An exhaust gas purification system for vehicle includes: a housing disposed on an exhaust pipe to receive a exhaust gas discharged from an engine and to exhaust the exhaust gas passed rearward; a front end catalyst disposed in the housing to purify the exhaust gas flowing into the housing through a front end of the housing; a rear end catalyst disposed in the housing to purify the exhaust gas passing through the front end catalyst before the exhaust gas flows out to a rear end of the housing; and a controller connected to the exhaust pipe at a front end of the housing to control a concentration of unburned fuel contained in the exhaust gas flowing into the housing.

An oxygen storage amount estimation device estimates an oxygen storage amount of a catalyst disposed in an exhaust passage of an internal combustion engine. The oxygen storage amount estimation device includes a storage device and processing circuitry. The storage device stores mapping data, which is data specifying a mapping that uses multiple variables including at least an excess-deficient amount variable and a previous value of a storage amount variable as an input to output a value of the storage amount variable. The processing circuitry executes a storage amount variable calculation process that repeatedly calculates a value of the storage amount variable based on an output of the mapping using the multiple variables and an operation process that operates predetermined hardware based on a calculation result of the storage amount variable calculation process. The mapping data includes data learned by machine learning.

A filling of an exhaust gas component storage of a catalytic converter is regulated. An actual fill level of the exhaust gas component storage is ascertained using a first system model, and a base lambda setpoint value for a first control loop is predefined by a second control loop. An initial value for the base lambda setpoint value is converted into a fictitious fill level, the fictitious fill level being compared with a setpoint value for the fill level output, and the base lambda setpoint value being iteratively changed as a function of the comparison result, if a difference between the setpoint value for the fill level and the fictitious fill level is greater than a predefined degree. The base lambda setpoint value is not changed if no difference exists between the setpoint value for the fill level and the fictitious fill level.

A catalyst degradation detection apparatus includes an air-fuel ratio detector disposed downstream of a catalyst and configured to detect an air-fuel ratio of exhaust gas flowing out from the catalyst, and an electronic control unit configured to control an air-fuel ratio of inflow exhaust gas flowing into the catalyst and determine whether the catalyst is degraded. The electronic control unit is configured to execute degradation determination control that brings the air-fuel ratio of the inflow exhaust gas to an air-fuel ratio leaner or richer than a stoichiometric air-fuel ratio. The electronic control unit is configured to determine whether precious metal of the catalyst is degraded based on the air-fuel ratio detected by the air-fuel ratio detector when an oxygen storage amount of the catalyst is varying in the degradation determination control.

A method for controlling an air-fuel ratio based on an oxygen storage amount of a catalyst may include: performing, by a controller, a catalyst oxygen storage amount (OSA) feedback control for a rich control of the air-fuel ratio so that the oxygen storage amount of the catalyst is within a threshold value; and performing, by the controller, a target voltage feedback control for a lean or rich control of the air-fuel ratio so that an output voltage value of an oxygen sensor provided in the rear of the catalyst satisfies a target voltage value.

An exhaust purification system of an internal combustion engine is provided with: an exhaust purification catalyst supporting a precious metal and able to store oxygen; and a control device controlling an amount of fuel fed to a combustion chamber. When a predetermined condition for performing a fuel cut operation stands, the control device is configured to perform fuel feed control in which fuel is temporarily fed to the combustion chamber so that the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is a rich air-fuel ratio richer than the stoichiometric air-fuel ratio, then start fuel cut control stopping the feed of fuel to the combustion chamber in the state the internal combustion engine is operating.

A control system for a fuel cutoff system of a motor vehicle includes a fuel cutoff module that generates a fuel cutoff signal for disabling a supply of fuel to an engine, in response to the fuel cutoff module detecting a deceleration fuel cutoff (DFCO) event. The control system further includes an oxygen storage module determining an amount of oxygen accumulated in a catalyst and comparing this amount to an oxygen storage capacity (OSC) of the catalyst, in response to the fuel cutoff module determining the DFCO event. The control system further includes an intake valve timing module generating a phasing signal to actuate a plurality of cam phasers to reduce a flow rate of oxygen to the catalyst, in response to the fuel cutoff module determining the DFCO event and the oxygen storage module determining that the amount of oxygen stored in the catalyst is less than the OSC.

A catalyst deterioration diagnosis system includes an air-fuel ratio detection element and a NOx detection element on a downstream side with respect to a catalyst, and a control element. The control element causes an engine to perform diagnosis operation performed with an exhaust gas temperature being kept at 600° C. or higher, such that at a timing when a downstream air-fuel ratio in a lean operation state reaches a threshold value, the engine is transitioned to a rich operation state, and at a timing that is a predetermined period after a downstream air-fuel ratio in a rich operation state reaches a threshold value, the engine is transitioned to a lean operation state. The diagnosis element compares NOx concentration during the rich operation state to a diagnosis threshold value, thereby to diagnose a degree of deterioration of NOx reduction capability of the catalyst.

Methods and systems are provided for enabling diagnostics of an exhaust catalyst regardless of a level of oxygen stored in the catalyst. In one example, a method may include initiating diagnostics of the catalyst in response to an oxygen sensor coupled downstream of the catalyst recording a measurement that crosses a stoichiometric air-fuel ratio output more than a threshold number of times.

Systems and methods for operating an engine that includes one or more fuel injectors are described. The systems and methods may characterize fuel injector operation during a time when injecting fuel may be useful to maintain balance of a catalyst to reduce engine emissions. Further, large or small amounts of fuel may be injected without affecting engine combustion.