Patent ID: 8781350

Claim:
An image forming apparatus comprising: a first photosensitive member; a second photosensitive member; a third photosensitive member; a first scorotron-type charger that is configured to charge the first photosensitive member; a second scorotron-type charger that is configured to charge the second photosensitive member; a third scorotron-type charger that is configured to charge the third photosensitive member; a first voltage applying circuit, which is connected to the first scorotron-type charger, and which is configured to apply a voltage to the first scorotron-type charger; and a second voltage applying circuit, which is commonly connected to the second scorotron-type charger and the third scorotron-type charger, and which is configured to apply a voltage to the second scorotron-type charger and the third scorotron-type charger, wherein the first scorotron-type charger, the second scorotron-type charger and the third scorotron-type charger comprises a wire and a grid, respectively, wherein the image forming apparatus further comprises: a current detection unit that is configured to detect grid current values flowing in the grids of the second scorotron-type charger and the third scorotron-type charger; and a controller that is configured to control the second voltage applying circuit so as to make the respective grid current values become a predetermined value or greater, and wherein the controller is further configured to: determine a grid current indicating the smallest current value of the respective grid current values; and control the second voltage applying circuit so as to make the grid current indicating the smallest current value become a constant current of the predetermined value or greater.