U.S. patent application number 11/314478 was filed with the patent office on 2006-05-11 for hydrodynamic pivot bearing.
This patent application is currently assigned to Minebea Co., Ltd.. Invention is credited to Martin Hafen, Joerg Hoffmann, Andreas Kull, Olaf Winterhalter.
Application Number | 20060098905 11/314478 |
Document ID | / |
Family ID | 28675253 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060098905 |
Kind Code |
A1 |
Kull; Andreas ; et
al. |
May 11, 2006 |
Hydrodynamic pivot bearing
Abstract
The present invention provides a bearing comprised of a
hydrodynamic bearing and a pivot bearing, which can be used with a
spindle motor. It also provides a spindle motor utilizing a
hydrodynamic bearing and a pivot bearing.
Inventors: |
Kull; Andreas;
(Donaueschingen, DE) ; Winterhalter; Olaf;
(Epfendorf, DE) ; Hoffmann; Joerg; (Mettlach,
DE) ; Hafen; Martin; (Spaichingen, DE) |
Correspondence
Address: |
SCHULTE ROTH & ZABEL LLP;ATTN: JOEL E. LUTZKER
919 THIRD AVENUE
NEW YORK
NY
10022
US
|
Assignee: |
Minebea Co., Ltd.
Nagano-Ken
JP
|
Family ID: |
28675253 |
Appl. No.: |
11/314478 |
Filed: |
December 21, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10387047 |
Mar 12, 2003 |
7008110 |
|
|
11314478 |
Dec 21, 2005 |
|
|
|
60363784 |
Mar 12, 2002 |
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Current U.S.
Class: |
384/107 |
Current CPC
Class: |
F16C 33/74 20130101;
F16C 33/107 20130101; H02K 7/086 20130101; F16C 2370/12 20130101;
H02K 7/085 20130101; F16C 17/10 20130101; H02K 7/09 20130101 |
Class at
Publication: |
384/107 |
International
Class: |
F16C 32/06 20060101
F16C032/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2002 |
DE |
DE10232933.8 |
Aug 19, 2002 |
DE |
DE10237848.7 |
Sep 2, 2002 |
DE |
DE10240634 |
Claims
1. A spindle motor comprising: a stator; a rotor; a pivot bearing;
a fluid dynamic journal bearing; a magnetic shield; and a cap.
2. The spindle motor of claim 1 wherein: said stator comprises a
bracket, a sleeve affixed to said bracket, a core affixed to said
bracket, and coils wound around said core; said rotor comprises a
shaft, a rotating hub, and a rotor magnet; said pivot bearing
comprises a pivot point at an end of said shaft rotating on said
sleeve; said fluid dynamic journal bearing comprises said shaft,
said sleeve, a fluid, and pressure generating grooves formed on a
vertical surface of one of said shaft and said sleeve; said
magnetic shield is positioned underneath said rotor magnet and
affixed to said bracket; said cap is affixed to said sleeve and
positioned partially over said shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of application Ser. No.
10/387,047, filed Mar. 12, 2003. Application Ser. No. 10/387,047
claims priority from U.S. Provisional Patent Application No.
60/363784, filed Mar. 12, 2002. Application Ser. No. 10/387,047
also claims priority from Fed. Rep. Of Germany Patent Application
Nos. DE1 0232933.8, filed Jul. 19, 2002, DE10237848.7, filed Aug.
19, 2002, and DE10240634, filed Sep. 2, 2002.
BACKGROUND OF THE INVENTION
[0002] The following invention relates to electronic spindle motors
of the type used in disk drives and in particular relates to
improvements in fluid bearings for such motors.
[0003] Disc drive systems have been used in computers and other
electronic devices for many years for storage of digital
information. Information is recorded on concentric memory tracks of
a magnetic disc medium, the actual information being stored in the
form of magnetic transitions within the medium. The discs
themselves are rotatably mounted on a spindle, the information
being accessed by means of transducers located on a pivoting arm
which moves radially over the surface of the disc. The read/write
heads or transducers must be accurately aligned with the storage
tracks on the disc to ensure proper reading and writing of
information; thus the discs must be rotationally stable.
[0004] Electric spindle motors of the type used in disk drives
conventionally rely on ball bearings to support a rotary member,
such as a rotating hub, on a stationary member, such as a shaft.
Ball bearings are wear parts and in time friction will cause
failure of the motor. In addition, ball bearings create debris in
the form of dust or fine particles that can find their way into
"clean" chambers housing the rotary magnetic disks which are driven
by the motor. The mechanical friction inherent in ball bearings
also generates heat and noise, both of which are undesirable in a
disk drive motor.
[0005] Fluid dynamic bearings represent a considerable improvement
over conventional ball bearings in spindle drive motors. In these
types of systems, lubricating fluid--either gas or
liquid--functions as the actual bearing surface between a
stationary base or housing in the rotating spindle or rotating hub
of the motor. For example, liquid lubricants comprising oil, more
complex ferro-magnetic fluids or even air have been utilized in
hydrodynamic bearing systems.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
spindle motor with a fluid dynamic pivot bearing which saves
run-current and, therefore, reduces power consumption of the
spindle motor. The present inventions combines the benefit of
increased stability provided by hydrodynamic bearings with the
benefit of low power consumption provided by pivot bearings.
[0007] The above and other objects, aspects, features and
advantages of the invention will be more readily apparent from the
description of the preferred embodiments thereof taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention is illustrated by way of example and not
limitation and the figures of the accompanying drawings in which
like references denote like or corresponding parts, and in
which:
[0009] FIG. 1 is a is a side cut-away view of an electronic spindle
motor having a rotational shaft, a magnetic shield, and a journal
bearing according to the first embodiment of the present
invention.
[0010] FIG. 2 is a side cut-away view of an electronic spindle
motor having a fixed shaft, a journal bearing, a counterplate, and
a thrust bearing according to the second embodiment of the present
invention.
[0011] FIG. 3 is a side cut-away view of an electronic spindle
motor having a rotational shaft, a journal bearing, a counterplate,
and a thrust bearing according to the second embodiment of the
present invention.
[0012] FIG. 4 is a side cut-away view of an electronic spindle
motor having a rotational shaft, a thrust-washer, a journal
bearing, a counterplate, and a thrust bearing according to the
third embodiment of the present invention.
[0013] FIG. 5 is a side cut-away view of an electronic spindle
motor having a fixed shaft, a thrust-washer, a journal bearing, a
counterplate, and a thrust bearing according to the third
embodiment of the present invention.
DETAILED DESCRIPTION
[0014] The first embodiment of the present invention is shown in
FIG. 1. A spindle motor includes a stator 10 and a rotor 6 that is
arranged for rotation relative to stator 10.
[0015] The rotor 6 comprises a rotor hub 18 and a tubular shaft 20
fixed coaxially to the rotor hub 18. A rotor magnet 12 is bonded to
the inner side of a circumferential wall of the rotor hub 18. The
outer side of the circumferential wall of the rotor hub 18 is
shaped to hold a magnetic disk (not shown).
[0016] Stator 10 comprises bracket 4 which is to be mounted on a
disk drive device (not shown); sleeve 8; core 52, which is fixedly
mounted to bracket 4, and coils 54 wound on the core 52. Coils 54
are radially spaced by a small gap from and arranged opposite to
the rotor magnet 12.
[0017] Sleeve 8 is a tubular member into which is formed a
cylindrical hole 85. With the exception of its upper most portion,
cylindrical hole 85 has a constant radius A. The uppermost portion
of cylindrical hole 85 has a slightly increased radius to provide
for a capillary seal 11. Cap 9 is affixed to the upper surface of
sleeve 8. Cap 9 has an inner radius B that is less than the radius
of cylindrical hole 85. The cap 9 prevents the shaft 20 from being
dislodged from cylindrical hole 85 when the motor receives a
physical shock.
[0018] Shaft 20 extends through hub 18 and cap 9 down into
cylindrical hole 85. The portion of shaft 20 that is inserted into
cylindrical hole 85 comprises an upper shaft section 205 and a
lower shaft section 206. Upper shaft section 205 has a constant
radius C that is greater than the inner radius B of the cap 9 and
that is slightly less than the radius of cylindrical hole 85. Lower
shaft section 206 is a contiguous with upper shaft section 205 and
the radius of lower shaft section 206 decreases from the radius C
of upper shaft section 205 to a radius of zero at the bottom of
cylindrical hole 85. Hence lower shaft section 206 is in contact
with sleeve 8 at a pivot point 13.
[0019] The gap comprised of the spaces between sleeve 8 and shaft
20 is filled with an appropriate lubricating fluid. Pressure
generating grooves 14 are formed either onto the outer surface of
upper shaft section 205 or onto the inner surface of sleeve 8
opposite to upper shaft section 205 so as to create a journal
bearing. If necessary, a second set of grooves can be added to form
a second journal bearing. Additionally, pressure generating grooves
can be placed on the bottom of lower shaft section 206 or on the
opposing surface of sleeve 8 to minimize material contact between
the shaft 20 and the sleeve 8.
[0020] A magnetic shield 15 is attached to bracket 4. Magnetic
shield 15 interacts with rotor magnet 12 to apply a downward force
on rotor 6.
[0021] The second embodiment of the present invention is shown in
FIG. 2 and in FIG. 3. The rotating shaft version of this spindle
motor is shown in FIG. 3. A spindle motor includes a stator 10 and
a rotor 6 that is arranged for rotation relative to stator 10.
[0022] The rotor 6 comprises a rotor hub 18 and a tubular shaft 20
fixed coaxially to the rotor hub 18. A rotor magnet 12 is bonded to
the inner side of a circumferential wall of the rotor hub 18. The
outer side of the circumferential wall of the rotor hub 18 is
shaped to hold a magnetic disk (not shown).
[0023] Stator 10 comprises bracket 4 which is to be mounted on a
disk drive device (not shown); sleeve 8; core 52, which is fixedly
mounted to bracket 4, and coils 54 wound on the core 52. Coils 54
are radially spaced by a small gap from and arranged opposite to
rotor magnet 12.
[0024] Sleeve 8 is a tubular member into which is formed a
cylindrical hole 85. Cylindrical hole 85 has: a constant radius A.
Directly above cylindrical hole 85 and coaxial with cylindrical
hole 85 is counterplate opening 88. Counterplate opening 88 extends
from the top of cylindrical hole 85 to the upper surface of sleeve
8. Counterplate opening 88 has a constant radius B that is greater
than the radius A of the cylindrical hole 85. Counterplate 19 is
securely fit inside of counterplate opening 88. Counterplate 19 has
an inner radius C that is less than the radius of cylindrical hole
85. The inner radius of counterplate 19 increases near the top of
counterplate 19 to provide for capillary seal 11.
[0025] Shaft 20 extends through hub 18 and counterplate 19 down
into cylindrical hole 85. The portion of shaft 20 that is inserted
into cylindrical hole 85 comprises an upper shaft section 205 and a
lower shaft section 206. Upper shaft section 205 has a constant
radius C that is greater than the inner radius B of the
counterplate 19 and that is slightly less than the radius A of
cylindrical hole 85. Lower shaft section 206 is a contiguous with
upper shaft section 205 and the radius of lower shaft section 206
decreases from the radius C of upper shaft section 205 to a radius
of zero at the bottom of cylindrical hole 85. Hence lower shaft
section 206 is in contact with sleeve 8 at a pivot point 13.
[0026] The gap comprised of the spaces between sleeve 8,
counterplate 19 and shaft 20 is filled with an appropriate
lubricating fluid. Pressure generating grooves 14 are formed either
onto the outer surface of upper shaft section 205 or onto the inner
surface of sleeve 8 opposite to upper shaft section 205 so as to
create a journal bearing. If necessary, a second set of grooves can
be added to form a second journal bearing. Pressure generating
grooves 16 are formed either on the upper surface of upper shaft
section 205 or on the opposing surface of counterplate 19 so as to
create a thrust bearing. Additionally, pressure generating grooves
may be placed on the bottom of lower shaft section 206 or on the
opposing surface of sleeve 8 to minimize material contact between
the shaft 20 and the sleeve 8.
[0027] The fixed shaft version the second embodiment is shown in
FIG. 2. It includes a stator 10 and a rotor 6 that is arranged for
rotation relative to stator 10.
[0028] The rotor 6 comprises a rotor hub 18 and sleeve 8 fixed
coaxially to rotor hub 18. A rotor magnet 12 is bonded to the inner
side of a circumferential wall of the rotor hub 18. The outer side
of the circumferential wall of the rotor hub 18 is shaped to hold a
magnetic disk (not shown).
[0029] Sleeve 8 is a tubular member into which is formed a
cylindrical hole 85. Cylindrical hole 85 has a constant radius A.
Directly below cylindrical hole 85 and coaxial with cylindrical
hole 85 is counterplate opening 88. Counterplate opening 88 extends
from the bottom of cylindrical hole 85 to the lower surface of
sleeve 8. Counterplate opening 88 has a constant radius B that is
greater than the radius A of the cylindrical hole 85. Counterplate
19 is securely fit inside of counterplate opening 88. Counterplate
19 has an inner radius C that is less than the radius of
cylindrical hole 85. The radius of shaft 20 decreases near the
bottom of counterplate 19 to provide for capillary seal 11.
[0030] Stator 10 comprises bracket 4, shaft 20, core 52 fixedly
fitted to bracket 4; and coils 54 wound on the core 52. Stator 10
is radially spaced by a small gap from and arranged opposite to the
rotor magnet 12.
[0031] Shaft 20 extends through hub 18 and counterplate 19 up into
cylindrical hole 85. The portion of shaft 20 that is inserted into
cylindrical hole 85 comprises an upper shaft section 205 and a
lower shaft section 206. However, in this fixed shaft version of
the second embodiment, upper shaft section 205 is physically below
lower shaft section 206. Upper shaft section 205 has a constant
radius C that is greater than the inner radius B of the
counterplate 19 and that is slightly less than the radius A of
cylindrical hole 85. Lower shaft section 206 is a contiguous with
upper shaft section 205 and the radius of lower shaft section 206
decreases from the radius C of upper shaft section 205 to a radius
of zero at the top of cylindrical hole 85. Hence lower shaft
section 206 is in contact with sleeve 8 at a pivot point 13.
[0032] The gap comprised of the spaces between sleeve 8,
counterplate 19 and shaft 20 is filled with an appropriate
lubricating fluid. Pressure generating grooves 14 are formed either
onto the outer surface of upper shaft section 205 or onto the inner
surface of sleeve 8 opposite to upper shaft section 205 so as to
create a journal bearing. If necessary, a second set of grooves can
be added to form a second journal bearing. Pressure generating
grooves 16 are formed either on the upper surface of upper shaft
section 205 or on the opposing surface of counterplate 19 so as to
create a thrust bearing. Additionally, pressure generating grooves
may be placed on the top of lower shaft section 206 or on the
opposing surface of sleeve 8 to minimize material contact between
the shaft 20 and the sleeve 8.
[0033] The third embodiment of the present invention is shown in
FIG. 4 and in FIG. 5. The rotating shaft version of this spindle
motor is shown in FIG. 4. It includes a stator 10 and a rotor 6
that is arranged for rotation relative to stator 10.
[0034] Rotor 6 comprises a rotor hub 18 and a tubular shaft 20
fixed coaxially to the rotor hub 18. A rotor magnet 12 is bonded to
the inner side of a circumferential wall of the rotor hub 18. The
outer side of the circumferential wall of the rotor hub 18 is
shaped to hold a magnetic disk (not shown).
[0035] Stator 10 comprises bracket 4, which is to be mounted on a
disk drive device (not shown); sleeve 8; core 52, which is fixedly
mounted to bracket 4; and coils 54 wound on the core 52. Coils 54
are radially spaced by a small gap from and arranged opposite to
the rotor magnet 12.
[0036] Sleeve 8 is a tubular member into which is formed a
cylindrical hole 85. Cylindrical hole 85 has a constant radius A.
Directly above cylindrical hole 85 and coaxial with cylindrical
hole 85 is thrust-washer opening 89. Thrust-washer opening 89 has a
constant radius D that is greater than the radius A of the
cylindrical hole 85 Directly above thrust-washer opening 89 and
coaxial with thrust-washer opening 89 is counterplate opening 88.
Counterplate opening 88 extends from the top of thrust-washer
opening 89 to the upper surface of sleeve 8. Counterplate opening
88 has a constant radius B that is greater than the radius D of
thrust-washer opening 89. Counterplate 19 is securely fit inside of
counterplate opening 88. Counterplate 19 has at its lowest point an
inner radius C that is the same as the radius A of cylindrical hole
85. However, the inner radius of counterplate 19 increases near the
top of counterplate 19 to provide for capillary seal 11.
[0037] Shaft 20 extends into sleeve 8 through hub 18, counterplate
19, thrust-washer opening 89, and cylindrical hole 85. The portion
of shaft 20 that is inserted into sleeve 8 comprises an upper shaft
section 205 and a lower shaft section 206. Upper shaft section 205
has a constant radius C that is less than the radius A of
cylindrical hole 85. Lower shaft section 206 is a contiguous with
upper shaft section 205 and the radius of lower shaft section 206
decreases from the radius C of upper shaft section 205 to a radius
of zero at the bottom of cylindrical hole 85. Hence lower shaft
section 206 is in contact with sleeve 8 at a pivot point 13.
Thrust-washer 207 is fixedly attached to shaft 20. Thrust-washer
207 has an outer radius E that is slightly less than the radius of
thrust-washer opening 89. Thrust-washer 207 contains a channel 208
that provides for the circulation of lubricating fluid. The
distance between thrustwasher 207 and counterplate 19 is preferably
between 4 and 7 microns. The distance between thrustwasher 207 and
sleeve 8 is preferably 0.1 mm. Providing this relatively large
diameter between the thrust-washer 207 and sleeve 8 reduces power
consumption.
[0038] The gap comprised of the spaces between sleeve 8,
counterplate 19, thrust-washer 207, and shaft 20 is filled with an
appropriate lubricating fluid. Pressure generating grooves 14 are
formed either onto the outer surface of upper shaft section 205 or
onto the inner surface of sleeve 8 opposite to upper shaft section
205 so as to create a journal bearing. If necessary, a second set
of grooves can be added to form a second journal bearing. Pressure
generating grooves 16 are formed either on the upper surface of
thrust-washer 207 or on the opposing surface of counterplate 19 so
as to create a thrust bearing. Additionally, pressure generating
grooves may be placed on the bottom of lower shaft section 206 or
on the opposing surface of sleeve 8 to minimize material contact
between the shaft 20 and the sleeve 8.
[0039] The fixed shaft version the third embodiment is shown in
FIG. 5. It includes a stator 10 and a rotor 6 that is arranged for
rotation relative to stator 10.
[0040] Rotor 6 comprises a rotor hub 18 and sleeve 8 fixed
coaxially to the rotor hub 18. A rotor magnet 12 is bonded to the
inner side of a circumferential wall of the rotor hub 18. The outer
side of the circumferential wall of the rotor hub 18 is shaped to
hold a magnetic disk (not shown).
[0041] Sleeve 8 is a tubular member into which is formed a
cylindrical hole 85. Cylindrical hole 85 has a constant radius A.
Directly below cylindrical hole 85 and coaxial with cylindrical
hole 85 is thrust-washer opening 89. Thrust-washer opening 89 has a
constant radius D that is greater than the radius A of the
cylindrical hole 85 Directly below thrust-washer opening 89 and
coaxial with thrust-washer opening 89 is counterplate opening 88.
Counterplate opening 88 extends from the bottom of thrust-washer
opening 89 to the lower surface of sleeve 8. Counterplate opening
88 has a constant radius B that is greater than the radius D of
thrust-washer opening 89. Counterplate 19 is securely fixed inside
of counterplate opening 88. Counterplate 19 has at its highest
point an inner radius C that is the same as the radius A of
cylindrical hole 85. However, the radius of shaft 20 decreases near
the bottom of counterplate 19 to provide for capillary seal 11.
[0042] Stator 10 comprises bracket 4; shaft 20; core 52, which is
fixedly mounted to bracket 4; and coils 54 wound on the core 52.
Coils 54 are radially spaced by a small gap from and arranged
opposite to the rotor magnet 12.
[0043] Shaft 20 extends into sleeve 8 through hub 18, counterplate
19, thrust-washer opening 89, and cylindrical hole 85. The portion
of shaft 20 that is inserted into sleeve 8 comprises an upper shaft
section 205 and a lower shaft section 206. However, in this fixed
shaft version of the third embodiment, upper shaft section 205 is
physically below lower shaft section 206. Upper shaft section 205
has a constant radius C that is less than the radius A of
cylindrical hole 85. Lower shaft section 206 is a contiguous with
upper shaft section 205 and the radius of lower shaft section 206
decreases from the radius C of upper shaft section 205 to a radius
of zero at the top of cylindrical hole 85. Hence lower shaft
section 206 is in contact with sleeve 8 at a pivot point 13.
Thrust-washer 207 is fixedly attached to shaft 20. Thrust-washer
207 has an outer radius E that is slightly less than the radius of
thrust-washer opening 89. Thrust-washer 207 contains a channel 208
that provides for the circulation of lubricating fluid. The
distance between thrustwasher 207 and counterplate 19 is preferably
between 4 and 7 microns. The distance between thrustwasher 207 and
sleeve 8 is preferably 0.1 mm. Providing this relatively large
diameter between the thrust-washer 207 and sleeve 8 reduces power
consumption.
[0044] The gap comprised of the spaces between sleeve 8,
counterplate 19, thrust-washer 207, and shaft 20 is filled with an
appropriate lubricating fluid. Pressure generating grooves 14 are
formed either onto the outer surface of upper shaft section 205 or
onto the inner surface of sleeve 8 opposite to upper shaft section
205 so as to create a journal bearing. If necessary, a second set
of grooves can be added to form a second journal bearing. Pressure
generating grooves 16 are formed either on the lower surface of
thrust-washer 207 or on the opposing surface of counterplate 19 so
as to create a thrust bearing. Additionally, pressure generating
grooves may be placed on the top of lower shaft section 206 or on
the opposing surface of sleeve 8 to minimize material contact
between the shaft 20 and the sleeve 8.
* * * * *