Magnet Roller Flux Profile for Stable Developer Coating
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Solution Overview
Problem
Existing developing devices using a two-component developer face issues with developer stagnation and deterioration due to large and rapidly changing magnetic flux densities, particularly at the upstream side of the regulating member, leading to increased torque and toner deterioration, especially in high-speed image forming apparatuses.
Innovation Solution
A developing device design with a magnet roller having a regulating magnetic pole with two maximum magnetic flux densities in the normal direction, where the minimum position is downstream of the first maximum and upstream of the second maximum, with a 20° to 50° angle between them, and the regulating member is positioned between these peaks, ensuring a balanced magnetic attraction force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a magnetic flux density distribution with two peaks is used to stabilize developer coating amount, then developer coating stability is improved, but magnetic attraction force becomes large causing developer stagnation and toner deterioration
Solution Approach 1:
The patent applies local quality by creating different magnetic flux density characteristics at different angular positions around the magnet roller. Specifically, the upstream side (before the regulating member) has a magnetic flux density distribution with a gentle slope and smaller rate of change, while the downstream side has a steeper slope. This localized differentiation allows the upstream region to exert minimal magnetic attraction force on the carrier, preventing developer stagnation and toner deterioration, while still maintaining overall developer coating stability through the two-peak distribution.
Solution Approach 2:
The patent employs asymmetry in the magnetic flux density distribution by making the slope on the upstream side of the regulating member gentler than the slope on the downstream side. This asymmetric configuration ensures that the rate of change of magnetic flux density is smaller upstream, reducing the magnetic attraction force on the carrier in that region. Consequently, developer stagnation is prevented upstream of the regulating member while maintaining effective developer regulation downstream.
2Manufacturing precision
If magnetic flux density is increased to improve developer regulation, then developer amount control is improved, but magnetic attraction force increases causing developer stagnation upstream
Solution Approach 1:
The patent applies local quality by creating different magnetic flux density characteristics at different angular positions around the magnet roller. Specifically, the upstream side (before the regulating member) has a magnetic flux density distribution with a gentle slope and smaller rate of change, while the downstream side has a steeper slope. This localized differentiation allows the upstream region to exert minimal magnetic attraction force on the carrier, preventing developer stagnation and toner deterioration, while still maintaining overall developer coating stability through the two-peak distribution.
Solution Approach 2:
The patent applies partial action by concentrating the strong magnetic flux density peaks primarily on the downstream side of the regulating member, while keeping the upstream side's magnetic flux density with a gentler slope. This partial concentration of magnetic force achieves effective developer regulation at the regulating member location without subjecting the upstream developer to excessive magnetic attraction forces that would cause stagnation.
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 design stabilizes the developer coating amount and reduces toner deterioration by minimizing fluctuations in magnetic attraction force, thereby enhancing the reliability and performance of the developing process.
Implementation Method 1
a magnetic flux density distribution such that a magnetic flux density Br of a regulating pole, of a plurality of magnetic poles of a magnet roller, in a normal direction relative to the regulating pole opposing a regulating member has two maximum values (peaks)
Implementation Method 2
a magnetic attraction force Fr in a developing sleeve center direction induced in the carrier by the magnetic flux density
Data Source
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AI summary
An absolute value of a first maximum value is smaller than an absolute value of the second maximum value. With respect to a rotational direction of a rotatable developing member (24), an angle from a second maximum position to a position where a magnetic flux density of a regulating pole in a normal direction relative to an outer peripheral surface of the rotatable developing member is a half value of the second maximum value on a side downstream of the second maximum position is smaller than an angle from a position where the magnetic flux density of the regulating pole in the normal direction relative to the outer peripheral surface of the rotatable developing member is a half value of the first maximum value on a side upstream of the first maximum position to the first maximum value.