Abstract: An engine control unit of an exhaust gas purification system of an internal combustion engine measures a pressure difference between an upstream and a downstream of a diesel particulate filter (DPF) after heating the DPF at least to a predetermined temperature and maintaining the DPF at the temperature for a while. The DPF is disposed in an exhaust pipe of the engine. A soluble organic fraction included in particulate matters in exhaust gas can be eliminated at the predetermined temperature. The ECU calculates a quantity of the particulate matters trapped by the DPF from the measured pressure difference. Thus, the quantity of the trapped particulate matters is calculated precisely, independently of a composition of the particulate matters or a state of the soluble organic fraction.

Abstract: Particulate material collected in a filter (PM) is burnt through a selected one of partial and perfect regenerating processes. The partial regenerating process starts, when an amount of PM is predicted to exceed a value between 2 to 10 g/l, and terminates, when the amount of PM is predicted to fall below a value between 1 to 4 g/l, whereby a part of PM is burned to an extent that incombustible ash contained in the filter (ASH) can not easily pass through the filter. The prefect regenerating process starts, when an amount of ASH is predicted to exceed a value between 0.05 to 0.25 g/l, and terminates, when the amount of PM is predicted to fall below 1 g/l, whereby a substantially entire part of PM is burnt to an extent that ASH can easily pass through the filter.

Abstract: The engine control system has an ECU that supplies relatively large amount of EGR gas and delays an injection timing in order to decrease temperature in a combustion chamber. When an engine is operated under a warming up operation or a low engine load, the ECU deactivates an EGR cooler to increase intake air temperature in order to stabilize engine operation. When the engine is operated under a high engine load, the ECU activates the EGR cooler, delays a closing timing of an intake valve, and increases a boost pressure of a forced induction system. As a result, both of a compression end temperature and a maximum combustion temperature are decreased so that emissions of NOx and particulates are reduced.

Abstract: The engine control system has an ECU that supplies relatively large amount of EGR gas and delays an injection timing in order to decrease temperature in a combustion chamber. When an engine is operated under a warming up operation or a low engine load, the ECU deactivates an EGR cooler to increase intake air temperature in order to stabilize engine operation. When the engine is operated under a high engine load, the ECU activates the EGR cooler, delays a closing timing of an intake valve, and increases a boost pressure of a forced induction system. As a result, both of a compression end temperature and a maximum combustion temperature are decreased so that emissions of NOx and particulates are reduced.