U.S. patent application number 13/171650 was filed with the patent office on 2012-01-05 for blower fan.
This patent application is currently assigned to NIDEC CORPORATION. Invention is credited to Jumpei KITAMURA.
Application Number | 20120003109 13/171650 |
Document ID | / |
Family ID | 45399842 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120003109 |
Kind Code |
A1 |
KITAMURA; Jumpei |
January 5, 2012 |
BLOWER FAN
Abstract
A blower fan includes an impeller cup; a shaft including an end
arranged to project axially upward from the impeller cup; a rotor
magnet fixed to the shaft; a first bearing and a second bearing
arranged axially above and below, respectively, the impeller cup; a
first bearing support portion and a second bearing support portion
arranged to support the first and second bearings, respectively;
and a first housing and a second housing arranged on axially upper
and lower sides, respectively. The first and second housings are
joined to each other at an axial level higher than an axial
position of a joint between the second housing and a second joining
portion arranged to join the second housing and the second bearing
support portion to each other.
Inventors: |
KITAMURA; Jumpei; (Kyoto,
JP) |
Assignee: |
NIDEC CORPORATION
Kyoto
JP
|
Family ID: |
45399842 |
Appl. No.: |
13/171650 |
Filed: |
June 29, 2011 |
Current U.S.
Class: |
417/423.14 |
Current CPC
Class: |
F04D 29/056 20130101;
F04D 29/522 20130101; F04D 29/051 20130101; F04D 29/053 20130101;
F04D 25/0606 20130101 |
Class at
Publication: |
417/423.14 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 1, 2010 |
JP |
2010-151324 |
Claims
1. A blower fan comprising: an impeller including a substantially
cylindrical impeller cup including a cover portion, and a plurality
of blades arranged on an outer circumferential surface of the
impeller cup; a shaft fixed directly or indirectly to the impeller
cup, and including an end arranged to project axially upward from
the cover portion of the impeller cup; a rotor magnet fixed
directly or indirectly to the shaft; a first bearing arranged
axially above the cover portion of the impeller cup, and arranged
to support the shaft such that the shaft is rotatable with respect
to the stator; a first bearing support portion arranged to support
the first bearing; a first housing arranged radially outward of the
impeller on an axially upper side; a first joining portion arranged
to join the first housing and the first bearing support portion to
each other; a second bearing arranged axially below the cover
portion of the impeller cup, and arranged to support the shaft such
that the shaft is rotatable with respect to the stator; a second
bearing support portion arranged to support the second bearing; a
second housing arranged radially outward of the impeller on an
axially lower side; a second joining portion arranged to join the
second housing and the second bearing support portion to each
other; a stator arranged radially outward of the rotor magnet and
opposite the rotor magnet; and a stator support portion arranged to
support the stator; wherein the first and second housings are
joined to each other at an axial level higher than an axial
position of a joint between the second joining portion and the
second housing.
2. The blower fan according to claim 1, wherein the impeller cup
includes a recessed portion defined in a central portion of the
cover portion; and at least a lower end of the first bearing
support portion is arranged inside the recessed portion.
3. The blower fan according to claim 1, wherein the first housing,
the first bearing support portion, and the first joining portion
are integral with one another; and the second housing, the second
bearing support portion, and the second joining portion are
integral with one another.
4. The blower fan according to claim 3, wherein the first bearing
support portion and the second bearing support portion are defined
by metallic members coupled to the first housing and the second
housing, respectively, by being at least partially embedded within
the first housing and the second housing.
5. The blower fan according to claim 1, wherein the second joining
portion defines a stationary vane.
6. The blower fan according to claim 1, further comprising a
substantially cylindrical rotor holder fixed to the shaft, wherein
the rotor magnet is fixed to an outside wall of the rotor
holder.
7. The blower fan according to claim 6, wherein the rotor holder is
coupled to the impeller cup by being at least partially embedded
within the impeller cup.
8. The blower fan according to claim 3, wherein the second housing,
the second bearing support portion, the second joining portion, and
the stator support portion are integral with one another.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a blower fan capable of
being used, for example, to cool an electronic device.
[0003] 2. Description of the Related Art
[0004] Outer-rotor motors, in which a rotor is arranged outside of
a stator, have been predominantly used as motors for driving blower
fans because of an easier assembling procedure, a reduced number of
parts, and so on. In addition, in terms of performance, the
outer-rotor motors have a greater moment of inertia and are able to
achieve increased driving torque, and are therefore able to
maintain a constant speed more easily.
[0005] Meanwhile, as electronic devices have become increasingly
dense in recent years, the amount of heat generated from the
electronic devices has increased. There has accordingly been a
demand for blower fans used to cool such electronic devices to
rotate at a greater speed to provide a greater cooling effect.
However, in outer-rotor motors, an increased rotational speed of
the blower fan leads to an increased vibration because of the great
moment of inertia of the outer-rotor motors which thus may cause a
problem in terms of strength.
[0006] Use of inner-rotor motors, in which the rotor is arranged
inside of the stator, allows a greater rotational speed, because
the inner-rotor motors have a smaller moment of inertia than the
outer-rotor motors.
[0007] U.S. 2009/0180901, for example, describes a conventional
blower fan using an inner-rotor motor. This blower fan includes a
motor support portion in which a support portion arranged to
support a bearing and a support portion arranged to support a
stator are defined by a single continuous member.
[0008] The blower fan using the inner-rotor motor as described in
U.S. 2009/0180901 (hereinafter referred to simply as an
"inner-rotor blower fan"), however, has a disadvantage as compared
to a blower fan using an outer-rotor motor (hereinafter referred to
simply as an "outer-rotor blower fan") because of its
structure.
[0009] Specifically, in the inner-rotor blower fan, a bearing
support portion, a rotor holder (a rotor magnet), a stator, a
stator support portion, an impeller cup, and blades are
sequentially arranged in this order from a rotation axis to a
radial outside. In addition, specified radial gaps are arranged
between the bearing support portion and the rotor holder, between
the rotor holder and the stator, and between the stator support
portion and the impeller cup.
[0010] In contrast, in the outer-rotor blower fan, a bearing
support portion, a stator, a rotor holder (a rotor magnet), an
impeller cup, and blades are arranged, and the bearing support
portion additionally functions as a stator support portion. Since
the impeller cup is press fitted to an outer circumference of the
rotor holder, a specified radial gap is arranged only between the
stator and the impeller cup.
[0011] As described above, the inner-rotor blower fan has a greater
number of components arranged in a radial direction than the
outer-rotor blower fan, and accordingly has a disadvantage of an
increased radial dimensions. Moreover, the inner-rotor blower fan
includes a greater number of gaps between the components, and
therefore also has a disadvantage of an inability to secure a large
radial clearance.
[0012] Furthermore, as mentioned above, the inner-rotor blower fan
is capable of producing only a relatively small driving torque as
compared to the outer-rotor blower fan. Therefore, the inner-rotor
blower fan needs to have an increased axial dimension of the rotor
magnet in order to increase the driving torque. As such, the
inner-rotor blower fan also has a disadvantage of the increased
axial dimension.
SUMMARY OF THE INVENTION
[0013] According to preferred embodiments of the present invention,
in a blower fan including an inner-rotor motor, one end of a shaft
is arranged to project axially upward from an impeller cup. In
addition, a pair of bearings are arranged such that one of the
bearings is arranged near the end of the shaft axially above the
impeller cup, and the other bearing is arranged near the other end
of the shaft axially below the impeller cup. Moreover, bearing
support portions each of which is arranged to support a separate
one of the bearings are joined to separate housings that are
divided from each other in the axial direction.
[0014] Specifically, a blower fan according to a preferred
embodiment of the present invention preferably includes an impeller
including a substantially cylindrical impeller cup including a
cover portion, and a plurality of blades arranged on an outer
circumferential surface of the impeller cup; a shaft fixed directly
or indirectly to the impeller cup that includes an end arranged to
project axially upward from the cover portion of the impeller cup;
a rotor magnet fixed either directly or indirectly to the shaft; a
first bearing arranged axially above the cover portion of the
impeller cup, and arranged to support the shaft such that the shaft
is rotatable with respect to the stator; a first bearing support
portion arranged to support the first bearing; a first housing
arranged radially outward of the impeller on an axially upper side;
a first joining portion arranged to join the first housing and the
first bearing support portion to each other; a second bearing
arranged axially below the cover portion of the impeller cup, and
arranged to support the shaft such that the shaft is rotatable; a
second bearing support portion arranged to support the second
bearing; a second housing arranged radially outward of the impeller
on an axially lower side; a second joining portion arranged to join
the second housing and the second bearing support portion to each
other; a stator arranged radially outward of the rotor magnet and
opposite the rotor magnet; and a stator support portion arranged to
support the stator. The first and second housings are arranged to
be joined to each other at a level higher than that of a position
of joint between the second joining portion and the second
housing.
[0015] In the above-described preferred embodiments, two separate
bearings are preferably arranged one axially above and the other
axially below the rotor magnet and the stator, which define
portions of a motor, while at the same time two separate bearing
support portions are arranged one axially above and the other
axially below the rotor magnet and the stator. This makes it
possible to reduce the radial dimensions of the motor, and to
thereby realize an inner-rotor blower fan that possesses reduced
radial dimensions. Moreover, the assemblage of the blower fan is
more easily accomplished because the two bearing support portions
arranged at upper and lower levels, respectively, are joined to
separate housings that are divided from each other in the axial
direction.
[0016] The impeller cup may also preferably include a recessed
portion defined in a central portion of the cover portion, and at
least a lower end of the first bearing support portion may be
arranged inside the recessed portion. In this case, an inner-rotor
blower fan with a reduced increase in axial dimensions thereof is
realized.
[0017] A preferred embodiment of the present invention is able to
realize an inner-rotor blower fan with a reduced radial dimension
and a reduced increase in axial dimensions thereof.
[0018] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic cross-sectional view illustrating the
structure of a blower fan according to a preferred embodiment of
the present invention.
[0020] FIG. 2 is a schematic cross-sectional view illustrating the
structure of a blower fan according to an example modification of a
preferred embodiment of the present invention.
[0021] FIG. 3 is a schematic cross-sectional view illustrating the
structure of a blower fan according to another preferred embodiment
of the present invention.
[0022] FIG. 4 is a schematic cross-sectional view illustrating the
structure of a blower fan according to yet another preferred
embodiment of the present invention.
[0023] FIG. 5 is a schematic cross-sectional view illustrating the
structure of a blower fan according to yet another preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the accompanying
drawings. In the description of the preferred embodiments, a
direction parallel or substantially parallel to a rotation axis and
a radial direction centered on the rotation axis will be referred
to simply as an "axial direction" and a "radial direction",
respectively. Note that the present invention is not limited to the
preferred embodiments described below. Also note that the preferred
embodiments described below may be combined with other preferred
embodiments of the present invention.
[0025] FIG. 1 is a schematic cross-sectional view illustrating the
structure of a blower fan 100 according to a preferred embodiment
of the present invention. The blower fan 100 according to the
present preferred embodiment preferably is an axial fan using an
inner-rotor motor.
[0026] Referring to FIG. 1, the blower fan 100 includes a rotor 20
arranged to rotate about a rotation axis J together with a shaft
30, a stator 60 arranged radially outward of the rotor 20 and
opposite the rotor 20, and an impeller 10 arranged to rotate
together with the shaft 30. The rotor 20 preferably includes a
substantially cylindrical rotor holder 21 fixed to the shaft 30,
and a rotor magnet 22 fixed to an outer circumferential surface of
the rotor holder 21. In addition, the stator 60 is preferably
supported by a stator support portion 61. The impeller 10
preferably includes a substantially cylindrical impeller cup 11
including a cover portion arranged to be fixed to the shaft 30, and
a plurality of blades 12. The blades 12 are arranged on an outer
circumferential surface of the impeller cup 11, and arranged
radially outward of the stator 60. The blower fan 100 is arranged
to draw in air from one axial side and discharge the air to the
other axial side through the rotation of the blades 12. In the
following description, an inlet side and an outlet side along the
axial direction will be referred to as an "upper side" and a "lower
side", respectively, for the sake of convenience.
[0027] Note that the impeller cup 11 may not necessarily be
directly fixed to the shaft 30. For example, the impeller cup 11
may be indirectly fixed to the shaft 30 by being fixed to the rotor
holder 21 fixed to the shaft 30. In that case, the rotor holder 21
may be joined to the impeller cup 11 through, for example, insert
molding. Also note that, although the rotor magnet 22 is fixed to
the rotor holder 21 that is fixed to the shaft 30 in the present
preferred embodiment, the rotor magnet 22 could instead be directly
fixed to the shaft 30 if so desired, as mentioned below.
[0028] In the present preferred embodiment, one end of the shaft 30
is arranged to project axially upward from the cover portion of the
impeller cup 11. A bearing arranged to support the shaft 30 such
that the shaft 30 is rotatable is divided into a first bearing 40a
arranged axially above the cover portion of the impeller cup 11,
and a second bearing 40b arranged axially below the cover portion
of the impeller cup 11. Moreover, a first bearing support portion
50a arranged to support the first bearing 40a and a second bearing
support portion 50b arranged to support the second bearing 40b are
separately arranged, one above and the other below, in the axial
direction. Furthermore, a recessed portion 11a is defined in a
central portion of the cover portion of the impeller cup 11, and at
least a lower end of the first bearing support portion 50a is
arranged inside the recessed portion 11a. Here, each of the first
and second bearings 40a and 40b may be defined by bearing
structure, such as, for example, a ball bearing.
[0029] A housing arranged to cover an outer circumference of the
impeller 10 is divided into a first housing 51a and a second
housing 51b arranged radially outward of the impeller 10. The first
housing 51a is arranged axially above the second housing 51b. The
first housing 51a is joined to the first bearing support portion
50a through a first joining portion 52a. The second housing 51b is
joined to the second bearing support portion 50b through a second
joining portion 52b. The first and second housings 51a and 51b are
joined to each other at a level higher than that of a joint between
the second joining portion 52b and the second housing 51b.
[0030] Here, each of the first and second joining portions 52a and
52b is arranged to permit air currents to pass therethrough in the
axial direction. For example, each of the first and second joining
portions 52a and 52b may be defined by ribs. The ribs may be
arranged to extend radially from outside surfaces of the first and
second bearing support portions 50a and 50b to inside surfaces of
the first and second housings 51a and 51b, respectively, so as to
cross the air currents passing therethrough in the axial
direction.
[0031] The radial dimension of the first joining portion 52a and
that of the second joining portion 52b are preferably different
from each other. An increase in the radial dimension of the first
joining portion 52a contributes to reducing an obstruction of the
passage of incoming air currents from above in the axial direction.
In addition, the wind velocity of the air currents is increased
when the radial dimension of the second joining portion 52b is
arranged to be smaller than that of the first joining portion
52a.
[0032] That is, according to a preferred embodiment of the present
invention, in the blower fan 100 including the inner-rotor motor,
one end of the shaft 30 is arranged to project axially upward from
the impeller cup 11. In addition, the bearing 40a is arranged near
the end of the shaft 30 axially above the impeller cup 11, while
the bearing 40b is arranged near the other end of the shaft 30
axially below the impeller cup 11. Moreover, the bearing support
portions 50a and 50b arranged to support the bearings 40a and 40b,
respectively, are joined to the housings 51a and 51b, respectively,
which are divided from each other in the axial direction.
[0033] According to the present preferred embodiment, each of the
bearing and the bearing support portion preferably includes two
members separated from each other in the axial direction and
arranged one above the rotor magnet 22 and the stator 60, and the
other below the rotor magnet 22 and the stator 60. That is, the
bearing and the bearing support portion are prevented from being
provided in a same radial plane as the arrangement of components
including the rotor magnet 22 and the stator 60. Moreover, because
a need to arrange a gap between the bearing support portion and the
rotor magnet 22 is eliminated, it is possible to secure a large
radial clearance between different components. All of this makes it
possible to reduce the radial dimension of the motor.
[0034] Furthermore, the bearing support portions arranged at an
axially upper position and an axially lower position, respectively,
are joined to the separate housings divided from each other, one
above and the other below, in the axial direction. Therefore, it is
possible to prepare an assembly made up of the first housing 51a
combined with the first joining portion 52a and the first bearing
support portion 50a, and an assembly made up of the second housing
51b combined with the second joining portion 52b and the second
bearing support portion 50b (and the stator support portion 61),
before starting assemblage of the blower fan 100. This thereby
makes it easier to assemble the blower fan 100 of the present
preferred embodiment.
[0035] In FIG. 1, the second joining portion 52b is preferably
shaped so as to have a uniform axial dimension. Referring to FIG.
2, however, the second joining portion 52b may be shaped so as to
include a cutout portion defined in a radially outer end portion
thereof, the cutout portion extending axially downward from, for
example, an upper end portion thereof. Also in this case, the first
and second housings 51a and 51b are joined to each other at a level
higher than that of a position of the joint between the second
joining portion 52b and the second housing 51b.
[0036] Furthermore, because the first bearing 40a is arranged
axially above the impeller cup 11, the first bearing 40a is
directly exposed to air currents that are introduced into the
blower fan 100 from the inlet side. As a result, an improvement in
a heat radiation effect of the first bearing 40a is achieved.
[0037] Furthermore, as a result of one end of the shaft 30 being
arranged to project axially upward from the impeller cup 11, it is
possible to increase a bearing span (the term "bearing span" refers
to an axial distance between the first and second bearings 40a and
40b) to close to the maximum axial dimension of the blower fan 100.
This leads to an improved axial balance of the blower fan 100 to
thereby allow the blower fan 100 to be stable with limited
vibration. Here, it may be supposed that when one end of the shaft
30 is arranged to project axially upward from the impeller cup 11,
the axial dimension of the blower fan 100 is increased. Note,
however, that it is possible to reduce the increase in the axial
dimension of the blower fan 100 by defining the recessed portion
11a in the central portion of the cover portion of the impeller cup
11, and arranging at least the lower end of the first bearing
support portion 50a inside the recessed portion 11a.
[0038] In the present preferred embodiment, the first housing 51a,
the first bearing support portion 50a, and the first joining
portion 52a are preferably molded in one piece of a resin or the
like preferably through injection molding, for example. The second
housing 51b, the second bearing support portion 50b, and the second
joining portion 52b are also preferably molded in one piece of a
resin or the like preferably through injection molding, for
example. Note that, in this case, it is not necessary that
boundaries between the first and second bearing support portions
50a and 50b and the first and second joining portions 52a and 52b,
respectively, and boundaries between the first and second housings
51a and 51b and the first and second joining portions 52a and 52b,
respectively, should be defined definitely.
[0039] Here, as illustrated in FIG. 1, each of the first and second
bearing support portions 50a and 50b may be defined by a metallic
member. In this case, the metallic members may be coupled to the
first and second housings 51a and 51b, respectively, preferably
through, for example, insert molding. Moreover, the stator support
portion 61 may also be defined by a metallic member. In this case,
as illustrated in FIG. 1, the second bearing support portion 50b
and the stator support portion 61 may be coupled to a base portion
53. Thus, a sufficient vibration-resistant strength of each of the
bearing support portions 50a and 50b is secured even when the
blower fan 100 is caused to rotate at a great speed, and heat that
is generated from the stator 60 is sufficiently radiated even when
the blower fan 100 is caused to operate for a long time.
[0040] Furthermore, the second joining portion 52b may be arranged
to define stationary vanes. In this case, the stationary vanes
serve to regulate the flow of air currents that are to be
discharged in the axial direction, and to achieve a wind
acceleration effect by converting centrifugal components of the air
currents into axial components thereof.
[0041] Furthermore, it is possible to widen a space between the
stator support portion 61 and the shaft 30 because the axial
dimension of the second bearing support portion 50b arranged to
support the second bearing 40b can be reduced. Therefore, as
illustrated in FIG. 1, it is possible to arrange a circuit board 70
having a large area in that space. A Hall element arranged to
detect a change in magnetic flux which involves the rotation of the
rotor magnet 22, a motor driving-use IC arranged to control supply
of currents to coils of the stator 60, and so on, for example, may
preferably be mounted on the circuit board 70. Note that another
circuit board 71 may be arranged in a space below the second
bearing support portion 50b.
[0042] Here, in the case of the blower fan 100 in which the
inner-rotor motor is used, the rotor magnet 22 is fixed to the
outer circumferential surface of the rotor holder 21 as illustrated
in FIG. 1, and it is therefore impossible to press fit the impeller
cup 11 to the outer circumferential surface of the rotor holder 21.
Therefore, it is not possible to use the rotor holder 21 to
maintain the strength of the impeller cup 11. As illustrated in
FIG. 1, it is therefore preferable to arrange an annular metallic
member 80 in an opening end portion of the impeller cup 11 in order
to increase the strength of the impeller cup 11. In this case, the
annular metallic member 80 may be coupled to the impeller cup 11
preferably through, for example, insert molding. Moreover, the
rotor holder 21, in addition to the annular metallic member 80, may
be coupled to the impeller cup 11 through insert molding.
[0043] Next, with reference to FIG. 1, a method of assembling the
blower fan 100 according to the present preferred embodiment will
now be described below. Note that the method of assembling the
blower fan 100 is not limited to the method described below, and
that the order of steps in assembling the blower fan 100, methods
by which components of the blower fan 100 are assembled, and so on
may be modified appropriately.
[0044] First, the second housing 51b provided with the second
bearing support portion 50b, the second joining portion 52b, and
the stator support portion 61 are prepared. An axially upper end
portion of the second housing 51b is at least arranged at a level
higher than that of an upper end of the second joining portion 52b.
Note here that the second bearing support portion 50b, the second
joining portion 52b, and the stator support portion 61 may be
molded of, for example, a resin or the like preferably through
injection molding to be formed integrally together with the second
housing 51b. Also note that each of the second bearing support
portion 50b and the stator support portion 61 may preferably be
defined by, for example, a metallic member. In this case, each of
the metallic members may be coupled to the second housing 51b
through insert molding.
[0045] Next, the stator 60 provided with a stator core having coils
wound thereabout and the circuit board 70 to which end portions of
wires of the coils are connected (i.e., a stator assembly) is
prepared. Then, the stator assembly is inserted from axially above
into the stator support portion 61 and fixed thereto. The stator
assembly may be, for example, press fitted to the stator support
portion 61 with application of a slight force, adhered to the
stator support portion 61, or connected to the stator support
portion 61 using any other desirable method.
[0046] Next, the second bearing 40b (which is, for example, a ball
bearing) is inserted from axially below into the second bearing
support portion 50b.
[0047] Next, an assembly (i.e., a rotor assembly) preferably
including the shaft 30, the rotor 20 (i.e., the rotor holder 21 and
the rotor magnet 22), and the impeller 10 (i.e., the impeller cup
11 and the blades 12), the latter two being fixed to the shaft 30,
is prepared. Then, the rotor assembly is inserted from axially
above into the second bearing 40b.
[0048] Next, the first housing 51a provided with the first bearing
support portion 50a and the first joining portion 52a is prepared,
and the first housing 51a is fixed to the second housing 51b. Here,
the first housing 51a may be fixed to the second housing 51b
through, for example, snap fitting, welding, or any other desirable
fixing method. Note here that the first bearing support portion 50a
and the first joining portion 52a may preferably be molded from a
resin or the like through, for example, injection molding
integrally with the first housing 51a. Also note that the first
bearing support portion 50a may be defined by a metallic member. In
this case, the metallic member may be coupled to the first housing
51a through, for example, insert molding.
[0049] Finally, the first bearing 40a (which is, for example, a
ball bearing) is inserted from axially above into the first bearing
support portion 50a, and fixed through a ring 90, defined by, for
example, a snap ring, washer, etc. Meanwhile, the second bearing
40b is fixed through a coil spring 91 and a washer, to thereby
exert an axial force on the shaft 30.
[0050] As described above, because the bearing support portions 50a
and 50b, which are arranged respectively at upper and lower levels,
are coupled respectively to the housings 51a and 51b, which are
divided from each other in the axial direction, it is possible to
separately prepare the assembly made up of the first housing 51a
combined with the first joining portion 52a and the first bearing
support portion 50a, and the assembly including the second housing
51b combined with the second joining portion 52b and the second
bearing support portion 50b (and, in addition, the stator support
portion 61), before starting the assemblage of the blower fan 100.
This facilitates the assemblage of the blower fan 100.
[0051] Next, structures of blower fans according to other preferred
embodiments of the present invention will now be described below
with reference to FIGS. 3, 4, and 5. FIGS. 3 to 5 are each a
schematic cross-sectional view illustrating the structure of a
blower fan according to a preferred embodiment of the present
invention.
[0052] A blower fan 110 illustrated in FIG. 3 is different from the
blower fan 100 illustrated in FIG. 1 in that a lower end portion
61a of the stator support portion 61, which is preferably defined
by a metallic member, is arranged to extend further downward in the
axial direction, and that a lower end portion of the second joining
portion 52b is arranged substantially at the same level as that of
the lower end portion 61a of the stator support portion 61. This
structure of the blower fan 110 contributes to maintaining the
strength of the second joining portion 52b through the stator
support portion 61, which is defined by a metallic member.
[0053] A blower fan 120 illustrated in FIG. 4 is different from the
blower fan 100 illustrated in FIG. 1 in that each of the first
bearing support portion 50a, the second bearing support portion
50b, and the stator support portion 61 is preferably made of a
single monolithic resin member. This structure of the blower fan
120 makes it possible to easily mold, of a resin or the like, the
first housing 51a integrally with the first bearing support portion
50a and the first joining portion 52a through injection molding,
and also makes it possible to easily mold, of the resin or the
like, the second housing 51b integrally with the second bearing
support portion 50b, the second joining portion 52b, and the stator
support portion 61 preferably through, for example, injection
molding.
[0054] A blower fan 130 illustrated in FIG. 5 is different from the
blower fan 100 illustrated in FIG. 1 in that the rotor magnet 22 is
directly fixed to the shaft 30.
[0055] As described above, according to preferred embodiments of
the present invention, the bearings 40a and 40b, and the bearing
support portions 50a and 50b, are arranged separately, one above
and the other below, in the axial direction so that no bearing
support portion is arranged radially inside the stator 60. In a
conventional inner-rotor blower fan, a rotor magnet needs to be
fixed to an outer circumferential surface of a rotor holder
arranged radially outside a bearing support portion. However, a
need for this is eliminated in preferred embodiments of the present
invention, because no bearing support portion is arranged radially
inside the stator 60. This makes it possible to fix the rotor
magnet 22 directly to the shaft 30 as illustrated in FIG. 5. This
in turn makes it possible to reduce the size of the outside
diameter of the stator 60. Note that this makes it possible to
widen the gap between the stator support portion 61 and the
impeller cup 11, which in turn makes it possible to arrange the
stator support portion 61 and the impeller cup 11 to overlap with
each other in the radial direction as illustrated in FIG. 5. This
makes it possible to extend the lower end portion of the impeller
cup 11 further downward in the axial direction, thereby increasing
the area of each of the blades 12. A blower fan that enables a
greater air volume is thereby realized.
[0056] In addition to the structure of the blower fan 130
illustrated in FIG. 5, there are a variety of possible structures
of blower fans in which the rotor magnet 22 is directly fixed to
the shaft 30. For instance, it is possible to reduce the inside
diameter of the impeller cup 11 in accordance with a reduction in
the outside diameter of the stator 60. This makes it possible to
realize a blower fan with a reduced radial dimension. Also, a
reduction in the inside diameter of the stator 60 while maintaining
the outside diameter of the stator 60 makes it possible to reduce
the axial dimension of the stator 60. This makes it possible to
realize a blower fan with reduced axial dimensions.
[0057] 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.
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