JPH0749917Y2 - Aerial ultrasonic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to an aerial ultrasonic transducer used for a vehicle height sensor or the like of an automobile.

2. Description of the Related Art As an aerial ultrasonic transducer that emits an ultrasonic wave in a spreading vibration mode or a thickness longitudinal vibration mode of a piezoelectric element, an acoustic matching layer b is placed on a piezoelectric element a as an intermediate medium as shown in FIG. What is done is known as general.

The peculiar acoustic impedance of the piezoelectric element a is considerably larger than the peculiar acoustic impedance of air, and the acoustic matching layer b matches the peculiar acoustic impedances of both of them to efficiently emit ultrasonic waves.

Then, the conventional acoustic matching layer b was formed in a rectangular cross section with the corner portion c being a right angle.

Therefore, in the conventional acoustic matching layer b, the corner c on the air radiation surface d side is also formed at a right angle, but the rigidity of the corner c of the acoustic matching layer b is weak. However, there is a problem in that it causes unnecessary vibration and adversely affects the directivity of the airborne ultrasonic transducer. That is, FIG. 5 shows an example of the directional characteristics of the aerial ultrasonic transducer shown in FIG. 4. As shown in FIG. 5, the half-value angle is ± 3 ° 3 in the conventional case.
When the peak of the main lobe M of 0'is set to 0 dB, the peak of the side lobe S is about -20 dB at ± 14 °. Further, there is a problem that the corner portion c is mechanically weak in strength and may be chipped or cracked to cause a defective product.

An object of the present invention is to provide an aerial ultrasonic transducer that solves the above-mentioned conventional problems, sharpens the directivity, and contributes to the improvement of the transmission / reception sensitivity.

Means for Solving the Problems In order to achieve the above object, the present invention provides an aerial ultrasonic transducer in which an acoustic matching layer is mounted on a piezoelectric element. The gist is that it is formed into a chamfered shape.

Effects According to the above configuration, since the corners of the acoustic matching layer on the air radiating surface side are chamfered, generation of unnecessary vibration is suppressed, and an aerial ultrasonic transducer having good directivity and sensitivity can be obtained. You can

Embodiment Hereinafter, the present invention will be described in detail based on an illustrated embodiment.

FIG. 1 shows an aerial ultrasonic transducer as an example of the present invention, which includes a piezoelectric element 1 formed of PZT or the like and having a substantially rectangular cross section, and an acoustic matching layer 2 mounted on the piezoelectric element 1.
A case 3 having the piezoelectric element 1 therein, and the piezoelectric element 1
It is composed of a pair of lead wires 4 and 4 connected to the electrode terminals and the terminal plate 5.

The acoustic matching layer 2 is made of, for example, a resin layer having a glass or resin microballoon (not shown) therein,
The piezoelectric element 1 is formed in a substantially rectangular cross section having a thickness T corresponding to 1/4 wavelength of the resonance frequency of the piezoelectric element 1.

Further, in the acoustic matching layer 2, the corner portion 7 on the side of the aerial radiation surface 6 is formed into an inclined chamfered shape (C chamfer) so that unnecessary side ropes S due to the rigidity of the corner portion 7 are suppressed. Is composed of. Further, the vertical dimension D of the chamfered portion 8 is set to half or less of the wall thickness T of the acoustic matching layer 2, that is, D ≦ 1 / 2T, and the angle θ formed by the chamfered portion 8 and the vertical direction 9 is set.
Is set to θ ≦ 45 °. These dimensions are determined in consideration of the influence on the main lobe M and the like.

FIG. 2 is a diagram showing the directional characteristics of this embodiment, where θ =
This is for when 40 ° and D = 0.3T is set. When the peak of the main lobe M with a half-value angle of ± 3 ° 30 'is set to 0 dB as in the conventional case, the peak of the side lobe S becomes -26 dB at ± 14 °, which is about 1/2 of the conventional value (-20 dB). It was confirmed to decrease to.

Further, the aerial ultrasonic transducer according to the present invention is not limited to the C-chamfer as long as the corners of the acoustic matching layer on the aerial radiation surface side are chamfered. That is, as shown in FIG. 3, even if the corner portion 7 on the aerial radiation surface 6 side is chamfered in an R shape, the directivity and the like can be improved by the same operation as described above. still,
Also in this case, the vertical dimension D of the chamfered portion 8 is set to D ≦ 1 / 2T in consideration of the influence on the main lobe M and the like, as in the previous embodiment (FIG. 1).

Effect of the Invention As described in detail above, according to the present invention, in the aerial ultrasonic transducer in which the acoustic matching layer is mounted on the piezoelectric element, the corner portion on the aerial radiation surface side of the acoustic matching layer is formed into a chamfered shape. Therefore, unnecessary waves generated at the corners on the side of the aerial radiation surface are suppressed, only the side lobes can be reduced without affecting the sensitivity of the main lobe, and the aerial ultrasonic waves with good directivity and transmission / reception sensitivity. A transducer can be obtained. Further, it is possible to prevent damage such as cracking or chipping of the above-mentioned corners which causes defective products.

[Brief description of drawings]

FIG. 1 is a sectional view of an aerial ultrasonic transducer as an embodiment of the present invention, FIG. 2 is a diagram showing the directional characteristics of the aerial ultrasonic transducer of FIG. 1, and FIG. 3 is an aerial view of another embodiment. FIG. 4 is a sectional view of the ultrasonic transducer, FIG. 4 is a sectional view showing a conventional example, and FIG. 5 is a diagram showing directional characteristics of the conventional example. DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 2 ... Acoustic matching layer, 6 ... Aerial radiation surface, 7 ...
Corner.

Claims (1)

[Scope of utility model registration request] 1. An aerial ultrasonic transducer in which an acoustic matching layer is mounted on a piezoelectric element, wherein the corner of the acoustic matching layer on the aerial radiation surface side is chamfered. Transducer.