Sheet Stacking Apparatus Curl Detection Logic
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Solution Overview
Problem
Existing sheet stacking apparatuses face issues with accurate detection of the fully loaded state due to sheet curling, leading to erroneous detection and unstable image formation processes in image forming apparatuses, as the curl of sheets changes over time, causing instability in stopping and restarting image formation.
Innovation Solution
A sheet stacking apparatus with a stacking unit that can move up and down, equipped with a sheet detection unit, a lower-limit detection unit, and a determination unit that lifts the stacking unit based on the detection of the uppermost sheet and elapsed time to differentiate between curl-induced changes and actual sheet removal, thereby reducing erroneous detection of the fully loaded state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the fully loaded state is detected based only on the sheet surface sensor detecting the uppermost sheet, then the detection process is simple, but the detection accuracy deteriorates due to sheet curling changes over time
Solution Approach 1:
The detection system is segmented into multiple independent detection components: a sheet surface sensor for detecting the uppermost sheet position, and a lower-limit detection unit for detecting when the stacking unit reaches its lower limit position. This segmentation allows each component to perform its specific function without interference, improving overall detection accuracy while maintaining reasonable system complexity.
Solution Approach 2:
The determination unit incorporates feedback mechanisms by continuously monitoring the output of both the sheet surface sensor and the lower-limit detection unit. When the sheet surface sensor detects the uppermost sheet and the lower-limit detection unit detects the lower limit position, the determination unit confirms the fully loaded state. This feedback loop ensures accurate detection by cross-validating multiple sensor inputs.
2Reliability
If the tray is lifted up by a predetermined amount when fully loaded state is detected, then the curl loosening issue is addressed, but the detection stability deteriorates because the sheet surface sensor output changes over time as curl decreases
Solution Approach 1:
The stacking unit is designed with dynamic movement capability, allowing it to move between an upper limit position and a lower limit position. The determination unit dynamically adjusts the detection strategy by incorporating the lower-limit detection unit's output, which remains stable regardless of sheet curl changes. This dynamic approach maintains detection reliability while compensating for the sheet surface sensor's time-dependent measurements.
Solution Approach 2:
The lower-limit detection unit acts as an intermediary that provides a stable reference point for detection. Instead of relying solely on the sheet surface sensor's measurements that change with curl, the lower-limit detection unit detects the stacking unit's position at a fixed reference point, serving as a mediator that stabilizes the overall detection system against curl-induced variations.
3Device complexity
If the fully loaded state determination relies on sheet surface sensor output, then the system structure remains simple, but erroneous detection occurs when operator removes sheets or curl changes
Solution Approach 1:
The detection system is divided into functionally independent segments: the sheet surface sensor handles uppermost sheet detection, while the lower-limit detection unit handles position verification. This segmentation prevents erroneous detection by ensuring that both conditions must be met simultaneously for a valid fully loaded state determination, thereby maintaining simplicity while improving reliability.
Solution Approach 2:
The determination unit performs preliminary verification by checking the output of both detection units before confirming the fully loaded state. This preliminary action filters out erroneous detections caused by sheet removal or curl changes, ensuring that only valid conditions trigger the fully loaded state determination.
Data Source
AI summary
A stacking unit accommodates sheets stacked on it. The stacking unit is capable of moving up and down within an operation range from a predetermined upper limit to a predetermined lower limit. A determination unit releases a determination of the fully loaded state if elapsed time from the time when the determination unit determines that the stacking unit has been fully loaded with sheets to the time when a sheet detection unit again detects an uppermost sheet of the stacked sheets as a result of the stacking unit being lifted up when the sheet detection unit can no longer detect the sheet after detection of the sheet exceeding a first threshold time preset in correspondence with the amount of curl imparted to the sheet.