Straddle-Type Vehicle Exhaust Device Noise Reduction and Sensor Placement
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Solution Overview
Problem
Straddle-type vehicles face challenges in effectively reducing exhaust noise from engines while accurately detecting oxygen concentrations in exhaust gases, as existing solutions do not efficiently utilize space for muffling and sensor placement.
Innovation Solution
The vehicle incorporates an exhaust device with a catalyst, an inner tube, and an outer tube that creates a muffling space for noise reduction, along with upstream and downstream oxygen sensors placed strategically to detect oxygen concentrations before and after the catalyst, with a pipe member allowing for displacement to accommodate thermal expansion and flexible mounting for accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a muffling space is formed inside the exhaust device to reduce exhaust noise, then noise reduction effectiveness is improved, but the space for sensor placement and exhaust gas flow becomes limited
Solution Approach 1:
The exhaust device is segmented into distinct functional zones: an inner tube for exhaust gas flow and catalyst placement, an outer tube for structural support, and a muffling space between them for noise reduction. This segmentation allows each component to perform its function without interfering with others, resolving the space limitation contradiction.
Solution Approach 2:
The inner tube is nested within the outer tube, creating a concentric structure that utilizes vertical space efficiently. The muffling space is formed in the annular region between the two tubes, allowing noise reduction functionality without compromising the exhaust gas flow path through the inner tube.
2Measurement precision
If an oxygen sensor is placed inside the exhaust device to detect oxygen concentration, then detection accuracy is improved, but the sensor becomes vulnerable to thermal expansion damage
Solution Approach 1:
A flexible pipe member is introduced as an intermediary between the oxygen sensor and the rigid exhaust device structure. This pipe member absorbs thermal expansion stresses through its flexibility, protecting the sensor from damage while maintaining the sensor's position for accurate measurement.
Solution Approach 2:
The mounting structure incorporates flexible elements that allow dynamic adjustment and movement. The flexible pipe member can expand and contract with temperature changes, and the mounting position can be adjusted to accommodate thermal expansion, ensuring both sensor durability and measurement accuracy.
3Object-affected harmful factors
If the inner tube extends downstream of the catalyst to create a muffling space, then noise reduction is improved, but the structural rigidity decreases due to permissible displacement
Solution Approach 1:
The pipe member connecting the inner and outer tubes is made flexible rather than rigid. This flexible connection allows the structure to accommodate thermal expansion and vibration while maintaining the overall geometric stability needed for the muffling space to function effectively.
Solution Approach 2:
The exhaust device utilizes a composite structure combining rigid components (inner tube, outer tube, catalyst support) with flexible connection elements (flexible pipe member). This composite approach provides both the structural integrity needed for stability and the flexibility needed to accommodate thermal and vibrational stresses.
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 effectively reduces exhaust noise and accurately detects oxygen concentrations, preventing damage from thermal expansion and allowing for flexible design and improved vehicle balance.
Implementation Method 1
a catalyst which contacts the exhaust gas to clean the exhaust gas
Implementation Method 2
an outer tube which covers an outer peripheral surface of at least a region of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from an exit of the inner tube is flowed to reduce an exhaust noise radiated from the engine
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A straddle-type vehicle comprises an engine which generates driving power for allowing the straddle-type vehicle to travel and emits an exhaust gas; an exhaust device including: a catalyst which contacts the exhaust gas to clean the exhaust gas, an inner tube in which the catalyst is disposed in an inner passage thereof through which the exhaust gas flows, the inner tube extending to a location that is downstream of the catalyst, in a flow direction of the exhaust gas; and an outer tube which covers an outer peripheral surface of at least a region of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from an exit of the inner tube is flowed to reduce an exhaust noise radiated from the engine; at least one exhaust pipe through which the exhaust gas emitted from the engine is led to the catalyst; and a downstream oxygen sensor which is disposed to detect an oxygen concentration of the exhaust gas flowing through the inner passage of the inner tube after flowing through the catalyst, at a location that is downstream of the catalyst in the inner passage of the inner tube.