Dual Path Purge Ejector System for Evaporative Emissions Diagnostics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods fail to diagnose degradation in the ejector system downstream of an ejector outlet in fuel vapor recovery systems, leading to undetected undesired evaporative emissions during high load purge operations in boosted engine conditions.
Innovation Solution
A dual path purge system that allows for simultaneous purging of fuel vapors from a fuel vapor canister and diagnostic testing of the high load purge line, utilizing a check valve to enable vacuum drawing on the high load purge line during manifold vacuum conditions, thereby detecting degradation and preventing unmetered air flow during natural aspiration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-path purge system is used, then the system structure is simple, but degradation downstream of the ejector outlet cannot be diagnosed
Solution Approach 1:
The purge system is divided into two separate paths: a high load purge line for boosted conditions and a normal purge line for natural aspiration conditions. This segmentation allows independent diagnostic capability for the high load purge line while maintaining overall system simplicity.
Solution Approach 2:
A check valve is introduced as an intermediary component in the high load purge line to enable vacuum drawing during manifold vacuum conditions. This intermediary component facilitates diagnostic testing without requiring complex additional equipment.
2Measurement precision
If diagnostic testing is conducted separately from purging, then accurate detection is achieved, but engine operation disruption increases
Solution Approach 1:
The diagnostic testing function is merged with the normal purge operation. During natural aspiration conditions, the system simultaneously performs canister purging and high load purge line diagnostic testing through the dual-path configuration, eliminating the need for separate testing cycles and reducing engine operation disruption.
Solution Approach 2:
The system dynamically switches between different purge paths based on engine operating conditions (boosted vs. natural aspiration). This dynamic operation allows diagnostic testing to be performed during normal purge operations without interfering with high load purge functionality.
3Reliability
If vacuum is drawn on the high load purge line during manifold vacuum, then undetected degradation is revealed, but unmetered air may flow through the ejector
Solution Approach 1:
The purge system is segmented into separate paths with condition-specific operation. The high load purge line with check valve is activated only during natural aspiration for diagnostics, while the normal purge line handles boosted conditions, preventing unmetered air flow through the ejector during vacuum drawing.
Solution Approach 2:
The check valve extracts and isolates the vacuum drawing function to the high load purge line during natural aspiration conditions, preventing vacuum from pulling unmetered air through the ejector while still enabling diagnostic capability for the high load purge line.
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 effectively diagnoses the presence of undesired evaporative emissions in the high load purge line, reducing disruption to engine operation and ensuring accurate detection of system degradation, even during canister purging, by adjusting the purge conditions based on manifold air pressure.
Implementation Method 1
an ejector unit positioned downstream of the canister purge valve and upstream of the intake manifold, the ejector unit including an ejector and a one-way vacuum actuated check valve
Implementation Method 2
a one-way vacuum actuated check valve
Data Source
AI summary
Methods and systems are provided for diagnosing a high load purge line of a boosted engine system for undesired evaporative emissions. In one example, a method for diagnosing the high load purge line includes drawing vacuum in the high load purge line under natural aspiration conditions and concurrently purging a fuel vapor canister. In this way, the high load purge line may be diagnosed for undesired evaporative emissions without disrupting a canister purge schedule.