Image forming apparatus

Claim 2

An image forming apparatus for forming an image on a recording medium by allowing development particles to fly, comprising: positively charged development particles; a holder for holding said development particles; a counter electrode provided opposite to said holder; a control electrode having a plurality of gates for allowing the flying development particles to pass, said control electrode provided between said holder and said counter electrode; electric field forming means for forming a fixed electric field for allowing said development particles to fly from said holder to said counter electrode by generating a fixed potential difference across said holder and said counter electrode; and control means for controlling a potential to be supplied to said control electrode so as to control passage of said development particles through each gate, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes closer to a potential of said holder than a potential, that is generated on center portions of the gates by the electric field in the case where the potential is not supplied to said control electrode, when said development particles are allowed to pass the gates.

Claim 3

An image forming apparatus for forming an image on a recording medium by allowing development particles to fly, comprising: positively charged development particles; a holder for holding said development particles; a counter electrode provided opposite to said holder; a control electrode having a plurality of gates for allowing the flying development particles to pass, said control electrode provided between said holder and said counter electrode; electric field forming means for forming a fixed electric field for allowing said development particles to fly from said holder to said counter electrode by generating a fixed potential difference across said holder and said counter electrode; and control means for controlling a potential to be supplied to said control electrode so as to control passage of said development particles through each gate, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes closer to a potential of said holder than a potential, that is generated on center portions of the gates by the electric field in the case where the potential is not supplied to said control electrode, when said development particles are allowed to pass the gates.

Claim 4

The image forming apparatus as defined in claim 1, wherein: a surface of said holder can move at a fixed relative speed to said control electrode, said control means changes the potential to be supplied to said control electrode with a fixed period.

Claim 5

The image forming apparatus as defined in claim 4, wherein said control means controls a time for continuously supplying a potential, which allows said development particles to pass, to said control electrode becomes longer than a time required for allowing said development particles, which are held on positions on the surface of said holder corresponding to the gates, to fly.

Claim 6

The image forming apparatus as defined in claim 5, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes a potential which can allow all the development particles held on the positions on the surface of said holder corresponding to the gates to fly.

Claim 7

The image forming apparatus as defined in claim 1, wherein said recording medium is placed on a face of said counter electrode which is opposite to said holder.

Claim 8

The image forming apparatus as defined in claim 7, wherein said control means controls the potential to be supplied to said control electrode so that the following equation (1) is fulfilled: 2qvP(S/π) 1/2 ≧ (πMR 3 tanθ)/3-qS where q(g/cm 2 ) is density of said development particles on the surface of said holder per unit area, S(cm 2 ) is an area of a range, where an electric field which makes said development particles possible to fly is formed, on the surface of said holder at substantial moment, v(cm/sec) is a relative speed of the surface of said holder to said control electrode, M(g/cm 3 ) is specific gravity of said development particles, θ(°) is an angle of repose of said development particles on the recording medium, P(sec) is a time for continuously supplying the potential, which allows said development particles to pass, to said control electrode, and 2R(cm) is a maximum length of a range on the recording medium to which said development particles adhere at the substantial moment the potential starts to be supplied to said control electrode.

Claim 9

The image forming apparatus as defined in claim 8, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes a potential which can allow all the development particles, which are held on positions on the surface of said holder corresponding to the gates, to fly.

Claim 10

The image forming apparatus as defined in claim 1, wherein: the potential to be supplied to said holder by said electric field forming means is an earth potential, the potential to be supplied to said counter electrode by said electric field forming means is a potential having opposite polarity to of the development particles.

Claim 11

The image forming apparatus as defined in claim 1, wherein the the potential to be supplied to said holder by said electric field forming means is a vibrating potential that vibrates within a range such that a relationship between the potential and the potential of the counter electrode does not change.

Claim 12

The image forming apparatus as defined in claim 1, wherein said control means includes: an insulating substrate having a plurality of gates; and an electrode layer to which a potential is supplied, said electrode layer being formed on said substrate.

Claim 13

The image forming apparatus as defined in claim 12, wherein said electrode layer is composed of a plurality of ring-like electrodes provided around each gate.

Claim 14

The image forming apparatus as defined in claim 12, wherein the gates are provided in a grid pattern so as to be arranged along a first direction and a second direction that are different from each other, wherein said electrode layer includes: a first electrode layer composed of a plurality of first zonal electrodes that are provided so as to surround the plural gates arranged along the first direction, said first electrode layer being formed on the holder side of said substrate; and a second electrode layer composed of a plurality of second zonal electrodes that are provided so as to surround the plural gates arranged along the second direction, said second electrode layer being formed on the counter electrode side of said substrate.

Claim 15

The image forming apparatus as defined in claim 12, wherein said control electrode further includes an insulating layer provided so as to surround said electrode layer.

Claim 16

The image forming apparatus as defined in claim 1, wherein said counter electrode is a rotatable roller.

Claim 17

The image forming apparatus as defined in claim 1, further comprising cleaning means for removing toner adhered to the surface of said counter electrode by rubbing the surface of said counter electrode.

Claim 18

The image forming apparatus as defined in claim 16, wherein said holder is a holding roller which rotates in the same direction in which said counter electrode rotates.

Claim 19

The image forming apparatus as defined in claim 1, further comprising: said counter electrode is a belt member that is provided so as to be parallel with said control electrode at least in an area where the gates are formed.

Claim 20

The image forming apparatus as defined in claim 1, further comprising: electric charge supplying means for supplying electric charges with opposite polarity to that of said counter electrode to a recording medium, wherein said electric charge supplying means supplies electric charges for forming the fixed electric field by a difference between the sum of the potential formed by the electric charges supplied to the recording medium and of the potential of said counter electrode and the potential of said holder.

Claim 21

The image forming apparatus as defined in claim 20, wherein said counter electrode is a belt member provided so as to be parallel with said control electrode at least in an area where the gates are formed.

Claim 22

The image forming apparatus as defined in claim 20, wherein: the recording medium is provided on the counter face of the counter electrode to said holder, the potential to be supplied to said counter electrode by said electric field forming means has an opposite polarity to that of the developing particles, said electric charge supplying means includes: a contact member that contact with the recording medium; and potential supplying means for supplying a potential, that has a smaller absolute value than that of the potential to be supplied to said counter electrode, to said contact member.

Claim 23

The image forming apparatus as defined in claim 1, further comprising transfer means for transferring an image formed on said counter electrode onto the recording medium.

Claim 24

The image forming apparatus as defined in claim 23, further comprising cleaning means for removing said development particles adhered to the surface of said counter electrode by rubbing the surface of said counter electrode.

Claim 25

The image forming apparatus as defined in claim 23, wherein: said counter electrode is a rotatable roller, said recording medium is placed between said counter electrode and said transfer means so as to be contact with said counter electrode.

Claim 26

The image forming apparatus as defined in claim 23, wherein said control means includes: a transfer roller that rotates with the transfer roller contacting a rear face of a counter face of the recording medium to said counter electrode; and voltage applying means for applying a voltage to said transfer roller.

Claim 27

An image forming apparatus for forming an image on a recording medium by allowing developing particles to fly, comprising: charged developing particles; a holder for holding said developing particles that can move so that its surface at a relative speed to a control electrode; a counter electrode provided so as to be opposite to said holder; a control electrode having a plurality of gates for allowing the flew developing particles, said control electrode being provided between said holder and said counter electrode; electric field forming means for forming a prescribed electric field that allows said developing particles to fly from said holder towards said counter electrode by generating a prescribed potential difference across said holder and said counter electrode; and control means for controlling passage of said developing particles through each gate by changing a potential to be supplied to said control electrode at a prescribed period, wherein said control means controls a time for continuously supplying a potential, which allows said development particles to pass, to said control electrode becomes longer than a time required for allowing said development particles, which are held on positions on the surface of said holder corresponding to the gates, to fly.

Claim 28

The image forming apparatus as defined in claim 27, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes a potential which can allow all the development particles held on the positions on the surface of said holder corresponding to the gates to fly.

Claim 29

An image forming apparatus for allowing developing particles to fly so as to directly form an image on a recording medium by adhesion of the developing particles, comprising: charged developing particles; a holder for holding said developing particles; a counter electrode provided so as to be opposite to said holder; a control electrode having a plurality of gates for allowing the flew developing particles to pass, said control electrode being provided between said holder and said counter electrode; electric field forming means for forming a prescribed electric field for allowing said developing particles to fly from said holder towards said counter electrode by generating a prescribed potential difference across said holder and said counter electrode; and control means for controlling passage of said developing particles through each gate by changing the potential to be applied to said control electrode, wherein said control means controls the potential to be supplied to said control electrode so that the following equation (1) is fulfilled: 2qvP(S/π) 1/2 ≧ (πMR 3 tanθ)/3-qS where q(g/cm 2 ) is density of said development particles on the surface of said holder per unit area, S(cm 2 ) is an area of a range, where an electric field which makes said development particles possible to fly is formed, on the surface of said holder at substantial moment, v(cm/sec) is a relative speed of the surface of said holder to said control electrode, M(g/cm 3 ) is specific gravity of said development particles, θ(°) is an angle of repose of said development particles on the recording medium, P(sec) is a time for continuously supplying the potential, which allows said development particles to pass, to said control electrode, and 2R(cm) is a maximum length of a range on the recording medium to which said development particles adhere at the substantial moment the potential starts to be supplied to said control electrode.

Claim 30

The image forming apparatus as defined in claim 29, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes a potential which can allow all the development particles held on the positions on the surface of said holder corresponding to the gates to fly.

Claim 31

An image forming apparatus for forming an image on a recording medium by allowing developing particles to fly, comprising: charged developing particles; a holder for holding said developing particles; a counter electrode provided so as to be opposite to said holder; a control electrode having a plurality of gates for allowing the flew developing particles to pass, said control electrode being provided between said holder and said counter electrode; electric field forming means for forming a prescribed electric field for allowing said developing particles to fly from said holder towards said counter electrode by generating a prescribed potential difference across said holder and said counter electrode; control means for controlling passage of said developing particles through each gate by changing the potential to be applied to said control electrode so as to allow said developing particles to adhere to said counter electrode; and transfer means for transferring an image formed on said counter electrode onto the recording medium, wherein said control means controls the potential to be supplied to said control electrode so that the following equation (1) is fulfilled: 2qvP(S/π) 1/2 ≧ (πMR 3 tanθ)/3-qS where q(g/cm 2 ) is density of said development particles on the surface of said holder per unit area, S(cm 2 ) is an area of a range, where an electric field which makes said development particles possible to fly is formed, on the surface of said holder at substantial moment, v(cm/sec) is a relative speed of the surface of said holder to said control electrode, M(g/cm 3 ) is specific gravity of said development particles, θ(°) is an angle of repose of said development particles on the recording medium, P(sec) is a time for continuously supplying the potential, which allows said development particles to pass, to said control electrode, and 2R(cm) is a maximum length of a range on the recording medium to which said development particles adhere at the substantial moment the potential starts to be supplied to said control electrode.

Claim 32

The image forming apparatus as defined in claim 31, wherein said control means controls the potential to be supplied to said control electrode so that the potential becomes a potential which can allow all the development particles held on the positions on the surface of said holder corresponding to the gates to fly.

Claim 33

An image forming apparatus for forming an image on a recording medium by allowing developing particles to fly, comprising: charged developing particles; a holder for holding said developing particles; a counter electrode provided so as to be opposite to said holder; a control electrode having a plurality of gates for allowing the flew developing particles to pass, said control electrode being provided between said holder and said counter electrode; electric field forming means for forming a prescribed electric field for allowing said developing particles to fly from said holder towards said counter electrode by generating a prescribed potential difference across said holder and said counter electrode; and control means for controlling passage of said developing particles through each gate by changing the potential to be applied to said control electrode, wherein said control electrode includes: an insulating substrate having a plurality of gates; a first electrode layer to which a first potential is supplied, said first electrode layer being formed on the holder side of said substrate; and a second electrode layer to which a second potential is supplied, said second electrode layer being formed on the counter electrode side of said substrate, wherein said control means controls the second potential so that the second potential becomes closer to a potential of said holder than a potential on center portions of the gates, that is caused by the electric field in the case where the potential is not supplied to said second electrode layer, when said development particles are allowed to pass the gates.

Claim 34

The image forming apparatus as defined in claim 33, wherein: said gates are provided in a grid pattern so as to be arranged along a first direction and a second direction that are different from each other, said first electrode layer is composed of a plurality of first zonal electrodes that are provided so as to surround the gates arranged along the first direction, said second electrode layer is composed of a plurality of second zonal electrodes that provided so as to surround the gates arranged along the second direction.