Method and apparatus for optimizing purge fuel for purging emissions control device

• US 6,438,944 B1
• Filed: 03/17/2000
• Issued: 08/27/2002
• Est. Priority Date: 03/17/2000
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Surnilla, Gopichandra, Bidner, David Karl
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): NGUYEN, TU MINH
• Application Number:
  US09/528,809
• Time in Patent Office: 893 Days
• Field of Search: 602/74, 602/76, 602/77, 602/85, 602/86, 603/01
• US Class Current: 60/274
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F02D 2200/0814 Oxygen storage amount
• CPC Class Codes: F02D 2200/0816 Oxygen storage capacity
• CPC Class Codes: F02D 2250/36 Control for minimising NOx emissions
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/1462 with determination means using an estimation

Abstract

A method and apparatus for controlling the operation of a “lean-burn” internal combustion engine in cooperation with an exhaust gas purification system having an emissions control device capable of alternatively storing and releasing NO_x when exposed to exhaust gases that are lean and rich of stoichiometry, respectively, determines a performance impact, such as a fuel-economy benefit, of operating the engine at a selected lean or rich operating condition. The method and apparatus then enable the selected operating condition as long as such enabled operation provides further performance benefits.

Claims

1. A controller for controlling an engine operating in combination with an emissions control device that releases a previously-stored first exhaust gas constituent when the engine is operated at a rich operating condition for a predetermined duration, wherein the controller is arranged to determine a value related at least in part to the presence of a second exhaust gas constituent in the exhaust gas downstream of the device upon discontinuance of the rich operating condition,

the controller being further arranged to calculate the difference, if any, by which the determined value exceeds a reference value approximating a stoichiometric air-fuel ratio;

to accumulate the difference until the determined value is substantially equal to the reference value; and

to adjust the duration of the rich engine operating condition based upon the accumulated difference, and to reduce the duration until the accumulated difference is less than a predetermined threshold value.

2. The controller of claim 1, wherein the controller is further arranged to determine the value of the first exhaust gas constituent by sampling the output signal generated by a first sensor having a sensitivity to the second exhaust gas constituent.

3. A method for controlling the operation of an internal combustion engine in a motor vehicle, wherein the engine generates exhaust gas including at least a first and a second exhaust gas constituent, and wherein exhaust gas is directed through an emissions control device before being exhausted to the atmosphere, the device storing at least the first exhaust gas constituent when the exhaust gas directed through the device is lean of stoichiometry and releasing previously-stored first exhaust gas constituent when the exhaust gas directed through the device is rich of stoichiometry, the method comprising:

upon discontinuance of a rich engine operating condition of a predetermined duration, determining a value related at least in part to the presence of the second exhaust gas constituent in the exhaust gas downstream of the device;

calculating the difference, if any, by which the determined value exceeds a reference value;

accumulating the difference until the determined value is substantially equal to the reference value; and

adjusting the duration of the rich engine operating condition based upon the accumulated difference, wherein adjusting includes reducing the duration until the accumulated difference is less than a predetermined threshold value.

4. A method for controlling the operation of an internal combustion engine in a motor vehicle, wherein the engine generates exhaust gas including at least a first and a second exhaust gas constituent, and wherein exhaust gas is directed through an emissions control device before being exhausted to the atmosphere, the device storing at least the first exhaust gas constituent when the exhaust gas directed through the device is lean of stoichiometry and releasing previously-stored first exhaust gas constituent when the exhaust gas directed through the device is rich of stoichiometry, the method comprising:

upon discontinuance of a rich engine operating condition of a predetermined duration, determining a value related at least in part to the presence of the second exhaust gas constituent in the exhaust gas downstream of the device;

calculating the difference, if an, by which the determined value exceeds a stoichiometric value value;

accumulating the difference until the determined value is substantially equal to the stoichiomerric value; and

adjusting the duration of the rich engine operating condition based upon the accumulated difference, wherein adjusting includes reducing the duration until the accumulated difference is less than a predetermined threshold value.