Fixing Roller Temperature Control for Offset Prevention
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Solution Overview
Problem
In electrophotographic image forming apparatuses, the existing fixing apparatuses face challenges in maintaining the optimal temperature of the fixing roller across varying sheet transport speeds, leading to offset phenomena such as cold and hot offset, especially in four drum tandem engines with different monochrome and color image forming speeds.
Innovation Solution
The implementation of an external heating member that heats the outer surface of the fixing roller and a temperature control section that adjusts the heating member's temperature based on the selected transport speed, allowing for quick changes in the fixing roller's surface temperature to prevent offset phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sheet transport speed is increased to improve productivity, then the number of sheets processed per unit time increases, but the contact time between the sheet and fixing roller decreases causing insufficient heat transfer and cold offset
Solution Approach 1:
The patent changes the temperature parameter of the fixing roller based on the sheet transport speed. When transport speed increases, the fixing roller temperature is increased to compensate for reduced contact time, ensuring sufficient heat transfer to the toner image while maintaining high productivity
Solution Approach 2:
The patent performs preliminary heating of the fixing roller before sheet transport begins. The temperature control section pre-heats the fixing roller to an appropriate temperature based on the selected transport speed, ensuring optimal temperature is reached before images need to be fixed, thus preventing cold offset
2Reliability
If the sheet transport speed is decreased to improve image fixing quality, then sufficient heat transfer is achieved, but productivity decreases
Solution Approach 1:
The patent implements dynamic temperature adjustment where the fixing roller temperature is not fixed but varies according to the selected sheet transport speed. The temperature control section continuously adapts the temperature parameter to match current operating conditions, allowing optimal balance between productivity and image fixing quality at any speed
3Device complexity
If a halogen lamp is used as the heat source inside the fixing roller, then the structure is simple, but the heating speed is slow causing delay in reaching optimal temperature
Solution Approach 1:
The patent combines two heating methods: the internal halogen lamp and an external heating member (heating roller or heating belt). The external heating member provides rapid initial heating, while the halogen lamp maintains temperature, achieving both fast heating speed and simple structure
Solution Approach 2:
The external heating member acts as an intermediary that transfers heat to the fixing roller more efficiently than the internal halogen lamp alone. This intermediary heating element enables faster temperature rise without complicating the overall heating system design
4Reliability
If the temperature of the fixing roller is increased to prevent cold offset at high speed, then heat transfer is sufficient, but hot offset occurs due to excessive heating
Solution Approach 1:
The patent uses dynamic temperature control where the fixing roller temperature is adjusted in real-time according to the sheet transport speed. At high speeds, temperature is increased to prevent cold offset; at low speeds, temperature is reduced to prevent hot offset, thus eliminating both harmful effects through adaptive control
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 solution effectively suppresses offset phenomena by ensuring the fixing roller's temperature is optimized for the selected transport speed, enhancing image fixing quality across different image forming modes without the need for complex temperature control mechanisms.
Implementation Method 1
an external heating member which heats the outer surface of the fixing roller by external contact with the outer surface of the fixing roller
Implementation Method 2
a halogen lamp which is disposed as a heat source inside the shaft
Implementation Method 3
a temperature sensor which is provided on the surface of the fixing roller
Data Source
AI summary
In a fixing apparatus which is included in an image forming apparatus that is capable of selecting a sheet transport speed, a paper sheet is transported between a fixing roller and a pressure roller, so that an unfixed image formed on the paper sheet is fixed on the paper sheet under heat of the fixing roller. The fixing apparatus is provided with an endless belt which heats the outer surface of the fixing roller by external contact with the outer surface of the fixing roller, and a halogen lamp, a heat source control device, and a thermistor all of which are for changing a temperature of the endless belt in accordance with the sheet transport speed. This makes it possible to fix an image on a paper sheet without the occurrence of offset phenomena.