EVAP System Leak Detection via Idle-to-Off Pressure Monitoring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional evaporative emissions (EVAP) system diagnostics are intrusive and costly, requiring additional testing components and impacting engine performance and fuel economy.
Innovation Solution
A diagnostic system that utilizes a control valve, pressure sensor, and controller to monitor pressure changes during the engine idle-to-off transition, allowing for non-intrusive detection of malfunctions such as blockages and leaks in the EVAP system by creating a pressure differential and comparing pressure readings against diagnostic thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diagnostic routines are performed during engine operation, then EVAP system malfunctions can be detected, but engine performance and fuel economy deteriorate
Solution Approach 1:
The diagnostic routine is performed during the engine idle-to-off transition period, utilizing the natural pressure differential that occurs when the engine shuts down. This preliminary action during a transition state allows diagnosis without impacting normal engine operation and fuel economy during driving conditions.
Solution Approach 2:
The system uses the engine's own shutdown process and natural pressure changes to perform self-diagnosis of the EVAP system. No external testing equipment or additional energy input is required, as the system leverages its own operational characteristics for detection.
2Reliability
If additional testing components are added to EVAP diagnostic routines, then diagnostic capability is improved, but device complexity and cost increase
Solution Approach 1:
The existing pressure sensor in the EVAP system is used for multiple purposes: both for normal system operation monitoring and for diagnostic detection of malfunctions. This multi-functionality eliminates the need for separate dedicated diagnostic sensors or testing components.
Solution Approach 2:
The system performs self-diagnosis using its own existing components (pressure sensor, control valve, purge valve) without requiring external testing equipment. The control system utilizes naturally occurring pressure differentials during engine shutdown to detect leaks and malfunctions.
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
Enables accurate and cost-effective detection of EVAP system malfunctions without disrupting engine operation, improving diagnostic efficiency and reducing the need for additional componentry.
Implementation Method 1
a pressure sensor configured to measure pressure in the EVAP system at a point (i) in the vapor canister, (ii) in a first vapor transport line between the vapor canister and a fuel tank, or (iii) in a second vapor transport line between the vapor canister and the control valve
Data Source
AI summary
A diagnostic method and system includes a control valve configured to control an amount of air drawn into an evaporative emissions (EVAP) system through an air filter and a vapor canister, and a pressure sensor configured to measure pressure in the EVAP system. The system also includes a controller configured to detect an engine idle-to-off transition and, in response to detecting the engine idle-to-off transition: receive a first pressure from the pressure sensor, fully open a purge valve connected between the vapor canister and an intake port of an engine, fully close the control valve, monitor one or more second pressures received from the pressure sensor, and detect a malfunction of the EVAP system based on the first pressure, at least one of the one or more second pressures, and a diagnostic threshold.