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DESCRIPTION JPS50154089

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DESCRIPTION JPS50154089
1 Name of invention
Method of generating conical radiation pattern and piezoelectric transducer component
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of
generating an acoustic radiation pattern and to a piezoelectric transducer arrangement. As is well
known, the piezoelectric effect is a characteristic that causes distortion when an electrical signal
is applied to a certain material, and conversely generates electricity when an external force is
applied to the material to generate electricity, and such piezoelectricity The material exhibiting
the property may be natural or may be artificial. Heretofore, flat piezoelectric elements vibrating
at their natural resonant frequency have been used in transducer constructions, for example in
ultrasonic transducers. When vibrating at a natural resonance frequency, this type of flat platelike piezoelectric element has a center at a node formed in these elements. The element part on
one side of the node always vibrates in the direction opposite to the vibration direction of the
element part on the other side of the node. A flat piezoelectric element having this type of
vibration according to Japanese Patent Application Laid-Open No. 50-154089 (2) transmits or
receives compression waves in a direction substantially perpendicular to the surface of the base
plate. It is uneconomical to generate an omnidirectional radiation pattern when such a flat
piezoelectric element is used to generate ultrasonic waves only in a specific area of a
predetermined shape. There has already been proposed and developed a transducer device for
radiation that propagates over an umbrella-like space. An apparatus of this type will be described
with reference to FIGS. The entire transducer arrangement is indicated at 10 in FIGS. 1 and 2.
The construction 10 comprises a resonator 11, a transducer 12 and a reflector 13. The resonator
11 has two ends closed to form a resonator and is configured in a suitable form generally
referred to as a Helmholtz resonator. As shown in FIG. 1, the upper end of the resonator 11 is
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closed by a support 12 H supporting the transducer 12, and the lower end of the resonator 11 is
closed by a partition 14. The reflecting plate 13 actually extends outward in the circumferential
direction from the resonator 11 in a plane perpendicular to the longitudinal axis of the resonator
11. The transducer 12 is mounted in the resonator 11 so as to extend perpendicularly and
symmetrically across the longitudinal axis of said resonator. The transducer 12 is attached to the
support 12a in a suitable manner and comprises the piezoelectric element 20 shown in FIG. 3
and FIG. The element 20 is, for example, a flat plate-like surface such as a bending piezoelectric
element manufactured by the Flebitte company under the name of bimorph and is a piezoelectric
element, and in response to an electric field applied perpendicularly to the plane of the element,
the node 21 as shown. Curve around. As shown in FIG. 4, the element 20 has a round beveled
node 21. The position of the node 21 is indicated by a broken line in FIG.
As shown in FIG. 3, the end of the element always moves in the opposite direction to the
direction of movement of the element in the node 21. In FIG. 3, the bending position of the
wedge element 2 ° in the F direction is indicated by a solid line, and the downward bending is
indicated by a broken line. The piezoelectric element 20 has a predetermined, preferably
ultrasonic, natural resonant frequency and is attached to the transducer 12 so as to cause free
oscillation about the node 21 of said element. The transducer 12 is configured to generate and
phase shift compression waves on opposite sides of the node 21 of the element to combine the
individual compression waves for interference and enhancement. Also, with the element 20 in
the transducer 12 at an appropriate distance from the surface of the adjacent support 12a, the
sound waves generated on both sides of the plane of the element 20 are reflected so as to be
respectively interfered or enhanced. Also, the transducer 12 has electrical contacts and terminals
15a and 15b, and a piezoelectric element 20 is mounted in the transducer 12 for extracting an
electrical signal from the terminals or applying an electrical signal to both sides of the
piezoelectric element 20 and A suitable method of supporting is as described in U.S. Pat. No.
3.704.385, November 26, 1972, et al., Published November 26, 1972, which is known and
known that piezoelectric element 1-20 is electrically excited at its natural resonant frequency.
Then, the transducer 21 operates to produce an EndPage: 2 spherical radiation pattern 30 in the
resonator 11. Here, the resonance frequency of the element 20 is assumed to be an ultrasonic
resonance frequency. A cross-sectional view of the spherical radiation pattern 30 is shown in FIG.
Here, acoustic vectors 31.32 and 33 are shown. The vector 32 is on the longitudinal axis of the
resonator 11, while the acoustic energy vectors 31 and 33 are offset 45 ° from the vector 32 on
either side of the spherical pattern 30 in the diametrical direction. The Helmholtz resonator 11 is
formed from a resonant cavity having a suitable length and is axially adjustable with respect to
the support 12a to generate a resonant frequency corresponding to the resonant frequency of
the piezoelectric element 20. For this purpose, the acoustic output of the transducer 12 is
amplified by the resonant operation of the Hermholtz resonator 11. The resonator 11 is held by a
clamp ring 18 against a support 12a. At a predetermined distance from the reflecting plate 13, a
plurality of radially spaced openings 16 are formed on the cylindrical sidewall of the Helmholtz
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resonator 11 at circumferentially spaced intervals. The individual open "or holes" 16 are circles
having a diameter approximately equal to half the ultrasonic resonance frequency of the element
20. From now on, the wavelength of the resonant frequency is denoted by λ. The openings 16
are circumferentially spaced around the cylindrical sidewall of the resonator, the centers 17 of
the openings being in a plane parallel to the reflector 13 and spaced approximately λ from the
centers 17 of adjacent openings Have.
The distance 治 measured between the center point 17 of each aperture and the plane of the
reflector 13 and measured on the normal of the reflector 13 for reasons to be described later is
equal to mλ sin θ 0, where m is any integer, ie 1.2 .3. ... θ is defined as the angle between the
principal axis vector 36 and the vector 38 of energy to be enhanced. In operation of the device
according to the invention, the Helmholtz resonator 11 converts the spherical radiation pattern
30 generated along its axis by the transducer 12 into a plurality of substantially spherical
radiation patterns 35 generated by the aperture 16. Convert. Thus, as shown in FIG. 6, the
individual apertures 16 act as separate sources of sound producing a spherical radiation pattern
having a maximum energy component along the axis indicated by the vector 36. A plate 36,
which originates from the opening 16, extends parallel to the reflector 13 from the center point
17 of the opening. A plane perpendicular to the reflector 13 is formed by both the sound
components, ie the vectors 37 and 38, for the sake of discussion. The vectors 37 and 38 are
located on either side of the spherical radius (the diameter direction of the turn 35, at an angle of
θ to the axis of the opening given by the vector 36 The acoustic energy is maximally enhanced
when θ = 45 °, but the center 17 of the aperture 16 is suitably selected from the surface of the
reflector 13 so that the distance X satisfies the relation equal to mλ sin θ even when θ is other
than 45 °. By spacing them apart, the acoustic energy can be enhanced. Is the angle between
the principal axis vector 36 parallel to the reflector 13 and the vector 38 to which the desired
acoustic energy is to be enhanced. Due to the one-wavelength spacing between the aperture
centers 17, the spherical patterns 35 of ultrasound radiation add in phase to form a symmetrical,
outwardly radiating annular radiation pattern around the longitudinal axis of the resonator 11.
As shown in FIG. 1, when the above-mentioned annular radiation pattern radiates to the outside,
the portion having the vector 37 of the pattern is immediately reflected by the reflection plate
13.2. I am in touch with As shown, the vector 37 hits the reflector 13 at an incident angle of 45
°. Therefore, the traveling distance of the sound wave when the sound wave traveling along the
vector 37 hits the reflecting plate 13 is 7. 4 = by X / sin 45 °, where Z is the travel distance of
the sound wave along vector 37, X is the distance measured from the aperture center point 17 to
the normal of the reflector at 13 inch reflector . As described above, the distance χ is selected to
be equal to mλ5iT1θ. Then, using the above equation, it can be seen that ・ ·, -m; sin θ / sin θ
= mλ.
Thereby, the sound wave reflected from the reflector 13 along the path of the vector 37 is added
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to the white wave in the vector 38 and is added in phase to the zircon wave, and Hertz, Ho
EndPage: around the axis of the three Rutz resonator 11 Form an umbrella-shaped radiant
buttery 40. A cross-sectional view of the umbrella-shaped radiation pattern 40 is shown in FIG.
Here, the transducer assembly 10 is shown attached to the ceiling 41 of the room together with
the reflection plate 13. The axis 42 of the construction 10 extends vertically downward from the
ceiling 41. The umbrella-shaped toroidal radiation pattern 40 is formed 360.degree.
Symmetrically about the axis 42 and has the largest component of energy along a vector 43
extending in the direction of 45.degree. As is apparent, the radiation pattern 40 produces an
umbrella that protects the relatively large surface area of the floor 44. Further, as shown in FIG.
7, the radiation along the vector 43 causes the surface 44 to be reflected like 438, so that an
object located at a position A other than the area directly covered by the umbrella is normally
detected. Also, since the vector 438 is reflected by the ceiling 41, the area of the umbrella can be
greatly expanded if this is repeated several times. This is also true when using the multitran 1 JP
50-154089 (4) strainer construction. Also, the converter arrangement 10 can be operated in the
receiving mode. For example, if θ = 45 ° in FIG. 7, the maximum sensitivity of the structure 10
in the reception mode. Is obtained at a 45.degree. Slope along the vector 43, and essentially the
reception sensitivity pattern matches the transmission pattern shown. FIG. 8 shows the
Hermholtz resonator 11 of the construction 10 mounted in a cylindrical cavity 50. FIG. The
cavity 50 may be formed in the room ceiling or separately constructed to attach the wall still to
the ceiling. The cavity 50 is preferably cylindrical and is formed by an upper partition 51 and a
side cylindrical partition 52. When the upper partition 51 is formed of a suitable material so that
a suitable ceiling surface can be used as a reflector, it can be used as a reflector 13. Since the side
wall 52 is provided parallel to the axis of the resonator 11, the sound wave traveling along the
vector 36 is not reflected to the outside of the cavity 50. Also, the cavity should be large enough
to reflect the sound waves traveling along the vector 37 out of the cavity. If a sound wave
traveling along the vector 37 from the center point of the aperture 16 is reflected, the cavity is
sized so that the reflected wave is “in phase” with the transmit wave to enhance the transmit
wave.
In this case the spacing from the aperture 16 and the resonator 11 to the cavity wall 52 should
be equal to nλ, where n is chosen to be greater than or equal to one wavelength λ of the
acoustic wave transmitted in the desired umbrella pattern. As a result, a portion of the radiation
from the aperture 16 that hits the wall 52 is reflected so that the reflected wave is in phase with
the transmitted wave and enhances the transmitted wave. The wall 52 is advantageously
perpendicular to the main transmit radiation vector 36, but another angle is desired if maximum
sensitivity is required along vectors other than 45 °. Mounting the transducer arrangement in
the recess-is advantageous as the arrangement is less susceptible to damage. Resonator end 14 is
in the plane of ceiling 41 in FIG. 9 shows a shielding structural member 60 having a recess 50,
the shielding structural member 60 has a good appearance (and bevel edge to prevent collision
of the external object with the transducer structure as described above). The installation of the
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portion 61 is suitable for attachment to a ceiling. Generating a single spherical radiation pattern,
generating a plurality of substantially spherical radiation patterns from said pattern, combining
said plurality of patterns to form an annular radiation pattern; In addition, an umbrella type
toroidal radiation pattern can be generated by a method of forming an umbrella type toroidal
radiation pattern at the reflection portion of the annular pattern. The arrangement as described
above is particularly suitable for use in an ultrasound intruder detection system in which the area
to be protected is, for example, in the middle of a room. In many cases, however, it is desirable to
be able to control the shape of the radiation pattern of the transducer, especially if it is desired to
protect the aisles, corridors or large room areas in a building. Therefore, according to the present
invention, EndPage: 4 generates an annular acoustic energy radiation pattern having a selected
wavelength and being emitted to the outside about a predetermined axis, The reflecting surface
reflects a sound wave having the annular pattern emanating from at least one side of a virtual
plane extending through the in and out portions of the annular butter 7 perpendicular to the
axis, the reflecting surface being broad The side wall of an open truncated conical cavity at one
axial end, the side wall of the cavity being oblique at an acute angle to said predetermined axis,
said imaginary plane being said truncated cone A reflected parallel radiation wave extending a
selected distance away from the narrow axial end of the cavity and in phase with the outgoing
radiation wave propagating from the other side of the virtual plane So as to be selected around a
predetermined axis The length of the cone Joon - is generating sound energy radiation patterns.
According to the present invention, in a piezoelectric transducer structure having a piezoelectric
element having a spherical radiation transmission or detection pattern and a resonator
accommodating the piezoelectric element, the resonator has a plurality of openings, and the
openings The central point is located in one common plane at equal intervals from the center of
the spherical radiation pattern, and the position and size of each aperture is made to produce a
partial spherical radiation pattern having a resonant frequency outside the resonator The
apertures are spaced from one another to combine the spherical radiation patterns of all the
apertures to produce a toroidal radiation peak centered at the resonator, and further containing
the transducer arrangement therein The inner wall of the cavity has a truncated cone shape and
has an axis common to the predetermined axis, and the narrow axial end of the cavity is spaced
from the opening by a predetermined distance, and the reflected radiation wave is anti It is
synthesized that is not radiated wave in phase with the being configured to form a conical
radiation pattern. Next, one embodiment of a piezoelectric transducer according to the present
invention will be described in detail with reference to FIGS. FIG. 10 shows the transducer
assembly 10 mounted within the cavity 60 of the acoustically reflective member. The construct
10 consists of a Hermholtz resonator and a transducer contained therein. The plate-like bends
are advantageously used as piezoelectric elements for this transducer. The 1 ° resonator has a
plurality of openings in the outer peripheral surface, these openings being spaced apart from one
another by equal angular intervals around the resonator axis. The cages 1LL- in each aperture lie
in a common plane extending perpendicularly to the axis of the resonator. When the transducer
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is energized, an annular radiation pattern is emitted from each aperture. The acoustic reflection
member has a flat base supporting the annular member 62. The annular member 62 has a
triangular-shaped longitudinal cross section and forms the side wall of the cavity 60. The cavity
60 has a frusto-conical shape, and the cross section is enlarged as the distance from the base of
the reflecting member is increased. The ^ 1 surface of the side wall forms an acute angle B0 with
the longitudinal axis of the resonator. The central point of each aperture is spaced from the base
of the reflective member by a distance Y, which forms a cavity 6 o sized at mλ · Cos B ′ ′ to
maximize the radiant energy. The member may be a ceiling or a wall, or may be a separate
component attached to the wall or ceiling. The shape of the cavity 60 is advantageously frustoconical, but may be otherwise shaped, for example, with an inclined wall at an acute angle to the
longitudinal axis of the resonator.
Thus, when actuated, the transducer, when energized, generates spherical radiant butters /
within the resonator, resulting in a plurality of substantially spherical radial patterns from each
aperture. The plurality of spherical radiation patterns emitted from the aperture combine to form
an annular radiation pattern, portions of the annular pattern being reflected by the cavity wall to
form a conical shaped radiation pattern. The radiation pattern generated by the device of FIG. 10
is a fairly broad lobe as shown in FIG. 11 because the angle B is greater than 45 °. In the case of
the device of FIG. 12, the structure 10 is the same as that of FIG. 10, but since the inclination
angle of the side wall of the reflecting member forming the cavity to which the structure is
attached is smaller than -45. The resulting radiant butter / will be relatively narrow lobed as
shown in FIG.
4. Brief description of the drawings. EndPage: 5 FIG. 1 is a side view showing a part of the
embodiment of the piezoelectric transducer construction which has already been proposed cut
away, and FIG. 3 is a side view showing the piezoelectric element of the structure of FIG. 1, FIG. 4
is a plan view of the element of FIG. 3, and FIG. 5 is generated in the resonant cavity of the
transducer structure of FIG. Figure 6 is a side view of the transducer showing a cross section of
the radiation pattern, Figure 6 shows the cross section of the radiation pattern emitted in one of
the circular openings provided in the resonant cavity side wall of the arrangement of Figure 1;
FIG. 7 is a side view of the structure showing the cross section of the umbrella-shaped radiation
pattern produced by the structure of FIG. 1 mounted on a ceiling, and FIGS. 8 and 9 are
conversions of FIG. FIG. 7 is a side view, partly broken away, of an embodiment in which the
container arrangement is provided in two different cavities; FIG. 10 is a side view partially
showing an embodiment of a piezoelectric transducer arrangement according to the invention for
generating a broad conical radiation pattern, and FIG. 11 is a radiation pattern diagram of the
arrangement of FIG. FIG. 12 is a side view showing another embodiment of the piezoelectric
transducer structure of the present invention in a partially cut away view. FIG. 13 shows a
radiation pattern diagram of the structure shown in FIG. DESCRIPTION OF SYMBOLS 10 ...
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Converter structure, 11 ... Resonator, 12 ... Converter, 13 ... Reflective plate, 20 ... Piezoelectric
element, 41 ... Ceiling, 4'4 ... Floor , 60 ... cavity, 62 ... annular member. (Other 1 person) · j12
Figure 4) Figure 7 Figure 9 EndPage: 66, List of attached documents 7. Inventors other than the
above, patent applicants or agents IV names, (6181) patent attorney Toshi Yano M1 ~ EndPage:
7
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