Abstract: In an electrophotographic image forming apparatus of the type using single-ingredient type high resistance toner, a developing roller or similar toner conveyor roller is covered with a dielectric layer which is comparatively thick at opposite end portions than at an intermediate portion. A conductive or semiconductive elastic layer underlies the dielectric layer. With the above configuration, the dielectric layer is prevented from coming off the roller. This, coupled with the tact that the elastic layer does not contact a photoconductive element, eliminates current leaks and thereby extends the life of the roller and photoconductive element.

Abstract: In an image forming apparatus, a developing device of the type developing an electrostatic latent image formed on an image carrier by using single-component type toner has a regulating member for regulating the amount of the toner fed thereto, a first conveying member for conveying the toner regulated by the regulating member and deposited thereon, and a second conveying member for conveying the toner transferred from the first conveying member thereto to the image carrier. The first and second conveying members are each movable at a particular speed in a particular direction. The device is free from problems attributable to oppositely charged toner particles despite the use of the single-component type toner and, in addition, insures attractive images.

Abstract: A developing device for an image forming apparatus and using a single component type developer, i.e., toner, has a developing roller, a doctor blade, and an elastic intermediae roller. The developing roller and intermediate roller contact each other and rotate in the same directions such that they move in opposite directions at the position where they contact each other. The developing roller is provide with a surface roughness of Rz 10 .mu.m or less in terms of ten-point mean value as prescribed by JIS (Japanese Industrial Standards) in order to deposit an adequate charge on toner.

Abstract: A developing device for an image forming apparatus and having a relatively hard first developing roller formed with fine N-S magnetic poles on the periphery thereof, and a relatively soft second developing roller for conveying toner electrostatically transferred thereto from the first roller toward a photoconductive drum. The toner is charged by friction while being passed through between the first roller and a blade, and then magnetically deposited on the first roller. At a position where the first and second rollers contact each other, only the adequately charged toner is electrostatically transferred from the first roller to the second roller. The second roller conveys the toner toward the drum. As a result, the toner is brought to a developing position in an amount corresponding to a saturation or maximum image density. The second roller is made up of a metallic conductive core, a semiconductive foam layer, and an insulative surface layer implemented by resin.

Abstract: A developing device for an image forming apparatus and having a relatively hard first developing roller formed with fine N-S magnetic poles on the periphery thereof, and a relatively soft second developing roller for conveying toner electrostatically transferred thereto from the first roller toward a photoconductive drum. The toner is charged by friction while being passed through between the first roller and a blade, and then magnetically deposited on the first roller. At a position where the first and second rollers contact each other, the adequately charged toner is substantially evenly charged by friction and electrostatically transferred from the first roller to the second roller. The second roller conveys the toner toward the drum. The second roller has a surface roughness whose ratio to the mean particle size of the toner is selected to be less than or equal to 1.5.