A vehicle control apparatus for a vehicle includes a catalyst deterioration diagnosing unit, an engine controlling unit, and a diagnosis start determining unit. The catalyst deterioration diagnosing unit executes a deterioration diagnosis of a catalyst included in an exhaust system of an engine provided in the vehicle. The engine controlling unit controls an air-fuel ratio of the engine to a lean side and thereafter to a rich side during the deterioration diagnosis of the catalyst. The diagnosis start determining unit prohibits the deterioration diagnosis of the catalyst from being executed when a deceleration rate upon deceleration of the vehicle is high, and permits the deterioration diagnosis of the catalyst to be executed when the deceleration rate upon deceleration of the vehicle is low.

A catalyst deterioration detection system 1 comprises an air-fuel ratio sensor 41, a current detection device 61, a voltage application device 60, a voltage control part 71, an air-fuel ratio control part 72 and a deterioration judging part 73. The air-fuel ratio control part executes fuel cut control, and, after the fuel cut control, executes rich control. The voltage control part, if judging that the air-fuel ratio of the outflowing exhaust gas has reached the stoichiometric air-fuel ratio when setting the applied voltage to a first voltage in a limit current region during the rich control, changes the applied voltage from the first voltage to a second voltage in a limit current region. The deterioration judging part judges the degree of deterioration of the catalyst based on the output current of the air-fuel ratio sensor when the applied voltage is set to the second voltage.

The present invention provides a deterioration diagnosis apparatus for an exhaust gas purification apparatus, including a first sensor that measures the oxygen concentration of the exhaust gas flowing into the exhaust gas purification apparatus, a second sensor that measures the oxygen concentration of the exhaust gas flowing out of the exhaust gas purification apparatus, and diagnosing means for diagnosing deterioration of the exhaust gas purification apparatus on the basis of a difference that appears between a measurement value of the first sensor and a measurement value of the second sensor when the air-fuel ratio of the exhaust gas flowing into the exhaust pas purification apparatus is switched from a lean air-fuel ratio to a rich air-fuel ratio, wherein, when the air-fuel ratio of the exhaust gas is switched from a lean air-fuel ratio to a rich air-fuel ratio, a water-gas shift reaction is generated upstream of the first sensor.

An exhaust purification system of the internal combustion engine comprises: an upstream side catalyst 20 arranged in an exhaust passage, a downstream side catalyst 24 arranged at a downstream side of the upstream side catalyst, an air-fuel ratio sensor 41 detecting an air-fuel ratio of outflowing exhaust gas flowing out from the upstream side catalyst, an air-fuel ratio control part 31 controlling an air-fuel ratio of inflowing exhaust gas flowing into the upstream side catalyst to a target air-fuel ratio, and a temperature calculating part 32 calculating a temperature of the downstream side catalyst. The air-fuel ratio control part switches the first control to the second control when a temperature of the downstream side catalyst calculated by the temperature calculating part rises to a reference temperature which is equal to or higher than an activation temperature of the downstream side catalyst.

A method for controlling an exhaust gas purification apparatus as a catalyst oxygen purge control method during a cold engine period of an exhaust gas purification apparatus including a three way catalyst (TWC) converter purifying exhaust gas exhausted from the engine includes determining whether a fuel cut condition of an injector which injects the fuel to the combustion chamber is satisfied; performing a fuel cut of the injector when the fuel cut condition is satisfied; determining heat load of the three way catalyst by use of a temperature detector and an exhaust gas flow rate detector; measuring oxygen storage capacity (OSC) stored in the three way catalyst according to the heat load; determining an inflection point by use of variation amount of the OSC; and controlling oxygen purge period differently around the inflection point.

A catalyst abnormality diagnostic device is configured to diagnose an abnormality of a first purification catalyst having an oxygen storage capacity and a second purification catalyst having the oxygen storage capacity and a function of a particulate filter provided on an exhaust passage on a downstream side of the first purification catalyst. The catalyst abnormality diagnostic device adjusts a fuel injection amount so that an air-fuel ratio of an exhaust gas is repeatedly in a rich state and a lean state, obtains a first determination value indicating a catalytic performance of the first purification catalyst, obtains a second determination value indicating a catalytic performance of the second purification catalyst, and determines whether there is an abnormality in one or both of the first purification catalyst and the second purification catalyst on the basis of the first determination value, the second determination value, and a predetermined determination reference value.

An internal combustion engine comprises an exhaust purification catalyst. The control system comprises a temperature detecting means for detecting or estimating a temperature of the exhaust purification catalyst, performs feedback control so that an air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst becomes a target air-fuel ratio, and performs target air-fuel ratio setting control which alternately sets the target air-fuel ratio to a rich set air-fuel ratio and a lean set air-fuel ratio. In addition, the control system increases a variation difference, obtained by subtracting a rich degree of the rich set air-fuel ratio from a lean degree of a lean set air-fuel ratio, when a temperature of the exhaust purification catalyst detected or estimated by the temperature detecting means is a predetermined upper limit temperature or less compared with when it is higher than the upper limit temperature. As a result, a sulfur ingredient storage amount of an exhaust purification catalyst is maintained low.

Disclosed is a method for diagnosis of an oxygen probe for a combustion engine, with the steps: When an engine's fuel injection is inactive, measuring the output electric voltage from the oxygen probe; If the measured output electrical voltage of the oxygen probe is greater than a predetermined minimum voltage threshold, measuring a pressure prevailing in an intake distributor of the engine; If the measured pressure in the intake distributor is less than a predetermined minimum pressure threshold, increasing the pressure to a value greater than the predetermined minimum pressure threshold; Determining the time period between the time when the output electrical voltage of the probe falls below a second predetermined voltage threshold and the time when the output electrical voltage of the probe falls below a third predetermined voltage threshold; and diagnosing the oxygen probe depending on elapsed the time period.

A method for controlling a fill level of a catalytic converter that is in an exhaust aftertreatment system of an exhaust tract downstream from an internal combustion engine includes an exhaust gas sensor that is upstream of the catalytic converter measuring, and producing a signal representing, a concentration of an exhaust component; correcting a dynamic distortion present in the produced signal to produce a corrected signal; determining the fill level of the catalytic converter by inputting the corrected signal into a modeling function; and performing a control that modifies the fill level based on the determined fill level.

A deterioration diagnosis apparatus for an exhaust gas purification apparatus according to the invention performs an induction process when an internal combustion engine is operating at a lean air-fuel ratio, measures the air-fuel ratio of the exhaust gas flowing into the SCR catalyst and the air-fuel ratio of the exhaust gas flowing out of the SCR catalyst by the air-fuel ratio sensor during the period through which the induction process is performed, and diagnoses deterioration of the SCR catalyst based on the difference between the air-fuel ratios thus measured. The diagnosis apparatus adjusts the quantity of reducing agent supplied to a hydrogen production catalyst during the period through which the induction process is performed, taking account of the degree of deterioration of the hydrogen production catalyst.