Image Forming Apparatus Charging Control via DC Current Detection
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Solution Overview
Problem
In electrophotographic image forming apparatuses, charging rollers can become dirty, leading to deviations in the desired surface potential of photoconductors, resulting in unwanted images, and existing methods that use surface potential sensors are costly and limited in layout.
Innovation Solution
An image forming apparatus that detects direct current flowing between a photoconductor and a conductive member without using a surface potential sensor, switching between first and second DC biases based on the speed of the image bearer, and adjusting the first DC bias accordingly to maintain appropriate surface potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a surface potential sensor is used to detect and adjust the charging DC bias, then the surface potential control precision is improved, but the device cost increases and the layout flexibility is reduced
Solution Approach 1:
The patent introduces a current detector as an intermediary device to indirectly measure surface potential by detecting the DC component of current flowing between the photoconductor and conductive member. This current detection method serves as a mediator that avoids the need for direct surface potential sensing, thereby reducing device complexity and cost while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical/electrical surface potential sensor system with an electrical current detection system. By measuring the DC component of current and using it to infer surface potential, the system substitutes a simpler electrical measurement approach for the more complex surface potential sensing mechanism
2Stability of the object's composition
If the charging DC bias is adjusted to compensate for dirt on the charging roller, then the surface potential stability is improved, but the control complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the detected DC component of current is used to adjust the charging DC bias. The controller continuously monitors the current and modifies the charging bias accordingly, creating a closed-loop feedback system that automatically compensates for surface potential deviations caused by dirt or other issues
Solution Approach 2:
The system performs self-adjustment by using the detected current information to automatically modify its own charging parameters. The controller adjusts the charging DC bias based on the detected DC component, enabling the system to self-correct surface potential issues without external intervention
3Adaptability or versatility
If the DC bias is changed according to image bearer speed, then the adaptability to different operating conditions is improved, but the control complexity increases
Solution Approach 1:
The patent makes the charging DC bias dynamic by adjusting it according to the speed of the image bearer. The controller modifies the bias in real-time based on speed variations, transforming a static charging parameter into a dynamic one that adapts to changing operating conditions
Solution Approach 2:
The patent changes the charging DC bias parameter in response to speed changes. By adjusting this electrical parameter according to the mechanical parameter (speed), the system adapts its electrical characteristics to match varying operational conditions, improving performance across different speeds
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 method effectively maintains the desired surface potential of the photoconductor, reducing the occurrence of unwanted images caused by dirt or other issues, while avoiding the costs and layout limitations of surface potential sensors.
Implementation Method 1
The power source generates a voltage. The voltage is applied to the voltage applying device facing the image bearer.
Implementation Method 2
The circuitry detects a DC component of a current flowing between the power source and the image bearer during application of the second DC bias.
Data Source
AI summary
An image forming apparatus includes an image bearer, a power source to generate a voltage, a voltage applying device facing the image bearer, the voltage applying device being applied with the voltage, and circuitry to control the voltage of the power source. The circuitry switches the voltage between a first direct current (DC) bias and a second DC bias different from the first DC bias, and changes the first DC bias in accordance with a speed of the image bearer, based on a DC component of a current flowing between the power source and the image bearer during application of the second DC bias.