Patent ID: 9726999
Date: 2017-08-08
CPC Classifications: G03G

Claim:
1. An image forming apparatus comprising: a rotatable photosensitive member; a first corona charger that electrically charges a surface of said photosensitive member to provide a charged surface; a second corona charger that electrically charges a surface of said photosensitive member to a first predetermined potential in superposition on said charged surface of said photosensitive member charged by said first corona charger, said second corona charger being provided downstream of said first corona charger with respect to a rotational direction of said photosensitive member; an image former that forms an image on said photosensitive member charged by said first corona charger and said second corona charger; a voltage applier that applies voltages to said first corona charger and said second corona charger; a detector that detects a surface potential of said photosensitive member, said detector being provided downstream of said second corona charger with respect to the rotational direction of said photosensitive member; and a controller that controls the voltages applied to said first corona charger and said second corona charger, wherein said controller is capable of executing a test mode operation in which said first corona charger is operated and said second corona charger is not operated, and a first voltage to be applied to the first corona charger is determined so that the surface potential of said photosensitive member is charged to a second predetermined potential lower in absolute value than the first predetermined potential, and then said first corona charger and said second corona charger are both operated with the thus determined first voltage applied to the first corona charger, and a second voltage to be applied to the second corona charger is determined so that the surface potential of said photosensitive member is charged to the first predetermined potential by said first and second corona chargers, and wherein said controller is capable of controlling said voltage applier to apply the thus determined first voltage to the first corona charger and to apply the thus determined second voltage to the second corona charger during image formation.