Optical Sensor Unit for Transfer Belt Skew Detection
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately detecting image skew and shift due to improper placement of optical sensors relative to an endless moving member, leading to incorrect toner density adjustments and potential misregistration.
Innovation Solution
The apparatus includes a housing with a cover that exposes a loop-shaped moving member, allowing for precise placement of optical sensors along its width, with fixing members and engaging mechanisms to ensure accurate positioning and prevent displacement, enabling detection of light reflections or transmissions for calculating image skew, shift, and toner density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple optical sensors are arranged along the width of the transfer belt to detect image skew and shift, then measurement precision is improved, but device complexity increases due to the need for precise positioning and alignment mechanisms
Solution Approach 1:
The patent uses a single optical sensor that scans across the width of the transfer belt to detect image skew and shift, replacing the need for multiple simultaneously positioned sensors. The sensor captures light reflections at different positions sequentially, creating a complete measurement profile without requiring complex multi-sensor alignment mechanisms.
Solution Approach 2:
The optical sensor is mounted on a movable carriage that travels along the width of the transfer belt. This dynamic positioning system allows one sensor to occupy multiple measurement positions sequentially, achieving the same measurement coverage as multiple fixed sensors would provide, while eliminating the complexity of precisely positioning and aligning multiple sensors simultaneously.
2Measurement precision
If optical sensors are positioned close to the transfer belt surface for accurate light detection, then measurement precision is improved, but reliability decreases due to susceptibility to contamination from toner particles
Solution Approach 1:
The patent introduces a light guide as an intermediary component between the optical sensor and the transfer belt surface. The light guide transmits light from the sensor to the belt and redirects the reflected light back to the sensor, allowing the sensor to remain positioned away from the belt surface while still achieving accurate light detection. This intermediary structure protects the sensor from toner contamination while maintaining measurement precision.
Solution Approach 2:
Instead of positioning the sensor in close proximity to the belt surface (zero-dimensional contact), the light guide extends the optical path in the vertical dimension, allowing the sensor to be positioned at a safe distance while maintaining optical coupling with the belt surface through the light guide medium.
3Ease of operation
If the housing cover is designed to expose the transfer belt for easy maintenance access, then ease of operation is improved, but manufacturing precision requirements increase to ensure proper sensor alignment through the opening
Solution Approach 1:
The optical sensor unit is designed as a self-aligning module that attaches to the housing cover. The module includes positioning features such as guide pins or alignment marks that automatically ensure correct positioning of the sensor relative to the transfer belt when the cover is installed, eliminating the need for complex precision machining of the cover opening itself.
Solution Approach 2:
The sensor unit is pre-assembled and pre-positioned on the housing cover before the cover is installed on the main body. This preliminary positioning ensures that when the cover is closed, the sensor is already correctly aligned with the transfer belt, simplifying both manufacturing and assembly processes while maintaining precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures accurate detection and adjustment of image skew and shift, preventing misregistration and ensuring proper toner density, thereby improving the reliability and precision of image formation.
Implementation Method 1
detect respective amounts of light reflected therefrom or transmitted therethrough
Implementation Method 2
detect respective amounts of light reflected therefrom or transmitted therethrough
Data Source
AI summary
An image forming apparatus includes a housing including a cover configured to cover an opening provided in the housing, a transfer unit configured to move a loop-shaped moving member, a portion of which, across an entire width in a direction perpendicular to a moving direction thereof, being exposed through the opening when the cover is opened, and a sensor unit including a holding member configured to hold a plurality of optical sensors arranged in a direction perpendicular to the moving direction of the loop-shaped moving member and configured to detect detecting respective amounts of light at respective areas different from each other on the loop-shaped moving member, end portions of the sensor unit being fixed in the housing at end portions of the opening in a widthwise direction perpendicular to the moving direction of the loop-shaped moving member.