Exhaust Pipe Layout for Protected Sensor Assembly in Motorcycle Engines
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Solution Overview
Problem
Existing engines for straddle-type vehicles face challenges in assembling and protecting exhaust gas sensors due to the U-shaped exhaust pipe configuration, which complicates sensor placement and makes them susceptible to damage from foreign matter.
Innovation Solution
The exhaust gas sensor is positioned on the lateral side of the cylinder, with the exhaust pipe extending through the down frame to provide space for easy assembly and routing of the sensor's lead wire, while the pipe itself protects the sensor from foreign matter by extending below it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the exhaust pipe is curved in a U shape in front of the down frame, then the exhaust pipe can be routed from the cylinder head to the vehicle rear side, but it becomes difficult to assemble the exhaust gas sensor and route its lead wire
Solution Approach 1:
The exhaust gas sensor is positioned on the lateral side of the down frame rather than on the front surface, utilizing the lateral space created by the exhaust pipe's U-shaped routing. This dimensional shift in sensor placement resolves the assembly difficulty while maintaining the protective U-shaped pipe configuration.
2Ease of operation
If the exhaust gas sensor is positioned in front of the engine for easy assembly, then assembly is simplified, but the sensor may be damaged by foreign matter such as flying stones
Solution Approach 1:
The exhaust pipe serves as a protective intermediary between the foreign matter (flying stones) and the exhaust gas sensor. By positioning the sensor on the lateral side and having the exhaust pipe extend below it, the pipe acts as a shield that blocks harmful foreign matter while allowing the sensor to be easily assembled.
Solution Approach 2:
The exhaust pipe is configured to extend below the exhaust gas sensor in advance, creating a protective barrier before any foreign matter can reach the sensor. This preliminary protective arrangement prevents damage before it can occur.
3Reliability
If the exhaust pipe extends through the down frame to protect the sensor, then protective performance is improved, but the routing complexity increases
Solution Approach 1:
The exhaust pipe performs multiple functions: it conveys exhaust gas from the cylinder head to the vehicle rear side, and simultaneously serves as a protective shield for the exhaust gas sensor by extending below it. This multi-functionality achieves protection without adding separate protective components.
Data Source
AI summary
An engine in a straddle-type vehicle is mounted on a vehicle body frame in which a down frame extends downward from a head pipe. The engine is provided with a cylinder located rearward of the down frame, a cylinder head provided on an upper surface of the cylinder, an exhaust pipe extending from the cylinder head toward a vehicle rear side, and an exhaust gas sensor configured to detect a predetermined characteristic in exhaust gas. The exhaust pipe extends downward through one lateral side of the down frame, crosses front of the down frame, and then extends upward through the other lateral side of the down frame. The exhaust gas sensor is provided on a back surface side of the exhaust pipe on the one lateral side of the down frame, and is located on an outer side with respect to the cylinder in a vehicle width direction.