Developing Unit Magnetic Pole Segmentation for Developer Stability
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Solution Overview
Problem
In image forming apparatuses, the existing developing units using a two-component developer with non-magnetic toner and magnetic carrier face issues with developer deterioration, uneven image density, and coating defects due to unstable magnetic forces and shear, leading to rough images and decreased toner uniformity.
Innovation Solution
A developing unit with a cylindrical developing sleeve and a magnetic field generating portion having multiple fixed magnetic poles, including a drawing-up pole and a cut pole, is designed to maintain a stable magnetic field with a Fr flat area and Fr attenuation area, ensuring consistent developer conveyance and regulation, thereby reducing shear and stabilizing image density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single magnetic pole is used to draw up and regulate developer thickness, then developer compression is reduced and deterioration is suppressed, but magnetic force becomes weak causing unstable developer amount and coating defects
Solution Approach 1:
The magnetic pole is divided into multiple segments (first magnetic pole and second magnetic pole) arranged in the circumferential direction. This segmentation allows each pole to contribute to the overall magnetic force while distributing the load, preventing any single pole from causing excessive compression. The segmented structure maintains strong magnetic force for stable developer bearing while reducing localized compression effects.
Solution Approach 2:
Different regions of the magnetic pole structure are designed with different properties. The first and second magnetic poles are positioned to create specific magnetic field distributions in different areas. This local differentiation allows optimization of magnetic force in the developer bearing region while controlling compression in other regions, resolving the contradiction between force strength and compression reduction.
2Manufacturing precision
If two magnetic poles (drawing-up pole and cut pole) are provided, then developer thickness regulation is improved, but shear compression is applied causing developer deterioration and image quality issues
Solution Approach 1:
The magnetic pole structure is segmented into multiple poles (first and second magnetic poles) positioned at specific angular intervals. This segmentation distributes the magnetic force application points, reducing the shear compression that would occur with a single concentrated magnetic field. The segmented arrangement maintains effective thickness regulation while minimizing developer deterioration.
Solution Approach 2:
Instead of using a single strong magnetic pole that creates high compression, the invention uses multiple weaker poles arranged to achieve the same regulatory function with reduced compression. This inverted approach - multiple distributed poles rather than one concentrated pole - maintains thickness control while eliminating the harmful compression effect.
3Object-affected harmful factors
If magnetic force is lowered to reduce developer compression, then developer deterioration is reduced, but developer amount upstream of regulating blade decreases and coating defects occur
Solution Approach 1:
The magnetic pole is divided into multiple segments that collectively provide the necessary magnetic force. Each segment contributes a portion of the total magnetic force, and their combined effect maintains strong developer bearing capability upstream of the regulating blade. This segmented approach prevents the need to lower overall magnetic force while still reducing localized compression through distributed force application.
Solution Approach 2:
Multiple magnetic poles are combined to create a cumulative magnetic effect. The first and second magnetic poles work together to maintain sufficient magnetic force for stable developer amount upstream of the regulating blade. By merging the effects of multiple poles, the system achieves both strong overall magnetic force and reduced localized compression.
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 suppresses developer deterioration, stabilizes image formation, and maintains consistent image quality over a long period by optimizing magnetic forces for efficient developer conveyance and uniform toner distribution.
Implementation Method 1
a magnetic field generating portion configured to be disposed on an inner side of the developing sleeve, and to have a plurality of fixed magnetic poles which generates a magnetic field which bears the developer on the developing sleeve
Implementation Method 2
at least a drawing-up pole which draws up the developer in the developing container, and bears the developer on the developing sleeve
Data Source
AI summary
A developing unit includes a developing container, a developing sleeve, a developer regulating member, and a magnetic field generating portion. The magnetic field generating portion includes a drawing-up pole and a cut pole. In addition, in a peak-to-peak area, the magnetic field generating portion includes at least one of an Fr flat area in which Fr is substantially constant and an Fr attenuation area in which Fr attenuates toward the cut pole side from the drawing-up pole side, and is configured that Fθ is oriented toward the same direction as a direction of rotation of the developing sleeve in the entire peak-to-peak area.