U.S. patent application number 12/415666 was filed with the patent office on 2009-10-01 for fan motor.
This patent application is currently assigned to NIDEC SANKYO CORPORATION. Invention is credited to Keishi Otsubo.
Application Number | 20090246042 12/415666 |
Document ID | / |
Family ID | 41117539 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090246042 |
Kind Code |
A1 |
Otsubo; Keishi |
October 1, 2009 |
FAN MOTOR
Abstract
A fan motor may include a rotor part having a drive magnet, and
a stator part having a drive coil and rotatably holding the rotor
part. The rotor part may include a rotor yoke to which the drive
magnet is fixed on an inner peripheral side of the rotor yoke, an
impeller which is provided with a plurality of blades and which is
disposed on an outer peripheral side of the rotor yoke, and a hub
for fixing the impeller. The impeller is provided with a held part
which is sandwiched between and held by the rotor yoke and the hub
in an axial direction. The held part is abutted with an upper face
of a bottom part of the rotor yoke and a lower face of a plate part
of the hub, and the held part is held by the rotor yoke and the hub
in the axial direction
Inventors: |
Otsubo; Keishi; (Nagano,
JP) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
NIDEC SANKYO CORPORATION
Nagano
JP
|
Family ID: |
41117539 |
Appl. No.: |
12/415666 |
Filed: |
March 31, 2009 |
Current U.S.
Class: |
417/353 |
Current CPC
Class: |
F04D 25/06 20130101 |
Class at
Publication: |
417/353 |
International
Class: |
F04D 25/06 20060101
F04D025/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2008 |
JP |
2008-091712 |
Claims
1. A fan motor comprising: a rotor part which includes a drive
magnet; and a stator part which includes a drive coil and which
rotatably holds the rotor part; wherein the rotor part comprises; a
rotor yoke to which the drive magnet is fixed on an inner
peripheral side of the rotor yoke; an impeller which is provided
with a plurality of blades and which is disposed on an outer
peripheral side of the rotor yoke; and a hub for fixing the
impeller; wherein the impeller is provided with a held part which
is sandwiched between and held by the rotor yoke and the hub in an
axial direction.
2. The fan motor according to claim 1, wherein the rotor yoke is
formed in a bottomed cylindrical shape having a bottom part, the
hub is provided with a plate part, and the held part is abutted
with an upper face of the bottom part of the rotor yoke and a lower
face of the plate part of the hub, and the held part is sandwiched
between and held by the rotor yoke and the hub in the axial
direction.
3. The fan motor according to claim 2, wherein the held part is
formed in a flat shape substantially perpendicular to the axial
direction.
4. The fan motor according to claim 3, wherein the impeller is
formed in a bottomed cylindrical shape having a bottom part, a
step-shaped circular hole which is structured of a large diameter
hole that is located on an upper side in the axial direction and a
small diameter hole whose diameter is smaller than the large
diameter hole and that is located on a lower side in the axial
direction is formed at a center of the bottom part of the impeller
so as to penetrate in the axial direction, and the held part is a
flat part which is formed between a peripheral face of the large
diameter hole and a peripheral face of the small diameter hole and
which is sandwiched between and held by the rotor yoke and the hub
in a state that an upper face of the bottom part of the rotor yoke
is abutted with a lower face of the flat part and a lower face of
the plate part of the hub is abutted with an upper face of the flat
part.
5. The fan motor according to claim 1, wherein the hub is formed
with a protruded part protruding toward the rotor yoke in the axial
direction, the held part is formed with an arrangement hole in
which the protruded part is disposed, the rotor yoke is formed with
an engaging hole with which the protruded part is engaged, a tip
end of the protruded part which is disposed at an edge of the
engaging hole is protruded in the axial direction with respect to
the engaging hole and formed as a caulking fixed part with which
the hub and the rotor yoke are fixed to each other by caulking, and
the caulking fixed part is fixed to the rotor yoke by caulking.
6. The fan motor according to claim 5, wherein the hub is formed
with an abutting part which is abutted with the stator part to
restrict movement of the rotor part in the axial direction, and the
abutting part is protruded in same direction as the protruded part
and protruded in the axial direction with respect to the protruded
part.
7. The fan motor according to claim 5, wherein the tip end of the
protruded part is a projecting part which is formed in a
cylindrical shape and a tip end of the projecting part is used as
the caulking fixed part.
8. The fan motor according to claim 1, wherein the rotor yoke is
formed in a bottomed cylindrical shape, a protruded part which is
formed in a substantially cylindrical shape is formed at a center
of the hub so as to protrude in the axial direction toward the
rotor yoke, a center of the held part is formed with a circular
arrangement hole in which the protruded part is disposed, a center
of a bottom part of the rotor yoke is formed with a circular
engaging hole with which the protruded part is engaged, the
protruded part is press-fitted to the engaging hole and abutted
with a peripheral face of the engaging hole, and the rotor yoke and
the hub are positioned with an outer peripheral face of the
protruded part and a peripheral face of the engaging hole as
reference.
9. The fan motor according to claim 8, wherein the circular
arrangement hole and the circular engaging hole are formed in same
diameter, and the protruded part is press-fitted to the circular
arrangement hole and abutted with a peripheral face of the circular
arrangement hole.
10. The fan motor according to claim 1, wherein the hub is formed
of metal, and a rotation shaft structuring the rotor part is
press-fitted and fixed to the hub.
11. The fan motor according to claim 1, further comprising a
plurality of ribs which are protruded from at least one of an inner
peripheral face of the impeller and an outer peripheral face of the
rotor in a radial direction with a predetermined interval, wherein
the rotor yoke is press-fitted to the impeller so that one of the
inner peripheral face of the impeller and the outer peripheral face
of the rotor yoke is abutted with end parts in the radial direction
of the ribs, and wherein a gap space is formed between the inner
peripheral face of the impeller and the outer peripheral face of
the rotor yoke.
12. The fan motor according to claim 11, wherein the impeller is
formed of resin and formed in a bottomed cylindrical shape, the
rotor yoke is formed in a bottomed cylindrical shape having a
bottom part which is abutted with a bottom part of the impeller,
and the rib is formed on the inner peripheral face of the impeller
so as to reach at least to a boundary portion between the bottom
part of the impeller and the inner peripheral face of the
impeller.
13. The fan motor according to claim 12, wherein the bottom part of
the impeller is formed with radial ribs extending from end parts of
the ribs toward a center of the bottom part of the impeller so as
to protrude in the axial direction, and the bottom part of the
rotor yoke is abutted with the radial ribs.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present invention claims priority under 35 U.S.C.
.sctn.119 to Japanese Application No. 2008-91712 filed Mar. 31,
2008 the entire contents of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] An embodiment of the present invention may relate to a fan
motor.
BACKGROUND OF THE INVENTION
[0003] A fan motor for cooling has been conventionally mounted on
an electronic apparatus for radiating heat generated in its inside.
The fan motor has been known which includes a rotor part having a
rotor magnet and a stator part having a coil (see, for example,
Japanese Patent Laid-Open No. 2007-244045). In the fan motor
described in the Patent Reference, a rotor part includes an
impeller, which is made of resin and provided with a blade part,
and a rotor yoke to which a rotor magnet is fixed on its inner
peripheral face. The rotor yoke is press-fitted and fixed to an
inner peripheral side of the impeller in the fan motor.
[0004] With a higher performance of an electronic apparatus in
recent years, a higher cooling ability is required in a fan motor.
In other words, performance for speedily radiating heat at a higher
temperature is required in a fan motor and thus demand for
high-speed rotation of the fan motor has been increased. However,
like a fan motor as described in the Patent Reference, when a rotor
yoke is press-fitted on the inner peripheral side of the impeller,
unless a press-fitting margin of the rotor yoke to the impeller is
increased to obtain a larger holding force by which the rotor yoke
holds the impeller, slip may occur between the impeller and the
rotor yoke due to a centrifugal force occurred when the fan motor
is rotated at a high speed. On the other hand, when a press-fitting
margin of the rotor yoke is increased larger, the impeller may be
cracked due to a difference of the coefficients of thermal
expansion of the rotor yoke and the impeller.
SUMMARY OF THE INVENTION
[0005] In view of the problems described above, at least an
embodiment of the present invention may advantageously provide a
fan motor in which a holding force between a rotor yoke and an
impeller is increased while preventing cracking of the
impeller.
[0006] According to at least an embodiment of the present
invention, there may be provided a fan motor including a rotor
part, which includes a drive magnet, and a stator part which
includes a drive coil and rotatably holds the rotor part. The rotor
part includes a rotor yoke to which the drive magnet is fixed on
its inner peripheral side, an impeller which is provided with a
plurality of blades and disposed on an outer peripheral side of the
rotor yoke, and a hub for fixing the impeller. The impeller is
provided with a held part which is sandwiched between and held by
the rotor yoke and the hub in an axial direction.
[0007] Further, in accordance with an embodiment of the present
invention, the rotor yoke is formed in a bottomed cylindrical shape
having a bottom part, the hub is provided with a circular plate
part, and the held part is abutted with an upper face of the bottom
part of the rotor yoke and a lower face of the circular plate part
of the hub, and the held part is sandwiched between and held by the
rotor yoke and the hub in the axial direction. In addition, in
accordance with an embodiment of the present invention, the held
part is formed in a flat face shape substantially perpendicular to
the axial direction. Further, in accordance with an embodiment of
the present invention, the impeller is formed in a bottomed
cylindrical shape having a bottom part, a step-shaped circular hole
which is structured of a large diameter hole that is located on an
upper side in the axial direction and a small diameter hole whose
diameter is smaller than the large diameter hole and located on a
lower side in the axial direction is formed at a center of the
bottom part of the impeller so as to penetrate in the axial
direction, and the held part is a flat part which is formed between
a peripheral face of the large diameter hole and a peripheral face
of the small diameter hole and which is sandwiched between and held
by the rotor yoke and the hub in a state that an upper face of the
bottom part of the rotor yoke is abutted with a lower face of the
flat part and a lower face of the circular plate part of the hub is
abutted with an upper face of the flat part.
[0008] In the fan motor in accordance with an embodiment of the
present invention, the held part of the impeller is sandwiched
between and held by the rotor yoke and the hub in the axial
direction. Therefore, a contacting area of the rotor yoke with the
held part of the impeller is increased and thus a frictional
resistance between the rotor yoke and the impeller is increased and
a holding force with which the rotor yoke holds the impeller is
increased. Further, the held part is sandwiched between and held by
the rotor yoke and the hub in the axial direction and thus, even
when coefficient of thermal expansion of the rotor yoke is
different from coefficient of thermal expansion of the impeller, a
difference of deformation amounts at the time of thermal
deformation can be relieved in the radial direction. Therefore,
according to an embodiment of the present invention, cracking of
the impeller can be prevented.
[0009] In accordance with an embodiment of the present invention,
the hub is formed with a protruded part protruding toward the rotor
yoke in the axial direction, the held part is formed with an
arrangement hole in which the protruded part is disposed, the rotor
yoke is formed with an engaging hole with which the protruded part
is engaged, a tip end of the protruded part which is disposed at an
edge of the engaging hole is protruded in the axial direction with
respect to the engaging hole and formed as a caulking fixed part
with which the hub and the rotor yoke are fixed to each other by
caulking, and the caulking fixed part is fixed to the rotor yoke by
caulking. According to this structure, the rotor yoke and the hub
which sandwich and hold the held part of the impeller are directly
fixed to each other and thus a holding force for the impeller is
increased effectively. Therefore, the impeller is held in a stable
state.
[0010] In accordance with an embodiment of the present invention,
the hub is formed with an abutting part which is abutted with the
stator part to restrict movement of the rotor part in the axial
direction, and the abutting part is protruded in the same direction
as the protruded part and protruded in the axial direction with
respect to the protruded part. Further, in accordance with an
embodiment of the present invention, the tip end of the protruded
part is a projecting part which is formed in a cylindrical shape
and a tip end of the projecting part is used as the caulking fixed
part. According to this structure, the stator part does not abut
with the caulking fixed part and thus damage of the caulking fixed
part caused by abutting with the stator part is prevented.
Accordingly, the impeller can be surely held in a stable state by
means of that the rotor yoke and the hub are fixed to each other by
caulking.
[0011] In accordance with an embodiment of the present invention,
the rotor yoke is formed in a bottomed cylindrical shape, the
protruded part which is formed in a substantially cylindrical shape
is formed at a center of the hub so as to protrude in the axial
direction toward the rotor yoke, a center of the held part is
formed with a circular arrangement hole in which the protruded part
is disposed, a center of a bottom part of the rotor yoke is formed
with a circular engaging hole with which the protruded part is
engaged, the protruded part is press-fitted to the engaging hole
and abutted with a peripheral face of the engaging hole, and the
rotor yoke and the hub are positioned each other with an outer
peripheral face of the protruded part and a peripheral face of the
engaging hole as reference. According to this structure, the rotor
yoke is easily positioned in the radial direction by using a part
of the hub.
[0012] In accordance with an embodiment of the present invention,
the arrangement hole and the engaging hole are formed in the same
diameter, and the protruded part is press-fitted to the arrangement
hole and abutted with a peripheral face of the arrangement hole.
According to this structure, the impeller is easily positioned in
the radial direction by using a part of the hub.
[0013] In accordance with an embodiment of the present invention,
the hub is formed of metal, and a rotation shaft structuring the
rotor part is press-fitted and fixed to the hub. According to this
structure, concentricity of the rotation shaft fixed to the hub
with the rotor yoke is easily enhanced.
[0014] In accordance with an embodiment of the present invention, a
plurality of ribs are formed which are protruded from at least one
of an inner peripheral face of the impeller and an outer peripheral
face of the rotor yoke in a radial direction with a predetermined
interval. The rotor yoke is press-fitted to the impeller so that
one of the inner peripheral face of the impeller and the outer
peripheral face of the rotor yoke is abutted with end parts in the
radial direction of the ribs, and a gap space is formed between the
inner peripheral face of the impeller and the outer peripheral face
of the rotor yoke. According to this structure, even when stress
occurs in the impeller due to a centrifugal force, thermal
expansion or the like occurred at the time of high-speed rotation,
the gap space between the inner peripheral face of the impeller and
the outer peripheral face of the rotor yoke serves as a relief part
for the stress. Therefore, an excessive stress is not applied to
the impeller and cracking of the impeller is prevented.
[0015] In accordance with an embodiment of the present invention,
the impeller is formed of resin in a bottomed cylindrical shape,
the rotor yoke is formed in a bottomed cylindrical shape having a
bottom part which is abutted with the bottom part of the impeller,
and the rib is formed on the inner peripheral face of the impeller
so as to reach at least to a boundary portion between the bottom
part of the impeller and the inner peripheral face of the impeller.
Further, in accordance with an embodiment of the present invention,
the bottom part of the impeller is formed with radial ribs
extending from end parts of the ribs toward a center of the bottom
part of the impeller so as to protrude in the axial direction, and
the bottom part of the rotor yoke is abutted with the radial ribs.
According to this structure, even when the bottom part of the rotor
yoke is abutted with the bottom part of the impeller to position
the rotor yoke in the axial direction, a thickness of the bottom
part of the impeller may be set arbitrarily. Therefore, wall
thicknesses of respective portions of the impeller formed of resin
can be roughly equalized and thus shrinkage at the time of resin
molding can be prevented.
[0016] Other features and advantages of the invention will be
apparent from the following detailed description, taken in
conjunction with the accompanying drawings that illustrate, by way
of example, various features of embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Embodiments will now be described, by way of example only,
with reference to the accompanying drawings which are meant to be
exemplary, not limiting, and wherein like elements are numbered
alike in several Figures, in which:
[0018] FIG. 1 is a cross-sectional view showing a schematic
structure of a fan motor in accordance with an embodiment of the
present invention.
[0019] FIG. 2 is a perspective view showing a rotor part in FIG. 1
which is viewed from a lower side.
[0020] FIG. 3 is a bottom view showing the rotor part in FIG.
1.
[0021] FIG. 4 is an exploded perspective view showing the rotor
part in FIG. 1 which is viewed from a lower side.
[0022] FIG. 5 is an exploded perspective view showing the rotor
part in FIG. 1 which is viewed from an upper side.
[0023] FIG. 6 is a cross-sectional view showing a schematic
structure of a rotor part in accordance with another embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] An embodiment of the present invention will be described
below with reference to the accompanying drawings.
[0025] FIG. 1 is a cross-sectional view showing a schematic
structure of a fan motor 1 in accordance with an embodiment of the
present invention. FIG. 2 is a perspective view showing a rotor
part 4 in FIG. 1 which is viewed from a lower side. FIG. 3 is a
bottom view showing the rotor part 4 in FIG. 1. FIG. 4 is an
exploded perspective view showing the rotor part 4 in FIG. 1 which
is viewed from a lower side. FIG. 5 is an exploded perspective view
showing the rotor part 4 in FIG. 1 which is viewed from an upper
side. In FIGS. 2 through 5, a drive magnet 14 is not shown.
Further, in this specification, the "X1" direction in FIG. 1 is
referred to as an "upper side" and the "X2" direction is referred
to as a "lower side".
[0026] The fan motor 1 in this embodiment is a motor for cooling,
for example, for radiating heat generated in the inside of an
electronic apparatus. As shown in FIG. 1, the fan motor 1 includes
a case body 2, and a stator part 3 and a rotor part 4 which are
disposed in an inside of the case body 2. The stator part 3 is
fixed to the case body 2. The rotor part 4 is rotatably held by the
stator part 3.
[0027] The stator part 3 includes a bearing holder 6 which is
formed in a roughly cylindrical shape, two bearings 7 which are
disposed on an inner peripheral side of the bearing holder 6, a
stator core 8 which is fixed on an outer peripheral face of the
bearing holder 6, and a drive coil 9 which is wound around the
stator core 8.
[0028] A lower end side of the bearing holder 6 is fixed to a
stator fixing part 2a which is formed on a lower side of the case
body 2. Further, an inner peripheral face of the bearing holder 6
is formed with a protruded part 6a which protrudes inside in a
radial direction. One of two bearings 7 is disposed in the inside
on the lower side of the bearing holder 6 in a state that its upper
face is abutted with the protruded part 6a. Further, the other
bearing 7 is disposed in the inside on an upper end of the bearing
holder 6 in a state that its lower face is abutted with an upper
end of a compression coil spring 10 whose lower end is abutted with
the protruded part 6a. In other words, the protruded part 6a serves
as a positioning part for determining the positions of the bearings
7 which are disposed up and down.
[0029] The stator core 8 is, for example, a laminated core which is
formed by means of that thin plates made of magnetic material are
laminated on each other. The stator core 8 is formed with a
plurality of salient pole parts around which the drive coil 9 is
wound so as to protrude outside in the radial direction.
[0030] The rotor part 4 includes an impeller 12 having a plurality
of blades 12a, a hub 21 for fixing the impeller 12 and a rotation
shaft 13 rotating together with the impeller 12, a drive magnet 14
which is formed in a cylindrical shape, and a rotor yoke 15 to
which the drive magnet 14 is fixed.
[0031] Two positions of the rotation shaft 13, i.e., its upper side
and lower end, are rotatably supported by two bearings 7. An upper
end of the rotation shaft 13 is fixed to the hub 21. Further, the
lower end side of the rotation shaft 13 is formed with a fixing
groove 13a to which a retaining ring 16 for preventing coming-out
of the rotation shaft 13 from the bearing 7 is fixed. The retaining
ring 16 fixed to the fixing groove 13a is abutted with a lower face
of the bearing 7 which is disposed on the lower side. In this
embodiment, as described below, the impeller 12 is sandwiched
between and held by the rotor yoke 15 and the hub 21 in an axial
direction and thus the impeller 12 is fixed to the rotor yoke 15,
and the rotor yoke 15 and the hub 21 are fixed to each other by
caulking. In other words, in this embodiment, the impeller 12 is
fixed to the rotation shaft 13 through the hub 21.
[0032] The rotor yoke 15 is formed of magnetic material. The rotor
yoke 15 in this embodiment is formed of an electro-galvanized steel
plate (SECC). Further, the rotor yoke 15 in this embodiment is
formed by drawing work of a flat plate of SECC. The rotor yoke 15
is formed in a substantially bottomed cylindrical shape having a
bottom part 15a. Specifically, the rotor yoke 15 is structured of
the bottom part 15a, a small diameter cylindrical part 15b whose
upper end is connected with the bottom part 15a, and a large
diameter cylindrical part 15c whose upper end is connected with the
small diameter cylindrical part 15b and whose inner diameter and
outer diameter are larger than the small diameter cylindrical part
15b. A center of the bottom part 15a is formed with a circular
engaging hole 15d with which a tip end side of a protruded part 21b
formed in the hub 21 is engaged.
[0033] The drive magnet 14 is fixed on an inner peripheral face of
the large diameter cylindrical part 15c. Specifically, the drive
magnet 14 is fixed on an inner peripheral face of the large
diameter cylindrical part 15c in a state that its upper end is
abutted with a stepped part 15f formed at a boundary portion
between the small diameter cylindrical part 15b and the large
diameter cylindrical part 15c. In this embodiment, as shown in FIG.
1, the inner peripheral face of the drive magnet 14 is disposed on
an outer side of the inner peripheral face of the small diameter
cylindrical part 15b in the radial direction and thus the drive
magnet 14 does not protrude on the inner peripheral side with
respect to the small diameter cylindrical part 15b. In this
embodiment, the drive magnet 14 fixed to the rotor yoke 15 is
disposed on an outer side of the stator core 8 in the radial
direction so as to face each other. In other words, the fan motor 1
in this embodiment is an outer rotor type motor.
[0034] The impeller 12 is formed of resin. The impeller 12 in this
embodiment is formed of polybutylene terephthalate (PBT). Further,
the impeller 12 is formed in a roughly bottomed cylindrical shape
having a bottom part 12b abutting with an upper face of the bottom
part 15a of the rotor yoke 15. An outer peripheral face of the
impeller 12 is formed with a plurality of blades 12a formed in a
thin plate shape which are protruded on an outer side in the radial
direction. In this embodiment, eight blades 12a are formed on the
outer peripheral face of the impeller 12 with a substantially equal
angular pitch.
[0035] A center of the bottom part 12b of the impeller 12 is formed
with a step-shaped circular hole, which is structured of a large
diameter hole 12f formed in an upper portion and a small diameter
hole 12g whose diameter is smaller than the large diameter hole 12f
and which is formed at a portion located on the lower side of the
large diameter hole 12f, so as to penetrate in the axial direction.
As shown in FIG. 1, the large diameter hole 12f and the small
diameter hole 12g are concentrically formed with the rotation
center of the rotor part 4, i.e., the rotation shaft 13 as a
center. Further, the diameter of the small diameter hole 12g is set
to be substantially equal to a diameter of the engaging hole 15d
which is formed in the bottom part 15a of the rotor yoke 15. The
small diameter hole 12g of the impeller 12 in this embodiment is an
arrangement hole to which the protruded part 21b formed in the hub
21 is fitted.
[0036] A flat part 12h which is formed in a flat ring shape so as
to be substantially perpendicular to the axial direction is formed
in the radial direction between a peripheral face of the large
diameter hole 12f and a peripheral face of the small diameter hole
12g. In other words, the flat part 12h is formed in a ring shape
which protrudes on the inner side from the lower end of the large
diameter hole 12f in the radial direction, and the small diameter
hole 12g is formed at the center of the flat part 12h. In this
embodiment, the flat part 12h is a held part which is sandwiched
between and held by the rotor yoke 15 and the hub 21 in the axial
direction.
[0037] As shown in FIG. 4 and the like, a plurality of ribs 12d
which are protruded on inner sides in the radial direction and
formed in a substantially rectangular solid shape is formed on an
inner peripheral face 12c of a cylindrical part 12k of the impeller
12. Specifically, a plurality of the ribs 12d is formed on the
inner peripheral face 12c of the impeller 12 with a predetermined
interval in a circumferential direction over the entire region of
the cylindrical part 12k of the impeller 12 in the axial direction.
In this embodiment, eight ribs 12d are formed with a substantially
equal angular pitch so as to correspond to forming positions of the
blades 12a, i.e., on the inner sides of the blades 12a in the
radial direction. A thickness in the circumferential direction of
the rib 12d is roughly equal to a thickness of the blade 12a.
[0038] As shown in FIG. 4, radial ribs 12e which are formed in a
substantially rectangular solid shape and connected with the ribs
12d are formed on the lower face of the bottom part 12b of the
impeller 12 so as to protrude downward. Specifically, the radial
ribs 12e are radially formed from an upper end part of the rib 12d
formed on the inner peripheral face 12c of the impeller 12 to the
peripheral face of the small diameter hole 12g.
[0039] The hub 21 is, for example, formed of metal such as brass.
The hub 21 is provided with a circular plate part 21a, which is
formed in a circular plate shape and disposed on an upper side, and
the protruded part 21b whose diameter is smaller than the circular
plate part 21a and which is formed in a substantially cylindrical
shape and protruded downward from the circular plate part 21a.
Further, a fixing hole 21c to which the rotation shaft 13 is
press-fitted and fixed is formed at the center of the hub 21 so as
to penetrate in the axial direction.
[0040] An outer peripheral portion of the lower end of the
protruded part 21b is formed to be a projecting part 21d formed in
a cylindrical shape. Further, an abutting part 21e for abutting
with the upper face of the bearing 7 which is disposed on the upper
side is formed on an inner side of the projecting part 21d so as to
protrude toward the lower side. Specifically, the abutting part 21e
in a substantially cylindrical shape is formed at an edge of the
fixing hole 21c. In this embodiment, as shown in FIG. 1, the
abutting part 21e is protruded lower than the protruded part 21b.
The abutting part 21e is abutted with the bearing 7 to restrict
movement of the rotor part 4 in the axial direction. Further, the
projecting part 21d and the abutting part 21e are protruded lower
than the engaging hole 15d of the rotor yoke 15.
[0041] In this embodiment, the flat part 12h of the impeller 12 is
sandwiched between and held by the rotor yoke 15 and the hub 21 in
the axial direction and thus the impeller 12 is fixed to the rotor
yoke 15. In other words, the hub 21 has a function for fixing the
impeller 12 to the rotor yoke 15. Specifically, as shown in FIG. 1,
the circular plate part 21a is disposed in the large diameter hole
12f and the protruded part 21b is disposed in the small diameter
hole 12g and the engaging hole 15d. The flat part 12h is sandwiched
between and held by the lower face of the circular plate part 21a
abutting with the upper face of the flat part 12h and the upper
face of the bottom part 15a of the rotor yoke 15 abutting with the
lower face of the flat part 12h (specifically, the radial rib 12e)
and, as a result, the impeller 12 is fixed to the rotor yoke
15.
[0042] Further, in this embodiment, the rotor yoke 15 and the hub
21 are fixed to each other by caulking by utilizing the tip end of
the projecting part 21d and the edge part of the engaging hole 15d.
In other words, as shown in FIG. 1, the tip end of the projecting
part 21d which is disposed at the edge part of the engaging hole
15d is used as a caulking fixed part 21f for fixing the rotor yoke
15 to the hub 21 by caulking. Specifically, a portion of the
projecting part 21d which is protruded lower than the engaging hole
15d is the caulking fixed part 21f.
[0043] In addition, in this embodiment, the protruded part 21b is
lightly press-fitted to the small diameter hole 12g and the outer
peripheral face of the protruded part 21b is abutted with the
peripheral face of the small diameter hole 12g. In other words, in
this embodiment, the impeller 12 and the hub 21 are positioned each
other in the radial direction with the outer peripheral face of the
protruded part 21b and the peripheral face of the small diameter
hole 12g as references. Further, the protruded part 21b
(specifically, the projecting part 21d) is lightly press-fitted
into the engaging hole 15d and the outer peripheral face of the
protruded part 21b is abutted with the peripheral face of the
engaging hole 15d. In other words, in this embodiment, the rotor
yoke 15 and the hub 21 are positioned each other in the radial
direction with the outer peripheral face of the protruded part 21b
and the peripheral face of the engaging hole 15d as references. In
this embodiment, a slight gap space is formed between the outer
peripheral face of the circular plate part 21a and the peripheral
face of the large diameter hole 12f.
[0044] As shown in FIG. 1, the impeller 12 other than the bottom
part 12b is disposed on the outer peripheral side of the rotor yoke
15. In this embodiment, as shown in FIG. 3, the impeller 12 is
disposed on the outer peripheral side of the rotor yoke 15 in a
state that inner side ends 12m in the radial direction of the ribs
12d are abutted with the outer peripheral face 15e of the large
diameter cylindrical part 15c of the rotor yoke 15. Further, gap
spaces 17 are formed with a substantially equal angular pitch
between the inner peripheral face 12c of the impeller 12 and the
outer peripheral face 15e of the rotor yoke 15.
[0045] The bearing 7 abutting with the abutting part 21e is urged
upward by an urging force of the compression coil spring 10. In
other words, the hub 21 to which the rotation shaft 13 is fixed is
urged upward by the urging force of the compression coil spring 10.
Further, the retaining ring 16 abutting with the lower face of the
bearing 7 which is disposed on the lower side is fixed to the lower
end of the rotation shaft 13 and the upper face of the bearing 7
disposed on the lower side is abutted with the protruded part 6a of
the bearing holder 6. Therefore, coming-out of the rotation shaft
13 from the bearing 7 is prevented.
[0046] In the fan motor 1 structured as described above, firstly,
the rotation shaft 13 is press-fitted and fixed to the hub 21.
After that, the impeller 12 and the rotor yoke 15 are lightly
press-fitted to the protruded part 21b of the hub 21 and the rotor
yoke 15 and the hub 21 are fixed to each other by caulking. After
that, the drive magnet 14 is fixed on the inner peripheral face of
the rotor yoke 15 and then rotation balance of the rotor part 4 is
adjusted. In this embodiment, the outer peripheral face of the
rotor yoke 15 is shaved to adjust the rotation balance of the rotor
part 4. Specifically, two portions, i.e., the outer peripheral face
of the rotor yoke 15 near the lower end of the impeller 12 and the
outer peripheral face near the lower end of the rotor yoke 15 are
shaved to adjust rotation balance of the rotor part 4.
[0047] As described above, in this embodiment, the flat part 12h is
sandwiched between and held by the rotor yoke 15 and the hub 21 in
the axial direction and, in this manner, the impeller 12 is fixed
to the rotor yoke 15. Therefore, contacting area of the rotor yoke
15 with the flat part 12h and contacting area of the hub 21 with
the flat part 12h are comparatively increased. Therefore, a
frictional resistance between the rotor yoke 15 and the impeller 12
and a frictional resistance between the hub 21 and the impeller 12
are increased and thus a holding force of the rotor yoke 15 for the
impeller 12 can be enhanced.
[0048] Especially, in this embodiment, the hub 21 and the rotor
yoke 15 which sandwich and hold the flat part 12h are directly
fixed to each other by caulking. Therefore, a holding force for the
impeller 12 is increased effectively and thus the impeller 12 can
be held in a stable state.
[0049] Further, in this embodiment, the flat part 12h is sandwiched
between and held by the rotor yoke 15 and the hub 21 in the axial
direction and, in this manner, the impeller 12 is fixed to the
rotor yoke 15. Therefore, even when coefficient of thermal
expansion of the rotor yoke 15 is different from coefficient of
thermal expansion of the impeller 12, a difference of deformation
amounts at the time of thermal deformation can be relieved in the
radial direction.
[0050] Especially, in this embodiment, the ribs 12d are formed on
the inner peripheral face 12c of the impeller 12 and thus gap
spaces 17 are formed between the inner peripheral face 12c of the
impeller 12 and the outer peripheral face 15e of the rotor yoke 15.
Therefore, even when stress occurs in the impeller 12 due to a
centrifugal force, thermal expansion or the like occurred at the
time of high-speed rotation, the gap spaces 17 serve as a relief
part for the stress. Therefore, in this embodiment, even when the
fan motor 1 is rotated at a high speed or, even when the fan motor
1 is used under a high temperature situation, an excessive stress
which occurs in the impeller 12 can be relieved and cracking of the
impeller 12 can be restrained.
[0051] Further, in this embodiment, the rotor yoke 15 is formed in
a step-shaped cylindrical shape having the small diameter
cylindrical part 15b and the large diameter cylindrical part 15c,
and a gap space in the radial direction is formed between the outer
peripheral face of the small diameter cylindrical part 15b and the
inner side ends 12m in the radial direction of the ribs 12d in the
state that the impeller 12 is fixed to the rotor yoke 15.
Therefore, stress occurring in the impeller 12 due to a centrifugal
force, thermal expansion or the like occurred at the time of
high-speed rotation may be relieved by utilizing the gap space in
the radial direction.
[0052] In this embodiment, the abutting part 21e formed in the hub
21 is protruded lower than the projecting part 21d. Therefore, the
stator part does not abut with the caulking fixed part 21f and thus
damage of the caulking fixed part 12f caused by abutting with the
stator part 3 is prevented. Accordingly, the impeller 21 can be
surely held in a stable state by the rotor yoke 15 and the hub 21
which are fixed to each other by caulking.
[0053] In this embodiment, the hub 21 is formed of metal and the
rotation shaft 13 is press-fitted and fixed to the hub 21.
Therefore, concentricity of the rotation shaft 13 with the rotor
yoke 15 which are fixed to the hub 21 is easily enhanced.
[0054] In this embodiment, the protruded part 21b of the hub 21 is
lightly press-fitted to the engaging hole 15d of the rotor yoke 15
and abutted with the peripheral face of the engaging hole 15d.
Therefore, positioning of the rotor yoke 15 in the radial direction
can be easily performed by using a part of the hub 21 and thus
concentricity of the rotation shaft 13 that is press-fitted and
fixed to the hub 21 with the rotor yoke 15 is easily enhanced.
Accordingly, initial unbalanced quantity of the rotor part 4 can be
reduced. Further, in this embodiment, the protruded part 21b is
lightly press-fitted to the small diameter hole 12g of the impeller
12 and abutted with the peripheral face of the small diameter hole
12g. Therefore, the impeller 12 in the radial direction can be
easily positioned by using a part of the hub 21 and thus
concentricity of the rotation shaft 13 that is press-fitted and
fixed to the hub 21 with the impeller 12 is easily enhanced.
Accordingly, initial unbalanced quantity of the rotor part 4 can be
reduced.
[0055] In this embodiment, the ribs 12d are formed so as to
correspond to the forming positions of the blades 12a. Therefore,
shape of the impeller 12 including the blades 12a is stable.
[0056] Although the present invention has been shown and described
with reference to a specific embodiment, various changes and
modifications will be apparent to those skilled in the art from the
teachings herein.
[0057] In the embodiment described above, the hub 21 is provided
with the circular plate part 21a and the protruded part 21b.
However, for example, as shown in FIG. 6, the hub 21 may be
structured of only the circular plate part 21a. In this case, for
example, the hub 21 and the rotor yoke 15 are press-fitted to the
rotation shaft 13, and the flat part 12h of the impeller 12 is
sandwiched between and held by the hub 21 and the rotor yoke 15 in
the axial direction and, as a result, the impeller 12 is fixed to
the rotor yoke 15. Further, in this case, for example, the impeller
12 is lightly press-fitted to the rotation shaft 13. In FIG. 6, the
same notational symbol is used in the same structure as the
embodiment described above.
[0058] In the embodiment described above, the flat part 12h which
is sandwiched between and held by the hub 21 and the rotor yoke 15
over the entire circumference in the axial direction is formed in a
flat face shape substantially perpendicular to the axial direction.
However, the present invention is not limited to this embodiment.
For example, an inclined part whose upper face and/or lower face is
inclined in a direction perpendicular to the axial direction is
sandwiched between and held by the hub 21 and the rotor yoke 15 in
the axial direction.
[0059] In the embodiment described above, the protruded part 21b is
lightly press-fitted to the small diameter hole 12g and the outer
peripheral face of the protruded part 21b is abutted with the
peripheral face of the small diameter hole 12g. However, the
present invention is not limited to this embodiment. For example,
the protruded part 21b may be inserted into the small diameter hole
12g so that the outer peripheral face of the protruded part 21b is
abutted with the peripheral face of the small diameter hole 12g.
Further, in the embodiment described above, the protruded part 21b
is lightly press-fitted to the engaging hole 15d and the outer
peripheral face of the protruded part 21b is abutted with the
peripheral face of the engaging hole 15d. However, the protruded
part 21b may be inserted into the engaging hole 15d so that the
outer peripheral face of the protruded part 21b is abutted with the
peripheral face of the engaging hole 15d.
[0060] In the embodiment described above, the hub 21 is formed of
metal but the hub 21 may be formed of resin. When the hub 21 is
formed of metal, weight of the hub 21 which is disposed at the
center in the radial direction of the rotor part 4 is increased and
thus rotation balance of the rotor part 4 is enhanced. Therefore,
it is preferable that the hub 21 is formed of metal.
[0061] In the embodiment described above, a plurality of the ribs
12d protruding toward inner sides in the radial direction is formed
on the inner peripheral face 12c of the impeller 12. However, the
present invention is not limited to this embodiment. For example, a
plurality of ribs protruding toward outer sides in the radial
direction may be formed on the outer peripheral face 15e of the
rotor yoke 15 instead of the ribs 12d or in addition to the ribs
12d.
[0062] In the embodiment described above, eight ribs 12d are formed
on the inner sides in the radial direction of the blades 12a with a
substantially equal angular pitch. However, the present invention
is not limited to this embodiment. For example, a plurality of the
ribs 12d may be formed at positions shifted from the corresponding
inner sides in the radial direction to the blades 12a and may be
formed at a different angular pitch. Further, the number of the
ribs 12d is not limited to eight and the number may be more than 9
or may be 2 through 7.
[0063] In the embodiment described above, the rotation shaft 13 is
fixed to the hub 21 and the rotation shaft 13 is rotated together
with the impeller 12. However, the present invention is not limited
to this embodiment. For example, a fixed shaft is disposed in the
stator part 4 and the hub 21 may be rotatably supported by the
fixed shaft. In other words, the fan motor 1 described above is a
shaft rotatable type motor but the present invention may be applied
to a shaft fixed type motor.
[0064] While the description above refers to particular embodiments
of the present invention, it will be understood that many
modifications may be made without departing from the spirit
thereof. The accompanying claims are intended to cover such
modifications as would fall within the true scope and spirit of the
present invention.
[0065] The presently disclosed embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being indicated by the appended claims,
rather than the foregoing description, and all changes which come
within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein.
* * * * *