Patent ID: 7376375

Claim:
A belt-drive control device comprising: an endless belt; a belt driving unit that rotates the endless belt; at least one driven roller that is in contact with the endless belt; an encoder that is attached to the driven roller; a mark detecting unit that detects a mark that is a reference position of the endless belt; an angular-displacement-error detecting unit that detects an angular displacement error of the encoder caused by thickness fluctuation of the endless belt, based on an output signal from the mark detecting unit; a first calculating unit that calculates a phase and a maximum amplitude to the mark, based on the detected angular displacement error of the encoder; a nonvolatile memory that stores a result of calculation by the first calculating unit; a second calculating unit that calculates correction data according to a distance from the mark on the endless belt based on the result of calculation stored in the nonvolatile memory; and a volatile memory that stores the calculated correction data, wherein the belt-drive control device controls the belt driving unit by adding the correction data stored in the volatile memory to a preset control target value to stabilize speed fluctuation of the endless belt due to the thickness fluctuation.