Measuring and testing – With fluid pressure – Motor part or auxiliary
Reexamination Certificate
1999-08-17
2001-03-20
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Motor part or auxiliary
C073S04050A, C073S118040, C701S031000
Reexamination Certificate
active
06202478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to evaporative emission control systems for automotive vehicles and, more particularly, to a leak detection assembly and method for determining if a fuel cap sealing problem is present in an evaporative emission control system for an automotive vehicle.
2. Description of the Related Art
Modern automotive vehicles typically include a fuel tank and an evaporative emission control system that collects volatile fuel vapors generated in the fuel tank. The evaporative emission control system includes a vapor collection canister, usually containing an activated charcoal mixture, to collect and store volatile fuel vapors. Normally, the canister collects volatile fuel vapors which accumulate during refueling of the automotive vehicle or from increases in fuel temperature. The evaporative emission control system also includes a purge valve placed between an intake manifold of an engine of the automotive vehicle and the canister. The purge valve is opened by an engine control unit an amount determined by the engine control unit to purge the canister, i.e., the collected volatile fuel vapors are drawn into the intake manifold from the canister for ultimate combustion within a combustion chamber of the engine.
Recently, governmental regulations have required that certain automotive vehicles powered by volatile fuels such as gasoline have their evaporative emission control systems checked to determine if a leak exists in the system. As a result, on board vehicle diagnostic systems have been developed to determine if a leak is present in a portion of the evaporative emission control system. One such diagnostic system utilizes a vacuum regulator/sensor unit to draw a vacuum on the evaporative emission control system and sense whether a loss of vacuum occurs within a specified period of time.
Diagnostic systems also exist for determining the presence of a leak in an evaporative emission control system which utilizes positive pressurization rather than negative pressurization, i.e., vacuum. In positive pressurization systems, the evaporative emission control system is pressurized to a set pressure, typically through the use of an electric air pump. A sensor determines whether the pressure remains constant over a certain amount of time.
At times, a leak will exist in the system due to a fuel cap sealing problem. That is, the fuel cap is either missing, loose, or is not properly sized to the fuel tank fill tube. Present diagnostic systems do not specifically perform a test to identify this type of leak condition. As such, the sealing problem is not detected until operation of the standard diagnostic test. Further, conventional diagnostic systems treat such a leak condition the same as other types of leaks thereby activating the warning signals and/or setting fault codes. Such warning signals and fault codes are typically not cleared until after three cold starts, i.e., three days. As such, vehicle operators are taking their vehicles to dealerships for repair when a simple check and resealing of the fuel cap may resolve the situation.
In view of the foregoing, it would be desirable to provide a leak detection system for specifically determining if a fuel cap sealing problem is present in the evaporative emission control system of the automotive vehicle and informing the operator or service technician of the same.
SUMMARY OF THE INVENTION
It is, therefore, one object of the present invention to provide a leak detection system for use in testing the integrity of an evaporative emission control system for an automotive vehicle.
It is another object of the present invention to provide a leak detection system for use in testing the integrity of the fuel cap sealing in an evaporative emission control system after each refueling event.
It is yet another object of the present invention to provide a leak detection system for notifying the vehicle operator and/or service technician of a potential fuel cap sealing problem.
To achieve the foregoing objects, the present invention is a method of testing an evaporative emission control system for a missing or loose fuel cap comprising detecting a refueling event and running a leak detection test of the evaporative emission control system to determine if a large leak is present. If a large leak is detected, the methodology sets a fault code and activates a driver warning lamp indicating a potential cap sealing problem. The leak detection test is repeatedly re-executed after the large leak is detected to determine when the large leak condition ceases. When the large leak condition ceases, the previously set fault code is removed and the driver warning lamp is deactivated. If the large leak continues to be detected and is then detected again after the next refueling event (when an opportunity for resealing the cap existed), a new fault code is set indicating that the potential cap sealing problem is a persistent problem so that the integrity of the evaporative system may need to be tested. After setting the new fault code, fuel cap specific leak detection testing is suspended until the condition is serviced and the fault code is cleared or the standard leak detection test determines that the leak has been corrected. When no large leak is detected, the fuel cap is assumed to be properly sealed.
One advantage of the present invention is that a leak detection system is provided for an evaporative emission control system of an automotive vehicle. Another advantage of the present invention is that a potential fuel cap sealing problem is quickly identified after each refueling event. Yet another advantage of the present invention is that the potential fuel cap sealing problem is identified separately from other non-cap related leak conditions. Still yet another advantage of the present invention is that the indicator lamp and fault codes are immediately removed after the fuel cap sealing problem condition is corrected.
Other objects, features, and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in conjunction with the accompanying drawings.
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Blomquist William B.
Dawson Gary D.
Richardson Roland T.
Calcaterra Mark P.
Cygan Michael
DaimlerChrysler Corporation
Williams Hezron
LandOfFree
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