Patent ID: 7926331

Claim:
A fuel property detector for detecting a property of fuel injected by a fuel injector into a cylinder of an internal combustion engine, the fuel property detector comprising: an injection commander that commands the fuel elector to perform a fuel injection for fuel property detection into the cylinder of the engine; a change detector that detects a change in a rotational speed of the engine which is caused by the fuel injection for fuel property detection; a fuel property determiner that determines the property of the fuel based on the change in the rotational speed of the engine detected by the change detector; a torque estimator that estimates, based on the change in the rotational speed of the engine detected by the change detector, torque which is generated by the engine through the fuel injection for fuel property detection; an injection timing estimator; wherein the fuel property determiner determines the property of the fuel based on the torque estimated by the torque estimator; wherein the injection commander commands the fuel injector to perform a plurality of fuel injections for fuel property detection at different injection timings, the change detector detects, for each of the fuel injections for fuel property detection, the change in the rotational speed of the engine which is caused by the fuel injection for fuel property detection, the torque estimator estimates, for each of the fuel injections for fuel property detection, the torque generated by the engine through the fuel injection for fuel property detection based on the change detected by the change detector, the timing estimator estimates, based on all the torques estimated by the torque estimator, an injection timing necessary for causing the engine to generate a reference torque, and the fuel property determiner determines the property of the fuel based on the injection timing estimated by the timing estimator.