GAS CONCENTRATION-DETECTING APPARATUS OF INTERNAL ENGINE

摘要

PROBLEM TO BE SOLVED: To inhibit the progress of deterioration due to the increase in an element temperature accompanied by heater control for retaining each cell of a compound type gas concentration sensor in an active state.;SOLUTION: A voltage or current to be applied to a pump cell 110 and a monitor cell 120 of the compound gas concentration sensor 100 is switched temporarily at a specific period, and each element resistance of the monitor cell 120 and the pump cell 110 is detected according to the voltage change and the current change. The energization to a heater 151 is controlled so that the element resistances coincide with a desired target element resistance, and NOx concentration is successively detected by the detection value of current flowing to a sensor cell 130. In this case, when the element resistance of the monitor cell 120 or the pump cell 110 is outside a specific range, the control target of the element resistance is changed highly according to deterioration so that the element temperature can be maintained at the same temperature before the deterioration, thus inhibiting the deterioration of the gas concentration sensor 100.;COPYRIGHT: (C)2003,JPO