Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2002-03-12
2003-12-30
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S301000, C123S305000, C123S436000
Reexamination Certificate
active
06668791
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
This invention relates to a control system for an in-cylinder direct injection engine which controls behavior of fuel spray, directly injected into a combustion chamber in a cylinder, with a tumble to combust a mixture stratified around an electrode of a spark plug, and more particularly relates to the technical field of compensation control for suppressing deterioration in combustion quality of the mixture resulting from individual differences between injectors.
(b) Description of the Prior Art
Conventionally, control systems for in-cylinder direct injection engines of this type include one which is adapted to control penetration of fuel spray from an injector in accordance with the intensity of a tumble, carry the fuel spray toward a spark plug by means of the tumble and stratify a mixture around an electrode of the spark plug, as disclosed in, for example, Japanese Unexamined Patent publication No. 2000-204954.
Specifically, in the above control system, a tumble control valve (TCV) is provided in an intake passage of the engine downstream of a throttle valve. The TCV is opened or closed by an actuator to control the intensity of the tumble in the combustion chamber. At the same time, the fuel injection pressure of the injector is correspondingly controlled so that the fuel spray penetration is balanced against the tumble. In this manner, the fuel spray from the injector is carried by means of the tumble to reach the vicinity of the electrode of the spark plug, which enables stable stratified combustion.
However, for in-cylinder direct injection engines in which a fuel is injected directly into the high-pressure combustion chamber, their injectors generally have much higher fuel injection pressures as compared with those of injectors included in so-called port injection engines, and therefore the injectors are likely to have large variations in fuel injection pressure due to their individual differences.
Further, for multi-cylinder engines such as the above-mentioned prior art (Japanese Unexamined Patent Publication No. 2000-204954), a plurality of cylinders included in a single engine have individual intake ports of slightly different shapes and therefore the combustion chambers in the cylinders are not necessarily equal to each other in tumble intensity.
Accordingly, even if the fuel injection pressures of the injectors are commonly controlled in order to change in accordance with the tumble in the above-mentioned manner, balance is not strictly offered of the fuel spray penetration and the tumble in each cylinder. This results in the inconvenience that the mixture around the spark plug is held against stratification and thereby degrades its ignitability and combustion quality.
In addition, for the multi-cylinder engines such as the prior art, the degree of unbalance of fuel spray penetration and tumble is different from cylinder to cylinder. This also incurs another problem of increasing variations in combustion from cylinder to cylinder and in particular increasing noises and vibrations (idling vibrations) due to torque variations caused during idling operation and the like.
The present invention has been made in view of the forgoing problems, and therefore its object is to provide a control system for an in-cylinder direct injection engine which enables suitable mixture stratification by controlling behavior of fuel spray by means of a tumble, and particularly to provide suitable mixture stratification by considering a deviation of fuel injection pressure of a fuel from each injector and eliminating the unbalance of fuel spray and tumble which results from the deviation.
SUMMARY OF THE INVENTION
To attain the above object, in the present invention, the fuel injection pressure of a fuel injection valve is intentionally decreased or increased so that the unbalance of fuel spray and tumble is clarified, and a fuel injection timing is compensated so that even in such a condition combustion variations of an engine can fall within an allowable range.
Specifically, as shown as an example in
FIG. 1
, a first aspect of the invention has as a precondition a control system A for an in-cylinder direct injection engine which includes: a fuel injection valve
18
for directly injecting a fuel into a combustion chamber
6
in a cylinder
2
of an engine
1
; and a tumble generating means
10
for generating a tumble in the combustion chamber
6
, in which the fuel is injected against the tumble in the combustion chamber
6
by the fuel injection valve
18
during stratified-charge combustion operation of the engine
1
so that a flammable mixture stays in the vicinity of an electrode of a spark plug
16
at the ignition timing for the cylinder
2
.
Also, the control system A further includes: a fuel pressure control means
200
for controlling the fuel injection pressure of the fuel injection valve
18
; a fuel pressure forcibly changing means
50
b
for forcibly changing the fuel injection pressure to be controlled by the fuel pressure control means
200
from a reference injection pressure corresponding to operating conditions of the engine
1
; a combustion variation detecting means
50
c
for detecting the degree of combustion variation in the engine
1
when the fuel injection pressure has been changed by the fuel pressure forcibly changing means
50
b;
and an injection timing compensation means
50
e
for compensating the fuel injection timing of the fuel injection valve
18
so that the degree of combustion variation in the engine
1
detected by the combustion variation detecting means
50
c
becomes smaller than that in a preset reference condition.
First, according to part of the control system A which constitutes the precondition, the fuel is injected from the fuel injection valve
18
against a tumble generated by the tumble generating means
10
during stratified-charge combustion operation of the engine
1
, and the fuel spray is reduced in speed by the tumble and thereby stratified around the electrode of the spark plug
16
. In this case, if the fuel injection valves
18
have deviated fuel injection pressures due to their individual specificities, it can be expected that the fuel spray penetration is relatively weak so that the mixture may not sufficiently reach the vicinity of the spark plug
16
electrode or that contrarily the fuel spray penetration is relatively intense so that the mixture may pass over the vicinity of the spark plug
16
electrode whereby ignitability and combustion quality may be impaired.
On the other hand, according to the above-mentioned characteristic structure of the control system A, the fuel injection pressure of the fuel injection valve
18
is first changed forcibly by the fuel pressure forcibly changing means
50
b,
so that the deviation of penetration of fuel spray from the fuel injection valve
18
is amplified. This deteriorates ignitability and combustion quality of the mixture so that an increased degree of combustion variation of the engine
1
will be detected by the combustion variation detecting means
50
c.
Also, the fuel injection timing is compensated by the injection timing compensation means
50
e
such that even in that condition the degree of combustion variation of the engine
1
becomes smaller than that in the reference condition. In other words, for example, if the spray penetration is relatively weak, advancing the fuel injection timing allows the mixture to reach the vicinity of the spark plug
16
electrode at a suitable timing. On the other hand, if the spray penetration is relatively intense, a retarded fuel injection caused by retarding the injection timing allows the mixture to reach the vicinity of the spark plug
16
electrode at a suitable timing.
In short, according to the present invention, the unbalance of fuel spray and tumble can be eliminated by compensation for the fuel injection timing, thereby providing suitable mixture stratification. This enhances ignitability and combustion quality of the mixture thereby providing further improved fuel
Mamiya Kiyotaka
Tetsuno Masayuki
Yamauchi Takeo
Argenbright Tony M.
Mazda Motor Corporation
Nixon & Peabody LLP
Studebaker Donald R.
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