Voltage Offset Detection in Two-Point Lambda Sensors
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Solution Overview
Problem
Two-point lambda sensors in internal combustion engines face precision issues in regulating air/fuel mixtures due to manufacturing tolerances and aging effects, leading to imprecise determination of temperature-caused characteristic curve shifts, especially in engines with direct gasoline injection and small cylinder capacity, where short injection times are common.
Innovation Solution
A method to recognize and correct voltage offsets in the voltage-lambda characteristic curve of two-point lambda sensors by accounting for injection valve characteristic curve tolerances, involving a two-step process to determine the delay time and adjust the air/fuel mixture change, allowing for precise lambda regulation even in unfavorable engine operating points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two-point lambda sensors are used for constant lambda regulation, then manufacturing cost is reduced, but measurement precision deteriorates due to manufacturing tolerances and aging effects
Solution Approach 1:
The patent implements a feedback mechanism where the control device continuously monitors the sensor voltage and compares it against stored reference values. When deviations are detected, the system automatically adjusts the air/fuel mixture to compensate for manufacturing tolerances and aging effects, maintaining accurate lambda regulation despite sensor imperfections
Solution Approach 2:
The patent changes the operational parameters by storing multiple reference voltage-lambda characteristic curves in the control device, each corresponding to different operating conditions. The system selects and applies the appropriate reference curve based on current engine operating parameters, enabling accurate compensation across varying conditions
2Measurement precision
If temperature-caused characteristic curve shifts are recognized using conventional methods, then lambda regulation accuracy is improved, but measurement precision deteriorates in engines with short injection times
Solution Approach 1:
The patent performs preliminary actions by pre-storing reference voltage-lambda characteristic curves in the control device before actual measurement occurs. This allows the system to immediately compare actual sensor readings against pre-established references, eliminating the need for time-consuming real-time calculations during short injection events
Solution Approach 2:
The patent creates copies of the voltage-lambda characteristic curve under different operating conditions and stores them as references. During actual operation, the system compares the actual sensor characteristic against these stored copies to identify temperature-induced shifts, enabling rapid and accurate recognition without requiring lengthy measurement periods
3Ease of operation
If the voltage-lambda characteristic curve is linearized for constant lambda regulation, then ease of operation is improved, but device complexity increases due to multiple superposed effects
Solution Approach 1:
The patent segments the voltage-lambda characteristic curve into multiple discrete reference curves, each representing a specific operating condition or temperature range. The control device selects the appropriate segmented reference curve based on current operating parameters, simplifying the linearization process while accounting for multiple superposed effects without requiring complex real-time calculations
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 method enhances the precision and frequency of recognizing characteristic curve shifts, improving the accuracy of constant lambda regulation with two-point lambda sensors, reducing pollutant emissions by maintaining optimal air/fuel ratios.
Implementation Method 1
ceramic sensor elements are known that are based on the use of electrolytic properties of particular solid bodies, i.e., on ion-conducting properties of these solid bodies
Implementation Method 2
two-point lambda sensor, also called a discrete-level sensor or Nernst sensor
Data Source
AI summary
A method for a two-point lambda sensor includes, changing a composition of an air/fuel mixture supplied to an internal combustion engine from a predefined lambda value to lambda=1, determining a delay time of the voltage value reaching a value corresponding to the lambda=1, again changing the composition of the air/fuel mixture from the predefined lambda value to lambda=1, determining a characteristic of the changing performed in the second regulation based on the delay time, determining an actual value of lambda on an actual voltage-lambda characteristic curve of the two-point lambda sensor that corresponds to the predefined lambda value which is in reference to a reference voltage-lambda characteristic curve based on the determined characteristic, and identifying a voltage offset between the characteristic curves based on a deviation of the actual value from the predefined value.