Developing Sleeve Magnet With Local Minimum Magnetic Force Gradient
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Solution Overview
Problem
Toner scattering in image forming apparatuses using the two-component development method leads to contamination and adverse effects on image quality, particularly in the region between the developing roller and the regulation blade, where toner is scattered and collected by a magnetic brush, causing stains and internal contamination.
Innovation Solution
The developing device incorporates a developing container with a developer carrying member and a regulation member, featuring a magnet with a specific magnetic pole configuration and magnetic force gradient distribution, including a local minimum value near the position where the vertical magnetic force is 0, to minimize toner scattering by controlling the magnetic attraction and conveyance forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional magnet configuration is used in the developing roller, then the developer can be conveyed and images can be developed, but toner scattering occurs in the region from the regulation blade to the developing region, causing contamination and image stains
Solution Approach 1:
The magnet is designed with non-uniform magnetic pole arrangements where the density and strength of magnetic poles vary at different circumferential positions. Specifically, the magnetic pole density is reduced in the region from the regulation blade to the developing region to minimize toner scattering, while maintaining adequate magnetic force in other regions for proper developer conveyance and image development.
Solution Approach 2:
The invention changes the magnetic field parameters by creating a specific magnetic force distribution pattern. The magnetic force is designed to have a local minimum value in the region from the regulation blade to the developing region, and the gradient of magnetic force is controlled to have a local maximum value in this region, thereby suppressing toner scattering while maintaining development functionality.
2Productivity
If the magnetic force is increased to improve developer conveyance, then developer transport efficiency improves, but toner scattering increases and causes contamination
Solution Approach 1:
Different regions of the magnet are designed with different magnetic properties. The magnetic pole density and strength are locally optimized: regions requiring strong magnetic force for developer conveyance have higher pole density, while the region from the regulation blade to the developing region has reduced pole density to minimize toner scattering.
Solution Approach 2:
The magnet is segmented into multiple magnetic poles arranged at different densities around the circumference. This segmentation allows independent optimization of magnetic force in different regions, enabling efficient developer conveyance in some regions while suppressing toner scattering in the critical region from the regulation blade to the developing region.
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 toner scattering while maintaining optimal developer conveyance and image development properties, ensuring reduced contamination and improved image quality.
Implementation Method 1
a magnet having a plurality of magnetic poles arranged at a prescribed distance from each other in the circumferential direction
Implementation Method 2
a magnetic brush is formed on a surface of the developing sleeve
Implementation Method 3
the vertical magnetic force gradient has a local minimum value near a position at which the vertical magnetic force is 0 between the downstream-side surface of the regulation member and the downstream-side magnetic pole
Data Source
AI summary
A developing device includes a developing container storing a two-component developer containing a magnetic carrier and a toner, a developer carrying member carrying the developer on its outer circumferential surface, and a regulation member arranged to be opposed at a prescribed distance to the developer carrying member. The developer carrying member includes a developing sleeve on which a magnetic brush is formed, and a magnet secured in the developing sleeve and having a plurality of magnetic poles including a regulation pole opposed to the regulation member and a downstream-side magnetic pole arranged downstream of the regulation pole with respect to the rotation direction of the developing sleeve. The magnet is such that the vertical magnetic force gradient [mT/°] has a local minimum value near a position at which the vertical magnetic force is 0 [mT] between the downstream-side surface of the regulation member and the downstream-side magnetic pole.