Abstract: A fixing device is provided in an image forming apparatus. The fixing device has first and second rollers to form a nip portion therebetween. An image forming medium having a flat shape and a leading edge, on which an unfixed image is formed. The image forming medium is conveyed and approaches the nip portion between the first and second rollers. The fixing device also has a changing unit for changing the shape of the vicinity of the leading edge of the image forming medium from the flat shape to a convex shape while the image forming medium is being conveyed to approach the nip portion.

Abstract: A fixing device for use in a copying machine. The device has a heating roller, a pressure roller, and a separation pawl. The pawl has an end portion contacting the peripheral surface of the heating roller at a first point close to a second point where the pressure roller and the heating roller contact each other. The pawl separates a sheet, on which an image has been fixed, from the heating roller, and guides this sheet along a line tangent to the periphery of the heating roller and connected to the second point. The sheet is thus prevented from being deformed.

Abstract: An electronic copying apparatus of this invention has a function of partially changing a tone of an image reproduced from an original image. In this apparatus, a predetermined range of an original placed on an original table is designated by a spot light source, and the original is optically scanned by an exposure lamp. An optical image obtained by the exposure lamp is focused on a photoconductive drum having a predetermined surface potential by an optical system, and is developed by a developer constituting a developer unit. The image developed by the developer is transferred to a paper sheet by a transfer charger. An image outside the predetermined range designated by the spot light source is formed on the paper sheet in one tone, and an image inside the predetermined range is erased by an erasure array. The surface potential of the photoconductive drum is changed upon an instruction from a main processor.

Abstract: A fixing device for image forming apparatus utilizing image forming media of a plurality of different widths, comprises a core roller and a supporting roller parallel to and in contact with the core roller to supports the selected one of the image forming media with the toner image thereon and transporting the selected image forming medium, an electrically resistive heat layer on the core roller and a plurality of power supply electrodes for supplying power to at least two portions of the electrically resistive heat layer having sizes corresponding to the widths of at least two of the image forming media.

Abstract: A developing apparatus includes a vessel, set near a photosensitive drum and contains at least two magnetic developers bearing different colors, and at least two developing rollers which are held in the vessel and which deposit the developer on the surface of the photosensitive drum. In the apparatus, each developing roller includes a cylindrical rotatable sleeve prepared from a nonmagnetic material and a fixed magnetic roller received in the sleeve. On the peripheral portion of the magnetic roller, a number of charged magnetic poles with alternating polarities are arranged on such a manner that the polarity of the poles facing each other on the adjacent developing rollers is the same. Matching up polarities in this manner prevents the production of a magnetic flux between the adjacent developing rollers.

Abstract: An electronic copying machine having a control circuit with a microprocessor including a read-only memory which stores a predetermined timing constant to control a charging timing of a charger and an exposure timing of an exposure unit in such a manner that a leading end of a toner-image forming area of a photosensitive drum which corresponds to a leading end of a copying paper sheet is charged by the charger and exposed by the exposure unit only after the leading end is exposed to a transfer charger, separating charger, discharger and discharge lamp.