Duplex Sheet Position Correction via Edge Detection
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Solution Overview
Problem
Existing image forming apparatuses face challenges in minimizing the shift amount of the registration roller pair during sheet positioning, leading to potential skew and accuracy issues, especially when dealing with sheets that are not perfectly rectangular, which results in increased shift operations and reduced productivity.
Innovation Solution
The apparatus includes a detection system to determine the side edge position of the sheet, allowing the controller to adjust the registration roller pair's position based on the detected edge positions of both the leading and trailing edges, thereby minimizing the shift amount and maintaining accurate sheet alignment during duplex printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the shift amount of the registration roller pair is increased to correct large sheet deviations, then the sheet position alignment is improved, but the sheet becomes twisted and conveyance accuracy is degraded
Solution Approach 1:
The patent applies preliminary action by performing skew correction at the pre-registration roller pair before the sheet reaches the registration roller pair. The leading edge of the sheet is deflected and aligned while the sheet is still being conveyed, preventing twisted conveyance. This preliminary alignment allows the registration roller pair to perform only minimal shift operations, maintaining both alignment precision and conveyance accuracy.
2Volume of moving object
If the distance between the registration roller pair and upstream conveyance rollers is shortened for downsizing, then the apparatus size is reduced, but the shift operation time increases due to larger required shift amounts
Solution Approach 1:
The pre-registration roller pair performs preliminary skew correction and alignment before the sheet reaches the registration roller pair. This preliminary action reduces the distance the registration roller pair must shift the sheet, thereby reducing shift operation time and enabling apparatus downsizing without sacrificing productivity.
3Device complexity
If the widthwise edge position detection is performed only at the leading edge, then the detection system is simplified, but the sheet alignment accuracy is degraded due to parallelogram-shaped sheets
Solution Approach 1:
The patent segments the sheet widthwise position detection into two independent measurements: one at the leading edge and another at the trailing edge. By detecting widthwise edge positions at both locations, the system can identify and correct parallelogram-shaped sheet deviations, ensuring accurate alignment without significantly increasing detection system complexity.
Data Source
AI summary
An image forming apparatus includes an image forming portion to form an image on an image bearing member, and a transfer portion to transfer the image on a first image position on the image bearing member to a sheet. In addition, a controller determines a second image position, on the image bearing member, of an image to be transferred onto a second surface of a sheet re-conveyed to an adjustment portion by a reverse and re-conveyance portion based on a detected side edge position, of a trailing part of the sheet being conveyed with a first end as the leading edge. The trailing part of the sheet is positioned on a trailing edge side further than a center position, in the sheet conveyance direction, of the sheet, and the controller determines a shift amount based on the second image position and detected side edge position of the sheet, which has been re-conveyed, being conveyed with the second end as the leading edge.