Image Reading Apparatus Conveyance Speed Control for Sheet Length
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Solution Overview
Problem
Conventional image reading apparatuses may fail to read entire images from original sheets due to varying sheet lengths, as shorter sheets experience sudden conveyance speed increases upon separation from the supply roller, potentially missing image regions.
Innovation Solution
An image reading apparatus with a control device that distinguishes between first and second sheet types based on length, adjusting conveyance speed at separation timing to prevent incomplete image capture by slowing down shorter sheets when they separate from the supply roller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the conveyance speed is increased for shorter sheets to maintain productivity, then the reading speed improves, but image regions may be missed due to sudden speed increase upon separation
Solution Approach 1:
The conveyance speed is made dynamic rather than constant. The control device adjusts the conveyance speed based on sheet length classification, applying different speed profiles for first sheet type (shorter) and second sheet type (longer) to optimize both productivity and image capture completeness for each sheet type
Solution Approach 2:
The conveyance speed parameter is changed based on sheet length. By classifying sheets into two types and assigning different conveyance speeds, the system adapts the operational parameter to the specific condition, preventing image regions from being missed while maintaining overall productivity
2Reliability
If the conveyance speed is reduced for shorter sheets to ensure complete image capture, then image quality improves, but overall reading speed decreases
Solution Approach 1:
Different conveyance speed regimes are applied to different sheet types locally. First sheet type (shorter sheets) receives a reduced conveyance speed profile during critical separation timing to ensure complete image capture, while second sheet type (longer sheets) maintains a higher conveyance speed to preserve overall productivity
Solution Approach 2:
The conveyance speed parameter is adjusted based on sheet length classification. By changing the speed parameter selectively for different sheet types rather than uniformly reducing speed for all sheets, the system maintains image capture completeness while minimizing impact on overall productivity
3Device complexity
If a single conveyance speed is used for all sheet lengths, then device complexity is reduced, but image regions are missed for shorter sheets
Solution Approach 1:
The system uses parameter changes (conveyance speed) based on a simple classification criterion (sheet length) rather than implementing complex mechanical adjustments. This approach maintains relatively simple device structure while effectively preventing image regions from being missed by adapting the speed parameter to sheet type
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
Ensures that all image regions are read by controlling the conveyance speed of shorter sheets to prevent sudden increases, thereby preventing incomplete image capture and maintaining image quality.
Implementation Method 1
The supply roller is configured to rotate while being in contact with an original sheet placed on the sheet feed tray and to send out the original sheet one sheet by one sheet to a conveyance path
Implementation Method 2
The conveyance unit includes a first conveyance roller and a second conveyance roller and configured to convey, along the conveyance path, the original sheet that has been sent out by the supply roller
Data Source
AI summary
In an image reading apparatus, it is judged whether an original sheet is either one of a first sheet type, whose sheet length is longer than or equal to a first conveyance distance and shorter than a second conveyance distance, and a second sheet type, whose sheet length is longer than or equal to the second conveyance path, the first conveyance distance being distance between a first conveyance roller and a second conveyance roller, the second conveyance distance being distance between a supply roller and the second conveyance roller. The original sheet is conveyed at a separation timing, when the original sheet separates away from the supply roller, at a speed that is smaller for a case where the original sheet is of the first sheet type than for a case where the original sheet is of the second sheet type. An image is read from the conveyed original sheet.