Elastic Heat Roll Fixing Unit for Offset Suppression
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Solution Overview
Problem
Existing image forming apparatuses with heating rolls and pressure rolls face challenges in high-temperature, high-humidity environments, where hot offset and degradation of rub resistance occur, limiting the fixing latitude when using toners with specific molecular weight ranges and infrared absorption ratios.
Innovation Solution
An image forming apparatus with a fixing device featuring a heat roll and an endless belt, where the heat roll has an elastic component and a pressure pad that maintains contact without rotation, ensuring consistent pressure and reduced heat loss, and using toners with amorphous polyester resin binder, specific molecular weight ranges, and infrared absorption ratios to enhance fixability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heating roll and pressure roll are used in the fixing unit, then the toner image can be fixed on the recording medium, but hot offset and degradation of rub resistance occur in high-temperature, high-humidity environments
Solution Approach 1:
The patent changes the physical parameters of the fixing system by replacing the conventional pressure roll with a pressure pad that maintains constant pressure through elastic deformation. The pressure pad's material properties (elastic modulus, hardness) are selected to provide stable pressure without the harmful effects of roll-based fixing in high-temperature, high-humidity environments, thereby suppressing hot offset and rub resistance degradation while maintaining reliable toner fixation.
Solution Approach 2:
The fixing unit employs a composite structure combining a heating roll with an elastic pressure pad. The pressure pad is made of elastic material that can deform to maintain consistent contact pressure. This composite approach integrates the heating function with the pressure application function, achieving reliable fixing performance while eliminating the drawbacks of conventional separate roll-based systems in challenging environmental conditions.
2Reliability
If the pressure pad is made elastic to maintain consistent pressure, then fixing reliability improves, but the device complexity increases
Solution Approach 1:
The patent extracts the pressure application function from the rotating pressure roll and implements it through a stationary pressure pad. This separation allows the pressure pad to focus solely on providing consistent elastic pressure without the complexity of rotational mechanics, drive mechanisms, and alignment systems required for a pressure roll, thereby improving pressure consistency while actually simplifying the overall device structure.
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 hot offset and degradation of rub resistance, enlarging the fixing latitude and improving image quality in high-temperature, high-humidity conditions by maintaining consistent pressure and reducing heat loss.
Implementation Method 1
a heat roll that has an elastic component and is rotatable
Implementation Method 2
a heat roll that has an elastic component and is rotatable
Data Source
AI summary
An image forming apparatus includes an image holding member; a charging unit; an electrostatic image forming unit; a developing unit; a transfer unit; and a fixing unit that fixes the toner image on the recording medium. The toner has an amorphous polyester resin and has a weight-average molecular weight Mw in a range of 25,000 to 60,000, a ratio Mw/Mn is within a range of 5 to 10, a ratio of an absorbance at a wavenumber of 1500 cm−1 to an absorbance at a wavenumber of 720 cm−1 is 0.6 or less, and a ratio of an absorbance at a wavenumber of 820 cm−1 to the absorbance at a wavenumber of 720 cm−1 is 0.4 or less. The fixing unit includes a heat roll having an elastic component, an endless belt and a pressure pad that is disposed on an inner side of the endless belt.