| 摘要 |
PROBLEM TO BE SOLVED: To provide a control unit controlling a two-cell type air-fuel ratio sensor, capable of ensuring heater control performance while deviating timing of inverting a heater drive signal from a precision control period.SOLUTION: A control unit 1 controlling an air-fuel ratio sensor 3 that includes an electromotive force cell 3a, an oxygen pump cell 3b, and a heater 3c, comprises: a sensor driving IC 5 exerting a precision control to detect an output voltage (Nernst voltage) of the electromotive force cell 3a and to adjust a pump current to the oxygen pump cell 3b; and a heater control section 7 constituted by a microcomputer 8 and an output circuit 9 for outputting a heater drive signal in the form of a PWM signal to the heater 3c. A ROM 13 of the microcomputer 8 stores therein a period table 17 indicating time in a precision control period for which the sensor driving IC 5 exerts the precision control and time in a non-precision control period for which the sensor driving IC 5 does not exert the precision control. A CPU 11 of the microcomputer 8 determines timing of inverting a heater drive signal so that the timing deviates from the precision control period on the basis of the period table 17.SELECTED DRAWING: Figure 1 |
