Image forming apparatus

An image forming apparatus comprising:

• a plurality of image forming units each of which includes
• an image carrier having a photosensitive layer formed on a surface thereof, and
• a developing device including a developer carrier that is disposed to face the image carrier and carries a developer containing toner, and configured to form a toner image by adhering the toner to an electrostatic latent image formed on the image carrier, and forms an image by superimposing a toner image of a same color;
• a developing voltage power supply that applies, to the developer carrier, a developing voltage acquired by superimposing an AC voltage on a DC voltage;
• a current detection unit that detects a DC component of developing current that flows when the developing voltage is applied to the developer carrier;
• and
• a control unit that controls the image forming units and the developing voltage power supply, wherein
• the plurality of image forming units use the developer containing the toner of a same color and a same type, and substantially same development conditions are set to evenly divide an image density among the image forming units,
• the control unit detects whether there is an anomaly in each of the image forming units, based on at least one of white background portion current I1 being a DC component of developing current flowing through a non-exposed portion of the image carrier detected by the current detection unit during image formation, and image portion current I2 being a DC component of developing current flowing through an exposed portion of the image carrier, and
• when an anomaly is detected in any of the image forming units, the control unit inhibits use of the image forming unit, and resets the development conditions to evenly divide the image density among the usable image forming units.