Continuously Variable Valve Lift Air Charge Control
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Solution Overview
Problem
Existing engine systems face high pumping losses and sub-optimal combustion efficiency due to fixed valve lift and varying air charge control methods, leading to decreased fuel economy and responsiveness to torque requests.
Innovation Solution
A method of controlling air charge in a vehicular engine by determining a target valve lift based on required air charge and estimated engine intake manifold pressure, using a continuously variable valve lift system, which adjusts valve actuation to match changing pressure conditions, thereby optimizing air charge delivery and reducing overshooting or undershooting during transient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the valve lift of inlet valves is fixed and predetermined by cam profile, then the system structure is simple, but the air charge control is insufficient leading to high pumping losses
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed cam profile valve lift system to a continuously variable valve lift (CVVL) system. The CVVL system dynamically adjusts valve lift in real-time based on operating conditions, allowing optimization of air charge control across different engine loads and speeds, thereby reducing pumping losses while maintaining manageable system complexity through electronic control.
Solution Approach 2:
The patent implements parameter changes by varying the valve lift parameter continuously rather than fixing it. The CVVL system changes the lift parameter dynamically based on throttle position and engine operating conditions, enabling optimal air intake control that reduces the pressure differential across the inlet valve and minimizes pumping losses.
2Quantity of substance
If the throttle valve controls air charge by varying intake manifold pressure, then the air charge can be adjusted, but pumping losses increase particularly at idle and small throttle openings
Solution Approach 1:
The patent changes the control parameter from throttle valve position to inlet valve lift. By controlling the valve lift parameter directly, the system adjusts air charge quantity without creating excessive pressure differential across the valve, thereby reducing pumping losses while maintaining the required air charge control capability.
Solution Approach 2:
The patent applies preliminary action by predicting future intake manifold pressure based on current throttle position and engine state. This predicted pressure information is used in advance to determine the optimal valve lift, allowing the system to proactively optimize air charge control and minimize pumping losses before the actual pressure conditions occur.
3Quantity of substance
If the inlet valves remain open for longer or shorter period to achieve required air charge, then the air charge quantity can be adjusted, but combustion efficiency decreases
Solution Approach 1:
The patent optimizes the valve lift parameter to achieve the required air charge quantity while maintaining optimal valve timing. By controlling both the duration and extent of valve opening through variable lift, the system ensures optimal air charge motion within cylinders, thereby maintaining high combustion efficiency while meeting air charge requirements.
4Device complexity
If the valve lift is determined without considering future intake manifold pressure, then the control is simple, but the torque response overshoots or undershoots the torque request
Solution Approach 1:
The patent implements preliminary action by predicting future intake manifold pressure based on current operating conditions and throttle position. This predicted pressure information is obtained in advance and used to determine the optimal valve lift, allowing the control system to compensate for system delays and achieve accurate torque response without excessive overshoot or undershoot.
Solution Approach 2:
The patent applies feedback by using the predicted intake manifold pressure as a feedback signal in the valve lift determination process. This closed-loop approach ensures that the valve lift control accounts for future pressure conditions, improving torque response accuracy and reducing deviations from the requested torque.
Data Source
AI summary
A method, an apparatus, a computer program, an engine intake system, and a vehicle are provided. The method is for controlling an air charge provided to a vehicular engine. The method comprises determining a target valve lift of an inlet valve in a continuously variable valve lift system based, at least in part, on: a required air charge for a given torque request; and an estimate of a variable pressure of an engine intake manifold for a time when the inlet valve is to be actuated in accordance with the target valve lift. The method also comprises controlling actuation of the inlet valve in the continuously variable valve lift system in accordance with the determined target valve lift.