Duplex Down Frame Segmentation for Exhaust Routing in Straddled Vehicles
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Solution Overview
Problem
Existing straddled vehicle designs with diamond frames face limitations in engine design flexibility due to the fixed bottom end of the down tube, which restricts exhaust pipe positioning and affects vehicle stiffness and turning performance.
Innovation Solution
A straddled vehicle with a diamond frame where the lower left and right down frame portions are positioned to the left and right of the exhaust pipe, allowing for independent positioning without altering the exhaust pipe's connection, and are attached to the engine for enhanced stiffness and design freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the bottom end of the down tube is fixed to the engine in a diamond frame, then the vehicle-body frame weight is reduced and clearance is improved, but the exhaust pipe positioning is restricted and engine design flexibility is limited
Solution Approach 1:
The patent introduces a duplex cradle frame structure with separate left and right down frame portions that extend laterally beyond the engine width. This dimensional expansion in the lateral direction allows the exhaust pipe to be positioned between the down frame portions without interfering with the engine's vertical attachment point, thereby resolving the spatial conflict between frame fixation and exhaust routing.
Solution Approach 2:
The down frame portion is segmented into left and right separate structures rather than a single centralized down tube. This segmentation allows independent positioning of each down frame portion relative to the engine and exhaust pipe, enabling the exhaust pipe to pass between them while maintaining secure engine attachment points at the bottom ends of each down frame portion.
2Ease of operation
If the down tube is positioned forward of the engine, then the exhaust pipe must detour around it, but this restricts exhaust pipe positioning and affects vehicle stiffness
Solution Approach 1:
The down frame portions extend laterally beyond the engine width in the left-right direction, creating a spatial configuration where the exhaust pipe can be positioned between them. This lateral extension resolves the conflict between exhaust pipe routing and down tube positioning by utilizing the lateral dimension rather than forcing the exhaust pipe to detour forward or backward.
Solution Approach 2:
The patent employs a symmetric duplex structure with left and right down frame portions that are mirror images of each other. This symmetrical copying provides balanced structural support for vehicle stiffness while simultaneously creating the lateral space needed for exhaust pipe positioning between the two down frame portions.
3Device complexity
If a single down tube is used in a half-duplex cradle frame, then the structure is simplified, but the exhaust pipe and down tube positioning conflict cannot be resolved
Solution Approach 1:
The single down tube is segmented into left and right down frame portions that extend laterally beyond the engine. This segmentation creates the necessary lateral space for exhaust pipe positioning between the down frame portions while maintaining a relatively simple overall frame structure that builds upon the conventional cradle frame design.
Solution Approach 2:
The left and right down frame portions serve multiple functions: they provide structural support for vehicle stiffness, create lateral clearance for exhaust pipe routing, and maintain attachment points for engine fixation. This multi-functionality resolves the positioning conflict without significantly increasing overall structural complexity.
Data Source
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AI summary
The freedom in designing engines for straddled vehicles where the bottom end of the down tube is fixed to the engine is improved. A down tube, or down frame portion, includes an upper down frame portion and a lower down frame portion. The lower down frame portion extends from the upper down frame portion. The lower down frame portion includes a lower left down frame portion and a lower right down frame portion. The lower left down frame portion is located to the left of the central axis of the upper down frame portion. The lower left down frame portion extends from the upper down frame portion rearwardly and downwardly. The bottom end of the lower left down frame portion is attached to the engine. The lower right down frame portion is located to the right of the central axis of the upper down frame portion. The lower right down frame portion extends from the upper down frame portion rearwardly and downwardly. The bottom end of the lower right down frame portion is attached to the engine. The portion of the exhaust pipe connected to the engine is located to the right of the lower left down frame portion and to the left of the lower right down frame portion.