An internal combustion engine (1), with an engine regulating device (3) and an exhaust gas aftertreament device (16) with an SCR catalytic converter (4) for the reduction of at least one NO.sub.x component, and with a catalytic converter regulating device (6), wherein the engine regulating device (3) is prescribed a target value for an NO.sub.x mean value of the NO.sub.x component of the exhaust gases, which mean value results at an outlet point (7) of the exhaust gas aftertreatment device (16) in relation to a predefinable time period, and the engine regulating device (3) is configured at least in one operating mode to continuously calculate an NO.sub.x reference value for the catalytic converter regulating device (6) with consideration of No.sub.x components which have already been emitted and the predefined target value, which reference value is selected in such a way that the predefined target value results at the outlet point of the exhaust gas aftertreatment device (16) at the end of the predefinable time period when the calculated NO.sub.x reference value of the catalytic converter regulating device (6) is fed as NO.sub.x setpoint value to the regulating means.

To provide an exhaust purifying system and a method for controlling the exhaust purifying system that avoid occurrence of clogging, breakage, or the like of a reducing agent injection valve caused by the solidification of a reducing agent and prevent reduction in the efficiency of reducing agent recovery processing and exhaust gas purification. An exhaust purifying system and a method for controlling the exhaust purifying system according to an aspect of the present invention is configured to detect the injection valve temperature of the reducing agent injection valve according to detection of turn-off of an ignition switch for stopping the internal combustion engine or detection of an injection stop of the reducing agent injection valve, whichever is earlier, calculate the waiting time until reducing agent recovery processing starts based on the injection valve temperature, and permits the reducing agent recovery processing under condition of the detection of turn-off of the ignition switch and an elapse of the waiting time.

A diagnostic system for an internal combustion engine is disclosed. The diagnostic system may include an electronic control unit. The electronic control unit may determine whether a predetermined condition is satisfied. The predetermined condition may be a condition under which an amount of particulate matter that separates from a filter is larger than or equal to a predetermined separation amount as a urea water-originated deposit once accumulated in the filter separates in gaseous form. When the electronic control unit determines that the predetermined condition is satisfied, the electronic control unit may not execute a diagnosis of a malfunction in the filter based on a filter differential pressure until a predetermined period elapses from the point in time at which it is determined that the predetermined condition is satisfied.

A method for preheating a catalytic converter which is arranged in the exhaust-gas flow of a motor vehicle and which has an electrically heated catalyst is described. The catalytic converter is preheated with the electrically heated catalyst to a maximum temperature within a period of time before the initial engine starting operation. In the process, the temperature of the electrically heated catalyst and the battery state of the vehicle are monitored. During the preheating, it is checked whether or not the battery state has fallen below a state threshold. If so, the heating of the electrically heated catalyst is stopped, and engine-internal measures are implemented. If not, further heating of the electrically heated catalyst is implemented until the maximum temperature is reached again.

A system includes an exhaust aftertreatment system in exhaust gas receiving communication with an engine including a plurality of cylinders where the engine is structured to operate according to low load conditions and where a controller is structured to determine that at least one diesel emissions fluid (DEF) doser is frozen based on at least one of an ambient air temperature and a DEF source temperature. The controller is structured to operate the engine according to a skip-fire mode in response to a DEF flag indicating that the at least one DEF doser is frozen. The skip-fire mode comprises firing a portion of the plurality of cylinders that is less than a total amount of cylinders of the plurality of cylinders. The controller is structured to discontinue the skip-fire mode in response to determining that the at least one DEF doser is likely thawed.

An apparatus includes circuitry configured to calculate a temperature of exhaust flowing into an exhaust after-treatment system as a first exhaust temperature, calculate a temperature of exhaust flowing out from the exhaust after-treatment system as a second exhaust temperature, calculate a rate of change over time of the first exhaust temperature and a rate of change over time of the second exhaust temperature, and judge if the exhaust after-treatment system is in a removed state removed from the exhaust passage based on a difference between the rate of change over time of the first exhaust temperature and the rate of change over time of the second exhaust temperature.

A method for controlling a return valve of an exhaust system and to an exhaust system with a control unit which is configured to carry out the method. The method is based on the object of avoiding an overpressure in the line system for urea solution as a result of a reduction in the injection rate. The method includes the steps of determining whether one or more of the following states are present during the operation of the exhaust system: a) an injection rate per unit of time of urea solution of the dosing valve is less than or equal to a predefined injection limit, b) a pressure measured by the pressure sensor in the line system overshoots a predefined first upper pressure limit (P2). The return valve is opened for a first predefined opening duration (Δt1) if states a) and b) are present and at least one of the states has already been present for at least a predefined period of time (Δta). The return valve is closed after the first predefined opening duration (Δt1) has elapsed.

A heavy duty truck includes a diesel engine that generates an exhaust gas flow and an exhaust after-treatment system for treatment of the exhaust gas flow. The exhaust after-treatment system includes at least one temperature sensor at an underbody SCR system within the exhaust after-treatment system and a DEF injector upstream of a close-coupled SCR system within the exhaust after-treatment system. The DEF injector is operated to inject DEF into the exhaust gas flow at a rate that varies as a function of a temperature measured by the temperature sensor.

Methods and/or systems for operating an exhaust-gas aftertreatment system of an internal combustion engine include: setting the internal combustion engine to a diagnostic operating mode with relevant diagnostic operating parameters of the internal combustion engine are set to correspond with diagnostic default values; inducing a targeted, defined NH.sub.3 and/or NO.sub.X concentration change upstream of the filter; measuring the NH.sub.3 and/or NO.sub.X concentration change downstream of the filter; providing a correlating concentration comparison value; evaluating the concentration change on the basis of the respective concentration comparison value and predefined limit values; and diagnosing the SCR particle filter as defective if the evaluation yields that the concentration comparison value has overshot a predefined limit value.

An internal combustion engine comprises an engine body, a filter provided in an exhaust passage of the engine body and trapping particulate matter in the exhaust, and a temperature sensor detecting a temperature of gas flowing cut from the filter. A control device controlling this internal combustion engine comprises a fuel cut control pan configured to perform fuel cut control stopping a supply of fuel to a combustion chamber of the engine body and a forced ending part configured to forcibly make the fuel cut control end even if a condition for performance of fuel cut control had stood based on a trend in change of temperature of the gas temperature detected by the temperature sensor.