Developing Device Magnetic Pole Pattern for Density Control
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Solution Overview
Problem
In color image forming apparatuses using the electrophotographic method, density unevenness and developer overflow occur due to stress on the developer caused by magnetic forces and rotation torque, leading to unstable coating properties and increased maintenance needs.
Innovation Solution
A developing device with a multipolar magnet and a partition wall configuration that reduces magnetic stress, featuring a zero-gauss area between magnetic poles to minimize developer accumulation and ensure stable circulation, combined with a surface roughened opposed member to prevent developer fall-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnet is used to reduce developer amount on the developer container side of the regulating blade, then developer deterioration is reduced, but density unevenness is more likely to occur
Solution Approach 1:
The magnet is positioned at a specific location (upstream side of the regulating blade in the rotating direction) to create a localized magnetic field that reduces developer accumulation only where needed, while avoiding excessive magnetic force in other areas that would cause density unevenness
Solution Approach 2:
The magnetic field strength and position are optimized to balance two competing requirements: enough magnetic force to reduce developer deterioration, but not so much as to cause density unevenness in the developer distribution
2Manufacturing precision
If the developer conveying and stirring screw rotation speed is increased to enhance developer conveying ability, then coating property is stabilized, but stress on developer increases
Solution Approach 1:
The patent replaces increasing mechanical rotation speed with a magnetic field-based solution to control developer distribution and reduce stress on the developer particles
3Object-generated harmful factors
If the partition wall height is reduced to prevent developer accumulation, then developer overflow is prevented, but developer supply stability decreases
Solution Approach 1:
The partition wall is designed with different heights at different locations: lower height at the downstream end to prevent overflow, while maintaining sufficient height at the upstream end to ensure stable developer supply
Solution Approach 2:
The partition wall is divided into multiple sections with different heights, allowing different functional requirements to be met in different zones of the developing device
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 prevents density unevenness and developer overflow, maintaining stable coating properties and reducing maintenance requirements while ensuring efficient developer supply to the developing sleeve.
Implementation Method 1
a multipolar magnet which is arranged inside the developer bearing member; the multipolar magnet having a first magnetic pole which is arranged at a position opposing the regulating member or in an upstream side of a conveyance direction of the developer bearing member with respect to the position, and a second magnetic pole which is adjacent to the first magnetic pole in an upstream side of the first magnetic pole in the conveyance direction, and has the same polarity as that of the first magnetic pole
Implementation Method 2
the opposed part has surface roughness higher than an average particle diameter of the carrier
Data Source
AI summary
A magnet roller employs a magnetic pole pattern in which a first magnetic pole arranged substantially opposing a regulating blade in an upstream side of a rotation direction of a developing sleeve and a second magnetic pole next to the first magnetic pole in the upstream side have the same polarity, an opposing member having surface roughness higher than at least a particle diameter of carrier is arranged opposing the magnet roller at a position where magnetic force between the first magnetic pole and the second magnetic pole next to the first magnetic pole in the upstream side is almost zero, and an apex of a partition wall provided between a developer bearing member and a developer conveying member provided in a first chamber is positioned below a region where magnetic force formed by the magnet roller is almost zero.