Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
1999-03-01
2001-01-09
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C701S108000, C073S118040
Reexamination Certificate
active
06170475
ABSTRACT:
TECHNICAL FIELD
This invention relates to methods and systems for determining cylinder air charge for future engine events.
BACKGROUND ART
Optimum efficiency of a three-way catalyst is achieved when a spark ignited internal combustion engine operates at stoichiometry (i.e., ideal air-to-fuel ratio). This requires that the in-cylinder air charge (i.e., mass flow rate of air into the cylinder) be matched by an appropriate amount of fuel. At each engine event, in-cylinder air-charge is typically estimated based on the measurements from a throttle mass air flow (MAF) sensor or an intake manifold pressure (MAP) sensor.
However, the present air-charge estimate, which pertains to the cylinder presently on the intake stroke, is several (typically one or two) engine events late for a fueling decision. This happens because the optimal timing for fuel injection in port fuel injection engines is on the closed intake valve. Moreover, dispensing the fuel takes a finite amount of time and larger quantities at higher engine speed may not be dispensed in one event or less. Thus, the amount of fuel decided at time t will be dispensed into the port of a cylinder that is to start its intake several engine events into the future. An improvement in the ability to control air/fuel ratio will follow if future values of cylinder air-charge can be predicted based on the present and past measurement of engine operating conditions. Because measurement noise has detrimental effect on the accuracy of prediction, the challenge for the designer is to provide a system that responds fast to legitimate changes in the signals being measured, yet is robust against inevitable measurement noise.
Several methods have been established that predict air charge for future cylinder events. For example, U.S. Pat. No. 4,512,318, issued to Ito et al., discloses a method for correcting the fuel injection flow rate in order to obtain an ideal air/fuel ratio. A “correction coefficient” (a multiplier for the base fuel injection time) is determined based on the rates of change of the currently measured intake manifold pressure and throttle valve position signals.
Similarly, a second known method disclosed in U.S. Pat. No. 5,497,329, issued to Tang, addresses a method of predicting air mass induced into each cylinder based on a predicted value of MAP. The predicted value of MAP is based on the rates of change of the intake manifold pressure signal and the sensed throttle position. These methods are signal-based, non-recursive predictors. These methods fail to take into account the available model of the manifold filling dynamics thereby making the predictions sensitive to noise and prone to overshooting.
A prediction method based on the theory of Kalman Filtering has been disclosed in U.S. Pat. Nos. 5,270,935 and 5,273,019, issued to Dudek et al. and Matthews et al., respectively. Kalman filters are designed for linearized models obtained by standard least squares identification. The algorithms disclosed therein are “absolute” predictors wherein the modeling errors affect the predictions in steady state.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a method and system for determining cylinder air-charge one or more engine events into the future utilizing a method that does not affect predictions in steady state.
It is yet another object of the present invention to provide a method and system for determining future cylinder air-charge based on a predicted behavior of the engine.
In carrying out the above object and other objects, features, and advantages of the present invention, a method is provided for determining a future cylinder air charge for an internal combustion engine having a throttle plate for controlling the amount of air to be delivered to the engine and an intake manifold for receiving the air controlled by the throttle plate and for transferring the air into a cylinder. The method includes sensing a current position of the throttle plate, determining a future position of the throttle plate based on the sensed current position, determining a model governing a change in pressure of the intake manifold, and determining the future cylinder air charge based on the future position of the throttle plate and the model.
In further carrying out the above object and other objects, features, and advantages of the present invention, a system is also provided for carrying out the steps of the above described method. The system includes a throttle position sensor for sensing a current position of the throttle plate. The system also includes control logic operative to determine a future position of the throttle plate based on the sensed current position, determine a model governing a change in pressure of the intake manifold, and determine the future cylinder air charge based on the future position of the throttle plate and the model.
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Jankovic Mrdjan J.
Lewis Donald J.
Magner Stephen William
Suffredini Giuseppe D.
Ford Global Technologies Inc.
Lippa Allan J.
Wolfe Willis R.
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