An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust system of an internal combustion engine and reduces and purifies NOx in an exhaust gas; and a regeneration treatment unit, which recovers an NOx purification capacity of the NOx reduction type catalyst by lowering an excess-air-ratio of the exhaust gas to a predetermined target excess-air-ratio, wherein the regeneration treatment unit includes: a target setting unit, which sets a target intake air amount that is required for setting the exhaust gas to the target excess-air-ratio, based on a fuel injection amount of the internal combustion engine; and an air-system controller, which controls at least one of an intake air amount and an exhaust recirculating amount of the internal combustion engine, in response to the target intake air amount input from the target setting unit.

A control system for an engine is provided, which includes an engine body formed with a cylinder, a NO.sub.x catalyst, an oxidation catalyst, a PM filter, a fuel injector configured to perform a main injection and a post injection, and a controller configured to execute a DeNO.sub.x control in which the fuel injector is controlled to perform the main and post injections so that an air-fuel ratio of exhaust gas is brought close to the stoichiometric air-fuel ratio or becomes rich and fuel supplied into the cylinder by the post injection combusts therein, and a filter regenerating control in which the fuel injector is controlled to perform the main and post injections so that the air-fuel ratio becomes lean and the fuel supplied into the cylinder by the post injection causes no combustion therein, the controller executing the DeNO.sub.x control and the filter regenerating control consecutively in this order.

A method of removing sulfur from a lean NOx trap of a mild hybrid vehicle while the vehicle is stationary is disclosed, the method comprising connecting an electrical system of the vehicle to a large capacity external battery, operating an integrated starter generator driven by an engine of the vehicle as a generator to load the engine thereby allowing the engine to be operated at a higher torque level and rich of stoichiometric and storing the electrical energy produced by the integrated starter generator in the large capacity battery during the time period required for the removal of sulfur from the lean NOx trap.

A method and a system for preventing surge of a vehicle may include: determining whether an engine operation mode is a particulate filter regeneration mode or a catalyst desulfurization mode; determining, when the engine operation mode is the particulate filter regeneration mode or the catalyst desulfurization mode, a torque change; determining whether the torque change is smaller than a predetermined value; determining, when the torque change is smaller than the predetermined value, whether an intake pressure is higher than an exhaust pressure by at least a predetermined pressure; and opening, when the intake pressure is higher than the exhaust pressure by at least the predetermined pressure, an exhaust gas recirculation (EGR) valve and a throttle valve.

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.

An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust passage; an intake air amount sensor, which detects an intake air amount of the internal combustion engine; and a controller, which executes a regeneration treatment that recovers an NOx purification capacity of the NOx reduction type catalyst by switching an exhaust air fuel ratio from a lean state to a rich state by using: an air-system control to reduce the intake air amount; and an injection-system control to increase a fuel injection amount, wherein, in response to a detection value of the intake air amount sensor, the controller changes at least one of a fuel injection timing and the fuel injection amount in the internal combustion engine, in at least one period of switching of: a period of starting the regeneration treatment; and a period of ending the regeneration treatment.

A controller (an engine controller 100) feeds a fuel into a cylinder 11 through a fuel feeder (including a fuel injection valve 53 and a fuel feeding system 54) when the cylinder 11 is in an intake stroke and a compression stroke and if an engine body (an engine 1) is both in a cold running phase and under a heavy load. The engine body at or below a predetermined temperature is in the cold running phase. The load applied to the engine body is heavy when the engine body is under at least a predetermined load. The controller also lowers the upper limit of the charging efficiency of the engine body as the vaporization rate of the fuel fed into the cylinder decreases.

An exhaust gas purification system for an internal combustion engine includes an oxidation catalyst device on an upstream side in an exhaust passage of an internal combustion engine and a lean NOx trap catalyst device on a downstream side, a controller which controls the exhaust gas purification system is configured to, when a temperature-rising control of an exhaust gas in a regeneration control is performed to recover a purification ability of the exhaust gas purification system, perform a control that changes a measurement position of a control temperature which is a control amount of a feedback control in the temperature-rising control, according to an excess air ratio or an oxygen concentration of the exhaust gas passing through the exhaust passage.

An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust system of an internal combustion engine and reduces and purifies NOx in an exhaust gas; and a regeneration treatment unit, which recovers an NOx purification capacity of the NOx reduction type catalyst by lowering an excess-air-ratio of the exhaust gas to a predetermined target excess-air-ratio, wherein the regeneration treatment unit includes: a target setting unit, which sets a target intake air amount that is required for setting the exhaust gas to the target excess-air-ratio, based on a fuel injection amount of the internal combustion engine; and an air-system controller, which controls at least one of an intake air amount and an exhaust recirculating amount of the internal combustion engine, in response to the target intake air amount input from the target setting unit.

An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust system; a temperature acquisition unit, which acquires a catalyst temperature of the NOx reduction type catalyst; and a regeneration treatment unit, which executes a catalyst regeneration to recover an NOx purification capacity, wherein the regeneration treatment unit alternately executes a rich control, in which an exhaust air fuel ratio is set to a rich state to raise a temperature of the NOx reduction type catalyst to a predetermined target temperature, and a lean control, in which the exhaust air fuel ratio is set to a lean state to lower the temperature of the NOx reduction type catalyst, and sets an execution period of the lean control based on a deviation between the catalyst temperature acquired by the temperature acquisition unit during the previous rich control and the target temperature.