Battery Pack Mounting Structure That Decouples Cell Swelling Stress
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Solution Overview
Problem
The increased number of stacked battery cells in power supply devices for electric vehicles leads to excessive stress on fixing structures due to cell swelling, necessitating costly material changes and weight increases to manage elongation, which is inefficient and costly.
Innovation Solution
A power supply device design that fixes a lower plate, unaffected by battery swelling, to the power supply target equipment via a plate fixing mechanism, using a connecting structure that allows displacement between the lower plate and fastening members, reducing stress concentration on the fixing points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of stacked battery cells is increased to achieve higher capacity, then the power supply capacity is improved, but the elongation amount of the battery stack increases causing excessive stress on the fixing structure
Solution Approach 1:
The fixing structure is segmented into two independent parts: the lower plate fixed to the power supply target equipment, and the end plates/fastening members fixed to the battery stack. This segmentation allows each part to perform its function independently, with the lower plate bearing the fixing function and the end plates accommodating battery swelling, thereby resolving the stress transmission problem.
Solution Approach 2:
The connecting structure acts as an intermediary between the lower plate and the fastening members. It transmits the weight of the battery stack to the lower plate while allowing displacement due to battery swelling, thus preventing stress concentration on the fixing structure without compromising structural support.
2Length of stationary object
If the length of bind bars is increased to accommodate longer battery stacks, then the battery stack length is improved, but the stress on brackets increases due to accumulated swelling force
Solution Approach 1:
The swelling force reception function is extracted from the bind bars and transferred to the end plates and fastening members. The bind bars are shortened and only perform their original function of fastening end plates, while the end plates and fastening members accommodate the swelling force, thereby reducing stress on brackets.
3Strength
If expensive materials or increased plate thickness and bolt diameter are used to prepare brackets adapted to elongation amount, then the stress resistance is improved, but the cost and weight increase
Solution Approach 1:
The invention uses ordinary materials with standard plate thickness and bolt dimensions for both the lower plate and the end plates/fastening members. By redistributing the stress through structural design rather than relying on material strength or increased dimensions, the fixing structure achieves adequate stress resistance without increasing weight or cost.
Data Source
AI summary
Power supply device is a power supply device to be fixed to a power supply target equipment. Power supply device includes: a plurality of battery cells each having a prismatic outer covering can; a pair of end plates that covers both side end faces of a battery stack in which the plurality of battery cells are stacked; lower plate that covers a lower face of the battery stack; a plurality of fastening members that are sheets extending in a stacking direction of the plurality of battery cells and are arranged on opposed side faces of the battery stack to fasten end plates to each other in a state where the battery stack is placed on an upper surface of lower plate; a plate fixing mechanism for fixing lower plate to the power supply target equipment; and a connecting structure for connecting lower plate and fastening member to each other in a state where the displacement between lower plate and fastening member is allowed.