Image forming apparatus which measures time during which an image carrier contacts a toner carrier

An image forming apparatus comprising:

• an image carrier configured to carry an electrostatic latent image;
• a toner carrier configured to carry a toner and develop the electrostatic latent image;
• a switching member configured to perform a switching operation between a contact state where the toner carrier contacts the image carrier and a separation state where the toner carrier is separated from the image carrier;
• a first electrode member;
• a second electrode member arranged such that an electrostatic capacity between the first and second electrode members in the contact state is different from the electrostatic capacity therebetween in the separation state;
• a detection device configured to detect the electrostatic capacity between the first and second electrode members;
• and
• a measurement unit configured to measure a time during which the image carrier contacts the toner carrier,
• wherein the measurement unit starts the measurement when the electrostatic capacity changes exceeding a predetermined value along with the switching operation from the separation state to the contact state, thereafter, the measurement unit stops the measurement when the electrostatic capacity changes exceeding a predetermined value along with the switching operation from the contact state to the separation state.