Bleed Canister Diagnostics via Refueling Vapor Loading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing evaporative emissions control systems in vehicles lack regular diagnostics for the bleed canister, leading to potential undetected degradation and increased emissions, as the bleed canister is infrequently loaded and diagnosed, resulting in inefficient HC trapping and potential emissions release.
Innovation Solution
A method is implemented during refueling events where fuel vapors are directed solely to the bleed canister by opening bypass valves, and upon engine start, the bleed canister is purged, with the exhaust gas sensor monitoring the oxygen levels to determine its robustness, allowing for timely detection of degradation and adjustment of the purge schedule to mitigate emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bleed canister is positioned downstream of the fuel vapor canister in the vent line, then it can trap any HCs escaping the fuel vapor canister, but it receives bleed HCs only infrequently during refueling events, resulting in infrequent diagnostics and undetected degradation
Solution Approach 1:
The system performs preliminary action by intentionally loading the bleed canister with fuel vapors during refueling events before normal operation. This creates a known loaded state that enables subsequent diagnostic testing during engine start, transforming the infrequent passive trapping function into an actively testable system.
Solution Approach 2:
The system implements feedback by using the UEGO sensor to monitor exhaust gas composition during engine start and comparing it against expected values. This feedback mechanism enables automatic detection of bleed canister degradation and triggers appropriate diagnostic codes or corrective actions, converting undetected degradation into a monitored and responsive system.
2Object-generated harmful factors
If the fuel vapor canisters are sized to absorb all fuel vapors generated during refueling, then they prevent HC emissions, but they provide little opportunity for bleed canister loading and diagnostics
Solution Approach 1:
The system segments the vapor absorption function by distinguishing between the primary fuel vapor canisters (sized to absorb all vapors) and the bleed canister (used for diagnostics). By separating these functions and using valve control to direct vapors selectively, the system maintains effective emissions control while creating dedicated diagnostic opportunities for the bleed canister.
Solution Approach 2:
The system changes the operational parameters of the EVAP system during refueling by controlling valve positions to divert fuel vapors to the bleed canister when the fuel level reaches a threshold. This parameter change transforms the bleed canister from a passive downstream component into an actively loaded diagnostic test subject, enabling regular diagnostics without compromising the primary canisters' emissions control function.
3Measurement precision
If the bypass valves are opened to route fuel vapor to the bleed canister during refueling, then the bleed canister can be loaded for diagnostics, but it requires coordination with the fuel level threshold and valve timing
Solution Approach 1:
The system employs dynamic valve control where the bypass valve timing is adjusted based on real-time fuel level measurements. The valve opens only when the fuel level reaches a predetermined threshold during refueling, creating a dynamic, condition-based diagnostic test rather than a static or continuous operation. This dynamic approach enables precise degradation detection while managing complexity through event-driven control.
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 enables timely detection of bleed canister degradation, reducing the risk of undesired HC emissions and maintaining emissions quality, facilitating the operation of practically zero emissions vehicles (PZEV) by ensuring the bleed canister is effectively loaded and purged.
Implementation Method 1
vaporized hydrocarbons (HCs) from a fuel tank may be stored in one or more fuel vapor canisters packed with an adsorbent which adsorbs and stores the fuel vapors
Implementation Method 2
The bleed canister may include a highly restrictive structure of honeycombed patterns to trap any HCs escaping the one or more fuel vapor canisters
Implementation Method 3
indicating if the bleed canister is robust or degraded based on output of an exhaust gas sensor
Implementation Method 4
The fuel vapors are then consumed during combustion
Data Source
AI summary
Methods and systems are provided for carrying out diagnostics of a bleed canister of an evaporative emissions control system in a vehicle. In one example, a method may include, loading the bleed canister during a refueling event, and then during an immediately subsequent engine start, detecting if the bleed canister is degraded or not based on output of an exhaust gas oxygen sensor.