Fixing Heater Segmentation for Nip Temperature Control
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Solution Overview
Problem
Electrophotographic image forming apparatuses face challenges in stabilizing the fixing nip temperature, leading to local temperature rises and temperature unevenness when handling papers of varying sizes, which can cause thermal damage and affect toner fixability and image density.
Innovation Solution
The apparatus employs a dual-heater system with a first fixing heater having a high heat generating region at the center and a second heater with a high heat generating region at the end portion, along with temperature detection units and a control unit that adjusts the heat generation based on detected temperatures and paper size to maintain optimal temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a uniform heater is used in the width direction, then the structure is simple, but local temperature rise occurs at end portions when small-sized paper passes through
Solution Approach 1:
The heater is divided into multiple heating regions along the width direction, with each region having different heat generation characteristics. Specifically, the heater includes a first heating region, a second heating region with higher heat generation than the first, and a third heating region, creating a non-uniform heat distribution pattern that prevents local temperature rise at end portions while maintaining structural feasibility
Solution Approach 2:
The heater is segmented into multiple independent heating regions (first, second, and third heating regions) along the width direction. This segmentation allows each region to be controlled independently or as a group, enabling precise thermal management different from a single uniform heater
2Temperature
If heat radiation control is used to prevent local temperature rise, then temperature uniformity improves, but productivity decreases due to paper passing stop
Solution Approach 1:
The heater is designed with regions of different heat generation capacity before paper passing occurs, allowing the end portions to be pre-heated or pre-cooled as needed. This preliminary thermal preparation prevents excessive temperature rise during small paper passing without requiring interruption of the paper flow
Solution Approach 2:
The heating system provides dynamic thermal control by having multiple heating regions that can be adjusted based on paper size and position. This dynamic capability allows the system to adapt to different paper widths and maintain temperature uniformity continuously without stopping paper passing
3Productivity
If heat radiation from end portions is allowed, then productivity is maintained, but temperature drops at end portions of paper passing region causing density unevenness
Solution Approach 1:
The third heating region is designed with specific heat generation characteristics to compensate for heat loss at the end portions. This localized heating adjustment ensures that end portions of the paper passing region maintain appropriate temperature for toner fixation, preventing density unevenness while allowing continuous paper passing
4Device complexity
If temperature control based only on temperature sensing is used, then simplicity is maintained, but optimum control for different paper sizes is not achieved
Solution Approach 1:
Temperature sensors are strategically placed at the center and end portions of the fixing film to provide feedback on temperature distribution. This feedback mechanism allows the control system to detect temperature variations and adjust heater regions accordingly, achieving precise temperature control adapted to different paper sizes and positions
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 reduces local temperature rise and temperature unevenness in the paper passing region, enhancing productivity and image quality by preventing thermal damage and improving toner fixability across different paper sizes.
Implementation Method 1
When the fixing heater is energized, the fixing heater generates heat and the fixing film is heated from a back side
Implementation Method 2
a film heating fixing system through which a toner image formed on a paper as a recording material is heated via a fixing film to fix the toner on the paper
Implementation Method 3
heat is not taken at the fixing nip portion so that the temperature becomes very high (local temperature rise)... until the temperature falls by heat radiation
Data Source
AI summary
An image forming apparatus includes a fixing film for fixing a toner image formed on a recording material, and first and second fixing heaters configured to heat the fixing film. The first fixing heater has a high heat generation region at a center portion in a width direction of a fixing nip portion and the second fixing heater has a high heat generation region at an end portion in the width direction of the fixing nip portion. A center portion temperature detection unit detects a center portion temperature of a center portion of the fixing film in the width direction. An end portion temperature detection unit detects an end portion temperature of an end portion of the fixing film in the width direction. A size detection unit detects a size of the recording material. A control unit controls a heat generation amount of the fixing heaters.