Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2000-04-28
2001-08-21
Dolinar, Andrew M. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C123S305000
Reexamination Certificate
active
06278933
ABSTRACT:
TECHNICAL FIELD
The present invention relates to transient torque control systems and methods for direct injection spark ignition internal combustion engines.
BACKGROUND ART
Torque control systems for conventional port-injected engines are known in which the torque is generally adjusted by controlling ignition timing (spark), fuel quantity or timing, and/or airflow via the throttle plate. Because of the time delay associated with throttle-regulated airflow upstream of the cylinders, and because of the increased pumping losses associated with a throttled airflow, this parameter is generally undesirable or unsuitable for transient torque control. Spark is typically preferred for transient torque control because the engine output torque responds very quickly to changes in spark timing. Furthermore, spark has a broad range of authority over output torque, i.e. spark can be used to rapidly vary output torque to nearly zero, if desired. However, any departure of spark timing from the spark timing that gives maximum torque for a given amount of air and fuel (MBT) may result in a fuel economy penalty.
Transient torque control of conventional engines, whether using spark, air, or fuel, requires consideration of the effect on tailpipe emissions and associated emission control devices. Where three-way catalysts are used, air/fuel ratio must be tightly controlled near the stoichiometric ratio to prevent premature reduction of the catalyst conversion efficiency. Likewise, proper emissions control is more easily achieved by maintaining appropriate catalyst operating temperatures.
Many of the transient torque control strategies used in conventional IC engines have been adapted for use in direct fuel-injected spark-ignition engines, otherwise known as DISI engines. While these strategies may provide acceptable performance for many applications, they do not take advantage of the potential for improved efficiency afforded by differences in operating principles for DISI engines, and in particular lean burn DISI engines. Furthermore, some conventional control strategies are not applicable to DISI engines due to the differences in operation. As such, it would be desirable to provide a system and method for rapid transient torque control of various DISI engine configurations and operating modes which may result in improved engine efficiency and fuel economy.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a system and method for transient torque control in a DISI engine using the fuel flow and/or air flow as transient torque actuators rather than spark.
In carrying out the above object and other objects, advantages, and features of the present invention, a system and method for transient torque control on a direct injection spark ignition internal combustion engine include determining a desired value for engine torque and air/fuel ratio based on current engine operating conditions. The system and method determine air flow bounds for currently available cylinder air flow based on current engine operating conditions and determine desired fuel flow and air flow values with minimum deviation from MBT spark timing to obtain the desired engine torque value and desired air/fuel ratio. The invention includes controlling at least one actuator without substantially altering spark timing to deliver the desired cylinder air flow if the desired cylinder air flow is less than the upper bound, and setting the desired cylinder air flow to the upper bound if the desired cylinder airflow exceeds the upper bound. When the upper bound is exceeded, the maximum airflow value is then used to determine an appropriate fuel flow based on the desired output torque and air/fuel ratio.
The methods and systems for transient torque control according to the present invention are particularly suited for DISI engines having variable valve timing or variable cam timing, but may be used in any throttled or unthrottled DISI engines, including lean burn DISI engines.
The present invention provides a number of advantages over prior art control strategies. For example, the present invention recognizes that for lean burn DISI engines, fuel as well as spark can be used for transient torque control since the restrictions on air/fuel ratio are reduced. In addition, for applications where variable control of the engine valves is possible, flue flow, air flow and spark have approximately equal response times for controlling engine output torque. Because moving spark away from MBT may result in fuel economy penalties, the present invention preferably uses fuel flow, and may use air flow if necessary, to provide transient torque control without substantially impacting ignition timing. The transient torque control may be used for speed control, such as idle speed control or cruise control by determining a desired torque to maintain a particular desired engine speed or vehicle speed.
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Buckland Julia Helen
Grizzle Jessy W.
Dolinar Andrew M.
Ford Global Technologies Inc.
Russell John D.
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