Charging Roller Voltage Control for Lateral Stripe Suppression
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the DC charging type often experiences charging non-uniformity leading to lateral stripes due to unstable peeling discharges at the downstream charging gap, especially at high speeds, and the existing solutions either shorten the lifespan of components or increase energy consumption.
Innovation Solution
An image forming apparatus with a charging roller that applies only a DC voltage, equipped with a detecting member to monitor the current flow and adjust the DC voltage settings based on detected currents during non-image forming periods to ensure stable downstream discharge potential differences, preventing lateral stripe generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the photosensitive member moves faster to improve productivity, then productivity increases, but charging non-uniformity and lateral stripe generation worsen due to unstable peeling discharge at the downstream charging gap
Solution Approach 1:
The patent applies preliminary exposure to the upstream charging gap portion before the photosensitive member reaches the downstream charging gap. This pre-charges the upstream region, preventing unstable peeling discharge at the downstream gap even at high speeds, thereby maintaining charging uniformity while enabling high productivity
Solution Approach 2:
The patent changes the electrical parameters by applying a voltage higher than the discharge start voltage specifically to the upstream charging gap portion. This parameter change ensures stable charging at high speeds by preventing the conditions that lead to unstable peeling discharge at the downstream gap
2Manufacturing precision
If a voltage higher than discharge start voltage is applied to the upstream charging gap portion to prevent lateral stripe, then charging uniformity improves, but energy consumption increases
Solution Approach 1:
The patent applies a voltage higher than the discharge start voltage only to the upstream charging gap portion, not to the entire charging roller. This localized application of high voltage prevents lateral stripe generation while minimizing overall energy consumption by limiting the high voltage region to only where it is needed
3Manufacturing precision
If the potential difference at the downstream charging gap is increased to stabilize discharge, then lateral stripe generation decreases, but component stress increases potentially shortening lifespan
Solution Approach 1:
The patent applies preliminary exposure to the upstream charging gap portion, which prevents unstable peeling discharge at the downstream charging gap. This approach stabilizes the discharge process without requiring increased potential difference at the downstream gap, thereby maintaining charging uniformity while reducing stress on components
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 effectively suppresses lateral stripe generation without shortening the lifespan of components or increasing energy consumption, maintaining image quality and productivity even at high speeds.
Implementation Method 1
a voltage is applied to a core metal of the charging roller to cause minute electric discharge in the neighborhood of a contact nip between the charging roller and the photosensitive member and thus a surface of the photosensitive member is electrically charged
Implementation Method 2
a detecting member to detect a current flowing from the charging member into the photosensitive member
Data Source
AI summary
An image forming apparatus includes a photosensitive member, a charging roller, a voltage source, a current detecting member, and a setting portion configured to set the DC voltage applied to the charging roller in an image forming period on the basis of a detection result of the detecting member when a DC voltage less than a discharge start voltage is applied from the voltage source to the charging roller in a period other than the image forming period, wherein the setting portion sets the DC voltage so that an absolute value of the DC voltage when an absolute value of the detected current is a first value is larger than an absolute value of the DC voltage when the absolute value of the detected current is a second value smaller than the first value.