Internal-combustion engines – Combustion chamber means having fuel injection only
Reexamination Certificate
2000-03-01
2001-12-04
Kwon, John (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
C123S305000
Reexamination Certificate
active
06325040
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a cylinder direct injection engine and, more particularly, to a cylinder direct injection engine designed for stable combustion.
BACKGROUND OF THE INVENTION
Some engines disposed in a vehicle are of a type called a cylinder direct injection engine. This type of an engine has a spark plug provided in a cylinder head at a substantially central portion of a combustion chamber. The combustion chamber is formed between the underside of the cylinder head and a top surface of a piston. In addition, intake and exhaust valves are disposed in the cylinder head. The intake valve is positioned on one side of the cylinder head, but the exhaust valve is located on the other side thereof. Further, an injector is disposed in the cylinder head on one side thereof. The injector expels fuel in the form of a conical stream onto the top surface of the piston.
One such example of a cylinder direct injection engine is disclosed in published Japanese Patent Application Laid-Open No. 7-217478. A fuel injection controller for use in a spark ignition engine of a cylinder injection type as disclosed in this publication controls knocking without detracting from fuel efficiency when the knocking occurs.
Another example is disclosed in published Japanese Patent Application Laid-Open No. 9-144543. A direct injection spark ignition internal combustion engine as disclosed in this publication has a spark plug disposed at a substantially central portion of a combustion chamber. In addition, an intake port is positioned offset from the axis of a cylinder. Further, a fuel injection valve is provided at a depression angle (&thgr;=30°±10°) at the intake port adjacent to an opening of the combustion chamber in such a manner that cone angle &agr; of fuel spray is set to be 70°±20°. This construction provides improved engine performance.
A further example is disclosed in published Japanese Patent Application Laid-Open No. 10-288127. In a combustion chamber of an internal combustion engine as disclosed in this publication, a concave portion is provided on a cylinder head wall surface on the side of a spark plug near a nozzle aperture of a fuel injection valve. When the fuel injection valve discharges fuel therefrom under atmospheric pressure conditions outside the combustion chamber, then a first angle &thgr;
1
is defined between a central axis defined by the fuel spray and a peripheral surface of the fuel spray. In this state, a second angle &thgr; defined between a slanted wall surface at the concave portion and the conical surface of the fuel spray is set to be greater than the first angle &thgr;
1
. The conical surface of the fuel spray defines first angle &thgr;
1
with respect to the central axis of the fuel spray from the fuel injection valve after the same is fitted to the combustion chamber. Such a construction restrains or minimizes the occurrence of an attractive force, which otherwise would attract atomized fuel to the cylinder head wall surface. In addition, fuel is combusted in a stable manner, which results in a reduced amount of soot.
A further example is disclosed in published Japanese Patent Application Laid-Open No. 10-339145. A cylinder direct injection type of a spark ignition engine as disclosed in this publication includes a swirl control valve for imparting swirl to intake air that enters a cylinder through an intake port. Further, a pattern of atomized fuel driven out of an injector is set to have a hollow, conical shape that is in a state of initial atomization. In addition, a cap portion of a piston is formed with a cavity that is dented so as to receive the atomized fuel. This structure provides a combustion chamber adapted for this type of an engine.
A cylinder direct injection engine heretofore employed is designed to inject fuel directly into a combustion chamber from an injector during a compression stroke, thereby forming a stratified air-fuel mixture. For this reason, a large number of improvements in a piston pattern have been made.
However, injection timing of the injector as well as a piston phase influence the formation of the stratified mixture. In addition, the injection timing is limited to a narrow range.
FIG. 26
illustrates a cylinder direct injection engine (hereinafter simply called an “engine”)
102
. The engine
102
has a 75 mm cylinder bore and a 90 mm piston stroke.
FIG. 27
is a cross-sectional view, showing a spark plug portion of the engine
102
in a 30° crank angle (CA) BTDC (Before Top Dead Center) state.
FIG. 28
is a cross-sectional view, illustrating the spark plug portion of the engine
102
in a 45° crank angle (CA) BTDC state.
FIG. 29
is a cross-sectional view, illustrating the spark plug portion of the engine
102
in a 60° crank angle (CA) BTDC state.
The engine
102
has a piston
108
disposed in a cylinder block
104
for reciprocation therein. In addition, a concave area
132
is defined at a top surface
108
a
of the piston
108
.
The piston
108
is connected to a crankshaft (not shown) through a connecting rod (not shown). A combustion chamber
116
is formed between the underside of a cylinder head
106
and the top surface
108
a.
The cylinder head
106
is positioned on an upper surface of the cylinder block
104
. A spark plug
118
is provided in the cylinder head
106
at a substantially central portion of the combustion chamber
116
. An injector
120
is located in the cylinder head
106
on the intake side of the cylinder head
106
. The injector
120
permits fuel to be expelled therefrom in the form of a conical stream directly into the combustion chamber
116
.
The injector
120
injects the fuel therefrom into the concave area
132
during a second half of the compression stroke. At this time, atomized fuel “F” (
FIG. 27
) is captured at the concave area
132
, and is then collected near the spark plug
118
. Such collected fuel “F” forms a stratified mixture in cooperation with a lean mixture that surrounds the stratified mixture.
A certain period of time for the fuel to be atomized must be maintained between fuel injection and ignition. Such a period of time has requirements that vary, depending upon engine speed and engine load (i.e. a longer period of time between injection and ignition elapses for lower loads and speeds, and a shorter period of time between injection and ignition elapses for higher loads and speeds). Typically, ignition timing covers a range between a 30° and a 60° crank angle (CA) BTDC.
In the disclosed engine
102
, however, the 60° crank angle (CA) BTDC as illustrated in
FIG. 29
results in an improper positional relationship between the concave area
132
and the atomized fuel “F”. This causes inconveniences of insufficient fuel capture, unsatisfactory stratification, and unstable combustion, which are all disadvantageous in view of practical use.
FIG. 30
discloses an engine
202
having a reduced-diameter cylinder bore. In the engine
202
, a greater portion of atomized fuel “F” is shown adhered to a cylinder wall inside a cylinder block
204
. This undesirable condition leads to scuffing which is caused by oil film deposited on a wall surface of the cylinder block
204
, which is disadvantageous in view of practical use.
FIG. 31
illustrates another cylinder direct injection engine
302
heretofore employed. In this engine
302
, fuel is injected from an injector
320
during a compression stroke, and is then delivered to a location near a spark plug
318
by means of a tumble flow (or swirl flow), thereby forming a stratified mixture.
At this time, when a piston stroke is small or short, then the tumble flow (or swirl flow) is reduced in strength, with a concomitant deficiency in fuel delivery. This brings about yet further inconveniences of an unsuccessful stratified mixture and thus unstable combustion.
Moreover, when the cylinder bore is too large (in diameter) in each of the above-described engines, except for the engine having the reduced cylinder bore of
FIG. 30
, a still further convenience is encountered. More specifical
Flynn ,Thiel, Boutell & Tanis, P.C.
Kwon John
Suzuki Motor Corporation
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