Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2001-09-20
2004-03-09
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S243000
Reexamination Certificate
active
06704038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present intention relates to a dynamic pressure bearing apparatus, and more specifically a dynamic pressure bearing apparatus which is suited for use in a light deflecting apparatus such as a laser beam printer or a bar-code reader.
2. Related Background Art
A laser beam printer or a bar-code reader uses a light deflecting apparatus for scanning a medium to be scanned with a laser beam. In such a light deflecting apparatus a rotating polyhedral mirror which is rotated at a high speed is attached to a rotating shaft rotatably supported by a bearing Conventional bearing frequently used as such a bearing is a dynamic pressure bearing which can rotate stably and smoothly. Furthermore, dynamic pressure bearings are used widely in information storage appliances such as optical disks, magnetic disks and the like as a bearing for supporting a disk rotating at a high speed.
FIG. 1
is a schematic sectional view showing an example of main members of a conventional light deflecting apparatus such as that described above. In
FIG. 1
, a rotating shaft
101
is rotatable supported in a bearing slot formed in a sleeve
102
. At a lower end of the sleeve
102
, a fixed plate
103
is fixed to seal the above-described bearing slot and a thrust plate
104
is disposed on the fixed plate
103
. Between an inside surface of the bearing slot of the sleeve
102
and an outside surface of the rotating shaft
101
and between the thrust plate
104
and an end surface of the rotating shaft
101
, oil is filled as an operating fluid for generating a dynamic pressure. Furthermore, the end surface of the rotating shaft
101
is made of a material having low frictional resistance and composes a thrust bearing together with the thrust plate
104
.
A flange member
110
is fixed to an upper portion of the rotating shaft
101
. A rotating polyhedral mirror
111
having a reflecting surface
111
a
is mounted on the flange member
110
. This rotating polyhedral mirror is pressed by a pressing spring so as to be coupled integrally with the flange member
110
and a rotor
112
.
The rotor
112
has a permanent magnet
112
a
and a yoke
112
b
supporting the permanent magnet
112
a
. On the other hand, a circuit board
114
is fixed to the sleeve
102
and a stator core
113
b
of a stator
113
is erected and supported on the circuit board
114
. A stator coil
113
a
wound around the stator core
113
b
is opposed to the permanent magnet
112
a
of the rotor
112
, and a motor which rotatingly drives the rotating polyhedral mirror
111
is composed of the stator coil
113
a
and the permanent magnet
112
a.
An oil reservoir
102
a
is formed on a top end portion of the bearing slot of the sleeve
102
, thereby reserving a redundancy for rampage of a liquid surface of the oil in the bearing slot. Furthermore, large-diameter portions are formed also at the lower end portion and in a middle portion of the sleeve
102
so as to form relief portions
102
b
and
102
c
for reducing a loss of a dynamic pressure of the oil. Furthermore, herringbone dynamic pressure generating grooves
105
a
and
105
b
are formed on an outer circumferential surface of the rotating shaft
101
between the oil reservoir
102
a
at the top end and the relief portion
102
c
in the middle portion and between the relief portion
102
c
in the middle portion and the relief portion
102
b
at the lower end, respectively
A spiral groove (not shown) is formed on a top surface of the thrust plate
104
. An upper end of the rotating shaft
101
protrudes higher than the bearing slot of the sleeve
102
to compose a coupled portion of the rotating polyhedral mirror
111
together with the flange member
110
.
When the rotating shaft
101
rotates in the dynamic pressure bearing apparatus which is configured as described above, a dynamic pressure is generated in the oil by a function of the dynamic pressure generating grooves
105
a
and
105
b
formed in the bearing slot of the sleeve
102
and the rotating shaft
101
is rotated in a condition where the rotating shaft
101
is not in contact with the bearing slot of the sleeve
102
. Also in a thrust direction, a dynamic pressure is generated by a function of a spiral groove formed on the thrust plate
104
, whereby the rotating shaft
101
is supported in a floated condition.
In case of using a liquid such as oil as an operating fluid for a dynamic pressure bearing, however, the above-described conventional technology may allow air to be involved in the operating fluid when the sleeve
102
is fitted over the shaft
101
at an initial assembling step of the production. When the apparatus is heated by rotation or installed at a location kept at a low pressure such as a highland, if the involved air is stagnant in a large amount in the relief portions
102
b
and
102
c
, the involved air penetrates from the relief portions
102
b
and
102
c
into a bearing gap of the dynamic pressure bearing. As a result, the air which is formed into bubbles may carry out the oil when the air is exhausted outside from an opening of the bearing.
When the oil leaks out from the opening of the bearing as described above in a condition of use where a light deflecting apparatus is repeatedly started and stopped, the oil goes along the flange member
110
and the yoke
112
b
, and is splashed by centrifugal forces generated by rotations of the flange member
110
and the yoke
112
b
, thereby posing a problem to cause malfunctions of appliances
In order to solve a problem as described above, Japanese Patent Application Laid-Open No. 6-311696 discloses a method for providing a rotating shaft with an oil leakage preventive member. Furthermore, Japanese Patent Application Laid-Open No. 8-75011 discloses a method for disposing an oil absorbing sheet which absorbs leaked oil.
However, both the methods described above have problems of showing an insufficient leakage preventive effect and making assembling steps complicate.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the problems of the above-described prior art and provide a dynamic pressure bearing apparatus having high performance and excellent stability without hindering operations of appliances due to leaked oil.
An object of the present invention is to provide a dynamic pressure bearing apparatus comprising:
a rotating shaft inclined in a predetermined direction from a vertical direction;
a sleeve rotatably supporting the rotating shaft;
an operating fluid for generating a dynamic pressure, the operating fluid being filled in a gap formed between the sleeve and the rotating shaft; and
capturing means for capturing the operating fluid leaked from the gap, the capturing means being disposed on an outside surface of the sleeve in the predetermined direction.
Another object of the present invention is to provide a rotating apparatus comprising the dynamic pressure bearing apparatus as described above and a motor for rotating the rotating shaft.
Still another object of the present invention is to provide a light deflecting apparatus comprising the rotating apparatus as described above and a rotating polyhedral mirror attached to the rotating shaft.
A further object of the present invention is to provide a laser beam printer comprising a light source for emitting a laser beam, the above-described light deflecting apparatus for deflecting the laser beam emitted from the light source a photosensitive member and a scanning lens for condensing on the photosensitive member the laser beam deflected by the light deflecting apparatus.
REFERENCES:
patent: 5270737 (1993-12-01), Nakasugi et al.
patent: 5822846 (1998-10-01), Moritan et al.
patent: 6242830 (2001-06-01), Katagiri
patent: 6307293 (2001-10-01), Ichiyama
patent: 6397470 (2002-06-01), Saichi et al.
patent: 6-311696 (1994-11-01), None
patent: 8-75011 (1996-03-01), None
patent: 2000-60064 (2000-02-01), None
Asami Masayoshi
Kugioka Michihiro
Maekawa Ichiro
Masuda Hiromasa
Nakajima Nobuo
Canon Seiki Kabushiki Kaisha
Pham Hai
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