Engine RPM Estimation via Camshaft Sensor for Stall Prevention
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Solution Overview
Problem
Existing engine stall prevention methods using cam timing control are inadequate in preventing engine stall due to limitations in diagnosing errors with crank position sensors (CKPS), particularly when the CKPS abnormality is transient and inaccurate estimation of engine RPM occurs due to gear ratio variations.
Innovation Solution
A method that continuously models engine RPM using detection values from a camshaft position sensor (CMPS) to control engine operations, ensuring prevention of engine stall before error diagnosis is confirmed, and maintaining the variable valve timing system in a default state to stabilize engine RPM during abnormal CKPS conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cam timing control is performed using CKPS detection values, then engine ignition timing can be controlled to prevent engine stall, but engine stall cannot be completely prevented when CKPS abnormality occurs due to delayed error diagnosis and inaccurate RPM estimation
Solution Approach 1:
The system performs preliminary monitoring of CKPS detection value abnormalities and proactively switches to CMPS-based RPM estimation before a complete CKPS failure occurs. By detecting abnormal phenomena and switching control modes in advance, the system prevents engine stall without waiting for formal error diagnosis confirmation.
Solution Approach 2:
The CMPS serves as an intermediary sensor that provides alternative RPM detection data when CKPS becomes abnormal. The controller uses CMPS detection values to estimate engine RPM and maintain cam timing control, bridging the gap between CKPS failure and formal error diagnosis.
2Reliability
If DTC generation requires certain time period maintenance of trouble phenomenon, then transient CKPS disconnection can be ignored, but engine stall prevention is delayed during the monitoring period
Solution Approach 1:
The system performs preliminary detection of CKPS abnormality and immediately switches to CMPS-based control mode before the DTC monitoring period elapses. This preliminary action prevents engine stall during the monitoring period while still allowing transient issues to resolve themselves.
Solution Approach 2:
The control system dynamically adjusts its behavior based on the detected abnormality. When CKPS abnormality is detected, the system transitions from CKPS-based control to CMPS-based control, and then back to CKPS-based control once the abnormality resolves, without waiting for DTC confirmation.
3Productivity
If cam timing control uses estimation values of engine RPM based on CKPS detection values, then engine control can continue after CKPS error diagnosis, but inaccurate RPM estimation occurs due to gear ratio variation at cam advance/retard
Solution Approach 1:
The CMPS acts as an intermediary measurement device that provides accurate camshaft rotation detection independent of CKPS gear ratio variations. By basing RPM estimation on CMPS detection values rather than CKPS values during abnormal conditions, the system eliminates the source of measurement inaccuracy.
Solution Approach 2:
The system changes the measurement parameter from CKPS-based crankshaft rotation detection to CMPS-based camshaft rotation detection when abnormality is detected. This parameter change bypasses the gear ratio variation issue inherent in CKPS-based measurement during cam timing adjustments.
Data Source
AI summary
A method for reinforcing anti-engine stall may include performing a cam timing control for measuring engine speed of an engine wherein when abnormality of a crank position detector is detected by a controller, engine speed of the engine is controlled to be higher than that at the time when the abnormality of crank position detector occurs while maintaining position for cam phase control operation of a variable timing system.