U.S. patent application number 13/780460 was filed with the patent office on 2014-03-27 for spindle motor and disk drive apparatus.
This patent application is currently assigned to NIDEC CORPORATION. The applicant listed for this patent is NIDEC CORPORATION. Invention is credited to Yuichi SHIGEMATSU, Takunori SHINAO.
Application Number | 20140085749 13/780460 |
Document ID | / |
Family ID | 50338594 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140085749 |
Kind Code |
A1 |
SHINAO; Takunori ; et
al. |
March 27, 2014 |
SPINDLE MOTOR AND DISK DRIVE APPARATUS
Abstract
A spindle motor includes a stationary portion and a rotating
portion. The stationary portion includes a shaft and an upper
annular member. The rotating portion includes a sleeve. The shaft
includes an annular or substantially annular upper shaft recessed
portion recessed radially inward from an outside surface of the
shaft. The upper shaft recessed portion is arranged opposite to an
inside surface of a hole of the upper annular member. An adhesive
is arranged in a gap defined between the upper shaft recessed
portion and the inside surface of the hole of the upper annular
member.
Inventors: |
SHINAO; Takunori; (Kyoto,
JP) ; SHIGEMATSU; Yuichi; (Kyoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIDEC CORPORATION |
Kyoto |
|
JP |
|
|
Assignee: |
NIDEC CORPORATION
Kyoto
JP
|
Family ID: |
50338594 |
Appl. No.: |
13/780460 |
Filed: |
February 28, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61705264 |
Sep 25, 2012 |
|
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|
Current U.S.
Class: |
360/99.08 ;
310/90 |
Current CPC
Class: |
F16C 17/105 20130101;
H02K 5/1677 20130101; H02K 7/086 20130101; G11B 19/2036
20130101 |
Class at
Publication: |
360/99.08 ;
310/90 |
International
Class: |
H02K 7/08 20060101
H02K007/08 |
Claims
1. A spindle motor comprising: a stationary portion including a
stator; and a rotating portion including a rotor magnet, and
rotatably supported through a lubricating oil; wherein the
stationary portion includes: a shaft centered on a central axis
extending in a vertical direction; and an upper annular member
arranged on an axially upper portion of the shaft, and including a
hole through which the shaft is inserted; the rotating portion
includes a sleeve including a central hole through which the shaft
is inserted; the shaft includes a substantially annular upper shaft
recessed portion defined in an outside surface of the shaft,
arranged opposite to an inside surface of the hole of the upper
annular member, and recessed radially inward from the outside
surface; the lubricating oil is arranged to cover an inside surface
of the central hole, the outside surface of the shaft, and a
circumference of the upper annular member; and an adhesive is
arranged in a gap defined between the upper shaft recessed portion
and the inside surface of the hole of the upper annular member.
2. The spindle motor according to claim 1, wherein a surface of the
adhesive is arranged at an axial height lower than an axial height
of an axially upper end of the upper annular member.
3. The spindle motor according to claim 1, wherein the axially
upper end of the upper annular member is positioned axially higher
than a surface of the adhesive.
4. The spindle motor according to claim 1, wherein the adhesive is
arranged to extend all a way around a circumference of the upper
shaft recessed portion in the gap.
5. The spindle motor according to claim 1, wherein an axially upper
end portion of the upper annular member includes an upper tapered
surface inclined with respect to the central axis; the upper
tapered surface is arranged radially opposite the upper shaft
recessed portion; and a junction of the upper tapered surface with
an inside surface of the upper annular member is arranged at an
axial height lower than an axial height of a surface of the
adhesive.
6. The spindle motor according to claim 5, wherein a radial
distance between the central axis and the upper tapered surface is
arranged to gradually increase with increasing height; and the
upper tapered surface is arranged to extend all a way around an
inner circumference of the axially upper end portion of the upper
annular member.
7. The spindle motor according to claim 1, wherein the upper shaft
recessed portion includes: an upper first axial side surface; an
upper second axial side surface arranged on an axially lower side
of the upper first axial side surface; and a radial bottom portion
arranged to join the upper first axial side surface and the upper
second axial side surface to each other.
8. The spindle motor according to claim 7, wherein an angle defined
between the central axis and the upper first axial side surface is
arranged to be equal to an angle defined between the central axis
and the upper second axial side surface.
9. The spindle motor according to claim 7, wherein the outside
surface of the shaft includes an upper first outside diameter
portion arranged to connect with an end portion of the upper second
axial side surface.
10. The spindle motor according to claim 9, wherein the upper first
outside diameter portion is a portion of the shaft where an outside
diameter of the shaft is arranged to be substantially constant.
11. The spindle motor according to claim 9, wherein the outside
surface of the shaft includes an upper second outside diameter
portion arranged on an axially lower side of the upper first
outside diameter portion, and arranged to connect with the upper
first outside diameter portion; and a radial distance between the
central axis and the upper second outside diameter portion is
arranged to gradually increase with decreasing height.
12. The spindle motor according to claim 11, wherein an outside
diameter of the shaft in the upper first outside diameter portion
is arranged to be equal or substantially equal to a minimum outside
diameter of the shaft in the upper second outside diameter
portion.
13. The spindle motor according to claim 11, wherein an axial
length of the upper first outside diameter portion is arranged to
be shorter than an axial length of the upper second outside
diameter portion.
14. The spindle motor according to claim 11, wherein the outside
surface of the shaft includes an upper third outside diameter
portion arranged to connect with the upper second outside diameter
portion; and an outside diameter of the shaft is arranged to be
substantially constant in the third outside diameter portion.
15. The spindle motor according to claim 14, wherein a maximum
outside diameter of the shaft in the second outside diameter
portion is arranged to be equal or substantially equal to the
outside diameter of the shaft in the upper third outside diameter
portion.
16. The spindle motor according to claim 1, wherein the upper
annular member includes an upper third inclined surface inclined
with respect to the central axis in an axially lower end portion of
an inside surface of the upper annular member; the upper third
inclined surface is arranged opposite to the outside surface of the
shaft with a gap intervening therebetween; and the adhesive is
arranged in a gap defined between the upper third inclined surface
and the outside surface of the shaft.
17. The spindle motor according to claim 16, wherein the adhesive
is arranged to extend all a way around a circumference of the shaft
in the gap defined between the upper third inclined surface and the
outside surface of the shaft.
18. The spindle motor according to claim 1, wherein the upper
annular member is substantially tubular; and the upper annular
member includes: an upper first inclined surface arranged in an
axially lower portion of an outside surface of the upper annular
member, and inclined with respect to the central axis; and an upper
second inclined surface arranged in an axially upper portion of the
outside surface of the upper annular member, and inclined with
respect to the central axis.
19. The spindle motor according to claim 1, wherein the shaft is
press fitted to the upper annular member.
20. The spindle motor according to claim 19, wherein the adhesive
is arranged between the inside surface of the hole of the upper
annular member and the outside surface of the shaft.
21. The spindle motor according to claim 1, wherein the stationary
portion further includes a lower annular member arranged on an
axially lower portion of the shaft, and including a hole through
which the shaft is inserted; the shaft includes a substantially
annular lower shaft recessed portion defined in the outside surface
of the shaft, arranged opposite to an inside surface of the hole of
the lower annular member, and recessed radially inward from the
outside surface; and an adhesive is arranged in a gap defined
between the lower shaft recessed portion and the inside surface of
the hole of the lower annular member.
22. The spindle motor according to claim 21, wherein a surface of
the adhesive is arranged at an axial height higher than an axial
height of an axially lower end of the lower annular member.
23. The spindle motor according to claim 21, wherein an axially
lower end of the lower annular member is positioned axially lower
than a surface of the adhesive.
24. The spindle motor according to claim 21, wherein the adhesive
is arranged to extend all a way around a circumference of the lower
shaft recessed portion in the gap defined between the lower shaft
recessed portion and the inside surface of the hole of the lower
annular member.
25. A disk drive apparatus comprising the spindle motor of claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a spindle motor and more
specifically to a disk drive apparatus using the spindle motor.
[0003] 2. Description of the Related Art
[0004] Some known motors of disk drive apparatuses include bearing
mechanisms using fluid dynamic pressure. In some spindle motors
(hereinafter referred to simply as "motors"), a gap is defined
between an annular member fixed to a shaft portion and a sleeve
portion of a rotating portion positioned below the annular member.
In some such motors, a seal portion having a surface of a
lubricating oil defined therein is defined around the annular
member. The seal portion is, for example, covered with a cap member
fixed to the annular member.
[0005] When the annular member is press fitted to the shaft portion
during assemblage of the motor, an outer circumferential surface of
the shaft portion or an inner circumferential surface of the
annular member may become flawed. If a flaw occurs, the lubricating
oil in the gap defined between the annular member and the sleeve
portion may leak upwardly out of the annular member through the
flaw. Therefore, an operation of sealing a gap between the annular
member and the shaft portion is required. Accordingly, there is a
demand for a structure designed to easily prevent the lubricating
oil from leaking out through the gap between the annular member and
the shaft portion.
SUMMARY OF THE INVENTION
[0006] A spindle motor according to preferred embodiments of the
present invention includes a stationary portion including a stator;
and a rotating portion including a rotor magnet, and rotatably
supported through a lubricating oil. The stationary portion
includes a shaft and an upper annular member. The shaft is centered
on a central axis extending in a vertical direction. The upper
annular member is arranged on an axially upper portion of the
shaft, and includes a hole through which the shaft is inserted. The
rotating portion includes a sleeve including a central hole through
which the shaft is inserted.
[0007] The shaft includes a annular or substantially annular upper
shaft recessed portion. The upper shaft recessed portion is defined
in an outside surface of the shaft, is arranged opposite to an
inside surface of the hole of the upper annular member, and is
recessed radially inward from the outside surface of the shaft.
[0008] The lubricating oil is arranged over an inside surface of
the central hole, the outside surface of the shaft, and a
circumference of the upper annular member.
[0009] An adhesive is arranged in a gap defined between the upper
shaft recessed portion and the inside surface of the hole of the
upper annular member.
[0010] 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
[0011] FIG. 1 is a cross-sectional view of a motor according to a
preferred embodiment of the present invention.
[0012] FIG. 2 is a cross-sectional view of a bearing and an
adjacent area according to a preferred embodiment of the present
invention.
[0013] FIG. 3 is a cross-sectional view of a shaft according to a
preferred embodiment of the present invention.
[0014] FIG. 4 is an enlarged view of a portion of an outside
surface of the shaft according to a preferred embodiment of the
present invention.
[0015] FIG. 5 is an enlarged view of a portion of the outside
surface of the shaft according to a preferred embodiment of the
present invention.
[0016] FIG. 6 is an enlarged view of a portion of the bearing and
an adjacent area according to a preferred embodiment of the present
invention.
[0017] FIG. 7 is an enlarged view of a portion of the bearing and
an adjacent area according to a preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] It is assumed herein that an upper side and a lower side
along a central axis of a motor in FIG. 1 are referred to simply as
an "upper side" and a "lower side", respectively. It should be
noted, however, that the above definitions of the upper and lower
sides are not meant to indicate relative positions or directions of
different members or portions when they are actually installed in a
device. Also note that a direction parallel or substantially
parallel to the central axis is referred to by the term "axial
direction", "axial", or "axially", that radial directions centered
on the central axis are simply referred to by the term "radial
direction", "radial", or "radially", and that a circumferential
direction about the central axis is simply referred to by the term
"circumferential direction", "circumferential", or
"circumferentially".
[0019] FIG. 1 is a cross-sectional view of a spindle motor 1
according to a preferred embodiment of the present invention. In
the following description, the spindle motor 1 will be referred to
simply as the motor 1. The motor 1 is preferably used in a disk
drive apparatus (for example, a hard disk drive apparatus) or the
like. The disk drive apparatus preferably includes the motor 1, a
housing, at least one disk, an access portion, a connector, and so
on. The disk(s) is attached to the motor 1. The access portion is
arranged to perform at least one of reading and writing of
information from or to the disk(s). A base portion 21 defines a
portion of the housing together with a cover member. The housing is
arranged to contain the motor 1, the disk(s), the access portion,
and so on.
[0020] As illustrated in FIG. 1, the motor 1 is preferably an
outer-rotor motor. The motor 1 according to the present preferred
embodiment is preferably a three-phase motor, having three phases,
i.e., a U phase, a V phase, and a W phase. The motor 1 preferably
includes a stationary portion 2, which is a stationary assembly, a
rotating portion 3, which is a rotating assembly, and a fluid
dynamic bearing mechanism (hereinafter referred to as a "bearing
mechanism 4"). The rotating portion 3 is supported by the bearing
mechanism 4 such that the rotating portion 3 is rotatable about a
central axis J1 of the motor 1 with respect to the stationary
portion 2.
[0021] The stationary portion 2 preferably includes the base
portion 21, an annular stator 22, a circuit board 14, and a shaft
7. The base portion 21 is preferably a substantially plate-shaped
member. The base portion 21 includes a first recessed portion 211
arranged to be recessed axially downward. A bottom portion of the
first recessed portion 211 is arranged at an axial height lower
than an axial height of an upper surface of the base portion 21.
The base portion 21 includes a substantially cylindrical tubular
portion 212. The tubular portion 212 is arranged radially inside
the first recessed portion 211, and is arranged to extend axially
upward. The tubular portion 212 includes a first through hole 2121
passing therethrough in an axial direction.
[0022] The shaft 7 is substantially columnar. The shaft 7 is
inserted into the first through hole 2121 of the tubular portion
212. The shaft 7 is fixed to the tubular portion 212 preferably
through, for example, press fitting, adhesion, or the like. In
other words, the shaft 7 is fixed to the base portion 21.
[0023] The stator 22 preferably includes a stator core 221 and
coils 222. The coils 222 are arranged on the stator core 221. In
the stator 22, a plurality of lead wires 50 are drawn out of the
coils 222 of the U, V, and W phases. Each of the plurality of lead
wires 50 is electrically connected to the circuit board 14. Each
lead wire 50 is preferably connected to the circuit board 14 by
soldering, for example. In the present preferred embodiment, the
number of lead wires 50 is three. The circuit board 14 may include
a connector or the like.
[0024] The stator core 221 includes a core back (not shown) and a
plurality of teeth (not shown). The stator core is defined, for
example, by a plurality of electromagnetic steel sheets placed one
upon another. The core back is annular and centered on the central
axis J1. The core back is arranged in the shape of a tube extending
in the axial direction. The teeth are arranged to extend radially
outward from an outside surface of the core back. Each of the teeth
includes a winding portion and a tip portion. A conducting wire is
wound around the winding portion to define the coil 222. The tip
portion is arranged to extend to both sides in a circumferential
direction from an outer edge portion of the winding portion.
[0025] At least a portion of the tubular portion 212 is inserted in
a hole of the core back. In more detail, an axially upper top
portion of the tubular portion 212 is inserted in a hole defined by
an inside surface of the core back. The inside surface of the core
back is arranged radially opposite at least a portion of an outside
surface of the tubular portion. The stator core 221 is preferably
fixed to the tubular portion 212 through, for example, press
fitting, adhesion, or the like.
[0026] As illustrated in FIG. 1, the rotating portion 3 preferably
includes a rotor hub 31, a rotor magnet 321, and a yoke 322. The
rotor hub 31 preferably includes a hub body 311, a cylindrical
portion 312, and an annular disk mount portion 313. The hub body
311 is preferably substantially in the shape of a plate. The hub
body 311 preferably includes a plurality of fitting holes 3111.
When the disk drive apparatus is assembled, a top cover of a case
is fixed to the hub body 311 through fixing members, such as, for
example, screws, pins, small screws, bolts, or the like. That is,
the fixing members are inserted into the fitting holes. In
addition, the hub body 311 includes a bearing holding hole 3112
passing through the hub body 311 in the axial direction. A sleeve
41, which will be described below, is inserted into the bearing
holding hole 3112 and held therein. The sleeve 41 is fixed to the
bearing holding hole 3112 preferably through, for example, press
fitting, an adhesive, or the like. Moreover, the shaft 7 is passed
through the bearing holding hole 3112 through the sleeve 41. An
axially upper end portion of the shaft 7 is positioned at an axial
height higher than an axial height of an opening end portion of the
bearing holding hole 3112.
[0027] The cylindrical portion 312 is arranged to project downward
from an outer edge portion of the hub body 311. The disk mount
portion 313 is arranged to extend radially outward from a lower
portion of the cylindrical portion 312. The disk is mounted on the
disk mount portion 313. The rotor magnet 321 is preferably annular
or substantially annular and centered on the central axis J1. The
yoke 322, which is tubular and made of, for example, a metal, is
arranged radially inside the cylindrical portion 312. An axially
lower surface of the hub body 311 includes a groove 3113 recessed
axially upward defined therein. The groove 3113 is defined in an
annular shape. The yoke is held in the groove 3113 of the hub body
311. The rotor magnet 321 is arranged inside the cylindrical
portion 312, and is arranged radially inward of the yoke 322. The
disk mount portion 313 is positioned radially outside a lower
portion of the rotor magnet 321. A lower end projecting portion
3131 extending axially downward is arranged in a radially outer
portion of the disk mount portion 313. The lower end projecting
portion 3131 is preferably annular or substantially annular. An
inside surface of the first recessed portion 211 is arranged
radially opposite an outside surface of the lower projecting
portion 3131. The rotor magnet 321 is arranged radially outside the
stator 22. In the motor 1, a torque is produced between the rotor
magnet 321 and the stator 22. This enables the rotating portion 3
to rotate relative to the stationary portion 2.
[0028] Note that a substantially annular balancing ring may be
arranged on an inside surface of the lower projecting portion 3131
id so desired. This makes it possible to correct any unbalance in
the rotating portion 3 during a process of assembling the motor
1.
[0029] FIG. 2 is a cross-sectional view of the bearing mechanism 4
and an adjacent area. FIG. 3 is a cross-sectional view of the shaft
7. As illustrated in FIGS. 1 and 2, the bearing mechanism 4 is a
fluid dynamic bearing. The bearing mechanism 4 preferably includes
a lubricating oil, the sleeve 41, an upper cone member 42, and a
lower cone member 43. The sleeve 41 is preferably a substantially
cylindrical member. The sleeve is preferably made, for example, of
stainless steel. The sleeve 41 includes a central hole 411 passing
through the sleeve 41 in a vertical direction. The shaft 7 is
passed through the central hole 411. The lubricating oil travels
over an inside surface of the central hole 411, an outside surface
of the shaft, a circumference of the upper cone member 42, a
circumference of the lower cone member 43, and so on. The sleeve 41
is able to support the shaft 7. When the rotating portion 3 rotates
with respect to the stationary portion 2, the sleeve 41 rotates
relative to the shaft 7 with the lubricating oil intervening
therebetween.
[0030] A sleeve upper inclined surface 4111 is preferably arranged
in an axially upper portion of the inside surface defining the
central hole 411. The sleeve upper inclined surface 4111 is
inclined with respect to the central axis J1. The radial distance
between the sleeve upper inclined surface 4111 and the central axis
J1 gradually increases with increasing height. The axially upper
end portion of the shaft 7 is arranged at an axial height higher
than an axial height of the sleeve upper inclined surface 4111.
[0031] A sleeve lower inclined surface 4112 is preferably arranged
in an axially lower portion of the inside surface defining the
central hole 411. The sleeve lower inclined surface is inclined
with respect to the central axis J1. The radial distance between
the sleeve lower inclined surface 4112 and the central axis J1
gradually increases with decreasing height. An axially lower end
portion of the shaft 7 is arranged at an axial height lower than an
axial height of the sleeve lower inclined surface 4112.
[0032] The upper cone member 42, which is an exemplary upper
annular member, is arranged on an axially upper portion of the
shaft 7. The upper cone member 42 is a substantially tubular
member. An upper first inclined surface 421, which is inclined with
respect to the central axis J1, is arranged in an axially lower
portion of an outside surface of the upper cone member 42. The
radial distance between the upper first inclined surface 421 and
the central axis J1 gradually increases with increasing height. The
upper first inclined surface 421 is arranged opposite to the sleeve
upper inclined surface 4111.
[0033] An upper second inclined surface 422, which is inclined with
respect to the central axis J1, is arranged in an axially upper
portion of the outside surface of the upper cone member 42. The
radial distance between the upper second inclined surface 422 and
the central axis J1 gradually decreases with increasing height.
[0034] The upper cone member 42 includes an upper communicating
hole 423. The upper communicating hole 423 is arranged to provide
communication between the upper second inclined surface 422 and an
inside surface of the upper cone member 42. A direction in which an
inside surface defining the upper communicating hole 423 extends is
preferably parallel or substantially parallel to the upper first
inclined surface 421. The direction in which the inside surface
defining the upper communicating hole 423 extends is preferably
parallel or substantially parallel to the sleeve upper inclined
surface 4111. The cross-sectional area of an opening end portion of
the upper communicating hole 423 on the upper second inclined
surface is arranged to be smaller than the cross-sectional area of
an opening end portion of the upper communicating hole 423 on the
inside surface of the upper cone member 42.
[0035] An upper first inner recessed portion 424 extending in the
circumferential direction is arranged in the inside surface of the
upper cone member 42. An upper second inner recessed portion 425 is
arranged in the inside surface of the upper cone member 42 on an
axially lower side of the upper first inner recessed portion 424.
The upper second inner recessed portion 425 extends in the
circumferential direction. A direction in which the upper first
inner recessed portion 424 extends is parallel or substantially
parallel to a direction in which the upper second inner recessed
portion 425 extends.
[0036] The lower cone member 43, which is an exemplary lower
annular member, is arranged on an axially lower portion of the
shaft 7. The lower cone member 43 is preferably a substantially
tubular member. A lower first inclined surface 431, which is
inclined with respect to the central axis J1, is preferably
arranged in an axially upper portion of an outside surface of the
lower cone member 43. The radial distance between the lower first
inclined surface 431 and the central axis J1 gradually increases
with decreasing height. The lower first inclined surface 431 is
arranged opposite to the sleeve lower inclined surface 4112.
[0037] A lower second inclined surface 432, which is inclined with
respect to the central axis J1, is preferably arranged in an
axially lower portion of the outside surface of the lower cone
member 43. The radial distance between the lower second inclined
surface 432 and the central axis J1 gradually decreases with
decreasing height.
[0038] The lower cone member 43 preferably includes a lower
communicating hole 433. The lower communicating hole 433 is
arranged to provide communication between the lower second inclined
surface 432 and an inside surface of the lower cone member 43. A
direction in which an inside surface defining the lower
communicating hole 433 extends is preferably parallel or
substantially parallel to the lower first inclined surface 431. The
direction in which the inside surface defining the lower
communicating hole 433 extends is preferably parallel or
substantially parallel to the sleeve lower inclined surface 4112.
The cross-sectional area of an opening end portion of the lower
communicating hole 433 on the lower second inclined surface 432 is
arranged to be smaller than the cross-sectional area of an opening
end portion of the lower communicating hole 433 on the inside
surface of the lower cone member 43.
[0039] A lower first inner recessed portion 434 extending in the
circumferential direction is preferably arranged in the inside
surface of the lower cone member 43. A lower second inner recessed
portion 435 is preferably arranged in the inside surface of the
lower cone member 43 on an axially upper side of the lower first
inner recessed portion 434. The lower second inner recessed portion
435 extends in the circumferential direction. A direction in which
the lower first inner recessed portion 434 extends is parallel or
substantially parallel to a direction in which the lower second
inner recessed portion 435 extends.
[0040] An upper cap member 81 is arranged on an axially upper end
surface of the sleeve 41. The upper cap member 81 is a
substantially cylindrical member. The upper cap member 81
preferably includes an upper cover portion 811, an upper flange
portion 812, and an upper joining portion 813. The upper cover
portion 811 is substantially in the shape of a plate, and includes,
at its center, an upper shaft through hole 8111 through which the
shaft 7 is passed. An inside surface of the upper shaft through
hole 8111 is arranged opposite to the outside surface of the shaft
7 with a gap intervening therebetween. The upper cover portion 811
further includes an upper small through hole 8112. The upper small
through hole 8112 passes through the upper cover portion 811 in the
axial direction. When the motor 1 is assembled, the lubricating oil
is injected into the bearing mechanism 4 through the upper small
through hole 8112.
[0041] The upper joining portion 813 is arranged to extend radially
outward from the upper cover portion 811. The upper joining portion
813 is inclined with respect to the central axis J1. The radial
distance between the central axis J1 and the upper joining portion
813 gradually increases with decreasing height.
[0042] The upper flange portion 812 connects with a radially outer
end portion of the upper joining portion 813. An annular upper
shoulder portion 412 is arranged in the axially upper end surface
of the sleeve 41. Further, an upper groove 413 extending in the
circumferential direction is arranged in the upper shoulder portion
412. The upper flange portion 812 is arranged both axially and
radially opposite an axially upper end portion of the sleeve 41.
The upper flange portion 812 is preferably arranged on the upper
shoulder portion 412 through, for example, an adhesive. The
adhesive enters into the upper groove 413. An upper recessed
portion 8121 extending in the circumferential direction is arranged
on an axially upper side of the upper flange portion 812. This
reduces a stress at a junction of the upper joining portion 813
with the upper flange portion 812.
[0043] A lower cap member 82 is arranged on an axially lower end
surface of the sleeve 41. The lower cap member 82 is a
substantially cylindrical member. The lower cap member 82
preferably includes a lower cover portion 821, a lower flange
portion 822, and a lower joining portion 823. The lower cover
portion 821 is substantially in the shape of a plate, and includes,
at its center, a lower shaft through hole 8211 through which the
shaft 7 is passed. An inside surface of the lower shaft through
hole 8211 is arranged opposite to the outside surface of the shaft
7 with a gap intervening therebetween. The lower joining portion
823 is arranged to extend radially outward from the lower cover
portion 821. Further, the lower cover portion 821 includes a lower
small through hole 8212. The lower small through hole 8212 passes
through the lower cover portion 821 in the axial direction. When
the motor 1 is assembled, the lubricating oil is injected through
the lower small through hole 8212.
[0044] The lower joining portion 823 is inclined with respect to
the central axis J1. The radial distance between the central axis
J1 and the lower joining portion 823 gradually decreases with
decreasing height. The lower flange portion 822 connects with a
radially outer end portion of the lower joining portion 823. An
annular lower shoulder portion 414 is arranged in an axially lower
end surface of the sleeve 41. Further, a lower groove 415 extending
in the circumferential direction is preferably arranged in the
lower shoulder portion 414. The lower flange portion 822 is
arranged both axially and radially opposite an axially lower end
portion of the sleeve 41. The lower flange portion 822 is arranged
on the lower shoulder portion 414 preferably through, for example,
an adhesive. The adhesive enters into the lower groove 415. A lower
recessed portion 8221 extending in the circumferential direction is
arranged on an axially lower side of the lower flange portion 822.
This reduces a stress at a junction of the lower joining portion
823 with the lower flange portion 822.
[0045] As illustrated in FIGS. 1, 2, and 3, an upper shaft recessed
portion 71, which is recessed radially inward, is arranged in an
outside surface of the axially upper end portion of the shaft 7.
The upper shaft recessed portion 71 is substantially annular and
extends in the circumferential direction. A hole into which a
fixing member is inserted is preferably arranged in the axially
upper end portion of the shaft 7. When the disk drive apparatus has
been assembled, the cover of the case is fixed to the shaft 7
through the fixing member. A screw, a small screw, a pin, a bolt,
or the like, for example, is preferably used as the fixing
member.
[0046] FIG. 4 is a partial enlarged view of the upper shaft
recessed portion 71. As illustrated in FIG. 4, the upper shaft
recessed portion 71 preferably includes an upper first axial side
surface 711, an upper second axial side surface 712, and a radial
bottom portion 713. The upper first axial side surface 711 is
inclined with respect to the central axis J1. The upper first axial
side surface 711 connects with the radial bottom portion 713. The
radial bottom portion 713 connects with the upper second axial side
surface 712. The upper second axial side surface 712 is arranged
axially opposite the upper first axial side surface 711. The upper
second axial side surface 712 is inclined with respect to the
central axis J1. An angle .theta.1 defined between the central axis
J1 and the upper first axial side surface 711 is preferably
arranged to be equal or substantially equal to an angle .theta.2
defined between the central axis J1 and the upper second axial side
surface 712.
[0047] Note that the angle .theta.1 defined between the central
axis J1 and the upper first axial side surface 711 and the angle
.theta.2 defined between the central axis J1 and the upper second
axial side surface 712 may be different from each other.
[0048] The outside surface of the shaft 7 preferably includes an
upper first outside diameter portion 72 connecting with an end
portion of the upper second axial side surface 712. The upper first
outside diameter portion 72 is a portion of the shaft 7 where the
outside diameter of the shaft 7 is arranged to be substantially
constant.
[0049] The outside surface of the shaft 7 includes an upper second
outside diameter portion 73 arranged on an axially lower side of
the upper first outside diameter portion 72. The upper second
outside diameter portion 73 connects with the upper first outside
diameter portion 72. The radial distance between the central axis
J1 and the upper second outside diameter portion 73 (i.e., the
outside diameter) is arranged to vary with increasing or decreasing
height. In more detail, the radial distance between the central
axis J1 and the upper second outside diameter portion 73 is
arranged to gradually increase with decreasing height. The outside
diameter of the shaft 7 in the upper first outside diameter portion
72 is preferably equal or substantially equal to a minimum outside
diameter of the shaft 7 in the upper second outside diameter
portion 73. The axial length of the upper first outside diameter
portion 72 is arranged to be shorter than the axial length of the
upper second outside diameter portion 73.
[0050] The outside surface of the shaft 7 preferably includes an
upper third outside diameter portion 74 connecting with the upper
second outside diameter portion 73. The outside diameter of the
shaft 7 is preferably arranged to be substantially constant in the
upper third outside diameter portion 74. A maximum outside diameter
of the shaft 7 in the upper second outside diameter portion 73 is
preferably equal or substantially equal to the outside diameter of
the shaft 7 in the upper third outside diameter portion 74.
[0051] As illustrated in FIGS. 3 and 5, a lower shaft recessed
portion 75, which is recessed radially inward, is preferably
arranged in an outside surface of the axially lower end portion of
the shaft 7. A hole into which a fixing member can be inserted is
also preferably arranged in the axially lower end portion of the
shaft 7, as in the axially upper end portion of the shaft 7.
[0052] The lower shaft recessed portion 75 preferably includes a
lower first axial side surface 751, a lower second axial side
surface 752, and a lower radial bottom portion 753. The lower first
axial side surface 751 is inclined with respect to the central axis
J1. The lower first axial side surface 751 connects with the lower
radial bottom portion 753. The lower radial bottom portion 753
connects with the lower second axial side surface 752. The lower
second axial side surface 752 is arranged axially opposite the
lower first axial side surface 751. The lower second axial side
surface 752 is inclined with respect to the central axis J1. An
angle defined between the central axis J1 and the lower first axial
side surface 751 is equal to the angle .theta.1 defined between the
central axis J1 and the upper first axial side surface 711. An
angle defined between the central axis J1 and the lower second
axial side surface 752 is equal to the angle .theta.2 defined
between the central axis J1 and the upper second axial side surface
712.
[0053] Note that the angle defined between the central axis J1 and
the lower first axial side surface 751, the angle defined between
the central axis J1 and the upper first axial side surface 711, the
angle defined between the central axis J1 and the lower second
axial side surface 752, and the angle .theta.2 defined between the
central axis J1 and the upper second axial side surface 712 may be
different from one another, or any pair of the above angles may be
the same.
[0054] The outside surface of the shaft 7 preferably includes a
lower first outside diameter portion 76 connecting with an end
portion of the lower second axial side surface 752. The lower first
outside diameter portion 76 is a portion of the shaft 7 where the
outside diameter of the shaft 7 is arranged to be substantially
constant.
[0055] The outside surface of the shaft 7 preferably includes a
lower second outside diameter portion 77 arranged on an axially
upper side of the lower first outside diameter portion 76. The
lower second outside diameter portion 77 connects with the lower
first outside diameter portion 76. The radial distance between the
central axis J1 and the lower second outside diameter portion 77
(i.e., the outside diameter) is arranged to vary with increasing or
decreasing height. In more detail, the radial distance between the
central axis J1 and the lower second outside diameter portion 77 is
arranged to gradually increase with increasing height. The outside
diameter of the shaft 7 in the lower first outside diameter portion
76 is preferably equal or substantially equal to a minimum outside
diameter of the shaft 7 in the lower second outside diameter
portion 77.
[0056] The outside surface of the shaft 7 preferably includes a
lower third outside diameter portion 78 connecting with the lower
second outside diameter portion 77. The outside diameter of the
shaft 7 is preferably arranged to be constant or substantially
constant in the lower third outside diameter portion 78. A maximum
outside diameter of the shaft 7 in the lower second outside
diameter portion 77 is substantially equal to the outside diameter
of the shaft 7 in the upper third outside diameter portion 78.
[0057] Note that the outside diameter in the upper third outside
diameter portion 74 and the outside diameter in the lower third
outside diameter portion 78 may be either the same or different
from each other.
[0058] FIG. 6 is an enlarged view of a portion of the bearing
mechanism 4 and an adjacent area. As illustrated in FIGS. 1, 2, and
6, the upper shaft recessed portion 71 is arranged radially
opposite an axially upper end portion of the upper cone member 42.
The inside diameter of the upper cone member 42 is arranged to be
smaller than the outside diameter of the shaft 7. Therefore, the
upper cone member 42 is preferably fixed to the shaft 7 through,
for example, press fitting once the shaft 7 is inserted into a hole
of the upper cone member 42 during assemblage of the motor 1.
[0059] Moreover, an adhesive is preferably previously applied to an
inside surface of the hole of the upper cone member 42 or the
outside surface of the shaft 7 during the assemblage of the motor
1. The shaft 7 is thereafter, for example, press fitted into the
hole of the upper cone member 42. Accordingly, at least a portion
of the adhesive is arranged between the inside surface of the hole
of the upper cone member 42 and the outside surface of the shaft 7.
That is, the upper cone member 42 is fixed to the shaft 7 through
adhesion as well.
[0060] In a process of inserting the shaft 7 into the hole of the
upper cone member 42 in accordance with a preferred embodiment of
the present invention, a portion of the adhesive arranged between
the outside surface of the shaft 7 and the inside surface of the
hole of the upper cone member 42 travels axially upward or axially
downward along the outside surface of the shaft 7 or the inside
surface of the hole of the upper cone member 42.
[0061] As illustrated in FIG. 6, at least a portion of a portion of
the adhesive which has traveled axially upward is arranged in a gap
defined between the upper shaft recessed portion 71 and the inside
surface of the hole of the upper cone member 42. In the gap between
the upper shaft recessed portion 71 and the upper cone member 42, a
surface of the adhesive A is preferably arranged at an axial height
lower than an axial height of an axially upper end of the upper
cone member 42. In other words, the axially upper end of the upper
cone member 42 is positioned higher than the surface of the
adhesive A. Note that the adhesive is preferably arranged to extend
all the way around a circumference of the upper shaft recessed
portion 71 in the above gap.
[0062] Note that the axially upper end portion of the upper cone
member 42 preferably includes an upper tapered surface 426 which is
inclined with respect to the central axis J1. The upper tapered
surface 426 is arranged radially opposite the upper shaft recessed
portion 71. The radial distance between the central axis J1 and the
upper tapered surface 426 is arranged to gradually increase with
increasing height. Furthermore, the upper tapered surface 426 is
preferably arranged to extend all the way around an inner
circumference of the axially upper end portion of the upper cone
member 42.
[0063] Furthermore, a junction of the upper tapered surface 426
with the inside surface of the upper cone member 42 is arranged at
an axial height lower than an axial height of the surface of the
adhesive A. That is, an axially lower end of the upper tapered
surface 426 is arranged at an axial height lower than an axial
height of the surface of the adhesive A.
[0064] The adhesive A arranged in the gap between the upper shaft
recessed portion 71 and the upper cone member 42 closes at least a
portion of a gap defined between the inside surface of the hole of
the upper cone member 42 and the outside surface of the shaft 7. As
a result, even if the lubricating oil travels from a vicinity of an
axial middle portion of the shaft 7 toward an axial end portion of
the shaft 7 along the outside surface of the shaft 7 while the
sleeve 41 rotates relative to the shaft 7 during drive of the motor
1, the lubricating oil is preferably prevented from leaking toward
the axial end portion of the shaft 7 through the gap between the
inside surface of the upper cone member 42 and the outside surface
of the shaft 7.
[0065] In addition, as illustrated in FIGS. 2 and 6, an upper third
inclined surface 427, which is inclined with respect to the central
axis J1, is arranged in an axially lower end portion of the inside
surface of the upper cone member 42. The radial distance between
the upper third inclined surface 427 and the central axis J1 is
preferably arranged to gradually increase with decreasing height.
The upper third inclined surface 427 is arranged opposite to the
outside surface of the shaft 7 with a gap intervening
therebetween.
[0066] In the above-described process of inserting the shaft into
the hole of the upper cone member 42, the shaft 7 is moved axially
downward relative to the upper cone member 42. At this time, even
if a portion of the adhesive A travels axially downward through the
gap between the outside surface of the shaft 7 and the inside
surface of the hole of the upper cone member 42, or a portion of
the adhesive A arranged on the shaft travels to an axially lower
end portion of the upper cone member 42, the adhesive A enters into
a gap defined between the upper third inclined surface 427 and the
outside surface of the shaft 7. The adhesive A closes at least a
portion of the gap between the outside surface of the shaft 7 and
the inside surface of the upper cone member 42. Note that the
adhesive is preferably arranged to extend all the way around a
circumference of the shaft 7 in the gap defined between the outside
surface of the shaft 7 and the inside surface of the upper cone
member 42.
[0067] Therefore, during driving of the motor 1, the lubricating
oil is preferably prevented from entering into the gap between the
outside surface of the shaft 7 and the inside surface of the hole
of the upper cone member 42 along the outside surface of the shaft
7. This prevents the lubricating oil from leaking out along the
shaft 7. Moreover, since the adhesive A enters into the gap defined
between the upper third inclined surface 427 and the outside
surface of the shaft 7, the likelihood that an excessive amount of
the adhesive A will be adhered to the outside surface of the shaft
7 or the inside surface of the upper cone member 42 is reduced.
Moreover, the adhesive A is prevented from closing the
communicating hole 423, which enables the lubricating oil to
circulate around the bearing mechanism 4 by passing through the
communicating hole 423.
[0068] FIG. 7 is an enlarged view of a portion of the bearing
mechanism 4 and an adjacent area. As illustrated in FIGS. 1, 2, and
7, the lower shaft recessed portion 75 is arranged radially
opposite an axially lower end portion of the lower cone member 43.
The inside diameter of the lower cone member 43 is arranged to be
smaller than the outside diameter of the shaft 7. Therefore, the
lower cone member 43 is fixed to the shaft 7 through, for example,
press fitting once the shaft 7 is inserted into a hole of the lower
cone member 43 during the assemblage of the motor 1.
[0069] Moreover, an adhesive A is previously applied to an inside
surface of the hole of the lower cone member 43 or the outside
surface of the shaft 7 during the assemblage of the motor 1. The
shaft 7 is thereafter preferably, for example, press fitted into
the hole of the lower cone member 43. Accordingly, at least a
portion of the adhesive is arranged between the inside surface of
the hole of the lower cone member 43 and the outside surface of the
shaft 7. That is, the lower cone member 43 is preferably fixed to
the shaft 7 through adhesion as well.
[0070] In a process of inserting the shaft 7 into the hole of the
lower cone member 43, a portion of the adhesive arranged between
the outside surface of the shaft 7 and the inside surface of the
hole of the lower cone member 43 travels axially upward or axially
downward along the outside surface of the shaft 7 or the inside
surface of the hole of the lower cone member 43. As illustrated in
FIG. 7, at least a portion of a portion of the adhesive A which has
traveled axially downward is arranged in a gap defined between the
lower shaft recessed portion 75 and the inside surface of the hole
of the lower cone member 43.
[0071] In the gap between the lower shaft recessed portion 75 and
the lower cone member 43, a surface of the adhesive A is arranged
at an axial height higher than an axial height of an axially upper
end of the lower cone member 43. In other words, the axially lower
end of the lower cone member 43 is positioned lower than the
surface of the adhesive A.
[0072] Note that the axially lower end portion of the lower cone
member 43 preferably includes a lower tapered surface 436 which is
inclined with respect to the central axis J1. The lower tapered
surface 436 is arranged radially opposite the lower shaft recessed
portion 75. The radial distance between the central axis J1 and the
lower tapered surface 436 is arranged to gradually increase with
decreasing height. Furthermore, the lower tapered surface 436 is
preferably arranged to extend all the way around an inner
circumference of the axially lower end portion of the lower cone
member 43.
[0073] Furthermore, a junction of the lower tapered surface 436
with the inside surface of the lower cone member 43 is arranged at
an axial height higher than an axial height of the surface of the
adhesive A. That is, an axially upper end of the lower tapered
surface 436 is arranged at an axial height higher than an axial
height of the surface of the adhesive A.
[0074] As illustrated in FIG. 7, the adhesive A arranged in the gap
between the lower shaft recessed portion 75 and the inside surface
of the hole of the lower cone member 43 closes at least a portion
of a gap defined between the inside surface of the hole of the
lower cone member 43 and the outside surface of the shaft 7. As a
result, even if the lubricating oil travels from the vicinity of
the axial middle portion of the shaft 7 toward an axial end portion
of the shaft 7 along the outside surface of the shaft 7 while the
sleeve 41 rotates relative to the shaft 7 during the drive of the
motor 1, the lubricating oil is prevented from leaking toward the
axial end portion of the shaft 7 through the gap between the inside
surface of the lower cone member 42 and the outside surface of the
shaft 7.
[0075] In addition, a lower third inclined surface 437, which is
inclined with respect to the central axis J1, is arranged in an
axially upper end portion of the inside surface of the lower cone
member 43. The radial distance between the lower third inclined
surface 437 and the central axis J1 is arranged to gradually
decrease with increasing height. The lower third inclined surface
437 is arranged opposite to the outside surface of the shaft 7 with
a gap intervening therebetween.
[0076] In the above-described process of inserting the shaft into
the hole of the lower cone member 43, the shaft 7 is preferably
moved axially downward relative to the lower cone member 43. At
this time, even if a portion of the adhesive A travels axially
upward through the gap between the outside surface of the shaft 7
and the inside surface of the hole of the lower cone member 43, or
a portion of the adhesive A arranged on the shaft 7 travels to an
axially upper end portion of the lower cone member 43, the adhesive
A enters into a gap defined between the lower third inclined
surface 437 and the outside surface of the shaft 7. The adhesive A
closes at least a portion of the gap between the outside surface of
the shaft 7 and the inside surface of the lower cone member 43.
[0077] Therefore, during the drive of the motor 1, the lubricating
oil is prevented from entering into the gap between the outside
surface of the shaft 7 and the inside surface of the hole of the
lower cone member 43 along the outside surface of the shaft 7. This
preferably prevents the lubricating oil from leaking out along the
shaft 7. Moreover, since the adhesive A enters into the gap defined
between the lower third inclined surface 437 and the outside
surface of the shaft 7, the likelihood that an excessive amount of
the adhesive A will be adhered to the outside surface of the shaft
7 or the inside surface of the lower cone member 43 is reduced.
Moreover, the adhesive A is preferably prevented from closing the
communicating hole 433, which enables the lubricating oil to
circulate around the bearing mechanism 4 by passing through the
communicating hole 433.
[0078] Note that, according to the present preferred embodiment,
the shape of the upper cone member 42 and the shape of the lower
cone member 43 are substantially the same. However, the shape of
the upper cone member 42 may be different from the shape of the
lower cone member 43.
[0079] While preferred embodiments of the present invention have
been described above, the present invention allows a variety of
modifications other than those mentioned above.
[0080] Note that each shaft recessed portion does not need to be
entirely filled with the adhesive according to the above-described
preferred embodiments.
[0081] In addition, the radial bottom portion of each shaft
recessed portion may not necessarily be parallel or substantially
parallel to the central axis J1. The radial bottom portion may be a
curved surface or an uneven surface.
[0082] Each of the first and second axial side surfaces does not
need to be an inclined surface. Each of the first axial side
surfaces may be a curved surface or an uneven surface. Each of the
second axial side surfaces may also be a curved surface or an
uneven surface.
[0083] In each shaft recessed portion, the first axial side surface
may be arranged to connect with the radial bottom portion either
smoothly or so as to define an angle. The second axial side surface
may be arranged to connect with the radial bottom portion either
smoothly or so as to define an angle. The first axial side surface,
the second axial side surface, and the radial bottom portion may be
arranged to together define a single curved surface.
[0084] Each shaft recessed portion may be annular, extending in the
circumferential direction. A plurality of shaft recessed portions
may be arranged in the circumferential direction in each of the
axially upper portion and the axially lower portion of the shaft 7.
In this case, each shaft recessed portion may have the same shape,
or alternatively, the shaft recessed portions may have different
shapes.
[0085] Also note that each inclined surface of the sleeve 41 may be
either an inclined surface which is inclined with respect to the
central axis J1 or a curved surface which is curved. A groove which
extends in the circumferential direction, and which is recessed in
a radial direction, may be defined in a substantial axial middle
portion of the inside surface of the sleeve 41. Also, a groove (for
example, a herringbone groove or the like) which produces a fluid
dynamic pressure in the lubricating oil may be defined in at least
one of a portion of the sleeve 41 which is opposed to the upper
cone member 42, a portion of the sleeve 41 which is opposed to the
lower cone member 43, and a portion of the sleeve 41 which is
opposed to the shaft 7.
[0086] Note that the stator core 221 may not necessarily be defined
by laminated steel sheets. For example, the stator core 221 may be
a core made from sintered metal powder or any other desirable type
of stator core. The upper annular member may not necessarily be the
upper cone member, but may be, for example, an annular member in
the shape of a plate. Also, the lower annular member may not
necessarily be the lower cone member, but may be, for example, an
annular member in the shape of a plate.
[0087] The preferred embodiments of the present invention are
applicable to motors for use in disk drive apparatuses, and also to
motors used for other applications than the disk drive
apparatuses.
[0088] Features of the above-described preferred embodiments and
the modifications thereof may be combined appropriately as long as
no conflict arises.
[0089] 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.
* * * * *