Fuel Cell Cover Thermal Expansion Parallelism
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Solution Overview
Problem
In fuel cell devices, the reduction in parallelism between unit cells due to thermal expansion and varying rigidity of components leads to uneven surface pressures, potentially lowering power generation performance.
Innovation Solution
A fuel cell device configuration where the thermal expansion coefficient of the cover portion is higher than that of the fastening member, with the fastening member having lower rigidity, helps reduce dimensional changes and maintain parallelism between unit cells, using materials like aluminum for the cover and iron for the fastening member, and employing multiple rod members to distribute compressive loads efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the tension shaft is made with smaller cross-sectional area than the case, then the device complexity is reduced and ease of manufacture is improved, but the rigidity of the tension shaft becomes lower than the case, causing dimensional change difference under thermal expansion and reducing parallelism between unit cells
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) of the tension shaft by selecting a material with a lower thermal expansion coefficient than the case material. This parameter change allows the tension shaft to compensate for its lower rigidity by expanding less thermally, thereby maintaining parallelism between unit cells despite having a smaller cross-sectional area for ease of manufacture
Solution Approach 2:
The patent employs different materials for the case and tension shaft, creating a composite structure where each component is made of material optimized for its specific function. The case uses a material with higher thermal expansion coefficient while the tension shaft uses a material with lower thermal expansion coefficient, allowing differential thermal expansion that compensates for rigidity differences
2Volume of moving object
If the cross-sectional area of the fastening member is reduced, then the device size is reduced, but the rigidity of the fastening member decreases, leading to larger dimensional change under compressive load and reduced parallelism
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) of the fastening member by selecting a material with a lower thermal expansion coefficient than the cover portion. This allows the fastening member to maintain dimensional stability under thermal expansion despite having reduced cross-sectional area, thereby preventing parallelism reduction while achieving compact device size
3Reliability
If multiple rod members are used as fastening members, then the load distribution is improved and reliability is increased, but the device complexity increases
Solution Approach 1:
The patent divides the fastening function into multiple separate rod members instead of using a single fastening component. Each rod member independently fastens the cell stack, end plate, and case, distributing the compressive load across multiple elements. This segmentation improves reliability and load distribution while maintaining relatively simple individual component designs
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 effectively prevents the reduction in parallelism between unit cells, maintains stable fastening, and reduces the size of the fuel cell device while ensuring efficient load distribution and power generation performance.
Implementation Method 1
the thermal expansion coefficient of the cover portion is larger than a thermal expansion coefficient of the fastening member... in the case where the rigidity of the fastening member is lower than the rigidity of the cover portion, it is possible to reduce a difference in dimensional change in the stacking direction between the side of the fastening member and the side of the cover portion in the cell stack resulting from the difference in rigidity
Data Source
AI summary
A fuel cell device includes: a cell stack; a case including a cover portion that covers one of side surfaces of the cell stack along a stacking direction; an end plate connected to one end portion of the cover portion in the stacking direction; and a fastening member that extends in parallel with the stacking direction on an opposite side of the cell stack from the cover portion, that includes one end portion in the stacking direction connected to the end plate and another end portion in the stacking direction connected to the case, and that fastens the cell stack, the end plate, and the case to each other. A thermal expansion coefficient of the cover portion is larger than a thermal expansion coefficient of the fastening member.