METHOD FOR DETERMINING SOOT MASS STORED WITH A PARTICULATE FILTER

• US 20120216507A1
• Filed: 02/28/2011
• Published: 08/30/2012
• Est. Priority Date: 02/28/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Nieuwstadt, Michiel J. Van
• Granted Patent: US 9,151,206 B2
• Time in Patent Office: Days
• US Class Current: 60/274
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2550/04 Filtering activity of particulate filters
• CPC Class Codes: F01N 2560/025 for measuring or detecting O2, e.g. lambda sensors
• CPC Class Codes: F01N 2560/14 having more than one sensor of one kind
• CPC Class Codes: F01N 2900/1606 Particle filter loading or soot amount
• CPC Class Codes: F01N 2900/1624 Catalyst oxygen storage capacity
• CPC Class Codes: F01N 3/101 Three-way catalysts
• CPC Class Codes: F02D 2200/0812 Particle filter loading
• CPC Class Codes: F02D 2200/0814 Oxygen storage amount
• CPC Class Codes: F02D 41/029 the exhaust gas treating apparatus being a particulate filter
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for determining soot mass oxidized during a particulate filter oxidation procedure is disclosed. In one example, soot mass is determined via an Arrhenius equation. The approach may provide cost savings and reliability improvements as compared to other ways of determining soot mass.

Claims

1. A method for operating a particulate filter, comprising:

estimating soot mass oxidized from a particulate filter via first and second oxygen sensors; and

indicating degradation of the particulate filter when a difference between the estimated soot mass oxidized from the particulate filter and a desired soot mass held in the particulate filter is greater than a threshold soot mass.

2. The method of claim 1, where the first oxygen sensor is positioned in an exhaust system upstream of the particulate filter, and where the second oxygen sensor is positioned downstream of the particulate filter in the exhaust system.

3. The method of claim 1, where the soot mass is estimated via an Arrhenius equation.

4. The method of claim 1, where the first oxygen sensor is located upstream of the particulate filter and where the second oxygen sensor is located downstream of the particulate filter and a three-way catalyst.

5. The method of claim 4, where the first and second oxygen sensors are linear oxygen sensors, and where the estimated soot mass oxidized from the particulate filter is based on the first oxygen sensor, the second oxygen sensor, and an oxygen storage estimate of the three-way catalyst.

6. The method of claim 1, where an output of at least one of the first and second oxygen sensors is compensated during a soot oxidation process of the particulate filter in response to a difference between output of the first oxygen sensor and output of the second oxygen sensor during a period of time when oxidation of soot within the particulate filter is not expected.

7. The method of claim 6, where compensation is provided to at least one of the first and second oxygen sensors via adding an offset to an output of the first or second oxygen sensor.

8. A method for operating a particulate filter, comprising:

adjusting a lean portion of an engine air-fuel ratio cycle in response to soot mass held within a particulate filter; and

indicating degradation of the particulate filter when a difference between an estimated soot mass oxidized from the particulate filter via first and second oxygen sensors, and a desired soot mass held in the particulate filter, is greater than a threshold soot mass.

9. The method of claim 8, where the lean portion of the engine air-fuel ratio cycle is further adjusted in response to an output of the second oxygen sensor, and where the second oxygen sensor is located downstream of the particulate filter.

10. The method of claim 9, where a three-way catalyst is positioned in an engine exhaust system downstream of the particulate filter and an engine, and where the engine is a spark ignition engine.

11. The method of claim 9, where the lean portion of the engine air-fuel ratio cycle is further leaned when an oxygen concentration output from the second oxygen sensor is less than expected.

12. The method of claim 9, where the lean portion of the engine air-fuel ratio cycle is enriched when and oxygen concentration output from the second oxygen sensor is higher than expected.

13. The method of claim 8, further comprising adjusting a duty cycle of the engine air-fuel ratio cycle in response to an output of the second oxygen sensor, the second oxygen sensor positioned in an exhaust system downstream of the particulate filter.

14. The method of claim 13, further comprising ceasing to estimate the soot mass oxidized from the particulate filter in response to the output of the second oxygen sensor.

15. A method for operating a particulate filter, comprising:

adjusting a lean portion of an engine air-fuel ratio cycle in response to soot mass held within a particulate filter;

initiating combustion of an air-fuel mixture in a cylinder of an engine via a spark, the air-fuel mixture derived from the air-fuel ratio cycle;

estimating soot mass oxidized from the particulate filter via first and second oxygen sensors; and

indicating degradation of the particulate filter when a difference between the estimated soot mass a desired soot mass is greater than a threshold soot mass.

16. The method of claim 15, where an output of at least one of the first and second oxygen sensors is compensated during a soot oxidation process of the particulate filter in response to a difference between an output of the first oxygen sensor and an output of the second oxygen sensor during a period of time when oxidation of soot within the particulate filter is not expected.

17. The method of claim 16, where compensation includes compensation for signal phase delay between the first and second oxygen sensors.

18. The method of claim 17, where compensation further includes compensation for an offset difference between the output of the first oxygen sensor and an output of the second oxygen sensor.

19. The method of claim 15, where a three-way catalyst is located in an exhaust system of an engine downstream of the particulate filter.

20. The method of claim 15, further comprising where the engine air-fuel ratio cycle is adjusted to provide on average a substantially stoichiometric mixture of exhaust gases exiting the particulate filter.