METHOD AND DEVICE FOR MEASURING AMOUNT OF SUCTION AIR

摘要

PURPOSE:To measure with high accuracy by converting the analog output voltage of a suction air flowmeter into a pulse train and measuring its time width, and calculating a mean period of one pulse. CONSTITUTION:The suction air flowmeter 11 provided to the intake conduit of an engine outputs an analog voltage corresponding to a flow rate. This analog voltage is converted by a V/F converter 9 into a pulse train having the number of cycles proportional to the analog voltage. A microcomputer which counts data incorporates a free-running counter (FRC) 5 which measures time and an input capture register (ICR) 6 which holds the value of the FRC when the edge of a gate is generated. The counter 2 counts the pulses which are converted by a V/F converter 9. Further, a D latch 4 synchronizes the gate for sampling with the leading edges of the pulses. The time width of plural pulse trains is measured to calculate the mean period of one pulse and an intake air amount is calculated based upon the mean period.