Fixing Film Temperature Control to Prevent Thermal Deformation
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Solution Overview
Problem
The existing fixing devices in electro-photographic image forming apparatuses suffer from deformation of the rotating film due to thermal stress, leading to dent marks, which result in insufficient fixing of toner images and potential cracking, especially in low temperature environments.
Innovation Solution
A fixing device with a control portion that variably controls the heating temperature of the heating unit when transitioning from a rotating to a halt state, ensuring a controlled temperature difference between the fixing nip and other portions of the film to prevent deformation, by starting the rotation of the film when the temperature difference is within a predetermined range and maintaining energization of the heater during post-rotation to reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film is continuously heated with the film being stopped to transfer toner from the pressure roller to the film, then the pressure roller is cleaned and toner contamination is suppressed, but the temperature rises greatly only in the fixing nip portion and the temperature of other portions does not largely change, causing thermal stress and deformation of the film
Solution Approach 1:
The patent applies preliminary action by rotating the film at a predetermined speed before stopping it for heating during discharge control. This preliminary rotation ensures that the film is in motion when heating begins, preventing localized thermal stress and deformation that would occur if heating started while the film was completely stationary. The film is rotated, then stopped, and heating is performed with controlled duration to achieve toner transfer while maintaining temperature uniformity.
Solution Approach 2:
The patent implements periodic action through the cyclic operation of the film: rotating during normal fixing operations, stopping for discharge control heating, and then rotating again. This periodic alternation between rotation and stationary heating states allows the film to undergo thermal cycles that prevent permanent deformation while still achieving the necessary toner transfer from the pressure roller to the film surface.
2Reliability
If the film is stopped and heated to transfer toner, then discharge control is achieved, but thermal stress is applied in the vicinity of the boundary between the portion that has thermally expanded and the portion that has not thermally expanded, causing distortion and dent marks
Solution Approach 1:
The film is rotated at a predetermined speed before being stopped for heating during discharge control. This preliminary rotation ensures uniform initial conditions and prevents the film from being completely stationary when heating begins, thereby reducing thermal stress concentration at boundaries and preventing distortion and dent marks while still achieving effective toner transfer.
Solution Approach 2:
The patent controls the heating duration as a variable parameter during discharge control. By adjusting the heating time to be within a specific range (not too long), the temperature rise is limited to prevent excessive thermal expansion differences between the heated fixing nip portion and the cooler portions of the film, thereby maintaining film surface flatness while achieving sufficient toner transfer.
3Productivity
If the film rotates with thermal stress applied, then the film is pulled by the pressure roller, but the stress is further concentrated, permanently deforming the film and causing dent marks
Solution Approach 1:
The film is rotated at a predetermined speed before stopping for heating, creating a preliminary motion state. This preliminary action ensures that when the film is subsequently stopped and heated during discharge control, the thermal stress is distributed more evenly, preventing concentration of stress that would lead to permanent deformation and dent marks while maintaining fixing operation continuity.
Solution Approach 2:
The film undergoes periodic cycles of rotation during normal fixing operations and stationary heating during discharge control. This periodic action allows the film to alternate between states, preventing continuous stress concentration during rotation while still achieving necessary toner transfer during the stationary heating phase, thereby maintaining both productivity and film shape stability.
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 film deformation, ensuring consistent and reliable fixing of toner images across various temperature conditions, preventing image failures and film cracking, while maintaining the film's integrity.
Implementation Method 1
a heating unit configured to heat the rotating unit
Implementation Method 2
the film in the vicinity of the fixing nip portion (broken line portion) locally thermally expands and the other portion (solid line portion) does not thermally expand
Implementation Method 3
thermal stress is applied in the vicinity of the boundary between the portion that has thermally expanded and the portion that has not thermally expanded in the rotation direction (circumferential direction) of the film
Data Source
AI summary
A fixing device includes a rotating unit, a heating unit configured to heat the rotating unit, and a pressure member configured to nip a recording material between the rotating unit and the pressure member and to convey the recording material. In addition, a control portion is configured to variably control, when the rotating unit is changed from a rotating state to a halt state, a heating temperature of the heating unit in the halt state according to the heating temperature of the heating unit in the rotating state.