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A CARBON CANISTER INTEGRITY DIAGNOSTIC FOR PHEV USING DIURNAL TEMPERATURE CYCLE

IP.com Disclosure Number: IPCOM000240457D
Publication Date: 2015-Jan-30
Document File: 1 page(s) / 220K

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A CARBON CANISTER INTEGRITY DIAGNOSTIC FOR PHEV USING DIURNAL TEMPERATURE CYCLE

Vehicles sold in North America must adsorb running loss, diurnal and refueling vapors inside a carbon canister. CARB recently inquired OEMs to investigate methods for diagnosing the integrity of carbon canisters, i.e., canister's ability to adsorb and desorb hydrocarbons (HC). In ordinary vehicles, the canister integrity is easily diagnosable using temperature sensors inside the canister or through feedback O2 sensor response. Adsorption is validated during refueling event and desorption is validated during purging. With PHEV vehicles, purging is infrequent due to limited engine run time which constrains purging the canister. Also, refueling events are rare if driver chooses to plug in and recharge the battery every day. Hence, a different method is needed to perform canister integrity diagnostics for PHEV.

Method

The NIRCOS PHEV fuel tank is sealed, hence the tank always develops vacuum or pressure. This is due to the diurnal temperature cycle that fluctuates between day and night.Invention idea is to perform diagnostics on the canister using the natural vacuum/pressure that develops inside the always-sealed fuel tank. A temperature sensor at the load side of the canister is used to infer canister integrity. Future Tier III canister designs include heated elements and a thermocouple to facilitate better HC desorption.When the fuel tank is under a pressure condition (daytime hours)...