ABNORMALITY DIAGNOSIS APPARATUS FOR INTERNAL COMBUSTION ENGINE

• US 20080110239A1
• Filed: 10/30/2007
• Published: 05/15/2008
• Est. Priority Date: 11/10/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: MAEGAWA, Yoshinori
• Granted Patent: US 7,721,591 B2
• Time in Patent Office: Days
• US Class Current: 73/23.32
• CPC Class Codes: F02D 13/0203 Variable control of intake and exhaust valves
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 2041/288 for performing a transformation into the frequency domain, e.g. Fourier transformation
• CPC Class Codes: F02D 2200/025 Engine noise, e.g. determined by using an acoustic sensor
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A cylinder deviation of an actual air-fuel ratio before an air-fuel-ratio dither control is obtained based on a variation of an actual air-fuel ratio by the dither control, a variation amount of detected air-fuel ratio, and a cylinder deviation of detected air-fuel ratio before the dither control A cylinder deviation of actual air-fuel ratio of each cylinder is accurately estimated. When the number of times in which the cylinder deviation of air-fuel ratio exceeds a decision value is greater than a predetermined number, it is determined that an abnormality occurs in the cylinder.

Claims

1. An abnormality diagnosis apparatus for an internal combustion engine comprising:

an air-fuel ratio sensor provided in a confluent portion of exhaust gas discharged from each cylinder of the internal combustion engine, and detecting air-fuel ratio of the exhaust gas;

an information detecting means for estimating an air-fuel ratio of each cylinder or a cylinder deviation of the air-fuel ratio based on an output of the air-fuel ratio sensor while an air-fuel-ratio dither control is performed for compulsorily varying the air-fuel ratio of each cylinder; and

an abnormality determination means for determining that an abnormality occurs in a specified cylinder when a number of times in which the air-fuel ratio of the specified cylinder estimated by the information detecting means or a cylinder deviation of the air-fuel ratio exceeds a decision value is greater than a predetermined number.

2. An abnormality diagnosis apparatus for an internal combustion engine comprising:

an air-fuel ratio sensor detecting an air-fuel ratio of an exhaust gas of the internal combustion engine;

an information detecting means for estimating an air-fuel ratio of each cylinder or a cylinder deviation of the air-fuel ratio based on an output of the air-fuel ratio sensor with respect to every region of a plurality of abnormality diagnosis areas which is defined according to an engine driving condition; and

an abnormality determination means for determining that an abnormality occurs in a specified cylinder when the air-fuel ratio estimated by the information detecting means or the cylinder deviation of the air-fuel ratio of the specified cylinder exceeds a decision value in all abnormality diagnosis area.

3. An abnormality diagnosis apparatus for an internal combustion engine comprising:

an air-fuel ratio sensor detecting an air-fuel ratio of an exhaust gas of the internal combustion engine;

an information detecting means for estimating an air-fuel ratio of each cylinder or a cylinder deviation of the air-fuel ratio based on an output of the air-fuel ratio sensor with respect to every region of a plurality of abnormality diagnosis areas which is defined according to an engine driving condition; and

an abnormality determination means for determining that an abnormality occurs in a specified cylinder when the air-fuel ratio estimated by the information detecting means or the cylinder deviation of the air-fuel ratio of the specified cylinder exceeds a decision value in a predetermined number of the abnormality diagnosis area or more.