Patent ID: 9243978
Filing Date: 2016-01-26
CPC Classification: F02D,G01M

Claim Text:
1. A misfire detection apparatus for an internal combustion engine, which is configured to detect misfire in the internal combustion engine including a plurality of cylinders each connected to an exhaust pipe for exhausting an exhaust gas, and each including, on the exhaust pipe, an air/fuel ratio sensor for detecting an air/fuel ratio of the exhaust gas, the misfire detection apparatus being configured to carry out air/fuel ratio control for controlling the air/fuel ratio of the exhaust gas exhausted from each of the plurality of cylinders, the misfire detection apparatus comprising: an air/fuel ratio state determination part for determining, based on a detection signal from a first air/fuel ratio sensor corresponding to a first cylinder that is a misfire determination subject among the plurality of cylinders, whether or not a first air/fuel ratio of the exhaust gas exhausted from the first cylinder is in a lean state; an air/fuel ratio control determination part for determining, based on a detection signal from a second air/fuel ratio sensor corresponding to a second cylinder that is a remaining cylinder different from the first cylinder among the plurality of cylinders, whether or not lean control is being carried out as the air/fuel ratio control carried out on the internal combustion engine; an air/fuel ratio adjustment part for carrying out enrichment processing for the first air/fuel ratio at a time (t1) after an enrichment wait period (T a misfire determination part for determining that misfire occurs in the first cylinder when the air/fuel ratio adjustment part has carried out the enrichment processing at the time (t1), and when the air/fuel ratio state determination part determines that the first air/fuel ratio is still in the lean state at a time (t2) after a misfire determination wait period (T