Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-06-08
2002-05-21
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S198100, C347S259000
Reexamination Certificate
active
06392771
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a bearing device having a sleeve fitted to a shaft and supporting it for rotation relative to the shaft, and a deflecting-scanning apparatus using the same.
2. Related Background Art
Heretofore, a deflecting-scanning apparatus of this kind has been used in an image forming apparatus such as a laser beam printer or a laser facsimile apparatus, and to make this deflecting-scanning apparatus highly accurate, a highly accurately rotatable bearing device has been required, and a dynamic pressure fluid bearing rotatable in a non-contact manner is used in such a bearing device.
FIG. 1
of the accompanying drawings is a cross-sectional view of a deflecting-scanning apparatus using a bearing device by a dynamic pressure fluid bearing which is disclosed in Japanese Laid-Open Patent Application No. 8-5951. A fixed shaft
22
formed of a ceramic material is fixed to the housing
21
of a drive motor, and a rotatable sleeve
24
formed of a ceramic material is rotatably fitted to the fixed shaft
22
. Also, a flange
25
formed of aluminum or brass is fixed to the outer periphery of the rotatable sleeve
24
as by shrinkage fitting, and a driving magnet
26
is adhesively secured to the outer periphery of this flange
25
. Further, a stator
28
is disposed on a base plate
27
fixed onto the housing
21
so as to be opposed to the driving magnet
26
, whereby a drive motor is constituted.
On the other hand, a second permanent magnet
30
is mounted on the upper end of the fixed shaft
22
, and a first permanent magnet
29
is fixed to the rotatable sleeve
24
so that magnetic poles of different kinds may be vertically (axially of the fixed shaft) opposed to the second permanent magnet
30
.
Thus, the rotatable sleeve
24
is floated up by a magnetic repulsive force and an air pool
31
is created between the fixed shaft
22
and the first permanent magnet
29
. Also, a through-hole
23
a
for communicating the air pool
31
with the outside is provided in the first permanent magnet
29
, and a plug
32
is removably mounted in this through-hole
23
a
. Further, a rotatable polygon mirror
34
is fixed onto the flange
25
by a leaf spring
33
fixed to the rotatable sleeve
24
.
When with such a construction, the fixed shaft
22
and the rotatable sleeve
24
are fitted together with the plug
32
being removed, they can be easily fitted together with the air in the rotatable sleeve
24
flowing out of the through-hole
23
a
. Also, when the rotatable sleeve
24
is rotated, the rotatable sleeve
24
is supported in a radial direction by the air film between the rotatable sleeve
24
and the fixed shaft
22
, and is supported in a thrust direction by the repulsive forces of the permanent magnets
29
and
30
. At this time, the air in the air pool
31
enveloped by the plug
32
acts so as to attenuate the vertical movement of the rotatable sleeve
24
, and holds the rotatable sleeve
24
in its stable floated-up position.
As described above, in this example of the prior art, the two permanent magnets for thrust floating-up are provided so as to be opposed to each other axially of the fixed shaft.
In such a construction, the rotatable sleeve
24
is very unstably vibrated vertically (axially) relative to a disturbance such as vibration to the apparatus. The vertical vibration of the rotatable sleeve is alleviated to some extent by the air pool
31
, but it alone is insufficient.
Such vibration of the rotatable sleeve provides the vertical movement of the rotatable polygon mirror mounted thereon, and binders good deflection and scanning.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-noted problem and to provide a bearing device in which the disposition of permanent magnets for thrust floating-up is contrived to thereby prevent the vibration of a rotor portion (a rotatable sleeve or a rotary shaft), and a deflecting-scanning apparatus using the same.
To achieve the above object, a bearing device according to the present invention is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
Also, a deflecting-scanning apparatus according to the present invention is structured to include a light source, a deflector for deflectively scanning a light beam from the light source, and a rotating device for rotatively driving the deflector. The bearing device of the rotating device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
Also, to achieve the above object, the bearing device according to the present invention is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device, and one of the first permanent magnet and the second permanent magnet is of such a shape as to surround the other of the first and second permanent magnets.
Also, the deflecting-scanning apparatus according to the present invention is structured to include a deflector for deflectively scanning a light beam, and a rotating device for rotatively driving the deflector. The bearing device of the rotating device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet and the second permanent magn
Fukita Taku
Fukutomi Akihiro
Miyamoto Hideyuki
Nakasugi Mikio
Sato Isshin
Boutsikaris Leo
Schuberg Darren
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