JP2008167272A - Piezoelectric sounder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric sounder which can improve a sound pressure, can be wholly miniaturized and enables a conductive terminal to surely contact a piezoelectric diaphragm. <P>SOLUTION: This piezoelectric sounder 2 has: a piezoelectric diaphragm 4; a case 10 for holding the piezoelectric diaphragm 4 in its inside; and a pair of conductive terminals 12A, 12B electrically connected to the piezoelectric diaphragm 4. At least any one of the pair of conductive terminals 12A, 12B has: outside portions 121a, 121b piercing through the case 10 and protruding from the inside of the case 10 to the outside thereof; fixing portions 122a, 122b fixed on the case 10; rising portions 123a, 123b extending from the fixing portions 122a, 122b toward the piezoelectric diaphragm 4 respectively; and contacting portions 124a, 124b positioned on the substantial tips of the rising portions 123a, 123b and contacting the piezoelectric diaphragm 4. At least a part of the rising portions 123a, 123b has a spring constant smaller than the spring constants of the contacting portions 124a, 124b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric sounding body, and more specifically, it is possible to improve sound pressure, to reduce the overall size, and to reliably contact a conductive terminal with a piezoelectric diaphragm. Concerning pronunciation bodies.

  The piezoelectric sounding body mainly includes a piezoelectric diaphragm, a case that holds the piezoelectric diaphragm, and a pair of conductive terminals that are fixed to the case and electrically connected to the piezoelectric diaphragm. Such a piezoelectric sounding body is generally mounted on a domestic electric device (such as a refrigerator, a washing machine, an air conditioner remote control), a sounding part of a fire alarm, or the like.

  In the piezoelectric sounding body disclosed in Patent Literature 1, each conductive terminal starts from the inner wall of the case and rises vertically toward the piezoelectric diaphragm, and bends from the tip of the standing part to the piezoelectric diaphragm. A contact portion that extends in an oblique direction and contacts the piezoelectric diaphragm. Each conductive terminal has a plate-like structure. As a result, the contact portion of each conductive terminal acts as a leaf spring, so that the sound pressure is improved without impeding the vibration of the piezoelectric diaphragm.

  However, in Patent Document 1, since each conductive terminal has an upright portion that stands vertically from the inner wall of the case, it is difficult to reduce the size (lower height) of the piezoelectric sounding body.

  In addition, when the conductive terminal is twisted and the relative position between the contact portion and the piezoelectric vibration plate is slightly shifted, the plate-like contact portion and the piezoelectric vibration plate are not surely in surface contact, and the contact portion and the piezoelectric vibration plate are not in contact with each other. There is a risk of poor continuity with the diaphragm. The poor conduction may cause the vibration characteristics to become unstable.

  Furthermore, as a result of the edge (corner) of the contact portion having a plate-like structure scraping the surface of the piezoelectric vibration plate (electrodes covering the piezoelectric element, etc.), the contact portion and the piezoelectric vibration plate cannot be reliably contacted. There is a risk that the contact portion and the piezoelectric diaphragm may have poor conduction.

  In addition, since the plate-like conductive terminal (flat pin-like conductive terminal) is expensive, the manufacturing cost of the piezoelectric sounding body increases. Furthermore, since the plate-like conductive terminal has low strength, the conductive terminal may be damaged when the piezoelectric sounding body is manufactured and mounted on the circuit board.

If a round pin-shaped (cylindrical) metal terminal with a low price and high strength (spring constant) is used instead of an expensive plate-shaped conductive terminal with low strength (spring constant), the metal terminal for the piezoelectric diaphragm Contact pressure becomes high. As a result, the vibration of the piezoelectric diaphragm is hindered, the amplitude of the piezoelectric diaphragm is reduced, and the sound pressure may be reduced.
JP-A-5-53586

  The present invention has been made in view of such a situation, and an object of the present invention is to improve sound pressure, to reduce the overall size (to reduce the height), and to convert a conductive terminal into a piezoelectric diaphragm. It is to provide a piezoelectric sounding body that can be brought into contact with certainty.

In order to achieve the above object, a piezoelectric sounding body according to the present invention comprises:
A piezoelectric diaphragm;
A case for holding the piezoelectric diaphragm inside;
A piezoelectric sounding body having a pair of conductive terminals electrically connected to the piezoelectric diaphragm,
At least one of the pair of conductive terminals is
An outer portion penetrating the case and projecting from the inside of the case to the outside;
A fixing portion fixed to the case;
A rising portion extending from the fixed portion toward the piezoelectric diaphragm (in an oblique direction);
A contact portion located at substantially the tip of the rising portion and in contact with the piezoelectric diaphragm,
The spring constant of at least a part of the rising portion is lower than the spring constant of the contact portion. Hereinafter, the spring constant is also referred to as rigidity or bending rigidity.

  Preferably, the spring constant of the entire rising portion starting from the fixed portion is lower than the spring constant of the contact portion.

  By making the bending rigidity of the rising portion lower than that of the contact portion, the rising portion functions as a flexible spring. Therefore, the conductive terminal is easily bent at the rising portion according to the vibration of the piezoelectric diaphragm. Therefore, when the piezoelectric diaphragm is vibrated, the contact pressure of the contact portion with the piezoelectric diaphragm can be reduced. As a result, it is possible to prevent the vibration of the piezoelectric diaphragm from being disturbed by the contact portion, and to improve the sound pressure of the piezoelectric sounding body.

  Further, by making the rigidity of the contact portion higher than the rigidity of the rising portion, the contact portion can be reliably brought into contact with the piezoelectric diaphragm.

  Preferably, the conductive terminal is an integrated body constituted by the outer portion, the fixed portion, the rising portion, and the contact portion.

  By forming one metal pin or the like, it is possible to obtain a conductive terminal integrally having an outer portion, a fixed portion, a rising portion, and a contact portion. As a result, it is possible to reduce the number of parts, the number of manufacturing steps, and the manufacturing cost required for manufacturing the piezoelectric sounding body.

  Preferably, a cross section perpendicular to the longitudinal direction of the contact portion is substantially circular.

Preferably, the tip of the contact portion is bent,
The tip of the contact portion and the piezoelectric diaphragm are substantially parallel,
The tip of the contact portion and the piezoelectric diaphragm are in line contact.

  In the present invention, the contact portion has a substantially cylindrical structure having a substantially circular cross section. That is, the contact portion has rotational symmetry with respect to the major axis direction. Further, the tip of the contact portion is bent, and the tip of the contact portion and the piezoelectric diaphragm are in a substantially parallel positional relationship. Therefore, even if the direction of the contact portion with respect to the piezoelectric diaphragm is slightly changed, the side surface of the tip of the contact portion and the piezoelectric diaphragm can always be brought into line contact. As a result, poor conduction between the contact portion and the piezoelectric diaphragm can be prevented, and the vibration characteristics of the piezoelectric sounding body can be stabilized. In addition, since the side surface of the contact portion that is in line contact with the piezoelectric diaphragm is a smooth circular curved surface, the piezoelectric diaphragm is not scraped off by the contact portion (tip thereof). As a result, poor conduction between the contact portion and the piezoelectric diaphragm can be prevented.

  Preferably, a flat portion having a plate-like structure is formed in at least a part of the rising portion.

  When a flat part is formed in the rising part, the bending rigidity of the rising part is lowered in the flat part. Therefore, the conductive terminal easily bends at the flat portion formed at the rising portion according to the vibration of the piezoelectric diaphragm. As a result, the vibration of the piezoelectric diaphragm is not inhibited by the contact pressure of the contact portion in contact with the piezoelectric diaphragm, and the sound pressure of the piezoelectric sounding body can be improved.

  Preferably, the flat portion is formed along the longitudinal direction of the conductive terminal.

  By pressing a part of a cylindrical (round pin-shaped) conductive terminal, a flat portion can be easily formed along the longitudinal direction of the terminal. As a result, the manufacturing cost of the conductive terminal can be reduced compared to the case of manufacturing a conventional leaf spring-shaped (flat pin) conductive terminal. Furthermore, the conductive terminal having a flat portion can function as a flexible spring in the same manner as the plate spring-like metal terminal, although it is less expensive than the plate spring-like metal terminal. Sound pressure can be improved.

  Preferably, the outer diameter of at least a part of the rising portion is smaller than the outer diameter of the contact portion.

  By making the outer diameter of the rising portion smaller than the outer diameter of the contact portion, the bending rigidity of the rising portion is lowered. Therefore, with the vibration of the piezoelectric diaphragm, the conductive terminal is easily bent at the rising portion. As a result, the sound pressure of the piezoelectric sounding body can be improved without hindering the vibration of the piezoelectric diaphragm due to the contact pressure of the contact portion in contact with the piezoelectric diaphragm.

  Preferably, a guide convex portion for guiding the conductive terminal in a predetermined direction is formed on the inner wall of the case.

  Each conductive terminal can be easily fixed in a predetermined direction by the guide convex portion. As a result, the contact portion can be brought into contact with a predetermined position of the piezoelectric diaphragm precisely and stably, and the vibration characteristics of the piezoelectric sounding body can be stabilized.

  Preferably, the fixing portion is fixed to the case by heat caulking. Preferably, a heat caulking convex portion is formed on the inner wall of the case.

  The fixing portion can be firmly fixed to the case by heat caulking, and the fixing portion (conductive terminal) can be prevented from falling out of the case. Further, since the case has the heat caulking convex portion, the fixing portion can be heat caulked reliably.

  Preferably, the fixing portion is integrally fixed to the case by insert molding.

  That is, by embedding the fixing portion (a part of the conductive terminal) in the case, the fixing portion can be firmly fixed to the case, and the fixing portion (conductive terminal) can be prevented from falling off the case.

Preferably, a guide groove is formed on the inner wall of the case,
At least a part of the conductive terminal is located in the guide groove.

  Each conductive terminal can be easily fixed in a predetermined direction by the guide groove. As a result, each contact portion can be brought into precise and stable contact with a predetermined position of the piezoelectric diaphragm, and the vibration characteristics of the piezoelectric sounding body can be stabilized. In addition, the piezoelectric sounding body can be reduced in height by the depth of the guide groove. Furthermore, the contact pressure of the contact portion with respect to the piezoelectric diaphragm can be reduced, and the sound pressure can be improved. In addition, the height of the conductive terminal before assembly can be increased, and contact failure between the contact portion and the piezoelectric diaphragm can be prevented.

  Preferably, the rising portion extends toward the piezoelectric diaphragm starting from the same surface as the inner wall surface of the case or a position recessed from the inner wall surface.

  As a result, the piezoelectric sounding body can be further reduced in height.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a schematic sectional view of a piezoelectric sounding body according to an embodiment of the present invention.
FIG. 2 is a schematic view of a case body included in a piezoelectric sounding body according to an embodiment of the present invention as viewed from the Z direction (inside the case).
FIG. 3 is a schematic view of the case lid of the piezoelectric sounding body according to the embodiment of the present invention as viewed from the Z direction (inside the case).
FIG. 4 is a schematic view of a case lid of a piezoelectric sounding body according to an embodiment of the present invention as viewed from the Z direction (outside of the case).
FIG. 5 is a perspective view of a conductive terminal included in the piezoelectric sounding body according to the embodiment of the present invention.
FIG. 6 is a perspective view of a conductive terminal before completion according to an embodiment of the present invention,
FIG. 7 is a cross-sectional view of a piezoelectric sounding body according to another embodiment of the present invention cut in a direction perpendicular to the surface direction of the case lid and the major axis direction of the conductive terminals. Sectional drawing which shows the guide groove and guide convex part which were formed in the inner wall,
FIG. 8 is a schematic cross-sectional view of a conductive terminal and a case lid included in a piezoelectric sounding body according to another embodiment of the present invention,
FIG. 9 is a schematic cross-sectional view of a conductive terminal and a case lid included in a piezoelectric sounding body according to another embodiment of the present invention.

(Overall configuration of piezoelectric sounding body 2)
As shown in FIG. 1, a piezoelectric sounding body 2 according to an embodiment of the present invention includes a case 10, a piezoelectric diaphragm 4, a pair of conductive terminals (a first conductive terminal 12A and a second conductive terminal 12B), Consists of The case 10 includes a case body 10a and a case lid 10b. A piezoelectric diaphragm 4 is held inside the case 10. The piezoelectric vibration plate 4 has a structure in which a piezoelectric vibrator 4d is bonded to a disk-shaped metal plate 4a with an adhesive. The piezoelectric vibrator 4d has a structure in which electrodes 4b and 4c are formed. The metal plate 4a may also serve as the electrode 4b. The pair of first conductive terminals 12A and second conductive terminals 12B are fixed to the case lid 10b. The first conductive terminal 12A is in contact with and electrically connected to the piezoelectric vibrator 4d (the electrode 4c included) of the piezoelectric diaphragm 4. Further, the second conductive terminal 12B is in contact with and electrically connected to the metal plate 4a of the piezoelectric vibration plate 4.

  When an AC voltage is applied between the first conductive terminal 12A and the second conductive terminal 12B, the piezoelectric vibrator 4d is expanded and contracted in the X direction. Along with the expansion and contraction vibration of the piezoelectric vibrator 4d, the metal plate 4a (the entire piezoelectric vibration plate 4) vibrates in the Z direction and generates a sound.

(Case body 10a)
As shown in FIG. 2, the case main body 10a has a circular structure in the XY plane direction. The diameter of the case body 10a in the XY direction is not particularly limited, but is usually about 10 to 30 mm. The height of the case body 10a (the height in the Z direction) is not particularly limited, but is usually about 3 to 15 mm.

  A sound emitting hole 14 is formed in a substantially central portion of the case main body 10a in the XY plane direction. The hole diameter of the sound emitting hole 14 in the XY plane direction is not particularly limited, but is usually about 2 to 10 mm.

  As shown in FIG. 1, a case step portion 16 is formed at a substantially middle portion of the case main body 10a in the Z direction. As shown in FIG. 2, the case step portion 16 is formed along the outer periphery of the case body 10a in the XY plane direction.

  As shown in FIG. 2, sound pressure braking holes 20 penetrating from the inside of the case body 10a to the outside are formed at equal intervals in the outer peripheral end 18 of the case body 10a. The resonance frequency of the piezoelectric sounding body 2 can be adjusted by the sound pressure braking hole 20. Further, by forming the sound pressure braking hole 20, it is easy to fit the case lid 10b to the case main body 10a.

  On the inner side of the outer peripheral end 18, the preliminary holes 22 are formed at equal intervals. If the case body 10a and the case lid 10b are loosely fitted, the case body 10a and the case lid 10b can be firmly bonded by injecting an adhesive into the preliminary hole 22.

  The material of the case body 10a is not particularly limited, but usually synthetic resin or the like is used.

(Case lid 10b)
3 and 4 show the case lid 10b before the first conductive terminal 12A and the second conductive terminal 12B are fixed for convenience of explanation.

  The case lid 10b has a circular structure in the XY plane direction. The diameter of the case lid in the XY direction is substantially equal to that of the case body 10a.

  The case lid 10b has a pair of terminal through holes 24a and 24b for allowing the first conductive terminal 12A and the second conductive terminal 12B to penetrate from the inside of the case to the outside.

  As shown in FIG. 3, an outer peripheral convex portion 28 for supporting the piezoelectric diaphragm 4 is formed on the outer periphery of the case lid 10b.

  As shown in FIG. 4, on the back surface 8b of the case lid 10b, first boss portions 30a and 30b and a second boss portion 32 are formed. As a result, when the piezoelectric sounding body 2 is mounted on a circuit board or the like, the piezoelectric sounding body 2 can be stabilized with respect to the substrate surface. Further, by bringing the boss portions into close contact with the substrate surface, it is possible to prevent the flux used in the soldering process from flowing backward from the terminal through holes 24a and 24b into the case 10.

  The material of the case lid 10b is not particularly limited, but usually the same synthetic resin as the case main body 10a is used.

  As shown in FIG. 3, a pair of guide grooves 26a and 26b are formed on the surface 8a of the case lid 10b. The first conductive terminal 12A is disposed in the guide groove 26a, and the second conductive terminal 12B is disposed in the guide groove 26b. In FIG. 1, the guide grooves 26a and 26b are not shown.

  The first conductive terminal 12A and the second conductive terminal 12B can be easily fixed in predetermined directions by the guide grooves 26a and 26b. As a result, each of the contact portions 124a and 124b can be brought into precise and stable contact with a predetermined position of the piezoelectric diaphragm 4, and the vibration characteristics of the piezoelectric sounding body 2 can be stabilized. Further, the piezoelectric sounding body 2 can be reduced in height by the depth of the guide grooves 26a and 26b. Furthermore, the contact pressure of the contact portions 124a and 124b with respect to the piezoelectric diaphragm 4 can be reduced, and the sound pressure can be improved. In addition, since the height of the conductive terminals 12A and 12B before assembly can be increased, contact failure between the contact portions 124a and 124b and the piezoelectric diaphragm can be prevented.

(Piezoelectric diaphragm 4)
As shown in FIG. 1, the piezoelectric diaphragm 4 includes a metal plate 4a and a piezoelectric vibrator 4d having electrodes 4b and 4c formed on both surfaces thereof. The piezoelectric vibrator 4d is bonded to the metal plate 4a via the electrode 4b. The metal plate 4a, the electrodes 4b and 4c, and the piezoelectric vibrator 4d are bonded to each other with a conductive adhesive or the like.

  Although it does not specifically limit as a material of the metal plate 4a, Usually Ni alloy etc. are used.

  The material of the electrodes 4b and 4c is not particularly limited, but usually Ag or the like is used.

  The material of the piezoelectric vibrator 4d is not particularly limited as long as it has piezoelectric vibration, but usually a ferroelectric ceramic such as PZT (lead zirconate titanate) is used.

  Each shape of the metal plate 4a, the electrodes 4b and 4c, and the piezoelectric vibrator 4d is not particularly limited, but usually has a concentric structure in the XY plane direction. In the XY plane direction, the diameter of the metal plate 4a is larger than the diameters of the electrodes 4b and 4c and the piezoelectric vibrator 4d, and the diameters of the electrodes 4b and 4c are equal to or smaller than the diameter of the piezoelectric vibrator 4d.

  The diameter of the metal plate 4a in the XY plane direction is not particularly limited, but is usually about 8 to 28 mm. The thickness of the metal plate 4a (Z-direction thickness) is not particularly limited, but is usually about 30 to 300 μm.

  The diameter of the piezoelectric vibrator 4d in the XY plane direction is not particularly limited, but is usually about 5 to 25 mm. The thickness of the piezoelectric vibrator 4d (thickness in the Z direction) is not particularly limited, but is usually about 50 to 300 μm.

  The thickness (thickness in the Z direction) of the electrodes 4b and 4c is not particularly limited, but is usually about 5 to 20 μm.

  As shown in FIG. 1, the outer peripheral portion of the metal plate 4 a is sandwiched between the stepped portion 16 of the case body 10 a and the outer peripheral convex portion 28 of the case lid 10 b, so that the entire piezoelectric diaphragm 4 is placed inside the case 10. Retained and fixed. The outer peripheral convex portion 28 is in line contact with the outer peripheral portion of the metal plate 4a. As a result, the vibration of the piezoelectric diaphragm 4 is not easily disturbed by the contact of the outer peripheral convex portion 28.

(Conductive terminals 12A, 12B)
As shown in FIGS. 1 and 5, the first conductive terminal 12 </ b> A is an integral body including an outer portion 121 a, a fixing portion 122 a, a rising portion 123 a, and a contact portion 124 a. Similarly, the second conductive terminal 12B is also an integral body including an outer portion 121b, a fixing portion 122b, a rising portion 123b, and a contact portion 124b. The material of each conductive terminal is not particularly limited as long as it is a conductive material, but metal is used in this embodiment.

  The second conductive terminal 12B has the same shape and arrangement in the piezoelectric sounding body 10 as the first conductive terminal 12A, except that the contact portion 124b is in contact with and electrically connected to the metal plate 4a. Therefore, hereinafter, the first conductive terminal 12A will be mainly described.

  As shown in FIG. 1, the outer portion 121 a of the first conductive terminal 12 </ b> A passes through the case lid 10 b (terminal through hole 24 a in FIGS. 3 and 4) and protrudes from the inside of the case 10 to the outside.

  The first conductive terminal 12A is fixed to the surface 8a of the case lid 10b by heat caulking at the fixing portion 122a. Preferably, a heat caulking convex portion 34 is formed on the surface 8a of the case lid 10b.

  The fixing portion 122a can be firmly fixed to the case lid 10b by heat caulking, and the fixing portion 122a (first conductive terminal 12A) can be prevented from falling out of the case 10. In addition, since the case lid 8 includes the heat caulking convex portion 34, the heat caulking of the fixing portion 122a can be reliably performed.

  The rising portion 123a extends obliquely from the fixed portion 122a toward the piezoelectric diaphragm 4.

  As shown in FIG. 5, a flat portion 125a having a plate-like structure is formed on the entire rising portion 123a of the first conductive terminal 12A. That is, in the present embodiment, the entire rising portion 123a is the flat portion 125a. In the present embodiment, the entire rising portion 123b in the second conductive terminal 12B is also the flat portion 125b.

  When the flat portion 125a is formed on the entire rising portion 123a, the bending rigidity of the entire rising portion 123a (flat portion 125a) becomes lower than the bending rigidity of the contact portion 124a. Therefore, the first conductive terminal 12 </ b> A is easily bent at the rising portion 123 a (flat portion 125 a) according to the vibration of the piezoelectric diaphragm 4. As a result, the vibration of the piezoelectric diaphragm 4 is not hindered by the contact pressure of the contact portion 124a in contact with the piezoelectric diaphragm 4 (electrode 4c) in the piezoelectric diaphragm 4, and the sound pressure of the piezoelectric sounding body 2 is suppressed. Can be improved.

  Preferably, as shown in FIGS. 1 and 5, the flat portion 125a is formed along the longitudinal direction of the first conductive terminal 12A.

  As shown in FIG. 6, the flat part 125a can be easily formed along the longitudinal direction of the metal pin 12C by pressing a part of the cylindrical (round pin shape) metal pin 12C. By further forming the metal pin 12c, the first conductive terminal 12A (FIG. 5) integrally including the outer portion 121a, the fixing portion 122a, the rising portion 123a (flat portion 125a), and the contact portion 124a is obtained. Can do. As a result, the number of parts, the number of manufacturing steps, and the manufacturing cost required for manufacturing the first conductive terminal 12A and the piezoelectric sounding body 2 can be reduced as compared with the case of manufacturing a conventional leaf spring-shaped conductive terminal.

  Furthermore, the first conductive terminal 12A having the flat portion 125a can function as a flexible spring in the same manner as the plate spring-like metal terminal, although it is less expensive than the plate spring-like metal terminal. The sound pressure of the piezoelectric sounding body 2 can be improved.

  As shown in FIG. 1, the contact part 124a is located at the tip of the rising part 123a. The tip of the contact portion 124a is bent, and the tip of the contact portion 124a and the piezoelectric diaphragm 4 are parallel. Further, the cross section perpendicular to the longitudinal direction of the contact portion 124a is substantially circular as shown in FIG. Therefore, the tip of the contact portion 124a and the electrode 4c of the piezoelectric diaphragm 4 are in line contact and are electrically connected.

  As shown in FIG. 5, the entire first conductive terminal excluding the rising portion 123a (flat portion 125a) is a metal pin having a substantially circular cross section.

  In the present embodiment, the rising portion 123a functions as a flexible spring by making the bending rigidity of the rising portion 123a (flat portion 125a) lower than the bending rigidity of the contact portion 124a. Therefore, the first conductive terminal 12A is easily bent at the rising portion 123a according to the vibration of the piezoelectric diaphragm 4. Therefore, when the piezoelectric diaphragm 4 vibrates, the contact pressure of the contact portion 124a against the piezoelectric diaphragm 4 can be reduced. As a result, the vibration of the piezoelectric diaphragm 4 is not inhibited by the contact portion 124a, and the sound pressure of the piezoelectric sounding body 2 can be improved. Further, by making the bending rigidity of the contact portion 124a higher than the bending rigidity of the rising portion 123a, the contact portion 124a can be reliably brought into contact with the piezoelectric diaphragm 4.

  In the present embodiment, the contact portion 124a has a cylindrical structure having a circular cross section. That is, the contact portion 124a has rotational symmetry with respect to the major axis direction. Further, the tip of the contact portion 124a is bent, and the tip of the contact portion 124a and the piezoelectric diaphragm 4 (electrode 4c) are in a substantially parallel positional relationship. Therefore, even if the orientation of the contact portion 124a with respect to the piezoelectric diaphragm 4 is slightly changed, the side surface at the tip of the contact portion 124a and the piezoelectric diaphragm 4 (electrode 4c) are always in line contact and electrically connected. be able to. As a result, poor conduction between the contact portion 124a and the piezoelectric diaphragm 4 (electrode 4c) can be prevented, and the vibration characteristics of the piezoelectric sounding body 2 can be stabilized. Further, since the side surface of the contact portion 124a that makes line contact with the piezoelectric vibration plate 4 (electrode 4c) is a smooth circular curved surface, the piezoelectric vibration plate 4 (electrode 4c) is not scraped off by the contact portion 124a. As a result, poor conduction between the contact portion 124a (first conductive terminal 12A) and the piezoelectric diaphragm 4 (electrode 4c) can be prevented.

  In the present embodiment, since the entire first conductive terminal 12A excluding the rising portion 123a (flat portion 125a) has a round pin shape (substantially circular in cross section), the whole has higher strength than the flat pin-shaped conductive terminal. Have. As a result, the first conductive terminal 12A is unlikely to be damaged when the piezoelectric sounding body 2 is manufactured and mounted on the circuit board. The same applies to the second conductive terminal 12B.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, in the above-described embodiment, each of the first conductive terminal 12A and the second conductive terminal 12B has a flat portion at the rising portion, and the bending rigidity of the rising portion is lower than the bending rigidity of the connection portion. Only one conductive terminal 12A may have a flat portion 125a in the rising portion 123a. That is, at least in the first conductive terminal 12A in contact with the vicinity of the central portion having a large amplitude in the piezoelectric diaphragm 4, the bending rigidity of the rising portion 123a may be made lower than the bending rigidity of the connection portion 124a. In this case, the same effects as those of the above-described embodiment can be obtained.

  Instead of forming the flat portion 125a at the rising portion 123a of the first conductive terminal 12A, the outer diameter of at least a part of the rising portion 123a may be smaller than the outer diameter of the contact portion 124a. The same applies to the second conductive terminal 12B.

  By making the outer diameter of the rising portion 123a smaller than the outer diameter of the contact portion 124a, the bending rigidity of the rising portion 123a becomes lower than that of the contact portion 124a. Accordingly, the first conductive terminal a easily bends at the rising portion 123a as the piezoelectric diaphragm 4 vibrates. As a result, the vibration pressure of the piezoelectric diaphragm 4 is not hindered by the contact pressure of the contact portion 124a in contact with the piezoelectric diaphragm 4, and the sound pressure of the piezoelectric sounding body 2 can be improved.

  As shown in FIG. 7, a guide convex portion 70 that guides the first conductive terminal 12 </ b> A in a predetermined direction may be formed on the surface 8 a of the case lid 10 b. By the guide convex portion 70, the first conductive terminal 12A can be easily fixed in a predetermined direction. As a result, the contact portion 124a can be brought into precise and stable contact with a predetermined position of the piezoelectric diaphragm 4 (electrode 4c), and the vibration characteristics of the piezoelectric sounding body 2 can be stabilized. A guide convex portion that guides the second conductive terminal 12B in a predetermined direction may be formed on the surface 8a of the case lid 10b.

  The fixing portions 122a and 122b may be integrally fixed to the case lid 10b by insert molding.

  That is, by embedding each fixing portion 122a, 122b (a part of each conductive terminal 12A, 12B) in the case lid 10b, each conductive terminal 12A, 12B can be firmly fixed to the case lid 10b, and each conductive terminal 12A. , 12B can be prevented from falling out of the case.

  As shown in FIG. 8, the rising portion 123a of the first conductive terminal 12A may extend toward the piezoelectric diaphragm 4 starting from the same surface as the surface 8a of the case lid 10b. Alternatively, as shown in FIG. 9, the rising portion 123a may extend toward the piezoelectric diaphragm 4 starting from a position recessed from the surface 8a of the case lid 10b. As a result, the piezoelectric sounding body 2 can be further reduced in height. The same applies to the rising portion 123b of the second conductive terminal 12B.

  Next, the present invention will be described based on a more specific example, but the present invention is not limited to this example.

Example 1
In Example 1, piezoelectric sounding body samples 1 to 10 similar to the piezoelectric sounding body 2 shown in FIG. 1 were produced except that a flat portion was not formed on the rising portion 123b of the second conductive terminal 12B. The flat portion 125a of the first conductive terminal 12A was formed by press molding a metal pin having a circular cross section. The dimensions of each sample of Example 1 were as follows.
Diameter of the case body 10a in the XY direction: 21.25mm,
Case body 10a height (Z-direction height): 11 mm,
Case 10 diameter: 22 mm
Hole diameter of sound emitting hole 14: 7 mm,
Diameter of the metal plate 4a in the XY plane direction: 20mm,
Metal plate 4a thickness (Z-direction thickness): 200 μm,
Diameter of the piezoelectric vibrator 4d in the XY plane direction: 15 mm,
Thickness of piezoelectric vibrator 4d (Z-direction thickness): 200 μm.

  Next, the sound pressure (unit: dBA / 10 cm) of each sample of Example 1 was measured. Further, the average value AVE, the maximum value MAX, and the minimum value MIN of the sound pressure were obtained from each sample. The results are shown in Table 1.

Comparative Example 1
In Comparative Example 1, the piezoelectric sounding having the same structure as that of Example 1 except that no flat portion is formed in any of the rising portions 123a and 123b of the first conductive terminal 12A and the second conductive terminal 12B. Body samples 1-10 were produced. That is, in the comparative example 1, the 1st conductive terminal and the 2nd conductive terminal which only bent and formed the metal pin which has a circular cross section were used. Further, sound pressure was evaluated in the same manner as in Example 1 for Samples 1 to 10 of Comparative Example 1. The results are shown in Table 1.

Comparative Example 2
Comparative Example 2 is the same as Example 1 except that the first conductive terminal and the second conductive terminal obtained by bending a flat pin that is more expensive than the conductive terminal used in Example 1 were used. Piezoelectric sounding body samples 1 to 10 were produced. In addition, sound pressure was evaluated in the same manner as in Example 1 for Samples 1 to 10 in Comparative Example 2. The results are shown in Table 1.

The piezoelectric sounding body 2 of Example 1 in which the evaluation first conductive terminal 12A has the flat portion 125a having low bending rigidity has a higher sound pressure than the comparative example 1 in which the flat portion is not formed on each conductive terminal. confirmed.

  Moreover, in the piezoelectric sounding body 2 of Example 1, it was confirmed that a sound pressure equivalent to that of Comparative Example 2 having a flat pin-shaped conductive terminal that is more expensive than the conductive terminal used in Example 1 was obtained. . Furthermore, in the piezoelectric sounding body of Example 1, the entire first conductive terminal 12A excluding the rising portion 123a (flat portion 125a) has a round pin shape (substantially circular in cross section). It was confirmed that it had higher strength than Comparative Example 2 used.

FIG. 1 is a schematic sectional view of a piezoelectric sounding body according to an embodiment of the present invention. FIG. 2 is a schematic view of the case main body of the piezoelectric sounding body according to the embodiment of the present invention as viewed from the Z direction (inside the case). FIG. 3 is a schematic view of the case lid of the piezoelectric sounding body according to the embodiment of the present invention as viewed from the Z direction (inside the case). It is the schematic which looked at the case cover which the piezoelectric sounding body which concerns on one Embodiment of this invention has from the Z direction (case exterior). FIG. 5 is a perspective view of a conductive terminal included in the piezoelectric sounding body according to the embodiment of the present invention. FIG. 6 is a perspective view of a conductive terminal before completion according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of a piezoelectric sounding body according to another embodiment of the present invention cut in a direction perpendicular to the surface direction of the case lid and the longitudinal direction of the conductive terminals, and the inner wall of the case lid It is sectional drawing which shows the guide groove and guide convex part which were formed in this. FIG. 8 is a schematic cross-sectional view of a conductive terminal and a case lid included in a piezoelectric sounding body according to another embodiment of the present invention. FIG. 9 is a schematic cross-sectional view of a conductive terminal and a case lid included in a piezoelectric sounding body according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Piezoelectric sounding body 4 ... Piezoelectric diaphragm 4a ... Metal plate 4b, 4c ... Electrode 4d ... Piezoelectric vibrator 10 ... Case 10a ... Case main body 10b ... Case lid 12A ... First conductive terminal 12B ... Second conductive terminal 121a, 121b ... Outer part 122a, 122b ... Fixed part 123a, 123b ... Rising part 124a, 124b ... Contact part 125a, 125b ... Flat part

Claims (14)

A piezoelectric diaphragm;
A case for holding the piezoelectric diaphragm inside;
A piezoelectric sounding body having a pair of conductive terminals electrically connected to the piezoelectric diaphragm,
At least one of the pair of conductive terminals is
An outer portion penetrating the case and projecting from the inside of the case to the outside;
A fixing portion fixed to the case;
A rising portion extending from the fixed portion toward the piezoelectric diaphragm;
A contact portion located at substantially the tip of the rising portion and in contact with the piezoelectric diaphragm,
The piezoelectric sounding body, wherein a spring constant of at least a part of the rising portion is lower than a spring constant of the contact portion.   2. The piezoelectric sounding body according to claim 1, wherein a spring constant of the entire rising portion is lower than a spring constant of the contact portion.   3. The piezoelectric sounding body according to claim 1, wherein the conductive terminal is an integrated body including the outer portion, the fixing portion, the rising portion, and the contact portion.   The piezoelectric sounding body according to claim 1, wherein a cross section of the contact portion is substantially circular.   The piezoelectric sounding body according to any one of claims 1 to 4, wherein a flat portion having a plate-like structure is formed in at least a part of the rising portion.   6. The piezoelectric sounding body according to claim 5, wherein the flat portion is formed along a longitudinal direction of the conductive terminal.   The piezoelectric sounding body according to claim 1, wherein an outer diameter of at least a part of the rising portion is smaller than an outer diameter of the contact portion.   The piezoelectric sounding body according to any one of claims 1 to 7, wherein a guide convex portion for guiding the conductive terminal in a predetermined direction is formed on an inner wall of the case.   The piezoelectric sounding body according to claim 1, wherein the fixing portion is fixed to the case by heat caulking.   The piezoelectric sounding body according to claim 9, wherein a heat caulking convex portion is formed on an inner wall of the case.   The piezoelectric sounding body according to claim 1, wherein the fixing portion is integrally fixed to the case by insert molding. A guide groove is formed on the inner wall of the case,
The piezoelectric sounding body according to claim 1, wherein at least a part of the conductive terminal is located in the guide groove.   The rising portion extends toward the piezoelectric diaphragm starting from the same surface as the inner wall surface of the case or a position recessed from the inner wall surface of the case. The piezoelectric sounding body described in 1. The tip of the contact portion is bent,
The tip of the contact portion and the piezoelectric diaphragm are substantially parallel,
The piezoelectric sounding body according to claim 1, wherein the tip of the contact portion and the piezoelectric diaphragm are in line contact.

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