| 摘要 |
An ultrasonic sensor (20) mounted on a bumper (30) of an automobile transmits ultrasonic wave and receives ultrasonic wave reflected by obstacles, and thereby detects obstacles. The ultrasonic sensor (20) has an unequal directional characteristic in its horizontal and vertical directions (a wider angle is covered in the horizontal direction). A cylindrical ultrasonic resonator (10) is positioned in a cylindrical sensor case (22) so that its directional characteristic accords with a predetermined direction. A pair of flat surfaces (17) are formed on the outer cylindrical surface of the resonator (10) to identify its horizontal direction when the resonator is assembled into the sensor case (22). The sensor case (22) also has flat surfaces (26) to identify its horizontal direction when it is mounted on the bumper (30). <IMAGE> |
