Developing Sleeve AC Voltage Control for Image Density Fluctuations
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Solution Overview
Problem
High-speed image forming apparatuses using two-component development face issues with cyclic density fluctuations, voids at density boundaries, and degradation of granularity due to eccentric developing sleeves, which affect image quality.
Innovation Solution
A developing device with a cylindrical developing sleeve that rotates and bears developer using a magnetic field generator, applying an AC development voltage with a frequency of 2.0 kHz or lower and a positive-side duty ratio between 4% to 20% to inhibit cyclic density fluctuations and improve granularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If DC bias development is used, then development simplicity is maintained, but cyclic density fluctuation occurs due to developing sleeve eccentricity
Solution Approach 1:
The patent applies AC bias development with a specifically controlled positive-side duty ratio (4%-20%) to create periodic voltage cycles that alternately attract and release toner. This periodic action compensates for the cyclic density fluctuations caused by developing sleeve eccentricity, as the varying voltage during each cycle counteracts the density variations produced by the eccentric rotation.
Solution Approach 2:
The patent changes the electrical parameter (bias voltage waveform) from DC to AC with a controlled positive-side duty ratio. This parameter change transforms the development mechanism to one that can dynamically compensate for mechanical imperfections in the developing sleeve, thereby improving image density uniformity while maintaining development effectiveness.
2Manufacturing precision
If AC bias development with high frequency is used, then cyclic density fluctuation is reduced, but void at density boundaries occurs
Solution Approach 1:
The patent precisely controls the positive-side duty ratio parameter within 4%-20% range and limits AC frequency to 2.0 kHz or lower. This optimized parameter combination reduces cyclic density fluctuation while preventing the excessive toner attraction and release that causes voids at density boundaries, achieving a balance between the two competing requirements.
3Object-affected harmful factors
If AC bias development with low frequency is used, then void at density boundaries is suppressed, but granularity degradation occurs
Solution Approach 1:
The patent optimizes the positive-side duty ratio to 4%-20% and sets AC frequency at 2.0 kHz or lower, creating a specific voltage waveform profile. This optimized waveform provides sufficient toner attraction time while limiting excessive release, thereby suppressing granularity degradation even at lower frequencies where void prevention is achieved.
4Ease of manufacture
If developing sleeve eccentricity is not controlled, then manufacturing cost is reduced, but cyclic density fluctuation and image quality degradation occur
Solution Approach 1:
The patent converts the harmful effect of developing sleeve eccentricity into a beneficial one by using AC bias development with controlled positive-side duty ratio. The periodic voltage cycles create corresponding periodic toner distribution patterns that can be synchronized with or counteract the mechanical eccentricity, transforming a manufacturing defect into a controllable parameter.
Solution Approach 2:
The patent changes the electrical control parameter (bias voltage waveform with specific duty ratio) to compensate for mechanical parameter variations (developing sleeve eccentricity). This electrical compensation approach allows relaxed mechanical tolerances while maintaining image quality, reducing manufacturing costs.
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
The solution effectively suppresses cyclic density fluctuations, voids at density boundaries, and degradation of granularity, maintaining high image quality by optimizing the AC development voltage parameters.
Implementation Method 1
a magnetic field generator provided inside the developing sleeve generates a magnetic field that causes developer particles to stand on end, in the form of a magnetic brush, on the developing sleeve
Implementation Method 2
the cylindrical developing sleeve to rotate and bear developer on an outer circumferential surface thereof with magnetic force of the magnetic field generator disposed inside the developing sleeve
Implementation Method 3
toner borne on the developing sleeve moves toward the latent image bearer due to differences in surface potential between the developing sleeve, to which development voltage is applied, and the latent image bearer
Data Source
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AI summary
A developing device (5) includes a developer bearer (50) to carry, by rotation, developer including toner and magnetic carrier to a development range facing a latent image bearer (1) to bear a latent image. The developer bearer (50) includes a magnetic field generator (55) having multiple magnetic poles (P1, P2, P3, P4, P5) and a cylindrical developing sleeve (51) to rotate and bear developer on an outer circumferential surface thereof with magnetic force of the magnetic field generator (55) disposed inside the developing sleeve (51). The developing sleeve (51) receives development voltage including an AC component having a frequency of 2.0 kHz or lower, and a duty ratio of a component having a polarity opposite a toner normal charge polarity of the AC component is within a range from 4% to 20%.