Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-10-06
2001-05-29
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
Reexamination Certificate
active
06237561
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to fuel injection control apparatus and method for a directly injected fuel engine, and more particularly to control of fuel injection of an engine capable of switching between stratified combustion and homogeneous combustion and which provides a reduction in fuel when decelerating or the like, whereby the start of fuel injection from the condition in which the fuel is reduced is controlled.
In recent years, direct injection engines have been developed for use as automotive engines, a fuel injection valve that injects fuel such as gasoline directly into the combustion chamber being provided, wherein in the low-load and medium-load regions, by injecting fuel during the compression stroke, stratified combustion is achieved by generating a stratified combustible mixture only in the region of the spark plug, thereby enabling a great increase in the leanness of the air-fuel ratio, and providing a great improvement in fuel consumption and emissions performance. In this system, however, when the load exceeds a predetermined load, to achieve the desired torque with a limited cylinder volume, fuel is injected on the intake stroke, thereby forming a homogeneous air-fuel mixture for the performance of homogeneous combustion.
As a measure to improve fuel economy, in the decelerating condition, in which the throttle valve is fully closed with the engine speed at or above a predetermined speed, the injection of fuel into the engine has been cut in the past, in what has come to be known as the deceleration fuel-cutoff mode.
SUMMARY OF THE INVENTION
According to an investigation by the inventor, in an engine of the past, when in the deceleration fuel-cutoff condition, if the throttle valve is opened in order to accelerate, thereby starting the injection of fuel again, there can be envisioned differences in response, such as torque up-ramping, depending upon whether the injection is resumed so as to perform stratified combustion or resumed so as to start homogeneous combustion.
More specifically; in the case in which the throttle opening D is in the fully closed condition, so that the fuel is cutoff, if the driver operates the accelerator, so that the throttle opening D goes into the opened condition and fuel injection is started, the torque T and vehicle forward and reverse acceleration “a” characteristics in response to engine fuel combustion are as shown in FIG.
4
A and FIG.
4
B.
That is, when the fuel cutoff is ended and fuel injection is started again, the typical torque T up-ramping response and vehicle acceleration “a” response are as particularly shown by the broken lines a
P
and T
P
of
FIG. 4A
, with respect to stratified combustion, and are as shown in
FIG. 4B
, with respect to homogeneous combustion, the response tending to differ, depending upon the mode of combustion.
Additionally, consider the case shown in FIG.
5
A and
FIG. 5B
, in which the fourth cylinder (#4cyl) is observed, with the fuel cutoff stopped and fuel injection started at the time T
R
. The top parts of FIG.
5
A and
FIG. 5B
show the reference signal (REF SIG), and the horizontal axis in both of these drawings represents the crank angle &thgr;
C
.
In the case of homogeneous combustion as shown in
FIG. 5A
, whereas it is not possible to inject fuel into the fourth cylinder and perform combustion therein, in the case of stratified combustion as shown in
FIG. 5B
, it is possible to inject fuel into the fourth cylinder and perform combustion therein. This is because, with homogeneous combustion, because it is necessary to inject fuel on the intake stroke, which is relatively far from the timing of ignition, even though the fourth cylinder is about to go into the compression stroke, it is not possible to perform fuel injection. In contrast to this, with stratified combustion, however, it is preferable to inject fuel on the compression stroke, and this is what enables actual fuel injection into the fourth cylinder. The result of this is that, in the case of stratified combustion it is possible to start combustion one cylinder earlier than the case of homogeneous combustion.
That is, referring again to the broken line in FIG.
4
A and to
FIG. 4B
, when ending the cutoff of fuel injection and starting fuel injection, with respect to the response of torque T up-ramping and the acceleration “a” of the vehicle, indicated by the delay time D
P
from fuel cutoff with stratified combustion and the response, indicated by the delay time D′
P
from fuel cutoff with homogeneous combustion, the delay time D
P
tends to be smaller than the delay time D′
P
.
Therefore, because of the above-noted difference in combustion characteristics between stratified combustion and homogeneous combustion, when fuel injection is started after fuel has been in the cutoff condition, it is thought that there is a tendency for a mutual difference in the torque T up-ramping characteristics and in the vehicle acceleration “a” characteristics.
The difference in response that occurs and is dependent upon the combustion mode when fuel injection is resumed causes such noticeable effects as acceleration shock to a rider of the vehicle, and can represent a deterioration in the feeling of quality of the vehicle as a product.
The present invention was developed as a result of the above-noted investigation, and has as an object the provision of a fuel injection control apparatus and method for a direct injection engine, whereby, when fuel injection is to be resumed from the condition in which the fuel is in the cutoff condition, such as during deceleration, it is possible to achieve equivalent drivability, regardless of whether the combustion is made in the stratified combustion or homogeneous combustion mode, thereby enabling the avoidance of such effects as acceleration shock.
In order to achieve the above-noted object, a direct injection engine fuel injection control apparatus comprises: a fuel injection valve injecting fuel directly into a combustion chamber; a combustion switching section, which, in accordance with driving conditions, switches between homogeneous combustion, in which the fuel is injected from the fuel injection valve during an intake stroke and combusted, and stratified combustion, in which the fuel is injected from the fuel injection valve during a compression stroke and combusted; a fuel cutoff section, which, in a predetermined deceleration driving condition, stops injection of the fuel from the fuel injection valve; and a resumption delay section, which, in the case that a fuel-cutoff recovery condition in which the injection of the fuel from the fuel injection valve is resumed after a fuel cutoff is satisfied, and also that resumption of the injection of the fuel from the fuel injection valve is to be done by the stratified combustion, delays the resumption of the injection of the fuel from the fuel injection valve by a predetermined amount of time.
In other words, a direct injection engine fuel injection control apparatus of the invention comprises fuel injection means for injecting fuel directly into a combustion chamber; combustion switching means for switching between homogeneous combustion, in which the fuel is injected from the fuel injection means during an intake stroke and combusted, and stratified combustion, in which the fuel is injected from the fuel injection means during a compression stroke and combusted; a fuel cutoff means for stopping injection of the fuel from the fuel injection means; and a resumption delay means, in the case that resumption of the injection of the fuel from the fuel injection means is to be done by the stratified combustion, for delaying the resumption of the injection of the fuel from the fuel injection means by a predetermined amount of time.
Besides, a method of controlling fuel injection in a direct injection engine of the present invention, comprises the steps of: switching, in accordance with driving conditions, between homogeneous combustion, in which fuel is injected from a fuel injection valve during an intake st
Castro Arnold
Dolinar Andrew M.
Foley & Lardner
Nissan Motor Co,. Ltd.
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