Engine Valve Timing Control for Knock Suppression
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Solution Overview
Problem
Internal combustion engines face challenges in maintaining smooth operation at low-rotation, high-load states due to increased intake valve lift leading to advanced opening times and increased overlap with exhaust valves, resulting in knocking phenomena.
Innovation Solution
A valve opening/closing timing control apparatus with a phase adjustment mechanism that adjusts the relative rotational phase of the intake camshaft to increase intake amount without changing the opening timing, using an electrically powered actuator to displace the phase in advancing and retarding directions, thereby generating a tumble flow and suppressing knocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the lift amount of the intake valve is increased to increase the intake amount, then the intake amount increases, but the opening timing advances and overlap with exhaust valve increases causing knocking phenomenon
Solution Approach 1:
The patent separates the control of valve lift amount and valve opening timing into independent control mechanisms. The lift amount is controlled by the camshaft profile while the opening timing is controlled by the variable valve timing mechanism, allowing independent optimization of each parameter without the trade-off that previously existed
Solution Approach 2:
The patent employs a variable valve timing mechanism that dynamically adjusts the opening timing of the intake valve based on engine operating conditions. This allows the system to maintain optimal timing across different lift amounts and engine speeds, preventing knocking while maximizing intake amount
2Quantity of substance
If the opening timing of the intake valve is advanced to increase intake amount, then the intake amount increases, but the overlap with exhaust valve increases causing knocking phenomenon
Solution Approach 1:
The variable valve timing mechanism dynamically adjusts the opening timing based on real-time engine conditions including load, speed, and temperature. This dynamic control allows the system to advance timing when beneficial for intake amount while retarding it when necessary to prevent knocking, optimizing performance across all operating ranges
Solution Approach 2:
The system incorporates feedback from various sensors monitoring engine parameters such as knock detection, intake manifold pressure, and exhaust gas temperature. This feedback is used by the control unit to continuously adjust the valve timing, preventing knocking while maintaining optimal intake amount
3Quantity of substance
If the overlap between intake valve and exhaust valve is increased to increase intake amount, then the intake amount increases, but knocking phenomenon occurs due to hot residual gas
Solution Approach 1:
The variable valve timing mechanism allows dynamic adjustment of the overlap duration between intake and exhaust valve opening. The control unit optimizes overlap timing based on engine load and speed, maintaining sufficient overlap for scavenging and intake charge replenishment while preventing excessive overlap that would allow hot residual gas to cause knocking
Data Source
AI summary
A control unit for an internal combustion engine is configured for allowing smooth operation of the internal combustion engine by increasing an intake amount while maintaining an opening timing of an intake valve constant, at the time of low-rotation, high-load state. A valve opening/closing timing control apparatus includes a phase adjustment mechanism configured to vary a relative rotational phase between a driving side rotary body rotatable in synchronism with a crankshaft of the internal combustion engine and a driven side rotary body rotatable together with an intake cam shaft. After an opening timing of the intake valve, the relative rotational phase is displaced in the advancing direction.