Image forming apparatus

An image forming apparatus, comprising:

• a plurality of image bearing members which bears visible images on rotating surfaces thereof;
• a plurality of drive sources which individually drives the image bearing members, each of the plurality of drive sources comprising a drive gear;
• a plurality of driven gears which individually engages the image bearing members on rotation axes of the image bearing members and mesh with the drive gears;
• a visible image forming unit which forms the visible images on each of the image bearing members based on image information;
• an endless traveling member which endlessly moves a surface thereof to sequentially pass positions facing the image bearing members;
• a transfer unit which transfers the visible images formed on each of the surfaces of the image bearing members to a recording medium held on the surface of the endless traveling member, or to the surface of the endless traveling member and to the recording medium;
• an image detection unit configured to detect the visible images formed on the surface of the endless traveling member;
• and
• a controller configured to control rotation of the plurality of image bearing members according to a velocity fluctuation pattern of each surface of the image bearing members,
• wherein the velocity fluctuation pattern is based on a detection time interval between forming predetermined visible detection images on the surface of the image bearing member and detecting, by the image detection unit, the predetermined visible detection images transferred from the surface of the image bearing member to the endless traveling member,
• wherein each of the plurality of driven gears comprises a gear portion and an engaging portion integrated therewith, the gear portion having a geared circumference and the engaging portion engaging the image bearing member,
• wherein the engaging portion of each of the driven gears includes a cylindrical concave portion which receives a coupling of each of the image bearing members,
• wherein an inner gear circumference is provided in the cylindrical concave portion and the coupling includes gears which mesh with the inner geared circumference of the engaging portion,
• wherein each of the plurality of driven gears further comprises a marking blade member provided on the gear portion which protrudes in a direction of rotation of the driven gear, the marking blade member rotates coaxially with the image bearing member,
• wherein the velocity fluctuation pattern is a velocity fluctuation pattern detected based on a rotation lap of the image bearing member, and
• wherein the controller determines a timing of starting forming the predetermined visible detection images on each surface of the image bearing members based on detection results from each of a plurality of rotation angle detection units, each rotation angle detection unit detects when rotation of the corresponding driven gear arrives at a predetermined angle when the marking blade member faces a position sensor and the marking blade member is detected by the position sensor.