Loop Forming Rollers for Sheet Skew Correction
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Solution Overview
Problem
Conventional skew prevention techniques in image forming apparatuses are insufficient for achieving high positional accuracy, especially in electrophotographic systems that require precise image positioning on various types of paper, as they struggle to maintain the required skew correction to 0.2% or less.
Innovation Solution
An image forming apparatus with a conveyance section that includes a registration roller, loop forming rollers, and skew detection sensors, where the control section independently controls the loop forming rollers based on skew detection results to form a loop upstream of the registration roller, allowing for precise timing and speed adjustments to correct sheet skew and tension biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional loop conveyance using a registration roller is used, then sheet skew is corrected to some extent, but image position accuracy cannot achieve 0.2% or less
Solution Approach 1:
The patent divides the single registration roller into multiple loop forming rollers (first, second, third loop forming rollers) arranged at different positions. Each roller independently forms a loop with the sheet at different stages, allowing segmented correction of skew throughout the conveyance path rather than attempting single-point correction, thereby achieving the required 0.2% image position accuracy
Solution Approach 2:
The patent performs preliminary skew correction by having the first loop forming roller form a loop upstream before the sheet reaches the registration roller. This preliminary action prevents skew from developing further during conveyance, enabling more accurate final image positioning
2Manufacturing precision
If multiple loop forming rollers are used to improve skew correction, then image position accuracy improves, but device complexity increases
Solution Approach 1:
The patent combines the functions of multiple loop forming rollers into a coordinated system where each roller works in sequence along the conveyance path. The first, second, and third loop forming rollers are merged into a unified skew correction mechanism that operates together, managing complexity through functional integration rather than independent operations
Solution Approach 2:
Each loop forming roller is positioned at a specific location along the conveyance path to address local skew conditions at that stage. The first loop forming roller handles upstream skew, while subsequent rollers address skew development at intermediate and final stages, allowing localized correction without requiring complete system redesign
Data Source
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AI summary
An image forming apparatus includes: an image forming section which forms an image on a sheet; a conveyance section (100) which conveys the sheet to the image forming section, having a registration roller (103), a plurality of loop forming rollers (102) which cause the sheet to form a loop, provided upstream of the registration roller (103) in a sheet conveyance direction and arranged in a direction perpendicular to the sheet conveyance direction, a skew detection sensor (SE1,SE2,SE3) which detects a skew of the sheet, and a conveyance roller (101) provided upstream of the loop forming roller (102); and a control section which controls a driving of the conveyance section. The control section controls independently each of the plurality of loop forming rollers (102) based on the detected result of the skew detection sensor.