Aluminum-Iron Seat Frame Joining via Melt-Solidification
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Solution Overview
Problem
Current joining techniques for automobile seat frames, which involve replacing iron-based materials with aluminum-based materials, face challenges such as reduced joint strength due to diverted electric current during welding, potential electric corrosion from insulating coatings, and increased operation time for penetrating rivets, as well as high machining accuracy requirements for forming projections in fasteners.
Innovation Solution
A joined body design featuring a thin plate with through holes, first members with protruding portions inserted into these holes, and second members made of the same material as the first members, connected through melt-solidification, with a post-joining hardness difference within specific limits to ensure strong and easy joining between plate-like and pipe-like members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If aluminum-based materials are used to replace iron-based materials for weight reduction, then weight is reduced, but joint strength becomes insufficient
Solution Approach 1:
The invention uses a composite joining structure combining aluminum-based material (thin plate) and iron-based material (first members with protruding portions). The protruding portions are inserted into holes of the thin plate and connected by melt-solidification, creating a hybrid joint that leverages the weight advantage of aluminum while maintaining the strength advantage of iron-based materials through the protruding portion connection.
2Strength
If rivet penetration technique is used to join aluminum-based material and iron-based material, then joining is achieved, but electric current is diverted causing large current requirement and insulating coating peeling
Solution Approach 1:
The invention extracts the harmful penetration step from the joining process. Instead of forcing the rivet/protruding portion through the aluminum thin plate (which causes coating peeling and current diversion), the protruding portions are inserted into pre-formed holes from one side only, and connection is achieved by melt-solidification of the protruding portion ends. This eliminates the harmful effects of bilateral penetration while maintaining joint strength.
3Strength
If rivet penetration technique is used for joining, then connection is achieved, but operation time is increased due to additional penetration step
Solution Approach 1:
The invention removes the time-consuming rivet penetration step from the joining process. The protruding portions are inserted into pre-formed holes without requiring forceful penetration through the thin plate, and the connection is achieved through melt-solidification. This streamlines the operation and reduces manufacturing time while maintaining joint strength.
4Strength
If projections are formed in fastener by dents for joining different materials, then joining is achieved, but high machining accuracy is required
Solution Approach 1:
The invention changes the joining mechanism from mechanical interlocking via dents/projections requiring high precision to melt-solidification connection. The protruding portions are connected by melting and solidifying the material at the ends, which is less sensitive to dimensional tolerances and machining accuracy requirements compared to precision dent formation and projection insertion.
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 approach enables easy and strong joining of plate-like and pipe-like members, facilitating weight reduction while minimizing the production of intermetallic compounds and reducing operation complexity.
Implementation Method 1
the second member and an end portion of the protruding portion are connected together by melt-solidification of a part of the second member and a part of the end portion
Data Source
AI summary
A joined body includes: a thin plate including through holes; first members each including: a base portion and a protruding portion inserted into one of the through holes; and a second member placed oppositely to the base portion via the thin plate and made of a material that is of a same kind as a material of the first members. The thin plate is made of a material having a specific gravity smaller than the materials of the first and the second members. The second member and an end portion of the protruding portion are connected together by melt-solidification. A post-joining hardness difference in a range of 30% along a direction orthogonal to a joint interface between the second member and the protruding portion, the range being centered on the joint interface, is equal to or less than 90% of a pre-joining hardness difference.