Patent ID: 9217951
Filing Date: 2015-12-22
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: an image carrier configured to have an electrostatic latent image formed on a surface and carry a toner image; a developing device including a development housing configured to store a developer containing toner to be charged to a predetermined polarity and carrier, a magnetic roller configured to receive the developer in the development housing and carry a developer layer by being rotated and a developing roller configured to receive the toner from the developer layer, carry a toner layer and supply the toner to the image carrier by being rotated in a state in contact with the developer layer; a bias applying unit configured to apply development biases, in which an alternating-current voltage is superimposed on a direct-current voltage, to the magnetic roller and the developing roller; a leakage detecting unit configured to detect leakage occurring between the image carrier and the developing roller or leakage occurring between the developing roller and the magnetic roller; a bias control unit configured to provide a predetermined potential difference between the magnetic roller and the developing roller so that the toner is transferred from the magnetic roller to the developing roller by controlling the bias applying unit during a developing operation in which the toner is supplied from the developing roller to the image carrier; and a leakage detection control unit configured to perform a leakage detecting operation of detecting a value of an inter-peak voltage, at which the leakage occurred, as a leakage causing voltage at a time different from that of the developing operation while increasing the inter-peak voltage of the alternating-current voltage of the development bias; wherein: four or more of developing devices and four or more of bias applying units are arranged in correspondence with different colors of toner; and the leakage detection control unit simultaneously starts the leakage detecting operations for a plurality of developing devices and performs the leakage detecting operations of the developing devices, in which leakage simultaneously occurred, while switching the leakage detecting operations one by one if the leakage simultaneously occurs in a plurality of developing devices at an inter-peak voltage.