Fuel Cell Stack Datum Nesting for Inter-Cell Sliding Resistance
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Solution Overview
Problem
Fuel cell stacks in vehicles face challenges in maintaining relative position and alignment under high acceleration and impact loads, leading to inter-cell sliding and displacement, exacerbated by thermal contraction and low friction surface treatments, which existing solutions address inadequately with weight and complexity additions.
Innovation Solution
The design incorporates enhanced datum structures on bipolar plates with increased thickness along the stacking dimension, providing a nesting relationship to resist inter-cell movement, and optional datum pins for additional resistance, allowing for improved alignment and sliding resistance without permanent connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesives or supplemental support structures are used to prevent inter-cell sliding, then resistance to inter-cell movement is improved, but weight and device complexity increase
Solution Approach 1:
The patent applies nesting by placing one datum structure inside another datum structure. Specifically, a first datum structure on one bipolar plate is nested within a second datum structure on an adjacent bipolar plate, creating an interlocking arrangement that prevents relative sliding movement between cells without requiring additional support structures or adhesives
Solution Approach 2:
The datum structures serve dual functions: they provide alignment references during stack assembly and simultaneously provide collision protection and sliding resistance during vehicle operation. The nested arrangement of datums on adjacent plates makes the system self-supporting, eliminating the need for separate adhesives or supplemental support structures
2Reliability
If adhesives are used to secure fuel cells, then inter-cell sliding resistance is improved, but ease of repair deteriorates due to inability to disassemble
Solution Approach 1:
The patent divides the collision protection function into separate, discrete datum structures on each bipolar plate rather than using a continuous adhesive bond. This segmentation allows individual cells to be separated by removing the mechanical datum structures, enabling stack disassembly for repair while maintaining sliding resistance during operation
Solution Approach 2:
The nested datum structures act as reversible mechanical intermediaries between adjacent bipolar plates. They provide the necessary friction and geometric constraint to prevent sliding during operation, but can be removed to allow disassembly, unlike permanent adhesive bonds
3Temperature
If thermal contraction is considered in cold start conditions, then Y-axis compressive retention load decreases, but inter-cell sliding increases
Solution Approach 1:
The nested datum structures are designed in advance to compensate for thermal contraction effects. The geometric configuration of the nested datums creates preliminary mechanical constraints that counteract the tendency for cells to slide apart when Y-axis compressive retention load decreases during cold start conditions
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 dimension that substantially coincides with the cell stacking dimension to promote a nested fit with a comparable datum on an adjacently-stacked bipolar plate. This nesting facilitates an interference fit that enhances the resistance to sliding movement between respective 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. In one form, the use of welding, bonding or related attachment of the datum to the plate promotes enhanced metallic support without the need for increasing the plate footprint and without having to overmold the datum directly onto the plate.