Variable-Length Fixing Heater Segmentation for Hot Offset Control
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Solution Overview
Problem
The issue of non-passing portion temperature rise during printing of small-size paper leads to overheating and hot offset when large-size paper is printed subsequently, causing downtime and reduced efficiency in image forming apparatuses due to the need for temperature equalization control after printing small-size paper.
Innovation Solution
An image forming apparatus with a heater comprising first and second heat generating members of different lengths, where the first member is longer than the second, and power control to adjust electric power supply based on the size of the paper being printed, allowing simultaneous printing of small and large-size papers without downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If electric power is supplied to the heat generating member having a length corresponding to large-size paper in addition to the heat generating member having a length corresponding to small-size paper to heat the fixing film, then the temperature difference between the heated portion and the unheated portion of the pressure roller is reduced, preventing thermal expansion and fixing film distortion, but a non-passing portion temperature rise occurs easily
Solution Approach 1:
The heat generating member is divided into multiple segments with different lengths (first heat generating member with length L1, second heat generating member with length L2 where L1 > L2). This segmentation allows different portions of the pressure roller to be heated independently according to the paper size being processed, preventing both thermal expansion distortion and non-passing portion temperature rise.
Solution Approach 2:
Different lengths of the heat generating member correspond to different paper sizes (A4, A3, A2, etc.). The control unit selects which heat generating member to activate based on the paper size, applying heat locally only where needed. This ensures temperature uniformity in the heated region while leaving non-passing portions cooler.
2Temperature
If temperature equalization control is performed after printing small-size paper to prevent hot offset, then non-passing portion temperature rise is suppressed, but downtime of the image forming apparatus occurs and operation efficiency decreases
Solution Approach 1:
The control unit determines in advance whether to perform temperature equalization control based on the paper size being processed. For paper sizes of A4 or smaller, temperature equalization control is performed before image formation starts. For larger paper sizes, it is not performed. This preliminary determination eliminates unnecessary downtime while still preventing hot offset when needed.
Solution Approach 2:
The system dynamically adjusts the heating strategy based on paper size. For small papers (A4 and smaller), the full-length heat generating member is activated with temperature equalization control. For larger papers, only the appropriate segment is activated without temperature equalization control, optimizing both temperature control and productivity.
3Temperature
If only the heat generating member corresponding to small-size paper is used to heat the fixing film during small-size paper printing, then non-passing portion temperature rise is suppressed, but the temperature difference between heated and unheated portions causes pressure roller thermal expansion and fixing film twisting
Solution Approach 1:
The heat generating member is segmented into multiple sections with different lengths that correspond to different paper sizes. This segmentation allows the system to activate only the necessary heating sections, maintaining temperature uniformity across the entire pressure roller surface even when processing small papers, thereby preventing fixing film distortion.
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 prevents overheating and hot offset, maintaining operational efficiency by controlling power supply to the heat generating members based on paper size, reducing downtime and enhancing productivity.
Implementation Method 1
a heater configured to heat the first rotatable member; the heater provided with a first heat generating member and a second heat generating member
Implementation Method 2
a first rotatable member configured to heat a recording material; the second rotatable member fixing a toner image on the recording material with the first rotatable member
Data Source
AI summary
An image forming apparatus includes a heater including first and second heating members, the first heating member is longer than the second heating member in a widthwise direction. The image forming apparatus performs image formation on a first recording material shorter than the second heating member and a second recording material shorter than the first heating member and longer than the second heating member. In a case that first and second sheets are the first recording material, an electric power supplied to the first heating member is a first electric power while the first sheet passes through a nip, and in a case that the first sheet is the first recording material and the second sheet is the second recording material, the electric power is a second electric power smaller than the first electric power while the first sheet passes through the nip.