# US 10,372,056 B2 · Image forming apparatus having grid electrode with opening and non-opening portions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,372,056 B2 - Document ID: US10372056B2 - Status: Granted - Kind: B2 - Application number: 15/964,897 - Filed: 2018-04-27 - Published: 2018-11-01 - Granted: 2019-08-06 - Earliest claimed: 2017-04-28 - Assignees: Canon Kabushiki Kaisha - Applicants: Canon Kabushiki Kaisha - Inventors: Motohiro Fujiwara; Kunihiko Kitayama - Web page: https://patentgrep.com/patent/US10372056B2 ## CPC - G03G 15/0291: {corona discharge devices, e.g. wires, pointed electrodes, means for cleaning the corona discharge device} - G03G 2215/027: using wires - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An image forming apparatus includes a corona charger including a discharging wire and a grid electrode for charging a photosensitive drum at a charging position and an exposure device for exposing the drum charged by the charger at an exposure position which is at a downstream side of the charger (in a rotational direction of the drum) at the charging position. The grid electrode includes a first portion having openings and a second portion having only a non-opening portion in a charging region for charging the drum in a longitudinal direction of the charger, and the second portion includes a downstream side peripheral portion at a downstream end of the grid electrode with respect to the rotational direction. In a cross-section orthogonal to the longitudinal direction and including the charging region, the downstream side peripheral portion is intersected by a straight line passing through the exposure position and the wire. ## Claims ### Claim 1 An image forming apparatus comprising: a rotatable photosensitive member; a corona charger including a discharging wire and a plate-like grid electrode and being configured to charge a surface of said photosensitive member at a charging position; and an exposure device configured to expose the surface of said photosensitive member charged by said corona charger at an exposure position, which is at a downstream side of said corona charger in a rotational direction of said photosensitive member at the charging position, to form an electrostatic image, wherein said grid electrode includes a first portion having a plurality of openings and a second portion provided adjacent to said first portion with respect to the rotational direction, said second portion including a downstream side peripheral portion not provided with an opening in a charging region in a longitudinal direction of said corona charger, and wherein in a cross-section orthogonal to the longitudinal direction and including the charging region, the downstream side peripheral portion extends from a downstream end portion of said plate-like grid electrode at least to a position crossing with a straight line A passing through the exposure position and said discharging wire. ### Claim 2 (depends on 1) An image forming apparatus according to claim 1, wherein said corona charger includes upstream and downstream shield portions sandwiching said discharging wire and being substantially perpendicular to said grid electrode, and a gap is provided in the cross-section between said downstream shield portion and a downstream side end portion of said downstream side peripheral portion with respect to the rotational direction. ### Claim 3 (depends on 1) An image forming apparatus according to claim 1, wherein said grid electrode includes an upstream side peripheral portion at an upstream end of said grid electrode with respect to the rotational direction, and a length of the downstream side peripheral portion measured in the rotational direction is longer than a length of the upstream side peripheral portion measured in the rotational direction. ### Claim 4 (depends on 1) An image forming apparatus according to claim 1, further comprising a fan capable of generating a flow of air in the direction from a discharging wire side surface of said grid electrode toward a photosensitive member side surface of said grid electrode. ### Claim 5 (depends on 1) An image forming apparatus according to claim 1, wherein the downstream side peripheral portion extends toward the downstream side at least to a tangential line B of said photosensitive member passing through said discharging wire at the downstream side in the rotational direction. ### Claim 6 An image forming apparatus comprising: a rotatable photosensitive member; a corona charger including a discharging wire and upstream and downstream shield portions sandwiching said discharging wire, and being configured to charge a surface of said photosensitive member at a charging position; an exposure device configured to expose the surface of said photosensitive member charged by said corona charger at an exposure position, which is at a downstream side of said corona charger in a rotational direction of said photosensitive member at the charging position, to form an electrostatic image; and a shielding member configured to shield said photosensitive member from said discharging wire, said shielding member extending from the downstream shield portion at least to a straight line A passing through the exposure position and said discharging wire in a cross-section orthogonal to the longitudinal direction and including a charging region. ### Claim 7 (depends on 6) An image forming apparatus according to claim 6, wherein a plate-like grid electrode is provided between said shielding member and said discharging wire.