Heating Unit Position Stability in Image Fixing Apparatus
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Solution Overview
Problem
The existing image heating apparatuses face issues with maintaining the appropriate position of the heating unit during the rotation of the pressure roller, leading to variations in heat distribution and potential fixing failures such as cold or hot offsets, due to dimension tolerances and thermal expansion affecting the relative position of the heating unit with respect to the fixing nip.
Innovation Solution
The image heating apparatus incorporates a guide groove that guides the heating unit's fitting portions along the rim, ensuring that at least two points abut against the downstream rim, and a pressure member applies a rotation moment to counteract the rotation moment generated by the pressure roller, maintaining a stable position of the heating unit even during rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the heating unit is loosely inserted into the guide groove to allow movement, then the heating unit can be easily installed and adjusted, but the position of the heating unit becomes unstable during pressure roller rotation causing heat distribution variations
Solution Approach 1:
The heating unit is designed to be movable along the guide groove during installation and adjustment, but during operation, a pressing member applies force to press the heating unit against the downstream side rim of the guide groove, dynamically transitioning from a static loose fit to a dynamically constrained position that eliminates instability during pressure roller rotation
Solution Approach 2:
The pressing member applies a preliminary counteracting force to the rotation moment generated by pressure roller rotation. By pressing the heating unit against the downstream side rim before instability occurs, the invention prevents position variations and heat distribution issues that would otherwise result from the loose fit during operation
2Ease of manufacture
If dimension tolerances and thermal expansion are accommodated with a loose fit, then assembly is easier, but the relative position of the heating unit varies during operation causing fixing failures
Solution Approach 1:
The positioning function is segmented into two phases: during assembly, the loose fit accommodates dimension tolerances and thermal expansion; during operation, the pressing member activates to provide precise positioning by pressing the heating unit against the downstream side rim, separating the accommodation function from the precision positioning function
Solution Approach 2:
The effective clearance between the heating unit and guide groove changes from a constant loose fit during assembly to a dynamically controlled minimal clearance during operation. The pressing member reduces the effective gap by pressing the heating unit against the downstream side rim, transforming the parameter of position precision without changing the physical dimensions of components
3Reliability
If the heating unit is firmly fixed in the guide groove, then position stability is improved, but the heating unit cannot accommodate thermal expansion and dimension tolerances
Solution Approach 1:
The fixing mechanism is made dynamic rather than static. The heating unit can move freely along the guide groove during assembly to accommodate tolerances and thermal expansion, but during operation, the pressing member dynamically engages to press the heating unit against the downstream side rim, providing stability only when needed during the fixing process
Solution Approach 2:
The pressing member performs a preliminary action by pressing the heating unit against the downstream side rim before the pressure roller rotation begins. This preliminary positioning action ensures that the heating unit is correctly positioned to accommodate thermal expansion and dimension tolerances while maintaining stability during the actual fixing operation
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 stabilizes the position of the heating unit, reducing the occurrence of fixing failures like cold or hot offsets by ensuring consistent heat distribution and pressure alignment, thereby improving the fixability of toner images.
Implementation Method 1
a heater configured to be in contact with an inner surface of the sleeve
Implementation Method 2
a pressure spring (125) for pressing the heating unit (126)
Implementation Method 3
a pressure roller (118) serving as a press-contact member in press-contact with the heating unit (126)
Data Source
AI summary
The present invention relates to an image heating apparatus in which a nip portion is formed by a heating unit, which includes a flexible sleeve and a heater, and a pressure roller. The position of the heating unit is appropriately maintained by pressing the heating unit against the pressure roller using a pressure member so that the heating unit can contact two or more portions of a downstream side rim of a groove arranged on a frame that holds the heating unit, even when the pressure roller is rotated.