Asymmetric Cycle Engine Torque Control via Intake Pressure Adjustment
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Solution Overview
Problem
In internal combustion engines with asymmetric Atkinson or Miller cycles, a malfunction of the variable valve timing system leads to uncontrollable air charge, resulting in increased knocking and degradation of engine performance, particularly at high compression ratios.
Innovation Solution
A method for controlling torque in internal combustion engines with asymmetric cycles, involving detection of variable valve timing system unavailability, calculation of an effective compression ratio, and adjustment of intake manifold pressure to maintain maximum achievable torque, thereby mitigating knocking and preserving engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the variable valve timing system is unavailable, then the engine cannot control air charge, but this leads to increased knocking and performance degradation
Solution Approach 1:
The control method proactively detects variable valve timing system unavailability and immediately calculates compensating throttle positions based on pre-established relationships between intake valve closure timing and effective compression ratios. This preliminary action prevents knocking before it occurs by anticipating the harmful effect of uncontrolled air charge.
Solution Approach 2:
The system continuously monitors engine operating conditions and feedback from knocking sensors to dynamically adjust the throttle body position. When variable valve timing failure is detected, the feedback loop maintains optimal throttle positioning to prevent excessive compression ratios and knocking, ensuring engine performance reliability despite the system failure.
2Quantity of substance
If the throttle body is closed to reduce air flow, then air charge is controlled, but pumping losses increase and efficiency decreases
Solution Approach 1:
The system changes the control parameter from direct throttle body positioning to calculated throttle positions based on effective compression ratio requirements. By determining the optimal throttle position that achieves the desired air charge control while minimizing pumping losses, the system maintains efficiency even when variable valve timing is unavailable.
3Loss of energy
If the intake valve closes later (Atkinson cycle), then pumping losses are reduced, but air charge control becomes more critical
Solution Approach 1:
The throttle body serves as an intermediary control element that compensates for variable valve timing system failures. By positioning the throttle body to achieve the desired effective compression ratio, it mediates between the uncontrolled air charge and the engine's combustion requirements, maintaining reliability without sacrificing the pumping loss benefits of the Atkinson cycle.
Data Source
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AI summary
This method for controlling the torque of an internal combustion engine of an asymmetric cycle motor vehicle equipped with a variable timing system, comprises the steps of: a) Determining an intake valve closing delay (RFA) value corresponding to a blockage of the variable timing system; b) Calculating a ratio between the volume occupied at atmospheric pressure by the air admitted into the combustion chamber, at the time of the closing of the intake valves, and the residual volume of the combustion chamber at top dead center; c) Calculating a maximum quantity of air admissible at atmospheric pressure and the temperature of the intake manifold; d) Calculating the maximum pressure in the intake manifold as a function of the instantaneous temperature of the intake manifold and a maximum torque; e) Adjusting the pressure in the intake manifold.