Abstract: In an image forming apparatus, a developing device operable with toner or single component type developer has a hard first developing roller and a soft second developing roller. Fine magnetic N-S poles are formed on the periphery of the first roller. The second roller conveys the toner, electrostatically transferred thereto from the first roller, to an image carrier. The device frees a toner image from deterioration due to toner particles charged to a polarity opposite to an expected polarity. The toner forms a uniform thin layer on the first roller and is uniformly charged. Toner for use with this type of developing device is also disclosed.

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 fact 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 operable with toner or single component type developer has a hard first developing roller and a soft second developing roller. Fine magnetic N-S poles are formed on the periphery of the first roller. The second roller conveys the toner, electrostatically transferred thereto from the first roller, to an image carrier. The device frees a toner image from deterioration due to toner particles charged to a polarity opposite to an expected polarity. The toner forms a uniform thin layer on the first roller and is uniformly charged. Toner for use with this type of developing device is also disclosed.

Abstract: In an electrophotographic recording apparatus of the type using a single-ingredient type developer, i.e., toner, a developing device has a developing roller for conveying the toner deposited thereon, and an intermediate roller for conveying the toner transferred theretofrom the developing roller and depositing it on a latent image electrostatically formed on an image carrier to thereby produce a corresponding toner image. During the development of an area of the image carrier other than a latent image area, a bias assigned to the developing roller is switched over to thereby form an electric field different in direction from an electric field assigned to the formation of the toner image between the two rollers. Further, before the rotation of the image carrier is stopped, the bias assigned to the developing roller is again switched in order to form the electric field for the formation of the toner image between the rollers. As a result, a toner layer is formed on the intermediate roller.

Abstract: In an image forming apparatus using a corona discharge type charging device and a contact type image transferring device, a toner deposited on a photoconductive element in the form of a black stripe is prevented from being transferred to the image transferring device; otherwise, the toner would be transferred from the image transferring device to the rear of the following recording medium. Because the toner forming the black stripe is limited to the toner charged to a polarity opposite to an expected polarity, toner consumption ascribable to the stripe is reduced.

Abstract: In an image forming apparatus, a developing device operable with toner or single component type developer has a hard first developing roller and a soft second developing roller. Fine magnetic N-S poles are formed on the periphery of the first roller. The second roller conveys the toner, electrostatically transferred thereto from the first roller, to an image carrier. The device frees a toner image from deterioration due to toner particles charged to a polarity opposite to an expected polarity. The toner forms a uniform thin layer on the first roller and is uniformly charged. Toner for use with this type of developing device is also disclosed.

Abstract: An image forming apparatus including a developing device having various components with specific relationships between their lengths. There is an image bearing member such as a photoconductive drum or belt having a photosensitive layer. The photosensitive layer has a length A. A first toner transporting roller has two ends, the length between the two ends being defined as B. Additionally, there is a second toner transporting roller, disposed between and contacting both the image bearing member and the first toner transporting roller. The length of the second toner transporting roller being defined as C. The components of the image forming apparatus are constructed such the length of the second toner transporting roller is less than or equal to the lengths of both the first toner transporting roller and the photosensitive layer of the image bearing member. This means that the relationships A>C and B>C may exist. As an alternative, B is approximately equal to C with A being greater than both B and C.

Abstract: A developing apparatus is capable of providing stable charging ability for a developer and stable transfer ability for transferring the developer to a photoreceptor for electronic photography to prevent residual positive images and stain of texture which appear on a toner image. A first toner transfer roller 23 has a core supported to be rotatable and a sheet type insulation layer wound around the outer periphery of the core. The insulation layer is made of elastic rubber in which magnetic material having a specified particle size is uniformly dispersed and the magnetic material is formed with ferromagnetic substance such as magnet and magnetized in advance. The first toner transfer roller 23 attracts toner T by actuating magnetism on the insulation layer since the magnetic material added to the insulation layer is magnetized.

Abstract: In an image forming apparatus, a developing device has a first developer carrier for depositing a developer thereon, a regulating member for regulating the amount of the developer deposited on the first developer carrier, and a second developer carrier having an elastic surface, and contacting the first developer carrier while biting into it by a predetermined amount. The developer is provided with a preselected degree of fluidity. Hence, even when the same portion of the surface of the second developer carrier runs a plurality of times past a position where the two developer carriers contact each other without any developer being fed from the second developer carrier to an image carrier, the first developer carrier can surely strip the developer from the second developer carrier. As a result, a developer on which a predetermined amount of charge is deposited is transferred from the first developer carrier to the second developer carrier. This successfully protects images from defects.

Abstract: In an image forming apparatus, a developing device operable with toner or single component type developer has a hard first developing roller and a soft second developing roller. Fine magnetic N-S poles are formed on the periphery of the first roller. The second roller conveys the toner, electrostatically transferred thereto from the first roller, to an image carrier. The device frees a toner image from deterioration due to toner particles charged to a polarity opposite to an expected polarity. The toner forms a uniform thin layer on the first roller and is uniformly charged. Toner for use with this type of developing device is also disclosed.

Abstract: In an image forming apparatus, a developing device operable with toner or single component type developer has a hard first developing roller and a soft second developing roller. Fine magnetic N-S poles are formed on the periphery of the first roller. The second roller conveys the toner, electrostatically transferred thereto from the first roller, to an image carrier. The device frees a toner image from deterioration due to toner particles charged to a polarity opposite to an expected polarity. The toner forms a uniform thin layer on the first roller and is uniformly charged. Toner for use with this type of developing device is also disclosed.

Abstract: A developing device which includes a first toner transporting roller, a second toner transporting roller to which toner is transported from the first toner transporting roller and an image bearing member such as a photoconductive drum or belt. Seals are located between the circumferential ends of one of the toner transporting rollers and a bottom portion of a toner hopper. When the seals are between the bottom of toner hopper and the first toner transporting roller, the first toner transporting roller is longer than the second toner transporting roller and the circumferential portions of the first toner transporting roller which contact the seals do not contact the second toner transporting roller.

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: In an image forming apparatus, a developing device for developing a latent image electrostatically formed on an image carrier by toner has a first rotatable conveying member for causing the toner to deposit thereon, a regulating member for regulating the amount of toner deposited on the first conveying member, and a second conveying member for causing the toner transferred from the first conveying member and regulated by the regulating member to deposit thereon, and supplying the toner to the latent image. The pressure of the regulating member, abutting against the first conveying member, includes a component parallel to a line connecting the axes of the first and second conveying members, and directed from the axis of the first conveying member toward the axis of the second conveying member.

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.

Abstract: A developing device includes a developing sleeve driven to rotate for transporting a film of charged developer as carried thereon past a developing station where the film of developer is applied to an electrostatic latent image to have it developed. Also provided is a sponge roller pressed against and driven to rotate in the same rotating direction as that of the developing sleeve, so that the developer is supplied to the developing sleeve at one side of the contact between the developing sleeve and the sponge roller and any residual developer on the developing sleeve is removed at the other side of the contact. Preferably, a desired voltage difference is established between the developing sleeve and the sponge roller. Furthermore, the sponge roller is preferably so structured to have a sufficient conductivity level at least at its outer peripheral surface thereby allowing the residual charge on the developing sleeve to be discharged sufficiently.