JPH02288500A - Ultrasonic wave transducer - Google Patents

Abstract

PURPOSE:To absorb thermal expansion due to a temperature change, to improve the propagation efficiency of sound and to improve an S/N and a distance resolution by pressing an ultrasonic wave vibrator onto the bottom inner face of a package via an insulation member with a retainer metal always energized with a spring fixed to the package. CONSTITUTION:An ultrasonic wave vibrator 13 arranged to the bottom inner face of closed packages 1, 2 via a liquid is pressed onto the bottom inner face of the package via an insulation member 18 with a retainer metal 16 toward the lower face of the ultrasonic wave vibrator 13 with a plate spring 14. Thus, even when there is a recessed part on the bottom inner face of the container, the recessed part is filled by the liquid and the container contact face of the ultrasonic wave vibrator 13 is in contact with the bottom inner face of the container flexibly and the thermal expansion caused between the ultrasonic wave vibrator 13 and the bottom inner face of the container due to a temperature change is absorbed together with a silicone oil even when the retainer metal 16 provided with the plate spring 14 energized thereto is moved. Moreover, the propagation efficiency of the sound is improved and the distortion of the ultrasonic wave waveform is improved. Thus, the S/N is improved and the distance resolution is improved and the stable performance is ensured with immunity to environmental change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an ultrasonic transducer used, for example, for measuring distance.

(Prior Art) A conventional ultrasonic transducer will be explained with reference to FIG. In FIG. 2, a cylindrical planar case 1 and a cover 2 sealing the opening of the case 1 are attached to the case 1 by adhesive to form a closed container. Reference numeral 3 denotes a disk-shaped ultrasonic vibrator made of, for example, lithium niobate, which is disposed on the inner surface of the bottom of the case l. Reference numeral 4 denotes a disc-shaped presser member holding plate, and the outer peripheral edge of the presser member holding plate 4 is fixed to a stepped portion formed on the inner circumferential surface of the case 1 with screws 6. 5 is a support column attached to the cover 2. 7 is a vibrator holding coil spring. This coil spring 7 is a bonding member baked at 800°C on the inner surface of the bottom of the case 1, and a silver paste 8 which also serves as an ultrasonic propagation member.
The ultrasonic transducer 3 is interposed between the ultrasonic transducer 3 and the holding plate 4 whose outer periphery is fixed to the inner circumferential surface of the case 1. It is constantly biased toward the bottom of case 1. 10 is case cover 2
A connector 11 is an electric wire attached through the connector 10 and the ultrasonic transducer 3. 12 is a cable connected to the seal connector 10.

The conventional ultrasonic transducer is configured as described above, and when a predetermined voltage is applied to the ultrasonic transducer 3 sealed by the case 1 and the case cover 2, it emits ultrasonic waves with a frequency of 2.5 MHz and a pulse width of 50 μsec. The ultrasonic waves are transmitted through the silver paste 8 and the bottom of the case 1 and sent out to the outside of the case 1. The directivity angle at this time is 1
．． At 3° (-6 dB), the S/N ratio was at most 20 dB.

(Problem to be Solved by the Invention) In the conventional ultrasonic transducer as described above, the ultrasonic transducer 3 bonded to the bottom inner surface of the case 1 with silver paste 8 is attached to the bottom of the case 1 by the transducer holding coil spring 7. However, the suppression of the transducer pressing coil spring 7 uniformly presses the surface of the ultrasonic transducer 3 on the opposite side from the case contact surface. Therefore, case 1
When there is a microscopic depression on the inner surface of the bottom of the ultrasonic transducer 3, a part of the case contact surface of the ultrasonic transducer 3 does not follow the inner surface of the bottom of the case 1 because the pressing force of the transducer holding coil spring 7 is uniform. There is. As a result, an air layer may be formed in some parts, the thickness of the silver paste 8 may become non-uniform, and the transmittance of the ultrasonic waves generated by the ultrasonic vibrator 3, that is, the propagation efficiency of sound, may deteriorate. Also.

There was a problem in that the waveform of the ultrasonic wave was distorted, the S/N ratio was decreased, and the pulse width was increased, resulting in a decrease in distance resolution.

In addition, when the coil spring 7 is located on the back side of the ultrasonic vibrator 3, since the mass of the coil spring is small, it vibrates together with the ultrasonic vibrator 3 and transfers the vibration energy of the ultrasonic vibrator 3 to the bottom side of the case 1. As a result, the S/N ratio decreases and the pulse width increases, making it impossible to obtain the desired performance.

Furthermore, in the holding structure using the coil spring 7, the holding force changes due to the change in the spring constant of the coil spring 7 when the temperature rises and the achievement of individual thermal expansion of the case 1 and the holding part holding plate 4. The problem was that it was difficult to ensure the performance of the transducer.

This invention was made to solve such problems, and has a good S/N ratio, improved distance resolution, and
An object of the present invention is to provide an ultrasonic transducer that is insensitive to environmental changes and can ensure stable performance.

[Structure of the invention]

(Means for Solving the Problems) An ultrasonic transducer according to the present invention includes a sealed container, an ultrasonic transducer disposed on the inner surface of the bottom of the container, the ultrasonic transducer and the inner surface of the bottom of the container. an insulating member placed on the top surface of the ultrasonic transducer with a liquid interposed between them; a pusher having a curvature surface such that the pusher is curved and an uneven surface on the opposite side of the insulating member; It is characterized by comprising a plate-shaped spring that constantly biases the ultrasonic vibrator.

(Function) In the present invention, the ultrasonic transducer disposed on the inner surface of the bottom of a sealed container via a liquid is pushed by a plate spring toward the lower surface of the ultrasonic transducer via an insulating member. It is pressed and fixed to the inner surface of the bottom of the container. Therefore, even if there is a depression on the inner surface of the bottom of the container, the depression is filled with liquid, and the container contact surface of the ultrasonic transducer flexibly follows the inner surface of the bottom of the container. A presser bar, which is biased by a plate spring, moves to absorb the thermal expansion generated between the inner surface and the silicone oil. In addition, by holding the ultrasonic vibrator from the back with a presser metal that has sufficient mass compared to the ultrasonic vibrator, the holding structure (
The vibrations of the ultrasonic transducer can be efficiently propagated to the container side without causing the conventional spring structure to resonate. Therefore, the transmittance of the ultrasonic wave generated by the ultrasonic transducer until it passes through the container, that is, the sound propagation efficiency is improved, and the distortion of the waveform of the ultrasonic wave can be improved.

(Embodiment) An embodiment of the ultrasonic transducer according to the present invention will be described with reference to FIG. In Figure 1, reference numeral 1
is a stainless steel case, 2 is a stainless steel cover,
13 is a disc-shaped ultrasonic transducer made of lead titanate-based ceramics placed inside the case 1, and has a cue point of 3.
60℃, electromechanical coupling coefficient 0.45, frequency approximately 2.5
It has a pulse width of 20μsec at MHz and has a different thermal expansion coefficient from stainless steel. 14 is a plate spring,
Its outer peripheral edge is fixed to a step formed on the inner peripheral surface of the case 1 with screws 6. Reference numeral 15 indicates a column attached to the upper surface of the cover 2, and reference numeral 16 indicates a block-shaped metal pusher with a bottom, which is movable in the axial direction. 17 is a through hole into which the leg portion of the connector 20 and the cable 12 are inserted.

The lower surface of the pusher 16, that is, the insulating member 18 side, has a curved surface that applies a large force to the center of the ultrasonic transducer 13, and the opposite surface has a curved surface that has a large contact area with the plate spring 14. An uneven surface is formed to prevent slippage. Reference numeral 18 is a flexible insulating member made of polyimide, for example, and has heat resistance of 250° C., insulation of 1017 Ω/hole, and radiation resistance of the order of IX107 Rad or more. 19 is liquid silicone oil, case 1
The ultrasonic transducer 13 is interposed between the bottom inner surface of the ultrasonic transducer 13 and the ultrasonic transducer 13 .

To attach the ultrasonic vibrator 13 to the case 1, first apply silicone oil 19 to the bottom inner surface of the case 1, and then place the ultrasonic vibrator 13 on the bottom inner surface of the case 1 coated with the silicone oil 19. Set up An insulating member 18 is provided on the surface of the ultrasonic transducer 13 opposite to the case contact surface.
A polyimide sheet, which is a heat-resistant sheet with high flexibility, is placed. Next, a pusher 16 and a plate spring 14 are placed on this sheet. Then, the outer peripheral edge of this plate-shaped spring 14 is fixed to a stepped portion formed on the inner peripheral surface of the case 1 with screws 6. Thereafter, the ultrasonic transducer 13 is pressed and fixed to the bottom inner surface of the case 1 by the biasing force of the spring 14. Finally, cover case 1 with cover 2,
The joint surfaces are attached by welding.

In the ultrasonic transducer configured as described above, an ultrasonic transducer 1 made of lead titanate-based ceramic is used.
3 has a cue point of 360°C, so even if the transducer is used at a temperature of 200°C to 250°C, it will operate normally without being affected by temperature, and the electromechanical coupling coefficient is 0.45, which is higher than conventional transducers. The electromechanical coupling coefficient was higher than that of the ultrasonic transducer 3 made of lithium niobate, the conversion efficiency between electricity and ultrasonic waves was good, and the ultrasonic energy was increased, resulting in an improved S/N ratio. In addition, the ultrasonic transducer 13 disposed on the inner surface of the bottom of the case 1 is pressed and fixed to the inner surface of the bottom of the case 1 via the polyimide sheet 18 with a pusher 16, and the inner surface of the bottom and the case of the ultrasonic transducer 13 are Since the silicone oil 19 is interposed between the contact surface and the bottom surface of the case 1, even if there is a microscopic depression on the inner surface of the bottom of the case 1, the depression is filled with the silicone oil 19. The vibrator 13 is locally pressed through the polyimide sheet 18. Therefore, the case contact surface of the ultrasonic transducer 13 flexibly follows the inner surface of the bottom of the case 1, and the distortion caused by the thermal PLB tension generated between the ultrasonic transducer 13 and the inner surface of the bottom of the case 1 due to temperature changes is suppressed by pressing. 16 moves and absorbs it together with silicone oil 19.

In addition, by pressing the ultrasonic vibrator 13 from the back with the presser metal 16, which has a sufficient mass compared to the ultrasonic vibrator 13, the vibration of the ultrasonic vibrator 13 and the holding structure (conventionally, a spring structure) The vibration of the ultrasonic transducer 13 can be efficiently propagated to the container side without causing resonance. Furthermore, the transmittance of the ultrasonic wave generated by the ultrasonic transducer 18 until it passes through the case 1, that is, the sound propagation efficiency, is improved, the S/N ratio is improved, and the waveform of the ultrasonic wave is distorted. disappears. Therefore, the S/N ratio is improved, the pulse width is shortened, and the distance resolution is also improved. Also, pusher 1
The insulating member 18 provided to insulate the ultrasound transducer 13 from the ultrasonic transducer 13 is made of a polyimide sheet, which has heat resistance and flexibility.
This is because it is possible to adjust the suppression when pressed, and is most suitable for making it conform to the inner surface of the bottom of the case 1.

Generally, when the ultrasonic vibrator 13 is pressed down with a rigid body such as the pusher 16, there is a possibility that the vibration of the ultrasonic vibrator 13 is transmitted through the inside of the rigid body as an ultrasonic conduction medium. If such a phenomenon occurs, the ultrasonic waves may be reflected on the surface of the pusher 16 opposite to the surface in contact with the ultrasonic vibrator 13, resulting in noise in the signal input from the case. Taking this into consideration, a first
As shown in the figure, providing a certain inclination has the effect of preventing reflected waves from returning to the vibrator 13. This allows the ultrasonic transducer 13 to reliably capture signals from the case side without noise input from the back side, resulting in a high S/
A transducer can be provided that provides an N ratio.

Furthermore, the ultrasonic vibrator 13 made of lead titanate-based ceramics does not have interfolding properties like lithium niobate, so it is less likely to crack and is resistant to thermal shock. Therefore, the yield when manufacturing the ultrasonic vibrator is good. At the same time, the lifespan also improves.

In this embodiment, the ultrasonic transducer 13 is made of lead titanate-based ceramics with a cue point of 300° C. or higher; however, it is not limited to this, and even if the coefficient of thermal expansion is different from that of the case 1, Of course, the present invention can be applied as long as it has a large electromechanical coupling coefficient and is used at high temperatures.For example, lead zirconate titanate ceramics are available as a ceramic other than lead titanate ceramics. Further, in this embodiment, a polyimide sheet is used as the insulating member 18, but it is needless to say that the material is not limited to this as long as it has insulating properties and is flexible. Although silicone oil 19 is used as the liquid, other oils,
It goes without saying that even when liquid metal is used, it exhibits the same function as silicone oil. Furthermore, although the container is made of stainless steel in this example, other metals,
It goes without saying that the present invention can also be practiced by using ceramics or engineering plastics.

〔Effect of the invention〕

According to this invention, the ultrasonic transducer disposed on the inner surface of the bottom of a sealed container via a liquid is a cylinder with a bottom that is constantly biased toward the lower surface of the ultrasonic transducer by a spring fixed to the container. with a shaped pusher.

It is press-fixed to the bottom inner surface of the container via an insulating member. Therefore, even if there is a depression on the inner surface of the bottom of the container, the depression will be filled with liquid and there will be no air space. In addition, the container contact surface of the ultrasonic transducer flexibly follows the inner surface of the bottom of the container, and the tip of each transducer cap screw is able to absorb the thermal expansion that occurs between the ultrasonic transducer and the inner surface of the bottom of the container due to temperature changes. A presser bar, which is biased by a spring, moves and absorbs the silicone oil.

By holding down the ultrasonic transducer from the back with a pusher metal that has sufficient mass compared to the ultrasonic transducer, the ultrasonic transducer is prevented from resonating with the vibration of the ultrasonic transducer (conventionally a spring structure). The vibrations of the sonic vibrator can be efficiently propagated to the container side. Therefore, the sound propagation efficiency until the ultrasonic wave generated by the ultrasonic transducer passes through the container is good, and the Sl
This has the effect that the N ratio is improved, the waveform of the ultrasonic wave is not distorted, the pulse width is shortened, and the distance resolution is improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an ultrasonic transducer according to the present invention, and FIG. 2 is a longitudinal sectional view showing a conventional ultrasonic transducer. 1 case 2"° cover 6...screw 12 cable 13...ultrasonic vibrator 14...plate spring 16...push metal 17 through hole 18...insulating member
19...Silicone oil 20...Connector agent Patent attorney Yoshiaki Inomata (1 person) Kaya I Zutezu

Claims (1)

[Claims] A sealed container, an ultrasonic transducer disposed on the inner surface of the bottom of the container, a liquid interposed between the ultrasonic transducer and the inner surface of the bottom of the container, and placed on the upper surface of the ultrasonic transducer. an insulating member disposed on the insulating member and having a curvature surface on the insulating member side that applies a large force to the center of the ultrasonic transducer, and an insulating member on the opposite side of the insulating member. It consists of a pusher having an uneven surface, and a plate-shaped spring that is in contact with the uneven surface of the pusher and whose outer periphery is fixed to the inner surface of the container, and that presses the pusher and constantly biases the ultrasonic vibrator. An ultrasonic transducer featuring: