Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-05-31
2001-03-13
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S900000, C359S850000, C359S198100
Reexamination Certificate
active
06201624
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polygonal mirror type scanner included in an electrophotographic copier, laser printer, facsimile apparatus or similar image forming apparatus. More particularly, the present invention relates to a rotary body included in a polygonal mirror type scanner and a method of machining the same.
A polygonal mirror type scanner for the above application includes a scanner motor made up of a rotor portion and a stator portion. The rotor portion includes a flange on which a polygonal mirror is mounted. The scanner motor causes the polygonal mirror to rotate while reflecting light incident thereto and representative of image data. A magnet is mounted on the bottom or the inner circumference of a rotor yoke also included in the rotor portion.
To produce the above scanner motor, a rotary shaft is inserted in the flange while a rotor is affixed to the flange, in parallel with the machining of a flat polygonal mirror. The machined polygonal mirror is mounted to the subassembly of the flange, rotary shaft and rotor. Thereafter, the axis of rotation of the polygonal mirror is aligned with the axis of the rotary shaft and then fixed in place.
However, the problem with the above conventional scanner is that it is bulky because the polygonal mirror and scanner motor are physically separate from each other and because the scanner motor cannot be sufficiently reduced in size. The scanner therefore occupies a substantial space when mounted to a laser printer or similar image forming apparatus, obstructing the miniaturization of the apparatus.
In light of the above, Japanese Patent Laid-Open Publication No. 8-62527, for example, discloses a scanner motor constructed to miniaturize a polygonal mirror type scanner. The scanner motor taught in this document includes a hexagonal rotor yoke and chip mirrors separate from the rotor yoke. The chip mirrors are adhered to the hexagonal circumferential surfaces of the rotor yoke.
The chip mirrors, however, not only increase the number of parts of the scanner, but also need highly accurate adhesion to the rotor yoke. In addition, the chip mirrors are apt to come off or deform after adhesion due to a centrifugal force. Further, because a permanent magnet is mounted on the flat bottom of the rotor yoke, should the permanent magnet be inaccurately positioned relative to the rotor yoke, the magnet and shaft would become offset. This would disturb the dynamic balance and would thereby degrade the jitter characteristic and bring about oscillation and noise. Moreover, the rotor yoke is apt to come off or deform due to a centrifugal force. In addition, the positional adjustment of the polygonal mirror relative to the shaft needs highly accurate measuring means and affixing means.
Japanese Patent Laid-Open Publication No. 5-241090 proposes a polygonal mirror including a ceramic ring, a yoke and a rotor magnet constructed integrally with each other by casting aluminum. After the surfaces of the ceramic ring, yoke and rotor magnet have been machined, mirror surfaces are formed by deposition. However, a magnet positioned below the mirror surfaces is apt to reduce the accuracy of the mirror surfaces due to a centrifugal force acting on the magnet during high-speed rotation.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 5-257078, 7-287183, 62-164017, 9-230269, and 6-98517.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a rotary body for a polygonal mirror type scanner needing a minimum number of parts, obviating the need for highly accurate adhesion, durable, easy to produce, and free from distortion apt to occur on its side.
In accordance with the present invention, a rotary body formed with a plurality of surfaces on its side includes an element for causing the rotary body to rotate, and a mounting portion for mounting the element to the rotary body by press fitting while preventing a stress ascribable to press fitting from being transferred to the side. The mounting portion is formed integrally with one of opposite major surfaces of the rotary body perpendicular to the side.
Also, in accordance with the present invention, a rotary polygonal mirror includes a mirror forming portion including a side formed with a plurality of mirror surfaces at equally spaced locations in the circumferential direction, a first major surface perpendicular to the side, and a second major surface also perpendicular to the side and facing the first major surface at the opposite side of the above side. An annular thin portion is formed integrally with the first major surface. The annular thin portion has a substantially cylindrical configuration coaxial with the rotary shaft of the polygonal mirror and an outer circumference positioned closer to the rotary shaft than the side. The annular thin portion is displaced by a force ascribable to the press fitting of a magnet at a boarder between the first major surface and the annular thin portion.
Further, in accordance with the present invention, rotary unit includes a rotary polygonal mirror including a mirror forming portion having a side formed with a plurality of mirror surfaces at equally spaced locations in the circumferential direction, a first major surface perpendicular to the side, and a second major surface also perpendicular to the side and facing the first major surface at the opposite side of the side. A magnet is mounted on the polygonal mirror. A body faces the magnet and includes a yoke. A rotary shaft is affixed to either one of the body and polygonal mirror. The magnet and yoke cooperate to cause the polygonal mirror to rotate about the rotary shaft. An annular thin portion is formed integrally with the first major surface. The annular thin portion includes a substantially cylindrical inner circumference coaxial with the rotary shaft and an outer circumference positioned closer to the rotary shaft than the side. The annular thin portion is displaced by a force ascribable to the press fitting of a magnet at a boarder between the first major surface and the annular thin portion.
Moreover, in accordance with the present invention, a method of machining a rotary body including a side formed with a plurality of surfaces begins with the step of press fitting an element for causing the rotary body to rotate and having a cylindrical inner circumference in a mounting portion formed integrally with a major surface of the rotary body perpendicular to the side. A rotary shaft for causing the rotary body to rotate is mounted to the center of the rotary body. A plurality of rotary bodies each including the element and rotary shaft are stacked one upon the other. Collars are positioned between nearby rotary bodies, and each is caused to engage with the outer circumference of the respective mounting portion. In this condition, the rotary bodies have their sides machined at the same time.
REFERENCES:
patent: 62-164017 (1987-07-01), None
patent: 5-241090 (1993-09-01), None
patent: 5-257078 (1993-10-01), None
patent: 6-098517 (1994-04-01), None
patent: 7-287183 (1995-10-01), None
patent: 8-062527 (1996-03-01), None
patent: 9-230269 (1997-09-01), None
Andoh Fumikata
Konno Hideki
Ozaki Shin-ichi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Phan James
Ricoh & Company, Ltd.
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