NOx feedback for combustion control

• US 9,038,611 B2
• Filed: 11/14/2011
• Issued: 05/26/2015
• Est. Priority Date: 11/14/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Lyon, Peter Mitchell, Riffle, Chris, Van Nieuwstadt, Michiel J., Korpics, Frank M., Reich, Jeff, Pennala, Dean
• Primary Examiner(s): Cronin, Stephen K
• Assistant Examiner(s): DALLO, JOSEPH J
• Application Number:
  US13/295,648
• Publication Number:
  US 20130118461A1
• Time in Patent Office: 1,289 Days
• Field of Search: 731/147.1, 731/147.4, 123/568.11, 123/681, 606/052, 606/11, 602/74, 602/76
• US Class Current: 123/568.11
• CPC Class Codes: F02B 2075/125 Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
• CPC Class Codes: F02B 37/007 with exhaust-driven pumps arranged in parallel , e.g. at least one pump supplying alternatively
• CPC Class Codes: F02D 13/0207 changing valve lift or valve lift and timing
• CPC Class Codes: F02D 13/0219 by shifting the phase, i.e. the opening periods of the valves are constant
• CPC Class Codes: F02D 21/08 the other gas being the exhaust gas of engine
• CPC Class Codes: F02D 2250/36 Control for minimising NOx emissions
• CPC Class Codes: F02D 41/0065 Specific aspects of external EGR control constructional details of EGR system F02M26/00
• CPC Class Codes: F02D 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1461 of the exhaust gases emitted by the engine
• CPC Class Codes: F02M 26/05 High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/06 Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor
• CPC Class Codes: F02M 26/08 for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor
• CPC Class Codes: F02M 26/15 in relation to engine exhaust purifying apparatus
• CPC Class Codes: F02M 26/24 with two or more coolers
• CPC Class Codes: F02M 26/38 with two or more EGR valves disposed in parallel
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for controlling combustion in an engine is provided. The method comprises under a first condition, adjusting an EGR amount of a total cylinder charge in response to engine out NOx levels being below a first threshold. In this way, NOx levels may be used as feedback to control combustion stability.

Claims

1. A method for controlling combustion in an engine, comprising:

under a first condition, decreasing an EGR amount of a total cylinder charge in response to engine out NOx levels being below a first threshold and increasing the EGR amount of the total cylinder charge in response to the engine out NOx levels being above a second threshold, the first threshold being lower than the second threshold; and

under a second condition, maintaining the EGR amount of the total cylinder charge even when NOx levels are below the first threshold.

2. The method of claim 1, wherein increasing the EGR amount of the total cylinder charge comprises adjusting an EGR valve to increase a percentage of EGR in the total cylinder charge.

3. The method of claim 1, wherein the first condition includes one or more of a reductant amount in an SCR system being above a first level and an efficiency of one or more emission control devices being above an efficiency threshold, and wherein the second condition includes one or more of the reductant amount being below the first level and the efficiency of the one or more emission control devices being below the efficiency threshold.

4. The method of claim 1, wherein decreasing the EGR amount of the total cylinder charge further comprises closing an EGR valve to decrease an EGR percentage of total cylinder charge.

5. The method of claim 4, further comprising opening an intake throttle concurrently with the EGR valve.

6. The method of claim 1, further comprising adjusting an EGR percentage of total cylinder charge based on engine speed and load.

7. The method of claim 1, further comprising adjusting one or more of a throttle and fuel injection timing in response to the engine out NOx levels being above the second threshold.

8. The method of claim 1, further comprising adjusting injection timing in response to the engine out NOx levels being below the first threshold.

9. A system comprising:

an engine including at least one cylinder and an exhaust passage coupled to at least one emission control device;

an exhaust gas recirculation (EGR) system to divert a portion of exhaust from the engine to an air intake of the engine;

a NOx sensor arranged in the exhaust passage upstream of the at least one emission control device;

and a controller including instructions to;

decrease an EGR amount of a total cylinder charge in response to NOx levels in the exhaust being below a first threshold, the NOx levels determined by the NOx sensor;

increase the EGR amount of the total cylinder charge in response to the NOx levels in the exhaust being above a second threshold, the first threshold being lower than the second threshold; and

not decreasing the EGR amount of the total cylinder charge in response to NOx levels in the exhaust being below the first threshold when an amount of reductant for injection is low.

10. The system of claim 9, wherein the EGR system comprises a high pressure EGR system (HP-EGR) controlled by an HP-EGR valve and a low pressure EGR system (LP-EGR) controlled by an LP-EGR system.

11. The system of claim 10, wherein the controller includes instructions to decrease the EGR amount of total cylinder charge by adjusting the HP-EGR valve or the LP-EGR valve based on the NOx levels in the exhaust from the engine.

12. The system of claim 11, wherein the controller includes instructions to decrease the EGR amount of total cylinder charge by adjusting the HP-EGR valve under low load conditions, and decrease the EGR amount of total cylinder charge by adjusting the LP-EGR valve under medium to high load conditions.

13. The system of claim 9, wherein the controller includes instructions to increase the EGR amount of the total cylinder charge in response to NOx levels in the exhaust being above a second threshold, greater than the first threshold.

14. A method of reducing vehicle emissions, comprising:

under a first condition, delivering HP-EGR to one or more cylinders of an engine;

under a second condition, delivering LP-EGR to one or more cylinders of the engine; and

under both the first and second conditions,

decreasing an EGR amount of total cylinder charge in response to engine out NOx levels being below a first threshold;

increasing the EGR amount of total cylinder charge in response to engine out NOx levels being above a second threshold, higher than the first threshold; and

not decreasing the EGR amount of the total cylinder charge in response to NOx levels in the exhaust being below the first threshold when efficiency of an emissions control device is low.

15. The method of claim 14, wherein the first condition comprises medium to high engine load.

16. The method of claim 14, wherein the second condition comprises low engine load.

17. The method of claim 14, further comprising decreasing internal EGR when NOx levels are below the first threshold by adjusting one or more of intake and exhaust valve timing.

18. The method of claim 14, further comprising opening an intake throttle when NOx levels are below the first threshold.

19. The method of claim 14, further comprising adjusting fuel injection timing when NOx levels are below the first threshold.