Spark Ignition Engine Fuel Control via Binary Lambda Sensor
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Solution Overview
Problem
Spark ignition engines face challenges in maintaining stoichiometric combustion due to fuel composition variability, particularly with gaseous or liquid fuels like natural gas, which requires precise air/fuel ratio control, often relying on expensive and complex linear lambda sensors or oscillating binary sensors that stress three-way catalysts.
Innovation Solution
The method involves sampling air/fuel ratios during consecutive switchings of a binary lambda sensor to calculate an average 'learned stoichiometry' value, allowing for closed loop control to converge towards this average, effectively managing fuel supply independently of feedback control, and adjusting fuel injection based on air mass flow or throttle valve operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear lambda sensors are used to ensure precise stoichiometric combustion control, then measurement precision and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive linear lambda sensors with binary lambda sensors that generate simple ON/OFF signals. These binary sensors are much cheaper and simpler, and the patent compensates for their lower precision through software-based air/fuel ratio calculation using consecutive switching signals, thus achieving precise control with inexpensive components
Solution Approach 2:
The patent substitutes the analog continuous signal output of linear lambda sensors with digital binary ON/OFF signals from binary lambda sensors. The continuous measurement function is replaced by calculating air/fuel ratio from the timing and frequency of binary sensor switchings, transforming an analog measurement problem into a digital signal processing solution
2Device complexity
If binary lambda sensors are used to reduce cost and complexity, then device complexity and cost are reduced, but measurement precision deteriorates due to oscillating air/fuel ratio control
Solution Approach 1:
The patent uses the binary lambda sensor's ON/OFF switching signals as feedback to continuously calculate and adjust the air/fuel ratio. By measuring the time intervals between consecutive switchings and the duration of rich/lean states, the system derives the actual air/fuel ratio and uses this feedback to maintain precise stoichiometric control despite using a simple binary sensor
Solution Approach 2:
The patent exploits the periodic ON/OFF switching behavior of the binary lambda sensor around the stoichiometric point. By sampling consecutive switching events and calculating the average air/fuel ratio from these periodic transitions, the system transforms the oscillating binary signal into a precise continuous measurement of the actual air/fuel ratio
3Adaptability or versatility
If closed loop control with binary lambda sensor is used to manage fuel supply, then adaptability to fuel composition changes is improved, but three-way catalyst stress increases due to bi-stable oscillating operation
Solution Approach 1:
The patent calculates the average air/fuel ratio from consecutive binary sensor switchings before applying correction to the fuel injection system. This preliminary calculation of the actual air/fuel ratio allows the control system to anticipate the needed correction and adjust fuel injection accordingly, reducing unnecessary oscillations and stabilizing catalyst operation
Solution Approach 2:
The patent enables the control system to self-adjust fuel injection based on calculated air/fuel ratio from binary sensor switchings. The system automatically determines the deviation from stoichiometric ratio and applies appropriate correction factors, reducing reliance on aggressive oscillating control and thereby decreasing catalyst stress while maintaining adaptability
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 approach enables quick adjustments to fuel composition changes, ensuring stoichiometric combustion and reducing the stress on three-way catalysts, while being cost-effective and capable of operating with traditional feedback control systems.
Implementation Method 1
a binary lambda sensor (B), which switches between two logical conditions according to the air/fuel ratio
Implementation Method 2
the three-way catalyst (3WC) is forced to work on a stoichiometric condition, in a bi-stable situation, namely continuously oscillating between an oxidizing operation and a reducing operation
Data Source
Figure 1~2
Figure 3~4
Figure 5~5b
AI summary
A method for managing a supply of a spark ignition internal combustion engine (E), the method comprising a procedure of commanding a supply of said engine based on a switching between two logical conditions of a binary sensor (B), so that said fuel oscillates around a stoichiometric fuel condition, the method comprising a first procedure carried out in stationary operating conditions of the internal combustion engine formed by a first step of registering at least two values of said air/fuel ratio (Lambda1 and Lambda2) for as many other consecutive switches, a second step of calculating an average value (Lambdam) of said two registered values, a third step of setting said calculated average as a reference value (Ref) of the air/fuel ratio.