Straddled Vehicle Foot Frame Layout and Exhaust Integration
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Solution Overview
Problem
Straddled vehicles with integrated foot frames face increased manufacturing costs and reduced flexibility due to interference with engine and exhaust pipe components, as well as vehicle body frames, leading to compromised layout and design constraints.
Innovation Solution
A straddled vehicle design featuring a straight foot frame extending in the vehicle width direction, with the catalyst positioned forward of the foot frame, allowing the exhaust pipe to be narrowly constructed and the foot frame to pass between the engine and exhaust pipe, and the engine supported by both the down frame and main frame, eliminating the need for a vehicle body frame to support the engine from below.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If foot frames are provided as separate right and left members, then flexibility in layout is improved, but manufacturing cost increases due to increase in number of components and assembling steps
Solution Approach 1:
The patent merges the right and left foot frames into a single integrated foot frame structure. This integration reduces the number of components and assembling steps, thereby lowering manufacturing cost while maintaining the necessary flexibility in layout through the unified design that can accommodate various engine and exhaust pipe configurations.
2Ease of manufacture
If foot frames are provided as an integrated member, then manufacturing cost is reduced, but flexibility in layout degrades due to interference with exhaust pipe and vehicle body frame
Solution Approach 1:
The patent positions the catalyst in the exhaust pipe at a location that is forward of the foot frame in the vehicle width direction. This spatial arrangement in the width dimension allows the integrated foot frame to extend below the engine without interfering with the exhaust pipe, thereby maintaining layout flexibility while keeping the integrated structure that reduces manufacturing cost.
Solution Approach 2:
The patent segments the exhaust pipe into different sections with the catalyst positioned in a specific section forward of the foot frame. This segmentation allows the exhaust pipe to be routed in a manner that avoids interference with the integrated foot frame, preserving layout flexibility while maintaining the cost benefits of integration.
3Reliability
If exhaust pipe is designed with large wall thickness for catalyst activation, then catalyst efficiency is improved, but outer diameter of exhaust pipe is enlarged degrading foot frame layout flexibility
Solution Approach 1:
The patent resolves this contradiction by positioning the catalyst forward of the foot frame in the vehicle width direction. This dimensional arrangement allows the exhaust pipe to maintain its large wall thickness for efficient catalyst activation without increasing the overall width that would interfere with foot frame layout. The spatial separation in the width dimension eliminates the conflict between pipe thickness and layout flexibility.
4Strength
If vehicle body frame supports engine from below, then engine support is improved, but flexibility in foot frame layout degrades due to interference with vehicle body frame
Solution Approach 1:
The patent positions the catalyst and exhaust pipe in the vehicle width direction forward of the foot frame, creating a spatial arrangement that allows the integrated foot frame to extend below the engine without interfering with the vehicle body frame structure. This dimensional positioning maintains both engine support capability and foot frame layout flexibility.
Data Source
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AI summary
A foot frame (41) has a straight shape and extends in a vehicle width direction. In a vehicle plan view, at least portion of a cylinder head (23) overlaps with a crankcase (21). A front portion of an engine (5) is supported by a down frame (16). A rear portion of the engine is supported by a main frame (15). A catalyst (34) is disposed forward of the foot frame. An exhaust pipe (27) extends backward from a front side of the engine through a lower position than the engine. The foot frame is disposed between a bottom surface of the engine and the exhaust pipe in a vehicle up-and-down direction.