Lateral Catalyst Offset in Saddle-Driven Vehicle Exhaust
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Solution Overview
Problem
The existing structure of a straddled vehicle with a single-cylinder four-stroke engine unit requires a complicated exhauster support to maintain catalyst durability due to the catalyst's placement below the engine, which complicates the structure and may not effectively improve exhaust gas purification performance.
Innovation Solution
The catalyst is positioned closer to the combustion chamber by shortening the path length from the cylinder exhaust passage to the catalyst, and it is placed partially below the engine main body to allow hot exhaust gas to flow directly into the catalyst, improving purification performance while simplifying the exhauster structure by reducing the need for complex support systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst is provided below the engine main body, then the activation of the catalyst is facilitated and purification performance is improved, but the exhauster must employ a complicated structure to secure durability
Solution Approach 1:
The catalyst is positioned in the left-right direction (lateral dimension) rather than only in the up-down direction below the engine. By placing the catalyst laterally offset from the exhaust pipe centerline, the patent creates a new spatial arrangement that reduces vibration exposure while maintaining hot gas contact, thereby improving reliability without increasing structural complexity
Solution Approach 2:
The exhaust pipe serves as an intermediary structure that naturally supports the catalyst. Instead of requiring separate support structures from the vehicle body frame, the catalyst is integrated into the exhaust pipe assembly, which already exists to convey hot exhaust gas. This eliminates the need for additional support components while maintaining catalyst durability
2Temperature
If the catalyst is provided below the engine main body, then hot exhaust gas flows into the catalyst effectively, but support rigidity requires modification of the engine main body structure
Solution Approach 1:
The catalyst support function is merged with the exhaust pipe structure. The exhaust pipe, which already exists to deliver hot exhaust gas to the silencer, is designed to also support the catalyst laterally. This combination eliminates the need for separate support structures or engine main body modifications while maintaining effective thermal contact between exhaust gas and catalyst
Solution Approach 2:
The exhaust pipe serves dual purposes: conveying hot exhaust gas and supporting the catalyst. The existing exhaust pipe structure, designed to withstand thermal and mechanical loads, is utilized to support the catalyst without requiring additional support components or modifications to the engine main body or vehicle body frame
3Volume of moving object
If the catalyst is provided in the middle of the narrow exhaust pipe, then the structure is compact, but the exhauster durability is compromised due to vibrations
Solution Approach 1:
The catalyst is positioned laterally offset from the exhaust pipe centerline rather than at the center. This lateral displacement moves the catalyst away from the primary vibration axis (up-down direction) while maintaining compact overall dimensions. The catalyst remains within the exhaust system volume but is strategically positioned to reduce vibration exposure, improving durability without increasing volume
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 configuration enhances the purification performance of exhaust gas and secures the exhauster's durability against vibrations without requiring a complex support structure, resulting in a more efficient and simplified exhaust system.
Implementation Method 1
The exhauster includes an exhaust pipe, a silencer, and a catalyst
Implementation Method 2
hot exhaust gas flows into the catalyst which is highly activated when it becomes hot
Data Source
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AI summary
An object is to provide a straddled vehicle on which a single-cylinder four-stroke engine unit is mounted, which improves the purification performance of purifying exhaust gas by a catalyst and simplifying the structure of an exhauster. It is assumed that a straddled vehicle 1 is viewed in a direction of a linear line L2 which is orthogonal to a crankshaft axis Cr1 and orthogonal to a cylinder axis Cy1. The center of an upstream end 35a of a silencer 35 is provided one of leftward and rightward in a left-right direction of the center of a downstream end 31 b of a cylinder exhaust passage member 31. A main catalyst 39 is arranged so that the center of the downstream end is on the one of the leftward and rightward of the center of the upstream end. The main catalyst 39 is provided to at least partially overlap a quadrangle S10 which is formed by a side S11 which passes the downstream end 31 b of the cylinder exhaust passage member 31 and is in parallel to a cylinder axis Cy1, a side S12 which passes the downstream end 31b of the cylinder exhaust passage member 31 is in parallel to a crankshaft axis Cr1, a side S13 which passes the upstream end 35a of the silencer 35 and is in parallel to the cylinder axis Cy1, and a side S14 which passes the upstream end 35a of the silencer 35 is in parallel to the central axis of the crankshaft axis Cr1.