Developing Roller Magnet Layout for Vertical Stripe Suppression
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Solution Overview
Problem
The existing developing device design, where developer is delivered from a first developing roller to a second developing roller positioned vertically above, results in developer movement due to magnetic fields, leading to deposition on the image bearing member and vertical stripe image defects.
Innovation Solution
The developing device incorporates a first rotatable member with a first magnet having specific magnetic pole configurations and a second rotatable member with opposing magnetic pole configurations, ensuring controlled developer transfer and minimizing magnetic flux density variations to prevent developer deposition on the image bearing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
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 transferred vertically, but a magnetic field is generated between adjacent magnetic poles that attracts the developer and causes movement and deposition on the image bearing member
Solution Approach 1:
The patent changes the magnetic polarity arrangement from alternating poles (N-S-N-S) to a configuration where poles of the same polarity are adjacent (N-N-S-S). This parameter change in magnetic pole arrangement eliminates the harmful magnetic attraction between adjacent poles while maintaining the developer transfer function through the magnetic field between delivering and receiving poles.
Solution Approach 2:
The patent introduces asymmetry in the magnetic pole configuration by placing identical poles (N-N or S-S) adjacent to each other rather than using symmetric alternating patterns. This asymmetric arrangement prevents the generation of harmful magnetic fields between adjacent poles while maintaining effective developer delivery and reception.
2Speed
If the delivering pole and receiving pole are positioned to enable vertical developer delivery, then the developer can be transferred to the upper developing roller, but the magnetic field generated causes developer movement and floating deposition
Solution Approach 1:
The patent modifies the magnetic field parameters by changing the pole arrangement to eliminate alternating polarity patterns. This ensures that while the magnetic field strength and delivery speed remain effective, the harmful lateral magnetic attractions that compromise image quality are eliminated.
3Force
If alternating magnetic poles are used for developer delivery, then the magnetic field can attract developer between poles, but this same magnetic field causes developer movement between delivering and receiving poles
Solution Approach 1:
The patent changes the magnetic polarity parameter from alternating (N-S-N-S) to adjacent identical poles (N-N-S-S). This maintains the necessary magnetic attraction force for developer transfer while eliminating the unstable lateral magnetic forces that cause developer movement and position instability.
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 effectively suppresses image defects by stabilizing developer movement, maintaining image quality and reducing vertical stripe artifacts.
Implementation Method 1
to which the second rotatable member is delivered from the first rotatable member by a magnetic field generated by the first magnet
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 first rotatable member surface, a magnetic flux density of the delivering pole is maximum is a point T, of positions each where the magnetic flux density of the delivering pole is a half value of the maximum, the position on a downstream side is a point Hd, the position on an upstream side is point Hu, an angle formed by a rectilinear line L10 connecting a rotation center R1 of the first rotatable member and the point T and a rectilinear line L12 connecting the rotation center R1 and the point Hu is w1, and an angle formed by L10 and a rectilinear line L11 connecting R1 and Hd is w2, the following relationship is satisfied: w1−w2≥0.