Straddled Vehicle Link Member Cross Pipe Diagonal Orientation
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Solution Overview
Problem
The unit swing-type engine in straddled vehicles faces challenges in suppressing the outward protrusion of the link member while maintaining torsional rigidity, as existing designs either compromise on layout and installment of peripheral components or suffer from insufficient torsional rigidity due to the shape of the cross pipe.
Innovation Solution
A straddled vehicle design featuring a link member with a cross pipe whose central axis diagonally crosses the head pipe axes, allowing the cross pipe to be positioned on the inner side and preventing outward protrusion, while maintaining a larger dimension perpendicular to the vehicle width direction to ensure torsional rigidity without increasing head pipe width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cross pipe is positioned with its central axis perpendicular to the head pipe axes to ensure welding margin, then the welding quality is improved, but the link member protrudes outwardly which limits layout and installment of peripheral components
Solution Approach 1:
The patent applies asymmetry by positioning the cross pipe's central axis diagonally to the head pipe axes rather than perpendicularly. This asymmetric arrangement allows the cross pipe to be offset toward the inner side, preventing outward protrusion while maintaining adequate welding margins through the diagonal orientation.
Solution Approach 2:
The patent utilizes dimensional optimization by adjusting the cross pipe's orientation angle diagonally between the perpendicular position and the parallel position. This angular adjustment in another dimension (orientation angle) enables the cross pipe to clear peripheral components without protruding outward, while still providing sufficient welding margin.
2Shape
If the installment interval between head pipes is shortened to satisfy bank angle requirements, then the vehicle body design is improved, but the torsional rigidity of the link member becomes insufficient
Solution Approach 1:
The patent applies local quality by optimizing the cross pipe's dimensional ratios locally. Specifically, the ratio of the cross pipe's dimension in the direction perpendicular to the vehicle width direction to its dimension in the vehicle width direction is set to 0.5 or more. This local dimensional optimization allows the cross pipe to maintain adequate torsional rigidity even when the head pipe installment interval is shortened for bank angle requirements.
3Strength
If the cross pipe dimension in the vehicle width direction is increased to ensure torsional rigidity, then the structural strength is improved, but the head pipe width increases which affects vehicle layout
Solution Approach 1:
The patent applies parameter changes by optimizing the cross pipe's dimensional parameters, specifically setting the ratio of its dimension perpendicular to the vehicle width direction to its dimension in the vehicle width direction at 0.5 or more. This parameter optimization allows the cross pipe to achieve adequate torsional rigidity through its cross-sectional geometry rather than increasing its width, thereby preventing head pipe width increase and maintaining compact vehicle layout.
Data Source
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AI summary
A link member (30) of a straddled vehicle (1) includes left and right head pipes (31, 32) and a cross pipe (33). The cross pipe includes: a central portion (33C) whose central axis (33ax) extends in a vehicle width direction (DW) at a distance from head pipe axes (31ax, 32ax); a left curved portion (33L) extending from the central portion to the left head pipe; and a right curved portion (33R) extending from the central portion to the right head pipe. At at least one of a first end and a second end of the cross pipe, a dimension d2 of the cross pipe in a direction (DP) perpendicular to the vehicle width direction is larger than a dimension d1 thereof in the vehicle width direction, and the central axis of the cross pipe diagonally crosses the head pipe axes.