Abstract: A developing unit includes a developing roller which rotates about a rotational axis to supply toner to a photoreceptor, and a magnetic roller which forms a magnetic brush with a two-component developing agent having carrier and the toner and thereby forms a toner layer on the developing roller, the developing roller including: a cylindrical core portion which includes an electric conductor; a first resistive layer which covers a cylindrical surface of the core portion; a second resistive layer which covers the first resistive layer, and has electric-resistivity lower than that of the first resistive layer; and a current leakage control member which prevents leakage of electric current from the core portion toward the second resistive layer through an end of the developing roller along a direction of the rotational axis.

Abstract: A developing unit has a voltage-applicator (80) to apply a developing bias voltage to a developing roller (72). The voltage-applicator (80) applies the developing bias voltage for a first duration to apply an AC voltage having a rectangular waveform, and a second duration to stop applying the AC voltage. The AC voltage has a duty ratio of 50% or more in a direction for causing toner to develop an electrostatic latent image. The number of cycles of the AC voltage in the first duration is two or more, and the AC voltage has a voltage in a direction for pulling the toner back to the developing roller, just before transition to the second duration. The developing unit suppresses occurrence of image unevenness due to a fluctuation in developing gap. Thus, an image forming apparatus equipped with the developing unit forms a high-quality image while suppressing image unevenness.

Abstract: A developing unit includes a developing roller which rotates about a rotational axis to supply toner to a photoreceptor, the developing roller including: a cylindrical core portion which includes an electric conductor; a first resistive layer which covers a cylindrical surface of the core portion; a second resistive layer which covers the first resistive layer, and has electric-resistivity lower than that of the first resistive layer; and a current leakage control member which prevents leakage of electric current from the core portion toward the second resistive layer through an end of the developing roller along a direction of the rotational axis.

Abstract: An image forming apparatus having a touchdown-development type developing apparatus, in which a toner collecting roller that collects scattered toner suspended in the vicinity of a toner holding body and a two-component developer holding body is arranged on the downstream side in a rotational direction of the two-component developer holding body from a closest position of the two-component developer holding body and the toner holding body, and between the two-component developer holding body and the housing wall, and further, bias means that applies a bias voltage for collecting the scattered toner to the toner collecting roller, and image density sensing means for sensing a density of a toner image developed on the electrostatic latent image holding body surface or a toner image on a transfer body onto which the toner image developed on the electrostatic latent image holding body surface is transferred to control the bias voltage are provided.

Abstract: A developing device uses a two-component developer including at least carriers and toners. The toners are supplied to an image bearing member bearing an electrostatic latent image so that a toner image is developed from the electrostatic latent image. The developing device has a developing roller arranged to oppose the image bearing member; and a magnetic roller arranged to oppose the developing roller. The magnetic roller retains the two-component developer to supply toners to the developing roller. The developing roller and the magnetic roller are rotationally driven in directions to be opposite from one another at an opposed position, and a magnetic pole of the magnetic roller and a magnetic pole of the developing roller have magnetic polarities different from one another at the opposed position. A surface roughness of the magnetic roller is greater than a surface roughness of the developing roller.

Abstract: An image forming apparatus has a photoconductive member, and a developing roller develops a latent image on the photoconductive member by a first alternating-current bias in the form of a rectangular wave. The following relationships are satisfied in calculating the duty ratio (D1) of the first alternating-current bias using an application period of voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: a CV value in the number particle size distribution of the toner is ?25%, 4 ?m?Dt?7 ?m, 105 ?·cm?pv?109 ?·cm, 0.4 ?m?Ra?1.5 ?m, and 35%?D1?75%. where Dt denotes the volume average particle diameter of the toner, pv denotes the intrinsic resistance value of a developing roller surface, Ra denotes the arithmetic average roughness of the developing roller surface.

Abstract: A developing device is provided for visualizing an electrostatic latent image previously formed on the surface of an image carrier as a toner image. The developing device has a developing roller placed at a position facing the image carrier, carrying a toner on the surface thereof, conveying the toner and flying the conveyed toner onto the surface of the image carrier; and a resin layer coated on the surface of the developing roller. The absolute value of the difference in charge between the toners in the upper and lower layers of the toner layer formed on the developing roller as the toner carried on the developing roller is 6 ?C/g or less.

Abstract: An image forming apparatus includes a latent image carrying member, a two-component developer carrying member holding on an outer surface a developer containing carrier beads and toner particles, the two-component developer carrying member having a first magnetic element mounted therein, a toner carrying member carrying a thin toner layer on an outer surface, a toner collecting roller for collecting the toner particles scattered and suspended in the vicinity of the two-component developer carrying member and the toner carrying member, the toner collecting roller having a second magnetic element mounted therein, and a housing accommodating the two-component developer carrying member, the toner carrying member and the toner collecting roller. The toner collecting roller is located face to face with the two-component developer carrying member with the first and second magnetic elements disposed to face each other with oppositely directed polarities.

Abstract: An image forming apparatus has a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image on the photoconductive member by a first bias. A magnetic roller forms a magnetic brush thereon with a two-component developer and forms a thin toner layer on the developing roller by a second bias. The developing roller is aluminum with a surface treated for high resistance. The thickness (T) of the toner layer and the duty ratio (D1) of the first alternating-current bias satisfy relationships of the following equations for calculating the duty ratio (D1) using an application period of a voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: 7 ?m?T?13 ?m, and 35%?D1?70%.

Abstract: This invention relates to a developing device 18 for use in an image-forming apparatus comprising a developing roller 100 having a conductive base surface 19 which may be covered with a resin layer 17 layer comprising an ion conductive material and a silicone-modified urethane resin having an ether structure.

Abstract: A developer includes a developer carrying body that carries a two-component developer having a magnetic toner and a carrier. A toner carrying body opposes the developer carrying body and receives toner from the developer carrying body. An image carrying body develops an electrostatic latent image by toner carried on the toner carrying body. A first magnetic member is inside the developer carrying body and opposes a surface of the toner carrying body. A second magnetic member is inside the toner carrying body and opposes the surface of the developer carrying body. The second magnetic member is magnetized to an opposite polarity to the first magnetic member and generates a magnetic force at least on the surface of the toner carrying body in a range of 25 mT to 40 mT in a direction perpendicular to the surface of the toner carrying body.

Abstract: An image forming apparatus uses a two-component developer containing a toner and a carrier. The apparatus has a latent image bearer for bearing an electrostatic latent image. A toner bearer bears the toner to be conveyed to a development region to develop the electrostatic latent image. A developer bearer bears the two-component developer and supplies the toner to the toner bearer. A regulator sets the thickness of a toner layer carried on the toner bearer to 6 ?m to 15 ?m and sets a difference between a half width of a first toner charge number distribution as a number distribution of the charge amount of the toner carried on the toner bearer and that of a second toner charge number distribution as a number distribution of the charge amount of the toner in the two-component developer carried on the developer bearer to 0.8 (10?10 C/m) or smaller.

Abstract: A developing unit includes a developing roller which rotates about a rotational axis to supply toner to a photoreceptor, the developing roller including: a cylindrical core portion which includes an electric conductor; a first resistive layer which covers a cylindrical surface of the core portion; a second resistive layer which covers the first resistive layer, and has electric-resistivity lower than that of the first resistive layer; and a current leakage control member which prevents leakage of electric current from the core portion toward the second resistive layer through an end of the developing roller along a direction of the rotational axis.

Abstract: A developing device visualizing an electrostatic latent image previously formed on the surface of an image carrier as toner image, comprising: a developing roller placed at a position facing the image carrier, carrying a toner on the surface thereof, conveying the toner and flying the conveyed toner onto the surface of the image carrier; and a resin layer coated on the surface of the developing roller, wherein the absolute value of the difference in charge between the toners in the upper and lower layers of the toner layer formed on the developing roller as the toner carried on the developing roller is 6 ?C/g or less.

Abstract: An image forming apparatus uses a two-component developer containing a toner and a carrier. The apparatus has a latent image bearer for bearing an electrostatic latent image. A toner bearer bears the toner to be conveyed to a development region to develop the electrostatic latent image. A developer bearer bears the two-component developer and supplies the toner to the toner bearer. A regulator sets the thickness of a toner layer carried on the toner bearer to 6 ?m to 15 ?m and sets a difference between a half width of a first toner charge number distribution as a number distribution of the charge amount of the toner carried on the toner bearer and that of a second toner charge number distribution as a number distribution of the charge amount of the toner in the two-component developer carried on the developer bearer to 0.8 (10?10 C/m) or smaller.

Abstract: The present invention provides an image-forming apparatus comprising a magnetic roll for magnetically holding a two-component developer in which toner and a magnetic carrier are electrostatically bonded, a developing roll in which a thin layer of the toner transferred from the two-component developer on the magnetic roll is formed on the surface, and a latent image support in which a latent image is developed with using the toner on the developing roll by a developing bias applied in relation to the developing roll, wherein the developing roll has a coating layer composed of silicone-modified polyurethane on a surface.

Abstract: A developing device uses a two-component developer including at least carriers and toners. The toners are supplied to an image bearing member bearing an electrostatic latent image so that a toner image is developed from the electrostatic latent image. The developing device has a developing roller arranged to oppose the image bearing member; and a magnetic roller arranged to oppose the developing roller. The magnetic roller retains the two-component developer to supply toners to the developing roller. The developing roller and the magnetic roller are rotationally driven in directions to be opposite from one another at an opposed position, and a magnetic pole of the magnetic roller and a magnetic pole of the developing roller have magnetic polarities different from one another at the opposed position. A surface roughness of the magnetic roller is greater than a surface roughness of the developing roller.

Abstract: An image forming apparatus is characterized in that an absolute value of a difference between a first coefficient of variation in a number distribution of the particle diameter of a toner carried on a developing roller and a second coefficient of variation in a number distribution of the particle diameter of a toner in a two-component developer carried on the magnetic roller is within 5% and an absolute value of a difference between a third coefficient of variation in a number distribution of the particle diameter of a toner of a toner image developed on the outer surface of an image bearing member and the second coefficient of variation is within 6%. With such an image forming apparatus, high-quality images can be stably formed over a long term.

Abstract: An image forming apparatus has a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image on the photoconductive member by a first bias. A magnetic roller forms a magnetic brush thereon with a two-component developer and forms a thin toner layer on the developing roller by a second bias. The developing roller is aluminum with a surface treated for high resistance. The thickness (T) of the toner layer and the duty ratio (D1) of the first alternating-current bias satisfy relationships of the following equations for calculating the duty ratio (D1) using an application period of a voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: 7 ?m?T?13 ?m, and 35%?D1?70%.

Abstract: An image forming apparatus has a photoconductive member, and a developing roller develops a latent image on the photoconductive member by a first alternating-current bias in the form of a rectangular wave. The following relationships are satisfied in calculating the duty ratio (D1) of the first alternating-current bias using an application period of voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: a CV value in the number particle size distribution of the toner is ?25%, 4 ?m?Dt?7 ?m, 105 ?·cm?pv?109 Q?cm, 0.4 ?m?Ra?1.5 ?m, and 35%?D1?75%. where Dt denotes the volume average particle diameter of the toner, pv denotes the intrinsic resistance value of a developing roller surface, Ra denotes the arithmetic average roughness of the developing roller surface.