Electrophotography – Image formation – Development
Reexamination Certificate
1999-12-06
2001-05-01
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Development
C399S053000, C399S302000
Reexamination Certificate
active
06226481
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a copier, facsimile apparatus, printer or similar image forming apparatus. More particularly, the present invention relates to an image forming apparatus of the type including a revolver type developing unit rotatably mounted on an apparatus body and having a plurality of developing sections, and an intermediate image transfer body having an endless movable surface to which a toner image is transferred from an image carrier.
2. Discussion of the Background
It is a common practice with an image forming apparatus of the type described to rotate a developing unit to bring a desired developing section thereof to a developing position for development, then cause an intermediate image transfer body carrying a toner image transferred from an image carrier to run idle, and then transfer the toner image from the image transfer body to a recording medium. For example, when a thick sheet mode for forming a toner image on, e.g., a thick sheet or an OHP (OverHead Projector) sheet is selected, the above idle run of the intermediate image transfer body is effected in order to slow down the movement of the body for again determining the position of the same. Further, when toner images sequentially formed on the image carrier by the developing sections are transferred to the intermediate image transfer body one above the other, it is likely that the leading edge of, e.g., the toner image of a first color formed on the image transfer body moves away from a transfer position where the image carrier and image transfer body face each other before the developing section assigned to a second color arrives at the developing position. In such a case, too, the intermediate image transfer body is caused to run idle.
However, the problem with the conventional image forming apparatus is that when the developing unit is inadvertently rotated during the idle run of the intermediate image transfer body, toner deposited on the image carrier by the developing section moving past or brought to the developing position is apt to deposit on the toner image forming area of the image transfer body. Such toner cause band-like contamination (lateral color band in the case of a color image) extending in the lateral or widthwise direction of a recording medium.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 7-152218, 8-76590, 8-190258, 9-106152, and 11-174776.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an image forming apparatus capable of reducing, during the idle run of an intermediate transfer body, the background contamination of a recording medium ascribable to toner transferred from a developing section located at a developing position to an image carrier, particularly band-like contamination extending in the lateral direction of the recording medium.
In accordance with the present invention, an image forming apparatus includes an apparatus body. An image carrier carries a latent image thereon. A developing unit includes a plurality of developing sections each for developing a particular latent image formed on the image carrier to thereby produce a toner image. The developing unit is rotatably supported by the apparatus body. A drive source causes the developing unit to rotate. An intermediate image transfer body has an endless movable surface to which the toner image is transferred from the image carrier. A controller controls, while the intermediate image transfer body is running idle, the drive source such that one of the developing sections operated last before the start of the idle run remains at a developing position. Alternatively, the controller may control, while the intermediate image transfer body is running idle, the drive means such that one of the developing sections operated last before idle run is located at a position other than a developing position and such that none of the developing sections moves via the developing position.
Also, in accordance with the present invention, an image forming apparatus includes an apparatus body. An image carrier carries a latent image thereon. A developing unit includes a plurality of developing sections each for developing a particular latent image formed on the image carrier to thereby produce a toner image. The developing unit is rotatably supported by the apparatus body. A first drive mechanism for causes the developing unit to rotate. A second drive mechanism includes a drive gear capable of meshing with, among drive input gears respectively included in the developing sections, the drive input gear of one developing section brought to a developing position where the developing section faces the image carrier, thereby transmitting a drive force to a developer carrier included in the developing section. An intermediate image transfer body has an endless movable surface to which the toner image is transferred from the image carrier. The drive input gears and drive gear are arranged such that when any one of the developing sections moves toward the developing position while the intermediate image transfer body is running idle, a developer deposited on the developer carrier starts contacting the image carrier with the developer carrier rotating. A controller controls the first and second drive mechanisms.
Further, in accordance with the present invention, an image forming apparatus includes an apparatus body. An image carrier carries a latent image thereon. A latent image forming devices scans the uniformly charged surface of the image carrier with light in accordance with image data to thereby form a latent image on the image carrier. A developing unit includes a plurality of developing sections each for developing a particular latent image formed on the image carrier to thereby produce a toner image. The developing unit is rotatably supported by the apparatus body. A drive source causes the developing unit to rotate. A power supply applies a voltage to a developer carrier included in each of the developing sections. An intermediate image transfer body has an endless movable surface to which the toner image is transferred from the image carrier. One developing section located at a developing position is replaced with another developing section while the intermediate transfer body is running idle. A controller controls, while the intermediate image transfer body is running idle, the latent image forming device and power supply such that at least one of a condition for charging the image carrier and a condition for applying the voltage to the developer carrier of one developing section located at the developing position is switched to a condition causing a minimum of toner to move from the developer carrier to the image carrier to thereby reduce contamination of the background.
REFERENCES:
patent: 4916547 (1990-04-01), Katsumata et al.
patent: 5612769 (1997-03-01), Sugihara et al.
patent: 5657115 (1997-08-01), Sugihara
patent: 5671470 (1997-09-01), Maruta et al.
patent: 5724634 (1998-03-01), Maruta
patent: 5768662 (1998-06-01), Sugihara et al.
patent: 5826146 (1998-10-01), Maruta et al.
patent: 5835825 (1998-11-01), Maruta
patent: 5970278 (1999-10-01), Munakata
patent: 7-152218 (1995-06-01), None
patent: 8-76590 (1996-03-01), None
patent: 8-190258 (1996-07-01), None
patent: 9-106152 (1997-04-01), None
patent: 11-174776 (1999-07-01), None
Maruta Takayuki
Sugihara Kazuyuki
Yoneda Takuzi
Chen Sophia S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Tran Hoan
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