Vehicle Ambient Air Temperature Sensor Heat Interference
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Solution Overview
Problem
Conventional vehicle systems for measuring ambient air temperature are influenced by heat generated from the engine and exhaust, leading to inaccurate readings, especially when the vehicle is stationary or moving slowly, as existing methods fail to effectively correct for these heat sources.
Innovation Solution
A temperature sensor is mounted in the airflow path of a vehicle's radiator fan, with a controller monitoring vehicle parameters to activate the fan and ensure ambient air is drawn across the sensor, applying a correction factor to compensate for residual heat, and continuously taking readings at specific speed thresholds to obtain accurate ambient air temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature sensor is placed on the vehicle in a location exposed to ambient air, then the sensor can measure ambient air temperature, but the measurement is influenced by heat generated by the vehicle engine and exhaust
Solution Approach 1:
The temperature sensor is extracted from the vehicle body and mounted on the rearview mirror assembly, positioning it outside the vehicle's heat-generating components. This physical separation removes the sensor from the harmful thermal environment created by the engine and exhaust, allowing it to measure true ambient air temperature without contamination from vehicle-generated heat.
Solution Approach 2:
The rearview mirror assembly serves as an intermediary structure that positions the temperature sensor in a location exposed to ambient air flow while being physically separated from the vehicle's heat sources. The mirror assembly acts as a mounting platform that mediates between the sensor's measurement function and the vehicle's thermal environment.
2Measurement precision
If the vehicle is stationary or moving slowly, then the vehicle generates less kinetic energy, but a boundary layer of hot air exists around the engine compartment and exhaust components, influencing temperature measurement
Solution Approach 1:
The sensor is extracted from the vehicle body and mounted on the rearview mirror, positioning it outside the boundary layer of hot air that forms around the engine compartment and exhaust components. This physical relocation removes the sensor from the contaminated thermal environment, enabling accurate ambient temperature measurement even when the vehicle is stationary or moving slowly.
Solution Approach 2:
The sensor is positioned in a different spatial dimension - mounted on the exterior of the vehicle body rather than integrated into the vehicle structure. This dimensional change places the sensor in a location where ambient air flow is not obstructed by the vehicle's heat-generating components, eliminating the boundary layer effect.
3Object-affected harmful factors
If the temperature sensor is mounted on the radio antenna to locate it as far as possible from vehicle heat sources, then the sensor is positioned away from heat sources, but this location may not be optimally exposed to ambient air flow
Solution Approach 1:
The rearview mirror assembly provides a specific local position on the vehicle that optimally combines both requirements: it is sufficiently distant from the engine and exhaust heat sources while being exposed to ambient air flow generated by the vehicle's motion. This local position has the quality of being both thermally isolated and aerodynamically exposed.
Solution Approach 2:
The rearview mirror assembly serves multiple functions: it is a structural component of the vehicle, a mounting platform for the temperature sensor, and a position that provides both thermal isolation from heat sources and exposure to ambient air flow. This multi-functionality makes it an optimal mounting location.
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 method provides accurate ambient air temperature readings by effectively mitigating the influence of vehicle-generated heat, allowing for precise temperature data communication to vehicle components, enhancing the reliability of temperature-based functions such as exhaust aftertreatment and condensation protection.
Implementation Method 1
A temperature sensor is mounted in the airflow path of a vehicle's radiator fan, with a controller monitoring vehicle parameters to activate the fan and ensure ambient air is drawn across the sensor
Data Source
AI summary
A method for determining ambient air temperature outside of a vehicle with a sensor mounted on the vehicle, includes the steps of determining a road speed of the vehicle, comparing the determined road speed to a reference road speed value, if the determined road speed is below the reference road speed value, activating a device to move ambient air across the sensor, the ambient air being drawn from a location outside the vehicle, taking a temperature reading with the sensor, and, if the temperature reading is lower than a stored temperature value, storing the lower temperature reading as the ambient air temperature.