Fuel state sensing device

1. 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.

2. The fuel state sensing device as in claim 1 , further comprising:

a fuel pressure sensor mounted to the injector for sensing the fuel pressure, wherein

the fuel pressure decrease amount calculating means calculates the decrease amount based on pressure difference between the fuel pressure sensed with the fuel pressure sensor before an injection start and the fuel pressure sensed with the fuel pressure sensor after an injection end, and

the injection quantity calculating means calculates the injection quantity based on a fluctuation waveform of the sensed pressure sensed with the fuel pressure sensor.

3. The fuel state sensing device as in claim 1 , wherein

the fuel temperature sensing means is a fuel temperature sensor mounted to the injector for sensing the fuel temperature.

4. The fuel state sensing device as in claim 1 , wherein

the fuel state sensing device reports occurrence of a clogging abnormality or a pipe damage abnormality in a fuel supply route extending from a fuel tank to the injection hole when the calculated air mixing quantity or the calculated air mixing ratio is equal to or larger than a predetermined value.

5. A method of sensing a fuel state of fuel injected by an injector and supplied from a fuel pump, though an injection hole, the method comprising:

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;

sensing fuel temperature; and

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

a decrease amount of the fuel pressure occurring with a single injection is calculated and an injection quantity of the single injection is calculated, and

the bulk modulus is calculated based on the calculated decrease amount and the calculated injection quantity.

6. The method as in claim 5 , wherein:

a fuel pressure sensor is mounted to the injector for sensing the fuel pressure;

the decrease amount is calculated based on a pressure difference between the fuel pressure sensed with the fuel pressure sensor before an injection start and the fuel pressure sensed with the fuel pressure sensor after an injection end, and

the injection quantity is calculated based on a fluctuation waveform of the pressure sensed with the fuel pressure sensor.

7. The method as in claim 5 , wherein

occurrence of a clogging abnormality or a pipe damage abnormality in a fuel supply route extending from a fuel tank to the injection hole is reported when the calculated air mixing quantity or the calculated air mixing ratio is equal to or larger than a predetermined value.