CVVL Engine Control Method for Idle State Knocking Prevention
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Solution Overview
Problem
Existing control methods for continuous variable valve lift (CVVL) engines fail to prevent the knocking phenomenon and deteriorating fuel efficiency when the engine is in an idle state due to insufficient oil pressure, which prevents the intake cam from advancing.
Innovation Solution
A control method that determines the engine's idle state and oil temperature, switching between a control state with a maximum advancing intake cam and high valve lift, and a passive state with a parking intake cam and low valve lift, to manage errors and maintain optimal engine operation, thereby preventing knocking and improving fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the intake cam is maximally advanced and valve lift is high to decrease valid compression ratio, then fuel efficiency is improved, but knocking phenomenon occurs when oil pressure is insufficient
Solution Approach 1:
The patent applies dynamics by making the valve lift and cam timing adjustable rather than fixed. The control unit dynamically changes the valve lift between high lift and low lift states, and adjusts cam timing between maximum advancing and parking positions based on real-time monitoring of error occurrence time and oil pressure conditions, allowing the system to adapt to varying oil pressure availability
Solution Approach 2:
The patent changes physical parameters (valve lift height and cam timing position) based on operating conditions. When oil pressure is sufficient and no errors occur, the system uses high valve lift and maximum cam advancing for optimal fuel efficiency. When errors occur or oil pressure is insufficient, the system switches to low valve lift and parking cam position to prevent knocking
2Reliability
If the intake cam is advanced to prevent knocking, then reliability is improved, but the control cannot be executed when oil pressure is insufficient
Solution Approach 1:
The patent implements feedback by continuously monitoring error occurrence time and comparing it against a preset threshold. The control unit receives feedback about cam timing execution status and oil pressure conditions, then adjusts the valve lift and cam timing accordingly. This closed-loop control ensures the system only attempts cam advancing when oil pressure is sufficient to execute the command
Solution Approach 2:
The patent applies preliminary action by checking error occurrence time before attempting to advance the cam. The system proactively determines whether oil pressure is sufficient based on historical error data, and only initiates cam advancing when conditions are favorable, preventing execution failures before they occur
3Loss of energy
If the valve lift is high to improve fuel efficiency, then energy loss is reduced, but knocking occurs due to increased compression ratio
Solution Approach 1:
The system dynamically adjusts valve lift between high and low states based on real-time conditions. High valve lift is used when oil pressure is sufficient and no errors occur, providing optimal fuel efficiency. When errors occur or oil pressure drops, the system switches to low valve lift to reduce compression ratio and eliminate knocking, making the valve lift a dynamic rather than static parameter
4Device complexity
If the cam timing is fixed to simplify control, then device complexity is reduced, but the system cannot adapt to oil pressure variations
Solution Approach 1:
The control unit performs multiple functions: it monitors error occurrence time, determines oil pressure sufficiency, controls valve lift position, and adjusts cam timing. This multi-functional approach consolidates what could be separate complex systems into a single control unit, achieving adaptability without proportionally increasing overall system complexity
Data Source
AI summary
A continuous variable valve lift engine may include determining whether an engine is in an idle state and an oil temperature of an engine is within a predetermined range, controlling, the engine in a predetermined control state when the engine is in the idle state and the oil temperature is within the predetermined range, and measuring, an error occurrence time when an error occurs in controlling the engine in the control state, and controlling the engine while switching the engine to a predetermined passive state when the error occurrence time is more than a preset time.