Samsung Electronics Co., Ltd.

Ui-Choon Lee

Su-jong Jeong

Byoung-chul Bae

Dyoung-chul Bae

An electrophotographic image-forming apparatus and a charging voltage control method therefor. The electrophotographic image-forming apparatus has a charging roller applying a predetermined voltage to a photosensitive medium, a developing roller for developing with a developing agent an electrostatic latent image formed on the photosensitive medium by a laser scanning unit, a transfer roller transferring onto a sheet of recording paper the image developed by the developing agent, and a high voltage power supply (HVPS) applying predefined voltages to the respective rollers. The apparatus also includes a charging roller resistance detection unit detecting a resistance value of the charging roller, a transfer roller resistance detection unit detecting a resistance value of the transfer roller, and a control unit determining the charging voltage to be applied to the charging roller based on the charging roller resistance value detected by the charging roller resistance detection unit and the transfer roller resistance value detected by the transfer roller resistance detection unit. Accordingly, the present invention can adaptively select a charging voltage to be applied to the charging roller depending upon the changes of the transfer roller resistance value and the charging roller resistance value.

Electrophotographic image-forming apparatus and charging voltage control method thereof

A charging voltage controller of an image forming apparatus includes a charging roller charging a photoconductive drum with a predetermined charging voltage, a high voltage supply unit supplying the predetermined charging voltage to the charging roller, an electric current detecting unit detecting an electrical current flowing the charging roller, and a control unit supplying first and second test voltages of different degrees to the charging roller, determining a first reference voltage to be applied to the charging roller based on data from the electric]current detecting unit outputted in response to the first test voltage, calculating slope data based on the electrical current data detected from the electric current detecting unit in response to the first and second test voltages, and determining the charging voltage to be applied to the charging roller as a sum of the first reference voltage and a preset offset voltage that corresponds to the slope data.

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Suwon, South Korea

Ui-Choon Lee