Monitor for lean capable engine

Details Monitor for lean capable engine Monitor for lean capable engine

2000-03-06

2001-10-23

Yuen, Henry C. (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Combustible mixture stratification means

C123S430000

Reexamination Certificate

active

06305347

ABSTRACT:

FIELD OF THE INVENTION
The field of the invention relates to monitoring of electronically controlled drive units in vehicles.
BACKGROUND OF THE INVENTION
In some engines, an electronically controlled throttle is used for improved performance. In addition, engines may also be controlled using engine output, or torque control where the actual engine torque is controlled to a desired engine torque through an output adjusting device, such as with the electronic throttle, ignition timing, air-fuel ratio, or various other devices.
Also, engines using torque control and electronic throttles may also operate lean of stoichiometry to improve engine thermal efficiency and increase vehicle fuel economy. In these systems, the engine is operated lean of stoichiometry and relatively unthrottled, thereby decreasing engine pumping work and further increasing fuel efficiency. To increase the range of lean operation, direct injection can be used where fuel is injected directly into the engine.
Engines can also operate rich of stoichiometry. For example, rich operation may be required to purge stored emissions or to provide additional engine torque, as well as during various other situations.
One method to monitor engine control systems determines if actual engine torque is greater than desired engine torque. Actual engine torque is determined in accordance with engine airflow and/or injected fuel amount, and various other factors. Such a method is described in U.S. Pat. No. 5,692,472.
The inventors herein have recognized a disadvantage of the above approach. In particular, when such a method is utilized with engines that operate both lean of stoichiometry and rich of stoichiometry, differing torque estimates are produced depending on the operating state. Stated another way, when lean, engine torque determined from airflow is greater than engine torque determined from fuel injection amount. Similarly, when rich, engine torque determined from fuel injection amount is greater than engine torque determined from airflow. As such, engine torque may be over-estimated in one operating condition or another. Such over-estimation may degrade monitoring performance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide methods for monitoring powertrains capable of operating rich of stoichiometry, near stoichiometry, and lean of stoichiometry.
The above object is achieved and disadvantages of prior approaches overcome by a method for monitoring a vehicle powertrain having an engine inducting air and fuel, the method comprising: determining a preselected powertrain output; calculating an actual powertrain output based on air when the powertrain is operating rich of stoichiometry; calculating said actual powertrain output based on fuel when the powertrain is operating lean of stoichiometry; and initiating a reaction when said actual powertrain output is greater than said preselected powertrain output.
By calculating powertrain output based on air when rich of stoichiometry and based on fuel when lean of stoichiometry, it is possible to obtain an accurate and robust estimate of powertrain output. In particular, in either lean or rich conditions, a relatively few number of parameters need be considered. Stated another way, excess parameters to modify estimates are minimized and robustness is achieved concurrently.
An advantage of the above aspect of the invention is improved monitoring.
Another advantage of the above aspect of the invention is that over-estimation can be minimized.
In another aspect of the present invention, the above object is achieved and disadvantages of prior approaches overcome by a monitoring system comprising: a powertrain having an engine inducting air and fuel, wherein said engine is a direct injection engine capable of operating both in a stratified and a homogeneous mode, said engine also capable of operating rich of stoichiometry, lean of stoichiometry, and substantially near stoichiometry; a powertrain monitor for monitoring an engine control system, said monitor determining a preselected powertrain torque, calculating an actual powertrain torque based on first and second independent signals indicative of air when said powertrain is operating rich of stoichiometry, calculating said actual powertrain torque based on third and fourth independent signals indicative of fuel when said powertrain is operating lean of stoichiometry, and initiating a reaction when said actual powertrain torque is greater than said preselected powertrain torque.
An advantage the above aspect of the invention is improved estimation through improved monitoring. In particular, by providing two estimates of fuel from independent sources for lean conditions and two estimates of air from independent sources for rich conditions, over-estimation can be minimized while providing redundancy.


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patent: 6006717 (1999-12-01), Suzuki et al.
patent: 6014604 (2000-01-01), Kuroiwa et al.

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