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JPS60232798

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DESCRIPTION JPS60232798
[0001]
FIELD OF THE INVENTION This invention relates generally to the use of transducers in an
environment which is generally detrimental to the operation of the transducer and components,
and in particular to use in such an environment. The present invention relates to a capacitive
ultrasonic transducer using a vibrating diaphragm. BACKGROUND OF THE INVENTION
Transducers are generally known as devices for converting energy in the form of mechanical
vibrations to other forms of energy such as electrical signals or vice versa. Many different types
of transducers are used to measure various quantities, such as the distance to the target, the
temperature of the object, or the gas pressure, not to mention many examples. Used in For
example, Polaroid, Inc., Cambridge, Mass., Currently manufactures several different types of autodeveloped cameras, each of which is automated by a distance meter using capacitive transducers
to determine subject distance. Use a focusing lens system that is focused on. The subject distance
is determined by measuring the elapsed time from when a transducer transmits a burst of
ultrasound energy towards a particular subject and the same transducer detects that energy
burst reflected from that particular subject. Be done. An electrical signal representing this
elapsed time, and thus the subject distance, originating from the rangefinder is later used to
accurately control the focusing of the lens arrangement. Capacitive ultrasonic transducers use a
vibrating diaphragm for sound generation / detection consisting of a thin plastic film with a layer
or coating of gold several hundred angstroms thick on one side. Under normal circumstances, as
in the case of the autofocus autofocus camera described above, the gold coating of the imaging
diaphragm is attached to the outside of the apparatus using it so that the apparatus is placed or
used Directly in physical contact with the atmosphere or environment of the In many
applications, the ambient environment has little or no detrimental effect on either the gold
coating of the diaphragm or the transducer operation. However, in certain applications,
popularity includes corrosive gases and foreign particles, which can be detrimental to transducer
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components and can degrade the operation of the transducer.
According to a distance meter using a capacitive ultrasonic transducer of the type described
above, the distance to an object which is fairly close (within 12, 19 m (40 feet)) can be reduced
within a relatively small error range (about ± 1.27 ann (± 0.5 inch) can be determined.
However, if this type of distance meter is used on the outer surface of a vehicle, such as an Ilance juicer exposed to a combined environment of misty salt water (salt mist) and wear (sand),
the distance The meter can not work after a relatively short period of time or does not work
properly. The reason why the rangefinder does not work partially or at all in such an
environment is that it causes corrosion of the electrical elements after the salt mist has entered
the inside of the transducer or near it through the aperture of the rangefinder. Or by striking
against the exposed gold-coated surface of the vibrating diaphragm, which significantly degrades
the operation of the transducer and thus the distance meter. OBJECTS AND SUMMARY OF THE
INVENTION Accordingly, it is an object of the present invention to provide transducers that
operate normally in environments that are normally detrimental to transducer operation and
components. Another object of the present invention is to provide a capacitive ultrasonic
transducer which operates properly in corrosive and / or abrasive environments. Another object
of the present invention is to provide a range finder using a capacitive ultrasonic transducer that
can operate properly in corrosive and / or abrasive environments. Other aspects, features and
advantages of the present invention will become apparent in the following description of an
embodiment made with reference to the accompanying drawings. In the present invention, a
transducer device is provided that can degrade the operation of a conventional transducer and /
or operate normally in an environment that would damage a conventional transducer or
transducer related component. This device contains a vibrating diaphragm-shaped ultrasound
transducer in one part of a housing divided into two volume parts by a thin plastic film. Means
are provided to eliminate temperature induced pressure differences that may occur between the
gas adjacent to both sides of the vibrating diaphragm. One volume portion of the housing directly
interrogates the atmosphere, and the other volume portion completely completes the transducer,
except for the portion of the conduit which passes inside the volume portion to the atmosphere
in a remote, protected position. It is surrounded by
By having both volume portions of the housing be vented to the atmosphere, pressure between
the two volume portions is degraded, the transducer operation is degraded, and / or the pressure
difference that distorts the plastic film is eliminated, and The atmosphere containing the
transducer, and the ambient atmosphere that may be detrimental to the operation and / or
elements of the transducer, by having the volume portion containing the transducer be vented to
the atmosphere in the remote protection position. And are prevented from direct contact during
the process of eliminating the pressure difference. DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENT Referring to FIGS. 1a and 1b, a capacitive ultrasonic transducer 10 constructed in
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accordance with the present invention is shown. The transducer 10 has a cylindrical housing 12,
one end of which is an open end 14 and the other end is a partially open perforated end 16. The
housing 12 also has a flange portion 18 near its open end 14. A flat vibrating diaphragm 20 is
disposed between the support ring 22 and the housing 12 so as to cover the entire opening of
the housing open end 14. The passages 21a and 21b formed in the flange portion 18 of the
housing 12 are for preventing the formation of a hermetic seal between the diaphragm 20 and
the housing at the flange portion 18. The vibrating diaphragm 20 is preferably E, I. It is assumed
that it is made of thin polyamide film 11 sold under the registered trademark of KAPTON from
duPont de Nemours Company, Inc. One surface of the diaphragm 20 is made conductive by being
coated with a thin gold layer (about 300 thick), and the other surface is made of dielectric, ie
nonconductive, Kapton. The support ring 22 is of circular cross section with an opening 23
through the central portion and has a flanged end for cooperative engagement with the flange
portion 18 of the housing 12. The back plate 24, which has a circular cross section, has an
electrically conductive raised surface for cooperative engagement with the vibrating diaphragm
20. The leaf spring 26 provides mechanical pressure to keep the back plate 24 and the
diaphragm 20 in correct physical contact. A protective diaphragm 28 having the function of
preventing harmful gases and / or additives from entering the perforated end of the housing 12
completely covers the perforated end of the housing. The diaphragm 28 is preferably E, It is
assumed that it is made of a thin polyester film sold by duPont de Nemours Company, Inc. under
the registered trademark MYLAR.
When assembled, the transducer element shown in FIG. 1 assumes the position shown in FIGS. 2a
and 3. Assembly of the transducer 10 will be described with reference to FIGS. 2a, 2b and 3. FIG.
The diaphragm 20 is placed over the opening 14 (FIG. 1) of the transducer housing 12 with a
relatively flat planar force with the application of a weak uniform force in the radial direction.
The back plate 24 is then engaged to make the diaphragm 20 concave, which is in the shape of
the mid-high surface of the back plate. Next, after the circumference of the diaphragm 200 is
sandwiched between the flange end of the support ring 22 and the flange portion 18 of the
housing 12, the open end of the housing 12 is tightened on the flange portion of the ring 22. The
flange portion keeps the circumference of the diaphragm 20 in a fixed position relative to the
housing 12. Passages 21a and 21b prevent the formation of a hermetic seal between diaphragm
20 and transducer housing 12. The high back plate 24 is disposed within the opening 23 of the
support ring 22 so that the middle high surface of the back plate 24 engages the dielectric or
insulating surface of the diaphragm 20. After the rear plate 24 is so positioned, the leaf spring
26 is inserted through each of the holes 30a and 30b (FIG. 1) of the support ring 22, whereby
the central portion of the leaf spring 26 pulls the rear plate 24. Pushing causes the ends of the
leaf spring 26 to be supported on the walls of the holes 30 a, 30 b of the support ring 22. Such
placement of the leaf spring 26 keeps the diaphragm 20 in proper cooperative engagement with
the mid-high surface of the back plate 24. After the transducer 10 is fully assembled as described
above, the protective diaphragm 28 is adhered to the perforated end 16 of the transducer
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housing 12. The diaphragm 28 has an adhesive coating (not shown) previously applied along the
outer edge of one surface of the diaphragm 28. After the diaphragm 28 is placed on the
perforated end of the housing 12 with its adhesive coated surface facing the perforated end of
the housing 12, the diaphragm 28 is assembled by means of an assembly tool (not shown).
Spreading over the perforated end, the diaphragm 28 is then adapted to the shape of the outer
contour of the perforated end of the housing 12. When the diaphragm 28 is held open and in the
0 profiled position of the housing, the assembly tool supplies the required amount of heat to the
diaphragm and the thermosetting adhesive coating already thereon And thereby bonding the
outer edge of one surface of the diaphragm 28 onto the outer lateral surface 32 of the housing
12.
An example of this type of assembly tool used to bond the protective diaphragm 28 to the
housing 12 is shown in US Pat. No. 4.403,117 by PAGE Summer A. The combination of the
transducer 10 and the bonded diaphragm 28 is then inserted into the protective housing 34 as
shown in FIGS. 4, 5 and 6. An exploded perspective view of the protective housing assembly 34
and a perspective view of the transducer 10 are shown in FIG. 4 where it is bonded to the
transducer 10 with one of the pressure equalization passages of the vibrating diaphragm 20. The
protective diaphragm 28 is shown disposed within the housing device 34 so as to provide
protection from potentially corrosive and / or abradable environments. In FIGS. 4, 5 and 6, the
protective housing 34 includes a base member 36, which is one of the transducers 10 when the
transducer 10 is fully incorporated into the housing device a34. It has a recess 38 for causing the
part to project. Furthermore, near the outer end edge of the base member 36, a plurality of
equally spaced regular gages 4o are circumferentially formed. The protective housing 34 further
includes a cover member 42, which has a plurality of screw holes 44 formed at equal intervals
corresponding to the above-mentioned common edge near the outer edge, and a central portion
And a large circular opening 46 extending therethrough. One end of the opening 46 is reduced in
diameter, and a shoulder 48 is formed between the large diameter end and the small diameter
end. The cover member 42 also has a circular groove 50 of semicircular cross section, and after
the 0-ring seal 52 is housed in the groove 50, the base member 36 is put in place with respect to
the cover member 42. The O-ring 52 forms a seal between the base member 36 of the transducer
device and the cover member 42 and the O-ring 54 forms a seal between the protective
diaphragm 28 and the shoulder 48 of the cover member 42 The cover piece 42 is rigidly
attached to the base member 36 by means of the small screws 56 when the parts are completely
assembled. The plastic tube 58 passes through the bore of the base member 36 into the recess
38 formed therein. The silicon-based seal 60 forms a hermetic seal between the outer surface of
the tube 58 and the base member 36 where the plastic tube 58 enters the base member 36. A
pair of electrical leads 62 are routed through the plastic tube 58 from a remote location into the
base 38.
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A protective grate 64 (FIG. 6) bonded to the surface 66 of the cover member 42 has a relatively
large object entering through the opening 46 of the cover member 42 and is mounted in a
protective position within the protective device 34 It prevents the diaphragm 28 from being
damaged. The transducer 10 is housed in the protective housing 34 as follows. First, the resilient
O-ring 54 is placed on the shoulder 48 in the opening 46 of the cover member 42. Next, the
transducer 10 is opened until the perimeter of the diaphragm 28 engages the resilient O-ring 54,
with the perforated end covered by the protective diaphragm 28 facing the shoulder 48 of the
opening 46 Insert in 46 Next, the male terminal member connected to the back plate 24 of the
ultrasonic transducer user 10 and the conductive surface of the diaphragm 20 is connected to
the spade type male terminal member to which the tip of the electric wire pair 62 is connected.
Fit into the Next, after the resilient O-ring 52 is placed in the positioning groove 50 of the cover
member 42, the base member 36 is placed such that the formed surface 68 of the recess 38
engages with the O-ring 52. When the base member 36 is so placed, an O-ring 52 forms a
hermetic seal between the cover 42 and the base member 36. The surface 68 of the base
member 36 also compresses the 0-ring 54 further by engaging the end of the support ring 22 of
the transducer 10, thereby providing a tighter seal between the protective diaphragm 28 and the
cover member 42. Is formed. After the base member 36 is placed on the cover member 42 so
that the holes 40 of the base member 36 are aligned with the screw holes 44 of the cover
member 42, the machine screws 56 are inserted into both holes, 36 is tightened and fixed to the
cover member 42. With both members fixed, the transducer 10 is vented by the rigid plastic base
member 36, the rigid plastic cover member 42, the protective diaphragm 28, and the O-rings 52
and 54. It is housed in an airtight Chi-A 7 board that has only one. Commentary: Due to the
temperature between the gas directly adjacent to both sides of the diaphragm 20, which will
strain the protective diaphragm 28 even if the transducer 10 is housed in an airtight chamber
having only one vent. The occurrence of pressure differentials is prevented by the presence of
pressure equalization passages 21a and 21b. If a hermetic seal is formed between the vibrating
diaphragm 20 and the shoulder 18 of the housing 12, then between the vibrating diaphragm 20
and the protective diaphragm 28 when the transducer assembly 34 (FIG. 5) is fully assembled.
An airtight chamber is formed in the
When the transducer device 34 is mounted on the exterior surface of the vehicle, the protective
diaphragm 28 is the chamber formed by the diaphragm if the gas or air in the chamber formed
by these two diaphragms is heated by solar radiation or the like. Air trapped inside is expanded
by thermal expansion. When the diaphragm 28 is expanded, permanent creases may occur there,
which substantially reduces the hearing of object detection ultrasound energy transmitted or
received by the diaphragm 28. As mentioned above, the air or spatial volume near both sides of
the protective diaphragm 28 avoids degradation of the frequency characteristics of the ultrasonic
energy transmitted and received by the diaphragm 28 and / or degrades the operation of the
diaphragm 28 In order to prevent a temperature-induced pressure differential which distorts 2.8,
it must have substantially the same pressure. Such air pressure equalization is not possible if the
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chamber 38 in the protective housing device 34 is completely air tight. Also, if the interior of the
chamber 38 is open to an operating environment containing, for example, corrosive gases, the
transducers 10 and / or the interface electrical components of the transducer 10 will be severely
damaged. Harmful temperature-induced pressure differences between gases adjacent to the
diaphragm 20 in the transducer 10 can be prevented by the passages 21a and 21b (FIGS. 2a and
2b) as described above. The apparatus of the present invention connects the interior of the
chamber 38 to a remote environment free of corrosive gases and particles by means of an airtight plastic tube or conduit 58 in order to solve these problems. One end is open within the
corrosive gas and particle free environment. In the example, it is merely for convenience that the
electrical leads 62, which supply the transducer 10 with electrical energy for generating
vibrations, are passed through the conduit 58. It may not be possible to use separate paths for
the pressure equalization gas path and the electrical leads for energizing the transducer 10, if
such an arrangement is considered appropriate. Absent. With the transducer 10 enclosed within
the housing device 34, some of the transducer 10 and interface electrical elements are protected
from any corrosive gases present in the operating environment and from abrasion by foreign
particles.
However, just enclosing the transducer 10 in the chamber for protection purposes does not allow
the ultrasound energy to pass through the chamber walls, or the level of the passing energy is
substantially attenuated. In the present invention, the protective chamber in which the
transducer is enclosed is a rigid portion consisting of the base member 36 and the cover member
42, and a flexible portion consisting of the protective diaphragm 28 that delivers ultrasonic
energy efficiently and effectively. Contains. The ultrasonic energy generated by the vibrating
diaphragm 20 of the ultrasonic transducer 10 is transferred to the protective diaphragm 28,
which thereby has substantially the same frequency and amplitude as the diaphragm 20, for the
same length of time It resonates. The ultrasonic energy generated by the resonance of the
protective diaphragm 28 is sent to a particular remote object or location for the purpose of
detecting the object. In order to minimize interference with the ultrasonic energy generated by
the vibrating diaphragm 20, the protective diaphragm 28 is at a point on the plane substantially
at a half wavelength distance from the diaphragm 2o (a point at which the wave amplitude is
minimal ), And the protective grating 64 on the cover member 42 is another half on the plane at
a distance of substantially half wavelength from the protective diaphragm 28 transmitting
ultrasonic energy and just one wavelength from the vibrating diaphragm 20. It is attached to the
node. Those skilled in the art will appreciate from the detailed description of the present
invention that various improvements and modifications may be made to the above-described
embodiments without departing from the true scope of the present invention. is there. The
embodiments described above are merely illustrative and should not be considered as the only
embodiments that include all of the present invention.
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[0002]
Brief description of the drawings
[0003]
FIG. 1a is an exploded elevational view in partial section of a capacitive ultrasonic transducer
with a protective diaphragm according to the invention, and FIG. 1b is a pressure equalization
formed in the housing as viewed from the right of FIG. 1a. 2a is a partial sectional view with the
protective diaphragm attached to the protected position of the transducer of FIG. 1 and fully
assembled, FIG. 2b is the right side of FIG. 2a. FIG. 3 is a partial elevation view of the ultrasonic
transducer used in the present invention and the pressure equalizing passage formed in its
housing, as seen from the side of FIG. 3, and the perforated housing of the transducer shown in
FIG. FIG. 4 is a bottom view of the protective diaphragm, FIG. 4 is an exploded perspective view
of the present, bright ultrasonic transducer device that can also operate in corrosive and / or
abrasive environments, and FIG. Partial cross both sectional view of an ultrasonic transducer
device of FIG. 4 assembled in, FIG. 6 is a bottom view of an ultrasonic transducer device of FIG. 5.
DESCRIPTION OF REFERENCES 10: Capacitive ultrasonic transducer, 12: cylindrical housing, 16:
right hole end, 20: vibrating diaphragm, 21a, 21b-! NB, 24: back plate, 28: protective diaphragm,
34: protective housing, 38: air tight chamber, 46: circular opening, 52.54: 0 ring, 58.・ Plastic
tube, 62 ・ ・ ・ Electric wire, 64 ・ ・ ・ Protective grid. Agent Atsushi Asamura
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