Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2003-11-20
2004-11-23
Kwon, John T. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S480000
Reexamination Certificate
active
06820595
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2002-344564 filed on Nov. 27, 2002, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to fuel injection amount control method and apparatus of an internal combustion engine, and, more particularly, to apparatus and method of controlling a fuel injection amount so that the air/fuel ratio can be kept substantially constant even during transient operations of the engine.
2. Description of Related Art
In an internal combustion engine of an electronically-controlled fuel injection type, fuel is supplied to each of cylinders of the engine through fuel injection immediately before the suction stroke of the cylinder or during the suction stroke. The cylinder that currently needs to be supplied with the fuel will be hereinafter called “fuel injection cylinder”. This type of the engine is required to calculate an amount of intake air drawn into the fuel injection cylinder during the suction stroke, and inject fuel in an amount matching the calculated intake air amount by the time when a corresponding intake valve is closed at the end of the suction stroke (i.e., by a point in time when the intake valve shifts from an open state to a closed state) at the latest. In some cases, the fuel needs to be injected prior to a start of the suction stroke.
To meet the above requirements, a control apparatus of an internal combustion engine as disclosed in, for example, U.S. Pat. No. 6,014,955 estimates an opening angle of a throttle valve as one of operating state quantities of the engine up to the time of closing of the intake valve of the fuel injection cylinder, and estimates an amount of intake air that will be present in the fuel injection cylinder at the time of closing of the intake valve, based on at least the estimated throttle opening and an air model that models the behavior of air in the intake system of the engine, at a point in time prior to the time of closing of the intake valve. The control apparatus then generates a command to inject fuel into the cylinder in an amount that matches the estimated intake air amount.
The conventional control apparatus as described above may suffer from the following problem: if a difference (or estimation error) arises between the estimated intake air amount and the actual intake air amount, for example, due to a difference between the estimated throttle opening and the actual throttle opening, the control apparatus, which is not provided with a means for compensating for the estimation error, cannot produce an appropriate value of the fuel injection amount, and the air/fuel ratio may fluctuate or deviate from a target value.
In the case where the conventional control apparatus is provided with a general feedback controller for performing feedback control so as to compensate for the estimation error, a feedback control system is desirably constructed so that feedback control constants, such as a proportional gain and an integration gain, used by the controller need not be frequently changed in response to frequently varying operating conditions (e.g., the engine speed and the temperature) of the engine, thereby making the feedback controller simple in construction.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a fuel injection amount control method and a fuel injection amount control apparatus, which use a feedback controller having a simple construction or arrangement, for promptly compensating for an estimation error in the intake air amount, thereby to promptly make the air/fuel ratio stable particularly during a transient engine operation, e.g., upon a sudden change of the throttle opening.
To accomplish the above and/or other object(s), there is provided according to a first aspect of the invention a method of controlling a fuel injection amount of an internal combustion engine with respect to a suction stroke for which fuel is injected, comprising the steps of (a) estimating an operating state quantity of the engine to be established at the time of closing of an intake valve in the suction stroke in question, at a point in time prior to the time of closing of the intake valve, (b) estimating an intake air amount in the suction stroke based on the estimated operating state quantity, (c) calculating, as a pre-correction estimated necessary fuel amount, a provisional fuel amount that is needed along with the estimated intake air amount to achieve a target air/fuel ratio, (d) calculating an actual necessary fuel amount as an amount of fuel actually needed for achieving the target air/fuel ratio in a previous suction stroke that precedes the suction stroke in question, based on a known value of the operating state quantity, at a point in time after closing of the intake valve in the previous suction stroke, (e) calculating an actual intake fuel amount as an amount of fuel actually inducted into a cylinder of the engine during the previous suction stroke, based on at least an amount of fuel actually injected for the previous suction stroke, (f) determining an excess or shortage of the fuel in the previous suction stroke based on the calculated actual necessary fuel amount and the calculated actual intake fuel amount, and calculating a fuel feedback correction amount corresponding to the determined excess or shortage of the fuel, (g) calculating a normal estimated necessary fuel amount by correcting the pre-correction estimated necessary fuel amount with the calculated fuel feedback correction amount, (h) calculating a fuel injection amount based on at least the calculated normal estimated necessary fuel amount, and (i) injecting the fuel having the calculated fuel injection amount for the suction stroke in question, at a point in time before the time of closing of the intake valve in the suction stroke.
The above-mentioned “suction stroke in question” may refer to the present suction stroke in which the cylinder for which the fuel injection amount is controlled according to the above method is currently placed, or to the coming suction stroke of the cylinder, namely, the suction stroke into which the cylinder comes next. In the method according to the above aspect of the invention, the “suction stroke in question”, “previous suction stroke” and the “second previous suction stroke” may be the current or coming, previous and second previous suction strokes with respect to a particular cylinder that is an arbitrarily selected one of the cylinders provided in the engine, or may be the current or coming, previous and second previous suction strokes with respect to a non-particular cylinder for which fuel injection is performed next, out of the cylinders of the engine that successively enter the suction stroke.
In the fuel injection amount control method as described above, the amount of intake air that will be present in the cylinder at the time of closing of the intake valve in the suction stroke in question is estimated based on the estimated operating state quantity (e.g., an opening angle of a throttle valve), at a point in time earlier than the time of closing of the intake valve. Then, the pre-correction estimated necessary fuel amount is calculated as a provisional amount of fuel needed for achieving the target air/fuel ratio (e.g., the stoichiometric air/fuel ratio) if the estimated intake air amount is actually provided. Namely, the pre-correction estimated necessary fuel amount is calculated based on the estimated intake air amount and the target air/fuel ratio. Accordingly, the pre-correction estimated necessary fuel amount is influenced by an estimation error in the estimated intake air amount.
In the meantime, since the operating state quantity established at the time of closing of the intake valve in the previous suction stroke is known after closing of the intake valve in the previous suction stroke, the actual intake air amount in the previous suction stroke can be determined from the known operating s
Kobayashi Daisuke
Kojima Kazunori
Kwon John T.
Oliff & Berridg,e PLC
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