Induction Fixing Core Segmentation for Lower Core Loss
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Solution Overview
Problem
Existing electro-magnetic induction heating type fixing units using sintered ferrite magnetic cores face challenges in suppressing core loss, particularly when using compacted magnetic core materials.
Innovation Solution
A fixing unit design incorporating a rotary member with a conductive layer and a core made of compacted magnetic core material, divided into multiple columnar cores aligned along the longitudinal direction, with the hard-magnetization axis oriented to intersect the longitudinal direction, to guide magnetic field lines and reduce core loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a magnetic core is made of compacted magnetic core material, then manufacturing flexibility and cost are improved, but core loss increases
Solution Approach 1:
The magnetic core is divided into multiple divided cores (first divided core, second divided core, etc.) arranged along the longitudinal direction. Each divided core has a columnar shape with specific aspect ratio (1:5 or less). This segmentation allows the use of compacted magnetic core material while reducing overall core loss through optimized magnetic field distribution and reduced eddy current paths.
Solution Approach 2:
The patent specifies that the hard-magnetization axis of the compacted magnetic core material is oriented in an intersection direction (radial direction) perpendicular to the longitudinal direction. This local orientation optimization reduces magnetic losses while maintaining the benefits of compacted material manufacturing.
2Productivity
If high-frequency alternating current is used for heating, then heating efficiency is improved, but core loss increases
Solution Approach 1:
The divided cores create multiple magnetic paths that distribute the high-frequency alternating magnetic field more effectively. This segmentation reduces eddy current losses and hysteresis losses in the core while maintaining efficient heating of the recording material through the conductive layer.
Solution Approach 2:
The patent converts the potential harmful effect of core loss into a beneficial heating mechanism. The controlled core loss in the divided cores generates heat that contributes to the overall heating efficiency, while the segmented structure prevents excessive loss accumulation.
3Loss of energy
If the magnetic core is divided into multiple portions, then core loss is reduced, but device complexity increases
Solution Approach 1:
The magnetic core is divided into multiple simple columnar portions arranged linearly along the longitudinal direction. Each divided core has a straightforward columnar shape with aspect ratio of 1:5 or less, making the segmentation simple to manufacture and assemble while effectively reducing core loss through the distributed magnetic path structure.
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 design enhances heat generation efficiency and durability by minimizing core loss and ensuring uniform heating of toner images on recording materials, even with high-frequency alternating current.
Implementation Method 1
a coil configured to generate an alternating magnetic field to generate heat in the conductive layer
Implementation Method 2
a core disposed inside the rotary member and configured to guide magnetic field lines of the alternating magnetic field
Implementation Method 3
made of compacted magnetic core material disposed such that a hard-magnetization axis thereof is oriented in an intersection direction intersecting the longitudinal direction
Data Source
AI summary
A fixing unit includes a rotary member including a conductive layer and having a tubular shape extending in a longitudinal direction, a coil configured to generate an alternating magnetic field to generate heat in the conductive layer, and a core disposed inside the rotary member and configured to guide magnetic field lines of the alternating magnetic field. The core is constituted by a plurality of divided cores aligned along the longitudinal direction. At least one of the plurality of divided cores is formed in a columnar shape having an aspect ratio of 1:5 or less between a maximum width in a cross section orthogonal to the longitudinal direction and a length in the longitudinal direction, and is made of compacted magnetic core material disposed such that a hard-magnetization axis thereof is oriented in an intersection direction intersecting the longitudinal direction.