US Patent 8099999 Purge gas concentration estimation apparatus

A purge gas concentration estimation apparatus has a canister having a casing that is filled with adsorbent which adsorbs and desorbs evaporated fuel and a heat capacity detection device that is disposed in the casing. The heat capacity detection device detects a heat capacity of an inside of the casing. An adsorption amount of the evaporated fuel that is adsorbed in the casing is detected from the heat capacity of the inside of the casing detected by the heat capacity detection device, and a purge gas concentration is estimated from the detected adsorption amount of the evaporated fuel.