Sheet Conveyance Skew Detection Using Speed-Adaptive Thresholds
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Solution Overview
Problem
Existing sheet conveyance systems inaccurately detect skew in documents due to increased detection timing differences caused by reduced conveyance speed, leading to erroneous skew detection and potential damage to sheets.
Innovation Solution
A sheet conveyance apparatus with multiple sensors to detect sheet skew, adjusting threshold values based on measured conveyance speed, and selectively executing stop processing or not based on speed conditions to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed threshold value is used for skew detection, then the detection system is simple to operate, but the skew detection accuracy deteriorates when conveyance speed varies
Solution Approach 1:
The patent applies dynamics by making the threshold value adaptive rather than fixed. The control unit dynamically adjusts the threshold value based on the actual conveyance speed measured during operation. When conveyance speed decreases, the threshold value is increased to compensate for the larger detection timing differences, thereby maintaining accurate skew detection despite varying operating conditions
Solution Approach 2:
The patent changes the parameter of the threshold value based on conveyance speed conditions. The control unit measures the actual conveyance speed and modifies the threshold value accordingly - using a first threshold value at normal speed and a second, higher threshold value when speed decreases. This parameter adaptation resolves the contradiction by maintaining detection accuracy without requiring complex additional hardware
2Measurement precision
If the threshold value is increased to accommodate slower conveyance speeds, then skew detection accuracy is maintained, but erroneous detection of skewing increases at normal speeds
Solution Approach 1:
The system dynamically adjusts the threshold value based on real-time conveyance speed measurement. At normal conveyance speeds, the first (lower) threshold value is used to prevent erroneous skew detection. When conveyance speed decreases, the system switches to the second (higher) threshold value to maintain accurate skew detection. This dynamic adaptation ensures both detection accuracy and reliability across varying operating conditions
Solution Approach 2:
The control unit implements feedback by continuously measuring the actual conveyance speed and using this information to adjust the threshold value for skew detection. The speed measurement feedback loop ensures that the threshold value always corresponds to the current conveyance conditions, preventing both false positives at normal speed and false negatives at reduced speed
3Measurement precision
If skew detection is performed without considering conveyance speed, then the processing is simple and fast, but the accuracy of skew detection deteriorates
Solution Approach 1:
The system performs preliminary action by measuring the conveyance speed before conducting skew detection. The control unit first measures the actual conveyance speed using the detection timings from the sheet detection sensors, then selects the appropriate threshold value based on this speed measurement. This preliminary speed assessment enables accurate skew detection without requiring complex real-time calculations during the detection process itself
Data Source
AI summary
A sheet conveyance apparatus includes a conveyance unit, a sensor unit, and a control unit executing a first stop processing of stopping conveyance of a sheet by the conveyance unit when, until a threshold value time has elapsed after one of a first sensor and a second sensor detected the sheet, the other one of them does not detect the sheet, and a speed detection processing of measuring a speed of the sheet conveyed by the conveyance unit based on a detection result of the sensor unit. The control unit sets the threshold value time to a first time when the speed of the sheet measured in the speed detection processing is a first speed, and sets the threshold value time to a second time that is longer than the first time when the speed of the sheet is a second speed that is slower than the first speed.