Patent ID: 7546047

Claim:
An image forming apparatus, comprising: an electrifying apparatus; a laser scanning unit; a photoconductive medium electrified by the electrifying apparatus to a predetermined electric potential; a developing apparatus having a developing roller to develop an electrostatic latent image formed on the photoconductive medium by the laser scanning unit and a supplying roller to supply a toner to the developing roller, the developing apparatus being fixed around the photoconductive medium; a voltage supplying apparatus to supply a predetermined bias voltage to the developing roller and the supplying roller; and a controlling apparatus to control a degree and a timing of the bias voltage supplied to the developing roller and the supplying roller to thereby control a movement state of the toner between the supplying roller and the developing roller, wherein, if the bias voltage supplied to the developing roller is denoted by Vd and the bias voltage supplied to the supplying roller is denoted by Vs, the controlling apparatus controls the voltage supplying apparatus to satisfy equation 1 as follows when performing a developing operation and satisfies equation 2 after a predetermined time has elapsed |Vd|<|Vs| [Equation 1] |Vd|=|Vs| [Equation 2].