Image forming apparatus capable of accurately calculating opc drum wear amount

An image forming apparatus with a monochrome OPC drum and a color OPC drum, comprising:

• a charger configured to charge a surface of a photosensitive layer of the color OPC drum;
• a developer configured to perform development using a developing agent including a toner and a carrier;
• and
• a calculating portion configured to calculate a wear amount of the photosensitive layer of the color OPC drum;
• wherein
• the charger charges the photosensitive layer of the color OPC drum during monochrome printing to a surface potential that is lower than a surface potential during color printing, and that suppresses a change in the wear amount of the photosensitive layer of the color OPC drum during monochrome printing and during color printing.

An image forming apparatus with a monochrome OPC drum and a color OPC drum, comprising:

• a charger configured to charge a surface of a photosensitive layer of the color OPC drum;
• a developer configured to perform development using a developing agent including a toner and a carrier;
• and
• a calculating portion configured to calculate a wear amount of the photosensitive layer of the color OPC drum;
• wherein
• the charger charges the photosensitive layer of the color OPC drum during monochrome printing so that a surface potential of the photosensitive layer of the color OPC drum decreases as a film thickness of the photosensitive layer of the color OPC drum decreases.