Abstract: In a method according to the present invention for calculating the combustion ratio RC of fuel added to an exhaust passage, the temperature To of the exhaust gas flowing in the exhaust passage located downstream of a region in which the fuel added to the exhaust passage is burned is acquired; the thermal capacity CE of the exhaust gas is acquired; the energy quantity QF of the fuel supplied to the exhaust passage is acquired; an increase ?To in exhaust temperature To immediately before the exhaust gas is heated is obtained; a change ratio dTo of the exhaust temperature To immediately before the exhaust gas is heated is obtained; a parameter Z relevant to the exhaust gas flowing in the exhaust passage is acquired; and the combustion ratio RC of the fuel added to the exhaust passage is calculated in accordance with RC=(CE/QF)(Z·dTo+?To).

Abstract: There is provided an operation control method for an internal combustion engine, in which if an exhaust gas purifier needs to be warmed, a second glow plug is heated in an exhaust passage upstream of the purifier to a fuel ignition temperature or higher while fuel supplied to the exhaust passage is ignited and burned. In this method, if it is determined that the purifier and an engine need to be warmed, a first glow plug disposed in a combustion chamber is first heated to a predetermined temperature prior to the warm-up of the purifier to start the warm-up of the engine, and then the second glow plug begins to be heated when the temperature of the purifier is equal to or higher than a glow plug energization starting temperature which is lower than a warm-up start determination temperature of the purifier.

Abstract: In a method according to the present invention for calculating the combustion ratio RC of fuel added to an exhaust passage, the temperature To of the exhaust gas flowing in the exhaust passage located downstream of a region in which the fuel added to the exhaust passage is burned is acquired; the thermal capacity CE of the exhaust gas is acquired; the energy quantity QF of the fuel supplied to the exhaust passage is acquired; an increase ?To in exhaust temperature To immediately before the exhaust gas is heated is obtained; a change ratio dTo of the exhaust temperature To immediately before the exhaust gas is heated is obtained; a parameter Z relevant to the exhaust gas flowing in the exhaust passage is acquired; and the combustion ratio RC of the fuel added to the exhaust passage is calculated in accordance with RC=(CE/QF)(Z·dTo+?To).

Abstract: Inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged. On the exhaust purification catalyst (13), platinum Pt (51) is carried and a basic layer (53) is formed. The concentration of hydrocarbons which flows into the exhaust purification catalyst (13) is made to vibrate within a predetermined range of amplitude and within a predetermined range of period, whereby the NOx which is contained in the exhaust gas is reduced by the exhaust purification catalyst (13). A clogging degree detecting means is provided for detecting a degree of clogging of a nozzle opening of the hydrocarbon feed valve (15). The NOx purification rate is estimated from the degree of clogging of the nozzle opening of the hydrocarbon feed valve (15) which is detected.

Abstract: Inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged. On the exhaust purification catalyst (13), platinum Pt (51) is carried and a basic layer (53) is formed. The concentration of hydrocarbons which flows into the exhaust purification catalyst (13) is made to vibrate within a predetermined range of amplitude and within a predetermined range of period, whereby the NOx which is contained in the exhaust gas is reduced by the exhaust purification catalyst (13). A clogging degree detecting means is provided for detecting a degree of clogging of a nozzle opening of the hydrocarbon feed valve (15). The NOx purification rate is estimated from the degree of clogging of the nozzle opening of the hydrocarbon feed valve (15) which is detected.