Insert-Molded Power Storage Terminal Seal Against Resin Cracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power storage devices face issues with crack formation in the resin member due to thermal expansion differences between the case member, terminal member, and resin member, leading to potential seal failures.
Innovation Solution
A power storage device is designed with a resin member molded using a resin material comprising a thermoplastic main resin with a glass transition temperature of 70°C or higher, a thermoplastic elastomer with specific glass transition temperatures ranging from −10°C to 20°C and −40°C or lower, and a filler, which helps in reducing stress and preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a main resin with high glass transition temperature (e.g., PPS with Tg=90°C) is used to ensure the resin member has sufficient hardness, then the resin member can properly fix the terminal member to the case lid member, but cracks may form in the resin member at room temperature due to thermal expansion differences between the case member, terminal member, and resin member
Solution Approach 1:
The patent uses a composite resin material consisting of a main resin (with Tg≥70°C) and an elastomer (with Tg between -10°C and 20°C). This composite structure combines the hardness and structural integrity of the main resin with the flexibility and stress-absorbing capability of the elastomer, preventing crack formation while maintaining fixing strength
Solution Approach 2:
The patent changes the glass transition temperature parameter of the resin material by adding an elastomer component with a lower Tg than the main resin. This creates a multi-phase material system where the elastomer phase remains flexible at room temperature, reducing thermal expansion stress and preventing cracks while the main resin phase provides structural hardness
2Reliability
If an elastomer is added to the resin material to increase toughness and prevent cracks, then the resin member can better withstand thermal expansion stress, but the resin member may become too soft to properly fix the terminal member to the case lid member
Solution Approach 1:
The patent creates a composite material where the elastomer component (providing toughness and crack resistance) is combined with the main resin component (providing hardness and structural strength). The synergistic effect of this composite allows the resin member to simultaneously achieve both crack resistance and sufficient hardness for proper fixing
Solution Approach 2:
The elastomer provides localized flexibility and stress absorption at the molecular level within the resin matrix, while the overall resin member maintains its structural hardness. This local quality differentiation allows different regions of the material to perform different functions - the elastomer phases absorb stress to prevent cracks, while the main resin phases provide structural integrity
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 described solution effectively curbs crack formation in the resin member when the power storage device is at room temperature, maintaining a good seal even under varying temperature conditions during cooling/heating cycles.
Implementation Method 1
an elastomer that easily deforms elastically may be further added to the resin material so as to increase the toughness of the resin member, for the reason as follows. The elastomer thus added disperses stress applied to the resin member and prevents cracks from forming in the resin member or extending when the resin member is molded and cooled to room temperature or when the battery is in actual use.
Implementation Method 2
the elastomer has a second glass transition temperature Tg2 that is equal to or higher than −10° C. and equal to or lower than 20° C. (−10≤Tg2≤20) and a third glass transition temperature Tg3 that is equal to or lower than −40° C. (Tg3≤−40)
Implementation Method 3
cracks may form due to cohesive failure along the boundary between the resin member and the terminal member, in a region of the resin member close to the boundary, under the stress generated in the resin member due to thermal expansion differences between the case member and terminal member, and the resin member
Data Source
AI summary
A power storage device has a case member, a terminal member, and a resin member subjected to insert molding to fix the terminal member to the case member. The resin member is made of a resin material including a thermoplastic main resin having a first glass transition temperature equal to or higher than 70° C., a thermoplastic elastomer, and a filler. The elastomer has a second glass transition temperature that is equal to or higher than −10° C. and equal to or lower than 20° C. and a third glass transition temperature equal to or lower than −40° C.