Oxygen sensor operability sensing arrangement

• US 4,928,518 A
• Filed: 02/17/1989
• Issued: 05/29/1990
• Est. Priority Date: 02/25/1988
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Tamura, Hideyuki
• Primary Examiner(s): MYRACLE, JERRY
• Application Number:
  US07/311,796
• Time in Patent Office: 466 Days
• Field of Search: 73/118.1, 73/117.3, 73/23
• US Class Current: 73/114.73
• CPC Class Codes: F02D 41/1474 by detecting the commutation time of the sensor
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system

Abstract

The output of an oxygen sensor and the engine operation are monitored and, in the event that the voltage generated by the sensor remains within a predetermined window for a predetermined time while the engine temperature is above a predetermined level and the engine is operating within a given set of conditions which define a suitable testing zone, the sensor is indicated as malfunctioning.

Claims

1. A method of monitoring the operation of a oxygen sensor and diagnosing a malfunction thereof, comprising the steps of:

sensing the oxygen content of exhaust gases emitted from an internal combustion engine using an oxygen sensor, said oxygen sensor being operatively disposed in an exhaust conduit and arranged to be exposed to the exhaust gases emitted from said engine;

sensing said engine having assumed a warmed-up status;

sensing the engine load and the engine speed and determining the instant engine operational status using said engine load and engine speed after the engine has warmed-up;

determining if the instant engine operational status falls within a predetermined operational zone; and

indicating a oxygen sensor malfunction in the event that the oxygen sensor output remains continuously below a first predetermined value and above a second predetermined value for a predetermined period of time with said engine operating in said predetermined operational zone.

2. An oxygen malfunction detection arrangement comprising:

an oxygen sensor, said oxygen sensor being operatively disposed in an exhaust conduit and arranged to be exposed to the exhaust gases emitted from an engine;

an engine temperature sensor, said engine temperature sensor being arranged to issue a signal indicative of the engine coolant temperature;

an engine crank angle sensor;

means for producing a signal indicative of engine load;

a control circuit, said control circuit including means for;

sensing the engine load and the engine speed, based on the outputs of said engine crankangle sensor and said engine load indicating signal means and for determining the instant vehicle driving status;

determining if the instant engine operational status falls within a predetermined operational zone; and

indicating a oxygen sensor malfunction in the event that the oxygen sensor output remains continuously below a first predetermined value and above a second predetermined value for a predetermined period of time after the engine temperature sensor indicates that the engine has warmed-up and the engine is detected as operating in said predetermined operational zone.

3. A method of monitoring the operation of an oxygen sensor mounted in the exhaust system of an internal combustion engine and diagnosing a malfunction of the oxygen sensor, comprising the steps of:

sensing engine temperature to determine if it exceeds a predetermined temperature level;

sensing an engine speed;

sensing an engine load;

determining from said engine speed and said engine load if engine operation is in a predetermined engine speed/load zone;

comparing an oxygen sensor output with first and second predetermined values while engine operation is in said predetermined engine speed/load zone and engine temperature is above said predetermined temperature level;

determining a timing period when said oxygen sensor output remains continuously within said first and second predetermined values;

indicating that said oxygen sensor is malfunctioning when said timing period exceeds a predetermined value.

4. A method as claimed in claim 3, wherein said first and second predetermined values are less than and greater than said oxygen sensor output when operating properly and exposed to rich and lean air fuel mixtures respectively.

5. An internal combustion engine having an oxygen sensor for sensing the amount of oxygen contained in the exhaust gases of the engine, the arrangement comprising:

means for sensing when engine temperature exceeds a predetermined temperature level;

means for sensing an engine speed;

means for sensing an engine load;

means for determining from said engine speed and said engine load if engine operation is in a predetermined engine speed/load zone;

means for comparing an oxygen sensor output with first and second predetermined values while engine operation is in said predetermined engine speed/load zone and engine temperature is above said predetermined temperature level;

timing a period said oxygen sensor output remains continuously within the said first and second predetermined values; and

indicating that said oxygen sensor is malfunctioning when said oxygen sensor output remains continuously within said first and second predetermined values for a predetermined period.

6. An arrangement as claimed in claim 5, wherein said first and second predetermined values are less than and greater than said oxygen sensor output when operating properly and exposed to rich an lean air fuel mixtures respectively.