Developing Apparatus Magnetic Seal Member Thickness Variation
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Solution Overview
Problem
High-speed image forming apparatuses face challenges in suppressing toner scattering and adhesion to the developing sleeve due to increased rotational speeds, while existing magnetic seal solutions either enhance sealing performance but risk clogging or maintain low load but allow leakage.
Innovation Solution
A developing apparatus with a magnetic seal member having a thin and thick portion along its radial direction, where the thin portion is farther from the developing sleeve to reduce clogging and the thick portion is closer to enhance sealing, ensuring a stronger magnetic field at the outer direction to prevent leakage and a weaker field at the inner direction to prevent adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between the developing sleeve and the magnetic seal member is narrowed to increase sealing performance, then toner scattering is suppressed, but developer clogging occurs and large load is applied to the developing sleeve
Solution Approach 1:
The magnetic seal member is designed with non-uniform thickness, having a first thickness in the rotational axis direction and a second thickness in the radial direction. This local variation in thickness creates different magnetic field strengths at different locations, providing strong sealing where needed while avoiding excessive magnetic force that causes clogging and load.
2Productivity
If the rotational speed of the developing sleeve is accelerated to realize sufficient developing efficiency, then image formation speed is improved, but toner scattering increases
Solution Approach 1:
The magnetic seal member's thickness parameters are specifically optimized to maintain effective sealing performance at high rotational speeds. By adjusting the first and second thickness values, the magnetic field strength is tuned to prevent toner scattering even when the developing sleeve rotates at accelerated speeds for high productivity.
3Reliability
If a plate-shaped magnet is provided as a magnetic seal member surrounding the developing sleeve, then leakage of toner is suppressed, but the structure becomes more complex
Solution Approach 1:
Instead of using a complex plate-shaped magnet surrounding the entire developing sleeve, the invention employs a magnet member with localized thickness variations. This simplified structure provides the necessary sealing function through strategic placement of magnetic material with different thicknesses, reducing overall structural complexity while maintaining leakage suppression.
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
Effectively suppresses both toner scattering and adhesion to the developing sleeve, maintaining efficient image development while preventing developer clogging and leakage, even at high rotational speeds.
Implementation Method 1
a magnet portion arranged to oppose to the outer peripheral surface of the developer rotary member... having a magnetic pole with opposite polarity to the first magnetic pole... configured to generate a magnetic field
Implementation Method 2
The magnet roller has multiple magnet poles arranged along a rotation direction of the developing sleeve, and since only very little magnetic force is generated in a release area formed by an N3 pole and an N2 pole among the multiple magnetic poles, developer can be released from the developing sleeve
Data Source
AI summary
A developing apparatus includes a developer rotary member, a magnetic field generating portion, and a magnet portion. If an area of the magnet portion on an inner side from the end portion of the magnetic field generating portion with respect to the rotational axis direction of the developer rotary member is defined a first magnet area and an area of the magnet portion on an outer side from the end portion with respect to the rotational axis direction is defined a second magnet area, an average value of a component, in a normal direction of the developer rotary member, of a magnetic flux density of the magnet portion in the second magnet area is greater than an average value of a component, in a normal direction of the developer rotary member, of a magnetic flux density of the magnet portion in the first magnet area by 100 gauss or more.