US 8,285,177 B2 · Charging device and image forming apparatus

Abstract

A charging device includes a charging roll, a voltage application member and a confronting potential varying unit. The charging roll is disposed so as to be in contact with an image holding body on whose surface an electrostatic latent image is to be formed, and charges the image holding body. The voltage application member is disposed so as to be in contact with the charging roll, and applies a voltage to a surface of the charging roll. The confronting potential varying unit varies a surface potential profile of the charging roll in its axial direction in a contact region between the charging roll and the image holding body according to both the number of image-formed sheets and a wear situation of the image holding body so that a surface potential of the image holding body becomes approximately constant in an axial direction of the image holding body.

Claims11

Dependent claims

A charging device comprising:

a charging roll that is disposed so as to be in contact with an image holding body on whose surface an electrostatic latent image is to be formed, and that charges the image holding body;
a voltage application member that is disposed so as to be in contact with the charging roll, and that applies a voltage to a surface of the charging roll;
and
a confronting potential varying unit that varies a surface potential profile of the charging roll in an axial direction of the charging roll in a contact region where the charging roll is in contact with the image holding body according to both the number of image-formed sheets and a wear situation of the image holding body so that a surface potential of the image holding body becomes approximately constant in an axial direction of the image holding body.

1 more element

A charging device comprising:

a charging roll that is disposed so as to be in contact with an image holding body on whose surface an electrostatic latent image is to be formed, and that charges the image holding body;
and
a voltage application member that is disposed so as to be in contact with the charging roll, and that applies a voltage to a surface of the charging roll, wherein
the voltage application member is divided in an axial direction of the voltage application member into (i) a steady wear region voltage application portion for applying a voltage to a surface of a portion of the charging roll which is opposed to a steady wear region of the image holding body and (ii) an accelerated wear region voltage application portion for applying a voltage to a surface of a portion of the charging roll which is opposed to an accelerated wear region of the image holding body, and
the voltage application member moves one of the steady wear region voltage application portion and the accelerated wear region voltage application portion along the surface of the charging roll according to the number of image-formed sheets.

2 more elements

Dependencies are inferred from the claim text.

Charging device and image forming apparatus

Life of this patent

Charging device and image forming apparatus

Life of this patent

Abstract

Claims11