Developing Bias Correction Using Low Exposure Toner Patches
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Solution Overview
Problem
Conventional image forming apparatuses face difficulties in accurately correcting developing biases, especially when dealing with high exposure area ratios, as the change in reflected light amount is small, making it challenging to measure the correct density of toner patches.
Innovation Solution
An image forming apparatus and control method that involve setting and applying multiple testing biases smaller than the old developing bias, forming developer images on a belt, detecting their densities, and calculating the developing bias using a controller to ensure accurate correction, even at high exposure area ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional developing bias correction is performed using toner patches with high exposure area ratios, then the correction process can be completed, but the measurement accuracy deteriorates due to small changes in reflected light amount
Solution Approach 1:
The patent inverts the conventional approach by forming toner patches with low exposure area ratios (10-30%) instead of high exposure area ratios. This inversion allows for larger changes in reflected light amount when developing bias changes, significantly improving measurement accuracy. The sensor can detect reflected light changes of 10% or more, compared to less than 1% in conventional high exposure ratio patches.
Solution Approach 2:
The patent changes the exposure area ratio parameter from conventional high values (70-100%) to low values (10-30%). This parameter change fundamentally alters the optical properties of the toner patches, enabling the sensor to detect reflected light amount changes more effectively. The low exposure area ratio creates a stronger relationship between developing bias changes and reflected light changes.
2Measurement precision
If multiple testing biases are applied to improve correction accuracy, then the precision of developing bias correction is improved, but the process time increases
Solution Approach 1:
The patent applies preliminary action by forming multiple toner patches with different low exposure area ratios (10%, 20%, 30%) before the actual correction measurement. These pre-formed patches with known characteristics allow for more efficient calculation of the optimal developing bias, reducing the time required for iterative adjustments while maintaining high accuracy.
Solution Approach 2:
The patent segments the correction process into distinct stages: forming multiple toner patches with different exposure ratios, measuring their reflected light characteristics, and using this segmented data to calculate the optimal developing bias. This segmentation allows for systematic analysis and reduces the complexity of real-time adjustments.
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 approach allows for precise correction of developing biases, improving detection accuracy and maintaining correct printing density across varying exposure area ratios.
Implementation Method 1
the change in reflected light amount is small, making it challenging to measure the correct density of toner patches
Data Source
AI summary
There is provided image forming apparatus including: photosensitive member; developing roller configured to supply a developer to the photosensitive member; belt to which a developer image is to be transferred from the photosensitive member; sensor; and controller configured to execute a developing bias correcting process for correcting a developing bias to be applied to the developing roller. The developing bias correcting process includes: a setting process for setting testing biases, all of the testing biases being smaller than an old developing bias; a forming process for forming developer images on the belt by using the testing biases set in the setting process; a detecting process for detecting densities of the developer images formed in the forming process by the sensor; and a calculating process for calculating the developing bias based on the densities of the developer images detected in the detecting process.