# US 10,310,402 B2 · Image forming apparatus and cartridge having charging roller

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- Number: US 10,310,402 B2
- Document ID: US10310402B2
- Status: Granted
- Kind: B2
- Application number: 16/006,945
- Filed: 2018-06-13
- Published: 2018-12-20
- Granted: 2019-06-04
- Earliest claimed: 2017-06-15
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Jiro Kinokuni; Kota Mori; Yuya Nagatomo; Michihiro Yoshida; Takeshi Fujino
- Web page: https://patentgrep.com/patent/US10310402B2

## CPC

- G03G 15/0216: {by bringing a charging member into contact with the member to be charged, e.g. roller, brush chargers}
- G03G 15/0233: {Structure, details of the charging member, e.g. chemical composition, surface properties}
- G03G 5/00: Recording-members for original recording by exposure, e.g. to light, to heat or to electrons; Manufacture thereof; Selection of materials therefor
- G03G 15/0266: {Arrangements for controlling the amount of charge}
- G03G 15/751: {relating to drum (G03G15/757 takes precedence)}
- G03G 2215/021: by contact, friction or induction
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

An image forming apparatus includes a photosensitive member having a surface having elastic deformation power of 47% or more, a charging roller forming a nip between itself and the photosensitive member, and an image forming portion. When a nip region corresponding to the nip is formed and then an area of independent contact portions between the charging member and a measuring contact member is measured, the following relationship is satisfied: (contact width X)×(Contact area ratio α)≤0.1, where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of the charging roller is the contact width X, and a ratio of a sum of areas of the independent contact portions to an entire area of a measuring region is the contact area ratio α.

## Claims

### Claim 1

An image forming apparatus comprising:
a rotatable photosensitive member having a value, obtained by dividing an elastic deformation work amount by an entire work amount, of 47% or more;
a charging roller including an elastic layer and configured to electrically charge said photosensitive member under application of only a DC voltage, wherein said charging roller forms a nip with elastic deformation along the surface of said photosensitive member by being urged against said photosensitive member with a predetermined urging force, and in the nip, a surface of said charging roller and the surface of said photosensitive member are in contact to each other at a plurality of independent contact portions; and
an image forming portion configured to form a toner image on said photosensitive member charged by said charging roller,
wherein when a nip region corresponding to the nip is formed by urging the charging roller against a measuring contact member with the predetermined urging force and then an area of a plurality of independent contact portions at which the surface of said charging member and the measuring contact member are in contact to each other is measured, the following relationship is satisfied:
(Contact width X) (mm)×(Contact area ratio α)≤0.1 (mm),
where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of said charging roller is the contact width X, and a ratio of a sum of areas (mm2) of the independent contact portions to an entire area (mm2) of a measuring region in which the independent contact portions are provided is the contact area ratio α,
wherein the measuring region is a rectangular region in which one edge has a unit length (mm) extending in the longitudinal direction of said charging member and another edge has the contact width X (mm) extending in the direction perpendicular to the longitudinal direction of said charging roller and which falls within the nip region.

### Claim 2 (depends on 1)

An image forming apparatus according to claim 1, wherein the following relationship is satisfied:
(Contact width X) (mm)×(Contact area ratio α)≤0.05 (mm).

### Claim 3 (depends on 1)

An image forming apparatus according to claim 1, wherein particles are dispersed in an outermost surface layer of said charging roller so as to satisfy the relationship.

### Claim 4 (depends on 1)

An image forming apparatus according to claim 1, wherein a plurality of independent recesses are provided on the surface of said photosensitive member so as to satisfy the relationship.

### Claim 5

A cartridge detachably mountable to a main assembly of an image forming apparatus, said cartridge comprising:
a rotatable photosensitive member having a surface having a value, obtained by dividing an elastic deformation work amount by an entire work amount, of 47% or more;
a charging roller including an elastic layer and configured to electrically charge said photosensitive member under application of only a DC voltage, wherein said charging roller forms a nip with elastic deformation along the surface of said photosensitive member by being urged against said photosensitive member with a predetermined urging force, and in the nip, a surface of said charging roller and the surface of said photosensitive member are in contact to each other at a plurality of independent contact portions,
wherein when a nip region corresponding to the nip is formed by urging the charging roller against a measuring contact member with the predetermined urging force and then an area of a plurality of independent contact portions at which the surface of said charging member and the measuring contact member are in contact to each other is measured, the following relationship is satisfied:
(Contact width X) (mm)×(Contact area ratio α)≤0.1 (mm),
where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of said charging roller is the contact width X, and a ratio of a sum of areas (mm2) of the independent contact portions to an entire area (mm2) of a measuring region in which the independent contact portions are provided is the contact area ratio α,
wherein the measuring region is a rectangular region in which one edge has a unit length (mm) extending in the longitudinal direction of said charging member and another edge has the contact width X (mm) extending in the direction perpendicular to the longitudinal direction of said charging roller and which falls within the nip region.

### Claim 6 (depends on 5)

A cartridge image according to claim 5, wherein the following relationship is satisfied:
(Contact width X) (mm)×(Contact area ratio α)≤0.05 (mm).

### Claim 7 (depends on 5)

A cartridge according to claim 5, wherein particles are dispersed in an outermost surface layer of said charging roller so as to satisfy the relationship.

### Claim 8 (depends on 5)

A cartridge according to claim 5, wherein a plurality of independent recesses are provided on the surface of said photosensitive member so as to satisfy the relationship.