Apparatus and method for controlling oxygen sensor heating
AssigneeDenso Corporation
InventorsYukihiro Yamashita, Hisashi Iida, Jun Hasegawa
Life of this patent
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Abstract
A sensing element of an oxygen sensor is controlled to keep a target impedance for maintaining activation temperature of the oxygen sensor. As the sensing element deteriorates, its internal impedance increases and power supply to a heater for heating the sensing element increases. The oxygen sensor temperature rises excessively above an activation temperature. To restrict excessive temperature rise, the target impedance is altered when the supply power to the heater exceeds a predetermined reference. The target impedance may be increased with increase in the power supply to the heater. Alternatively, the heater supply power is limited to a predetermined maximum for restricting excessive temperature rise.
Claims11
An oxygen sensor heating control apparatus comprising:
- an oxygen sensor having a sensing element and a heater for heating the sensing element;
- power supply means for supplying the heater with heater supply power thereby to heat the sensing element;
- power determining means for determining a required power;
- limit setting means for setting a limit indicative of a maximum of the heater supply power to be supplied to the heater;
- and
- power limiting means for limiting the heater supply power to the limit when the required power exceeds the limit.
An oxygen sensor heating control apparatus comprising:
- an oxygen sensor having a sensing element and a heater for heating the sensing element;
- power supply means for supplying the heater with heater supply power thereby to heat the sensing element;
- limit setting means for setting a limit indicative of a maximum of the heater supply power to be supplied to the heater;
- and
- power limiting means for limiting the heater supply power to the limit;
- wherein the limit is set in accordance with an impedance of the sensing element.
An oxygen sensor heating apparatus comprising:
- an oxygen sensor having a sensing element and a heater for heating the sensing element;
- power supply means for supplying the heater with heater supply power thereby to heat the sensing element;
- limit setting means for setting a limit indicative of a maximum of the heater supply power to be supplied to the heater;
- power limiting means for limiting the heater supply power to the limit;
- impedance detecting means for detecting an element impedance of the sensing element so that the power supply means changes the heater supply power in response to the detected element impedance and a target element impedance;
- limit time determining means for determining that the heater supply power is limited to the limit for a predetermined time;
- and
- impedance altering means for altering the target impedance to a higher value in response to a determination output of the limit time determining means.
An oxygen sensor heating control apparatus comprising:
- an oxygen sensor having a sensing element and a heater for heating the sensing element;
- power supply means for supplying the heater with heater supply power thereby to heat the sensing element;
- limit setting means for setting a limit indicative of a maximum of the heater supply power to be supplied to the heater;
- power limiting means for limiting the heater supply power to the limit;
- impedance detecting means for detecting an element impedance of the sensing element so that the power supply means changes the heater supply power in response to the detected element impedance and a target element impedance;
- impedance relation determining means for determining that the detected element impedance is higher than the target element impedance;
- and
- limit increasing means for increasing the limit in response to a determination output of the impedance relation determining means.
A control method for a current-limiting type oxygen sensor having an oxygen sensing element and a heater, the control method comprising:
- detecting a parameter varying with an oxygen sensing element temperature;
- determining a required electric power to be supplied to the heater based on the detected parameter;
- comparing the required electric power with a maximum limit power;
- and
- supplying the heater with (a) the required electric power as determined when the required electric power is less than the maximum limit power and (b) the maximum limit power when the required electric power is more than the maximum limit power.
Dependencies are inferred from the claim text.