Developing Unit Magnetic Brush Geometry for Density Unevenness
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Solution Overview
Problem
High resistance carrier particles in image forming apparatuses lead to back edge density unevenness in outline characters, which is not adequately addressed by existing counter development methods, particularly when high quality images are required.
Innovation Solution
An image forming apparatus with a developing unit that uses a two-component developing agent, where the image carrier and developer carrier move in opposite directions, and an alternating electric field with a DC and AC component is applied, with the contact width of the magnetic brush bristle being 70% or less of the development width, and the center positioned upstream relative to the image carrier's rotation direction, and the development main magnetic pole is angled 25° to 35° with respect to the conveying magnetic pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high resistance carrier particles are used in the counter development method, then developing characteristics are improved, but back edge density unevenness in outline characters occurs
Solution Approach 1:
The invention changes the geometric parameters of the development area by controlling the contact width to be 70% or less of the development width and positioning the center of the contact width upstream relative to the center of the development width. This parameter adjustment resolves the contradiction by preventing toner scratching at the back edge while maintaining effective development in the contact region.
2Productivity
If the contact width of the magnetic brush bristle is increased to improve development efficiency, then developing characteristics are enhanced, but back edge density unevenness worsens
Solution Approach 1:
The invention optimizes the contact width parameter to be 70% or less of the development width, which balances development efficiency with prevention of back edge density unevenness. This parameter setting ensures sufficient toner transfer while avoiding excessive contact that would cause scratching.
Solution Approach 2:
The invention introduces a positional dimension by offsetting the center of the contact width upstream relative to the center of the development width. This dimensional adjustment allows the development process to occur effectively while preventing the magnetic brush bristle from scratching the back edge of outline characters.
3Productivity
If the development main magnetic pole is positioned at the closest part between image carrier and developer carrier, then development efficiency is maximized, but outline character quality deteriorates
Solution Approach 1:
The invention positions the development main magnetic pole upstream relative to the closest part between the image carrier and developer carrier. This positional adjustment in the rotation direction dimension allows the magnetic brush to form and contact the image carrier at an optimal location, preventing back edge scratching while maintaining development effectiveness.
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 significantly improves outline character back edge density unevenness, ensuring high-quality images by preventing toner scratching and maintaining development efficiency.
Implementation Method 1
having inside a development main magnetic pole for forming a bristle of a magnetic brush
Implementation Method 2
an alternating electric field having a DC component and an AC component superimposed on each other is used as a development bias applied to the developing agent carrier
Implementation Method 3
a plurality of magnetic poles for conveying the developing agent
Data Source
AI summary
An image forming apparatus having an image carrier for forming an electrostatic latent image and a developing unit for developing the electrostatic latent image with a two-component developing agent, the developing unit includes: a developing agent carrier for developing the electrostatic latent image to form a visible image, having inside thereof a development main magnetic pole for forming a bristle of a magnetic brush; and a plurality of magnetic poles for conveying the developing agent, wherein the developing unit performs a counter type contact developing method, and wherein, a development area is formed so that, a contact width of the bristle of the magnetic brush is 70% or less with respect to a development width, and a center position of the contact width is positioned on an upstream side with respect to a center position of the development width in a rotation direction of the image carrier.