Patent ID: 6434929
Filing Date: 2002-08-20
Classification: F01N,F02B,F02D,F02M,Y02T

Abstract:
A control apparatus for a direct injection engine, which comprises a spark plug, an injector for directly injecting fuel into a combustion chamber, performs lean combustion by setting an air-fuel ratio higher than a stoichiometric air-fuel ratio in a low-load range of the engine, and comprises a lean NOx catalyst that adsorbs NOx in an excess oxygen atmosphere and releases NOx as an oxygen concentration decreases, and fuel injection timing setting means for setting the fuel-injection timing of the injector in the air-fuel ratio higher than a stoichiometric air fuel ratio on a low-load range of the engine to latter period at compression stroke which is divided to three equal first, middle and latter periods comprising:air-fuel ratio changing means to changing the air-fuel ratio of the combustion chamber to be equal to or less than the stoichiometric air-fuel ratio temporarily when a NOx adsorption amount of the lean NOx catalyst becomes not less than a predetermined value during lean combustion; exhaust gas recirculation means for recirculating some exhaust gas to an intake system; and control means for, when the air-fuel ratio of the combustion chamber is changed from the air-fuel ratio higher than the stoichiometric air-fuel ratio to the air-fuel ratio substantially equal to or less than the stoichiometric air-fuel ratio by the air-fuel ratio changing means, implementing catalyst regeneration control in accordance with a period which the air-fuel ratio is actually changed to a rich side, the catalyst regeneration control is to divide fuel injection from the injector, throughout the actual air-fuel ratio of the combustion chamber is substantially equal to or less than the stoichiometric air-fuel ratio, in at least two injections including a leading injection which starts within an intake stroke period and a trailing injection which starts within a compression stroke period by the fuel injection timing setting means and to set the injection start timing of the trailing injection within a middle period of the equally divided three periods of compression stroke where piston speed is higher so as to urge a mixture of air and fuel of the trailing injection in the compression stroke and to control said exhaust gas recirculation means to recirculate the exhaust gas in the set injection timing.