Diagnostic arrangement for use with automotive engine systems

• US 5,297,047 A
• Filed: 07/05/1991
• Issued: 03/22/1994
• Est. Priority Date: 07/06/1990
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Matsuno, Osamu
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): ZANELLI, MICHAEL J
• Application Number:
  US07/725,063
• Time in Patent Office: 991 Days
• Field of Search: 364/424.03, 364/424.04, 364/551.01, 364/575, 364/558, 364/483, 364/484, 364/485, 364/554, 364/431.06, 73/117.2, 73/117.3, 73/119 R
• US Class Current: 701/107
• CPC Class Codes: F01N 2550/00 Monitoring or diagnosing the deterioration of exhaust systems
• CPC Class Codes: F02B 77/08 Safety, indicating or supervising devices thermal insulation F02B77/11; rendering engines inoperative or idling F02D17/04; dependent on lubricating conditions F01M1/22; dependent on cooling F01P11/14
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: F02M 26/49 Detecting, diagnosing or indicating an abnormal function of the EGR system
• CPC Class Codes: F02M 26/57 using electronic means, e.g. electromagnetic valves
• CPC Class Codes: F02M 26/60 in response to air intake pressure
• CPC Class Codes: G01M 15/09 by monitoring pressure in fluid ducts, e.g. in lubrication or cooling parts
• CPC Class Codes: G01M 15/104 using oxygen or lambda-sensors testing catalytic converters F01N3/18, F01N11/007
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In order to quickly and accurately determine if a given system is malfunctioning or not, a selected parameter is sampled and an average value developed. As the number of sequential samples increases and the average becomes more reliable, the standard against which it is judged is also varied so as to render the test for normal operation more severe.

Claims

1. A diagnostic apparatus for an internal combustion engine for an automotive vehicle, comprising:

means for sampling a magnitude of an operating parameter based on the presence of a malfunction of the engine;

means for recording a plurality of operating parameters sequentially sampled through said sampling step;

means for recording the number of times the operating parameter is sampled;

means for determining an average sample value on the basis of the sequentially sampled operating parameters;

means for determining a reference value necessary to judge the malfunction of the engine;

means for comparing the average sample value and the reference value to generate a signal representative of the difference between the average sample value and the reference value;

means responsive to the signal generated by said comparing means, for determining that the malfunction has occurred in the engine in the event that the average sample value exhibits a predetermined relationship with the reference value, and for generating a malfunction indicative signal; and

a warning indicator provided in the automotive vehicle and responsive to the malfunction indicative signal, for warning of the malfunction of the engine,

wherein said reference value is variably determined depending on the number of times the operating parameter has been sampled, such that diagnostic severity for the malfunction of the engine, in a comparison between the reference value and the magnitude of the operating parameter, is enhanced in accordance with an increase in the number of times the operating parameter is sampled.

2. The diagnostic apparatus as set forth in claim 1, wherein said means for determining said average sample value includes means for dividing an average value of the sequentially sampled operating parameters with a predetermined value to obtain a dividend and for replacing the dividend as the average sample value.

3. A diagnostic apparatus for an EGR (Exhaust Gas Recirculating) system for an internal combustion engine for an automotive vehicle comprising:

the EGR system including an EGR conduit which leads from an exhaust system employed in the engine to an induction system employed in the engine and through which a portion of the exhaust gases from the exhaust system is recycled to the induction system;

valve means for controlling the flow of exhaust gases through the EGR conduit, said valve means including a solenoid controlled valve via which the EGR conduit is selectively cut-off;

an induction pressure sensor disposed in the induction system for sensing the induction pressure and outputting a signal indicative thereof; and

diagnostic means responsive to the output of said induction pressure sensor, for;

taking a first pressure measurement at the moment that the solenoid controlled valve is conditioned to cut-off the flow of exhaust gas through the EGR conduit,

taking a second pressure measurement at the moment that the solenoid controlled valve is subsequently conditioned to permit exhaust gas to again flow through the EGR conduit, and

taking a third pressure measurement at a predetermined time after the second pressure measurement;

determining a first difference between the first and second pressure measurements;

determining a second difference between the second and third pressure measurements;

determining an average of the first and second differences;

dividing the average with a predetermined value to obtain a first dividend;

dividing the dividend with the number of times the first, second and third pressure measurements have been sequentially taken to obtain an average dividend;

determining a criterion necessary to judge a malfunction of the EGR system, based on the number of times the first, second and third pressure measurements have been taken;

comparing the criterion with the average dividend and

determining that the malfunction has occurred in the EGR system in the event that the average dividend is less than the criterion,

wherein said criterion is variably determined depending on the number of times the first, second, and third measurements have been taken, such that diagnostic severity for the malfunction of the EGR, in a comparison between the criterion and the average dividend, is enhanced in accordance with an increase in the number of times the first, second and third measurements are taken.

4. A diagnostic apparatus for an air-fuel ratio sensor for an internal combustion engine for an automotive vehicle comprising;

an air-fuel ratio sensor disposed in an exhaust system employed in the engine, for sensing the air-fuel ratio of the gases flowing therein; and

diagnostic means responsible to the output of said air-fuel ratio sensor, for;

recording the time required for the output of the sensor to change from one extremum to another;

averaging sequentially recorded times to derive an average of the recorded times;

comparing the average of the recorded times with a criterion which is varied in accordance with the number of recorded times used to determine the average; and

determining that the air-fuel ratio sensor has deteriorated to a predetermined degree in the event that the average of the recorded times is greater than the criterion,

wherein said criterion is variably determined depending on the number of recorded times, such that diagnostic severity for the malfunction of the air-fuel ratio sensor, in a comparison between the criterion and the average of recorded times, is enhanced in accordance with an increase in the number of recorded times.