Fixing Device Nip Width Control for Warm-Up Speed and Belt Life
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Solution Overview
Problem
Conventional fixing devices with high heat capacity pressure rollers cause heat loss, leading to delayed temperature reaching during warm-up and potential overheating of the endless belt, which accelerates its deterioration.
Innovation Solution
A fixing device with an adjustment mechanism that controls the nip width between the heating member and pressure element, ensuring A>B≥N, where A is the nip width during fixing, B is the nip width during temperature raising, and N is the heat generating element's length, to optimize heat transfer and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the pressure roller is separated from the endless belt during warm-up to eliminate heat escape path, then the temperature raising performance is improved, but the contact region of the endless belt with the heat generating member may be excessively heated, accelerating the speed of deterioration of the endless belt
Solution Approach 1:
The patent applies dynamics by making the pressure roller movable between two positions: a first position during warm-up where it is separated from the endless belt to prevent heat loss and accelerate temperature rise, and a second position during fixing operations where it contacts the endless belt to apply pressure. This dynamic repositioning resolves the contradiction by adapting the pressure roller's contact state to different operational phases.
Solution Approach 2:
The patent applies preliminary action by performing the warm-up operation with the pressure roller separated from the endless belt before fixing operations begin. This preliminary separation prevents heat loss during the critical warm-up phase, allowing the heating member to reach operating temperature faster, and then the pressure roller is positioned for contact when fixing operations start.
2Stability of the object's composition
If the pressure roller has a high heat capacity to maintain temperature, then the temperature stability during fixing is improved, but the heat for heating the endless belt is taken away by the pressure roller, causing delay in reaching specified temperature
Solution Approach 1:
The patent resolves this contradiction by dynamically controlling the pressure roller's position. During warm-up, the pressure roller is separated from the endless belt, preventing its high heat capacity from absorbing heating energy and delaying temperature rise. During fixing operations, the pressure roller is positioned to contact the endless belt, where its heat capacity then helps maintain temperature stability. This dynamic positioning allows the pressure roller's thermal properties to benefit the system at the appropriate operational phase.
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 allows for quicker temperature reaching of the heating member while preventing excessive heat transfer to the pressure roller, thereby reducing the risk of endless belt deterioration and improving the fixing device's performance.
Implementation Method 1
the heating member is in contact with the inner surface of an endless belt... thereby heating the sheet via the endless belt
Implementation Method 2
the pressure roller and the second surface of the sheet are in contact with each other, allowing the plate-shaped heat generating member and the pressure roller to produce pressure
Data Source
AI summary
An image forming apparatus includes a transfer unit for transferring a toner image onto a sheet, a fixing device for fixing the image, the fixing device including a heating member including a heat generating element and electrodes on both sides of the heat generating element in a sheet conveyance direction and connected to the heat generating element, and a pressure element for pressing against the heating member, and a controller for controlling an adjustment mechanism so that a distance between the heating member and the pressure element becomes a first distance during a fixing process and a second distance larger than the first distance during temperature raising of the heating member, which is conducted before the fixing process.