Image forming apparatus with thickness detecting unit

An image forming apparatus comprising:

• a photosensitive member, a photosensitive layer formed on a surface of the photosensitive member;
• a charging device that charges the photosensitive member;
• an exposing device that exposes the surface of the photosensitive member, which has been charged by the charging device;
• a developing device that forms a toner image on the surface of the photosensitive member;
• a cleaning member that is in sliding friction with the surface of the photosensitive member to remove residue on the surface of the photosensitive member;
• a thickness detecting unit that detects a thickness of the photosensitive layer on a basis of an integration value of a current supplied to the charging device;
• and
• a friction reducing unit, when the thickness detecting unit is to detect the thickness of the photosensitive layer, the friction reducing unit reducing a coefficient of friction between the surface of the photosensitive member and the cleaning member,
• wherein the friction reducing unit causes the developing device to supply the toner to the surface of the photosensitive member during a period in which the thickness detecting unit is detecting the thickness of the photosensitive layer or before the thickness detecting unit starts detecting the thickness of the photosensitive layer, and
• when the supply of the toner to the surface of the photosensitive member is conducted before the thickness detecting unit starts detecting the thickness of the photosensitive layer, the supplied toner exists at the surface of the photosensitive member whenever the thickness detecting unit starts detecting the thickness of the photosensitive layer.