Internal-combustion engines – Engine speed regulator – Idle speed control
Reexamination Certificate
1999-09-23
2001-01-23
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Idle speed control
C123S339220
Reexamination Certificate
active
06176218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally pertains to an engine control system for governing the idle of an internal combustion engine. More particularly, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, the present invention relates to a stabilizing system used in conjunction with a torque based idle control system.
2. Discussion
The motor vehicle is an increasingly complicated, dynamically changing machine. In order to maximize performance and increase component durability, it is desirable to have the capability of controlling an engine to produce a specific engine flywheel torque. To accomplish this task, an accurate estimate of the engine's internal frictional loss must be calculated. In a torque based idle control system, the engine friction characterization is one of the primary requesters of torque. Because the engine friction estimate is a function of engine rotational speed and intake manifold pressure, small fluctuations in either component may cause similar fluctuations in the frictional loss estimate. Accordingly, an unstable idle may result due to the fluctuating, “noisy”, estimate of the torque required to overcome friction.
During idle conditions, the driver's flywheel torque request is theoretically constant. Therefore, the desired torque during unloaded idle is equal to the friction torque estimate plus an idle control torque. The idle control torque is the additional torque required to idle the engine as determined by the idle speed control module. Instabilities can occur at idle because both the friction torque estimate and the idle control torque request vary with changes in engine speed and intake manifold pressure. De-coupling the friction torque estimate and the idle control torque requests at idle will allow for better idle control, especially in small displacement engines, resulting in greater customer satisfaction.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a stabilizing function for a torque based idle control system.
It is another object of the present invention to provide a system using actual engine speed during normal driving conditions and a target idle speed when the engine is unloaded at idle.
It is yet another object of the present invention to provide a smooth transition when switching between the torque based idle control algorithms and the non-idle control systems.
The present invention relates to a method for stabilizing the idle of an engine for a motor vehicle. The method includes measuring an engine rotational speed, modifying the engine rotational speed to define a friction engine speed, estimating a mechanical friction loss as a function of the friction engine speed, defining a torque request as a function of the mechanical friction loss and utilizing the torque request to control the engine at idle.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from a reading of the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.
REFERENCES:
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Beechie Brian E.
Ohl Gregory L.
Prucka Michael J.
Yip James W.
Argenbright Tony M.
Calcaterra Mark P.
DaimlerChrysler Corporation
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