Saw-Tooth Charging Device Current Control for Ozone Reduction
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Solution Overview
Problem
Image forming apparatuses using saw-tooth type charging devices face issues with discharge defects, image blurring, and white spots due to excessive ozone generation, which shortens the photoreceptor's life and affects image quality.
Innovation Solution
An image forming apparatus with a control system that adjusts the saw-tooth current based on print cumulative count, increasing it for charging and decreasing it during cleaning to minimize ozone generation, while using a cleaning member to maintain the saw teeth, thereby stabilizing image quality and extending the charging portion's life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the saw-tooth current is increased to maintain charge life under initial conditions, then the charging performance is improved, but excessive ozone is generated causing image defects
Solution Approach 1:
The patent applies dynamics by making the saw-tooth current adjustable rather than fixed. The control unit dynamically changes the current value based on the accumulated number of sheets, allowing the system to adapt charging conditions to actual usage state, thereby reducing ozone generation while maintaining charge life
Solution Approach 2:
The patent changes the electrical parameter (saw-tooth current value) based on usage accumulation. By adjusting this parameter according to the number of sheets processed, the system optimizes the balance between charging performance and ozone generation, resolving the contradiction between charge life and harmful emissions
2Object-generated harmful factors
If the saw-tooth current is decreased to reduce ozone generation, then image defects are reduced, but the charging performance deteriorates
Solution Approach 1:
The patent implements periodic adjustment of the saw-tooth current based on accumulated usage. The current is reduced at specific intervals (when certain number of sheets are accumulated) to minimize ozone generation, while maintaining adequate charging performance through timely adjustments
Solution Approach 2:
The system uses feedback from the accumulated sheet count to automatically adjust the saw-tooth current. This feedback mechanism ensures that the current is optimized based on actual usage patterns, preventing both excessive ozone generation and charging performance deterioration
3Reliability
If a cleaning member is used to clean the saw teeth, then discharge defects are prevented, but the cleaning member has limited life and requires replacement
Solution Approach 1:
The patent applies self-service by enabling the cleaning member to automatically clean the saw teeth during operation. The cleaning member rotates and contacts the saw teeth to remove accumulated contaminants, allowing the charging device to maintain discharge performance without external intervention
Solution Approach 2:
The cleaning member performs preliminary cleaning action before contaminants can cause significant discharge defects. By continuously or periodically cleaning the saw teeth, the system prevents accumulation of toner and dust that would lead to discharge failures
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 effectively reduces image defects such as blurring and white spots, stabilizes image quality, and prolongs the life of the charging portion by controlling ozone generation and maintaining the saw teeth's cleanliness.
Implementation Method 1
a cleaning member that cleans the needle electrode by moving along an array direction of the plurality of the saw teeth while sequentially contacting with tip portions of the plurality of the saw teeth
Implementation Method 2
a cleaning member that cleans the needle electrode by moving along an array direction of the plurality of the saw teeth while sequentially contacting with tip portions of the plurality of the saw teeth
Implementation Method 3
The noncontact type charging device charges the surface of the photoreceptor by discharge from an electrode to which high-voltage power supply is applied, so-called corona discharge
Data Source
AI summary
In an image forming apparatus for forming an image by electrophotography, a charging device is comprised of a needle electrode in which a plurality of saw teeth are arrayed in one direction; a cleaning rubber roller that cleans the needle electrode; a cleaning member supporter; a moving portion that moves the cleaning member supporter; and a control portion that controls the charging device, and the control portion includes a function to increase a saw-tooth current value by increasing print cumulative count; and a function to decrease the saw-tooth current value at the time of performing cleaning.