Heater with Segmented Resistors for Uniform Heat Distribution
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Solution Overview
Problem
Conventional heaters in image forming apparatuses of the conveyance direction energizing type suffer from heat generation unevenness in the longitudinal direction and insufficient tolerance against heater cracking, leading to potential image defects and safety issues.
Innovation Solution
A heater design featuring first and second heating resistors with PTC characteristics, connected in parallel, and strategically placed conductive portions to manage heat generation and reduce thermal stress, along with a switching mechanism to adjust the connection state of the heating resistors based on power supply voltage, ensuring uniform heat distribution and enhanced cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heating resistors are connected in parallel to power supply portions, then heat generation is suppressed in non-paper-passing regions, but heat generation unevenness occurs in the longitudinal direction of the heater
Solution Approach 1:
The heater is divided into multiple heating zones with separate heating resistors (first heating resistor 15a and second heating resistor 15b) positioned at different locations along the longitudinal direction. Each heating zone can be independently controlled through separate power supply portions (21 and 22), allowing differential heat generation management to achieve uniform temperature distribution across the heater surface.
Solution Approach 2:
Different regions of the heater are assigned different heating characteristics through the parallel connection of heating resistors to separate power supply portions. The first and second heating resistors are positioned to address specific thermal requirements at different longitudinal locations, with the conductive portions (37a-37d) strategically placed to optimize local heat generation and achieve overall temperature uniformity.
2Reliability
If heating resistors are positioned closer to the end of the substrate, then tolerance against heater cracking is improved, but heat generation unevenness in the longitudinal direction worsens
Solution Approach 1:
The heating resistors are segmented into multiple independent units (first heating resistor 15a and second heating resistor 15b) positioned at different longitudinal locations. This segmentation allows the heater to maintain structural reliability by positioning resistors near substrate ends while achieving heat generation uniformity through the distributed arrangement and independent control of each segment.
Solution Approach 2:
The heater configuration enables dynamic heat generation control through the parallel connection of heating resistors to separate power supply portions. By independently adjusting the power supply to each heating resistor, the system can adapt heat generation distribution to maintain both cracking tolerance and temperature uniformity under varying operating conditions.
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 solution effectively suppresses heat generation unevenness in the longitudinal direction and provides sufficient tolerance against heater cracking, ensuring reliable operation and improved image quality.
Implementation Method 1
the heating resistors 15a and 15b generate heat
Implementation Method 2
the heating resistors 15a and 15b generate heat (hereinafter, such a type of heater is referred to as a conveyance direction energizing type). In the heater, when a small-size recording material is passed through a region (large-size paper passing region) through which a large-size recording material used in a printer passes, a non-paper-passing region is generated outside the region through which the small-size recording material passes (small-size paper passing region).
Data Source
AI summary
A heater of an image heating device, the heater including: a substrate; a first heating resistor and a second heating resistor on the substrate; first to third electric contact portions for electric connection to a power supply; a first conductive portion that connects the first electric contact portion with the first heating resistor; a second conductive portion that connects the second electric contact portion the second heating resistor; and a third conductive portion that connects the third electric contact portion and the first heating resistor and also connects the third contact portion with the second heating resistor, wherein the first electric contact portion is provided close to one longitudinal end of the substrate, the second electric contact portion is provided close to the other longitudinal end of the substrate, and the third electric contact portion is provided close to the center of the substrate in the longitudinal direction.