JP2004208130A - Piezo-electric transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezo-electric transducer having improved vibration characteristics of a vibration member without requiring that the vibration member driven and vibrated by a piezo-electric element is held. <P>SOLUTION: The piezo-electric transducer 1 has a curved piezo-electric actuator 10 formed by bonding the piezo-electric element 11, which is a piezo-electric material 12 having electrodes 13 formed on the front and rear sides thereof, and a curved reinforcing plate 14 consisting of a resilient material, a substrate 15 on which the piezo-electric actuator 10 is fixed, and a diaphragm 16 mounted on near the vertex on the convex surface side of the piezo-electric actuator 10. Even though the reinforcing plate 14 extends and contracts longitudinally, when the piezo-electric element 11 is so driven that a spread mode displacement occurs in the piezo-electric plate 12 but, because both ends of the reinforcing plate 14 are fixed, the central part of the reinforcing plate 14 vibrates in the thickness direction of the plate 14 to vibrate the diaphragm 16. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric transducer that converts a vibration generated by driving a piezoelectric actuator into an acoustic signal or the like.
[0002]
[Prior art]
2. Description of the Related Art In portable electronic devices such as a mobile phone, a PDA device, and a notebook-sized small personal computer, a liquid crystal panel and a sounding body that generates an alarm sound or a confirmation sound are usually configured separately. However, in such a configuration, for example, when trying to increase the driving efficiency of the sounding body, the vibrating body becomes large, so that there is a problem that miniaturization of the portable electronic device is hindered.
[0003]
In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. H10-1111659 (Patent Document 1) discloses a method of driving a piezoelectric element and a piezoelectric element on one of two glasses constituting a liquid crystal panel. A liquid crystal display device in which related circuits are mounted and the periphery of a liquid crystal panel is held in a case is disclosed. In such a liquid crystal display device, since the sound is generated by vibrating the glass with the piezoelectric element, it is not necessary to separately provide a diaphragm, thereby making it possible to reduce the size of the liquid crystal display device. Further, even if the display capacity is increased by enlarging the liquid crystal panel, since this is equivalent to increasing the size of the diaphragm of the sounding body, the sounding body can be efficiently driven.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-1111659 (pages 2, 3; FIGS. 1, 3)
[0005]
[Problems to be solved by the invention]
However, in the liquid crystal display device disclosed in Patent Literature 1, since the periphery of the liquid crystal display panel (that is, the periphery of the glass constituting the liquid crystal display panel) is held in the case, the vibration of the glass is suppressed. As a result, it is difficult to generate good quality sound, and power is required to drive the piezoelectric element in order to obtain a predetermined sound pressure. In addition, there is a problem that the sound quality changes depending on the attachment state between the glass and the case.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a piezoelectric transducer that does not need to hold a vibrating member that vibrates by driving a piezoelectric element and has improved vibration characteristics of the vibrating member. I do.
[0007]
[Means for Solving the Problems]
According to the present invention, a piezoelectric element in which electrodes are formed on the front and back surfaces of a thin plate-shaped piezoelectric element, and a curved reinforcing plate made of an elastic material,
Holding means for fixing both ends of the reinforcing plate,
A vibrating member attached near a vertex on the convex surface side of the piezoelectric actuator, and vibrating in a thickness direction vibration generated in a convex portion of the piezoelectric actuator by expanding and contracting the piezoelectric body in a planar direction;
And a piezoelectric transducer comprising:
[0008]
In such a piezoelectric transducer, a reinforcing plate having a protrusion protruding on the convex surface side near a curved vertex may be used, and a vibration member may be attached to the protrusion. The piezoelectric element is mounted on the concave side of the reinforcing plate.
[0009]
Further, according to the present invention, a curved piezoelectric actuator formed by bonding a piezoelectric element having electrodes formed on the front and back surfaces of a thin plate-shaped piezoelectric body and a curved reinforcing plate made of an elastic material,
Holding means for fixing both ends of the curved piezoelectric actuator,
A massive or rod-shaped projection member provided near the vertex on the convex side of the curved piezoelectric actuator,
A vibrating member attached to the projecting member, vibrating in a thickness direction generated in a convex portion of the piezoelectric actuator by expanding and contracting the piezoelectric body in a plane direction;
And a piezoelectric transducer comprising:
[0010]
In such a piezoelectric transducer, it is possible to adopt a structure in which a member made of an insulating material is used as the projecting member, and the piezoelectric element is attached to the convex surface of the reinforcing plate, and the projecting member is attached to the piezoelectric element. Alternatively, the piezoelectric element may be mounted on the concave side of the reinforcing plate, and the protruding member may be mounted near the top of the convex side of the reinforcing plate.
[0011]
According to such a piezoelectric transducer, since the vibration member is held by the piezoelectric actuator, it is not necessary to fix the vibration member at another portion such as a peripheral portion thereof. Thus, the vibration of the vibration member can be largely vibrated with low power without suppressing the vibration of the vibration member. In addition, since the problem that the vibration characteristics change depending on the fixed state of the peripheral portion of the vibration member or the like does not occur, the variation in the vibration characteristics of the plurality of piezoelectric transducers is suppressed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view of the piezoelectric transducer 1. The piezoelectric transducer 1 includes a curved piezoelectric actuator 10 formed by laminating a piezoelectric element 11 in which electrodes 13 are formed on the front and back surfaces of a thin plate-shaped piezoelectric body 12 and a curved reinforcing plate 14 made of an elastic material. And a diaphragm 16 attached near the apex on the convex side of the piezoelectric actuator 10 (that is, on the surface side of the piezoelectric element 11).
[0013]
As the piezoelectric body 12, for example, lead zirconate titanate (PZT) -based piezoelectric ceramics is used. As a method for manufacturing the piezoelectric element 11, a conventionally known method, for example, a ceramic powder is formed into a sheet, a rectangular plate is punched out of a green sheet or the like, and the obtained rectangular plate is fired to obtain a piezoelectric body 12, A method is used in which electrodes 13 are formed by printing and baking a silver paste or the like on the front and back surfaces of the piezoelectric body 12, and a predetermined voltage is applied between the electrodes 13 to polarize the piezoelectric body 12.
[0014]
The reinforcing plate 14 maintains a curved state without receiving any external force. As the reinforcing plate 14, a metal plate having a spring property such as stainless steel, copper, and phosphor bronze is preferably used. As the reinforcing plate 14, a substrate in which a thin metal foil is pasted on a resin plate can be used. In this case, a curved resin plate and a curved metal foil are bonded together by bonding or welding. It is preferable to use
[0015]
The piezoelectric element 11 manufactured by the above-described manufacturing method has a flat shape, but is curved when bonded to the reinforcing plate 14. Conversely, when the piezoelectric element 11 is bonded to the reinforcing plate 14, it is necessary that the piezoelectric element 11 has such flexibility that it can be bent along the shape of the reinforcing plate 14. Specifically, it is necessary to reduce the thickness of the piezoelectric plate 12, and the thickness of the piezoelectric plate 12 is appropriately set in consideration of the curvature of the reinforcing plate 14. The bonding between the piezoelectric element 11 and the reinforcing plate 14 is performed using a resin adhesive.
[0016]
For example, the reinforcing plate 14 has a total length of 30 mm, a thickness of 50 μm to 200 μm, and a curvature of 180 mm. The piezoelectric element 11 having a total length of 26 mm and a thickness of 50 μm to 200 μm is bonded to such a reinforcing plate 14, The piezoelectric actuator 10 can be configured. This dimension is merely an example, and is not limited to this. The shape of the piezoelectric actuator 10 is appropriately adjusted in consideration of the size of the diaphragm 16, the position to be attached to the diaphragm 16, the number of attachments to the diaphragm 16, the strength and displacement required for the piezoelectric actuator 10, and the like. Is set to
[0017]
Both ends of the reinforcing plate 14 are fixed to the substrate 15. The board 15 is, for example, a printed wiring board to which electronic components for driving the piezoelectric actuator 10 are attached. Examples of a method of fixing the reinforcing plate 14 to the substrate 15 include a method using an adhesive and a method of embedding the end of the reinforcing plate 14 in the substrate 15. When a metal foil is attached to the surface of the substrate 15 or when the substrate 15 is a metal plate, both ends of the reinforcing plate 14 can be fixed to such a substrate by soldering, spot welding, or the like. It is.
[0018]
The vibration plate 16 is attached to the surface of the piezoelectric element 11 using an adhesive. In order to make these bonding areas constant, for example, there is a method in which an adhesive is applied with a certain thickness to a certain area of the diaphragm 16 and pressed against the piezoelectric element 11 with a certain force. The vibration plate 16 is preferably made of an insulating material such as a glass plate or a ceramic plate in order to be in contact with the electrode 13 of the piezoelectric element 11. However, even if a metal plate is used, the surface thereof may be subjected to insulation treatment. For example, it can be used similarly to a glass plate or the like.
[0019]
In the piezoelectric transducer 1 having such a structure, driving in landscape mode for stretching the piezoelectric element 11 in the piezoelectric plate 12 in length direction (surface direction) (d ₃₁ mode), reinforced by a force received from the piezoelectric element 11 plate 14 Also try to expand and contract in the longitudinal direction. However, here, since both ends of the reinforcing plate 14 are fixed, as shown by an arrow A in FIG. 1, the vicinity of the curved apex of the reinforcing plate 14 (that is, the vicinity of the apex of the piezoelectric actuator 10) is increased. Vibrates in the thickness direction. That is, the piezoelectric actuator 10 bends and vibrates with both ends fixed. Due to this vibration, the diaphragm 16 also vibrates in the same direction.
[0020]
Since the end face of the diaphragm 16 is not fixed, the vibration of the diaphragm 16 is not hindered. For this reason, the generated force and the displacement amount required for the piezoelectric actuator 10 to generate the vibration of the predetermined strength on the vibration plate 16 can be made smaller than those in the related art. Further, when the end face or the like of the diaphragm 16 is fixed, the vibration form of the diaphragm 16 may be different due to the difference in the fixing state, that is, the vibration characteristics of the diaphragm 16 are different for each product, and the quality is stable. May not be possible. However, such a problem does not occur in the piezoelectric transducer 1.
[0021]
The piezoelectric element 11 can be driven at any frequency in the low frequency to ultrasonic range. When the resonating driving the piezoelectric actuator 10, it is preferable to use a material having a high mechanical quality factor Qm for the piezoelectric element 12, in the case where the non-resonant drive is, the piezoelectric constant d ₃₁ and the electromechanical coupling coefficient as the piezoelectric 12 it is preferable to use a material having a high k _31. When driving at a high frequency, it is preferable to use a material having a small dielectric loss δ in order to suppress heat generation.
[0022]
In the above-described piezoelectric transducer 1, when the diaphragm 16 is a liquid crystal panel of a portable electronic device, a function as a speaker can be added to the liquid crystal panel. Thus, the size of the portable electronic device can be reduced. The substrate 15 can be mounted on a control substrate of a liquid crystal panel. If this control substrate is mounted on a case of a portable electronic device, it is not necessary to fix the end face of the liquid crystal panel to the case of the portable electronic device. For example, if the edge of the liquid crystal panel is brought into contact with a member made of soft rubber or the like that does not hinder the vibration of the liquid crystal panel, no gap is formed between the case and the liquid crystal panel. The substrate 15 may be a control substrate of a liquid crystal panel. With such a configuration, the sound quality can be kept constant, and the occurrence of variations in the sound quality of the product can be suppressed.
[0023]
In the piezoelectric transducer 1, by driving the piezoelectric actuator 10 in the ultrasonic wavelength range, the piezoelectric transducer 1 can be used as a sonar or a medical ultrasonic diagnostic device. In this case, the diaphragm 16 can be brought into direct contact with the object to be measured, or the ultrasonic wave can be indirectly applied to the object to be measured. Further, the piezoelectric transducer 1 can also be used as a pressure sensor or the like that measures the magnitude of the applied force from electric power (voltage) generated in the piezoelectric element 11 when a force is applied to the vibration plate 16.
[0024]
Next, another embodiment of the piezoelectric transducer (piezoelectric transducers 1a to 1c) will be described. FIG. 2 is a schematic side view of the piezoelectric transducer 1a. The piezoelectric transducer 1a has a piezoelectric actuator 10a in which the piezoelectric element 11 is bonded to the concave surface side of the reinforcing plate 14, and has a structure in which the vibration plate 16 is bonded to the reinforcing plate 14. The piezoelectric transducer 1 and the piezoelectric transducer 1a have equivalent characteristics.
[0025]
FIG. 3 is a schematic side view of the piezoelectric transducer 1b. The piezoelectric transducer 1b is different from the piezoelectric transducer 1 shown in FIG. 1 described above in that a bar-shaped projection member 17 having a longitudinal direction perpendicular to the paper surface of FIG. That is, the diaphragm 16 is attached to the projection member 17.
[0026]
In the piezoelectric transducers 1 and 1a, for example, even if an adhesive is printed linearly on the vibration plate 16 and attached to the piezoelectric element 11, the bonding between the vibration plate and the piezoelectric element 11 is caused by the spread of the adhesive. The area may be large. When the bonding area increases, the stress generated at the bonding portion between the piezoelectric element 11 and the vibration plate 16 increases. Further, the vibration of the piezoelectric actuator 10 is hindered. Further, when the vibration plate 16 is bonded to the piezoelectric element 11, if the bonding area between the vibration plate and the piezoelectric element 11 changes due to the spread of the adhesive, the vibration characteristics of the individual piezoelectric transducers 1 may vary. is there.
[0027]
However, in the piezoelectric transducer 1b, by connecting the piezoelectric element 11 and the vibration plate 16 via the protruding members 17, the bonding area thereof can be reduced, so that occurrence of such a problem can be suppressed. it can.
[0028]
The projection member 17 is not limited to a rod-shaped member having a substantially circular cross section. For example, a rod-shaped member having a polygonal cross section (for example, a regular octahedron) is used in order to stably hold the diaphragm 16 while reducing the adhesion area between the piezoelectric element 11 and the diaphragm 16. You may. Further, a spherical member can be used as the projection member 17. Thereby, the area of adhesion with the piezoelectric element 11 and the area of adhesion with the diaphragm 16 can be further reduced. Further, a polyhedron (for example, a regular dodecahedron or a regular icosahedron) or the like may be used as the protruding member 17, whereby the bonding surface can be stabilized.
[0029]
FIG. 4 is a schematic side view of the piezoelectric transducer 1c. The piezoelectric transducer 1c has a curved shape, and includes a reinforcing plate 14a having a projection 18 protruding outward at an apex portion thereof, and a piezoelectric actuator including a piezoelectric element 11 mounted on a concave side of the reinforcing plate 14a. 10b, a substrate 15 for fixing the reinforcing plate 14a, and a diaphragm 16 attached to the protrusion 18 of the reinforcing plate 14a.
[0030]
The protruding portion 18 has a tunnel shape, and a longitudinal direction is a direction perpendicular to the paper surface of FIG. 4. Similarly to the piezoelectric transducer 1b, the bonding area of the piezoelectric transducer 1c can be reduced by bonding the vibration plate 16 to the projection 18, so that the vibration of the piezoelectric actuator 10a is hardly hindered. In 1c, it is possible to suppress the occurrence of variation in the vibration characteristics of the diaphragm 16.
[0031]
The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment. For example, in the piezoelectric transducer 1b shown in FIG. 3, the piezoelectric element 11 is mounted on the concave surface side of the reinforcing plate 14 like the piezoelectric transducer 1a shown in FIG. Is attached, and the diaphragm 16 can be further deformed into a form in which the diaphragm 16 is bonded to the projecting member 17.
[0032]
As the protruding member 17, a rod member having a substantially semicircular cross section or a hemispherical member may be used. Further, in the piezoelectric transducer 1c, the projection 18 may have a hemispherical shape. Thereby, the bonding area between the projection 18 and the diaphragm 16 can be reduced. The method of attaching the diaphragm 16 to the protrusion 18 formed on the reinforcing plate 14a is not limited to the method using an adhesive. For example, when the reinforcing plate 14a is made of metal and the diaphragm is also made of metal, they can be connected by welding with the projections 18. However, since electricity flows through the reinforcing plate 14a when the piezoelectric element 11 is driven, electricity also flows through the vibration plate 16. For this reason, it may be necessary to perform a process such as forming an insulating film on the surface / side surface of the diaphragm 16.
[0033]
The diaphragm 16 is not limited to a simple plate shape having a constant thickness. For example, the diaphragm 16 may have irregularities on its surface, and a slit (hole) penetrating in the thickness direction may be formed in a predetermined shape at a predetermined position.
[0034]
【The invention's effect】
As described above, according to the piezoelectric transducer of the present invention, since the vibration member is held by the piezoelectric actuator, it is not necessary to fix the vibration member at another portion such as a peripheral portion thereof. Thus, the vibration of the vibration member can be largely vibrated with low power without suppressing the vibration of the vibration member. Further, since the problem that the vibration characteristics change depending on the fixed state of the peripheral portion of the vibration member or the like does not occur, it is possible to suppress the occurrence of variations in the vibration characteristics of the plurality of piezoelectric transducers.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a piezoelectric transducer.
FIG. 2 is a schematic side view of another piezoelectric transducer.
FIG. 3 is a schematic side view of still another piezoelectric transducer.
FIG. 4 is a schematic side view of still another piezoelectric transducer.
[Explanation of symbols]
1.1a, 1b, 1c; piezoelectric transducers 10, 10a, 10b; piezoelectric actuator 11, piezoelectric element 12, piezoelectric body 13, electrode 14, reinforcing plate 15, substrate 16, diaphragm 17, projecting member 18, projecting portion

Claims (5)

A curved piezoelectric actuator formed by bonding a piezoelectric element having electrodes formed on the front and back surfaces of a thin plate-shaped piezoelectric body and a curved reinforcing plate made of an elastic material,
Holding means for fixing both ends of the reinforcing plate,
A vibrating member attached near a vertex on the convex surface side of the piezoelectric actuator, and vibrating in a thickness direction vibration generated in a convex portion of the piezoelectric actuator by expanding and contracting the piezoelectric body in a planar direction;
A piezoelectric transducer comprising: The reinforcing plate has a protruding portion protruding to the convex side near the curved vertex,
The piezoelectric transducer according to claim 1, wherein the piezoelectric element is mounted on a concave surface side of the reinforcing plate, and the vibration member is mounted on the protrusion. A curved piezoelectric actuator formed by bonding a piezoelectric element having electrodes formed on the front and back surfaces of a thin plate-shaped piezoelectric body and a curved reinforcing plate made of an elastic material,
Holding means for fixing both ends of the curved piezoelectric actuator,
A massive or rod-shaped projection member provided near the vertex on the convex side of the curved piezoelectric actuator,
A vibrating member attached to the projecting member, vibrating in a thickness direction generated in a convex portion of the piezoelectric actuator by expanding and contracting the piezoelectric body in a plane direction;
A piezoelectric transducer comprising: 4. The piezoelectric transducer according to claim 3, wherein the protrusion is made of an insulating material, the piezoelectric element is mounted on a convex surface of the reinforcing plate, and the protrusion is mounted on the piezoelectric element. 5. 4. The piezoelectric transducer according to claim 3, wherein the piezoelectric element is mounted on a concave side of the reinforcing plate, and the protruding member is mounted on the reinforcing plate near a vertex on a convex side of the reinforcing plate.

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