Patent ID: 8095028

Claim:
An image forming apparatus comprising: plural image carriers each having a visible image carried on a rotating surface thereof; a first driving source that is a driving source for only any one of the image carriers; a second driving source that is a driving source for another image carrier; a rotation detection unit that separately detects whether the image carrier driven by the first driving source and another image carrier driven by the second driving source have a predetermined rotational angle; an endless movement body that causes a front surface thereof to be endlessly moved; a transfer unit that transfers the visible images formed on front surfaces of the image carriers to the front surface of the endless movement body or a recording member held on the front surface of the endless movement body so as to be superimposed one on another; and a control unit that controls driving of the first and second driving sources based on an output from the rotation detection unit, the image forming apparatus using the first driving source as a shared driving source between the image carrier and a predetermined member other than a driving transmission unit for driving the image carrier; wherein a waveform recognition unit is provided that recognizes a first waveform as a waveform of a first speed fluctuation and a second waveform as a waveform of a second speed fluctuation based on a result obtained by detecting the first speed fluctuation per rotation of the image carrier driven by a driving force of the first driving source driven at a predetermined speed and the second speed fluctuation per rotation of another image carrier driven by a driving force of the second driving source driven at a predetermined speed, and the control unit is configured to recognize a reference timing per rotation of the image carrier driven by the first driving source and a reference timing per rotation of another image carrier driven by the second driving source based on the output from the rotation detection unit and control the driving of the second driving source based on the reference timings and the first and second waveforms recognized by the waveform recognition unit, thereby matching a phase and an amplitude of the second waveform of another image carrier driven by the second driving source to a phase and an amplitude of the first waveform of the image carrier driven by the driving force of the first driving source driven at the predetermined speed.