Cast Magnesium Alloy Seat Frame with Variable Wall Thickness
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Solution Overview
Problem
Seat frames made from magnesium or aluminum alloys by casting often suffer from shrinkage cracks and porosities due to differences in cooling rates between the top and side walls, which can render them unusable as structural elements in vehicles like motorcycles.
Innovation Solution
The seat frame design incorporates a pair of frame members with distinct cross-sectional regions, featuring a U-shaped cross-section in the first region for seat attachment and an H-shaped cross-section in the second region, reducing the thickness difference between connecting walls and side walls, thus minimizing cooling rate disparities and preventing casting defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the top wall is made larger to increase strength, then the strength of the frame member is improved, but the difference in cooling rate between the top wall and side walls increases, leading to shrinkage cracks and porosities
Solution Approach 1:
The patent applies local quality by making the top wall thickness equal to or smaller than the side wall thickness in specific regions, rather than uniformly increasing thickness throughout. This localized thickness adjustment prevents excessive cooling rate differences at critical boundaries while maintaining adequate strength where needed, thereby preventing shrinkage cracks and porosities during casting.
Solution Approach 2:
The patent changes the thickness parameter of the top wall relative to the side wall, specifically making the top wall thickness equal to or smaller than the side wall thickness in certain regions. This parameter adjustment optimizes the cooling rate distribution during casting, preventing shrinkage defects while maintaining structural integrity.
2Force
If the thickness of the top wall is made larger to support rider and passenger seats, then the load-bearing capacity is improved, but the cooling rate difference between top wall and side walls increases, causing shrinkage defects
Solution Approach 1:
The patent implements local quality by varying the top wall thickness locally - making it equal to or smaller than the side wall thickness in regions where thickness difference would cause cooling rate problems, while maintaining adequate thickness for load bearing in other regions. This localized adjustment prevents shrinkage defects without compromising load-bearing capacity.
Solution Approach 2:
The patent segments the frame member into different regions with different thickness characteristics. By dividing the structure into regions with optimized thickness distributions, it prevents shrinkage defects in critical areas while maintaining load-bearing capacity in load-bearing regions.
3Weight of moving object
If magnesium or aluminum alloy is used instead of steel to reduce weight, then the fuel consumption and running performance are improved, but the strength per unit area is lower, requiring larger thickness which causes cooling rate differences and casting defects
Solution Approach 1:
The patent applies local quality by optimizing the thickness distribution of the aluminum or magnesium alloy frame member, making the top wall thickness equal to or smaller than the side wall thickness in specific regions. This prevents excessive cooling rate differences that would cause shrinkage defects, enabling successful casting of lightweight alloys without compromising structural integrity.
Solution Approach 2:
The patent changes the thickness parameter of the top wall relative to side walls, making it equal to or smaller in certain regions. This parameter optimization enables the use of lightweight aluminum or magnesium alloys by preventing casting defects, thereby achieving weight reduction without sacrificing manufacturing quality.
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 design enhances the strength of the seat frame, reduces the likelihood of casting defects, and allows for easier seat fixation while maintaining a lightweight and cost-effective structure, improving both fuel efficiency and running performance of vehicles.
Implementation Method 1
The shrinkage crack is generated due to the shrinkage caused by the solidification of molten metal
Implementation Method 2
the thickness is made different (or the thickness difference is increased) between the top wall and the side walls. As a result, the cooling rate at the time of casting is made different (or the difference in the cooling rate is increased) between the top wall and the side walls
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
The generation of a casting defect is suppressed which would otherwise occur to frame members of a seat frame when being formed of a magnesium alloy or an aluminum alloy by casting. The seat frame (100) according to the present invention is for a saddle-riding type transporter (200), and includes a pair of frame members (10L,10R) formed of a magnesium alloy or an aluminum alloy by casting. The pair of frame members (10L,10R) each include a first side wall (11), a second side wall (12) located outer with respect to the first side wall (11) in a vehicle width direction (B), and a connecting wall (13) for connecting the first side wall (11) and the second side wall (12) to each other. The connecting wall (13) includes seat fixing section (13a,13b,13c) for fixing a seat (136,139). The pair of frame members (10L,10R) each include a first region (R1) in which a top end of the first side wall (11) and a top end of the second side wall (12) are connected to each other by the connecting wall (13), and a second region (R2) in which a portion below the top end of the first side wall (11) and a portion below the top end of the second side wall (12) are connected to each other by the connecting wall (13). The seat fixing section (13a,13b,13c) is located in the first region (R1).