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DESCRIPTION JPH01157199

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DESCRIPTION JPH01157199
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of adjusting the frequency of an ultrasonic transducer using a piezoelectric vibrator.
[Prior Art] An example of an ultrasonic transducer is shown in FIG. The ultrasonic transducer is
used as a pack sensor of a car and has a cylindrical case l. The piezoelectric ceramic vibrator 3 is
bonded to the inside of the top surface 2 of the case 1 to form a vibrating portion, and the other
side of the case 1 is formed with an opening 4 through the sealing member 5.6. It is closed by a
terminal plate 9 provided with a terminal 7.8. 10. A lead wire II is connected to the terminal
7.8, the other end of the lead wire IO is connected to the piezoelectric ceramic vibrator 3, and the
other end of the lead wire jl is connected to the top surface 2. The top surface portion 2 forming
a part of the vibrating portion has a thickness which is smaller than that of the peripheral wall
portion 12 in order to reduce the influence of the support of the peripheral wall portion 12 of
the case 1. Configured thinner. By the way, the case l and the piezoelectric ceramic vibrator 3
have variations in production, errors, etc. at all times, and due to these variations or errors or at
the request of the user, the center related to the sensitivity and sound pressure of ultrasonic
waves. The frequency may have to be adjusted. Such adjustment is performed in the case of this
type of ultrasonic transducer having a frequency of 1. And the thickness of the piezoelectric
ceramic vibrator 3 are proportional to the sum of the thickness and the thickness of the case top
2 after attaching the piezoelectric ceramic vibrator 3 to the top 2 in a conventional manner. In
order to lower the frequency, a method is employed in which the case top 2 is shaved from the
outside to reduce the thickness tl (see, for example, Japanese Patent Application Laid-Open No.
50-83012). . However, when the outside of the case top 2 is scraped off, the outer surface of the
case top 2 must be finished sufficiently flat so that the sensitivity and sound pressure of the
transducer itself are not reduced by scraping. Required high skill. Further, in the case of a dripproof transducer used for outdoor use, such as a back sensor of an automobile, the outer surface
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of the case l is subjected to rustproofing and insulation treatment (for example, the case 1) Is
made of aluminum and the outer surface is subjected to anodizing treatment), so if the outside of
the top surface portion 2 is scraped off, there is a disadvantage that the anticorrosive and
insulating effects disappear. SUMMARY OF THE INVENTION Therefore, according to the present
invention, in an ultrasonic transducer using this type of piezoelectric vibrator, frequency
adjustment can be performed by extremely simple processing without scraping the outside of the
case top surface. The purpose is
[Summary of the Invention] The present invention utilizes bending vibration of a transducer of
this type or a piezoelectric vibrator, and while the center frequency related to the sensitivity and
sound pressure is proportional to the thickness Q ++ tt), Focusing on being inversely proportional
to the square of the diameter of the surface portion, at least the inner surface of the connecting
portion that integrally connects the case top surface portion and the case peripheral wall is
formed as a tapered surface, and a portion of the tapered surface is deleted. Thus, the frequency
is adjusted by substantially increasing the diameter of the top of the case. The present invention
will now be described in detail with reference to the attached drawings. The present invention
will be described in detail with reference to FIGS. 2 and 3. In FIGS. 2 and 3, the parts
corresponding to those in FIG. 1 are shown with the corresponding reference numerals, and the
redundant description will be omitted. In FIG. 2, the upper part of the case 21 is formed like a
truncated cone and the lower part is formed like a cylinder. That is, the flat case top surface 2
having a constant thickness and the case peripheral wall 12 extending perpendicularly to the
case top surface 2 at a position larger in diameter than the case top 2 are integrally connected to
form a tapered shape. The connecting portion 13 is formed. The connecting portion 13 forms an
outer tapered surface 13 b and an inner tapered surface 13 a extending from the inner side
surface of the case top surface 2 to the inner side surface of the case peripheral wall 12.
Preferably, the thickness t of the case top surface 2 and the thickness L3 of the connecting
portion 13 are equal, for example, 0.6 mm. On the other hand, the thickness t of the case
peripheral wall 12. Have a thickness of 1. so as not to damp the vibration of the vibrating part. .
1. The thickness is selected to be about 5 times thicker than, or about 3 mm. However, if there is
a request for processing or strength, the thickness L3 of the connecting portion 13 is set to the
thickness of the case top surface 2. It may be larger. On the other hand, in FIG. 3, the case 1 has a
cylindrical shape, and only the inside of the connecting portion 13 integrally connecting the case
top surface portion 2 and the thick case peripheral wall portion 12 is formed as a tapered
surface 13a. Further, the terminal plate provided with the terminals 7 and 8 is fitted to the
annular step portion 14 formed in the opening 4 of the case and fixed with an adhesive 15 or the
like. The terminal 7.8 is provided below the case peripheral wall 12 to provide strength. The
terminal 7 is connected to an electrode on one side of the piezoelectric vibrator 3 through the
lead wire 10. Further, the terminal 8 insulated from the terminal 7 is connected to the inner
surface of the case peripheral wall 12 through the lead wire 11, and is connected to the other
electrode of the piezoelectric vibrator 3 through the case 1. In the ultrasonic transducer shown in
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FIG. 2 and FIG. 3, when adjusting the center frequency r related to the sensitivity and sound
pressure of ultrasonic waves, as shown in FIG. Delete the optional part 16 of 13a.
If the case 1 is made of aluminum, it can be easily cut because it is soft. By cutting, the node
point of the bending vibration of the piezoelectric vibrator 3 moves outward. On the other hand,
after cutting, the diameter of the top surface 2 related to the vibration before cutting becomes
substantially larger or larger. This reduces the frequency f. If the relationship between the
amount of cutting at a predetermined cutting position and the frequency change Δr is
determined in advance, an ultrasonic transducer with a desired frequency can be obtained by a
uniform processing process. This is suitable for lot production at the request of the user.
Although the above embodiment is described as the ultrasonic transducer, the present invention
can be similarly applied to an apparatus having only a single function of a transmitter or a
receiver. When the piezoelectric vibrator is bonded to almost the entire inside of the case
peripheral wall (as shown in FIG. 4 for example), as shown by the cutting point 16 in FIG. In
relation, the base of the tapered surface can be cut without damaging the piezoelectric vibrator,
and in this sense, cutting the tapered surface formed as in the embodiment has a great
advantage. [Effects] As described above, according to the present invention, a part of the tapered
surface on the inner side of the connection portion between the case top surface and the case
peripheral wall portion is scraped to perform the adjustment of the frequency. The frequency can
be easily adjusted by the extremely simple processing, and cutting of the case top front outside
that requires high skill as in the past is not necessary, and the rust prevention and insulation
property consideration is not necessary. Close.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a schematic cross-sectional view of an ultrasonic transducer to which the conventional
frequency shift and 5j adjustment method is applied, and FIGS. 2 and 3 are schematic diagrams
showing an ultrasonic transducer to which the present invention is applied. Sectional structural
drawing, FIG. 4 is explanatory drawing which concerns on frequency adjustment.
1 · · · Case, 2 · · · top surface portion, 3 piezoelectric vibrator, 4 · · · opening, 9 · · · terminal plate,
12 · · · peripheral wall portion, 13 · · · connection portion, 13a · · · taper surface. Patent Assignee:
Attorney at Murata Manufacturing Co., Ltd. Patent Attorney Formerly: Two people Fig. 1 Fig. 2
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Side Fig. 3 Fig. 4
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