Charging device for an image forming apparatus and charging roller therefor

In an image forming apparatus including a charging device for charging a surface of a body to be charged, said charging device comprising a charge roller made up of a metallic core, an elastic member covering a surface of said core, and films respectively wrapped around opposite end portions of said charge roller such that said charge roller contacts said body to be charged via said films, a voltage being applied between said charge roller and said body to be charged, when said elastic member deforms due to compression ascribable to contact of said charge roller with said body to be charged, said films deform along an outer periphery of said elastic member by a maximum amount, as measured in a radial direction of said charge roller, which is smaller than a thickness of said films.

In an image forming apparatus including a charge roller, which comprises a metallic core and an elastic member covering said core, for charging a surface of a drum-like image carrier in response to a voltage applied between said charge roller and said image carrier to thereby allow a latent image to be optically formed on said surface, films are respectively wrapped around portions of said image carrier corresponding to opposite end portions of said charge roller such that said opposite end portions of said charge roller respectively contact said films, and portions of said elastic member deformed due to compression ascribable to contact of said charge roller with said image carrier have a maximum deformation, as measured in a radial direction of said charge roller, which is smaller than a thickness of said films.

In an image carrier unit removably mounted to a body of an image forming apparatus and comprising a charge roller, which comprises a metallic core and an elastic member covering said core, for charging a surface of an image carrier in response to a voltage applied between said charge roller and said image carrier to thereby allow a latent image to be optically formed on said surface, films are respectively wrapped around opposite end portions of said charge roller such that said charge roller contacts said image carrier via said films, and when said elastic member deforms due to compression ascribable to contact of said charge roller with said body to be charged, said films deform along an outer periphery of said elastic member by a maximum amount, as measured in a radial direction of said charge roller, which is smaller than a thickness of said films.

In an image carrier unit removably mounted to a body of an image forming apparatus and comprising a charge roller, which comprises a metallic core and an elastic member covering said core, for charging a surface of an image carrier in response to a voltage applied between said charge roller and said image carrier to thereby allow a latent image to be optically formed on said surface, films are respectively wrapped around portions of said image carrier corresponding to opposite end portions of said charge roller such that said opposite end portions of said charge roller respectively contact said films, and portions of said elastic member deformed due to compression ascribable to contact of said charge roller with said image carrier have a maximum deformation, as measured in a radial direction of said charge roller, which is smaller than a thickness of said films.

In an electrophotographic image forming apparatus including an image carrier unit removably mounted to a body of an image forming apparatus and comprising a charge roller, which comprises a metallic core and an elastic member covering said core, for charging a surface of an image carrier in response to a voltage applied between said charge roller and said image carrier to thereby allow a latent image to be optically formed on said surface, films are respectively wrapped around opposite end portions of said charge roller such that said charge roller contacts said image carrier via said films, and when said elastic member deforms due to compression ascribable to contact of said charge roller with said body to be charged, said films deform along an outer periphery of said elastic member by a maximum amount, as measured in a radial direction of said charge roller, which is smaller than a thickness of said films.

In an electrophotographic image forming apparatus including an image carrier unit comprising a charge roller, which comprises a metallic core and an elastic member covering said core, for charging a surface of a drum-like image carrier in response to a voltage applied between said charge roller and said image carrier to thereby allow a latent image to be optically formed on said surface, films are respectively wrapped around portions of said image carrier corresponding to opposite end portions of said charge roller such that said opposite end portions of said charge roller respectively contact said films, and portions of said elastic member deformed due to compression ascribable to contact of said charge roller with said image carrier have a maximum deformation, as measured in a radial direction of said charge roller, which is smaller than a thickness of said films.

In a charging roller comprising a metallic core and an elastic member covering said core, a stripe-like or a wire-like spacer member is spirally wrapped around said elastic member.