Transfer Voltage Control for Toner Image Density Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In image forming apparatuses, when the length of the adjustment toner image exceeds the circumferential length of the photosensitive drum, applying a voltage higher than the discharge start voltage leads to density unevenness and potential reversal, causing issues with image density adjustment and subsequent image formation due to remaining photo-carriers.
Innovation Solution
Applying a voltage of the same polarity as the toner charge but less than the discharge start voltage while the optical sensor-irradiated region passes through the transfer portion, and switching to a voltage greater than or equal to the discharge start voltage after the region has rotated once, to prevent density unevenness and photo-carrier retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a voltage higher than the discharge start voltage is applied to the transfer unit, then the optical sensor trace is reduced, but density unevenness is formed on the adjustment toner image due to photosensitive drum potential change
Solution Approach 1:
The patent applies a voltage that dynamically changes over time: initially applying a voltage higher than the discharge start voltage to reduce optical sensor traces, then switching to a voltage lower than the discharge start voltage to prevent density unevenness. This temporal dynamic adjustment resolves the contradiction between reducing traces and maintaining density uniformity.
Solution Approach 2:
The patent implements periodic voltage application cycles where the transfer unit voltage is alternately adjusted between high (for trace reduction) and low (for uniform density) levels. This periodic action allows the system to achieve both trace reduction and density uniformity by cycling through different voltage states at appropriate times.
2Measurement precision
If the length of the adjustment toner image is increased to improve adjustment accuracy, then detection precision is improved, but photosensitive drum potential changes causing density unevenness
Solution Approach 1:
The patent uses dynamic voltage adjustment during the transfer process to accommodate long adjustment toner images. By changing the voltage level at appropriate intervals, the system maintains consistent photosensitive drum potential throughout the entire image formation process, enabling both long image lengths for accuracy and uniform density.
3Object-affected harmful factors
If voltage of negative polarity greater than discharge start voltage is applied to reduce optical sensor trace, then trace is reduced, but photo-carriers remain on photosensitive drum causing traces in subsequent images
Solution Approach 1:
The patent segments the voltage application process into distinct phases: a first phase with high voltage for trace reduction, and a second phase with low voltage to eliminate photo-carriers. This segmentation allows each voltage level to perform its specific function without causing harmful side effects.
Solution Approach 2:
The patent applies voltage periodically in two stages: first applying high voltage to reduce optical sensor traces, then applying low voltage to discharge remaining photo-carriers. This periodic two-stage approach eliminates both types of traces without leaving photo-carriers on the drum.
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 prevents density unevenness and exposure traces on subsequent images by maintaining consistent image formation conditions and ensuring photo-carriers are effectively discharged, enhancing image quality and accuracy.
Implementation Method 1
A detection unit irradiates the adjustment toner image on the photosensitive member with light to detect the adjustment image
Implementation Method 2
A potential of an irradiated portion on the adjustment toner image which has been irradiated with light thus locally shifts to the positive polarity on the photosensitive member
Implementation Method 3
a transfer member configured to transfer the toner image on the photosensitive member to a transfer material in a transfer portion
Implementation Method 4
a voltage of the same polarity as the charge polarity of toner and greater than or equal to a discharge start voltage to the transfer member while the photosensitive member rotates at least once after the region of the photosensitive member which the optical sensor has irradiated with light passes through the transfer portion
Data Source
AI summary
If the length of an adjustment toner image is longer than a circumferential length of a photosensitive member, a voltage which is less than a discharge start voltage is applied while a region of the photosensitive member irradiated with light by an optical sensor passes through a transfer portion. Further, a voltage which is greater than or equal to the discharge start voltage is applied while the photosensitive member rotates at least once after the region of the photosensitive member irradiated with light by the optical sensor passes through the transfer unit. As a result, density unevenness in the adjustment toner image and a potential change in the photosensitive member due to the optical sensor exposing the adjustment toner image are prevented.