Development Device Bias Control for Carrier Development
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Solution Overview
Problem
The touchdown development method in image forming apparatuses faces issues with carrier development, leading to white or black spots in printed images, especially under high-humidity conditions, due to the deterioration of magnetic carriers, which affects image quality and longevity.
Innovation Solution
A development device employing a toner carrying member and a toner supply member with specific bias configurations to prevent carrier movement, using a two-component developer with a magnetic brush, where the potential difference between the development and supply biases is controlled to maintain a thin toner layer and prevent carrier transfer, and an alternating-current bias is adjusted based on temperature and humidity or accumulated drive time to prevent carrier development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the two-component development method is used to maintain stable charge on toner for longer life, then toner longevity is improved, but carrier deteriorates under high-humidity conditions causing carrier development and white or black spots in printed images
Solution Approach 1:
The patent divides the development process into two distinct stages: a charging area where the two-component developer contacts the toner to transfer charge, and a development area where only the charged toner contacts the photoconductor without carrier presence. This spatial segmentation prevents carrier deterioration and carrier development while maintaining stable toner charging over extended periods.
Solution Approach 2:
The patent extracts the magnetic carrier from the development area, allowing it to remain only in the charging area. This removal of the carrier from the development zone eliminates the problem of carrier deterioration and subsequent carrier development on the photoconductor, while the charged toner continues to be transferred effectively to form images.
2Reliability
If the one-component development method is used to achieve higher image quality by contacting toner only with photoconductor, then image quality is improved, but toner charging capacity decreases due to additive adhesion on charge roller
Solution Approach 1:
The patent introduces a separate charging area where the two-component developer performs the charging function, distinct from the development area where image formation occurs. This segmentation allows effective toner charging without the limitations of the one-component method, maintaining both charge quantity and image quality.
3Reliability
If the touchdown development method is used to combine advantages of both methods, then toner life and image quality are improved, but carrier is transferred through development roller to photoconductor causing carrier development under high-humidity conditions
Solution Approach 1:
The patent extracts the carrier from the development area, preventing its transfer to the photoconductor. By confining the carrier to the charging area only and eliminating its presence in the development zone, the harmful effect of carrier development is completely prevented while retaining the benefits of stable toner charging.
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
Effectively prevents carrier development and maintains image quality by controlling the toner layer thickness and development performance, ensuring consistent image density and reducing the occurrence of white or black spots across various environmental conditions.
Implementation Method 1
forming with a magnetic brush a thin toner layer on the toner carrying member
Implementation Method 2
adheres, by receiving a development bias composed of a first direct-current bias and a first alternating-current bias, toner to the surface of the image carrying member to develop an electrostatic latent image
Implementation Method 3
a potential difference between a peak voltage of the development bias on the opposite polarity side to the polarity of the toner and a peak voltage of the supply bias is set at a predetermined value or below
Data Source
AI summary
The first direct-current bias power supply applying the first direct-current bias Vdc1 and the first alternating-current bias power supply applying the first alternating-current bias Vac1 are connected to a development roller. The second direct-current bias power supply applying the second direct-current bias Vdc2 and the second alternating-current bias power supply applying the second alternating-current bias Vac2 are connected to a magnetic roller. The peak-to-peak value Vpp of the first alternating-current bias Vac1 applied to the development roller remains the same, and the second alternating-current bias Vac2 that is in phase with the first alternating-current bias Vac1 and that has a peak-to-peak value of a predetermined value or above is applied to the magnetic roller. Thus, the potential difference between the peak voltage of the development bias on the opposite polarity side to the polarity of the toner and the peak voltage of a supply bias is set at a predetermined value or below.