Color electrophotographic method and apparatus employed therefor

A color electrophotographic apparatus which comprises a plurality of movable image forming units each having at least a photosensitive member and a developing unit, a transfer paper holding member for holding transfer paper so as to transfer toner image onto the transfer paper, and an exposure means, with the respective developing units of said image forming units having toner in a plurality of colors, said color electrophotographic apparatus including a color mode and a single color mode, and a moving means of said image forming units so controlled as to displace said image forming units in turn, to a first image forming position during said color mode, whereby, after forming an electrostatic latent image on the photosensitive member of said image forming unit by the exposure means and developing said electrostatic latent image by toner, toner images of the respective colors are successively transferred onto the paper sheet held on the transfer paper holding member to form the color image on the transfer paper, and, to displace a predetermined image forming unit to a second image forming position during said single color mode, with the toner image in the single color developed thereat being transferred onto the paper sheet without employing said transfer paper holding member.

A color electrophotographic apparatus which comprises a plurality of movable image forming units each having at least a photosensitive member and a developing unit, a transfer paper holding member for holding transfer paper so as to transfer toner image onto the transfer paper, and an exposure means, with the respective developing units of said image forming units having toner in a plurality of colors, said color electrophotographic apparatus including a color mode and a single color mode, each of said image forming units having a first image forming position confronting said transfer paper holding member, and a second image forming position spaced from said transfer paper holding member, said exposure means being arranged to be changed over between a first state acting on the image forming unit at said first image forming position during the color mode, and a second state acting on the image forming unit at said second image forming position during the single color mode.

A color electrophotographic apparatus which comprises a plurality of movable image forming units each having at least a photosensitive member and a developing unit, a transfer paper holding member for holding transfer paper so as to transfer toner image onto the transfer paper, and a paper feeding means for feeding the paper for transfer to an image forming portion, with the respective developing units of said image forming units having toner in a plurality of colors, said color electrophotographic apparatus including a color mode and a single color mode, each of said image forming units having a first image forming position confronting said transfer paper holding member, and a second image forming position spaced from said transfer paper holding member, said paper feeding means begin arranged to be changed over between a first state for feeding the paper to said transfer paper holding member during the color mode, and a second state for feeding the paper to the image forming unit at said second image forming position during the single color mode.

A color electrophotographic apparatus which comprises a plurality of image forming units each having at least a photosensitive member and a developing unit, a transfer paper holding member for holding transfer paper so as to transfer a toner image onto the transfer paper, and a single exposure device, the respective developing units of said image forming units having toner in a plurality of colors with a transfer position of said transfer paper holding member and the exposure position of said exposure device being fixed, said color electrophotographic apparatus further including a moving means of said image forming units so controlled as to rotate the group plurality of said image forming units on the whole and to displace said image forming units in turn, to the same image forming position during the color image formation, whereby, after forming an electrostatic latent image on the photosensitive member of said image forming unit by said exposure device and developing said electrostatic latent image by color toner, the toner images are transferred onto the paper sheet held on the transfer paper holding member to form the color image on the transfer paper.

A color electrophotographic apparatus which comprises a plurality of movable image forming units each having at least a photosensitive member and a developing unit, a transfer image holding member for holding transfer image so as to transfer toner image, and a single exposure device, the respective developing units of said image forming units having toner in a plurality of colors, with a transfer position of said transfer image holding member and the exposure position of said exposure device being fixed, said color electrophotographic apparatus further including a moving means of said image forming units so controlled as to displace said image forming units in turn, to the same image forming position during the color image formation whereby, after forming an electrostatic latent image on the photosensitive member of said image forming unit by said exposure device and developing said electrostatic latent image by toner, the toner images are transferred onto said transfer image holding member to form the color image thereon.

A color electrophotographic method which comprises the steps of forming respective single color images in a plurality of colors, and combining said respective single color images to form a color image, wherein, when time for using a photosensitive member during said respective single color image forming step for the color image formation is represented by T, and time for electrostatically resting the photosensitive member up to the next use of said photosensitive member, by t, a step in a relation of T<t is repeated to form the color image.

A color electrophotographic method for continuously forming a same image for a plurality of times, which comprises the steps of forming a color image by combining a plurality of single color images, and electrostatically resting a photosensitive member employed therefor during continuous use thereof for the color image formation.

A color electrophotographic method which comprises the steps of forming respective single color images in a plurality of colors, and combining said respective single color images to form a color image, wherein time for electrostatically resting a photosensitive member employed therefor is provided between said respective single color image formations in the plurality of colors.