Ionization Current Air-Fuel Ratio Control for Engine Adaptability
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Solution Overview
Problem
Existing carburation control systems for small two-stroke engines, used in portable tools like power saws and brush cutters, are inadequate for varying operating conditions and suffer from slow regulation times and wear-related issues, particularly at high altitudes and in poor atmospheric conditions.
Innovation Solution
A control system that continuously monitors and adjusts the air/fuel ratio by calculating the integral of the ionization current over a crankshaft angular interval, intervening to regulate fuel injection based on threshold differences, ensuring optimal performance and emission levels, and activating safety procedures for critical conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a standard calibration with fixed carburation value is used, then the engine operates correctly at sea level and optimum conditions, but the air/fuel ratio becomes inadequate for varying operating conditions such as high altitude and poor atmospheric conditions
Solution Approach 1:
The patent implements dynamic adjustment of the air/fuel ratio through continuous monitoring of ionization current and real-time modification of carburation parameters. The system transitions from a fixed calibration approach to a dynamic control system that adapts the carburation value λT based on actual operating conditions, thereby resolving the contradiction between adaptability and reliability.
Solution Approach 2:
The system employs feedback control by continuously measuring the ionization current in the exhaust gases and using this information to adjust the air/fuel ratio. The control unit compares the measured ionization current against reference values and modifies the carburation parameters accordingly, ensuring the engine maintains optimal performance across varying operating conditions.
2Ease of operation
If known control systems using ionization current are used, then the air/fuel ratio can be regulated, but the regulation time is excessively long and the results are affected by spark plug wear and fouling
Solution Approach 1:
The patent applies preliminary action by establishing reference ionization current values for different operating conditions before actual operation. The control unit stores pre-determined reference values that correspond to optimal air/fuel ratios under various conditions. When operating, the system quickly compares current measurements against these pre-established references, enabling rapid regulation without lengthy calibration periods.
Solution Approach 2:
The system uses partial action by monitoring specific critical parameters (ionization current at particular crankshaft angles) rather than requiring complete system re-calibration. This selective monitoring approach enables faster regulation responses while maintaining control accuracy, reducing the time loss associated with comprehensive re-calibration procedures.
3Measurement precision
If the ionization current is monitored continuously, then the air/fuel ratio can be adjusted in real-time, but the measurement is affected by spark plug wear and fouling which reduces the ionization current
Solution Approach 1:
The system implements self-service through self-diagnosis and self-compensation mechanisms. The control unit continuously monitors the ionization current and automatically detects deviations caused by spark plug wear or fouling. When such conditions are detected, the system self-adjusts by modifying the carburation parameters or switching to alternative measurement strategies, thereby maintaining measurement reliability without external intervention.
Solution Approach 2:
The patent applies beforehand cushioning by establishing compensation algorithms that anticipate and counteract the effects of spark plug wear and fouling. The control unit pre-programmes correction factors and alternative measurement procedures that are activated when degradation is detected, cushioning against the negative effects of wear before they significantly compromise measurement reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This system enables rapid and continuous adjustment of the air/fuel ratio, maintaining optimal engine performance and reducing emissions, while being resistant to wear and fouling, thus improving engine efficiency and reliability across varying conditions.
Implementation Method 1
measuring, while the engine is operating with a certain value of factor λ, the ionization current ci as a function of the rotation angle of the crankshaft
Data Source
AI summary
A control system for carburation of an internal combustion engine in use conditions comprising following activities: starting the engine with a value of λ equals λ0=λT; constructing a curve ci(α) of the ionization current α as a function of the angular position a of the crank shaft; selecting, on this curve ci(α), a number of points at intervals Δα of the rotation angle a; calculating value z, equal to integral from 0 to 360° of the curve ci(α), is done by summing products Δα×ci for all preselected points; interrupting supply of fuel for some cycles in order to externally modify factor λ0 and take it to value λ1; for value λ1 constructing curve ci(α) and calculating value z1; calculating difference Δz=z1−z0, and if the difference is >Δzref in absolute value, intervening on carburation by increasing the quantity of fuel injected in a case of a positive difference (lean mixture) and by reducing the quantity of fuel injected in a case of a negative difference (rich mixture).