| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve the early activation of a sensor element while preventing the crack of an element of an exhaust gas sensor. Ž<P>SOLUTION: In a heater control unit, preheating control for reducing the electric current-carrying duty of a heater 27 (hereinafter called to be "heater electric current-carrying duty") to make an electric current pass is executed so as to preheat the sensor element of the exhaust gas sensor 25 at a temperature not causing the crack of the sensor element by water coating until a predetermined preheating period is elapsed from a starting time. The temperature rising quantity of cooling water after starting is calculated on the basis of the detection history of a cooling water temperature sensor 29 during this preheating period while a heater electric current-carrying duty integrated value after starting is calculated and a target range of the heater electric current-carrying duty integrated value after starting is set on the basis of the temperature rising quantity of cooling water after starting to correct the heater electric current-carrying duty so as put the heater electric current-carrying duty integrated value after starting in a target range. By this method, the heater electric current-carrying duty can be corrected so as to put the temperature of the sensor element during the preheating period in a temperature range not causing the cracking of the sensor element by water covering. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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