Dual hego method for identification and mitigation of air-fuel imbalance faults

Patent metadata

Field	Value
Publication number	US-2016018291-A1
Application number	US-201414334375-A
Country	US
Kind code	A1
Filing date	Jul 17, 2014
Priority date	Jul 17, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

Systems and methods for identifying and mitigating air-fuel imbalance faults specific to an engine cylinder are provided. In one embodiment, a method comprises indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst. In this way, an air-fuel imbalance fault may be accurately detected in a non-uniform exhaust flow so that mitigating actions can be taken, resulting in reduced tailpipe emissions.

First claim

1 . A method, comprising:
indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst.

2 . The method of claim 1 , wherein comparing time-aligned readings from exhaust gas oxygen sensors comprises computing a ratio of the time-aligned readings from exhaust gas oxygen sensors.

3 . The method of claim 2 , wherein the cylinder imbalance is indicated when the ratio is outside a threshold range centered at one.

4 . The method of claim 3 , wherein the threshold range is based on an exhaust gas oxygen sensor setpoint.

5 . The method of claim 1 , wherein comparing time-aligned readings from exhaust gas oxygen sensors comprises computing a difference of the time-aligned readings from exhaust gas oxygen sensors.

6 . The method of claim 5 , wherein the cylinder imbalance is indicated when the difference is outside a threshold range centered at zero.

7 . The method of claim 6 , wherein the threshold range is based on an exhaust gas oxygen sensor setpoint.

8 . The method of claim 1 , wherein the exhaust gas oxygen sensors comprise two heated exhaust gas oxygen sensors.

9 . A method, comprising:
indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst; and selecting one of the exhaust gas oxygen sensors to use for outer loop control.

10 . The method of claim 9 , wherein comparing time-aligned readings from exhaust gas oxygen sensors comprises computing a ratio of the time-aligned readings from exhaust gas oxygen sensors.

11 . The method of claim 10 , wherein selecting one of the exhaust gas oxygen sensors comprises selecting a first sensor of the exhaust gas oxygen sensors responsive to the ratio above a threshold range.

12 . The method of claim 10 , wherein selecting one of the exhaust gas oxygen sensors comprises selecting a second sensor of the exhaust gas oxygen sensors responsive to the ratio below a threshold range.

13 . The method of claim 9 , wherein comparing time-aligned readings from exhaust gas oxygen sensors comprises computing a difference of the time-aligned readings from exhaust gas oxygen sensors.

14 . The method of claim 13 , wherein selecting one of the exhaust gas oxygen sensors comprises selecting a first sensor of the exhaust gas oxygen sensors responsive to the difference above a threshold range.

15 . The method of claim 13 , wherein selecting one of the exhaust gas oxygen sensors comprises selecting a second sensor of the exhaust gas oxygen sensors responsive to the difference below a threshold range.

16 . A method, comprising:
indicating a cylinder imbalance by comparing time-aligned readings from exhaust gas oxygen sensors, the exhaust gas oxygen sensors positioned symmetrically opposite each other within an exhaust passage downstream of a catalyst; selecting one of the exhaust gas oxygen sensors for outer loop control; and adjusting fuel sequentially to individual cylinders to indicate which cylinder is imbalanced.

17 . The method of claim 16 , wherein comparing the time-aligned readings from the exhaust gas oxygen sensors is continuous and instantaneous.

18 . The method of claim 16 , wherein adjusting fuel sequentially to individual cylinders to indicate which cylinder is imbalanced comprises:
adjusting a fuel pulse width based on the selected exhaust gas oxygen sensor; and sequentially commanding the adjusted fuel pulse width to individual cylinders until comparing the time-aligned readings from the exhaust gas oxygen sensors no longer indicates the cylinder imbalance.

19 . The method of claim 18 , wherein adjusting the fuel pulse width based on the selected exhaust gas oxygen sensor is further based on the individual cylinders.

20 . The method of claim 18 , further comprising assigning a fault to the imbalanced cylinder.

Assignees

• Ford Global Tech Llc

Inventors

• Uhrich Michael James
• Santillo Mario Anthony
• Magner Stephen William
• Jankovic Mrdjan J

Classifications

• G01M15/104 Primary

  using oxygen or lambda-sensors (testing catalytic converters F01N3/18, F01N11/007) · CPC title

• F01N11/007 Primary

  the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus · CPC title

• F01N2550/02

  Catalytic activity of catalytic converters · CPC title

• F01N13/008

  Mounting or arrangement of exhaust sensors in or on exhaust apparatus (sensor arrangements for engine control F02D41/1439) · CPC title

• G01M1/14

  Determining imbalance (G01M1/30 takes precedence) · CPC title