JP2011160586A - Ultrasonic vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact Langevin ultrasonic vibrator of outside clamping type wherein vibration of a piezoelectric element unit can be taken out efficiently. <P>SOLUTION: A through-hole 331 through which the electrode of the piezoelectric element unit 2 is taken out is formed in a lining member 33 so that the opening on the side of the abutment surface 33a thereof is formed at a position where the shortest distance of the center O of the abutment surface 33a of the lining member 33 and the opening of the through-hole 331 (the distance from the center O to the end of the opening on the center O side) is larger than 90% (0.9r) but smaller than 100% (r) of the radius of the piezoelectric element unit 2. Furthermore, the piezoelectric element unit 2 is arranged not to close the through-hole 331, and the periphery of each piezoelectric element 21 constituting the piezoelectric element unit 2 is located within 110% (1.1r) of the radius of the piezoelectric element 21 from the center of the abutment surface 33a of the lining member 33. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultrasonic transducer that generates ultrasonic vibrations due to electrical distortion of a piezoelectric element.

  Conventionally, there is a Langevin type ultrasonic transducer having a structure in which a piezoelectric element unit formed by alternately laminating a plurality of piezoelectric elements and electrode terminal plates is disposed between a front plate and a backing plate made of a metal block. Are known.

  As a structure for fixing the piezoelectric element unit, a piezoelectric element or electrode terminal plate constituting the piezoelectric element unit is formed in a ring shape to form a through hole in the center of the piezoelectric element unit, and a bolt is attached to the through hole. A bolt tightening type is known in which these piezoelectric elements and electrode terminal plates are integrally coupled by being inserted (see, for example, Patent Document 1).

By the way, in medical use, for example, a small-sized and small-diameter ultrasonic vibrator is strongly desired to be applied to a handy type device used for removal of tartar or the like.
However, in bolted Langevin type ultrasonic transducers that require the piezoelectric element to be formed in a ring shape, the outer dimensions of the piezoelectric element are less than the minimum area required for vibration and the area of the hole through which the bolt is inserted. There is a problem that the piezoelectric element itself cannot be sufficiently miniaturized and the ultrasonic transducer configured using the piezoelectric element unit cannot be sufficiently miniaturized. .

  On the other hand, it is composed of a front plate, a backing plate, and a side plate formed in a cylindrical shape to which the front plate is fixed at one end and the backing plate is fixed at the other end, and the front plate or the backing plate is made of solder or caulking, Alternatively, an externally tightened type in which a piezoelectric element unit housed in the side plate is sandwiched between a front plate and a backing plate has a structure that is fixed to the side plate by screwing (for example, a cited document). 2-4).

  In order to efficiently transmit the vibration generated by the piezoelectric element unit to the vibration radiation surface of the front plate, the piezoelectric element unit is usually fixed so as to be located at the center of the front plate or the backing plate.

JP-A-3-236835 JP 2003-199195 A JP 2004-160081 A JP 2003-264773 A

By the way, it is necessary to provide a through hole for taking out the electrode of the piezoelectric element unit in the backing plate.
However, as shown in FIG. 9A, when the center of the piezoelectric element unit M1 is fixed so as to coincide with the center O of the backing plate M2, a space for forming the through hole M3 comes into contact with the piezoelectric element unit M1. Although it is ensured over the entire outer periphery of the part, there is a problem that a dead space is formed except for the part where the through-hole M3 is formed, and sufficient miniaturization cannot be achieved.

  In order to solve the above problems, an object of the present invention is to provide a small, externally tightened Langevin type ultrasonic transducer that can efficiently extract the vibration of a piezoelectric element unit to the outside.

  In order to achieve the above object, the present invention provides an ultrasonic transducer having an external fastening structure in which a piezoelectric element unit is sandwiched between a front member and a backing member and is housed in a side member, and a piezoelectric element feed line is inserted. Therefore, the opening of the through hole formed in the backing member is located at the non-contact portion of the piezoelectric element unit, and the shortest distance between the center of the backing member and the opening of the through hole is relative to the stacking direction of the piezoelectric elements. It is characterized in that it is larger than 90% and smaller than 100% of the radial length of the inscribed circle inscribed in the cross section of the piezoelectric element in the orthogonal plane.

The cross-sectional shape of the piezoelectric element is preferably a circle, a regular polygon, a point-symmetric shape, or the like.
In the ultrasonic transducer according to the present invention configured as described above, as shown in FIG. 9B, the center of the inscribed circle M1 of the piezoelectric element and the center O of the backing member M2 are fixed so as to coincide with each other. Compared to (see FIG. 9A), since the through hole M3 is formed at a position close to the center O of the backing member M2, the backing member M2, and thus the ultrasonic transducer can be downsized. .

  In addition, the piezoelectric element unit can be disposed at a position where the deviation from the center of the backing member is within 10% and does not block the through hole. By realizing such an arrangement, the piezoelectric element The vibration generated by the unit can be taken out efficiently.

  Here, FIG. 8 is a graph showing the result of measuring the attachment position of the piezoelectric element unit (ratio of deviation from the center of the backing member) and the amplitude reduction ratio relative to the amplitude when the piezoelectric element unit is attached to the center of the backing member. It is. However, the cross-sectional shape of the piezoelectric element (and thus the piezoelectric element unit) was circular. As shown in FIG. 8, it can be seen that if the deviation rate is within 10%, the reduction rate of the tip vibration (vibration on the vibration extraction surface of the front member) can be suppressed to within 3%.

  In the present invention, when the cross-sectional shape of the piezoelectric element is circular, the distance between the center of the backing member and the outer periphery of the piezoelectric element unit is preferably within 110% of the radial length of the piezoelectric element. In this case, the piezoelectric element unit is surely disposed at a position where the deviation ratio from the center of the backing member is within 10% of the radial length of the piezoelectric element.

In the present invention, the backing member may be assembled to the side member while being integrated with the piezoelectric element unit.
In this case, by assembling the piezoelectric element unit with respect to the backing member with high accuracy, it is possible to ensure the mounting accuracy of the piezoelectric element unit with respect to the side member and the front member, so that the assembling work can be facilitated.

  That is, since the backing member and the piezoelectric element unit can be integrated outside the side member, an assembly jig for alignment can be used, and as a result, the required positioning accuracy can be easily achieved. Can be secured.

  By the way, when the backing member and the piezoelectric element unit are integrated in advance as described above, it is necessary to ensure adhesion between the piezoelectric element unit and the front member when the backing member and the front member are integrated. There is.

For this purpose, it is desirable to provide an inclusion that is formed in a plate shape or a foil shape and has ductility or malleability superior to the piezoelectric element unit between the front member and the piezoelectric element unit.
When providing such an inclusion, the following manufacturing method can be used.

  That is, the backing member is integrated with the piezoelectric element unit and then fixed to the side member, and the inclusion formed in a plate shape or foil shape and having ductility or malleability superior to that of the piezoelectric element unit is replaced with the front member and the piezoelectric element. The front member and the side member are assembled in a state of being interposed between the element units.

  In this way, by interposing an inclusion between the piezoelectric element unit and the front member, the adhesion between the two can be improved as compared with the case where the front member and the piezoelectric element unit are in direct contact with each other. it can. As a result, the vibration generated by the piezoelectric element unit can be efficiently transmitted to the front member, that is, the vibration characteristics can be improved, and variations in the vibration characteristics for each ultrasonic transducer can be suppressed.

  By the way, in the ultrasonic transducer of the present invention, a screw portion is formed on each of the inner peripheral surface of the side member to which the front member is fixed and the outer peripheral surface of the front member, and one of the screw portions is a male screw. The other is a female screw, and the side member and the front member may have a structure that is fixed by screwing the female screw and the male screw.

  In this case, when the front member is screwed to the side member, the inclusions reduce the friction between the front member and the piezoelectric element unit and suppress the twisting stress from being applied to the piezoelectric element unit. In addition, an appropriate weight can be applied to the piezoelectric element unit while preventing the stacking deviation. That is, by providing inclusions, the influence of torsional stress is reduced, so that even if an inexpensive screwing structure is employed, highly accurate manufacturing can be performed.

  Further, when the front member and the side member are screwed in this way, the cross-sectional shape of the hollow portion of the side member in a cross section orthogonal to the axial direction of the side member is further formed into a non-circular shape, You may provide the 2nd inclusion formed in plate shape between piezoelectric element units. However, the second inclusion enables movement of the second inclusion along the axial direction of the side member in the hollow portion, and the second inclusion around the rotation axis along the axial direction in the hollow portion. It is formed in a shape that prevents the rotation of the object, and is disposed so that the inclusion exists at least between the front member and the second inclusion.

When such a second inclusion is provided, the following manufacturing method can be used.
That is, when the front member and the side member are screwed together, an inclusion is interposed at least between the front member and the second inclusion.

  By interposing such a second inclusion, it is possible to convert the screwing rotation motion by the front member into a linear motion, so that the characteristic deterioration due to misalignment or stacking error, and the parallelism and adhesion are reduced. Vibration inhibition due to can be further suppressed.

It is sectional drawing which shows the whole structure of an ultrasonic transducer | vibrator. It is a perspective view shown in the state which decomposed | disassembled the exterior body. It is a perspective view shown in the state which decomposed | disassembled the piezoelectric element unit. It is explanatory drawing which shows the formation position of the through-hole in the contact surface of a backing member, and arrangement | positioning of a piezoelectric element unit. It is explanatory drawing which shows the manufacturing method of an ultrasonic transducer | vibrator. It is sectional drawing which shows other embodiment of an ultrasonic transducer | vibrator. It is explanatory drawing which shows the modification of the cross-sectional shape of a side member, and the external shape of a 2nd inclusion. It is a graph which shows the relationship between the position shift of a piezoelectric element unit, and the reduction | decrease of a tip vibration width. It is explanatory drawing which shows the conventional problem and the effect of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing the overall configuration of a hand-held ultrasonic transducer 1 used for medical purposes for removing tartar.

  As shown in FIG. 1, the ultrasonic transducer 1 houses a piezoelectric element unit 2 that operates by energization and becomes a generation source of ultrasonic vibration, and a piezoelectric element unit 2, and an ultrasonic wave generated by the piezoelectric element unit 2. It consists of the exterior body 3 which radiates | emits a sonic vibration.

[Exterior body]
FIG. 2 is a perspective view showing a configuration of the exterior body 3 in an exploded state.
As shown in FIG. 2, the exterior body 3 is fixed to a side member 31 formed in a cylindrical shape, a front member 32 fixed to one opening end of the side member 31, and the other opening end of the side member 31. The backing member 33 is made of. In addition, the side member 31, the front member 32, and the backing member 33 are configured using a metal (for example, Ti, Ti alloy, stainless steel, etc.) excellent in corrosion resistance.

  The side surface member 31 has a female screw formed on the inner peripheral wall at least at both ends (in the present embodiment, over the entire inner peripheral wall), and further, an insulating coating is applied to the entire inner peripheral wall to provide a short-circuit prevention layer. Is formed.

  The front member 32 has a contact surface 32a for contacting the piezoelectric element unit 2 at one end and a vibration radiation surface 32b for radiating ultrasonic vibrations at the other end. In the embodiment, it is configured as a substantially conical metal block whose diameter continuously decreases from φ4.0 mm) toward a small diameter portion (φ1.6 mm in this embodiment) located on the vibration radiation surface 32 b side.

  Further, in the front member 32, the end on the side of the contact surface 32 a of the side member 31 has a columnar part having the same outer diameter as the inner diameter of the side member 31, and the outer periphery of the columnar part The wall is formed with a male screw that is screwed with a female screw formed on the inner peripheral wall of the side member 31.

  Further, the front member 32 is configured such that the length in the axial direction from the contact surface 32a to the vibration radiation surface 32b is, for example, λ / 4, where λ is the wavelength at the resonance frequency of the piezoelectric element unit 2. The ultrasonic vibration generated in the piezoelectric element unit 2 is configured to function as a horn that transmits the vibration radiation surface 32b.

  On the other hand, the backing member 33 is configured as a substantially cylindrical metal block having a contact surface 33a for contacting the piezoelectric element unit 2 at one end and provided with a step having a small diameter on the contact surface 33a side.

  Further, in the backing member 33, the outer diameter of the small diameter portion has the same length as the inner diameter of the side member 31, and the female screw formed on the inner peripheral wall of the side member 31 is formed on the outer peripheral wall of the small diameter portion. A male screw is formed to be screwed together.

  Further, the backing member 33 is formed with a through hole 331 for inserting a power supply line to the piezoelectric element unit 2, and this through hole 331 penetrates from the contact surface 33a to the end surface 33b on the large diameter part side. It is formed as follows.

  The opening on the contact surface 33a side of the through hole 331 is located at the non-contact portion of the piezoelectric element unit 2 and is the shortest between the center O of the contact surface 33a of the backing member 33 and the opening of the through hole 331. A position where the distance (distance from the center O to the center O side end in the opening) is larger than 90% and smaller than 100% of the radial length of the piezoelectric element unit 2, that is, the center in the opening of the through hole 331 The O-side end is formed so as to be located outside the circle having a radius of 0.9r (r is the radius length of the piezoelectric element 21) and inside the circle having the radius r in FIG.

[Piezoelectric element unit]
FIG. 3 is a perspective view showing the piezoelectric element unit 2 in an exploded state.
As shown in FIG. 3, the piezoelectric element unit 2 is formed in a disk shape by a plurality of piezoelectric elements 21 (21a to 21d) formed in a disk shape and having electrode layers formed on upper and lower end surfaces, and a conductive material. The power supply electrode terminal plates 22 (22a to 22c) are alternately laminated, and are integrally fixed by an adhesive such as an epoxy resin.

  Hereinafter, the electrode terminal plate 22a positioned between the piezoelectric elements 21a and 21b and the electrode terminal plate 22c positioned between the piezoelectric elements 21c and 21d are used as the positive electrode terminal plate and the electrode terminal positioned between the piezoelectric elements 21b and 21c. The plate 22b is also called a negative electrode terminal plate.

  Among these, the piezoelectric element 21 is polarized in the thickness direction by applying a conductive paste to both end surfaces after press molding and firing using lead zirconate titanate (PZT) and performing a polarization treatment in oil. Then, the conductive layer is formed by grinding and polishing into a predetermined shape and depositing silver (Ag) on both end faces. In the present embodiment, the piezoelectric element 21 is formed with a diameter of 2.5 mm and a thickness of 1.0 mm.

  On the other hand, the electrode terminal plate 22 is made of beryllium copper, and includes a disc portion 221 having the same diameter as the piezoelectric element 21 and a protruding portion 222 projecting in the radial direction of the disc portion 221 for connection to the feeder line. Yes. In the present embodiment, the electrode terminal plate 22 is formed with a diameter of 2.5 mm (that is, the same diameter as the piezoelectric element 21) and a thickness of 0.05 mm. Further, the protrusion 222 of the electrode terminal plate 22 has a minimum size (in this embodiment, the protrusion amount so as not to contact the side surface member 31 or impede the vibration of the piezoelectric element unit 2. 0.2 mm).

  In order to prevent the positive electrode terminal plates 22a and 22c and the negative electrode terminal plate 22b from short-circuiting each other, the protrusions 222 of the positive electrode terminal plates 22a and 22c protrude in the same direction, and the protrusions 222 of the negative electrode terminal plate 22b The positive electrode terminal plates 22a and 22b are fixed so as to protrude in a direction different from the protruding portion 222 (here, the opposite direction).

  The piezoelectric element unit 2 configured as described above is held in the hollow portion formed by the side member 31 while being sandwiched between the contact surface 32a of the front member 32 and the contact surface 33a of the backing member 33. Is done.

  However, the piezoelectric element unit 2 is in direct contact with the backing member 33 and is in contact with the front member 32 via an inclusion 4 made of a metal foil (thickness of 0 (greater than 0) to about 0.5 μm). It is configured.

  This inclusion 4 is a metal (Au, Cu, Re, Ru, etc.) that is more ductile or malleable than the electrode (Ag, etc.) of the piezoelectric element 21 and the material (Ti, Ti alloy, stainless steel, etc.) constituting the front member 32. , Pt, Sn, In, Pb, etc.). The inclusion 4 is not limited to a foil shape, and may be a plate shape or a hybrid shape (a combination of two or more foils and plates).

  The piezoelectric element unit 2 is positioned substantially at the center of the contact surface 32a of the backing member 33, and the distance between the protrusion 222 of the positive terminal plates 22a and 22c and the through hole 331 of the backing member 33 is the shortest. It is arranged in such a direction.

Further, lead wires L1 and L2 made of ultra fine wires or metal rods are connected to the protrusions 222 of the positive electrode terminal plates 22a and 22c and the protrusion 222 of the negative electrode terminal plate 22b by solder. And the lead wire L1 connected to the positive electrode terminal plates 22a and 22c is wired in a state of being inserted through the through hole 331 so that one end of the lead wire L1 protrudes to the outside of the exterior body 3. However, the portion of the lead wire L1 wired in the through hole 331 is covered with an insulating material so as not to be short-circuited with the backing member 33. On the other hand, the end portion of the lead wire L2 connected to the negative electrode terminal plate 22b is connected to the contact surface 33a of the backing member 33 by solder, that is, the negative electrode terminal plate 22b and the backing member 33 (as a result, via the side member 31). The front member 32) is short-circuited.
[Method of manufacturing vibrator]
Next, a method for manufacturing the ultrasonic transducer 1 will be described with reference to FIG.

First, as shown in FIGS. 5A and 5B, the piezoelectric elements 21 and the electrode terminal plates 22 are alternately laminated and integrated with the contact surface 33a of the backing member 33 with an epoxy adhesive.
At this time, the piezoelectric element unit 2 does not block the through-hole 331 provided in the backing member 33, and the outer periphery of each piezoelectric element 21 constituting the piezoelectric element unit 2 is in contact with the backing member 33. A dedicated jig for stacking is used so as to obtain positional accuracy that is located within a radius 1.1r (110% of the radial length of the piezoelectric element 21) from the center of the surface 33a (see FIG. 4). Do work. In FIG. 4, the hatched portion indicates the fixing position of the piezoelectric element unit 2 on the contact surface 33 a of the backing member 33.

  At this time, the positive electrode terminal plates 22a and 22c are arranged in such a direction that the distance between the protruding portion 222 and the through hole 331 is the shortest, and the negative electrode terminal plate 22b has the protruding portion 222 having the positive electrode terminal plates 22a and 22c. It is arranged in a direction protruding in a different direction (in this case, the opposite direction).

  Next, as shown in FIGS. 5B and 5C, the lead wire L1 is inserted through the through hole 331 of the backing member 33 integrated with the piezoelectric element unit 2, and the lead wire L1 exposed to the contact surface 33a side is exposed. Are soldered to the protrusions 222 of the positive electrode terminal plates 22a and 22c. As a result, the portion of the lead wire L1 protruding toward the end face 33b becomes the positive electrode of the ultrasonic transducer 1.

  Further, another lead wire L2 is soldered to the protruding portion 222 of the negative electrode terminal plate 22b, and one end thereof is soldered to a non-contact portion of the piezoelectric element unit 2 on the contact surface 33a of the backing member 33. As a result, the entire backing member 33 becomes the negative electrode of the ultrasonic transducer 1.

At this time, if the amount of solder at the protrusions 222 of each electrode terminal plate 22 is excessive, it becomes a factor that hinders vibration, so the amount of solder used for solder connection is kept to a minimum.
Next, as shown in FIGS. 5C and 5D, the male screw formed on the inner peripheral surface of the side member 31 and the male surface formed on the outer peripheral surface of the backing member 33 in which the piezoelectric element unit 2 is integrated. Screw them together to fix them together.

  Next, as shown in FIGS. 5D and 5E, in the state in which the inclusion 4 is interposed between the non-fixed end of the piezoelectric element unit 2 and the contact surface 32a of the front member 32, the side member The piezoelectric element unit 2 is pressure-tightened by screwing a female screw formed on the inner peripheral surface of 31 and a male screw formed on the outer peripheral surface of the front member 32. As a result, the ultrasonic transducer 1 having an outer fastening structure is completed.

The tightening strength at this time is controlled so that, for example, the capacitance of the piezoelectric element unit 2 is about 1.2 times (180 pF → 220 pF in this embodiment).
[Function and effect]
In the ultrasonic vibrator 1 configured as described above, the through hole 331 is made to contact the contact surface 33a as compared with the case where the center of the piezoelectric element unit 2 is aligned with the center O of the contact surface 33a of the backing member 33. Therefore, the dead space generated by providing the through-hole 331 can be reduced, and the backing member 33 and thus the ultrasonic transducer 1 can be reduced in size.

  In addition, in the ultrasonic transducer 1, since the deviation between the center of the piezoelectric element unit 2 and the center O of the contact surface 33a is within 10%, vibration generated by the piezoelectric element unit 2 can be efficiently performed. It can be taken out.

  In the ultrasonic transducer 1, since the piezoelectric element unit 2 and the backing member 33 are integrally formed and then assembled to the side member 31, the piezoelectric element unit 2 and the backing member 33 are integrally formed. In doing so, since the work can be performed without being restricted by the side member 31, high positional accuracy can be easily realized by using a dedicated jig.

  Further, in the ultrasonic vibrator 1, when the front member 32 is assembled to the side member 31 integrated with the piezoelectric element unit 2 and the backing member 33, the inclusion 4 is interposed between the piezoelectric element unit 2. The front member 32 is screwed.

  Thereby, compared to the case where the front member 32 and the piezoelectric element unit 2 are brought into direct contact with each other, it is possible to increase the slipperiness between the two at the time of tightening, so that the torsional stress is transmitted to the piezoelectric element unit 2. In addition, it is possible to improve adhesion between the two at the end of tightening.

  As a result, it is possible to suppress the deterioration and variation of the vibration characteristics caused by the displacement of the piezoelectric element unit 2 and the element displacement due to the torsional stress, and the vibration generated by the piezoelectric element unit 2 is radiated by the vibration of the front member 32. Since it can transmit to the surface 32a efficiently, the small ultrasonic transducer | vibrator 1 excellent in the vibration characteristic can be provided.

[Evaluation experiment]
An evaluation experiment was conducted on the effect of inclusion 4.
The above-described ultrasonic vibrator 1 is an example, and the above-described ultrasonic vibrator 1 with the inclusions 4 omitted is a comparative example, and the vibration radiation surface 32b is changed while changing the tightening strength of the front member 32 for both of them. The amplitude at (however, the amplitude at the resonance frequency) was measured. A laser Doppler device was used to measure the amplitude.

As the inclusion 4, an Au foil having a thickness of 0.2 μm was used.
In the example, an amplitude larger by 4 μm or more than that of the comparative example was obtained.
[Other Embodiments]
In the above embodiment, when the front member 32 is attached to the side member 31, the inclusion 4 is interposed between the backing member 33 fixed to the side member 31 and the piezoelectric element unit 2 integrated with the backing member 33. However, as shown in FIG. 6A, a rotational movement caused by screwing of the front member 32 between the inclusion 4 and the piezoelectric element unit 2 is further performed in a straight line along the axial direction of the side member 31. A second inclusion (hereinafter referred to as “lock plate”) 5 for conversion into motion may be interposed.

In this case, as shown in FIG.6 (b), the cross-sectional shape of the hollow part of the side member 31 and the outer peripheral shape of the lock plate 5 are made into a non-circular shape and the shape which mutually engages.
As a specific shape, as shown in FIG. 6B, the lock plate 5 has a shape in which two convex portions 5a protruding in the radial direction across the center of the disc are provided. It is conceivable that the peripheral surface has a shape in which two concave grooves 31a that engage with these protrusions are provided.

  As a result, the lock plate 5 can be linearly moved in the hollow portion along the axial direction of the side member 31 and is prevented from rotating around the rotation axis along the axial direction in the hollow portion. As a result, it is possible to more reliably prevent the torsional stress due to the front member 32 from being transmitted to the piezoelectric element unit 2.

  Further, the cross-sectional shape of the hollow portion of the side member 31 and the outer peripheral shape of the lock plate 5 are obtained by increasing the number of the convex portions 5a and the concave grooves 31a as shown in FIG. 7), or as shown in FIG. 7B, a recess 5b is provided on the lock plate 5 side, and protrusions 31b are provided on the inner peripheral surface of the side member 31 (however, in this case, at the tip of the protrusion 31b) A female screw may be formed), or as shown in FIG. 7C, both shapes may be formed in an elliptical shape. The cross-sectional shape of the hollow portion of the side member 31 and the outer peripheral shape of the second inclusion 5 are not limited to these, and may be a polygonal shape, or may be a convex portion 5a, a concave portion 5b, a concave groove 31a, a convex strip. The number of 31b may be one, three, or five or more. In FIG. 7, the portion indicated by the alternate long and short dash line indicates the position of the male screw when the front member 32 is screwed, that is, the position where the female screw is formed on the side member 31.

  When the lock plate 5 is provided, the inclusion 4 is provided not only on the front member 32 side with respect to the lock plate 5 but also on the piezoelectric element unit 2 side with respect to the lock plate 5 (that is, on both surfaces of the lock plate 5). Also good. The inclusions 4 are preferably provided on both sides for the purpose of improving adhesion, and provided on the front member 32 side for the purpose of reducing torsional stress.

The inclusions 4 and 5 may also serve as a negative electrode plate.
In the above embodiment, the side member 31 and the backing member 33 are fixed by inexpensive screwing, but may be fixed by welding, caulking, or the like. In this case, it is necessary to perform work (welding or caulking) in a state where the members to be integrated (side member 31 and backing member 33) are pressed, but the piezoelectric element block 2 (side member) is easier than the case of screwing. 31) and the backing member 33 can be assembled in close contact with each other.

  The welding under pressure is a known technique described in, for example, Japanese Patent Application Laid-Open No. 2006-303443, Japanese Patent Application Laid-Open No. 2006-303444, and the like, and thus detailed description thereof is omitted here.

  In the above embodiment, various conditions to be satisfied are defined for the piezoelectric element 21 having a disk shape, that is, a case where the cross-sectional shape in a plane orthogonal to the stacking direction is circular. However, the cross-sectional shape is not limited to a circular shape. For example, it may be a regular polygon or other point-symmetric shape. If the shape is point-symmetric, the isotropicity of the generated ultrasonic vibration is increased, so that not only unnecessary vibration can be suppressed, but also the output efficiency with respect to the input power can be improved. However, in this case, it is necessary to satisfy the condition defined by the inscribed circle of the cross section.

  DESCRIPTION OF SYMBOLS 1 ... Ultrasonic vibrator 2 ... Piezoelectric element unit 4,5 ... Inclusion 5a ... Convex part 5b ... Concave part 21 ... Piezoelectric element 22 ... Electrode terminal board 31 ... Side surface member 31a ... Concave groove 31b ... Convex line 32 ... Front member 32a ... Abutting surface 32b ... Vibrating radiation surface 33 ... Backing member 33a ... Abutting surface 33b ... End surface 331 ... Through hole L1, L2 ... Lead wire M1 ... Piezoelectric element unit M2 ... Backing member M3 ... Through hole

Claims (8)

A piezoelectric element unit formed by laminating a piezoelectric element and an electrode plate;
A front member and a backing member for sandwiching the piezoelectric element unit;
A side member for housing the piezoelectric element unit and holding the piezoelectric element unit sandwiched between the front member and the backing member;
In an ultrasonic transducer with an outer fastening structure equipped with
An opening of a through-hole formed in the backing member for inserting a feeding line of the piezoelectric element is located at a non-contact portion of the piezoelectric element unit;
The shortest distance between the center of the backing member and the opening of the through hole is 90% of the radial length of the inscribed circle inscribed in the cross section of the piezoelectric element in a plane orthogonal to the stacking direction of the piezoelectric elements. An ultrasonic transducer characterized by being larger and smaller than 100%. The piezoelectric element has a circular cross section.
The ultrasonic transducer according to claim 1, wherein the distance between the center of the backing member and the outer periphery of the piezoelectric element unit is within 110% of the radial length of the piezoelectric element.   The ultrasonic transducer according to claim 1, wherein the backing member is assembled to the side member in a state of being integrated with the piezoelectric element unit.   The inclusion which is formed in plate shape or foil shape and has ductility or malleability superior to the piezoelectric element unit is provided between the front member and the piezoelectric element unit. Ultrasonic transducer. On the inner peripheral surface of the side member to which the front member is fixed, and on the outer peripheral surface of the front member, thread portions are formed, respectively.
One of the screw portions is a male screw, the other is a female screw,
The ultrasonic transducer according to claim 4, wherein the side member and the front member are fixed by screwing the female screw and the male screw. Forming a non-circular cross-sectional shape of the hollow portion of the side member in a cross section perpendicular to the axial direction of the side member;
A second inclusion formed in a plate shape is provided between the front member and the piezoelectric element unit,
The second inclusion enables movement of the second inclusion along the axial direction of the side member in the hollow portion, and around the rotation axis along the axial direction in the hollow portion. Formed in a shape to prevent rotation of the second inclusion,
The ultrasonic transducer according to claim 5, wherein the inclusion exists at least between the front member and the second inclusion. A piezoelectric element unit formed by laminating a piezoelectric element and an electrode plate;
A front member and a backing member for sandwiching the piezoelectric element unit;
A side member for housing the piezoelectric element unit and holding the piezoelectric element unit sandwiched between the front member and the backing member;
A method of manufacturing an ultrasonic transducer having an outer tightening structure comprising:
The backing member is fixed to the side member after being integrated with the piezoelectric element unit,
The front member and the side surface in a state where an inclusion formed in a plate shape or a foil shape and having ductility or malleability superior to the piezoelectric element unit is interposed between the front member and the piezoelectric element unit. A method of manufacturing an ultrasonic transducer, characterized by performing assembly with a member. The ultrasonic transducer has threaded portions formed on an inner peripheral surface of the side member to which the front member is fixed and an outer peripheral surface of the front member, and the side member, the front member, Has a structure fixed by screwing the female screw and the male screw,
When the cross-sectional shape of the hollow portion of the side member in a cross section orthogonal to the axial direction of the side member is formed in a non-circular shape,
A second inclusion formed in a shape that enables movement of the side member in the hollow portion along the axial direction and prevents rotation around the rotation axis in the hollow portion in the hollow portion; use,
The ultrasonic transducer according to claim 7, wherein the inclusion is interposed between at least the front member and the second inclusion when the front member and the side member are screwed together. Manufacturing method.

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