United States Patent
US Patent 5704339: method and apparatus for improving vehicle fuel…
US 5704339 · granted 1998-01-06
| Patent Number | 5704339 |
|---|---|
| Title | method and apparatus for improving vehicle fuel economy |
| Filed | 1996-04-26 |
| Granted | 1998-01-06 |
| Inventor(s) | Carole Marie Choe, Robert Matthew Marzonie, Michael John Cullen |
| Assignee | Ford Global Technologies LLC |
| CPC Classification | F01N3/0828, F01N3/0842, F01N3/0807 |
| Number of Claims | 5 |
Abstract
A managed fuel air control system is provided that transitions between a closed loop stoichiometric A/F mode and an open loop lean A/F mode of operation. When conditions permit open loop lean operation, the engine A/F is ramped from stoichiometric to the desired lean A/F. Periodically, while operating in the open loop lean mode, the system returns to the closed loop stoichiometric mode to update an open loop correction factor used during the open loop lean mode. The time at stoichiometric is usually limited to the time it takes to correct errors in calibration data that have occurred during open loop operation. During lean operation, the adaptive corrections learned at stoichiometric A/F are applied.
Claims Summary
1. A method of controlling the air/fuel ratio of an internal combustion engine comprising a sequence of the following steps:detecting, while in a closed loop fuel control mode, whether the air/fuel ratio of the engine is rich or lean with respect to a stoichiometric ratio and modifying a short term fuel correction factor as necessary to achieve said stoichiometric ratio,