Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2003-07-08
2004-09-21
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S480000, C701S109000
Reexamination Certificate
active
06792927
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2002-201569 filed on Jul. 10, 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 apparatus and method for controlling a fuel injection amount of an internal combustion 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 intake stroke of the cylinder or during the intake stroke. The cylinder to which the fuel needs to be supplied will be hereinafter referred to as “particular cylinder” or “fuel injection cylinder”. During an operation of the engine, an amount of intake air that is drawn into the fuel injection cylinder during the intake stroke is initially calculated, and fuel is injected in an amount corresponding to the calculated intake air amount, by the time when a corresponding intake valve is closed at the end of the intake stroke (i.e., by a point of time when the intake valve shifts from an open state to a closed state) at the latest. Depending upon the case, the fuel is injected before the start of the intake stroke.
To enable the internal combustion engine to operate in the manner as described above, a control apparatus of an internal combustion engine as disclosed in, for example, U.S. Pat. No. 6,014,955 predicts 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 predicts 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 the predicted throttle opening and an air model that models the behavior of air in the intake system of the engine. The control apparatus then injects fuel into the cylinder in an amount corresponding to the predicted 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 predicted intake air amount and the actual intake air amount, for example, due to a difference between the predicted throttle opening and the actual throttle opening, the fuel injection amount calculated by the control apparatus deviates from an appropriate value, and the air/fuel ratio fluctuates or deviates from a target value.
In the meantime, there is widely known a fuel injection amount control apparatus that controls the fuel injection amount in a feedback fashion. More specifically, in order that the air/fuel ratio of an air-fuel mixture introduced into the engine coincides with a target air/fuel ratio, the control apparatus uses an air/fuel ratio sensor provided in an exhaust passage of the engine to detect the air/fuel ratio of exhaust gas, and controls the fuel injection amount in a feedback manner depending upon a deviation of the detected air/fuel ratio from the target air/fuel ratio. This arrangement makes it possible to reduce a steady-state deviation of the air/fuel ratio of the air-fuel mixture from the target air/fuel ratio due to, for example, changes in the properties of fuel, variations in the performance of injectors resulting from manufacturing errors, and the like.
It is, however, to be noted that the air/fuel ratio measured by the air/fuel ratio sensor is the air/fuel ratio of exhaust gas that is emitted from the combustion chamber after combustion of an air-fuel mixture supplied to the engine in the past, and then reaches the air/fuel ratio sensor through the exhaust passage. Therefore, the feedback control involves a large wasteful time. Furthermore, if the feedback control utilizing the detected air/fuel ratio is designed to promptly compensate for fluctuations in the air/fuel ratio due to estimation errors in the predicted intake air amount, the feedback control gain needs to be increased. If the control gain is excessively large, the air/fuel ratio may undergo hunting.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide fuel injection amount control apparatus and method of an internal combustion engine, which are able to promptly compensate for estimation errors in the intake air amount, while at the same time making use of the advantages of the feedback control, so that the air/fuel ratio of an air-fuel mixture supplied to the engine can be stably made equal to the target air/fuel ratio.
To accomplish the above and/or other object(s), a fuel injection amount control apparatus according to a first aspect of the invention includes a predicted in-cylinder intake air amount calculating unit B
1
, a basic fuel injection amount calculating unit B
3
, an actual in-cylinder intake air amount calculating unit B
4
, a feedfoward correction amount calculating unit (B
5
-B
7
), a feedforward fuel injection amount calculating unit A
1
, an air/fuel ratio sensor
69
, a feedback correction amount calculating unit (B
8
-B
11
), a final fuel injection amount calculating unit A
2
and a fuel injector
39
, as shown in FIG.
2
. The control apparatus injects a fuel having the calculated final fuel injection amount into a particular cylinder during a particular intake stroke.
The control apparatus including the above-indicated units calculates a predicted in-cylinder intake air amount (klfwd) based on a predicted operating state quantity of the engine, and calculates a basic fuel injection amount (finjb(k)) based on the predicted in-cylinder intake air amount. On the other hand, the control apparatus calculates an actual in-cylinder intake air amount (klcyl(k−1)) from the actual (confirmed) engine operating state quantity, and calculates a feedforward fuel injection amount (finjfwd(k)) by correcting an excess or shortage of fuel due to a difference between the predicted in-cylinder intake air amount and the actual in-cylinder intake air amount by using a feedforward correction amount (finjk(k)). Also, the control apparatus calculates a feedback correction amount (finjfb(k)) for reducing a deviation between the actual air/fuel ratio (abyfs) detected by the air/fuel ratio sensor and an air/fuel ratio of an air-fuel mixture that is determined by the feedforward fuel injection amount (finjfwd(k)), and obtains a final fuel injection amount (finjfinal(k)) by correcting the feedforward fuel injection amount by using the feedback correction amount. In the following, each of the above-indicated units will be described.
The predicted in-cylinder intake air amount calculating unit B
1
predicts an operating state quantity of the engine to be established at a point of time ahead of the current point of time. For example, the engine operating state quantity is an opening angle of a throttle valve of the engine, or the like, which is required for predicting or estimating the intake air amount of the engine. The predicted in-cylinder intake air amount calculating unit then calculates the predicted in-cylinder intake air amount (klfwd) that is an amount of intake air drawn into the particular cylinder of the engine during the particular intake stroke, based on the predicted engine operating state quantity, at a point of time before completion of the particular intake stroke of the particular cylinder. Namely, this unit predicts, prior to completion of a certain intake stroke, an amount of intake air drawn in this intake stroke, based on a future engine operating state quantity.
The basic fuel injection amount calculating unit B
3
calculates the basic fuel injection amount (finjb(k)) for achieving a target air/fuel ratio, based on the predicted in-cylinder intake air amount thus calculated and the target air/fuel ratio. For example, the basic fuel injection amount (finjb(k)) is calculated by dividing the predicted in-cylinder intake air amount (klfwd) by the target air/fuel ratio (abyfref).
The actual in-cylinder intake air amount calculating unit B
4
calculates the a
Argenbright Tony M.
Toyota Jidosha & Kabushiki Kaisha
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