Dual-Sensor Sheet Detection for Jam Prevention
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in accurately detecting sheet jams and preventing sheet misalignment during the printing process, leading to potential paper tears and reduced productivity due to unnecessary jam handling.
Innovation Solution
The apparatus employs a dual-sensor system with predetermined detection positions and margin times to sense the passage of the sheet's rear end, allowing for continued feeding even if the first sensor fails to detect the sheet, thereby preventing unnecessary stops and maintaining printing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single sensor is used to detect sheet passage, then the device complexity is low, but the measurement precision of sheet detection is insufficient leading to incorrect jam detection
Solution Approach 1:
The sheet detection function is segmented into two separate sensors positioned at different locations (first sensor at upstream position, second sensor at downstream position). Each sensor independently detects sheet passage, and the control unit analyzes both signals to determine actual jam conditions, thereby improving detection accuracy while distributing system complexity across multiple simple components
Solution Approach 2:
The control unit acts as an intermediary that receives detection signals from both sensors and processes them to distinguish between actual sheet jams and false detection conditions. By introducing this intermediate processing layer, the system achieves high measurement precision without requiring the sensors themselves to be overly complex
2Reliability
If the sheet feed portion feeds sheets continuously without verification, then the productivity is high, but the reliability of sheet conveyance is reduced leading to paper tears
Solution Approach 1:
The system performs preliminary detection of sheet passage at two different positions before determining whether a jam has actually occurred. By预先 checking sheet conveyance status at both the first sensor position and second sensor position, the system can verify successful sheet passage before proceeding to the next feed operation, ensuring reliability without significantly impacting productivity
Solution Approach 2:
The control unit changes the detection parameter by comparing timing information from two different sensor positions. By analyzing whether the interval between detections at the first sensor and second sensor matches expected values, the system dynamically adjusts its judgment of jam conditions, maintaining both reliability and productivity
3Reliability
If the system stops feeding on detection of sheet passage issue, then the reliability improves by preventing paper tears, but the productivity decreases due to unnecessary stops
Solution Approach 1:
The control unit implements feedback processing by continuously monitoring detection signals from both sensors and comparing them against expected timing patterns. This feedback mechanism allows the system to distinguish between temporary detection anomalies and actual jam conditions, stopping only when truly necessary, thereby maintaining both reliability and productivity
Solution Approach 2:
The system performs excessive detection by using two sensors instead of one, creating redundant verification. This partial redundancy allows the system to be more selective about when to stop feeding, reducing unnecessary stops while still preventing actual paper tears through thorough verification
Data Source
AI summary
An image forming apparatus has a sheet feed portion, a conveying portion, a control portion, a first sensor having the detection position at a first position in the sheet conveying passage, and a second sensor having the detection position at a second position downstream of the first position in the sheet conveying direction. The control portion performs first sensing to sense whether the sheet's rear end has passed the first position within a first time of the start of the feeding and second sensing to sense whether the sheet's rear end has passed the second position within a second time of the start of the feeding. Even if the control portion is unable to sense passage of the sheet's rear end in the first sensing, when it senses passage of the sheet's rear end in the second sensing, it makes the conveying portion continue feeding the sheet.