Sheet Conveyance Correction via Dual-Stage Roller Speed Control
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Solution Overview
Problem
Existing sheet conveying devices in image forming apparatuses often fail to accurately correct angular and lateral displacements of sheets, leading to further movement in the rotation and width directions during conveyance, compromising the precision of image formation.
Innovation Solution
A sheet conveying device equipped with a pair of sheet holding rollers that utilize contact image sensors (CIS) for real-time detection and correction, performing primary and secondary corrections to ensure precise alignment and stabilization of sheets before reaching the image forming area, thereby preventing further displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sheet conveying device uses multiple pairs of sheet conveying rollers to convey sheets, then the sheet can be conveyed through the sheet conveyance passage, but the sheet may abut against a stopper causing angular displacement correction, and subsequently lateral displacement correction by lateral registration rollers, yet the sheet may still be displaced again in rotation and width directions while being held by sheet holding rollers
Solution Approach 1:
The patent employs detection means (sensors) to detect the position of the sheet at multiple points along the conveyance path. The control unit processes this feedback information and adjusts the rotation speeds of individual sheet conveying rollers to correct angular and lateral displacements. This closed-loop feedback system continuously monitors and corrects sheet position, preventing displacement while the sheet is being held by the sheet holding rollers, thereby resolving the contradiction between correction accuracy and position stability.
2Manufacturing precision
If the sheet is corrected for angular and lateral displacements by lateral registration rollers, then the sheet position is improved, but the sheet may be displaced again while being held and conveyed by sheet holding rollers
Solution Approach 1:
The patent replaces complex mechanical correction mechanisms with a control system that adjusts the rotation speeds of existing sheet conveying rollers. Instead of adding more physical correction devices, the control unit calculates required speed adjustments based on detected sheet positions and commands the rollers to compensate for angular and lateral displacements through differential rotation. This substitution reduces device complexity while maintaining correction accuracy.
3Manufacturing precision
If the sheet conveying device uses a pair of lateral registration rollers to correct lateral displacement, then the sheet position in width direction is improved, but the sheet may still move in rotation direction and width direction after correction
Solution Approach 1:
The patent segments the sheet conveyance path into multiple zones with individual rollers or roller pairs, each responsible for specific correction functions. Detection means are positioned at multiple locations to monitor sheet position at different stages. The control unit processes segmented position data and applies targeted speed adjustments to specific rollers to correct both angular and lateral displacements comprehensively, ensuring high final position accuracy without sheet movement after correction.
Data Source
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Figure 5A~5D
AI summary
A sheet conveying device (30), which is included in an image forming apparatus (1), includes a pair of sheet holding rollers (31) to convey a sheet (P), a gate (31) to which a leading end of the sheet (P) contacts, a first detector (36) disposed upstream from the pair of sheet holding rollers (31) to detect a position of the sheet (P) and a second detector (37) disposed downstream from the pair of sheet holding rollers (31) to detect a position of the sheet (31). The pair of sheet holding rollers (31) performs a primary correction to detect and correct a lateral displacement amount of the sheet (P) by moving while holding the sheet (P), and then a secondary correction to detect and correct at least one of a subsequent lateral displacement of the sheet (P) and an angular displacement of the sheet (P).