JPS57175266A - Obstacle detector for car - Google Patents

Abstract

PURPOSE:To eliminate lowering of the detecting capacity for a close distance, by defining the directivity of a handset within range including the road surface and performing the self-checking by making use of the fact that the reflected wave on the road surface exists in the steady mode regardless of the presence or absence of an obstacle. CONSTITUTION:The directivity that decides the detecting range of an ultrasonic wave transmitter 1 expands toward the lower part from the horizontal direction of a car. Thus the ultrasonic wave reflected on the road surface is received at an ultrasonic wave receiver 1b regardless of the presence or absence of an obstacle that prevents the travelling of a car in the horizontal direction of the car to the ultrasonic wave radiated from an ultrasonic wave transmitter 1a. This receiving waveform 4 has a delay of time compared with a transmitting waveform 3 by a transmitting time required for going and coming-back between the trasnmitter 1 and the road surface. Thus the reflected wave on the road surface is detected at a road surface reflection detecting part 9 and by the signal supplied from a time discriminating part 8. Then the reflection on the road surface is synthetically discriminated by the time difference between the transmitted and received waves and the size of the receiving waveform. Based on this discrimination, the normal working of a detector is displayed at a normal working display part 10.