Image Forming Apparatus Guide Member Stiffness and Edge Positioning
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Solution Overview
Problem
Existing image forming apparatuses face issues with image quality degradation due to sheet posture instability and guide member interactions, leading to scratches and paper jams, as the leading edge of the sheet can rub against the guide member even after entering the nip, despite control measures to prevent such contact.
Innovation Solution
An image forming apparatus with a guide portion comprising a first guide member of lower stiffness and a second guide member of higher stiffness, arranged on opposite sides, where the downstream edge of the first guide member is closer to the nip than the second guide member, to effectively guide the sheet without causing scratches or jams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leading edge of the guide member is arranged close to the nip, then the sheet can be guided to the nip without causing paper jam, but the sheet and the leading edge of the guide member are brought into slide contact causing image scratches
Solution Approach 1:
The guide member is divided into two separate members: a first guide member with lower stiffness and a second guide member with higher stiffness. This segmentation allows each member to perform different functions - the first guide member contacts the sheet for guidance while the second provides structural support, preventing both paper jams and image scratches
Solution Approach 2:
Different parts of the guide structure are given different stiffness properties. The first guide member has lower stiffness to allow gentle contact with the sheet, while the second guide member has higher stiffness to maintain structural integrity. This local differentiation of properties enables the system to simultaneously achieve reliable conveyance and protect the image
2Device complexity
If a single guide member is used, then the structure is simple, but the sheet posture cannot be stabilized due to heat and wear variations
Solution Approach 1:
The invention changes the physical parameter of stiffness by using two guide members with different stiffness values. The first guide member (lower stiffness) flexes to accommodate sheet variations, while the second guide member (higher stiffness) maintains positional stability. This parameter differentiation enables the guide structure to adapt to heat and wear variations while stabilizing sheet posture
3Manufacturing precision
If the downstream edge of the first guide member is arranged closer to the nip than the second guide member, then sheet guidance is improved, but the structure becomes more complex
Solution Approach 1:
The guide member structure is designed asymmetrically, with the downstream edge of the first guide member positioned closer to the nip than the second guide member. This asymmetric arrangement optimizes sheet guidance precision by allowing the softer first guide member to make contact first, while the harder second guide member provides support from a slightly recessed position
Data Source
AI summary
An image forming apparatus includes an image forming portion configured to form an image on a sheet; a pair of conveyance rotary members arranged downstream of the image forming portion in a sheet conveyance direction and configured to convey the sheet, on which the image is formed, by a conveyance nip; and a guide portion configured to guide the sheet to the conveyance. The guide portion includes a first guide member formed into a sheet shape and having a first stiffness and an abutment surface configured to abut the sheet and a second guide member formed into a sheet shape and having a second stiffness higher than the first stiffness and arranged on a side opposite to the abutment surface of the first guide member, wherein a downstream edge of the first guide member is closer to the conveyance nip than a downstream edge of the second guide member.