Image forming apparatus capable of properly controlling ac voltage applied to a charger

An image forming apparatus comprising:

• an image bearing member for bearing a toner image:
• transfer means for transferring the toner image onto a transfer material from said image bearing member;
• charging means for electrically charging said image bearing member, said charging means being effective to collect residual toner remaining on said image bearing member after transfer of the toner image by said transfer means;
• voltage application means for applying DC and AC voltages to said charging means, said voltage application means applying a voltage which is effective to return, in an non-image-forming area, the toner collected by said charging means to said image bearing member using an electric field;
• image forming means for forming an electrostatic image on said image bearing member charged by said charging means;
• developing means for developing the electrostatic image by toner;
• integrating means for integrating a degree of usage of said apparatus;
• and
• control means for controlling the voltage applied to said charging means;
• wherein said control means controls the voltage to be applied to return the collected toner to said image bearing member in accordance with the integrated degree of usage provided by said integrating means.