Motorcycle Silencer Bank Angle and Width Optimization
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Solution Overview
Problem
Existing silencers for straddled vehicles, such as motorcycles, face a conflict between increasing the bank angle and maintaining a reduced width dimension, as inclining the silencer to enhance the bank angle results in increased width, which is undesirable for such vehicles.
Innovation Solution
The silencer is designed with an outer pipe that overlaps with the swingarm and inclines such that its rear end is higher than the front end, featuring a separator to section the expansion chamber into upstream and downstream chambers, with inner pipes connecting them, allowing for a reduced width dimension while maintaining an increased bank angle, and includes a catalytic converter to prevent overheating and improve exhaust gas cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the silencer is inclined to increase the bank angle, then the bank angle is improved, but the width dimension increases
Solution Approach 1:
The silencer is nested within the exhaust pipe structure, with the expansion chamber positioned inside the cylindrical main body. This nesting allows the silencer to be integrated into the existing exhaust system without increasing the overall width dimension, while still achieving the desired bank angle through strategic positioning.
Solution Approach 2:
The expansion chamber is positioned in the width direction relative to the exhaust pipe, allowing the silencer to achieve its function without increasing the top-and-bottom dimension. By utilizing the width direction for the expansion chamber placement, the design maintains a compact vertical profile while accommodating the inclined configuration for improved bank angle.
2Area of stationary object
If the silencer overlaps with the swingarm in the vehicle side view, then the width dimension is reduced, but the accessibility for inspection deteriorates
Solution Approach 1:
The silencer is positioned to overlap with the swingarm in the vehicle side view, creating a compact width dimension. The light-transmitting window is strategically placed on the crankcase to provide local accessibility for oil level inspection without requiring the entire silencer structure to be accessible, thus maintaining ease of operation at the specific inspection point.
Solution Approach 2:
The light-transmitting window acts as an intermediary element that provides access to the oil level information without requiring direct access to the oil storage or engine internals. This window allows riders to inspect oil levels easily from the side of the vehicle, compensating for the reduced accessibility caused by the silencer's overlapping position with the swingarm.
Data Source
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AI summary
An upstream expansion chamber E1 and a downstream expansion chamber E2 are provided in an outer pipe 51. An exhaust pipe 40 extends to the upstream expansion chamber E1 through the downstream expansion chamber E2. An inner pipe 52 leads an exhaust gas from the upstream expansion chamber E1 to the downstream expansion chamber E2. An inner pipe 53 allows an exhaust gas to pass through the upstream expansion chamber E1 from the downstream expansion chamber E2 and be led to the outside of the outer pipe 51. In a vehicle side view, the inner pipes 52, 53 are respectively arranged at a position further downward than the exhaust pipe 40 and a position further upward than the exhaust pipe 40. The outer pipe 51 is provided to incline such that a rear end is higher than a front end, and inclines to pass through a position further upward than an axle of a rear wheel. In a cross section orthogonal to a direction in which the outer pipe 51 extends, a dimension of the outer pipe 51 in a width direction is smaller than a dimension of the outer pipe 51 in a top-and-bottom direction.