial flow fan on the
intake side are connected to each other, the first axial flow fan
including a first impeller that rotates about the central axis, a
first motor portion that rotates the first impeller, a first
housing that includes a first cylindrical portion that surrounds an
outside of the first impeller in a radial direction, and a first
support rib that extends inwards from an inner surface of the first
cylindrical portion and that supports the first motor portion, the
first impeller including a plurality of first blades that extend
outwards in the radial direction and that are arranged in a
circumferential direction, the second axial flow fan including a
second impeller that rotates about the central axis, a second motor
portion that rotates the second impeller, a second housing that
includes a second cylindrical portion that surrounds an outside of
the second impeller in the radial direction, and a second support
rib that extends inwards from an inner surface of the second
cylindrical portion and that supports the second motor portion, a
number of the second support ribs being equal to a number of the
first support ribs, and the second impeller including a plurality
of second blades that extend outwards in the radial direction and
that are arranged in the circumferential direction, auxiliary blade
portions being included in at least either of the first blades and
the second blades, and Nin<Nout<Nrib being satisfied, where a
number of first blades is Nin, a number of second blades is Nout,
and a number of first support ribs and a number of second support
ribs are each Nrib.
[0008] The exemplification of the serial axial flow fan of the
present disclosure is capable of improving static pressure and air
volume with regards to the input shaft power, and is capable of
reducing noise.
[0009] The above and other elements, features, steps,
characteristics and advantages of the present disclosure will
become more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of an example of a serial axial
flow fan according to the present disclosure.
[0011] FIG. 2 is a cross-sectional view of the serial axial flow
fan illustrated in FIG. 1 cut along a plane including a central
axis.
[0012] FIG. 3 is a perspective view of the first axial flow fan
viewed from above.
[0013] FIG. 4 is a perspective view of the first axial flow fan
viewed from below.
[0014] FIG. 5 is an exploded perspective view of the first axial
flow fan illustrated in FIG. 3.
[0015] FIG. 6 is a cross-sectional view of the first axial flow fan
illustrated in FIG. 3 cut along a plane including the central
axis.
[0016] FIG. 7 is a perspective view of a second axial flow fan
viewed from above.
[0017] FIG. 8 is a perspective view of the second axial flow fan
viewed from below.
[0018] FIG. 9 is an exploded perspective view of the second axial
flow fan illustrated in FIG. 7.
[0019] FIG. 10 is a cross-sectional view of the second axial flow
fan illustrated in FIG. 7 cut along a plane including the central
axis.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Hereinafter, exemplary embodiments of the present disclosure
will be described in detail with reference to the drawings. Note
that in the present specification, in a serial axial flow fan 1, a
direction parallel to a central axis J1 of the serial axial flow
fan 1 is referred to as an "axial direction", a direction
orthogonal to the central axis J1 of the serial axial flow fan 1 is
referred to as a "radial direction", and a direction extending
along an arc about a center of the central axis J1 of the serial
axial flow fan 1 is referred to as a "circumferential direction".
Furthermore, in the serial axial flow fan 1, the axial direction is
referred to as an up-down direction, and an upper side IS and a
lower side OS are defined with the state illustrated in FIG. 1 as a
reference. Note that the up-down direction is a term used for
description and does not limit the positional relationship and the
direction of the serial axial flow fan 1 while in use.
[0021] A serial axial flow fan of an exemplary embodiment of the
present disclosure will be described hereinafter. FIG. 1 is a
perspective view of an example of a serial axial flow fan according
to the present disclosure. FIG. 2 is a cross-sectional view of the
serial axial flow fan illustrated in FIG. 1 cut along a plane
including the central axis. The serial axial flow fan 1 illustrated
in FIGS. 1 and 2 draws in air through an end portion on the upper
side IS. Furthermore, the air that has been drawn in is compressed
and (or) accelerated inside the serial axial flow fan 1 and is
discharged from an end portion on the lower side OS. Note that in
the description hereinafter, the upper side may be referred to as
an intake side, and the lower side may be referred to as an exhaust
side.
[0022] As illustrated in FIGS. 1 and 2, the serial axial flow fan 1
includes a first axial flow fan 2 and a second axial flow fan 3.
The first axial flow fan 2 is disposed on the upper side of the
second axial flow fan 3. In other words, the first axial flow fan 2
is disposed on the intake side of the second axial flow fan 3.
Furthermore, in the serial axial flow fan 1, the first axial flow
fan 2 and the second axial flow fan 3 are connected in series along
the central axis J1. In other words, centers of the first axial
flow fan 2 and the second axial flow fan 3 coincides with the
central axis J1.
[0023] The upper sides IS of the first axial flow fan 2 and the
second axial flow fan 3 are both the intake sides, and the lower
sides OS thereof are the exhaust sides. Furthermore, the exhaust
side of the first axial flow fan 2 and the intake side of the
second axial flow fan 3 are connected to each other. In other
words, the air discharged through a first exhaust portion 2302
described later provided at an end face of the first axial flow fan
2 on the lower side OS is drawn in through a second intake portion
3301 described later provided at an end face of the second axial
flow fan 3 on the upper side IS.
[0024] In other words, the first axial flow fan 2 blows the air
drawn in from the intake side out from the exhaust side.
Furthermore, the second axial flow fan 3 connected to the first
axial flow fan 2 along the central axis J1 of the first axial flow
fan 2 blows the air drawn in from the intake side out from the
exhaust side. Furthermore, in the serial axial flow fan 1, the end
portion of the first axial flow fan 2 on the exhaust side is
connected to the end portion of the second axial flow fan 3 on the
intake side.
[0025] FIG. 3 is a perspective view of the first axial flow fan
viewed from above. FIG. 4 is a perspective view of the first axial
flow fan viewed from below. FIG. 5 is an exploded perspective view
of the first axial flow fan illustrated in FIG. 3. FIG. 6 is a
cross-sectional view of the first axial flow fan illustrated in
FIG. 3 cut along a plane including the central axis. As illustrated
in FIGS. 3 to 6, the first axial flow fan 2 includes a first
impeller 21, a first motor portion 22, a first housing 23, and a
plurality of first support ribs 24.
[0026] The first housing 23 is an outer package of the first axial
flow fan 2, and protects the first impeller 21, the first motor
portion 22, and other components.
[0027] The first housing 23 includes a first cylindrical portion
230, a first intake flange portion 2311, and a first exhaust flange
portion 2321. The first cylindrical portion 230 is a cylinder
penetrating from an upper end portion 231 to a lower end portion
232 along the central axis J1. The upper end portion 231 of the
first cylindrical portion 230 is a first intake portion 2301, and
the lower end portion 232 is the first exhaust portion 2302. As
illustrated in FIGS. 3 to 6, the first cylindrical portion 230
includes four outer flat surfaces 236 each having a shape formed
when the outer peripheral surface of the circular cylinder is cut
by a plane parallel to the central axis J1. The outer flat surfaces
236 are disposed at equal intervals in the circumferential
direction. The outer flat surfaces 236 are surfaces that are
parallel to the central axis J1.
[0028] In the first axial flow fan 2, the first impeller 21 rotates
inside first cylindrical portion 230 about the central axis J1, and
generates an airflow. In other words, while the first cylindrical
portion 230 is a portion of the outer package, the first
cylindrical portion 230 is also a wind tunnel. In other words, the
first housing 23 includes the first cylindrical portion 230 that
surrounds the other side of the first impeller 21 in the radial
direction. Furthermore, the first impeller 21 rotates about the
central axis J1.
[0029] The first intake flange portion 2311 is provided at the
upper end portion 231 of the first housing 23. The first intake
flange portion 2311 has a square shape when viewed in a central
axis J1 direction and a length of each side is longer than an
inside diameter of the first cylindrical portion 230. Corner
portions of the first intake flange portion 2311 when viewed in the
central axis J1 direction expand from the outer peripheral surface
of the first cylindrical portion 230 towards the outside in the
radial direction. Note that the corner portions are portions that
include the corners of the square, and are portions that include
the areas having a predetermined width in the circumferential
direction that include the corners. Corner portions described
hereinafter will be similar to the above corner portions.
Furthermore, the surfaces that constitute the sides of the square
first intake flange portion 2311 when viewed in the central axis J1
direction are each flush with the corresponding outer flat surface
236.
[0030] The first exhaust flange portion 2321 is provided at the
lower end portion 232 of the first housing 23. The first exhaust
flange portion 2321 has a square shape when viewed in the central
axis J1 direction and a length of each side is longer than the
inside diameter of the first cylindrical portion 230. Corner
portions of the first exhaust flange portion 2321 when viewed in
the central axis J1 direction expand from the outer peripheral
surface of the first cylindrical portion 230 towards the outside in
the radial direction. Furthermore, the surfaces that constitute the
sides of the first exhaust flange portion 2321 when viewed in the
central axis J1 direction are each flush with the corresponding
outer flat surface 236. Moreover, when viewed in the central axis
J1 direction, the first intake flange portion 2311 and the first
exhaust flange portion 2321 overlap each other.
[0031] The first cylindrical portion 230 includes a first inside
diameter portion 233 and a second inside diameter portion 234. The
first inside diameter portion 233 is disposed on the intake side
with respect to the second inside diameter portion 234, in other
words, the first inside diameter portion 233 is disposed on the
upper side IS. The first inside diameter portion 233 is tubular,
and an inside diameter D11 thereof does not change in the axial
direction. The minimum inside diameter of the first cylindrical
portion 230 is the inside diameter D11. In other words, the first
inside diameter portion 233 is a minimum inside diameter portion.
In the first cylindrical portion 230, the second inside diameter
portion 234 is disposed on the lower end portion 232 side, in other
words, the second inside diameter portion 234 is disposed at the
end portion on the exhaust side. The second inside diameter portion
234 includes a portion that has a diameter that is larger than that
of the first inside diameter portion 233. The portions of the
second inside diameter portion 234 that overlap the outer flat
surfaces 236 in the radial direction are inner flat surfaces 2341,
and portions that connect the inner flat surfaces 2341 to each
other in the circumferential direction are inner curved surfaces
2342. The section of the lowermost side of each inner curved
surface 2342 of the second inside diameter portion cut along a
plane orthogonal to the central axis has an arc shape and an inside
diameter thereof is an inside diameter D12. Furthermore, the inside
diameter D11 of the first inside diameter portion 233 is smaller
than the inside diameter D12 of each inner curved surface 2342 of
the second inside diameter portion 234.
[0032] The inner curved surfaces 2342 include conical portions 235.
Each conical portion 235 is a portion of a conical inner surface
and the diameter of each conical portion 235 widens towards the
lower side, in other words, the exhaust side.
[0033] The first axial flow fan 2 includes 11 first support ribs
24. The 11 first support ribs 24 extend from the second inside
diameter portion 234 towards the inner side in the radial
direction, and are disposed at equal intervals in the
circumferential direction. Inner sides of the first support ribs 24
in the radial direction are connected to a base portion 2221
(described later) of the first motor portion 22. With the above,
the first motor portion 22 is supported by the first housing 23
with the first support ribs 24. The first housing 23, the first
support ribs 24, and the base portion 2221 are formed as a resin
molded body formed in an integrated manner with resin. In the first
axial flow fan 2, the first support ribs 24 are disposed on the
lower end side of the first housing 23. In other words, the first
support ribs 24 extend from an inner circumferential surface of the
first cylindrical portion 230 towards the inner side, and support
the first motor portion 22.
[0034] When viewed in the central axis J1 direction, the first
support ribs 24 are disposed inside the first cylindrical portion
230. Furthermore, each first support ribs 24 traverses at least a
portion of the airflow generated inside the first cylindrical
portion 230 with the rotation of the first impeller 21. The airflow
generated by the rotation of the first impeller 21 has a velocity
component in the axial direction and has a velocity component in
the direction in which the first impeller 21 rotates, in other
words, in the circumferential direction. Accordingly, the first
support ribs 24 each have an inclination that does not cause the
airflow to flow back due to the velocity component of the airflow
in the circumferential direction, in other words, the first support
ribs 24 each have an inclination in which the lower side is
positioned on the downstream side in the rotation direction with
respect to the upper side IS. Although the details will be
described later, when the first axial flow fan 2 and the second
axial flow fan 3 are connected to each other, the first support
ribs 24 and second support ribs 34 constitute stator blades, and
regulates the airflow in the axial direction. In other words, the
first support ribs 24 support the first motor portion 22 and, at
the same time, serve as stator blades that regulate the airflow.
The first motor portion 22 is of a so-called outer rotor type. As
illustrated in FIG. 6, the first motor portion 22 includes a first
rotor portion 221 and a first stator portion 222. The first motor
portion 22 rotates the first impeller 21.
[0035] The first stator portion 222 includes the base portion 2221,
a bearing holding portion 2222, an armature 2223, and a circuit
board 2224. The base portion 2221 is formed as an integrally molded
body together with the first housing 23 and the first support ribs
24. The base portion 2221 has a disk shape orthogonal to the
central axis J1. The center of the disk shape overlaps the central
axis J1. The bearing holding portion 2222 has a cylindrical shape,
is disposed at a center portion of the base portion 2221, and
extends towards the upper side IS. Note that the bearing holding
portion 2222 may be an integrally molded body molded together with
the base portion 2221. A ball bearing 2225 and a ball bearing 2226
are attached to an upper portion and a lower portion inside the
bearing holding portion 2222. Furthermore, a shaft 2213 (described
later) of the first rotor portion 221 is rotatably supported
through the ball bearing 2225 and the ball bearing 2226. Note that
the ball bearing 2225 and the ball bearing 2226 are examples of a
bearing mechanism, and the bearing mechanism is not limited to the
ball bearing 2225 and the ball bearing 2226. Bearings that are
structured to rotatably support the shaft 2213 may be widely
employed.
[0036] The armature 2223 is fixed external to the bearing holding
portion 2222 in the radial direction. The armature 2223 includes a
stator core 2227, a coil 2228, and an insulator 2229. The stator
core 2227 is a stacked body in which electromagnetic steel sheets
are stacked in the axial direction. Note that the stator core 2227
is not limited to a stacked body in which electromagnetic steel
sheets are stacked, and may be a single member, such as a fired
body of powder or a casting, for example. The stator core 2227
includes an annular core back and a plurality of (nine, herein)
teeth. The nine teeth extend towards the outside in the radial
direction from an outer peripheral surface of the core back and are
formed radially. With the above, the nine teeth are arranged in the
circumferential direction. The coil 2228 is configured by winding a
length of conducting wire around the teeth on which the insulator
2229 has been attached.
[0037] The core back of the stator core 2227 is press-fitted in the
bearing holding portion 2222, and the stator core 2227 is fixed to
the bearing portion 2222. The press-fitting may be a so-called
stationary fit, or may be a light press-fit that is a so-called
transition fit in which the press-fitting force is weaker than the
press-fitting. The core back and the bearing holding portion 2222
may be fixed to each other by another method, such as adhesion.
When the stator core 2227 is fixed to the bearing holding portion
2222, the center thereof overlaps the central axis J1. Furthermore,
the nine teeth of the stator core 2227 are arranged at equal
intervals in the circumferential direction to smoothly and
efficiently rotate the first motor portion 22.
[0038] The circuit board 2224 is attached to the base portion 2221.
The circuit board 2224 is electrically connected to the coil 2228
of the first stator portion 222. The circuit board 2224 includes a
drive circuit that drives the coil 2228.
[0039] The base portion 2221 of the first stator portion 222 is an
integrally molded body formed together with the first support ribs
24. With the above, the first stator portion 222, in other words,
the first motor portion 22 is supported by the first support ribs
24. Furthermore, the first support ribs 24 are also an integrally
molded body formed together with the first housing 23. Accordingly,
the first motor portion 22 is connected to the first housing 23
through the first support ribs 24, in other words, the first motor
portion 22 is supported by the first housing 23.
[0040] The first rotor portion 221 includes a yoke 2211, a field
magnet 2212, the shaft 2213, and a shaft fixing member 2214. The
yoke 2211 is made of metal and has a lidded cylindrical shape about
the central axis J1. The shaft fixing member 2214 is fixed to the
center of the lid-shaped portion of the yoke 2211. The shaft 2213
is fixed to the shaft fixing member 2214 with a fixing method, such
as press-fitting. Note that the fixing method is not limited to
press-fitting and may be another method, such as adhesion. In other
words, the yoke 2211 is fixed to the shaft 2213 through the shaft
fixing member 2214.
[0041] The field magnet 2212 has a circular cylinder shape. The
field magnet 2212 is fixed to an inner surface of the yoke 2211.
The field magnet 2212 is magnetized to the N-pole and the S-pole
alternately in the circumferential direction. Note that in place of
the field magnet 2212 having a circular cylinder shape, a plurality
of field magnets may be arranged in the circumferential
direction.
[0042] The shaft 2213 is made of metal and has a columnar shape.
The shaft 2213 is rotatably supported by the bearing holding
portion 2222, in other words, by the first stator portion 222
through the ball bearing 2225 and the ball bearing 2226. The center
of the shaft 2213 rotatably supported by the bearing holding
portion 2222 overlaps the central axis J1.
[0043] In the first motor portion 22, by having the shaft 2213 be
rotatably supported through the ball bearing 2225 and the ball
bearing 2226, the first rotor portion 221 is supported by the first
stator portion 222 in a rotatable manner about the central axis J1.
In the above, an inner surface of the field magnet 2212 of the
first rotor portion 221 in the radial direction and an outer
surface of the stator core 2227 in the radial direction oppose each
other with a gap therebetween in the radial direction. An operation
of the first motor portion 22 will be described in detail
later.
[0044] As illustrated in FIGS. 5 and 6, the first impeller 21
includes a plurality of first blades 211, a cup 212, and auxiliary
blade portions 213. The cup 212 has a lidded cylindrical shape.
Note that while the cup 212 has a lidded cylindrical shape, the
shape is not limited to the above, and may be a truncated cone
shape in which the outside diameters of an outer peripheral surface
differ in the axial direction.
[0045] The first blades 211 each protrude from the outer surface of
the cup 212 in the radial direction towards the outside in the
radial direction. The first impeller 21 is provided with five first
blades 211. The five first blades 211 are aligned at equal
intervals in the circumferential direction. In other words, the
first impeller 21 includes the plurality of first blades 211 that
extend outwards in the radial direction and that are arranged in
the circumferential direction. The first blades 211 are inclined in
the circumferential direction and generate an airflow from the
upper side towards the lower side when the first impeller 21 is
rotated. In other words, the first blades 211 are each inclined to
a direction that generates an airflow from the upper side IS
towards the lower side. Surfaces of the first blades 211 on the
exhaust side, in other words, the surfaces on the lower side are
the pressure surfaces. Furthermore, surfaces of the first blades
211 on the intake side, in other words, the surfaces on the upper
side IS are negative pressure surfaces.
[0046] Furthermore, the auxiliary blade portions 213 are provided
at outer edge portions of the first blades 211 in the radial
direction. With the above configuration, a vortex can be generated
by the auxiliary blade portions 213 and the backflow of air in the
gaps between outer edge portions of the auxiliary blade portions
213 in the radial direction and an inner surface of the first
cylindrical portion 230 can be suppressed. Details will be
described later. The auxiliary blade portions 213 are each formed
in the entire area of the outer edge portion of the corresponding
first blade 211 from a front end in the rotation direction to a
rear end in the rotation direction. By configuring the auxiliary
blade portions 213 in the above manner, the pressure in the entire
outer edge portions of the first blades 211 can be increased with
the auxiliary blade portions 213. With the above, a pressure
increasing effect can be obtained. Furthermore, there are cases in
which the manufacturing is easier compared with a case in which the
auxiliary blade portion 213 is formed in a portion of the outer
edge portion. Moreover, the auxiliary blade portions 213 are each
warped towards the outside in the radial direction and to the upper
side in the axial direction, in other words, to the intake side.
With the above configuration, the pressure generated with each
auxiliary blade portion can be increased with the auxiliary blade
portion with a simple shape. Furthermore, manufacturing is easier
compared to a configuration in which the auxiliary blade portions
are attached in an additional manner.
[0047] In the first axial flow fan 2, an inflow of air in the outer
edge portions of the first blades 211 in the radial direction from
the pressure surface side towards the negative pressure surface
side is suppressed with the auxiliary blade portions 213. Note that
an operation of suppressing the flow of air will be described in
detail later.
[0048] As described above, the first stator portion 222 of the
first motor portion 22 is assembled by attaching the bearing
holding portion 2222, the armature 2223, and the circuit board 2224
to the base portion 2221 formed integrally with the first housing
23. In other words, the first stator portion 222 is supported by
the first housing 23 through the first support ribs 24.
[0049] Furthermore, the yoke 2211 of the first rotor portion 221 is
fixed inside the cup 212 of the first impeller 21. The yoke 2211
may be fixed in the cup 212 by press-fitting or by adhesion.
Furthermore, the yoke 2211 may be fixed with a fastening member,
such as a screw. The cup 212 suppressing deviation from the yoke
2211 is fixed to the yoke 2211. In other words, the first impeller
21 is fixed to the first rotor portion 221.
[0050] Furthermore, the shaft 2213 of the first rotor portion 221
to which the first impeller 21 is fixed is fixed to the inner rings
of the ball bearing 2225 and the ball bearing 2226 attached inside
the bearing holding portion 2222. Note that while the shaft 2213 is
fixed to the inner rings of the ball bearing 2225 and the ball
bearing 2226 by press-fitting, the fixing method is not limited to
press-fitting. For example, a fixing method, such as adhesion or
welding, that suppresses the relative movement between the shaft
2213 and the inner rings, and that fixes the shaft 2213 about the
central axis J1 in a rotatable manner can be widely employed. The
first rotor portion 221 to which the first impeller 21 is attached
is rotatably attached to the first stator portion 222 in the above
manner.
[0051] By attaching the first rotor portion 221 to the first stator
portion 222, the first impeller 21 is accommodated inside the first
housing 23. The outer sides of the auxiliary blade portions 213 in
the radial direction, the auxiliary blade portions 213 being
provided at the outer edge portions of the first blades 211 in the
radial direction, oppose the inner surface of the first cylindrical
portion 230 in the radial direction.
[0052] An electric current is supplied to the coil 2228 of the
first motor portion 22 at a good timing from the drive circuit
mounted on the circuit board 2224. With the above, the first rotor
portion 221 of the first motor portion 22 is rotated in a
predetermined direction. Note that, herein, the rotation direction
of the first rotor portion 221 is anticlockwise when viewing the
central axis J1 from the upper side IS.
[0053] By rotating the first motor portion 22 about the central
axis J1, the first impeller 21 fixed to the first rotor portion 221
is also rotated about the central axis J1. With the rotation of the
first impeller 21, an airflow that, while swirling in the
circumferential direction, flows in the axial direction is
generated in the first housing 23, in other words, inside the first
cylindrical portion 230.
[0054] With the rotation of the first impeller 21, the first blades
211 push the air. Accordingly, the surfaces on the lower side (the
surfaces on the exhaust side) of the first blades 211 are pressure
surfaces, and the surfaces on the upper side IS (the surfaces on
the intake side) are negative pressure surfaces. The first impeller
21 has five first blades 211, and the inclination of each first
blade 211 with respect to the central axis J1 is large.
Accordingly, a pressure difference between each pressure surface
and the corresponding negative pressure surface is large. In the
first axial flow fan 2, the outer edge portions of the first blades
211 in the radial direction and the inner surface of the first
cylindrical portion 230 oppose each other in the radial direction
with a gap in between. Accordingly, when the first impeller 21 is
rotated and a pressure difference is generated in the first blades
between the pressure surfaces and the negative pressure surfaces, a
flow of air from the pressure surface side towards the negative
pressure surface side, in other words, from the lower side OS
towards the upper side IS, is easily generated in the outer edge
portions of the first blades 211 in the radial direction.
[0055] The auxiliary blade portions 213 are provided at the outer
edge portions of the first blades 211 in the radial direction. The
auxiliary blade portions 213 are warped towards the upper side IS
(the intake side). When the first impeller 21 is rotated, the
auxiliary blade portions 213 generate a vortex in the gap between
the outer edge portions of the auxiliary blade portions 213 in the
radial direction and the inner surface of the first cylindrical
portion 230. With the above vortex, a flow of air on the lower side
towards the upper side in the gap between the outer edge portions
of the auxiliary blade portions 213 and the inner surface of the
first cylindrical portion 230 can be suppressed. Accordingly, by
suppressing the flow of air from the lower side towards the upper
side, a decrease in the pressure difference between the pressure
surfaces and the negative pressure surfaces is suppressed, in other
words, pressure loss is suppressed. As a result, the first axial
flow fan 2 is capable of discharging an airflow with high pressure
through the first exhaust portion 2302. A vortex is formed in the
gap between the inner surface of the first cylindrical portion 230
and the outer edge portions of the auxiliary blade portions 213 in
the radial direction, and backflow of air in the gap is suppressed
by the vortex. In order to have the vortex effectively suppress the
backflow of air in the gap between the inner surface of the first
cylindrical portion 230 and the outer edge portions of the
auxiliary blade portions 213 in the radial direction, the gap
between the inner surface of the first cylindrical portion 230 and
the outer edge portions of the auxiliary blade portions 213 in the
radial direction is desirably as narrow as possible. Furthermore,
the gap between the inner surface of the first cylindrical portion
230 and the outer edge portions of the auxiliary blade portions 213
in the radial direction is desirably uniform. Note that the gap
between the inner surface of the first cylindrical portion 230 and
the outer side of the auxiliary blade portions 213 in the radial
direction being uniform not only includes a case in which the gap
is uniform in an accurate manner, but also may include a case in
which the gap has variations that do not affect the operation of
the first axial flow fan 2. With such a configuration, the gap can
be prevented from becoming partially large. With the above, partial
change in the gap is suppressed and the pressure balance is
maintained; accordingly, the first impeller 21 can rotate smoothly,
and vibration, noise, and the like are suppressed. In other words,
noise of the serial axial flow fan 1 can be reduced.
[0056] By making the gap between the inner surface of the first
cylindrical portion 230 and the outer edge portions of the
auxiliary blade portions 213 in the radial direction uniform, the
variation in the effect of suppressing the backflow with the vortex
is suppressed. With the above, the pressure balance in the
circumferential direction of the first impeller 21 is not easily
lost. As a result, the first impeller 21 can be rotated smoothly,
and vibration and (or) noise can be suppressed. In other words,
noise of the serial axial flow fan 1 can be reduced.
[0057] The auxiliary blade portions 213 are contained inside the
length of the first cylindrical portion 230 in the axial direction.
Since the auxiliary blade portions 213 reliably oppose the first
cylindrical portion 230, the pressure increasing effect can be
increased. Furthermore, by containing the auxiliary blade portions
213 inside the circular cylinder, the shape of each auxiliary blade
portion 213 forming the gap with the inner surface of the first
cylindrical portion 230 in the radial direction at an equal
distance can be simplified. The ease of manufacturing the first
impeller 21 is facilitated more, accordingly. Furthermore, by
having the surfaces opposing the auxiliary blade portions 213 in
the radial direction be a circular cylinder, the changes in the
outside diameters of the auxiliary blade portions 213 becomes
small, and the changes in the pressure and the flow velocity can be
suppressed. With the above, the effect of increasing the pressure
of the discharged airflow can be increased.
[0058] In the first axial flow fan 2, desirably, the outer edges of
the auxiliary blade portions 213 in the radial direction oppose the
inner surface of the first inside diameter portion 233 of the first
cylindrical portion 230 in the radial direction. In other words, in
the inner surface of the first cylindrical portion 230, at least
the portion that opposes the auxiliary blade portions 213 in the
radial direction is, desirably, a circular cylinder. Since the
change in the inside diameter of the portion of the first
cylindrical portion 230 that opposes the auxiliary blade portions
213 is small, the pressure and the flow velocity do not easily
change and the pressure can be increased.
[0059] Note that the auxiliary blade portions 213 may oppose the
second inside diameter portion 234 in the radial direction. In such
a case as well, the shapes of the outer edges of the auxiliary
blade portions 213 are shapes in which the gap between the outer
edges of the auxiliary blade portions 213 in the radial direction
and the inner surface of the second inside diameter portion 234,
and the gap between the outer edges of the auxiliary blade portions
213 in the radial direction and the inner surface of the first
inside diameter portion 233 are the same. With the above
configuration, the above-described effect of suppressing vibration
and (or) noise can be obtained. In other words, noise of the serial
axial flow fan 1 can be reduced.
[0060] Note that in the first impeller 21, the auxiliary blade
portions 213 are each formed in the entire area of the outer edge
portion of the corresponding first blade 211 in the radial
direction from a front end in the rotation direction to a rear end
in the rotation direction. With the above, the pressure loss is
reduced, and the pressure of the airflow discharged through the
first exhaust portion 2302 is increased. Meanwhile, there are cases
in which the pressure of the airflow discharged through the first
exhaust portion 2302 is required to be only of a certain amount. In
such a case, the auxiliary blade portions 213 may be formed in a
partial manner in the outer edge portions of the first blades 211
in the radial direction from the front end in the rotation
direction to the rear end in the rotation direction. With the above
configuration, the pressure of the airflow discharged from the
first exhaust portion 2302 can be adjusted. Note that the portions
in which the auxiliary blade portions 213 are formed are,
desirably, formed at the same portions in the plurality of first
blades 211. With such a configuration, the distribution of pressure
in each first blade 211 with the corresponding auxiliary blade
portion 213 can be the same or substantially the same, and the
pressure acting on the first impeller 21 can be balanced. With the
above, vibrate and (or) noise can be suppressed.
[0061] In other words, noise of the serial axial flow fan 1 can be
reduced.
[0062] FIG. 7 is a perspective view of the second axial flow fan
viewed from above. FIG. 8 is a perspective view of the second axial
flow fan viewed from below. FIG. 9 is an exploded perspective view
of the second axial flow fan illustrated in FIG. 7. FIG. 10 is a
cross-sectional view of the second axial flow fan illustrated in
FIG. 7 cut along a plane including the central axis. As illustrated
in FIGS. 7 to 10, the second axial flow fan 3 includes a second
impeller 31, a second motor portion 32, a second housing 33, and
the plurality of second support ribs 34.
[0063] The second housing 33 is an outer package of the second
axial flow fan 3 and the serial axial flow fan 1, and protects the
second impeller 31, the second motor portion 32, and other
components.
[0064] The second housing 33 includes the second cylindrical
portion 330, a second intake flange portion 3311, and a second
exhaust flange portion 3321. The second cylindrical portion 330 is
a cylinder penetrating from an upper end portion 331 to a lower end
portion 332 along the central axis J1. The upper end portion 331 of
the second cylindrical portion 330 is a second intake portion 3301,
and the lower end portion 332 is a second exhaust portion 3302. As
illustrated in FIGS. 7 to 9, the second cylindrical portion 330
includes four outer flat surfaces 336 each having a shape formed
when the outer peripheral surface of the circular cylinder is cut
by a plane parallel to the central axis J1. The outer flat surfaces
336 are disposed at equal intervals in the circumferential
direction. The outer flat surfaces 336 are surfaces that are
parallel to the central axis J1.
[0065] In the second axial flow fan 3, the second impeller 31
rotates inside second cylindrical portion 330 about the central
axis J1, and generates an airflow. In other words, while the second
cylindrical portion 330 is a portion of the outer package, the
second cylindrical portion 330 is also a wind tunnel. In other
words, the second housing 33 includes the second cylindrical
portion 330 that surrounds the other side of the second impeller 31
in the radial direction. Furthermore, the second impeller 31
rotates about the central axis J1.
[0066] The second intake flange portion 3311 is provided at the
upper end portion 331 of the second housing 33. The second intake
flange portion 3311 has a square shape when viewed in a central
axis J1 direction and a length of each side is longer than an
inside diameter of the second cylindrical portion 330. Corner
portions of the second intake flange portion 3311 when viewed in
the central axis J1 direction expand from the outer peripheral
surface of the second cylindrical portion 330 towards the outside
in the radial direction. Furthermore, the surfaces that constitute
the sides of the square second intake flange portion 3311 when
viewed in the central axis J1 direction are each flush with the
corresponding outer flat surface 336.
[0067] The second exhaust flange portion 3321 is provided at the
lower end portion 332 of the second housing 33. The second exhaust
flange portion 3321 has a square shape when viewed in the central
axis J1 direction and a length of each side is longer than the
inside diameter of the second cylindrical portion 330. Corner
portions of the second exhaust flange portion 3321 when viewed in
the central axis J1 direction expand from the outer peripheral
surface of the f second cylindrical portion 330 towards the outside
in the radial direction. Furthermore, the surfaces that constitute
the sides of the second exhaust flange portion 3321 when viewed in
the central axis J1 direction are each flush with the corresponding
outer flat surface 336. Moreover, when viewed in the central axis
J1 direction, the second intake flange portion 3311 and the second
exhaust flange portion 3321 overlap each other.
[0068] The second cylindrical portion 330 includes a first inside
diameter portion 333 and a second inside diameter portion 334. The
first inside diameter portion 333 is disposed on the exhaust side
with respect to the second inside diameter portion 334, in other
words, the first inside diameter portion 333 is disposed on the
lower side OS. The first inside diameter portion 333 is tubular,
and an inside diameter D21 thereof does not change in the axial
direction. The minimum inside diameter of the second cylindrical
portion 330 is the inside diameter D21. In other words, the first
inside diameter portion 333 is a minimum inside diameter portion.
In the second cylindrical portion 330, the second inside diameter
portion 334 is disposed on the upper end portion 331 side, in other
words, the second inside diameter portion 334 is disposed at the
end portion on the intake side. The portions of the second inside
diameter portion 334 that overlap the outer flat surfaces 336 in
the radial direction are inner flat surfaces 3341, and portions
that connect the inner flat surfaces 3341 to each other in the
circumferential direction are inner curved surfaces 3342. The inner
curved surfaces 3342 include conical portions 335. Each conical
portion 335 is a portion of a conical inner surface and the
diameter of each conical portion 335 widens towards the upper side,
in other words, the intake side.
[0069] The section of the uppermost side of each inner curved
surface 3342 of the second inside diameter portion 334 cut along a
plane orthogonal to the central axis has an arc shape and an inside
diameter thereof is an inside diameter D22. Furthermore, the inside
diameter D21 of the first inside diameter portion 333 is smaller
than the inside diameter D22 of each inner curved surface 3342 of
the second inside diameter portion 334.
[0070] Furthermore, when the first axial flow fan 2 and the second
axial flow fan 3 are connected to each other, the second inside
diameter portion 234 of the first cylindrical portion 230 and the
second inside diameter portion 334 of the second cylindrical
portion 330 are connected to each other in the axial direction in a
continuous manner. In so doing, in order to connect the inner
curved surfaces 2342 of the second inside diameter portion 234 of
the first cylindrical portion 230 and the inner curved surfaces
3342 of the second inside diameter portion 334 of the second
cylindrical portion 330 to each other in a smooth manner, the
inside diameter D12 and the inside diameter D22 are the same.
[0071] Furthermore, in order to connect the inner flat surfaces
2341 of the second inside diameter portion 234 of the first
cylindrical portion 230 and the inner flat surfaces 3341 of the
second inside diameter portion 334 of the second cylindrical
portion 330 to each other in a smooth manner, the inside diameter
D11 and the inside diameter D12 are the same.
[0072] Furthermore, the lower end portion 332 of the second
cylindrical portion 330 in the axial direction includes diameter
expanded portions 337, in which the lower portions thereof in the
axial direction are curved outwardly in the radial direction, at
areas that overlap the corner portions of the second exhaust flange
portion 3321 in the radial direction, in other words, in areas that
overlap the inner curved surfaces 3342 of the second inside
diameter portion 334 in the axial direction. The inside diameters
of the diameter expanded portions 337 becomes gently larger as the
diameter expanded portions 337 extend in the direction of the
airflow. By shaping the diameter expanded portions 337 in the above
manner, the airflow discharged through the second exhaust portion
3302 of the second cylindrical portion 330 does not become
disrupted easily. When the diameter expanded portion 337 is cut
along a plane including the central axis J1, the shape of the
section is a curved surface. In other words, the diameter expanded
portions 337 has a so-called bell-mouth shape.
[0073] In other words, the second housing 33 includes, at the end
portion on the exhaust side, the square second exhaust flange
portion 3321 that has sides that are each larger than the inside
diameter of the inner circumferential surface of the second
cylindrical portion 330. The portions of the end portion of the
inner circumferential surface of the second cylindrical portion 330
on the exhaust side that overlap the corner portions of the second
exhaust flange portion 3321 in the radial direction are curved
outwards in the radial direction towards the edge on the exhaust
side. With the above, by forming the diameter expanded portions 337
in shapes that expand gradually, even when compared with a case in
which the diameter expanded portions 337 are formed as a cone, the
airflow is not easily disturbed and decrease in the pressure and in
the air volume can be suppressed.
[0074] The second axial flow fan 3 includes 11 second support ribs
34. The 11 second support ribs 34 extend from the second inside
diameter portion 334 towards the inner side in the radial
direction, and are disposed at equal intervals in the
circumferential direction. Inner sides of the second support ribs
34 in the radial direction are connected to a base portion 3221
(described later) of the second motor portion 32. With the above,
the second motor portion 32 is supported by the second housing 33
with the second support ribs 34. The second housing 33, the second
support ribs 34, and the base portion 3221 are formed as a resin
molded body formed in an integrated manner with resin. In the
second axial flow fan 3, the second support ribs 34 are disposed on
the upper end portion 331 side of the second housing 33. In other
words, the second support ribs 34 extend from an inner
circumferential surface of the second cylindrical portion 330
towards the inner side, and support the second motor portion
32.
[0075] When viewed in the central axis J1 direction, the second
support ribs 34 are disposed inside the second cylindrical portion
330. In combination with the first support ribs 24 of the first
axial flow fan 2, the second support ribs 34 are used as stator
blades. Accordingly, the second support ribs 34 are inclined in the
same directions as the first support ribs 24 when the second axial
flow fan 3 is connected to the lower side OS of the first axial
flow fan 2. In other words, the lower sides of the second support
ribs 34 in the axial direction are positioned on the downstream
side in the rotation direction of the first impeller 21.
[0076] The second motor portion 32 is of a so-called outer rotor
type. As illustrated in FIG. 10, the second motor portion 32
includes a second rotor portion 321 and a second stator portion
322. The second motor portion 32 rotates the second impeller 31.
The second stator portion 322 includes the base portion 3221, a
bearing holding portion 3222, an armature 3223, and a circuit board
3224. The base portion 3221 is formed as an integrally molded body
together with the second housing 33 and the second support ribs 34.
The base portion 3221 has a disk shape orthogonal to the central
axis J1. The center of the disk shape overlaps the central axis J1.
The bearing holding portion 3222 has a cylindrical shape, is
disposed at a center portion of the base portion 3221, and extends
towards the lower side in the axial direction. Note that the
bearing holding portion 3222 may be an integrally molded body
molded together with the base portion 3221. A ball bearing 3225 and
a ball bearing 3226 are attached to an upper portion and a lower
portion inside the bearing holding portion 3222. Furthermore, a
shaft 3213 (described later) of the second rotor portion 321 is
rotatably supported through the ball bearing 3225 and the ball
bearing 3226. Note that the ball bearing 3225 and the ball bearing
3226 are examples of bearings, and the bearings are not limited to
the ball bearing 3225 and the ball bearing 3226. Bearing that are
structured to rotatably support the shaft 3213 may be widely
employed.
[0077] The armature 3223 is fixed external to the bearing holding
portion 3222 in the radial direction. The armature 3223 includes a
stator core 3227, a coil 3228, and an insulator 3229. The stator
core 3227 is a stacked body in which electromagnetic steel sheets
are stacked in the axial direction. Note that the stator core 3227
is not limited to a stacked body in which electromagnetic steel
sheets are stacked, and may be a single member, such as a fired
body of powder or a casting, for example.
[0078] The stator core 3227 includes an annular core back and a
plurality of (nine, herein) teeth. The nine teeth extend towards
the outside in the radial direction from an outer peripheral
surface of the core back and are formed radially. With the above,
the nine teeth are arranged in the circumferential direction. The
coil 3228 is configured by winding a length of conducting wire
around the teeth on which the insulator 3229 has been attached. The
core back of the stator core 3227 is press-fitted in the bearing
holding portion 3222, and the stator core 3227 is fixed to the
bearing portion 3222. The press-fitting may be a so-called
stationary fit, or may be a light press-fit that is a so-called
transition fit in which the press-fitting force is weaker than the
press-fitting. The core back and the bearing holding portion 3222
may be fixed to each other by another method, such as adhesion.
When the stator core 3227 is fixed to the bearing holding portion
3222, the center thereof overlaps the central axis J1. Furthermore,
the nine teeth of the stator core 3227 are arranged at equal
intervals in the circumferential direction to smoothly and
efficiently rotate the second motor portion 32.
[0079] The circuit board 3224 is attached to the base portion 3221.
The circuit board 3224 is electrically connected to the coil 3228
of the second stator portion 322. The circuit board 3224 includes a
drive circuit that drives the coil 3228.
[0080] The base portion 3221 of the second stator portion 322 is an
integrally molded body formed together with the second support ribs
34. With the above, the second stator portion 322, in other words,
the second motor portion 32 is supported by the second support ribs
34. Furthermore, the second support ribs 34 are also an integrally
molded body formed together with the second housing 33.
Accordingly, the second motor portion 32 is connected to the second
housing 33 through the second support ribs 34, in other words, the
second motor portion 32 is supported by the second housing 33.
[0081] The second rotor portion 321 includes a yoke 3211, a field
magnet 3212, the shaft 3213, and a shaft fixing member 3214. The
yoke 3211 is made of metal and has a lidded cylindrical shape about
the central axis J1. The shaft fixing member 3214 is fixed to the
center of the lid-shaped portion of the yoke 3211. The shaft 3213
is fixed to the shaft fixing member 3214 with a fixing method, such
as press-fitting. Note that the fixing method is not limited to
press-fitting and may be another method, such as adhesion. The yoke
3211 is fixed to the shaft 3213 through the shaft fixing member
3214.
[0082] The field magnet 3212 has a circular cylinder shape. The
field magnet 3212 is fixed to an inner surface of the yoke 3211.
The field magnet 3212 is magnetized to the N-pole and the S-pole
alternately in the circumferential direction. Note that in place of
the field magnet 3212 having a circular cylinder shape, a plurality
of field magnets may be arranged in the circumferential
direction.
[0083] The shaft 3213 is made of metal and has a columnar shape.
The shaft 3213 is rotatably supported by the bearing holding
portion 3222, in other words, by the f second stator portion 322
through the ball bearing 3225 and the ball bearing 3226. The center
of the shaft 3213 rotatably supported by the bearing holding
portion 3222 overlaps the central axis J1.
[0084] In the second motor portion 32, by having the shaft 3213 be
rotatably supported through the ball bearing 3225 and the ball
bearing 3226, the second rotor portion 321 is supported by the
second stator portion 322 in a rotatable manner about the central
axis J1. In the above, an inner surface of the field magnet 3212 of
the second rotor portion 321 in the radial direction and an outer
surface of the stator core 3227 in the radial direction oppose each
other with a gap therebetween in the radial direction. An operation
of the second motor portion 32 will be described in detail
later.
[0085] As illustrated in FIGS. 9 and 10, the second impeller 31
includes a plurality of second blades 311, and a cup 312. The cup
312 has a lidded cylindrical shape. Note that while the cup 312 has
a lidded cylindrical shape, the shape is not limited to the above,
and may be a truncated cone shape in which the outside diameters of
an outer peripheral surface differ in the axial direction.
[0086] The second blades 311 each protrude from the outer surface
of the cup 312 in the radial direction towards the outside in the
radial direction. The second impeller 31 is provided with seven
second blades 311. The seven second blades 311 are aligned at equal
intervals in the circumferential direction. In other words, the
second impeller 31 includes the plurality of second blades 311 that
extend outwards in the radial direction and that are arranged in
the circumferential direction. The second blades 311 are inclined
in the circumferential direction and generate an airflow from the
upper side IS towards the lower side OS when the second impeller 31
is rotated. In other words, the second blades 311 are each inclined
to a direction that generates an airflow from the upper side IS
towards the lower side OS.
[0087] As described above, the second stator portion 322 of the
second motor portion 32 is assembled by attaching the bearing
holding portion 3222, the armature 3223, and the circuit board 3224
to the base portion 3221 formed integrally with the second housing
33. In other words, the second stator portion 322 is supported by
the second housing 33 through the second support ribs 34.
[0088] Furthermore, the yoke 3211 of the second rotor portion 321
is fixed inside the cup 312 of the second impeller 31. The yoke
3211 may be fixed in the cup 312 by press-fitting or by adhesion.
Furthermore, the yoke 2211 may be fixed with a fastening member,
such as a screw. The cup 312 suppressing deviation from the yoke
3211 is fixed to the yoke 3211. In other words, the second impeller
31 is fixed to the second rotor portion 321.
[0089] Furthermore, the shaft 3213 of the second rotor portion 321
to which the second impeller 31 is fixed is fixed to the inner
rings of the ball bearing 3225 and the ball bearing 3226 attached
inside the bearing holding portion 3222. Note that while the shaft
3213 is fixed to the inner rings of the ball bearing 3225 and the
ball bearing 3226 by press-fitting, the fixing method is not
limited to press-fitting. For example, a fixing method, such as
adhesion or welding, that suppresses the relative movement between
the shaft 3213 and the inner rings, and that fixes the shaft 3213
about the central axis J1 in a rotatable manner can be widely
employed. The second rotor portion 321 to which the second impeller
31 is attached is rotatably attached to the second stator portion
322 in the above manner.
[0090] By attaching the second rotor portion 321 to the second
stator portion 322, the second impeller 31 is accommodated inside
the second housing 33. The outer sides of the second blades 311 in
the radial direction oppose the inner surface of the second
cylindrical portion 330 in the radial direction. Furthermore, the
second blades 311 are contained inside the length of the second
cylindrical portion 330 in the axial direction. Furthermore, the
gap in the radial direction between the inner surface of the second
cylindrical portion 330 and the outer sides of the second blades
311 in the radial direction is uniform. Note that the gap between
the inner surface of the second cylindrical portion 330 and the
outer sides of the second blades 311 in the radial direction being
uniform not only includes a case in which the gap is uniform in an
accurate manner, but also includes a case in which the gap has
variations that do not affect the operation of the second axial
flow fan 3.
[0091] An electric current is supplied to the coil 3228 of the
second motor portion 32 at a good timing from the drive circuit
mounted on the circuit board 3224. With the above, the second rotor
portion 321 of the second motor portion 32 is rotated in a
predetermined direction. Note that, herein, the rotation direction
of the second rotor portion 321 is anticlockwise when viewing the
central axis J1 from the upper side IS.
[0092] By rotating the second motor portion 32 about the central
axis J1, the second impeller 31 fixed to the second rotor portion
321 is also rotated about the central axis J1. With the rotation of
the second impeller 31, an airflow that, while swirling in the
circumferential direction, flows in the axial direction is
generated in the second housing 33, in other words, inside the
second cylindrical portion 330.
[0093] Compared with the first blades 211 of the first axial flow
fan 2, the inclination of each second blade 311 of the second axial
flow fan 3 with respect to the shaft is small, and the pressure
difference between each pressure surface and the corresponding
negative pressure surface is small. Accordingly, suppression of
pressure loss can be achieved without providing any auxiliary blade
portions in the outer edge portions of the second blades 311 in the
radial direction. Furthermore, in an impeller in which each blade
has a small inclination with respect to the shaft, rather than an
effect of compressing air, an effect of increasing the flow
velocity is obtained more easily by rotation of the impeller. In
other words, compared with the first axial flow fan 2, the ability
of increasing the discharge flow rate is high in the second axial
flow fan 3. In other words, compared with the second axial flow fan
3, the ability of increasing the discharge pressure is high in the
first axial flow fan 2. In the serial axial flow fan 1, the above
axial flow fans having different abilities are connected in series
to increase the pressure and the flow rate. A detailed description
of the serial axial flow fan 1 will be given next.
[0094] The serial axial flow fan 1 is formed by serially connecting
the first axial flow fan 2 and the second axial flow fan 3 to each
other in the axial direction. The lower end portion of the first
axial flow fan 2 and the upper end portion of the second axial flow
fan 3 are connected to each other. The first exhaust flange portion
2321 of the first axial flow fan 2 and the second intake flange
portion 3311 of the second axial flow fan 3 are in contact with and
are fixed to each other in the axial direction. Screwing can be
cited as a method for fixing the first exhaust flange portion 2321
and the second intake flange portion 3311 to each other; however,
the method is not limited to screwing. For example, adhesion can be
cited as an example. The first exhaust portion 2302 of the first
axial flow fan 2 and the second intake portion 3301 of the second
axial flow fan 3 are connected to each other without any gap. With
the above, air that has been discharged from the first exhaust
portion 2302 of the first axial flow fan 2 can be prevented from
leaking out through the connection between the first axial flow fan
2 and the second axial flow fan 3.
[0095] The first support ribs 24 are disposed on the exhaust side
of the first axial flow fan 2. Furthermore, the second support ribs
34 are disposed on the intake side of the second axial flow fan 3.
Furthermore, by connecting the first axial flow fan and the second
axial flow fan 3 to each other in the axial direction, the surfaces
of the first support ribs 24 facing the exhaust side and the
surfaces of the second support ribs 34 facing the intake side
overlap each other in the axial direction. Note that the surfaces
of the first support ribs 24 that face the exhaust side and the
surfaces of the second support ribs 34 that face the intake side
may be in contact with each other, or gaps may be formed
therebetween to the extent that turbulent flow is not created. In
other words, the first support ribs 24 are disposed on the exhaust
side of the first housing 23, the second support ribs 34 are
disposed on the intake side of the second housing 33, and the
surfaces of the first support ribs 24 that face the exhaust side
and the surfaces of the second support ribs that face the intake
side overlap each other in the axial direction. With the above
configuration, the first support ribs 24 and the second support
ribs 34 in combination form the stator blades. With the above, the
velocity component of the airflow in the rotation direction can be
oriented towards the axial direction, and the pressure and the flow
rate in the axial direction can be increased.
[0096] When the first axial flow fan 2 and the second axial flow
fan 3 are connected to each other, the inner flat surfaces 2341 of
the second inside diameter portion 234 of the first cylindrical
portion 230 and the inner flat surfaces 3341 of the second inside
diameter portion 334 of the second cylindrical portion 330 are
disposed on the same plane. Furthermore, the inner curved surfaces
2342 of the second inside diameter portion 234 of the first
cylindrical portion 230 and the inner curved surfaces 3342 of the
second inside diameter portion 334 of the second cylindrical
portion 330 are disposed on the same circular cylindrical surface.
With such a connection, the second inside diameter portion 234 of
the first cylindrical portion 230 and the second inside diameter
portion 334 of the second cylindrical portion 330 are connected to
each other in the axial direction in a smooth manner.
[0097] In other words, the first housing 23 includes, at the end
portion on the exhaust side, the square first exhaust flange
portion 2321 that has sides that are each larger than the inside
diameter of the inner surface of the first cylindrical portion 230.
Furthermore, the second housing 33 includes, at the end portion on
the intake side, the square second intake flange portion 3311 that
has sides that are each larger than the inside diameter of the
inner surface of the second cylindrical portion 330. The first
exhaust flange portion 2321 and the second intake flange portion
3311 are connected to each other in the axial direction so as to
overlap each other, and the inside diameter D12 of the end portion
of the inner surface of the first cylindrical portion 230 on the
exhaust side that overlaps the corner portions of the first exhaust
flange portion 2321 in the radial direction, and the inside
diameter D22 of the end portion of the inner surface of the second
cylindrical portion 330 on the intake side that overlaps the corner
portions of the second intake flange portion 3311 in the radial
direction are larger than the minimum inside diameters D11 and D21,
respectively, of the cylindrical portions 230 and 330,
respectively, in the axial direction. By widening the connection
between the first housing 23 and the second housing 33 outwards
with respect to the first inside diameter portion 233 and the first
inside diameter portion 333, the flow velocity of the airflow in
the cylindrical portion is decreased. With the above, wind noise
generated when the airflow passes the first support ribs 24 and the
second support ribs 34 can be reduced. With the above, noise and
(or) vibration can be suppressed. In other words, noise of the
serial axial flow fan 1 can be reduced.
[0098] In the serial axial flow fan 1, the first axial flow fan 2
and the second axial flow fan 3 are driven at the same time. With
the above, in the serial axial flow fan 1, air is drawn in through
the first intake portion 2301 with the rotation of the first
impeller 21. Furthermore, the first impeller 21 compresses and
accelerates the air and discharges the air through the first
exhaust portion 2302. The air that has been discharged through the
first exhaust portion 2302 of the first axial flow fan 2, while
being prevented from leaking to the outside, flows into the second
axial flow fan 3 through the second intake portion 3301. In the
second axial flow fan 3, the air that has flowed in is compressed
and accelerated further with the rotation of the second impeller
31, and is discharged from the second exhaust portion 3302. In
other words, in the serial axial flow fan 1, air is drawn in
through the first intake portion 2301 at the end portion of the
first axial flow fan 2 on the upper side IS, is compressed and
accelerated with the first impeller 21 and the second impeller 31,
and is discharged through the second exhaust portion 3302 at the
end portion of the second axial flow fan 3 on the lower side. The
second inside diameter portion 234 of the first cylindrical portion
230 and the second inside diameter portion 334 of the second
cylindrical portion 330 are connected to each other in the axial
direction in a smooth manner so that turbulence in the airflow is
small and decreases in air volume and pressure can be suppressed.
In the wind tunnel of the serial axial flow fan 1 formed by
connecting the first cylindrical portion 230 and the second
cylindrical portion 330 to each other, the inside diameter of the
portion where the first axial flow fan 2 and the second axial flow
fan 3 are connected to each other, in other words, the center
portion in the axial direction, increases. With the above, the flow
velocity of the airflow discharged through the first exhaust
portion 2302 of the first axial flow fan 2 is decreased. With the
above, the wind noise generated when the wind passes the first
support ribs 24 disposed at the lower end portion of the first
cylindrical portion 230, and the second support ribs 34 disposed on
the intake side of the second housing 33 can be made smaller. By
disposing the surfaces of the first support ribs 24 that face the
exhaust side and the surfaces of the second support ribs 34 that
face the intake side overlap each other in the axial direction, the
first support ribs 24 and the second support ribs 34 constitute the
stator blades. The lower sides OS of the first support ribs and the
second support ribs 34 in the axial direction are inclined surfaces
that are oriented towards the downstream side in the rotation
direction of the first impeller 21. The airflow generated with the
rotation of the first impeller 21 includes a velocity component
that swirls in the rotation direction of the first impeller 21 and
a velocity component in the axial direction. Furthermore, the
velocity component of the airflow in the circumferential direction
is bent in the axial direction with the stator blades formed by the
first support ribs 24 and the second support ribs 34. With the
above, the pressure and the flow velocity in the axial direction
can be increased. Furthermore, by providing a gap between the first
support ribs 24 and the second support ribs 34, direct transmission
of the vibration of the armature 2223 and the vibration of the
armature 3223 to each other can be suppressed, and large vibration
and (or) noise generated by interference between the vibrations can
be suppressed from occurring. In other words, noise of the serial
axial flow fan 1 can be reduced.
[0099] The first axial flow fan 2 includes auxiliary blade portions
213 in the outer edges of the first blades 211 of the first
impeller 21 in the radial direction, and increases the pressure of
the airflow discharged through the first exhaust portion 2302.
Airflow with high pressure is discharged from the first axial flow
fan 2. Furthermore, the airflow with a high pressure discharged
through the first exhaust portion 2302 of the first axial flow fan
2 flows into the second axial flow fan 3 through the second intake
portion 3301.
[0100] Meanwhile, the second axial flow fan 3 has a larger number
of blades compared with the number of the first blades 211 of the
first impeller 21, and the inclination of the blades of the second
axial flow fan 3 with respect to the shaft is smaller than the
inclination of the first blades 211. Accordingly, the effect of
increasing the flow rate of the airflow is larger in the second
axial flow fan 3 than that in the first axial flow fan 2. The
airflow from the first axial flow fan 2 having a high pressure is
accelerated in the second axial flow fan 3 to increase the flow
rate. With the above, the serial axial flow fan 1 is capable of
discharging an airflow having a high pressure and a large low rate.
As described above, by providing the auxiliary blade portions 213
in the outer edge portions of the first blades 211 of the first
impeller 21 in the radial direction, the first axial flow fan 2
increases the pressure of the airflow generated by the first
impeller 21. The first axial flow fan 2 has a high pressure
increasing effect. The second axial flow fan 3 has a high flow
velocity increasing effect, in other words, a high flow rate
increasing effect.
[0101] Features of the serial axial flow fan 1 according to the
present disclosure were evaluated through computer simulations.
Simulations were conducted by changing Nin, Nout, and Nrib of the
serial axial flow fan 1, where Nin is the number of blades of the
impeller of the axial flow fan on the intake side, Nout is the
number of blades of the impeller of the axial flow fan on the
exhaust side, and Nrib is the number of first support ribs and the
number of second support ribs. Note that in the configuration
assuming the present disclosure, auxiliary blade portions in which
the outer sides thereof are warped towards the intake side were
formed in the outer edge portions of the blades of the impeller of
the axial flow fan in the radial direction.
[0102] A maximum efficiency point, the discharge pressure, and the
flow rate of an example of the conventional art including no
auxiliary blades were measured, in a case in which Nin=5, Nout=7,
and Nrib=11. Furthermore, measurements that are the same as those
of the example of the conventional art were measured in a
configuration, serving as the exemplary embodiment, satisfying
Nin=5, Nout=7, and N=11 and including auxiliary blade portions in
the outer edge portions of the blades on the intake side in the
radial direction.
[0103] As a result, while the maximum efficiency point of the
example of the conventional art was 46%, that of the exemplary
embodiment was increased to 47%. Furthermore, regarding the
pressure in a case in which the flow rate of the discharged airflow
was 4.0 m.sup.3/min, while the example of the conventional art was
about 1230 Pa, the exemplary embodiment was about 1250 Pa. In the
above case, while the input shaft power of the example of the
conventional art was 168 W, that of the exemplary embodiment was
165 W.
[0104] The maximum efficiency point of the exemplary embodiment was
higher than that of the example of the conventional art, as well as
the pressure under the same flow rate. Furthermore, although the
pressure-flow characteristics of the exemplary embodiment was
higher than that of the example of the conventional art, the input
shaft power was lower.
[0105] As a result of the simulation, it was understood that in the
configuration satisfying Nin<Nout<Nrib, when the auxiliary
blade portions were provided in at least either of the blades on
the intake side and the blades on the exhaust side, there were
cases in which the efficiency was higher, the pressure was higher,
and the air volume was larger than a case in which there was no
auxiliary blade.
[0106] Note that Nin, Nout, and Nrib are a set of prime integers.
In other words, Nin, Nout, and Nrib are a set of integral numbers
that do not have a common divisor other than 1. With such a
configuration, vibrational resonance between the first impeller 21,
the second impeller 31, the first support ribs 24, and the second
support ribs 34 is suppressed. Noise caused by resonance is
suppressed and the noise of the serial axial flow fan 1 can be
reduced.
[0107] Furthermore, while changing Nin, Nout, and Nrib, similar
simulations were as carried out with a configuration satisfying
Nin<Nout<Nrib, in which auxiliary blade portions were
provided at the blades on the intake side. A case satisfying (Nin,
Nout, Nrib)=(5, 7, 11) was assumed as the exemplary embodiment,
(Nin, Nout, Nrib)=(4, 7, 11) as a first comparative example, (Nin,
Nout, Nrib)=(5, 9, 11) as a second comparative example, (Nin, Nout,
Nrib)=(5, 11, 11) as a third comparative example, and (Nin, Nout,
Nrib)=(5, 7, 13) as a fourth comparative example.
[0108] Furthermore, when the flow rate of the discharged air was
4.0 m.sup.3/min, the pressure in the first comparative example was
about 800 kPa, the pressure in the second comparative example was
about 990 kPa, the pressure in the third comparative example was
about 1150 kPa, and the pressure in the fourth comparative example
was about 990 kPa in the.
[0109] The number Nin of the blades of the impeller of the axial
flow fan on the intake side was five in the exemplary embodiment
and was four in the first comparative example. It was understood
that a pressure difference is created in the discharged air
depending on the number Nin of the blades of the impeller of the
axial flow fan on the intake side.
[0110] The number Nout of the blades of the impeller of the axial
flow fan on the exhaust side was seven in the exemplary embodiment
and was nine in the third comparative example. It was understood
that a pressure difference is also created in the discharged air
depending on the number Nout of the blades of the impeller of the
axial flow fan on the exhaust side. The pressure of the discharged
air was larger in the case of Nout=11 than in the case of Nout=9.
Moreover, it was understood that in the case of Nout=7, the
pressure of the discharged air was even more larger.
[0111] Moreover, the number Nrib of the first support ribs and the
number Nrib of the second support ribs in the exemplary embodiment
were 11, and those in the fourth comparative example were 13. It
was understood that a pressure difference is created in the
discharged air depending on the number Nrib of the first support
ribs and that of the second support ribs. The pressure of the
discharged air was larger in the case of Nrib=11 than in the case
of Nrib=13.
[0112] In other words, the pressure-flow characteristics of the
discharged airflow in the exemplary embodiment was higher compared
with the first to fourth comparative examples.
[0113] Furthermore, as a result of conducting more simulations, it
was confirmed that a configuration in which the auxiliary blade
portions were provided in the blades and in which Nin=5 was
satisfied was most optimum in increasing the airflow. Furthermore,
by satisfying Nout=7, it was possible to increase the inclination
and maintain the blade areas of each blades, and it was confirmed
that Nout=7 is most optimum in increasing the air volume.
Furthermore, by satisfying Nrib=11, it was confirmed that the
largest pressure and the largest wind force could be obtained while
obtaining the required mechanical strength to support the first
motor portion and the second motor portion in a stable manner at
the maximum efficiency point.
[0114] In the exemplary embodiment, the first impeller 21 and the
second impeller 31 rotate in the same direction. Accordingly, by
having the velocity component of the airflow discharged in the
circumferential direction from the first axial flow fan 2 and the
rotation direction of the second impeller 31 be the same, the speed
of the airflow in the rotation direction relative to the speed of
the end portions of the second blades 311 of the second impeller 31
on the upstream side becomes small; accordingly, the vibration and
noise can be suppressed. In other words, noise of the serial axial
flow fan 1 can be reduced. Furthermore, since the above direction
is the same as the direction of the airflow flowing into the second
blades 311, resistance of the second blades 311 can be suppressed.
With the above, the input shaft power can be suppressed.
[0115] Note that the second blades 311 of the second impeller may
be inclined to opposite directions, and the rotation direction of
the second impeller 31 may be opposite to the rotation direction of
the first impeller 21. With the above, the effect of the second
blades 311 of the second impeller 31 bending the velocity component
of the airflow in the rotation direction in the axial direction
becomes larger. With the above, the pressure of the airflow
discharged from the serial axial flow fan 1 can be increased.
[0116] Furthermore, while the present embodiment includes the first
axial flow fan 2 in which the auxiliary blade portions 213 are
provided at the outer edge portions of the first blades 211 in the
radial direction, the configuration is not limited to the above.
The auxiliary blade portions may be provided at the outer edge
portions of the second blades 311 in the radial direction, which
are provided in the second axial flow fan 3. Furthermore, the
auxiliary blade portions may be provided at both of the outer edge
portions of the first blades and the second blades in the radial
direction. In other words, at least either of the first blades 211
and the second blades 311 are provided with the auxiliary blade
portions 213.
[0117] Important capacities of the axial flow fan include pressure
and air volume. The serial axial flow fan 1 of the present
disclosure can, overall, obtain a high pressure and a large air
volume at the time of maximum efficiency by separating the two
impellers 21 and 31 into an impeller for pressure (the first
impeller 21) and an impeller for air volume (the second impeller
31). In other words, by adding the auxiliary blades (the auxiliary
blade portions 213) to the impeller (the first impeller 21), a high
pressure can be obtained and the impeller can be used as an
impeller for pressure. The impeller for pressure (the first
impeller 21) has a large pressure difference in each pressure
surface and the corresponding negative pressure surface.
Accordingly, air leaks through the gap between the outer peripheral
portion of the impeller (the first blades 211), and the housing
inner circumferential surface (the inner circumferential surface of
the first cylindrical portion 230), and pressure loss becomes
large. The pressure loss can be reduced by providing the auxiliary
blades (the auxiliary blade portions 213) at the outer peripheral
portion of the impeller (the first impeller 21). Meanwhile, by not
providing any auxiliary blades in the impeller (the second impeller
31), the impeller can be used as an impeller for air volume having
a large air volume. The impeller for air volume (the second
impeller 31) pushes the air with the entire surface to obtain a
large air volume. As described above, by combining the impeller for
pressure (the first impeller 21) and the impeller for air volume
(the second impeller 31), an airflow with high pressure and a large
air volume can be obtained.
[0118] While the exemplary embodiment of the present disclosure has
been described above, the exemplary embodiment can be modified in
various ways within the scope of the present disclosure. The serial
axial flow fan according to the present disclosure may be, for
example, used as a cooling fan that sends air to electronic
components disposed inside devices, such as a computer, a network
communication device, and a server, and cool the electronic
components.
[0119] Features of the above-described preferred embodiments and
the modifications thereof may be combined appropriately as long as
no conflict arises.
[0120] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
* * * * *