Patent ID: 8855508
Filing Date: 2014-10-07
Classification: G03G

Abstract:
1. An image forming apparatus comprising: a toner storage portion for storing a toner and, a carrier; a developing portion for performing development using a dual-component developer including the toner and the carrier; a toner replenishing portion for replenishing the toner from the toner storage portion to the developing portion; a toner density detecting portion for detecting a toner density of the developing portion; a photoreceptor drum for carrying a toner image visualized by the developing portion; a toner patch forming portion for forming a toner patch for detecting an image density on the photoreceptor drum; an image density detecting portion for detecting a density of the toner patch; and a storage portion for storing a density of a reference toner patch serving as a reference of an image density and a reference developing bias value to be applied to the developing portion, an image density control portion for comparing the density of the toner patch that is detected and the density of the reference toner patch to correct the image density; and a toner density control portion for controlling a developing bias value to be applied to the developing portion in such a manner as to fall within a first developing potential control range determined by a first upper threshold and a first lower threshold, wherein when a difference between the reference developing bias value and a developing bias value after correction of the image density exceeds the first upper threshold, the toner density control portion performs control to consume toner forcibly, and when the difference between the reference developing bias value and the developing bias value after correction of the image density exceeds the first lower threshold, the toner density control portion performs control to replenish toner forcibly, the image density control portion corrects the image density again after performing the control of toner replenishment or the control of toner consumption, the toner density control portion performs control in such a manner that the developing bias value after correction of the image density falls within a second developing potential control range determined by a second upper threshold and a second lower threshold, and the toner density control portion, when the difference between the reference developing bias value and the developing bias value after correction of the image density exceeds the second upper threshold, performs control to consume toner forcibly, and when the difference between the reference developing bias value and the developing bias value after correction of the image density exceeds the second lower threshold, performs control to replenish toner forcibly.