Patent ID: 9347352
Filing Date: 2016-05-24
CPC Classification: F01N,F02D

Claim Text:
1. A correction device for a limiting current type air/fuel ratio sensor, comprising: a catalyst installed in an exhaust passage of an internal combustion engine and having oxygen storage capacity; the limiting-current type air/fuel ratio sensor installed on a downstream side from the catalyst of the exhaust passage and issuing an output according to an air/fuel ratio of an exhaust gas on the downstream side from the catalyst; an air/fuel ratio control unit that is configured to control an air/fuel ratio of an exhaust gas on the upstream side from the catalyst to switch between a rich air/fuel ratio which is richer and a lean air/fuel ratio which is leaner than a stoichiometric air/fuel ratio; an output correction coefficient calculating unit that is configured to calculate an output correction coefficient for resolving discrepancy of an output of the limiting-current type air/fuel ratio calculated based on a difference between the output of the limiting-current type air/fuel ratio sensor in a predetermined period and a reference output corresponding to the stoichiometric air/fuel ratio, the predetermined period being a period during which an air/fuel ratio of an exhaust gas flowing out from the catalyst is maintained close to the stoichiometric air/fuel ratio and thereby the output of the limiting-current type air/fuel ratio sensor is held in equilibrium, wherein the predetermined period begins after the rich air/fuel ratio is switched to the lean air/fuel ratio until before the lean air/fuel ratio is switched to the rich air/fuel ratio, or begins after the lean air/fuel ratio is switched to the rich air/fuel ratio until before the rich air/fuel ratio is switched to the lean air fuel ratio; and a correction unit that is configured to correct the output of the limiting-current type air/fuel ratio sensor by the output correction coefficient, wherein the air/fuel ratio controller controls the air/fuel ratio according to the corrected output.