Optical Sensor Shutter for Density Control Accuracy
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Solution Overview
Problem
Image forming apparatuses with reflection-type density sensors face errors in detecting image density due to soiling of the exposure window, and existing shutter mechanisms either suffer from reduced accuracy or require additional space to maintain the shutter and referential reflective plate at a safe distance, leading to increased dimensional tolerance and potential errors in density control.
Innovation Solution
The apparatus incorporates a movable image bearing member with optical sensor units, blocking members, calibration members, and a link mechanism that allows for precise positioning and calibration, reducing the risk of soiling and improving accuracy by adjusting the light intensity and positioning of the referential reflective plate relative to the exposure window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shutter is kept open to allow the density sensor to detect the density control patch, then the detection function is maintained, but the exposure window becomes soiled with toner over time, causing detection errors
Solution Approach 1:
The referential reflective plate is positioned to face the exposure window in advance, ready to compensate for soiling effects before they occur. The system prepares the compensation mechanism beforehand so that when soiling happens, the density sensor can immediately adjust using the referential plate's reflection characteristics.
Solution Approach 2:
The referential reflective plate acts as an intermediary element that introduces a known reflection characteristic into the optical path. This intermediary allows the density sensor to distinguish between actual density variations and soiling effects by comparing the referential plate's consistent reflection against the density control patch's variable reflection.
2Reliability
If the shutter is kept closed to prevent toner from reaching the exposure window, then soiling is prevented, but the density sensor cannot detect the density control patch
Solution Approach 1:
The referential reflective plate is positioned in advance to provide a baseline reflection reference. This preliminary positioning allows the system to prepare compensation data before actual detection occurs, enabling accurate measurements even when the shutter is closed to prevent soiling.
3Device complexity
If the opening of the shutter and the referential reflective plate are positioned close to each other, then the structure is compact, but toner enters through the shutter opening and soils the reflective plate, making adjustment impossible
Solution Approach 1:
The referential reflective plate is positioned in a different spatial dimension relative to the shutter opening, specifically on the shutter surface facing the exposure window rather than adjacent to it. This dimensional repositioning protects the reflective plate from direct toner exposure while maintaining optical functionality.
4Reliability
If the opening of the shutter and the referential reflective plate are positioned far apart, then toner soiling is prevented, but the distance increases requiring additional space and increasing dimensional tolerance
Solution Approach 1:
Instead of increasing the distance along the optical axis, the referential reflective plate is positioned on the shutter surface in a perpendicular dimension. This allows close proximity protection while avoiding the increased dimensional tolerance issues that would result from stretching the optical path distance.
5Ease of operation
If a link mechanism is used to move the shutter, then the shutter can be positioned accurately, but the dimensional tolerance is amplified by the ratio between the link movement amount and the shutter movement amount
Solution Approach 1:
The stopper on the shutter itself provides the positioning function, eliminating the need for external link mechanisms to determine shutter position. The shutter's own structural feature (the stopper) serves the positioning purpose, reducing the amplification of dimensional tolerances through mechanical advantage ratios.
Solution Approach 2:
The positioning function is extracted from the link mechanism and transferred to the shutter component itself. By making the shutter self-positioning through its integrated stopper, the system eliminates the dimensional tolerance amplification problem inherent in link-based positioning systems.
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 configuration enhances the accuracy of density control by minimizing errors caused by soiling and reduces the overall size of the image forming apparatus while maintaining high blocking performance and efficiency.
Implementation Method 1
a first optical sensor unit configured to project light toward the image bearing member and to detect the light projected to the density adjustment toner image
Data Source
AI summary
An image forming apparatus includes optical sensor units provided opposed to an image bearing member; light blockers provided between the image bearing member and the optical sensor units, respectively, the blockers being movable between locking and exposing positions, respectively; calibration members provided where the light is incident when the blockers are in the blocking positions, respectively, the calibration members calibrating data acquired by the optical sensor units; a movable link connected with the blockers; a switching portion for switching the blockers between the exposing and blocking positions; and a positioning portion for determining the blocking position, the positioning portion being disposed at a position where at least one of the blockers is contacted to the positioning portion when the blockers are switched from the exposing positions to the blocking positions.