Developing Unit Conveying Member Design for Toner Circulation
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the reduction in size of developing units leads to decreased magnetic flux density of magnet rollers, limiting developer movement and causing toner stagnation and decreased electrostatic properties, which affects developability, especially in the latter half of the device's life.
Innovation Solution
A developing unit design with a conveying member that includes a rotation shaft and a sheet portion, where the free end of the sheet enters the developing chamber through a partition opening, satisfying the relations C>A and B>A, enhancing toner circulation and mixing between the developing and developer chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the developing unit is reduced in size, then the compactness of the image forming apparatus is improved, but the magnetic flux density of the magnet roller decreases, causing developer movement to be limited and leading to developer stagnation
Solution Approach 1:
The developing unit is divided into two separate chambers: a developing chamber where the developer bearing member is disposed, and a developer chamber where the conveying member is disposed. This segmentation allows independent optimization of each chamber's function while maintaining compact overall size.
Solution Approach 2:
A conveying member with a sheet portion acts as an intermediary between the developer chamber and developing chamber. The sheet portion enters the developing chamber through a communication opening to convey developer, enabling circulation without requiring a large magnet roller.
2Length of moving object
If the magnet roller diameter is decreased to reduce developing unit size, then the compactness is improved, but the magnetic force decreases, limiting developer movement to areas close to the developing sleeve surface
Solution Approach 1:
The conveying member's sheet portion serves as a mediator that physically transports developer from the developer chamber to the developing chamber, compensating for the reduced magnetic force of the smaller magnet roller.
Solution Approach 2:
Instead of relying solely on magnetic force in the radial direction, the invention introduces a mechanical conveyance dimension through the rotating conveying member, creating a new pathway for developer movement that is independent of magnetic flux density.
3Volume of moving object
If the developing unit size is reduced, then the apparatus compactness is improved, but developer circulation between chambers is hindered, causing stagnation and decreased electrostatic properties
Solution Approach 1:
By separating the developing and developer chambers while providing a controlled communication path, the invention enables efficient developer circulation in a compact space through functional segmentation.
Solution Approach 2:
The conveying member rotates to dynamically convey developer from the developer chamber to the developing chamber, creating an active circulation system that maintains developer electrostatic properties despite the compact size.
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 improves toner circulation and mixing, maintaining stable image formation over a long period, even with smaller magnet rollers and reduced magnetic flux density, preventing developer stagnation and maintaining electrostatic properties.
Implementation Method 1
a developer bearing member supported by the developing frame and including a magnetic-field generating member
Implementation Method 2
configured to carry a developer having a magnetic property
Implementation Method 3
the upstream end of the opening is lower in a direction of gravitational force than the downstream end
Data Source
AI summary
A developing unit includes a conveying member which rotates to convey the developer to the developer bearing member. The conveying member includes a sheet portion with one end fixed to a rotation shaft and a free end which enters the developing chamber through an opening when the conveying member rotates around a rotation center, wherein relations C>A and B>A are satisfied, where A is a distance from the rotation center to an upstream end of the opening in a rotational direction, B is a distance from the rotation center to a downstream end of the opening in the rotational direction, and C is a length from the rotation center to the free end of the sheet portion in an unbent state. The upstream end of the opening is lower in a direction of gravitational force than the downstream end at an orientation in use.