Registration Roller Switching for Skew Correction Without Sheet Damage
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Solution Overview
Problem
Existing image forming apparatuses face issues with sheet damage due to skew feeding and twisting, particularly when sheets with varying thicknesses pass through registration rollers, leading to misalignment and potential damage.
Innovation Solution
The apparatus incorporates a separation mechanism that adjusts the registration rollers' state based on sheet thickness, switching between abutment and separation to prevent sheet damage and maintain stable conveyance, using a controller to manage the transition at specific points during the conveyance process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pair of registration rollers maintains abutment state for all sheets to correct skew feeding, then skew feeding correction is improved, but sheets with large twist may be stamped or pressed causing damage
Solution Approach 1:
The registration roller pair dynamically switches between abutment state and separated state based on sheet characteristics (basis weight). The separation mechanism adjusts the distance between rollers in real-time, making the system adaptive rather than static. This resolves the contradiction by applying pressure only when needed for skew correction on suitable sheets, while separating to prevent damage on sheets prone to twisting.
Solution Approach 2:
The system changes the physical parameter of roller separation distance based on sheet basis weight. For sheets with basis weight within a predetermined range, the rollers remain in abutment state for skew correction. For sheets outside this range (particularly thin sheets prone to twisting), the rollers are separated to avoid damage. This parameter change resolves the contradiction by adapting the mechanical interaction to sheet properties.
2Object-affected harmful factors
If the pair of registration rollers is separated for thin sheets to prevent damage, then sheet damage is prevented, but skew feeding correction capability is reduced
Solution Approach 1:
The system applies different treatment (abutment vs. separation) to different categories of sheets based on their local characteristics (basis weight). Thin sheets outside the predetermined range receive separation to prevent damage, while sheets within the range receive abutment for skew correction. This local quality approach resolves the contradiction by tailoring the roller interaction to specific sheet properties rather than applying a uniform approach.
3Stability of the object's composition
If the registration rollers continuously nip the sheet for conveyance, then conveyance stability is improved, but images may be stretched or shrunk due to sheet warping
Solution Approach 1:
The system performs preliminary separation of the registration rollers before the sheet reaches a state where warping would cause image distortion. By separating the rollers in advance for thin sheets, the sheet is allowed to maintain its natural warped state without being nipped, preventing subsequent stretching or shrinking that would occur during nipping. This preliminary action resolves the contradiction by preventing the harmful effect before it occurs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents sheet damage and maintains consistent conveyance rates, ensuring accurate image transfer and reducing variations in image magnification across different sheet types.
Implementation Method 1
a transfer portion including a belt configured to bear the toner image formed by the image forming portion, a transfer member forming a second nip portion with the transfer member abutting on an outer side of the belt
Implementation Method 2
a pair of registration rollers including a first roller member, and a second roller member forming a first nip portion with the second roller member abutting on the first roller member, the pair of registration rollers being configured to convey a sheet while the sheet is being nipped by the first nip portion
Data Source
AI summary
According to an image forming apparatus, for conveyance of the sheet having a first basis weight as a basis weight to the second nip portion, the pair of registration rollers is in the separated state with the sheet at a position to which the sheet is conveyed by a predetermined distance after the leading end in the conveyance direction of the sheet reaches the second nip portion, and for conveyance of the sheet having, as the basis weight, a second basis weight larger than the first basis weight to the second nip portion, the pair of registration rollers is in the abutment state with the sheet at the position to which the sheet is conveyed by the predetermined distance after the leading end in the conveyance direction of the sheet reaches the second nip portion.