U.S. patent application number 12/653665 was filed with the patent office on 2010-04-22 for centrifugal blower.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Kouji Matsunaga, Yasushi Mitsuishi, Masaharu Sakai.
Application Number | 20100098535 12/653665 |
Document ID | / |
Family ID | 26618807 |
Filed Date | 2010-04-22 |
United States Patent
Application |
20100098535 |
Kind Code |
A1 |
Sakai; Masaharu ; et
al. |
April 22, 2010 |
Centrifugal blower
Abstract
A centrifugal multi-blade fan has multiple blades about a
rotational shaft and draws in air along the rotational shaft and
then blows the air approximately perpendicular to the rotational
shaft to reduce wind noise. A scroll casing encloses the
multi-blade fan and defines a scroll-shaped airflow passage for
directing the air blown from the multi-blade fan. The scroll casing
has an intake opening and an outlet opening at a scroll end, in a
downstream scroll casing portion. The scroll casing expands such
that a flow passage cross-sectional area on the airflow downstream
side is larger than that on an airflow upstream side. A ratio of a
blade length to a diameter of the multi-blade fan is greater than
or equal to 0.12, and an outer scroll casing radius, relative to
the rotational axis, increases as a logarithmic spiral, its
expansion angle being from 3.3.degree. to 4.8.degree..
Inventors: |
Sakai; Masaharu;
(Kariya-city, JP) ; Matsunaga; Kouji;
(Kariya-city, JP) ; Mitsuishi; Yasushi;
(Anjo-city, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
26618807 |
Appl. No.: |
12/653665 |
Filed: |
December 16, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11888080 |
Jul 31, 2007 |
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12653665 |
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10192131 |
Jul 10, 2002 |
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11888080 |
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Current U.S.
Class: |
415/205 |
Current CPC
Class: |
F04D 29/30 20130101;
F04D 29/4233 20130101 |
Class at
Publication: |
415/205 |
International
Class: |
F04D 29/44 20060101
F04D029/44 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2001 |
JP |
2001-215649 |
Oct 19, 2001 |
JP |
2001-322201 |
Claims
1. A centrifugal blower comprising: a centrifugal multi-blade fan
having multiple blades about a rotational shaft, wherein said
centrifugal fan takes in air along an axial direction of said
rotational shaft and blows said air outward in a radial direction
with respect to said rotational shaft; and a scroll casing for
storing said centrifugal multi-blade fan, said scroll casing
defining a scroll-shaped airflow passage for directing said air
blown out from said centrifugal multi-blade fan, said scroll casing
having an intake opening at a first end of said rotational shaft
and an outlet opening at a scroll end at an airflow downstream
portion; wherein a first expanded part and a second expanded part
are expanded in a direction parallel with said rotational shaft and
are provided in said airflow passage such that a flow passage
cross-sectional area on the airflow downstream side is larger than
that on an airflow upstream side; a ratio of a blade length of said
blades to a diameter of the centrifugal multi-blade fan is equal to
or over 0.12; an outer peripheral radius of said scroll casing
expands as a logarithmic spiral, and its expansion angle is from
3.3.degree. to 4.8.degree.; a first expanded part expands the flow
passage cross-sectional area on the side of the inlet opening and
is formed proximate the scroll end toward the outlet opening; and
the second expanded part expands the flow passage cross-sectional
area on the opposite side of the inlet opening and is formed from a
range of a part up to about 60.degree. from a neighborhood of the
nose in the rotational direction of the fan toward the outlet
opening.
2. The centrifugal blower according to claim 1, wherein a dimension
of said scroll end portion in a direction parallel with said
rotational shaft is from 1.1 times to 2.3 times a dimension of a
nose in said scroll casing in a direction parallel with said
rotational shaft.
3. The centrifugal blower according to claim 1, wherein a dimension
of said scroll end portion in a direction parallel with said
rotational shaft is from 1.3 times to 2.1 times of a dimension of a
nose in said scroll casing in a direction parallel with said
rotational shaft.
4. The centrifugal blower according to claim 1, wherein said
airflow passage has an approximately rectangular cross-section.
5. The centrifugal blower according to claim 1, wherein said
airflow passage has an approximately rectangular cross-section with
rounded interior passage corners.
6. The centrifugal blower according to claim 1, wherein a
protrusion protruding toward said centrifugal multi-blade fan is
provided on an inner wall on an outer peripheral side of said
scroll casing, and has an approximately triangular shape protruding
toward said centrifugal multi-blade fan when viewed from a primary
flow direction of the air flowing through said airflow passage.
7. A centrifugal blower comprising: a centrifugal multi-blade fan
having multiple blades about a rotational shaft, wherein said
centrifugal fan takes in air along an axial direction of said
rotational shaft and blows said air outward in a radial direction
with respect to said rotational shaft; and a scroll casing for
storing said centrifugal multi-blade fan, said scroll casing
defining a scroll-shaped airflow passage for directing said air
blown out from said centrifugal multi-blade fan, said scroll casing
having an intake opening at a first end of said rotational shaft
and an outlet opening at a scroll end at an airflow downstream
portion, wherein: a first expanded part and a second expanded part
are expanded in a direction parallel with said rotational shaft and
are provided in said airflow passage such that a flow passage
cross-sectional area on the airflow downstream side is larger than
that on an airflow upstream side; a ratio of a blade length of said
blades to a diameter of the centrifugal multi-blade fan is equal to
or over 0.12; an outer peripheral radius of said scroll casing
expands as a logarithmic spiral, and its expansion angle is from
3.3.degree. to 4.8.degree.; and an expanded dimension (Hup) on the
side of the inlet opening is less than 0.4 times an expanded
dimension (HLR) on the opposite side of the inlet opening in the
first and second expanded parts.
8. The centrifugal blower according to claim 7, wherein a dimension
of said scroll end portion in a direction parallel with said
rotational shaft is from 1.1 times to 2.3 times a dimension of a
nose in said scroll casing in a direction parallel with said
rotational shaft.
9. The centrifugal blower according to claim 7, wherein a dimension
of said scroll end portion in a direction parallel with said
rotational shaft is from 1.3 times to 2.1 times of a dimension of a
nose in said scroll casing in a direction parallel with said
rotational shaft.
10. The centrifugal blower according to claim 7, wherein said
airflow passage has an approximately rectangular cross-section.
11. The centrifugal blower according to claim 7, wherein said
airflow passage has an approximately rectangular cross-section with
rounded interior passage corners.
12. The centrifugal blower according to claim 7, wherein a
protrusion protruding toward said centrifugal multi-blade fan is
provided on an inner wall on an outer peripheral side of said
scroll casing, and has an approximately triangular shape protruding
toward said centrifugal multi-blade fan when viewed from a primary
flow direction of the air flowing through said airflow passage.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/888,080 filed Jul. 31, 2007 which is a divisional of
U.S. patent application Ser. No. 10/192,131 filed on Jul. 10, 2002.
This application is based upon, claims the benefit of priority of
Japanese Patent Applications No. 2001-215649 filed Jul. 16, 2001,
and No. 2001-322201 filed Oct. 19, 2001. All of the above
referenced U.S. and Japanese patent applications are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a centrifugal blower having
a centrifugal multiblade fan (abbreviated as a centrifugal fan
hereafter) applied to a vehicular air-conditioning apparatus.
[0004] 2. Description of the Related Art
[0005] Generally, centrifugal fans use a centrifugal force to take
in air in an axial direction, and to blow the air outward in a
radial direction. The air blown out from the centrifugal fan has an
airflow of an axial direction component directed from an intake
side to a counter-intake side.
[0006] In the invention disclosed in Japanese Patent Laid-Open
Publication No. Hei. 5-195995, an expanded part for expanding an
airflow passage on the counter-intake side is formed in the airflow
passage outside a centrifugal fan, and a side wall on a side of the
centrifugal fan is tilted as a tilted surface in the expanded part
(See FIGS. 20A and 20B). FIG. 20B is an enlargement of the area
noted by the circular portion XXB of FIG. 20A. With this
construction, the air blown out from the centrifugal fan flows
smoothly along the tilted surface as shown as a solid line in FIG.
20B, and generation of airflow flowing toward the inlet opening
along the inner wall surface on the outer peripheral side is
restrained. As a result, interference (collision) of air directly
flowing from the centrifugal fan toward the inner wall surface on
the outer peripheral side of the scroll casing, air blown outward
in the radial direction, and the air flowing toward the inlet
opening along the inner wall surface on the outer periphery side is
prevented from reducing wind noise.
[0007] The inventors produced and examined the blower described in
the publication above, investigated the flow of the air in detail,
and found the following points.
[0008] When the quantity of the airflow blown out from the
centrifugal fan is relatively large, the air flows as described
above (the solid line in FIG. 20B) and a stable swirling flow is
generated. When the quantity of the airflow blown out from the
centrifugal fan is relatively small, the quantity of the airflow is
not enough for air which has collided with a wall surface 74f to
flow along a wall surface 74g and a tilted surface 74h. Therefore,
the flow does not extend over the entire expanded part, and a
stable swirling flow is not generated. As a result, the flow
becomes unstable, the airflow tends to be disturbed, and wind noise
becomes worse.
SUMMARY OF THE INVENTION
[0009] In view of the foregoing problems, an object of the present
invention is to provide a centrifugal blower which can sufficiently
reduce the wind noise even when the airflow quantity is small.
[0010] To attain the above object, a centrifugal blower according
to a first aspect of the present invention comprises a centrifugal
multiblade fan provided with multiple blades about a rotational
shaft for taking in air in an axial direction of the rotational
shaft and blowing the air outward in a radial direction with
respect to the rotational shaft. A scroll casing is used for
storing the centrifugal multiblade fan, the scroll casing
constituting a scroll-shaped airflow passage for channeling the air
blown out from the centrifugal multiblade fan, and having an intake
opening on one end in the axial direction of the rotational shaft,
and an outlet opening on an airflow downstream side of a scroll
end.
[0011] The centrifugal blower is characterized in that expanded
parts, expanded in a direction parallel with the rotational shaft,
are provided in the airflow passage such that a flow passage
cross-sectional area on the airflow downstream side is larger than
that on the airflow upstream side. Additionally, a ratio of a blade
length of the blades to a diameter of the centrifugal multiblade
fan is 0.12 and over, an outer peripheral radius of the scroll
casing extends as a logarithmic spiral, and its expansion angle n
is from 3.3.degree. to 4.8.degree..
[0012] With this construction, noise is sufficiently reduced even
when the airflow quantity is small as shown in FIGS. 8 and 9 as
described below.
[0013] A centrifugal blower according to a second aspect of the
present invention comprises a centrifugal multiblade fan provided
with multiple blades about a rotational shaft for taking in air
along an axial direction of the rotational shaft, and blowing the
air outward in a radial direction. Additional components include a
scroll casing for storing the centrifugal multi-blade fan, the
casing constituting a scroll-shaped airflow passage for the air
blown out from the centrifugal multiblade fan. Also evident are an
intake-opening on one end in the axial direction of the rotational
shaft, and an outlet opening on the airflow downstream side of the
scroll end. This centrifugal blower is characterized in that
expanded parts, expanded in a direction parallel with the
rotational shaft, are provided in the airflow passage such that a
flow passage cross-sectional area on the airflow downstream side is
larger than that on the airflow upstream side, a ratio of a blade
length of the blades to a diameter of the centrifugal multiblade
fan is 0.12 or above, an outer peripheral radius of the scroll
casing extends as a logarithmic spiral, and its expansion angle is
from 3.5.degree. to 4.5.degree..
[0014] With this construction, airflow noise is sufficiently
reduced even when the airflow quantity is small as shown in FIGS. 8
and 9 described below.
[0015] A dimension of the winding-end portion in the direction
parallel with the rotational shaft is 1.1 times to 2.3 times a
dimension of a nose in the scroll casing in the direction parallel
with the rotational shaft in a third aspect of the invention. With
this constitution, noise is sufficiently reduced even when the
airflow quantity is small as shown in FIGS. 8 and 10 described
below.
[0016] The dimension of the winding-end portion in the direction
parallel with the rotational shaft is from 1.3 times to 2.1 times
of the dimension of a nose in the scroll casing in the direction
parallel with the rotational shaft in a fourth aspect of the
invention. With this constitution, noise is sufficiently reduced
even when the airflow quantity is small as shown in FIGS. 8 and 10
described below.
[0017] The airflow passage may be constituted so as to have an
approximately rectangular cross-section in a fifth aspect of the
invention. The airflow passage is constituted so as to have an
approximately rectangular cross-section whose corners are formed as
an arc (rounded internal corners) in a sixth aspect of the
invention. With this constitution, since an unstable swirling flow
is prevented from being generated at the corners in the airflow
passage, and simultaneously, a generated swirling flow is
circulated smoothly, the swirling flow is stabilized, and the noise
is reduced.
[0018] A protrusion protruding toward the centrifugal multiblade
fan is provided on the inner wall on the outer periphery of the
scroll casing, and has an approximately triangular shape protruding
toward the centrifugal multi-blade fan as seen from a primary flow
direction of the air flowing through the airflow passage in a
seventh aspect of the invention.
[0019] When the protrusion is provided at a part with which air
with the highest flow rate of the air blown out from the
centrifugal multiblade fan collides, the air blown out from the
centrifugal multiblade fan is easily split into the inlet opening
side and the outlet opening side. As a result, generation of a
swirling flow is promoted, and wind noise is reduced.
[0020] A centrifugal blower according to an eighth aspect of the
present invention comprises a centrifugal multiblade fan provided
with multiple blades about a rotational shaft for taking in air
along an axial direction of the rotational shaft, and for blowing
the air outward in a radial direction. The blower also exhibits a
scroll casing for storing the centrifugal multi-blade fan,
constituting a scroll-shaped airflow passage for channeling and
directing the air blown away from the centrifugal multi-blade fan.
The blower has an intake opening on one end in the axial direction
of the rotational shaft, and an outlet opening on an airflow
downstream side of a scroll end. The centrifugal blower is
characterized in that a ratio of a blade length of the blades to a
diameter of the centrifugal multi-blade fan is 0.12 and over, a fan
inlet opening angle of the centrifugal multi-blade fan is from
55.degree. to 85.degree., a fan outlet opening angle of the
centrifugal multi-blade fan is from 15.degree. to 45.degree., and a
fan advancing angle, which is an angle between a line connecting an
inlet-opening-side end of the blade with the rotational center of
the multiblade fan, and a line connecting an outlet opening end of
the blade with the rotational center of the multi-blade fan, ranges
from 4.degree. to 10.degree.. With this construction, noise is
sufficiently reduced even when the airflow quantity is small as
shown in FIGS. 16 to 19 described below.
[0021] It is preferable that a curvature radius of the blade on the
inlet opening side is equal to or less than a curvature radius of
the blade on the outlet opening side in a ninth aspect of the
invention.
[0022] It is preferable that the blades have a shape for smoothly
connecting curved surfaces having two or more curvature radii with
one another in a tenth aspect of the invention.
[0023] An outer peripheral side radius of the scroll casing extends
as a logarithmic spiral, and its expansion angle n is from
3.3.degree. to 4.8.degree. in an eleventh aspect of the
invention.
[0024] With this constitution, noise is sufficiently reduced even
when the airflow quantity is small as shown in FIG. 8, FIG. 9, and
FIGS. 16 to 19 described below.
[0025] The outer peripheral radius of the scroll casing extends as
a logarithmic spiral, and its expansion angle n is from 3.5.degree.
to 4.5.degree. in a twelfth aspect of the invention.
[0026] With this constitution, noise is sufficiently reduced even
when the airflow quantity is small as shown in FIG. 8, FIG. 9, and
FIGS. 16 to 19 described below.
[0027] It is preferable that expanded parts, expanded in a
direction parallel with the rotational shaft, are provided in the
airflow passage such that a flow passage cross-sectional area on
the airflow downstream side is larger than that on the airflow
upstream side in a thirteenth aspect of the invention.
[0028] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic drawing of an air-conditioning
apparatus according to embodiments of the present invention;
[0030] FIG. 2 is a sectional view of a blower according to a first
embodiment of the present invention;
[0031] FIG. 3 is a descriptive drawing for an outlet-opening angle
.beta.2;
[0032] FIG. 4 is a view seen from a direction indicated by an arrow
A in FIG. 2;
[0033] FIG. 5 is a view seen from a direction indicated by an arrow
B in FIG. 2;
[0034] FIG. 6A is a descriptive drawing for describing an air
flowing effect of the present invention;
[0035] FIG. 6B is a descriptive drawing for describing an air
flowing effect of the present invention;
[0036] FIG. 7 is a schematic drawing showing airflow in an airflow
passage of a scroll casing;
[0037] FIG. 8 is a graph showing a relationship between specific
noise level and blade length divided by fan diameter (L/D);
[0038] FIG. 9 is a graph showing a relationship between the
specific noise level and an expansion angle;
[0039] FIG. 10 is a graph showing a relationship between the
specific noise level and an expansion ratio in an axial
direction;
[0040] FIG. 11 is a schematic drawing showing a sectional shape of
an airflow passage according to a second embodiment of the present
invention;
[0041] FIG. 12 is a schematic drawing showing a sectional shape of
an airflow passage according to a third embodiment of the present
invention;
[0042] FIG. 13 is a descriptive drawing showing an inlet-opening
angle .beta.1, an outlet-opening angle .beta.2, and an advancing
angle .gamma.;
[0043] FIG. 14A is a descriptive drawing showing a relationship
between the inlet-opening angle .beta.1, the outlet-opening angle
.beta.2, the advancing angle .gamma., and airflow;
[0044] FIG. 14B is a descriptive drawing showing a relationship
between the inlet-opening angle .beta.1, the outlet-opening angle
.beta.2, the advancing angle .gamma., and airflow;
[0045] FIG. 15A is a descriptive drawing showing a relationship
between the inlet-opening angle .beta.1, the outlet-opening angle
.beta.2, the advancing angle .gamma., and the airflow;
[0046] FIG. 15B is a descriptive drawing showing a relationship
between a large blade length and airflow;
[0047] FIG. 16 is a chart showing a relationship between the
minimum specific noise level, the ratio of blade length to fan
diameter L/D, and the airflow rate;
[0048] FIG. 17 is a chart showing a relationship between the fan
inlet-opening angle .beta.1, the specific noise level, and the
airflow rate;
[0049] FIG. 18 is a chart showing a relationship between the fan
outlet-opening angle .beta.2, and the specific noise level; and a
relationship between the fan-outlet-opening angle .beta.2 and the
airflow quantity;
[0050] FIG. 19 is a chart showing a relationship between the
advancing angle .gamma. and the specific noise level; and a
relationship between the advancing angle .gamma. and the airflow
quantity; and
[0051] FIG. 20A is a perspective view of a blower according to the
prior art; and
[0052] FIG. 20B is an enlarged view of encircled area XXB in FIG.
20A according to the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
First Embodiment
[0053] A centrifugal blower is applied to a blower in a vehicle
air-conditioning apparatus according to a first embodiment of the
present invention. FIG. 1 is a schematic drawing of a vehicle
air-conditioning apparatus 1 for a vehicle equipped with a
water-cooled engine, and the centrifugal blower (abbreviated as a
blower hereafter) according to the present invention.
[0054] An internal air intake opening 3 for taking in cabin air,
and an external air intake opening 4 for taking in outside air are
formed on an airflow upstream side of an air conditioner casing 2
forming an airflow passage. An intake-opening switching door 5 is
provided for selectively opening and closing the intake openings 3
and 4. Drive means such as a servomotor, or manual operation opens
and closes the intake-opening switching door 5.
[0055] A filter (not shown) for removing dust in the air, and a
blower 7 according to the present invention are provided on the
airflow downstream side of the intake-opening switching door 5. The
blower 7 blows air drawn from both of the intake openings 3 and 4
to the individual outlet openings 14, 15, and 17 which will be
described later.
[0056] An evaporator 9 for cooling the air blown out into a cabin
is provided on the airflow downstream side of the blower 7, and the
entire volume of air blown by the blower 7 passes through the
evaporator 9. A heater core 10 for heating the air blown out into
the cabin is provided on the airflow downstream side of the
evaporator 9, and this heater core 10 uses the coolant for the
engine 11 as a heat source to heat the air. The blower shown in
FIG. 1 is a schematic drawing, and its detail will be described
later.
[0057] A bypass passage 12 for bypassing the heater core 10 is
formed in the air conditioner casing 2. An air mix door 13 for
adjusting an airflow quantity ratio between an airflow quantity
passing through the heater core 10, and an airflow quantity passing
through the bypass passage 12 to adjust the temperature of the air
blown into the cabin, is provided on the airflow upstream side of
the heater core 10.
[0058] A face aperture 14 for blowing out the air-conditioned air
to the upper body of passengers in the cabin, a foot aperture 15
for blowing out the air to the feet of the passengers in the cabin,
and a defroster aperture 17 for blowing out the air on the inner
surface of a windshield 16 are formed on an extreme airflow
downstream side of the air conditioner casing 2.
[0059] Blow mode switching doors 18, 19, and 20 are provided on the
airflow upstream side of the individual apertures 14, 15, and 17,
respectively. Drive means such as a servomotor, or a manual
operation opens and closes these blow mode switching doors 18, 19,
and 20.
[0060] Generally, since a large airflow is required in a face mode
where the air is blown out from the face aperture 14 for the
vehicle air-conditioning apparatus, a draft resistance (a pressure
loss) for the face mode is smaller than that for the other blow
modes (a foot mode for blowing out the air from the foot aperture
15, and a defroster mode for blowing out the air from the defroster
aperture 17).
[0061] The blower 7 is a centrifugal blower which draws in air
parallel to the direction of a rotational shaft and blows it away
from the shaft in a radial direction (perpendicular to the
rotational shaft). A centrifugal multi-blade fan 72 (abbreviated as
a fan hereafter) is made of resin (polypropylene in the present
embodiment) or other plastic or metal, and has a large number of
blades 71 about a rotational shaft. A boss 71a is present for
holding the multiple blades 71.
[0062] In the present embodiment, the fan 72 is a radial fan where
a fan outlet opening angle (.beta.2) of the blade 71 is more than
60.degree., and less than 120.degree., and the specification of the
fan 72 is set such that the ratio of the blade length L of the
blade 71 (see FIG. 3) to the diameter D of the fan 72 (see FIG. 2)
(L/D) is 0.12 and higher (L/D=0.14 in the present embodiment).
[0063] The fan outlet opening angle .beta.2 is an angle between the
tangent line of the blade 71 and the tangent line of an outside
edge of the fan 72, and is measured on a forward side of the
rotational direction of the fan 72 as shown in FIG. 3. The blade
length L of the blade 71 is a difference between the outside radius
and the inside radius of the fan 72.
[0064] An electric motor 73 is driven to rotate the fan 72 in FIG.
2. A scroll casing 74 (abbreviated as a casing hereafter) stores
the fan 72, and constitutes an airflow passage 74a for circulating
the air blown out from the fan 72.
[0065] As shown in FIGS. 4 and 5, the casing 74 is made of resin
(polypropylene in the present embodiment), and is made in a scroll
shape about the rotational shaft of the fan 72 such that an outer
peripheral radius r1 increases as a logarithmic spiral function of
a scroll angle .theta.. An outlet opening 74b is formed in a part
on the airflow downstream of a scroll end in the casing 74 for
connecting with the air conditioner casing 2.
[0066] The logarithmic spiral is represented as Equation 1
described below, and an expansion angle n is from 3.5.degree. to
4.5.degree. or from 3.3.degree. to 4.8.degree. (4.degree. in the
present embodiment).
r1=r0e.sup.(.pi./180)n.theta. (Equation 1)
[0067] In this equation, .theta. is an angle in radians measured
from a base line connecting the center of the curvature radius of a
nose 74c with the rotational center of the fan 72 in the rotational
direction of the fan, and ro is the outer peripheral inner radius
on the base line (.theta.=0).
[0068] The nose 74c is a part where a scroll start side and a
scroll end side overlap in the casing 74. A part of the airflow
downstream side, and a part of the airflow upstream side
communicate with each other through a slight gap (not shown) in the
nose 74c.
[0069] An inlet opening 75 for introducing the air into the casing
74 opens on the opposite side of the motor 73 in the rotational
axial direction on the casing 74 as shown in FIG. 2. A bellmouth 76
is formed on an opening-outer edge of the inlet opening 75.
[0070] In a section including the rotational shaft, a circular
shroud 77 has a shape along the airflow which changes direction
from the inlet opening 75 toward the outside in the radial
direction (perpendicular to the shaft), and is formed on an end of
the blades 71 on the side of the inlet opening 75. An opposing bent
wall 78 is formed on the casing 74 near the bellmouth 76, opposite
to the shroud 77 with a predetermined gap 77a, and smoothly bends
from the bellmouth 76 toward the outside in the radial direction
along the shape of the shroud 77.
[0071] In the airflow passage 74a of the casing 74, the inner
radius of the outer periphery r1 increases as a logarithmic spiral
such that the flow passage cross-sectional area in the airflow
downstream side (the side of the outlet opening 74) is larger than
that in the airflow upstream side (the side of the nose 74c in the
casing 74). Simultaneously, expanded parts 74d and 74e expanded in
the direction parallel with the rotational shaft are provided to
gradually increase the flow passage cross-sectional area as shown
in FIG. 2.
[0072] A dimension H1 of the winding-end portion parallel with the
rotational shaft is from 1.3 times to 2.1 times, or from 1.1 times
to 2.3 times (1.5 times in the present embodiment) a dimension H0
of the nose 74c (at scroll angle .theta.=0) parallel with the
rotational shaft. An expanded dimension Hup on the side of the
inlet opening 75 is less than 0.4 times an expanded dimension HLR
on the opposite side of the inlet opening 75 (0<Hup/HLR<0.4)
in the expanded parts 74d and 74e.
[0073] The expanded dimension Hup on the side of the inlet opening
75 is a dimension from the inner wall on the side of the inlet
opening 75 to an inner wall of an upper side expanded part in the
casing 74 measured parallel with the rotational shaft as shown in
FIG. 2. The upper side expanded part is a part of the casing 74 on
the scroll end side shifted by the outer diameter dimension D of
the fan 72 from a part corresponding to the rotational center (the
rotation shaft) of the fan 72 toward the outlet opening 74b as
shown in FIG. 4.
[0074] The expanded dimension HLR on the opposite side of the inlet
opening 75 is a dimension from the inner wall on the opposite side
of the inlet opening 75 to an inner wall of a lower (far) side
expanded part in the casing 74 measured parallel to (along) the
rotational shaft. The lower side expanded part is a part of the
casing 74 on the scroll end side shifted by the outer diameter
dimension D of the fan 72 from the part corresponding to the
rotation center (the rotation shaft) of the fan 72 to the outlet
opening 74b.
[0075] The expanded part 74d out of the expanded parts 74d and 74e
of the present embodiment expands the flow passage cross-sectional
area on the side of the inlet opening 75, and is formed proximate
the scroll end toward the outlet opening 74b of the casing 74. The
expanded part 74e out of the expanded parts 74d and 74e expands the
flow passage cross-sectional area on the opposite side of the inlet
opening 75, and is formed from a range of a part up to about
60.degree. from a neighborhood of the nose 74c in the rotational
direction of the fan 72 toward the outlet opening 74b of the casing
74.
[0076] The following section describes characteristics (actions and
effects) of the present embodiment. As described above in the
summary of the invention, when the quantity of the airflow blown
out from the fan 72 is relatively small, the quantity of the
airflow is not enough for air which has collided with a wall
surface 74f to flow along a wall surface 74g, and the tilted
surface 74h. Particularly, the flow does not move across or over
the entire expanded part 74e, and a stable swirling flow is not
generated.
[0077] The air taken into the fan 72 flows into gaps between blades
71 from a direction tilted with respect to the height direction
(the direction parallel with the rotational shaft) of the blades
71, and is blown out from the fan 72 as shown in FIGS. 6A and
6B.
[0078] Since the blade 71 does not add momentum to the airflow
parallel to the rotational shaft between the blades 71, the air
between the blades 71 has a constant velocity component in the
rotational shaft direction. When the blade length L of the blade 71
increases (L1>L2), because a time required for air flowing out
from the gap between the blades 71 after flowing thereinto
increases, a travel distance of the air between the blades 71 in
the rotational shaft direction increases (h1>h0).
[0079] When it is assumed that the airflow quantity blown out from
the fan 72 is constant regardless of the blade length L, the flow
rate of the air blown out from the fan 72 increases as the blade
length L of the blade 71 increases. Thus, increasing the blade
length L prevents a decrease of the flow rate of the air blown out
from the fan 72 when the blown air quantity is small. As a result,
the flow extends over the expanded part 74e, a stable swirling flow
is generated, and wind noise is reduced.
[0080] Since the airflow passage 74a curves in a scroll shape, when
the air flows along the airflow passage 74a, a secondary flow (a
swirling flow) is generated as shown in FIG. 7. Since the swirling
flow of the air blown out from the fan 72 matches this secondary
flow (the swirling flow), the swirling flow is more stably
generated, and wind noise is reduced.
[0081] When the inventors measured the specific noise level using
the ratio of the blade length L of the blade 71 to the diameter D
of the fan 72 (L/D), the expansion angle n of the scroll and the
expanding ratio in the axial direction (winding end portion with
respect to the dimension H0 parallel to the rotational axis and
nose portion 74c within casing 74, and the dimension H1 (ratio
H1/H0) which is parallel to the rotational axis) as parameters, the
results as shown in FIG. 8 and FIG. 9 have been obtained.
[0082] FIG. 8 and FIG. 9 respectively show results when the
cross-sectional area of the scroll air passage with respect to the
winding direction angle .theta. are set as equal, but the expansion
angle n and the expanding ratio in the axial direction are varied.
Therefore, when the expansion angle n is large and the expansion
ratio in the axial direction is 1.0, the cross-sectional shape of
the air passage 74a becomes oblong in the horizontal direction
(perpendicular to the rotational shaft). To the contrary, when the
expansion angle n is small, the expansion ratio in the axial
direction becomes larger and the cross-sectional shape of the air
passage 74a becomes oblong in the vertical direction (parallel to
the rotational shaft).
[0083] As clearly shown by the test results, when L/D is set to
0.12 and over, the expansion angle n is set to 3.3.degree. and over
and 4.8.degree. and below, so the wind noise can be reduced.
[0084] As in the first embodiment, when the expansion angle
n=4.degree. and the expansion ratio in the axial direction is 1.5,
the ratio of cross-section of air passage 74a in length and breadth
becomes approximately 2:1, which is a favorable shape in terms of a
pair of swirling movement of the air flow situated above and below
each other. Therefore, the airflow becomes stable and the wind
noise can be greatly reduced.
[0085] On the other hand, when the expansion angle n is larger)
(n>4.8.degree., the distance from the fan 72 to the wall surface
74g (the outer peripheral side inner wall of the casing 74) becomes
larger. Therefore, when the airflow amount is small, as in the foot
mode, the momentum of air blown out from the fan 72 becomes small
when it collides with the wall surface 74g. As a result, swirling
airflow is hardly generated. Also, when the expansion angle n is
larger, the momentum of air blown out from the fan 72 becomes
larger and swirling airflow is generated by making the blade length
longer. However, since the cross-sectional shape of the air passage
becomes oblong in the horizontal direction, there is not enough
space for swirling movement. As a result, airflow becomes unstable
and the noise cannot be reduced so much.
[0086] To the contrary, when the expansion angle n is smaller)
(n<3.3.degree., the cross-sectional shape of the airflow passage
74a becomes oblong in the vertical direction. Therefore, when the
airflow amount is small, as in the foot mode, the airflow does not
reach the wall surface 74g and stable swirling airflow is not
generated. Also, even though the expansion angle n is small, the
air reaches the wall surface 74g by lengthening the blade length.
However, the swirling airflow becomes oblong in the vertical
direction and the airflow becomes unstable.
[0087] FIG. 10 shows a test result with a ratio of the dimension H1
to the dimension H0 (H1/H0) as a parameter, where H1 is the
dimension of the winding-end portion parallel with the rotational
shaft, and H0 is the dimension of the nose 74c parallel with the
rotational shaft in the casing 74. As the test results clearly
show, when H1/H0 is 1.3 to 2.1, the specific noise level can be
reduced. Here, FIG. 10 shows the test result when L/D=0.14 and the
expansion angle n=4.0.degree..
[0088] The definition of the specific noise level follows JIS B
0132, and the test method is based on JIS B 8340.
[0089] In the present embodiment, L/D is set to 0.12 and over, the
expansion angle n is set to from 3.5.degree. to 4.5.degree., and
H1/H0 is set from 1.3 to 2.1. However, the present embodiment is
not limited to these conditions. It is only necessary to set L/D to
0.12 and over and to set the expansion angle n from 3.5.degree. to
4.5.degree., or to set L/D to 0.12 and over, and to set H1/H0 from
1.3 to 2.1.
Second Embodiment
[0090] The cross-section of the flow passage 74a can be set as an
approximately rectangular shape whose corners are arcs in a second
embodiment as shown in FIG. 11. With this structure, since an
unstable swirling flow is prevented from being generated at the
corners of the airflow passage 74a, and simultaneously, a generated
swirling flow is smoothly circulated, the swirling flow is
stabilized, and wind noise is reduced. It is preferable that the
curvature radius of the arcs is properly set according to the
radius of the swirling flow generated in the airflow passage
74a.
Third Embodiment
[0091] FIG. 12 shows a third embodiment of the present invention. A
protrusion 74j protruding toward the fan 72 is formed along almost
the entire airflow passage 74a on the inner wall of the outer
peripheral portion of the casing 74, and the cross-section of the
protrusion 74j is approximately triangular (wedge-shaped) and
protrudes toward the fan 72 when the protrusion 74j is seen from a
primary flow direction of the air flowing through the airflow
passage 74a.
[0092] With this structure, since the protrusion 74j is provided at
a part with which air with the highest flow rate of the air blown
out from the fan 72 collides, the air blown out from the fan 72 is
easily divided into the side of the inlet opening 75 and the
opposite side. This promotes the generation of swirling flow to
reduce wind noise generation.
Fourth Embodiment
[0093] In the present embodiment, the blade length L is extended to
shift the air blown out from the fan 72 toward the opposite side of
the inlet opening 75 for increasing the flow rate. Also, the air
blown out from the fan 72 collides with the wall surface 74f to
generate a stable swirling flow as described above. In a fourth
embodiment, L/D is set to 0.12 and over, a fan inlet opening angle
.beta.1 is set from 55.degree. to 85.degree., a fan outlet opening
angle .beta.2 is set from 15.degree. to 45.degree., and a fan
advancing angle .gamma. is set to 4.degree. to 10.degree.. With
these settings, the air is prevented from separating from the
blades 71 and from between the blades 71. Also, air counter-flow is
prevented from forming between the blades 71 at the outlet opening
side of the fan, and wind noise is reduced.
[0094] With reference to FIG. 13, the fan inlet opening angle
.beta.1 is an angle between the tangent line of the blade 71 and
the tangent line of an inside edge of the fan 72, and is measured
on the forward-facing side of the blade in the rotational direction
of the fan 72 as shown in FIG. 13. The fan advancing angle .gamma.
is an angle between a line L1 connecting an end of the blade 71
closest to an inlet opening side with the rotational center of the
fan 72 and a line L2 connecting an end of the blade 71 near an
outlet opening side with the rotation center of the fan 72. That
is, line L1 is drawn from the rotational center of the fan 72
tangent to a first end of the blade 71 that is closest to the
rotational center. This first point of tangency is on the front
side of the blade that leads during the rotation of the blade 71.
The line L2 is drawn from the rotational center of the fan 72
tangent to a second end of the blade 71 farthest from the
rotational center. This second point of tangency is on the front
side of the blade 71 that leads during the rotation of the blade
71.
[0095] The following section describes characteristics (actions and
effects) of the present embodiment.
[0096] FIG. 14A shows a state of the air flowing between the blades
71 when the fan inlet opening angle .beta.1 is large (about
90.degree.). When the fan inlet opening angle .beta.1 is larger
than an angle at which the air flows into the fan 72 (theoretical
flow-in angle is about 30.degree.), the air between the blades 71
is separated from the blade 71 on the forward side in the
rotational direction. Thus, a flow rate distribution on the fan
outlet opening side becomes uneven, and noise tends to be
generated.
[0097] FIG. 14B shows a state of the air flowing between the blades
71 when the fan inlet opening angle .beta.1 is set to the
theoretical flow-in angle. In this state, though, the separation of
the air from the blade 71 on the forward side in the rotation
direction is prevented on the inlet opening side. However, when the
fan advancing angle .gamma. is small, the air separated from the
blade 71 on the forward side in the rotation direction is blown out
without being attached to the blade 71 again on the outlet opening
side. As a result, a counter-flow is generated on the forward side
in the rotation direction, and new noise may be generated.
[0098] In the present embodiment, L/D, the fan inlet opening angle
.beta.1, the fan outlet opening angle .beta.2, and the fan
advancing angle .gamma. are set to proper values, and the
separation on the inlet opening side is restrained, and
simultaneously, the air separated from the blade 71 on the forward
side in the rotational direction is attached again as shown in
FIGS. 15A and 15B. As a result, the airflow between the blades 71
is optimized, a stable swirling flow is generated, and noise is
reduced.
[0099] FIG. 16 represents a test result showing a relationship
between L/D and the minimum specific noise level, and a
relationship between L/D and the airflow rate. FIG. 17 represents a
test result showing a relationship between the fan inlet opening
angle .beta.1 and the specific noise level, and a relationship
between the fan inlet opening angle .beta.1 and the airflow rate.
FIG. 18 represents a test result showing a relationship between the
fan outlet opening angle .beta.2 and the specific noise level, and
a relationship between the fan outlet opening angle .beta.2 and the
airflow rate. FIG. 19 represents a test result showing a
relationship between the advancing angle .gamma. and the specific
noise level, and a relationship between the advancing angle .gamma.
and the airflow rate. The test conditions and the definitions of
the technical terms are the same as those in the embodiments
described above.
[0100] As these test results clearly show, L/D should be set to
0.12 and over (0.15 in the present embodiment), the fan inlet
opening angle .beta.1 should be set to from 55.degree. to
85.degree. (65.degree. in the present embodiment), the
fan-outlet-opening angle .beta.2 should be set from 15.degree. to
45.degree. (35.degree. in the present embodiment), and the fan
advancing angle .gamma. should be set from 4.degree. to 10.degree.
(7.degree. in the present embodiment).
[0101] In the present embodiment, the curvature radius r1 on the
inlet opening side of the blade 71 is equal to or less than the
curvature radius r2 on the outlet opening side of the blade 71, and
curved surfaces having more than two curvature radii r1 and r2 are
smoothly connected to form the blade 71 such that the fan inlet
opening angle .beta.1, the fan outlet opening angle .beta.2, and
the fan advancing angle .gamma. satisfy the advantageous conditions
described above. However, the present embodiment is not limited to
this construction, and the curvature radius may increase gradually
from the inlet opening side to the outlet opening side, or may be
constant as long as the conditions above are satisfied.
[0102] The present embodiment may be combined with the embodiments
described above. As shown in FIGS. 8 and 9, and FIGS. 16 to 19, L/D
is set to 0.12 and over, the fan inlet opening angle .beta.1 is set
from 55.degree. to 85.degree., the fan outlet opening angle .beta.2
is set from 15.degree. to 45.degree., the fan advancing angle
.gamma. is set from 4.degree. to 10.degree., and the expansion
angle n is set from 3.3.degree. to 4.8.degree.. Alternatively, L/D
is set to 0.12 and over, the fan inlet opening angle .beta.1 is set
from 55.degree. to 85.degree., the fan outlet opening angle .beta.2
is set from 15.degree. to 45.degree., the fan advancing angle
.gamma. is set from 4.degree. to 10.degree., and the expansion
angle n is set from 3.5.degree. to 4.5.degree..
[0103] The present embodiment may be applied to a casing not
including the expanded parts 74d and 74e (the dimension of the
airflow passage 74a parallel with the rotational shaft is
constant).
Other Embodiments
[0104] While the tilted surface 74h is provided in the expanded
part 74e in the first embodiment, the present invention is not
limited to this construction, and the airflow passage may have
other shapes such as a simple rectangle, a circle, and an
ellipse.
* * * * *