Sheet Stacking Control via Humidity Detection in Image Formers
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Solution Overview
Problem
Small-sized image forming apparatuses face challenges in preventing stacking failure due to the limited size of the sheet stacking unit, which increases the risk of sheets falling out, and existing solutions like dedicated sheet-height detecting units are costly and space-intensive, while also failing to adapt to changes in sheet curl caused by moisture absorption.
Innovation Solution
An image forming apparatus that uses a humidity detecting unit to indirectly assess the moisture-absorbed condition of sheets, allowing for control of the number of sheets ejected and stacked without a dedicated sheet-height detecting unit, by predicting the shape or degree of curl and adjusting the maximum load based on humidity data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the sheet stacking unit is decreased to reduce apparatus size, then the apparatus becomes more compact and cost-effective, but the maximum number of sheets that can be stacked decreases, increasing the risk of stacking failure
Solution Approach 1:
The control unit pre-determines the maximum load (number of sheets) for the sheet stacking unit based on stored correspondence data before actual stacking occurs. This preliminary setting prevents stacking failure by ensuring the stack height never exceeds the safe threshold, even in compact apparatus with limited stacking space.
Solution Approach 2:
The system changes the parameter of maximum sheet capacity dynamically by selecting different maximum load values from stored data based on sheet type. This allows the compact apparatus to adapt its stacking capacity to match actual sheet characteristics, preventing both underutilization and overflow of the limited stacking space.
2Reliability
If a dedicated sheet-height detecting unit is provided to detect sheet height and prevent stacking failure, then stacking reliability improves, but apparatus cost and space requirements increase
Solution Approach 1:
The invention uses an intermediary approach by employing a sheet presence detecting unit (already present in the apparatus for other purposes) to count sheets, rather than installing a dedicated sheet-height detecting unit. The control unit combines this count with pre-stored maximum load data to determine when to stop ejection, achieving reliable stacking control without additional complex detection hardware.
Solution Approach 2:
The system uses a copy of the existing sheet presence detecting unit's functionality for a new purpose (counting sheets to determine full status). Instead of creating a new dedicated detection system, the invention repurposes the signal from the existing sensor to achieve stacking control, reducing device complexity while maintaining reliability.
3Reliability
If the maximum number of sheets is strictly limited to prevent stacking failure, then stacking reliability improves, but the productivity of the image forming apparatus decreases
Solution Approach 1:
The maximum load value is not fixed but dynamically adjusted based on sheet type. The control unit selects different maximum sheet capacity values from stored correspondence data according to the actual sheet being processed. This dynamic adjustment allows the system to maximize productivity for each sheet type while maintaining stacking reliability, rather than using a conservative fixed limit.
Solution Approach 2:
The system changes the maximum sheet capacity parameter based on sheet characteristics (type, basis weight, curl tendency). By adjusting this parameter dynamically, the apparatus achieves optimal productivity for each sheet type while preventing stacking failure, resolving the contradiction between reliability and productivity.
4Device complexity
If sheet curl caused by moisture absorption is not accounted for, then the maximum load setting remains simple, but stacking failure risk increases due to varying sheet shape
Solution Approach 1:
The control unit pre-determines the maximum load based on sheet type characteristics including moisture absorption properties and curl tendency, before actual stacking occurs. This preliminary setting accounts for potential sheet shape changes due to humidity, ensuring the maximum load is set conservatively enough to prevent stacking failure even when sheets curl.
Solution Approach 2:
The system adjusts the maximum sheet capacity parameter based on sheet characteristics that include moisture absorption behavior and curl tendency. By incorporating these environmental factors into the parameter selection, the system maintains stacking reliability without requiring complex real-time monitoring, balancing simplicity and reliability.
Data Source
AI summary
An image forming apparatus includes an image forming unit forming an image on a sheet transported along a transport path in a printing operation; a sheet stacking unit in which the sheet ejected at the end of the transport path is stacked; a sheet detecting unit detecting the presence or absence of the sheet in the transport path; a counting unit counting number-of-sheet data of the sheet detected by the sheet detecting unit; and a control unit controlling the printing operation in accordance with a first print request from a print instructing unit for a print job and based on a count value obtained by the counting unit. The control unit clears the count value in the absence of a next print request from the print instructing unit within a predetermined time after completion of the printing operation.