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: A plurality of ultrasonic sensors is provided in both front and rear bumpers of a vehicle to detect obstacles around the vehicle. Each sensor sets up a transmission frequency of an ultrasonic pulse signal that should be set up in a frequency adjustment circuit and a center frequency in filter processing in a filter circuit in response to a frequency setting frame transmitted from an ECU. The ECU stores a combination of the transmission frequency and the center frequency for each ultrasonic sensor.

Abstract: A vehicle-surroundings monitor apparatus according is provided with a sensor having a transmission/reception means for transmitting an ultrasonic wave to surroundings of a vehicle and receiving a reflected ultrasonic wave from the surroundings, a transmission circuit for generating an ultrasonic wave to be transmitted from the transmission/reception means, and a reception-processing means for processing an ultrasonic wave received by the transmission/reception means, and a control means for supplying a power-supply voltage to the sensor. A power-supply voltage supplied by the control means to the sensor is split into a power-supply voltage to be supplied to the transmission circuit and a power-supply voltage to be supplied to the reception-processing means.

Abstract: In an apparatus for detecting a distance and improving the SN ratio of received signals, an angular frequency (?1) of sinusoidal wave signals generated by a sinusoidal wave generator is brought into synchronism with an angular frequency (?) of burst pulse signals, and signals received by a transmitter/receiver microphone are orthogonally demodulated by using sinusoidal wave signals of the synchronized angular frequency. A microcomputer adds up the vectors of the demodulated signals for only a period of time equal to a section of transmitting the transmission waves from the transmitter/receiver microphone. A distance to a body is detected by using the received signals of which the vectors are added up.

Abstract: A pair of distance measurement sensors provided at different heights measures distances to an obstruction. When the measured distances are shorter than a threshold distance, the height of the vehicle is found based on the measured distances. When the height of the vehicle is found greater than a threshold height, the existence of the obstruction is reported to the driver. When the height of the vehicle is found smaller than the threshold height, on the other hand, a change in obstruction height is found and compared with a threshold. When the change in obstruction height is greater than the threshold, the existence of the obstruction is reported to the driver since the height is determined to be an unreliable result of computation.

Abstract: A plurality of ultrasonic sensors are installed at predetermined positions of an automotive vehicle. Each sensor has the capability of performing calculation for measuring a distance between an obstacle and the automotive vehicle and transmitting distance information representing a measured distance of the obstacle. A control unit receives the distance information and generates an alarm signal based on the distance information.

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: 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: A plurality of ultrasonic sensors are installed at predetermined positions of an automotive vehicle. Each sensor has the capability of performing calculation for measuring a distance between an obstacle and the automotive vehicle and transmitting distance information representing a measured distance of the obstacle. A control unit receives the distance information and generates an alarm signal based on the distance information.

Abstract: An air purifier has discharge electrodes which generate a corona emission. These discharge electrodes are disposed within a flow passage provided in the air purifier along with a blower. Also included in the air purifier is a filter which scavenges contaminant particles in the air charged by the discharge electrodes. A control unit detects a discharge current of the discharge electrodes to control a rotational speed of the blower in accordance with the detected emission current.