Variable Valve Timing Control for Engine Stop Phase Adjustment
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Solution Overview
Problem
Existing variable valve timing systems face limitations in changing valve timing after the engine has stopped, resulting in a limited amount of possible change, which can cause discomfort to the driver and affect engine starting characteristics.
Innovation Solution
A variable valve timing apparatus that includes an actuator, a changing mechanism, a target value setting portion, a determining portion, a stop permitting portion, a stop process delaying portion, and a termination forcing portion, which allows for delayed engine stop processing and increased valve timing change by adjusting the camshaft rotation phase relative to the crankshaft, ensuring the valve timing reaches a suitable position for the next engine start.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the engine stop process is executed immediately after the ignition key is turned off, then the driver experiences no uncomfortable feeling, but the amount of valve timing change is limited
Solution Approach 1:
The system performs preliminary valve timing adjustment before the engine stop process is completed. The controller delays the engine stop process to allow the camshaft phase to be adjusted to a target value (suitable for next start) before finally stopping the engine, thus achieving both driver comfort and sufficient timing change.
Solution Approach 2:
The system dynamically adjusts the engine stop process timing based on the current camshaft phase and target phase. The stop process is delayed only when needed to achieve the target timing, and the delay duration is dynamically determined based on the required phase adjustment amount.
2Reliability
If the valve timing is adjusted to reach the target value before engine stop, then the engine starting characteristics are improved, but the engine stop process time is extended
Solution Approach 1:
The valve timing is adjusted preliminarily before the engine stop is finalized. The controller sets a target camshaft phase value suitable for the next start and delays the engine stop process only until this target is reached, ensuring good starting characteristics while minimizing the time extension.
Solution Approach 2:
The controller continuously monitors the current camshaft phase and compares it with the target phase. The engine stop process is delayed only for the necessary duration until the phase difference is within the predetermined threshold, providing feedback-based timing control that minimizes unnecessary delays.
3Manufacturing precision
If the camshaft rotation phase is changed by a large amount, then the valve timing reaches the suitable position for next start, but the actuator operation amount increases
Solution Approach 1:
The system calculates the required camshaft phase adjustment in advance and delays the engine stop process to allow this pre-calculated adjustment to be completed. This ensures the valve timing reaches the suitable position without requiring excessive actuator operation, as the delay is precisely matched to the needed phase change.
Solution Approach 2:
The controller adjusts the target camshaft phase value based on the current phase and operational conditions. By dynamically setting the target value and using feedback control, the system achieves accurate valve timing with optimized actuator operation, avoiding both insufficient adjustment and excessive operation.
Data Source
AI summary
In valve timing control after issuance of an engine stop instruction with a prescribed value set as a target phase, an ECU delays permission of an engine stop process within a prescribed time period while an intake valve phase has not yet reached the target value, so that a valve timing control operation is continued while the engine operation is continued in an idle state. After the lapse of a prescribed time period from the issuance of the engine stop instruction, however, the ECU permits the engine stop process no matter whether the intake valve phase has reached the target value or not. As a result, the amount of valve timing that can be changed by the valve timing control in the engine stop operation can be increased, without causing any uncomfortable feeling of the driver.