Degradation detection method for an engine having a NOx sensor

• US 7,059,112 B2
• Filed: 04/09/2004
• Issued: 06/13/2006
• Est. Priority Date: 03/17/2000
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Surnilla, Gopichandra, Bidner, David Karl
• Primary Examiner(s): NGUYEN, TU MINH
• Application Number:
  US10/822,111
• Publication Number:
  US 20040187482A1
• Time in Patent Office: 795 Days
• Field of Search: 602/74, 602/76, 602/85, 602/86, 602/77, 204/424, 204/425, 73/232.1, 73/233.1, 73/233.2
• US Class Current: 60/277
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 3/0807 by using absorbents or adsorbents
• CPC Class Codes: F01N 3/0885 Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
• CPC Class Codes: F02D 2041/389 for injecting directly into the cylinder
• CPC Class Codes: F02D 2200/023 Temperature of lubricating oil or working fluid
• CPC Class Codes: F02D 2200/0802 Temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 2200/0806 NOx storage amount, i.e. amount of NOx stored on NOx trap
• CPC Class Codes: F02D 2200/0808 NOx storage capacity, i.e. maximum amount of NOx that can be stored on NOx trap
• CPC Class Codes: F02D 2200/0811 NOx storage efficiency
• CPC Class Codes: F02D 2200/703 Atmospheric pressure
• CPC Class Codes: F02D 41/028 Desulfurisation of NOx traps or adsorbent
• CPC Class Codes: F02D 41/1446 the characteristics being exhaust temperatures
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/1465 with determination means using an estimation
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02D 41/22 Safety or indicating devices for abnormal conditions in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An engine diagnostic system for use with an internal combustion engine coupled to a lean NOx trap with a NOx sensor coupled downstream of the trap. Degradation of the NOx sensor is determined by estimated NOx exiting the trap based on engine out NOx and various other operating conditions. When the difference between the measured NOx and estimated NOx is greater than a predetermined value for a predetermined duration, degradation is indicated.

Claims

1. An emission control system for an internal combustion engine, comprising:

a NOx absorbent disposed in an exhaust passage of the internal combustion engine that stores and reacts NOx under certain operating conditions;

a NOx sensor disposed in the exhaust passage downstream of the NOx absorbent, an output of the NOx sensor corresponding to a NOx concentration of exhaust gas flowing out of the NOx absorbent;

a controller calculating an operating condition of the internal combustion engine and determining a deviation of the output value of the NOx sensor from a predetermined value when preselected engine operating conditions are met;

an air-fuel ratio sensor disposed in the engine exhaust passage; and

said controller further indicating whether predetermined engine operating conditions are present, and in response to said determination, adjusting a fuel injection amount into the internal combustion engine based on said air-fuel ratio sensor, wherein said controller further adjusts said fuel injection amount into the internal combustion engine independent of said air-fuel ratio sensor when said controller indicates said predetermined engine operating conditions are not present.

2. The system recited in claim 1 further comprising a three-way catalyst disposed in said engine exhaust passage upstream of the NOx absorbent.

3. The system recited in claim 1 wherein said controller further changes engine operation from a lean air-fuel ratio to a stoichiometric or rich air-fuel ratio based on said output of the NOx sensor.

4. An emission control system for an internal combustion engine, comprising:

a NOx absorbent disposed in an exhaust passage of the internal combustion engine that stores and reacts NOx under certain operating conditions;

a NOx sensor disposed in the exhaust passage downstream of the NOx absorbent, an output of the NOx sensor corresponding to a NOx concentration of exhaust gas flowing out of the NOx absorbent;

a controller calculating an operating condition of the internal combustion engine and determining a difference of the output value of the NOx sensor from a predetermined value when preselected engine operating conditions are met at least during stoichiometric operating conditions, and determining degradation of said NOx sensor based on said difference determined during said preselected conditions; and

said controller further performing a sulfur decontamination process based on engine operating conditions and in response to said NOx sensor, said controller further adjusting an air-fuel ratio of the engine in response to said NOx sensor.

5. The system recited in claim 4 further comprising a three-way catalyst disposed in said engine exhaust passage upstream of the NOx absorbent.

6. The system recited in claim 4 further comprising an air-fuel ratio sensor disposed in the exhaust passage of the engine upstream of the NOx absorbent.

7. The system recited in claim 4 wherein said controller further changes engine operation from a lean air-fuel ratio to a stoichiometric or rich air-fuel ratio based on said output of the NOx sensor.