U.S. patent application number 14/990261 was filed with the patent office on 2016-10-06 for centrifugal fan.
The applicant listed for this patent is Nidec Corporation. Invention is credited to Ryosuke HAYAMITSU, Jumpei KITAMURA.
Application Number | 20160290358 14/990261 |
Document ID | / |
Family ID | 55345740 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160290358 |
Kind Code |
A1 |
HAYAMITSU; Ryosuke ; et
al. |
October 6, 2016 |
CENTRIFUGAL FAN
Abstract
A centrifugal fan includes an impeller, a motor rotating the
impeller about a center axis, and a housing accommodating the
impeller. The housing includes an intake port arranged above the
impeller, an exhaust port arranged radially outward of the
impeller, an annular upper flow path, and a lower flow path
arranged below the upper flow path and connected to the upper flow
path. The annular upper flow path can be partially arranged between
a housing inner circumferential surface and the impeller in a
radial direction. The upper flow path and the lower flow path are
arranged to define a flow path having a scroll shape. The lower
flow path extends along the housing inner circumferential surface.
The lower flow path has a lower flow path terminal end opened
toward the exhaust port. The lower flow path has a lower flow path
start end closed with respect to the exhaust port.
Inventors: |
HAYAMITSU; Ryosuke; (Kyoto,
JP) ; KITAMURA; Jumpei; (Kyoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nidec Corporation |
Kyoto |
|
JP |
|
|
Family ID: |
55345740 |
Appl. No.: |
14/990261 |
Filed: |
January 7, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/441 20130101;
F04D 29/281 20130101; F04D 29/4226 20130101; F04D 29/4233 20130101;
F04D 25/06 20130101; F04D 25/08 20130101; F04D 17/16 20130101 |
International
Class: |
F04D 29/42 20060101
F04D029/42; F04D 25/08 20060101 F04D025/08; F04D 29/28 20060101
F04D029/28; F04D 17/16 20060101 F04D017/16 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2015 |
JP |
2015-070176 |
Claims
1. A centrifugal fan comprising: an impeller arranged to rotate
about a center axis extending in an up-down direction; a motor
arranged below the impeller and arranged to rotate the impeller
about the center axis; and a housing arranged to accommodate the
impeller, wherein the housing includes an intake port arranged
above the impeller, an exhaust port arranged radially outward of
the impeller, an annular upper flow path at least partially
arranged between a housing inner circumferential surface as an
inner circumferential surface of the housing and the impeller in a
radial direction, and a lower flow path arranged below the upper
flow path and connected to the upper flow path, the upper flow path
and the lower flow path are arranged to define a flow path having a
scroll shape, the lower flow path extends along the housing inner
circumferential surface, the lower flow path has a lower flow path
terminal end as one circumferential end thereof opened toward the
exhaust port, and the lower flow path has a lower flow path start
end as the other circumferential end thereof closed with respect to
the exhaust port.
2. The fan according to claim 1, wherein a radial dimension of the
lower flow path grows larger from the lower flow path start end
toward the lower flow path terminal end.
3. The fan according to claim 1, wherein the housing includes an
upper housing having the intake port and a lower housing attached
to a lower side of the upper housing.
4. The fan according to claim 3, wherein the lower housing includes
a portion of the upper flow path and the lower flow path, and an
axial dimension of the lower flow path in the vicinity of the
exhaust port is one half or more of an internal axial dimension of
the lower housing.
5. The fan according to claim 3, wherein the upper housing includes
an upper housing cover portion having the intake port and
overlapping with the impeller in an axial direction and a upper
housing wall portion connected to a lower end of the upper housing
cover portion and arranged to surround the impeller in a
circumferential direction, and the upper housing wall portion has
an inner circumferential surface extending downward and radially
outward.
6. The fan according to claim 1, wherein a radial dimension of the
upper flow path grows larger as the upper flow path extends from a
reference position existing between the exhaust port and the lower
flow path start end toward the exhaust port in a rotation direction
of the impeller.
7. The fan according to claim 1, wherein the exhaust port is
connected to the upper flow path and the lower flow path.
8. The fan according to claim 7, wherein an axial dimension of a
portion of the exhaust port connected to the lower flow path is
larger than an axial dimension of a portion of the exhaust port
connected to the upper flow path.
9. The fan according to claim 1, wherein the exhaust port is
connected to only the lower flow path.
10. The fan of claim 1, wherein a position of a lower end portion
of the lower flow path goes away from the upper flow path as the
lower flow path extends from the lower flow path start end toward
the lower flow path terminal end.
11. The fan according to claim 1, wherein an axial dimension of the
lower flow path is larger than an axial dimension of the upper flow
path.
12. The fan according to claim 1, wherein the entirety of the lower
flow path is opened toward the upper flow path.
13. The fan according to claim 1, wherein the housing includes a
tongue portion arranged between the exhaust port and the lower flow
path start end in a circumferential direction, and when seen in a
plan view, the lower flow path start end is located in a position
where a circumferential angle from a straight line passing through
the center axis and meeting with the tongue portion becomes 75
degrees or less.
14. The fan according to claim 1, wherein the motor is arranged
radially inward of the lower flow path, the housing includes a
motor cover portion arranged to cover the motor, and the lower flow
path is arranged between an outer circumferential surface of the
motor cover portion and the housing inner circumferential surface.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present disclosure relates to a centrifugal fan.
[0003] 2. Description of the Related Art
[0004] There is available a centrifugal fan which includes an air
flow path positioned radially outward of an impeller and a wind
tunnel positioned below the air flow path. The air discharged
radially outward from the impeller flows from the air flow path
toward the wind tunnel. Then, the air is discharged to the outside
from an exhaust port.
[0005] In the centrifugal fan mentioned above, the wind tunnel
positioned below the air flow path has an annular shape. For that
reason, there may be a case where a part of the air guided to the
vicinity of the exhaust port through the wind tunnel flows toward
the upstream side of the wind tunnel without being discharged from
the exhaust port. This poses a problem in that a loss of airflow is
generated and the efficiency of the centrifugal fan is reduced.
SUMMARY OF THE INVENTION
[0006] In one aspect of the present disclosure, there is provided a
centrifugal fan includes: an impeller arranged to rotate about a
center axis extending in an up-down direction; a motor arranged
below the impeller and arranged to rotate the impeller about the
center axis; and a housing arranged to accommodate the impeller.
The housing includes an intake port arranged above the impeller, an
exhaust port arranged radially outward of the impeller, an annular
upper flow path, and a lower flow path arranged below the upper
flow path and connected to the upper flow path. The annular upper
flow path is at least partially arranged between a housing inner
circumferential surface as an inner circumferential surface of the
housing and the impeller in a radial direction. The upper flow path
and the lower flow path are arranged to define a flow path having a
scroll shape. The lower flow path extends along the housing inner
circumferential surface. The lower flow path has a lower flow path
terminal end as one circumferential end thereof opened toward the
exhaust port. The lower flow path has a lower flow path start end
as the other circumferential end thereof closed with respect to the
exhaust port.
[0007] 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 made with reference to the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view illustrating a centrifugal fan
according to one preferred embodiment.
[0009] FIG. 2 is an exploded perspective view illustrating the
centrifugal fan according to one preferred embodiment.
[0010] FIG. 3 is a sectional view taken along line III-III in FIG.
1, illustrating the centrifugal fan according to one preferred
embodiment.
[0011] FIG. 4 is a sectional view taken along line IV-IV in FIG. 3,
illustrating the centrifugal fan according to one preferred
embodiment.
[0012] FIG. 5 is a side view illustrating the centrifugal fan
according to one preferred embodiment.
[0013] FIG. 6 is a side view illustrating a centrifugal fan
according to another example of one preferred embodiment.
[0014] FIG. 7 is a sectional view illustrating a portion of a
centrifugal fan according to a further example of one preferred
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A centrifugal fan according to one preferred embodiment of
the present disclosure will now be described with reference to the
drawings. The scope of the present disclosure is not limited to the
preferred embodiment described below but may be arbitrarily changed
without departing from the scope of the technical idea of the
present disclosure. In the drawings referred to below, for the sake
of making individual configurations easily understandable,
individual structures are sometimes shown in the reduced scale and
number differing from those of actual structures.
[0016] In the drawings, an XYZ coordinate system is appropriately
shown as a three-dimensional rectangular coordinate system. In the
XYZ coordinate system, the Z-axis direction is a direction parallel
to the axial direction of a center axis J illustrated in FIG. 1.
The X-axis direction is a direction orthogonal to the Z-axis
direction and orthogonal to an exhaust port 62 illustrated in FIG.
1. The Y-axis direction is a direction orthogonal to both the
X-axis direction and the Z-axis direction.
[0017] In the following description, the extension direction of the
center axis J (the Z-axis direction is an up-down direction. The
positive side (+Z side) in the Z-axis direction will be referred to
as an "upper side". The negative side (-Z side) in the Z-axis
direction will be referred to as a "lower side". The terms "up-down
direction", "upper side" and "lower side" are used merely for the
purpose of descriptions and are not intended to limit the actual
positional relationships or the actual directions. Unless
specifically mentioned otherwise, the direction (the Z-axis
direction) parallel to the center axis J will be merely referred to
as an "axial direction". The radius direction extending from the
center axis J will be merely referred to as a "radial direction".
The circumference direction about the center axis J (.theta..sub.Z
direction), namely the direction extending around the center axis
J, will be merely referred to as a "circumferential direction".
[0018] In the subject specification, the phrase "extending in the
axial direction" includes not only a case where something extends
strictly in the axial direction but also a case where something
extends in a direction inclined at an angle of less than 45 degrees
with respect to the axial direction. In the subject specification,
the phrase "extending in the radial direction" includes not only a
case where something extends strictly in the radial direction,
namely in the direction perpendicular to the axial direction but
also a case where something extends in a direction inclined at an
angle of less than 45 degrees with respect to the radial
direction.
[0019] FIG. 1 is a perspective view of a centrifugal fan according
to one preferred embodiment. FIG. 2 is an exploded perspective view
of the centrifugal fan according to one preferred embodiment. FIG.
3 is a sectional view of the centrifugal fan according to one
preferred embodiment, which is taken along line III-III in FIG. 1.
FIG. 4 is a sectional view of the centrifugal fan according to one
preferred embodiment, which is taken along line IV-IV in FIG. 3.
FIG. 5 is a side view of the centrifugal fan according to one
preferred embodiment. FIG. 3 is a sectional view of the centrifugal
fan according to one preferred embodiment, which is viewed in the
direction orthogonal to the exhaust port 62 (in the X-axis
direction). FIG. 4 is a sectional view of the centrifugal fan
according to one preferred embodiment, which is viewed from the
upper side toward the lower side. In the subject specification, the
term "side view" refers to a view seen in the X-axis direction.
[0020] As illustrated in FIGS. 1 to 3, the centrifugal fan 10
preferably includes a housing 20, an impeller 30 and a motor 40. As
illustrated in FIG. 3, the motor 40 is accommodated within the
housing 20. The motor 40 is disposed radially inward of a motor
cover portion 27 which will be described later. The motor 40
preferably includes a shaft 41 which is concentric with the center
axis J extending in the up-down direction. The upper end portion of
the shaft 41 protrudes toward the upper side of the motor cover
portion 27 through an output shaft hole 27a which will be described
later.
[0021] The motor 40 is disposed below the impeller 30. The motor 40
rotates the impeller 30 about the center axis J. In the present
preferred embodiment, the motor 40 rotates the impeller 30
counterclockwise (in the +.theta..sub.Z direction) when viewed from
the upper side toward the lower side.
[0022] In the following descriptions, there may be a case where the
counterclockwise forward side (-.theta..sub.Z side) when viewed
from the upper side toward the lower side is referred to as a
"rotation direction front side" and the clockwise (-.theta..sub.Z)
forward side (-.theta..sub.Z side) when viewed from the upper side
toward the lower side is referred to as a "rotation direction back
side".
[0023] The impeller 30 is disposed above the motor 40. The impeller
30 is fixed to the upper end portion of the shaft 41. Thus, the
impeller 30 is rotatable (in the .+-..theta..sub.Z directions)
about the center axis J extending in the up-down direction.
[0024] The impeller 30 preferably includes an impeller body portion
31, a plurality of blade portions 32 and a shroud portion 33. The
impeller body portion 31 is a portion fixed to the shaft 41. The
upper surface of the impeller body portion 31 is a gentle slant
surface which extends downward and radially outward from the center
axis J.
[0025] The blade portions 32 are disposed on the upper surface of
the impeller body portion 31. The blade portions 32 extend upward
from the upper surface of the impeller body portion 31. While not
shown in the drawings, the blade portions are disposed at regular
intervals in the circumferential direction. The upper end portions
of the blade portions 32 are connected to the shroud portion
33.
[0026] The shroud portion 33 is disposed above the blade portions
32. The shroud portion 33 is connected to the impeller body portion
31 via the blade portions 32. As illustrated in FIG. 2, the shroud
portion 33 has an annular shape centered at the center axis J. The
shroud portion 33 is shaped to extend downward and radially
outward. In other words, the shroud portion 33 preferably includes
a curved surface or a slant surface inclined with reference to the
center axis J.
[0027] As illustrated in FIG. 3, the housing 20 accommodates the
impeller 30 and the motor 40. The housing 20 preferably includes an
intake port 61, a flow path 50 and the exhaust port 62. The intake
port 61 is a hole opened upward and arranged to bring the outside
and inside of the housing 20 into communication with each other.
The intake port 61 is arranged above the impeller 30. As
illustrated in FIGS. 1 and 2, when seen in a plan view, the edge of
the intake port 61 has a circular or substantially circular shape
centered at the center axis J. The plan-view shape of the edge of
the intake port 61 is not limited to the circular shape and is not
particularly limited.
[0028] As illustrated in FIG. 3, the flow path 50 is provided
within the housing 20. The flow path 50 interconnects the intake
port 61 and the exhaust port 62. The flow path 50 has, e.g., a
scroll or substantially scroll shape. The flow path 50 preferably
includes an upper flow path 51 and a lower flow path 52. That is to
say, the upper flow path 51 and the lower flow path 52 constitute
the flow path 50 having a scroll or substantially scroll shape.
[0029] As used herein, the term "scroll shape" refers to a shape in
which the radial dimension of the flow path grows larger as the
flow path extends in the circumferential direction. The expression
"the flow path has a scroll shape" includes a case where at least
one of the upper flow path and the lower flow path has a scroll
shape. That is to say, the expression "the flow path has a scroll
shape" includes a case where only the upper flow path has a scroll
shape, a case where only the lower flow path has a scroll shape and
a case where both the upper flow path and the lower flow path have
a scroll shape.
[0030] The upper flow path 51 and the lower flow path 52 are
disposed along the axial direction. The lower flow path 52 is
arranged below the upper flow path 51. The lower flow path 52 is
connected to the upper flow path 51. The upper flow path 51 and the
lower flow path 52 will be described later.
[0031] As illustrated in FIG. 4, the exhaust port 62 is arranged
radially outward of the impeller 30. In the present preferred
embodiment, the exhaust port 62 is opened in the direction (X-axis
direction) orthogonal to the axial direction. As illustrated in
FIG. 1, the exhaust port 62 is defined by connecting an upper
housing 21 and a lower housing 22 which will be described later. As
illustrated in FIG. 5, the exhaust port 62 is connected to the
upper flow path 51 and the lower flow path 52.
[0032] In order to reduce a loss of the airflow discharged from the
centrifugal fan 10, it is preferred that, for example, the opening
area of the exhaust port 62 is equal to or larger than the opening
area of the intake port 61. In a configuration in which the exhaust
port 62 is connected to only one of the upper flow path 51 and the
lower flow path 52, the axial dimension of the upper flow path 51
or the axial dimension of the lower flow path 52 needs to be
increased in order to secure the opening area of the exhaust port
62. This poses a problem in that the centrifugal fan 10 becomes
larger in the axial direction.
[0033] In contrast, according to the present preferred embodiment,
the exhaust port 62 is connected to the upper flow path 51 and the
lower flow path 52. This makes it possible to provide the exhaust
port 62 over the upper flow path 51 and the lower flow path 52.
Thus, the opening area of the exhaust port can be increased without
having to increase the axial dimension of the upper flow path 51
and the axial dimension of the lower flow path 52. Accordingly, it
is possible to restrain the centrifugal fan 10 from becoming larger
in size.
[0034] In the present preferred embodiment, the axial dimension L2
of the portion of the exhaust port 62 connected to the lower flow
path 52 is larger than the axial dimension L1 of the portion of the
exhaust port 62 connected to the upper flow path 51.
[0035] In FIG. 3, the airflow is indicated by thick arrows. As
illustrated in FIG. 3, if the motor 40 rotates the impeller 30, an
air is introduced into the housing 20 through the intake port 61.
The air introduced into the housing 20 is blown toward the radial
outer side of the impeller 30 through the interior of the impeller
30, namely through the gap between the shroud portion 33 and the
impeller body portion 31. The air blown radially outward from the
impeller 30 is moved through the upper flow path 51 and the lower
flow path 52 and is discharged to the outside of the housing 20
from the exhaust port 62.
[0036] As illustrated in FIGS. 1 and 2, the housing 20 preferably
includes the upper housing 21 and the lower housing 22. That is to
say, the housing 20 is configured by interconnecting two separate
members. Thus, when assembling the centrifugal fan 10, it is
possible for a worker to easily bring the impeller 30 into the
housing 20. This makes it easy to assemble the centrifugal fan
10.
[0037] As illustrated in FIG. 3, the upper housing 21 accommodates
the impeller 30 at the radial inner side thereof. The upper housing
21 preferably includes an upper housing cover portion 23 and an
upper housing wall portion 24.
[0038] The upper housing cover portion 23 is arranged above the
impeller 30. That is to say, the upper housing cover portion
overlaps with the impeller 30 in the axial direction. The upper
housing cover portion 23 includes the intake port 61. That is to
say, the upper housing 21 includes the intake port 61. The intake
port 61 axially extends through the upper housing cover portion
23.
[0039] The upper housing cover portion 23 preferably includes a
cover inner edge portion 23a extending downward from the inner edge
of the intake port 61. The cover inner edge portion 23a has a
tubular shape. The lower end of the cover inner edge portion 23a is
arranged radially inward of an inner edge 33a of the shroud portion
33. The intake port 61 communicates with the interior of the
impeller 30 through the inside of the cover inner edge portion
23a.
[0040] The upper housing cover portion 23 is radially widened along
the shape of the shroud portion 33. The upper housing cover portion
23 is shaped to extend downward and radially outward. In other
words, the upper housing cover portion 23 preferably includes a
curved surface or a slant surface inclined with respect to the
center axis J.
[0041] The upper housing wall portion 24 is connected to the lower
end of the upper housing cover portion 23. The upper housing wall
portion 24 is arranged radially outward of the impeller 30. The
upper housing wall portion 24 surrounds the impeller 30 in the
circumferential direction. As illustrated in FIG. 5, the upper
housing wall portion 24 preferably includes a portion of the
exhaust port 62.
[0042] An upper wall portion inner circumferential surface 24a is
the inner circumferential surface of the upper housing wall portion
24. As illustrated in FIG. 3, the upper wall portion inner
circumferential surface 24a extends downward and radially outward.
In other words, the upper wall portion inner circumferential
surface 24a is a curved surface or a slant surface inclined with
respect to the center axis J. Thus, the air discharged radially
outward from the impeller 30 can flow into the lower flow path 52
along the upper wall portion inner circumferential surface 24a.
[0043] As illustrated in FIG. 1, the upper housing wall portion 24
preferably includes a tongue portion 25. That is to say, the
housing 20 preferably includes the tongue portion 25. The tongue
portion 25 is a portion of the upper housing wall portion 24
connected to the exhaust port 62. As illustrated in FIG. 4, the
tongue portion 25 is arranged between the exhaust port 62 and the
below-mentioned lower flow path start end 52a in the
circumferential direction. In the present preferred embodiment, the
tongue portion 25 protrudes toward the side of the upper flow path
51 (namely, toward the rotation direction back side (-.theta..sub.Z
side) in the example of FIG. 4). Preferably, the tongue portion 25
is smoothly curved. An outer end portion 25a is the radial outer
end portion of the tongue portion 25. The outer end portion 25a
constitutes a portion of the rotation direction front side
(+.theta..sub.Z side) edge of the exhaust port 62.
[0044] As illustrated in FIG. 3, the lower housing 22 is attached
to the lower side of the upper housing 21. As illustrated in FIG.
2, the lower housing 22 preferably includes the motor cover portion
27, a lower housing bottom portion 28, a lower housing wall portion
26 and a closing portion 29. That is to say, the housing 20
preferably includes the motor cover portion 27.
[0045] As illustrated in FIG. 3, the motor cover portion 27 has a
roofed tubular shape opened downward. The motor 40 is disposed
radially inward of the motor cover portion 27. The motor cover
portion 27 covers the motor 40. As illustrated in FIGS. 2 and 3,
the motor cover portion 27 has a cylindrical shape centered at the
center axis J. As illustrated in FIG. 3, the motor cover portion 27
has the output shaft hole 27a axially extending through a cover
region of the motor cover portion 27.
[0046] The impeller 30 is arranged above the motor cover portion
27. As illustrated in FIG. 4, when seen in a plan view, the motor
cover portion 27 substantially overlaps with the impeller 30 in its
entirety.
[0047] As illustrated in FIG. 3, the lower housing bottom portion
28 extends radially outward from the lower end of the motor cover
portion 27. The lower housing wall portion 26 extends upward from
the radial outer end of the lower housing bottom portion 28. The
axial position of the upper end of the lower housing wall portion
26 is flush with the axial position of the upper surface of the
motor cover portion 27. As illustrated in FIG. 5, the lower housing
wall portion 26 preferably includes a portion of the exhaust port
62.
[0048] As illustrated in FIG. 2, the closing portion 29 is arranged
between the motor cover portion 27 and the lower housing wall
portion 26 in the radial direction. The closing portion 29 is
connected to the motor cover portion 27, the lower housing wall
portion 26 and the lower housing bottom portion 28. Thus, the
closing portion 29 closes a circumferential portion of the gap
between the motor cover portion 27 and the lower housing wall
portion 26.
[0049] The upper surface of the closing portion 29 is arranged on
the same axially-orthogonal plane as the upper surface of the motor
cover portion 27. The upper surface of the motor cover portion 27,
the upper surface of the closing portion 29 and the upper end of
the lower housing wall portion 26 are connected to one another with
no difference in level.
[0050] As illustrated in FIG. 4, when seen in a plan view, the
closing portion 29 is arranged between the tongue portion 25 and
the impeller 30 in the radial direction. The closing portion 29 is
connected to the rotation direction front side (-.theta..sub.Z
side) edge of the exhaust port 62.
[0051] Next, the upper flow path 51 and the lower flow path 52 will
be described in detail. As illustrated in FIG. 3, the boundary
between the upper flow path 51 and the lower flow path 52 is the
boundary between the upper housing 21 and the lower housing 22.
[0052] In the present preferred embodiment, the entirety of the
upper flow path 51 is arranged within the upper housing 21. That is
to say, the upper housing 21 preferably include the entirety of the
upper flow path 51. At least a portion of the upper flow path 51 is
arranged between the upper wall portion inner circumferential
surface 24a and the impeller 30 in the radial direction. A housing
inner circumferential surface 20a is the inner circumferential
surface of the housing 20. The upper wall portion inner
circumferential surface 24a is a portion of the housing inner
circumferential surface 20a. That is to say, at least a portion of
the upper flow path 51 is arranged between the housing inner
circumferential surface 20a and the impeller 30 in the radial
direction.
[0053] As illustrated in FIG. 4, the upper flow path 51 has an
annular or substantially annular shape. The upper flow path extends
along the upper wall portion inner circumferential surface 24a.
That is to say, the upper flow path 51 extends along the housing
inner circumferential surface 20a. As indicated by thick arrows in
FIG. 4, the air introduced into the upper flow path 51 from the
impeller 30 flows through the upper flow path 51 in the same
direction as the rotation direction of the impeller 30 (in the
+.theta..sub.Z direction). A part of the air flowing through the
upper flow path 51 is introduced into the lower flow path 52 until
the air reaches the exhaust port 62.
[0054] In the present preferred embodiment, the radial dimension L7
of the upper flow path 51 grows larger as the upper flow path 51
extends from a reference position P1 toward the exhaust port 62 in
the rotation direction of the impeller 30 (in the -.theta..sub.Z
direction). In other words, the upper flow path 51 has a scroll or
substantially scroll shape. Thus, it is possible to suppress
generation of an air vortex within the upper flow path 51 and to
smoothly discharge the air from the exhaust port 62. This makes it
possible to reduce a loss of airflow in the centrifugal fan 10.
[0055] The reference position P1 is positioned between the exhaust
port 62 and the below-mentioned lower flow path start end 52a. In
the present preferred embodiment, the reference position P1 is a
point at which a line extending in the direction orthogonal to the
exhaust port 62 (in the X-axis direction) via the center axis J
intersects the upper flow path 51.
[0056] The radial dimension L7 of the upper flow path 51 becomes
smallest in the reference position P1. An inner end portion 25b is
the radial inner end portion of the tongue portion 25. Within a
range from the reference position P1 to the inner end portion 25b
in the circumferential direction, the radial dimension L7 of the
upper flow path 51 is equal to the radial dimension L7 of the upper
flow path 51 in the reference position P1. That is to say, the
radial dimension L7 of the upper flow path 51 becomes smallest over
the range from the reference position P1 to the inner end portion
25b in the circumferential direction.
[0057] The axial dimension L3 of the upper flow path 51 illustrated
in FIG. 3 is equal to the internal axial dimension L5 of the upper
housing wall portion 24. The axial dimension L3 of the upper flow
path 51 grows smaller from the radial inner side toward the radial
outer side. The entirety of the upper flow path 51 is opened
downward.
[0058] The upstream end of the upper flow path 51 is, for example,
a position where the radial dimension L7 of the upper flow path 51
illustrated in FIG. 4 becomes smallest. That is to say, the
position of the upstream end of the upper flow path 51 is the
position where the upstream end of the upper flow path 51 is
identical in the circumferential position with the inner end
portion 25b of the tongue portion 25.
[0059] The term "upper flow path" refers to, e.g., an annular flow
path arranged above the lower flow path having one closed end. That
is to say, in the present preferred embodiment, the radial outer
portion of the axial gap between the impeller 30 and the motor
cover portion 27 illustrated in FIG. 3 is included in the upper
flow path 51.
[0060] As illustrated in FIG. 2, the entirety of the lower flow
path 52 is arranged inside the lower housing 22. A lower wall
portion inner circumferential surface 26a is the inner
circumferential surface of the lower housing wall portion 26. A
motor cover portion outer circumferential surface 27b is the outer
circumferential surface of the motor cover portion 27. A closing
portion side surface 29a is the side surface of the closing portion
29. That is to say, the lower housing 22 preferably includes the
entirety of the lower flow path 52. The lower flow path 52 is a
flow path surrounded by the upper surface of the lower housing
bottom portion 28, the lower wall portion inner circumferential
surface 26a, the motor cover portion outer circumferential surface
27b and the closing portion side surface 29a.
[0061] The housing inner circumferential surface 20a is the inner
circumferential surface of the housing 20. The lower wall portion
inner circumferential surface 26a is a portion of the housing inner
circumferential surface 20a. That is to say, the lower flow path 52
is arranged between the motor cover portion outer circumferential
surface 27b and the housing inner circumferential surface 20a.
[0062] As described above, the motor 40 is arranged radially inward
of the motor cover portion 27. Thus, the motor 40 is arranged
radially inward of the lower flow path 52. Accordingly, when the
motor 40 is accommodated within the housing 20, it is possible to
dispose the motor 40 in a radially overlapping relationship with
the lower flow path 52. It is therefore possible to reduce the size
of the centrifugal fan 10 in the axial direction.
[0063] As illustrated in FIG. 4, the lower flow path 52 extends
along the lower wall portion inner circumferential surface 26a.
That is to say, the lower flow path 52 extends along the housing
inner circumferential surface 20a. As indicated by thick arrows in
FIG. 4, the air introduced from the upper flow path 51 into the
lower flow path 52 flows through the lower flow path 52 in the same
direction as the rotation direction of the impeller 30 (in the
-.theta..sub.Z direction).
[0064] As illustrated in FIGS. 2 and 4, a lower flow path terminal
end 52b is one circumferential end (-.theta..sub.Z side end) of the
lower flow path 52 and is opened in the exhaust port 62. A lower
flow path start end 52a is the other circumferential end
(-.theta..sub.Z side end) of the lower flow path 52 and is closed
with respect to the exhaust port 62.
[0065] Thus, within the lower flow path 52, the air guided from the
lower flow path start end 52a toward the lower flow path terminal
end 52b does not flow from the vicinity of the exhaust port 62
toward the upstream side, namely the side of the lower flow path
start end 52a. Accordingly, the entirety of the air flowing through
the lower flow path 52 is discharged from the exhaust port 62. This
makes it possible to reduce a loss of airflow.
[0066] If the air flowing toward the vicinity of the exhaust port
62 impinges against the tongue portion 25 (see FIG. 4), a turbulent
flow of air is generated in the vicinity of the tongue portion 25.
This poses a problem in that a noise is generated by the turbulent
flow.
[0067] In contrast, according to the present preferred embodiment,
the lower flow path start end 52a is closed with respect to the
exhaust port 62. For that reason, a tongue portion is not provided
within the lower flow path 52. Thus, the air flowing through the
lower flow path 52 does not impinge against a tongue portion. This
makes it possible to suppress generation of a turbulent flow of
air. As a result, it is possible to suppress generation of a
noise.
[0068] Referring to FIG. 4, a straight line passing through the
center axis J and the center P2 of the exhaust port 62 is referred
to as a "straight line C3". As used herein, the term "the vicinity
of the exhaust port" includes a range in which the circumferential
angle .theta.2 from the straight line C3 toward the rotation
direction back side (-.theta..sub.Z side) becomes 75 degrees or
less. The center P2 of the exhaust port 62 is, for example, the
center of the exhaust port 62 in the direction orthogonal to the
center axis J and parallel to the exhaust port 62 (in the Y-axis
direction).
[0069] As illustrated in FIG. 5, all the upper flow path 51 and the
lower flow path 52 are connected to the exhaust port 62. The upper
flow path 51 has an annular or substantially annular shape. Thus,
there is a possibility that a part of the air guided from the
interior of the upper flow path 51 toward the vicinity of the
exhaust port 62 flows toward the upstream side of the upper flow
path 51. Furthermore, there is a possibility that the air flowing
toward the upstream side of the upper flow path 51 impinges against
the tongue portion 25 and generates a noise.
[0070] In contrast, according to the present preferred embodiment,
the axial dimension L2 of the portion of the exhaust port 62
connected to the lower flow path 52 is larger than the axial
dimension L1 of the portion of the exhaust port 62 connected to the
upper flow path 51. This makes it possible to reduce the flow rate
of the air flowing through the upper flow path 51. It is therefore
possible to restrain the air guided to the vicinity of the exhaust
port 62 from flowing toward the upstream side of the upper flow
path 51. Accordingly, it is possible to further reduce a loss of
airflow and to further suppress generation of a noise.
[0071] In the case of closing one circumferential end of the lower
flow path, it is preferable that one end of the lower flow path is
closed in the circumferential direction. That is to say, even when
closing one circumferential end of the lower flow path, one
circumferential end of the lower flow path may be opened
upward.
[0072] As illustrated in FIGS. 2 and 4, the lower flow path start
end 52a is closed by the closing portion 29. That is to say, the
circumferential position of the lower flow path start end 52a is
the same as the circumferential position of the rotation direction
front side (+.theta..sub.Z side) end of the closing portion 29.
[0073] Preferably, the lower flow path start end 52a is arranged
near the exhaust port 62 in the circumferential direction. If the
lower flow path start end 52a is excessively spaced apart from the
exhaust port 62 in the circumferential direction, the length of the
lower flow path 52 becomes small. For that reason, the air
discharged from the impeller 30 is not efficiently guided to the
exhaust port 62. Thus, the blowing efficiency of the centrifugal
fan 10 is reduced.
[0074] Referring to FIG. 4, when seen in a plan view, a straight
line C2 is a straight line passing through the center axis J and
meeting with the lower flow path start end 52a. A straight line C1
is a straight line passing through the center axis J and meeting
with the tongue portion 25. The angle between the straight line C1
and the straight line C2 is assumed to be .theta.. The
circumferential angle from the straight line C1 is assumed to be
.theta.1. In this case, it is preferred that the angle .theta. is
75 degrees or less. That is to say, when seen in a plan view, the
lower flow path start end 52a is located in the position where the
circumferential angle .theta.1 from the straight line C1 becomes 75
degrees or less. The angle .theta.1 is a circumferential angle from
the straight line C1 toward the rotation direction front side
(+.theta..sub.Z side).
[0075] By positioning the lower flow path start end 52a within this
angular extent, it is possible to have the circumferential position
of the lower flow path start end 52a lie near the exhaust port 62.
It is therefore possible to suppress reduction of the blowing
efficiency of the centrifugal fan 10.
[0076] The radial dimension L8 of the lower flow path 52 grows
larger from the lower flow path start end 52a toward the lower flow
path terminal end 52b. That is to say, the lower flow path 52 has a
scroll or a substantially scroll shape. It is therefore possible to
suppress generation of an air vortex within the lower flow path 52
and to smoothly discharge the air from the exhaust port 62. This
makes it possible to further reduce a loss of airflow.
[0077] Furthermore, the upper housing wall portion 24 constitutes
the radial outer inner circumferential surface of the upper flow
path 51. The lower housing wall portion 26 constitutes the radial
outer inner circumferential surface of the lower flow path 52. In
the present preferred embodiment, the upper flow path 51 has a
scroll shape or a substantially scroll shape. This makes it easy to
interconnect the upper housing 21 having the upper flow path 51 and
the lower housing 22 having the lower flow path 52. Specifically,
the upper housing wall portion 24 and the lower housing wall
portion 26 may be shaped to go away from the center axis J as they
extend in the circumferential direction. This makes it easy to
connect the upper housing wall portion 24 to the lower housing wall
portion 26.
[0078] In the present preferred embodiment, the axial dimension L4
of the lower flow path 52 illustrated in FIG. 3 is uniform. The
axial dimension L4 of the lower flow path 52 is equal to the
internal axial dimension L6 of the lower housing 22. This makes it
easy to increase the axial dimension L4 of the lower flow path
52.
[0079] The flow velocity of the air flowing through the flow path
50 tends to become larger in the position closer to the lower
housing bottom portion 28. If the air having a large flow velocity
is introduced from the vicinity of the exhaust port 62 toward the
upstream side of the flow path 50, the loss of airflow grow larger.
Moreover, the air having a large flow velocity impinges against the
tongue portion 25. Thus, a turbulent flow is easily generated and a
noise is increased. The upstream side of the flow path 50 is, for
example, the upstream side of the upper flow path 51.
[0080] In contrast, according to the present preferred embodiment,
it is possible to increase the axial dimension L4 of the lower flow
path 52. This makes it possible to reliably prevent the air having
a large flow velocity from being introduced toward the upstream
side of the flow path 50. Accordingly, it is possible to further
reduce the loss of airflow.
[0081] As illustrated in FIGS. 2 and 4, the entirety of the lower
flow path 52 is opened upward toward the upper flow path 51. For
that reason, the air discharged radially outward from the impeller
30 is easily introduced from the upper flow path 51 into the lower
flow path 52. This makes it easy to discharge the air from the
exhaust port 62 via the lower flow path 52. Accordingly, it is
possible to further reduce the loss of airflow.
[0082] As illustrated in FIG. 3, the axial dimension L4 of the
lower flow path 52 is larger than the axial dimension L3 of the
upper flow path 51. For that reason, the air discharged radially
outward from the impeller 30 easily flows from the upper flow path
51 toward the lower flow path 52. This makes it possible to further
reduce the loss of airflow.
[0083] The present disclosure is not limited to the configurations
described above. In the following descriptions, there may be a case
where the same configurations as described above are appropriately
designated by like reference symbols with the descriptions thereof
omitted.
[0084] One of the upper flow path 51 and the lower flow path 52 may
not have a scroll shape. In this case, one of the upper flow path
51 and the lower flow path 52 may have, e.g., an annular or
substantially annular shape. A portion of the lower flow path 52
may not be opened toward, e.g., the upper flow path 51.
[0085] The lower housing 22 may have a portion of the upper flow
path 51 and the lower flow path 52. In this case, the axial
dimension L4 of the lower flow path 52 in the vicinity of the
exhaust port 62 may be one half or more of the internal axial
dimension L6 of the lower housing 22. According to this
configuration, it is possible to sufficiently increase the axial
dimension L4 of the lower flow path 52 and to prevent the air
having a large flow velocity from flowing from the vicinity of the
exhaust port 62 toward the upstream side of the upper flow path
51.
[0086] In the configuration in which the lower housing 22 has a
portion of the upper flow path 51 and the lower flow path 52, for
example, the axial position of the upper surface of the closing
portion 29 illustrated in FIG. 2 may be lower than the axial
position of the upper surface of the motor cover portion 27. In
this case, the internal portion of the lower housing 22 arranged
higher than the closing portion 29 has an annular or substantially
annular shape. Thus, within the lower housing 22, a portion of the
upper flow path 51 is provided above the upper surface of the
closing portion 29, and the lower flow path 52 is provided below
the upper surface of the closing portion 29.
[0087] FIG. 6 is a side view illustrating a centrifugal fan 110
according to another example of one preferred embodiment. As
illustrated in FIG. 6, the exhaust port 62 may be connected to only
the lower flow path 52.
[0088] As illustrated in FIG. 6, the centrifugal fan 110 preferably
includes a housing 120. The housing 120 preferably includes an
intake port 61, a flow path 50 and an exhaust port 162. The housing
120 preferably includes an upper housing 121 and a lower housing
122.
[0089] The upper housing 121 preferably includes an upper housing
cover portion 23 and an upper housing wall portion 124. The
configuration of the upper housing wall portion 124 is the same as
the configuration of the upper housing wall portion 24 illustrated
in FIG. 5, except that the upper housing wall portion 124 does not
have a portion of the exhaust port 62. In FIG. 6, the upper housing
wall portion 124 has a shape obtained by closing a portion of the
exhaust port 62 defined by the upper housing wall portion 24
illustrated in FIG. 5.
[0090] The lower housing 122 preferably includes a lower housing
bottom portion 28, a lower housing wall portion 126 and a closing
portion 29. While not shown in the drawings, the lower housing 122
includes a motor cover portion 27. The configuration of the lower
housing wall portion 126 is the same as the configuration of the
lower housing wall portion 26 illustrated in FIG. 5, except that
the lower housing wall portion 126 has the entirety of the exhaust
port 162.
[0091] In this configuration, the exhaust port 162 is connected to
only the lower flow path 52. For that reason, the entirety of the
air discharged from the exhaust port 162 is discharged from the
lower flow path 52. It is therefore possible to enable the air
existing within the upper flow path 51 to easily flow toward the
lower flow path 52 while the air flows from the upstream side of
the upper flow path 51 to the vicinity of the exhaust port 162.
Accordingly, it is possible to further restrain the air from
flowing from the vicinity of the exhaust port 162 toward the
upstream side of the upper flow path 51. As a result, it is
possible to further reduce the loss of airflow and to further
suppress generation of a noise.
[0092] In this configuration, the axial dimension of the lower
housing 122 may be made larger than the axial dimension of the
lower housing 22 (see FIG. 5). By doing so, it is possible to set
the opening area of the exhaust port 162 larger than the opening
area of the intake port 61.
[0093] Other configurations of the exhaust port 162 are the same as
the configurations of the exhaust port 62 illustrated in FIG. 5.
Other configurations of the centrifugal fan 110 are the same as the
configurations of the centrifugal fan 10 illustrated in FIG. 5.
[0094] FIG. 7 is a sectional view illustrating a portion of a
centrifugal fan 210 according to a further example of one preferred
embodiment. As illustrated in FIG. 7, the lower end portion of the
lower flow path 52 may be a slant surface.
[0095] As illustrated in FIG. 7, the centrifugal fan 210 preferably
includes a housing 220. The housing 220 preferably includes a flow
path 250. The flow path 250 preferably includes an upper flow path
51 and a lower flow path 252. The housing 220 preferably includes
an upper housing 21 and a lower housing 222. The lower housing 222
preferably includes a lower housing bottom portion 228, a lower
housing wall portion 26 and a closing portion 29. While not shown
in the drawings, the lower housing 222 preferably includes a motor
cover portion 27.
[0096] A bottom surface 228a of the lower housing bottom portion
228 is a slant surface. The bottom surface 228a extends downward in
the portion connected to the closing portion 29. That is to say,
the bottom surface 228a extends downward from a lower flow path
start end 252a toward the rotation direction front side
(+.theta..sub.Z side). In other words, the bottom surface 228a is a
slant surface inclined with respect to the center axis J or a
curved surface. In the portion connected to the closing portion 29,
the axial position of the bottom surface 228a is preferably the
same as the axial position of the upper surface of the closing
portion 29. That is to say, at the lower flow path start end 252a,
the axial position of the bottom surface 228a is preferably the
same as the axial position of the upper surface of the closing
portion 29.
[0097] The bottom surface 228a is the lower end portion of the
lower flow path 252. The position of the lower end portion of the
lower flow path 252 goes away from the upper flow path 51 as the
lower flow path 252 extends from the lower flow path start end 252a
toward the lower flow path terminal end (not illustrated). In other
words, the distance between the lower end portion of the lower flow
path 252 and the upper flow path 51 grows larger from the lower
flow path start end 252a toward the lower flow path terminal end
(not illustrated). Thus, the axial dimension of the lower flow path
252 becomes larger from the lower flow path start end 252a toward
the lower flow path terminal end.
[0098] The air introduced from the intake port 61 into the impeller
30 is discharged from the circumferential entirety of the impeller
30 to the upper flow path 51. A part of the air introduced into the
upper flow path 51 flows toward the lower flow path 52 while moving
through the upper flow path 51 in the rotation direction of the
impeller 30 (-.theta..sub.Z direction). For that reason, at the
upstream side of the upper flow path 51 from which the air begins
to flow, the amount of the air flowing from the upper flow path 51
toward the lower flow path 52 is small. Thus, for example, in the
case where the axial dimension of the lower flow path 52 is uniform
over the entirety of the lower flow path 52, the air tends to stay
within the lower flow path 52 in the vicinity of the lower flow
path start end 52a. Thus, an air vortex is easily generated.
Accordingly, there is a possibility that the loss of airflow
becomes larger.
[0099] In contrast, according to the aforementioned configuration,
the lower end portion of the lower flow path 252 goes away from the
upper flow path 51 as the lower flow path 252 extends from the
lower flow path start end 252a toward the lower flow path terminal
end. In other words, the distance between the lower end portion of
the lower flow path 252 and the upper flow path 51 grows larger
from the lower flow path start end 252a toward the lower flow path
terminal end. Thus, it is possible to reduce the axial dimension of
the lower flow path 252 at the upstream side where the amount of
the air introduced from the upper flow path 51 into the lower flow
path 252 is small. This makes it possible to restrain the air from
staying within the lower flow path 252. Accordingly, it is possible
to restrain the loss of airflow from becoming larger.
[0100] At the downstream side, the amount of the air introduced
from the upper flow path 51 into the lower flow path 252 is large.
According to this configuration, it is possible to increase the
axial dimension of the lower flow path 252 at the downstream side.
Thus, it is possible to enable the air to efficiently flow from the
upper flow path 51 toward the lower flow path 252.
[0101] According to the configuration described above, as indicated
by thick arrows in FIG. 7, it is possible to enable the air to
smoothly flow along the bottom surface 228a which is a slant
surface. This makes it possible to enable the air to smoothly flow
through the flow path 250, thereby further suppressing generation
of an air vortex within the flow path 250.
[0102] Preferably, the axial dimension of the lower flow path 252
in the vicinity of the exhaust port 62 is, for example, one half or
more of the axial dimension of the lower housing 222. This makes it
possible to further reduce the loss of airflow.
[0103] According to the configuration described above, it is
possible to further improve the blowing efficiency of the
centrifugal fan 210. Other configurations of the centrifugal fan
210 are the same as the configurations of the centrifugal fan 10
illustrated in FIGS. 1 to 5.
[0104] Furthermore, the upper housing 21 may have the entirety of
the upper flow path 51 and the entirety of the lower flow path 52.
The housing 20 may be configured by axially interconnecting three
or more independent members. The housing 20 may be a single
member.
[0105] The upper housing 21 may not include the tongue portion 25.
The motor 40 may not be accommodated within the housing 20.
[0106] Features of the above-described preferred embodiments and
the modifications thereof may be combined appropriately as long as
no conflict arises.
[0107] 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.
* * * * *