Engine Start Control Apparatus Variable Valve Timing Abnormality Compensation
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Solution Overview
Problem
In vehicles with variable valve timing mechanisms, abnormalities can prevent the intended advancement of intake valve closing timing during engine cranking, leading to reduced startability due to insufficient intake air, especially at low temperatures.
Innovation Solution
An engine start control apparatus and method that determines an advance amount for the intake valve closing timing and instructs the variable valve timing mechanism, with an abnormality determination unit identifying issues and an electric rotating machine control unit increasing output torque or rotational speed when an abnormality is detected to ensure necessary intake air and improved startability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the closing timing of the intake valve is advanced during cranking to improve engine startability at low temperatures, then the actual compression ratio increases and startability improves, but if the variable valve timing mechanism has an abnormality, the intended advance cannot be achieved and startability deteriorates
Solution Approach 1:
The control device determines an advance amount for the intake valve closing timing before cranking starts and instructs the variable valve timing mechanism in advance. This preliminary determination allows the system to prepare the optimal valve timing configuration before the engine starts, ensuring that the compression ratio is appropriately adjusted for cold start conditions.
Solution Approach 2:
The control device detects whether the intake valve closing timing has actually advanced by monitoring the relationship between the instructed advance amount and the actual valve timing. Based on this feedback, the system determines whether the variable valve timing mechanism is operating normally and adjusts the cranking torque accordingly to compensate for any abnormality.
Solution Approach 3:
The control device changes the cranking torque parameter based on the operational status of the variable valve timing mechanism. When an abnormality is detected (i.e., when the valve timing has not advanced as instructed), the control device increases the cranking torque to compensate for the insufficient compression ratio caused by the timing abnormality, thereby maintaining engine startability.
2Quantity of substance
If the variable valve timing mechanism operates normally and advances the closing timing, then intake air quantity increases and startability improves, but if the mechanism has an abnormality, the advance is not achieved and intake air becomes insufficient
Solution Approach 1:
The control device continuously monitors whether the intake valve closing timing advance is actually achieved by comparing the instructed advance amount with the actual valve timing position. This feedback mechanism allows the system to detect abnormalities in the variable valve timing mechanism operation and respond appropriately by adjusting cranking torque to maintain sufficient intake air quantity for engine starting.
3Object-affected harmful factors
If the closing timing is retarded to reduce vibrations during engine starting, then vibrations decrease, but at low temperatures the compression ratio becomes insufficient and startability deteriorates
Solution Approach 1:
The control device dynamically adjusts the intake valve closing timing based on engine operating conditions, particularly temperature. During normal operation, the timing is retarded to reduce vibrations. However, when cold start conditions are detected, the control device determines a larger advance amount to increase the compression ratio and improve startability, demonstrating dynamic adaptation to changing conditions.
Data Source
AI summary
When cranking is started, a control unit of an ECU determines an advance amount by which an intake valve closing timing is advanced from a fully retarded position toward a bottom dead center, and transmits the determined advance amount to a variable valve timing mechanism. After cranking is started, the control unit determines that there is an abnormality in the variable valve timing mechanism, when the advance amount is larger than 0, and when an actual intake valve closing timing, determined using an intake cam angle from a cam angle sensor and a crank angle from a crank angle sensor, is not advanced from the fully retarded position. When it is determined that there is an abnormality in the variable valve timing mechanism, the control unit outputs a control signal to an inverter to increase an output torque of a motor, which is a driving source for cranking.