Fixing Belt Tension Roll Heating and Thermal Stripping
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Solution Overview
Problem
The two-roll type fixing unit in image forming apparatuses faces challenges in maintaining high-speed fixing performance due to heat supply issues, leading to temperature drops and image quality defects, particularly with thick paper sheets, and the use of a fixing belt with a stripping claw results in wear and contamination, affecting image quality.
Innovation Solution
A fixing unit configuration that includes a rotatable fixing roll, a fixing belt stretched on tension rolls, and a pressurization member with a stripping pad disposed near the nip portion to maintain consistent heat supply and prevent wear, using a pressurization roll or belt to ensure stable toner image fixation and detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a two-roll type fixing unit with a heater disposed in the fixing roll is used, then the fixing unit can provide heating and pressurizing functions, but the surface temperature of the fixing roll gradually decreases during continuous sheet feed, leading to deteriorating fixing performance
Solution Approach 1:
The patent applies preliminary action by pre-heating the fixing belt using tension rolls with heating elements before the fixing belt enters the nip portion. This ensures the fixing belt is already at the required temperature when sheets are continuously fed through the nip, preventing temperature drops during high-speed operation. The heating is performed in advance on the belt itself rather than relying on the core bar to conduct heat through the elastic layer during the fixing process.
2Ease of operation
If a stripping claw is used to detach the recording sheet from the fixing belt, then the recording sheet can be stripped from the fixing belt, but the fixing belt surface becomes worn and contaminated, affecting image quality
Solution Approach 1:
The patent replaces the mechanical stripping claw system with a thermal detachment mechanism. The fixing belt is heated to a temperature high enough to melt the toner's adhesive properties, causing the recorded sheet to naturally detach from the fixing belt without mechanical contact. This substitution of mechanical stripping with thermal release eliminates wear and contamination of the fixing belt surface while achieving effective sheet detachment.
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 maintains consistent fixing temperatures, prevents temperature drops, and reduces image defects by ensuring stable toner image detachment and preventing wear on the fixing belt, thereby enhancing image quality and fixing unit reliability.
Implementation Method 1
previously heating the fixing belt with a heater disposed inside the tension rolls before the fixing belt enters the nip portion
Implementation Method 2
heating the recording sheet and the toner image through the heated fixing belt in the nip portion
Data Source
AI summary
A fixing unit for fixing a toner image on a recording material includes: a rotatable fixing roll; a fixing belt stretched on the fixing roll; at least one tension roll stretching the fixing belt with the fixing roll; a pressurization member disposed to give a pressure to the fixing roll; and a stripping member disposed to press the outer surface of the fixing belt onto the pressurization member in a vicinity of a downstream side of a first contact portion between the fixing roll and the pressurization member.