Abstract: A relationship 150?Rs (?)/Rm (?)?4000 is established in an environment of a temperature of 15° C. and a humidity of 10% in a case where a surface resistance of a transfer roller is Rs (?) when a current is fed between a pair of electrodes facing each other in an axial direction of the transfer roller and arranged on a surface of the transfer roller with an interval of 5 mm therebetween, the electrodes having a width of 20 mm in a circumferential direction of the transfer roller in a state of being arranged on the transfer roller, and in a case where a combined resistance of a first layer and a second layer is Rm (?) when the current is fed from a core portion to an outer peripheral surface of the second layer.

Abstract: An image forming apparatus includes an image bearing member; a developing device; a transfer member; a contact member provided downstream of the transfer member and upstream of the developing device with respect to a movement direction of a surface of the image bearing member and contacting the image bearing member at a contact portion, wherein the surface of the image bearing member passed through a transfer portion reaches the contact portion without being cleaned, a detecting portion for detecting a size of the sheet; and a controller for executing an operation in a cleaning mode for cleaning the contact member. The controller executes the operation in the cleaning mode when the controller discriminates that the size of the sheet detected by the detecting portion is smaller than a size of the toner image.

Abstract: There is provided an image forming apparatus including a configuration in which a voltage of a polarity opposite to a toner charging polarity is applied. In the image forming apparatus, a guide region of a pre-transfer guide is located on a photosensitive drum side with respect to a common tangent line of a photosensitive drum and a development roller to reduce contamination of the pre-transfer guide and prevent contamination of recording materials.

Abstract: An image forming apparatus includes a developing unit which develops a toner image on a surface of a photosensitive member and which collects toner which remains on the surface of the photosensitive member after the developed toner image is transferred to a transfer member. The image forming apparatus includes a controller configured to determine whether a cleaning operation of cleaning the surface of the photosensitive member is to be performed after an image forming operation is performed or control a period of time in which the cleaning operation is performed in accordance with a measured downtime of the image forming apparatus which is a period of time after the image forming operation is terminated and before a next image forming operation is started.

Abstract: A relationship 150?Rs (?)/Rm (?)?4000 is established in an environment of a temperature of 15° C. and a humidity of 10% in a case where a surface resistance of a transfer roller is Rs (?) when a current is fed between a pair of electrodes facing each other in an axial direction of the transfer roller and arranged on a surface of the transfer roller with an interval of 5 mm therebetween, the electrodes having a width of 20 mm in a circumferential direction of the transfer roller in a state of being arranged on the transfer roller, and in a case where a combined resistance of a first layer and a second layer is Rm (?) when the current is fed from a core portion to an outer peripheral surface of the second layer.

Abstract: In a configuration in which a voltage of polarity opposite to charging polarity of toner is applied to a conveyance guide, controlling deposition of toner on the conveyance guide has been difficult. When performing duplex image formation, a potential difference between a surface potential of a photoconductive drum charged by a charging roller and a potential of the conveyance guide is smaller during printing on the second surface than during printing on the first surface.

Abstract: An image forming apparatus includes an image bearing member; a developing device; a transfer member; a contact member provided downstream of the transfer member and upstream of the developing device with respect to a movement direction of a surface of the image bearing member and contacting the image bearing member at a contact portion, wherein the surface of the image bearing member passed through a transfer portion reaches the contact portion without being cleaned, a detecting portion for detecting a size of the sheet; and a controller for executing an operation in a cleaning mode for cleaning the contact member. The controller executes the operation in the cleaning mode when the controller discriminates that the size of the sheet detected by the detecting portion is smaller than a size of the toner image.

Abstract: An image forming apparatus includes a discharging device for discharging the drum at a discharging portion opposing the surface of the drum; and a control unit for executing, during non-image formation, a cleaning operation for transferring the toner deposited on the transfer member onto the drum by applying a voltage from transfer voltage source to the transfer member. The control unit does not effect discharge by the discharging device for at least a region of the drum where a transfer voltage for transferring a normal-polarity toner of the toner deposited on the transfer member onto the drum is applied to the transfer member in the cleaning operation, and then passes the region of the drum through the charging portion in a state in which a voltage larger than a surface potential of the drum in a normal polarity side is applied to the charging member.

Abstract: A fixing device configured to fix a toner image on a recording material by heating while conveying the recording material that bears the toner image by a nip portion, the fixing device includes a fixing roller having a rubber layer, a rotating member configured to form a contact portion between the rotating member and the fixing roller, and a pressure member configured to form the nip portion cooperatively with the fixing roller. In the fixing device, heat of the rotating member transfers to the fixing roller from the rotating member via the contact portion, and the contact portion includes a region where the pressure is increased after being decreased on a downstream side further than a center of the contact portion in the rotational direction of the rotating member.

Abstract: An image heating apparatus for heating a recording material, on which a toner image is carried, while conveying the recording material in a nip includes: a fixing roller including a metal core, a heat insulating layer formed on a surface of the core metal, and a high heat transfer layer which is formed on an outer peripheral surface of the heat insulating layer and has a higher thermal conductivity than the heat insulating layer; a heating member for heating the fixing roller from an outside; and a back-up member for forming the nip together with the fixing roller. When the fixing roller and the back-up member opposing the fixing roller are supplied with the same heat quantity, the temperature rise rate in a neighborhood of the surface of the back-up member supplied with the heat quantity is higher than that of the fixing roller.

Abstract: An image heating apparatus for heating a toner image formed on a recording material includes a first rotatable member contactable to the toner image; and a heating unit, including a second rotatable member rotating while contacting a surface of the first rotatable member, for heating the first rotatable member. The toner image on the recording material is heated by receiving heat from the first rotatable member heated by the heating unit. The image heating apparatus further includes a potential controller for maintaining a polarity of a surface potential of the second rotatable member so as to be opposite to a charge polarity of the toner.

Abstract: Image fixing apparatus for fixing a toner image through a nip, the apparatus including a cylindrical film; a nip forming member contacting an inner surface of the film; a pressing rotatable member forming the nip in cooperation with the nip forming member with the film interposed therebetween; and a regulating member for regulating movement of the film in a direction of a generatrix of the film, wherein the regulating member has an opposing surface opposing an edge of an end portion of the film with respect to the direction of the generatrix, and the opposing surface has a regulation region for regulating the edge of the film when the film is driven and moves in the generatrix direction, wherein the regulation region is narrower in a downstream side of a center portion of the nip than in an upstream side thereof with respect to a sheet feeding direction.

Abstract: A fixing device configured to heat a recording material bearing a toner image at a nip portion while conveying the recording material includes a tubular film, a nip portion forming member contacting an inner surface of the film, a pressure member forming the nip portion together with the nip portion forming member via the film, and a regulating member configured to regulate a movement of the film by contacting an end surface of the film. The regulating member includes, in a vicinity of the nip portion, a regulating surface inclined such that a distance from an imaginary plane including the end surface is gradually decreased as the regulating surface extends away from the nip portion to a circumferential direction of the film, and that the distance therefrom is gradually increased as the regulating surface extends in a radial direction of the film.

Abstract: A fixing device configured to fix a toner image on a recording material by heating while conveying the recording material that bears the toner image by a nip portion, the fixing device includes a fixing roller having a rubber layer, a rotating member configured to form a contact portion between the rotating member and the fixing roller, and a pressure member configured to form the nip portion cooperatively with the fixing roller. In the fixing device, heat of the rotating member transfers to the fixing roller from the rotating member via the contact portion, and the contact portion includes a region where the pressure is increased after being decreased on a downstream side further than a center of the contact portion in the rotational direction of the rotating member.

Abstract: A fixing device configured to heat a recording material bearing a toner image at a nip portion while conveying the recording material includes a tubular film, a nip portion forming member contacting an inner surface of the film, a pressure member forming the nip portion together with the nip portion forming member via the film, and a regulating member configured to regulate a movement of the film by contacting an end surface of the film. The regulating member includes, in a vicinity of the nip portion, a regulating surface inclined such that a distance from an imaginary plane including the end surface is gradually decreased as the regulating surface extends away from the nip portion to a circumferential direction of the film, and that the distance therefrom is gradually increased as the regulating surface extends in a radial direction of the film.

Abstract: An image heating apparatus for heating a recording material, on which a toner image is carried, while conveying the recording material in a nip includes: a fixing roller including a core metal, a heat insulating layer formed on a surface of the core metal, and a high heat transfer layer which is formed on an outer peripheral surface of the heat insulating layer and has a higher thermal conductivity than the heat insulating layer; a heating member for heating the fixing roller from an outside; and a back-up member for forming the nip together with the fixing roller. When the fixing roller and the back-up member opposing the fixing roller are supplied with the same heat quantity, a temperature rise rate in a neighborhood of the surface of the back-up member supplied with the heat quantity is higher than that of the fixing roller.

Abstract: Image fixing apparatus for fixing a toner image through a nip, the apparatus including a cylindrical film; a nip forming member contacting an inner surface of the film; a pressing rotatable member forming the nip in cooperation with the nip forming member with the film interposed therebetween; and a regulating member for regulating movement of the film in a direction of a generatrix of the film, wherein the regulating member has an opposing surface opposing an edge of an end portion of the film with respect to the direction of the generatrix, and the opposing surface has a regulation region for regulating the edge of the film when the film is driven and moves in the generatrix direction, wherein the regulation region is narrower in a downstream side of a center portion of the nip than in an upstream side thereof with respect to a sheet feeding direction.

Abstract: An image forming apparatus forms an unfixed toner image on a sheet and includes a fixing unit including a fixing roller, a back-up member forming a nip with the fixing roller, and a rotatable heater contactable to and heating the fixing roller. The sheet is output from the apparatus after the unfixed toner image is fixed on the sheet. In a cleaning mode for cleaning the fixing unit, a predetermined unfixed toner image is formed on the sheet, the sheet is fed to the fixing unit, the toner is transferred from the sheet onto the fixing roller in the fixing nip, the toner transferred onto the fixing roller is brought into contact to the heating member, and thereafter, the toner on the fixing roller is transferred onto the sheet in the fixing nip.

Abstract: An image heating apparatus for heating a toner image formed on a recording material includes a first rotatable member contactable to the toner image; and a heating unit, including a second rotatable member rotating while contacting a surface of the first rotatable member, for heating the first rotatable member. The toner image on the recording material is heated by receiving heat from the first rotatable member heated by the heating unit. The image heating apparatus further includes a potential controller for maintaining a polarity of a surface potential of the second rotatable member so as to be opposite to a charge polarity of the toner.

Abstract: An image forming apparatus for forming an unfixed toner image on a sheet includes a fixing unit including a fixing roller, a back-up member for cooperating with the fixing roller to form a nip therebetween, and a rotatable heating member contactable to a surface of the fixing roller to heat the fixing roller; wherein the sheet is outputted from the apparatus after the unfixed toner image is fixed on the sheet, wherein the apparatus is operable in a cleaning mode for cleaning the fixing unit, wherein when the cleaning mode is selected, a predetermined unfixed toner image is formed on the sheet, and the sheet is fed to the fixing unit, and the toner is transferred from the sheet onto the fixing roller in the fixing nip, and then the toner transferred onto the fixing roller is brought into contact to the heating member, and thereafter, the toner on the fixing roller is transferred onto the sheet in the fixing nip.