Image Forming Apparatus Voltage Control for Graininess
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in maintaining optimal graininess and density difference in toner images due to changes in AC developing bias voltage frequency, leading to increased toner consumption and carrier adhesion issues.
Innovation Solution
An image forming apparatus that adjusts the frequency of the AC developing bias voltage and DC developing bias voltage in conjunction with the charging bias voltage, specifically stopping AC voltage output, changing DC voltage, and then restarting AC voltage at a different frequency, while ensuring the charging bias voltage is set appropriately to prevent carrier adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the frequency of AC developing bias voltage is changed to optimize graininess, then image quality improves, but carrier adhesion to toner image occurs
Solution Approach 1:
The patent applies preliminary action by changing the DC developing bias voltage before changing the AC voltage frequency. This sequence prevents carrier adhesion from occurring during the frequency transition, while still allowing the AC frequency to be optimized for graininess. The DC voltage is adjusted first to a predetermined value, then the AC frequency is changed, ensuring that carriers do not adhere to the toner image during the parameter transition.
2Manufacturing precision
If DC developing bias voltage is changed to control image density, then density difference improves, but carrier adhesion increases
Solution Approach 1:
The patent uses preliminary action by establishing the DC voltage at a predetermined value before initiating AC frequency changes. This pre-setting of DC voltage controls the density difference while preventing carrier adhesion from occurring during subsequent frequency adjustments. The predetermined DC voltage level is chosen to optimize density difference while maintaining carrier stability.
3Adaptability or versatility
If AC voltage frequency is adjusted dynamically, then image quality adapts to different screen rulings, but toner consumption increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the AC voltage frequency based on the screen ruling of the image data. When high-resolution images requiring fine screen rulings are detected, the AC frequency is increased to improve graininess. When lower resolution is sufficient, the frequency is reduced to minimize toner consumption. This adaptive parameter adjustment optimizes the balance between image quality and resource efficiency.
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 maintains low graininess and density difference, prevents toner consumption increases, and avoids carrier adhesion to the toner image, enabling high-quality image formation with controlled voltage changes.
Implementation Method 1
a developing bias is applied to the developing roller so as to form an electric field for movement of the toner from the developing roller to the photosensitive drum
Implementation Method 2
an electrostatic latent image support member; an electrostatic latent image forming section for forming an electrostatic latent image on the electrostatic latent image support member
Data Source
AI summary
An image forming apparatus having: an electrostatic latent image support member; an electrostatic latent image forming section; a developer support member; a first voltage applying device for applying a developing bias voltage that is a superimposed voltage of a first DC voltage and a first AC voltage to the developer support member; and a controller for controlling the first voltage applying device. The first voltage applying device is controlled to stop an output of the first AC voltage at a first frequency, to change the first DC voltage outputted therefrom from a first voltage value to a second voltage value and to start an output of the first AC voltage at a second frequency, in this order. The controller selects a screen ruling for each page in accordance with image data and determines the output from the first voltage applying device in accordance with the selected screen ruling.