Method and system for determining air-fuel ratio imbalance via engine torque

Patent metadata

Field	Value
Publication number	US-9759148-B2
Application number	US-201514712202-A
Country	US
Kind code	B2
Filing date	May 14, 2015
Priority date	May 14, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Methods and systems are presented for assessing the presence or absence of engine torque deviation which may indicate air-fuel ratio imbalance between engine cylinders. In one example, the method may include assessing the presence or absence of engine torque variation based on engine torque deviation from a desired engine torque during a deceleration fuel shut-off event.

First claim

The invention claimed is:

1. A method, comprising:
during a deceleration fuel shut-off (DFSO) event where all engine cylinders are deactivated, selectively sequentially fueling and combusting air and fuel in cylinders of a cylinder group in an engine, and
after termination of the DFSO event, adjusting fuel injected to one or more cylinders in the cylinder group in response to a difference between an engine torque measured during the DFSO event and an expected engine torque.

2. The method of claim 1 , further comprising adjusting subsequent engine operation based on the difference.

3. The method of claim 2 , where the cylinder group is selected based on one or more of a firing order and a cylinder position within the firing order.

4. The method of claim 2 , where the fueling of the cylinder group occurs only after a maximum lean air-fuel ratio is measured during the DFSO event.

5. The method of claim 2 , where adjusting subsequent engine operation includes adjusting a fuel injector pulse width in response to the difference.

6. The method of claim 1 , where the cylinder group is fueled and operated to perform a combustion cycle a plurality of times during the DFSO event, producing a plurality of engine torque responses that are together used to identify an imbalance.

7. A method for an engine-driven vehicle, comprising:
after disabling all cylinders of an engine during a deceleration fuel shut-off (DFSO) event, in response to an air-fuel ratio of an exhaust gas output of the engine reaching a maximum lean air-fuel ratio, individually fueling one or more of the disabled cylinders to combust a lean air-fuel mixture; and
after termination of the DFSO event, adjusting fuel injected to at least one of the individually fueled cylinders in response to a variation of engine torque produced via the combustion of the lean air-fuel mixture during the DFSO event from a base engine torque produced by the lean air-fuel mixture.

8. The method of claim 7 , where the base engine torque is compensated for vehicle mass.

9. The method of claim 7 , where the base engine torque is compensated for a grade of a road on which the vehicle is traveling.

10. The method of claim 7 , where the base engine torque is compensated for a present active transmission gear.

11. The method of claim 7 , further comprising not determining variation of engine torque from the base engine torque in response to a request to change a transmission gear.

12. The method of claim 7 , where the lean air-fuel mixture is a predetermined air-fuel ratio from a lean air-fuel ratio combustion stability limit.

13. The method of claim 7 , further comprising increasing an amount of fuel injected to the at least one of the individually fueled cylinders in response to less than a desired amount of torque being produced by the cylinder.

14. A method, comprising:
after disabling all cylinders of an engine during a deceleration fuel shut-off (DFSO) event, in response to an air-fuel ratio of an exhaust gas output of the engine reaching a maximum lean air-fuel ratio, delaying individually fueling one or more of the disabled cylinders to combust a lean air-fuel mixture in response to a driveline zero torque point; and
after termination of the DFSO event, adjusting fuel injected to at least one of the individually fueled cylinders in response to a variation of engine torque produced by the combustion of the lean air-fuel mixture during the DFSO event from a base engine torque produced by the lean air-fuel mixture.

15. The method of claim 14 , where the driveline zero torque point is based on torque converter impeller speed and torque converter turbine speed.

16. The method of claim 14 , further comprising reactivating all engine cylinders in response to force applied to an accelerator pedal.

17. The method of claim 14 , where all cylinders are disabled responsive to an engine load less than a threshold.

Assignees

• Ford Global Tech Llc

Inventors

• Jammoussi Hassene
• Makki Imad Hassan
• Kluzner Michael Igor
• Jentz Robert Roy

Classifications

• F02D41/247

  Behaviour for small quantities · CPC title

• F02D41/1497

  With detection of the mechanical response of the engine · CPC title

• F02D41/1454

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title

• F02D41/123 Primary

  the fuel injection being cut-off · CPC title

• F02D41/042 Primary

  for stopping the engine · CPC title