Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-02-22
2001-02-27
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S118040, C073S049700, C123S520000, C123S516000, C137S907000
Reexamination Certificate
active
06192743
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a module for an on-board leak detection system that detects fuel vapor leakage from an evaporative emission space of an automotive vehicle fuel system, and more especially to an electric-operated, pump-type module for such a leak detection system.
BACKGROUND OF THE INVENTION
A known on-board evaporative emission control system for an automotive vehicle comprises a vapor collection canister that collects volatile fuel vapors generated in the headspace of the fuel tank by the volatilization of liquid fuel in the tank and a purge valve for periodically purging fuel vapors to an intake manifold of the engine. A known type of purge valve, sometimes called a canister purge solenoid (or CPS) valve, comprises a solenoid actuator that is under the control of a microprocessor-based engine management system, sometimes referred to by various names, such as an engine management computer or an engine electronic control unit.
During conditions conducive to purging, evaporative emission space that is cooperatively defined primarily by the tank headspace and the canister is purged to the engine intake manifold through the canister purge valve. A CPS-type valve is opened by a signal from the engine management computer in an amount that allows intake manifold vacuum to draw fuel vapors that are present in the tank headspace and/or stored in the canister for entrainment with combustible mixture passing into the engine's combustion chamber space at a rate consistent with engine operation so as to provide both acceptable vehicle driveability and an acceptable level of exhaust emissions.
Certain governmental regulations require that certain automotive vehicles powered by internal combustion engines which operate on volatile fuels such as gasoline, have evaporative emission control systems equipped with an on-board diagnostic capability for determining if a leak is present in the evaporative emission space. It has heretofore been proposed to make such a determination by temporarily creating a pressure condition in the evaporative emission space which is substantially different from the ambient atmospheric pressure, and then watching for a change in that substantially different pressure which is indicative of a leak.
It is believed fair to say that there are two basic types of vapor leak detection systems for determining integrity of an evaporative emission space: a positive pressure system that performs a test by positively pressurizing an evaporative emission space; and a negative pressure (i.e. vacuum) system that performs a test by negatively pressurizing (i.e. drawing vacuum in) an evaporative emission space.
Commonly owned U.S. Pat. No. 5,146,902 discloses a positive pressure system. Commonly owned U.S. Pat. No. 5,383,437 discloses the use of a reciprocating pump to create positive pressure in the evaporative emission space. Commonly owned U.S. Pat. No. 5,474,050 embodies advantages of the pump of U.S. Pat. No. 5,383,437 while providing certain improvements in the organization and arrangement of a reciprocating pump.
The commonly assigned applications identified above relate to novel leak detection modules containing electric-operated pumping mechanisms and vent valves.
SUMMARY OF THE INVENTION
One general aspect of the invention relates to further improvements in the leak detection modules of the general type disclosed in the above-identified applications.
Another general aspect relates to a module for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle, the module comprising: a walled enclosure comprising an interior space adapted to be communicated to atmosphere; a pump disposed within the interior space comprising a pumping chamber having an inlet in communication with the interior space and a flow passage for communicating the pumping chamber with an evaporative emission space to allow the evaporative emission space to be pressurized by the pump; a vent valve that is disposed within the interior space and is selectively operable to a first state that vents the flow passage to the interior space to thereby vent the evaporative emission space to atmosphere and to a second state that does not vent the flow passage to the interior space; and an electrio-operated actuator mechanism disposed within the interior space for operating the pump and the vent valve to perform a leak test on the evaporative emission space; the actuator mechanism comprising a coupling through which one of the pump and the vent valve is operated, the coupling comprising a lever that has first and second lever arms and comprises a part having a formation that is proximate proximal ends of the first and second lever arms and is received in a complementary formation in a wall of the enclosure to thereby pivotally mount the lever on the wall of the enclosure.
Still another general aspect of the invention relates to an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle and that comprises: a pump for creating in the evaporative emission space a pressure condition suitable for performing a leak test; a vent valve that is selectively operable to a first state for venting the evaporative emission space to atmosphere and to a second state for closing the evaporative emission space to atmosphere; and an electric-operated actuator mechanism for operating at least one of the pump and the vent valve to perform a leak test on the evaporative emission space; the actuator mechanism comprising a coupling through which one of the pump and the vent valve is operated, the coupling comprising a lever that has first and second lever arms and comprises a non-metallic part having a formation that is proximate proximal ends of the first and second lever arms and is received within a complementary formation of a non-metallic mounting to thereby pivotally mount the lever for rocking motion to operate the one of the pump and the vent valve.
Still another general aspect of the invention relates to a module for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle, the module comprising: a walled enclosure comprising an interior space adapted to be communicated to atmosphere; a pump disposed within the interior space comprising a pumping chamber having an inlet in communication with the interior space and a flow passage for communicating the pumping chamber with an evaporative emission space to allow the evaporative emission space to be pressurized by the pump; a vent valve that is disposed within the interior space and is selectively operable to a first state that vents the flow passage to the interior space to thereby vent the evaporative emission space to atmosphere and to a second state that does not vent the flow passage to the interior space; an electric-operated actuator mechanism disposed within the interior space for operating the pump and closing the vent valve to perform a leak test on the evaporative emission space; a pressure sensor for sensing pressure in the flow passage; and an electric circuit board assembly containing electric circuitry operatively connected to both the electric-operated actuator mechanism and the pressure sensor.
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Siemens Canada Limited
Wiggins David J.
Williams Hezron
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