Exhaust Pipe Plate Reflection Wave Noise Cancellation
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Solution Overview
Problem
Conventional exhaust gas apparatuses face challenges in suppressing air column resonance in tail pipes, leading to increased weight and production costs due to the need for large resonance chambers and sub-mufflers, which fail to effectively mute low-frequency noise at low engine speeds.
Innovation Solution
The exhaust gas apparatus incorporates a plate with an opened portion and a closed portion at the tail pipe ends, creating reflection waves with a 180-degree phase difference to cancel each other, reducing sound pressure levels without requiring a sub-muffler or large resonance chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large resonance chamber is used to suppress air column resonance in the tail pipe, then the sound pressure level is reduced, but the weight and volume of the exhaust gas apparatus increase
Solution Approach 1:
The invention divides the tail pipe into multiple sections with different diameters, creating expansion and contraction portions that generate reflection waves. This segmentation approach replaces the need for a large resonance chamber with distributed acoustic impedance changes along the pipe, thereby reducing overall apparatus weight while maintaining sound suppression effectiveness.
Solution Approach 2:
The invention introduces an intermediary structure consisting of expansion and contraction portions that act as acoustic mediators. These portions create reflection waves with specific phase relationships to cancel air column resonance, replacing the direct large-volume resonance chamber approach with a more compact intermediary mechanism.
2Object-affected harmful factors
If a sub-muffler is added to suppress air column resonance, then sound pressure is reduced, but device complexity and production cost increase
Solution Approach 1:
The invention merges the sound suppression function directly into the tail pipe structure by incorporating expansion and contraction portions within the tail pipe itself. This eliminates the need for a separate sub-muffler component, thereby reducing device complexity and production cost while achieving the same acoustic suppression effect.
Solution Approach 2:
The tail pipe is designed to perform multiple functions: it serves as both the exhaust gas discharge conduit and the sound suppression device. The expansion and contraction portions integrated into the tail pipe create reflection waves that cancel air column resonance, making the tail pipe a multi-functional component that eliminates the need for dedicated sub-muffler hardware.
3Object-affected harmful factors
If the resonance chamber volume is increased to suppress low-frequency noise, then noise suppression effectiveness is improved, but the volume and weight of the apparatus increase
Solution Approach 1:
The invention uses dynamic geometric variations along the tail pipe (expansion and contraction portions) to create frequency-dependent acoustic impedance changes. This dynamic approach allows effective low-frequency noise suppression through distributed reflection wave generation rather than requiring a static large-volume resonance chamber, thereby reducing overall apparatus 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 design effectively suppresses air column resonance, reducing muffled sounds in the passenger compartment at low engine speeds and minimizing the weight and production costs of the exhaust gas apparatus.
Implementation Method 1
a plate formed with an opened portion and provided at at least one of the upstream opened end and the downstream opened end in opposing relationship with an exhaust gas discharging direction
Implementation Method 2
creating reflection waves with a 180-degree phase difference to cancel each other, reducing sound pressure levels
Implementation Method 3
with a through bore passing through the outer peripheral portion and the inner peripheral portion of the exhaust gas pipe
Data Source
AI summary
An exhaust gas apparatus suppresses sound pressure level from increasing, and reducing its weight and production cost without need of a sub-muffler in a tail pipe and a sound deadening device having an air column resonance of a large capacity provided at the upstream opened end of the tail pipe. The exhaust gas apparatus is provided with an exhaust gas pipe, an upstream opened end connected to the sound deadening device positioned at the upstream side of an exhaust gas discharging direction, and a downstream opened end through which the exhaust gas is discharged to the atmosphere. A plate is provided at least one of the upstream opened end and the downstream opened end in opposing relationship with the exhaust gas discharging direction, and formed with an opened portion. The exhaust gas pipe is formed at its peripheral wall axially inwardly spaced apart from the plate with a through bore.