U.S. patent application number 09/897284 was filed with the patent office on 2002-01-10 for centrifugal fan.
Invention is credited to Miyata, Manabu.
Application Number | 20020004008 09/897284 |
Document ID | / |
Family ID | 18702600 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020004008 |
Kind Code |
A1 |
Miyata, Manabu |
January 10, 2002 |
Centrifugal fan
Abstract
According to the present invention, there are provided diffusers
115 which extend from portions close to the outer diameter of the
centrifugal impeller 111 to the downstream side of a current of
air, on the outer diameter side of the centrifugal impeller 111 and
around the circumference. Due to the foregoing, while a current of
air blown out from the impeller 111 is being straightened by the
diffusers 115, the dynamic pressure of the current of air is
converted into static pressure. Consequently, it is possible to
make the current of air flow stably into the outlet 114 side
without disturbing it. Therefore, while the generation of noise is
being suppressed, the total pressure of the fan 110 can be
sufficiently increased.
Inventors: |
Miyata, Manabu; (Oobu-city,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, PLC
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
18702600 |
Appl. No.: |
09/897284 |
Filed: |
July 2, 2001 |
Current U.S.
Class: |
415/206 ;
415/208.3; 415/211.2 |
Current CPC
Class: |
F04D 29/444
20130101 |
Class at
Publication: |
415/206 ;
415/208.3; 415/211.2 |
International
Class: |
F04D 029/44 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2000 |
JP |
2000-205529 |
Claims
1. A centrifugal fan comprising: a centrifugal impeller having a
number of blades around a rotary shaft, the centrifugal impeller
sucking air in the axial direction of the rotary shaft and blowing
it out in the radial direction; a casing for accommodating the
centrifugal impeller, the casing having a plurality of outlets for
blowing out air; and stator blades arranged in the casing,
extending from the outer diameter side of the centrifugal impeller
to the downstream side of an air current.
2. A centrifugal fan according to claim 1, wherein the stator
blades are arranged around the circumference on the outer diameter
side of the centrifugal impeller.
3. A centrifugal fan according to claim 1, wherein the centrifugal
impeller has blades arranged backward, the impeller outlet angle of
which is larger than 90.degree..
4. A centrifugal fan according to claim 1, wherein the entrance
angle of the stator blade is not more than 20.degree..
5. A centrifugal fan according to claim 1, wherein the
cross-section of the stator blade is an airfoil shape.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a centrifugal fan which
sucks air in the axial direction of a rotary shaft and blows it out
in the radial direction. This centrifugal fan is effectively
applied to an air purifier for vehicle use or an air-conditioner
recessed in a ceiling.
[0003] 2. Description of the Related Art
[0004] A centrifugal fan, which will be referred to as a fan in
this specification hereinafter, which is described in Japanese
Unexamined Utility Model Publication No. 61-29222, is composed as
follows. Outside a centrifugal multi-blade impeller, which will be
referred to as an impeller in this specification hereinafter, there
are provided two air passages which are formed into a spiral. Due
to the above structure, air streams can be simultaneously blown out
from a plurality of outlets.
[0005] However, in the case of the above fan having a plurality of
outlets, the length of the air passage (the winding angle of the
air passage) is shorter than that of a fan having one outlet.
Therefore, the following problems may be encountered. The air
stream in the fan is unstable, and turbulence tends to occur in the
air stream. For the above reasons, noise tends to be generated, and
further the total pressure of the fan can not be sufficiently
increased.
SUMMARY OF THE INVENTION
[0006] The present invention has been achieved to solve the above
problems. It is an object of the present invention to decrease the
occurrence of noise and increase the total pressure of a fan having
a plurality of outlets.
[0007] In order to accomplish the above object, the present
invention provides a centrifugal fan comprising: a centrifugal
impeller (111) having a number of blades (112) around a rotary
shaft, the centrifugal impeller (111) sucking air in the axial
direction of the rotary shaft and blowing it out in the radial
direction; a casing (113) for accommodating the centrifugal
impeller (111), the casing (113) having a plurality of outlets
(114) for blowing out air; and stator blades (115) arranged in the
casing (113), extending from the outer diameter side of the
centrifugal impeller (111) to the downstream side of an air
current.
[0008] Due to the above structure, while a stream of air blown out
from the centrifugal impeller (111) is being straightened by the
stator blades (115), dynamic pressure of the stream of air is
converted into static pressure. Accordingly, it is possible to make
the stream of air flow stably onto the outlet (114) side without
disturbing the stream of air. Therefore, it is possible to
sufficiently increase the total pressure of the centrifugal fan and
suppress the generation of noise.
[0009] In this connection, it is preferable that the stator blades
(115) are arranged all over the circumference on the outer diameter
side of the centrifugal impeller (111).
[0010] It is also preferable that the centrifugal impeller (111)
has blades (112) arranged backward, the impeller delivery angle
(.beta.) of which is larger than 90.degree..
[0011] It is also preferable that the entrance angle (.alpha.) of
the stator blade (115) is not more than 20.degree..
[0012] Further, it is preferable that the cross-section of the
stator blade (115) is an airfoil shape.
[0013] In this connection, reference numerals in parentheses in
each means described above show the correspondence to the specific
means described in the embodiments which will be stated later.
[0014] The present invention may be more fully understood from the
description of preferred embodiments of the invention set forth
below, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the drawings:
[0016] FIG. 1 is a perspective view showing the inside of a
passenger compartment of a vehicle into which an air purifier using
a fan of an embodiment of the present invention is
incorporated;
[0017] FIG. 2 is a front view showing an air purifier in which a
fan of an embodiment of the present invention is used;
[0018] FIG. 3 is a front cross-sectional view of a fan of an
embodiment of the present invention;
[0019] FIG. 4 is a cross-sectional view taken on line A-A in FIG.
3;
[0020] FIG. 5 is an enlarged view of an impeller and diffuser of a
fan of an embodiment of the present invention;
[0021] FIG. 6 is a graph showing a relation between the total
pressure .DELTA.P and the volume of blown air and also showing a
relation between the specific noise Ks and the volume of the blown
air;
[0022] FIG. 7 is a schematic illustration showing a model of a fan
of the prior art; and
[0023] FIG. 8 is a schematic illustration showing a model of a fan
in which diffusers have been removed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] In this embodiment, a fan of the present invention is
applied to an air purifier, for vehicle use, by which air in a
passenger compartment of a vehicle is cleaned. FIG. 1 is a
perspective view of the inside of a passenger compartment of a
vehicle showing a state in which the air purifier 100 is
incorporated onto the rear package tray 200 of the vehicle. FIG. 2
is a front view showing an air purifier 100 for vehicle use.
[0025] In this embodiment, the air purifier 100 is set in motion or
stopped by an output signal of a smoke sensor (not shown), which
detects the degree of fouling of the air in the compartment, or by
a manual switch operated by a driver. When this purifier 100 is
operating, air is introduced into the inlet 101 arranged at a
substantial center of the air purifier 100 as shown in FIG. 1, and
air, which has been cleaned, is blown out from the outlet 102.
[0026] Next, the fan 110 of this embodiment will be explained
below.
[0027] FIG. 3 is a front cross-sectional view, which is taken on
line B-B in FIG. 4, of the fan 110 of this embodiment. FIG. 4 is a
cross-sectional view taken on line A-A in FIG. 3. Reference numeral
111 is a centrifugal impeller, which will be referred to as an
impeller hereinafter, having a number of blades 112 around the
rotary shaft 111a, for blowing out air, which has been sucked in
the axial direction of the rotary shaft 111a, in the radial
direction. In this embodiment, an impeller (turbo-impeller) is
adopted, the blades of which are arranged backward, the delivery
angle .beta. of each blade 112 of which is larger than
90.degree..
[0028] In this connection, the delivery angle .beta. of each blade
112 is an angle formed between the blade 112 and the outer diameter
edge L1 of the impeller 111 as shown in FIG. 5. This delivery angle
.beta. is measured from the proceeding side of the rotary direction
of the impeller 111.
[0029] As shown in FIG. 3, the impeller 111 is accommodated in the
casing 113 made of resin (polypropylene in this embodiment). In
this casing 113, there are provided a plurality (two in this
embodiment) of outlets 114 from which air is blown out.
[0030] In each outlet 114 formed in the casing 113, there is
provided a filter 103 for cleaning air which has been blown out
from the impeller 111.
[0031] In the casing 113, on the outer diameter side of the
impeller 111, there are provided stationary blades (diffusers) 115
extending from portions close to the outer diameter of the impeller
111 toward the downstream side of the air current, wherein these
diffusers 115 are arranged around the circumference on the outer
diameter side of the impeller 111. In this embodiment, the entrance
angle .alpha. of the diffuser 115 is set at not more than
20.degree.. In this figure, the entrance angle .alpha. of the
diffuser 115 is set at 20.degree.. In this connection, as shown in
FIG. 5, the entrance angle .alpha. of the diffuser 115 is defined
as an angle of the inner diameter edge (the circular locus
connecting the side end portions of the diffusers 115 of the
impeller 111) L2 of the diffuser 115 with the diffusers 115,
wherein the entrance angle .alpha. of the diffuser 115 is measured
from the proceeding side of the rotary direction of the impeller
111.
[0032] In this connection, reference numeral 116 is a suction port
for introducing air, which has been introduced from the inlet 101,
into the casing 113. At the inner diameter edge of this suction
port 116, there is provided a bell-mouth 117 for introducing air,
which has been sucked from the suction port, onto the inner
diameter side of the impeller 111. This bell-mouth 117 is molded
and integrated with the casing 113.
[0033] Reference numeral 118 is an electric motor (drive means) for
driving the impeller 111. When this electric motor 118 is
controlled by being turned on, the air purifier 100 is
operated.
[0034] Next, the characteristic of this embodiment will be
described below.
[0035] Immediately after air has been blown out from the impeller
111 into the casing 113, its flow velocity is greatly changed, and
further the thus blown air collides with the side (the inner wall
of the casing 113 located on the outer diameter side of the
impeller 111) of the casing 113. Since a current of air on the
upper face side (the suction port 116 side) of the casing 113 and a
current of air on the lower face side (the electric motor 118 side)
are reverse to each other, noise tends to be generated, and further
it is impossible to sufficiently increase the total pressure of the
fan.
[0036] On the other hand, in this embodiment, on the outer diameter
side of the impeller 111, there are provided diffusers 115 which
extend from portions close to the outer diameter side of the
impeller 111 to the downstream side of the air current.
Accordingly, while a current of air, which has been blown out from
the impeller 111, is being straightened, its dynamic pressure is
converted into static pressure.
[0037] Consequently, it is possible to make the current of air flow
stably into the outlet 114 side without disturbing it. Therefore,
the generation of noise can be suppressed and the total pressure of
the fan 110 can be sufficiently increased.
[0038] After the current of air has been straightened by the
diffusers 115 so that the distribution of air velocity can be made
uniform, the current of air flows into the filter 103. Therefore,
it is possible to prevent the occurrence of a problem in which the
clogging of the filter occurs in one portion of the filter 103
compared with the other portion. Accordingly, the life of the
filter 103 can be extended.
[0039] In this connection, FIG. 6 is a graph showing the results of
experiments on the total pressure .DELTA.P and the specific noise
Ks with respect to the conventional fan shown in FIG. 7 (having a
scroll casing, the air passage length of which is small (the
winding angle of the air passage of which is small)), also with
respect to the fan in which the diffusers 115 are abolished from
the fan of this embodiment shown in FIG. 8, and also with respect
to the fan of this embodiment. As can be seen from this graph,
according to the present invention, it is possible to sufficiently
increase the total pressure of the fan 110 and suppress the
generation of noise.
[0040] In this connection, the definition of terminology of total
pressure .DELTA.P and specific noise Ks is based on JIS B 0132, and
the above method of the experiment is based on JIS B 8340.
[0041] In this connection, as shown in FIG. 6, the smaller the
entrance angle .alpha. of the diffuser 115 is made, the more the
level of the specific noise Ks can be decreased (by about 2 dB).
However, as can be seen in this embodiment, when the entrance angle
.alpha. of the diffuser 115 is set at a value not more than
20.degree. from the viewpoint of practical use, it is possible to
guide the air, which has been blown out from the impeller 111, into
the outlet 114 side while the dynamic pressure of the air is
effectively converted into static pressure.
[0042] In this embodiment, an impeller (turbo-impeller), the blades
of which are arranged backward, the delivery angle .beta. of each
blade 112 of which is larger than 90.degree., is adopted.
Therefore, it is possible to increase the static pressure of the
air itself which is blown out from the impeller 111. Accordingly,
the total pressure .DELTA.P can be increased.
[0043] Another embodiment will be explained below. In the
embodiment described above, the number of the outlets 114 of the
fan 110 is two, however, it should be noted that the present
invention is not limited to the above specific embodiment. It is
possible to apply the present invention to a fan having not less
than three outlets 114.
[0044] In the above embodiment, the fan of the present invention is
applied to an air purifier for vehicle use, however, it should be
noted that the present invention is not limited to the above
specific embodiment. The fan of the present invention can be
applied to an air-conditioner recessed in a ceiling or to another
apparatus.
[0045] In the above embodiment, the impeller is used, the blades of
which are arranged backward and the impeller delivery angle .beta.
of which is not less than 90.degree.. However, it possible to use
an impeller, the blades of which are arranged forward and the
impeller delivery angle .beta. of which is not more than
90.degree..
[0046] In the above embodiment, the diffusers 115 are arranged
around the circumference on the outer diameter side of the impeller
111, however, the diffusers 115 may be arranged only in a portion
of the circumference on the outer diameter side of the impeller
111.
[0047] In the above embodiment, the each diffuser 115 is
plate-shaped and the thickness is constant. However, it should be
noted that the present invention is not limited to the above
specific embodiment. The cross section of each diffuser 115 may be
an airfoil shape, the impeller 111 side of which is a side of the
chord of blade, or a streamline shape.
[0048] While the invention has been described by reference to
specific embodiments chosen for purposes of illustration, it should
be apparent that numerous modifications could be made thereto by
those skilled in the art without departing from the basic concept
and scope of the invention.
* * * * *