Ultrasonic sensor

1. An ultrasonic sensor, comprising:

an ultrasonic element including an ultrasonic oscillator for sending, receiving or transceiving ultrasonic waves, an element body having an opening for passage of ultrasonic waves formed on one surface, the ultrasonic oscillator being arranged within the element body, and terminal portions protruding from the element body to feed an electric current to the ultrasonic oscillator;

a housing having an opening formed on one surface for communication with the opening of the element body, the housing including a receiving portion for receiving the ultrasonic element and a positioning portion integrally formed with the receiving portion to position the ultrasonic element in place; and

a printed wiring board arranged to interpose the ultrasonic element between the printed wiring board and the receiving portion of the housing, the terminal portions of the ultrasonic element being mounted to the printed wiring board.

2. The ultrasonic sensor of claim 1 , wherein the receiving portion includes a peripheral wall surrounding the ultrasonic element, the positioning portion being a plurality of ribs integrally formed with the peripheral wall to make contact with the ultrasonic element under pressure.

3. The ultrasonic sensor of claim 1 , wherein the receiving portion includes a peripheral wall surrounding the ultrasonic element, the positioning portion being a plurality of thin wall sections formed in the peripheral wall, the thickness of the thin wall sections in a radial direction of the peripheral wall being set smaller than the thickness of the remaining sections of the peripheral wall.

4. The ultrasonic sensor of claim 1 , wherein the positioning portion of the housing is formed by deformable elements which are adapted to contact the ultrasonic element under pressure after said ultrasonic element has been forcedly inserted into the receiving portion.