JP2006319404A - Ultrasonic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized light weight ultrasonic transducer with a wider band and higher efficiency acoustic radiation characteristic and excellent durability. <P>SOLUTION: The ultrasonic transducer includes a bolt-tightened Langevin vibrator wherein piezoelectric ceramics laminators 13, 16 each inside of which includes a through-hole 14 are arranged between a head mass 11 and a tail mass 12, and a bolt 15 is provided to be engaged with the head mass 11 and the tail mass 12 through the through-hole 14 of the piezoelectric ceramics laminators 13, 16 to exert a compressive stress to the piezoelectric ceramics laminators 13, 16. The thread part of the bolt 15 is engaged with a thread part 43 provided to part of the tail mass 12, a projection 21 is provided in front of the head mass 11, and an acoustic cap 10 is fixed to the head mass 11 in a way of covering the projection 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic transducer of a broadband piezoelectric transducer.

  Conventionally, a bolt-clamped Langevin transducer (hereinafter abbreviated as BLT) is widely used as a high-efficiency ultrasonic transducer capable of high-power transmission in a frequency band used for acoustic detection in water.

  The basic structure of the BLT is such that a laminated ceramic is sandwiched between a head mass and a tail mass and these are tightened with bolts. A light metal such as aluminum or magnesium is generally used for the head mass. On the other hand, heavy metals such as stainless steel and brass are used for the tail mass. The vibration of the BLT generally uses resonance in the longitudinal direction of the bolt, and a beautiful longitudinal vibration without coupling with other vibration modes can be obtained.

  In an acoustic transmission / reception apparatus using this BLT, there are cases where it is desired to change the drive frequency in order to avoid acoustic wave competition or perform transmission by FM modulation. In response to such a demand for a wider band, the following Patent Document 1 discloses a BLT basic thickness mode and a flexural vibration plate bending mode by providing a concave portion on the front surface of the head mass and fixing the flexural vibration plate to the front surface of the head mass. A configuration for increasing the bandwidth by superimposing is disclosed.

In Patent Document 2 below, a slit or groove is formed in the bent front mass portion from the outer edge portion to the center portion, and an acoustic radiation front mass is provided from the vicinity of the outer edge portion of the bent front mass via a hinge. A configuration is disclosed in which a wide band is transmitted by transmitting an enlarged displacement from an outer edge portion to an acoustic front mass via a hinge.
Japanese Patent No. 3005611 Japanese Patent Laid-Open No. 62-176396 Japanese Patent Laid-Open No. 2004-312119

The above-described technologies for widebanding in Patent Document 1 and Patent Document 2 have a problem that they are not suitable for long-term use due to large amplitude operation. In order to solve this problem, in the above-mentioned Patent Document 3, the present inventor has realized a small-sized and lightweight ultrasonic transducer having a broadband and highly efficient acoustic radiation characteristic, capable of high-power transmission.
However, in an acoustic transmission / reception apparatus using BLT, it is desired to have a wider band and further durability.
An object of the present invention is to provide a small-sized and lightweight ultrasonic transducer having a further broadband and highly efficient acoustic radiation characteristic and excellent in durability.

Means and effects for solving the problems

(1)
An ultrasonic transducer according to the present invention includes a piezoelectric ceramic laminate having a through-hole disposed between a head mass and a tail mass, and is engaged with the head mass and the tail mass through the through-hole of the piezoelectric ceramic laminate. In an ultrasonic transducer having a bolted Langevin vibrator provided with a bolt for applying a compressive stress to a body, a screw hole that can be screwed with a screw portion of a bolt is formed in a part of a through hole of a tail mass. .

  In the ultrasonic transducer according to the present invention, a screw hole that can be screwed with a screw portion of a bolt is formed in a part of the through hole of the tail mass. Thereby, unlike the conventional structure in which a nut is provided outside the tail mass to fix the tail mass, the resonance generated depending on the length of the bolt portion can be moved to the high frequency side. As a result, an ultrasonic transducer having a broadband and highly efficient acoustic radiation characteristic can be realized. In addition, there is no need to add another new member and the number of fixing points can be increased, so that a small and lightweight ultrasonic transducer having excellent durability can be realized.

(2)
The tail mass has a first tail mass in which a through hole larger than the screw thread of the bolt is formed, a through hole smaller than the screw thread of the bolt, and a screw hole that can be screwed with the screw thread of the bolt in the through hole. And a formed second tail mass.

  In this case, the first tail mass and the second tail mass are formed as individual members. Further, since it is only necessary to form through holes in the first tail mass and the second tail mass and to form screw holes only in the second tail mass, it is possible to reduce manufacturing costs.

(3)
The first tail mass and the second tail mass may be fixed by screw connection. In this case, since the first tail mass and the second tail mass have integral rigidity, an ultrasonic transducer having a broadband and highly efficient acoustic radiation characteristic can be realized.

(4)
In the tail mass, a through hole may be formed on the piezoelectric ceramic laminate, and a screw hole may be formed on the end opposite to the end in contact with the piezoelectric ceramic laminate.

  In this case, the resonance generated depending on the length of the bolt part can be reliably moved to the high frequency side. As a result, an ultrasonic transducer having a broadband and highly efficient acoustic radiation characteristic can be realized.

(5)
A convex portion may be provided on the front surface of the head mass, and the acoustic cap may be fixed to the head mass so as to cover the convex portion.

  In this case, since the head mass with the acoustic cap is used, it is possible to achieve a broadband and highly efficient acoustic radiation characteristic. Further, the portion where the stress is most generated by the bending of the acoustic cap has an integral structure called a cap, and can be particularly excellent in durability.

(6)
The acoustic cap may include a cylindrical portion that covers the peripheral surface of the convex portion and a vibrating portion that is integrally formed so as to close one end of the cylindrical portion.

  In this case, if the acoustic cap has an integral structure of the cylindrical portion and the vibrating portion, it can be excellent in durability.

(7)
The cylindrical portion may have a portion whose inner diameter is larger than the outer diameter of the convex portion of the head mass. In this case, if the cylindrical portion of the acoustic cap is larger than the outer diameter of the convex portion, high-efficiency broadbanding can be appropriately achieved by adjusting the space generated between the two.

(8)
A screw portion may be formed on the peripheral surface of the convex portion, and a screw portion that can be engaged with the screw portion may be formed on the inner surface of the cylindrical portion of the acoustic cap.

  In this case, the acoustic cap can be reliably fixed by engaging the threaded portion of the convex portion with the threaded portion of the inner surface of the acoustic cap.

Embodiments according to the present invention will be described below. In the embodiment according to the present invention, four types of ultrasonic transducers 100a, 100b, 100c and 100d will be described.
(First embodiment)
FIG. 1 is a cross-sectional view showing an example of the overall configuration of the ultrasonic transducer 100a according to the first embodiment of the present invention.

  An ultrasonic transducer 100a shown in FIG. 1 mainly includes a head mass 11, a tail mass 12, piezoelectric ceramic laminates 13, 16, bolts 15, an acoustic cap 10, a nut 17, and an electrode plate 50.

  In the configuration of the ultrasonic transducer 100a in FIG. 1, piezoelectric ceramic laminates 13 and 16 each having a through hole 14 are arranged between a head mass 11 and a tail mass 12, and the through holes 14 of the piezoelectric ceramic laminates 13 and 16 are arranged. And a bolt-clamped Langevin vibrator provided with a bolt 15 for applying a compressive stress to the piezoelectric ceramic laminates 13 and 16. An acoustic cap 10 is fixed to the head mass 11. An electrode plate 50 is provided between the piezoelectric ceramic laminate 13 and the piezoelectric ceramic laminate 16.

  The tail mass 12 is formed of heavy metal such as stainless steel or brass. The shape of the tail mass 12 is a columnar shape having a hole 25 from one end side to the center portion of the center axis of the tail mass 12 and a screw hole 43 from the center portion to the other end side of the center axis of the tail mass 12. As shown in FIG. 1, the portion where the screw hole 43 is formed is a distance t1, and the portion where the hole 25 is formed is a distance t2.

  In the present embodiment, the tail mass 12 is made of a cylindrical member. However, the present invention is not limited to this, and the tail mass 12 may be made of any other shape such as a triangular prism or a rectangular parallelepiped.

  The head mass 11 is made of a light metal such as aluminum or magnesium. As for the shape of the head mass 11, a convex portion 21 is integrally provided on the front surface of the main body portion 24, and a screw hole 22 is provided at the center of the bottom surface of the main body portion 24. The shape of the main body 24 is not particularly limited, but it is preferable to have a shape that widens toward the tip as shown. The convex portion 21 is a column having a narrower width than the front surface of the main body portion 24. A screw portion 23 is formed on the peripheral surface of the convex portion 21 and on the base side thereof.

  As with the head mass 11, the acoustic cap 10 is made of a light metal. The shape is a shape that covers the convex portion 21 of the head mass 11. Specifically, the acoustic cap 20 includes a cylindrical portion 31 that covers the convex portion 21, and a vibrating portion 32 that is integrally formed so as to close one end on the distal end side of the cylindrical portion 31. A threaded portion 33 that can be engaged with the threaded portion 23 of the convex portion 21 is formed on the inner surface of the cylindrical portion 31 and on the base side thereof. The cylindrical portion 31 has an outer shape that is continuous with the main body portion 24 of the head mass 11. Although the shape of this cylinder part 31 is not specifically limited, It is preferable to make it the shape which spreads as it goes to a front end like illustration. The vibration part 32 integral with the cylinder part 31 is disk-shaped.

  The cylindrical portion 31 of the acoustic cap 10 has a recess 34. The inner diameter of the concave portion 34 is larger than the outer diameter of the convex portion 21, and a slit-like space 35 is formed between the two. Moreover, the depth of this recessed part 34 is deeper than the height of the convex part 21, and the disk-shaped space 36 is formed between both.

  The piezoelectric ceramic laminates 13 and 16 are made of piezoelectric ceramics, for example, lead zirconate titanate, which is polarized in the thickness direction. The piezoelectric ceramic laminates 13 and 16 are arranged so that their polarization directions are opposite to each other, and are electrically connected in parallel via the electrode plate 50 and driven.

  The bolt 15 is formed of a high tension metal material. The screw rod 41 at the tip of the bolt 15 is engaged with the screw hole 22 of the head mass 11, the piezoelectric ceramic laminate 16, the electrode plate 50, the piezoelectric ceramic laminate 13 and the hole 25 of the tail mass 12 are passed through the bolt 15 in this order. 15 screw rods 42 are engaged with screw holes 43 formed in a part of the tail mass 12, and finally the nut 17 is engaged with the screw rod 42 at the end of the bolt 15 and tightened.

  The bolt 15 applies compressive stress to the piezoelectric ceramic laminates 13 and 16 by the engagement of the screw holes 43 and the screw rods 42 provided in the tail mass 12. The nut 17 can further apply a compressive stress to the piezoelectric ceramic laminates 13 and 16 by engaging with the screw holes 43 provided in the tail mass 12. Note that the pressure stress due to the nut 17 can be entirely transferred to the pressure stress due to the screw rod 42 and the screw hole 43, and therefore the nut 17 can be omitted.

  Further, as will be described later, the bolt resonance point generated in the bolt 15 is moved. In this manner, a static pressure bias is applied to the head mass 11, the tail mass 12, and the piezoelectric ceramic laminates 13 and 16. Since the piezoelectric ceramics 13 and 16 have a strength against tension that is only a fraction of the strength against pressure, the bolt 15 that applies such a static compressive stress is necessary. By tightening with the bolt 15, the bolt-tightened Langevin vibrator can be forcibly excited with high power.

  Further, in comparison with the conventional BLT, when there is one fixed end (node) at the location of the nut 17 of the bolt 15 and when there is the other fixed end (node) at the location of the head mass 11 of the bolt 15, the nut 17. The bolt 15 having a distance (t1 + t2) between the head mass 11 and the head mass 11 is in a free state. However, in the present embodiment, the screw hole 43 of the head mass 11 is formed, and the position of one fixed end (node) is changed by engaging with the bolt 15, and the other of the locations of the head mass 11 of the bolt 15 is changed. The distance from the fixed end (node) is shortened by a distance t1, and the free state length of the bolt 15 is shortened. Thereby, the resonance point of the bolt 15 moves, and the resonance point of the bolt 15 can be moved to the high frequency side by shortening the distance of the bolt 15 in the free state.

  As described above, in the ultrasonic transducer 100 a according to the first embodiment, the screw hole 43 that can be screwed with the screw rod 42 of the bolt 15 is formed in a part of the through hole 25 of the tail mass 12. Thereby, unlike the conventional structure in which the nut 17 is provided outside the tail mass 12 to fix the tail mass 12, the resonance generated depending on the length of the bolt 15 can be moved to the high frequency side. As a result, it is possible to realize an ultrasonic transducer 100a having a broadband and highly efficient acoustic radiation characteristic. In addition, there is no need to add another new member and the number of fixing points can be increased, so that a small and lightweight ultrasonic transducer 100a having excellent durability can be realized.

  In addition, since the head mass 11 with the acoustic cap 10 is used, it is possible to have a broadband and highly efficient acoustic radiation characteristic. Further, the portion where the stress is most generated by the bending of the acoustic cap 10 has an integral structure called a cap, and can be particularly excellent in durability. Further, when the cylindrical portion 31 of the acoustic cap 10 is larger than the outer diameter of the convex portion 21, high-efficiency broadening of the bandwidth can be made appropriate by adjusting the space generated between them.

(Second Embodiment)
FIG. 2 is a schematic diagram showing an example of the overall configuration of an ultrasonic transducer 100b according to the second embodiment of the present invention.

  The ultrasonic transducer 100b shown in FIG. 2 differs from the configuration of the ultrasonic transducer 100a of FIG. 1 in the following points.

  An ultrasonic transducer 100b shown in FIG. 2 has a tail mass 12a and a tail mass 12b instead of the tail mass 12 of FIG.

  A hole 25 is formed in the central axis of the tail mass 12a. Further, a screw hole 43b that can be engaged with a screw of the bolt 15 is formed in the central axis of the tail mass 12b.

  In the ultrasonic transducer 100b, the screw rod 41 at the tip of the bolt 15 is engaged with the screw hole 22 of the head mass 11, and the bolt 15 in the order of the piezoelectric ceramic 16, the electrode plate 50, the piezoelectric ceramic laminate 13 and the hole 25 of the tail mass 12a. Further, the screw rod 42 of the bolt 15 is engaged with the screw hole 43 formed in the tail mass 12b and tightened, and finally the nut 17 is engaged with the screw rod 42 at the end of the bolt 15 and tightened.

  As described above, in the ultrasonic transducer 100b according to the second embodiment, the tail mass 12b is formed with the screw hole 43b that can be screwed with the screw rod 42 of the bolt 15. Thereby, unlike the conventional structure in which the nut 17 is provided outside the tail mass 12 to fix the tail mass 12, the resonance generated depending on the length of the bolt 15 can be moved to the high frequency side. As a result, it is possible to realize an ultrasonic transducer 100b having a broadband and highly efficient acoustic radiation characteristic. In addition, there is no need to add another new member and the number of fixing points can be increased. Therefore, a small and lightweight ultrasonic transducer 100b having excellent durability can be realized.

  Although not shown, the tail mass 12a and the tail mass 12b may each have a screw fastening structure including a screw hole and a screw groove, and the tail mass 12a and the tail mass 12b may be coupled by screw fastening.

(Third embodiment)
FIG. 3 is a schematic diagram showing an example of the overall configuration of an ultrasonic transducer 100c according to the third embodiment of the present invention.
The ultrasonic transducer 100c shown in FIG. 3 is different from the configuration of the ultrasonic transducer 100a of FIG. 1 in the following points.

  An ultrasonic transducer 100c shown in FIG. 3 includes a head mass 11c instead of the acoustic cap 10 and the head mass 11 shown in FIG. The head mass 11c is made of a light metal such as aluminum or magnesium. The shape of the head mass 11c is a shape having the same cross section toward the tip.

  As described above, in the ultrasonic transducer 100 c according to the third embodiment, the screw hole 43 c that can be screwed with the screw rod 42 of the bolt 15 is formed in a part of the through hole 25 of the tail mass 12. Thereby, unlike the conventional structure in which the nut 17 is provided outside the tail mass 12 to fix the tail mass 12, the resonance generated depending on the length of the bolt 15 can be moved to the high frequency side. As a result, it is possible to realize an ultrasonic transducer 100c having a broadband and highly efficient acoustic radiation characteristic. In addition, there is no need to add another new member and the number of fixing points can be increased. Therefore, a small and lightweight ultrasonic transducer 100c having excellent durability can be realized.

(Fourth embodiment)
FIG. 4 is a schematic diagram showing an example of the overall configuration of an ultrasonic transducer 100d according to the fourth embodiment of the present invention.

  The ultrasonic transducer 100d shown in FIG. 4 is different from the configuration of the ultrasonic transducer 100b shown in FIG. 2 in the following points.

  An ultrasonic transducer 100d shown in FIG. 4 includes a head mass 11d instead of the acoustic cap 10 and the head mass 11 shown in FIG.

  The head mass 11d is made of a light metal such as aluminum or magnesium. The shape of the head mass 11d is a shape having the same cross section toward the tip.

  As described above, in the ultrasonic transducer 100d according to the fourth embodiment, the screw hole 43d that can be screwed with the screw rod 42 of the bolt 15 is formed in a part of the hole 25 of the tail mass 12b. Thereby, unlike the conventional structure in which the nut 17 is provided outside the tail mass 12 to fix the tail mass 12, the resonance generated depending on the length of the bolt 15 can be moved to the high frequency side. As a result, an ultrasonic transducer 100d having a broadband and highly efficient acoustic radiation characteristic can be realized. In addition, there is no need to add another new member, and the number of fixing points can be increased. Therefore, a small and lightweight ultrasonic transducer 100d having excellent durability can be realized.

  In the first to fourth embodiments, the acoustic cap 10, the head mass 11, the tail mass 12, and the piezoelectric ceramic laminates 13 and 16 have been described with respect to a circular cross section. However, the present invention is not limited to this. Instead, it may be any other shape, for example, a shape having a polygonal cross section such as a square cross section or a hexagon cross section. Further, in the fixing of the acoustic cap 10 and the head mass 11 and the fixing of the tail mass 12a and the tail mass 12b, the screw fixing method is used, but the present invention is not limited to this, and it is fixed by welding or any other bonding method. Also good.

(Example with actual machine)
Hereinafter, the BLTs of Example 1 and Example 2 are created corresponding to the BLTs 100a and 100b shown in FIG. 1 and FIG. 2, and the BLT of Comparative Example 1 is created corresponding to the conventional BLT, respectively. A frequency characteristic measurement experiment was conducted.

(Evaluation)
FIG. 5 shows transmission power sensitivity (SP) frequency characteristics in Example 1, Example 2, and Comparative Example 1. In FIG. 5, the vertical axis represents transmission power sensitivity SP (dB), and the horizontal axis represents frequency (kHz).

  Further, from the result of the graph of FIG. 5, the ultrasonic transducer 100k of the comparative example 1 has a reduced transmission power sensitivity (SP) value near a frequency of 38 kHz, and acoustic energy is efficiently radiated by the resonance phenomenon of the bolt 15. I found out.

  On the other hand, in the ultrasonic transducers 100a and 100b in Example 1 and Example 2, no decrease in the transmitted power sensitivity (SP) value was observed near the frequency of 38 kHz.

  From the above results, in the ultrasonic transducer 100K of the comparative example 1, the operation range is limited due to the decrease in the transmission power sensitivity (SP) value in the vicinity of 38 Hkz, but the ultrasonic transducers in the first and second embodiments are limited. In 100a and 100b, the transmission power sensitivity (SP) value in the vicinity of 38 Hkz does not decrease, so the operating range is not limited, and it is possible to operate from 20 KHz to about 45 KHz. That is, the ultrasonic transducers 100a and 100b in the first and second embodiments can expand the bandwidth of the operable frequency with respect to the ultrasonic transducer 100K in the first comparative example.

  In the first to fourth embodiments, the head mass 11 corresponds to a head mass, the tail mass 12 corresponds to a tail mass, the piezoelectric ceramic laminates 13 and 16 correspond to piezoelectric ceramic laminates having through holes, and bolts 15 corresponds to a bolt, the ultrasonic transducers 100a to 100d correspond to ultrasonic transducers, the hole 25 corresponds to a through hole larger than the through hole of the tail mass and the screw thread of the bolt, and the screw hole 43 corresponds to the screw portion of the bolt. The tail mass 12a corresponds to the first tail mass, the tail mass 12b corresponds to the second tail mass, the convex portion 21 corresponds to the convex portion, and the acoustic cap 10 serves as the acoustic cap. The cylindrical portion 31 corresponds to the cylindrical portion, the vibrating portion 32 corresponds to the vibrating portion, and the screw portion 33 is a screw on the inner surface of the cylindrical portion of the acoustic cap. Corresponds to.

  Although the present invention has been described in the first to fourth preferred embodiments described above, the present invention is not limited thereto. It will be understood that various other embodiments may be made without departing from the spirit and scope of the invention. Furthermore, in this embodiment, although the effect | action and effect by the structure of this invention are described, these effect | actions and effects are examples and do not limit this invention.

Sectional drawing which shows an example of the whole structure of the ultrasonic transducer | vibrator which concerns on the 1st Embodiment of this invention The schematic diagram which shows an example of the whole structure of the ultrasonic transducer | vibrator which concerns on the 2nd Embodiment of this invention. The schematic diagram which shows an example of the whole structure of the ultrasonic transducer | vibrator which concerns on the 3rd Embodiment of this invention. The schematic diagram which shows an example of the whole structure of the ultrasonic transducer | vibrator which concerns on the 4th Embodiment of this invention. The figure which shows the measurement result in Examples 1, 2 and Comparative Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transducer 10 Acoustic cap 11 Head mass 12 Tail mass 12a, 12b Tail mass 13,16 Piezoelectric ceramic laminated body 14 Through-hole 21 Convex part 23 Screw part 31 Cylindrical part 25 Hole 32 Vibration part 33 Screw part 34 Concave part 35 Space 36 Space

Claims (8)

A piezoelectric ceramic laminate having a through hole is disposed between the head mass and the tail mass, and is engaged with the head mass and the tail mass through the through hole of the piezoelectric ceramic laminate, and compressive stress is applied to the piezoelectric ceramic laminate. In an ultrasonic transducer having a bolted Langevin transducer provided with a bolt for adding
An ultrasonic transducer, wherein a screw hole that can be screwed with a screw portion of the bolt is formed in a part of a through hole of the tail mass. The tail mass is
A first tail mass formed with a through hole larger than the thread of the bolt;
2. A second tail mass, wherein a through hole smaller than a screw thread of the bolt is formed, and a screw hole that can be screwed into the screw portion of the bolt is formed in the through hole. Ultrasonic transducer.   The ultrasonic transducer according to claim 2, wherein the first tail mass and the second tail mass are fixed by screw connection.   4. The tail mass according to claim 1, wherein a through hole is formed on the piezoelectric ceramic laminate, and a screw hole is formed on an end opposite to the end contacting the piezoelectric ceramic laminate. The ultrasonic transducer in any one.   The ultrasonic transducer according to claim 1, wherein a convex portion is provided on a front surface of the head mass, and an acoustic cap is fixed to the head mass so as to cover the convex portion. The acoustic cap is
A cylindrical portion covering the peripheral surface of the convex portion;
6. The ultrasonic transducer according to claim 5, further comprising a vibrating portion integrally formed so as to close one end of the cylindrical portion.   The ultrasonic transducer according to claim 6, wherein the cylindrical portion has a portion whose inner diameter is larger than an outer diameter of the convex portion of the head mass.   2. A screw portion is formed on a peripheral surface of the convex portion, and a screw portion that can be engaged with the screw portion is formed on an inner surface of the cylindrical portion of the acoustic cap. The ultrasonic transducer according to claim 6.

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