JP2007209073A - Ultrasonic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply pressing force without breaking a piezoelectric laminate to enhance driving force transmitted to a driven body. <P>SOLUTION: A ultrasonic transducer 1 includes: the piezoelectric laminate 4 formed by laminating multiple piezoelectric ceramic sheets 2 having an internal electrode 3 on their surface; a pressing-side protection plate 8 that covers the side faces of the piezoelectric laminate 4 in the direction of pressing against a driven body X and is formed of a material higher in ductility than the piezoelectric laminate 4; a pressing member 7 that applies pressing force to the substantial center of the piezoelectric laminate 4 in the direction of the length through the pressing-side protection plate 8; and a frictional contactor 5 that is disposed on the side directly opposite the pressing member 7 and is brought into contact with the driven body X. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic transducer.

In recent years, an ultrasonic motor including an ultrasonic vibrator has attracted attention as a new motor that replaces an electromagnetic motor.
Conventional ultrasonic transducers include structures disclosed in Patent Document 1 and Patent Document 2.

  The ultrasonic transducer disclosed in Patent Document 1 includes a friction contact that is brought into close contact with a driven body on one side surface of a piezoelectric laminate formed by laminating a plurality of piezoelectric ceramic sheets having internal electrodes on the surface. And a pin projecting from substantially the center of two side surfaces adjacent to the side surface on which the friction contact is provided. The friction contact is pressed against the surface of the driven body by the pressing force applied via the pin, and the driven body can be driven by the frictional force corresponding to the pressing force.

On the other hand, the ultrasonic transducer disclosed in Patent Document 2 is of a type in which a friction contact is brought into close contact with a driven body by applying a pressing force directly or via a pressing member to a side surface of a piezoelectric element. Since the magnitude of the pressing force is proportional to the magnitude of the driving force transmitted from the friction contact to the driven body, securing it as much as possible directly leads to an improvement in the performance of the ultrasonic transducer.
JP 7-163162 A JP 2004-96984 A

  However, in the ultrasonic vibrator of Patent Document 1, since the pin for applying the pressing force protrudes directly from the side surface of the piezoelectric laminate, it is considered that a large stress is concentrated on the piezoelectric laminate disposed at the base of the pin. It is done. Also, in the ultrasonic vibrator of Patent Document 2, a local pressing force is applied directly or indirectly to the side surface of the piezoelectric laminate through a pressing member. It is conceivable that a large stress concentrates on the piezoelectric laminate at the corner portion of the pressing member that comes into contact, and the piezoelectric laminate breaks from the stress concentration position when a large pressing force is applied.

  The present invention has been made in view of the above-described circumstances, and it is possible to apply a large pressing force without breaking the piezoelectric laminated body, and to improve the driving force transmitted to the driven body. The object is to provide a vibrator.

In order to achieve the above object, the present invention provides the following means.
The present invention covers a piezoelectric laminate formed by laminating a plurality of piezoelectric ceramic sheets having internal electrodes on the surface, and a side surface in the pressing direction of the piezoelectric laminate to a driven body, A pressing side protection plate made of a highly ductile material, a pressing member that applies a pressing force to a substantially central position in the length direction of the piezoelectric laminate through the pressing side protection plate, and a side opposite to the pressing member. Provided is an ultrasonic transducer comprising a friction contact disposed and brought into contact with a driven body.

  According to the present invention, by supplying two layers of alternating voltages having a predetermined phase difference and a predetermined driving frequency to the internal electrode, two different vibration modes are simultaneously generated in the piezoelectric laminate, and the friction contactor is substantially Elliptical vibration can be generated to drive the driven body that contacts the friction contact. In this case, the contact between the friction contact and the driven body is increased by the pressing force supplied to the approximate center position in the length direction of the piezoelectric laminate through the pressing member, and the magnitude of the contact pressure is increased. Generates a dependent friction force. Therefore, the driving force of the driven body via the friction contact can be increased as the pressing force is increased.

  In the present embodiment, the pressure-side protective plate made of a material having higher ductility than the piezoelectric laminated body made of the piezoelectric ceramic sheet is disposed between the pressing member and the piezoelectric laminated body. The generated stress concentration is dispersed, and the piezoelectric laminate can be prevented from breaking due to the stress concentration. Therefore, a larger pressing force can be applied to the piezoelectric laminate, and a large driving force can be obtained.

In the said invention, the said press side protection plate is good also as being comprised with the metal or resin.
By doing in this way, the ultrasonic transducer | vibrator which can obtain big driving force can be comprised simply.

Moreover, in the said invention, it is preferable that the said press side protection plate and the said press member are comprised integrally.
By doing in this way, a number of parts can be reduced and cost reduction can be aimed at.

In the above invention, a contact-side protection plate that covers a side surface of the piezoelectric laminate on which the friction contact is provided is provided, and the friction contact is connected to the piezoelectric via the contact-side protection plate. It is good also as being fixed to the side of a layered product.
By doing so, the stress concentration generated in the piezoelectric laminate in the vicinity of the attaching portion of the friction contact is dispersed by the contact-side protection plate, and it is possible to prevent the piezoelectric laminate from being broken in this portion as well. . Therefore, it becomes possible to apply a larger pressing force to the piezoelectric laminate and obtain a large driving force.

Moreover, in the said invention, the said contactor side protection plate is good also as being comprised with the metal or resin.
Moreover, in the said invention, it is good also as the said friction contact and the said contact side protection plate being comprised integrally.
By doing in this way, a number of parts can be reduced and cost reduction can be aimed at.

Moreover, in the said invention, it is good also as providing the connection member which connects the said press side protection plate and the said contactor side protection plate.
By doing so, it is possible to prevent the pressing-side protection plate and the contact-side protection plate covering the two side surfaces of the piezoelectric laminate that vibrate in two different vibration modes from being peeled off from the piezoelectric laminate. be able to. Moreover, if the piezoelectric side protection plate and the contactor side protection plate connected by the connection member are integrally formed on the two side surfaces of the piezoelectric laminate, for example, by resin, the manufacturing cost can be reduced and the number of parts can be reduced. Reduction can be achieved.

Moreover, in the said invention, the said connection member is good also as urging | biasing the said press side protection plate and the contactor side protection plate in the direction pressed against the side surface of the said piezoelectric laminated body.
By doing so, it is possible to keep the pressing-side protection plate and the contact-side protection plate in close contact with the two side surfaces of the piezoelectric laminate that vibrates in two different vibration modes, and to peel off from the piezoelectric laminate. Can be prevented.

Moreover, in the said invention, the said press side protection plate and the said contactor side protection plate are good also as arrange | positioning at the both end side surface of the lamination direction of the piezoelectric ceramic sheet in the said piezoelectric laminated body.
By doing in this way, it becomes possible to suppress peeling between the laminated piezoelectric ceramic sheets by the urging force by the connecting member.

  According to the present invention, it is possible to apply a large pressing force without breaking the piezoelectric laminated body, and it is possible to improve the driving force transmitted to the driven body.

Hereinafter, the ultrasonic transducer | vibrator which concerns on the 1st Embodiment of this invention is demonstrated below with reference to FIGS.
As shown in FIG. 1, the ultrasonic transducer 1 according to the present embodiment includes a plurality of rectangular plate-like piezoelectric ceramic sheets 2 provided with a sheet-like internal electrode 3 (see FIG. 3) on one side surface. A stacked rectangular parallelepiped piezoelectric laminate 4, two friction contacts 5 adhered to one side surface of the piezoelectric laminate 4 and brought into close contact with the driven body X, and the friction contacts 5 are provided. And a pressing member 7 for projecting the pin 6 from the side surface adjacent to the side surface.

  The piezoelectric laminate 4 has protective plates (press-side protective plate, contact-side protective plate) 8 and 9 covering the side surface to which the friction contact 5 is bonded and the opposite side surface thereof. It is glued. The protection plates 8 and 9 are made of a material having higher ductility than the piezoelectric ceramic sheet 2 such as resin or metal. The thickness dimension of each protection plate 8 and 9 is about 1/10 of the thickness dimension L of the piezoelectric laminated body 4, for example.

As shown in FIG. 2, the piezoelectric laminate 4 has external dimensions of, for example, a length of 18 mm, a width of 4.4 mm, and a thickness of 2 mm.
The piezoelectric ceramic sheet 2 constituting the piezoelectric laminate 4 is, for example, a lead zirconate titanate-based piezoelectric ceramic element (hereinafter referred to as PZT) having a thickness of about 80 μm, as shown in FIG. As PZT, a hard material having a large Qm value was selected. The Qm value is about 1800.

  The internal electrode 3 is made of, for example, a silver palladium alloy having a thickness of about 4 μm. The piezoelectric ceramic sheet 2a disposed at one end in the stacking direction does not include an internal electrode. The other piezoelectric ceramic sheet 2 includes two types of internal electrodes 3 as shown in FIG.

  The piezoelectric ceramic sheet 2 shown in FIG. 3A includes an internal electrode 3 on almost the entire surface. Two internal electrodes 3 are arranged with an insulation distance of about 0.4 mm in the length direction of the piezoelectric ceramic sheet 2. Each internal electrode 3 is disposed with a gap of about 0.4 mm from the periphery of the piezoelectric ceramic sheet 2, and a part thereof extends to the periphery of the piezoelectric ceramic sheet 2.

  The piezoelectric ceramic sheet 2 shown in FIG. 3B is provided with an internal electrode 3 in substantially half of its width direction. Two internal electrodes 3 are arranged with an insulation distance of about 0.4 mm in the length direction of the piezoelectric ceramic sheet 2. Each internal electrode 3 is disposed with a gap of about 0.4 mm from the periphery of the piezoelectric ceramic sheet 2, and a part thereof extends to the periphery of the piezoelectric ceramic sheet 2.

  The piezoelectric ceramic sheet 2 provided with these internal electrodes 3 is formed by laminating a plurality of sheets each having a large internal electrode 3 shown in FIG. 3A and a small internal electrode 3 shown in FIG. As a result, a rectangular parallelepiped piezoelectric laminate 4 is formed.

  A total of four external electrodes 10 are provided on each end face in the length direction of the piezoelectric laminate 4, two each. All the internal electrodes 3 arranged at the same position of the same kind of piezoelectric ceramic sheet 2 are connected to each external electrode 10. Thereby, the internal electrodes 3 arranged at the same position of the same kind of piezoelectric ceramic sheet 2 are set to the same potential. The external electrode 10 is connected to a wiring (not shown). The wiring may be any wiring as long as it is flexible, such as a lead wire or a flexible substrate.

Next, the operation of the piezoelectric laminate 4 configured as described above will be described.
Two external electrodes 10 formed at one end in the longitudinal direction of the piezoelectric laminate 4 are A phase (A +, A−), and two external electrodes 10 formed at the other end are B phase (B +, B−). To do. When an alternating voltage having the same phase and corresponding to the resonance frequency is applied to the A phase and the B phase, the primary longitudinal vibration as shown in FIG. 4 is excited. Further, when an alternating voltage corresponding to the resonance frequency is applied to the A phase and the B phase in opposite phases, a secondary bending vibration as shown in FIG. 5 is excited. 4 and 5 are diagrams showing computer analysis results by the finite element method.

  The frictional contacts 5 are bonded to the piezoelectric laminate 4 via protective plates 9 at two positions that become antinodes of secondary bending vibration of the piezoelectric laminate 4. Thus, when primary longitudinal vibration occurs in the piezoelectric laminate 4, the friction contact 5 is displaced in the length direction of the piezoelectric laminate 4 (X direction shown in FIG. 1). On the other hand, when secondary bending vibration occurs in the piezoelectric laminate 4, the frictional contact 5 is displaced in the width direction of the piezoelectric laminate 4 (Z direction shown in FIG. 1).

  Therefore, by applying an alternating voltage corresponding to the resonance frequency whose phase is shifted by 90 ° to the A phase and the B phase of the ultrasonic vibrator 1, the primary longitudinal vibration and the secondary bending vibration are generated simultaneously. Thus, as indicated by an arrow C in FIG. 1, a substantially elliptical vibration that is clockwise or counterclockwise is generated at the position of the friction contact 5.

  The pressing member 7 includes a holding portion 11 having a substantially U-shaped cross section, and a pin 6 integral with the holding portion 11 protruding perpendicularly from both side surfaces of the holding portion 11. The holding unit 11 is bonded to the piezoelectric laminate 4 with, for example, a silicone resin or an epoxy resin so as to surround the piezoelectric laminate 4 from the side surface side of the piezoelectric laminate 4 covered with the protective plate 8. In a state where the holding unit 11 is bonded to the piezoelectric laminate 4, the two pins 6 integrally provided on both side surfaces of the holding unit 11 serve as a common node for the longitudinal vibration and the bending vibration of the piezoelectric laminate 4. It is arranged coaxially at the position. By holding the pin 6 in the positioning state, the ultrasonic vibrator 1 can be held in the positioning state without affecting the vibration of the piezoelectric laminate 4.

The operation of the ultrasonic transducer 1 according to this embodiment configured as described above will be described below. To drive the driven body X by operating the ultrasonic transducer 1 according to the present embodiment, as shown in FIG. 1, the pressing force F is applied to the pressing member 7 so that the friction contact 5 is driven. High-frequency voltages (A phase and B phase) that are 90 ° different in phase are supplied through a wire that is in close contact with X and connected to the external electrode 10.
As a result, a substantially elliptical vibration in which the longitudinal vibration mode and the bending vibration mode are mixed is generated in the frictional contact 5 bonded to the ultrasonic vibrator 1 and driven along the tangential direction of the substantially elliptical vibration mode. The driven body X is propelled by the frictional force generated between the body X and the body X.

  In this case, according to the ultrasonic transducer 1 according to this embodiment, the protective plate 8 that covers the side surface of the piezoelectric laminate 4 is disposed between the pressing member 7 that applies the pressing force F and the piezoelectric laminate 4. Since the protective plate 8 is made of a material having higher ductility than the piezoelectric ceramic sheet 2 constituting the piezoelectric laminate 4, the piezoelectric plate near the corner of the pressing member 7 is applied by the pressing force F. Stress concentration generated in the laminate 4 is dispersed by the protective plate 8.

  Therefore, even if a relatively large pressing force F is applied, the piezoelectric laminate 4 can be protected without breaking. Then, by applying a large pressing force F, there is an advantage that a large driving force can be obtained by increasing the frictional force generated between the friction contact 5 and the driven body X.

  On the other hand, according to the ultrasonic vibrator 1 according to the present embodiment, the protective plate 9 that covers the surface of the piezoelectric laminate 4 is also disposed between the friction contact 5 and the piezoelectric laminate 4. The stress concentration generated in the piezoelectric laminate 4 in the vicinity of the corners of the friction contact 5 by the pressure F is also dispersed by the protective plate 9. Therefore, also in this part, it is possible to protect the piezoelectric laminate 4 without breaking it.

  As described above, according to the ultrasonic vibrator 1 according to the present embodiment, it is possible to apply a large pressing force F without breaking the piezoelectric laminated body 4, and between the friction contact 5 and the driven body X. A larger frictional force can be generated in the first, and a larger driving force can be obtained.

  In the present embodiment, an example in which the pressing member 7 and the protection plate 8 are provided separately has been shown, but instead, the pressing member 7 and the protection plate 8 are integrated as shown in FIG. Alternatively, it may be configured as a single pressing member 7 '. By doing in this way, there exists an advantage that reduction of a number of parts and reduction of an assembly man-hour can be aimed at, and cost can be reduced.

  Moreover, although the example which provided the friction contact 5 and the protection plate 9 separately was shown, it replaces with this and you may comprise the friction contact 5 and the protection plate 9 integrally as a single component. Similarly, there is an advantage that the cost can be reduced by reducing the number of parts and the number of assembly steps.

  Moreover, although the example which provided separately the protective plates 8 and 9 which coat | cover two side surfaces of the piezoelectric laminated body 4 was shown, it replaces with this and as shown in FIG. It is good also as providing the connection member 12 connected to. In the drawing, the external electrode 10 is not shown.

  By doing in this way, since it maintains so that the space | interval of the protective plates 8 and 9 may not change with the connection member 12, it can hold | maintain so that the protective plates 8 and 9 may not peel from the surface of the piezoelectric laminated body 4. FIG. . In particular, if the protective plates 8 and 9 and the connecting member 12 are integrally formed on the outer surface of the piezoelectric laminate 4 by outsert resin molding or the like, it is easy to manufacture and the product cost can be reduced.

  In the present embodiment, the ultrasonic vibrator 1 in which the friction contact 5 is bonded to the side surface in the width direction of the piezoelectric ceramic sheet 2 constituting the piezoelectric laminate 4 is described as an example. In the ultrasonic vibrator 1 in which the friction contact 5 is bonded to one side surface of the piezoelectric ceramic sheet 2 in the stacking direction, the side surface to which the friction contact member 5 is bonded and the opposite side surface thereof are protected by protective plates 8 and 9. It is good also as providing, and providing the connection member 12 which connects both the protection plates 8 and 9. By doing so, the connecting member 12 can prevent not only the protective plates 8 and 9 from being peeled off from the piezoelectric laminate 4 but also the peeling between the piezoelectric ceramic sheets 2 constituting the piezoelectric laminate 4. It becomes.

  Further, as the connecting member 12, in addition to those integrally provided with the protective plates 8 and 9 as shown in FIGS. 7 and 8, as shown in FIGS. 9 and 10, the protective plates 8 and 9 and Alternatively, a connecting member 12 'constituted by another member may be adopted. In this case, it is preferable to apply an urging force that presses the protective plates 8 and 9 against the surface of the piezoelectric laminate 4 by the elasticity of the connecting member 12 ′. FIG. 9 shows the ultrasonic transducer 1 of FIG. 1 provided with a connecting member 12 ′, and FIG. 10 shows the ultrasonic transducer 1 of FIG. 6 provided with a connecting member 12 ′. Is omitted. Although not shown, a connecting member 12 'may be attached to the ultrasonic transducer 1 shown in FIG.

  Further, in the present embodiment, a U-shaped member arranged so as to cover the piezoelectric laminate 4 from one side surface direction is adopted as the holding portion 11 that holds the pin 6. 11, the first block 13 that is fixed to the piezoelectric laminate 4 via the protective plate 8 and the second block 14 that is opposed to the first block 13 with a gap therebetween. It is good also as comprising holding | maintenance part 11 'and pinching the pin 6 in V-shaped groove 13a, 14a formed in these blocks 13,14. The pressing force F is transmitted to the piezoelectric laminate 4 through the blocks 13 and 14 and the pin 6 and holds the pin 6 in a sandwiched state.

1 is a perspective view showing an ultrasonic transducer according to a first embodiment of the present invention. It is a perspective view which shows the piezoelectric laminated body which comprises the ultrasonic transducer | vibrator of FIG. It is a perspective view which shows the piezoelectric ceramic sheet which comprises the piezoelectric laminated body of FIG. It is a figure which shows a mode that the piezoelectric laminated body of FIG. 1 vibrates in the primary longitudinal vibration mode by computer analysis. It is a figure which shows a mode that the piezoelectric laminated body of FIG. 1 vibrates in a secondary bending vibration mode by computer analysis. FIG. 6 is a perspective view showing a first modification of the ultrasonic transducer of FIG. 1. FIG. 10 is a perspective view showing a second modification of the ultrasonic transducer in FIG. 1. FIG. 10 is a perspective view showing a third modification of the ultrasonic transducer in FIG. 1. FIG. 10 is a perspective view showing a fourth modification of the ultrasonic transducer in FIG. 1. FIG. 10 is a perspective view showing a fifth modification of the ultrasonic transducer in FIG. 1. It is a perspective view which shows the 6th modification of the ultrasonic transducer | vibrator of FIG.

Explanation of symbols

X Driven body 1 Ultrasonic vibrator 2 Piezoelectric ceramic sheet 3 Internal electrode 4 Piezoelectric laminate 5 Friction contact 7, 7 'Pressing member
8 Protection plate (Pressure side protection plate)
9 Protection plate (Contact side protection plate)
12, 12 'connecting member

Claims (9)

A piezoelectric laminate formed by laminating a plurality of piezoelectric ceramic sheets having internal electrodes on the surface;
A pressure-side protective plate made of a material having a higher ductility than the piezoelectric laminate, covering the side surface in the pressing direction of the piezoelectric laminate to the driven body;
A pressing member that applies a pressing force to a substantially central position in the length direction of the piezoelectric laminate through the pressing side protection plate;
An ultrasonic transducer comprising a friction contact disposed on a side opposite to the pressing member and brought into contact with a driven body.   The ultrasonic transducer according to claim 1, wherein the pressing side protection plate is made of metal or resin.   The ultrasonic transducer according to claim 1, wherein the pressing side protection plate and the pressing member are integrally configured. A contact-side protection plate that covers a side surface of the piezoelectric laminate on which the friction contact is provided;
The ultrasonic vibrator according to claim 1, wherein the friction contact is fixed to a side surface of the piezoelectric laminate through the contact-side protection plate.   The ultrasonic transducer according to claim 4, wherein the contact-side protection plate is made of metal or resin.   The ultrasonic transducer according to claim 4, wherein the friction contact and the contact-side protection plate are integrally formed.   The ultrasonic transducer according to claim 4, further comprising a connecting member that connects the pressing side protection plate and the contactor side protection plate.   The ultrasonic transducer according to claim 7, wherein the connecting member biases the pressing-side protection plate and the contactor-side protection plate in a direction to press the side surface of the piezoelectric laminate.   The ultrasonic transducer according to claim 8, wherein the pressing-side protection plate and the contactor-side protection plate are arranged on both side surfaces in the stacking direction of the piezoelectric ceramic sheets in the piezoelectric laminate.

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