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AN ELCM EVAP MONITOR COMPENSATION METHOD FOR CANISTER LOADING STATE

IP.com Disclosure Number: IPCOM000237181D
Publication Date: 2014-Jun-06
Document File: 1 page(s) / 241K

Publishing Venue

The IP.com Prior Art Database

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AN ELCM EVAP MONITOR COMPENSATION METHOD FOR CANISTER LOADING STATE

Vehicles sold in North America are required to perform Evap leak detection. Green states required to monitor for 0.02" leaks. Federal states are required to perform 0.04" leak check. Heavy duty applications are required to perform 0.09" leak checks. Future PHEV fuel tanks will have a 0.01" leak requirement.For HEV, engine run time is limited hence a vacuum pump is required for leak detection. One such vacuum pump is the ELCM made by Denso Corporation.ELCM test sequence begins by obtained a "reference check" by turning on pump and evacuating small volume where internal 0.02" reference orifice is located. Reference vacuum value obtained becomes pass/fail threshold.The internal reference orifice is used to compensate for environmental conditions such as temperature, barometric pressure, humidity, etc... However, it does not compensate for canister loading state. Canister loading can cause the ELCM pump to work harder to evacuate the space in the Evap system which can result in false fails.

Method

The invention centers around compensating the ELCM pumpdown time for canister loading. Canister loading is inferred via several methods. If canister loading is high, monitor is allotted more time proportionately to make the pass/fail call. First method of inferring canister loading is during purge flow. Strategy calculates a "purge flow HC concentration" from the HEGO sensor feedback. If canister loadin...