Patent ID: 8718865
Filing Date: 2014-05-06
Classification: B60K,F02D,Y02T

Abstract:
1. An abnormality diagnosis method for an internal combustion engine installed in a vehicle, the internal combustion engine provided with a first variable valve timing mechanism that modifies a phase of a first intake valve provided to a first cylinder within a range extending from a first phase to a second phase and a second variable valve timing mechanism that modifies a phase of a second intake valve provided to a second cylinder, which is separate from the first cylinder, within the range extending from the first phase to the second phase, the abnormality diagnosis method comprising: detecting a rotation variation amount of an output shaft of the internal combustion engine; varying the phase of the first intake valve and the phase of the second intake valve in accordance with a load of the internal combustion engine and a rotation speed of the output shaft of the internal combustion engine; adjusting the phase of the first intake valve and the phase of the second intake valve to the first phase, the first phase is a most retarded phase; and diagnosing a presence of an air-fuel ratio abnormality on a basis of the detected rotation variation amount of the output shaft of the internal combustion engine in a state where the vehicle installed with the internal combustion engine travels and the phase of the first intake valve and the phase of the second intake valve have been adjusted to the first phase, when the load of the internal combustion engine is not smaller than a first load and not larger than a second load which is larger than the first load, and the rotation speed of the output shaft of the internal combustion engine is not larger than a predetermined rotation speed; wherein the first load is larger than a load of the internal combustion engine in an idling state.