Document Reading Apparatus Variable Drive Speed Control
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Solution Overview
Problem
Document reading apparatuses face challenges in achieving high-speed operation and maintaining image quality when conveying thick sheets through small-diameter, curved conveyance paths, leading to increased conveyance resistance and reduced image reading speed.
Innovation Solution
A document reading apparatus with a control portion that adjusts the drive speed of motors based on document thickness, switching between high and low speed modes to optimize conveyance speed and image reading speed, ensuring quality and preventing image extension in the sub-scanning direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the conveyance path has a small diameter and curved shape to downsize the ADF, then the apparatus size is reduced, but the conveyance resistance increases when conveying thick sheets
Solution Approach 1:
The patent applies dynamics by making the drive speed variable rather than fixed. The control portion dynamically adjusts the drive speed of the driving motor based on document thickness detection, switching between high speed mode for thin sheets and low speed mode for thick sheets. This dynamic adjustment optimizes the balance between conveyance resistance and conveyance speed, allowing the compact ADF to handle various sheet types effectively.
2Productivity
If the conveyance speed is increased for high-speed reading, then productivity is improved, but the read image extends in the sub-scanning direction when conveying thick sheets
Solution Approach 1:
The patent applies parameter changes by adjusting the drive speed parameter based on document thickness. The control portion detects document thickness and changes the drive speed parameter accordingly: using first drive speed for thin sheets to achieve high productivity, and second drive speed (slower) for thick sheets to prevent image extension and maintain image quality. This parameter adjustment resolves the contradiction between speed and precision.
3Device complexity
If a single drive speed is used for all document types, then the control system is simple, but the conveyance speed decreases when conveying thick sheets due to increased conveyance resistance
Solution Approach 1:
The patent applies dynamics by implementing variable drive speed control based on document thickness. The control portion detects document thickness and dynamically switches between high speed mode (first drive speed) for thin sheets and low speed mode (second drive speed) for thick sheets. This dynamic control optimizes conveyance speed for different document types while maintaining acceptable system complexity through automated detection and control.
4Use of energy by moving object
If the drive motor current is optimized for thin sheets, then power consumption is reduced, but the conveyance capability for thick sheets is insufficient
Solution Approach 1:
The patent applies parameter changes by adjusting the drive speed parameter based on document thickness. For thin sheets, the system uses higher drive speed to minimize conveyance time and power consumption. For thick sheets, the system uses lower drive speed to ensure sufficient conveyance capability despite higher conveyance resistance. This parameter adjustment optimizes the balance between power consumption and conveyance capability for different document types.
Data Source
AI summary
A document reading apparatus includes a document supporting portion, a conveyance portion, a driving motor, an image reading unit, and a control portion. The control portion is configured to execute a high speed mode in which the conveyance speed is set to a first conveyance speed and a low speed mode in which the conveyance speed is set to a second conveyance speed slower than the first conveyance speed. When the control portion executes the low speed mode, if the document has a first thickness, the control portion is configured to execute a first low speed mode where a first drive speed is set to the driving motor. If the document has a second thickness thicker than the first thickness, the control portion is configured to execute a second low speed mode where a second drive speed faster than the first drive speed is set to the driving motor.