Surface Heater Slits for Thermal Expansion Compensation
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Solution Overview
Problem
Existing surface heaters in image forming apparatuses face issues with thermal expansion, leading to separation and reduced heat conduction between metal and insulation layers, resulting in abnormal heating and poor temperature sensing due to differences in thermal expansion coefficients.
Innovation Solution
A surface heater design with a heating body interposed between insulation layers and support layers, featuring slits in the second support layer to compensate for arc length differences, reducing the likelihood of separation and enhancing heat conduction and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the surface heater operates at high temperature, then heating efficiency is improved, but thermal expansion causes separation between layers and reduces heat conduction
Solution Approach 1:
The patent applies the thermal expansion principle by designing the second support layer with slits that allow controlled expansion and contraction. The slits enable the support layer to accommodate dimensional changes during heating and cooling cycles, preventing separation between the heating body, insulation layers, and support layers. This resolves the contradiction by allowing the structure to expand thermally without compromising layer bonding stability.
Solution Approach 2:
The second support layer is segmented into multiple regions (first region superposed on heating body, second region not superposed) with different slit configurations. This segmentation allows differential expansion compensation in different areas, maintaining structural integrity while accommodating thermal expansion. The first region has fewer or no slits to maintain heat conduction, while the second region has more slits to accommodate expansion, resolving the contradiction between heating efficiency and layer bonding stability.
2Strength
If the support layer is made rigid to maintain structural integrity, then mechanical strength is improved, but thermal expansion differences cause separation and reduce heat conduction
Solution Approach 1:
The support layer is designed with local quality variations through selective slit placement. The first region (superposed on heating body) has fewer or no slits to maintain heat conduction and structural integrity, while the second region (not superposed) has more slits to accommodate thermal expansion. This local differentiation resolves the contradiction by providing rigidity where needed while allowing expansion compensation where applicable, maintaining both structural integrity and heat conduction stability.
3Reliability
If slits are added to accommodate thermal expansion, then layer separation is prevented, but heat conduction may be reduced
Solution Approach 1:
Slits are selectively placed only in the second region of the support layer where they will not interfere with heat conduction to the heating body. The first region maintains continuous material for optimal heat conduction, while the second region incorporates slits for expansion accommodation. This local differentiation resolves the contradiction by preventing layer separation without significantly compromising heat conduction efficiency.
Solution Approach 2:
The patent applies partial action by implementing slits only in the portion of the support layer where they are most beneficial (second region not superposed on heating body), rather than throughout the entire structure. This partial implementation achieves sufficient expansion compensation while minimizing impact on heat conduction, resolving the contradiction between layer bonding stability and heat conduction 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 design effectively mitigates thermal expansion issues, ensuring consistent heat distribution and improved temperature sensing, preventing abnormal heating and maintaining the insulating function of the layers.
Implementation Method 1
a heating body (583) interposed between an insulation layer (582) and another insulation layer (584)
Implementation Method 2
insulation layers (582, 584) having a planar shape one on top of another; the heating body (583) is interposed between the insulation layers (582, 584)
Data Source
AI summary
A surface heater includes a heating body, insulation layers, and a first support layer and a second support layer. The heating body is interposed between the insulation layers. The heating body and the insulation layers are interposed between the first support layer and the second support layer. The first support layer has a first region superposed on the heating body and a second region not superposed on the heating body. The first support layer has at least one slit which is located at a side of an inner circumferential surface of the surface heater bent into an arc shape. The second region has the at least one slit and the first region has no slit, or the at least one slit includes a plurality of slits and the second region has a greater number of slits out of the plurality of slits than the first region has.