Stepped Punch Stretching for Variable-Wall Battery Cases
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Solution Overview
Problem
Existing battery case bodies face issues of poor reliability and stability due to welding seams, leading to potential fractures and low space utilization in battery packs, while roll-sealing processes are limited by the need for uniform wall thickness, which increases material and weight costs without ensuring strength.
Innovation Solution
A punch and die system with a stepped design, featuring a thick and thin rod section transitioned by tapered or curved surfaces, is used to create a variable-wall-thickness battery case body, allowing for thinner middle sections and thicker ends, optimized by multiple thinning rings and controlled ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wall thickness of the case body is increased to ensure reliability during roll-sealing, then the sealing reliability is improved, but the material cost and weight increase, resulting in decreased energy density
Solution Approach 1:
The patent applies local quality by creating a variable wall thickness distribution where the end sections have greater thickness for reliable roll-sealing while the middle section has reduced thickness to minimize material usage. The punching tool with different diameter sections (first section with larger diameter for ends, second section with smaller diameter for middle) enables this localized thickness variation, ensuring sealing reliability only where needed rather than uniformly throughout the entire case body.
2Loss of substance
If the wall thickness of the case body is uniformly reduced to save materials, then material cost decreases, but the case body becomes prone to tearing during roll-sealing and loses reliability during use
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through variable wall thickness. The punching tool design with a first section (larger diameter) corresponding to end sections and a second section (smaller diameter) corresponding to the middle section creates thicker walls at ends and thinner walls in the middle. This ensures sufficient material thickness at critical sealing locations to prevent tearing while reducing material consumption in non-critical areas.
3Ease of manufacture
If welding is used to assemble the case body and lid, then the components can be joined, but the welded battery cases cannot be closely arranged due to welding seams, resulting in low space utilization
Solution Approach 1:
The patent replaces the welding process with a roll-sealing process. The case body is designed with a rolled edge at the end section that can be sealed to the lid through rolling and crimping operations. This mechanical sealing method eliminates welding seams entirely, allowing battery cases to be placed in close proximity without the clearance requirements necessary for welding access, thereby maximizing space utilization in the battery pack.
4Loss of substance
If the case body is designed with variable wall thickness to save materials, then material efficiency improves, but the manufacturing process becomes more complex requiring specialized punching tools
Solution Approach 1:
The punching tool is segmented into multiple functional sections: a first section with a larger diameter corresponding to the end sections of the case body, and a second section with a smaller diameter corresponding to the middle section. This segmentation of the punching tool enables the creation of variable wall thickness in the case body while keeping the tool design relatively simple and modular, balancing manufacturing complexity with material efficiency gains.
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 enhances material efficiency, reduces weight, and improves the reliability and space utilization of battery packs by ensuring strong sealing and minimizing material usage.
Implementation Method 1
a punch for stretching the battery case body... the thin rod section and the thick rod section are transitioned by means of at least one tapered surface or/and curved surface
Data Source
AI summary
A punch and a die for stretching battery case body and its stretching process. The die includes a stepped punch as a male die, at least one thinning ring as a female die, and a variable-wall-thickness stretching step, which belongs to the thinning stretching. When the sheet or plate is stretched to the cup-shaped stretching piece by at least one-time forming stretching, and then through the thinning stretching to finally obtain the variable-wall-thickness battery case body with thin wall in the middle and thick wall at one end or both ends in the axial direction. The body can reduce the material consumption of the middle section of the case body and ensure the roll-sealing strength of one end or both ends, thus solving the problem between the amount of materials and the reliability of the roll sealing caused by the wall thickness of the battery case body.