Variable Valve Mechanism Fail-Safe Control for Locked Cam Shafts
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Solution Overview
Problem
In variable valve mechanisms of internal combustion engines with a double shaft structure, locking defects in either the outer or inner cam shafts can lead to inefficient engine operation, including increased residual gas and unstable combustion due to improper valve timing control.
Innovation Solution
A control apparatus and method that determines the current phase of the abnormal cam shaft and adjusts the phase of the other cam shaft to maintain optimal valve timing, using a cam controller to monitor and adjust the phases of the main and sub cams to prevent excessive overlap and ensure efficient engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phase control is performed using a double shaft structure with outer and inner cam shafts, then valve timing control precision is improved, but system reliability deteriorates due to potential locking defects in either cam shaft
Solution Approach 1:
The control device detects abnormalities in the cam shaft rotation phases beforehand and executes phase adjustment control to compensate for potential locking defects. By monitoring the rotation phases of both outer and inner cam shafts and detecting deviations from expected phases, the system can proactively adjust the non-locked cam shaft's phase to maintain proper valve timing, preventing engine stall before it occurs.
Solution Approach 2:
The system changes the operational parameters by dynamically adjusting the phase of the non-locked cam shaft based on detected abnormalities. When a locking defect is detected in one cam shaft, the control device modifies the phase parameter of the other cam shaft to compensate, thereby maintaining appropriate valve opening and closing timings despite the defect in one component.
2Device complexity
If the outer cam shaft is locked at an advanced angle position, then the valve mechanism structure is simplified, but combustion stability deteriorates due to increased residual gas from excessive valve overlap
Solution Approach 1:
The control device continuously monitors the rotation phases of both cam shafts and uses this feedback to detect when a locking defect occurs. By comparing the detected phases against expected phases, the system identifies abnormal conditions and executes corrective phase adjustment control to optimize valve timing, thereby maintaining combustion stability even when one cam shaft is locked.
Solution Approach 2:
When a locking defect is detected, the control device changes the phase parameter of the non-locked cam shaft to compensate for the advanced angle position caused by the lock. This parameter adjustment optimizes the valve overlap period, reducing residual gas accumulation and maintaining stable combustion despite the structural simplification from the locked cam shaft.
3Reliability
If abnormality detection and phase adjustment control are implemented, then engine operation reliability is improved, but control system complexity increases
Solution Approach 1:
The control device performs multiple functions using a single integrated system: it detects abnormalities in cam shaft rotation phases, determines which cam shaft is locked, calculates the appropriate phase adjustment, and executes the control. This multi-functional approach improves reliability without proportionally increasing control system complexity, as the same control unit handles detection, diagnosis, and correction.
Solution Approach 2:
The system performs self-diagnosis and self-correction by monitoring its own cam shaft rotation phases and automatically adjusting the non-locked cam shaft's phase when a defect is detected. This self-service capability improves engine operation reliability without requiring external intervention or significantly complicating the control system, as the system manages its own fault detection and correction.
Data Source
AI summary
An control apparatus for a variable valve mechanism, is capable of executing fail safe control in a case in which locking occurs in either one of a cam shaft of a double shaft structure. The control apparatus for a variable valve mechanism has a cam shaft of a double shaft structure including an outer cam shaft and an inner cam shaft, such that it is possible to adjust the phase of a sub cam of inner cam shaft with respect to an main cam of outer cam shaft, and by means these cams, at least one of an intake valve and an exhaust valve of an internal combustion engine is operated. When an abnormality is detected in one of the cam shafts, the control apparatus controls the phase of the cam of the other cam shaft, in accordance with the determined current phase of the cam.