Developing apparatus and color electrophotographic apparatus using the same

Claim 2

In a developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a deformable thin metal sleeve and an elastic roll fitted into said deformable thin metal sleeve, said developing roller being arranged for contact with said photoconductor; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller.

Claim 3

A developing apparatus according to claim 1, wherein a ratio between the circumferential speed of said magnetic conveying roller and the circumferential speed of said developing roller is set within a range of 1.5-5.0.

Claim 4

A developing apparatus according to claim 1, wherein said developer includes a ferrite carrier having a mean particle diameter of 20-80 μm and toner having a mean particle diameter of 5-8 μm.

Claim 5

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller; a toner reservoir for temporarily collecting toner which is supplied from a toner hopper; and a guiding plate member positioned above said magnetic conveying roller to form an opening which guides toner toward a side of said magnetic conveying roller from a lower portion of said toner reservoir.

Claim 6

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller; a toner reservoir for temporarily collecting toner which is supplied from a toner hopper; and a guiding plate member positioned above said magnetic conveying roller to form an opening which guides toner toward a side of said magnetic conveying roller from a lower portion of said toner reservoir.

Claim 7

A developing apparatus according to claim 4, wherein fresh toner is supplied to said opening formed by said guiding plate member at the side of said magnetic conveying roller, and additionally comprising: a further magnetic conveying roller for mixing toner which is regulated by said regulating plate member so as to flow back toward said opening.

Claim 8

A developing apparatus according to claim 5, wherein said further magnetic conveying roller comprises an agitating member.

Claim 9

A developing apparatus according to claim 5 or claim 6, wherein another agitating member is provided adjacent said further magnetic conveying roller.

Claim 10

A developing apparatus according to claim 7, wherein said another agitating member provided adjacent said further magnetic conveying roller comprises a pair of screw-augers, which cause toner to move along an axial direction of said further magnetic conveying roller.

Claim 11

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said magnetic conveying roller is set to have 8-64 magnetic poles and to have a magnetic force at a magnetic pole portion within a range of 250-1000 gausses.

Claim 12

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said magnetic conveying roller is set to have 8-64 magnetic poles and to have a magnetic force at a magnetic pole portion within a range of 250-1000 gausses.

Claim 13

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein an absolute value of the difference between the width of a first gap which is formed between said developing roller and said magnetic conveying roller and the width of a second gap which is formed between said regulating plate member and said magnetic conveying roller is set within a range of 0-0.4 mm.

Claim 14

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein an absolute value of the difference between the width of a first gap which is formed between said developing roller and said magnetic conveying roller and the width of a second gap which is formed between said regulating plate member and said magnetic conveying roller is set within a range of 0-0.4 mm.

Claim 15

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein a bias voltage is applied to said developing roller which comprises an alternating current voltage superposed on a direct current voltage.

Claim 16

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller is arranged to contact an electrostatic latent image formed on a surface of a photoconductor, said electrostatic latent image being formed on said photoconductor to attract toner, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein a bias voltage is applied to said developing roller which comprises an alternating current voltage superposed on a direct current voltage.

Claim 17

A color electrophotographic system apparatus wherein each of plural developing apparatuses charged by a developer corresponding to a respective color is arranged at a periphery of a respective one of plural photoconductors, each of said plural photoconductors forming a respective electrostatic latent image corresponding to a respective color, respective color toner images developed by said plural developing apparatuses are formed on said respective photoconductors, and a toner image having plural colors is formed on a surface of said respective photoconductors, wherein said plural developing apparatuses each comprise a developing apparatus as defined in one of claims 1-5, 8, 9, and 11, and wherein at least one of the electric field and a circumferential speed ratio between said developing roller and said magnetic conveying roller is controlled in accordance with the respective color toner images.

Claim 18

In a developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a deformable thin metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said deformable thin metal sleeve, said developing roller being arranged for contact with said photoconductor; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller.

Claim 19

In a developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a deformable thin metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said deformable thin metal sleeve, said developing roller being arranged for contact with said photoconductor; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller.

Claim 20

A developing apparatus according to claim 13, further comprising: a current detection unit for detecting a secondary side current of a bias current applied to said magnetic conveying roller; a toner compensation controlling unit; and a drive transmitting mechanism for carrying out on-off operation of rotation of an agitating member for compensation of the toner; whereby in accordance with the detected current, toner compensation is controlled intermittently.

Claim 21

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller; a toner reservoir for temporarily collecting toner which is supplied from a toner hopper; a developer chamber provided on a side of said magnetic conveying roller opposite said developing roller for circulating said developer; and a guiding plate member for guiding the toner to said developer chamber from a lower portion of said toner reservoir, whereby the toner is supplied from said toner reservoir according to the volume change of said developer in said developer chamber.

Claim 22

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller; a toner reservoir for temporarily collecting toner which is supplied from a toner hopper; a developer chamber provided on a side of said magnetic conveying roller opposite said developing roller for circulating said developer; and a guiding plate member for guiding the toner to said developer chamber from a lower portion of said toner reservoir, whereby the toner is supplied from said toner reservoir according to the volume change of said developer in said developer chamber.

Claim 23

A developing apparatus according to claim 15, wherein said guiding plate member is provided above said magnetic conveying roller.

Claim 24

A developing apparatus according to one of claims 13 and 15, wherein said developer includes conductive resin coated carrier having a mean particle diameter of 30-80 μm and toner with a conductive additive agent having a mean particle diameter of 5-8 μm.

Claim 25

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said magnetic conveying roller is formed with plural magnet bodies arranged as magnetic pole pairs having the same polarity.

Claim 26

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said magnetic conveying roller is formed with plural magnet bodies arranged as magnetic pole pairs having the same polarity.

Claim 27

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said magnetic conveying roller is set to have 8-64 magnetic poles, and wherein a ratio between the circumferential speed of said magnetic conveying roller and the circumferential speed of said developing roller is set within a range of 1.5-5.0.

Claim 28

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said magnetic conveying roller is set to have 8-64 magnetic poles, and wherein a ratio between the circumferential speed of said magnetic conveying roller and the circumferential speed of said developing roller is set within a range of 1.5-5.0.

Claim 29

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein an absolute value of the difference between the width of a first gap which is formed between said developing roller and said magnetic conveying roller and the width of a second gap which is formed between said regulating plate member and said magnetic conveying roller is set within a range of 0-0.4 mm.

Claim 30

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein an absolute value of the difference between the width of a first gap which is formed between said developing roller and said magnetic conveying roller and the width of a second gap which is formed between said regulating plate member and said magnetic conveying roller is set within a range of 0-0.4 mm.

Claim 31

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein a bias voltage is applied to said developing roller which comprises alternating current voltage superposed on a direct current voltage.

Claim 32

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein a bias voltage is applied to said developing roller which comprises alternating current voltage superposed on a direct current voltage.

Claim 33

A color electrophotographic apparatus wherein each of plural developing apparatuses charged by a developer corresponding to a respective color is arranged at a periphery of a respective one of plural photoconductors, each of said plural photoconductors forming a respective electrostatic latent image corresponding to a respective color, respective color toner images developed by said plural developing apparatuses are formed on said respective photoconductors, and a toner image having plural colors is formed on a surface of said respective photoconductors, wherein each of said plural developing apparatuses comprises a developing apparatus as defined in one of claims 13, 15, 18, 19, 20 and 21, and wherein at least one of the electric field and a circumferential speed ratio between said developing roller and said magnetic conveying roller is controlled in accordance with the respective color toner image.

Claim 34

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; and a distributing member provided at an intermediate position between said first magnetic conveying roller and said second magnetic conveying roller; wherein said distributing member distributes a developer, including a carrier and toner held on said first magnetic conveying roller to said second magnetic conveying roller; the developer held on said first magnetic conveying roller and the developer held on said second magnetic conveying roller are conveyed into contact with said developing roller; and electric fields having different directions from each other are applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 35

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; and a distributing member provided at an intermediate position between said first magnetic conveying roller and said second magnetic conveying roller; wherein said distributing member distributes a developer, including a carrier and toner held on said first magnetic conveying roller to said second magnetic conveying roller; the developer held on said first magnetic conveying roller and the developer held on said second magnetic conveying roller are conveyed into contact with said developing roller; and electric fields having different directions from each other are applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 36

A developing apparatus according to claim 23, wherein, the developer held on said first magnetic conveying roller is caused to contact said developing roller while rotating in a direction opposite the rotating direction of said developing roller, and the developer held on said second magnetic conveying roller is caused to contact said developing roller while moving in the same rotating direction as the rotating direction of said developing roller.

Claim 37

A developing apparatus according to claim 23, wherein at the intermediate positions between said first magnetic conveying roller and said second magnetic conveying roller, the magnetic force of said second magnetic conveying roller is set to be larger than the magnetic force of said first magnetic conveying roller.

Claim 38

A developing apparatus according to claim 23, wherein the width of a first roller gap formed between said developing roller and said first magnetic conveying roller is set to be smaller than the width of a second roller gap formed between said developing roller and said second magnetic conveying roller.

Claim 39

A developing apparatus according to claim 23, wherein a ratio between the circumferential speed of said second magnetic conveying roller and the circumferential speed of said developing roller is set within a range of 1.5-3.0.

Claim 40

A developing apparatus according to claim 23, wherein said developer includes a ferrite carrier having a mean particle diameter of 20-60 μm and toner having a mean particle diameter of 5-8 μm.

Claim 41

A developing apparatus according to claim 23, wherein a bias voltage is applied to said developing roller which comprises an alternating current voltage superposed on a direct current voltage.

Claim 42

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; and a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; and a distributing member provided at an intermediate position between said first magnetic conveying roller and said second magnetic conveying roller; wherein said distributing member distributes a developer, including a carrier and toner, held on said first magnetic conveying roller to said second magnetic conveying roller; the developer held on said first magnetic conveying roller is conveyed into contact with said developing roller in the same rotating direction as the rotating direction of said developing roller; the developer held on said second magnetic conveying roller is conveyed into contact with said developing roller in a rotating direction opposite the rotating direction of said developing roller; and electric fields having the same directions are applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 43

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; and a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; and a distributing member provided at an intermediate position between said first magnetic conveying roller and said second magnetic conveying roller; wherein said distributing member distributes a developer, including a carrier and toner, held on said first magnetic conveying roller to said second magnetic conveying roller; the developer held on said first magnetic conveying roller is conveyed into contact with said developing roller in the same rotating direction as the rotating direction of said developing roller; the developer held on said second magnetic conveying roller is conveyed into contact with said developing roller in a rotating direction opposite the rotating direction of said developing roller; and electric fields having the same directions are applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 44

A color electrophotographic system apparatus wherein each of plural developing apparatuses charged by a developer corresponding to a respective color is arranged at a periphery of a respective one of plural photoconductors, each of said plural photoconductors forming a respective electrostatic latent image corresponding to a respective color, respective color toner images developed by each of said plural developing apparatuses are formed on respective photoconductors, wherein said plural developing apparatuses each comprise a developing apparatus as defined in one of claims 23-30, at least one of the electric field and a circumferential speed ratio between said developing roller and said second magnetic conveying roller is controlled in accordance with a respective color toner image.

Claim 45

A developing apparatus in which developing is carried out by causing a photoconductor to contact a developing roller having a toner layer formed on a surface thereof, comprising: a developing roller constituted by an elastic roll, a first magnetic conveying roller having a first magnet body and rotatively arranged close to said developing roller, and a second magnetic conveying roller having a second magnet body and rotatively arranged close to said developing roller, wherein a developer, which has been absorbed and sucked by said first magnetic conveying roller onto a surface thereof, is distributed to said second magnetic conveying roller, and a toner layer is formed on the surface of said developing roller by applying a bias voltage into said first magnetic conveying roller and said second magnetic conveying roller.

Claim 46

A developing apparatus in which developing is carried out by causing a photoconductor to contact a developing roller having a toner layer formed on a surface thereof, comprising: a developing roller constituted by an elastic roll, a first magnetic conveying roller having a first magnet body and rotatively arranged close to said developing roller, and a second magnetic conveying roller having a second magnet body and rotatively arranged close to said developing roller, wherein a developer, which has been absorbed and sucked by said first magnetic conveying roller onto a surface thereof, is distributed to said second magnetic conveying roller, and a toner layer is formed on the surface of said developing roller by applying a bias voltage into said first magnetic conveying roller and said second magnetic conveying roller.

Claim 47

A developing apparatus in which the developing is carried out by causing a photoconductor to contact a developing roller having a toner layer formed on a surface thereof, comprising: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve, a first magnetic conveying roller having a first magnet body and rotatively arranged close to said developing roller, a second magnetic conveying roller having a second magnet body and rotatively arranged close to said developing roller, and a regulating plate member for regulating the thickness of a developer which has been absorbed magnetically by said first magnetic conveying roller on a surface thereof, wherein a relationship, among a gap (Go) formed between said first magnetic conveying roller and said regulating plate member, a first roller gap (G1) formed between said first magnetic conveying roller and said developing roller, and a second roller gap (G2) formed between said second magnetic conveying roller and said developing roller, is satisfied by a first following formula (1) and by a second following formula (2): G1<Go (1) G2≦Go-G1 (2) developer absorbed by said first magnetic conveying roller is distributed to said second magnetic conveying roller, and a toner layer is formed on said developing roller by applying a bias voltage to said first magnetic conveying roller and said second magnetic conveying roller.

Claim 48

A developing apparatus in which the developing is carried out by causing a photoconductor to contact a developing roller having a toner layer formed on a surface thereof, comprising: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve, a first magnetic conveying roller having a first magnet body and rotatively arranged close to said developing roller, a second magnetic conveying roller having a second magnet body and rotatively arranged close to said developing roller, and a regulating plate member for regulating the thickness of a developer which has been absorbed magnetically by said first magnetic conveying roller on a surface thereof, wherein a relationship, among a gap (Go) formed between said first magnetic conveying roller and said regulating plate member, a first roller gap (G1) formed between said first magnetic conveying roller and said developing roller, and a second roller gap (G2) formed between said second magnetic conveying roller and said developing roller, is satisfied by a first following formula (1) and by a second following formula (2): G1<Go (1) G2≦Go-G1 (2) developer absorbed by said first magnetic conveying roller is distributed to said second magnetic conveying roller, and a toner layer is formed on said developing roller by applying a bias voltage to said first magnetic conveying roller and said second magnetic conveying roller.

Claim 49

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said metal sleeve is constituted by a nonmagnetic body layer or a feeble magnetic body layer on a surface of a Ni electrocast sleeve.

Claim 50

A developing apparatus in which a toner layer is formed on a surface of a developing roller, said toner layer formed on said developing roller being positioned to contact electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve formed by one of a non-magnetic body and a feeble magnetic body and an elastic roll fitted into said metal sleeve; a magnetic conveying roller rotatively arranged at a position close to said developing roller and having a multi-magnetic-pole type magnet body; and a regulating plate member for regulating the thickness of a layer of a developer, including a carrier and a toner, on the magnetic conveying roller; wherein a developer layer regulated by said regulating plate member contacts said developing roller during rotation of said developer layer; and an electric field is applied between said magnetic conveying roller and said developing roller, so that said toner layer is formed on said surface of said developing roller, wherein said metal sleeve is constituted by a nonmagnetic body layer or a feeble magnetic body layer on a surface of a Ni electrocast sleeve.

Claim 51

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; a developer, including a carrier and toner, being held on said first magnetic conveying roller and said second magnetic conveying roller, the developer held on said first magnetic conveying roller and the developer held on said second magnetic conveying roller being conveyed into contact with said developing roller; and electric fields having different directions from each other being applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 52

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; a developer, including a carrier and toner, being held on said first magnetic conveying roller and said second magnetic conveying roller, the developer held on said first magnetic conveying roller and the developer held on said second magnetic conveying roller being conveyed into contact with said developing roller; and electric fields having different directions from each other being applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 53

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; and a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; a developer, including a carrier and toner, being held on said first magnetic conveying roller and said second magnetic conveying roller, the developer held on said first magnetic conveying roller being conveyed into contact with said developing roller in the same rotating direction as the rotating direction of said developing roller, and the developer held on said second magnetic conveying roller being conveyed into contact with said developing roller in a rotating direction opposite the rotating direction of said developing roller; and electric fields having the same directions being applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.

Claim 54

In a developing apparatus where a toner layer is formed on a surface of a developing roller, said toner layer on said developing roller being positioned to contact an electrostatic latent image formed on a surface of a photoconductor, the developing apparatus comprises: a developing roller constituted by a metal sleeve and an elastic roll fitted into said metal sleeve; a first magnetic conveying roller rotatively arranged close to said developing roller and having a first magnet body; and a second magnetic conveying roller rotatively arranged close to said developing roller and having a second magnet body; a developer, including a carrier and toner, being held on said first magnetic conveying roller and said second magnetic conveying roller, the developer held on said first magnetic conveying roller being conveyed into contact with said developing roller in the same rotating direction as the rotating direction of said developing roller, and the developer held on said second magnetic conveying roller being conveyed into contact with said developing roller in a rotating direction opposite the rotating direction of said developing roller; and electric fields having the same directions being applied between said first magnetic conveying roller and said second magnetic conveying roller and said developing roller, whereby only a layer of toner is formed on said surface of said developing roller.