Abstract: An ultrasonic sensor includes an inner case mainly made of plastic and having a shape of a cylinder with a bottom portion. A conductive film is attached to the bottom portion. An electrode formed at a surface of the piezoelectric vibrator is attached to the conductive film to be electrically connected with the conductive film. Therefore, by connecting leads with the conductive film and another electrode at the other side of the piezoelectric vibrator, the electric conduction between an external circuit and both electrodes at both surfaces of the piezoelectric vibrator is ensured.

Abstract: An object detector capable of reliably detecting objects around a vehicle is mounted on a wall of a bumper of a vehicle. Thicknesses of the bumper and of a bottom surface portion of a housing are less than one-half the wavelength of ultrasonic waves generated by a piezoelectric vibrator. This suppresses the reflection of ultrasonic waves by the bumper and by the bottom surface portion of the housing, and enhances the ultrasonic wave propagation efficiency, making it possible to reliably detect objects positioned around the vehicle.

Abstract: An object detector capable of reliably detecting objects around a vehicle is mounted on a wall of a bumper of a vehicle. Thicknesses of the bumper and of a bottom surface portion of a housing are less than one-half the wavelength of ultrasonic waves generated by a piezoelectric vibrator. This suppresses the reflection of ultrasonic waves by the bumper and by the bottom surface portion of the housing, and enhances the ultrasonic wave propagation efficiency, making it possible to reliably detect objects positioned around the vehicle.

Abstract: An ultrasonic sensor includes an inner case mainly made of plastic and having a shape of a cylinder with a bottom portion. A conductive film is attached to the bottom portion. An electrode formed at a surface of the piezoelectric vibrator is attached to the conductive film to be electrically connected with the conductive film. Therefore, by connecting leads with the conductive film and another electrode at the other side of the piezoelectric vibrator, the electric conduction between an external circuit and both electrodes at both surfaces of the piezoelectric vibrator is ensured.

Abstract: An ultrasonic sensor includes a piezoelectric vibrator, a reverberation measuring device and a compensating device. The piezoelectric vibrator vibrates to transmit an ultrasonic wave, receives a reflected wave of the transmitted ultrasonic wave and produces an output signal corresponding to vibration of the piezoelectric vibrator. The reverberation measuring device measures a reverberation period of the piezoelectric vibrator from the output signal. The compensating device compensates for an operation characteristic of the piezoelectric vibrator in accordance with the measured reverberation period. Thus, the ultrasonic sensor can decrease a reverberation period, which may cause reduction in detection accuracy and impossibility of detection of an obstacle at a short distance.

Abstract: In an ultrasonic transceiver, an inner housing has a bottom portion, a first tubular side wall extending from one end surface of the bottom portion and a first flange portion formed on an outer peripheral portion of the first tubular side wall. The bottom portion and first tubular side wall provide a tubular cavity formed therebetween, and the piezoelectric member is mounted on the one end surface of the bottom portion in the tubular cavity. An outer housing has a second tubular side wall coaxially arranged around the outer peripheral portion of the first tubular side wall with a predetermined gap therebetween. The second tubular side wall is provided with one end portion which is opposite to one end surface of the first flange portion and contacted thereto. A first absorption member is inserted in the gap between the first tubular side wall and the second tubular side wall.

Abstract: An ultrasonic sensor includes a piezoelectric vibrator, a reverberation measuring device and a compensating device. The piezoelectric vibrator vibrates to transmit an ultrasonic wave, receives a reflected wave of the transmitted ultrasonic wave and produces an output signal corresponding to vibration of the piezoelectric vibrator. The reverberation measuring device measures a reverberation period of the piezoelectric vibrator from the output signal. The compensating device compensates for an operation characteristic of the piezoelectric vibrator in accordance with the measured reverberation period. Thus, the ultrasonic sensor can decrease a reverberation period, which may cause reduction in detection accuracy and impossibility of detection of an obstacle at a short distance.

Abstract: Metal wiring segments, which are located at peripheral positions of a diaphragm, are formed on a main surface of a thick portion of a semiconductor substrate. A ratio S/d is larger than 100, where an area of the diaphragm is S &mgr;m2 and a thickness thereof is d &mgr;m. Further, a total area of the metal wiring segments arranged on first sides of the substrate is larger than total area of the metal wiring segments arranged on second sides of the substrate, where the first sides indicate the sides in parallel with <110> crystalline axis and the second sides indicate the sides in parallel with <100> crystalline axis.

Abstract: In an ultrasonic transceiver, an inner housing has a bottom portion, a first tubular side wall extending from one end surface of the bottom portion and a first flange portion formed on an outer peripheral portion of the first tubular side wall. The bottom portion and first tubular side wall provide a tubular cavity formed therebetween, and the piezoelectric member is mounted on the one end surface of the bottom portion in the tubular cavity. An outer housing has a second tubular side wall coaxially arranged around the outer peripheral portion of the first tubular side wall with a predetermined gap therebetween. The second tubular side wall is provided with one end portion which is opposite to one end surface of the first flange portion and contacted thereto. A first absorption member is inserted in the gap between the first tubular side wall and the second tubular side wall.

Abstract: Metal wiring segments, which are located at peripheral positions of a diaphragm, are formed on a main surface of a thick portion of a semiconductor substrate. A ratio S/d is larger than 100, where an area of the diaphragm is S &mgr;m2 and a thickness thereof is d &mgr;m. Further, a total area of the metal wiring segments arranged on first sides of the substrate is larger than total area of the metal wiring segments arranged on second sides of the substrate, where the first sides indicate the sides in parallel with <110> crystalline axis and the second sides indicate the sides in parallel with <100> crystalline axis.