Image forming apparatus and layer thickness calculating method

An image forming apparatus comprising:

• rotatable image carrying means for carrying a toner image by a surface layer disposed on a surface thereof;
• charging means for charging the surface layer of the image carrying means while the image carrying means completes one or more rotations;
• a power supply that supplies a current to the charging means;
• detecting means for detecting the current that the power supply outputs;
• leak current detecting means for detecting a leak current included in the current that the detecting means has detected;
• layer thickness calculating means for calculating a numerical value relating to the thickness of the surface layer of the image carrying means on the basis of the current that the detecting means has detected;
• and
• current leak state determining means for determining a current leak state on the basis of the current that the detecting means has detected and the leak current that the leak current detecting means has detected.

A layer thickness calculating method comprising:

• while an image carrier that rotates and carries a toner image by a surface layer disposed on its surface completes one or more rotations, charging the surface layer while detecting a current that is supplied in order to charge the surface layer;
• detecting a leak current included in the detected current;
• determining a current leak state on the basis of the detected current and the leak current;
• and
• calculating a numerical value relating to the thickness of the surface layer in accordance with the determined current leak state.