Diagnosis of deterioration in air/fuel ratio sensor

• US 6,901,741 B2
• Filed: 01/27/2003
• Issued: 06/07/2005
• Est. Priority Date: 02/28/2002
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kobayashi, Hideaki, Kobayashi, Masato, Takatsuto, Rie
• Primary Examiner(s): NGUYEN, TU MINH
• Application Number:
  US10/351,356
• Publication Number:
  US 20030159432A1
• Time in Patent Office: 862 Days
• Field of Search: 602/74, 602/76, 602/77, 602/85, 73/233.1, 73/233.2, 731/181, 731/182, 123/198.F, 123/481, 123/479, 123/688, 701/109, 701/114
• US Class Current: 60/274
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 3/101 Three-way catalysts
• CPC Class Codes: F02D 2200/0814 Oxygen storage amount
• CPC Class Codes: F02D 41/0295 Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
• CPC Class Codes: F02D 41/123 the fuel injection being cut-off
• CPC Class Codes: F02D 41/1408 Dithering techniques
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

An air/fuel ratio sensor (4) and a three-way catalytic converter (3A) having an oxygen storage function are provided in an exhaust passage (2) of an internal combustion engine (1). A controller (6) runs the engine (1) under the alternating application of a stoichiometric air/fuel ratio and a rich air/fuel ratio, and a diagnosis of deterioration in the air/fuel ratio sensor (4) is performed on the basis of the amplitude of variation in the air/fuel ratio detected by the air/fuel ratio sensor (4). By executing the diagnosis only immediately after a fuel cut, the amount of oxygen stored in the three-way catalytic converter (3A) at the start point of the diagnosis is equal to the maximum amount. When the rich air/fuel ratio is applied, the converter (3A) releases the stored oxygen to maintain the exhaust gas purification performance of the converter (13).

Claims

1. A deterioration diagnosis method of an air/fuel ratio sensor for use with an internal combustion engine which burns an air/fuel mixture of fuel injected by an injector and air, and discharges combustion gas through an exhaust passage as exhaust gas, the engine comprising a catalytic converter provided in the exhaust passage and having an oxygen storage function, wherein the air/fuel ratio sensor is disposed in the exhaust passage upstream of the catalytic converter for detecting an air/fuel ratio of the air-fuel mixture, the deterioration diagnosis method comprising:

determining whether a fuel cut, during which fuel is not injected by the fuel injector while the engine is running, has been executed or not;

controlling a fuel injection amount of the fuel injector only immediately after an execution of a fuel cut to cause the engine to be operated under an alternating application of a rich air/fuel ratio and a non-rich air/fuel ratio; and

performing a diagnosis of deterioration in the air/fuel ratio sensor based on a variation in the air/fuel ratio detected by the air/fuel ratio sensor during the period in which the engine is operated under the alternating application of the rich air/fuel ratio and the non-rich air/fuel ratio.

2. A deterioration diagnosis device of an air/fuel ratio sensor for use with an internal combustion engine which burns an air/fuel mixture of fuel injected by an injector and air, and discharges combustion gas through an exhaust passage as exhaust gas, the engine comprising a catalytic converter provided in the exhaust passage and having an oxygen storage function, wherein the air/fuel ratio sensor is disposed in the exhaust passage upstream of the catalytic converter for detecting an air/fuel ratio of the air-fuel mixture, the deterioration diagnosis device comprising:

means for determining whether a fuel cut, during which fuel is not injected by the fuel injector while the engine is running, has been executed or not;

means for controlling a fuel injection amount of the fuel injector only immediately after an execution of a fuel cut to cause the engine to be operated under an alternating application of a rich air/fuel ratio and a non-rich air/fuel ratio; and

means for performing a diagnosis of deterioration in the air/fuel ratio sensor based on a variation in the air/fuel ratio detected by the air/fuel ratio sensor during the period in which the engine is operated under the alternating application of the rich air/fuel ratio and the non-rich air/fuel ratio.

3. A deterioration diagnosis device of an air/fuel ratio sensor for use with an internal combustion engine which burns an air/fuel mixture of fuel injected by an injector and air, and discharges combustion gas through an exhaust passage as exhaust gas, the engine comprising a catalytic converter provided in the exhaust passage and having an oxygen storage function, wherein the air/fuel ratio sensor is disposed in the exhaust passage upstream of the catalytic converter for detecting an air/fuel ratio of the air-fuel mixture, the deterioration diagnosis device comprising:

a controller functioning to;

determine whether a fuel cut, during which fuel is not injected by the fuel injector while the engine is running, has been executed or not;

control a fuel injection amount of the fuel injector only immediately after an execution of a fuel cut to cause the engine to be operated under an alternating application of a rich air/fuel ratio and a non-rich air/fuel ratio; and

perform a diagnosis of deterioration in the air/fuel ratio sensor based on a variation in the air/fuel ratio detected by the air/fuel ratio sensor during the period in which the engine is operated under the alternating application of the rich air/fuel ratio and the non-rich air/fuel ratio.

4. The deterioration diagnosis device as defined in claim 3, wherein the controller further functions to execute, following the diagnosis, feedback control of the fuel injection amount in which a stoichiometric air/fuel ratio is set as a target air/fuel ratio in accordance with a difference between the air/fuel ratio detected by the air/fuel ratio sensor and the stoichiometric air/fuel ratio based on a predetermined gain, and immediately after a commencement of the feedback control of the fuel injection amount, to temporarily reduce the predetermined gain.

5. The deterioration diagnosis device as defined in claim 3, wherein the controller further functions to determine that the air/fuel ratio sensor has deteriorated when an amplitude of variation in the air/fuel ratio detected by the air/fuel ratio sensor is smaller than a reference value.

6. The deterioration diagnosis device as defined in claim 3, wherein the catalytic converter comprises a three-way catalyst which performs optimum exhaust gas purification in an exhaust gas composition corresponding to a stoichiometric air/fuel ratio, and the oxygen storage function of the catalytic converter is a function to store oxygen in the exhaust gas when the oxygen concentration in the exhaust gas corresponds to the non-rich air/fuel ratio, and releasing the stored oxygen when the oxygen concentration in the exhaust gas corresponds to the rich air/fuel ratio.

7. The deterioration diagnosis device as defined in claim 3, wherein the controller further functions to prevent the diagnosis from being performed until an oxygen storage amount of the catalytic converter reaches a maximum amount.

8. The deterioration diagnosis device as defined in claim 3, wherein the non-rich air/fuel ratio is a stoichiometric air/fuel ratio.

9. The deterioration diagnosis device as defined in claim 8, wherein the engine further comprises a spark plug for igniting the air/fuel mixture, and the controller further functions to control the spark plug to cause an ignition timing during the application of the rich air/fuel ratio to be retarded in comparison with an ignition timing during the application of the stoichiometric air/fuel ratio.

10. The deterioration diagnosis device as defined in claim 3, wherein the device further comprises a sensor which detects a running condition of the engine, and the controller further functions to interrupt the diagnosis when the running condition varies in excess of a predetermined range.

11. The deterioration diagnosis device as defined in claim 10, wherein the running condition detecting sensor comprises either one of a sensor which detects a rotation speed of the engine and a sensor which detects an intake air amount of the engine.