An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust passage; an intake air amount sensor, which detects an intake air amount of the internal combustion engine; and a controller, which executes a regeneration treatment that recovers an NOx purification capacity of the NOx reduction type catalyst by switching an exhaust air fuel ratio from a lean state to a rich state by using: an air-system control to reduce the intake air amount; and an injection-system control to increase a fuel injection amount, wherein, in response to a detection value of the intake air amount sensor, the controller changes at least one of a fuel injection timing and the fuel injection amount in the internal combustion engine, in at least one period of switching of: a period of starting the regeneration treatment; and a period of ending the regeneration treatment.

When a purge valve opens, a CPU calculates a purge concentration learning value based on an air-fuel ratio detected by an air-fuel ratio sensor. Additionally, under the condition that a temperature increase request of a three-way catalyst is generated, the CPU performs dither control that sets one of a plurality of cylinders as a rich combustion cylinder, which is richer than a theoretical air-fuel ratio, and the remaining cylinders as lean combustion cylinders, which are leaner than the theoretical air-fuel ratio. When the dither control is performed, the CPU forbids the update of the purge concentration learning value.

A controller includes an air-fuel ratio control unit that calculates an air-fuel ratio F/B correction value and an air-fuel ratio learning value and corrects an amount of fuel supplied to each cylinder based on the air-fuel ratio F/B correction value FAF and the air-fuel ratio learning value KG. The controller further includes a dither control unit that executes dither control to adjust the amount of fuel supplied to each cylinder, corrected by the air-fuel ratio control unit, so that at least one of the cylinders is set to a rich combustion cylinder and at least a further one of the cylinders is set to a lean combustion cylinder. When the dither control is executed, the air-fuel ratio control unit prohibits execution of air-fuel ratio learning control and executes air-fuel ratio feedback control.

The air-fuel ratio feedback control is performed by using a first correction value which is determined depending on a difference between a detected air-fuel ratio (A/F) of an air-fuel mixture and a target A/F and a second correction value which is determined depending on the property of the fuel. Further, fuel property learning control is carried out to correct the first correction value and the second correction value so that an absolute value of the first correction value is not more than a threshold value, when the absolute value of the first correction value is larger than the threshold value after performing the charging with fuel. A combustion continuing correction value range, which is a range of the second correction value to allow the A/F of the mixture to be included in an A/F range in which combustion can be continued, is stored, and the second correction value is set to a value within the combustion continuing correction value range if the A/F feedback control and the fuel property learning control are interrupted.

To optimize fuel supply of an engine with a carburetor during engine operation, a throttle opening degree detection sensor detecting a throttle opening degree and a control unit controlling a valve body variably controlling an opening degree of a fuel discharge part or a fuel supply passage based on a map are included. The map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body set for each section. The opening degree of the valve body set for each section is the opening degree of the valve body at which the engine rotation speed is highest in each section. The control unit controls an electric actuator driving the valve body to achieve the opening degree of the valve body set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections.

A diagnostic device for a sensor 100 provided in an exhaust passage 11 of an internal combustion engine 10 of a vehicle and detecting nitrogen compounds in exhaust gas, the diagnostic device including an offset diagnosis unit 42 which diagnoses, during deceleration of the vehicle in which the internal combustion engine 10 stops fuel injection, an offset amount of a sensor value of the sensor 100 from a zero point based on the sensor value of the sensor value, and a diagnosis prohibition unit 44 which prohibits the diagnosing of the offset amount when a flow rate of the exhaust gas of the internal combustion engine 10 rapidly increases while the offset amount is diagnosed by the offset diagnosis unit 42.

A control device for an internal combustion engine includes an electronic control unit configured to determine whether or not cylinder-specific air-fuel ratio processing is being executed in which an air-fuel ratio of at least one of a plurality of cylinders is controlled to be a rich air-fuel ratio and an air-fuel ratio of at least one of the other cylinders is controlled to be a lean air-fuel ratio. The electronic control unit updates a first learning value in which a result of comparison between a knock strength of the internal combustion engine and a first determination value is reflected when the cylinder-specific air-fuel ratio processing is not being executed. The electronic control unit prohibits updating of the first learning value and calculates a target ignition timing of the internal combustion engine based on the first learning value when the cylinder-specific air-fuel ratio processing is being executed.

An ECU has a fuel pressure sensor that detects fuel pressure inside of a common rail. The ECU detects the fuel pressure at a predetermined frequency and calculates a drop amount of the fuel pressure in accordance with fuel injection by fuel injectors based on the detected fuel pressure. The ECU acquires a fluctuation amount of a fuel injection amount of each of the fuel injectors based on the drop amount of the fuel pressure and learns an injection characteristic of each of the fuel injectors, the injection characteristic indicating a correlation between the fuel injection amount and the fluctuation amount of the fuel injection. In a case in which a detection timing of the fuel pressure is within a fuel injection period of a predetermined fuel injector, the ECU disallows the learning of the injection characteristic using the fuel pressure detected in the fuel injection period.

An exhaust purification system is provided with a NOx-occlusion-reduction-type catalyst and a NOx purge rich control unit that executes NOx purge in a case where a catalyst temperature of the NOx-occlusion-reduction-type catalyst is equal to or higher than a catalyst temperature threshold value and a NOx occlusion amount of the NOx-occlusion-reduction-type catalyst is equal to or higher than an NOx occlusion amount threshold value and executes the NOx purge even when the catalyst temperature is lower than a catalyst temperature threshold value in a case where the NOx occlusion amount is equal to or greater than the occlusion amount threshold value, a fuel injection amount resulting from an accelerator operation is equal to or greater than an injection amount threshold value, and an exhaust temperature detected by a first exhaust temperature sensor is equal to or higher than an exhaust temperature threshold value.

Since a factor affecting an individual difference learning result is reduced or eliminated regardless of a valve body behavior, it is possible to highly accurately detect an individual difference of a fuel injector caused by the valve body behavior and to reliably detect the individual difference even when the fuel injector is replaced. When a valve opening/closing timing of the fuel injector is learned by a learning unit, a unit of interrupting the learning if a predetermined condition is established, a unit of prohibiting the learning of the valve closing timing using the learning unit if a predetermined condition is established, or a unit of prohibiting the learning of the valve opening/closing timing of the fuel injector using the learning unit if a fuel pressure of a common rail supplying a fuel to the plurality of fuel injectors changes by a predetermined value or more within a predetermined time is provided.