| 摘要 |
PURPOSE:To enable detecting of an obstacle existing in a space having a given length, by which at least a full area of a vehicle width is extended, irrespective of a directional property of an ultrasonic transmitter, by a method wherein a sensor, consisting of an ultrasonic transmitter and an ultrasonic receiver, is mounted in a given position at a car or other vehicle. CONSTITUTION:A sensor, consisting of an ultrasonic transmitter 5 and an ultrasonic receiver 9, is securely attached to an under surface of a car body 2, positioned on a center line of a car width W and apart by at least a distance l in the forward direction of the car from the rear end surface of the car. Said distance l is set by an equality of l=(W/2) cosec theta provided the horizontal plane directional property of the ultrasonic transmitter 5 is symmetrical with the axis of the ultrasonic transmitter 5. This causes existing of a dead angle of ultrasonic wave from the ultrasonic transmitter 5 outside the width of the car, and permits the detection of a barrier in a space having a given length by which the full area of the car width is extended. During a time which corresponds to the distance l from a transmitting time of an ultrasonic wave from the ultrasonic transmitter 5, the ultrasonic wave is cut off by means of an analogue switch, and thereby the output of the ultrasonic receiver 9 is not processed. |
