Fixing Apparatus Graphite Sheet Thermal Management
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Solution Overview
Problem
Existing fixing apparatuses experience temperature rise at sheet non-passing portions during continuous printing, leading to potential damage and high-temperature offsetting issues, particularly when using thick graphite sheets which are difficult to manufacture and increase heat capacity, thereby prolonging the first printout time.
Innovation Solution
A fixing apparatus configuration with an endless film, a contact member, and a nip portion forming member, where multiple thin graphite sheets with high thermal conductivity in the planar direction are superposed on the contact member's surface, sandwiched between the ceramic heater and heater holder, to effectively suppress temperature rise at sheet non-passing portions without degrading the first printout time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thick graphite sheet is used to suppress temperature rise at sheet non-passing portions, then the thermal conductivity in planar direction increases, but the first printout time is prolonged due to increased heat capacity
Solution Approach 1:
The graphite sheet is divided into multiple thin sheets (each less than 100 μm thick) that are superposed together. This segmentation achieves the desired total thickness for heat transport while keeping individual sheet heat capacity low, thus suppressing temperature rise at sheet non-passing portions without excessively prolonging the first printout time.
Solution Approach 2:
Multiple graphite sheets are superposed to create a composite structure that combines the high thermal conductivity of graphite in the planar direction with reduced heat capacity through thin individual layers, resolving the contradiction between heat transport efficiency and heating speed.
2Temperature
If a thick graphite sheet is used to increase heat transport, then the effect of suppressing temperature rise improves, but the manufacturing difficulty increases significantly
Solution Approach 1:
Instead of manufacturing one thick graphite sheet with high thermal conductivity (which is difficult), the invention segments it into multiple thin sheets that are easier to manufacture. Each thin sheet can be produced with standard processes, and when superposed, they achieve the required heat transport effect.
Solution Approach 2:
The invention changes the thickness parameter of the graphite sheet from thick (difficult to manufacture) to thin (easy to manufacture), while compensating for the total heat transport capability by superposing multiple thin sheets, thus achieving the desired temperature uniformity without manufacturing difficulties.
3Temperature
If a thick graphite sheet is used to suppress temperature rise, then the thermal management improves, but heat radiates more to the heater holder, degrading heat supply efficiency
Solution Approach 1:
The graphite heat leveling sheet is segmented into multiple thin sheets superposed together. This structure provides thermal management at the sheet non-passing portions while the thin individual sheets reduce the overall heat capacity and thermal mass, thereby reducing heat radiation to the heater holder and maintaining heat supply efficiency.
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
The superposition of thin graphite sheets with high thermal conductivity in the planar direction enhances heat transport, effectively suppressing temperature rise at sheet non-passing portions while maintaining a short first printout time and preventing heat radiation to the heater holder, thus ensuring efficient heat supply to the recording material.
Implementation Method 1
Graphite provides high thermal conductivity in a direction parallel to the plane of the ceramic heater (in a direction parallel to the plane of covalent bond layers of graphite). Therefore, temperature rise at the sheet non-passing portions for small-size paper can be prevented by providing a graphite sheet on a ceramic substrate.
Implementation Method 2
A certain fixing apparatus mounted on an image forming apparatus, such as a copying machine and a printer, includes an endless film, a ceramic heater in contact with the inner surface of the endless film
Data Source
AI summary
On a second surface of a contact member opposite to a first surface in contact with an endless film, a plurality of sheets, each having a thermal conductivity in a planar direction higher than in a thickness direction and having a thickness of less than 100 μm, are superposed.