Two-Stroke Engine Control Using Crankcase Pressure Feedback
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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 relying solely 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, using an engine control unit (ECU) to adjust fuel injection, ignition timing, and exhaust valve position based on multiple parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If throttle valve position is used as the sole input for engine control, then the control system is simple, but engine performance deteriorates due to inability to account for inlet pressure changes and engine variation
Solution Approach 1:
The patent changes the control parameters from solely throttle valve position to multiple parameters including crankcase pressure, manifold pressure, air temperature, and engine speed. This allows the ECU to accurately determine engine load and compensate for inlet pressure changes, resolving the contradiction between simple control and engine performance.
Solution Approach 2:
The ECU is designed to process multiple input parameters simultaneously (throttle position, crankcase pressure, manifold pressure, temperature, speed) to perform comprehensive engine control functions including fuel injection timing, ignition timing, and turbocharger control, achieving both simplicity and performance through multi-functional integration.
2Productivity
If multiple engine parameters are measured and processed, then engine performance and efficiency improve, but device complexity increases
Solution Approach 1:
The ECU serves as an intermediary that receives multiple sensor inputs (crankcase pressure sensor, manifold pressure sensor, temperature sensors, speed sensor) and processes them to generate control outputs. This centralizes complexity in the control unit while keeping individual sensor and actuator components relatively simple.
Solution Approach 2:
The patent combines multiple measurement functions (pressure, temperature, speed sensing) and control functions (fuel injection, ignition, turbocharger control) into an integrated system managed by a single ECU, reducing overall system complexity through consolidation while maintaining comprehensive control capability.
3Measurement precision
If direct crankcase pressure measurement is implemented, then measurement precision improves for load determination, but device complexity increases due to additional sensors
Solution Approach 1:
The patent uses direct crankcase pressure measurement as a primary parameter for determining engine load, replacing indirect estimation methods. This provides accurate real-time load information that accounts for inlet pressure changes, justifying the added sensor through significant improvements in measurement precision.
Solution Approach 2:
The crankcase pressure sensor provides continuous feedback to the ECU about the actual engine load condition, enabling real-time adjustments to fuel injection and ignition timing. This closed-loop feedback ensures accurate load determination despite variations in inlet pressure and engine conditions.
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.