Charging Bias Timing Synchronization for Drum Uniformity
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Solution Overview
Problem
Electrophotographic image forming apparatuses face issues with nonuniform charging of the photosensitive drum due to improper timing of primary transfer bias voltage application, leading to unwanted horizontal stripes and increased First Copy Output Time (FCOT).
Innovation Solution
An image forming apparatus with a controller that synchronizes the primary transfer bias voltage with the charging bias voltage, ensuring the primary transfer bias begins to rise when the area of the photosensitive drum passing the charging position reaches the transfer position and completes rising when the charging bias has finished rising, maintaining a preset potential level to prevent nonuniform charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the primary transfer bias voltage is applied before the charging bias voltage reaches the desired level, then the First Copy Output Time is reduced, but the photosensitive drum becomes nonuniformly charged causing horizontal stripes
Solution Approach 1:
The controller starts raising the primary transfer bias voltage in advance, before the charging bias voltage reaches the desired level. This preliminary action allows the primary transfer bias to be ready when needed, reducing the First Copy Output Time while ensuring proper charging uniformity is maintained through coordinated timing control.
Solution Approach 2:
The system dynamically adjusts the timing of voltage application based on the actual charging state. The controller monitors the charging bias voltage level and coordinates the primary transfer bias voltage application accordingly, creating a dynamic timing relationship that optimizes both speed and image quality.
2Manufacturing precision
If the primary transfer bias voltage is delayed to ensure uniform charging, then horizontal stripes are prevented, but the First Copy Output Time increases
Solution Approach 1:
Instead of delaying the primary transfer bias voltage until charging is complete, the system applies it in advance and coordinates the timing. This preliminary application, combined with synchronized control, eliminates the need for waiting time while maintaining charging uniformity.
Solution Approach 2:
The controller ensures continuous coordination between charging bias and primary transfer bias voltage application. By maintaining synchronized timing throughout the process, the system achieves both uniform charging and reduced output time without interruption or delay.
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 reduces FCOT by ensuring uniform charging and preventing the occurrence of horizontal stripes, resulting in improved image quality and reduced wait time for the user.
Implementation Method 1
The peripheral surface of the photosensitive drum is negatively charged by charge bias high voltage
Implementation Method 2
In the transferring position 4, electrical discharge occurs because of the difference in potential level between the peripheral surface of the photosensitive drum and primary transfer roller
Implementation Method 3
scanning (exposing) the uniformly charged peripheral surface of the photosensitive drum to a beam of laser light or the like emitted while being modulated
Data Source
AI summary
An image forming apparatus includes an image bearing drum; a drum charging member, disposed at a charging position opposed to the drum, for applying the drum with a charging bias; a developing member for developing an electrostatic image formed on the drum with toner, with a developing bias; a transfer member for transferring a toner image from the drum onto a sheet, with a transfer bias; a transfer bias source for outputting the transfer bias; and a controller for effecting control to start raising of the transfer bias so as to correspond to a timing at which an area of the drum passing at a timing of starting of raising of the charging bias passes the transfer position and to complete the raising of the transfer bias so as to correspond to a timing at which an area of the drum passing at a timing of completion of raising of the charging bias passes the transfer position.