System and method for reducing NOx emissions after fuel cut-off events

• US 7,051,514 B2
• Filed: 07/27/2004
• Issued: 05/30/2006
• Est. Priority Date: 07/27/2004
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Midlam-Mohler, Shawn
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): EDWARDS, LOREN C
• Application Number:
  US10/710,650
• Publication Number:
  US 20060021326A1
• Time in Patent Office: 672 Days
• Field of Search: 602/78, 602/74, 602/85, 123/90.11
• US Class Current: 60/278
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 3/20 specially adapted for catalytic conversion F01N3/22 takes precedence; Methods of operation or control of catalytic converters
• CPC Class Codes: F02D 17/04 rendering engines inoperative or idling, e.g. caused by abnormal conditions dependent on lubricating conditions F01M1/22; dependent on cooling F01P5/14
• CPC Class Codes: F02D 41/0055 Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus
• CPC Class Codes: F02D 41/042 for stopping the engine
• CPC Class Codes: F02D 41/062 for starting F02D41/061 takes precedence
• CPC Class Codes: F02D 41/123 the fuel injection being cut-off
• CPC Class Codes: F02D 41/126 transitional corrections at the end of the cut-off period
• CPC Class Codes: F02M 25/08 adding fuel vapours drawn from engine fuel reservoir electrical control of purge system F02D41/003
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A method of controlling exhaust emission oxides of nitrogen (NOx) from an internal combustion engine (ICE) includes the steps of determining when an engine speed is below a first predetermined level, and controlling an oxygen displacement valve (ODV) such that at least a portion of exhaust gas generated by the ICE is directed into an intake air flow of the ICE.

Claims

1. A method of controlling exhaust emission oxides of nitrogen (NOx) from an internal combustion engine (ICE), the method comprising:

commanding an engine shutdown;

determining when an engine speed is below a first predetermined level after the engine shutdown is commanded; and

controlling an oxygen displacement valve (ODV) such that at least a portion of exhaust gas generated by the ICE is directed into an intake air flow of the ICE when it is determined that the engine speed is below the first predetermined level.

2. The method set forth in claim 1 wherein the engine shutdown is commanded during a deceleration operation of a conventional powertrain vehicle.

3. The method set forth in claim 1 further comprising fully closing an engine throttle to facilitate the engine shutdown.

4. The method set forth in claim 1 further comprising providing a rich air to fuel ratio (AFR) to the ICE for a first predetermined period of time after the engine shutdown is commanded.

5. The method set forth in claim 4 further comprising stopping delivery of fuel to the engine to facilitate the engine shutdown.

6. The method set forth in claim 1 further comprising:

commanding an engine restart; and

controlling the ODV valve such that no exhaust gas is directed into the intake air flow after the engine restart is commanded.

7. The method set forth in claim 6 further comprising spinning up the engine up to a starting speed.

8. The method set forth in claim 7 further comprising providing a rich AFR to the engine for a second predetermined period of time after the engine reaches the starting speed.

9. The method set forth in claim 8 wherein the rich AFR is provided by controlling an evaporative control valve such that at least a portion of fuel evaporative vapors are directed to the intake air flow.

10. The method set forth in claim 6 further comprising opening a throttle after the engine restart is commanded.

11. A system for controlling exhaust emission oxides of nitrogen (NOx) from an internal combustion engine (ICE), the system comprising:

sensors for determining operating conditions of the ICE; and

a controller configured to command an engine shutdown, determine when an engine speed is below a first predetermined level, and control an oxygen displacement valve (ODV) such that at least a portion of exhaust gas generated by the ICE is directed into an intake air flow of the ICE after an engine shutdown is commanded and the engine speed is below the first predetermined level.

12. The system set forth in claim 11 wherein the controller is configured to command an engine shutdown during a deceleration operation of a conventional powertrain vehicle.

13. The system set forth in claim 11 wherein the controller is further configured to fully close an engine throttle to facilitate an engine shutdown.

14. The system set forth in claim 11 wherein the controller is further configured to provide a rich air to fuel ratio (AFR) to the ICE for a first predetermined period of time after an engine shutdown is commanded.

15. The system set forth in claim 14 wherein the rich AFR is provided by controlling an evaporative control valve such that at least a portion of fuel evaporative vapors are directed to the intake air flow.

16. The system set forth in claim 14 wherein the controller is further configured to stop delivery of fuel to the engine to facilitate an engine shutdown.

17. The system set forth in claim 11 wherein the controller is further configured to command an engine restart, and to operate the ODV valve such that no exhaust gas is directed into the intake air flow when a decision is made to restart the engine after an engine restart is commanded.

18. The system set forth in claim 17 wherein the controller is further configured to control spinning up the engine up to a starting speed.

19. The system set forth in claim 18 wherein the controller is further configured to provide a rich AFR to the engine for a second predetermined period of time after the engine reaches the starting speed.

20. The system set forth in claim 17 wherein the controller is further configured to open a throttle after an engine restart is commanded.

21. A method of controlling exhaust emission oxides of nitrogen (NOx) from a variable valve internal combustion engine (ICE), the method comprising:

commanding an engine shutdown;

determining when an engine speed is below a first predetermined level after the engine shutdown is commanded; and

controlling the variable valves such that at least a portion of exhaust gas generated by the ICE is directed into an intake air flow of the ICE when it is determined that the engine speed is below the first predetermined level.

22. The method set forth in claim 21 further including the steps of:

commanding an ICE restart; and

controlling the variable valves such that no exhaust gas is directed into the intake air flow after the ICE is commanded to restart.