Magnetism Adjusting Member for Induction Heating Temperature Control
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Solution Overview
Problem
Existing image forming apparatuses face challenges in preventing excessive temperature increases in heating rollers during electromagnetic induction heating, particularly when handling sheets of varying sizes, as the magnetic shielding effect is limited by the size of the shielding plate, which can hinder induction heating if enlarged.
Innovation Solution
An image forming apparatus with a fixing unit that includes a heating member, a pressing member, and a magnetism adjusting member with a closed frame made of nonmagnetic material, capable of switching between shielding and non-shielding states to manage magnetic fields effectively, allowing for efficient induction heating without excessive temperature rise, even when the shielding plate is retracted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the area of the shielding plate is enlarged to suppress excessive temperature increase, then the excessive temperature increase suppressing effect is improved, but the magnetic field is influenced even when the shielding plate is retracted, causing induction heating to become insufficient
Solution Approach 1:
The shielding plate is divided into a plate body and a protruding portion that can be moved independently. The protruding portion is segmented from the main body and can be positioned to shield magnetic flux at the ends of the heating roller, while the main body remains fixed. This segmentation allows selective shielding without affecting the entire magnetic field.
Solution Approach 2:
The protruding portion of the shielding plate is made movable relative to the plate body, allowing dynamic adjustment of the shielding configuration. The protruding portion can be moved to different positions to shield magnetic flux at the ends of the heating roller when needed, and retracted when not needed, enabling dynamic control of the magnetic field distribution.
2Temperature
If the shielding plate is made larger to prevent magnetic flux leakage at the ends, then temperature control is improved, but the shielding plate occupies more space and influences the magnetic field even when retracted
Solution Approach 1:
The shielding function is segmented into a fixed plate body and a movable protruding portion. Only the protruding portion needs to be present in the magnetic field path when shielding is required, while the main body can be compact. This reduces the overall area occupied by the shielding plate while maintaining effective temperature control.
Solution Approach 2:
The protruding portion can be moved into and out of the magnetic field path as needed. When the sheet width requires end area shielding, the protruding portion is positioned to block magnetic flux leakage. When not needed, it is retracted, minimizing the shielding plate's influence on the magnetic field and reducing the effective area occupied.
3Temperature
If magnetic member pieces are moved away from the exciting coil in sheet non-passage areas, then heating efficiency decreases but excessive temperature increase is suppressed
Solution Approach 1:
The protruding portion of the shielding plate acts as an intermediary to control magnetic flux leakage at the ends of the heating roller. It selectively shields the magnetic field in the end areas where sheets do not pass, preventing excessive temperature increase without requiring movement of magnetic member pieces away from the exciting coil, thus maintaining heating efficiency in the sheet passage area.
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 solution effectively suppresses excessive temperature increases at the ends of heating rollers and maintains efficient induction heating, allowing for quick warm-up times and improved productivity without the need for excessively large shielding plates.
Implementation Method 1
a coil for forming a magnetic field by generating magnetism for induction heating the heating member
Implementation Method 2
a magnetism adjusting member made of a nonmagnetic material, arranged on the magnetic path and having a closed frame, and a switcher capable of switching the magnetism adjusting member between a first state where the magnetism adjusting member generates an induction current resulting from the magnetic field to shield the magnetism in the first area
Data Source
AI summary
A fixing unit (14) of an image forming apparatus (1) includes a heating member (48) having a first area where a sheet does not come into contact with the heating member (48) and a second area where the sheet comes into contact with the heating member (48). The fixing unit (14) further includes a coil (52) forming a magnetic field, cores (54,56) forming a magnetic path near the coil (52), a nonmagnetic magnetism adjusting member (90) arranged on the magnetic path and having a closed frame, and a switcher (58,60) capable of switching the magnetism adjusting member (90) between a first state where the magnetism adjusting member (90) generates an induction current resulting from the magnetic field to shield the magnetism in the first area, and a second state where the magnetism adjusting member (90) generates no induction current and the magnetism is not shielded in the first area.