Overprint Image Alignment Using Eye Mark and Speed Feedback
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Solution Overview
Problem
Conventional image forming apparatuses experience significant positional deviations between overprint and base images due to variations in sheet conveyance time, which are not adequately analyzed or controlled, leading to defective printed products.
Innovation Solution
The apparatus includes a conveyer with a driving roller, an eye mark detector, and a speed detector, where the eye mark detector is positioned at specific intervals relative to the driving and speed detection rollers, and a controller performs feedback control to stabilize sheet conveyance speed, using frequency analysis to correct for eccentricity and diameter changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If feedback control of driving roller rotation speed is implemented, then sheet conveyance speed fluctuation is suppressed, but positional deviation between overprint image and base image still occurs due to insufficient analysis of conveyance time factors
Solution Approach 1:
The patent segments the sheet conveyance path into multiple sections with different conveyance speeds. The conveyance path includes a first section with first conveyance speed and a second section with second conveyance speed. This segmentation allows independent control and analysis of each section's contribution to total conveyance time, enabling precise positioning despite speed fluctuations.
Solution Approach 2:
The patent dynamically adjusts conveyance speeds at different sections of the path. By varying the conveyance speed between sections rather than maintaining a constant speed throughout, the system can compensate for variations in conveyance time and achieve more accurate positioning of the overprint image relative to the base image.
2Manufacturing precision
If intermediate transfer belt system is used for electrophotographic printing, then image quality is improved, but sheet conveyance time variation increases due to multiple transfer processes
Solution Approach 1:
The patent segments the conveyance path into distinct sections corresponding to different processing stages (first conveyance section and second conveyance section). Each section has its own speed control, allowing the system to manage and compensate for time variations introduced by multiple transfer processes in the intermediate transfer belt system.
Solution Approach 2:
The patent changes the conveyance speed parameter between different sections of the path. By setting different conveyance speeds in different sections, the system can optimize for both image quality (maintaining stable transfer processes) and time control (compensating for variations in total conveyance time).
Data Source
AI summary
An image forming apparatus according to the present disclosure includes: a conveyer; an eye mark detector disposed in a conveyance path and detecting an eye mark formed on a sheet in advance; an image former forming an overprint image at a predetermined position on the sheet with reference to a position of the eye mark on the sheet; and a speed detector including a speed detection roller to be brought into contact with the sheet and detecting a conveyance speed of the sheet. The eye mark detector is disposed at a position separated by an integral multiple of a roller circumferential length of a driving roller and also by a non-integral multiple of a roller circumferential length of the roller from a position at which the image former forms the overprint image on the sheet.