NOx Sensor Heating via Cumulative Heat Energy
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Solution Overview
Problem
Current methods for heating NOx sensors during engine off conditions are limited, reducing opportunities for On-Board Diagnostics (OBD) to conduct self-diagnostic and offset tests, particularly due to restricted exhaust gas temperatures in hybrid vehicles, which can impact the accuracy of NOx emission monitoring.
Innovation Solution
A method where the NOx sensor is heated at vehicle off based on cumulative heat energy applied over a drive cycle, determining if sufficient heat was applied to drive off ammonia accumulated on the sensor, with conditions including energy thresholds and sensor offset levels to decide on heater activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the NOx sensor is heated during engine off conditions based on limited conditions (dew point temperature and exhaust gas temperature range), then the sensor offset can be minimized, but the number of opportunities for OBD to conduct self-diagnostic and offset tests is reduced
Solution Approach 1:
The patent changes the heating decision parameter from instantaneous exhaust gas temperature to cumulative heat energy applied over the drive cycle. This allows the system to accumulate thermal energy data throughout operation, enabling more flexible heating decisions that can accommodate hybrid vehicle operating patterns while ensuring sufficient heat is applied to drive off ammonia and minimize sensor offset.
Solution Approach 2:
The system performs preliminary assessment of cumulative heat energy applied to the sensor during the drive cycle before deciding whether to activate the heater during engine off conditions. This preliminary evaluation allows the system to determine in advance whether heating is needed, enabling more frequent and timely OBD testing opportunities.
2Measurement precision
If the heater is activated during engine off conditions, then the NOx sensor offset is minimized, but battery charge is consumed
Solution Approach 1:
The system uses feedback from cumulative heat energy measurements to control heater activation. By continuously monitoring the total heat energy applied to the sensor during the drive cycle and comparing it against thresholds, the system intelligently decides whether heater activation is necessary, thereby minimizing unnecessary battery charge consumption while ensuring sensor accuracy when needed.
Solution Approach 2:
The patent introduces cumulative heat energy as a new control parameter that replaces simple temperature-based switching. This allows the system to account for the total thermal history of the sensor, enabling more efficient heater control that reduces battery consumption by avoiding redundant heating when sufficient heat has already been applied during operation.
3Device complexity
If exhaust gas temperature is used as the sole criterion for heater activation, then the control logic is simple, but hybrid vehicle low temperature operation reduces testing opportunities
Solution Approach 1:
The patent adds a temporal dimension to the control logic by integrating heat energy over the entire drive cycle rather than relying solely on instantaneous temperature. This dimensional change from a single-point-in-time parameter to a cumulative parameter allows the system to make informed heating decisions even when instantaneous exhaust temperatures are low in hybrid vehicles, thereby increasing OBD test frequency without significantly increasing control complexity.
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 NOx sensor testing by ensuring adequate heating, thereby improving the detection of sensor degradation and offset, while conserving battery charge by optimizing heater activation.
Implementation Method 1
a first heater arranged in the first NOx sensor and a second heater arranged in the second NOx sensor
Data Source
AI summary
Methods and systems are provided for a NOx sensor. In one example, a method includes heating a NOx sensor during a vehicle off in response to a cumulative heat energy applied to the NOx.