Displacement Rollers for Image Registration Skew Correction
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in accurately aligning sheets with images due to sub-scanning skew, leading to misregistration and distortion, especially with elongated sheets, as existing correction methods fail to consistently prevent skew and overrun of registration rollers.
Innovation Solution
An image forming apparatus with displacement rollers and a detection system that adjusts displacement control information based on real-time detection of sheet position, employing a high-speed and low-speed displacement strategy to precisely align sheets with images, preventing excessive displacement and overrun.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If registration rollers are displaced before a sheet reaches a secondary transfer roller to correct sheet leaning, then the position of the side end part of the sheet is adjusted, but sub-scanning skew occurs due to misalignment of rollers and sheet distortion
Solution Approach 1:
The registration rollers are displaced in advance before the sheet reaches the secondary transfer roller to correct sheet leaning. This preliminary action adjusts the sheet position proactively, preventing sub-scanning skew and ensuring accurate image formation by addressing sheet alignment issues before they affect the printing process
Solution Approach 2:
A line sensor detects the position of the side end part of the sheet downstream of the registration rollers. The detected position information is fed back to the control section, which automatically corrects the displacement amount of the registration rollers for subsequent sheets, creating a closed-loop control system that continuously improves alignment precision
2Measurement precision
If skew correction is performed by bringing a front end of a sheet into abutment with registration rollers, then the skew of the front end is corrected, but the rear end side remains uncorrected causing distortion and sub-scanning skew
Solution Approach 1:
Instead of only correcting skew at the front end in one dimension, the system displaces the registration rollers in the sheet width direction to correct leaning across the entire sheet. This multi-dimensional approach ensures both front and rear ends are properly aligned, eliminating distortion and sub-scanning skew
3Productivity
If registration displacement correction is performed during conveyance by a secondary transfer roller, then sheet position is adjusted, but the sheet may be skewed again after stoppage or registration rollers may overrun due to position variation and sheet tension
Solution Approach 1:
The system dynamically adjusts the displacement amount of the registration rollers based on real-time detection results from the line sensor. This dynamic correction approach adapts to variations in sheet position and tension, preventing overrun and maintaining stable position control while ensuring reliable alignment throughout the conveyance process
Data Source
AI summary
An image forming apparatus that highly precisely suppresses misregistration of an image relative to a sheet due to sub-scanning skew and a control method are provided. The image forming apparatus includes: displacement rollers including at least a pair of rollers conveying a sheet that is being conveyed, toward a transfer section; a detection section that detects a position of a side end part of the sheet; and a hardware processor that performs processing for displacing the displacement rollers based on displacement control information and correcting the displacement control information for next and subsequent sheets based on a detection result of detection by the detection section after the displacement of the displacement rollers.