A control apparatus, which is configured to control a hybrid vehicle, is provided with: a device configured to determine whether or not there is a response delay of the supercharger; a device configured to control torque of the rotary electric machine to compensate for an insufficiency of torque of a drive shaft if there is the response delay when an output limit value of the battery is greater than or equal to a predetermined value; a device configured to estimate a NOx storage amount in the NOx storage/reduction catalyst; and a device configured to control an air-fuel ratio of the internal combustion engine to be rich if the NOx storage amount is greater than or equal to a predetermined value, or if there is the response delay when the output limit value of the battery is less than the predetermined value.

A method for regenerating a lean NOx trap (LNT) of an exhaust purification system having the LNT and a selective catalytic reduction (SCR) catalyst includes determining whether a regeneration release condition of the LNT is satisfied; determining whether a regeneration demand condition of the LNT is satisfied; and performing regeneration of the LNT if the regeneration release condition of the LNT and the regeneration demand condition of the LNT are satisfied, wherein satisfaction of the regeneration release condition of the LNT is determined based on an NOx amount absorbed in the LNT, an NH3 amount stored in the SCR catalyst and temperature at an upstream of the SCR catalyst.

A control method for improving nitrogen oxide purification performance (NO.sub.x) includes starting NO.sub.x regeneration, comparing first and second lambda values measured at first and second lambda sensors in a control unit, checking the lean NO.sub.x trap (LNT) temperature, and measuring a second time that has elapsed after the first and second lambda values are found to be the same, and checking whether the second time is greater than or equal to a predetermined time when it is observed that the temperature of the LNT is greater than or equal to the predetermined temperature value.

A PCV valve that ventilates a crankcase is provided. A three-way catalyst and a NOx storage/reduction catalyst are provided in an exhaust passage. An electronic control unit performs a stoichiometric control and a lean control. When a crankcase ventilation request is issued, a relationship between a ventilation amount of ventilation achieved by the PCV valve and a fuel consumption resulting from the ventilation is calculated. Furthermore, an operational condition under which the ventilation amount meets a required ventilation amount and the fuel consumption is minimized is calculated. The operational condition is calculated so that a constant engine torque is maintained and the air-fuel ratio falls within a range that ensures purification.

A method is disclosed for operating an automotive system having an internal combustion engine equipped with an exhaust gas aftertreatment system including a Lean NO.sub.x Trap (LNT) upstream of a Selective Catalytic Reduction washcoated particulate filter (SCRF). A LNT inlet temperature is monitored. A parameter representative of a quantity of NO.sub.x stored in the LNT is also monitored. A map correlating the LNT inlet temperature and the quantity of NO.sub.x stored in the LNT is used to estimate an ammonia quantity produced during a LNT regeneration. A LNT regeneration is performed, if the estimated ammonia quantity is greater than a threshold value thereof.

A three-way catalyst, an NSR catalyst, and an SCR catalyst are provided in this order for an exhaust gas passage, wherein the air-fuel ratio (AFR) is set to a first AFR which is a rich AFR before the AFR is switched from a theoretical AFR to a lean AFR, and then the AFR is set to a second AFR which is higher than the first AFR and lower than the theoretical AFR if a NOx occlusion amount is less than a threshold value during a period until an NH.sub.3 adsorption amount of the SCR catalyst becomes a predetermined adsorption amount, while the AFR is set to a third AFR which is higher than the first AFR and lower than the second AFR if the NOx occlusion amount is not less than the threshold value.

The control device executes transition control when the operating state of the air flow control valve is switched during implementation of the lean burn operation, and the NOx storage amount which is estimated is smaller than a determination value. According to the transition control, a combustion air-fuel ratio in a cycle of which an intake stroke overlaps a time period of switching the operating state of the air flow control valve is made fuel-leaner than the theoretical air-fuel ratio and fuel-richer than the predetermined air-fuel ratio. When the estimated value of the NOx storage amount is the determination value or more, rich spike is executed during a predetermined time period including the time period of switching the operating state of the air flow control valve.

A three-way catalyst (20) having an oxygen storage function and an exhaust purification catalyst (22) are arranged in the exhaust passage of an internal combustion engine. During medium-load operation of the engine the degree of lean of the air-fuel ratio in the combustion chamber (5) is increased so as to increase the oxygen storage amount of the three-way catalyst (20) to the maximum oxygen storage amount, and the air-fuel ratio in the combustion chamber (5) even after the oxygen storage amount of the three-way catalyst (20) has reached the maximum oxygen, storage amount is maintained at lean, after which the air-fuel ratio is returned to rich, and at this time, as the amount of poisoning of a noble metal catalyst when the air-fuel ratio in the combustion chamber (5) is rich increases, the amount of time for which the air-fuel ratio in the combustion chamber (5) is maintained at lean is increased.

A method includes initiating a low engine-out NOx (LEON) mode by controlling a component of a vehicle having an aftertreatment system to decrease an instantaneous engine-out NOx (EONOx) amount. The method also includes comparing a temperature of the aftertreatment system to a threshold temperature. The method also includes responsive to determining that the temperature of the aftertreatment system exceeds the threshold temperature, disengaging the LEON mode. The method also includes responsive to determining that the temperature of the aftertreatment system is below the threshold temperature, comparing a NOx value to a NOx value threshold. The method also includes disengaging the LEON mode responsive to determining that the NOx value exceeds the NOx value threshold.