Fuel Cell Stack Datum Structure for Collision Protection
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Solution Overview
Problem
Fuel-cell stacks in vehicles face challenges in maintaining the relative position of cells during high acceleration loads and impacts, leading to inter-cell shifting, which existing solutions like datum pins and adhesives either increase assembly costs or hinder disassembly for maintenance.
Innovation Solution
A method involving the use of a potting material to create a thick datum structure along the stacking dimension of bipolar plates, providing enhanced resistance to inter-cell movement by forming a snug fit with the stack housing, eliminating the need for datum pins and allowing for easier disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If datum pins are used to prevent inter-cell shifting during high acceleration events, then resistance to shearing movement is improved, but assembly cost and device complexity increase
Solution Approach 1:
The patent removes the datum pins from the final stack assembly, extracting only the essential alignment function. Instead of permanent pins, temporary alignment features are used during assembly that are discarded or removed afterward, eliminating the complexity and cost of permanent pin retention while maintaining stacking precision.
Solution Approach 2:
Alignment features are incorporated into the bipolar plates during manufacturing, enabling preliminary alignment to be performed during the stacking process itself. This preliminary action ensures proper positioning before the stack is compressed and sealed, eliminating the need for post-assembly pin retention.
2Reliability
If conventional datum pins are used to maintain stacking alignment, then inter-cell shifting is prevented, but disassembly for service becomes difficult
Solution Approach 1:
The alignment function is segmented into temporary features that serve their purpose during assembly and then become separable. The alignment protrusions and recesses are designed to facilitate initial stacking but do not permanently lock the cells, allowing the stack to be disassembled for maintenance while maintaining alignment during operation.
Solution Approach 2:
Temporary alignment features are used during the stacking process and then effectively discarded or rendered inactive in the final assembly. These features accomplish their alignment purpose and are removed or deactivated, leaving no obstruction to disassembly while having served their function during construction.
3Ease of manufacture
If inter-cell friction is reduced through surface treatments, then cell assembly is easier, but resistance to shearing force during crashes is reduced
Solution Approach 1:
The solution combines low-friction surface treatments on cell surfaces with high-friction potting material in the inter-cell gaps. This composite approach allows cells to be easily assembled due to low surface friction, while the potting material provides high friction to resist shearing forces during crashes, simultaneously achieving both ease of assembly and crash resistance.
Solution Approach 2:
Different friction characteristics are applied to different locations: the cell surfaces have low-friction treatments for easy assembly, while the inter-cell gap material has high-friction properties for crash resistance. This local differentiation of friction properties resolves the contradiction between assembly ease and shear resistance.
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 solution effectively resists inter-cell shifting under high acceleration loads, such as up to 160 g, without adding assembly costs and facilitates disassembly for maintenance, while maintaining the structural integrity of the fuel-cell stack.
Implementation Method 1
a liquid form of the potting material is poured into the mold such that upon curing, the potting material forms a datum
Data Source
AI summary
A system and method for aligning and reducing the relative movement between adjacent fuel cells within a fuel cell stack. The inter-cell cooperation between fuel cells along a stacking dimension is enhanced by one or more datum placed along the edge of a bipolar plate that makes up a part of a cell-containing assembly. The datum is shaped along a thickness that substantially coincides with the cell stacking dimension to avoid shifting between adjacently-stacked cells that may otherwise arise out of the occurrence of a significant acceleration along the dimension that defines the major surfaces of the plates, cells and their respective assemblies. By having the datum be integrally formed with numerous stacked cells, the need to affix individual tabs each plate is avoided.