Control device for spark-ignition engine

A control device for a four-cycle multicylinder spark-ignition engine of which individual cylinders provided with spark plugs go through successive cycles of intake, compression, expansion and exhaust strokes with specific phase delays, said engine having an intercylinder gas channel interconnecting a pair of preceding and following cylinders whose exhaust and intake strokes overlap each other for introducing burned gas discharged from the preceding cylinder which is currently in the exhaust stroke into the following cylinder which is currently in the intake stroke;

• wherein said preceding cylinder is provided with an intake port connected to an intake passage, a first exhaust port connected to an exhaust passage and a second exhaust port connected to the intercylinder gas channel, while said following cylinder is provided with a first intake port connected to the intake passage, a second intake port connected to the intercylinder gas channel and an exhaust port connected to the exhaust passage;
• wherein first and second exhaust valves for opening and closing the first and second exhaust ports of the preceding cylinder as well as first and second intake valves for opening and closing the first and second intake ports of the following cylinder are made individually switchable between activated and deactivated states;
• wherein a two-cylinder interconnect configuration is formed in a low-load, low-speed operating range such that burned gas discharged from the preceding cylinder which is currently in the exhaust stroke is introduced into the following cylinder which is currently in the intake stroke by bringing the second exhaust valve and the second intake valve to the activated state;
• wherein exhaust gas discharged from the exhaust port of the following cylinder is caused to go through a three-way catalyst provided in the exhaust passage when the engine is in the two-cylinder interconnect configuration;
• 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 to the burned gas generated by combustion in the preceding 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.

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 control unit for controlling the engine;
• wherein said control unit controls 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 to the burned gas generated by combustion in the preceding 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.