JPS6022718Y2 - Polymer piezoelectric membrane ultrasonic transducer with multiple array configuration - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ultrasonic transducer in which a curved polymeric piezoelectric film is phase-aligned.

Due to their low acoustic impedance and favorable flexibility, polymeric piezoelectric films have recently found application as transducers for ultrasonic waves in liquids, as well as for ultrasonic waves in air.

However, this type of transducer does not have sufficient electroacoustic conversion efficiency when applied to conventional devices using transducers made of inorganic piezoelectric materials.

An object of the present invention is to provide an ultrasonic transducer in liquid or in air that is made of such a polymeric piezoelectric film and can improve electroacoustic conversion efficiency.

According to the present invention, in a polymer piezoelectric membrane ultrasonic transducer having a multi-array configuration that utilizes the stretching vibration of a plurality of polymer piezoelectric membranes having electrodes attached to both the front and back sides, the plurality of polymer piezoelectric membranes each have both ends. They are fixed and curved and arranged at half-wavelength intervals, and the ultrasonic waves emitted from each polymeric piezoelectric film are arranged on the front and back sides of each polymeric piezoelectric film so that the phase matching condition is satisfied at the receiving point. An ultrasonic transducer is provided having electrodes electrically connected in parallel.

The present invention will be explained in detail below with reference to the drawings.

As shown in FIG. 1, metal electrodes 2 and 2' are attached to the front and back sides of a known polymer piezoelectric film 1 such as polyvinylidene fluoride that has been subjected to a stretch polarization treatment, and an alternating current voltage e is applied between the front and back electrodes. The piezoelectric film 1 has stretching vibrations 3, 3' parallel to the film surface.
occurs.

Therefore, this piezoelectric film 1 is curved as shown in FIG.
When both ends 4, 4' are fixed, the expansion and contraction vibration of the membrane can be converted into a piston movement 5 perpendicular to the membrane surface, so that sound waves can be radiated using the membrane surface as a sound radiation surface.

A curved converter takes advantage of this.

FIG. 3 shows a specific example of the present invention, in which curved converters such as those shown in FIG. 2, law lb, let...
・.

A plurality of 1n are arranged one on top of the other at a certain interval.

Reference numerals 6 and 6' indicate input/output electrical terminals, which are connected to an alternating current voltage.

Here, each curved transducer is configured to be excited in an independent vibration mode.

When the polarization directions of each curved transducer are aligned in the same direction, the intervals 7a, 7b, . . . between the curved transducers are
If the polarities of the front and back electrodes of each piezoelectric film are alternately reversed and electrically connected in parallel, the ultrasonic waves radiated independently from each curved transducer will be Since the phase matching condition is satisfied, the output sound pressure is superimposed at the sound receiving point in the axial direction that is sufficiently far away from the transducer.

Therefore, the output sound pressure can be increased in proportion to the number of curved transducers for the same input terminal.

If the polarization directions of the curved transducers are not aligned in the configuration shown in Figure 3, electrical connections must be made so that the ultrasonic waves emitted from each piezoelectric film satisfy the phase matching condition. good.

By changing the interval between each curved transducer and the size of the piezoelectric film, the specific direction in which the output sound pressure is superimposed can be changed.

In addition, a baffle plate is provided around each curved transducer, and the distance from one end of the baffle plate to the other end of the other baffle plate via the piezoelectric film is adjusted in relation to the wavelength, thereby reducing the wave diffraction effect. The effect of increasing sound pressure in a specific direction can be made more noticeable by controlling the sound pressure in a particular direction, or by providing a wall surface instead of a baffle plate so as to have an acoustic mirror effect in a direction parallel to the vibration direction of the piezoelectric film.

In FIG. 3, a specific example according to the present invention is explained in which a curved transducer is applied. However, in the present invention, it is not necessary to use a curved transducer, and the transducer may have an omnidirectional cylindrical shape or a partially shaped transducer. It may be a cylindrical shape with a chipped part, a spherical shape, a spherical shape with a part chipped off, for example, a hemispherical shape.

In order to maintain this shape, an appropriate method can be adopted such as supporting it with an elastic material with low sound absorbing properties, such as foamed polyurethane.

The polymeric piezoelectric film used in the present invention includes vinylidene fluoride homopolymers, vinylidene fluoride copolymers, vinylidene fluoride resins such as compositions containing any of these as main components, vinyl fluoride resins, and general vinylidene fluoride resins. A composition in which a piezoelectric substance is dispersed in a polymer, a laminate having one layer of any of these, and the like are used, but vinylidene fluoride resin is most preferred.

Next, as another specific example of the present invention, an aerial transducer using a polyvinylidene fluoride piezoelectric film will be described in detail.

Figure 4 shows five polyvinylidene fluoride piezoelectric films 1a to 1e.
FIG.

The dimensions of the piezoelectric films are 4-x4-, and the radius of curvature is 4-, and the spacing between the piezoelectric films was set to be 1277 EIN (exaggerated and enlarged in the drawing).

Both ends AB and CD of each piezoelectric film 1a to 1e are metal frames (
(not shown), and the AC and BD were supported by metal frames (not shown).

In this case, the metal frame is designed not to touch the metal electrodes 2, 2' of the piezoelectric film.

Since the piezoelectric films are stacked so that their polarization directions are the same, the connections between the electrodes are not shown, but are made in the same way as in FIG. 3.

When such a transducer was used and the frequency was about 14 KHz, the output sound pressure exceeded 14 dB at a certain angle, expressed as a relative sound pressure level with the output voltage in the case of one piezoelectric film being OdB.

As described above, the present invention can significantly improve the electroacoustic transducing efficiency and provide a particularly preferred aerial ultrasonic transducer in liquid or in air.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the piezoelectric action of a polymer piezoelectric film, Fig. 2 is an explanatory diagram of an electroacoustic conversion action of a polymer piezoelectric film, Fig. 3 is an explanatory diagram of a specific example of the present invention, and Fig. 4 FIG. 2 is a perspective view of another embodiment according to the present invention. la, lb...piezoelectric film, 2,2'...
Electrode, 3.3'...Stretching vibration direction, 4,4'.
...Both ends of the curved piezoelectric film, 5...Piston movement direction of the curved piezoelectric film, 6, 6'...Electric terminals for input/output, 7a, 7b...・Distance between curved piezoelectric membranes.

Claims (1)

[Scope of utility model registration request] In a polymer piezoelectric film ultrasonic transducer with a multi-array configuration that utilizes the stretching vibration of a plurality of polymer piezoelectric films having electrodes attached to both the front and back sides, each of the plurality of polymer piezoelectric films is fixed at both ends and has a curved surface shape. The front and back electrodes of each polymer piezoelectric film are electrically parallel to each other so that the ultrasonic waves emitted from each polymer piezoelectric film reach the reception point and satisfy phase matching conditions. A polymer piezoelectric membrane ultrasonic transducer characterized by being connected to.