Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
1998-06-30
2001-03-06
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S533000, C123S1980DA
Reexamination Certificate
active
06196202
ABSTRACT:
The contents of commonly owned co-pending Non-provisional U.S. patent application Ser. No. 08/824,938, filed Mar. 26, 1997 in the names of Cook et al and entitled “Evaporative Emission Leak Detection System”, and the contents of commonly-owned U.S. Pat. No. 5,551,406 are hereby incorporated in their entirety by reference as if fully disclosed herein.
FIELD OF THE INVENTION
This invention relates generally to an evaporative emission control system of an automotive vehicle fuel system, and more especially to an evaporative emission control system that does not depend exclusively on engine intake system vacuum for purging fuel vapors to an engine.
BACKGROUND OF THE INVENTION
A known evaporative emission control system for a fuel system of an internal combustion engine that powers an automotive vehicle comprises an evaporative emission containment space for containing volatile fuel vapors and a purge valve through which the fuel vapors are purged from the evaporative emission containment space to an intake system of the engine for combustion. The evaporative emission containment space includes headspace of a fuel tank that contains a supply of volatile liquid fuel for the engine and an associated fuel vapor collection canister, e.g. a charcoal canister, through which the tank headspace is vented to atmosphere.
The purge valve opens when conditions are conducive to purging, commnicating the evaporative emission containment space to the engine intake system. Atmospheric venting of the tank headspace maintains the tank headspace pressure near atmospheric. Intake system vacuum communicated through the open purge valve draws gases present in the evaporative emission containment space (a mixture of fuel vapors and air) through the purge valve and into the intake system. There the purge flow entrains with intake flow into the engine, ultimately to be disposed of by combustion within the engine. A known purge valve comprises an electric actuator that receives a control signal developed by an engine management computer to open the purge valve in the proper amount for various operating conditions, thereby developing the desired purge flow.
Because the evaporative emission control system relies solely on intake system vacuum to draw fuel vapors from the evaporative emission containment space, the intensity of the vacuum directly effects the purge flow rate. At larger vacuum intensities, the engine management computer can adjust the purge valve to compensate for changes in vacuum. However, when system vacuum falls below a certain threshold that is determined by various factors, there is insufficient pressure differential between the evaporative emission containment space and the intake system to develop the requisite purge flow.
Some automotive vehicle internal combustion engines may develop nominal intake system vacuums that range from about 10 inches Hg to about 20 inches Hg. Purge valves used with such engines are designed for such a range. For any one or more of various reasons however, actual intake system vacuum in a particular engine may be incapable of exhibiting that nominal range. That characteristic may impair operation of an evaporative emission control system because there is insufficient pressure differential to develop the desired purge flows. An engine that has direct high-pressure gasoline fuel injection may exhibit a nominal system vacuum range that is much closer to atmospheric pressure than the nominal range of intake system vacuum for other engines.
SUMMARY OF THE INVENTION
The present invention relates to an evaporative emission control system which can develop requisite vapor purge flow even when intake system vacuum falls below a threshold at which the pressure differential between the evaporative emission containment space and the intake system becomes insufficient to attain the requisite purge flow. Accordingly, the invention provides an evaporative emission control system that can develop the proper purge flow independent of prevailing engine intake system vacuum.
One general aspect of the invention relates to an evaporative emission control system for an evaporative emission containment space of a fuel system of an internal combustion engine of an automotive vehicle, the evaporative emission control system comprising: a purge flow path through which fuel vapors are purged from the containment space to an intake system of the internal combustion engine; a purge valve for controlling purge flow through the purge flow path; and an electrically controlled device that is responsive to a condition associated with purging of the containment space to the engine intake system through the purge valve for creating a condition that augments the purge flow controlled by the purge valve.
Some of the more specific aspects that characterize the invention include: the device creating, in the purge flow path between the evaporative emission containment space and the purge valve, a pressure rise that augments purge flow controlled by the purge valve; the device having an inlet for communication to the evaporative emission containment space and an outlet communicated to the purge valve; including a canister comprising a fuel vapor zone for communication to the containment space, an atmospheric zone for communication to atmosphere, and a fuel vapor adsorbent medium that separates the two zones from each other; the device being disposed to create the pressure rise in the purge flow path between the canister and the purge valve; the device; the device comprising an electric-controlled prime mover, such as an electric-motor-driven blower, that is selectively operable to a pressure-creating condition for augmenting the purge flow through the purge valve and to a non-pressure-creating condition that allows bi-directional flow through the purge flow path; the condition to which the electrically controlled device is responsive being pressure differential across the purge valve as sensed by a differential pressure sensor; an electric controller for processing input data, such as the differential pressure sensor signal to control operation of both the device and the purge valve; and the purge valve including a sensor providing a feedback signal to the controller indicative of actual operation of the purge valve mechanism.
Another general aspect of the invention relates to an automotive vehicle comprising: an internal combustion engine for powering the vehicle; a tank for holding a supply of volatile fuel for the engine; and an evaporative emission control system for containing and disposing of fuel vapors resulting from the volatilization of fuel in the tank, the evaporative emission control system comprising a purge flow path through which contained fuel vapors are purged to the engine for disposal, a purge valve for controlling purge flow through the purge flow path, and a purge flow path through which fuel vapors are purged from the containment space to an intake system of the internal combustion engine; and an electrically controlled device that is responsive to a condition associated with purging of the containment space to the engine intake system through the purge valve for creating a condition that augments the purge flow controlled by the purge valve.
Still another general aspect of the invention relates to a method of enabling a purge valve to accurately control the purging of volatile fuel vapors through a purge flow path extending from an evaporative emission containment space, through the purge valve, to an intake system of an internal combustion engine, the method comprising: operating an electrically controlled device in response to a condition associated with purging of the containment space to the engine intake system through the purge valve to create a condition that augments the purge flow controlled by the purge valve.
More specific aspects of the method include: creating pressure differential to augment the purge flow controlled by the purge valve; sensing pressure differential across the purge valve and utilizing the sensed pressure differential in control of at least one
Busato Murray F.
Cook John Edward
Miller Carl S.
Siemens Canada Limited
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