Flexible Guide Members for Sheet Transfer Alignment
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in preventing transfer defects, particularly with thin and thick sheets, due to gaps between the sheet and photosensitive drum, leading to discharge and bending issues.
Innovation Solution
A process cartridge with flexible first and second guide members, where the first guide member is inclined upward and the second guide member is disposed to cross the first guide member's plane at the upstream side, ensuring smooth guidance of sheets of varying thicknesses to the transfer position, reducing discharge and bending defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single guide member is used to guide the sheet to the photosensitive drum, then the structure is simple, but transfer defects occur in the rear end of the sheet
Solution Approach 1:
The guide member is divided into two separate guide members (first guide member and second guide member) positioned at different locations. The first guide member guides the front end of the sheet, while the second guide member guides the rear end of the sheet, ensuring both ends are properly aligned with the photosensitive drum to prevent transfer defects.
2Object-affected harmful factors
If the guide member is positioned close to the photosensitive drum to prevent discharge, then discharge is suppressed, but thick sheets cause bending and transfer defects
Solution Approach 1:
The guide members are positioned at different distances from the photosensitive drum along the sheet conveying direction. The first guide member is positioned closer to prevent discharge at the front end, while the second guide member is positioned further away to accommodate thick sheets and prevent bending, thus solving the problem in a spatial dimension.
3Shape
If the guide member is positioned far from the photosensitive drum to accommodate thick sheets, then bending is reduced, but gaps occur and discharge happens
Solution Approach 1:
By segmenting the guidance function into two guide members at different positions, the system can simultaneously achieve close positioning (to prevent discharge) and adequate distance (to prevent bending) by assigning different guide members to different functions and locations along the conveying path.
4Reliability
If parallel guide members are used to guide the rear end of the sheet, then transfer defects in the rear end are reduced, but thick sheets still cause bending due to the angle of contact
Solution Approach 1:
The second guide member is positioned asymmetrically relative to the first guide member, not in direct parallel alignment. This asymmetric positioning allows the second guide member to guide the rear end of the sheet at a more favorable angle, reducing the resistant force and preventing bending of thick sheets while still ensuring proper transfer alignment.
Data Source
AI summary
A first guide member and a second guide member, which are flexible, are disposed at an upstream side of a transfer position. The first guide member is fixed at a first base end at an upstream side of a first leading end so that the first leading end is closer to a photosensitive drum at the upstream side of the transfer position. The second guide member is fixed at a second base end at an upstream side of a second leading end so that the second leading end is closer to the photosensitive drum between the first leading end and the transfer position. A first plane connecting the first leading end and the first base end and a second plane connecting the second leading end and the second base end, are made to cross each other at an upstream side of the first base end.