Cylinder-injection type internal combustion engine and a fuel in

Details Cylinder-injection type internal combustion engine and a fuel in Cylinder-injection type internal combustion engine and a fuel in

1997-04-15

1998-03-03

Nelli, Raymond A.

Internal-combustion engines

Combustion chamber means having fuel injection only

Having a particular relationship between injection and...

F02B 500

Patent

active

057223637

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a cylinder-injection type internal combustion engine suited for use in a motor vehicle and to a fuel injection control apparatus for such an engine.


BACKGROUND ART

In recent years, cylinder-injection type internal combustion engines are under development for use as internal combustion engines for motor vehicles. In such cylinder-injection type internal combustion engines, fuel is injected directly into combustion chambers, that is, cylinders of the engine, and therefore, various measures are adopted to cause a mixture of air and fuel having an air-fuel ratio close to the stoichiometric ratio to be formed only in the vicinity of a spark plug. Thus, even if the mixture fed into a cylinder of the cylinder-injection type internal combustion engine is lean as a whole, that is, even if an average air-fuel ratio is greater than the stoichiometric ratio, fuel can be ignited so that it can be satisfactorily burned. As a result, carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas from the internal combustion engine are reduced, and it is also possible to greatly cut down the consumption of fuel during idling operation of the internal combustion engine or when a motor vehicle equipped with the engine is traveling in steady condition. In an ordinary type internal combustion engine in which fuel is injected to an intake passage, a mixture is produced in the intake passage, and accordingly, there is a time lag before the mixture actually flows into the cylinder. In the case of the cylinder-injection type internal combustion engine, by contrast, no such time lag occurs, providing excellent response characteristics with respect to acceleration and deceleration of the internal combustion engine.
This advantage of the cylinder-injection type internal combustion engine is, however, available only when the engine is operated in relatively low-load condition. Specifically, when the quantity of fuel injection is increased as the load on the internal combustion engine increases, the mixture produced around the spark plug becomes excessively rich, so that the fuel cannot be ignited, causing misfire. Namely, with the cylinder-injection type internal combustion engine, it is difficult to produce a mixture having an optimum air-fuel ratio only in the vicinity of the spark plug over the entire operating region.
To overcome the drawback, Unexamined Japanese Patent Publication (KOKAI) No. 5-79370 discloses a cylinder-injection type internal combustion engine which has, as fuel injection modes, a former-stage injection mode in which fuel is injected during the suction stroke and a latter-stage injection mode in which fuel is injected during the compression stroke, and the switching between the former- and latter-stage injection modes is controlled in accordance with the load on the engine. In the latter-stage injection mode, fuel injected creates a mixture having an air-fuel ratio close to the stoichiometric ratio only in the vicinity of the spark plug. Therefore, even if the mixture in the cylinder is lean as a whole, the fuel can be ignited, making it possible to reduce CO and HC in the exhaust gas. Also, the consumption of fuel can be greatly cut down when the internal combustion engine is idling or the vehicle is traveling in steady condition. In the former-stage injection mode, on the other hand, fuel is injected during the suction stroke and a mixture having a uniform concentration of fuel throughout the cylinder is formed. Consequently, the air utilization factor is high, whereby the quantity of fuel injection can be increased, making it possible to fully enhance the output of the internal combustion engine.
Thus, in the above cylinder-injection type internal combustion engine known in the art, although the fuel injection mode is switched to the latter- or former-stage injection mode in accordance With steady operating state, no consideration is given to transitional operating states such as at vehicle start, acceleration, deceleration or during cold state. Therefo

REFERENCES:
patent: 5170759 (1992-12-01), Ito
patent: 5205254 (1993-04-01), Ito et al.
patent: 5628290 (1997-05-01), Iida et al.
patent: 5642706 (1997-07-01), Wirth et al.

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