Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2000-03-09
2001-07-03
Chen, Sophia S (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
Reexamination Certificate
active
06256466
ABSTRACT:
This application is based on an application No. 11-70951 filed in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus for developing by toner particles an electostatic latent image formed by an electrophotographic system.
2. Description of the Related Art
When an electrostatic latent image formed on the surface of a photosensitive drum is developed by toner particles, to transfer the toner image on paper, a black stripe may appear on the paper, and the contour of an image in a solid portion may be slightly distorted.
When the cause thereof is investigated, it is considered that the toner particles are accumulated at a front end of a cover member disposed on the upstream side in the direction of rotation of a developing roller provided in a developing device, and the accumulated toner particles adhere to the surface of the photosensitive drum.
On the other hand, the cover member in the developing device is a member required to prevent the toner particles supplied to the photosensitive drum from the developing roller from being scattered to the peripheries of the developing device and the photosensitive drum. Accordingly, the cover member cannot be omitted to prevent the toner particles from being accumulated at the front end of the cover member.
SUMMARY OF THE INVENTION
Under such a background, the inventors of the present invention have created an image forming apparatus capable of forming a good image by preventing toner particles from being accumulated at a front end of a cover member.
An object of the present invention is to provide an image forming apparatus capable of forming a sharp and clear image which is not distorted and has no unnecessary black stripe.
Another object of the present invention is to provide an image forming apparatus in which unnecessary toner particles are not accumulated in a cover member in a developing device.
In an image forming apparatus comprising a photosensitive drum and a developing device, the present invention employs the following construction for the developing device.
A developing device has a housing, and a developing roller whose surface is partially exposed from the housing, the exposed surface being arranged opposite to the surface of the photosensitive drum. A cover member in contact with the surface of the photosensitive drum is provided on the upstream side of the developing roller, as viewed in the direction of rotation of the photosensitive drum (in other words, as viewed in the direction of rotation of the developing roller). The cover member is at a predetermined potential which is the same in polarity as a potential at which the photosensitive drum is charged.
According to this construction, toner particles are not easily accumulated in the vicinity of the cover member, thereby making it possible to prevent the toner particles from being undesirably moved toward the surf ace of the photosensitive drum from a front end of the cover member.
It is preferable that the cover member has a conductive cover plate, and a non-conductive seal attached to a front end of the cover plate, extending parallel to the axes of the photosensitive drum and the developing roller, and in contact with the surface of the photosensitive drum, and a predetermined voltage is applied to the cover plate so that the non-conductive seal is at a predetermined potential.
In this construction, the non-conductive seal is uniformly kept at a predetermined potential.
A voltage applied to the cover member is preferably an arbitrary potential which is not less than a developing bias applied to the developing roller and is not more than a potential at which the photosensitive drum is charged. More preferably, if a voltage equal to the developing bias is applied to the cover member by a power supply for supplying the developing bias, the construction is simplified.
In this construction, the potential on the cover member does not affect an image on the surface of the photosensitive drum. Moreover, the toner particles are prevented from being drawn to the surface of the photosensitive drum from the cover member, thereby making it possible to improve the developing performance.
The present invention can provide, by not only applying the developing bias to the developing roller as in the conventional example but also causing the cover member, in contact with the peripheral surface of the photosensitive drum in the developing device, other than the developing roller, to be at a predetermined potential which is the same in polarity as the potential at which the photosensitive drum is charged, an image forming apparatus capable of forming a sharp and clear image in which no toner particles are accumulated in the vicinity of a contact between the cover member and the photosensitive drum
1
, and no black stripe appears.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
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patent: 5044313 (1991-09-01), Yuge et al.
patent: 5640648 (1997-06-01), Komakine et al.
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patent: 11-265118 (1999-09-01), None
Copy of (translated) JPO Official Action dated Dec. 19, 2000; reference No. 54-00068.
Kobayashi Masahiko
Ota Katsuya
Chen Sophia S
Kyocera Mita Corporation
Smith , Gambrell & Russell, LLP
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