Document-scanning control apparatus for image-forming apparatus

摘要

A rotational velocity control apparatus of a document-scanning motor in a copying machine comprises a first velocity detector for detecting the rotational velocity of a photosensitive drum and for generating a signal of a frequency corresponding to the detected velocity, a frequency converter circuit for multiplying the frequency of the output signal from the first velocity detector and for frequency dividing the signal in accordance with a selected magnification, a second velocity detector for detecting the rotational velocity of a scanning motor and for generating a signal having a frequency corresponding to the detected velocity, and a motor controller for controlling the rotational velocity of the scanning motor such that the frequency of the output signal from the second velocity detector is proportional to that of the output signal from the frequency converter circuit. The frequency converter circuit has a phase locked loop control circuit having a frequency divider in its feedback loop, the frequency division ratio of which is changed in accordance with magnification. The motor controller also has in its feedback loop a frequency divider having a frequency division ratio which is changed in accordance with magnification. The proportional constant of the frequency of the output signal from the second velocity detector to that of the output signal from the frequency converter circuit is changed in accordance with the selected magnification.