Patent ID: 9207565
Filing Date: 2015-12-08
Classification: G03G

Abstract:
1. A developing device, comprising: a development housing configured to store a developer containing toner to be charged to a predetermined polarity and carrier; a developer carrier configured to receive the developer in the development housing and carry a developer layer by being rotated; a toner carrier configured to receive the toner from the developer layer, carry a toner layer and supply the toner to an image carrier having an electrostatic latent image formed on a surface and carrying a toner image developed by the toner by being rotated in a state in contact with the developer layer; a bias applying unit including one transformer and configured to apply direct-current voltages and alternating-current voltages having the same frequency and phases opposite to each other to the developer carrier and the toner carrier; a leakage detecting unit configured to detect leakage occurring between the image carrier and the toner carrier or leakage occurring between the toner carrier and the developer carrier; a bias control unit configured to provide a predetermined potential difference of the direct-current voltage between the toner carrier and the developer carrier and apply the alternating-current voltages so that the toner is transferred from the developer carrier to the toner carrier by controlling the bias applying unit during a developing operation in which the toner is supplied from the toner carrier to the image carrier; and a leakage detection control unit configured to detect a value of an inter-peak voltage, at which the leakage occurs, by changing inter-peak voltages in a state where a ratio of the inter-peak voltages of the alternating-current voltages applied to the toner carrier and the developer carrier is fixed and determine whether the leakage occurs between the image carrier and the toner carrier or between the toner carrier and the developer carrier during a leakage detecting operation different from the developing operation; wherein the bias control unit sets a value obtained by subtracting a first offset voltage set in advance from a first inter-peak voltage as the inter-peak voltage of the alternating-current voltage to be applied during the next developing operation if the occurrence of leakage between the image carrier and the toner carrier at the first inter-peak voltage is determined by the leakage detection control unit and sets a value obtained by subtracting a second offset voltage set in advance and larger than the first offset voltage from the first inter-peak voltage as the inter-peak voltage of the alternating-current voltage to be applied during the next developing operation if the occurrence of leakage between the developer carrier and the toner carrier at the first inter-peak voltage is determined by the leakage detection control unit.