Dual Path Evaporative Emissions System for Check Valve Stiction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing evaporative emissions systems face challenges in overcoming wet stiction in check valves, which can lead to incomplete purging of the canister under boost conditions, limiting diagnostic accuracy and system efficiency.
Innovation Solution
A vehicle system with a dual path purge mechanism, utilizing a second compressor driven by an electric motor to create a vacuum and draw out moisture from the check valves, ensuring they remain open and reducing stiction, thereby facilitating effective purging and diagnostics under both vacuum and boost conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single purge path is used in the evaporative emissions system, then the system structure is simple, but the system cannot effectively purge the canister under both vacuum and boost conditions due to wet stiction in check valves
Solution Approach 1:
The evaporative emissions system is divided into two separate purge paths: a vacuum purge path and a boost purge path. Each path has its own check valve and control strategy, allowing independent optimization for different operating conditions. This segmentation enables reliable purging under both vacuum and boost conditions without requiring a single complex valve mechanism.
Solution Approach 2:
The system dynamically switches between different purge paths based on engine operating conditions. The control module monitors engine vacuum and boost conditions, and selectively activates either the vacuum purge path or the boost purge path. This dynamic adaptation ensures optimal purge effectiveness across varying operating conditions while maintaining simple valve designs.
2Ease of operation
If check valves are used to control purge flow, then the system is simple to control, but wet stiction causes the valves to fail to open under boost conditions
Solution Approach 1:
The system uses two separate check valves instead of one, with each valve dedicated to a specific purge path and operating condition. The vacuum purge check valve handles vacuum conditions, while the boost purge check valve handles boost conditions. This segmentation allows each valve to be optimized for its specific function, reducing the likelihood of stiction-related failures.
Solution Approach 2:
The system changes the pressure parameter to overcome stiction. During boost conditions, the control module increases manifold pressure above atmospheric pressure, creating a pressure differential that forces the boost purge check valve open despite moisture presence. This parameter change (from vacuum to positive pressure) fundamentally alters the valve opening mechanism to overcome wet stiction.
3Measurement precision
If the system runs diagnostics periodically, then the diagnostic coverage is limited, but running diagnostics continuously improves detection accuracy
Solution Approach 1:
The system performs diagnostics periodically at scheduled intervals rather than continuously. The control module is configured to execute diagnostic routines at predetermined times or under specific driving conditions. This periodic approach balances diagnostic accuracy with vehicle performance, ensuring thorough detection while minimizing interruptions to normal vehicle operation.
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 solution effectively reduces stiction in check valves, allowing for reliable purging of the canister under boost conditions and improving diagnostic accuracy, ensuring the evaporative emissions system operates efficiently and accurately.
Implementation Method 1
A vehicle with a fuel tank is provided with a fuel vapor recovery system or an evaporative emissions system... A valve in the purge lines may need to overcome wet stiction in the valve to provide desired purge or diagnostics of the system
Implementation Method 2
An ejector has an inlet positioned to receive compressed air from the air intake system downstream of the first and second compressors, and an outlet positioned to provide compressed air into the air intake system upstream of the first and second compressors
Data Source
AI summary
A vehicle system and a method of controlling the system are provided. A second check valve is positioned between and fluidly connects a canister purge valve and an ejector. A controller closes the canister purge valve and controls an electrically driven compressor to open the second check valve to remove moisture and reduce stiction after vehicle key off and during a cold soak. A vehicle system is provided with a controller to open the canister purge valve during one of a plurality of boost events associated with a vehicle driving state to open the second check valve, and open the canister purge valve in response to a subsequent one of the plurality of boost events to open the second check valve and evacuate the canister.