Exhaust Sensor Heat Shield Mounting Boss Seal
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Solution Overview
Problem
Exhaust constituent sensors in off-road recreational vehicles face challenges due to high temperatures, which can damage the sensors and affect their performance, especially since the exhaust systems are enclosed within the vehicle's bodywork, leading to increased component temperatures and heat retention.
Innovation Solution
A heat insulating cover is mounted around the exhaust pipe with a mounting boss that forms a mechanical seal to prevent high-temperature air from reaching the sensor and transfers heat to the cover, acting as a heat sink to dissipate the heat into the environment, thereby protecting the sensor from excessive heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the exhaust constituent sensor is mounted directly to the exhaust pipe to sense exhaust constituents, then the sensor can accurately detect exhaust gas composition, but the sensor is exposed to high temperatures that can damage it and affect performance
Solution Approach 1:
A heat insulating cover is introduced as an intermediary component between the exhaust pipe and the sensor mounting location. This cover creates a thermal barrier that blocks direct heat transfer to the sensor while still allowing the sensor to access exhaust gases through a sealed opening, thus protecting the sensor from high temperatures while maintaining measurement capability
Solution Approach 2:
The exhaust pipe is segmented into a high-temperature zone (the exhaust pipe itself) and a low-temperature zone (the sensor mounting area on the heat insulating cover). This spatial segmentation allows the sensor to be located in the cooler zone while still being able to sense exhaust constituents through the sealed opening in the cover
2Reliability
If the exhaust system is enclosed inside the vehicle bodywork to meet emissions regulations, then emissions control is improved, but heat is retained inside the bodywork causing increased component temperatures
Solution Approach 1:
The heat insulating cover acts as a thermal intermediary between the enclosed exhaust system and the sensor, blocking heat flow into the bodywork interior while allowing the exhaust system to remain enclosed for emissions control
Solution Approach 2:
The heat insulating cover provides localized thermal insulation at the sensor mounting location, creating a cool zone for the sensor while allowing the rest of the enclosed exhaust system to operate at high temperatures for effective emissions control
3Reliability
If the sensor is protected from heat by insulating it from the exhaust pipe, then the sensor durability is improved, but heat transfer to the sensor may be insufficient for proper operation
Solution Approach 1:
The heat insulating cover provides thermal insulation at locations where heat blocking is needed (around the sensor mounting area) while leaving the sensing opening area open to allow exhaust gases and heat to reach the sensor tip, thus providing localized protection without compromising heat transfer for operation
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
The solution effectively reduces heat transfer to the sensor by convection and promotes heat dissipation through conduction, ensuring the sensor operates within a safe temperature range and maintaining its performance even in high-temperature environments.
Implementation Method 1
The direct contact of the mounting boss with the inner surface of the planar section forms a mechanical seal preventing high temperature air from around the exhaust pipe from flowing toward a proximal end portion of the exhaust constituent sensor
Implementation Method 2
The direct contact of the annular flange with the inner surface forms a metal to metal mechanical seal between the mounting boss and the heat insulating cover. The mechanical seal transfers heat generated by the exhaust pipe by conduction to the heat insulating cover
Implementation Method 3
the cover acts as a heat sink absorbing and dissipating the transferred heat into an associated surrounding environment
Data Source
AI summary
An exhaust system includes an exhaust pipe and a heat insulating cover surrounding an outer surface of the exhaust pipe. The cover includes a planar section defining a surface area. An inner surface of the planar section is spaced from the outer surface to define a gap there between. A separate reinforcement is mounted to the planar section. A mounting boss provided in the gap is in direct contact with the inner surface. An exhaust constituent sensor is mounted to the exhaust pipe. A distal end portion of the sensor is received in the mounting boss and projects through an opening in the outer surface and into an exhaust passage. The direct contact of the mounting boss with the inner surface forms a mechanical seal preventing high temperature air from around the exhaust pipe from flowing toward a proximal end portion of the sensor.