Battery Pack Case Joint Structure to Prevent Ultrasonic Welding Burrs
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Solution Overview
Problem
Existing battery pack cases suffer from external defects such as burrs due to over-fusion during ultrasonic welding, which current prevention structures fail to completely prevent.
Innovation Solution
A battery pack case design featuring a projecting portion and grooved portion with a uniform gap and support structure, including stopper ribs and recesses, to maintain a consistent distance and prevent over-fusion during thermal fusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ultrasonic welding is performed to couple the battery pack case, then the coupling strength is improved, but burrs are generated due to over-fusion
Solution Approach 1:
The patent applies preliminary action by pre-forming a gap between the first and second cases before ultrasonic welding. This gap is created through the engagement of the projecting portion with the grooved portion, establishing a predetermined spacing that prevents resin overflow during the subsequent welding process while still allowing adequate coupling strength to be achieved.
Solution Approach 2:
The patent uses the gap between the cases as an intermediary element that mediates between the need for strong coupling and the need to prevent burr generation. This gap acts as a buffer zone that contains the molten resin during ultrasonic welding, allowing the energy director to melt and fuse the cases together without the resin flowing outward to form burrs.
2Strength
If pressing force is increased to improve fusion, then coupling strength is improved, but resin flows outwards generating burrs
Solution Approach 1:
The patent applies preliminary action by pre-establishing the gap structure through engagement of the projecting portion with the grooved portion before applying pressing force during welding. This predetermined gap configuration ensures that when pressing force is applied to achieve proper fusion, the resin remains contained and prevents overflow that would otherwise occur with increased pressing force.
3Object-generated harmful factors
If uniform distance is maintained to prevent burrs, then defect rate is reduced, but coupling precision becomes more difficult to control
Solution Approach 1:
The patent applies preliminary action by pre-forming the uniform gap through the mechanical engagement of the projecting portion with the grooved portion. This engagement structure automatically establishes the correct spacing before welding begins, eliminating the need for complex real-time control during the welding process and making it easier to maintain consistent coupling precision while preventing defects.
Solution Approach 2:
The patent uses self-service by designing the engagement structure between the projecting portion and grooved portion to automatically maintain the uniform gap without requiring external control mechanisms. The geometry of these features themselves serves to control the spacing, making the system self-regulating and reducing the difficulty of maintaining coupling precision.
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
Prevents burrs and reduces external defects by maintaining a uniform coupling distance, ensuring stable fusion without resin overflow.
Implementation Method 1
there is used a method of pressurizing the polymer resin in a molten state using frictional heat by ultrasonic vibration
Implementation Method 2
pressurizing the polymer resin in a molten state using frictional heat by ultrasonic vibration
Implementation Method 3
the energy director 15 is melted in the grooved portion 22 of the second case 20 while being vibrated
Implementation Method 4
the energy director 15 is melted in the grooved portion 22 of the second case 20 while being vibrated
Data Source
AI summary
Discussed is a battery pack case configured to receive a plurality of battery cells, the battery pack case including a first case and a second case coupled to each other through and engagement between first case and the second case. A projecting portion is on a coupling portion of the first case at a middle part of the first case in a thickness direction to project therefrom, a grooved portion is in a coupling portion of the second case at a middle part of the second case in a thickness direction thereof such that the projecting portion is inserted into the grooved portion, and a uniform gap between the outside of the projecting portion of the first case and the outside of the grooved portion of the second case in the state in which the first case and the second case are coupled and thermally fused to each other.