U.S. patent application number 09/092995 was filed with the patent office on 2002-02-21 for bearing device and deflecting-scanning apparatus using the same.
Invention is credited to FUKITA, TAKA, FUKUTOMI, AKIHIRO, MIYAMOTO, HIDEYUKI, NAKASUGI, MIKIO, SATO, ISSHIN, SUZUKI, YASUO.
Application Number | 20020021477 09/092995 |
Document ID | / |
Family ID | 27320764 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020021477 |
Kind Code |
A1 |
FUKITA, TAKA ; et
al. |
February 21, 2002 |
BEARING DEVICE AND DEFLECTING-SCANNING APPARATUS USING THE SAME
Abstract
A bearing 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. 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. 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.
Inventors: |
FUKITA, TAKA; (SUSONO-SHI,
JP) ; NAKASUGI, MIKIO; (TOKYO, JP) ; SUZUKI,
YASUO; (NUMAZU-SHI, JP) ; MIYAMOTO, HIDEYUKI;
(NUMAZU-SHI, JP) ; SATO, ISSHIN; (SHIZUOKA-KEN,
JP) ; FUKUTOMI, AKIHIRO; (NUMAZU-SHI, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
27320764 |
Appl. No.: |
09/092995 |
Filed: |
June 8, 1998 |
Current U.S.
Class: |
359/200.1 |
Current CPC
Class: |
G02B 26/121
20130101 |
Class at
Publication: |
359/200 |
International
Class: |
G02B 026/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 1997 |
JP |
9-168098 |
Jun 12, 1997 |
JP |
9-155068 |
Jun 18, 1997 |
JP |
9-161196 |
Claims
What is claimed is:
1. A bearing device comprising: a rotor portion comprising one of a
shaft and a sleeve, said shaft being fitted into said sleeve so as
to be capable of relative rotation between said shaft and said
sleeve; a stator portion comprising the other of said shaft and
said sleeve; a first permanent magnet mounted on the upper end
portion of said rotor portion; and a second permanent magnet
mounted on the upper end portion of said stator portion so as to be
opposed to said first permanent magnet in a circumferential
direction perpendicular to an axial direction.
2. A bearing device according to claim 1, wherein said rotor
portion is floated up relative to said stator portion by a magnetic
force working between said first permanent magnet and said second
permanent magnet.
3. A bearing device according to claim 1, wherein said rotor
portion is a rotatable sleeve, and said stator portion is a fixed
shaft.
4. A bearing device according to claim 1, wherein said shaft and
said sleeve are formed of a ceramic material.
5. A bearing device according to claim 1, further comprising a
cover provided on the upper end portion of said first permanent
magnet.
6. A light deflecting apparatus comprising: a rotor portion
comprising one of a shaft and a sleeve, said shaft being fitted
into said sleeve so as to be capable of relative rotation between
said shaft and said sleeve; a stator portion comprising the other
of said shaft and said sleeve; a deflector mounted on said rotor
portion for deflecting and scanning a light beam; a first permanent
magnet mounted on the upper end portion of said rotor portion; and
a second permanent magnet mounted on the upper end portion of said
stator portion so as to be opposed to said first permanent magnet
in a circumferential direction perpendicular to an axial
direction.
7. A light deflecting apparatus according to claim 6, wherein said
deflector is a rotatable polygon mirror.
8. A light deflecting apparatus according to claim 6, wherein said
rotor portion is floated up relative to said stator portion by a
magnetic force working between said first permanent magnet and said
second permanent magnet.
9. A light deflecting apparatus according to claim 6, wherein said
rotor portion is a rotatable sleeve, and said stator portion is a
fixed shaft.
10. A light deflecting apparatus according to claim 6, wherein said
shaft and said sleeve are formed of a ceramic material.
11. A light deflecting apparatus according to claim 6, further
comprising a cover provided on the upper end portion of said first
permanent magnet.
12. A deflecting-scanning apparatus comprising: a light source; a
rotor portion comprising one of a shaft and a sleeve, said shaft
being fitted into said sleeve so as to be capable of relative
rotation between said shaft and said sleeve; a stator portion
comprising the other of said shaft and said sleeve; a deflector
mounted on said rotor portion for deflecting and scanning a light
beam from said light source; a first permanent magnet mounted on
said upper end portion of said rotor portion; and a second
permanent magnet mounted on the upper end portion of said stator
portion so as to be opposed to said first permanent magnet in a
circumferential direction perpendicular to an axial direction.
13. A deflecting-scanning apparatus according to claim 12, wherein
said deflector is a rotatable polygon mirror.
14. A deflecting-scanning apparatus according to claim 12, wherein
said rotor portion is floated up relative to said stator portion by
a magnetic force working between said first permanent magnet and
said second permanent magnet.
15. A deflecting-scanning apparatus according to claim 12, wherein
said rotor portion is a rotatable sleeve, and said stator portion
is a fixed shaft.
16. A deflecting-scanning apparatus according to claim 12, wherein
said shaft and said sleeve are formed of a ceramic material.
17. A deflecting-scanning apparatus according to claim 12, further
comprising a cover provided on the upper end portion of said first
permanent magnet.
18. An image forming apparatus comprising: a light source; a
recording medium; a rotor portion comprising one of a shaft and a
sleeve, said shaft being fitted into said sleeve so as to be
capable of relative rotation between said shaft and said sleeve; a
stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and
scanning a light beam from said light source; a first permanent
magnet mounted on said upper end portion of said rotor portion; and
a second permanent magnet mounted on the upper end portion of said
stator portion so as to be opposed to said first permanent magnet
in a circumferential direction perpendicular to an axial
direction.
19. An image forming apparatus according to claim 18, wherein said
deflector is a rotatable polygon mirror.
20. An image forming apparatus according to claim 18, wherein said
rotor portion is floated up relative to said stator portion by a
magnetic force working between said first permanent magnet and said
second permanent magnet.
21. An image forming apparatus according to claim 18, wherein said
rotor portion is a rotatable sleeve, and said stator portion is a
fixed shaft.
22. An image forming apparatus according to claim 18, wherein said
shaft and said sleeve are formed of a ceramic material.
23. An image forming apparatus according to claim 18, further
comprising a cover provided on the upper end portion of said first
permanent magnet.
24. A bearing device comprising: a rotor portion comprising one of
a shaft and a sleeve, said shaft being fitted into said sleeve so
as to be capable of relative rotation between said shaft and said
sleeve; a stator portion comprising the other of said shaft and
said sleeve; a first permanent magnet mounted on said rotor
portion; and a second permanent magnet mounted on said stator
portion so as to be opposed to said first permanent magnet in a
circumferential direction perpendicular to an axial direction;
wherein one of said first and second permanent magnets is of such a
shape as to surround the other of said first and second
magnets.
25. A bearing device according to claim 24, wherein said one of
said first and second permanent magnets is a magnet made of
plastic.
26. A bearing device according to claim 24, wherein said rotor
portion is floated up relative to said stator portion by a magnetic
force acting between said first permanent magnet and said second
permanent magnet.
27. A bearing device according to claim 24, wherein said shaft and
said sleeve are formed of a ceramic material.
28. A light deflecting apparatus comprising: a rotor portion
comprising one of a shaft and a sleeve, said shaft being fitted
into said sleeve so as to be capable of relative rotation between
said shaft and said sleeve; a stator portion comprising the other
of said shaft and said sleeve; a deflector mounted on said rotor
portion for deflecting and scanning a light beam; a first permanent
magnet mounted on said rotor portion; and a second permanent magnet
mounted on said stator portion so as to be opposed to said first
permanent magnet in a circumferential direction perpendicular to an
axial direction; wherein one of said first and second permanent
magnets is of such a shape as to surround the other of said first
and second magnets.
29. A light deflecting apparatus according to claim 28, wherein
said deflector is a rotatable polygon mirror.
30. A light deflecting apparatus according to claim 28, wherein
said one of said first and second permanent magnets is a magnet
made of plastic.
31. A light deflecting apparatus according to claim 28, wherein
said rotor portion is floated up relative to said stator portion by
a magnetic force acting between said first permanent magnet and
said second permanent magnet.
32. A light deflecting apparatus according to claim 28, wherein
said shaft and said sleeve are formed of a ceramic material.
33. A deflecting-scanning apparatus comprising: a light source; a
rotor portion comprising one of a shaft and a sleeve, said shaft
being fitted into said sleeve so as to be capable of relative
rotation between said shaft and said sleeve; a stator portion
comprising the other of said shaft and said sleeve; a deflector
mounted on said rotor portion for deflecting and scanning a light
beam from said light source; a first permanent magnet mounted on
said rotor portion; and a second permanent magnet mounted on said
stator portion so as to be opposed to said first permanent magnet
in a circumferential direction perpendicular to an axial direction;
wherein one of said first and second permanent magnets is of such a
shape as to surround the other of said first and second
magnets.
34. A deflecting-scanning apparatus according to claim 33, wherein
said deflector is a rotatable polygon mirror.
35. A deflecting-scanning apparatus according to claim 33, wherein
said one of said first and second permanent magnets is a magnet
made of plastic.
36. A deflecting-scanning apparatus according to claim 33, wherein
said rotor portion is floated up relative to said stator portion by
a magnetic force acting between said first permanent magnet and
said second permanent magnet.
37. A deflecting-scanning apparatus according to claim 33, wherein
said shaft and said sleeve are formed of a ceramic material.
38. An image forming apparatus comprising: a light source; a
recording medium; a rotor portion comprising one of a shaft and a
sleeve, said shaft being fitted into said sleeve so as to be
capable of relative rotation between said shaft and said sleeve; a
stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and
scanning a light beam from said light source; a first permanent
magnet mounted on said rotor portion; and a second permanent magnet
mounted on said stator portion so as to be opposed to said first
permanent magnet in a circumferential direction perpendicular to an
axial direction; wherein one of said first and second permanent
magnets is of such a shape as to surround the other of said first
and second magnets.
39. An image forming apparatus according to claim 38, wherein said
deflector is a rotatable polygon mirror.
40. An image forming apparatus according to claim 38, wherein said
one of said first and second permanent magnets is a magnet made of
plastic.
41. An image forming apparatus according to claim 38, wherein said
rotor portion is floated up relative to said stator portion by a
magnetic force acting between said first permanent magnet and said
second permanent magnet.
42. An image forming apparatus according to claim 38, wherein said
shaft and said sleeve are formed of a ceramic material.
43. A bearing device comprising: a fixed shaft; and a rotatable
sleeve rotatably fitted to said fixed shaft, said rotatable sleeve
being provided with a level difference portion for locally changing
the inner diameter of said rotatable sleeve.
44. A bearing device according to claim 43, wherein the inner
diameter of said rotatable sleeve is designed to be locally
enlarged by said level difference portion.
45. A bearing device according to claim 43, wherein a magnet
constituting a thrust bearing is assembled to said level difference
portion.
46. A light deflecting apparatus comprising: a fixed shaft; a
rotatable sleeve rotatably fitted to said fixed shaft, said
rotatable sleeve being provided with a level difference portion for
locally changing the inner diameter of said rotatable sleeve; a
deflector for deflecting and scanning a light beam; and coupling
means for integrally coupling said deflector to said rotatable
sleeve.
47. A light deflecting apparatus according to claim 46, wherein
said rotatable sleeve is provided with an engagement portion for
engaging said coupling means, and said rotatable sleeve is provided
with said level difference portion in said engagement portion.
48. A light deflecting apparatus according to claim 47, wherein the
inner diameter of said rotatable sleeve is designed to be locally
enlarged in said engagement portion by said level difference
portion.
49. A light deflecting apparatus according to claim 47, wherein
said coupling means is designed to integrally couple said deflector
to said rotatable sleeve through a washer.
50. A light deflecting apparatus according to claim 46, wherein
said deflector is a rotatable polygon mirror.
51. A light deflecting apparatus according to claim 46, wherein a
magnet constituting a thrust bearing is assembled to said level
difference portion.
52. A deflecting-scanning apparatus comprising: a light source; a
fixed shaft; a rotatable sleeve rotatably fitted to said fixed
shaft, said rotatable sleeve being provided with a level difference
portion for locally changing the inner diameter of said rotatable
sleeve; a deflector for deflecting and scanning a light beam from
said light source; and coupling means for integrally coupling said
deflector to said rotatable sleeve.
53. A deflecting-scanning apparatus according to claim 52, wherein
said rotatable sleeve is further provided with an engagement
portion for engaging said coupling means, and said level difference
portion is provided in said engagement portion.
54. A deflecting-scanning apparatus according to claim 53, wherein
the inner diameter of said rotatable sleeve is designed to be
locally enlarged in said engagement portion by said level
difference portion.
55. A deflecting-scanning apparatus according to claim 53, wherein
said coupling means is designed to integrally couple said deflector
to said rotatable sleeve through a washer.
56. A deflecting-scanning apparatus according to claim 52, wherein
said deflector is a rotatable polygon mirror.
57. A deflecting-scanning apparatus according to claim 52, wherein
a magnet constituting a thrust bearing is assembled to said level
difference portion.
58. An image forming apparatus comprising: a light source; a
recording medium; a fixed shaft; a rotatable sleeve rotatably
fitted to said fixed shaft, said rotatable sleeve being provided
with a level difference portion for locally changing the inner
diameter of said rotatable sleeve; a deflector for deflecting and
scanning a light beam from said light source; and coupling means
for integrally coupling said deflector to said rotatable
sleeve.
59. An image forming apparatus according to claim 58, wherein said
rotatable sleeve is further provided with an engagement portion for
engaging said coupling means, and said level difference portion is
provided in said engagement portion.
60. An image forming apparatus according to claim 59, wherein the
inner diameter of said rotatable sleeve is designed to be locally
enlarged in said engagement portion by said level difference
portion.
61. An image forming apparatus according to claim 59, wherein said
coupling means is designed to integrally couple said deflector to
said rotatable sleeve through a washer.
62. An image forming apparatus according to claim 58, wherein said
deflector is a rotatable polygon mirror.
63. An image forming apparatus according to claim 58, wherein a
magnet constituting a thrust bearing is assembled to said level
difference portion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Related Background Art
[0004] 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 non-contact is used in such a bearing
device.
[0005] 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.
[0006] 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.
[0007] 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
23a 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 23a. Further a rotatable polygon
mirror 34 is fixed onto the flange 25 by a leaf spring 33 fixed to
the rotatable sleeve 24.
[0008] 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 23a. 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.
[0009] 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.
[0010] 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.
[0011] 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
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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 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.
[0017] Also, in the above-described example of the prior art, as
previously described, a dynamic fluid bearing is used in the
bearing portion of the rotatable polygon mirror to thereby cope
with the higher speed or the like of the apparatus, but there is a
problem still left to be solved that if the pressure force of the
leaf spring 33 for assembling the rotatable polygon mirror 34 to
the flange 25 is strong, the bearing surface of the rotatable
sleeve 24 will be deformed by the reaction force thereof and as the
result, the dimension of the bearing gap will change and the
performance of the dynamic pressure fluid bearing will be
spoiled.
[0018] The present invention has been made in view of the
above-noted unsolved problem peculiar to the prior art, and an
object thereof is to provide a bearing device which can prevent the
bearing surface of a rotatable sleeve from being deformed by the
pressure force of coupling means such as a spring for assembling a
rotatable polygon mirror to the rotatable sleeve to thereby spoil
the bearing characteristic and can greatly contribute to
improvements in the higher speed and rotational performance of the
rotatable polygon mirror, and a deflecting-scanning apparatus using
the same.
[0019] To achieve the above object, the bearing device of the
present invention has a fixed shaft and a rotatable sleeve
rotatably fitted to the fixed shaft, and is characterized in that
the rotatable sleeve is provided with a level difference portion
for locally changing the inner diameter of the rotatable
sleeve.
[0020] Also, to achieve the above object, the deflecting-scanning
apparatus of the present invention has a rotatable polygon mirror
which is a deflector for reflecting a light beam, driving means for
rotating it, dynamic pressure fluid bearing means provided with a
rotatable sleeve rotatably fitted to a fixed shaft, and coupling
means for coupling the rotatable polygon mirror integrally to the
rotatable sleeve, and is characterized in that the rotatable sleeve
is provided with an engagement portion for engaging the coupling
means, and a level difference portion for locally changing the
inner diameter of the rotatable sleeve in the engagement
portion.
[0021] Also, design may preferably be made such that the inner
diameter of the engagement portion of the rotatable sleeve is
locally enlarged by the level difference portion.
[0022] Also, a magnet constituting a thrust bearing may preferably
be assembled to the level difference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 shows the construction of a bearing device according
to the prior art.
[0024] FIG. 2 shows the construction of a first embodiment of the
bearing device of the present invention.
[0025] FIG. 3 shows the construction of a second embodiment of the
bearing device of the present invention.
[0026] FIG. 4 shows the construction of a deflecting-scanning
apparatus using the bearing device of the present invention.
[0027] FIG. 5 shows the construction of a third embodiment of the
bearing device of the present invention.
[0028] FIG. 6 shows the construction of a fourth embodiment of the
bearing device of the present invention.
[0029] FIG. 7 shows the construction of a fifth embodiment of the
bearing device of the present invention.
[0030] FIG. 8 shows the construction of a sixth embodiment of the
bearing device of the present invention.
[0031] FIG. 9 shows the construction of a seventh embodiment of the
bearing device of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The bearing device of the present invention and a
deflecting-scanning apparatus using the same will hereinafter be
described in detail with respect to embodiments thereof shown in
FIGS. 2 to 4.
[0033] FIG. 2 is a cross-sectional view of a first embodiment of
the bearing device of the present invention by a dynamic pressure
fluid bearing.
[0034] Referring to FIG. 2, a fixed shaft 22 (a stator portion)
formed of a ceramic material is fixed to the housing 21 of a drive
motor, and a rotatable sleeve 24 (a rotor portion) formed of a
ceramic material is rotatably fitted to the fixed shaft 22. 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 or otherwise 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.
[0035] On the other hand, a circular ring-shaped first permanent
magnet 2 is mounted on the upper end portion of the rotatable
sleeve 24, and a cylindrically shaped second permanent magnet 1 is
mounted on the upper end portion of the fixed shaft 22 at a
position opposed to the inner peripheral surface of the first
permanent magnet 2 in a circumferential direction (the radial
direction of the shaft) perpendicular to an axial direction. The
inner peripheral surface of the first permanent magnet 2 and the
outer peripheral surface of the second permanent magnet 1 are
designed such that magnetic poles opposed to each other in a
circumferential direction (the radial direction of the shaft)
perpendicular to the axial direction of the fixed shaft are
different kinds of magnetic poles.
[0036] Thus, the rotatable sleeve 24 is floated up relative to the
fixed shaft 22 by a magnetic force working between the first
permanent magnet 2 and the second permanent magnet 1. Further, a
rotatable polygon mirror 34 is fixed onto the flange 25 by a leaf
spring 33 fixed to the rotatable sleeve 24.
[0037] 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 magnetic force working
between the first permanent magnet 2 and the second permanent
magnet 1.
[0038] As described above, the first permanent magnet mounted on
the rotor portion and the second permanent magnet mounted on the
stator portion are provided in opposed relationship with each other
in the circumferential direction (the radial direction of the
shaft) perpendicular to the axial direction, whereby they are
supported so as to be opposed to each other on the side of
permanent magnets for thrust floating-up and therefore, as compared
with the repulsive support in the vertical direction (axial
direction) shown in FIG. 1, the positional restraining force in the
thrust direction is very much strong, and against disturbance such
as the vibration of the apparatus, the vertical vibration of the
rotatable sleeve which is the rotor portion becomes very small. The
vertical movement of the rotatable polygon mirror mounted on the
rotatable sleeve can also be suppressed to a small level.
[0039] Also, as compared with the construction of the repulsive
support in the vertical direction (axial direction) shown in FIG.
1, the size in the height direction (axial direction) can be made
small and therefore, the apparatus can be made compact.
[0040] FIG. 3 shows a second embodiment of the bearing device of
the present invention. In this second embodiment, a cover 23 is
provided on the upper end portion of a circulating-shaped first
permanent magnet 2 mounted on the upper end portion of a rotatable
sleeve 24. The same reference numerals as those in FIG. 2 designate
the same members, and need not be described.
[0041] In this second embodiment, in addition to the effect of the
first embodiment, an air pool 31 is created between the fixed shaft
22 and the cover 23, and the air in this air pool 31 acts so as to
attenuate the vertical movement of the rotatable sleeve 24 and
therefore, it is possible to hold the rotatable sleeve 24 in a
stabler floated-up position than in the first embodiment.
[0042] FIG. 4 shows the construction of a deflecting-scanning
apparatus using the bearing device according to the above-described
first or second embodiment. A laser unit 36 is mounted on an
optical box 35, and on an optical path L from the laser unit 36, a
rotatable polygon mirror 34 and lenses 37, 38 are disposed in the
optical box 35, and a photosensitive member 39 which is a recording
medium is disposed outside the optical box 35. The housing 21 of
the drive motor is disposed in the optical box 35.
[0043] A laser beam emitted from the laser unit 36 is deflected and
scanned by the rotatable polygon mirror 34 supported and rotated by
the bearing device described above in the first or second
embodiment, and is projected as a spotlight onto the
photo-sensitive member 39 outside the optical box 35 via the lenses
37 and 38, whereby main scanning is done.
[0044] A point image formed on the photosensitive member 39 forms
an electrostatic latent image with the main scanning by the
rotation of the rotatable polygon mirror 34 and the sub-scanning by
the photosensitive member 39 being rotated about the shaft of a
rotatable drum.
[0045] Around the photosensitive member 39, there are disposed a
corona discharger for uniformly charging the surface of the
photosensitive member 39, a developing device for visualizing the
electrostatic latent image formed on the surface of the
photosensitive member 39 into a toner image, a transferring device
for transferring the toner image to recording paper, etc., and the
recording information by the light beam emitted from the laser unit
36 is printed on the recording paper.
[0046] By using the bearing device according to the present
embodiment, there can be provided a deflecting-scanning apparatus
in which the vertical movement of the rotatable polygon mirror by
disturbance such as the vibration of the apparatus can be
suppressed and high-speed and highly accurate deflection and
scanning are stably possible.
[0047] As described above, the bearing device according to the
present invention and the deflecting-scanning apparatus using the
same are a bearing device comprising a sleeve fitted around a shaft
for rotation relative to the latter, one of said shaft and said
sleeve being a stator portion and the other being a rotor portion,
a first permanent magnet mounted on said rotor portion, and a
second permanent magnet mounted at a position opposed to said first
permanent magnet, said rotor portion being floated up relative to
said stator portion by a magnetic force working between said first
permanent magnet and said second permanent magnet, and a
deflecting-scanning apparatus using the same, wherein said first
permanent magnet is mounted on the upper end portion of said rotor
portion, said second permanent magnet is mounted on the upper end
portion of said stator portion, and said first permanent magnet and
said second permanent magnet are provided in opposed relationship
with each other in a circumferential direction perpendicular to an
axial direction.
[0048] As described above, in the bearing device according to the
present invention and the deflecting-scanning apparatus using the
same, the permanent magnets for thrust floating-up are provided on
the upper end portions of the rotor portion and the stator portion,
respectively, so as to be opposed to each other in the
circumferential direction perpendicular to the axial direction,
whereby the vibration of the rotor portion (rotatable sleeve) can
be prevented and high-speed and highly accurate rotation support
and deflection and scanning can be made possible.
[0049] The invention will be further described in detail with
respect to embodiments thereof shown in FIGS. 5 to 7.
[0050] FIG. 5 is a cross-sectional view of a third embodiment of
the bearing device of the present invention by a dynamic pressure
fluid bearing.
[0051] Referring to FIG. 5, a fixed shaft 22 (a portion of a stator
portion) formed of a ceramic material is fixed to the housing 21 of
a drive motor, and a rotatable sleeve 24 (a portion of a rotor
portion) formed of a ceramic material is rotatably fitted to the
fixed shaft 22. 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 or otherwise secured
to the outer periphery of this flange 25. Further, a stator 28
comprised of a coil and a core 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.
[0052] On the other hand, a circular ring-shaped first permanent
magnet 2 is mounted on the upper end portion of the rotatable
sleeve 24, and a cylindrically shaped second permanent magnet 1 is
mounted on the upper end portion of the fixed shaft 22 at a
position opposed to the inner peripheral surface of the first
permanent magnet 2 in a circumferential direction (the radial
direction of the shaft) perpendicular to an axial direction. The
inner peripheral surface of the first permanent magnet 2 and the
outer peripheral surface of the second permanent magnet 1 are
designed such that magnetic poles opposed to each other in the
circumferential direction (the radial direction of the shaft)
perpendicular to the axial direction of the fixed shaft are
different kinds of magnetic poles. The disposition of the magnetic
poles is not restricted thereto.
[0053] The circular ring-shaped first permanent magnet 2 is made of
plastic and is of such a shape as to cover the upper portion of the
second permanent magnet 1 mounted on the upper end portion of the
fixed shaft 22. That is, the first permanent magnet 2 made of
plastic has a circular ring-shaped portion and a lid-shaped portion
magnetized so as to integrally have a thrust-supported magnet
function. To form the circular ring-shaped portion and the
lid-shaped portion integrally with each other as described above, a
permanent magnet made of plastic composed of a magnetic material
mixed with resin and injection molded is suitable.
[0054] Thus, the rotatable sleeve 24 is floated up relative to the
fixed shaft 22 by a magnetic force and an air pool 31 (an air
damper chamber) is created among the fixed shaft 22, the second
permanent magnet 1 and the first permanent magnet 2. Further, a
rotatable polygon mirror 34 is fixed onto the flange 25 by a leaf
spring 33 fixed to the rotatable sleeve 24.
[0055] 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 a magnetic force working between
the first permanent magnet 2 and the second permanent magnet 1. At
this time, the air in the air pool 31 enveloped by the first
permanent magnet 2 acts so as to attenuate the vertical movement of
the rotatable sleeve 24, and can hold the rotatable sleeve 24 in a
stable floated-up position.
[0056] As described above, the first permanent magnet mounted on
the rotor portion and the second permanent magnet mounted on the
stator portion are provided in opposed relationship with each other
in the circumferential direction (the radial direction of the
shaft) perpendicular to the axial direction, whereby they are
supported so as to be opposed to each other on the side of a
permanent magnet for thrust floating-up and therefore, as compared
with the vertical (axial) repulsive support shown in FIG. 1, the
positional restraining force in the thrust direction is very much
strong and against disturbance such as the vibration of the
apparatus, the vertical vibration of the rotatable sleeve which is
the rotor portion becomes very small. Therefore, the vertical
movement of the rotatable polygon mirror mounted on the rotatable
sleeve can also be suppressed to a small level.
[0057] Also, as compared with the construction of the vertical
(axial) repulsive support shown in FIG. 1, the size in the height
direction (axial direction) can be made small and therefore, the
apparatus can be made compact.
[0058] Also, a cover member for covering the upper portion of the
permanent magnet mounted on the upper end portion of the fixed
shaft by the use of the permanent magnet made of plastic is
integrally molded and formed and therefore, the number of the
assembling steps can be decreased and the number of parts can also
be decreased, and this leads to a reduction in cost.
[0059] FIG. 6 shows a fourth embodiment of the bearing device of
the present invention. In this fourth embodiment, a through-hole
23a for communicating the air pool 31 with the outside is formed in
the first permanent magnet 2, and a plug 32 is removably mounted in
this through-hole 23a. The same reference numerals as those in FIG.
5 designate the same members and need not be described.
[0060] In this fourth embodiment, in addition to the effect of the
third embodiment, when the fixed shaft 22 and the rotatable sleeve
24 are to be fitted together with the plug 32 being removed, the
air in the rotatable sleeve 24 flows out of the through-hole 23a
and they can be easily fitted together.
[0061] FIG. 7 shows a fifth embodiment of the bearing device of the
present invention. This fifth embodiment is an embodiment of a
deflecting-scanning apparatus using the bearing device by a dynamic
pressure fluid bearing of the shaft rotation type, and use is made
of a rotary shaft 3 formed of a ceramic material and a fixed sleeve
4 formed of a ceramic material. A groove portion for mounting a
leaf spring 33 therein is provided in the upper portion of the
rotary shaft 3.
[0062] A circular ring-shaped second permanent magnet 5 is mounted
on the lower end portion of a fixed sleeve 4 which is a stator
portion, and a cylindrically shaped first permanent magnet 6 is
mounted on the lower end portion of the rotary shaft 3 at a
position opposed to the inner peripheral surface of this second
permanent magnet 5 in a circumferential direction (the radial
direction of the shaft) perpendicular to an axial direction. The
inner peripheral surface of the second permanent magnet 5 and the
outer peripheral surface of the first permanent magnet 6 are
designed such that magnetic poles opposed to each other in the
circumferential direction (the radial direction of the shaft)
perpendicular to the axial direction of the rotary shaft are
different kinds of magnetic poles.
[0063] The circular ring-shaped second permanent magnet 5 is made
of plastic and is of such a shape as to cover the lower portion of
the first permanent magnet 6 mounted on the lower end portion of
the rotary shaft 3. That is, the second permanent magnet 5 made of
plastic has a circular ring-shaped portion and a lid-shaped portion
magnetized so as to integrally have a thrust-supported magnet
function. To form the circular ring-shaped portion and the
lid-shaped portion integrally with each other as described above, a
permanent magnet made of plastic composed of a magnetic material
mixed with resin and injection molded is suitable. Further, a
through-hole 23a for communicating an air pool 31 with the outside
is formed in the second permanent magnet 5, and a plug 32 is
removably mounted in this through-hole 23a. The same reference
numerals as those in FIG. 6 designate the same members and need not
be described.
[0064] In this fifth embodiment, in addition to the effect of the
fourth embodiment, the shaft is of a rotary type and therefore a
cylindrically shaped magnet small in inertia can be disposed on the
rotary member side (the rotor portion side), and this leads to the
effect that the inertia of the rotary member can be made small.
[0065] The bearing devices according to the abovedescribed third,
fourth and fifth embodiments are also used in the
deflecting-scanning apparatus as shown in FIG. 4. A laser unit 36
is mounted on an optical box 35, and on an optical path L from the
laser unit 36, a rotatable polygon mirror 34 and lenses 37, 38 are
disposed in the optical box 35, and a photosensitive member 39
which is a recording medium is disposed outside the optical box 35.
The housing 21 of a drive motor is disposed in the optical box
35.
[0066] A laser beam emitted from the laser unit 36 is deflected and
scanned by the rotatable polygon mirror 34 supported and rotated by
the bearing device described above in the third, fourth and fifth
embodiments, and is projected as a form of light spot onto the
photosensitive member 39 outside the optical box 35 via the lenses
37 and 38, whereby main scanning is done.
[0067] Around the photosensitive member 39, there are disposed a
corona discharger for uniformly charging the surface of the
photosensitive member 39, a developing device for visualizing the
electrostatic latent image formed on the surface of the
photosensitive member 39 into a toner image, a transferring device
for transferring the toner image to recording paper, etc., and
recording information by the laser beam emitted from the laser unit
36 is printed on the recording paper or the like.
[0068] By using the bearing device according to the present
embodiment, there can be provided a deflecting-scanning apparatus
in which the vertical movement of the rotatable polygon mirror by
disturbance such as the vibration of the apparatus can be
suppressed and high-speed and highly accurate deflection and
scanning become stably possible and of which the cost can be
reduced.
[0069] As described above, the bearing device according to the
present invention and the deflecting-scanning apparatus using the
same are a bearing device comprising a sleeve fitted around a shaft
for rotation relative to the latter, one of said shaft and said
sleeve being a stator portion and the other being a rotor portion,
a first permanent magnet mounted on said rotor portion, and a
second permanent magnet mounted at a position opposed to said first
permanent magnet, said rotor portion being floated up relative to
said stator portion by a magnetic force working between said first
permanent magnet and said second permanent magnet, and a
deflecting-scanning apparatus using the same, wherein said first
permanent magnet and said second permanent magnet are provided in
opposed relationship with each other in a circumferential direction
perpendicular to an axial direction, and said first permanent
magnet or said second permanent magnet is of such a shape as to
cover said second permanent magnet or said first permanent magnet
provided on the end portion of said shaft.
[0070] As described above, in the bearing device according to the
present invention and the deflecting-scanning apparatus using the
same, the permanent magnets for thrust floating-up are provided on
the end portions of the rotor portion and the stator portion so as
to be opposed to each other in the circumferential direction
perpendicular to the axial direction, whereby the vibration of the
rotor portion (the rotatable sleeve or the rotary shaft) can be
prevented and high-speed and highly accurate rotation support and
deflection and scanning are made possible, and an air damper
chamber can also be constructed by the use of the permanent magnets
for thrust floating-up and therefore, the cost can be reduced.
[0071] The invention will be further described in detail with
respect to embodiments thereof shown in FIGS. 8 and 9.
[0072] FIG. 8 shows the essential portions of a sixth embodiment of
the bearing device of the present invention. In this embodiment, a
washer 44 which is a flange is made integral with a rotatable
sleeve 43 fitted to a fixed shaft 42 and constituting dynamic
pressure fluid bearing means and a rotor magnet 45 is secured to
the washer 44, and a rotatable polygon mirror 34 is urged against
the washer 44 by a resilient urging mechanism 46 which is coupling
means and integrally coupled thereto and a motor base plate 27 is
supported by a motor housing 47 to which the fixed shaft 42 is
fixed, and the rotor magnet 45 constitute a motor which is driving
means with a stator coil 49 uprightly provided on the motor base
plate 27. This motor rotates the rotor magnet 45 and the rotatable
polygon mirror 34 together with each other by the stator coil 49
being excited. As described above, the coupling means is designed
to couple the rotatable polygon mirror 34 integrally to the
rotatable sleeve 43 through the washer 44.
[0073] The rotatable sleeve 43 forms air film between it and the
fixed shaft 42 by the rotation thereof and constitutes dynamic
pressure fluid bearing means rotated in non-contact with the fixed
shaft 42. As described above, by using the dynamic pressure fluid
bearing in the bearing portion of the rotatable polygon mirror 34,
the higher speed of the deflecting-scanning apparatus can be
expedited to thereby improve the rotational performance
thereof.
[0074] The resilient urging mechanism 46 for urging the rotatable
polygon mirror 34 against the washer 44 has a fixed ring 46a and an
E-ring 46c for urging the fixed ring 46a against the rotatable
polygon mirror 34 through a spring 46b, and the E-ring 46c is
engaged with an annular groove portion 43a provided in the
rotatable sleeve 43.
[0075] The fixed shaft 42 and rotatable sleeve 43 constituting the
dynamic pressure fluid bearing are made of a ceramic material such
as high strength silicon nitride (Si.sub.3N.sub.4) or a metallic
material having its surface plated with a wear resisting material
in order to reduce the friction between the two and prevent the
galling or the like by the entry of dust or the like. The washer 44
is made of a metal such as aluminum or brass and is made integral
with the rotatable sleeve 43 by shrinkage fitting, and the rotor
magnet 45 is adhesively or otherwise secured to the washer 44.
[0076] When the spring pressure (pressure force) by the spring 46b
of the resilient urging mechanism 46 is strong, the inner
peripheral surface of the upper portion of the rotatable sleeve 43
is deformed by a reaction force created in the groove portion 43a
of the rotatable sleeve 43. When such deformation of the inner
peripheral surface spreads to the bearing surface 43b of the
rotatable sleeve 43 which faces the dynamic pressure generating
groove 42a of the fixed shaft 42, the dimension of the bearing gap
changes and the bearing characteristic as designed cannot be
obtained.
[0077] For this reason, in the tip end portion (engagement portion)
of the rotatable sleeve 43 having the groove portion 43a, the inner
diameter thereof is locally changed to form a level difference 43c
to the bearing surface 43b. This level difference 43c serves to
locally enlarge the inner diameter of the rotatable sleeve 43 to
thereby prevent the deformation in the tip end portion of the
rotatable sleeve 43 from spreading to the bearing surface 43b of
the rotatable sleeve 43.
[0078] Simply by providing the simple level difference on the inner
peripheral surface of the rotatable sleeve 43, the bearing
characteristic of the dynamic pressure fluid bearing can be
prevented from being degraded due to the spring pressure of the
resilient urging mechanism 46. The bearing performance of the
rotatable polygon mirror 34 is improved in this manner, whereby the
rotational performance of the deflecting-scanning apparatus can be
stabilized and the higher speed thereof can be expedited.
[0079] A magnet 50a is assembled to the level difference portion
43c of the rotatable sleeve 43. This magnet is opposed to a magnet
50b secured to the upper end of the fixed shaft 42, and the two
magnets 50a and 50b together constitute a thrust bearing 50 for
axially supporting the rotatable sleeve 43 and keeping the lower
end of the rotatable sleeve 43 in non-contact with a motor housing
47. The inside of the groove portion 43a of the rotatable sleeve 43
is reinforced by the magnet 50a assembled to the level difference
portion 43c, and this also leads to the advantage that the amount
of deformation by the urging force of the resilient urging
mechanism 46 can be reduced.
[0080] Also, the upper end opening of the rotatable sleeve 43 is
closed by a lid member 51, whereby an air pool is formed on the
upper end of the fixed shaft 42. This air pool, with the thrust
bearing 50 comprising the magnets 50a and 50b, serves to stabilize
the axial position of the rotatable sleeve 43.
[0081] While in the present sixed embodiment, the resilient urging
mechanism including the spring and the E-ring is used to couple the
rotatable polygon mirror to the washer integral with the rotatable
sleeve, utilization can also be made of simple coupling means in
which the inner end of a belleville spring or the like is directly
engaged with the groove portion of the rotatable sleeve.
[0082] FIG. 9 shows a seventh embodiment of the bearing device of
the present invention. In this embodiment, a flange portion 54
against which the underside of a rotatable polygon mirror 34 bears
is integrally provided on a rotatable sleeve 53 made of a metal and
the washer 44 of the device of FIG. 8 is omitted. The number of the
assembled parts of the device can be curtailed and the
manufacturing cost thereof can be reduced and moreover, there is
the advantage that the working of the groove portion 53a and the
level difference 53c is simple because the rotatable sleeve 53 is
made of a metal.
[0083] The bearing devices of the above-described sixth and seventh
embodiments are both used in the deflecting-scanning apparatus as
shown in FIG. 4. A laser unit 36 is mounted on an optical box 35,
and on an optical path L from the laser unit 36, a rotatable
polygon mirror 34 and lenses 37, 38 are disposed in the optical box
35, and a photosensitive member 39 which is a recording medium is
disposed outside the optical box 35. The housing 21 of a drive
motor is disposed in the optical box 35.
[0084] A laser beam emitted from the laser unit 36 is deflected and
scanned by the rotatable polygon mirror 34 supported and rotated by
the bearing device described in the sixth or seventh embodiment,
and is projected as a spotlight onto the photosensitive member 39
outside the optical box 35 via the lenses 37 and 38, whereby main
scanning is done.
[0085] Around the photosensitive member 39, there are disposed a
corona discharger for uniformly charging the surface of the
photosensitive member 39, a developing device for visualizing an
electrostatic latent image formed on the surface of the
photosensitive member 39 into a toner image, a transferring device
for transferring the toner image to recording paper, etc., and the
recording information by the laser beam emitted from the laser unit
36 is printed on the recording paper or the like.
[0086] As described above, in the deflecting-scanning apparatus of
the present invention, the rotatable polygon mirror 34 abuts
against the washer 44 integral with the rotatable sleeve 43, and is
integrally coupled to the rotatable sleeve 43 by the resilient
urging mechanism 46. The rotatable sleeve 43 has a groove portion
43a for assembling the resilient urging mechanism 46, and this
portion is apt to be deformed by the reaction force of the urging
force of the resilient urging mechanism 46. So, a level difference
43c is provided between the upper end portion of the rotatable
sleeve 43 having the groove portion 43a and the bearing surface 43b
to thereby prevent the deformation by the resilient urging
mechanism 46 from spreading to the bearing surface 43b.
[0087] According to the present invention, there is constructed a
dynamic pressure fluid bearing for rotatably supporting a rotatable
polygon mirror or the like by air film formed between a fixed shaft
and a rotatable sleeve. This is because if the rotatable polygon
mirror is coupled to the rotatable sleeve by coupling means, a
reaction force such as the pressing force of the coupling means may
be applied to the engagement portion of the rotatable sleeve to
thereby deform the bearing surface, whereby the bearing performance
of the dynamic pressure fluid bearing may be spoiled. So, a level
difference for locally changing the inner diameter of the
engagement portion of the rotatable sleeve is provided so that even
if the engagement portion of the rotatable sleeve is deformed by
the above-mentioned coupling means, the deformation may be absorbed
by the level difference and prevented from spreading to the bearing
surface.
[0088] The present invention is constructed as described above and
therefore achieves the following effects.
[0089] It can be avoided that the rotatable sleeve is deformed by
the resilient urging mechanism or the like for assembling the
rotatable polygon mirror to the rotatable sleeve and the bearing
performance of the dynamic pressure fluid bearing is spoiled.
Thereby, the present invention can greatly contribute to an
improvement in the rotational performance of the
deflecting-scanning apparatus and the higher speed thereof.
[0090] By using such a deflecting-scanning apparatus, there can be
realized an image forming apparatus of high performance suited for
a higher speed.
* * * * *