Image forming apparatus and method thereof

An image forming apparatus comprising:

• an image carrier member;
• an image forming unit including a charging unit configured to charge the surface of the image carrier member evenly and control the amount of electric charge by a charging potential to be applied, an exposure unit configured to form a latent image on the image carrier member, and a developing unit configured to apply a developing bias, supply toner to the latent image on the image carrier member, and develop the same, the image forming unit performing an image forming process on the image carrier member for forming a toner image;
• an estimating unit configured to estimate the unexposed surface potential value of the image carrier member as a continuous function of the charging potential of the charging unit by the first approximate expression and estimate the exposed surface potential value of the image carrier member as a continuous function of the charging potential of the charging unit by the second approximate expression in the image forming unit;
• a first computing unit configured to select any one or more of the peripheral environment in the vicinity of the image carrier member, the fatigue, and the exposure value at the time of forming the latent image to define the first and second approximate expressions for estimating the amount of the surface potential of the image carrier member as a continuous function
• a second calculating unit configured to compute the charging potential to be applied to the image carrier member and the developing bias of the developing unit for realizing the developing potential and the background potential required for the image forming process on the image carrier member using the first and second approximate expressions;
• and a control unit configured to control the image forming unit using the computed result of the second computing unit.

An image forming method for forming a toner image on an image carrier member by performing an image forming process having a charging process for applying the charging potential to the image carrier member at a processing velocity switchable to a plurality of levels, an exposing process for forming a latent image on the image carrier member, and an developing process for applying a developing bias and supplying toner to the latent image on the image carrier member comprising:

• estimating the unexposed surface potential value of the image carrier member as a continuous function of the charging potential of the charging unit by a first approximate expression and estimating the exposed surface potential value of the image carrier member as a continuous function of the charging potential of the charging unit by a second approximate expression for the respective processing velocities of the plurality of levels;
• defining the continuous function by selecting any one or more of the peripheral environment in the vicinity of the image carrier member, the fatigue, and the exposure value of the exposure unit;
• computing the charging potential to be applied to the image carrier member and the developing bias of the developing unit for realizing the developing potential and the background potential required for the image forming process on the image carrier member using the first and second approximate expressions;
• and performing the charging process on the image carrier member at the computed charging potential for the respective processing velocities of the plurality of levels, and performing the developing process for supplying toner to the latent image on the image carrier member by applying the computed developing bias.