Ultrasonic sensor

• US 20040226378A1
• Filed: 05/13/2004
• Published: 11/18/2004
• Est. Priority Date: 05/16/2003
• Status: Active Grant

• Current Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Original Assignee: DENSO Corporation, Nippon Soken, Inc. (DENSO Corporation)
• Inventors: Maeda, Manabu, Matsuoka, Hisanaga, Sato, Yoshihisa, Takeichi, Masakazu, Oda, Kiyonari
• Granted Patent: US 7,004,031 B2
• Time in Patent Office: Days
• US Class Current: 73/586
• CPC Class Codes: B06B 1/0215 for generating pulses, e.g. bursts of oscillations, envelopes
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature
• CPC Class Codes: Y10S 367/901 Noise or unwanted signal reduction in nonseismic receiving system
• CPC Class Codes: Y10S 367/903 Transmit-receive circuitry

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.

Claims

1. An ultrasonic sensor, comprising:

a piezoelectric vibrator which 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;

a reverberation measuring means for measuring a reverberation period of the piezoelectric vibrator from the output signal; and

a compensating means for compensating for an operation characteristic of the piezoelectric vibrator in accordance with the measured reverberation period.

2. The ultrasonic sensor according to claim 1, wherein

the compensating means compensates for the operation characteristic of the piezoelectric vibrator so that the reverberation period is adjusted to be within a predetermined range when the reverberation period measured by the reverberation measuring means is not within the predetermined range.

3. The ultrasonic sensor according to claim 1, wherein

the compensating means compensates for the operation characteristic of the piezoelectric vibrator so that the reverberation period is adjusted to be the shortest when the reverberation period measured by the reverberation measuring means is not within a predetermined range.

4. The ultrasonic sensor according to claim 1, wherein

the compensating means normally compensates for the operation characteristic of the piezoelectric vibrator so that the reverberation period is adjusted to be the shortest.

5. The ultrasonic sensor according to claim 1, further comprising:

a temperature sensor for detecting a temperature in a place where the piezoelectric vibrator is disposed,

wherein the compensating means compensates for the operation characteristic of the piezoelectric vibrator in accordance with the reverberation period measured by the reverberation measuring means and the temperature detected by the temperature sensor.

6. The ultrasonic sensor according to claim 1, wherein:

the compensating means includes at least one of a capacitor and a coil; and

the compensating means compensates for the operation characteristic of the piezoelectric vibrator by changing a combination of the capacitor and the coil which are connected to the piezoelectric vibrator.

7. The ultrasonic sensor according to claim 6, wherein:

the reverberation measuring means measures a reverberation period of the piezoelectric vibrator for all or some of combinations of the capacitor and the coil which are connected to the piezoelectric vibrator; and

the compensating means selects a combination from the combinations of the capacitor and the coil connected to the piezoelectric vibrator, whose reverberation periods are measured by the reverberation measuring means.

8. The ultrasonic sensor according to claim 6, wherein:

the ultrasonic sensor is mounted in a vehicle in order to detect an obstacle around the vehicle; and

the compensating means changes the combination of the capacitor and the coil connected to the piezoelectric vibrator when a speed of the vehicle is more than a predetermined value.

9. The ultrasonic sensor according to claim 6, wherein:

the ultrasonic sensor is mounted on a front side of a vehicle in order to detect an obstacle in front of the vehicle; and

the compensating means changes the combination of the capacitor and the coil connected to the piezoelectric vibrator when the vehicle moves back.

10. The ultrasonic sensor according to claim 6, wherein:

the ultrasonic sensor is mounted on a rear side of a vehicle in order to detect an obstacle behind the vehicle; and

the compensating means changes the combination of the capacitor and the coil connected to the piezoelectric vibrator when the vehicle moves forward.

11. The ultrasonic sensor according to claim 1, wherein:

the compensating means includes a plurality of capacitors; and

the compensating means compensates for the operation characteristic of the piezoelectric vibrator by changing a combination of the plurality of capacitors which are connected to the piezoelectric vibrator.

12. The ultrasonic sensor according to claim 1, wherein:

the compensating means includes a plurality of coils; and

the compensating means compensates for the operation characteristic of the piezoelectric vibrator by changing a combination of the plurality of coils which are connected to the piezoelectric vibrator.