An object is to reduce the influence of a hydrogen-ascribable difference between the measurement value of an oxygen sensor and the actual value. An exhaust system includes an oxygen sensor configured to measure the air-fuel ratio of exhaust gas provided in an exhaust passage of an internal combustion engine and including a diffusion rate limiting layer and a controller configured to correct the measurement value of the oxygen sensor in such a way as to increase the measurement value of the oxygen sensor by an amount of correction that is made larger when the responsivity of the oxygen sensor to changes in the air-fuel ratio of the internal combustion engine is high than when it is low in the same operation state of the internal combustion engine.

The control system of an internal combustion engine of the present invention comprises an S/V ratio changing mechanism able to change an S/V ratio of a combustion chamber and a detection device having an output value changing in accordance with a hydrogen concentration in exhaust gas, which increases along with an increase in the S/V ratio, the internal combustion engine being controlled by the output value of the detection device. Further, the output value of the detection device or a parameter relating to operation of the internal combustion engine is corrected in accordance with the S/V ratio of the above S/V ratio changing mechanism. Due to this, even if the hydrogen concentration in the exhaust gas increases along with an increase in the S/V ratio, the internal combustion engine can be suitably controlled.

Method for the operation of an internal combustion engine having a plurality of cylinders (11 to detect misfires. An exhaust gas sensor at the exhaust gas of every cylinder of the internal combustion engine measures at least one actual exhaust gas value individually for the respective cylinder, and the respective measured actual exhaust gas value is compared with a reference exhaust gas value to determine at least one cylinder-specific deviation between the reference exhaust gas value and the actual exhaust gas value for each of the cylinders. It is determined for every cylinder based on the cylinder-specific deviation or based on every cylinder-specific deviation whether or not misfires are occurring at the respective cylinder.

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.

A control apparatus for an internal combustion engine includes an electronic control unit. The electronic control unit corrects a target air-fuel ratio in an air-fuel ratio control with a first correction value set based on a degree of variation among cylinders in terms of a fuel amount to be injected from the port injector, and a second correction value set based on a degree of variation among the cylinders in terms of a fuel amount to be injected from the in-cylinder injector. A first correction amount of the target air-fuel ratio by the first correction value is set to be larger as an injection amount ratio of the intake-port fuel injection valve is larger, and a second correction amount of the target air-fuel ratio by the second correction value is set to be larger as an injection amount ratio of the in-cylinder fuel injection valve is larger.

A deterioration diagnosis device for an exhaust gas purification apparatus which performs inducement processing when the internal combustion engine is operated at a lean air fuel ratio, measures, by means of air fuel ratio sensors, the air fuel ratio of exhaust gas flowing into the SCR catalyst and the air fuel ratio of exhaust gas flowing out from the SCR catalyst during a period while the inducement processing is performed, and diagnoses deterioration of the SCR catalyst based on a difference between the measured values of these sensors, wherein an amount of hydrogen produced by each of a three-way catalyst and an NSR catalyst is estimated based on the deterioration degree thereof, and an air fuel ratio of exhaust gas discharged from the internal combustion engine is feedback-controlled so that the air fuel ratio of the exhaust gas flowing into one of the three-way catalyst and the NSR catalyst in which the hydrogen production amount thus estimated is larger than that in the other becomes a target value.

A controller for a hydrogen engine that includes an in-cylinder pressure sensor and an air-fuel ratio sensor includes processing circuitry. The processing circuitry is configured to execute a process that calculates a fluctuation amount of a combustion pressure based on an output of the in-cylinder pressure sensor and a process that calculates a correction amount based on the fluctuation amount. The correction amount is used to correct a rich deviation of an output of the air-fuel ratio sensor due to unburned hydrogen in exhaust gas.

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.