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JPH01162183

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DESCRIPTION JPH01162183
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer used, for example, for distance measurement, and more particularly to an
ultrasonic transducer for improving distance resolution. PRIOR ART FIG. 3 is a cross-sectional
view showing a conventional ultrasonic transducer. In the figure, (1) is a cylindrical case with a
curved surface, and (2) is a case cover for sealing the opening of the case (1), which is assembled
to the case (1) by adhesion to form a sealed container. Ru. (3) is a disk-shaped ultrasonic
transducer made of, for example, lithium niobate disposed on the inner surface of the bottom of
the case (1). (4) is a disk-like holding member holding plate, and the outer peripheral edge of the
holding member holding plate (4) is fixed to the stepped portion formed on the inner peripheral
surface of the case (1) with a screw (8). (7) is a vibrator holding coil spring, and an ultrasonic
vibrator (3) and a case (1) joined with a silver paste (8) which is a bonding member sintered at
800 ° C. on the inner surface of the bottom of the case (1) Of the case (1) with the ultrasonic
transducer (3) through the circular insulating plate (9), which is interposed between the pressing
member holding plate (4) whose outer peripheral edge is fixed to the inner peripheral surface
portion of It is always biased towards the bottom. (10) is a connector attached through the case
cover (2), (11) is a wire, and connects the connector (10) and the ultrasonic transducer (3). (12)
is a cable connected to the seal connector (10), and (13) is a post attached to the case cover (2).
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), the frequency is 2. An ultrasonic wave of 50 μsec in a pulse is oscillated at 5
MHz, and the ultrasonic wave is transmitted out of the case (1) through the silver paste (8) and
the bottom of the case (1). The directivity angle at this time was 1.3 '(-6 dB) and the S / N ratio
was at most 20 dB. [Problems to be Solved by the Invention] In the conventional ultrasonic
transducer as described above, the ultrasonic transducer (3) joined by silver paste (8) to the inner
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surface of the bottom of the case (1) is a transducer holding coil It is pressed by the spring (7)
toward the bottom of the case (1), but the pressure of the transducer holding coil spring (7) is the
surface on the opposite side to the case contact surface of the ultrasonic transducer (3) Since it is
a method to press uniformly, when there is a micro dent on the inner surface of the bottom of the
case (1), the pressing force of the transducer holding coil spring (7) is uniform, so that the
ultrasonic transducer (3) A part of the case contact surface may not conform to the inner surface
of the bottom of the case (1), so that an air layer may be formed in part or the thickness of the
silver paste (8) may become uneven. Transmission rate of ultrasonic wave generated in (3)
Propagation efficiency of the acoustic is deteriorated, further cause distortion in the ultrasonic
wave in the pulse becomes longer with the S / N ratio is reduced, the distance resolution
disadvantageously decreases.
The present invention has been made to solve the above problems, and it is an object of the
present invention to obtain an ultrasonic transducer having a good S / N ratio and an improved
distance resolution. [Means for Solving the Problems] In the ultrasonic transducer according to
the present invention, an ultrasonic transducer is disposed on the inner surface of the bottom of
a container via a liquid, and the outer peripheral edge is fixed to the inner peripheral surface of
the container The ultrasonic vibrator is configured to be pressed against the inner surface of the
bottom of the container through the insulating member by the vibrator holding screw screwed
into the plurality of screw holes provided in the member holding plate. [Operation] In the present
invention, the ultrasonic vibrator disposed on the inner surface of the bottom of the container
through the liquid has a plurality of vibrator holding screws screwed to the holding member
holding plate fixed to the container through the insulating member. Since the ultrasonic
transducer is not fixed in a direction parallel to the joint surface with the case, since the pressure
is fixed to the inner surface of the bottom of the container, the temperature change causes the
ultrasonic transducer and the inner surface of the bottom of the container to It can absorb the
thermal expansion occurring between them. Furthermore, even if there is a recess on the inner
surface of the bottom of the container, the recess is filled with liquid, and the pressure on the
ultrasonic transducer can be adjusted locally by each transducer holding screw, so the container
contact surface of the ultrasonic transducer Can follow the inner surface of the bottom of the
container, so that the transmissivity, that is, the sound transmission efficiency, is improved and
the distortion of the waveform of the ultrasonic waves can be improved until the ultrasonic
waves generated by the ultrasonic transducer pass through the container. FIG. 1 is a sectional
view showing one embodiment of the present invention, and FIG. 2 is a partially enlarged
sectional view showing a pressing mechanism of an ultrasonic transducer. In the figure, the same
components as those of the conventional example are denoted by the same reference numerals,
and the description of the duplicated components is omitted. (1) is a stainless steel case, (2) is a
stainless steel case cover, (14) is a disk-like holding member holding plate having a plurality of
screw holes (14a) at equal intervals from one another. It fixes with the screw | thread (6) in the
step part formed in the inner peripheral surface part of 2.). (15) is a vibrator holding screw which
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is screwed into each screw hole (14a) of the holding member holding plate (14), and (16) is a
stainless steel holding piece screwed to the tip of the vibrator holding screw (te) And (17) is a
flexible polyimide which is an insulating member, and has heat resistance of 250 ° C., insulation
of 10 17 Ω / cm, and radiation resistance of I X 107 Rad or more. (18) is a disk-shaped
ultrasonic transducer made of lead titanate-based ceramic with a Curie point of 360 ° C, an
electromechanical coupling coefficient of 0.45, a frequency of about 2.5 MHz and a pulse width
of 20 μsec. And stainless steel have different coefficients of thermal expansion.
(19) is a liquid silicone oil, which is interposed between the inner surface of the bottom of the
stainless steel case (1) and the ultrasonic transducer (18). m To attach the ultrasonic transducer
(18) to the stainless steel case (1), first apply silicone oil (19) to the inner surface of the bottom
of the stainless steel case (1), and then apply ultrasonic wave (18) to the silicone oil -Arranged on
the inner surface of the bottom of the stainless steel case (1) coated with (19). A polyimide sheet
(17), which is a heat-resistant sheet having flexibility as an insulating member, is placed on the
surface of the ultrasonic transducer (18) opposite to the case contact surface. Next, screw the
outer peripheral edge of the holding member holding plate (14) in which the vibrator holding
screw (15) is screwed into each screw hole (14a) to the step formed in the inner peripheral
surface of the stainless steel case (1) Fix with (6). After that, screw each vibrator holding screw
(15) and press the polyimide sheet (17) with the holding piece (1B) attached to the tip of the
vibrator holding screw (15). The ultrasonic transducer (18) is pressed and fixed to the inner
surface of the bottom of the stainless steel case (1) by the pressing force of 15). Finally, attach
the stainless steel case cover (2) to the stainless steel case (1) by welding. In the ultrasonic
transducer configured as described above, since the ultrasonic transducer (15) made of lead
titanate-based ceramic has a Curie point of 360 ° C., the transducer use condition is a
temperature of 200 ° C. to 250 ° C. Even, the electromechanical coupling coefficient is 0.45,
which is higher than the electromechanical coupling coefficient of the conventional ultrasonic
transducer (3) made of lithium niobate, and operates normally without being affected by the
temperature. The conversion efficiency between electricity and ultrasonic waves was good, and
the ultrasonic energy was increased to improve the S / N ratio. The ultrasonic transducer (18)
disposed on the inner surface of the bottom of the stainless steel case (1) has a plurality of
transducer holding screws screwed to the holding member holding plate (14) fixed to the
stainless steel case (1) The pressure is fixed to the inner surface of the bottom of the stainless
steel case (1) through the polyimide sheet (17) in (15), and silicone oil (19) is formed between
the inner surface of the bottom and the case contact surface of the ultrasonic transducer (18).
Since the ultrasonic transducer (18) is not fixed in the direction parallel to the bonding surface
with the stainless steel case (1), the ultrasonic transducer (18) and the stainless steel case are
changed when a temperature change occurs. Since the thermal expansion difference generated
during (1) can be absorbed, it is possible to have excellent durability with little deterioration.
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Furthermore, even if there is a micro dent on the inner surface of the bottom of the stainless steel
case (1), the concave is filled with silicone oil (19), and ultrasonic waves are generated by the
holding piece (16) of each vibrator holding screw (15) Since the transducer (18) is locally
pressed through the polyimide sheet (17), the case contact surface of the ultrasonic transducer
(18) follows the inner surface of the bottom surface of the stainless steel case (1), so that the
ultrasonic vibration is generated. The transmissivity until the ultrasonic wave generated by the
child (18) passes through the stainless steel case (1), that is, the sound transmission efficiency is
improved, the S / N ratio is improved and the waveform of the ultrasonic wave is distorted. It
disappears. Therefore, the S / N ratio is improved, the pulse width is shortened, and the distance
resolution is also improved. In addition, the polyimide sheet (17) is used as an insulating member
provided to insulate the vibrator retaining screw, (11) and the ultrasonic vibrator (18) from the
viewpoint of heat resistance and flexibility. When pressing the ultrasonic transducer (1B) with
the transducer holding screw (11), the pressure can be adjusted locally, so it is the best one to
follow the inner surface of the bottom of the stainless steel case (1) It is. Furthermore, although
the coefficient of thermal expansion of the ultrasonic transducer (18) made of lead titanate-based
ceramic and the stainless steel case (1) differ greatly, the bottom inner surface of the stainless
steel case (1) and the case of the ultrasonic transducer (18) Since the silicone oil (19) intervenes
between the contact surface and the ultrasonic oscillator (18) generated by temperature change,
the silicone oil (19) absorbs the warpage, and the direction by the warpage caused by the
conventional soldering The problems of deterioration of sex and peeling do not occur. In
addition, since the ultrasonic transducer (1B) made of lead titanate-based ceramics does not have
intercalation like lithium niobate, it is resistant to cracking << and to thermal shock. Accordingly,
the yield at the time of manufacturing the ultrasonic transducer is improved and the life is also
improved. In this embodiment, although the ultrasonic transducer (18) is formed of lead titanatebased ceramics having a Curie point of 300 ° C. or higher, the present invention is not limited
thereto, and the stainless steel case (1) and the thermal expansion coefficient However, it is a
matter of course that the present invention can be applied if the electromechanical coupling
coefficient is large and the one for high temperature is used. For example, lead zirconate titanate
ceramics are other than lead titanate ceramics. Moreover, although a polyimide sheet is used as
the insulating member (17) in this embodiment, it is a matter of course that the material is not
limited to this as long as it is an insulating material having flexibility.
Furthermore, although silicone oil is used as the liquid, it is needless to say that the same
function as silicone oil is exhibited even if other oils and liquid metals are used. Further, although
the container is made of stainless steel in this embodiment, it is a matter of course that the
present invention can be practiced even if it is made of other metals, ceramics, and engineering
plastics. [Effects of the Invention] As described above, the ultrasonic transducer disposed on the
inner surface of the bottom portion of the container via the liquid is a plurality of transducer
presses screwed to the pressing member holding plate fixed to the stainless steel case. The
ultrasonic transducer is pressed and adjusted to the inner surface of the bottom of the container
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via an insulating member with a screw, and the ultrasonic transducer can be locally adjusted by
each vibrator holding screw, so that the ultrasonic transducer is parallel to the bonding surface
with the container Because it is not fixed, it can absorb the thermal expansion difference
generated between the ultrasonic transducer and the container when a temperature change
occurs, so it can have excellent durability with less deterioration. Furthermore, even if there is a
depression on the inner surface of the bottom of the container, the depression is filled with the
liquid and there is no air layer, and furthermore, the ultrasonic wave is locally pressed through
the insulating member by the pressure screw. The container contact surface of the acoustic
transducer conforms to the inner surface of the bottom of the container, so that the sound
propagation efficiency until the ultrasonic wave generated by the ultrasonic transducer passes
through the container is improved, and the S / N ratio is improved. There is an effect that
distortion does not occur in the waveform of the ultrasonic wave, the pulse width becomes short,
and the distance resolution is improved.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partial
enlarged sectional view showing a pressing mechanism of an ultrasonic transducer, and FIG. 3 is
a sectional view showing a conventional ultrasonic transducer.
In the figure, (1) is a stainless steel case (container), (2) is a stainless steel case cover (container),
(14) is a holding member holding plate, (14a) is a screw hole, (15) is a vibrator holding screw,
17) is a polyimide sheet (insulation member), (18) is an ultrasonic transducer, and (19) is a
silicone oil (liquid).
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