Variable Voltage Oxygen Sensor Exhaust Pressure Estimation
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Solution Overview
Problem
Existing methods for estimating exhaust pressure in internal combustion engines are often inaccurate, especially when operating outside modeled conditions, leading to reduced engine control accuracy due to errors in exhaust pressure models.
Innovation Solution
A method utilizing a variable voltage oxygen sensor to estimate exhaust pressure by measuring the difference in pumping current outputs at two different voltage levels, allowing for more accurate engine control across a wider range of operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated exhaust pressure sensor is installed, then exhaust pressure measurement accuracy is improved, but engine system cost and control complexity increase
Solution Approach 1:
The exhaust oxygen sensor is made multi-functional by enabling it to perform both oxygen concentration measurement and exhaust pressure measurement. The sensor operates in variable voltage mode where the voltage level (450mV or 1100mV) determines the measurement function, eliminating the need for a separate dedicated pressure sensor and reducing system complexity while maintaining measurement capability.
Solution Approach 2:
The exhaust oxygen sensor serves itself by utilizing its existing structure and operating principles to measure exhaust pressure. By applying variable voltage levels to the sensor, the same physical component that measures oxygen concentration also measures pressure through its pumping current response, without requiring additional external sensing elements.
2Device complexity
If exhaust pressure is modeled based on engine operating conditions, then system cost is reduced, but measurement accuracy decreases especially outside modeled operating windows
Solution Approach 1:
The sensor's operating parameters (voltage level) are changed to enable direct measurement across a wide range of exhaust pressure conditions. By switching between 450mV and 1100mV voltage levels, the sensor can accurately measure pressure both within and outside previously modeled operating windows, eliminating the accuracy limitations of model-based estimation.
Solution Approach 2:
The patent replaces the computational modeling approach with a direct physical measurement approach using the oxygen sensor's electrical response. Instead of calculating pressure from engine operating parameters through complex models, the system directly measures pressure through the sensor's pumping current at variable voltage levels, providing accurate results across all operating conditions.
3Stability of the object's composition
If the oxygen sensor operates at base voltage (450mV), then water molecules are not dissociated, but exhaust pressure measurement capability is limited
Solution Approach 1:
The sensor's voltage operating point is made dynamic rather than fixed. The control system switches the sensor voltage between 450mV (for stable water molecule conditions and oxygen measurement) and 1100mV (for exhaust pressure measurement), allowing the same sensor to adapt its function based on the measurement requirement while maintaining stability of water molecules during oxygen measurement operations.
Solution Approach 2:
The sensor operates in periodic cycles, alternating between base voltage operation for oxygen measurement and variable voltage operation for pressure measurement. This periodic switching allows the system to maintain water molecule stability during oxygen measurement phases while periodically enabling pressure measurement capability when needed.
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 enhances the accuracy of engine control by providing a more precise estimation of exhaust pressure, reducing errors and improving engine operation across various conditions.
Implementation Method 1
the higher, target voltage may be a voltage at which water molecules are partially or fully dissociated at the oxygen sensor while the base voltage is a voltage at which water molecules are not dissociated at the sensor
Implementation Method 2
exhaust pressure changes may be reflected in the sensor's pumping current output, especially while operating in VVs mode
Data Source
AI summary
Methods and systems are provided for estimating an engine exhaust pressure based on outputs from an exhaust oxygen sensor. In one example, a method may include estimating an exhaust pressure of exhaust gas flowing through an engine exhaust passage based on a difference between a first output of an oxygen sensor disposed in the exhaust passage and a second output of the oxygen sensor and then adjusting engine operation based on the estimated exhaust pressure. As one example, both the first and second outputs may be taken while operating the sensor in a variable voltage mode, after increasing a reference voltage of the oxygen sensor from a lower, first voltage to a higher, second voltage.