Optical Unit Rail Support for Smooth Scanning
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Solution Overview
Problem
Conventional image reading devices experience snagging and vibration issues when the optical unit moves in the sub scanning direction due to the moment produced between the optical unit and the central shaft, making smooth scanning difficult, and this is exacerbated by the need to prevent thickness increase by arranging components vertically.
Innovation Solution
The image reading device incorporates a pair of rail portions that support the optical unit for sliding in the sub scanning direction, with the driving device engaging at the center of gravity in the main scanning direction, and the rail portions are arranged equidistant from this position to prevent moment creation, allowing smooth scanning while maintaining a reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single central shaft (rail portion) is used to support the optical unit, then the device structure is simplified, but the optical unit experiences snagging and vibration due to moment creation during movement
Solution Approach 1:
The single central shaft is segmented into a pair of rail portions positioned on both sides of the optical unit. This segmentation distributes the support function across multiple elements, preventing moment creation and eliminating snagging while maintaining structural simplicity through the symmetric arrangement.
2Reliability
If the driving device is positioned away from the center of gravity to avoid moment creation, then scanning smoothness improves, but the device thickness increases due to vertical component arrangement
Solution Approach 1:
The support structure transitions from a single central shaft to a pair of rail portions arranged in the width direction (lateral dimension) rather than vertically stacking components. This dimensional rearrangement maintains scanning smoothness by distributing support forces while reducing device thickness by utilizing the lateral space.
3Adaptability or versatility
If the optical unit is moved by the driving device during scanning, then fixed-document reading is enabled, but snagging occurs due to moment creation between the optical unit and the central shaft
Solution Approach 1:
The driving device is positioned asymmetrically at the center of gravity of the optical unit while the rail portions are symmetrically arranged on both sides. This asymmetric positioning of the driving force combined with symmetric support eliminates moment creation during movement, enabling smooth operation for both sheet-through and fixed-document reading methods.
4Ease of manufacture
If a single central shaft is used to support the optical unit, then manufacturing cost is reduced, but creep-deformation of the carriage increases
Solution Approach 1:
The pair of rail portions acts as counterbalancing support elements that distribute the optical unit's weight and operational forces evenly. This counterweight arrangement prevents localized stress concentration on a single shaft, reducing creep-deformation while maintaining manufacturing simplicity through the use of standard rail components.
Data Source
AI summary
An image reading device has an optical unit, a pair of rail portions, and a driving device. The optical unit reads an image on the document. The pair of rail portions support the optical unit such that this is slidable in the sub scanning direction. The driving device enables the optical unit to move in the sub scanning direction. The driving device engages with the optical unit substantially at the position of its center of gravity in the main scanning direction, and the pair of rail portions are arranged one on each of one and the other sides in the main scanning direction so as to be equidistant from the position of the center of gravity.