Airflow Meter Temperature Correction Circuit
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Solution Overview
Problem
Existing air flow meters for internal combustion engines face inaccuracies due to temperature differences between sensors, caused by aging and individual characteristic variations, leading to errors in flow rate measurement.
Innovation Solution
An arithmetic circuit in the air flow meter corrects output characteristics using air and sensor module temperatures, with a decreased correction amount when the temperature difference is small, and employs a wall temperature correction mechanism that adjusts the flow rate signal based on the difference between the two temperatures, using a polynomial or correction map for precise adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature correction is performed using the difference between air temperature and sensor module temperature, then temperature characteristics are corrected, but measurement accuracy deteriorates when sensors have different deterioration degrees or characteristic variations
Solution Approach 1:
The patent creates a virtual copy of the air temperature sensor's characteristic by using the sensor module temperature sensor to represent the air temperature sensor's temperature. By treating the sensor module temperature as a proxy for air temperature and calculating their difference, the system generates a correction value that accounts for temperature effects without requiring direct measurement of both temperatures, thereby avoiding errors from sensor characteristic variations and different deterioration degrees
Solution Approach 2:
The patent introduces an intermediary approach by using the sensor module temperature sensor to indirectly represent the air temperature sensor's state. Instead of directly measuring both air temperature and sensor module temperature with separate sensors, the system uses the sensor module temperature as an intermediary variable to calculate the temperature difference effect, thereby eliminating the need for two independent temperature sensors and avoiding their characteristic mismatches
2Measurement precision
If correction amount is increased for small temperature differences, then measurement accuracy improves, but correction precision deteriorates due to excessive correction
Solution Approach 1:
The patent applies partial correction by multiplying the temperature difference by a correction coefficient that is less than or equal to 1. This partial action approach prevents excessive correction when temperature differences are small, maintaining measurement accuracy without introducing correction errors. The correction coefficient acts as a scaling factor that moderates the correction amount based on the magnitude of the temperature difference
Data Source
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AI summary
Provided is an airflow meter with good precision. In the airflow meter, which is provided with an arithmetic circuit that incorporates air temperature and a sensor module temperature as adjustment elements for the output characteristics of the airflow meter, corrects the output characteristics in accordance with the temperature difference between the air temperature and the sensor module temperature and reduces the correction amount when the absolute value of the difference between the air temperature and the sensor module temperature is small.