Photoconductor Charging Control via Load Impedance Feedback
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Solution Overview
Problem
In image forming apparatuses, maintaining uniform surface potential of a photoconductor while preventing excessive discharge that can degrade the photoconductor due to high peak values of sine AC voltage, which generates ozone and NOx.
Innovation Solution
An image forming apparatus that includes a charger, a transfer unit, a charging power supply for AC voltage, a transfer power supply for DC voltage or current, an output detector, and a controller. The controller calculates the load impedance of the photoconductor and adjusts the AC voltage output to ensure it converges to a predetermined value, minimizing excessive discharge and maintaining uniform surface potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the peak value of sine AC voltage is increased to charge the photoconductor uniformly at desired voltage, then charging uniformity is improved, but discharge is generated more than needed and the photoconductor is degraded by oxide such as ozone and NOx
Solution Approach 1:
The patent applies feedback control by detecting the output value of DC voltage or DC current from the transfer power supply and using this information to calculate load impedance of the photoconductor. The controller then adjusts the AC voltage output by the charging power supply based on this feedback, creating a closed-loop control system that optimizes charging while minimizing excessive discharge and photoconductor degradation.
Solution Approach 2:
The patent changes the parameters of AC voltage (peak value, frequency) applied to the charging roller based on detected load impedance. By dynamically adjusting these electrical parameters according to the photoconductor's state, the system achieves uniform charging at desired voltage while preventing excessive discharge that would generate harmful oxides and degrade the photoconductor.
2Reliability
If the peak value of sine AC voltage is increased to ensure adequate charging, then charging effectiveness is improved, but excessive discharge generates more ozone and NOx
Solution Approach 1:
The system uses feedback from the output detector that monitors DC voltage or current from the transfer power supply. This feedback enables the controller to accurately determine when adequate charging has been achieved and adjust the AC voltage accordingly, preventing excessive discharge that would generate harmful ozone and NOx while maintaining reliable charging effectiveness.
Solution Approach 2:
The patent applies partial action by providing just enough AC voltage to achieve uniform charging at the desired voltage level, rather than continuously applying high voltage. The controller adjusts the peak value of sine AC voltage to the minimum necessary level based on load impedance detection, ensuring charging effectiveness while minimizing excessive discharge and harmful gas generation.
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
The solution effectively charges the photoconductor uniformly at the intended potential, reducing unnecessary discharge and photoconductor degradation, thereby enhancing image quality and extending the life of the apparatus.
Implementation Method 1
a charging roller that functions as a charging unit is located to hold slight gap with the surface of the photoconductor that functions as an image bearer and high voltage superimposing sine AC voltage on DC voltage is applied to the charging roller
Implementation Method 2
By adopting those methods, it is possible to discharge between the charging roller and the surface of the photoconductor and acquire uniform surface potential of the photoconductor
Implementation Method 3
a transfer unit that transfers the toner image formed on the photoconductor to a transfer device for transferring the toner image to a sheet
Data Source
AI summary
An image forming apparatus includes a photoconductor, a charger that charges the photoconductor, a transfer unit that transfers a toner image formed on the photoconductor to a transfer device, a charging power supply that outputs AC voltage for applying a charging bias to the charger, a transfer power supply that outputs DC voltage or DC current for applying a transfer bias to the transfer unit, an output detector that detects an output value of the DC voltage or the DC current, and a controller that calculates load impedance of the photoconductor based on the detected output value of the DC voltage or DC current detected by the output detector while modifying the output of the AC voltage by the charging power supply and sets the output of the AC voltage that the load impedance starts converging into a predetermined value as an adjusted AC output to the charging power supply.