Control device for spark-ignition engine

A control device for a spark-ignition engine in which a mixture in a combustion chamber is fired by compression ignition in a part-load range under warm-running conditions, said control device comprising:

• an octane rating identifier for determining the octane number of fuel supplied;
• a firing assist unit for inducing the compression ignition by firing the mixture in the combustion chamber at a point preceding a top dead center in a compression stroke at least in part of an operating range in which the mixture is fired by the compression ignition;
• and
• a firing assist ignition timing setter for setting an ignition point according to the octane number determined by said octane rating identifier in the operating range in which the mixture is fired by the compression ignition for inducing the compression ignition;
• wherein said firing assist ignition timing setter progressively advances the ignition point as the octane number increases.

A control device for a spark-ignition engine having a plurality of cylinders in which successive combustion cycles occur with specific phase delays, wherein a special operation mode is selected as the mode of controlling intake and exhaust operation and conditions of combustion in a part-load range of the engine, and

• wherein a pair of preceding and following cylinders of which exhaust and intake strokes overlap is connected to form a two-cylinder interconnect configuration in the special operation mode in which 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 through an intercylinder gas channel and exhaust gas discharged from the following cylinder is led to an exhaust passage, a lean mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio is combusted in the preceding cylinder, and fuel is supplied to the burned gas having a high air-fuel ratio introduced from the preceding cylinder into the following cylinder so that a mixture thus produced is combusted in the following cylinder, said control device comprising:
• a firing assist unit for accelerating compression ignition in the following cylinder;
• wherein the air-fuel ratio in the preceding cylinder is set to a value equal to or larger than the stoichiometric air-fuel ratio while said firing assist unit accelerates the compression ignition in the following cylinder in a lower-load, lower-speed region within the part-load range in which combustion is made in the special operation mode.

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, wherein gas flow paths can be connected to form a two-cylinder interconnect configuration in which a pair of preceding and following cylinders of which exhaust and intake strokes overlap is connected in such a way that 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 exhaust gas discharged from the following cylinder is led to an exhaust passage, and said control device offers at least a special operation mode as an engine operation mode in which the gas flow paths are connected to form the two-cylinder interconnect configuration so that a lean mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio by a specific amount is combusted in the preceding cylinder while homogeneous charge combustion is produced in the following cylinder by firing a mixture produced by supplying fuel to the burned gas having a high air-fuel ratio introduced from the preceding cylinder into the following cylinder, said control device comprising:

• an air-fuel ratio controller for setting the air-fuel ratio in each of the cylinders;
• an ignition controller for setting an ignition point of a spark plug disposed in each of the cylinders;
• and
• a knocking detector for detecting engine knock;
• wherein the EGR ratio is increased in the following cylinder in an engine operating region on a relatively high-load side and said ignition controller enhances anti-knock performance of the engine by retarding a firing assist ignition point in a case where the mixture in the following cylinder is fired by compression ignition by performing a firing assist operation while the engine is operated in the special operation mode;
• and
• wherein said air-fuel ratio controller decreases the air-fuel ratio in the preceding cylinder to enrich the mixture therein when said knocking detector has detected engine knock.

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,

• wherein gas flow paths can be connected to form a two-cylinder interconnect configuration in which a pair of preceding and following cylinders of which exhaust and intake strokes overlap is connected in such a way that 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 exhaust gas discharged from the following cylinder is led to an exhaust passage, and
• said control device offers at least a special operation mode as an engine operation mode in which the gas flow paths are connected to form the two-cylinder interconnect configuration so that a lean mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio by a specific amount is combusted in the preceding cylinder while homogeneous charge combustion is produced in the following cylinder by firing a mixture produced by supplying fuel to the burned gas having a high air-fuel ratio introduced from the preceding cylinder into the following cylinder, said control device comprising:
• an air-fuel ratio controller for setting the air-fuel ratio in each of the cylinders;
• an ignition controller for setting an ignition point of a spark plug disposed in each of the cylinders;
• and
• a knocking detector for detecting engine knock;
• wherein the EGR ratio is increased in the following cylinder in an engine operating region on a relatively high-load side and said ignition controller retards a firing assist ignition point in a case where the mixture in the following cylinder is fired by compression ignition by performing a firing assist operation while the engine is operated in the special operation mode;
• and
• wherein the air-fuel ratio in the preceding cylinder is made equal to the stoichiometric air-fuel ratio and combustion in the following cylinder is interrupted if said knocking detector detects engine knock at least a predetermined number of times in succession while the firing assist ignition point of the following cylinder is being retarded.

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,

• wherein gas flow paths can be connected to form either of a two-cylinder interconnect configuration, in which a pair of preceding and following cylinders of which exhaust and intake strokes overlap is connected in such a way that 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 exhaust gas discharged from the following cylinder is led to an exhaust passage, and an independent cylinder configuration, in which fresh air is drawn through an intake passage to intake ports of the individual cylinders and the exhaust gas discharged through exhaust ports of the individual cylinders is led to the exhaust passage, and
• said control device offers as engine operation modes a special operation mode to be selected in a low-load, low-speed operating range in which the gas flow paths are connected to form the two-cylinder interconnect configuration so that a lean mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio by a specific amount is combusted in the preceding cylinder while homogeneous charge combustion is produced in the following cylinder by firing a mixture produced by supplying fuel to the burned gas having a high air-fuel ratio introduced from the preceding cylinder into the following cylinder, and
• a normal operation mode to be selected in a high-load, high-speed operating range, in which combustion in the individual cylinders is produced with the gas flow paths connected to form the independent cylinder configuration, said control device comprising:
• an air-fuel ratio controller for setting the air-fuel ratio in each of the cylinders;
• and
• an ignition controller for setting an ignition point of a spark plug disposed in each of the cylinders;
• wherein the EGR ratio is increased in the following cylinder in an engine operating region on a relatively high-load side in a case where the mixture in the following cylinder is fired by compression ignition by performing a firing assist operation while the engine is operated in the special operation mode, and
• said control device performs a special control operation to make the air-fuel ratio in the preceding cylinder equal to the stoichiometric air-fuel ratio and to interrupt combustion in the following cylinder for a predetermined period of time before the engine is completely transferred to the normal operation mode when the engine has reached the operating range in which the normal operation mode should be selected at a load increasing rate higher than a predetermined rate.