U.S. patent application number 13/422660 was filed with the patent office on 2013-06-27 for spindle motor.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. The applicant listed for this patent is Hyun Ho SHIN, Chang Jo YU. Invention is credited to Hyun Ho SHIN, Chang Jo YU.
Application Number | 20130163116 13/422660 |
Document ID | / |
Family ID | 48578164 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130163116 |
Kind Code |
A1 |
SHIN; Hyun Ho ; et
al. |
June 27, 2013 |
SPINDLE MOTOR
Abstract
There is provided a spindle motor. The spindle motor includes a
fixed member; and a rotating member rotating relatively to the
fixed member, and having oil filling a bearing clearance formed
between the fixed member and the rotating member, wherein the fixed
member and the rotating member are provided with an oil diffusion
path communicating an air/oil interface formed at a boundary
between the oil filled in the bearing clearance and air with the
outside, and at least one of the fixed member and the rotating
member is provided with at least one dummy oil groove opened to the
oil diffusion path and having oil filled in at least a portion of
the inside thereof.
Inventors: |
SHIN; Hyun Ho; (Yongin,
KR) ; YU; Chang Jo; (Suwon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHIN; Hyun Ho
YU; Chang Jo |
Yongin
Suwon |
|
KR
KR |
|
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon
KR
|
Family ID: |
48578164 |
Appl. No.: |
13/422660 |
Filed: |
March 16, 2012 |
Current U.S.
Class: |
360/99.08 ;
310/90; G9B/17.002 |
Current CPC
Class: |
G11B 19/2036
20130101 |
Class at
Publication: |
360/99.08 ;
310/90; G9B/17.002 |
International
Class: |
G11B 17/02 20060101
G11B017/02; H02K 7/08 20060101 H02K007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2011 |
KR |
10-2011-0141670 |
Claims
1. A spindle motor, comprising: a fixed member; and a rotating
member rotating relatively to the fixed member, and having oil
filling a bearing clearance formed between the fixed member and the
rotating member, the fixed member and the rotating member being
provided with an oil diffusion path communicating an air/oil
interface formed at a boundary between the oil filled in the
bearing clearance and air with the outside of the spindle motor,
and at least one of the fixed member and the rotating member being
provided with at least one dummy oil groove opened to the oil
diffusion path and the dummy oil groove having oil filled in at
least a portion of the inside thereof.
2. The spindle motor of claim 1, wherein the dummy oil groove is
provided to have an annular shape in a circumferential
direction.
3. The spindle motor of claim 1, wherein the dummy oil groove has
an inclined side so that a width of a cross section thereof is
increased in a direction from a bottom of the dummy oil groove
toward the oil diffusion path.
4. The spindle motor of claim 1, further comprising at least one
communication hole communicating the dummy oil groove with an
outside of the spindle motor, wherein the communication hole is
sealed with a cap.
5. The spindle motor of claim 4, wherein the cap is detachable.
6. The spindle motor of claim 1, wherein the dummy oil groove is
opened to a portion at which the oil diffusion path is formed of a
labyrinth seal.
7. The spindle motor of claim 1, wherein oil filled in the dummy
oil groove is the same as the oil filled in the bearing
clearance.
8. The spindle motor of claim 1, wherein the rotating member
includes a shaft.
9. The spindle motor of claim 1, wherein the fixed member includes
a shaft.
10. A hard disk drive, comprising: a spindle motor of claim 1
coupled with a housing to rotate a disk; a magnetic head writing
data to and reading the data from the disk; and a head transfer
part moving the magnetic head to a predetermined position on the
disk through electromagnetic interaction between a magnet and a
coil.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent
Application No. 10-2011-0141670 filed on Dec. 23, 2011, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a spindle motor.
[0004] 2. Description of the Related Art
[0005] A hard disk drive (HDD), an information storage device,
reads data stored on a disk or writes data to a disk using a
read/write head.
[0006] The hard disk drive requires a disk driving device capable
of driving the disk. In the disk driving device, a small-sized
spindle motor is used.
[0007] The small-sized spindle motor has included a fluid dynamic
bearing assembly. A lubricating fluid is interposed between a
rotating member and a fixed member of the fluid dynamic bearing
assembly, such that a shaft is supported by fluid pressure
generated in the lubricating fluid.
[0008] In addition, in the spindle motor adopting the fluid dynamic
bearing assembly, the lubricating fluid (oil) forms an air/oil
interface at a boundary with air due to surface tension and a
capillary phenomenon. A sealing part of the fluid is formed by
using the air/oil interface.
[0009] However, oil may be leaked to the outside due to other
factors and oil may be scattered by being diffused according to a
concentration gradient of oil generated by a mole fraction
difference. Therefore, a need exists for a method for reducing an
amount of oil leaked due to diffusion.
RELATED ART DOCUMENT
[0010] (Patent Document 1) U.S. Pat. No. 6,380,651. [0011] (Patent
Document 2) Japanese Patent Laid-Open Publication No.
2006-211795.
SUMMARY OF THE INVENTION
[0012] An aspect of the present invention provides a motor
structure capable of preventing oil from being leaked due to an oil
diffusion phenomenon according to a concentration gradient of oil
generated by a mole fraction difference.
[0013] According to an aspect of the present invention, there is
provided a spindle motor, including: a fixed member; and a rotating
member rotating relatively to the fixed member, and having oil
filling a bearing clearance formed between the fixed member and the
rotating member, wherein the fixed member and the rotating member
are provided with an oil diffusion path communicating an air/oil
interface formed at a boundary between the oil filled in the
bearing clearance and air with the outside, and at least one of the
fixed member and the rotating member is provided with at least one
dummy oil groove opened to the oil diffusion path and having oil
filling at least a portion of the inside thereof.
[0014] The dummy oil groove may be provided to have an annular
shape in a circumferential direction.
[0015] The dummy oil groove may have an inclined side so that a
width of a cross section thereof is increased in a direction from a
bottom of the dummy oil groove toward the oil diffusion path.
[0016] The spindle motor may further include at least one
communication hole communicating the dummy oil groove with an
outside, wherein the communication hole is sealed with a cap.
[0017] The cap may be detachable.
[0018] The dummy oil groove may be opened to a portion at which the
oil diffusion path is formed of a labyrinth seal.
[0019] Oil filling the dummy oil groove may be the same as the oil
filling the bearing clearance.
[0020] The rotating member may include a shaft.
[0021] The fixed member may include a shaft.
[0022] According to another aspect of the present invention, there
is provided a hard disk drive, including: the spindle motor as
described above, the spindle motor coupled with a housing to rotate
a disk; a magnetic head writing data to and reading the data from
the disk; and a head transfer part moving the magnetic head to a
predetermined position on the disk through electromagnetic
interaction between a magnet and a coil.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0024] FIG. 1 is a cross-sectional view schematically showing a
motor according to an embodiment of the present invention;
[0025] FIG. 2 is an enlarged view of portion A of FIG. 1;
[0026] FIG. 3 is a cross-sectional perspective view schematically
showing a rotor in a motor according to an embodiment of the
present invention;
[0027] FIG. 4 is a cross-sectional view schematically showing a
motor according to another embodiment of the present invention;
[0028] FIGS. 5A and 5B are an enlarged view of portions `B` and `B"
of FIG. 4;
[0029] FIG. 6 is a perspective view schematically showing a shaft
in the motor according to another embodiment of the present
invention;
[0030] FIG. 7 is a perspective view schematically showing a base
member in the motor according to another embodiment of the present
invention;
[0031] FIGS. 8A and 8B are a cross-sectional view schematically
showing a disk driving apparatus using the motor according to the
embodiment of the present invention; and
[0032] FIGS. 9A and 9B are graphs showing a mole fraction of a
lubricating fluid in an oil diffusion path in the motor according
to the embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0033] Embodiments of the present invention will now be described
in detail with reference to the accompanying drawings. However, it
should be noted that the spirit of the present invention is not
limited to the embodiments set forth herein and those skilled in
the art and understanding the present invention can easily
accomplish retrogressive inventions or other embodiments included
in the spirit of the present invention by the addition,
modification, and removal of components within the same spirit, but
those are construed as being included in the spirit of the present
invention.
[0034] Further, like reference numerals will be used to designate
like components having similar functions throughout the drawings
within the scope of the present invention.
[0035] FIG. 1 is a cross-sectional view schematically showing a
motor according to an embodiment of the present invention, FIG. 2
is an enlarged view of portion A of FIG. 1, and FIG. 3 is a
cross-sectional perspective view schematically showing a rotor in a
motor according to an embodiment of the present invention.
[0036] Referring to FIGS. 1 to 3, a motor 100 including a fluid
dynamic bearing assembly 110 according to an embodiment of the
present invention may include a fluid dynamic bearing assembly 110
including a thrust plate 113 and a cap member 114, a stator 130
including a core 131 having a coil 132 wound therearound, and a
rotor 120 including a rotor case 121.
[0037] Hereinafter, the above configuration will be described in
detail.
[0038] The fluid dynamic bearing assembly 110 may include a shaft
111, a sleeve 112, a thrust plate 113, and a cap member 114.
[0039] First, terms with respect to directions will be first
defined. As viewed in FIG. 1, an axial (axially) direction refers
to a vertical direction based on the shaft 111, and a radially
outer or inner direction refers to a direction towards an outer end
of the rotor 120 based on the shaft 111 or a direction towards a
center of the shaft 111 based on the outer end of the rotor
120.
[0040] Further, a rotating member described below may be a rotating
member including a rotor 120 including the shaft 111, a thrust
plate 113, a rotor case 121, and a magnet 122 mounted thereon, or
the like, and the fixed member may be a member other than the
rotating members. For example, the fixed member may be relatively
fixed members, for example, such as the sleeve 112, the stator 130,
a base, or the like, as compared with the rotating members.
[0041] The sleeve 112 may support the shaft 111 so that a top end
of the shaft 111 is protruded axially upwardly, and may be formed
by forging Cu or Al or sintering Cu--Fe-based alloy powders or
SUS-based powders.
[0042] Here, the shaft 111 may be inserted into a shaft hole of the
sleeve 112 so as to have a bearing clearance C therebetween. The
bearing clearance C may be filled with oil that is the lubricating
fluid, and the rotation of the rotor 200 may be more smoothly
supported by a radial dynamic groove formed in at least one of an
outer circumferential surface of the shaft 111 and an inner
circumferential surface of the sleeve 120.
[0043] The radial dynamic groove may be formed in an inner
peripheral surface of the sleeve 112 that is the inside of the
shaft hole of the sleeve 112 and may form pressure so that the
shaft 111 is smoothly rotated at a predetermined distance from the
inner side of the sleeve 112 at the time of the rotation of the
shaft 111.
[0044] However, the radial dynamic groove is not necessarily formed
in the inner peripheral surface of the sleeve 112 as described
above but may also be formed in an outer circumferential portion of
the shaft 111. In addition, the number of radial dynamic grooves is
not limited.
[0045] The sleeve 112 may include a bypass channel 112a formed
therein in order to allow top and bottom portions of the sleeve 112
to communicate with each other, such that pressure of oil that is
the lubricating fluid in a fluid dynamic bearing assembly 110 is
dispersed, thereby equalizing the pressure, and may move bubbles,
or the like, present in the fluid dynamic bearing assembly 110 so
as to be discharged by circulation.
[0046] A cover plate 115 may be coupled with the bottom portion of
the sleeve 112, keeping the bearing clearance C therebetween while
accommodating the lubricating fluid, oil, in the bearing clearance
C.
[0047] The cover plate 115 may serve as a bearing supporting a
bottom portion of the shaft 111 in the state in which the clearance
between the cover plate 150 and the sleeve 112 is filled with the
lubricating fluid.
[0048] The thrust plate 113 may be disposed on the top portion of
the sleeve 120 in an axial direction and includes a hole formed in
the center thereof, wherein the hole corresponds to a cross section
of the shaft 111. Meanwhile, the shaft 110 may be inserted into
this hole.
[0049] Here, the thrust plate 113 may be separately fabricated and
then coupled to the shaft 111. However, the thrust plate 130 may be
integrally formed with the shaft 111 at the time of fabrication
thereof and may rotate together with the shaft 111 at the time of
the rotation of the shaft 111.
[0050] In addition, the bottom surface of the thrust plate 113 may
be provided with a thrust dynamic groove providing thrust dynamic
pressure to the shaft 111.
[0051] The thrust dynamic groove is not necessarily formed in the
bottom surface of the thrust plate 113 as described above but may
also be formed in the top surface of the sleeve 112 corresponding
to the bottom surface of the thrust plate 113.
[0052] The cap member 114 is a member that is press-fitted on the
top portion of the thrust plate 113 to seal the lubricating fluid
between the cap member 114 and the thrust plate 113.
[0053] The cap member 114 may include a horizontal part 114a
disposed above the thrust plate and a vertical part 114b downwardly
extending from an outer edge of the horizontal part 114a. That is,
an inner peripheral surface of the vertical part 114b is
press-fitted in an outer peripheral surface of the sleeve 112 or
may be bonded thereto by an adhesive.
[0054] A bottom surface of the cap member 114 facing the thrust
plate 113 may be provided in a tapered shape in order to seal the
lubricating fluid, which uses a capillary phenomenon and a surface
tension of the lubricating fluid in order to prevent the
lubricating fluid from being leaked to the outside at the time of
driving of the motor.
[0055] The stator 130 may include a coil 132, a core 133, and a
base member 131.
[0056] In other words, the stator 130 maybe a fixed structure
including the coil 132 generating electromagnetic force having a
predetermined magnitude at the time of application of power and a
plurality of cores 133 having the coil 132 wound therearound.
[0057] The core 133 maybe fixedly disposed above abase member 131
including a printed circuit board (not shown) having pattern
circuits printed thereon, a plurality of coil holes having a
predetermined size may be formed in portions of the base member 310
corresponding to the winding coil 132 to penetrate through the base
member 131 so as to expose the winding coil 132 downwardly and the
winding coil 132 may be electrically connected to the printed
circuit board (not shown) so that external power is supplied
thereto.
[0058] An outer peripheral surface of the sleeve 112 may be
press-fitted into the base member 131 and the core 133 having the
coil 132 wound therearound may be inserted into the base member
131. In addition, the base member 310 and the sleeve 112 may be
assembled with each other by applying an adhesive to an inner
surface of the base member 310 or an outer surface of the sleeve
120.
[0059] The rotor 120, a rotational structure rotatably provided
with respect to the stator 130, may include a rotor case 121 having
an annular ring shaped magnet 122 provided on an outer peripheral
surface thereof, wherein the annular ring shaped magnet 122 is
located to correspond to the core 133, having a predetermined
interval therebetween.
[0060] In addition, as the magnet 122, a permanent magnet
generating magnetic force having a predetermined strength by
alternately magnetizing an N pole and an S pole in a
circumferential direction may be used.
[0061] Here, the rotor case 121 may include a hub base 121a
press-fitted into the top end of the shaft 111 to thereby be fixed
thereto and a magnet support part 121b extending from the hub base
121a in an outer diameter direction and bent axially downwardly to
thereby support the magnet 122.
[0062] Meanwhile, according to the embodiment of the present
invention, a member for preventing oil that is the lubricating
fluid from being scattered or leaked due to the diffusion at an oil
interface may be used.
[0063] Referring to FIGS. 9A and 9B, when a separate member for
preventing the diffusion of oil is not provided, as shown in FIG.
9A, the concentration gradient of oil is approximately linearly
reduced from the air/oil interface to the outside, thereby
continuing to leak the oil due to the diffusion.
[0064] Therefore, in the embodiment of the present invention, at
least one dummy oil groove 123 filled with oil may be provided in
an oil diffusion path R1 communicating the air/oil interface with
the outside, wherein the air/oil interface is formed at the
boundary between the oil filling the bearing clearance C and air.
That is, at least one of the fixed member and the rotating member
forming the oil diffusion path R1 may be provided with at least one
dummy oil groove 123 having oil filling at least a portion of the
inside thereof, while the dummy oil groove 123 is opened to the oil
diffusion path R1.
[0065] When the dummy oil groove 123 opened to the oil diffusion
path R1 to further diffuse oil is provided, as shown in FIG. 9B,
the concentration gradient of oil may be reduced from the air/oil
interface to a portion at which the dummy oil groove 123 is
positioned and then increased. The concentration gradient of oil
may be linearly reduced to the outside after the oil passes through
the portion at which the dummy oil groove 123 is positioned, and
therefore, scattering or the leak of the oil filling the bearing
clearance C of the motor may be generated after the oil filling the
dummy oil groove 123 is completely scattered or leaked, thereby
effectively preventing the oil filling the bearing clearance C from
being leaked due to the diffusion.
[0066] Herein, the dummy oil groove 123 may be provided to have an
annular shape in a circumferential direction. As shown in FIG. 3,
the dummy oil groove 123 is provided in a direction corresponding
to a front of the air/oil interface by filling the dummy oil groove
123 provided in the annular shape along the circumferential
direction, with oil, thereby effectively preventing oil from being
scattered.
[0067] Further, the dummy oil groove 123 may have an inclined side
so that a width of a cross section thereof is increased in a
direction from the bottom portion of the dummy oil groove 123
toward the oil diffusion path. That is, the dummy oil groove 123
may have an inclined side so that the width of the cross section
thereof is increased outwardly from the bottom portion of the dummy
oil groove 123. This may effectively generate the capillary
phenomenon, thereby precisely sealing oil.
[0068] Further, the dummy oil groove 123 may be opened to a portion
at which the oil diffusion path R1 is formed of a labyrinth seal
L1. The oil diffusion path R1 may be formed by various members
(fixed member and rotating member) and a diameter thereof may be
various according to the mounted position thereof. That is, a size
of the cross section of the oil diffusion path R1 may be various
according to the structure of the motor. Therefore, the dummy oil
groove 123 provided in terms of preventing oil from being diffused
due to the mole fraction difference may be formed to be positioned
at a portion at which the size of the cross section of the oil
diffusion path R1 is relatively small, thereby effectively
preventing oil from being diffused.
[0069] In addition, the oil filling the dummy oil groove 123 may be
the same as the oil filling the bearing clearance C. However, the
embodiment of the present invention is not limited thereto.
Therefore, various kinds of oil may be used for embodiments of the
present invention.
[0070] Meanwhile, at least one communication hole 124 communicating
between the dummy oil groove 123 and the outside may be provided
and the communication hole 124 may be sealed by the cap 125. That
is, when the oil filling the dummy oil groove 123 may be completely
diffused, the communication hole 124 may be provided as a member
for further refilling oil. Further, the communication hole 124 may
be sealed with the detachable cap 125 so as to be repeatedly
used.
[0071] Although the embodiment of the present invention discloses
the case in which the dummy oil groove 123 is provided in the rotor
120, the position at which the dummy oil groove 123 is provided is
not limited thereto. Therefore, the oil diffusion path R1 may be
provided at any position. For example, as shown by a dotted line in
FIGS. 1 and 2, a dummy oil groove 127 may be provided to be opened
between the outer peripheral surface of the vertical part 114b of
the cap member 114 and a main wall part 129. Further, the dummy oil
groove 127 may be provided in any member regardless of the rotating
member and the fixed member. FIGS. 1 and 2 show that the dummy oil
groove 123 is formed in the rotor 120 that is the rotating member,
but is not limited thereto. Therefore, the dummy oil groove 123 may
also be formed in the cap member 114 opposed thereto.
[0072] Further, FIGS. 1, 2 and 3 show that a length direction of
the dummy oil groove 125 is provided to be perpendicular to a
diffusion direction of the oil diffusion path R1, but is not
limited thereto. Therefore, the dummy oil groove 125 may be
provided to have an inclined shape to the oil diffusion path R1
(see FIG. 4 or 5).
[0073] FIG. 4 is a cross-sectional view schematically showing a
motor according to another embodiment of the present invention,
FIG. 5 is an enlarged view of portions `B` and `B" of FIG. 4, and
FIG. 6 is a perspective view schematically showing a shaft in the
motor according to another embodiment of the present invention.
[0074] Referring to FIGS. 4 to 6, a spindle motor 200 according to
another embodiment of the present invention may include a base
member 210, a lower thrust member 220, a shaft 230, a sleeve 240, a
rotor hub 250, and an upper thrust member 260.
[0075] Here, the fluid dynamic bearing assembly may include the
shaft 230, the sleeve 240, upper and lower thrust members 260 and
220, and a rotor hub 250.
[0076] Here, terms with respect to directions will be defined. As
viewed in FIG. 4, an axial direction refers to a vertical
direction, that is, a direction from a lower portion of the shaft
230 toward an upper portion thereof or a direction from the upper
portion of the shaft 230 toward the lower portion thereof, and as
viewed in FIG. 4, a radial direction refers to a horizontal
direction, that is, a direction from the shaft 230 toward an outer
peripheral surface of the rotor hub 250 or from the outer
peripheral surface of the rotor hub 250 toward the shaft 230, and a
circumferential direction refers to a direction rotating along the
circumference of a circle having a radius at a predetermined
distance from the rotating center.
[0077] Further, the rotating member described to be below may be a
rotating member including a sleeve 240, the rotor hub 250, a magnet
280 mounted thereon, or the like, and the fixed member may be a
member other than the rotating members. For example, the fixed
member may be relatively fixed members with regard to the rotating
members, for example, such as the shaft 230, the upper and lower
thrust members 260 and 220, the base member 210, or the like.
[0078] The base member 210 may include amounting groove 212 so as
to form a predetermined space together with the rotor hub 250. In
addition, the base member 210 may include a coupling part 214
extending axially upwardly and having a stator core 202 installed
on an outer peripheral surface thereof.
[0079] In addition, the coupling part 214 may include a seat
surface 214a provided on the outer peripheral surface thereof so
that the stator core 202 may be seated thereon. Further, the stator
core 202 seated on the coupling part 214 may be disposed above the
mounting groove 212 of the base member 210 described above.
[0080] The shaft 230 may be fixedly mounted on the base member 210.
That is, the bottom end portion of the shaft 230 may be inserted
into an installation hole 210a formed in the base member 210. In
addition, the bottom end portion of the shaft 230 may be bonded to
an inner surface of the base member 210 by an adhesive and/or
welding. Therefore, the shaft 230 may be fixed.
[0081] Meanwhile, the shaft 230 may also be included in the fixed
member, that is, the stator, together with the upper and lower
thrust members 260 and 220 and the base member 210 to be described
below.
[0082] Meanwhile, the top surface of the shaft 230 may be provided
with a coupling unit, for example, a screw part having a screw
screwed thereto so that a cover member (not shown) is fixedly
installed thereto.
[0083] In addition, at least one of the outer peripheral surface of
the shaft 230 and the inner peripheral surface of the sleeve 240
may be provided with top and bottom radial dynamic grooves 241 for
forming the fluid dynamic pressure at the time of the rotation of
the sleeve 240. Further, a reservoir part 231 in which the bearing
clearance is wider than other portions may be provided between the
top and bottom radial dynamic grooves 241.
[0084] The sleeve 240 maybe rotatably installed on the shaft 230.
To this end, the sleeve 240 may include a shaft support part
provided as a through hole into which the shaft 230 is inserted.
Meanwhile, when the sleeve 240 is installed on the shaft 230, the
inner peripheral surface of the sleeve 240 and the outer peripheral
surface of the shaft 230 may be disposed to be spaced apart from
each other by a predetermined interval to thereby form the bearing
clearance C therebetween. Further, the bearing clearance C may be
filled with the lubricating fluid.
[0085] In addition, the sleeve 240 may be provided with top and
bottom groove parts 248 and 249 in which the upper and lower thrust
members 260 and 220 to be described below may be received. The top
and bottom groove parts 248 and 249 may each be formed by bottoms
248a and 249a of the groove part and side walls 248b and 249b of
the groove part. In the embodiment of the present invention, the
term of bottoms of the groove part may refer to a surface
vertically formed to an axial direction in the groove parts 248 and
249 and the term of side walls of the groove part may refer to a
surface formed to be parallel with the axial direction.
[0086] In addition, the inner surface of the sleeve 240 may be
provided with a radial dynamic groove 241 generating the fluid
dynamic pressure via the lubricating fluid (oil) filling the
bearing clearance C at the time of the rotation of the sleeve 240.
That is, as shown in FIG. 4, the radial dynamic groove 241 may be
provided at the top and bottom portions of the sleeve.
[0087] However, the radial dynamic groove is not limited to the
formation thereof in the inner surface of the sleeve 240 but may
also be formed in the outer peripheral surface of the shaft 230 and
may be provided in various shapes such as herringbone, spiral,
helical shapes, or the like.
[0088] Further, the sleeve 240 may further include a circulation
hole 247 communicating between the top groove part 248 of the
sleeve 240 and the bottom groove part 249 thereof. The circulation
hole 247 may discharge bubbles included in the lubricating fluid of
the bearing clearance C to the outside therethrough and may
facilitate circulation of the lubricating fluid.
[0089] The rotor hub 250 may be coupled to the sleeve 240 to
thereby rotate together with the sleeve 240.
[0090] The rotor hub 250 may include a rotor hub body 252 including
an insertion part 252a formed therein, the insertion part 252a
including the sleeve 240 inserted into an inner portion thereof,
amounting part 254 extending from an edge of the rotor hub body 252
and including a magnet assembly 280 mounted on an inner surface
thereof, and an extension part 256 extending from an end of the
mounting part 254 radially outwardly.
[0091] Meanwhile, an inner circumferential surface of the rotor hub
body 252 may be bonded to an outer circumferential surface of the
sleeve 240. That is, the inner circumferential surface of the rotor
hub body 252 may be bonded to the bonding surface 245 of the sleeve
240 by an adhesive and/or welding. In addition, the inner
circumferential surface of the rotor hub body 252 may also be
press-fitted in the bonding surface 245 of the sleeve 240.
[0092] Therefore, the sleeve 240 may rotate together with the rotor
hub 250 at the time of the rotation of the rotor hub 250.
[0093] In addition, the mounting part 254 may extend axially
downwardly from the rotor hub body 152. Further, the magnet
assembly 280 may be fixedly mounted on the-inner surface of the
mounting part 254.
[0094] Meanwhile, the magnet assembly 280 may include a yoke 282
fixedly mounted on the inner surface of the mounting part 254 and a
magnet 284 mounted on an inner peripheral surface of the yoke
282.
[0095] The yoke 282 may serve to direct a magnetic field from the
magnet 284 toward the stator core 202 to thereby increase magnetic
flux density. Meanwhile, the yoke 282 may have a circular ring
shape or have a shape in which one end portion thereof is bent so
as to increase the magnetic flux density by the magnetic field
generated from the magnet 284.
[0096] The magnet 284 may have an annular ring shape and be a
permanent magnet generating a magnetic field having a predetermined
strength by alternately magnetizing an N pole and an S pole in a
circumferential direction.
[0097] Meanwhile, the magnet 284 may be disposed to face a leading
end of the stator core 202 having a coil 201 wound therearound and
generate driving force by electromagnetic interaction with the
stator core 202 having the coil 201 wound therearound so that the
rotor hub 250 may rotate.
[0098] That is, when power is supplied to the coil 201, the driving
force rotating the rotor hub 250 may be generated by the
electromagnetic interaction between the stator core 202 having the
coil 201 wound therearound and the magnet 284 disposed to face the
stator core 102, such that the rotor hub 250 may rotate together
with the sleeve 240.
[0099] The upper thrust member 260 may be fixedly mounted on the
top end portion of the shaft 230 and may form a top air/oil
interface F3 together with the side wall 248b of the top groove
part of the sleeve 240. The upper thrust member 260 may include an
inner peripheral surface 262 bonded to the shaft 230 and an outer
peripheral surface 264 forming the air/oil interface together with
the side wall 248b of the top groove part. Here, the outer
peripheral surface 264 may be formed to have a top inclined part
261 of which an outer diameter of the top portion is formed to be
smaller than that of the bottom portion thereof.
[0100] Meanwhile, the thrust dynamic groove for generating thrust
dynamic pressure may be formed in at least one of the bottom
surface of the top upper thrust member 260 and the bottom surface
248a of the top groove part of the sleeve 240 disposed to face the
bottom surface of the upper thrust member 260. In the embodiment of
the present invention, when the circulation hole 247 is not
provided in the sleeve 240, the thrust dynamic groove may include
all kinds of the thrust dynamic grooves provided in a radial
direction. For example, one or two or more thrust dynamic grooves
may be provided in a radial direction. Meanwhile, in the embodiment
of the present invention, when the circulation hole 247 is provided
in the sleeve 240, the thrust dynamic groove may refer to only the
thrust dynamic groove 243a provided in a radially inner side based
on the circulation hole 247.
[0101] In addition, the upper thrust member 260 may include a top
cap 291 provided with the top portion thereof, the top cap 291
serving as a sealing member preventing the lubricating fluid
filling the bearing clearance C from being leaked upwardly. The top
cap 291 may terminate the top groove part 248 at the top portion
thereof in an axial direction to serve to prevent the lubricating
fluid from being leaked due to the scattering through the top
groove part 248. That is, the top cap 291 may be fixedly bonded to
the side wall 248b of the top groove part of the sleeve 240 by a
press-fit or adhesive coupling method, and the clearance between
the shaft hole of the top cap 291 through which the shaft protrudes
upwardly in an axial direction, and the shaft 230, may be
relatively narrow to suppress the leaking of air containing the
evaporated lubricating fluid to the outside, thereby suppressing
the reduction in an amount of the lubricating fluid filling the top
bearing clearance C.
[0102] The lower thrust member 220 may be fixedly mounted on the
bottom end portion of the shaft 230 and may form a bottom air/oil
interface F4 together with the side wall 249b of the bottom groove
part of the sleeve 240. The lower thrust member 220 may include an
inner peripheral surface 222 bonded to the shaft 230 and an outer
peripheral surface 224 provided to form the air/oil interface
together with the side wall 249b of the bottom groove part. Here,
the outer peripheral surface 224 may be formed to have a bottom
inclined part 221 of which an outer diameter of the bottom portion
is formed to be smaller than that of the top portion thereof.
[0103] Meanwhile, the thrust dynamic groove generating the thrust
dynamic pressure may be formed in at least one of the top surface
of the lower thrust member 220 and the bottom surface 249a of the
bottom groove part of the sleeve 240 provided to face the top
surface of the lower thrust member 220. In the embodiment of the
present invention, when the circulation hole 247 is not provided in
the sleeve 240, the thrust dynamic groove may include all kinds of
the thrust dynamic grooves formed in a radial direction. For
example, one or two or more thrust dynamic grooves formed in a
radial direction may be included therein. Meanwhile, in the
embodiment of the present invention, when the circulation hole 247
is provided in the sleeve 240, the thrust dynamic groove may refer
to only the thrust dynamic groove 243a formed in a radially inner
side based on the circulation hole 247.
[0104] In addition, The lower thrust member 220 may include a
bottom cap 293 provided with a bottom portion thereof, the bottom
cap 293 serving as a sealing member preventing the lubricating
fluid filling the bearing clearance C from being leaked
downwardly.
[0105] The bottom cap 293 may terminate the bottom groove part 249
at the top portion thereof in an axial direction to serve to
prevent the lubricating fluid from being leaked due to the
scattering through the bottom groove part 249. That is, the bottom
cap 293 may be fixedly adhered to the side wall 249b of the bottom
groove part of the sleeve 240 by a press-fit or adhesive coupling
method, and the clearance between the shaft hole of the bottom cap
293 through which the shaft protrudes downwardly, and the shaft
230, may be relatively narrow to suppress air containing the
evaporated lubricating fluid from being leaked to the outside,
thereby suppressing the reduction of the lubricating fluid filling
the top bearing clearance C.
[0106] Meanwhile, according to another embodiment of the present
invention, a member for preventing oil that is the lubricating
fluid from being scattered or leaked due to the diffusion at the
oil interface may be used.
[0107] Referring to FIGS. 9A and 9B, when a separate member for
preventing the diffusion of oil is not provided, as shown in FIG.
9A, the concentration gradient of oil may be approximately linearly
reduced from the air/oil interface to the outside, thereby
continuing to leak the oil due to the diffusion.
[0108] Therefore, in another embodiment of the present invention,
at least one of the dummy oil grooves 233 and 213 filled with oil
may be provided in the oil diffusion paths R2 and R3 communicating
between the air/oil interface and the outside, wherein the air/oil
interface is formed at the boundary between the oil filling the
bearing clearance C and air.
[0109] That is, at least one of the fixed member and the rotating
member forming the oil diffusion paths R2 and R3 may be provided
with at least one of the dummy oil grooves 233 and 213 having oil
filling at least a portion of the inside thereof, while the dummy
oil grooves 233 and 213 are opened to the oil diffusion paths R2
and R3.
[0110] Further, the embodiment of the present invention has a
structure in which two air/oil interfaces are respectively formed
on the top and the bottom, and therefore, two oil diffusion paths
R2 and R3 may be formed. As a result, the dummy oil grooves 233 and
213 may be respectively provided in paths.
[0111] When the dummy oil grooves 233 and 213 opened to the oil
diffusion paths R2 and R3 to further diffuse oil is provided, as
shown in FIG. 9B, the concentration gradient of oil may be reduced
from the air/oil interface to a portion at which the dummy oil
grooves 233 and 213 are positioned and is then increased. The
concentration gradient of oil may be approximately linearly reduced
to the outside after the oil passes through the portion at which
the dummy oil grooves 233 are 213 are positioned, and therefore,
scattering or the leaking of the oil filling the bearing clearance
C of the motor may be generated after the oil filling the dummy oil
grooves 233 and 213 is completely scattered or leaked, thereby
effectively preventing the oil filling the bearing clearance C from
being leaked due to the diffusion.
[0112] Here, the dummy oil grooves 233 and 213 may be provided to
have an annular shape in a circumferential direction. As shown in
FIGS. 6 and 7, the dummy oil grooves 233 and 213 may be provided in
a direction corresponding to a front of the air/oil interface by
filling oil in the dummy oil grooves 233 and 213 provided in the
annular shape along the circumferential direction, thereby
effectively preventing oil from being scattered.
[0113] That is, the dummy oil grooves 233 and 213 may have inclined
sides so that the width of cross sections thereof is increased from
the inside to the outside thereof. This may effectively generate
the capillary phenomenon, thereby precisely sealing oil.
[0114] Further, the dummy oil grooves 233 and 213 maybe opened to a
portion at which the oil diffusion paths R2 and R3 are formed of a
labyrinth seal L2. The oil diffusion paths R2 and R3 may be formed
of various members (fixed member and rotating member) and a
diameter thereof may be various according to the mounted position
thereof. That is, a size of cross sections of the oil diffusion
paths R2 and R3 may be various according to the structure of the
motor. Therefore, the dummy oil grooves 233 and 213 provided in
terms of preventing oil from being diffused due to the mole
fraction difference may be positioned at a portion at which the
size of the cross sections of the oil diffusion paths R2 and R3 is
relatively small, thereby effectively preventing oil from being
diffused.
[0115] In addition, the oil filling the dummy oil groove 123 may be
the same as the oil filling the bearing clearance C. However, the
embodiment of the present invention is not limited thereto.
Therefore, various kinds of oil may be used for the embodiment of
the present invention.
[0116] Meanwhile, at least one communication hole 234 communicating
between the dummy oil groove 233 and the outside may be provided
and the communication hole 234 may be sealed with the cap 235. That
is, when the oil filling the dummy oil groove 233 is completely
consumed due to the diffusion, the communication hole 234 may be
used as a member for further refilling oil. Further, the
communication hole 234 may be sealed with the detachable cap 235 so
as to be repeatedly used.
[0117] Although the embodiment of the present invention describes
that the dummy oil grooves 233 and 213 are provided in the shaft
230 or the base member 210, the position at which the dummy oil
groove is provided is not limited thereto. Therefore, the oil
diffusion paths R2 and R3 may be provided at any position. For
example, as shown by a dotted line FIGS. 4 and 5, the dummy oil
groove 215 may be provided to be opened between the lower thrust
member 293 and the base member 210. Further, the dummy oil groove
215 may be applied to any member regardless of the rotating member
and the fixed member. Although the drawing shows the case in which
the dummy oil grooves 233 and 213 are provided in the shaft 230 and
the base member 210 that are the fixed members, the embodiment of
the present invention is not limited thereto. Therefore, the dummy
oil grooves 233 and 213 may also be formed in the upper thrust
member 291, the lower thrust member 293, or the sleeve 240.
[0118] Further, as shown in the drawings, the dummy oil grooves 233
and 213 may be provided to be longitudinally inclined or vertical
to the direction of the oil diffusion path R1.
[0119] Referring to FIGS. 8A and 8B, a recording disk driving
device 800 having the motors 100 or 200 according to the embodiment
of the present invention mounted therein may be a hard disk driving
device and may include the motor 100 or 200, a head transfer part
810, and a housing 820.
[0120] The motors 100 and 200 have all the characteristics of the
motor according to the embodiment of the present invention
described above and may have a recording disk 830 mounted
thereon.
[0121] The head transfer part 810 may transfer a magnetic head 815
detecting information of the recording disk 830 mounted in the
motors 100 and 200 to a surface of the recording disk of which the
information is to be detected.
[0122] Here, the magnetic head 815 may be disposed on a support
portion 817 of the head transfer part 810.
[0123] The housing 820 may include a motor mounting plate 822 and a
top cover 824 shielding an upper portion of the motor mounting
plate 822 in order to form an internal space receiving the motors
100 or 200 and the head transfer part 810.
[0124] As set forth above, according to the embodiments of the
present invention, the motor capable of preventing oil from being
leaked due to the diffusion phenomenon of oil according to the
concentration gradient of oil generated by the mole fraction
difference may be provided.
[0125] Further, according to the embodiments of the present
invention, the above-mentioned defect may be solved by simplifying
the structure using the diffusion principle, thereby manufacturing
the motor without adding the separate manufacturing line.
[0126] While the present invention has been shown and described in
connection with the embodiments, it will be apparent to those
skilled in the art that modifications and variations can be made
without departing from the spirit and scope of the invention as
defined by the appended claims.
* * * * *