| 摘要 |
PURPOSE: A method is provided to detect over-run of fuel injection system even when a micro processor is broken down or upon occurrence of software error. CONSTITUTION: A sensing gear(1) is connected to a cam of diesel engine or a crank shaft, and a rotational frequency sensor(2) is attached to the sensing gear so as to output a signal for rotational frequency of the gear. The signal is converted into a waveform signal by a waveform circuit(3), and input to an external interrupt terminal(5) of a micro processor(4) and at the same time, to a frequency/voltage converter(6). Subsequently, it is judged whether the rotation frequency is excessive or normal using a software program. The value for the rotational frequency is converted into a linear voltage by the frequency/voltage converter. The converted voltage is compared with a preset voltage, i.e., preset rotational frequency, in Schmitt circuit(7), and output as a signal indicating whether the rotational frequency is normal or excessive.
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