Electrophotography – Image formation – Transfer
Reexamination Certificate
2002-09-11
2004-07-06
Ngo, Hoang (Department: 2852)
Electrophotography
Image formation
Transfer
C399S121000
Reexamination Certificate
active
06760564
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a picture image forming apparatus, and more particular, to a construction, in which a mechanism for peeling-off a sheet after toner picture images have been transferred to a sheet from an intermediate transfer means is simplified, in a picture image forming apparatus comprising a photoreceptor belt driven by a drive device, developing means for forming toner picture images on the photoreceptor belt, intermediate transfer means, to which toner picture images on the photoreceptor belt are transferred, and a transfer roller for pushing a sheet against the intermediate transfer means in order to transfer toner picture images to the sheet.
BACKGROUND OF THE INVENTION
With respect to a picture image forming apparatus comprising a photoreceptor belt driven by a drive device, a plurality of developing means for forming toner picture images on the photoreceptor belt, an intermediate transfer belt, to a surface of which toner picture images on the photoreceptor belt are transferred plural times when a picture image is to be formed on a single page, and a transfer roller for pushing a sheet against the intermediate transfer belt in order to transfer toner picture images to the sheet, JP-A-11-95517 has proposed a construction with a photoreceptor belt and an intermediate transfer drum.
Also, JP-A-2000-330358 has proposed a picture image forming apparatus comprising an intermediate transfer belt trained around rollers having the same diameter.
In a picture image forming apparatus, in which a plurality of toner picture images are overlapped on a surface of an intermediate transfer means to form a picture image on a single page for multicolored printing, there is a need of an intermediate transfer means having an outer circumference having a length at least equal to or longer than a length of a picture image being printed.
In the case where an intermediate transfer means is formed from a drum as in the prior art described above, a diameter of the drum is large and so curvature at a transfer portion becomes large, so that a sheet and the intermediate transfer means contact with each other in a transfer position, in which toner picture images are transferred to the sheet from the intermediate transfer means, in a wide area in a transfer direction.
Therefore, the sheet is bent to a small extent, and a force for peeling off the sheet from the intermediate transfer means becomes weak, thus giving rise to a need of electricity removing means for assisting peeling-off and including a high-voltage source.
SUMMARY OF THE INVENTION
An object of the invention is to provide a picture image forming apparatus, in which electricity removing means for assisting peeling-off is unnecessary or only a simple electricity removing means is necessary, a sheet can be readily peeled off, an intermediate transfer belt is free from abnormal deformation, and picture images of high image quality are obtained.
The invention proposes a picture image forming apparatus comprising a photoreceptor belt driven by a drive device, a plurality of developing means for forming toner picture images on the photoreceptor belt, intermediate transfer means, to a surface of which toner picture images on the photoreceptor belt are overlappingly transferred plural times when a picture image is to be formed on a single page, and a transfer roller for pushing a sheet against the intermediate transfer means in order to transfer toner picture images to the sheet, and wherein the intermediate transfer means is an intermediate transfer belt contacted by the photoreceptor belt to be driven thereby, and the intermediate transfer belt is trained around a photoreceptor-side roller and a transfer-side roller for pushing the sheet against the transfer roller, and wherein a diameter d2 of the transfer-side roller is smaller than a diameter d1 of the photoreceptor-side roller.
The invention also proposes a picture image forming apparatus comprising a photoreceptor belt driven by a drive device, a plurality of developing means for forming toner picture images on the photoreceptor belt, intermediate transfer means, to a surface of which toner picture images on the photoreceptor belt are overlappingly transferred plural times when a picture image is to be formed on a single page, and a transfer roller for pushing a sheet against the intermediate transfer means in order to transfer toner picture images to the sheet, and wherein the intermediate transfer means is an intermediate transfer belt contacted by the photoreceptor belt to be driven thereby, and the intermediate transfer belt is trained around a photoreceptor-side roller, around which the photoreceptor belt is wound with the intermediate transfer belt therebetween to be rotated, and a transfer-side roller for pushing the sheet against the transfer roller with the intermediate transfer belt therebetween, and wherein a diameter d2 of the transfer-side roller is smaller than a diameter d1 of the photoreceptor-side roller.
In these inventions, the transfer-side roller is small in curvature, and so rigidity of a sheet itself makes it possible to readily peel off the sheet from the intermediate transfer means.
Generally, in the case where the transfer-side roller is made small for the purpose of further improving the peeling-off property, creep deformation is generated in the intermediate transfer belt along the roller. Such deformation causes fluctuation in a gap between the photoreceptor belt and the intermediate transfer belt at a nip between the photoreceptor belt and the intermediate transfer belt and fluctuation in a gap between the intermediate transfer belt and the photoreceptor-side roller, such fluctuation varying a state of transfer, which leads to degradation in image quality.
Hereupon, in the above second invention, the photoreceptor belt is wound around the photoreceptor-side roller with the intermediate transfer belt therebetween, and the photoreceptor belt pushes the intermediate transfer belt concavely against the photoreceptor-side roller. Therefore, even in a state, in which the intermediate transfer belt is deformed convexly toward the photoreceptor belt, the photoreceptor belt and the intermediate transfer belt surely contact with each other, and also the intermediate transfer belt and the photoreceptor-side roller surely contact with each other, so that degradation in image quality is eliminated.
The invention proposes a picture image forming apparatus comprising a photoreceptor belt driven by a drive device, a plurality of developing means for forming toner picture images on the photoreceptor belt, intermediate transfer means, to a surface of which toner picture images on the photoreceptor belt are overlappingly transferred plural times when a picture image is to be formed on a single page, a transfer roller for pushing a sheet against the intermediate transfer means in order to transfer tonner picture images to the sheet, and developing means for melting and fixing toner having been transferred to the sheet, and wherein the intermediate transfer means is an intermediate transfer belt contacted by the photoreceptor belt to be driven thereby, and the intermediate transfer belt is trained around a photoreceptor-side roller and a transfer-side roller for pushing the sheet against the transfer roller, and wherein a diameter d2 of the transfer-side roller is smaller than a diameter d1 of the photoreceptor-side roller, and a point of pressure and fixation on a developing roller of the developing means is disposed nearer the photoreceptor-side than a contact point between the transfer roller and the transfer-side roller is.
Further, the invention proposes a picture image forming apparatus comprising a photoreceptor belt driven by a drive device, a plurality of developing means for forming toner picture images on the photoreceptor belt, intermediate transfer means, to a surface of which toner picture images on the photoreceptor belt are overlappingly transferred plural times when a picture image is to be formed on a single page, a transfer rol
Kikuchi Kazuo
Matsumoto Shogo
Nakano Masaru
Onose Atsushi
Oohara Shunichi
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Ngo Hoang
LandOfFree
Picture image forming apparatus with intermediate transfer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Picture image forming apparatus with intermediate transfer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Picture image forming apparatus with intermediate transfer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3232864