Laser-Expanded Shaft Case Assembly for Door Lock Alignment
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Solution Overview
Problem
Existing vehicle door lock devices face issues with shaft deformation and operational hindrance due to misalignment and dimensional precision challenges, leading to potential shear fractures and vibration, which increase manufacturing costs.
Innovation Solution
A case design featuring a first member with a shaft portion and a second member with a shaft support portion, where the shaft portion is enlarged in diameter via laser welding, ensuring a secure and precise fit even with lower processing precision, reducing the likelihood of deformation and operational issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shaft portion is inserted into the housing portion with high positional and dimensional precision, then the shaft portion maintains structural integrity and resists deformation, but the manufacturing cost increases
Solution Approach 1:
The shaft portion is preliminarily inserted into the housing portion before laser welding, establishing the correct positional relationship in advance. This preliminary positioning action allows the subsequent laser welding to proceed with lower precision requirements while still achieving reliable structural integrity, thereby reducing manufacturing cost.
Solution Approach 2:
The outer diameter of the shaft portion is changed through laser melting and enlargement, transforming it from a precise fit component to an interference-fit component. This parameter change allows the shaft to be securely held in the housing portion without requiring high positional and dimensional precision during assembly, thus reducing manufacturing cost while maintaining reliability.
2Reliability
If the outer diameter of the shaft portion is larger than the inner diameter of the housing portion, then the shaft portion is supported by the circumferential wall portion and prevents deformation, but the insertion becomes difficult without causing large loads and potential bending
Solution Approach 1:
The shaft portion is preliminarily inserted into the housing portion with clearance before laser welding, avoiding difficult forced insertion. This preliminary action establishes the correct positional relationship without subjecting the shaft to large loads that could cause bending, while the subsequent laser enlargement creates the interference fit for reliable support.
Solution Approach 2:
The fit between the shaft portion and housing portion transitions from a clearance fit during insertion to an interference fit after laser welding. This dynamic change in fit type allows easy insertion initially, then provides strong support and prevents deformation after the laser enlargement process.
3Device complexity
If the shaft portion is welded only at the top surface to the bottom portion, then the manufacturing process is simple, but the load concentrates on the welded portion causing shear fracture under radial loads
Solution Approach 1:
The mechanical welding process is replaced with laser melting and enlargement. Instead of creating a welded joint at the top surface, the laser melts and enlarges the shaft portion to create an interference fit with the circumferential wall portion. This substitution distributes the load along the circumferential contact surface rather than concentrating it at a single welded point, preventing shear fracture while maintaining process simplicity.
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 enlarged-diameter shaft portion maintains structural integrity and smooth operation, preventing deformation and shear fractures, while reducing manufacturing costs by tolerating lower precision tolerances.
Implementation Method 1
radiating laser light from a side of the second member toward a top surface of the one end portion of the shaft portion, and thereby melting the one end portion of the shaft portion and enlarging the one end portion in diameter
Implementation Method 2
The second member is made of a material that transmits laser light. Laser light is radiated from a side of the second member toward the top surface of the shaft portion of the first member. The laser light passes through the second member and reaches the top surface of the shaft portion of the first member.
Implementation Method 3
The heat is transmitted to the bottom surface of the housing portion of the second member, and the bottom surface of the housing portion is also thereby melted.
Data Source
AI summary
A case includes a first member and a second member configured in such a way that a closed space is formed between the first and second members in a state where the first and second members abut against each other. The first member includes a shaft portion extending toward the second member. The second member includes a shaft support portion including a circumferential wall portion that surrounds one end portion of the shaft portion. The shaft portion includes an enlarged-diameter portion that is the one end portion melted in such a way as to be enlarged in diameter.