| 摘要 |
PROBLEM TO BE SOLVED: To provide an obstruction detector for a vehicle constituted to change the directivity range of an ultrasonic sensor, making use of an impedance characteristic of a circuit including a boost means for driving the ultrasonic sensor, as a resonance system. SOLUTION: The ultrasonic sensor 10 provided at a rear bumper of a passenger car constitutes a circuit (a circuit including the resonance system) including a boost transformer 30b of a driving circuit 30 for driving the ultrasonic sensor, as the resonance system. An oscillating circuit 40 outputs an oscillation signal generated at medium frequency between the resonance frequency of the circuit including the resonance system, and anti-resonance frequency higher than the resonance frequency, under the control of a microcomputer 60. The driving circuit 30 boosts the oscillation signal amplified by an amplifying circuit 30a, and outputs it as a driving signal to the ultrasonic sensor 10 through a switching circuit 20. The ultrasonic sensor 10 is driven by the driving signal so as to narrow the directivity of ultrasonic wave.
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