Fixing Unit Sheet Speed Control for Lopsided Loop Stability
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Solution Overview
Problem
Conventional image forming apparatuses face issues with unstable sheet conveyance, leading to defective images and creases due to lopsided loops, where the loop amount cannot be appropriately controlled, causing the sheet to either contact internal members or become electrically charged, resulting in print defects.
Innovation Solution
An image forming apparatus equipped with multiple detection units to monitor the loop amounts on both sides of the sheet, allowing a control unit to adjust the conveyance speed of the fixing unit between two speeds, ensuring stable conveyance even with lopsided loops by setting the speed to a predetermined value between the first and second conveyance speeds based on detected loop amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conveyance speed of the fixing unit is controlled to maintain loop amount within a predetermined range, then sheet conveyance stability is improved, but the system becomes vulnerable to lopsided loops where loop amounts differ at both end portions in the width direction
Solution Approach 1:
The patent divides the sheet width direction into multiple detection zones by placing separate loop detection sensors at different positions (central portion and both end portions). This segmentation allows independent monitoring of loop amounts at each location, enabling the control unit to detect lopsided loops and adjust conveyance speed accordingly to maintain stable sheet conveyance.
2Device complexity
If only a single loop detection sensor is used to control conveyance speed, then device complexity is reduced, but measurement precision of loop amounts at different width positions cannot be obtained
Solution Approach 1:
The patent applies local quality by placing loop detection sensors at specific critical locations (central portion and both end portions of the sheet width). Each sensor measures loop amount at its specific location, allowing the control unit to identify variations in loop distribution across the sheet width and adjust conveyance speed to prevent lopsided looping.
3Reliability
If conveyance speed is adjusted to compensate for lopsided loops, then sheet conveyance stability is improved, but the control system becomes more complex with multiple detection units and speed control levels
Solution Approach 1:
The patent implements dynamics by enabling the control unit to adjust the conveyance speed of the fixing unit dynamically based on real-time loop detection results. The system can switch between multiple conveyance speeds (first conveyance speed when loop amount is within range, second conveyance speed when lopsided loop is detected) to maintain stable sheet conveyance under varying conditions.
Data Source
AI summary
An image forming apparatus includes a fixing unit, detection units, and a control unit. The control unit switches a sheet speed at the fixing unit to either a first or second sheet speed that is faster than the first sheet speed based on a first detection unit signal where the control unit detects that both a loop amount of a sheet loop at second and third detection unit positions are greater than or less than a predetermined amount. The control unit sets the fixing unit sheet speed as a predetermined sheet speed between the first and second sheet speed where the control unit detects that one of two loop amounts detected the second and third detection units is greater than the predetermined amount when the other one of the two loop amounts is less than the predetermined amount.