Patent ID: 8215161

Claim:
A fuel state sensing device applied to an injector injecting fuel, which is supplied from a fuel pump, though an injection hole, the fuel state sensing device comprising: a bulk modulus sensing means for sensing a bulk modulus of the fuel existing in a fuel passage extending from a discharge port of the fuel pump to the injection hole; a fuel temperature sensing means for sensing fuel temperature; and an air mixing state calculating means for calculating a quantity or a ratio of air mixing in the fuel as an air mixing quantity or an air mixing ratio based on the sensed bulk modulus and the sensed fuel temperature; wherein the bulk modulus sensing means includes a fuel pressure decrease amount calculating means for calculating a decrease amount of the fuel pressure occurring with a single injection and an injection quantity calculating means for calculating an injection quantity of the single injection, and the bulk modulus sensing means calculates the bulk modulus based on the calculated decrease amount and the calculated injection quantity.