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

Patent metadata

Field	Value
Publication number	US-2016333809-A1
Application number	US-201514712202-A
Country	US
Kind code	A1
Filing date	May 14, 2015
Priority date	May 14, 2015
Publication date	Nov 17, 2016
Grant date	—

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

1 . A method, comprising:
during a deceleration fuel shut-off (DFSO) event where all cylinders of an engine are deactivated, selectively sequentially combusting air and fuel in cylinders of a cylinder group in the engine, each cylinder fueled via a fuel pulse width, and adjusting fuel injected to one or more cylinders in the cylinder group in response to variation of engine torque from an expected engine torque during the DFSO event.

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

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 fueling of the cylinder group upon which the variation of engine torque is based occurs only after the maximum lean air-fuel ratio is measured during the DFSO.

5 . The method of claim 2 , where adjusting subsequent engine operation includes adjusting a fuel injector pulse width in response to an expected engine torque deviation.

6 . The method of claim 5 , where an expected air-fuel ratio deviation is based on a selected fuel pulse width.

7 . The method of claim 2 , where adjusting subsequent engine operation includes adjusting subsequent fuel injections to a cylinder based on the indicated engine torque variation following termination of the DFSO.

8 . 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 producing a plurality of engine torque responses that are together used to identify the imbalance.

9 . A method, comprising:
after disabling all cylinders leading to a substantially common exhaust gas output of an engine, individually fueling one or more of the disabled cylinders to combust a lean air-fuel mixture; and adjusting fuel injected to at least one cylinder in response to a variation of engine torque from a base engine torque produced via the lean air-fuel mixture, the base engine torque compensated for vehicle dynamics.

10 . The method of claim 9 , where vehicle dynamics include vehicle mass.

11 . The method of claim 9 , where vehicle dynamics include road grade.

12 . The method of claim 9 , where vehicle dynamics include present active transmission gear.

13 . The method of claim 9 , further comprising not determining variation of cylinder torque from the base cylinder torque in response to a request to change a transmission gear.

14 . The method of claim 9 , where the substantially common exhaust gas output is air, and where the lean air-fuel ratio is a predetermined air-fuel ratio from a lean air-fuel ratio combustion stability limit.

15 . The method of claim 9 , further comprising increasing an amount of fuel injected to the at least one cylinder in response to less than a desired amount of torque being produced by the cylinder.

16 . A method, comprising:
after disabling all cylinders leading to a substantially common exhaust gas output of an engine, 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 adjusting fuel injected to at least one cylinder in response to a variation of engine torque from a base engine torque produced by the lean air-fuel mixture.

17 . The method of claim 16 , where the driveline zero torque point is based on torque converter impeller speed and torque converter turbine speed.

18 . The method of claim 16 , where the variation of engine torque is a difference between a desired engine torque and an actual engine torque.

19 . The method of claim 16 , further comprising reactivating all engine cylinders in response to a driver demand.

20 . The method of claim 16 , 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

• F02D41/0087

  Selective cylinder activation, i.e. partial cylinder operation (deceleration cut-off F02D41/123) · CPC title

• F02D41/1454

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

• F02D41/247

  Behaviour for small quantities · CPC title

• F02D41/0085

  Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio · CPC title

• F02D41/042 Primary

  for stopping the engine · CPC title