Patent ID: 7783215

Claim:
An image forming apparatus comprising a storage portion, an image bearing member on which an electrostatic latent image is to be formed based on image data stored in the storage portion, and a development apparatus that develops the electrostatic latent image formed on the image bearing member as a toner image using a two-component developer including toner and a carrier, wherein the development apparatus is provided with: a developer bearing member that bears the developer, a circulation transport portion that circulates the developer in a loop shape such that the developer is transported in a transport direction along an axial direction of the developer bearing member while being supplied to a circumferential surface of the developer bearing member, and a toner concentration detection sensor that detects a concentration of toner in the developer that circulates in the circulation transport portion, and is configured to carry out replenishment of toner to the developer in the circulation transport portion, wherein the image forming apparatus is provided with: a toner concentration measuring means that measures the concentration of toner in the developer, which is detected by the toner concentration detection sensor, for each predetermined transport length along the developer transport direction, a storage means that stores in the storage portion a measured toner concentration value of the developer in each transport length measured by the toner concentration measuring means, a toner consumption amount predicting means that specifies, among image data stored in the storage portion, regions of the image data corresponding to the electrostatic latent image on the image bearing member to be developed by the developer in each transport length, and predicts toner consumption amounts of the developer in each corresponding transport length based on image data of the specified regions for the developer in each transport length that has been specified, a toner concentration estimating means that, based on the measured toner concentration values of the developer in each transport length stored in the storage portion by the storage means and the predicted toner consumption amounts of the developer in each corresponding transport length predicted by the toner consumption amount predicting means, estimates toner concentrations in the developer after development using the developer in each corresponding transport length, and a toner replenishment control means that, based on the estimated post-development toner concentration values of the developer in each transport length estimated by the toner concentration estimating means and a toner setting concentration value that has been set in advance, carries out control of toner replenishment to the developer in each corresponding transport length.