Method and device for controlling diesel engine

Abstract

This disclosure provides a method of controlling a diesel engine. The method includes adjusting an EGR ratio according to an engine load so that a cylinder O2 concentration decreases gradually to a predetermined load with an increase in the load of the engine, while the O2 concentration increases gradually above the predetermined load, operating the engine in a premix combustion mode where the fuel injection is terminated before a top dead center of a compression stroke in a low load operating range including the predetermined load where the O2 concentration is lowest and, after that, the fuel ignites and combusts, and operating in a diffusion combustion mode where the fuel injection is executed in parallel to the ignition and combustion of the fuel in an operating range where the load is higher than that of the operating range in the premix combustion mode and the O2 concentration is relatively high.

Description

technical field [0001] The invention relates to a method and device for controlling a diesel engine (or a diesel engine). Background technique [0002] To reduce NO in the exhaust x and soot, reducing noise and vibration, improving fuel consumption and torque, diesel engines installed in vehicles can inject fuel into the cylinder two or more times during one engine cycle. For example, Japanese Patent Application Laid-Open Publication JP2009-293383A discloses a diesel engine with a turbocharger in which five fuel injections are performed. The five fuel injections are: a main injection for torque generation, a pilot injection prior to the main injection for preheating the cylinders, and an ignition suppression for the main injection between the pilot injection and the main injection Delayed pre-injection, after injection after the main injection to increase the exhaust temperature, after injection to introduce fuel directly into the exhaust system after the after injection a...

AI Technical Summary

Problems solved by technology

[0004] However, as the engine load increases and the fuel injection quantity increases, the ignition delay gradually shortens

Especially in engines with turbochargers, the boost volume increases with increasing load, while at the end of the compression stroke, the temperature and pressure rise, whereby the ignition delay period is further shortened

Therefore, a sufficiently long ignition delay period cannot be ensured, and premixed combustion cannot be established

That is, the operating region in which the premixed combustion mode that is favorable for emission performance and NVH performance can be performed is limited to a part of the low load side region, which is disadvantageous because the operating region is relatively narrow

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