Two-Stroke Engine Control Using Crankcase Pressure Load Sensing
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Solution Overview
Problem
Modern two-stroke engines, especially those with boosting systems, suffer from underperformance, inefficiency, and poor emissions due to reliance on throttle valve position for engine control, which does not account for changes in engine inlet pressure and variation.
Innovation Solution
A method of controlling a two-stroke engine by selecting and re-selecting sets of engine parameter inputs, including direct measurements of crankcase pressure and engine speed, to optimize engine operations, such as fuel injection, ignition timing, and exhaust valve position, using an engine control unit (ECU).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If throttle valve position is used for engine control, then the control system is simple, but engine performance and efficiency deteriorate due to inability to account for inlet pressure changes
Solution Approach 1:
The patent changes the control parameter from throttle valve position to direct crankcase pressure measurement. This parameter change enables the control system to accurately reflect actual engine load and inlet conditions, resolving the contradiction by maintaining simple control architecture while dramatically improving engine performance and efficiency through physically meaningful measurements
Solution Approach 2:
The patent replaces the mechanical throttle valve position sensing system with a pressure-based measurement system using pressure sensors in the crankcase. This substitution eliminates the indirect mechanical linkage and provides direct feedback on actual engine conditions, improving performance without significantly increasing system complexity
2Device complexity
If throttle valve position is used for engine control, then the control system is simple, but emissions control deteriorates
Solution Approach 1:
By changing the control parameter to direct crankcase pressure measurement, the system gains accurate real-time data on actual engine load and air intake conditions. This enables precise fuel injection and ignition timing control, dramatically improving emissions control compared to the indirect throttle position method while maintaining simple control architecture
3Measurement precision
If direct crankcase pressure measurement is implemented, then engine load determination accuracy improves, but device complexity increases
Solution Approach 1:
The patent uses the crankcase as an intermediary chamber to house the pressure sensor and provide direct access to the air-fuel mixture before combustion. This intermediary approach allows accurate pressure measurement without requiring sensors in the combustion chamber itself, improving measurement precision while limiting the increase in device complexity to a single pressure sensor and associated electronics
Data Source
AI summary
Embodiments describe a method of controlling a two-stroke internal combustion engine is shown. The method includes selecting one set of two or more sets of engine parameter inputs or a weighted value of two or more sets of engine parameter inputs, determining an engine output parameter from the selection, and utilizing the determined engine output parameter to control one or more engine operations; re-selecting one set of two or more sets of engine parameter inputs or a weighted value of two or more sets of engine parameter inputs during engine operation, utilizing the reselected output parameters to adjust one or more engine operations. Each set of engine parameter inputs includes a direct measurement of crankcase pressure and engine speed and optionally one or more of barometric pressure, exhaust valve position, air temperature, engine coolant temperature, exhaust temperature, boost pressure, crankshaft position and direction of rotation, humidity, fuel pressure, fuel temperature, detonation sensor level, exhaust oxygen content, and throttle valve angle.