EXHAUST PURIFICATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

To estimate an amount of reducing agent adsorbed to a selective reduction type NOx catalyst with a higher degree of precision, an amount of variation over a predetermined time in a reducing agent amount adsorbed to a selective reduction type NOx catalyst is calculated from an upper limit value of a reducing agent amount that is adsorbed to the selective reduction type NOx catalyst when the reducing agent is supplied continuously by a supply unit, which is calculated on the basis of a temperature of the selective reduction type NOx catalyst, and the reducing agent amount adsorbed to the selective reduction type NOx catalyst, whereupon a reducing agent amount adsorbed to the selective reduction type NOx catalyst following the elapse of the predetermined time is estimated by adding the variation amount to the reducing agent amount adsorbed to the selective reduction type NOx catalyst.