JPH03194462A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To suppress the mechanical free vibration of a vibrator and to improve the distance resolution by providing a packing material, which is made of the same material with the piezoelectric element of an ultrasonic vibrator, in contact with the piezoelectric element. CONSTITUTION:On the opposite surface of the ultrasonic vibrator, composed of the piezoelectric element 1 and an acoustic lens 2, the packing material 3 made of the same material with the element 1 is formed in contact or integrally. Thus, the packing material and vibrator are made of the same material, so they become equal in acoustic impedance and the reflection of an ultrasonic wave at the border between the packing material and vibrator is eliminated to suppress the mechanical free vibration of the vibrator greatly. Consequently, the distance resolution at the time of acoustic wave distance measurement is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic probe used in an ultrasonic inspection apparatus that uses ultrasonic waves to inspect the surface of an object or the presence or absence of internal flaws.

[Conventional technology]

An ultrasonic probe consists of a vibrator that is excited to generate ultrasonic waves by applying a voltage, an acoustic lens that is in close contact with one side of the vibrator to focus the generated ultrasonic waves, and It is made of a backing material that adheres closely to the other side and absorbs the generated ultrasonic waves. The ultrasonic beam focused by the acoustic lens is radiated to the object to be inspected, and the reflected wave from the object passes through the acoustic lens again and reaches the transducer. The vibrator converts this reflected wave into a corresponding electrical signal and outputs it. This electrical signal is processed by a signal processing section, and based on this, the presence or absence of a wound on the subject is determined.

On the other hand, the backing material absorbs the emitted ultrasonic waves, suppresses the reflected waves returning from the backing material to the transducer as much as possible, suppresses the mechanical free vibration of the transducer due to repeated reflections, and suppresses the reflected waves from the subject. It has the function of preventing interference with the transducer and ensuring accurate analysis of the electrical signal output from the vibrator.

[Problem to be solved by the invention]

The above function of the backing material is achieved by configuring the backing material to have an acoustic impedance close to the acoustic impedance of the vibrator.

The acoustic impedance of the vibrator is 30 to 35 x 106K g / when a normal piezoelectric element is used as the vibrator.
It has a fairly high value of m z-se (-. Therefore,
A method has been used in which a heavy metal is used as the backing material and is adhered to the piezoelectric element.

By the way, in recent years, high resolution has been required for ultrasonic inspection equipment, and in order to obtain high resolution, a method has been adopted in which the thickness of the transducer is made thinner (thus increasing the resonant frequency of the transducer). However, it is extremely difficult to bond heavy metal to such a thin vibrator, and a gap is created between the vibrator and the metal, resulting in the problem that metal cannot be used as a backing material.

To solve this problem, we put a vibrator in the housing,
For example, a method has been adopted in which a resin mixed with tungsten powder is poured thereon, and the tungsten powder is concentrated on the vibrator side using a centrifugal separator to form a backing material. However, not only is this method time-consuming to manufacture, but the acoustic impedance of the backing material constructed using this method is, for example, 20xlO6Kg/
There is a considerable difference between the acoustic impedance of the vibrator and the acoustic impedance of the vibrator, which poses a problem in that the mechanical free vibration of the vibrator cannot be sufficiently suppressed.

The purpose of the present invention is to solve the problems in the above-mentioned prior art,
Mechanical free vibration of the vibrator can be sufficiently suppressed,
Further, it is an object of the present invention to provide an ultrasonic probe that can improve distance resolution based on electrical signals.

[Means to solve the problem]

In order to achieve the above object, the present invention generates ultrasonic waves by exciting a transducer having a unique resonant frequency, and uses the transducer to respond to the reflected waves of the ultrasonic waves from a subject. The ultrasonic probe is characterized in that a backing material made of the same material as the piezoelectric element of the vibrator is tightly attached to a surface of the vibrator opposite to the subject.

[Effect]

Ultrasonic waves emitted from the transducer to the backing material side have the same acoustic impedance because the backing material is the same material as the transducer, so there is no reflection at the boundary between the backing material and the transducer, and the ultrasonic wave emitted from the transducer is Mechanical free vibrations are suppressed.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1(a) is a top view of an ultrasound probe according to an embodiment of the present invention, and FIG. 1(b) is a sectional view of the ultrasound probe shown in FIG. 1(a). In each figure, 1 is a piezoelectric element, 1a is an upper electrode provided on the top surface of the piezoelectric element 1, and 1a' is an upper electrode 1.
A lead wire a, 1b a lower electrode provided on the lower surface of the piezoelectric element 1, and lb' a lead wire of the lower electrode 1b. A vibrator is composed of the piezoelectric element 1, the upper electrode 1a, and the lower electrode 1b. Reference numeral 2 denotes an acoustic lens provided in close contact with the lower electrode 1b, and its concave curved surface is formed at a position substantially facing the upper electrode 1a. 3 indicates a backing material. In this embodiment, the backing material 3 and the piezoelectric element 1 are made of the same material and are integrally constructed. That is, in a block made of one piezoelectric element material, by providing the upper electrode 1a at a position at a thickness t from the lower surface, the piezoelectric element 1 having a thickness t and the backing material 3 having a thickness t are configured to be distinguished from each other. Ru. As is clear from the figure, the piezoelectric element 1 and the backing material 3 are partially connected. Note that the means for forming electrodes within the piezoelectric element material is a well-known means for manufacturing laminated piezoelectric elements. Also, backing material 3
The thickness t of the piezoelectric element is determined by considering the attenuation, sensitivity, etc. of the piezoelectric element, but the thickness t is usually much larger than the thickness t.

When a voltage is applied between the upper electrode 1a and the lower electrode 1b, the vibrator resonates at Nt/l, where Nt is the frequency constant, and emits ultrasonic waves. This ultrasonic wave is focused by the concave curved surface of the acoustic lens 2 and radiated to the subject. On the other hand, since the backing material 3 is made of the same material as the piezoelectric element 1, the ultrasonic waves emitted from the vibrator toward the backing material 3 have the same acoustic impedance, so they are hardly reflected at the boundary between the two, and eventually , mechanical free vibration of the vibrator is sufficiently suppressed.

FIG. 2(a) is a state diagram of an inspection performed using the ultrasonic probe of this embodiment, and FIG. 2(b) is a waveform obtained by the ultrasonic probe shown in FIG. 2(a). It is a diagram. In each figure, 5
is the ultrasound probe of this example, 6 is the subject, and 7 is the subject 6.
Indicates defects within. Water is usually interposed between the ultrasound probe 5 and the subject 6 as an ultrasound medium. Reference numeral 8 indicates a display surface of an oscilloscope provided on the signal processing section side.

On the display surface 8, a waveform diagram of the electrical signal converted by the ultrasound probe 5 is displayed. This waveform diagram is for the subject 6.
It is drawn in a position corresponding to the position of . W, is subject 6
The reflected wave at the surface, W, indicates the reflected wave at the defect 7. As shown in the figure, the reflected wave from the defect 7 clearly appears.

FIGS. 3(a) and 3(b) are state diagrams and waveform diagrams of inspection using a conventional ultrasonic probe. In each figure, Figure 2 (a
) and (b), the same parts are given the same reference numerals. 10 is a conventional ultrasonic probe, ie, an ultrasonic probe whose backing material has low acoustic impedance. As is clear from FIG. 3(b), it is not easy for anyone other than an expert to clearly distinguish the reflected wave Wb indicating the defect 7 from other waveforms by looking at the displayed waveforms.

In this way, in this example, the backing material is constructed integrally with the piezoelectric element, so it can have the same acoustic impedance as the vibrator, and the mechanical free vibration of the vibrator can be sufficiently suppressed. The distance resolution of the ultrasonic probe can be improved.

In addition, in the explanation of the above embodiment, an example was explained in which the piezoelectric element and the backing material were integrated, but it is also possible to configure them as separate bodies.
The backing material may be adhered to the upper electrode.

〔Effect of the invention〕

As described above, in the present invention, since the backing material is made of the same material as the piezoelectric element of the vibrator, both have the same acoustic impedance, and it is possible to sufficiently suppress the mechanical free vibration of the vibrator. Therefore, the distance resolution of the ultrasonic probe can be improved.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are top views and cross-sectional views of an ultrasound probe according to an embodiment of the present invention, and FIGS. 2(a) and (b) are views of an ultrasound probe according to an embodiment of the present invention. Inspection state diagram and waveform diagram FIGS. 3(a) and 3(b) are an inspection state diagram and waveform diagram using a conventional ultrasonic probe. 1...Piezoelectric element, 1a...
・Top electrode, 1b...Lower electrode, 2...
...Acoustic lens, 3...Backing material, 5...Ultrasonic probe, 6...
......Test, 7...Defect. Figure 1(a)

Claims (1)

[Claims] In an ultrasonic probe that generates ultrasonic waves by exciting a transducer having a unique resonant frequency, and converts the reflected waves of the ultrasonic waves from the object into electrical signals corresponding to the reflected waves using the transducer. , on a surface of the vibrator opposite to the subject,
An ultrasonic probe characterized in that a backing material made of the same material as the piezoelectric element of the vibrator is brought into close contact with the piezoelectric element of the vibrator.