Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-03-30
2001-06-12
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S299000
Reexamination Certificate
active
06244241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a fuel injection control system and, in particular, to a fuel injection control system for a direct injection-spark ignition engine which learns a fuel injection quantity characteristic of an injector with respect to an injection pulse width.
2. Description of Related Art
Typically, direct injection-spark ignition engines are operative to perform stratified charge combustion by spraying fuel in a compression stroke in a specified engine operating zone, such as a lower engine load and speed zone, with the effect of improving fuel consumption. Such a direct injection-spark ignition engine is equipped with a fuel injector which is pulsed by an electronically controlled fuel injection system (which is hereafter referred to as a fuel injection system for simplicity) to open. The fuel injection system determines an injection pulse width upon which the quantity of fuel delivered by a given injector depends and an injection timing at which the injector is caused to open. The injector is operative to spray fuel according to a given fuel injection quantity characteristic with respect to injection pulse width. In order to eliminate differences in fuel injection quantity characteristics of the individual injectors, the fuel injection quantity characteristic of a given injector is modified or corrected by changing a conversion factor between fuel injection quantity and injection pulse width. Specifically, a fuel injection quantity characteristic between fuel injection quantity and pulse width, shown by means of example in
FIG. 12
, is different in proportional relationship between the major part (normal injection characteristic zone) A and a minute injection characteristic zone B. This results from an increase in the ratio of time spent on injector valve movement to time for which the injector remains open in the minute injection zone B. Further, shown by means of example in
FIG. 13
, variation in fuel injection quantity characteristic due to differences of the individual injectors becomes greater with a decrease in the quantity of fuel injection. Accordingly, there is not only a change in the given fuel injection quantity characteristic between the normal injection zone A and the minute injection zone B but also a greater variation in fuel injection quantity characteristic among the individual injectors in the minute injection zone B as compared with the normal injection zone A. In particular, since the direct injection-spark ignition engine often experiences cases where a quantity of fuel required according to a given engine operating condition must be sprayed within a considerably short period of time, it is necessary to equip the engine with injectors with a relatively large ratio of injection (a ratio of a quantity of fuel injection to an open time). However, such an injector is hard to be given a minute injection zone B. In addition, since the direct injection-spark ignition engine increases its combustion efficiency when stratified charge combustion is made by spraying fuel in a compression stroke to raise an air-fuel ratio and the quantity of fuel injection is reduced in consequence, the quantity of fuel injection is reduced to an extent which falls into the minute injection zone B during engine operation with lower engine load, such as during idling. Therefore, in these circumstances, when translating the quantity of fuel injection into an injection pulse using only a conversion factor specified according to the fuel injection quantity characteristic for the normal injection zone A, there occurs a determination of accuracy of the control of fuel injection quantity.
In order to prevent such a determination of accuracy of the control of fuel injection quantity, a fuel injection device for a multi-cylinder internal combustion engine has been proposed in, for example, Japanese Unexamined Patent Publication No. 5-214999 that publication differentiates between a conversion factor for a surge operating zone (which corresponds to the minute injection zone B) and a proportional zone in which the quantity of fuel injection is proportional to a period of time for which the injector remains open (which corresponds to the normal injection zone A) and corrects the conversion factor used in the surge operating zone so as to make output torque equal among cylinders.
While the prior art fuel injection device is designed and adapted to regulate relative variation in output torque among the respective cylinders by correcting the conversion factor so as to make output torque equal among cylinders in the surge operating zone, an error in the absolute quantity of fuel injection is not always eliminated. Further, any such correction of the conversion factor has to be made under such engine operating conditions that the quantity of fuel injection falls within the minute injection zone B, in which a demand for stratified charge combustion by compression stroke injection is made. However, since even a slight aberration of ignition timing causes a great change in cylinder pressure or in difference between cylinder pressure and fuel pressure, which affects the quantity of fuel injection, it is hard to make an accurate correction of the conversion factor.
The conversion factor may be determined and corrected according to fluctuations in fuel injection feedback correction value while the engine operates in an engine operating state in which fuel injection feedback control is accomplished according to an output representative of the air-fuel ratio from an oxygen (O
2
) sensor to maintain a stoichiometric air-fuel ratio. Since thermal efficiency is inferior in an engine operating state in which the engine operates in a stoichiometric air-fuel ratio as compared with an engine operating state in which the engine performs lean stratified charge combustion, the quantity of fuel injection for a given engine output torque is larger during the engine operation in the stoichiometric air-fuel ratio than during the engine operation with the lean stratified charge combustion. Therefore, a fuel injection quantity zone (marked “a” in
FIG. 12
) in which the determining and correcting of a conversion factor is accomplished is differentiated from a fuel injection quantity zone (marked “b” in
FIG. 12
) in the minute injection zone B for engine operation with stratified charge combustion, which results in an inaccurate correction of conversion factor.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a fuel injection control system for a direct injection-spark ignition engine which can accomplish an accurate correspondence of fuel injection quantity to injection pulse width in a minute injection zone B for an engine operating state in which the engine performs stratified charge combustion with lower engine loads and accurately determine and correct a conversion factor according to the variation in the correspondence of fuel injection quantity to injection pulse.
The foregoing object of the invention is accomplished by a fuel injection control system, for a direct injection-spark ignition engine equipped with an injector operative to spray fuel directly into a combustion chamber of the engine, which determines an injection pulse width corresponding to a quantity of fuel with which the injector is kept open to spray the quantity of fuel, and controls the injector to spray fuel through a compression stroke while the engine operates with a lower engine load in an engine operating zone specified for lean stratified charge combustion so that the fuel is stratified around an ignition plug to cause lean stratified charge combustion to, thereby provide an air-fuel ratio greater than a stoichiometric air-fuel ratio. The fuel injection control system accomplishes fuel injection feedback control to control the quantity of fuel injection based on the air-fuel ratio detected by an oxygen sensor, causes the injector to spray fuel through a plurality of intake stroke split injection in a specified engine operating zone in which the fu
Imada Michihiro
Mamiya Kiyotaka
Tetsuno Masayuki
Yamauchi Takeo
Dolinar Andrew M.
Mazada Motor Corporation
Nixon & Peabody LLP
Studebaker Donald R.
LandOfFree
Fuel injection control system for direct injection-spark... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel injection control system for direct injection-spark..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel injection control system for direct injection-spark... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2506340