Sheet Position Control for Image Alignment in Duplex Printers
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Solution Overview
Problem
Image forming apparatuses face issues with lateral displacement of sheets during image formation, leading to poor image quality due to differences in shift amounts between the first and second surfaces of a sheet, resulting in misalignment of images on both surfaces.
Innovation Solution
An image forming apparatus with a moving portion, re-conveyance portion, detection portion, and control portion that corrects the sheet's position in the width direction based on detected edge positions to ensure alignment of images on both surfaces, using a registration roller pair and sensors to adjust the sheet's position before image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the shift amount upper limit is set uniformly for both first surface and second surface image formation, then the device complexity is reduced, but the image alignment precision between first and second surfaces deteriorates
Solution Approach 1:
The patent applies dynamics by making the upper limit value of the shift amount variable rather than fixed. The control portion dynamically adjusts the upper limit value based on the conveyance path (first conveyance path for first surface, second conveyance path for second surface). This allows the system to adapt the shift amount constraints to the specific characteristics of each conveyance path, thereby achieving precise image alignment on both surfaces without requiring overly complex uniform control mechanisms.
Solution Approach 2:
The patent applies local quality by setting different upper limit values for the shift amount in different local contexts (different conveyance paths). The first upper limit value is set for the first conveyance path and the second upper limit value is set for the second conveyance path. This localized approach allows each path to have optimized parameters suited to its specific characteristics, improving image alignment precision without increasing overall system complexity.
2Manufacturing precision
If the shift amount is increased to correct large lateral displacement, then the image alignment on a single surface is improved, but the sheet may become skewed and the image alignment between first and second surfaces deteriorates
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the shift amount based on the detected edge position and the specific conveyance path. The control portion calculates the required shift amount to correct lateral displacement while ensuring it remains within the appropriate upper limit value for that path. This dynamic adjustment allows sufficient correction of large displacements without causing sheet skew that would result from excessive fixed shift amounts.
Solution Approach 2:
The patent applies feedback by using the edge position detection portion to continuously monitor the sheet position and adjusting the shift amount accordingly. The detection portion provides real-time feedback on the sheet's edge position, allowing the control portion to calculate the precise shift amount needed to correct lateral displacement without exceeding the upper limit that would cause skew. This closed-loop feedback mechanism ensures accurate correction while maintaining sheet stability.
3Manufacturing precision
If different upper limit values are set for first and second conveyance paths, then the image alignment precision between surfaces is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by using a single control portion to manage both conveyance paths with their respective upper limit values. The control portion universally handles the selection and application of appropriate upper limit values based on the active conveyance path, rather than requiring separate control mechanisms for each path. This multi-functional approach achieves precise image alignment while minimizing the increase in device complexity through centralized control logic.
Data Source
AI summary
An image forming apparatus includes a controller to move a sheet, in an image formation process on a first surface, to a standard position in a width direction and move the sheet, in an image formation process on a second surface, in the width direction based on a detected position in a case where a difference between the standard position and a first position in the width direction is equal to or smaller than a predetermined value. The controller moves the sheet, in the image formation process on the first surface, by the predetermined value in the width direction and moves the sheet, in the image formation process on the second surface, in the width direction based on detected positions in a case where the difference between the standard position and the first position in the width direction is larger than the predetermined value.