A particulate filter for trapping the particulate matter which is contained in the exhaust gas is provided inside an engine exhaust passage. Additional fuel is secondarily injected from a fuel injector in an engine expansion stroke or exhaust stroke or hydrocarbons are secondarily added from an addition valve which is provided upstream of the particulate filter in the exhaust pipe. An amount of hydrocarbons which come from the fuel injector or addition valve and then adhere in the form of a liquid to the inflow end of the particulate filter, and an amount of particulate matter which reaches the inflow end of the particulate filter are respectively estimated. A degree of clogging at the inflow end of the particulate filter is estimated based on the amount of hydrocarbons and the amount of particulate matter.

In a method for the diagnosis of an exhaust gas aftertreatment system for an internal combustion engine, the exhaust gas aftertreatment system comprises at least one NOx storage catalytic converter (10) and at least one SCR catalytic converter (30) which is arranged downstream of the NOx storage catalytic converter (10). According to the invention, a regeneration of the NOx storage catalytic converter (10) is blocked and/or interrupted in order to improve the frequency and/or quality of the diagnosis of the SCR catalytic converter (30).

The control system of an internal combustion engine performs normal operation control including lean control for making the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst a lean air-fuel ratio, and rich control for making the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst a rich air-fuel ratio. The normal operation control includes judgment reference decreasing control decreasing the judgment reference storage amount in the lean control when during the time period of performing the lean control, the air-fuel ratio of the exhaust gas flowing out from the exhaust purification catalyst becomes the lean judged air-fuel ratio or more. The control system judges that the exhaust purification catalyst is abnormal when the judgment reference storage amount becomes less than a deterioration judgment value.

An object of the present disclosure is to provide an exhaust gas purification catalyst device; an exhaust gas purification system; and a method for detecting deterioration of the above device.

The exhaust gas purification catalyst device includes a substrate, a first catalyst layer containing Pd and formed on the substrate, and a second catalyst layer formed on the first layer. Regarding the above device, ceria, Pd, and Rh are contained in a mixed state in the second layer; in the first and second layers, the total mass of ceria having a fluorite-type structure per 1 L volume of the substrate is 16.0 g or less; and in the second layer, the mass of Pd per 1 L volume of the substrate is 0.32 g or more.

An exhaust-gas purification system and method are provided for an internal combustion engine having an NOx storage catalytic converter and a downstream SCR catalytic converter. The NOx storage catalytic converter can be supplied in a first operating mode with an oxidizing exhaust gas and in a second operating mode with a reducing exhaust gas. A third operating mode is provided between the first operating mode and the second operating mode, in which an exhaust gas which has a lower content of oxidizing constituents than the first operating mode and a lower content of reducing constituents than the second operating mode can be supplied to the NOx storage catalytic converter to improve NH.sub.3 production at the start of converter regeneration.

An internal combustion engine arrangement includes an internal combustion engine, a catalytic converter, and a controller. The controller is configured to determine a maximum H.sub.2 production capacity of the catalytic converter. The catalytic converter is arranged downstream of the internal combustion engine. The controller is configured and adapted to determine the maximum H.sub.2 production capacity of the catalytic converter based on a first function that correlates an H.sub.2 production of the internal combustion engine with first internal combustion engine parameters.

A control device for an internal combustion engine includes: an upstream catalyst; a downstream catalyst that is provided further downstream than the upstream catalyst in the exhaust flow direction; a downstream air-fuel ratio detection device that is provided between these catalysts; a storage amount estimation device that estimates the oxygen storage amount of the downstream catalyst; and an inflow air-fuel ratio control device that controls the air-fuel ratio of the exhaust gas flowing into the upstream catalyst such that the air-fuel ratio of the exhaust gas reaches a target air-fuel ratio.

The invention relates to a diagnostic method for checking the functionality of a component for the exhaust-gas aftertreatment of an internal combustion engine. For this purpose, in an internal combustion engine, a secondary air supply is provided by means of which an excess of oxygen can be generated in the exhaust gas channel essentially independently of the operating conditions of the internal combustion engine, and wherein said excess of oxygen is utilized for the measurement of an oxygen storage capacity of the component or of a signal change at the component. It is provided that the component is subsequently subjected to a substoichiometric exhaust gas in order that the oxygen release capacity or the signal change upon a change from superstoichiometric exhaust gas to a substoichiometric exhaust gas is also taken into consideration in the diagnosis. The invention also relates to a device for exhaust-gas aftertreatment, which is designed to be able to carry out a method of said type.

An exhaust gas purifying system includes: a NOx trapping agent (2) which adsorbs nitrogen oxide when an excess air ratio of exhaust gas is more than 1, and releases nitrogen oxide when the excess air ratio is 1 or less; a NOx purifying catalyst (13) which reduces nitrogen oxide to nitrogen; and an oxygen concentration controller which controls oxygen concentration in the exhaust gas. When the excess air ratio of the exhaust gas is more than 1, nitrogen oxide is adsorbed to the NOx trapping agent (2). When the excess air ratio of the exhaust gas is 1 or less, the oxygen concentration controller controls the oxygen concentration of the exhaust gas at an inlet of the NOx purifying catalyst between 0.8 and 1.5% by volume, so that the NOx purifying catalyst reduces nitrogen oxide released from the NOx trapping agent.

Regarding a work vehicle configured to include an engine mounted on a travelling machine body and an exhaust gas purification device arranged in an exhaust gas path of the engine, it is an object to prevent the regeneration control of the exhaust gas purification device from being executed against an operator's will. The work vehicle of the present invention includes a regeneration switch 329 configured to cause the regeneration control of an exhaust gas purification device 50 to be executed. First, when a cumulative drive time of an engine 5 has passed in a prescribed time or longer, a regeneration control request warning is displayed on a meter panel 246. Then, only when a regeneration switch 329 is manually operated by an operator after the display of the regeneration control request warning on the meter panel 246, the regeneration control of the exhaust gas purification device 50 is started.