Provided is an engine control device for correcting output characteristics of an oxygen sensor and performing air-fuel ratio feedback control. The engine control device includes various sensors for detecting operating state information of an engine, an oxygen sensor, and air-fuel ratio feedback controller to adjust an amount of fuel injected into the engine, on the basis of the operating state information and an output voltage value of the oxygen sensor, wherein the air-fuel ratio feedback controller calculates, in accordance with the operating state information based on detection results from the various sensors, a coefficient for correcting the output voltage value, implements air-fuel ratio feedback control on the basis of an air-fuel ratio feedback control correction amount calculated using a corrected oxygen sensor output voltage value calculated on the basis of the coefficient, and adjusts the amount of fuel injected into the engine.

Method and apparatus for monitoring and/or detecting combustion misfire events in periodic combustion processes in internal combustion engines, using combustion signals derived from a first oxygen sensor exposed to exhaust gas of a periodic combustion process and a second oxygen sensor exposed to the same exhaust gas. The first oxygen sensor is resistive-based, and responds relatively faster to changes in the temperature and/or composition of the exhaust gas. The second oxygen sensor is voltaic-based or ampometric-based, and responds relatively slower to changes to the temperature and/or composition of the exhaust gas. When the temperature and/or composition of the exhaust changes rapidly but transiently due to a combustion misfire event, the different response rates of the first and second combustion signals allows for the combustion misfire event(s) to be detected. Either and/or both oxygen sensors may be used to control the engine in a conventional fashion.

A method for controlling an air-fuel ratio in an idle purge-off mode is provided. The method includes stopping feedback for an amount of fuel for a particular period of time when idle purging is terminated and performing freeze control with a constant lambda control value.

Sensing combustion events using a resistive based oxygen sensor exposed to exhaust gases of a periodic combustion process in a combustion engine. The oxygen sensor is disposed in the exhaust plenum of the engine and includes a metal oxide semiconductor layer bridging a gap between first and second electrodes. Spikes in the resistance of the metal oxide semiconductor layer, caused by its reaction to transient changes in the oxygen level and exhaust temperature, are indicated in a combustion signal. The combustion signal may be used to monitor for combustion misfire event(s). Further, a combustion misfire event may be detected by comparing the detected spike timing with expected spike timing, with a spike not being present at a time when a spike is expected indicating a combustion misfire event. Related devices and systems are also disclosed.

An O.sub.2 sensor includes a sensor element using a solid electrolyte layer and a pair of electrodes placed at a position to interpose the solid electrolyte layer, detects an exhaust gas from an internal combustion engine as an object of a detection, and outputs an electromotive force signal depending on an air-fuel ratio of the exhaust gas. The sensor element is connected with a constant current circuit supplying a constant current that is prescribed. A microcomputer calculates a resistance value (element resistance) of the sensor element, and performs a restriction on the constant current supplied by the constant current circuit on the basis of the element resistance.

An air-fuel ratio control device switches a target air-fuel ratio from a lean set air-fuel ratio to a rich set air-fuel ratio after judging that an air-fuel ratio of an outflowing exhaust gas has become a stoichiometric air-fuel ratio and an oxygen storage amount of an exhaust purification catalyst has become a switching reference storage amount, and makes an average value of the target air-fuel ratio the stoichiometric air-fuel ratio to less than the lean set air-fuel ratio, from after the estimated value of the oxygen storage amount has become the switching reference storage amount or more until judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio if the estimated value of the oxygen storage amount becomes the switching reference storage amount or more before judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio.

Provided is an engine control device for correcting output characteristics of an oxygen sensor and performing air-fuel ratio feedback control. The engine control device includes various sensors for detecting operating state information of an engine, an oxygen sensor, and air-fuel ratio feedback controller to adjust an amount of fuel injected into the engine, on the basis of the operating state information and an output voltage value of the oxygen sensor, wherein the air-fuel ratio feedback controller calculates, in accordance with the operating state information based on detection results from the various sensors, a coefficient for correcting the output voltage value, implements air-fuel ratio feedback control on the basis of an air-fuel ratio feedback control correction amount calculated using a corrected oxygen sensor output voltage value calculated on the basis of the coefficient, and adjusts the amount of fuel injected into the engine.

A control device of an internal combustion engine according to the present invention executes air-fuel ratio control based on an output of an air-fuel ratio sensor provided at an upstream side of a catalyst, with correction based on an output of an oxygen sensor at a downstream side of the catalyst. When it is determined that a degree of an output tendency in a predetermined lean region is not less than a predetermined lean degree, and that a degree of an output tendency in a predetermined rich region is less than a predetermined rich degree based on lean tendency and rich tendency values representing output tendencies of the oxygen sensor, a limit is set to the correction in a direction to more suppress enriching of an air-fuel ratio as a degree is larger in which the output of the oxygen sensor is shifted to a lean side.

An exhaust sensor 1 comprises a sensor cell 51, a voltage application circuit 61, a current detection circuit 62 and a concentration calculating part 80a. The current detection circuit detects a first current flowing through the sensor cell when fuel cut control is being performed in the internal combustion engine and a predetermined voltage is applied from the voltage application circuit to the sensor cell, and detect a second current flowing through the sensor cell when normal control is being performed in the internal combustion engine and the predetermined voltage is applied from the voltage application circuit to the sensor cell. The concentration calculating part is configured to calculate the concentration higher with respect to the second current when the first current is relatively low compared with when the first current is relatively high.

An oxygen sensor that has both an n-type oxygen sensing portion comprising an n-type semiconductor layer and a p-type oxygen sensing portion comprising an p-type semiconductor layer. The n-type sensing portion and the p-type sensing portion share the common electrode. The n-type semiconductor layer and the p-type semiconductor layer attach directly to the common electrode, but are not in physical contact with each other such that a lateral gap exists between the n-type semiconductor layer and the p-type semiconductor layer. The air:fuel ratio for a combustion process may be determined, using the same oxygen sensor, across a range of air:fuel values in both the rich and lean regions; as such, the oxygen sensor may act as a wideband oxygen sensor.