Fastening Assistance Plate for Battery Stack Thermal Expansion
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Solution Overview
Problem
In power supply devices for vehicles with multiple secondary battery cells, the difference in linear expansion coefficients between metal binding bars and cooling plates leads to loosening of screw connection members due to heat expansion, especially in varying temperature environments, affecting the stability of the heat radiation structure.
Innovation Solution
Incorporating a fastening assistance plate with the same linear expansion coefficient as the binding bars, positioned between the fixing plate and the binding bars, to absorb and cancel out linear expansions, preventing stress on screw connection members and thus preventing loosening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If binding bars and cooling plate are made of different metals to achieve strong fastening and good heat conduction, then fastening strength and cooling efficiency are improved, but screw connection members loosen due to differential thermal expansion
Solution Approach 1:
An intermediate layer is introduced between the binding bar and cooling plate to mediate the thermal expansion difference. This intermediate layer absorbs the differential expansion through its own deformation, preventing direct stress transmission to the screw connection members and eliminating the loosening problem while maintaining the different-metal construction for strength and heat conduction
Solution Approach 2:
The physical state or properties of the intermediate layer are utilized to accommodate thermal expansion. By selecting a material with appropriate elastic properties or phase change characteristics, the system absorbs expansion stresses without transmitting them to the fastening screws, thus maintaining connection stability under temperature variations
2Force
If binding bars are made of metal with high strength, then fastening capability is improved, but thermal expansion difference with aluminum cooling plate causes seating surfaces to slide and bolts to loosen
Solution Approach 1:
The intermediate layer serves as a mediator between the high-strength binding bar and aluminum cooling plate. It decouples the thermal expansion behaviors of the two metals, allowing the binding bar to maintain its high fastening force while the intermediate layer absorbs the expansion differential, preventing seating surface sliding and bolt loosening
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 maintains the fastening force of screw connection members over time, enhancing the reliability of the heat radiation structure and preventing thermal instability, even under extreme temperature conditions.
Implementation Method 1
the difference of size change amounts by linear expansions of binding bars 920 and cooling plate 930 is large, seating surfaces of bolts 941 and nuts 942 which fix binding bars 920 and cooling plate 930, slide or slip
Implementation Method 2
cooling plate 103 which incorporates heat exchanger 104 configured to forcibly cool by the heat of evaporation of a coolant circulating inside
Implementation Method 3
heat exchanger 104 configured to forcibly cool by the heat of evaporation of a coolant circulating inside
Data Source
AI summary
In order to enable the suppression of a decrease in screw fastening force due to a difference in linear expansion, a power supply device includes: a battery stacked body (11) including a plurality of stacked secondary battery cells (1); a fixing part configured to fix the battery stacked body (11); a fastening assistance plate (50) having the same linear expansion coefficient as the fixing part; a fixing plate (30) disposed between the fixing part and the fastening assistance plate (50), and having one surface on which the battery stack body (11) is disposed; and a plurality of screw connected members (40) passing through the fixing part, the fixing plate (30), and the fastening assistance plate (50). Each of the plurality of screw connected members (40) has a seating surface on which a frictional force operates, caused by an axial force, and the seating surface of each of the plurality of screw connected members (40) is in contact with the fixing plate (30) or the fastening assistance plate (50).