Method of and apparatus for reducing engine smoke emissions

Abstract

A method of and apparatus for reducing smoke emitted from a diesel engine are disclosed. The apparatus comprises: a trap for trapping black smoke particles which is disposed within the exhaust system of the engine, the trap including a ceramic trap assembly having a honeycomb structure in which a catalyst which enables lowering of the combustion temperature of black smoke is carried on internal passage walls; a pressure sensor provided at the inlet of the trap; an engine speed sensor; a butterfly valve provided in the intake system of the engine; and a combination of a controller and an actuator for the butterfly valve. In this apparatus and method the controller obtains a specified exhaust pressure range in the trap on the basis of a signal from the engine speed sensor, compares an exhaust pressure signal from the pressure sensor with the specified exhaust pressure range, and controls the actuator so that the actuator controls the degree of opening of the butterfly valve so that the exhaust pressure inside the trap is maintained within the specified exhaust pressure range. By this means, black smoke particles can be controllably burned by means of exhaust gas without causing any engine trouble. Since the trap can be regenerated with the ceramic trap assembly left in place in, for example, a construction machine, it is possible to provide a diesel engine smoke reducing apparatus which is superior in both serviceability and durability.