Paper Conveyance Control for Skew Correction and CPM
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Solution Overview
Problem
Existing paper conveying devices in image forming apparatuses face challenges in reducing conveyance variation, leading to increased intervals between sheets, which affects print quality and the ability to increase copies per minute (CPM) without sacrificing print quality.
Innovation Solution
A paper conveying device that includes paper feeding, registration, and conveyance control mechanisms, which temporarily stops and re-conveys sheets based on their length to maintain consistent intervals and adjust re-conveyance timing accordingly, ensuring precise alignment and skew correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the interval between sheets is shortened to increase CPM, then productivity increases, but conveyance variation increases leading to degraded print quality
Solution Approach 1:
The patent applies preliminary action by temporarily stopping the succeeding sheet at a prescribed position downstream before re-conveying it to the registration roller pair. This advance positioning and controlled stopping allows the system to prepare the sheet for precise conveyance, reducing conveyance variation even when sheets are fed at high speed. The temporary stop enables the conveyance control to synchronize the sheet arrival with the registration roller pair timing, thereby maintaining print quality while increasing CPM.
2Productivity
If sheets are fed at high speed to increase CPM, then productivity increases, but the succeeding sheet may arrive before the registration roller pair stops, causing skew correction failure
Solution Approach 1:
The patent implements feedback control by using a sensor to detect the leading edge of the succeeding sheet and based on this detection, the conveyance control adjusts the timing to start re-conveyance. This closed-loop control ensures that the succeeding sheet arrives at the registration roller pair at the correct timing, allowing proper skew correction to be performed even when sheets are fed at high speed. The feedback mechanism synchronizes sheet arrival with roller pair operation, maintaining reliability.
3Productivity
If the interval between sheets is reduced, then productivity increases, but positional deviation increases affecting image alignment
Solution Approach 1:
The patent applies dynamics by making the timing to start re-conveyance variable rather than fixed. The conveyance control adjusts the re-conveyance timing based on the detection timing of the leading edge of the succeeding sheet and the paper length. This dynamic adjustment allows the system to maintain precise position registration even when the interval between sheets is reduced for high productivity. The flexible timing control compensates for variations in sheet conveyance, ensuring accurate image alignment.
Data Source
AI summary
A paper conveying device includes: a registration roller pair provided along a paper conveying path; a pick-up roller, a paper feed roller and a separation roller for feeding sheets of paper to the paper conveying path; and a controller controlling conveyance of sheets of paper such that when a preceding sheet is stopped at the registration roller pair, a following, succeeding sheet is temporarily stopped at a prescribed position G downstream of a conveying roller in the paper conveying direction, and the succeeding sheet is re-conveyed toward the registration roller pair at a prescribed timing. The controller changes the timing to start re-conveyance of the succeeding sheet in accordance with paper length of the conveyed sheet of paper.