Developing Device Magnetic Pole Asymmetry for Fog Suppression
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Solution Overview
Problem
The existing developing device for electrostatic latent images experiences image defects such as vertical stripe-shaped fog due to developer movement between magnetic poles, leading to improper deposition on the image bearing member.
Innovation Solution
A developing device with a specific magnetic pole arrangement and magnetic flux density distribution, where the receiving pole of the second developing roller has a maximum magnetic flux density at point T, and half-value positions Hu and Hd, with a relationship that strengthens the magnetic field between the receiving pole and the second feeding pole, while weakening the magnetic field between the first feeding pole and the second feeding pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the developer is delivered from the first developing roller to the second developing roller using a magnetic field between delivering and receiving poles, then the developer can be transported vertically, but a magnetic field is generated between adjacent magnetic poles that causes developer movement and image defects
Solution Approach 1:
A non-magnetic sheet is introduced as an intermediary element between the first and second developing rollers. This sheet physically separates the magnetic fields of adjacent poles (delivering pole of first roller and receiving pole of second roller), preventing the harmful magnetic interaction that causes developer movement. The non-magnetic material blocks magnetic flux penetration, thereby eliminating the source of image defects while preserving the intended developer delivery function.
Solution Approach 2:
The harmful magnetic field interaction is extracted or isolated from the system by introducing the non-magnetic sheet. This sheet effectively removes the problematic magnetic coupling between adjacent poles, allowing the useful magnetic field (between delivering and receiving poles) to remain while eliminating the harmful component that causes developer displacement and fog formation.
2Productivity
If the magnetic field strength is increased to improve developer delivery, then developer transport efficiency improves, but developer movement between poles increases causing more image defects
Solution Approach 1:
The non-magnetic sheet serves as a spatial mediator that divides the magnetic field into distinct zones. It allows strong magnetic fields to exist between delivering and receiving poles for efficient developer transport, while simultaneously blocking harmful magnetic interactions between adjacent poles. This enables high productivity without compromising image quality.
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 developer movement between the first and second developing rollers, preventing image defects like vertical stripe-shaped fog and ensuring stable image output.
Implementation Method 1
delivery of the developer is made by a magnetic field formed between a delivering pole of a first magnet provided in the first developing roller and a receiving pole of a second magnet provided in the second developing roller
Implementation Method 2
between the first magnetic pole and the second magnetic pole, a magnetic field for attracting the developer to each of the rollers is generated
Data Source
AI summary
The developing device includes a first rotatable member, a first magnet, a second rotatable member, and a second magnet. When a position where on a second rotatable member surface, a magnetic flux density of the receiving pole is maximum is a point T, of positions each where the magnetic flux density of the receiving pole is a half value of the maximum, the position on an upstream side is a point Hu, the position, the position on a downstream side is a point Hd, an angle formed by a rectilinear line L20 connecting a rotation center R2 of the second rotatable member and the point T and a rectilinear line L21 connecting the rotation center R2 and the point Hu is wθ21, and an angle formed by L20 and a rectilinear line L22 connecting R2 and Hd is wθ22, the following relationship is satisfied: wθ22−wθ21≥0.