Oil Temperature Sensor Diagnostics During Engine Idle-Stop
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Solution Overview
Problem
Existing oil temperature sensor diagnostic devices face challenges in accurately diagnosing abnormalities when the engine is stopped by idle-stop control, as heat generation ceases, leading to stagnated lubricant temperature rise and potential false diagnostics.
Innovation Solution
An oil temperature sensor diagnostic device that adjusts the diagnostic value based on elapsed running time after cold start, interrupting its increase during idle-stop, and subtracts elapsed time during engine stops to reflect cooling phenomena, ensuring accurate diagnostics even during idle-stop conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diagnostic value is continuously increased based on elapsed running time, then the diagnostic can detect sensor abnormalities, but false abnormalities occur when the engine is stopped by idle-stop control
Solution Approach 1:
The diagnostic value increase is made dynamic by interrupting it during idle-stop periods. The control unit detects idle-stop conditions and pauses the diagnostic value accumulation, allowing the diagnostic threshold to adapt to the stopped engine state where no heat generation occurs, thereby preventing false abnormalities while maintaining detection accuracy during normal operation
Solution Approach 2:
The system changes the parameter of diagnostic value accumulation based on engine operating state. During idle-stop control, the diagnostic value increase is suspended, effectively changing the accumulation rate from positive to zero, which aligns the diagnostic threshold with the physical reality of no temperature rise during engine stops
2Measurement precision
If the diagnostic determines abnormality based on oil temperature rise over time, then sensor performance can be monitored, but inaccurate diagnostics result when heat generation stops during engine stops
Solution Approach 1:
The control unit continuously monitors engine operating conditions and provides feedback to the diagnostic value calculation. When idle-stop conditions are detected, the system adjusts the diagnostic value increase accordingly, creating a closed-loop system that adapts the diagnostic threshold to current engine state, ensuring accurate diagnostics across all operating conditions
Data Source
AI summary
An oil temperature sensor diagnostic device is configured to detect an abnormality in an oil temperature sensor provided in a vehicle, the vehicle including the oil temperature sensor configured to detect an oil temperature of a lubricant of an engine, and an idle-stop controller configured to execute an idle-stop control. The oil temperature sensor diagnostic device includes: a diagnostic value setting module configured to set a diagnostic value that is increased according to an elapsed running time; and an abnormality determination module configured to determine an abnormality of the oil temperature sensor in a case in which a rise in the oil temperature computed on a basis of an output of the oil temperature sensor is small compared to an amount of increase in the diagnostic value.