Image forming apparatus

An image forming apparatus comprising:

• a rotary unit having a plurality of development devices provided around a rotary shaft, the development device including a constituent unit, wherein the plurality of the development devices move to a development position where the development devices sequentially oppose an image carrier by rotation of the rotary unit, and the development device in the development position develops an electrostatic latent image on the image carrier,
• a state detection unit disposed at a position outside of a circumference of the rotary unit, the position being different from the development position, the state detection unit detects at least one of a state of the development devices and a state of the constituent unit of the development devices;
• and
• a rotation control unit that controls the rotary unit so as to effect rotation of the rotary unit for sequentially moving the development devices to the development position and to a detection position during the same rotation, wherein a detection of the state by the state detection unit and the development of the electrostatic latent image on the image carrier by the development devices are performed in the same rotations,
• wherein the rotation of the rotary unit solely for developing the electrostatic latent image on the image carrier and the rotation of the rotary unit for both developing the electrostatic latent image on the image carrier and detecting at least one of the state of the development devices and the state of the constituent unit by the state detection unit are selectively performed,
• wherein the state detection unit detects the state between a time that the developing device in the development position finishes developing the electrostatic latent image on the image carrier and a time that the next developing device arrives at the developing position, and a total time of the time required to detect the state by the state detection unit and the elapsed time between the time that the developing device in the development position finishes developing and the time that the next developing device arrives at the developing position is compared with a predetermined allowable time identified by a condition of image forming, and when the total time exceeds the allowable time, a rotation only for developing an electrostatic latent image on the image carrier is performed, and when the total time falls within the allowable time, a rotation including state detection by the state detection unit is performed.