AIS HC Trap Diagnostics Using Fuel Vapor Saturation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid vehicles operating without fuel combustion for prolonged periods lead to degradation of the air intake system hydrocarbon (AIS HC) trap, which is not effectively diagnosed, resulting in increased bleed emissions when the trap is purged.
Innovation Solution
A diagnostic method that utilizes existing engine components, such as a heated exhaust gas oxygen sensor and fuel pump, to test for adsorbent material degradation by saturating the AIS HC trap with fuel vapor during engine-off conditions and monitoring the exhaust air-fuel ratio, allowing for the detection of trap degradation and subsequent purging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hybrid vehicles operate without fuel combustion for prolonged periods, then fuel economy is improved, but the AIS HC trap degrades due to lack of purging opportunities
Solution Approach 1:
The system performs preliminary saturation of the AIS HC trap with fuel vapor during engine-off conditions, then executes a diagnostic purge sequence by cranking the engine to detect trap degradation before it causes excessive emissions during normal operation
Solution Approach 2:
The system uses existing engine components (fuel pump, throttle, oxygen sensor) to perform self-diagnosis of the AIS HC trap during engine-off conditions, eliminating the need for external testing equipment or additional sensors
2Reliability
If the AIS HC trap is purged during engine operation, then trap degradation is reduced, but bleed emissions increase when the trap is degraded
Solution Approach 1:
The system uses the oxygen sensor to monitor exhaust air-fuel ratio and provide feedback on the amount of hydrocarbon being purged from the AIS HC trap, enabling detection of trap degradation and adjustment of purge strategy to minimize emissions
Solution Approach 2:
The system performs a controlled diagnostic purge sequence that intentionally purges the trap during engine-off conditions to detect degradation, accepting temporary emissions in exchange for preventing excessive emissions during normal operation through informed control decisions
3Measurement precision
If additional sensors are added to monitor AIS HC trap health, then diagnostic accuracy is improved, but device complexity increases
Solution Approach 1:
The system uses the existing oxygen sensor, originally designed for exhaust gas analysis, to also detect hydrocarbon purge levels and diagnose AIS HC trap health, making the sensor multi-functional and eliminating the need for dedicated trap monitoring sensors
Solution Approach 2:
The system leverages existing engine management components (fuel pump, throttle actuator, oxygen sensor, engine control unit) to perform trap diagnostics, allowing the engine management system to serve both propulsion control and emissions system diagnosis functions
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 reduces bleed emissions by regularly monitoring the health of the AIS HC trap and performing diagnostics during engine-off conditions without the need for additional sensors, improving emissions quality.
Implementation Method 1
testing for degradation of an adsorbent material positioned in an intake of the engine by directing fuel vapor to the adsorbent material
Implementation Method 2
The engine may be cranked unfueled with the intake throttle closed in order to route any remaining, un-adsorbed, vapor from the intake manifold to the atmosphere via the exhaust passage. The intake throttle may then be opened while continuing to spin the engine, unfueled, such that the ambient air flow may be used to purge the AIS HC trap.
Implementation Method 3
indicating presence or absence of degradation of the adsorbent material based on an air fuel ratio state in an exhaust system of the engine upon opening the throttle
Data Source
AI summary
Methods and systems are provided for diagnostics of an intake air system hydrocarbon (AIS HC) trap during vehicle-off conditions. In one example, a method may include generating fuel vapor in a fuel tank, directing the generated vapor to the AIS HC trap, and then actively purging the AIS HC trap. Degradation of the AIS HC trap may be indicated based on an exhaust air fuel ratio during the active purging of the AIS HC trap.