Charging Roller AC Voltage Control for Image Quality
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Solution Overview
Problem
Image forming apparatuses using ion-conductive charging rollers face challenges in maintaining proper charging bias when the detected temperature and humidity by the main assembly's sensor differ from the actual charging roller's conditions, leading to improper charge images due to fluctuating charging characteristics and increased resistance in low humidity environments.
Innovation Solution
The apparatus employs a control system that calculates the absolute water content from temperature and humidity data and adjusts the AC voltage and frequency applied to the charging roller based on the detected environment, ensuring proper charging conditions even when the charging roller's temperature differs from the detected temperature, thereby maintaining optimal charging characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a charging roller using an ion-conductive agent is used to extend life, then the charging member strongly resists fluctuation by continuous use, but a change in charging characteristic by environment fluctuation becomes conspicuous
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the AC voltage amplitude and frequency based on detected environmental conditions (temperature and humidity). When the environment changes, the control unit modifies these parameters to compensate for the charging roller's reduced performance, thereby maintaining reliable charging characteristics while using an ion-conductive agent that provides extended life
2Ease of operation
If simple AC current control is applied to keep current constant, then control is straightforward, but the charging member cannot follow the change in charging characteristic in some cases
Solution Approach 1:
The patent implements feedback control by detecting the AC current passing through the photosensitive drum and using this information to adjust the AC voltage amplitude and frequency. This feedback mechanism allows the charging roller to adapt to environmental changes and maintain proper charging characteristics, going beyond simple constant current control while remaining practically operable
3Adaptability or versatility
If the charging roller resistance increases in low humidity environment, then the charging roller can operate in various conditions, but the electric discharge is not started until a considerably high peak AC voltage is applied
Solution Approach 1:
The patent addresses the high discharge start voltage issue in low humidity by dynamically changing the AC voltage parameters. The control unit detects humidity levels and adjusts both the amplitude and frequency of the AC voltage applied to the charging roller, enabling electric discharge to occur at appropriate voltage levels across different environmental conditions while maintaining the charging roller's versatility
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 suppresses the generation of improper charge images and ensures consistent charging performance by accurately accounting for environmental variations, improving the reliability of the image forming process.
Implementation Method 1
a charging member using a high electric charge-responsive substance such as an ion-conductive agent is used
Implementation Method 2
a surface of a photosensitive drum as a photosensitive member is electrically charged and exposed to light, so that an electrostatic latent image is formed
Implementation Method 3
the electric discharge is not started until a considerably high peak AC voltage is applied to the photosensitive drum
Data Source
AI summary
An image forming apparatus includes a photosensitive member (drum); a rotatable charging member for electrically charging the drum; a bias applying device for applying a charging bias to the charging member in the form of a DC voltage biased with an AC voltage; a current detector for detecting an AC current passing between the charging member and the drum; a temperature and humidity detector; a setting device for setting a condition of the charging bias on the basis of a plurality of detected AC currents passing between the charging member and the drum when a plurality of AC voltages depending on an output of the temperature and humidity detector are applied to the charging member; and a corrector for correcting the set condition of the charging bias on the basis of an output of the current detector when a predetermined AC voltage is applied to the charging member.