Image forming apparatus

An image forming apparatus comprising:

• an image carrier having a surface on which a photosensitive layer is formed;
• an electrifying member for electrifying the image carrier;
• a high voltage generating circuit for applying an oscillation voltage, in which a DC voltage and an AC voltage are superimposed, to the electrifying member;
• a voltage controller for controlling peak-to-peak voltage value Vpp and frequency of the AC voltage;
• a current detector for detecting DC current value Idc between the electrifying member and the image carrier;
• and
• a recovery process controller for performing a recovery process for decreasing frictional resistance of the surface of the image carrier, wherein
• the voltage controller determines whether or not two inflection points O and P exist, which exist on a characteristic curve on a two-dimensional coordinate system indicating a relationship between the voltage value Vpp and the current value Idc, when applying the oscillation voltage to the electrifying member by setting the frequency of the AC voltage as a first frequency or by rotating the image carrier at a first linear speed so as to increase the voltage value Vpp,
• when the oscillation voltage is applied to the electrifying member by setting the frequency of the AC voltage as the first frequency and if the two inflection points O and P exist, a first inter-inflection-point voltage OP between the inflection points O and P and a second inter-inflection-point voltage OP′ between two inflection points O′ and P′ are calculated, the two inflection points O′ and P′ existing on the characteristic curve when the oscillation voltage is applied to the electrifying member by setting the frequency of the AC voltage as a second frequency different from the first frequency so as to increase the voltage value Vpp,
• when the oscillation voltage is applied to the electrifying member by rotating the image carrier at the first linear speed and if the two inflection points O and P exist, the first inter-inflection-point voltage OP between the inflection points O and P and a third inter-inflection-point voltage OP″ between two inflection points O″ and P″ are calculated, the two inflection points O″ and P″ existing on the characteristic curve when the oscillation voltage is applied to the electrifying member by rotating the image carrier at a second linear speed different from the first linear speed so as to increase the voltage value Vpp, and
• the recovery process controller performs the recovery process when a potential difference between the first inter-inflection-point voltage OP and the second inter-inflection-point voltage OP′ or a potential difference between the first inter-inflection-point voltage OP and the third inter-inflection-point voltage OP″ is a predetermined value or less.