Welding Structure Between Electric Storage Device and Bus Bar
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Solution Overview
Problem
In electric storage apparatuses, the formation of blowholes in welds between external terminals and bus bars reduces weld strength, leading to potential failure in connection stiffness due to stress concentration and reduced air tightness.
Innovation Solution
The solution involves forming a second weld portion with its center displaced from the first weld portion, overlapping it to eliminate blowholes and reduce stress concentration, while using a smaller penetration depth and energy to prevent air tightness reduction, and configuring the welds in elliptical or circular ring shapes to enhance strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single weld portion is formed between the external terminal and bus bar, then the connection is simple and fast, but blowholes occur reducing weld strength
Solution Approach 1:
The weld portion is divided into a first weld portion and a second weld portion that are formed separately and then overlap. This segmentation allows each weld portion to be optimized independently, with the second weld portion specifically targeting blowhole elimination in the first weld portion, thereby resolving the contradiction between welding speed and weld strength.
Solution Approach 2:
The first weld portion is formed first, and then the second weld portion is formed to overlap and eliminate blowholes in the first weld portion. This preliminary action approach allows the blowhole elimination function to be performed in a dedicated subsequent step, ensuring weld strength without compromising the initial welding efficiency.
2Strength
If weld penetration depth is increased to eliminate blowholes, then weld strength improves, but air tightness deteriorates
Solution Approach 1:
The second weld portion is configured with different welding conditions (lower energy, smaller penetration depth) specifically in the region where blowholes need to be eliminated, while the first weld portion maintains higher penetration depth for overall strength. This localized quality adjustment resolves the contradiction by applying different welding parameters to different regions of the weld.
Solution Approach 2:
The welding parameters (energy, penetration depth) are changed between the first and second weld portions. The second weld portion uses reduced energy and penetration depth compared to the first, allowing blowhole elimination while preserving air tightness. This parameter change strategy resolves the contradiction between strength improvement and air tightness maintenance.
3Strength
If weld portion is formed to cover the entire connection region, then connection strength is maximized, but stress concentration increases
Solution Approach 1:
The weld portion is segmented into first and second weld portions with different functions. The first weld portion provides overall connection strength, while the second weld portion specifically addresses blowhole elimination. This segmentation distributes stress more effectively compared to a single continuous weld, resolving the contradiction between connection strength and stress concentration.
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 effectively suppresses the reduction in weld strength due to blowholes, enhances the connection's stiffness, and maintains air tightness by eliminating blowholes and distributing stress, thereby ensuring a robust and reliable connection.
Implementation Method 1
The external terminal 4 and the bus bar 6 are welded together in a state where the first connection surface 4a and the second connection surface 6a overlap each other. That is, a weld portion 9 in which the external terminal 4 and the bus bar 6 are partially melted and fused is formed
Data Source
AI summary
An electric storage apparatus including a welding structure between an electric storage device and a bus bar includes the electric storage device including an external terminal that includes a first connection surface, the bus bar including a second connection surface that overlaps the first connection surface, a first weld portion that is formed extending over the external terminal and the bus bar in a region where the first connection surface and the second connection surface are opposed to each other, and a second weld portion that is formed extending over the external terminal and the bus bar in the region where the first connection surface and the second connection surface are opposed to each other, the second weld portion directly overlapping the first weld portion in a region where the first connection surface and the second connection surface overlap each other.