Hydrocarbon Trap Purging via Intake Throttle Dynamics
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Solution Overview
Problem
In plug-in hybrid electric vehicles (PHEVs), the reduced engine operation time limits the intake manifold vacuum, resulting in reduced airflow across hydrocarbon traps, leading to incomplete purging and increased evaporative emissions.
Innovation Solution
During engine-off conditions, increasing airflow through the hydrocarbon trap by opening the intake throttle and using vehicle motion-induced airflow to purge fuel vapors into a fuel system canister, which has a larger storage capacity, thereby opportunistically cleaning the trap without relying on engine vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the engine operation time is reduced to improve fuel efficiency and emissions, then the intake manifold vacuum is limited, but the airflow across the hydrocarbon trap is reduced, leading to incomplete purging
Solution Approach 1:
The system performs preliminary purging action by transferring fuel vapors from the HC trap to the fuel system canister during engine-off conditions, before the engine needs to be restarted. This preliminary transfer prevents vapor accumulation in the HC trap and ensures ready-to-purge conditions when the engine starts, resolving the contradiction between reduced engine operation time and trap purging efficiency.
Solution Approach 2:
The fuel system canister serves as an intermediary storage device between the HC trap and the engine intake. During engine-off conditions, vapors are transferred from the HC trap to the canister, which then serves as a temporary storage bank. When the engine restarts, the canister can be quickly purged into the engine, enabling efficient vapor management despite limited engine operation time.
2Use of energy by moving object
If the engine is maintained shutdown during electric mode to improve fuel economy, then emissions are reduced, but the hydrocarbon trap cannot be purged due to lack of intake manifold vacuum
Solution Approach 1:
The system uses the vehicle's own motion-induced airflow to perform self-service purging of the HC trap during engine-off electric mode operation. The airflow generated by vehicle movement is directed through the HC trap via the open intake throttle, enabling the trap to purge its own vapors without requiring engine operation, thus maintaining both fuel economy and purging reliability.
3Productivity
If the intake throttle is opened during vehicle travel in electric mode to increase airflow, then motion-induced airflow can purge the hydrocarbon trap, but the primary function of the throttle (controlling engine intake) is compromised
Solution Approach 1:
The intake throttle operates dynamically with different functions depending on engine state. During engine-off electric mode, the throttle opens to enable airflow-based purging of the HC trap. During engine-on modes, the throttle returns to its conventional role of controlling intake airflow to the engine. This dynamic reconfiguration allows the same component to serve dual purposes without compromising either function.
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 effectively reduces hydrocarbon breakthrough and improves overall emissions and vehicle performance by ensuring more frequent purging of the hydrocarbon trap, even during engine shutdown.
Implementation Method 1
hydrocarbon (HC) traps coupled in an air induction system of the engine to adsorb evaporative emissions in the engine intake
Implementation Method 2
intake manifold vacuum draws the fuel vapors into the engine and also causes airflow across the trap, increasing desorption
Implementation Method 3
passive desorption of fuel vapors
Data Source
AI summary
Methods and systems are provided for improving air intake system hydrocarbon trap purging during engine-off time in a hybrid electric vehicle. One method includes opening the throttle during vehicle motion under battery operation and allowing airflow through the trap to purge its contents into the fuel canister via the canister purge valve. Upon transition into the engine-on mode, fuel vapors are released from the canister into the engine intake.