Ultrasonic sensor

An ultrasonic sensor for use in a vehicle obstacle detector configured to be provided at a mounting surface of a vehicle to detect an obstacle in a detection area by transmitting and receiving ultrasonic waves, the ultrasonic sensor comprising:

• an ultrasonic microphone which includes:
• a piezoelectric element configured to transmit and receive the ultrasonic waves;
• and
• an acoustic matching layer including a first and a second surface disposed opposite to each other, the piezoelectric element being attached to the first surface;
• a cylindrical holding rubber which accommodates and holds the ultrasonic microphone;
• and
• a housing which accommodates the ultrasonic microphone and the cylindrical holding rubber, the housing being configured to be inserted in a mounting hole which is formed through the mounting surface,
• wherein the housing includes:
• a cylindrical front housing part including an inner surface and an opening;
• and
• a flange part protruding from a periphery of the opening in an outward radial direction,
• wherein an outer surface of the cylindrical holding rubber is in contact with the inner surface of the cylindrical front housing part,
• wherein the flange part is configured to be in contact with the mounting surface when the housing is inserted in the mounting hole,
• wherein the second surface is configured to be parallel with the mounting surface when the housing is inserted in the mounting hole, and
• wherein the second surface is inclined with respect to the first surface in horizontal and vertical directions.