Patent ID: 7389769

Claim:
A fuel nature measuring device, for measuring the nature of fuel stored in a fuel tank of an internal combustion engine, the measuring device comprising: a measurement passage having an orifice therein; gas flow generating means for generating a gas flow in said measurement passage; differential pressure detecting means for detecting a differential pressure between opposite ends of said orifice; evaporated fuel concentration operating means for determining a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when said opposite ends of said measurement passage communicates with said fuel tank and the fuel in the fuel tank flows in said measurement passage; temperature detecting means for determining a temperature of the fuel in said fuel tank; volatility calculation means for calculating a volatility of the fuel in said tank as the fuel nature based on the concentration of the evaporated fuel determined by said evaporated fuel concentration operation means and the temperature determined by said temperature detecting means; and engine operation state detecting means for detecting an operation state of said internal combustion engine, wherein the fuel nature is measured provided that said internal combustion engine is in a stopped state.