Control device of spark-ignition gasoline engine

摘要

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.

主权项

1. A control device of a spark-ignition gasoline engine, comprising:
an engine body having a cylinder of which a geometric compression ratio is set to 14:1 or above, and being supplied with fuel containing at least gasoline; a fuel injection valve for injecting the fuel into the cylinder; an ignition plug arranged to be oriented inside the cylinder and for igniting an air-fuel mixture within the cylinder; a fuel pressure variable mechanism for changing a pressure of the fuel that is injected by the fuel injection valve; and a controller for operating the engine body by controlling at least the fuel injection valve, the ignition plug, and the fuel pressure variable mechanism, wherein when an operating state of the engine body is within a predetermined low engine load range, the controller sets a combustion mode to a compression-ignition mode in which a compression-ignition combustion is performed, wherein when the operating state is within a high engine load range where an engine load is higher than the compression ignition mode, the controller sets the combustion mode to a spark-ignition mode in which the controller controls the fuel pressure variable mechanism so that the fuel pressure is higher than that within a lower-half engine load range of the compression-ignition mode, the controller also operates the fuel injection valve to perform at least a fuel injection during a retard period from a late stage of compression stroke to an early stage of expansion stroke, and the controller also operates the ignition plug to ignite during the retard period and after the fuel injection, wherein when the operating state is within a range where the engine load is higher than a predetermined engine load of the spark-ignition mode, the controller performs an external EGR control of circulating a part of the burned gas back to an intake system of the engine body through an EGR passage, and the controller also controls an EGR ratio to be relatively high when the engine load is low in the spark-ignition mode, and wherein when the operating state is within a range where the engine load is below the predetermined load of the spark-ignition mode, the controller performs the external EGR control while setting the EGR ratio higher than that within the range where the engine load is higher than the predetermined engine load, and also performs a charging amount control of reducing an intake air charging amount to be less than in the compression-ignition mode.