US 6,550,305 B2Granted

Activation diagnosis method and activation diagnosis apparatus for air-fuel ratio sensor

AssigneeUnisia Jecs Corporation

InventorNaoki Tomisawa

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Abstract

Before starting an air-fuel ratio feedback control utilizing an air-fuel ratio sensor, activation of a wide-range air-fuel ratio sensor in an internal combustion engine is diagnosed by calculating heat transferred to and from the air-fuel ratio sensor, the output value of the wide-range air-fuel ratio sensor varies in response to oxygen concentration in exhaust which varies according to the air-fuel ratio of an intake air-fuel mixture of the internal combustion engine. The activation time from the starting of the engine until the air-fuel ratio sensor is activated is estimate based on the calculated result of the heat transfer. Alternatively, activation of the sensor is diagnosed under the condition that an output voltage of the oxygen concentration detecting unit of the sensor is fixed to a value either equal to or above a rich-side set voltage or equal to or under a lean-side set voltage, before starting the air-fuel ratio feedback control.

Claims9

Dependent claims

An activation diagnosis method for a wide-range type air-fuel ratio sensor, said air-fuel ratio sensor being equipped with an oxygen concentration detecting unit formed of a solid electrolyte and outputting detection signals corresponding to oxygen concentration inside a hollow chamber to which exhaust of an internal combustion engine is introduced, and an oxygen pump unit for pumping oxygen into or out of said hollow chamber by controlling a current being applied to a solid electrolyte wall separating said hollow chamber and the exhaust side of said engine so as to control the oxygen concentration inside said hollow chamber to predetermined oxygen concentration, said air-fuel ratio sensor detecting the current being applied to said solid electrolyte wall to output an air-fuel ratio signal corresponding to the oxygen concentration in the exhaust;

said activation diagnosis method comprising the steps of:
monitoring an output voltage of said oxygen concentration detecting unit after the starting of operation of said engine;
judging whether or not said output voltage of said oxygen concentration detecting unit is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage;
and
diagnosing that said air-fuel ratio sensor is activated under the condition that a status is detected where the output voltage of said oxygen concentration detecting unit is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage.

2 more elements

An activation diagnosis apparatus for a wide-range type air-fuel ratio sensor, said air-fuel ratio sensor being equipped with an oxygen concentration detecting unit formed of a solid electrolyte and outputting detection signals corresponding to oxygen concentration inside a hollow chamber to which exhaust of said internal combustion engine is introduced, and an oxygen pump unit for pumping oxygen into or out of said hollow chamber by controlling a current being applied to a solid electrolyte wall separating said hollow chamber and the exhaust side of said engine so as to control the oxygen concentration inside said hollow chamber to predetermined oxygen concentration, said air-fuel ratio sensor detecting the current being applied to said solid electrolyte wall to output an air-fuel ratio signal corresponding to the oxygen concentration in the exhaust;

said diagnosis apparatus comprising:
an output voltage monitoring device which monitors an output voltage of said oxygen concentration detecting unit after the starting of operation of said engine;
a judging device which judges whether or not said output voltage of said oxygen concentration detecting unit being monitored by said output voltage monitoring device is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage;
and
a diagnosis device which diagnoses that said air-fuel ratio sensor is activated under the condition that said judging device detects a status where the output voltage of said oxygen concentration detecting unit is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage.

2 more elements

said diagnosis apparatus comprising:
an output voltage monitoring means for monitoring an output voltage of said oxygen concentration detecting unit after the starting of operation of said engine;
a judging means for judging whether or not said output voltage of said oxygen concentration detecting unit being monitored by said output voltage monitoring means is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage;
and
a diagnosis means for diagnosing that said air-fuel ratio sensor is activated under the condition that said judging means detects a status where the output voltage of said oxygen concentration detecting unit is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/241,480Filed 12 Sep 2002 · division
Priority: JP 10-35823116 Dec 1998
Published: US 2003/0010088 A116 Jan 2003
Granted: 22 Apr 2003
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01N 27/4175
Using cells , i.e. more than one cell and probes with solid electrolytes: calibrating or checking the analyser
F02D 41/1494
Details: control of sensor heater
F02D 41/1456
The characteristics being an oxygen content or concentration or the air-fuel ratio: with sensor output signal being linear or quasi-linear with…
G01N
Investigating or analysing materials by determining their chemical or physical properties