PURPOSE: To prevent an automobile from hitting a motorcycle when turning right or left by receiving an ultrasonic wave generated by the exhaust noise of the motorcycle approaching the automobile from behind, measuring the period of the ultrasonic wave, and generating an alarm when the period is larger than a constant value.
CONSTITUTION: An ultrasonic vibrator 3 is fitted facing backward and detects a motor cycle 2 approaching from a rear zone. Ultrasonic noises generated synchronously with the combustion chamber of the engine of the motorcycle 2 are received by the ultrasonic vibrator 3. A fine signal from the ultrasonic vibrator 3 is amplified by an amplifying circuit 5. A signal from this amplifying circuit 5 is converted by a waveform shaping circuit 6 into a digital signal. The period t2 and width t1 of this digital signal are measured by a period measuring and deciding circuit 7. When the period t2 is larger than the specific value, an alarm circuit 4 is turned on to let the driver know the approach of the motorcycle 2.
INOUE HIRONOBU
AZUMA NAOYA
YAMANE TOSHIKI
TAKAGI TOSHIMASA
