Developing device and image forming apparatus using the same

In a developing device for causing, in a developing zone where a developer carrier whose surface is movable while carrying a developer made up of toner grains and magnetic grains thereon and an image carrier whose surface is movable while carrying a latent image thereon face each other, said developer to rise in a form of a magnet brush with a magnetic pole for development, and moving said developer carrier in a same direction as, but at a higher linear velocity than, said image carrier to thereby cause said magnet brush to rub said surface of said image carrier for thereby developing said latent image,

• a linear velocity of said developer carrier in the developing zone is 150 mm/sec or above, but below 500 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• when half-value points on a surface of said developer carrier where a flux density is one-half of a peak value of a flux density generated by the magnetic pole for development on said surface in a direction normal to said surface are seen from a curvature axis of said surface, an angular width between said half-value points in a direction of movement of said surface is 25° or less,
• the flux density in the direction normal to the surface of said developer carrier is between 100 mT and 200 mT on said surface, and
• the magnetic grains have a saturation magnetization value of 40×10−74ππ Wb·m/kg or above, but below 60×10−7×4 Wb·m/kg.

An image forming apparatus comprising:

• an image carrier;
• latent image forming means for forming a latent image on said image carrier;
• developing means for developing the latent image with a developer made up of toner grains and magnetic grains to thereby form a toner image;
• and
• image transferring means for transferring the toner image from said image carrier to a recording medium;
• said image carrier having a surface movable, in a developing zone where said surface and a surf ace of a developer carrier included in said developing means face each other, at a linear velocity of 100 mm/sec or above, but 300 mm/sec or below;
• wherein in said developing means a linear velocity of said developer carrier in the developing zone is 150 mm/sec or above, but below 500 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• a magnetic flux generated on the surface of said developer carrier in the developing zone by a magnetic pole for development has a flux density having an attenuation ratio of 40% in a direction normal to said surface of said developer carrier,
• the flux density in the direction normal to the surface of said developer carrier, as measured on said surface, is between 100 mT and 200 mT, and
• the magnetic grains have a saturation magnetization value of 40×10−7×4π Wb·m/kg or above, but below 50×10−7×4π Wb·m/kg.

An image forming apparatus comprising:

• an image carrier:
• latent image forming means for forming a latent image on said image carrier;
• developing means for developing the latent image with a developer made up of toner grains and magnetic grains to thereby form a toner image;
• and
• image transferring means for transferring the toner image from said image carrier to a recording medium;
• said image carrier having a surface movable, in a developing zone where said surface and a surface of a developer carrier included in said developing means face each other, at a linear velocity of 100 mm/sec or above, but 300 mm/sec or below;
• wherein in said developing means a linear velocity of said developer carrier in the developing zone is 150 mm/sec or above, but below 500 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• a linear velocity of said developer carrier in the developing zone is 150 mm/sec or above, but below 500 mm/sec, an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/m2,
• when half-value points on the surface of said developer carrier where a flux density is one-half of a peak value of a flux density generated by the magnetic pole for development on said surface in a direction normal to said surface are seen from a curvature axis of said surface, an angular width between said half-value points in a direction of movement of said surface is 25° or less,
• the flux density in the direction normal to the surface of said developer carrier is between 100 mT and 200 mT on said surface, and
• the magnetic grains have a saturation magnetization value of 40×10−7×4π Wb·m/kg or above, but below 60×10−7×4 Wb·m/kg.
• the flux density in the direction normal to the surface of said developer carrier is between 100 mT and 200 mT on said surface, and
• the magnetic grains have a saturation magnetization value of 40×10−74π Wb·m/kg or above, but below 60×10−7×4 Wb·m/kg.

In a developing device for causing, in a developing zone where a developer carrier whose surface is movable while carrying a developer made up of toner grains and magnetic grains thereon and an image carrier whose surface is movable while carrying a latent image thereon face each other, said developer to rise in a form of a magnet brush with a magnetic pole for development, and moving said developer carrier in a same direction as, but at a higher linear velocity than, said image carrier to thereby cause said magnet brush to rub said surface of said image carrier for thereby developing said latent image,

• a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• a magnetic flux generated on the surface of said developer carrier in the developing zone by the magnetic pole for development has a flux density having an attenuation ratio of 40% in a direction normal to said surface of said developer carrier,
• the flux density in the direction normal to the surface of said developer carrier, as measured on said surface, is between 100 mT and 200 mT, and
• the magnetic grains have a saturation magnetization value of 60×10−7×4π Wb·m/kg or above, but below 90×10−7×4π Wb·m/kg.

In a developing device for causing, in a developing zone where a developer carrier whose surface is movable while carrying a developer made up of toner grains and magnetic grains thereon and an image carrier whose surface is movable while carrying a latent image thereon face each other, said developer to rise in a form of a magnet brush with a magnetic pole for development, and moving said developer carrier in a same direction as, but at a higher linear velocity than, said image carrier to thereby cause said magnet brush to rub said surface of said image carrier for thereby developing said latent image,

• a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• when half-value points on a surface of said developer carrier where a flux density is one-half of a peak value of a flux density generated by the magnetic pole for development on said surface in a direction normal to said surface are seen from a curvature axis of said surface, an angular width between said half-value points in a direction of movement of said surface is 25° or less,
• the flux density in the direction normal to the surface of said developer carrier, as measured on said surface, is between 100 mT and 200 mT, and the magnetic grains have a saturation magnetization value of 60×10−7×4π Wb·m/kg or above, but below 90×10−7×4π Wb·m/kg.

An image forming apparatus comprising:

• an image carrier;
• latent image forming means for forming a latent image on said image carrier;
• developing means for developing the latent image with a developer made up of toner grains and magnetic grains to thereby form a toner image;
• and
• image transferring means for transferring the toner image from said image carrier to a recording medium;
• said image carrier having a surface movable, in a developing zone where said surface and a surface of a developer carrier included in said developing means face each others at a linear velocity of 300 mm/sec or above, but 600 mm/sec or below;
• wherein in said developing means a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/m2,
• a magnetic flux generated on the surface of said developer carrier in the developing zone by a magnetic pole for development has a flux density having an attenuation ratio of 40% in a direction normal to said surface of said developer carrier,
• the flux density in the direction normal to the surface of said developer carrier, as measured on said surface, is between 100 mT and 200 mT, and
• the magnetic grains have a saturation magnetization value of 60×10−74π Wb·m/kg or above, but below 90×10−7×4π Wb·m/kg.

An image forming apparatus comprising:

• an image carrier;
• latent image forming means for forming a latent image on said image carrier;
• developing means for developing the latent image with a developer made up of toner grains and magnetic grains to thereby form a toner image;
• and
• image transferring means for transferring the toner image from said image carrier to a recording medium;
• said image carrier having a surface movable, in a developing zone where said surface and a surface of a developer carrier included in said developing means face each other, at a linear velocity of 300 mm/sec or above, but 600 mm/sec or below;
• wherein in said developing means a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• when half-value points on the surface of said developer carrier where a flux density is one-half of a peak value of a flux density generated by the magnetic pole for development on said surface in a direction normal to said surface are seen from a curvature axis of said surface, an angular width between said half-value points in a direction of movement of said surface is 25° or less,
• the flux density in the direction normal to the surface of said developer carrier, as measured on said surface, is between 100 mT and 200 mT, and
• the magnetic grains have a saturation magnetization value of 60×10−7×4π Wb·m/kg or above, but below 90×10−7×4π Wb·m/kg.

In a developing device comprising a developer carrier whose surface is movable while carrying a developer made up of toner grains and magnetic grains thereon, exposing part of said surface via a casing, causing, in a developing zone where said surface of said developer carrier and a surface of an image carrier movable while carrying a latent image thereon face each other, said developer to rise in a form of a magnet brush with a magnetic pole for development, and moving said developer carrier in a same direction as, but at a higher linear velocity than, said image carrier to thereby cause said magnet brush to rub said surface of said image carrier for thereby developing said latent image,

• a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• an auxiliary magnetic pole is positioned downstream of, but adjacent, said magnetic pole for development in a direction of movement of the surface of said developer carrier such that a magnetic flux generated on the surface of said developer carrier in the developing zone by the magnetic pole for development has a flux density having an attenuation ratio of 40% in a direction normal to said surface of said developer carrier, and
• the casing is configured to cover the developer caused to rise by said auxiliary electrode.

In a developing device comprising a developer carrier whose surface is movable while carrying a developer made up of toner grains and magnetic grains thereon, exposing part of said surface via a casing, causing, in a developing zone where said surface of said developer carrier and a surface of an image carrier movable while carrying a latent image thereon face each other, said developer to rise in a form of a magnet brush with a magnetic pole for development, and moving said developer carrier in a same direction as, but at a higher linear velocity than, said image carrier to thereby cause said magnet brush to rub said surface of said image carrier for thereby developing said latent image,

• a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• auxiliary magnetic poles are positioned at both sides of said magnetic pole for development in a direction of movement of the surface of said developer carrier such that a magnetic flux generated on the surface of said developer carrier in the developing zone by the magnetic pole for development has a flux density having an attenuation ratio of 40% in a direction normal to said surface of said developer carrier,
• at least one of said auxiliary magnetic poles is positioned such that a normal line on the surface of said developer carrier where a flux density generated by said at least one auxiliary magnetic pole has a peak value on said surface is directed downward in a vertical direction, and
• the casing is configured to cover the developer caused to rise by said at least one auxiliary electrode.

An image forming-apparatus comprising:

• an image carrier;
• latent image forming means for forming a latent image on said image carrier;
• developing means for developing the latent image with a developer made up of toner grains and magnetic grains to thereby form a toner image;
• and
• image transferring means for transferring the toner image from said image carrier to a recording medium;
• wherein in said developing means a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• an auxiliary magnetic pole is positioned downstream of, but adjacent, a magnetic pole for development in a direction of movement of the surface of said developer carrier such that a magnetic flux generated on said surface of said developer carrier in the developing zone by said magnetic pole for development has a flux density having an attenuation ratio of 40 % in a direction normal to said surface of said developer carrier, and
• a casing included in said developing means is configured to cover the developer caused to rise by said auxiliary electrode.

An image forming apparatus comprising:

• an image carrier;
• latent image forming means for forming a latent image on said image carrier;
• developing means for developing the latent image with a developer made up of toner grains and magnetic grains to thereby form a toner image;
• and
• image transferring means for transferring the toner image from said image carrier to a recording medium;
• wherein in said developing means a linear velocity of said developer carrier in the developing zone is 500 mm/sec or above, but below 1,200 mm/sec,
• an amount of the developer deposited on said developer carrier and conveyed to the developing zone is between 65 mg/cm2 and 95 mg/cm2,
• auxiliary magnetic poles are positioned at both sides of a magnetic pole for development in a direction of movement of the surface of said developer carrier such that a magnetic flux generated on said surface of said developer carrier in the developing zone by said magnetic pole for development has a flux density having an attenuation ratio of 40% in a direction normal to said surface of said developer carrier,
• at least one of said auxiliary magnetic poles is positioned such that a normal line on the surface of said developer carrier where a flux density generated by said at least one auxiliary magnetic pole has a peak value on said surface is directed downward in a vertical direction, and
• the casing is configured to cover the developer caused to rise by said at least one auxiliary electrode.