Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
1999-08-30
2001-12-11
McCall, Eric S. (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
Reexamination Certificate
active
06327901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally relates to evaporative emission control systems for automotive vehicles and, more particularly, to a leak detection assembly and a method of determining if a leak is present in an evaporative emission control system of an automotive vehicle.
2. Discussion
Modern gasoline powered automotive vehicles typically include a fuel tank and an evaporative emission control system that collects fuel vapors generated in the fuel tank. The evaporative emission control system includes a vapor collection canister, usually containing activated carbon, to collect and store fuel vapors. The canister collects fuel vapors which are displaced from the fuel tank during refueling of the automotive vehicle or from increases in fuel temperature.
The evaporative emission control system also includes a purge valve between the intake manifold of the engine and the canister. When conditions are conducive to purging, a controller opens the purge valve a predetermined amount to purge the canister. That is, the collected fuel vapors are drawn into the intake manifold from the canister for ultimate combustion within the engine.
It has recently become desirable to check evaporative emission control systems for leaks. To this end, 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 method utilizes negative pressurization to check for leaks. In this method, a vent valve is used to seal the canister vent, a sensor to monitor system pressure, and a purge valve to draw a vacuum on the evaporative emission control system. As the vacuum is drawn, the method monitors whether a loss of vacuum occurs within a specified period of time. If so, a leak is presumed to be present.
Diagnostic systems also exist for determining the presence of a leak in an evaporative emission control system which utilize positive pressurization rather than negative pressurization. In positive pressurization systems, the evaporative emission control system is pressurized to a set pressure, typically through use of an air pump. Thereafter, a sensor detects whether a loss of pressure occurs over a certain amount of time.
While positive and negative pressurization systems are useful, there is room for improvement in the art. For instance, it would be desirable to provide a leak detection system which does not require either positive or negative pressurization of the system from an outside source. Additionally, it would be desirable to provide a leak detection system which functions when the vehicle is not operating. This would eliminate many of the complicated issues which make leak detection on an operating vehicle very difficult.
SUMMARY OF THE INVENTION
It is one object of the present invention to provide a leak detection assembly 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 method having a device for sealing the evaporative emission control system such that an internal pressure thereof is isolated from external influences.
It is yet another object of the present invention to provide a leak detection method having a device for monitoring the internal pressure of the evaporative emission control system after it has been sealed such that very small, moderate, and large leaks may be separately detected by noting if the pressure within the sealed evaporative emission control system goes below atmospheric pressure over predetermined periods of time as the evaporative emission control system components cool.
It is still yet another object of the present invention to provide a leak detection method for testing the rationality of the device used for monitoring the internal pressure of the evaporative emission control system.
It is another object of the present invention to provide a leak detection method for periodically cleaning the device for sealing the evaporative emission control system.
Some of the above and other objects are provided by a method of determining the rationality of a device for monitoring the pressure within an evaporative emission control system of an automotive vehicle. The method includes opening a valve of the evaporative emission control system and determining if a vacuum switch of the evaporative emission control system opened. If the vacuum switch opened, a code is set indicating that the vacuum switch passed an opening test. If the vacuum switch did not open, the method determines if a fail timer is greater than a first fail threshold value. The first fail threshold value corresponds to an amount of time within which a properly functioning vacuum switch should open after said valve is opened. If the fail timer is greater than the fail threshold value, the method sets a code indicating that the vacuum switch failed the opening test. If the fail timer is less than or equal to the first fail threshold value, the method increments the fail timer. If the vacuum switch passed the opening test, the method closes the valve of the evaporative emission control system and applies a vacuum thereto. The method then determines if the vacuum switch closed due to the vacuum. If the vacuum switch closed, the method sets a code indicating that the vacuum switch passed a closing test. If the vacuum switch did not close, the method determines if the fail timer is greater than a second fail threshold value. The second fail threshold value corresponds to an amount of time within which a properly functioning vacuum switch should close after the vacuum is applied. If the fail timer is greater than the second fail threshold value, the method sets a code indicating that the vacuum switch failed the closing test. If the fail timer is less than or equal to the second fail threshold value, the method increments the fail timer.
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Blomquist William B.
Booms Chris J.
Dawson Gary D.
Calcaterra Mark P
DaimlerChrysler Corporation
McCall Eric S.
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