Diesel engine for vehicle

摘要

The disclosure provides a diesel engine, which includes an engine body mounted in a vehicle and having a cylinder to be supplied with fuel containing diesel fuel as its main component, a geometric compression ratio ε of the cylinder being set within a range of 12:1 to 15:1, and an EGR system for allowing a part of burned gas to exist inside of the engine body cylinder when the engine body is at least in a particular operating state where an engine load and an engine speed are relatively low. The EGR system includes an EGR passage at least partially formed inside the engine body, and having a predetermined or shorter passage, an EGR control valve provided in a course of the EGR passage and for adjusting a flow rate of the burned gas inside the EGR passage, and a controller for controlling an opening of the EGR control valve.

主权项

1. A diesel engine for a vehicle, comprising:
an engine body to be mounted in the vehicle and having a cylinder to be supplied with fuel containing diesel fuel as its main component, a geometric compression ratio ε of the cylinder being set within a range of 12:1 to 15:1; and an EGR system for allowing a part of burned gas to exist inside the cylinder of the engine body when the engine body is at least in a particular operating state where an engine load and an engine speed are relatively low, wherein the EGR system includes an EGR passage at least partially formed inside the engine body, for re-circulating into an intake passage a part of the burned gas inside an exhaust passage, and having a predetermined or shorter passage length, an EGR control valve provided in a course of the EGR passage and for adjusting a flow rate of the burned gas inside the EGR passage, and a controller for controlling an opening of the EGR control valve, wherein in the particular operating state, the engine body is operated so that a relation between a mass of total gas (G) inside the cylinder and a mass of the fuel (F) to be supplied inside the cylinder (G/F) satisfies 30≦G/F≦60, and wherein when the engine body is in the particular operating state, the controller controls the opening of the EGR control valve so that an EGR ratio [%] defined by a volume ratio of the burned gas with respect to the entire gas inside the cylinder (burned gas amount/total gas amount inside the cylinder) satisfies,
(10−α)×(15−ε)+20−α≦EGR ratio≦60[%](here, α=0.2×external temperature [° C.])with respect to the geometric compression ratio ε of the engine body.