Patent ID: 8267511

Claim:
An image forming apparatus comprising: an ink discharge unit including a plurality of nozzles to discharge ink and to form an image on a recording medium by discharging the ink from the plurality of nozzles onto the recording medium; a conveyer belt to convey the recording medium so that the recording medium passes through an area facing the ink discharge unit, the conveyor belt including a plurality of blank discharge holes to let the ink for a blank discharge from the ink discharge unit through; a control unit to control an ink discharge operation of the ink discharge unit; a blank discharge receiver to receive the ink for the blank discharge discharged from the ink discharge unit, provided at a position facing the ink discharge unit across the conveyor belt; and a belt position detection unit to detect a position in a direction perpendicular to a belt moving direction of the conveyor belt, wherein the belt position detection unit includes a belt position detection mark provided on the conveyor belt, and a mark detection unit to detect the belt position detection mark, the belt position detection mark provided on the conveyor belt is shaped to include different lengths in the belt moving direction, at respective different positions in the direction perpendicular to the belt moving direction, and the belt position detection unit detects the position in the direction perpendicular to the belt moving direction based on a mark detection time of the mark detection unit detecting the belt position detection mark; and wherein the control unit controls a blank discharge start timing of the ink discharge unit based on a switching timing from a state detecting the belt position detection mark into a state not detecting the belt position detection mark.