Detecting device and method of an abnormality in an air-fuel ratio control system

• US 5,299,550 A
• Filed: 02/18/1993
• Issued: 04/05/1994
• Est. Priority Date: 03/30/1992
• Status: Expired due to Fees

• Current Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Inoue, Norikazu
• Primary Examiner(s): Nelli, Raymond A.
• Application Number:
  US08/019,311
• Time in Patent Office: 411 Days
• Field of Search: 123/674, 123/480, 123/486, 123/690, 123/673, 123/399, 364/431.02, 364/431.05, 364/431.01, 364/431.11, 364/431.12, 60/274, 60/276
• US Class Current: 123/674
• 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 41/2454 Learning of the air-fuel ratio control
• CPC Class Codes: F02D 41/2483 restricting learned values

Abstract

In an abnormality detecting device and method for an air-fuel ratio control system of an internal combustion engine, first discriminating whether a renewing number NLR of grids in a map of air-fuel ratio learning control is larger than a set value or not. If the number is larger than the set value, the difference between the number and previously renewed learning values is calculated. Then, judging whether the difference is larger than a predetermined value or not. If the difference is larger than the predetermined value, it is judged that an abnormality occurs in an intake air measurement system or a fuel injection system of an air-fuel ratio control system. Accordingly, the abnormality in the systems is distinguished from the deterioration due to normal aging.

Claims

1. A device for detecting an abnormality in an air-fuel control system mounted on an engine having, an intake air measurement system mounted in an intake pipe for measuring an amount of induced air into said engine, a fuel injection system for injecting a fuel into a cylinder, an air-fuel ratio sensor inserted in an exhaust pipe for detecting an air-fuel ratio near a catalyst, various sensors for detecting an engine operating condition and for generating an engine operating condition signal, and control means responsive to said engine operation signal for controlling said engine with data stored in a memory by a learning control, an improvement of the device which comprises:

judging means responsive to said engine operating condition signal for deciding whether said various sensors operate normally and for generating a normal signal if each output of said various sensors is in each predetermined normal range;

deciding means responsive to said normal signal for judging whether said engine operating condition is satisfied with every condition for diagnosis and for producing a diagnosis signal;

determining means responsive to said diagnosis signal for judging whether said engine is controlled in a closed-loop operation and for outputting a closed-loop signal;

learning control means responsive to said closed-loop signal for comparing a number of grids being renewed said data in said memory with a predetermined number and for generating a number signal when said number is larger than said predetermined number;

calculating means responsive to said a number signal for computing a difference between corrected values in said memory and for producing a difference signal;

comparing means responsive to said difference signal for comparing said difference signal with a predetermined difference and for generating an abnormal signal if said difference signal is larger than said both predetermined difference; and

warning means responsive to said abnormal signal for indicating an abnormality of said intake air measurement system and for storing said abnormality in a backup RAM in said memory so as to precisely and promptly identify said abnormality from that of deterioration of said sensors.

2. A device for detecting an abnormality in an air-fuel control system mounted on an engine having, an intake air measurement system mounted in an intake pipe for measuring an amount of induced air into said engine, a fuel injection system for injecting a fuel into a cylinder, an air-fuel ratio sensor inserted in an exhaust pipe for detecting an air-fuel ratio near a catalyst, various sensors for detecting an engine operating condition and for generating an engine operating condition signal, and control means responsive to said engine operation signal for controlling said engine with data stored in a memory by a learning control, an improvement of the device which comprises:

judging means responsive to said engine operating condition signal for deciding whether said various sensors operate normally and for generating a normal signal if each output of said various sensors is in each predetermined normal range;

deciding means responsive to said normal signal for judging whether said engine operating condition is satisfied with every condition for diagnosis and for producing a diagnosis signal;

determining means responsive to said diagnosis signal for judging whether said engine is controlled in a closed-loop operation and for outputting a closed-loop signal;

learning control means responsive to said closed-loop signal for comparing a number of grids being renewed said data in said memory with a predetermined number and for generating a number signal when said number is larger than said predetermined number;

calculating means responsive to said a number signal for computing a difference between corrected values in said memory and for producing a difference signal;

comparing means responsive to said difference signal for comparing said difference signal with a predetermined difference and for generating an abnormal signal if said difference signal is larger than said both predetermined difference; and

warning means responsive to said abnormal signal for indicating an abnormality of said fuel injection system and for storing said abnormality in a backup RAM in said memory so as to precisely and promptly identify said abnormality from that of deterioration of said sensors.

3. A method for detecting an abnormality in an air-fuel control system mounted on an engine having, an intake air measurement system mounted in an intake pipe for measuring an amount of induced air into said engine, a fuel injection system for injecting a fuel into a cylinder, an air-fuel ratio sensor inserted in an exhaust pipe for detecting an air-fuel ratio near a catalyst, various sensors ±

or detecting an engine operating condition and for generating an engine operating condition signal, and control means responsive to said engine operation signal for controlling said engine with data stored in a memory by a learning control, an improvement of the method which comprises the steps of;

deciding whether said various sensors operate normally and whether each output of said various sensors is in each predetermined normal range;

judging whether said engine operating condition is satisfied with every condition for diagnosis diagnosis signal;

determining whether said engine is controlled in a closed-loop operation;

comparing a number of grids being said memory with a predetermined number;

calculating a difference between corrected values in said memory;

comparing said difference if said difference is larger than said both predetermined difference; and

warning an abnormality of said intake air measurement system so as to precisely and promptly identify said abnormality from that of deterioration of said sensors.

4. A method for detecting an abnormality in an air-fuel control system mounted on an engine having, an intake air measurement system mounted in an intake pipe for measuring an amount of induced air into said engine, a fuel injection system for injecting a fuel into a cylinder, an air-fuel ratio sensor inserted in an exhaust pipe for detecting an air-fuel ratio near a catalyst, various sensors for detecting an engine operating condition and for generating an engine operating condition signal, and control means responsive to said engine operation signal for controlling said engine with data stored in a memory by a learning control, an improvement of the method which comprises the steps of:

deciding whether said various sensors operate normally and whether each output of said various sensors is in each predetermined normal range;

judging whether said engine operating condition is satisfied with every condition for diagnosis diagnosis signal;

determining whether said engine is controlled in a closed-loop operation;

comparing a number of grids being renewed said data in said memory with a predetermined number;

calculating a difference between corrected values in said memory;

comparing said difference if said difference is larger than said both predetermined difference; and

warning an abnormality of said fuel injection system so as to precisely and promptly identify said abnormality from that of deterioration of said sensors.