Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2000-09-28
2002-06-11
Mohanty, Bibhu (Department: 3765)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S673000, C123S339120, C123S295000
Reexamination Certificate
active
06401703
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and system for controlling fuel injection for a direct injection-spark ignition type of internal combustion engine which is supplied with fuel directly into a combustion chamber through a fuel injector, and, more particularly, to a fuel injection control system in which learning control is performed to learn quantitative variations of fuel injection due to individual differences of fuel injectors.
2. Description of the Related Art
Typically, fuel injection control systems for general gasoline engines control an air-fuel ratio of air-fuel mixture by performing quantitative regulation of fuel injection and intake air according to engine operating conditions. In order to avoid aggravation of controllability of fuel injection due to various factors such as individual differences of fuel injectors and changes in engine operation surroundings, it is popular to perform feedback control of the amount of fuel injection on an output signal provided by an oxygen (O
2
) sensor disposed in an exhaust passage of the engine. In the fuel injection control, learning quantitative variations in fuel injection from the output signal of the oxygen sensor and reflecting the result in basic fuel injection control is effective to improve transient responsiveness of air-fuel ratio control and air-fuel ratio control accuracy while the feedback control of air-fuel ratio is not implemented.
Because, in a direct injection-spark ignition type of internal combustion engine which is supplied with fuel directly into a combustion chamber under high pressure, fuel is sprayed at a pressure remarkably higher as compared with port injection, quantitative variations in fuel injection are apt to be large as a logical consequence. Furthermore, an injector for the direct injection-spark ignition type of internal combustion engine has to have a relatively large nozzle, which is one of causes of large quantitative variations, In particular, a micro-flow characteristic of the fuel injector is irregular in a period of engine idling in which a time for which the injector remains open is very short differently from a period other than the idling period in which the micro-flow characteristic is linear (see FIG.
7
). The micro-flow characteristics are significantly different due to individual differences of injectors. That is to say, since the injector for the direct injection-spark ignition type of internal combustion engine has the property of causing quantitative variations in fail injection while spraying a small amount of fuel, it is a reality that the direct ignition-spark ignition type of internal combustion engine has a strong demand for learning control of fuel injection for actual quantitative variations in fuel injection. However, the direct ignition-spark ignition type of internal combustion engine is usually operated in a stratified charge combustion state in an engine operating region of lower engine loads. In the stratified combustion state, a mean air-fuel ratio in a combustion chamber (which is hereafter referred to as a mean combustion chamber air-fuel ratio) is remarkably high, in other words, on a remarkably lean side, so that the oxygen sensor is hard to detect an air-fuel ratio with high precision as conventional. In consequence, although quantitative variations in fuel injection are apt to become large during idling in the lower load and stratified charge combustion region in which the engine is operate so often, it is difficult to perform the learning control of quantitative variations in fuel injection and the air-fuel ratio control accurately in that region.
In this regard, a fuel injection control system for a direct ignition-spark ignition type of internal combustion engine, such as disclosed in, for example, Japanese Unexamined Patent Publication No. 5- 99051, performs learning control of a deviation of an actual quantity of fuel injection from a target quantity of fuel injection, i.e. a quantitative variation in fuel injection, on the basis of a measurement of quantitative fuel consumption during a predetermined number of times of fuel injection while the engine is idling. In the fuel injection control, different values are employed as flow rate conversion coefficient Kps and Kpb for a regular flow characteristic of the fuel injector which is used in a proportional region where the quantity of fuel injection is proportional to a period of time for which the fuel injector is kept open (duration of injector opening) and a micro-flow characteristic of the fuel injector which is used in a non-proportional region where the quantity of fuel injection is not proportional to a period of time for which the fuel injector is kept open (duration of injector opening), respectively. For an intermediate region between the proportional and non-proportional regions, a conversion coefficient is gained by linear approximate calculation with use of the conversion coefficient Kpb and Kps.
The prior art fuel injection control system described above defines a micro-flow characteristic for the non-proportional region by a single flow rate conversion coefficient, the control of fuel injection can not be so precise in the non-proportional region. Specifically, as shown in
FIG. 7
by way of example, when an injection pulse width Ti, which is a measurement of how long the fuel injector is kept open, is smaller than a specified injection pulse width Ti*, the quantity of fuel injection by the fuel injector is not proportional to the injection pulse width Ti and irregularly changes with respect to a change in injection pulse width Ti. Therefore, in the case where the micro-flow characteristic, i.e. the relationship between a quantity of fuel injection and an injection pulse width is defined by a single conversion efficiency Kps, the control of fuel injection is not precise at all in the non-proportional region. In consequence, though the prior art fuel injection control system is adapted to correct the conversion efficiency Kps by learning quantitative variations of fuel injection through a fuel injector, it can not be said that the fuel injection control is precise during engine idling where a quantity of fuel injection is small and, therefore, the prior art fuel injection control system leaves room for further improvement in regard to emission control and fuel consumption.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a fuel injection control system capable of learning quantitative variations of fuel injection with high precision in a region of narrow injection pulse widths which is realized through a fully worked-out control sequence.
The foregoing object of the present invention is accomplished by a fuel injection control system which, while feedback controlling a quantity of fuel injection so as to provide a constant idling engine speed during idling, performs learning quantitative variations in fuel injection on the basis of a feedback control value for various duration of injector opening by forcibly changing a quantity of fuel injection, necessary to keep the constant idling engine speed, for a plurality of specified fuel injection timings which take place in turn.
Specifically, as shown in
FIG. 1
, the fuel injection control system, that is incorporated with a direct injection-spark ignition type of internal combustion engine equipped with a fuel injector
12
for spraying fuel directly into a combustion chamber
6
of the engine
1
in a compression stroke of each cylinder
2
so as to cause stratified charge combustion in a specified engine operating region of lower engine loads and lower engine speeds defined for stratified charge combustion, comprises intake air quantity regulation means
220
for regulating a quantity of intake air that is admitted into the combustion chamber
6
, learning control means
52
learning a quantitative variation of an actual quantity of fuel injection from a target quantity of fuel injection while the engine idles in the specified engine oper
Araki Keiji
Mamiya Kiyotaka
Yamamoto Hiroyuki
Mazda Motor Corporation
Mohanty Bibhu
Nixon & Peabody LLP
Studebaker Donald R.
LandOfFree
Method and system for controlling fuel injection for direct... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for controlling fuel injection for direct..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for controlling fuel injection for direct... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2906822