Fixing Apparatus Heater Reverse Crown Control
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Solution Overview
Problem
Existing fixing apparatuses with reverse crown pressure rollers face issues with paper crease occurrence due to uneven heat distribution and thermal expansion, leading to warped recording materials and defective images, especially when starting from a cooled state.
Innovation Solution
A fixing apparatus with a heater that adjusts heat generation ratios between its center and end portions to maintain an appropriate reverse crown shape of the pressure roller, using a ceramic heater with varying resistance per unit length to ensure consistent heat distribution and thermal expansion, thereby preventing paper crease regardless of the roller's status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a pressure roller with reverse crown shape is used, then the recording material is conveyed faster at the end portions reducing warp and crease, but the temperature at the end portions becomes lower than the center portion leading to reduced reverse crown amount
Solution Approach 1:
The heater is designed with non-uniform heat generation characteristics, where the end portions generate more heat than the center portion. This local differentiation in heat generation compensates for the higher heat dissipation at the end portions, ensuring uniform temperature distribution across the pressure roller surface while maintaining the reverse crown shape.
2Stability of the object's composition
If the amount of reverse crown is reduced, then the thermal expansion at the center portion is greater, but the conveying speed becomes uneven causing warp and crease of the recording material
Solution Approach 1:
The heater control is activated before the recording material reaches the nip portion, pre-heating the pressure roller to the appropriate temperature. This preliminary thermal conditioning ensures that the reverse crown shape is established before material processing begins, preventing warp and crease during conveying.
Solution Approach 2:
The system includes temperature detection at the end portions of the pressure roller, with the heater control adjusting heat generation based on the detected temperature. This feedback mechanism maintains the reverse crown shape by compensating for temperature variations, ensuring consistent conveying speed and preventing material deformation.
3Shape
If the pressure roller is cooled, then the reverse crown shape is maintained, but the conveying speed at the end portions becomes faster causing warp and crease
Solution Approach 1:
The heater control dynamically adjusts the temperature parameter of the pressure roller by controlling heat generation at different portions. By increasing heat generation at the end portions, the system changes the temperature distribution parameter to maintain the reverse crown shape while preventing excessive cooling that would cause material warp and crease.
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 maintains an appropriate reverse crown shape, preventing paper crease and ensuring consistent image quality by dynamically controlling heat distribution and thermal expansion, even when starting from a warm or cooled state.
Implementation Method 1
a heater (16) contacting an inner surface of the film (20) and generating heat in a generatrix direction of the cylindrical film (20)
Implementation Method 2
since the thermal expansion at the center portion of the pressure roller in the longitudinal direction will be greater than the end portions of the pressure roller
Data Source
AI summary
A fixing apparatus includes a film, a heater that contacts the inner face of the film and is capable of changing heat distribution, and a pressure member that forms the nip portion with the heater via the film, the pressure member including a region on which a diameter is increased from a center portion toward an end portion, wherein the fixing apparatus performs heater control so that a ratio of an amount of heat generation at the end portion of the heater to an amount of heat generation at the center portion of the heater is changed based on a temperature of the end portion of the pressure member, during a period at least from when the warm-up of the fixing apparatus is started until the recording material reaches the nip portion.