Color misregistration-free color image forming apparatus

摘要

In a color image forming apparatus such as a color laser printer, misregistration of colors of an output image along a subscanning direction is minimized so as to prevent accumulation of color misregistrations in the output image. In the apparatus, a photosensitive drum motor and a transfer drum motor are driven by motors exclusively provided thereto. The apparatus includes a photosensitive drum motor controller and a transfer drum motor controller respectively provided for speed-controlling the photosensitive drum motor and the transfer drum motor. By these motor controllers, a phase difference between a frequency generator signal from the motor and a phase reference signal is checked. Even if the phase difference exceeds a predetermined range of phase, the motor controller controls the motor so that the phase difference quickly falls within the predetermined range of phase.