Asymmetric Soaking Member for Fixing Roller Temperature Control
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Solution Overview
Problem
In electrophotographic printing systems, the temperature of non-passed areas of the fixing roller rises excessively when printing small-size recording materials, leading to issues like toner offset and lower image gloss due to inadequate heat distribution.
Innovation Solution
A fixing apparatus with a metallic soaking member extending from the upstream to the downstream side of the fixing nip portion, where the center of gravity is positioned on the upstream side, effectively equalizes temperature across the fixing nip portion using high thermal conductivity materials like aluminum, preventing excessive temperature rise in non-passed areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metallic soaking member is arranged from upstream end to downstream end of the fixing nip portion, then the temperature of non-passed area is restrained, but the temperature margin for defective image such as toner offset decreases
Solution Approach 1:
The soaking member is designed with asymmetric structure where the cross-sectional area on the upstream side is larger than on the downstream side. This creates different thermal characteristics at different positions: the upstream side with larger area provides stronger heat absorption to restrain temperature rise in non-passed areas, while the downstream side with smaller area reduces excessive heat transfer that would decrease temperature margin for toner offset prevention.
Solution Approach 2:
The soaking member employs asymmetric geometry with the center of gravity positioned on the upstream side of the nip portion center. The cross-sectional area ratio between upstream and downstream sides is set between 1.1:1 and 3:1, creating intentional asymmetry that optimizes heat distribution - stronger cooling effect upstream where temperature rise is most problematic, and gentler effect downstream where maintaining temperature margin is critical.
2Temperature
If the cross-sectional area of the soaking member is increased, then the heat absorption effect is improved, but the device complexity and material usage increase
Solution Approach 1:
Instead of uniformly increasing the soaking member's cross-sectional area throughout, the design applies local quality variation where the upstream cross-section is larger and the downstream cross-section is smaller. This asymmetric configuration provides enhanced heat absorption where needed (upstream) while avoiding excessive complexity and material usage in regions where strong cooling is not required (downstream).
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 maintains a stable temperature across the fixing nip portion, reducing toner offset and improving image quality by ensuring uniform heat distribution, even during continuous printing of small-size recording materials.
Implementation Method 1
a soaking member (metallic member) made of a thermally conductive metallic material to restrain the temperature rise of a non-passed area of the fixing roller
Data Source
AI summary
A fixing apparatus for fixing an image onto recording material, includes a heating rotary member, film of a cylindrical shape, and pressure member configured to press the film from inside the film toward the heating rotary member to form a nip portion as an area where the heating rotary member and film contact. The pressure member includes a metallic member extending from an upstream side of a center in a recording material conveyance direction of the nip portion to a downstream side, wherein the recording material on which the image is formed is conveyed while being heated at the nip portion to fix the image onto the recording material. A center of gravity of the metallic member is on the upstream side of the center in the recording material conveyance direction of the nip portion in a cross-section perpendicular to a rotation axis direction of the heating rotary member.