Patent ID: 7454150

Claim:
An image forming apparatus comprising: a belt endlessly stretched across a drive roller and a plurality of driven rollers; a drive-roller driver configured to rotate the drive roller at a plurality of different first velocities; a detector that detects information representative of any one of a rotational displacement and a velocity of at least one driven roller; a fixing rotary member that fixes an image formed on a recording medium conveyed on the belt by sandwiching the recording medium with the belt; a fixing-rotary-member driver configured to rotate the fixing rotary member at a plurality of different second velocities; a rotation controlling unit configured to rotate any one of the drive roller with the first velocities and the fixing rotary member with the second velocities, and obtains a correlation between information detected by the detector and any one of the first velocities and the second velocities; and a target velocity determining unit that determines a target velocity at which a difference between information when the recording medium is in contact with both the belt and the fixing rotary member and information when the recording medium is not in contact with at least any one of the belt and the fixing rotary member is minimum from the correlation, wherein any one of the drive-roller driver rotates the drive roller and the fixing-rotary-member driver rotates the fixing rotary member at the target velocity.