Method for air-fuel ratio sensor diagnosis

• US 6,736,121 B2
• Filed: 06/04/2002
• Issued: 05/18/2004
• Est. Priority Date: 06/04/2002
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Gopichandra, Surnilla
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US10/064,021
• Publication Number:
  US 20030221682A1
• Time in Patent Office: 714 Days
• Field of Search: 123/443, 123/481, 123/688, 123/691, 123/692, 73/233.1, 73/233.2, 731/16, 731/181, 204/401, 701/109
• US Class Current: 123/688
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/011 having two or more purifying devices arranged in parallel
• CPC Class Codes: F01N 13/107 More than one exhaust manifold or exhaust collector
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F02D 2200/0404 Throttle position
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/003 Adding fuel vapours, e.g. drawn from engine fuel reservoir
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/064 at cold start F02D41/067 takes precedence
• CPC Class Codes: F02D 41/1443 with one sensor per cylinder or group of cylinders
• CPC Class Codes: F02D 41/1446 the characteristics being exhaust temperatures
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/1465 with determination means using an estimation
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system
• 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: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: F02P 5/1506 with particular means during starting

Abstract

A method is disclosed for controlling operation of an engine coupled to an exhaust treatment catalyst. Under predetermined conditions, such as after an engine cold start, the method operates an engine with a first group of cylinders having a first ignition timing, and a second group of cylinders having a second ignition timing more retarded than the first group. In addition, the engine control method also provides the following features in combination with the above-described split air/lean mode: idle speed control, sensor diagnostics, air/fuel ratio control, adaptive learning, fuel vapor purging, catalyst temperature estimation, default operation, and exhaust gas and emission control device temperature control. In addition, the engine control method also can change to combusting all cylinders at substantially the same ignition timing under preselected operating conditions such as fuel vapor purging, manifold vacuum control, and purging of stored oxidants in an emission control device.

Claims

1. A system, comprising:

an engine having a first group of cylinders and a second group of cylinders;

a sensor coupled at least to said first group of cylinders in an engine exhaust;

a controller for operating said first group with air and substantially no injected fuel, operating said second group with air and injected fuel, reading an output of said sensor, and determining degradation of said sensor based on said reading.

2. The system recited in claim 1 wherein said controller operates said second group in each of the following modes:

lean of stoichiometry and substantially at stoichiometry.

3. The system recited in claim 1 wherein said controller adjusts said injected fuel based on said sensor reading.

4. The system recited in claim 1 wherein said sensor is an exhaust gas oxygen sensor and said sensor is coupled only to said first group.

5. The system recited in claim 1 wherein said controller determines degradation when said sensor reading is other then lean of stoichiometry.

6. The system recited in claim 1 wherein said controller transitions the engine to operate with injected fuel in both said first and second cylinder groups.

7. A method for controlling an engine having a first and second group of combustion chambers, comprising:

determining whether a sensor coupled in an exhaust path of the engine is exposed to a mixture comprising a first stream of air and no fuel and a second stream of combusted air and fuel;

determining whether the sensor is exposed to only said stream of air and not fuel;

determining degradation of the sensor based on a first method in response to said determining that the sensor is exposed to said mixture of said first and second stream; and

determining degradation of the sensor based on a second method in response to said determination that the sensor is exposed to said stream of air and not fuel.

8. The method recited in claim 7 wherein said sensor is an exhaust gas oxygen sensor.

9. The method recited in claim 7 wherein said second method determines whether said sensor indicates lean of stoichiometry.

10. A method for controlling an engine having a first and second group of combustion chambers, comprising:

determining whether a sensor coupled in an exhaust path of the engine is exposed to a mixture comprising a first stream of air and no fuel and a second stream of combusted air and fuel;

determining whether the sensor is exposed to only said stream of air and not fuel;

determining degradation of the sensor based on a first method in response to said determining that the sensor is exposed to said mixture of said first and second stream; and

determining degradation of the sensor based on a second method in response to said determination that the sensor is exposed to said stream of air and not fuel.