Image forming apparatus

An image forming apparatus, comprising:

• an image forming portion including:
• an image carrying member that includes a photosensitive layer formed on a surface thereof;
• a charging device that charges the surface of the image carrying member;
• an exposure device that exposes to light the surface of the image carrying member charged by the charging device so as to form an electrostatic latent image thereon;
• and
• a developing device including:
• a developing container that contains a two-component developer containing a carrier and toner;
• a developer carrying member that is rotatably supported in the developing container and carries the two-component developer on a surface thereof;
• and
• a toner concentration sensor that detects a toner concentration in the two-component developer in the developing container,
• the developing device being configured to develop the electrostatic latent image into a toner image;
• a toner container that contains the toner with which the developing device is to be replenished;
• and
• a control portion that controls, based on an output value of the toner concentration sensor, replenishment of the developing device with the toner from the toner container and corrects, based on an integrated consumption amount of the toner from a start of use of the developing device, a target value of the toner concentration,
• a storage portion that stores a first integrated consumption amount that is the integrated consumption amount on a first production line of the image forming apparatus,
• wherein
• the control portion calculates a second integrated consumption amount that is the integrated consumption amount in a setup operation for the image forming apparatus and an image output operation performed after a start of use thereof, and uses a sum of the first integrated consumption amount and the second integrated consumption amount to determine a correction value for correcting the target value of the toner concentration.