Control device and control method for spark ignition gasoline engine

Abstract

A control device of a spark-ignition gasoline engine is provided. The control device includes a controller for operating the engine body by controlling at least a fuel injection valve, an ignition plug, and a fuel pressure variable mechanism. Depending on the engine load range, the controller sets the combustion mode to a compression-ignition mode or a spark-ignition mode. In each mode, the controller also controls the fuel pressure, and the timing of fuel injection and ignition. The controller may also performs external EGR control in each mode.

Description

technical field [0001] The present invention relates to techniques for controlling spark ignition gasoline engines. Background technique [0002] An HCCI (Homogeneous Compression Ignition) engine that compression-ignites a lean air-fuel mixture disclosed in Japanese Patent Laid-Open Publication No. 2009-91994 is known as a technique for both improving exhaust emissions and improving thermal efficiency. However, as the engine load becomes higher, the compression ignition combustion becomes a premature ignition combustion with a sharp pressure rise. This leads to an increase in combustion noise, abnormal combustion such as knocking, and an increase in raw NOx due to high combustion temperature. For this reason, in such an HCCI engine, compression ignition combustion is limited only to the low-load operating range, and spark ignition combustion by spark plug operation is generally performed in the high-load operating range. [0003] Furthermore, the engine operates at an air-...

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Problems solved by technology

[0004] However, from the standpoint of combustion stability, the amount of external EGR gas that can be introduced into the cylinder is limited to a relatively small amount

Therefore, when the engine load is high and the amount of fuel and fresh air is relatively large, although it is not necessary to reduce the amount of intake air by introducing external EGR gas, when the engine load is in the load region where compression ignition combustion is performed and spark ignition combustion is performed, for example, When the fuel volume is relatively small at a medium load level near the boundary of the load range, even if the external EGR gas is introduced to the maximum, the amount of fresh air must be reduced by throttling control, so there is a problem that the pump loss can hardly be improved.

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