Fuel Evaporative Emission Control Device for Air-Fuel Ratio Stability
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Solution Overview
Problem
Existing fuel evaporative emission control systems experience variations in air-fuel ratio due to highly-concentrated fuel evaporative gas remaining in the intake passage, leading to unstable engine performance and emissions when the engine restarts after a high-pressure purge.
Innovation Solution
A fuel evaporative emission control device that conducts a connecting-passage purge followed by a canister purge, ensuring that fuel evaporative gas is emitted into the intake passage, stabilizing pressure and preventing the accumulation of highly-concentrated gas, thereby maintaining a stable air-fuel ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the sealing valve is opened to purge high-pressure fuel evaporative gas into the intake passage, then the pressure in the fuel tank decreases, but highly-concentrated fuel evaporative gas remains in the connecting passage causing air-fuel ratio variations
Solution Approach 1:
The system performs a connecting-passage purge before canister purge to preliminarily clear highly-concentrated fuel evaporative gas from the connecting passage. This preliminary action prevents the gas from being drawn into the intake passage during subsequent engine operation, thereby maintaining air-fuel ratio stability while still achieving the desired pressure reduction in the fuel tank
2Productivity
If the sealing valve is closed immediately after fuel-tank purge, then the purge operation is completed efficiently, but highly-concentrated fuel evaporative gas remains trapped in the connecting passage
Solution Approach 1:
The control unit keeps the sealing valve open for a predetermined time period after the fuel-tank purge is completed to preliminarily purge the connecting passage. This ensures that highly-concentrated fuel evaporative gas is removed from the connecting passage before the valve is closed, preventing gas accumulation and subsequent air-fuel ratio variations
3Stability of the object's composition
If the sealing valve remains open for a long time to clear the connecting passage, then air-fuel ratio stability is improved, but the purge operation efficiency decreases
Solution Approach 1:
The system implements a timed preliminary purge of the connecting passage for a predetermined short duration, which is sufficient to clear highly-concentrated fuel evaporative gas. This predetermined time period balances the need for air-fuel ratio stability with the requirement for efficient purge operation, avoiding excessive time loss
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
Prevents abrupt changes in the air-fuel ratio by ensuring all fuel evaporative gas is emitted into the intake passage, reducing engine output variations and improving emissions by stabilizing the pressure in the connecting passage and canister.
Implementation Method 1
a canister (31) for adsorbing fuel evaporative gas incoming through the connecting passage (38, 39)
Data Source
AI summary
When fuel tank internal pressure is at a first predetermined pressure P1 or above over a first predetermined time length t1, a fuel tank shutoff valve is opened and a vapor solenoid valve is closed to make piping internal pressure equal to the fuel tank internal pressure. Then, a purge control valve is opened to emit fuel evaporative gas from the fuel tank into an intake passage. When the fuel tank internal pressure is continuously at a second predetermined pressure P2 or below over the first predetermined time length t1, the fuel tank shutoff valve is closed, and when accumulated volume in high-pressure purge finishing phase reaches a second predetermined volume iv2 or above, the vapor solenoid valve is opened. When the accumulated volume in high-pressure purge finishing phase reaches a first predetermined volume iv1 or above, the purge control valve is opened and the engine is stopped.