US 7,742,727 B2Granted

Image forming apparatus

AssigneeKyocera Mita Corporation

InventorsShoichi Sakata, Takahisa Nakaue, Toyotsune Inoue, Akihiro Watanabe, Masashi Fujishima, Yukihiro Mori

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Abstract

An image forming apparatus has a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image on the photoconductive member by a first bias. A magnetic roller forms a magnetic brush thereon with a two-component developer and forms a thin toner layer on the developing roller by a second bias. The developing roller is aluminum with a surface treated for high resistance. The thickness (T) of the toner layer and the duty ratio (D1) of the first alternating-current bias satisfy relationships of the following equations for calculating the duty ratio (D1) using an application period of a voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: 7 μm≦T≦13 μm, and 35%≦D1≦70%.

Claims13

Dependent claims

An image forming apparatus, comprising:

a photoconductive member on which a latent image is to be formed;
a developing roller for developing the latent image formed on the photoconductive member by a first bias;
a magnetic roller for forming a magnetic brush thereon with a two-component developer containing a carrier and a toner and forming a thin toner layer on the developing roller by a second bias;
and
a bias applying device for applying biases to the developing roller and the magnetic roller,
wherein:
the developing roller has a base body thereof made of aluminum and having a surface cleaned with an acid and treated with fluorine containing fine particles after being anodized in an acid aqueous solution and sealed in a nickel acetate solution;
the first bias includes a first alternating-current bias in the form of a rectangular wave;
and
if T denotes the thickness of the thin toner layer and D1 denotes the duty ratio of the first alternating-current bias, the thickness T and the duty ratio D1 satisfy relationships of the following equations in the case of calculating the duty ratio D1 using an application period of a voltage in a direction to transfer the toner from the developing roller toward the photoconductive member as a positive period:
7 μm≦T≦13 μm, and
35%≦D1≦70%.

9 more elements

An image forming apparatus, comprising:

a photoconductive member on which a latent image is to be formed;
a developing roller for developing the latent image formed on the photoconductive member by a first bias;
a magnetic roller for forming a magnetic brush thereon with a two-component developer containing a carrier and a toner and forming a thin toner layer on the developing roller by a second bias;
and
a bias applying device for applying biases to the developing roller and the magnetic roller,
wherein:
the developing roller has a base body thereof made of aluminum and having a high resistance treatment layer on the surface thereof;
the first bias includes a first alternating-current bias in the form of a rectangular wave and the second bias includes a second alternating-current bias in the form of a rectangular wave;
and
if T denotes the thickness of the thin toner layer, D1 denotes the duty ratio of the first alternating-current bias and D2 denotes the duty ratio of the second alternating-current bias, the thickness T, the duty ratio D1 and the duty ratio D2 satisfy relationships of the following equations in the case of calculating the duty ratio D1 using an application period of a voltage in a direction to transfer the toner from the developing roller toward the photoconductive member as a positive period and calculating the duty ratio D2 using an application period of a voltage in a direction to transfer the toner from the magnetic roller toward the developing roller as a positive period:
7 μm≦T≦13 μm,
35%≦D1≦70%, and
D1>100−D2.

10 more elements

Dependencies are inferred from the claim text.