Apparatus for controlling air-fuel ratio of internal-combustion engine

摘要

An apparatus for controlling an air-fuel ratio of an internal-combustion engine includes an air-fuel ratio detector, a fluctuation signal generating device, an air-fuel ratio fluctuation device, a 0.5th-order frequency component strength calculator, a fluctuation frequency component strength calculator, a reference component strength calculator, and an imbalance fault determining device. The reference component strength calculator is configured to calculate strength of a reference component in accordance with strength of a first frequency component and strength of a second frequency component. The imbalance fault determining device is configured to make a determination of an imbalance fault in which air-fuel ratios of a plurality of cylinders vary beyond a tolerance limit on a basis of a relative relationship between strength of the 0.5th-order frequency component and the strength of the reference component.

主权项

1. An apparatus for controlling an air-fuel ratio of an internal-combustion engine, the apparatus comprising:
an air-fuel ratio detector configured to detect an air-fuel ratio in an exhaust path of the internal-combustion engine including a plurality of cylinders; a fluctuation signal generating device configured to generate a fluctuation signal for causing the air-fuel ratio to fluctuate using a first signal with a first frequency and a second signal with a second frequency, the first frequency being different from a 0.5th-order frequency, the 0.5th-order frequency being equal to ½ of a frequency corresponding to a rotation speed of the internal-combustion engine, the second frequency being higher than the first frequency and different from the 0.5th-order frequency; an air-fuel ratio fluctuation device configured to cause the air-fuel ratio to fluctuate in accordance with the fluctuation signal; a 0.5th-order frequency component strength calculator configured to calculate strength of a 0.5th-order frequency component corresponding to the 0.5th-order frequency contained in an output signal of the air-fuel ratio detector; a fluctuation frequency component strength calculator configured to calculate strength of a first frequency component corresponding to the first frequency and strength of a second frequency component corresponding to the second frequency during operation of the air-fuel ratio fluctuation device, the first frequency component and the second frequency component being contained in the output signal of the air-fuel ratio detector; a reference component strength calculator configured to calculate strength of a reference component in accordance with the strength of the first frequency component and the strength of the second frequency component; and an imbalance fault determining device configured to make a determination of an imbalance fault in which air-fuel ratios of the plurality of cylinders vary beyond a tolerance limit on a basis of a relative relationship between the strength of the 0.5th-order frequency component and the strength of the reference component.