Patent ID: 8139962

Claim:
An image forming apparatus configured to form a toner image on a recording medium, comprising: a latent image carrier; a latent image forming unit configured to form an electrostatic latent image on the latent image carrier; a developing unit configured to develop the latent image with a two-component developer, the developing unit including a developer transport member configured to circulate the two-component developer along a developer circulation path, and a developer carrier configured to transport the two-component developer between a development area facing the latent image carrier and the developer circulation path; a toner supplier including a single driving source and a toner supply member, connected to the developer circulation path, and configured to supply toner at a predetermined supply position to the two-component developer circulating through the developer circulation path by driving the toner supply member with the driving source; a toner concentration detector located in the developer circulation path and configured to detect, continuously or intermittently, a toner concentration in the two-component developer passing a predetermined detection position located upstream of the predetermined supply position in a developer circulation direction; a prediction calculator configured to calculate, based on a detection result generated by the toner concentration detector, a prediction of changes in the toner concentration over time in the two-component developer passing a given prediction position, located at the predetermined supply position or downstream of the predetermined supply position and upstream of a developer feed position, where the two-component developer is fed to the developer carrier in the developer circulation direction when toner is not supplied; and a toner supply controller configured to reduce the changes in toner concentration over time in the developer at the given prediction position by controlling the driving source, based on the prediction calculated by the prediction calculator, to adjust an amount of the toner supplied to the two-component developer at the predetermined supply position.