Busbar-Terminal Weld Bead Geometry to Prevent Battery Pack Cracks
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Solution Overview
Problem
Vehicle battery modules require a welded structure that ensures strength reliability and conductivity while preventing weld cracks due to the high-temperature embrittlement behavior of terminal materials with high hardness properties, such as phosphor bronze, especially in narrow parts with small distances between bead facing parts.
Innovation Solution
A welding method that forms weld beads with specific geometries, such as bent parts, multiple lines or curves, circular arcs, ellipses, or spot shapes, ensuring a D/W≥2 relationship between bead width and center distance, using laser or arc welding to prevent tensile stress concentration during cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a bead shape with bent parts, multiple lines, or annular shape is formed in a narrow part to secure bonding area, then the welding area is sufficient, but tensile stress concentrates in the embrittled high temperature area causing weld cracks
Solution Approach 1:
The invention changes the geometric parameters of the weld bead by controlling the distance D between bead centers and bead width W to satisfy D/W≥2. This parameter optimization prevents tensile stress concentration while ensuring sufficient welding area, resolving the contradiction between welding area and crack prevention.
2Ease of manufacture
If single spot welding or single bead welding is used, then the welding process is simple, but the bonding area is insufficient in narrow parts
Solution Approach 1:
The invention divides the welding process into multiple spots or beads arranged in specific patterns (multiple lines, annular shapes, or bent parts). This segmentation increases the total bonding area in narrow parts while maintaining manufacturing simplicity through standardized welding sequences.
3Reliability
If terminal material with high hardness property such as phosphor bronze is used, then electrical conductivity is excellent, but high-temperature embrittlement behavior causes ductility decrease
Solution Approach 1:
The invention optimizes the welding process parameters including bead geometry (D/W≥2), welding speed, and heat input control to prevent excessive thermal exposure. This parameter optimization reduces high-temperature embrittlement effects while maintaining the excellent electrical conductivity of phosphor bronze terminal materials.
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 method prevents weld cracks in high-temperature conditions, maintaining excellent strength reliability and conductivity in vehicle battery modules.
Implementation Method 1
energy is applied from one side to melt and penetrate the upper member
Implementation Method 2
a displacement behavior in which the material contracts in a cooling procedure from solidification
Data Source
AI summary
A metal welded structure is provided that enables highly reliable laser welding at a connection between a busbar and a voltage detection terminal in a battery pack. The metal welded structure includes a first metal member, a second metal member having a part overlapping with the first metal member, and a welded part formed in the overlapping part. The welded part has a molten part formed by melting through the second metal member in a thickness direction to the inside of the first metal member. When viewed in the overlapping direction, the welded part has a U-shape including a first linear part and a second linear part extending from both sides of the first linear part in a longitudinal direction to respective ends, and the width D1 between two end points of the welded part and the bead width W of the welded part have a relationship of D1/W≥2.