Image forming apparatus with stopper for preventing rotation of a developing unit

An image forming apparatus comprising:

• an image carrier configured to retain electrostatic latent images on its surface;
• a rotatable developing unit comprising a holder configured to hold a plurality of developing devices;
• a motor configured to rotate the developing unit in an image forming direction and to move a selected developing device of the plurality of developing devices to a developing position opposed to the image carrier;
• and
• a stopper configured to be moved manually between an unstopping position and a stopping position,
• wherein, when the stopper is in the unstopping position, the stopper is unengaged with the holder,
• wherein, when the stopper is in the stopping position, the stopper prevents rotation of the holder in the image forming direction and prevents rotation of the holder in a direction opposite the image forming direction, and
• wherein, when the stopper is in the stopping position, the holder is stopped such that at least one of the developing devices is at an exchanging position for being exchanged.

An image forming method comprising:

• retaining electrostatic latent images on an image carrier;
• developing the electrostatic latent images to form developed images on the image carrier by using a developing unit comprising a holding unit holding plural developing devices;
• rotating the developing unit and moving a desired developing device to a developing position opposed to the image carrier;
• moving manually a stopping unit to an unstopping position unengaged with the holding unit and to a stopping position engaged with the holding unit, the stopping unit in the stopping position preventing rotation of the holding unit in the image forming direction, preventing rotation of the holding unit in a direction opposite the image forming direction, and positioning the holder such that at least one of the developing devices is at an exchanging position for being exchanged.