NOx Sensor Line Break Detection via COM Voltage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current NOx sensors in automotive engineering are prone to interference and coupling due to capacitive coupling and leakage currents, especially when using pulse width modulation (PWM) for temperature control, leading to unreliable NOx measurements and difficulty in diagnosing line breaks in the IP2 line.
Innovation Solution
A method that involves applying a predetermined electrical voltage to the common connection of the sensor cells for a short duration to generate a measurable signal at a resistor, allowing differentiation between open and closed circuits, and detecting line breaks by analyzing current changes across a measuring shunt, thereby ensuring continuous and reliable diagnostics without influencing NOx readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If PWM is used for temperature control of the sensor element, then temperature regulation is achieved, but capacitive coupling and leakage currents cause interference with the NOx measurement signal
Solution Approach 1:
The patent segments the electrical connections into separate lines (IP1, IP2, COM) with individual diagnostics. The COM line is specifically separated to allow voltage changes that generate diagnostic signals without affecting the NOx measurement lines, thus isolating the temperature control function from measurement interference.
Solution Approach 2:
The patent introduces an intermediary diagnostic signal through voltage changes on the COM line. This intermediary signal allows the system to detect line breaks and diagnose faults without directly interfering with the NOx measurement, acting as a mediator between temperature control and measurement reliability.
2Use of energy by moving object
If the NOx measurement signal is kept small to maintain low power consumption, then energy efficiency is improved, but the signal becomes extremely sensitive to interference and coupling
Solution Approach 1:
The patent implements feedback through continuous diagnostics of the electrical lines. By monitoring voltage changes and current flows on the COM and IP2 lines, the system can detect interference and line breaks, providing feedback that allows the control unit to compensate or flag measurement issues, thereby maintaining reliability despite small signal levels.
3Reliability
If continuous diagnostics of line breaks in the IP2 line are implemented, then diagnostic capability is improved, but the diagnostic process may influence or disturb the NOx readings
Solution Approach 1:
The patent uses periodic action by implementing diagnostics at specific intervals or under specific conditions rather than continuously. The control unit can activate diagnostic modes periodically or when triggered by specific events, allowing diagnostics to be performed without constantly disturbing the NOx measurement process.
Solution Approach 2:
The patent applies local quality by making different parts of the electrical system have different properties. The COM line is designed to accept voltage changes for diagnostics, while the IP1 and IP2 lines maintain stable potentials for accurate NOx measurement. This local differentiation allows diagnostics on one line without affecting measurements on other lines.
4Adaptability or versatility
If the sensor structure includes multiple pump cells and electrodes in close proximity, then sensor functionality is improved, but capacitive coupling between heating meanders and measurement lines increases
Solution Approach 1:
The patent applies equipotentiality by maintaining the same electrical potential on the COM connection for multiple cells (O2 cell and NOx cell). By keeping the COM line at a stable reference potential and making targeted changes only when needed for diagnostics, the system reduces potential differences that would cause capacitive coupling and interference between adjacent heating meanders and measurement lines.
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 allows for reliable detection of open circuits and NOx content, even at low concentrations, by generating a clear current change across the measurement shunt when the IP2 line is defective, providing a continuous and accurate diagnostic capability.
Implementation Method 1
a sensor element (110), wherein the sensor element has a first pump cell, which has an outer pump electrode (114) and an inner pump electrode (116) and which is attached to a first cavity (126), which is connected to the measurement gas
Implementation Method 2
a heating element (148), which is connected to a heating voltage (UHTR)
Implementation Method 3
the first pump current (IP1), which is generated in the first pump cell (112), transports a first portion of oxygen ions, which are formed from molecular oxygen from the gas mixture
Implementation Method 4
an electrical reference cell (130), which has a Nernst electrode (132) and a reference electrode (134)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for operating a sensor (100) for detecting at least a portion of a measurement gas component having bound oxygen in a measurement gas, more particularly in an exhaust gas of an internal combustion engine. In the method, an electronic control unit (122), which at least has a first separate connection point (P1) for a first pumping cell (112), a second separate connection point (P2) for a second pumping cell (140), a connection point for a Nernst voltage (Vs) and a common connection point (COM), is connected to the sensor element (110) of the sensor (100), a measurement resistor (160) being provided in a fourth electrically conductive connection (146), a predefined voltage (UCOM) being present at the common connection point (COM), the predefined voltage (UCOM) being changed for a predefined time by means of the control unit (122) in order to generate a measurement signal (174).