Abstract: An image forming apparatus equipped with a first image forming unit, plural second image forming units, and a test-pattern image forming control unit for controlling the first and second image forming units which controls the first and second image forming units to form a test-pattern image, in such a manner that first and second marks of different densities are disposed adjacent to one another, based on test-pattern image data. This test-pattern image data includes first data serving to arrange a plurality of first color lines, which have each a predetermined line width, at a predetermined pitch by the first image forming unit, second data serving to form the first mark overlapping with the plural first color lines by the second image forming units, and third data serving to form the second mark displaced in a direction perpendicular to the plural first color lines.

Abstract: An image-forming device such as a full color printer is provided which is designed to correct the speed of an image carrier such as a sheet conveyer belt for compensating for a shift between colors. The image-forming device forms electrostatic marks on the image carrier at regular intervals and detects the marks using a sensor(s) to determine a change in speed of the image carrier based on sensor signals.

Abstract: An image forming apparatus has a plurality of print assemblies for forming a color image, a fixing unit, and a paper conveyor belt for conveying a paper sheet through the print assemblies and the fixing unit. The fixing unit includes a pair of fixing rollers, a nip control mechanism for moving the pair of the fixing rollers between a nip position and a non-nip position, and a fixing unit securing means movable with the nip control mechanism. Thus, the fixing unit can be easily mounted and demounted.

Abstract: An image forming apparatus has a plurality of print assemblies for forming a color image, a fixing unit, and a paper conveyor belt for conveying a paper sheet through the print assemblies and the fixing unit. The fixing unit includes a pair of fixing rollers, a nip control mechanism for moving the pair of the fixing rollers between a nip position and a non-nip position, and a fixing unit securing member movable with the nip control mechanism. Thus, the fixing unit can be easily mounted and demounted.

Abstract: An image-forming device such as a full color printer is provided which is designed to correct the speed of a conveyer belt on which print sheets are transported or intervals between image-transferring units for compensating for a shift between colors. The image-forming device has a timer which measures an elapsed time from turning on of the device or release of a sleep mode, a print-off time and a print time and determines a correction value as a function of the times measured by the timer by look-up using a table.