Evaporative emission tester
First Claim
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1. A method for leakage testing a pressurized closed system, comprising the steps of:
- pressurizing the closed system with a pressurizing gas using a puff pressurization scheme by automatically activating and deactivating a pressurizing assembly a recurring number of times over a pressurization period;
monitoring pressure levels in the closed system only during each time the pressurizing assembly is deactivated;
determining when a given pressure level is reached; and
automatically comparing the pressure level in the closed system to a minimum allowable pass-test value a predetermined time period after the given pressure level is reached.
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Abstract
An evaporative emission tester is used to evaluate the integrity of a vehicle'"'"'s evaporative emission control system, including determining the system'"'"'s purge capability. The emission tester performs a purge flow test to determine whether fuel vapor stored in the vehicle'"'"'s evaporative canister and present in the fuel tank is being drawn into the engine for combustion at a minimum amount. The emission tester also performs a pressure test of the vehicle'"'"'s evaporative canister purge system, which includes the fuel tank and lines. The emission tester can function as a stand-alone unit or as an integrated product with a host computer.
89 Citations
19 Claims
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1. A method for leakage testing a pressurized closed system, comprising the steps of:
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pressurizing the closed system with a pressurizing gas using a puff pressurization scheme by automatically activating and deactivating a pressurizing assembly a recurring number of times over a pressurization period;
monitoring pressure levels in the closed system only during each time the pressurizing assembly is deactivated;determining when a given pressure level is reached; and automatically comparing the pressure level in the closed system to a minimum allowable pass-test value a predetermined time period after the given pressure level is reached. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An evaporative emission tester for performing a purge flow test and a pressure test of an evaporative emission system, the tester comprising:
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a flow sensor apparatus including a venturi coupled to the emission system for measuring fuel vapor flow rate through the venturi and generating differential pressure indicating signals indicative of the flow rate; a gas supplying solenoid assembly responsive to a solenoid control signal, for pressurizing the system to a predetermined level, and including a pressure sensor for monitoring the pressure level in the system; means for automatically intermittently pressurizing the system at first activation/deactivation intervals and then at second activation/deactivation intervals, smaller than said first activation/deactivation intervals, to avoid pressurization overshoot; and pass-fail determining means responsive to either said differential pressure indicating signals or to signals monitored by said pressure sensor to test the integrity of the emission system. - View Dependent Claims (8, 9, 10, 11, 12)
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13. An apparatus for leakage testing a pressurized closed system, comprising:
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a solenoid valve subassembly coupled to the closed system; a pressurizing assembly coupled to the solenoid valve subassembly for pressurizing the closed system with a pressurizing gas using a puff pressurization scheme by automatically activating and deactivating the solenoid valve subassembly a recurring number of times over a pressurization period; means for monitoring pressure levels in the closed system only during each time the solenoid valve subassembly is deactivated; means for determining when a given pressure level is reached; and means for automatically comparing the pressure level in the closed system to a minimum allowable pass-test value a predetermined time period after the given pressure level is reached. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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Specification