Abstract: A color image forming apparatus that automatically switches a printing mode between a single color printing mode and a color printing mode according to requested image data stores, when capturing of image data of a print job is started, the image data in an image memory unit, starts image formation of the image data in the color printing mode as an initial state, and maintains a color printing mode regardless of the image data until the number of printed copies reach a first number of copies for operation switching determination X1. When the number of printed copies reaches X1, the color image forming apparatus compares, in a comparing unit, the number of remaining pages of the print job and a second number of copies for operation switching determination X2 stored in a number-of-pages storing unit 36 and controls the printing mode on the basis of a result of the comparison and information concerning whether the remaining image data is color image data or single color image data.

Abstract: An image forming apparatus that forms a color image includes: a sensor that detects a density of an image formed on the transfer body; a density adjusting unit that forms a density test pattern on a transfer body and that adjusts process parameters such that a density of the density test pattern on the transfer body falls within a predetermined range of a reference density; and a gradation adjusting unit that forms a gradation test pattern on the transfer body and updates the gradation correction data such that a density for every gradation of the gradation test pattern on the transfer body falls within a predetermined range of a reference gradation density acquired and stored beforehand. The gradation adjusting unit updates the gradation correction data subsequently after the density adjusting unit adjusts the density of the density test pattern.

Abstract: An image forming apparatus that forms a color image includes: a sensor that detects a density of an image formed on the transfer body; a density adjusting unit that forms a density test pattern on a transfer body and that adjusts process parameters such that a density of the density test pattern on the transfer body falls within a predetermined range of a reference density; and a gradation adjusting unit that forms a gradation test pattern on the transfer body and updates the gradation correction data such that a density for every gradation of the gradation test pattern on the transfer body falls within a predetermined range of a reference gradation density acquired and stored beforehand. The gradation adjusting unit updates the gradation correction data subsequently after the density adjusting unit adjusts the density of the density test pattern.

Abstract: In an image forming apparatus, an image formation process is performed on image data in units of print jobs in a print mode of either one of a single-color print mode and a color print mode, the print mode is controlled to become the color print mode from the first page of the image data to a page of a designated page number, the print mode is controlled to become either one of the single-color print mode and the color print mode in a case where the designated page number is reached, and the designated page number is changed based on the number of the print jobs in a case where the image formation process reaches a designated number of times.

Abstract: According to an aspect of the invention, an image forming apparatus having a plurality of processing velocities is characterized by a control for determining the image forming process conditions by redefining a first approximate expression for estimating the unexposed surface potential value Vo of a photoconductive drum as a continuous function of the charging potential Vd according to the change of the natural environmental temperature, the change of the surface temperature of the photoconductive drum, the change of the photoconductive drum due to fatigue, or the exposure value, and a second approximate expression for estimating the exposed surface potential value VL of the photoconductive drum as a continuous function of the charging potential Vd according to the change of the processing velocity, using the first approximate expression and the second approximate expression to determine the optimal values of the developing potential, the background potential, and the exposure value for the respective process

Abstract: A color image forming apparatus that automatically switches a printing mode between a single color printing mode and a color printing mode according to requested image data stores, when capturing of image data of a print job is started, the image data in an image memory unit, starts image formation of the image data in the color printing mode as an initial state, and maintains a color printing mode regardless of the image data until the number of printed copies reach a first number of copies for operation switching determination X1. When the number of printed copies reaches X1, the color image forming apparatus compares, in a comparing unit, the number of remaining pages of the print job and a second number of copies for operation switching determination X2 stored in a number-of-pages storing unit 36 and controls the printing mode on the basis of a result of the comparison and information concerning whether the remaining image data is color image data or single color image data.

Abstract: A CPU computes a saturation moisture content on the basis of a temperature and a relative humidity detected by environment detection means, and multiplies the saturation moisture content by a square of the relative humidity, thus obtaining an environment parameter value. The CPU sets a proper development contrast potential using the environment parameter value according to a correlative approximation expression with pre-calculated development contrast potentials.

Abstract: A CPU computes a saturation moisture content on the basis of a temperature and a relative humidity detected by environment detection means, and multiplies the saturation moisture content by a square of the relative humidity, thus obtaining an environment parameter value. The CPU sets a proper development contrast potential using the environment parameter value according to a correlative approximation expression with pre-calculated development contrast potentials.

Abstract: A fixing apparatus according to the present invention includes a heating member, a belt support member, a heating belt, a press member, a first control section, and a second control section. The belt support member has a cylindrical shape partly cut out along an axis line direction and is capable of changing the size of the cross section area. The first control section controls the size of the cross section area of the belt support member. The second control section applies a force to the heating belt toward the press member and controls that magnitude.