Exhaust Device Layout Securing Compact Muffling Chamber Volume
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Solution Overview
Problem
Existing exhaust devices for straddle-type vehicles face challenges in securing a sufficient volume for the muffling chamber on the upstream side of the muffler, leading to increased muffler size and reduced design freedom.
Innovation Solution
The primary catalyst case is positioned in the front space of the engine, with the secondary catalyst case on the lower front part, and a muffling chamber is placed in the lower rear space, optimizing the layout to reduce muffler size and enhance noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the secondary catalyst case is disposed on the lower side of the engine, then the catalyst can be activated at an early stage by heated exhaust gas, but it becomes difficult to secure a muffling chamber with sufficient volume on the upstream side of the muffler, leading to increased muffler size
Solution Approach 1:
The invention changes the spatial arrangement from a conventional layout to one where the secondary catalyst case is positioned in front of the engine rather than below it. This dimensional repositioning allows the muffling chamber to be secured on the lower side of the engine with sufficient volume, while maintaining early catalyst activation through proximity to the exhaust port.
Solution Approach 2:
The exhaust device is segmented into distinct functional zones: the primary catalyst case positioned near the exhaust port for early activation, the secondary catalyst case positioned in front of the engine, and the muffling chamber positioned on the lower side. This segmentation allows each component to occupy its optimal space without interfering with others.
2Device complexity
If the secondary catalyst case is disposed on the lower side of the engine, then the catalyst system can be compactly arranged, but the muffler size must be increased to accommodate sufficient muffling chamber volume
Solution Approach 1:
By repositioning the secondary catalyst case from a vertical arrangement (below the engine) to a horizontal arrangement (in front of the engine), the invention creates sufficient vertical space on the lower side for the muffling chamber. This dimensional change allows the muffler to be reduced in size while maintaining adequate muffling volume.
3Object-affected harmful factors
If the muffling chamber volume is increased to compensate for the occupied lower space, then sufficient noise reduction can be achieved, but the overall vehicle size and weight increase
Solution Approach 1:
The exhaust system is segmented into functionally independent components positioned in optimal locations: primary catalyst near the exhaust port, secondary catalyst in front of the engine, and muffling chamber on the lower side. This segmentation allows the muffling chamber to be compact while still achieving sufficient noise reduction, as it is not constrained by the positions of other components.
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 allows for a compact design that secures a sufficient muffling chamber volume, reducing muffler size while maintaining effective noise reduction and minimizing heat damage risks.
Implementation Method 1
a primary catalyst case (53) in which a primary catalyst (54) that purifies the exhaust gas is accommodated
Implementation Method 2
a secondary catalyst case (61) in which a secondary catalyst (62) that purifies the exhaust gas is accommodated
Implementation Method 3
a chamber (71) in which a muffling chamber (72) that reduces an exhaust noise is formed
Data Source
Figure 1
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AI summary
An exhaust device that guides exhaust gas from an exhaust pipe in front of an engine to a muffler in a rear of the engine is provided. The exhaust device includes a primary catalyst case accommodating a primary catalyst configured to purify the exhaust gas at a downstream side from the exhaust pipe, a secondary catalyst case accommodating a secondary catalyst configured to purify the exhaust gas at a downstream side from the primary catalyst, and a chamber formed with a muffling chamber configured to reduce an exhaust noise at a downstream side from the secondary catalyst. The primary catalyst case is disposed in a front space of the engine. The secondary catalyst case is disposed on a front part of a lower space of the engine. The chamber is disposed so as to occupy at least a rear part of the lower space of the engine.