Image forming apparatus
AssigneeRicoh Company, Ltd.
InventorsHisashi Shoji, Tsukuru Kai, Kei Yasutomi, Nekka Matsuura, Nobutaka Takeuchi, Hirokatsu Suzuki
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Abstract
An electrophotographic image forming apparatus of the present invention frees images from various defects including the thinning of horizontal lines, the omission of the trailing edge of an image, background contamination, granularity particular to a halftone image, carrier scattering, and image noise. Further, the apparatus of the present invention solves problems ascribable to patches used to sense image density. Moreover, the apparatus of the present invention faithfully reproduces tonality and has a high developing ability.
Claims70
In an image forming method using a developer carrier for conveying a developer, which is made up of toner and a carrier, deposited thereon, and magnetic field generating means held stationary within said developer carrier for forming a magnet brush on said developer carrier, said magnet brush contacting an image carrier to thereby develop a latent image formed on said image carrier, an auxiliary magnetic pole exists between a main magnetic pole, which causes said developer to rise and form said magnet brush in a developing region, and a magnetic pole that conveys said developer,
- an amount of charge to deposit on the toner ranges from 10 μC/g to 35 μC/g, and
- a background potential is 100 V or above.
An image forming apparatus comprising:
- an image carrier;
- a developer carrier for conveying a developer, which is made up of toner and a carrier, deposited thereon;
- and
- magnetic field generating means held stationary within said developer carrier for forming a magnet brush on said developer carrier, said magnet brush contacting said image carrier for thereby developing a latent image formed on said image carrier;
- wherein an auxiliary magnetic pole helps a main magnetic pole, which causes the developer to rise and form the magnet brush in a developing region, exert a magnetic force, whereby a half width of said main magnetic pole is reduced,
- an amount of charge to deposit on the toner ranges from 10 μC/g to 35 μC/g, and
- a background potential is 100 V or above.
An image forming apparatus comprising:
- an image carrier;
- a developer carrier for conveying a developer, which is made up of toner and a carrier, deposited thereon;
- and
- magnetic field generating means held stationary within said developer carrier for forming magnet brush on said developer carrier, said magnet brush contacting said image carrier for thereby developing a latent image formed on said image carrier;
- wherein an auxiliary magnetic pole helps a main magnetic pole, which causes the developer to rise and form the magnet brush in a developing region, exert a magnetic force, whereby a half width of said main magnetic pole is reduced,
- assuming that said developer carrier and said image carrier rotate at peripheral speeds of vd and vp, respectively, a ratio vd/vp is 2.5 or below,
- the main pole has a flux density whose peak value is 60 mT or above, and
- the carrier of the developer has a saturation magnetization of 35 emu/g or above.
An image forming apparatus comprising:
- an image carrier;
- a developer carrier for conveying a developer, which is made up of toner and a carrier, deposited thereon;
- magnetic field generating means held stationary within said developer carrier for forming magnet brush on said developer carrier, said magnet brush contacting said image carrier for thereby developing a latent image formed on said image carrier;
- and
- a metering member for regulating a thickness of the developer deposited on said image carrier;
- wherein an auxiliary magnetic pole helps a main magnetic pole, which causes the developer to rise and form the magnet brush in a developing region, exert a magnetic force, whereby a half width of said main magnetic pole is reduced, and
- assuming that a gap between said developer carrier and said metering member and a gap between said image carrier and said developer carrier are Gd and Gp, respectively, a ratio Gd/Gp is between 0.8 and 1.0.
An image forming apparatus comprising:
- an image carrier;
- a developer carrier for conveying a developer, which is made up of toner and a carrier, deposited thereon;
- magnetic field generating means held stationary within said developer carrier for forming magnet brush on said developer carrier, said magnet brush contacting said image carrier for thereby developing a latent image formed on said image carrier;
- and
- a metering member for regulating a thickness of the developer deposited on said image carrier;
- wherein an auxiliary magnetic pole helps a main magnetic pole, which causes the developer to rise and form the magnet brush in a developing region, exert a magnetic force, whereby a half width of said main magnetic pole is reduced, and
- assuming that the developer has a height Hd at a position downstream of said metering member in a direction of rotation of said developer carrier and where said developer is lowest in height, and that a gap between said image carrier and said developer carrier is Gp, a ratio Hd/Gp is between 0.8 and 1.0.
An image forming apparatus comprising:
- an image carrier;
- a developer carrier for conveying a developer, which is made up of toner and a carrier, deposited thereon;
- magnetic field generating means held stationary within said developer carrier for forming magnet brush on said developer carrier, said magnet brush contacting said image carrier for thereby developing a latent image formed on said image carrier;
- and
- sensing means for sensing density of an image formed on said image carrier;
- wherein an auxiliary magnetic pole helps a main magnetic pole, which causes the developer to rise and form the magnet brush in a developing region, exert a magnetic force, whereby a half width of said main magnetic pole is reduced.
In an image forming apparatus comprising a developer carrier on which a developer is deposited in a form of a magnet brush, said magnet brush contacting an image carrier for developing a latent image formed on said image carrier, said developer carrier comprises a nonconductive sleeve and a magnet roller held stationary within said sleeve, said magnet roller including a magnetic pole for scooping up said developer to said developer carrier, a magnetic pole for conveying said developer, and a main magnetic pole for causing the developer to rise in a form of said magnet brush, said main magnetic pole has a flux density in a normal direction whose attenuation ratio is 40% or above, and
- a ratio of a distance between said image carrier and said developer carrier at a boundary of a nip for development to a distance at a position where said image carrier and said developer carrier are closest to each other is 1.5 or below.
In an image forming apparatus comprising a developer carrier on which a developer is deposited in a form of a magnet brush, said magnet brush contacting an image carrier for developing a latent image formed on said image carrier, said developer carrier comprising a nonconductive sleeve and a magnet roller held stationary within said sleeve, said magnet roller including a magnetic pole for scooping up said developer to said developer carrier, a magnetic pole for conveying said developer, and a main magnetic pole for causing said developer to rise in a form of said magnet brush, said main magnetic pole has a half width of 22° or below, and
- a ratio of a distance between said image carrier and said developer carrier at a boundary of a nip for development to a distance at a position where said image carrier and said developer carrier are closest to each other is 1.5 or below.
In an image forming apparatus comprising a developer carrier on which a developer is deposited in a form of a magnet brush, said magnet brush contacting an image carrier for developing a latent image formed on said image carrier, said developer carrier comprises a nonconductive sleeve and a magnet roller held stationary within said sleeve, said magnet roller including a magnetic pole for scooping up said developer to said developer carrier, a magnetic pole for conveying said developer, and a main magnetic pole for causing said developer to rise in a form of said magnet brush,
- an auxiliary magnetic pole helps said main magnetic pole exert a magnetic force, and
- a ratio of a distance between said image carrier and said developer carrier at a boundary of a nip for development to a distance at a position where said image carrier and said developer carrier are closest to each other is 1.5 or below.
In a developing method for scooping up a developer to a developer carrier and causing said developer to form a magnet brush on said developer and contact an image carrier to thereby develop a latent image formed on said image carrier, a distance between said image carrier and said developer carrier is three times or more greater than a mean particles size of a carrier included in said developer, but not greater than ten times, and
- a ratio of a distance between said image carrier and said developer carrier at a boundary of a nip for development to a distance at a position where said image carrier and said developer carrier are closest to each other is 1.5 or below.
In a developing device comprising a developer carrier to which a developer is scooped up, said developer forming a magnet brush on said developer carrier and contacting an image carrier to thereby develop a latent image formed on said image carrier, a distance between said image carrier and said developer carrier is three times or more greater than as a mean particles size of a carrier included in said developer, but not greater than ten times, and
- a ratio of a distance between said image carrier and said developer carrier at a boundary of a nip for development to a distance at a position where said image carrier and said developer carrier are closest to each other is 1.5 or below.
In an image forming apparatus comprising a developing device comprising a developer carrier to which a developer is scooped up, said developer forming a magnet brush on said developer carrier and contacting an image carrier to thereby develop a latent image formed on said image carrier, a distance between said image carrier and said developer carrier is three times or more greater than a mean particles size of a carrier included in said developer, but not greater than ten times, and
- a ratio of a distance between said image carrier and said developer carrier at a boundary of a nip for development to a distance at a position where said image carrier and said developer carrier are closest to each other is 1.5 or below.
An image forming apparatus comprising:
- an image carrier;
- an exposing device for exposing said image carrier imagewise to thereby form a latent image;
- and
- a developing device for developing the latent image;
- wherein said developing device includes a magnet roller held stationary within said developer carrier and having an auxiliary magnetic pole adjoining a main magnetic pole, which adjoins said image carrier, for adjusting a magnetic force and a half width of said main magnetic pole, and
- assuming that a light beam issuing from said exposing device for exposure has a spot diameter Db on said image carrier, and that a pixel pitch Dp determined by recording density is Dp, Db is smaller than 3 Dp.
An image forming apparatus comprising:
- an image carrier;
- an exposing device for exposing said image carrier imagewise to thereby form a latent image;
- and
- a developing device for developing the latent image;
- wherein said developing device includes a magnet roller held stationary within said developer carrier and having an auxiliary magnetic pole adjoining a main magnetic pole, which adjoins said image carrier, for adjusting a magnetic force and a half width of said main magnetic pole, and
- assuming that a light beam issuing from said exposing device for exposure has a spot diameter Db on said image carrier, and that a pixel pitch Dp determined by recording density is Dp, Db is greater than 0.8 Dp.
Dependencies are inferred from the claim text.