Evaporative Emissions Diagnostic Using Intake Manifold Vacuum
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Solution Overview
Problem
Hybrid electric vehicles pose challenges in effectively controlling evaporative emissions due to inadequate heat rejection, leading to false failures and decreased completion rates in evaporative emissions tests, especially when fuel slosh and fuel vaporization occur during pressure-based tests.
Innovation Solution
Conducting an evaporative emissions test by remotely starting the vehicle engine, sealing the fuel system and evaporative emissions system from atmosphere, and applying engine intake manifold vacuum to reduce pressure to a predetermined negative threshold, then monitoring for pressure increases indicative of undesired emissions, while ensuring the vehicle is unoccupied and fuel temperature is below a threshold to prevent vaporization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure-based evaporative emissions tests are conducted using engine intake manifold vacuum, then the ability to detect undesired emissions is improved, but fuel slosh and fuel vaporization cause false failures and decrease test completion rates
Solution Approach 1:
The system performs preliminary actions by remotely starting the engine before conducting the emissions test. This creates a controlled operating condition where the engine is running but the vehicle remains stationary and unoccupied, preventing fuel slosh while allowing intake manifold vacuum to be available for the pressure-based test.
Solution Approach 2:
The system changes operational parameters by utilizing engine intake manifold vacuum (a negative pressure source) to pressurize/evacuate the fuel system and emissions control system. This alternative pressure source replaces reliance on heat rejection, enabling tests under hybrid electric vehicle operating conditions where the engine runs for short periods.
2Productivity
If evaporative emissions tests are conducted during hybrid electric vehicle operation, then emissions diagnostics are performed, but inadequate heat rejection leads to false failures
Solution Approach 1:
The system introduces an intermediary pressure source (engine intake manifold vacuum) to mediate the emissions test process. This intermediary enables pressure-based diagnostics without relying on heat rejection, thereby eliminating false failures caused by inadequate thermal conditions in hybrid electric vehicles.
Solution Approach 2:
The system changes the physical parameter used for the test from thermal (heat rejection) to mechanical (intake manifold vacuum). This parameter change allows emissions diagnostics to proceed accurately under hybrid electric vehicle operating conditions where thermal conditions are insufficient.
3Ease of operation
If the vehicle is occupied or doors are open during pressure-based emissions tests, then normal vehicle operation is maintained, but fuel slosh increases pressure and causes false emissions indications
Solution Approach 1:
The system performs preliminary monitoring of vehicle occupancy and door status before initiating the emissions test. Entry conditions require the vehicle to be unoccupied and doors closed, ensuring that fuel slosh will not occur during the test while maintaining normal vehicle operation outside of test conditions.
Solution Approach 2:
The system uses feedback from sensors monitoring vehicle occupancy and door status to control test execution. The controller continuously monitors these conditions and only permits the emissions test when entry conditions are satisfied, preventing false indications while allowing normal vehicle operation at other times.
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 increases the reliability and completion rates of evaporative emissions tests by minimizing the impact of external noise and fuel vaporization, allowing for accurate detection of undesired emissions without false failures.
Implementation Method 1
applying engine intake manifold vacuum to reduce pressure to a predetermined negative threshold
Implementation Method 2
as liquid fuel vaporizes
Implementation Method 3
a vacuum is generated therein as fuel vapors condense to liquid fuel
Data Source
AI summary
Methods and systems are provided for conducting an evaporative emissions test responsive to an indication of a vehicle remote engine start event. In one example, responsive to an indication of a remote start and further indication that the vehicle is not occupied, intake manifold vacuum is utilized to reduce pressure in the fuel system and evaporative emissions system to a threshold, wherein the fuel system and evaporative emissions system are sealed, and undesired evaporative emissions indicated responsive to a pressure bleed-up rate greater than a threshold. In this way, by applying intake manifold vacuum on the fuel system and evaporative emissions system while the vehicle is stationary and not occupied, engine hesitations resulting from desorption of fuel vapors from a fuel vapor canister are not experienced by the vehicle operator and/or passengers, and noise factors from driving conditions, passenger movement, etc., do not impact the evaporative emissions test.