Exhaust purifier for internal combustion engine

Abstract

An exhaust purifier for an internal combustion engine is capable of properly heating a catalyst in consideration of a deterioration with time and manufacturing variation in an electric heater that heats the catalyst. The exhaust purifier has the catalyst 4 disposed in an exhaust pipe, the electric heater for forcibly heating the catalyst 4, a power source for supplying power to the heater, an estimate unit for estimating the temperature that the catalyst 4 will reach, a comparator for providing the difference between the estimated temperature and a target temperature, and an operation controller for controlling the operating conditions of the engine according to the temperature difference. The estimate unit measures the voltage and current of the heater, calculates the resistance or power of the heater according to the voltage and current, and estimates the temperature. The operation controller adjusts the quantity of intake air and ignition timing, or adjusts ignition timing and then the quantity of intake air to maintain an engine speed, or, if a battery 6 is abnormal, adjusts the quantity of intake air and ignition timing to increase the temperature of exhaust gas.