Transfer Bias Control for Electrophotographic Image Forming Apparatus
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Solution Overview
Problem
Image forming apparatuses face challenges in shortening the first image output time (FCOT) while minimizing power consumption and avoiding irregular image density and horizontal streaks due to timing issues with transfer bias application in electrophotographic processes.
Innovation Solution
The image forming apparatus controls the primary transfer bias by applying it when the charging start position of the photosensitive drum arrives at the transfer position, using a two-step voltage approach with an initial lower duty cycle to prevent overshoot and stabilize the transfer potential quickly, allowing for immediate image formation without horizontal streaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the process linear velocity is accelerated to shorten the first image output time, then the first image output time is reduced, but the power consumption increases
Solution Approach 1:
The transfer bias is applied in advance during the charging phase rather than waiting for the complete image formation process. Specifically, the transfer bias application timing is set to start when the charging start position arrives at the transfer position, which is before the developing and transferring positions are reached. This preliminary application of transfer bias prepares the photosensitive member surface in advance, allowing the system to achieve short first image output time without needing to accelerate the entire process linear velocity, thereby avoiding increased power consumption.
2Loss of time
If the transfer bias is applied early to shorten the first image output time, then the first image output time is reduced, but horizontal streaks and irregular image density occur
Solution Approach 1:
The patent applies a two-step voltage approach for the transfer bias. In the first step, a first transfer bias with a first voltage value is applied when the charging start position arrives at the transfer position. In the second step, a second transfer bias with a second voltage value (different from the first) is applied when the writing start position arrives at the transfer position. This parameter change in voltage timing and magnitude allows the system to achieve early transfer bias application for shortened first image output time while maintaining uniform image density and avoiding horizontal streaks.
Solution Approach 2:
The transfer bias voltage is made dynamic rather than static. The system transitions from a single fixed voltage value to a time-varying voltage profile with at least two distinct voltage levels applied at different timing phases. This dynamic adjustment of transfer bias parameters enables the system to optimize both the timing (for reduced first image output time) and the quality (for uniform image density without streaks).
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 configuration effectively reduces the first image output time (FCOT) while ensuring uniform image density and eliminating undesirable horizontal streaks, enhancing operational efficiency and image quality.
Implementation Method 1
a charging roller 15 serving as a charger... A place on a surface 102a of the photosensitive drum 102 charged by the charging roller 200 is referred to as a charging position
Implementation Method 2
illuminating the charged surface with laser light associated with an image data. The thus-obtained electrostatic latent image is developed with toner
Implementation Method 3
A place on the surface 102a at which the electrostatic latent image is developed by the developing roller 300, hence forming a toner image
Implementation Method 4
A place on the surface 102a at which the transfer roller 400 transfers the toner image onto a recording medium or an intermediate transfer belt is referred to as a transfer position
Data Source
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AI summary
An image forming apparatus (100) includes a charging bias output device (22), a developing bias output device (23), a transfer bias output device (24), and a controller (20). The controller (20) controls the transfer bias output device (24) to supply a transfer bias from a time at which a first position of a photosensitive member (2) arrives at a transfer position after the charging bias output device (22) starts supplying a charging bias. An initial value of the transfer bias is controlled to be smaller than a normal set value for a predetermined time period (Tc) which is a time after the transfer bias starts to be supplied and within a time corresponding to a rise time (Ta) during which a surface potential of the photosensitive member (2) reaches a predetermined potential after the charging bias starts to be output. The first position of the photosensitive member (2) is a position at which a charging device (15) start charging the photosensitive member (2).