Patent ID: 7182050
Filing Date: 2007-02-27
Classification: F01L,F02B,F02D,F02F,F02M,F02P,F16N,Y02T

Abstract:
1. A control device for a multicylinder spark-ignition engine of which individual cylinders go through successive cycles of intake, compression. expansion and exhaust strokes with specific phase delays, in which fresh air and gas flow paths are connected to form a two-cylinder interconnect configuration at least in a low-load, low-speed operating range such that, in a pair of preceding and following cylinders whose exhaust and intake strokes overlap each other, burned gas discharged from the preceding cylinder which is currently in the exhaust stroke is introduced directly into the following cylinder which is currently in the intake stroke through an intercylinder gas channel and gas discharged from only the following cylinder is led to an exhaust passage provided with a three-way catalyst, said control device comprising: a controller for controlling fuel supply to the individual cylinders in such a manner that combustion in the preceding cylinder is made under lean mixture conditions at an air-fuel ratio larger than the stoichiometric air-fuel ratio by a specific amount, fuel for the following cylinder is supplied in an amount corresponding to the burned gas which was generated by combustion in the preceding cylinder, and a whole amount of which is supplied to the following cylinder and combustion in the following cylinder is made under conditions of the stoichiometric air-fuel ratio when the engine is in the two-cylinder interconnect configuration; and a flow path switcher for switching the fresh air and gas flow paths to form an independent cylinder configuration in a high-load, high-speed operating range, in which intake ports and exhaust ports of the individual cylinders work independently of one another such that fresh air is introduced through an intake passage into the intake ports of the individual cylinders and exhaust gas discharged through the exhaust ports of the individual cylinders is led to the exhaust passage; wherein said controller makes the air-fuel ratio in the individual cylinders equal to or smaller than the stoichiometric air-fuel ratio in the high-load, high-speed operating range.