Image forming apparatus with correction of toner density control

摘要

An image forming apparatus in which a predetermined image density can be obtained by correcting a toner density control target value without consuming toner. The output The output value Vt of the magnetic permeability sensor and the target output value Vt ref are compared, and the toner density is controlled by controlling a powder pump on the basis of the comparative result thereof so that the output value Vt approximates the target output value Vt ref . In addition, the target output value Vt ref is corrected on the basis of the detected result of the image coverage ratio. The image coverage ratio is determined as a moving average wherein the sampling number (number N of images on which average is calculated) may be altered.