Heating Roller Surface Potential Control via Electromagnetic Induction
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Solution Overview
Problem
Existing image heating apparatuses face challenges in suppressing electrostatic offset, particularly due to variations in surface potential of rollers caused by triboelectric charges, which can lead to toner leakage and scattered images, and require complex electromotive force generating circuits to control surface charges effectively.
Innovation Solution
An image heating apparatus incorporating an exciting coil for high-frequency current application, a rotatable heating member with an insulating surface layer, and a pressing roller with an electroconductive surface layer, where diodes are connected to manage surface potentials to oppose the toner charge polarity, ensuring stable electrostatic control without the need for high-voltage sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If triboelectric charge methods are used to control surface potential, then high-voltage sources are not needed, but surface potential varies depending on recording material and friction conditions making it difficult to control
Solution Approach 1:
The patent replaces the mechanical triboelectric charge generation method with an electromagnetic induction system. An exciting coil generates alternating magnetic flux that induces eddy currents in the fixing roller core, creating controllable surface potential through electromagnetic fields rather than mechanical friction. This allows precise control of surface potential independent of recording material properties.
Solution Approach 2:
The patent controls surface potential by changing electromagnetic parameters (exciting coil current, frequency) rather than relying on variable friction parameters. By adjusting the alternating current parameters in the exciting coil, the surface potential can be precisely controlled and maintained at desired levels regardless of changes in recording material or friction conditions.
2Measurement precision
If electromotive force generating circuits are used to control surface charge, then surface potential can be controlled, but the circuit constitution becomes relatively complicated
Solution Approach 1:
The patent replaces complex electromotive force generating circuits with a simpler electromagnetic induction system. Instead of using capacitors, diodes, and resistors arranged in complex circuits, the invention uses an exciting coil that generates magnetic flux to induce eddy currents directly in the fixing roller, achieving surface potential control with minimal circuit components.
Solution Approach 2:
The fixing roller core serves dual functions: it generates heat through eddy currents for the fixing process and simultaneously generates the surface potential through electromagnetic induction. The system uses itself to achieve both heating and electrostatic control, eliminating the need for separate complex control circuits.
3Productivity
If triboelectric charge accumulates during continuous fixing, then surface potential is determined by friction, but leakage and scattered images occur
Solution Approach 1:
The patent uses periodic alternating current in the exciting coil to generate alternating magnetic flux, which continuously induces eddy currents in the fixing roller. This periodic action maintains a stable, controlled surface potential throughout continuous operation, preventing the accumulation of triboelectric charges that would otherwise occur during continuous fixing.
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 effectively suppresses electrostatic offset by maintaining stable surface potentials, preventing toner leakage and ensuring high-quality image formation even with continuous sheet passing, without the complications of triboelectric charge accumulation.
Implementation Method 1
a first electroconductive layer for generating heat by electromagnetic induction of magnetic flux from the exciting coil
Implementation Method 2
generating heat by electromagnetic induction of magnetic flux from the exciting coil
Implementation Method 3
a rectifying element configured to be connected between the second electroconductive layer and the ground in a direction in which a surface potential of the rotatable pressing member has an opposite polarity to a normal charge polarity of a toner
Data Source
AI summary
An image heating apparatus includes: an exciting coil; a current applying device configured to apply a high-frequency current to the exciting coil; a rotatable heating member configured to heat a toner image on a recording material at a nip, wherein the rotatable heating member includes a first electroconductive layer for generating heat by electromagnetic induction of magnetic flux from the exciting coil; a rotatable pressing member configured to press-contact the rotatable heating member to form the nip, wherein the rotatable pressing member includes a second electroconductive layer electrically insulated from the first electroconductive layer; and a rectifying element configured to be connected between the second electroconductive layer and the ground in a direction in which a surface potential of the rotatable pressing member has an opposite polarity to a normal charge polarity of a toner.