Image Heating Device With Symmetric Safety Circuits
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Solution Overview
Problem
Existing fixing devices in electrophotographic image forming apparatuses face issues with temperature rise in non-paper-passing portions, leading to potential damage and toner offset, especially when using split heaters with narrow heating blocks and limited space for safety elements like thermoswitches.
Innovation Solution
The image heating device employs a configuration with symmetrically arranged heating element groups powered by separate common circuits, incorporating safety elements on both sides of the conveyance reference position to ensure safe operation without layout restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a split heater with multiple heating blocks is used to suppress temperature rise in non-paper-passing portions, then temperature control is improved, but the space required for safety elements like thermoswitches increases
Solution Approach 1:
The patent combines multiple heating blocks that are symmetrically arranged with respect to the conveyance reference position into pairs, where each pair shares a common drive circuit. This merging approach reduces the total number of independent drive circuits needed, thereby reducing the installation space required for safety elements while maintaining temperature control across different paper sizes.
Solution Approach 2:
The common drive circuit is designed to serve multiple heating blocks simultaneously, making it a multi-functional component. This universal approach allows a single drive circuit to control symmetry-related heating blocks, reducing redundancy and minimizing the space required for safety elements without compromising temperature management.
2Reliability
If separate drive circuits are provided for each heating block to ensure safety, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges drive circuits by making them common to pairs of symmetrically arranged heating blocks. This reduces the total number of independent circuits while maintaining safety through the symmetric design, where each common drive circuit controls heating blocks that are mirror images with respect to the conveyance reference position.
Solution Approach 2:
The patent introduces asymmetry in the circuit configuration by differentiating between first and second common drive circuits based on their position relative to the conveyance reference position. This asymmetric arrangement allows for simplified circuit design while maintaining safety, as each common drive circuit serves a specific side of the heater assembly.
3Length of stationary object
If heating blocks are made narrow to fit limited space, then device size is reduced, but temperature distribution uniformity deteriorates
Solution Approach 1:
The patent uses asymmetric positioning of heating blocks relative to the conveyance reference position, creating pairs of symmetrically arranged blocks. This allows narrow heating blocks to be strategically positioned to achieve uniform temperature distribution across the heating width, compensating for the reduced individual block width through optimized spatial arrangement.
Solution Approach 2:
The patent applies local quality by having different heating blocks (or pairs of blocks) controlled by different common drive circuits, allowing independent temperature control in different regions. This enables each narrow heating block to be optimized for its specific location while maintaining overall temperature uniformity through coordinated control of multiple regions.
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 prevents temperature rise in non-paper-passing areas, ensuring safety and preventing damage to the device while maintaining efficient operation.
Implementation Method 1
a heater (1100) having a plurality of heating elements (1102)
Implementation Method 2
as a safety element, a small thermostat (hereinafter referred to as a thermoswitch)
Data Source
AI summary
An image heating device includes a heater having a plurality of heating elements which includes a first heating element group and a second heating element group, a control portion which supplies power to the first heating element group through a first common circuit and supplies power to the second heating element group through a second common circuit. The first common circuit includes a first safety element which responds to the temperature of the heating elements included in the first heating element group, and the second common circuit includes a second safety element which responds to the temperature of the heating elements included in the second heating element group. The first safety element is arranged on one side with respect to a conveyance reference position of a recording material, and the second safety element is arranged on the other side with respect to the conveyance reference position.