Abstract: An image forming apparatus that forms an image using a plurality photoconductor bodies includes a cleanerless transfer belt configured to convey paper to the plurality of photoconductor bodies and a switching unit configured to switch on/off a cleaner for each of the photoconductor bodies, on the basis of whether a single mono-colored developing agent is adhered to the transfer belt or whether two or more mono-colored developing agents are adhered to the transfer belt. A control unit is configured to control a change of a transfer bias for each of the photoconductor bodies, when the switching unit switches on/off the cleaners.

Abstract: Plural image forming sections transfer toner images of plural colors to a transfer target medium, so that a color image is formed on the transfer target medium. When a weight per particle of respective monochromatic toner particles calculated from a 50% volume average particle diameter of the respective monochromatic toner particles is m (kg), a charge amount per particle of the respective monochromatic toner particles calculated from a charge amount Q/M (C/kg) per weight measured by a suction type particle charge amount measuring device is q (C), and an average adhesive force between each of the monochromatic toner particles and each of the image carriers is F (N), F/q of the toner particle used in the image forming section in which order in transferring the monochromatic toner image to the transfer target medium is the first in the plural image forming sections is largest.

Abstract: A developing agent contains magnetic particles having a surface coated layer containing an organic material on at least a part of a surface thereof, and colored particles provided with an external additive having a weak charging property with respect to the surface coated layer of the magnetic particles on a surface of mother particles containing at least a resin and a colorant, whereby it has a high transfer efficiency, and an image with high quality can be obtained.

Abstract: A color image forming apparatus includes an intermediate transfer member, a first forming portion having a first transfer unit, a second forming portion provided downstream from the first forming portion, a third forming portion provided downstream from the second forming portion, a fourth forming portion provided downstream from the third forming portion, and a control portion. The control portion controls a bias of at least one of the corresponding developing unit and the corresponding transfer unit, when transfer of the toner image from the intermediate transfer member to the recording medium is completed, so that a toner-image residue toner material resting on the intermediate transfer member is returned to the corresponding developing unit through the image bearing member of at least one of the first to fourth forming portions.

Abstract: A color image forming apparatus includes an image forming section that is configured to adopt an intermediate transfer system for three colors of cyan, magenta and yellow, and a direct transfer system for black. A transfer medium is conveyed to a transfer medium convey belt. Cyan, magenta and yellow are intermediately transferred by an intermediate transfer belt and a secondary transfer roller. Black is directly transferred by a black photoconductor body and a transfer roller. Toners of the respective colors are fixed by a fixing device.

Abstract: There is provided an image forming apparatus comprising a developing device containing a toner having an average particle diameter of 2 to 5 ?m and a spherical degree of 1 to 1.2, and a transfer member which is pressed against the image carrier by a pressing force having a total load of 150 g to 1500 g and a surface load of 10 to 150 g/cm2 at the time of transfer.

Abstract: An image forming apparatus that forms an image using a photoconductor body includes a switching unit which effects switching between a state in which a cleaner is operated for the photoconductor body, and a state in which the cleaner is not operated for the photoconductor body. A control unit is provided which controls a setting change of an image formation condition between a case where the cleaner is operated by the switching unit, and a case where the cleaner is not operated by the switching unit. The switching unit includes a detection unit which detects the kind of paper on which an image is formed, and the switching unit switches on/off the cleaner in accordance with a detection result of the detection unit.

Abstract: An image forming method of forming an image by transferring a toner image, which is formed on an image bearing member by toner particles, to a transfer medium is provided. The toner particles include a coloring agent and a resin. When an average electrostatic adhesive force Fe of the toner particles to the image bearing member is expressed by the following expression, a/r satisfies 0.2?a/r?0.7: F e = ? ? - 1 ? ? + 1 · q 2 ? r 2 4 ? ?? 0 ? ( r 2 - a 2 ) 2 where ?? is a specific dielectric constant of the image bearing member, q is an electrification quantity per one toner particle, and r is a volume average radius of the toner particles.

Abstract: An image forming apparatus that forms an image using a photoconductor body includes a switching unit which effects switching between a state in which a cleaner is operated for the photoconductor body, and a state in which the cleaner is not operated for the photoconductor body. A control unit is provided which controls a setting change of an image formation condition between a case where the cleaner is operated by the switching unit, and a case where the cleaner is not operated by the switching unit. The switching unit includes a detection unit which detects the kind of paper on which an image is formed, and the switching unit switches on/off the cleaner in accordance with a detection result of the detection unit.

Abstract: The invention defines an adhesive force characteristic of a toner, which makes it possible to control behaviors of toner particles by applying an electric field, and defines, when an amount of charges before transfer per weight of the toner particles is Q (?C/g), an average adhesive force of the toner particles to the medium is F (N), a volume average particle diameter of the toner particles is d (?m), and a specific gravity of the toner particles is ? (g/cm3), an A value represented by A=(K×Q+F0/Q)×6/??d3) (K: an inclination at the time when F is approximated to a linear function of Q2, F0: a y intercept at the time when F is approximated to a linear function of Q2) in a range of 1×107?A?2.5×107 (N/C). Consequently, a developing agent has a highly efficient and stable transfer characteristic and it is possible to form a high-quality image.

Abstract: A color image forming apparatus includes an image forming section that is configured to adopt an intermediate transfer system for three colors of cyan, magenta and yellow, and a direct transfer system for black. A transfer medium is conveyed to a transfer medium convey belt. Cyan, magenta and yellow are intermediately transferred by an intermediate transfer belt and a secondary transfer roller. Black is directly transferred by a black photoconductor body and a transfer roller. Toners of the respective colors are fixed by a fixing device.

Abstract: The developing agent is selected to have a distribution of adhesive force to the surface of an image carrier, which is configured such that the ratio of the developing agent having an adhesive force which is not less than 2.5 times as high as an average value of a distribution of adhesive force is 3% by weight or less based on an entire weight of the developing agent.

Abstract: In an image forming apparatus of the present invention capable of forming a full-color image by superposing a black toner image formed by a black image forming unit using a developing and simultaneous cleaning type developing unit over color toner images obtained by color image forming units using developing and simultaneous cleaning developing units arranged in tandem, adhered toners generated from the black image forming unit or the color image forming units to be recovered are all recovered by a same single cleaner.

Abstract: A color image forming apparatus includes an image forming section that is configured to adopt an intermediate transfer system for three colors of cyan, magenta and yellow, and a direct transfer system for black. A transfer medium is conveyed to a transfer medium convey belt. Cyan, magenta and yellow are intermediately transferred by an intermediate transfer belt and a secondary transfer roller. Black is directly transferred by a black photoconductor body and a transfer roller. Toners of the respective colors are fixed by a fixing device.

Abstract: A cleanerless cartridge in which a photoconductor body and a charger are integrated, and a cleaner-equipped cartridge in which a photoconductor body, a charger and a cleaner are integrated are prepared. An image forming apparatus body is configured such that the cartridges are attachable to first- to fourth-stage image forming sections. When the cleanerless cartridge is attached to the first- to fourth-stage image forming sections, an image forming operation is controlled under an image formation condition for a cleanerless process. When the cleaner-equipped cartridge is attached to the first- to fourth-stage image forming sections, an image forming operation is controlled under an image formation condition for a cleaner-equipped process.

Abstract: The developing agent is selected to have a distribution of adhesive force to the surface of an image carrier, which is configured such that the ratio of the developing agent having an adhesive force which is not less than 2.5 times as high as an average value of a distribution of adhesive force is 3% by weight or less based on an entire weight of the developing agent.

Abstract: A color image forming apparatus includes an intermediate transfer member, a first forming portion having a first transfer unit, a second forming portion provided downstream from the first forming portion, a third forming portion provided downstream from the second forming portion, a fourth forming portion provided downstream from the third forming portion, and a control portion. The control portion controls a bias of at least one of the corresponding developing unit and the corresponding transfer unit, when transfer of the toner image from the intermediate transfer member to the recording medium is completed, so that a toner-image residue toner material resting on the intermediate transfer member is returned to the corresponding developing unit through the image bearing member of at least one of the first to fourth forming portions.

Abstract: In an image forming apparatus of the present invention capable of forming a full-color image by superposing a black toner image formed by a black image forming unit using a developing and simultaneous cleaning type developing unit over color toner images obtained by color image forming units using developing and simultaneous cleaning developing units arranged in tandem, adhered toners generated from the black image forming unit or the color image forming units to be recovered are all recovered by a same single cleaner.

Abstract: In a color image forming apparatus of the invention, a developing roller of a developing device includes a magnet roller that is configured such that a developer supply pole, a developer convey pole and a developer release pole are properly arranged and fixed. The developer roller also includes an outer cylindrical roller that is formed of an electrically conductive material such as aluminum. A surface of the cylindrical roller is processed to have irregularities. Using the developing roller, simultaneous development/cleaning is executed. Thus, 100% of toner contributes to image formation, and no waste toner is produced. Post-transfer residual toner on a photoconductor body is efficiently recovered to the developing roller, and occurrence of an image defect such as development memory can be prevented.

Abstract: The ratio of the particles of developing agent having a particle diameter of not more than A×0.5 (?m) (wherein A is a 50% average particle diameter (?m)) and the ratio of the particles of developing agent having a particle diameter of not less than A×1.5 (?m) (wherein A is a 50% average particle diameter (?m)) are both confined to not more than 5% by number in a number particle size distribution, the ratio of the developing agent having an adhesive strength of not more than 1.3×10?8(N) is confined to 10% by weight or less and the ratio of the developing agent having an adhesive strength of not less than 3×10?7(N) is confined to 5% by weight or less in a distribution of adhesive strength to the surface of the image carrier.