U.S. patent application number 10/196132 was filed with the patent office on 2002-11-21 for spindle motor and bearing assembly.
Invention is credited to Takayanagi, Shin-ichi.
Application Number | 20020171302 10/196132 |
Document ID | / |
Family ID | 18889230 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020171302 |
Kind Code |
A1 |
Takayanagi, Shin-ichi |
November 21, 2002 |
Spindle motor and bearing assembly
Abstract
The fixed shaft type spindle motor of the invention has a fixed
shaft vertically installed on a base and a rotor hub supported to
freely rotate by the fixed shaft through a bearing. The bearing is
composed of a compound ball bearing, and a larger diameter portion
of a stepped top-form connection member having the larger diameter
portion and a smaller diameter portion is fixedly engaged with the
upper end of the outer ring of the compound ball bearing. And, the
smaller diameter portion of the connection member is fastened to
the rotor hub. The rotary shaft type spindle motor has a rotary
shaft vertically installed on the rotor hub, in which the rotary
shaft is supported to freely rotate on the base through the
bearing. The bearing is composed of a compound ball bearing, and
the larger diameter portion of the stepped top-form connection
member having the larger diameter portion and the smaller diameter
portion is fixedly engaged with the lower end of the outer ring of
the compound ball bearing. And, the smaller diameter portion of the
connection member is fastened to the base. The compound ball
bearing, the shaft (the fixed shaft, the rotary shaft), and the
connection member may be assembled in advance integrally in one
unit, and the compound ball bearing may be replaced by a fluid
bearing. The above configuration will enhance the reliability of
the run-out accuracy/NRRO, the noises, the acoustic life, and the
rigidity etc., of the spindle motor, and reduce the manufacturing
cost.
Inventors: |
Takayanagi, Shin-ichi;
(Nagano-ken, JP) |
Correspondence
Address: |
LORUSSO & LOUD
3137 Mt. Vernon Avenue
Alexandria
VA
22305
US
|
Family ID: |
18889230 |
Appl. No.: |
10/196132 |
Filed: |
July 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10196132 |
Jul 17, 2002 |
|
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|
09861646 |
May 22, 2001 |
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Current U.S.
Class: |
310/90 ;
310/67R |
Current CPC
Class: |
F16C 19/08 20130101;
F16C 35/04 20130101; F16C 2370/12 20130101; H02K 7/086
20130101 |
Class at
Publication: |
310/90 ;
310/67.00R |
International
Class: |
H02K 005/16; H02K
007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2001 |
JP |
2001-024026 |
Claims
What is claimed is:
1. A fixed shaft type spindle motor in which a fixed shaft is
vertically installed on a base and a rotor hub is supported to
freely rotate by the fixed shaft through a bearing, wherein: said
bearing is a compound ball bearing, a larger diameter portion of a
stepped top-form connection member having the larger diameter
portion and a smaller diameter portion is fixedly engaged with an
upper end of an outer ring of said compound ball bearing, and said
smaller diameter portion of the connection member is fastened to
said rotor hub.
2. A fixed shaft type spindle motor in which a fixed shaft is
vertically installed on a base and a rotor hub is supported to
freely rotate by the fixed shaft through a bearing, wherein: said
bearing is a fluid bearing, a larger diameter portion of a stepped
top-form connection member having the larger diameter portion and a
smaller diameter portion is fixedly engaged with an upper end of a
sleeve of said fluid bearing, and said smaller diameter portion of
the connection member is fastened to said rotor hub.
3. A rotary shaft type spindle motor in which a rotary shaft is
vertically installed on a rotor hub and said rotary shaft is
supported to freely rotate on a base through a bearing, wherein:
said bearing is a compound ball bearing, a larger diameter portion
of a stepped top-form connection member having the larger diameter
portion and a smaller diameter portion is fixedly engaged with a
lower end of an outer ring of said compound ball bearing, and said
smaller diameter portion of the connection member is fastened to
said base.
4. A rotary shaft type spindle motor in which a rotary shaft is
vertically installed on a rotor hub and said rotary shaft is
supported to freely rotate on a base through a bearing, wherein:
said bearing is a fluid bearing, a larger diameter portion of a
stepped top-form connection member having the larger diameter
portion and a smaller diameter portion is fixedly engaged with a
lower end of a sleeve of said fluid bearing, and said smaller
diameter portion of the connection member is fastened to said
base.
5. A bearing assembly in which an inner ring of a compound ball
bearing with a pressurization applied is fixedly engaged with a
shaft, and a larger diameter portion of a stepped top-form
connection member having the larger diameter portion and a smaller
diameter portion is fixedly engaged with any of ends of an outer
ring of said compound ball bearing.
6. A bearing assembly in which a sleeve of a fluid bearing sheathes
a shaft, and a larger diameter portion of a stepped top-form
connection member having the larger diameter portion and a smaller
diameter portion is fixedly engaged with any of ends of said
sleeve.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a spindle motor and a
bearing assembly for use in office automation equipment such as a
computer and peripheral equipment thereof as a driving
device/component for the rotating mechanism thereof, specifically
to the spindle motor and the bearing assembly that achieve to
enhance the run-out accuracy/nonrepeatable runout (NRRO) of a
motor, and the reliability of the noises, acoustic life, and
rigidity, etc.
[0003] 2. Description of the Prior Art
[0004] The spindle motor for driving a magnetic disk on a hard disk
drive as a peripheral equipment of a computer is classified broadly
into two types in terms of the structure: the fixed shaft type in
which a fixed shaft is installed upright on a base, and a rotor hub
is supported to freely rotate by the fixed shaft through a bearing
interposed between the fixed shaft and the rotor hub ; and the
rotary shaft type in which a rotary shaft is vertically installed
on a rotor hub, and the rotary shaft is supported to freely rotate
on a base through a bearing interposed between the rotary shaft and
the base.
[0005] Generally, the fixed shaft type is provided with, as shown
in FIG. 9, a base (flange) 02, a fixed shaft 010 that is installed
upright on the base 02, a rotor hub (hub member) 03 that rotates
relatively to the base 02, and a bearing means 04 interposed
between the fixed shaft 010 and the rotor hub 03. A recording
medium such as a magnetic disk (not shown) is mounted on the rotor
hub 03. A stator 015 is installed on the outer peripheral surface
of an inner cylindrical wall 014 of the base 02, and a permanent
magnet 016 is installed on the inner peripheral surface of an outer
circumferential wall 013 of the rotor hub 03 so as to face the
outer peripheral surface of the stator 015. The symbol 017 denotes
a feeder part to the windings of the stator 015, which is connected
to a flexible printed circuit board 037.
[0006] The bearing means 04 employs a compound ball bearing, and an
inner ring 06 thereof is applied from the outside to the fixed
shaft 010 to be fixedly engaged with the shaft, and an outer ring
05 thereof is applied from the inside to the inner peripheral
surface of an inner circumferential wall 032 of the rotor hub 03 to
be fixedly engaged with the wall. A part of the inner ring 06 can
be formed integrally with the fixed shaft 010 according to
circumstances, as shown in FIG. 9; and the outer ring 05 can be
formed commonly integrally throughout the whole structure of the
compound ball bearing in certain cases, as shown in the same
figure.
[0007] The rotary shaft type is also provided with, as shown in
FIG. 10, the base (flange) 02, the rotor hub (hub member) 03 that
rotates relatively to the base , a rotary shaft 020 that is
vertically installed on the rotor hub 03, and the bearing means 04
interposed between the rotary shaft 020 and the base 02. The
recording medium such as a magnetic disk (not shown) is mounted on
the rotor hub 03. The stator 015 is installed on the outer
peripheral surface of the inner cylindrical wall 014 of the base
02, and the permanent magnet 016 is installed on the inner
peripheral surface of the outer circumferential wall 013 of the
rotor hub 03 so as to face the outer peripheral surface of the
stator 015. The symbol 017 denotes the feeder part to the windings
of the stator 015, which is connected to a flexible printed circuit
board 037.
[0008] The bearing means 04 employs a compound ball bearing, and
the inner ring 06 thereof is applied from the outside to the rotary
shaft 020 to be fixedly engaged with the shaft, and the outer ring
05 thereof is applied from the inside to the inner peripheral
surface of the cylindrical wall 014 of the base 02 to be fixedly
engaged with the wall. A part of the inner ring 06 can be formed
integrally with the rotary shaft 020 according to circumstances, as
shown in FIG. 10; and the outer ring 05 can be formed commonly
integrally throughout the whole structure of the compound ball
bearing in certain cases, as shown in the same figure.
[0009] In a certain case, the rotor hub 03 and the rotary shaft 020
each manufactured separately can be assembled in a unit, as shown
in FIG. 10; and in another case, they can be manufactured in an
integral unit from the beginning. In the latter case, a part of the
inner ring 06 cannot be formed integrally with the rotary shaft
020.
[0010] In any type of the spindle motor 01, the rotor hub 03
thereof is supported on the base 02 to freely rotate through the
compound ball bearing 04 as a rolling bearing interposed between
the base 02 and the rotor hub 03. And, the inner ring 06 of the
compound ball bearing 04 is applied from the outside to the fixed
shaft 010 vertically installed on the base 02 or to the rotary
shaft 020 vertically installed on the rotor hub 03 to be fixedly
engaged therewith. The outer ring 05 thereof is applied from the
inside to the inner peripheral surface of the inner circumferential
wall 032 of the rotor hub 03 or to the inner peripheral surface of
the inner cylindrical wall 014 of the base 02 to be fixedly engaged
therewith.
[0011] Now, the recent demand in the hard disk drive shows a
remarkable tendency to increase the recording capacity, to enhance
the impact resistance, to lower the noises, to increase the data
access speed, and so forth. In order to answer these requirements,
the rolling bearing of a spindle motor has gone through
improvements of the material composition, enhancements of the
working precision of the inner and outer rings and rolling
elements, etc.
[0012] However, when the inner and outer rings and the balls
(rolling elements) are made of the steels such as the bearing
steels, there occur metal contacts between the rolling surfaces of
the inner and outer rings and the surfaces of the balls, which
effects galling and wearing to deteriorate the acoustic
characteristic, leading to the problem of the acoustic life
(recently, the life of the spindle motor is evaluated not by the
fatigue life, but by the acoustic life). Further, there occur
fretting corrosions (impressions, dilapidated surfaces) on the
rolling surfaces due to shocks and vibrations during
transportation, which also deteriorates the acoustic life and the
precision of rotation.
[0013] Especially in recent years, the rotational speed of a
spindle motor is increased to higher than 7200 rpm, and the
rotating sound of the motor becomes increased to that degree, which
tends to shorten the acoustic life. Also in future, a still more
increase of the recording capacity is estimated in view of the
demand of recording video images and so forth. In order to answer
such demands and future problems estimated, the foregoing
improvements of the material composition and enhancements of the
working precision and the like will not be sufficient for the
countermeasure.
[0014] In recent years, the ball materials have been tested and
examined which exceed in the non-agglutination property and the
wear resistance, and the nitride silicon ceramics has been adopted
as the rolling element material. There have been discussions about
the limitation of the rolling bearing itself, including the ceramic
ball bearing made of such new materials, and it has been put
forward to employ the fluid bearing in order to solve these
problems.
[0015] FIG. 11 illustrates a rotary shaft type spindle motor 01
with such a fluid bearing loaded. This spindle motor 01 is provided
with the base (flange) 02, the rotor hub (hub member) 03 that
rotates relatively to the base 02, a rotary shaft 020 that is
vertically installed on the rotor hub 03, and a fluid bearing 030
interposed between the rotary shaft 020 and the base 02.
[0016] A sleeve 031 of the fluid bearing 030 sheathes the rotary
shaft 020, and is applied to the inner peripheral surface of the
inner cylindrical wall 014 of the base 02 to be fixedly engaged
with the wall. A lubricating oil is supplied into the sliding area
between the sleeve 031 and the rotary shaft 020, and herringbones
(.rarw.shaped grooves) 033 formed on the circumferential surface of
the rotary shaft 020 effect to raise the pressure of the
lubricating oil, along with the rotation of the rotary shaft 020,
which floats the rotary shaft 020 up from the sleeve 031.
[0017] Although not detailed in the drawing, similar herringbones
are formed on an edge surface of a thrust ring 034 fixedly engaged
with the lower part of the rotary shaft 020, and a lubricating oil
is supplied into a gap between the edge surface and an inner
surface of a counter plate 037 fixedly engaged with the lower end
of the sleeve 031. And, as the rotary shaft 020 turns, the
herringbones effect to raise the pressure of the lubricating oil,
which makes the counter plate 037 receive the thrust that acts on
the rotary shaft 020.
[0018] Therefore, the base 02 supports the rotary shaft 020 of the
rotor hub 03 to freely rotate through the fluid bearing 030
interposed therebetween. The other structure of the motor is
basically identical to the spindle motor having the compound ball
bearing used therein.
[0019] On the other hand, in the fixed shaft type spindle motor
with a fluid bearing loaded, which is not illustrated, the sleeve
031 of the fluid bearing 030 is fit to an inner peripheral surface
of a wall formed on the rotor hub 03, and a fixed shaft is
installed upright on the base 02. And, this fixed shaft is sheathed
with the sleeve 031. Therefore, the fixed shaft supports the rotor
hub 03 to freely rotate through the fluid bearing 030 interposed
therebetween.
[0020] Even though either the ball bearing or the fluid bearing is
used, and even though the spindle motor is the fixed shaft type or
the rotary shaft type, the installation of the bearing in the
spindle motor is carried out by any one of the methods: press
fitting to the counterpart (rotating components and fixed
components), adhesion by adhesives, and press-fit adhesion using
both of these.
[0021] In case of the press fitting method, the shape precision
(circularity, cylindricality, surface roughness) of the inner or
outer peripheral surface of the counterpart gives influence to
transfer the shape from the outer peripheral surface of the outer
ring and the inner peripheral surface of the inner ring of the
rolling bearing to the rolling surfaces of the inner and outer
rings, or to deform the rolling surfaces of the inner and outer
rings. Also, the external stress caused by a press fitting
propagates through the outer peripheral surface of the outer ring
or through the inner peripheral surface of the inner ring, and
produces permanent deformations on the rolling surfaces of the
inner and outer rings through the rolling elements to give
impressions thereon, which deteriorates the reliability of the
run-out accuracy/NRRO, the noises, and the acoustic life, etc., of
the motor. In the fluid bearing, the clearance between the sleeve
and the shaft sheathed with the sleeve varies, which varies the
rigidity.
[0022] And, in case of the adhesion, the stress is produced when
the adhesive is hardened, which deforms the bearing, also
deteriorating the reliability of the run-out accuracy, the noises,
and the acoustic life of the motor, and so forth. Further, in the
rotary shaft type spindle motor, the assembly of the stator 015 on
the outer peripheral surface of the cylindrical wall 014 of the
base 02 gives influence to deteriorate the accuracy of the inner
diameter of the cylindrical wall 014, which brings about
deterioration of the bearing accuracy.
[0023] Further, in case of the foregoing press fitting, adhesion,
or press-fit adhesion being adopted as the method of mounting the
bearing, an adhesion groove (refer to adhesion groove 040 in FIG.
9, adhesion groove 041 in FIG. 10) for filling adhesives and a
run-off groove are needed on the bearing mounting surface on the
side of the counterpart, which increases the man-hour to that
extent, leading to cost increase.
SUMMARY OF THE INVENTION
[0024] The present invention has been made in view of the foregoing
circumstances, and it is an object of the invention to provide a
spindle motor and a bearing assembly that achieve to resolve the
foregoing problems of the conventional spindle motor, to remove bad
influences on the precision of the rolling surfaces of the inner
and outer rings through the outer peripheral surface of the outer
ring and the inner peripheral surface of the inner ring of the
bearing, by the stress resulting from the shape precision
(circularity, cylindricality, surface roughness) of the inner or
outer peripheral surface of the counterpart in mounting the
bearing, or the stress caused by the press fitting, adhesion, or
press-fit adhesion as the method of mounting the bearing, to
enhance the reliability of the run-out accuracy/NRRO, the noises,
and the acoustic life, etc., of the spindle motor, and to reduce
the manufacturing cost thereof.
[0025] According to the first aspect of the invention, the spindle
motor to resolve the above problems is a fixed shaft type spindle
motor in which a fixed shaft is vertically installed on a base and
a rotor hub is supported to freely rotate by the fixed shaft
through a bearing, wherein the bearing is a compound ball bearing,
a larger diameter portion of a stepped top-form connection member
having the larger diameter portion and a smaller diameter portion
is fixedly engaged with an upper end of an outer ring of the
compound ball bearing, and the smaller diameter portion of the
connection member is fastened to the rotor hub.
[0026] Therefore, when the bearing is composed of the compound ball
bearing, the outer ring of the compound ball bearing is to be
fastened to the rotor hub through the connection member.
[0027] As a result, the rotor hub (the component on the rotating
side) being one of the two counterparts (the component on the
rotating side and the component on the fixing side) that mount the
compound ball bearing can be made up without the inner peripheral
surface of a wall, which has conventionally been regarded as
necessary to fit the outer ring of the compound ball bearing
thereto. Therefore, there does not exist the stress resulting from
the shape precision (circularity, cylindricality, surface
roughness) of the inner peripheral surface of the wall, or the
stress caused by the press fitting, adhesion, or press-fit adhesion
as the method of mounting the bearing; accordingly disappear bad
influences on the precision of the rolling surfaces of the inner
and outer rings through the outer peripheral surface of the outer
ring of the bearing, thereby enhancing the reliability of the
run-out accuracy/NRRO, the noises, and the acoustic life, etc., of
the spindle motor.
[0028] Further, since the rotor hub being the one of the two
counterparts that mount the compound ball bearing can be configured
without the inner peripheral surface of the wall, which has
conventionally been regarded as necessary to fit the outer ring of
the compound ball bearing thereto, the adhesion groove (the groove
for filling adhesives) and the run-off groove that are formed
conventionally on the inner peripheral surface of the wall become
unnecessary, thereby reducing the man-hour to lower the
manufacturing cost.
[0029] According to the second aspect of the invention, there is
provided a fixed shaft type spindle motor in which a fixed shaft is
vertically installed on a base and a rotor hub is supported to
freely rotate by the fixed shaft through a bearing, wherein the
bearing is a fluid bearing, a larger diameter portion of a stepped
top-form connection member having the larger diameter portion and a
smaller diameter portion is fixedly engaged with an upper end of a
sleeve of the fluid bearing, and the smaller diameter portion of
the connection member is fastened to the rotor hub.
[0030] Therefore, when the bearing is composed of the fluid
bearing, the sleeve of the fluid bearing is to be fastened to the
rotor hub through the connection member.
[0031] As a result, the rotor hub (the component on the rotating
side) being one of the two counterparts (the component on the
rotating side and the component on the fixing side) that mount the
fluid bearing can be made up without the inner peripheral surface
of a wall, which has conventionally been regarded as necessary to
fit the sleeve of the fluid bearing thereto. Therefore, there does
not exist the stress resulting from the shape precision
(circularity, cylindricality, surface roughness) of the inner
peripheral surface of the wall, or the stress caused by the press
fitting, adhesion, or press-fit adhesion as the method of mounting
the bearing; accordingly disappear bad influences on the precision
of the sliding surfaces of the sleeve and the fixed shaft and the
clearance between the sliding surfaces of the two through the outer
peripheral surface of the sleeve of the bearing, thereby enhancing
the reliability of the run-out accuracy/NRRO, the noises, the
acoustic life, and the rigidity, etc., of the spindle motor.
[0032] Further, since the rotor hub being the one of the two
counterparts that mount the fluid bearing can be configured without
the inner peripheral surface of the wall, which has conventionally
been regarded as necessary to fit the sleeve of the fluid bearing
thereto, the adhesion groove and the run-off groove that are formed
conventionally on the inner peripheral surface of the wall become
unnecessary, thereby reducing the man-hour to lower the
manufacturing cost.
[0033] According to the third aspect of the invention, there is
provided a rotary shaft type spindle motor in which a rotary shaft
is vertically installed on a rotor hub and the rotary shaft is
supported to freely rotate on a base through a bearing, wherein the
bearing is a compound ball bearing, a larger diameter portion of a
stepped top-form connection member having the larger diameter
portion and a smaller diameter portion is fixedly engaged with a
lower end of an outer ring of the compound ball bearing, and the
smaller diameter portion of the connection member is fastened to
the base.
[0034] Therefore, when the bearing is composed of the compound ball
bearing, the outer ring of the compound ball bearing is to be
fastened to the base through the connection member.
[0035] As a result, the base (the component on the fixing side)
being the other one of the two counterparts (the component on the
rotating side and the component on the fixing side) that mount the
compound ball bearing can be made up without the inner peripheral
surface of a wall, which has conventionally been regarded as
necessary to fit the outer ring of the compound ball bearing
thereto. Therefore, there does not exist the stress resulting from
the shape precision (circularity, cylindricality, surface
roughness) of the inner peripheral surface of the wall, or the
stress caused by the press fitting, adhesion, or press-fit adhesion
as the method of mounting the bearing; accordingly disappear bad
influences on the precision of the rolling surfaces of the inner
and outer rings through the outer peripheral surface of the outer
ring of the bearing, thereby enhancing the reliability of the
run-out accuracy/NRRO, the noises, and the acoustic life, etc., of
the spindle motor.
[0036] Further, since the base being the other one of the two
counterparts that mount the compound ball bearing can be configured
without the inner peripheral surface of the wall, which has
conventionally been regarded as necessary to fit the outer ring of
the compound ball bearing thereto, the adhesion groove and the
run-off groove that are formed conventionally on the inner
peripheral surface of the wall become unnecessary, thereby reducing
the man-hour to lower the manufacturing cost.
[0037] According to the fourth aspect of the invention, there is
provided a rotary shaft type spindle motor in which a rotary shaft
is vertically installed on a rotor hub, and the rotary shaft is
supported to freely rotate on a base through a bearing, wherein the
bearing is a fluid bearing, a larger diameter portion of a stepped
top-form connection member having the larger diameter portion and a
smaller diameter portion is fixedly engaged with a lower end of a
sleeve of the fluid bearing, and the smaller diameter portion of
the connection member is fastened to the base.
[0038] Therefore, when the bearing is composed of the fluid
bearing, the sleeve of the fluid bearing is to be fastened to the
base through the connection member.
[0039] As a result, the base (the component on the fixing side)
being the other one of the two counterparts (the component on the
rotating side and the component on the fixing side) that mount the
fluid bearing can be made up without the inner peripheral surface
of a wall, which has conventionally been regarded as necessary to
fit the sleeve of the fluid bearing thereto. Therefore, there does
not exist the stress resulting from the shape precision
(circularity, cylindricality, surface roughness) of the inner
peripheral surface of the wall, or the stress caused by the press
fitting, adhesion, or press-fit adhesion as the method of mounting
the bearing; accordingly disappear bad influences on the precision
of the sliding surfaces of the sleeve and the fixed shaft and the
clearance between the sliding surfaces of the two through the outer
peripheral surface of the sleeve of the bearing, thereby enhancing
the reliability of the run-out accuracy/NRRO, the noises, the
acoustic life, and the rigidity, etc., of the spindle motor.
[0040] Further, since the base being the other one of the two
counterparts that mount the fluid bearing can be configured without
the inner peripheral surface of the wall, which has conventionally
been regarded as necessary to fit the sleeve of the fluid bearing
thereto, the adhesion groove and the run-off groove that are formed
conventionally on the inner peripheral surface of the wall become
unnecessary, thereby reducing the man-hour to lower the
manufacturing cost.
[0041] Further, according to the fifth aspect of the invention, the
bearing assembly to resolve the foregoing problems is a bearing
assembly in which an inner ring of a compound ball bearing with a
pressurization applied is fixedly engaged with a shaft, and a
larger diameter portion of a stepped top-form connection member
having the larger diameter portion and a smaller diameter portion
is fixedly engaged with any of ends of an outer ring of the
compound ball bearing.
[0042] Therefore, since the bearing assembly according to the fifth
aspect of the invention is made up as above, the compound ball
bearing, the shaft, and the connection member are assembled in
advance into one assembly unit. As a result, fastening the shaft to
the one of the two counterparts (the component on the rotating side
and the component on the fixing side) that mount the bearing
assembly and fastening the smaller diameter portion of the
connection member to the other one will achieve to assemble the
compound ball bearing between the two counterparts, and thus the
mounting work of the compound ball bearing becomes extremely easy
to perform.
[0043] And, according to the sixth aspect of the invention, there
is provided a bearing assembly in which a sleeve of a fluid bearing
sheathes a shaft, and a larger diameter portion of a stepped
top-form connection member having the larger diameter portion and a
smaller diameter portion is fixedly engaged with any of ends of the
sleeve.
[0044] Therefore, since the bearing assembly according to the sixth
aspect of the invention is made up as above, the sleeve of the
fluid bearing, the shaft, and the connection member are assembled
in advance into one assembly unit. As a result, fastening the shaft
to the one of the two counterparts (the component on the rotating
side and the component on the fixing side) that mount the bearing
assembly and fastening the smaller diameter portion of the
connection member to the other one will achieve to assemble the
fluid bearing between the two counterparts, and thus the mounting
work of the fluid bearing becomes extremely easy to perform.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Preferred embodiments of the present invention will be
described in detail based on the followings, wherein:
[0046] FIG. 1 is a sectional view of a fixed shaft type spindle
motor in the first embodiment of the invention;
[0047] FIG. 2 is an exploded view of the same;
[0048] FIG. 3 is a sectional view of a rotary shaft type spindle
motor in the second embodiment of the invention;
[0049] FIG. 4 is an exploded view of the same;
[0050] FIG. 5 is a sectional view of a fixed shaft type spindle
motor in the third embodiment of the invention;
[0051] FIG. 6 is an exploded view of the same;
[0052] FIG. 7 is a sectional view of a rotary shaft type spindle
motor in the fourth embodiment of the invention;
[0053] FIG. 8 is an exploded view of the same;
[0054] FIG. 9 is a sectional view of a conventional fixed shaft
type spindle motor using the compound ball bearing;
[0055] FIG. 10 is a sectional view of a conventional rotary shaft
type spindle motor using the compound ball bearing; and
[0056] FIG. 11 is a sectional view of a conventional rotary shaft
type spindle motor using the fluid bearing.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0057] The first embodiment of the invention will be described with
reference to FIG. 1 and FIG. 2. FIG. 1 is a sectional view of a
fixed shaft type spindle motor of the first embodiment, and FIG. 2
is an exploded view of the same.
[0058] As shown in FIG. 1 and FIG. 2, a fixed shaft type spindle
motor 1 relating to the first embodiment has a fixed shaft 10
installed upright (vertically upward) on a flange base 2, in which
the fixed shaft 10 is fixedly engaged with a central circular hole
11 on the flange base 2. An inner ring 6 of an upper half unit ball
bearing portion of a compound ball bearing 4 is applied from the
outside to the upper reduced diameter portion of the fixed shaft 10
in FIG. 1 to be fixedly engaged therewith. The inner ring 6 (the
portion illustrated by (6) in the drawing) of a lower half unit
ball bearing portion of the compound ball bearing 4 is formed
integrally with the fixed shaft 10. Here, the "unit ball bearing
portion of the compound ball bearing" signifies a ball bearing
portion by each stage, when plural balls (rolling elements)
contained between the inner and outer rings with plural stages in
the axial direction are virtually partitioned into each stage.
[0059] An outer ring 5 of the compound ball bearing 4 is formed
commonly integrally throughout the whole structure of the compound
ball bearing 4. On the upper end of the outer ring 5 is formed a
step portion made by enlarging the inner diameter thereof. A larger
diameter portion 8a of a stepped top-form connection member 8
(without a rotary shaft) having the larger diameter portion 8a and
a smaller diameter portion 8b is fixedly engaged with the step
portion formed on the upper end of the outer ring 5 with the larger
diameter portion 8a applied from the inside to the step portion.
The smaller diameter portion 8b of the connection member 8 is
fixedly engaged with a central circular hole 9 of a rotor hub 3
with the smaller diameter portion 8b applied from the inside to the
central circular hole 9.
[0060] Therefore, since the rotor hub 3, connection member 8, and
the outer ring 5 of the compound ball bearing 4 are coupled in one
unit, the rotor hub 3 is supported to freely rotate by the fixed
shaft 10 of the base 2 through the connection member 8 and the
compound ball bearing 4. And, since the outer ring 5 of the
compound ball bearing 4 is fixed to the rotor hub 3 through the
connection member 8, an inner peripheral surface of a wall (refer
to the inner peripheral surface of the inner circumferential wall
032 of the rotor hub 03 in FIG. 9), which has conventionally been
regarded as necessary to fit the outer ring 5 of the compound ball
bearing 4 to the rotor hub 3, becomes unnecessary, so that the
rotor hub 3 is not provided with such inner peripheral surface.
[0061] A magnetic disk (not shown) is mounted on a mounting plane
12 of the rotor hub 3. The other rotating bodies requiring a high
run-out accuracy/NRRO and/or low noises can be mounted thereon.
[0062] Plural balls (rolling elements) 7 are accommodated in a
pressurized state between the outer ring 5 and the inner ring 6,
which are arrayed in the circumferential direction with a vertical
two-stage configuration. The balls 7 travel on concave rolling
surfaces that are formed to face each other on the inner peripheral
surface of the outer ring 5 and on the outer peripheral surface of
the inner ring 6, while rolling relatively to the outer ring 5 and
the inner ring 6.
[0063] A stator 15 is fit onto the outer peripheral surface of an
inner cylindrical wall 14 of the base 2, and a permanent magnet 16
is mounted circumferentially on the inner peripheral surface of an
outer circumferential wall 13 of a larger diameter portion of the
rotor hub 3 so as to face the outer peripheral surface of the
stator 15. The symbol 17 denotes a feeder part to the windings of
the stator 15, which is connected to a flexible printed circuit
board 37. The symbol 18 denotes a plaque.
[0064] In the first embodiment, the fixed shaft 10, the compound
ball bearing 4, and the connection member 8 are integrally
assembled in advance as a product, as shown in FIG. 2. With the
bearing assembly thus produced, the projected end of the fixed
shaft 10 thereof is fixedly engaged with the central circular hole
11 of the base 2, and the smaller diameter portion 8b of the
connection member 8 is fixedly engaged with the central circular
hole 9 of the rotor hub 3, whereby the fixed shaft type spindle
motor 1 of the first embodiment is made up.
[0065] As the first embodiment is configured as above, when the
power is supplied from the feeder part 17 connected to the flexible
printed circuit board 37 to the windings of the stator 15,
according to the principle of the synchronous motor, the rotor hub
3 with the permanent magnet 16 starts to rotate as one body with
the connection member 8 and the outer ring 5. That is, the rotor
hub 3 is borne by the compound ball bearing 4 through the
connection member 8 to rotate about the fixed shaft 10.
[0066] The first embodiment thus configured exhibits the following
effects.
[0067] In the fixed shaft type spindle motor 1 in which the fixed
shaft 10 is vertically installed on the base 2 and the rotor hub 3
is supported to freely rotate by the fixed shaft 10 through the
compound ball bearing 4, the outer ring 5 of the compound ball
bearing 4 is fixed to the rotor hub 3 through the connection member
8; and therefore, the rotor hub 3 being one of the two counterparts
(the rotor hub 3 being the component on the rotating side and the
base 2 as the component on the fixing side) that mount the compound
ball bearing 4 can be made up without the inner peripheral surface
of a wall, which has conventionally been regarded as necessary to
fit the outer ring 5 of the-compound ball bearing 4 to the rotor
hub 3. As a result, the stress resulting from the shape precision
(circularity, cylindricality, surface roughness) of the inner
peripheral surface of the wall, or the stress caused by the press
fitting, adhesion, or press-fit adhesion as the method of mounting
the bearing does not exist; accordingly disappear bad influences on
the precision of the rolling surfaces of the inner and outer rings
6, 5 through the outer peripheral surface of the outer ring 5 of
the compound ball bearing 4, so that the reliability of the run-out
accuracy/NRRO, the noises, and the acoustic life, etc., of the
spindle motor 1 can be enhanced.
[0068] Further, the rotor hub 3 being one of the two counterparts
that mount the compound ball bearing 4 can be configured without
the inner peripheral surface of the wall, which has conventionally
been regarded as necessary to fit the outer ring 5 of the compound
ball bearing 4 to the rotor hub 3; and therefore, the adhesion
groove for filling adhesives and the run-off groove that are formed
conventionally on the inner peripheral surface of the wall become
unnecessary, which reduces the man-hour to lower the manufacturing
cost.
[0069] Further, since the compound ball bearing 4, the fixed shaft
10, and the connection member 8 are assembled in advance into one
assembly unit, fastening the fixed shaft 10 to the base 2 being the
other one of the two counterparts that mount the bearing assembly
and fastening the smaller diameter portion 8b of the connection
member 8 to the rotor hub 3 being the one will achieve to assemble
the compound ball bearing 4 between these two counterparts, thus
the mounting work of the compound ball bearing 4 becomes extremely
easy to perform.
[0070] Since the inner ring portion (6) belonging to the lower half
unit ball bearing portion of the two unit ball bearing portions
constituting the compound ball bearing 4 is formed integrally with
the fixed shaft 10, assembling the compound ball bearing 4, the
fixed shaft 10, and the connection member 8 in advance into one
assembly unit as described above will produce a still greater
merit, with regard to the inner ring 6 of the compound ball bearing
4. Assuming that these components are not assembled in advance, to
mount the compound ball bearing 4 to the fixed shaft 10 with the
inner ring portion (6) integrally formed will lead to a troublesome
work that inserts the balls (rolling elements) 7 between the outer
ring 5 and the fixed shaft 10. Consequently, the mounting work of
the compound ball bearing 4 will become still more complicated and
difficult.
[0071] Next, the second embodiment of the invention will be
described with reference to FIG. 3 and FIG. 4. FIG. 3 is a
sectional view of a rotary shaft type spindle motor of the second
embodiment, and FIG. 4 is an exploded view of the same. The parts
corresponding to those of the fixed shaft type spindle motor in the
first embodiment are given the same symbols.
[0072] As shown in FIG. 3 and FIG. 4, a rotary shaft type spindle
motor 1 relating to the second embodiment has a rotary shaft 20
installed vertically downward on the rotor hub 3, in which the
rotary shaft 20 is fixedly engaged with the central circular hole 9
on the rotor hub 3. The inner ring 6 of the lower half unit ball
bearing portion of the compound ball bearing 4 is applied from the
outside to the lower reduced diameter portion of the rotary shaft
20 in FIG. 3 to be fixedly engaged therewith. The inner ring 6 (the
portion illustrated by (6) in the drawing) of the upper half unit
ball bearing portion of the compound ball bearing 4 is formed
integrally with the rotary shaft 20.
[0073] The outer ring 5 of the compound ball bearing 4 is formed
commonly integrally throughout the whole structure of the compound
ball bearing 4. On the lower end of the outer ring 5 is formed a
step portion made by enlarging the inner diameter thereof. The
larger diameter portion 8a of the stepped top-form connection
member 8 (without a rotary shaft) having the larger diameter
portion 8a and the smaller diameter portion 8b is fixedly engaged
with the step portion formed on the lower end of the outer ring 5
with the larger diameter portion 8a applied from the inside to the
step portion. The smaller diameter portion 8b of the connection
member 8 is fixedly engaged with the central circular hole 11 of
the flange base 2 with the smaller diameter portion 8b applied from
the inside to the central circular hole 11. Further, the larger
diameter portion 8a is seated on an inner surface surrounding the
central circular hole 11 of the base 2, however it is not
necessarily seated in this manner.
[0074] Therefore, since the base 2, connection member 8, and the
outer ring 5 of the compound ball bearing 4 are coupled in one
unit, the base 2 supports the rotary shaft 20 of the rotor hub 3 to
freely rotate through the connection member 8 and the compound ball
bearing 4. And, since the outer ring 5 of the compound ball bearing
4 is fixed to the base 2 through the connection member 8, the inner
peripheral surface of a wall (refer to the inner peripheral surface
of the inner cylindrical wall 014 of the base 02 in FIG. 10), which
has conventionally been regarded as necessary to fit the outer ring
5 of the compound ball bearing 4 to the base 2, becomes
unnecessary, so that the base 2 is not provided with such inner
peripheral surface. The base 2 has the inner cylindrical wall 14
formed upright thereon, and the inner cylindrical wall 14 has an
inner peripheral surface facing to the outer peripheral surface of
the outer ring 5. However, the outer ring 5 is not fixedly engaged
with this inner peripheral surface of the inner cylindrical wall
14.
[0075] In the second embodiment, the rotary shaft 20, the compound
ball bearing 4, and the connection member 8 are integrally
assembled in advance as a product, as shown in FIG. 4. With the
bearing assembly thus produced, the projected end of the rotary
shaft 20 thereof is fixedly engaged with the central circular hole
9 of the rotor hub 3, and the smaller diameter portion 8b of the
connection member 8 is fixedly engaged with the central circular
hole 11 of the base 2, whereby the rotary shaft type spindle motor
1 of the second embodiment is made up.
[0076] The second embodiment is different from the first embodiment
in terms of the foregoing points, however it is not different in
the other points of the internal structure of the compound ball
bearing 4, the structure of the motor, and so forth; and the
detailed description will be omitted.
[0077] As the second embodiment is configured as above, when the
power is supplied from the feeder part 17 connected to the flexible
printed circuit board 37 to the windings of the stator 15, the
rotor hub 3 with the permanent magnet 16 starts to rotate as one
body with the rotary shaft 20 and the inner ring 6. The base 2
supports the rotary shaft 20 of the rotor hub 3 to freely rotate
through the connection member 8 and the compound ball bearing
4.
[0078] The second embodiment thus configured exhibits the following
effects.
[0079] In the rotary shaft type spindle motor 1 in which the rotary
shaft 20 is vertically installed on the rotor hub 3 and is
supported to freely rotate through the compound ball bearing 4 on
the base 2, the outer ring 5 of the compound ball bearing 4 is
fixed to the base 2 through the connection member 8; and therefore,
the base 2 being the other one of the two counterparts (the rotor
hub 3 being the component on the rotating side and the base 2 as
the component on the fixing side) that mount the compound ball
bearing 4 can be made up without the inner peripheral surface of a
wall, which has conventionally been regarded as necessary to fit
the outer ring 5 of the compound ball bearing 4 to the base 2. As a
result, the stress resulting from the shape precision (circularity,
cylindricality, surface roughness) of the inner peripheral surface
of the wall, or the stress caused by the press fitting, adhesion,
or press-fit adhesion as the method of mounting the bearing does
not exist; accordingly disappear bad influences on the precision of
the rolling surfaces of the inner and outer rings 6, 5 through the
outer peripheral surface of the outer ring 5 of the compound ball
bearing 4, so that the reliability of the run-out accuracy/NRRO,
the noises, and the acoustic life, etc., of the spindle motor 1 can
be enhanced.
[0080] Further, the base 2 being the other one of the two
counterparts that mount the compound ball bearing 4 can be
configured without the inner peripheral surface of the wall, which
has conventionally been regarded as necessary to fit the outer ring
5 of the compound ball bearing 4 to the base 2; and therefore, the
adhesion groove and the run-off groove that are formed
conventionally on the inner peripheral surface of the wall become
unnecessary, which reduces the man-hour to lower the manufacturing
cost.
[0081] Further, since the compound ball bearing 4, the rotary shaft
20, and the connection member 8 are assembled in advance into one
assembly unit, fastening the rotary shaft 20 to the rotor hub 3
being the one of the two counterparts that mount the bearing
assembly and fastening the smaller diameter portion 8b of the
connection member 8 to the base 2 being the other one will achieve
to assemble the compound ball bearing 4 between these two
counterparts, thus the mounting work of the compound ball bearing 4
becomes extremely easy to perform. In the other aspects, the second
embodiment also exhibits the same effects as those by the bearing
assembly in the first embodiment.
[0082] Next, the third embodiment of the invention will be
described with reference to FIG. 5 and FIG. 6. FIG. 5 is a
sectional view of the fixed shaft type spindle motor of the third
embodiment, and FIG. 6 is an exploded view of the same. The parts
corresponding to those of the fixed shaft type spindle motor in the
first embodiment are given the same symbols.
[0083] As shown in FIG. 5 and FIG. 6, the fixed shaft type spindle
motor 1 relating to the third embodiment has the fixed shaft 10
installed upright (vertically upward) on the flange base 2, in
which the fixed shaft 10 is fixedly engaged with the central
circular hole 11 on the flange base 2. Also, the fixed shaft 10 is
sheathed with a sleeve 31 of a fluid bearing 30.
[0084] The sleeve 31 of the fluid bearing 30 is made of a
cylindrical member of a slightly thick wall, and has the step
portion formed on the upper end thereof, which is made by enlarging
comparably greatly the inner diameter thereof. The larger diameter
portion 8a of the stepped top-form connection member 8 (without a
rotary shaft) having the larger diameter portion 8a and the smaller
diameter portion 8b is fixedly engaged with the step portion formed
on the upper end of the sleeve 31 with the larger diameter portion
8a applied from the inside to the step portion. The smaller
diameter portion 8b of the connection member 8 is fixedly engaged
with the central circular hole 9 of the rotor hub 3 with the
smaller diameter portion 8b applied from the inside to the central
circular hole 9.
[0085] Therefore, since the rotor hub 3, connection member 8, and
the sleeve 31 of the fluid bearing 30 are coupled in one unit, the
rotor hub 3 is supported to freely rotate by the fixed shaft 10 of
the base 2 through the connection member 8 and the fluid bearing
30. And, since the sleeve 31 of the fluid bearing 30 is fixed to
the rotor hub 3 through the connection member 8, the inner
peripheral surface of a wall, which has conventionally been
regarded as necessary to fit the sleeve 31 of the fluid bearing 30
to the rotor hub 3, becomes unnecessary, so that the rotor hub 3 is
not provided with such inner peripheral surface. The rotor hub 3
has an inner peripheral surface facing to the outer peripheral
surface of the sleeve 31 of the fluid bearing 30 on the
circumferential wall 32 of the central smaller diameter portion
thereof. However, the sleeve 31 is not fixedly engaged with this
inner peripheral surface of the circumferential wall 32.
[0086] A magnetic disk (not shown) is mounted on the mounting plane
12 of the rotor hub 3. The other rotating bodies requiring a high
run-out accuracy/NRRO and/or low noises can be mounted thereon.
[0087] A lubricating oil is filled up in the gap between the sleeve
31 of the fluid bearing 30 and the fixed shaft 10 so as not to leak
out. The fixed shaft 10 has herringbone grooves 33 formed on the
outer circumferential surface thereof at two places separated in
the axial direction. As described later, as the rotor hub 3
rotates, the pressure of the lubricating oil in the herringbone
grooves 33 rises, whereby the sleeve 31 is floated up from the
fixed shaft 10. Here, a gaseous lubricant may replace the
lubricating oil.
[0088] A cylindrical thrust ring 34 is fixedly engaged with an
upper end of the fixed shaft 10 by the press fitting. The thrust
ring 34 is accommodated in a concave space surrounded by the inner
surface of the connection member 8 and a step portion 36 that is
formed by enlarging comparably small the inner diameter of the
upper end of the sleeve 31. When the sleeve 31 rotates integrally
with the rotor hub 3, the thrust ring 34 rotates in the concave
space relatively to the sleeve 31.
[0089] Although not detailed in the drawing, herringbones similar
to the herringbones 33 formed on the outer circumferential surface
of the fixed shaft 10 are formed on an edge surface of the thrust
ring 34. And, since the lubricating oil is supplied into a gap
between the edge surface and the inner surface of the connection
member 8 that faces to the edge surface, as the thrust ring 34
rotates relatively to the sleeve 31, the herringbones effect to
raise the pressure of the lubricating oil, which floats the
connection member 8 up from the edge surfaces of the thrust ring 34
and the fixed shaft 10. In this manner, the thrust force acting on
the connection member 8 is received by the fixed shaft 10, finally
by the base 2.
[0090] And, although not detailed in the drawing, herringbones are
formed on the lower edge surface of the sleeve 31. And, since the
lubricating oil is supplied into a gap between the lower edge
surface of the sleeve 31 and the inner surface near the central
circular hole 11 of the base 2, as the sleeve 31 rotates integrally
with the rotor hub 3, the herringbones formed on the lower edge
surface of the sleeve 31 effect to raise the pressure of the
lubricating oil, which floats the sleeve 31 up from the base 2. In
this manner, the base 2 also receives the thrust force acting on
the sleeve 31.
[0091] Further, these thrust bearing structures may be used at the
same time, or one of these may be omitted.
[0092] Although not detailed in the drawing, the lubricating oils
that each lubricate a radial bearing portion (the sliding portion
between the fixed shaft 10 and the sleeve 31) of the fluid bearing
30 and thrust bearing portions (the contacting/sliding portion
between the thrust ring 34 and the connection member 8, and the
contacting/sliding portion between the sleeve 31 and the base 2)
communicate mutually, and there is formed a closed circulating
passage that circulates the lubricating oils in a single direction
with the rotation of the sleeve 31.
[0093] The stator 15 is mounted on the outer peripheral surface of
the inner cylindrical wall 14 of the base 2, and the permanent
magnet 16 is mounted on the inner peripheral surface of the outer
circumferential wall 13 of the rotor hub 3 so as to face the outer
peripheral surface of the stator 15. The symbol 17 denotes a feeder
part to the windings of the stator 15, which is connected to the
flexible printed circuit board 37.
[0094] In the third embodiment, the fixed shaft 10, the fluid
bearing 30, the connection member 8, and the thrust ring 34 are
integrally assembled in advance as a product, as shown in FIG. 6.
With the bearing assembly thus produced, the projected end of the
fixed shaft 10 thereof is fixedly engaged with the central circular
hole 11 of the base 2, and the smaller diameter portion 8b of the
connection member 8 is fixedly engaged with the central circular
hole 9 of the rotor hub 3, whereby the fixed shaft type spindle
motor 1 of the third embodiment is made up.
[0095] As the third embodiment is configured as above, when the
power is supplied from the feeder part 17 connected to the flexible
printed circuit board 37 to the windings of the stator 15, the
rotor hub 3 with the permanent magnet 16 starts to rotate as one
body with the connection member 8 and the sleeve 31. That is, the
rotor hub 3 is borne by the fluid bearing 30 through the connection
member 8 to rotate about the fixed shaft 10.
[0096] The third embodiment thus configured exhibits the following
effects.
[0097] In the fixed shaft type spindle motor 1 in which the fixed
shaft 10 is vertically installed on the base 2 and the rotor hub 3
is supported to freely rotate by the fixed shaft 10 through the
fluid bearing 30, the sleeve 31 of the fluid bearing 30 is fixed to
the rotor hub 3 through the connection member 8; and therefore, the
rotor hub 3 being the one of the two counterparts (the rotor hub 3
being the component on the rotating side and the base 2 as the
component on the fixing side) that mount the fluid bearing 30 can
be made up without the inner peripheral surface of a wall, which
has conventionally been regarded as necessary to fit the sleeve 31
of the fluid bearing 30 to the rotor hub 3. As a result, there does
not exist the stress resulting from the shape precision
(circularity, cylindricality, surface roughness) of the inner
peripheral surface of the wall, or the stress caused by the press
fitting, adhesion, or press-fit adhesion as the method of mounting
the bearing; accordingly disappear bad influences on the precision
of the sliding surfaces of the sleeve 31 and the fixed shaft 10 and
the clearance between the sliding surfaces of the two to be ensured
at a constant quantity through the outer peripheral surface of the
sleeve 31 of the fluid bearing 30, so that the reliability of the
run-out accuracy/NRRO, the noises, the acoustic life, and the
rigidity, etc., of the spindle motor 1 can be enhanced.
[0098] Further, the rotor hub 3 being the one of the two
counterparts that mount the fluid bearing 30 can be configured
without the inner peripheral surface of the wall, which has
conventionally been regarded as necessary to fit the sleeve 31 of
the fluid bearing 30 to the rotor hub 3; and therefore, the
adhesion groove and the run-off groove that are formed
conventionally on the inner peripheral surface of the wall become
unnecessary, which reduces the man-hour to lower the manufacturing
cost.
[0099] Further, since the fluid bearing 30, the fixed shaft 10, the
connection member 8, and the thrust ring 34 are assembled in
advance into one assembly unit, fastening the fixed shaft 10 to the
base 2 being the other one of the two counterparts that mount the
bearing assembly and fastening the smaller diameter portion 8b of
the connection member 8 to the rotor hub 3 being the one will
achieve to assemble the fluid bearing 30 between these two
counterparts, thus the mounting work of the fluid bearing 30
becomes extremely easy to perform. Here, the lubricating oil is to
be filled up after finishing the mounting work.
[0100] Next, the fourth embodiment of the invention will be
described with reference to FIG. 7 and FIG. 8. FIG. 7 is a
sectional view of a rotary shaft type spindle motor of the fourth
embodiment, and FIG. 8 is an exploded view of the same. The parts
corresponding to those of the rotary shaft type spindle motor in
the second embodiment and those of the fixed shaft type spindle
motor in the third embodiment are given the same symbols.
[0101] As shown in FIG. 7 and FIG. 8, the rotary shaft type spindle
motor 1 relating to the fourth embodiment has the rotary shaft 20
installed vertically downward on the rotor hub 3, in which the
rotary shaft 20 is fixedly engaged with the central circular hole 9
on the rotor hub 3. Also, the rotary shaft 20 is sheathed with the
sleeve 31 of the fluid bearing 30.
[0102] The sleeve 31 of the fluid bearing 30 is made of a
cylindrical member of a slightly thick wall, and has the step
portion formed on the lower end thereof, which is made by enlarging
the inner diameter thereof comparably greatly. The larger diameter
portion 8a of the stepped top-form connection member 8 (without a
rotary shaft) having the larger diameter portion 8a and the smaller
diameter portion 8b is fixedly engaged with the step portion formed
on the lower end of the sleeve 31 with the larger diameter portion
8a applied from the inside to the step portion. The smaller
diameter portion 8b of the connection member 8 is fixedly engaged
with the central circular hole 11 of the base 2 with the smaller
diameter portion 8b applied from the inside to the central circular
hole 11.
[0103] Therefore, since the base 2, connection member 8, and the
sleeve 31 of the fluid bearing 30 are coupled in one unit, the base
2 supports the rotary shaft 20 of the rotor hub 3 to freely rotate
through the connection member 8 and the sleeve 31 of the fluid
bearing 30. And, since the sleeve 31 of the fluid bearing 30 is
fixed to the base 2 through the connection member 8, the inner
peripheral surface of a wall (refer to the inner peripheral surface
of the inner cylindrical wall 014 of the base 02 in FIG. 11), which
has conventionally been regarded as necessary to fit the sleeve 31
of the fluid bearing 30 to the base 2, becomes unnecessary, so that
the base 2 is not provided with such inner peripheral surface. The
base 2 has the inner cylindrical wall 14 formed upright thereon,
and the cylindrical wall 14 has an inner peripheral surface facing
to the outer peripheral surface of the sleeve 31. However, the
sleeve 31 is not fixedly engaged with this inner peripheral surface
of the cylindrical wall 14.
[0104] The cylindrical thrust ring 34 is fixedly engaged with a
lower end of the rotary shaft 20 by the press fitting. The thrust
ring 34 is accommodated in a concave space surrounded by the inner
surface of the connection member 8 and the step portion 36 that is
formed by enlarging comparably small the inner diameter of the
lower end of the sleeve 31. When the rotary shaft 20 rotates, the
thrust ring 34 rotates in the concave space integrally with the
rotary shaft 20.
[0105] Although not detailed in the drawing, herringbones similar
to the herringbones 33 formed on the outer circumferential surface
of the rotary shaft 20 are formed on the edge surface of the thrust
ring 34. And, since the lubricating oil is supplied into a gap
between the edge surface and the inner surface of the connection
member 8 that faces to the edge surface, as the thrust ring 34
rotates integrally with the rotary shaft 20, the herringbones
effect to raise the pressure of the lubricating oil, which floats
the rotary shaft 20 and the thrust ring 34 up from the inner
surface of the connection member 8. In this manner, the thrust
force acting on the rotary shaft 20 is received.
[0106] Although not detailed in the drawing, the lubricating oils
that each lubricate the radial bearing portion (the sliding portion
between the rotary shaft 20 and the sleeve 31) of the fluid bearing
30 and the thrust bearing portion (the contacting/sliding portion
between the thrust ring 34 and the connection member 8) communicate
mutually, and there is formed a closed circulating passage that
circulates the lubricating oils in a single direction with the
rotation of the rotary shaft 20. A through hole 35 shows a part of
the passage.
[0107] In the fourth embodiment, the rotary shaft 20, the fluid
bearing 30, the connection member 8, and the thrust ring 34 are
integrally assembled in advance as a product, as shown in FIG. 8.
With the bearing assembly thus produced, the projected end of the
rotary shaft 20 thereof is fixedly engaged with the central
circular hole 9 of the rotor hub 3, and the smaller diameter
portion 8b of the connection member 8 is fixedly engaged with the
central circular hole 11 of the base 2, whereby the rotary shaft
type spindle motor 1 of the fourth embodiment is made up.
[0108] The fourth embodiment is different from the third embodiment
in terms of the foregoing points, however it is not different in
the other points; and the detailed description will be omitted.
[0109] As the fourth embodiment is configured as above, when the
power is supplied from the feeder part 17 to the windings of the
stator 15, the rotor hub 3 with the permanent magnet 16 starts to
rotate as one body with the rotary shaft 20. The base 2 supports
the rotary shaft 20 of the rotor hub 3 to freely rotate through the
connection member 8 and the fluid bearing 30.
[0110] The fourth embodiment thus configured exhibits the following
effects.
[0111] In the rotary shaft type spindle motor 1 in which the rotary
shaft 20 is vertically installed on the rotor hub 3 and is
supported to freely rotate through the fluid bearing 30 on the base
2, the sleeve 31 of the fluid bearing 30 is fixed to the base 2
through the connection member 8; and therefore, the base 2 being
the other one of the two counterparts (the rotor hub 3 being the
component on the rotating side and the base 2 as the component on
the fixing side) that mount the fluid bearing 30 can be made up
without the inner peripheral surface of a wall, which has
conventionally been regarded as necessary to fit the sleeve 31 of
the fluid bearing 30 to the base 2. As a result, there does not
exist the stress resulting from the shape precision (circularity,
cylindricality, surface roughness) of the inner peripheral surface
of the wall, or the stress caused by the press fitting, adhesion,
or press-fit adhesion as the method of mounting the bearing;
accordingly disappear bad influences on the precision of the
sliding surfaces of the sleeve 31 and the rotary shaft 20 and the
clearance between the sliding surfaces of the two to be ensured at
a constant quantity through the outer peripheral surface of the
sleeve 31 of the fluid bearing 30, so that the reliability of the
run-out accuracy/NRRO, the noises, the acoustic life, and the
rigidity, etc., of the spindle motor 1 can be enhanced.
[0112] Further, the base 2 being the other one of the two
counterparts that mount the fluid bearing 30 can be configured
without the inner peripheral surface of the wall, which has
conventionally been regarded as necessary to fit the sleeve 31 of
the fluid bearing 30 to the base 2; and therefore, the adhesion
groove and the run-off groove that are formed conventionally on the
inner peripheral surface of the wall become unnecessary, which
reduces the man-hour to lower the manufacturing cost.
[0113] Further, since the fluid bearing 30, the rotary shaft 20,
the connection member 8, and the thrust ring 34 are assembled in
advance into one assembly unit, fastening the rotary shaft 20 to
the rotor hub 3 being the one of the two counterparts that mount
the bearing assembly and fastening the smaller diameter portion 8b
of the connection member 8 to the base 2 being the other one will
achieve to assemble the fluid bearing 30 between these two
counterparts, thus the mounting work of the fluid bearing 30
becomes extremely easy to perform. Here, the lubricating oil is to
be filled up after finishing the mounting work.
[0114] In the first through fourth embodiments, it is assumed that
the bearing assemblies each are applied to the spindle motors each;
however, they can be applied preferably to various rotating
machines that require a high run-out accuracy/NRRO and/or low
noises.
[0115] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
* * * * *