Internal-combustion engines – Engine speed regulator – Open loop condition responsive
Reexamination Certificate
1999-10-18
2001-02-06
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Open loop condition responsive
C123S090150, C123S090170, C123S478000, C123S568210
Reexamination Certificate
active
06182636
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention relates to engine speed control in lean burn internal combustion engines.
BACKGROUND OF THE INVENTION
In direct injection spark ignition engines, fuel is injected directly into an engine cylinder. Since the fuel is injected directly into the cylinder, it is possible to rapidly adjust engine torque. Such ability is advantageous for performing engine speed control, especially during idle operation. For example, sudden loading from ancillary devices such as the power steering pump, can be quickly compensated by adjusting fuel injection amount into the cylinder.
In direct injection spark ignition engines, ignition timing is generally tightly coupled to fuel injection timing. Therefore, prior approaches using ignition timing to control engine speed are not applicable. Also, when operating in a lean air/fuel mode, where the throttle is generally mostly open to reduce engine pumping work, the range of air/fuel ratios is limited by emission constraints or engine operability limits. For example, during stratified operation at idle conditions, there is a minimum air/fuel ratio limit due to emission constraints. Similarly, there is a maximum air/fuel ratio limit due to combustion stability limits. Since the engine is unthrottled, giving a relatively fixed airflow, idle speed control using only fuel injection amount has a disadvantage in that the range of control authority is limited.
Given limits of air/fuel operation, the throttle may be adjusted thereby moving the air/fuel ratio limits, giving more control authority to the fuel injection amount. However, this method suffers from the disadvantage that adjustments in the throttle cannot quickly change the cylinder air charge amount. Controlling flow entering the manifold cannot rapidly control cylinder charge due to manifold volume. For example, if the throttle is instantly closed, cylinder air charge does not instantly decrease to zero. The engine must pump down the air stored in the manifold, which takes a certain number of revolutions. Therefore, the cylinder air charge gradually decreases toward zero. Thus, by adjusting airflow entering the manifold to prevent air/fuel operation in undesirable air/fuel ranges, air/fuel operation will occur in the undesired ranges during a transient period.
SUMMARY OF THE INVENTION
An object of the present invention is to control engine speed to a desired engine speed while maintaining engine air/fuel ratio within desired limits.
The above object is achieved and disadvantages of prior approaches overcome by a method for controlling an engine having at least one cylinder, the engine also having an intake manifold and an outlet control device for controlling flow from the intake manifold into the cylinder and an inlet control device for controlling flow into the intake manifold, comprising: generating a fuel injection amount; and preventing an engine air/fuel ratio from entering a predetermined air/fuel ratio range by changing both the inlet control device and the outlet control device based on said fuel injection amount.
By changing both the outlet control device and the inlet control device, it is possible to rapidly change engine air charge so that the engine air/fuel ratio does not enter restricted regions. In other words, despite response delays from the manifold volume, it is possible to change engine air charge fast enough to compensate for rapid changes in fuel injection amount. Thus, even during transient conditions, engine operating is optimized by rapidly controlling engine air/fuel ratio.
An advantage of the above aspect of the invention is that greater range of authority can be given to fuel injection control.
Another advantage of the above aspect of the invention is improved idle speed control.
Yet another advantage of the above aspect of the invention is improved emissions.
In another aspect of the present invention, the above object is achieved and disadvantages of prior approaches overcome by a method for controlling an engine having at least one cylinder, the engine also having an intake manifold and an outlet control device for controlling flow from the intake manifold into the cylinder and an inlet control device for controlling flow into the intake manifold, comprising: generating a fuel injection amount; determining a restricted air amount range based on said fuel injection amount and a restricted air/fuel ratio range; and adjusting both the inlet control device and the outlet control device based on said restricted air amount range.
An advantage of the above aspect of the invention is that by determining the restricted air range based on the fuel injection amount, it is possible to prevent operating is restricted air/fuel ranges despite variation in operating engine load.
Other objects, features and advantages of the present invention will be readily appreciated by the reader of this specification.
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Kotwicki Allan Joseph
Russell John David
Argenbright Tony M.
Ford Global Technologies Inc.
Russell John D.
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