Image forming apparatus

An image forming apparatus, comprising:

• a photoconductor including a photoconductive layer forming a surface for carrying an electrostatic latent image;
• a charging member arranged in contact with or in proximity to the surface;
• a voltage applier for charging the surface by applying an oscillating voltage obtained by superimposing a direct-current voltage and an alternating-current voltage to the charging member;
• a storage unit for storing in advance relationship information representing a relationship between an electrical characteristic of discharge products adhering to the surface and a proper inter-peak voltage value which is an inter-peak voltage value of the alternating-current voltage capable of properly charging the surface;
• a current detector for detecting a current value of a current flowing from the charging member to the photoconductor;
• a characteristic deriver for deriving the electrical characteristic of the discharge products adhering to the surface on the basis of the oscillating voltage applied to the charging member by the voltage applier and the current value;
• and
• a voltage setter for setting the proper inter-peak voltage value corresponding to the electrical characteristic derived by the characteristic deriver in the relationship information as the inter-peak voltage value of the alternating-current voltage.