Diesel engine for automobile, control device and control method

摘要

A geometric compression ratio in an engine main body 1 is set to 15 or less. Injection control means (ECU 40) performs a main injection of injecting fuel near a compression top dead center, and a preceding injection prior to the main injection at a specific region of predetermined load within an operating region on a relatively low-speed side. The injection control means performs, as the preceding injection, a pilot injection of performing injection at a timing such that at least part of a fuel spray reaches outside a cavity 31 on a top face of a piston, and a pre-injection of injecting fuel at a predetermined timing after the pilot injection, to suppress thereby ignition of the fuel injected by the pilot injection and shorten an ignition delay of the fuel injected by the main injection.

主权项

1. A diesel engine for automobiles, comprising:
an engine main body which is installed in an automobile, to which fuel having diesel oil as a main component is supplied, and in which a geometric compression ratio according to reciprocation between a top dead center and a bottom dead center of a piston that is insertion-fitted in a cylinder is set to 15 or less; a fuel injection valve which is disposed facing into the cylinder and directly injects the fuel into the cylinder; and injection control part for controlling an injection mode of the fuel into the cylinder by the fuel injection valve, wherein the injection control part performs, at a specific region of predetermined load within an operating region on a relatively low-speed side when the engine main body is warm: a main injection of injecting fuel near a compression top dead center; and a preceding injection of injecting fuel in a compression stroke prior to the main injection, and the injection control part performs as the preceding injection: a pilot injection of injecting fuel at a timing such that at least part of a fuel spray reaches outside a cavity sunk in a top face of the piston; and a pre-injection of injecting fuel at a predetermined timing after the pilot injection, to suppress thereby ignition of the fuel injected by the pilot injection and shorten an ignition delay of the fuel injected by the main injection; wherein the injection control part prohibits the pilot injection serving as the preceding injection and performs the pre-injection, at a second specific region adjacent to the specific region on a low load side within the operating region on a relatively low-speed side, and wherein the injection control part increases a fuel injection proportion by the preceding injection with respect to a fuel injection proportion by the main injection or performs a premixed compression ignition combustion by carrying out only a preceding injection without carrying out the main injection at an operating region further on the low load side than the second specific region within the operating region on a relatively low-speed side.