JPH05183379A - Ultrasonic delay element - Google Patents

Abstract

PURPOSE:To miniaturize the element, to reduce the attenuation of vibration, and to reduce the production cost by providing an ultrasonic wave guide path connecting the vibration electrodes of the vibrator and resonator through the electrodes for bias application. CONSTITUTION:On one end of a thin piezoelectric substrate 2 made of piezoelectric ceramics, a vibrator 5 is provided formed between vibration electrodes 3, 4 formed to the opposing two upper and lower main surfaces with the piezoelectric substrate 2. A resonator 8 made from vibration electrodes 6 and 7 formed between the opposing two upper and lower main surfaces is provided on the other end of the piezoelectric substrate 2. Further, the electrodes 11 for bias application is provided by forming vibration electrodes 9 and 10 in the middle of the vibration electrodes 3, 6, 4 and 7. Further, wave guide paths 12a and 12b connecting the vibration electrodes 3 and 6 and vibration electrodes 6 and 9 are provided. The vibration electrodes 9 are put between the vibration electrodes 3 and 6. Wave guide paths 13a and 13b connecting vibration electrodes 4, 7 and vibration electrodes 7, 10 are provided and the vibration electrodes 9 are put between vibration electrodes 4 and 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic delay element, and more particularly to a small and high performance delay time externally utilizing energy trap type thickness vibration used for color televisions, video discs, video tape recorders and the like. The present invention relates to an ultrasonic delay element that can be adjusted by voltage.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional ultrasonic delay element is provided with input and detection vibrators 22 and 23 on an end face of a glass ultrasonic delay medium 21, and an input vibrator 2 is provided.
2 radiates an ultrasonic pulse, and this pulse propagates to a transducer 23 for detection while repeating reflection on the glass end surface of the ultrasonic delay medium 21, and the pulse reached by this transducer 23 is converted into an electric signal. The delay time required during this reflection propagation is utilized.

[0003]

The above-mentioned conventional ultrasonic delay element has a structure in which the glass propagates while repeatedly reflecting on the end surface of the ultrasonic wave propagation medium of glass. When the end surface of the ultrasonic wave propagation medium is fixed, vibration occurs. Was attenuated and could not exhibit its performance. Therefore, when assembling as parts, consideration such as enclosing in a metal case is necessary.
The external dimensions had to be large. Moreover, since the delay time is determined by the shape of the ultrasonic wave propagation medium made of glass, it is impossible to adjust the delay time. Further, since it is necessary to repeat the multiple reflection to reach the transducer for detection, an extremely accurate cut-out angle of this outer shape is required, and thus the manufacturing cost is high.

The present invention has been made in view of the above-mentioned circumstances of the prior art, and it is an object of the present invention to provide an ultrasonic delay element which is small in size, has reduced vibration attenuation, is adjustable in delay time, and has reduced manufacturing cost. To aim.

[0005]

An ultrasonic delay element according to the present invention comprises vibrating portion electrodes formed on two opposing main surfaces of a piezoelectric substrate made of piezoelectric ceramic so as to sandwich the piezoelectric substrate. A vibrator, a resonator, and a bias applying electrode are provided, and an ultrasonic waveguide that connects the vibrator and the resonator vibrating electrode of the resonator on the same main surface via the bias applying electrode is provided. In the present invention, the vibrator for excitation, the resonator for signal extraction, and the electrode for bias application are formed by vibrating portion electrodes formed so as to face each other on the two main surfaces facing each other with the piezoelectric substrate sandwiched therebetween. The partial electrodes are connected to form an ultrasonic waveguide. That is, a bias applying electrode is interposed in this waveguide. Oscillator,
The vibration modes excited by the resonator and the bias applying electrode utilize energy trapping type thickness longitudinal vibration, thickness sliding vibration, thickness torsional vibration and the like. The oscillator and the resonator are configured to be the same or similar. The ultrasonic waveguide is obtained by linearly forming an electrode and a mass load substance on a part of the two main surfaces of the piezoelectric substrate. These waveguides also utilize the energy trapping phenomenon in the piezoelectric medium.

[0006]

According to the present invention, the vibrator, the resonator and the bias applying electrode are respectively formed from the vibrating electrode formed on the two main surfaces of the piezoelectric substrate made of the piezoelectric ceramic so as to face each other. One oscillator of the vibrating part electrodes formed facing each other is an energy trap type vibrating part electrode to be a vibrator for excitation, and another resonator of the vibrating part electrodes formed opposite to each other is similar to the vibrator. An energy trap type vibrating electrode is used as a resonator for extracting a signal, and the vibrator and the resonator are connected by a waveguide. Further, the bias applying electrode interposed in the waveguide between the vibrator and the resonator is also formed by the vibrating portion electrodes formed facing each other. Then, it is excited by one of the vibrators, and this vibration propagates in the ultrasonic waveguide. At the time of this propagation, the delay time is adjusted by applying an electric field with the bias applying electrode to adjust the propagation speed, propagate to the resonator, and take out a signal from the resonator to the outside.

The energy trap type resonator of the input portion has a resonance frequency determined by the thickness of the substrate and the elastic constant, and is strongly excited when excited by a signal matching this resonance frequency. The excited elastic wave propagates in the waveguide. Since the waveguide is an energy trapping type, the vibration energy of elastic waves is logarithmically attenuated outside the waveguide, and the energy is concentrated and propagates in the waveguide. The propagating elastic wave is extracted by converting the energy trapping type vibration into an electric signal by a signal extracting resonator. This output signal causes a delay in time with respect to the propagation of the ultrasonic wave with respect to the input signal, and functions as a circuit. When an electric field is applied to the polarization in the forward direction by the bias applying electrode interposed in the waveguide, the elastic constant of the piezoelectric body increases due to the nonlinearity of the elastic modulus, and the sound velocity increases, so that the delay time decreases.

[0008]

EXAMPLES The present invention will be described in detail below with reference to examples.
FIG. 1 is a perspective view for explaining an embodiment of an ultrasonic delay element according to the present invention, and FIGS. 2 to 5 are views for explaining a part of respective manufacturing steps of the ultrasonic delay element according to the present embodiment. is there. In the present embodiment, an example in which thickness longitudinal vibration (TE mode) is used for piezoelectric ceramics polarized in the thickness longitudinal direction will be described. In the figure, reference numeral 1 denotes an ultrasonic delay element. This ultrasonic delay element 1 faces one end side of a piezoelectric substrate 2 which is a thin plate of piezoelectric ceramics, and faces two upper and lower main surfaces facing each other with the piezoelectric substrate 2 interposed therebetween. The vibrator 5 formed of the vibrating section electrodes 3 and 4 is provided, and the vibrating section electrodes 6 and 6 are formed on the other end side of the piezoelectric substrate 2 so as to face two upper and lower main surfaces facing each other with the piezoelectric substrate 2 interposed therebetween. 7, a resonator 8 formed of 7 is provided, and further, vibrating section electrodes 9 and 10 are formed in the intermediate portions of the vibrating section electrodes 3, 6 and 4, 7 and a bias applying electrode 11 is provided. Further, a waveguide 12a connecting the vibrating part electrode 3 and the vibrating part electrode 6 is provided, and a waveguide 12b connecting the vibrating part electrode 6 and the vibrating part electrode 9 is provided.
A vibrating part electrode 9 is interposed between the vibrating part electrode 6 and the vibrating part electrode 6, a waveguide 13a connecting the vibrating part electrode 4 and the vibrating part electrode 7 is provided, and a waveguide 13b connecting the vibrating part electrode 7 and the vibrating part electrode 10 is provided. The vibrating section electrode 9 is interposed between the vibrating section electrode 4 and the vibrating section electrode 7.

Next, an example of a method of manufacturing the ultrasonic delay element 1 according to this embodiment will be described. First, as shown in FIG.
Electrodes are formed on the entire upper and lower surfaces of the lead zirconate titanate (PZT) -based piezoelectric substrate 2 by vapor deposition, and three or more electrodes are formed between the electrodes.
An electric field of 5 KV / mm is applied for 30 minutes to polarize vertically (thickness). Next, as shown in FIG. 3A, resist ink is applied to the upper surface of the piezoelectric substrate 2 for the electrodes for the vibrating section electrodes, the extraction electrodes, etc., and then the vibrating section electrodes 3, 6, 9 and The extraction electrode 3a is connected to the vibration part electrode 3, the extraction electrode 6a is connected to the vibration part electrode 6, and the extraction electrode 9a is connected to the vibration part electrode 9. Similarly, as shown in FIG. 3 (b), after applying the resist ink to the required vibrating portion electrodes facing the vibrating portion electrodes 3, 6, 9 on the upper surface and the electrode portions for the lead-out electrodes, etc. , The vibrating portion electrodes 4, 7 and 10 by etching, and the extraction electrode 4a and the vibrating portion electrode 7 connected to the vibrating portion electrode 4.
To form the extraction electrode 7a and the vibration electrode 10 to form the extraction electrode 10a. The vibrating portion electrodes 3 and 4 and the vibrating portion electrodes 6 and 7 which face each other with the piezoelectric substrate 2 in between constitute a vibrator 5 and a resonator 8, respectively, and the vibrating portion electrodes 9 and 10 constitute a bias applying electrode 11. .

Next, as shown in FIG. 4A, between the vibrating portion electrodes 3 and 7 on the upper surface of the piezoelectric substrate 2 and between the vibrating portion electrodes 7 and 9.
Ink is printed in a desired pattern shape as a material for mass loading to form the waveguides 12a and 12b, respectively. Next, similarly, as shown in FIG. 4B, waveguides 13a and 13b are formed between the vibrating portion electrodes 4 and 8 and between the vibrating portion electrodes 8 and 10 in the same manner on the lower surface. And
Extraction electrodes 3a of the vibrating part electrodes 3, 6, 9 on the upper surface,
Input / output and applying leads 3b, 6b, 9b are connected to 6a, 9a, respectively. Similarly, the extraction electrodes 4a, 7a, 10 of the vibrating section electrodes 4, 7, 10 on the upper surface are formed.
Input / output and application leads 4b and 7 connected to a, respectively.
Install b and 10b respectively.

In the above embodiment, an example using the PZT type piezoelectric ceramics has been described.
The piezoelectric substrate of the system has a Poisson's ratio larger than 1/3,
It is a material capable of frequency-reduction type energy trapping in mode (thickness longitudinal vibration). This frequency-decreasing type reduces the piezoelectric reaction due to the electrode distribution to the vibrating part, or due to the mass load effect by adding a mass, etc.
This is a method of realizing energy confinement by lowering the resonance frequency of the vibrating section.

Further, not only the PZT system but also, for example, PbTi
Materials such as O ₃ series, PLZT series, and LiNbO ₃ single crystal are also used. These materials having a Poisson's ratio smaller than 1/3 are materials capable of frequency-raising energy trapping. As a method of realizing energy confinement with this frequency rising type material, a method of making the thickness of the opposing vibrating electrode portion thinner than that of the peripheral portion (FIG. 5A), and a method of partially applying Mn to the opposing vibrating electrode portion from the outside There is a method of selectively diffusing an element that increases the speed of sound such as (FIG. 5B).
Further, as the vibration mode, a mode such as a TS mode (thickness shear vibration) or a TT mode (thickness torsion vibration) that is oriented in the polarization direction in the plane of the piezoelectric substrate can be used. In this case, regardless of the Poisson's ratio, It is possible to confine the energy of the frequency reduction type. Further, the formation of the electrode is not limited to the vapor deposition electrode and may be a plating electrode. Besides, the present invention is not limited to the above-described embodiments, and changes and modifications can be implemented without departing from the scope of the invention.

[0013]

According to the ultrasonic delay element of the present invention,
Since the waveguide uses the energy confinement phenomenon, elastic waves do not leak from the waveguide and do not utilize multiple reflection at the end face of the waveguide medium, so the shape of the waveguide can be set arbitrarily and assembled as a delay element. In this case, the peripheral portion of the substrate may be held anywhere, and the characteristics do not deteriorate.
Further, the delay time can be easily adjusted by changing the voltage applied to the vibrating portion electrode interposed in the waveguide. Since the oscillator can be integrated with the waveguide medium, the size of the element can be reduced, and the step of attaching the oscillator can be omitted, so that the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an ultrasonic delay element according to the present invention.

FIG. 2 is a diagram illustrating a part of the manufacturing process of the above embodiment.

3A and 3B are diagrams illustrating another part of the manufacturing process of the above embodiment, FIG. 3A is a top view and FIG. 3B is a bottom view.

4A and 4B are views for explaining another part of the manufacturing process of the above embodiment, in which FIG. 4A is a top view and FIG. 4B is a bottom view.

FIG. 5 is a partial view illustrating an example of adjusting the characteristics of the vibrating electrode of the above-described embodiment.

FIG. 6 is a cross-sectional view showing a conventional example.

[Simple explanation of symbols]

 1 Ultrasonic Delay Element 2 Piezoelectric Substrate 3,4 Vibrating Part Electrode 5 Transducer 6,7 Vibrating Part Electrode 8 Resonator 9,10 Vibrating Part Electrode 11 Bias Applying Electrode 12a, 12b Waveguide 13a, 13b Waveguide

Claims (1)

[Claims] 1. A vibrator, a resonator, and a bias applying electrode, which are formed by vibrating electrodes, are formed on two opposing main surfaces of a piezoelectric substrate made of piezoelectric ceramic so as to face each other with the piezoelectric substrate interposed therebetween. An ultrasonic wave delay element, comprising an ultrasonic wave wave guide connecting the vibrator on the main surface and the vibration part electrode of the resonator through a bias applying electrode.