In-cylinder direct-injection spark-ignition engine

Details In-cylinder direct-injection spark-ignition engine In-cylinder direct-injection spark-ignition engine

1999-04-22

2001-01-16

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Combustible mixture stratification means

C123S298000, C123S301000, C123S302000, C123S305000

Reexamination Certificate

active

06173690

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an in-cylinder direct-injection spark-ignition engine with an electronic concentrated engine control system, employing a variable swirl-and-tumble control mechanism and an electronically-controlled fuel-injection system used to switch between a homogeneous combustion mode using tumble airflow and a stratified combustion mode using swirl airflow.
2. Description of the Prior Art
In recent years, there have been proposed and developed various in-cylinder direct-injection spark-ignition engines in which fuel is injected directly into the engine cylinder. The direct-injection spark-ignition engine uses at least two combustion modes, namely an early injection combustion mode or a homogeneous combustion mode where fuel-injection early in the intake stroke produces a homogeneous air-fuel mixture, and a late injection combustion mode or a stratified combustion mode where late fuel-injection delays the event until the end of the compression stroke to produce a stratified air-fuel mixture. One such cylinder direct-injection spark-ignition engine has been disclosed in Japanese Patent Provisional Publication No. 8-35429. This patent provisional publication teaches the provision of a non-circular piston bowl having a reentrant portion and a pair of intake ports, namely, a straight intake port with a so-called swirl control valve and a helical intake port.
SUMMARY OF THE INVENTION
With such a helical intake port, air flow is controlled from just before intake-port valves so as to strengthen swirl airflow. However, the use of the helical port results in increased airflow resistance against incoming intake-air flow, thus reducing a charging efficiency of intake air (a decrease in induction efficiency at high engine speeds, i.e., a drop in engine performance at full throttle). In contrast to the above, if a direct-injection spark-ignition engine is designed with a pair of straight intake ports, adequate swirl flow cannot be produced, and thus there is a problem of piston-bowl wetting during a stratified combustion mode. As mentioned above, it is desirable to more highly reconcile lean or ultra-lean stratified charge combustion for low fuel consumption and homogeneous charge combustion for high power output. Accordingly, it is an object of the invention to provide a direct-injection spark-ignition engine which avoids the aforementioned disadvantages of the prior art.
In order to accomplish the aforementioned and other objects of the present invention, an in-cylinder direct-injection spark-ignition engine comprises a cylinder block having a cylinder, a piston movable through a stroke in the cylinder, a cylinder head on the piston, a pentroof combustion chamber recessed in a bottom of the cylinder head and having first and second shallow-angled surfaces, a pair of intake valves disposed in the first shallow-angled surface of the pentroof combustion chamber, a pair of exhaust valves disposed in the second shallow-angled surface of the pentroof combustion chamber, a pair of substantially straight intake ports, in which the pair of intake valves operate, formed in the cylinder head, an intake-air control valve disposed in a first intake port of the pair of substantially straight intake ports for adjusting an amount of intake air passing through the first intake port, a spark plug installed in the cylinder head in a substantially center of the cylinder, a fuel injector disposed in the bottom of the cylinder head adjacent to the pair of intake valves so that an axial line of the fuel injector is directed to the substantially center of the cylinder, for injecting fuel directly into the cylinder, and a control unit being configured to be electronically connected to the fuel injector for switching between a homogeneous combustion mode where early fuel-injection on intake stroke produces a homogeneous air-fuel mixture while producing a tumbling action into the cylinder, and a stratified combustion mode where late fuel-injection on compression stroke produces a stratified air-fuel mixture while producing a swirling action into the cylinder, wherein a piston crown of the piston comprises an intake-valve side inclined surface generally parallel to the first shallow-angled surface, an exhaust-valve side inclined surface generally parallel to the second shallow-angled surface, and a piston bowl having an opening of a substantially complete round and arranged in an eccentric position with respect to an outside circle of an upper portion of the piston toward the pair of intake valves, and wherein the piston bowl has a deeply-recessed bowl cavity, and the deeply-recessed bowl cavity is arranged eccentrically to the opening of the piston bowl toward a second intake port of the pair of substantially straight intake ports.


REFERENCES:
patent: 4920937 (1990-05-01), Sasaki et al.
patent: 5553588 (1996-09-01), Gono et al.
patent: 5806482 (1998-09-01), Igarashi et al.

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