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DESCRIPTION JP2004033814

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DESCRIPTION JP2004033814
An array type piezoelectric vibrator having high sensitivity is provided. SOLUTION: A long
piezoelectric body 23 is composed of a plurality of piezoelectric ceramic members 26
sequentially arranged in the length direction via a resin filling portion 25, and the size of the
piezoelectric ceramic member and the resin filling portion Array type piezoelectric vibrator
whose size and size meet the following specifications. (1) 2 / 3W ≦ L 3 3 / 2W (2) 2 / 3T L L (3
/ 2T (3) 1 / 20L A A 1 1 / 5L [where L is the length direction of the long piezoelectric body W is
the length of the piezoelectric ceramic member along the width direction of the elongated
piezoelectric body, T is the thickness of the piezoelectric ceramic member, and A is the elongated
piezoelectric material It is the length of the resin-filled portion along the length direction of the
body].
Array type piezoelectric vibrator
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
array-type piezoelectric vibrator. [0002] An array-type piezoelectric vibrator is widely used as an
electroacoustic transducer of a medical ultrasonic diagnostic apparatus. In general, an array-type
piezoelectric vibrator is configured such that a plurality of piezoelectric vibrators made of a long
piezoelectric body provided with electrodes on both upper and lower surfaces are fixed in
parallel without contact with each other. Plate-shaped piezoelectric ceramics have been widely
used as long piezoelectric bodies of piezoelectric vibrators. In a piezoelectric vibrator using this
plate-like piezoelectric ceramic as a long piezoelectric body, when the ratio of the length to
thickness in the width direction of the piezoelectric ceramic (width / thickness ratio) is around
0.6, high electrical conductivity is obtained. Indicates mechanical conversion efficiency. In the
array type piezoelectric vibrator, in order to be able to transmit and receive high frequency
ultrasonic waves, it is necessary to make the thickness of the long piezoelectric body of each
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piezoelectric vibrator thin. However, if the thickness is too thin while maintaining the width /
thickness ratio of the piezoelectric ceramic at 0.6, the width of the elongated piezoelectric body
becomes too narrow. For this reason, in recent years, a piezoelectric vibrator using a 1-3 type
composite piezoelectric material exhibiting high electromechanical conversion efficiency as a
long piezoelectric body has attracted attention regardless of the width / thickness ratio. The
configuration of a typical array-type piezoelectric vibrator of the prior art, which is composed of
a piezoelectric vibrator using a composite piezoelectric material for a long piezoelectric body, is
shown in FIGS. 1 and 2 of the accompanying drawings. FIG. 1 is a view showing the configuration
of an array-type piezoelectric vibrator, FIG. 1 (a) is a plan view of the array-type piezoelectric
vibrator, and FIG. 1 (b) is an array-type piezoelectric vibrator FIG. 1C is a side view, and FIG. 1C is
a cross-sectional view taken along line I-I of FIG. FIG. 2 is an enlarged perspective view of a long
piezoelectric body used in the piezoelectric vibrator of FIG. In FIG. 1, the piezoelectric vibrators
10 are fixed in parallel in non-contact with each other on the sound absorbing material 11. A
resin 12 is filled between the adjacent piezoelectric vibrator 10 and the piezoelectric vibrator 10.
The piezoelectric vibrator 10 includes a long piezoelectric body 13 and electrodes 14 a and 14 b
provided on upper and lower surfaces of the long piezoelectric body 13. As shown in FIG. 2, in
the elongated piezoelectric body 13, a plurality of prismatic piezoelectric ceramic members 16
are provided in the length direction and the width direction of the elongated piezoelectric body
13 through the resin portion 15. It consists of a 1-3 type composite piezoelectric material fixed
parallel to each other and perpendicular to the electrodes 14a, 14b. In a piezoelectric vibrator
using this 1-3 type composite piezoelectric material as a long piezoelectric body, the volume
fraction of the piezoelectric ceramic member in the long piezoelectric body 13 is regardless of
the width / thickness ratio of the long piezoelectric body. When in the range of 50-60% (for lead
zirconate titanate), it exhibits high electro-mechanical conversion efficiency.
According to the research of the present inventor, a piezoelectric vibrator using the abovementioned 1-3 type composite piezoelectric material as a long piezoelectric body has a width /
thickness of the long piezoelectric body. Although high electromechanical conversion efficiency
is exhibited regardless of the height ratio, it has been found that it is difficult to obtain
transmission / reception sensitivity that can be said to be sufficiently high with a small-sized
piezoelectric vibrator that constitutes an array type piezoelectric vibrator. Therefore, an object of
the present invention is to develop a piezoelectric vibrator for an array-type piezoelectric
vibrator capable of obtaining high sensitivity regardless of the width / thickness ratio of the
elongated piezoelectric body, ie, high-sensitivity array-type piezoelectric vibration It is to provide
a child. According to the present invention, there is provided an array-type piezoelectric device in
which a plurality of piezoelectric vibrators comprising long piezoelectric members provided with
electrodes on both upper and lower surfaces are fixed in parallel without contact with each other.
A vibrator comprising: a plurality of piezoelectric ceramic members in which the elongated
piezoelectric body is sequentially arranged in the length direction via a resin filling portion; and
the size of the piezoelectric ceramic member and the resin filling portion There is an array-type
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piezoelectric vibrator characterized in that the size and the following specification are satisfied.
(1) 2 / 3W ≦ L ≦ 3 / 2W (2) 2 / 3T ≦ L ≦ 3 / 2T (3) 1/20 L ≦ A ≦ 1/5 L [wherein L Is the
length of the piezoelectric ceramic member along the length direction of the elongated
piezoelectric body, W is the length of the piezoelectric ceramic member along the width direction
of the elongated piezoelectric body, and T is the piezoelectric ceramic member The thickness, A,
is the length of the resin-filled portion along the longitudinal direction of the elongated
piezoelectric body. Preferred embodiments of the array-type piezoelectric vibrator of the present
invention are shown below. (A) The size of the piezoelectric ceramic member satisfies the
following requirements. (1) 3 / 4W ≦ L ≦ 4 / 3W (2) 3 / 4T ≦ L ≦ 4 / 3T (b) The size of the
piezoelectric ceramic member satisfies the following definition. (1) 4/5 W ≦ L ≦ 5/4 W (2) 4/5
T ≦ L ≦ 5/4 T (c) The thickness of the piezoelectric ceramic member is 0.1 to 0 It is in the range
of .3 mm. (D) The resin-filled portion is made of polyurethane resin. (E) The distance between the
adjacent piezoelectric vibrator and the piezoelectric vibrator is in the range of 4/5 to 5/4 times
the length of the resin-filled portion along the longitudinal direction of the long piezoelectric
body is there. (F) The epoxy resin is filled between the adjacent piezoelectric vibrator and the
piezoelectric vibrator. (G) The piezoelectric vibrator is concavely curved in its length direction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The array type piezoelectric vibrator of the
present invention will be described with reference to the attached drawings. FIG. 3 is a view
showing the configuration of an array-type piezoelectric vibrator according to the present
invention, FIG. 3 (a) is a plan view of the array-type piezoelectric vibrator, and FIG. 3 (b) is an
array-type piezoelectric It is a side view of a vibrator, and (c) of Drawing 3 is an II-II sectional
view of (a) of Drawing 3. Drawing 3 (c) is a side view. FIG. 4 is an enlarged perspective view of a
long piezoelectric body used in the piezoelectric vibrator of FIG. In FIG. 3, the piezoelectric
vibrators 20 are fixed in parallel in non-contact with each other on the sound absorbing material
21. A resin 22 is filled between the adjacent piezoelectric vibrator 20 and the piezoelectric
vibrator 20. The piezoelectric vibrator 20 includes an elongated piezoelectric body 23 and
electrodes 24 a and 24 b provided on upper and lower surfaces of the elongated piezoelectric
body 23. As a material of the resin 22, an epoxy resin can be mentioned. The elongated
piezoelectric body 23 is composed of a plurality of piezoelectric ceramic members 26
sequentially arranged via the resin filling portion 25 in the length direction. The configuration of
the elongated piezoelectric body 23 will be described with reference to FIG. In FIG. 4, L is the
length of the piezoelectric ceramic member 26 along the length direction of the elongated
piezoelectric body 23, and W is the piezoelectric ceramic member 26 along the width direction of
the elongated piezoelectric body 23. T is the thickness of the piezoelectric ceramic member 26,
and A is the length of the resin-filled portion 25 along the longitudinal direction of the elongated
piezoelectric body 23. Although the elongated piezoelectric body 23 can be said to be one form
of a composite piezoelectric material in that it is composed of the resin filling portion 25 and the
piezoelectric ceramic member 26, in the present invention, L of the elongated piezoelectric body
23 , W, T, and A are characterized by satisfying the following relationship. (1) 2 / 3W ≦ L ≦ 3 /
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2W (2) 2 / 3T ≦ L ≦ 3 / 2T (3) 1/20 L ≦ A ≦ 1/5 L Piezoelectric ceramic member 26
Preferably, the relationship between L, W, and T satisfies the following relationship. (1) 3 / 4W
≦ L ≦ 4 / 3W (2) 3 / 4T ≦ L ≦ 4 / 3T The relationship between L, W, and T of the piezoelectric
ceramic member 26 is further as follows: It is preferable to satisfy the following relationship. (1)
4/5 W ≦ L ≦ 5/4 W (2) 4/5 T ≦ L ≦ 5/4 T In the present invention, the resin-filled portion 25
of the elongated piezoelectric body 23, piezoelectric There is no restriction | limiting in particular
in the material of the ceramic member 26, The material used for a well-known composite
piezoelectric material can be used.
A polyurethane resin and an epoxy resin can be mentioned as an example of the material of the
material of the resin filling part 25. In particular, polyurethane resins are preferred. As an
example of the material of the piezoelectric ceramic member 26, lead zirconate titanate
(hereinafter referred to as PZT) can be mentioned. In the array-type piezoelectric vibrator of the
present invention, the length in the longitudinal direction of the elongated piezoelectric body 23
(the same as the length in the longitudinal direction of the piezoelectric oscillator 10) is usually
the width direction of the elongated piezoelectric body 2 to 200 times the length of The
thickness T of the piezoelectric ceramic member 26 is usually in the range of 0.1 to 0.3 mm. The
number of piezoelectric ceramic members 26 arranged in the elongated piezoelectric body 23 is
usually in the range of 3 to 100, and preferably in the range of 10 to 80. In the array-type
piezoelectric vibrator of the present invention, the distance between the adjacent piezoelectric
vibrator 20 and the piezoelectric vibrator 20 is the length of the resin-filled portion 25 along the
length direction of the elongated piezoelectric body 23. It is preferable to be in the range of 4/5
to 5/4 times that of A. The number of piezoelectric vibrators of the array-type piezoelectric
vibrator is not particularly limited, but is usually in the range of 5 to 300. The array-type
piezoelectric vibrator according to the present invention is, for example, a wide composite
piezoelectric material sheet composed of a plurality of piezoelectric ceramic members
sequentially arranged via a resin-filled portion provided with electrodes on upper and lower
surfaces as a sound absorbing material And then cutting a wide composite piezoelectric material
sheet to a desired width. A wide composite piezoelectric material sheet can be obtained, for
example, by performing the following operation. First, grooves having a depth corresponding to
the thickness of a plurality of desired sheets along the width direction are formed on the surface
of the piezoelectric ceramic block, and the grooves are filled with resin. Next, the piezoelectric
ceramic block is sliced along the surface to the same thickness as the depth of the grooves to
obtain a composite sheet. Next, electrodes are formed on the upper and lower surfaces of the
composite material sheet, and an electric field is applied between the upper and lower electrodes
to polarize the piezoelectric ceramic. The array-type piezoelectric vibrator of the present
invention comprises a plurality of piezoelectric ceramic members in which long piezoelectric
bodies of each piezoelectric vibrator are sequentially arranged in the length direction via a resinfilled portion. Therefore, each piezoelectric vibrator can be curved concavely in its length
direction relatively easily. An example of such an array-type piezoelectric vibrator is shown in
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FIG. FIG. 5 is a diagram showing another configuration of the array type piezoelectric vibrator
according to the present invention, and FIG. 5 (a) is a plan view of the array type piezoelectric
vibrator, and FIG. 5 (b) These are side views of an array-type piezoelectric vibrator, and (c) of FIG.
5 is a III-III sectional view of (a) of FIG.
In FIG. 5, the piezoelectric vibrators 30 are fixed in parallel in a non-contact manner on the
sound absorbing material 31 whose surface is curved. A resin 32 is filled between the adjacent
piezoelectric vibrator 30 and the piezoelectric vibrator 30. The piezoelectric vibrator 30 includes
an elongated piezoelectric body 33 and electrodes 34 a and 34 b provided on upper and lower
surfaces of the elongated piezoelectric body 33. The elongated piezoelectric body 33 is
constituted of a plurality of piezoelectric ceramic members 36 sequentially arranged in the
length direction via the resin filling portion 35. In FIG. 5, the piezoelectric vibrator 30 has a
shape which is concavely curved in the length direction. The radius of curvature of the
piezoelectric vibrator 30 is usually in the range of 4 to 10 times, preferably in the range of 4 to 7
times, with respect to the longitudinal direction of the piezoelectric vibrator. For example, if the
length of the piezoelectric vibrator in the longitudinal direction is 6 mm, the radius of curvature
is in the range of 24 to 60 mm, preferably in the range of 25 to 40 mm. EXAMPLE 1 A groove
(width 0.03 mm × depth 0.15 mm) is formed on the surface of a PZT block (length 6 mm ×
width 9 mm × thickness 1 mm) along the width direction. Were formed at intervals of 0.12 mm,
and the grooves were filled with polyurethane resin. The PZT block was then sliced at 0.15 mm
(groove depth) along its surface to obtain a composite sheet of 0.15 mm thickness. Gold
electrodes were formed on the upper and lower surfaces of the obtained composite material
sheet by vapor deposition, and then an electric field was applied between the upper and lower
electrodes to polarize the PZT, thereby obtaining a composite piezoelectric material sheet. Next,
after sticking the composite piezoelectric material sheet described above onto the sound
absorbing material, the composite piezoelectric material sheet is cut with a width of 0.03 mm at
intervals of 0.12 mm along its length direction. An array-type piezoelectric vibrator consisting of
60 piezoelectric vibrators (length 6 mm × width 0.12 mm) was obtained by inserting 59 pieces.
The long piezoelectric body of the piezoelectric vibrator has a length (L) of the piezoelectric
ceramic member along the length direction of the long piezoelectric body of 0.12 mm, and the
length of the piezoelectric ceramic member along the width direction of the long piezoelectric
body (W) is 0.12 mm, the thickness (T) of the piezoelectric ceramic member is 0.15 mm, and the
length (A) of the resin-filled portion along the longitudinal direction of the long piezoelectric
body is 0.03 mm The volume fraction of the piezoelectric ceramic member in the elongated
piezoelectric body was 80%. The sensitivity of the piezoelectric vibrator of this array-type
piezoelectric vibrator was −56 dB. Comparative Example 1 A groove (width 0.025 mm × depth
0.15 mm) of 0.05 mm is provided along the width direction on the surface of a PZT block (length
6 mm × width 9 mm × thickness 1 mm). Of 79 grooves at intervals of 0.05 mm, and then 119
grooves of width 0.025 mm × depth 0.15 mm at intervals of 0.05 mm along the length
direction, and polyurethane resin is formed in each groove. It was filled.
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Next, the surface of the PZT block was sliced at 0.15 mm (groove depth) to obtain a composite
sheet having a thickness of 0.15 mm. Gold electrodes were formed on the upper and lower
surfaces of the obtained composite material sheet by vapor deposition, and then an electric field
was applied between the upper and lower electrodes to polarize PZT, thereby obtaining a
piezoelectric sheet. Next, the piezoelectric sheet is attached to the sound absorbing material, and
then 59 cuts having a width of 0.02 mm are inserted into the piezoelectric sheet at intervals of
0.13 mm along the length direction. An array-type piezoelectric vibrator comprising 60
piezoelectric vibrators (length 6 mm × width 0.13 mm) was obtained. The long piezoelectric
member of the piezoelectric vibrator is a 1-3 type composite piezoelectric material including a
0.050 mm square prismatic piezoelectric ceramic member, and the volume fraction of the
piezoelectric ceramic member in the long piezoelectric member is 51%. Met. The sensitivity of
the piezoelectric vibrator of this array-type piezoelectric vibrator was −63 dB. According to the
array-type piezoelectric vibrator of the present invention, the sensitivity of each piezoelectric
vibrator is the same as that of the piezoelectric vibrator using the conventional general 1-3 type
composite piezoelectric material for the elongated piezoelectric body. Higher than sensitivity.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the configuration of a
typical array-type piezoelectric vibrator in the related art, in which (a) is a plan view of the arraytype piezoelectric vibrator, and (b) is a diagram It is a side view of an array type piezoelectric
vibrator, and (c) is a front view of Drawing 1 (a). 2 is an enlarged perspective view of a long
piezoelectric body used in the piezoelectric vibrator of FIG. 1; 3A is a plan view of the array-type
piezoelectric vibrator, and FIG. 3B is a side view of the array-type piezoelectric vibrator according
to the present invention. (C) is a II-II sectional view of (a). 4 is an enlarged perspective view of a
long piezoelectric body used in the piezoelectric vibrator of FIG. 3; 5A and 5B are diagrams
showing another configuration of the array-type piezoelectric vibrator according to the present
invention, in which FIG. 5A is a plan view of the array-type piezoelectric vibrator, and FIG. 5B is a
side view of the array-type piezoelectric vibrator It is a figure and (c) is a III-III sectional view of
(a). [Description of the code] 10 piezoelectric vibrator 11 sound absorbing material 12 resin 13
long piezoelectric body 14a, 14b electrode 15 resin portion 16 piezoelectric ceramic member 20
piezoelectric vibrator 21 sound absorbing material 22 resin 23 long piezoelectric body 24a, 24b
electrode 25 resin Filling part 26 Piezoelectric ceramic member 30 Piezoelectric vibrator 31
Sound absorbing material 32 Resin 33 Long piezoelectric body 34a, 34b Electrode 35 Resin
filling part 36 Piezoelectric ceramic member
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