Fixing Apparatus Heat Generating Element End Temperature Sagging
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Solution Overview
Problem
Existing fixing apparatuses in image forming devices face challenges with end temperature sagging and excessive temperature rise at non-sheet passing portions, particularly when handling sheets of varying widths, due to the temperature drop at the end portions of heat generating elements and the uneven heat distribution across the fixing film and pressure roller.
Innovation Solution
The fixing apparatus is designed with heat generating elements having varying widths and lengths along the substrate, with specific areas configured to have different electric resistance values and energy densities, ensuring that the end portions of larger sheets are adequately heated while preventing excessive heating of non-sheet passing areas by optimizing the heat generation per unit length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the heat generating element has a uniform width along its length, then the manufacturing is simple, but end temperature sagging occurs at the end portions of the fixing film and pressure roller
Solution Approach 1:
The heat generating element is designed with a width that varies along its length, creating different local heat generation characteristics. The end portions have a greater width than the central portion, which increases the heat generation amount at the ends to compensate for temperature sagging, while the central portion maintains a smaller width for efficient heat generation during normal sheet passing.
2Temperature
If the heat generating element width is increased at end portions to suppress end temperature sagging, then end portion heating is improved, but excessive temperature rise occurs at non-sheet passing portions when small width sheets are processed
Solution Approach 1:
The heat generating element features a non-uniform width profile with greater width at end portions and smaller width at the central portion. This local variation in geometry creates different heat generation characteristics: the wider ends provide sufficient heating for sheet end portions, while the narrower center reduces heat generation in the non-sheet passing areas when sheets with smaller longitudinal widths are processed, preventing excessive temperature rise.
3Area of stationary object
If the heat generating element length is made equal to the fixing film and pressure roller length, then complete coverage is achieved, but temperature distribution becomes uneven across the members
Solution Approach 1:
The heat generating element is designed with a length that is equal to or slightly less than the fixing film and pressure roller, but with a width that varies along its length. The greater width at end portions compensates for the reduced overall length, ensuring adequate heat generation at the ends while the varying width profile creates a more uniform temperature distribution across the fixing members compared to a uniform width design.
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 effectively suppresses end temperature sagging and excessive temperature rise at non-sheet passing portions, ensuring consistent toner fixation across different sheet widths, including A4 and LTR sizes, by managing heat distribution efficiently.
Implementation Method 1
a heat generating element 42a, 42b having a length 42l in a longitudinal direction CD and a width 42w in a widthwise direction WD orthogonal to the longitudinal direction CD. Each of the heat generating elements 42a, 42b is sectioned into a first area A, a second area B, and a third area C in order from an end portion in the longitudinal direction CD. The areas A, B, and C have energy densities P1, P2, and P3, respectively, satisfying a relationship of "P2>P3>P1"
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A fixing apparatus including a heat generating element having a first area, a second area, and a third area, the first area being located on an end portion side in an orthogonal direction orthogonal to a conveyance direction of a recording material and having a first heat generation amount per unit length in the orthogonal direction, the second area being located on an inner side than the first area in the orthogonal direction and having a second heat generation amount per unit length in the orthogonal direction, the third area being located on the inner side than the second area in the orthogonal direction and having a third heat generation amount per unit length in the orthogonal direction. The second heat generation amount is larger than the third heat generation amount, and the third heat generation amount is larger than the first heat generation amount.