Alternating-Current Bias Control for Image Uniformity
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Solution Overview
Problem
Existing image forming apparatuses face challenges in balancing the bias between the developing roller and the photoconductive member and the magnetic roller, leading to issues with forming a thin toner layer and collecting toner efficiently, especially with faster rotation and smaller diameters, which results in image nonuniformity and ghost phenomena.
Innovation Solution
An image forming apparatus with a developing roller and a magnetic roller using alternating-current biases with specific duty ratios and frequencies, where the duty ratio of the bias applied to the developing roller is greater than 100 minus the duty ratio of the bias applied to the magnetic roller, and the frequency of the magnetic roller's bias is higher than that of the developing roller's bias, to form a thin toner layer and improve developability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the photoconductive member and developing roller are rotated faster and made smaller in diameter to increase printing speed, then productivity is improved, but the bias balancing between the developing roller and photoconductive member and between the developing roller and magnetic roller becomes difficult to control, leading to image nonuniformity and ghost phenomena
Solution Approach 1:
The patent applies alternating-current biases with specific duty ratios to both the developing roller and magnetic roller. The periodic nature of alternating current allows the system to dynamically control toner transfer and collection, maintaining image uniformity even at high rotation speeds. The duty ratio parameters (D1 for developing roller, D2 for magnetic roller) create a periodic action pattern that balances the competing requirements of fast toner transfer and complete toner collection.
Solution Approach 2:
The patent introduces specific parameter relationships to control the bias balancing: the duty ratios must satisfy D1 > 100 - D2, and the frequency of the magnetic roller's alternating-current bias must be higher than that of the developing roller's bias. These parameter changes allow the system to maintain proper bias balance during high-speed operation, preventing image nonuniformity and ghost phenomena while preserving high productivity.
2Manufacturing precision
If an alternating-current bias is applied to the developing roller to improve toner transfer and prevent image fog, then developability is improved, but the bias balancing with the magnetic roller becomes more complex and difficult to control
Solution Approach 1:
Instead of using complex variable bias control, the patent employs alternating-current biases with fixed duty ratios applied periodically to both rollers. This periodic action simplifies the control mechanism while achieving the dual goals of improved toner transfer (via the developing roller's alternating-current bias) and proper toner collection (via the magnetic roller's alternating-current bias with higher frequency).
Solution Approach 2:
The patent establishes a feedback relationship between the two alternating-current biases through the duty ratio parameter relationship D1 > 100 - D2. This creates an interdependent control system where the bias parameters are linked, ensuring that adjustments to one roller's bias automatically consider the other roller's requirements, thereby simplifying overall bias balancing while maintaining high developability.
3Manufacturing precision
If the frequency of the alternating-current bias applied to the magnetic roller is increased to improve toner collection, then toner refresh capability is improved, but the bias balancing with the developing roller becomes more difficult
Solution Approach 1:
The patent uses periodic alternating-current biases with a specific frequency relationship (magnetic roller frequency > developing roller frequency). This periodic action with differentiated frequencies allows the magnetic roller to effectively collect and refresh toner while the duty ratio relationship D1 > 100 - D2 ensures that the bias balancing remains manageable despite the frequency difference.
Solution Approach 2:
The patent changes the frequency parameter of the magnetic roller's alternating-current bias to be higher than the developing roller's frequency, while simultaneously establishing the duty ratio parameter relationship D1 > 100 - D2. This combination of parameter changes enables improved toner collection efficiency through higher frequency action while maintaining manageable bias balancing through the compensating duty ratio relationship.
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 allows for easy balancing of biases, enhancing developability and reducing image nonuniformity, particularly for low tone images, while maintaining image density and preventing ghost phenomena.
Implementation Method 1
a magnetic roller for forming a magnetic brush thereon with a two-component developer containing a carrier and a toner
Implementation Method 2
a first alternating-current bias in the form of a rectangular wave... calculated using an application period of a voltage in a direction to transfer the toner from the developing roller toward the photoconductive member
Implementation Method 3
a second alternating-current bias in the form of a rectangular wave... calculated using an application period of a voltage in a direction to transfer the toner from the magnetic roller toward the developing roller
Data Source
AI summary
An image forming apparatus is provided with a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image formed on the photoconductive member by a first bias, and a magnetic roller for forming a magnetic brush thereon with a two-component developer and forming a thin toner layer on the developing roller by a second bias. If (D1) denotes the duty ratio of a first alternating-current bias included in the first bias and (D2) denotes the duty ratio of a second alternating-current bias included in the second bias, the duty ratios (D1, D2) satisfy the following relationship:D1>100−D2.