Fixing Device Nip Stability via Reverse Rotation Control
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Solution Overview
Problem
Conventional fixing devices for image forming apparatuses face issues with maintaining proper nip width and nip pressure due to the identical low friction sheets used by first and second pressure pads, leading to instability and poor fixability and conveyability of recording materials, especially after jam treatment or fixing mode changes.
Innovation Solution
A fixing device with a heating rotation unit, an endless pressure belt, and pressurizing members, where a sheet member is placed between the pressure belt and pressurizing members, and a control unit rotates the heating and pressure belts in a direction opposite to the recording material conveyance at startup to maintain proper nip width and pressure by changing contact positions using frictional force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the identical low friction sheet is used by first and second pressure pads, then the device complexity is reduced, but the independent actions of pressure pads are obstructed leading to poor nip width and nip pressure maintenance
Solution Approach 1:
The patent divides the pressure transmission system into separate functional zones by providing different sheet members for the first and second pressure pads. The first sheet member is positioned between the first pressure pad and pressure belt, while the second sheet member is positioned between the second pressure pad and pressure belt, allowing independent optimization of each pressure pad's function.
Solution Approach 2:
The patent applies different sheet members with potentially different properties to different locations where pressure pads contact the pressure belt. This allows each pressure pad to have optimized local characteristics for its specific function, with the first sheet member optimized for the first pressure pad and the second sheet member optimized for the second pressure pad.
2Object-affected harmful factors
If the low friction sheet is placed between pressure pads and pressure belt, then friction is reduced, but the independent actions of pressure pads are obstructed
Solution Approach 1:
The patent segments the friction reduction function by providing separate sheet members for each pressure pad rather than using a single continuous sheet. This allows each sheet member to be independently optimized and prevents the sheet from obstructing the independent actions of different pressurizing members.
3Adaptability or versatility
If the nip portion is not maintained properly after jam treatment or mode change, then operational flexibility is improved, but fixability and conveyability deteriorate
Solution Approach 1:
The patent implements preliminary actions through the control unit that detect operational states (such as after jam treatment or mode change) and automatically adjust the sheet members or pressure belt position before normal operation resumes. This ensures the nip portion is properly maintained without requiring manual intervention, preserving both operational flexibility and fixing reliability.
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 ensures excellent stability of the nip portion, enhancing fixability and conveyability of recording materials with a simple construction, preventing obstruction of pressurizing member actions and maintaining optimal pressure distribution.
Implementation Method 1
contact positions of the sheet member with respect to the plurality of pressurizing members are changed with used of a frictional force between the inner surface of the pressure belt and the sheet member
Implementation Method 2
a heating rotation unit heated by a heat source and rotated by a driving source
Data Source
AI summary
A fixing device has a heating rotor, a pressure belt, a sheet member, first and second pressurizing members, a motor and a control unit. The control unit controls the motor to rotate the heating rotor and the pressure belt in a direction opposite to a conveyance direction of a recording material at startup time after jam treatment of the recording material. Contact positions of the sheet member with respect to the first and second pressurizing members are changed, so that the sheet member is prevented from obstructing independent actions of each of the first and second pressurizing members, which allows the nip portion N to maintain proper nip width and proper nip pressure. Thus, the fixing device has excellent stability at the nip portion to improve fixability and conveyability of the recording material with a simple construction.