Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
2000-01-27
2002-01-15
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Fluid bearing
C384S114000
Reexamination Certificate
active
06338574
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Applications No.11-19129 filed on Jan. 27, 1999, No.11-27467 filed on Feb. 4, 1999 and No.11-101706 filed on Apr. 8, 1999 which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a bearing mechanism, a hard disk drive mechanism and a polygon mirror drive mechanism using the bearing mechanism, and a method for forming herringbone groove portions of a dynamic-pressure bearing, more specifically, a method for forming herringbone groove portions on a bearing shaft or bearing sleeve of a dynamic-pressure bearing.
Conventionally, for example in hard disk drive mechanisms of storage devices, polygon mirror drive mechanisms of copying machines or laser printer devices and the like, dynamic-pressure bearings have often been adopted in order to achieve rotations accompanied by less swaying-rotations. As such a dynamic-pressure bearing, there has been known one, for example as shown in Japanese Patent Laid-Open Publication HEI 5-215128, in which a rotating shaft is inserted inside a cylindrical-shaped bearing member while, for example, herringbone-shaped dynamic-pressure generating grooves are formed circumferentially in the outer circumferential surface of the rotating shaft. In this structure, when the rotating shaft is rotated at high speed inside the bearing member, a radial dynamic pressure is generated in a gap between the rotating shaft and the bearing member by a pumping effect of fluid on the dynamic-pressure generating grooves. As a result, for example when a radial force acts on the axis of rotation due to vibrations or other disturbance, the dynamic pressure acts as a restoring force, thus allowing a stable rotation accompanied by less swaying-rotations to be realized.
In another aspect, ball bearings have conventionally been used as a bearing for motors or the like that serve for rotationally driving the disk in polygon mirrors of laser printers, hard disk drives or the like. However, since a periodic sways would occur due to errors of sphericity of the ball or the like, it has recently been practiced to use dynamic-pressure bearings instead of the ball bearings.
In such a dynamic-pressure bearing, which is designed to generate a dynamic pressure to the fluid present in a gap of the bearing by a pumping effect, spiral dynamic-pressure generating grooves such as herringbone grooves are formed in either one of the bearing shaft or the bearing sleeve to generate the dynamic pressure.
FIG. 11
is a sectional view schematically showing a configuration in which a conventionally generally known pneumatic dynamic-pressure bearing
110
having a vacuum pump function is applied to a polygon-mirror dedicated scanner motor of a laser printer. In the polygon-mirror dedicated scanner motor shown here, a bearing shaft
114
of the dynamic-pressure bearing
110
is mounted on a base
113
so as to be installed in a fixed and closed state at a central position in a housing
112
, a bearing sleeve
115
is fitted around the bearing shaft
114
with a very slight gap, and a rotating mirror
118
is attached to this bearing sleeve
115
.
Further, a magnet
120
magnetized to N and S poles is provided on an outer circumferential surface of the bearing sleeve
115
, and a driving coil
116
as a motor is provided on an inner wall surface of the housing
112
so as to be opposed to the magnet
120
. In this arrangement, about a few &mgr;m deep V-shaped grooves
122
,
122
. . . (herringbone grooves) are carved at regular intervals in the direction of rotation in the outer circumferential surface of the bearing shaft
114
, where among these V-shaped grooves
122
,
122
. . . , those carved in upper and lower portions of the bearing shaft
114
play a role of a vacuum pump and those carved at central portion of the bearing shaft
114
are purposed to support the bearing shaft
114
itself.
FIG. 12A
shows an appearance view of the bearing shaft
114
of the dynamic-pressure bearing
110
shown in
FIG. 11
, and
FIG. 12B
shows a sectional view of the dynamic-pressure bearing
110
with the bearing sleeve included. As shown in
FIGS. 12A and 12B
, this bearing shaft
114
is internally formed into a hollow shape with one shaft end opened, gas inlet holes
124
,
124
. . . for letting in gas (e.g. air) are provided at upper and lower portions of the bearing shaft
114
, and gas inlet holes
125
,
125
. . . for introducing gas (air in the atmosphere in this example) to around the bearing shaft
114
are provided between the base
113
of the bearing shaft
114
and the bearing sleeve
115
.
In the dynamic-pressure bearing
110
constructed as shown above, when the rotating mirror
118
is rotated, air in the vessel is introduced through the gas inlet holes
125
into the bearing sleeve
115
, then flowing on so as to be introduced into the hollow of the bearing shaft
114
via the gas inlet holes
124
,
124
. . . of the bearing shaft
114
and discharged outside through the opening at one shaft end, as shown by arrows in the figure. Then, such a gas flow causes the internal pressure of the vessel to be reduced, enabling a smooth rotation without occurrence of a periodic sways or the like. When the rotating mirror
118
is stopped from rotating, the internal pressure of the vessel becomes equal to the external pressure.
Conventionally, groove machining by etching method has been used as a method for forming such dynamic-pressure generating grooves in the bearing shaft or the rotating mirror (bearing sleeve). This etching method includes masking in a specified configuration to form grooves at unmasked portions. Two types of methods are available to do this, one being wet etching which uses liquid phase—solid phase reaction with etchant and the other being dry etching which uses gas phase—solid phase reaction with reaction gas in plasma. Out of these two methods, the dry etching method is often used for groove formation by virtue of its relative superiority in machining precision. These etching methods are used for groove formation primarily in hard materials.
As another method for forming the grooves, rolling process has been used to form grooves of, for example, spiral or other shape. In this rolling process, material is sandwiched between dies or the like and, while being rotated by the dies or the like, plastically deformed, by which a specified configuration is formed. This rolling process is used for groove formation primarily in soft materials.
The formation of herringbone groove portions by the aforementioned etching method is largely affected in machining precision by the concentration of the etchant or the like. Also, the etchant erodes even inner circumferential surfaces of the herringbone groove portions, resulting in an unsatisfactory machining precision. Since configurational precision is required for herringbone groove portions to function as dynamic-pressure generating grooves, the etching method, which is low in machining precision, is unsuitable for the formation of herringbone groove portions. Furthermore, this etching method, which involves a totally large number of processes and moreover takes longer time for machining, is low in productivity and unsuitable for mass production, resulting in a poor practicability.
The rolling process, although suitable for machining of soft materials, is unsuitable for the formation of herringbone groove portions because dynamic-pressure bearings are made from hard material so as to withstand high-speed rotation. A hard material, if rolling processed, would tend to result in a considerable impairment of the shape of the dies or flaws of their surfaces. Deteriorations of the dies like this would cause the precision of the groove machining in a machining object to lower, and flaws of the surfaces of the dies would be transferred onto the surface of the machining object as they are, causing disadvantages that, for example, the surface of the machining object is unnecessarily cut out. This would result in an insufficient ma
Hisada Tatsuo
Kato Makio
Shimizu Narito
Yatazawa Jun
Daido Tokushuko Kabushiki Kaisha
Footland Lenard A.
Snider Ronald R.
Snider & Associates
LandOfFree
Bearing mechanism, hard disk drive mechanism and polygon... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bearing mechanism, hard disk drive mechanism and polygon..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bearing mechanism, hard disk drive mechanism and polygon... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2839088