Intake Air Temperature Sensor Diagnostic Deviation Analysis
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Solution Overview
Problem
Existing diagnostic devices for intake air temperature sensors in internal combustion engines struggle to accurately diagnose abnormalities early, especially before engine startup, due to environmental factors like sunlight, which can affect temperature readings and lead to incorrect diagnoses.
Innovation Solution
An abnormality diagnostic device that compares the lowest or average intake air temperature detected by the intake air temperature sensor with a second temperature sensor, such as a water or external air temperature sensor, to determine the magnitude of deviation and diagnose sensor abnormalities within a short period after engine startup, minimizing the impact of environmental effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diagnosis is performed after the engine is fully warmed up, then the temperature detection reliability is improved, but the early diagnosis capability and air-fuel ratio control performance deteriorate
Solution Approach 1:
The diagnostic procedure is performed preliminarily during the engine startup phase before the engine reaches fully warmed-up state. The control unit executes the diagnosis using temperature data from the startup period, allowing early detection of sensor abnormalities without waiting for the engine to reach stable operating temperature. This resolves the contradiction by performing diagnosis action before the traditional 'warm-up' condition is met.
2Loss of time
If the diagnosis is performed during engine startup, then the early diagnosis capability is improved, but the measurement precision deteriorates due to environmental factors like sunlight
Solution Approach 1:
The control unit introduces an intermediary evaluation mechanism that compares the intake air temperature sensor readings with expected temperature ranges or reference values during the startup phase. By using this intermediary comparison method, the system can filter out false positives caused by environmental factors like sunlight, maintaining measurement precision while enabling early diagnosis. The intermediary evaluation acts as a gatekeeper that validates sensor readings before triggering diagnostic conclusions.
3Device complexity
If the intake air temperature sensor readings are used directly for diagnosis, then the device complexity is reduced, but the measurement precision deteriorates due to environmental influences
Solution Approach 1:
The control unit implements a feedback mechanism where it continuously monitors the intake air temperature sensor readings during engine startup and compares them against expected temperature profiles or reference values. Based on this feedback comparison, the system dynamically determines whether the sensor is functioning correctly or if environmental factors are causing inaccurate readings. This feedback loop maintains measurement precision without requiring complex additional hardware, as the evaluation is performed through software logic within the existing control unit.
Data Source
AI summary
An abnormality diagnostic device diagnoses the presence/absence of abnormality of an intake air temperature sensor (21) on the basis of the magnitude of deviation between the lowest temperature of the intake air detected via the intake air temperature sensor (21) in a period from the startup of an internal combustion engine until the trend of change in the temperature of the air taken into the internal combustion engine becomes stable and a temperature detected via a water temperature sensor (22). If the decline in the temperature of the intake air detected via the intake air temperature sensor (21) within the aforementioned period is greater than or equal to a predetermined criterion value (IAT1), the abnormality diagnosis is suspended.