JP2005217253A - Piezoelectric device and electronic apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable piezoelectric device in which a piezoelectric device using a laminated piezoelectric element formed by laminating a plurality of piezoelectric elements has a high bonding strength between layers of the laminated piezoelectric elements and is less likely to be cracked or cracked. And to realize electronic equipment.
In a piezoelectric device using a laminated piezoelectric element formed by laminating a plurality of piezoelectric elements having electrodes, the laminated piezoelectric element has a hole, a reinforcing electrode located in the hole of the electrodes, a reinforcing electrode, A structure having an insulating portion for insulating other electrodes is used. In particular, a shaft portion connected to the hole portion is provided and the shaft portion is supported. The hole is provided at the vibration node of the laminated piezoelectric element.
[Selection] Figure 2

Description

  The present invention relates to piezoelectric devices such as actuators, sensors, transformers and the like using laminated piezoelectric elements, and electronic devices using the same, and more particularly to electrode structures and supporting structures of laminated piezoelectric elements.

Piezoelectric devices such as actuators, sensors, and transformers that utilize the piezoelectric effect of piezoelectric elements are applied in various fields. Recently, multilayer piezoelectric elements have been used as piezoelectric elements, and low voltage drive, small size, high output, high sensitivity, and high transformation ratio have been achieved.
In these piezoelectric devices, the support of the piezoelectric element is an important design factor. For example, in an ultrasonic motor that is a representative of an actuator, a hole is provided in a vibration node of a laminated piezoelectric element, and a shaft part is joined to the hole. The shaft portion is supported (see Patent Document 1). In order to extract a large output from the ultrasonic motor, it is necessary to generate a large frictional force with the moving body, and since a large pressing force is applied to the shaft portion, a highly rigid metal is generally used for the shaft portion. In this case, it is necessary to ensure insulation between the internal electrode and the shaft portion without providing an internal electrode around the hole of the multilayer piezoelectric element so that the electrode inside the multilayer piezoelectric device does not short-circuit through the shaft portion. Become.
JP 11-346486 A

  However, in the structure of the conventional piezoelectric device, the bonding strength of the part without electrodes on the bonding surface between the laminated piezoelectric elements is low, the finishing accuracy of the hole part is poor during drilling, and cracks and cracks may occur in some cases. there were. This portion is likely to change in shape and dimensions during the manufacturing process of the laminated piezoelectric element, and there is a fear that the coupling with the support member such as the shaft portion joined to the hole portion may not be successful.

  Further, the hole is often provided at a vibration node, but a large stress is often generated at the node, and there is a risk that a crack may enter from the hole and break when used.

  Therefore, in order to solve the above problems, in the piezoelectric device of the present invention, in the piezoelectric device using the laminated piezoelectric element formed by laminating a plurality of piezoelectric elements having electrodes, the laminated piezoelectric element includes a hole and an electrode. A structure having a reinforcing electrode located in the hole and an insulating part that insulates the reinforcing electrode from the other electrodes.

  In particular, the shaft portion connected to the hole portion is provided to support the shaft portion. Further, the hole is provided in the vibration node of the laminated piezoelectric element.

  According to the present invention, even if a hole is provided in the laminated piezoelectric element, the bonding strength between the layers of the laminated piezoelectric element can be increased, so that cracks and cracks are unlikely to occur and the finished surface is clean with good processing accuracy. In addition, a highly reliable piezoelectric device without using cracks through the hole even during use, and thus an electronic device equipped with the piezoelectric device can be realized. In other words, the laminated piezoelectric element can be driven with a large output. For example, when an actuator is configured, a very large output can be obtained.

(Embodiment 1)
Embodiments of the present invention will be described with reference to the drawings. Here, a linear ultrasonic motor using the laminated piezoelectric element 1 of the present invention is shown.
FIG. 1 shows a cross-sectional electrode configuration of a laminated piezoelectric element 1 of the present invention. Here, the cross section is a surface obtained by cutting the laminated piezoelectric element 1 shown in FIG. 5 which is a configuration example of an ultrasonic motor using the laminated piezoelectric element of the present invention, along the aa ′ plane indicated by a dotted line in the drawing. . FIG. 2 shows a configuration of an electrode that becomes an internal electrode, and FIG. 3 shows an external electrode. The laminated piezoelectric element 1 is configured by laminating piezoelectric elements 1a, 1b, 1c, and 1d. The piezoelectric element 1a has no electrode, but the piezoelectric element 1b has electrodes 10a, 10b, 10c, 10d, and 10e, the piezoelectric element 1c has electrodes 10f and 10g, and the piezoelectric element 1d has electrodes 10h and 10i on one surface. In FIG. 1, a dotted line indicates an internal electrode, and a solid line indicates an electrode portion drawn from the internal electrode of the laminated piezoelectric element 1 to the side surface.

  The laminated piezoelectric element 1 has a rectangular piezoelectric element 1c having an electrode 10f on the substantially front surface and piezoelectric elements 1b having substantially four divided electrodes 10a, 10b, 10c, and 10d. Rectangular piezoelectric elements 1d having electrodes 10h on the front surface are alternately stacked, and piezoelectric elements 1a having no electrodes are stacked thereon, and then sintered to form one piezoelectric element. External electrodes 11a, 11b, 11c, 11d, 11e, and 11f are provided on the side surfaces of the laminated piezoelectric element 1, and 10a, 10h, 10c, 10b, 10f, and 10d lead electrode portions 10a ′, 10h ′, 10c ′, 10b ′, 10f ′, 10d ′ are short-circuited. Then, the external electrodes 10e are set to GND, the high voltages in the positive direction are applied to the external electrodes 11a, 11f, and 11b, and the high voltages in the negative direction are applied to the external electrodes 11c and 11d. 1d is polarized in the thickness direction. The polarization directions between the electrode 10f and the electrodes 10a and 10d and between the electrode 10f and the electrodes 10c and 10b are reversed.

  By the way, a hole having a diameter smaller than that of the electrodes 10e, 10g, and 10i is provided in the central portion of the laminated piezoelectric element, that is, the electrodes 10e, 10g, and 10i in FIG. 10g and 10i appear as a cross section. As a result, even when a hole is provided in the laminated piezoelectric element with a drill, laser, or the like, the bonding strength between the layers of the piezoelectric elements laminated in the electrodes 10e, 10g, and 10i serving as the reinforcing electrodes can be increased. It is hard to occur and the finished surface is clean with good machining accuracy. In addition, a highly reliable laminated piezoelectric element can be realized without cracking through the hole even during use. In particular, in the case of the present embodiment, since the hole is made in the vibration node where the vibration stress is concentrated, the effect is great. Further, it is less susceptible to the deterioration of shape accuracy due to shrinkage that occurs during the manufacturing process (sintering) of the laminated piezoelectric element 1 and the effects of warpage and undulation. Further, in the present embodiment, the case where a hole is formed in an electrode provided in advance is shown, but an electrode may be provided later in a hole provided in advance. In this embodiment, by providing the insulating portions 9a and 9b having no electrodes around the electrodes 10g and 10i, there is no short-circuit through the electrodes 10f and 10h and the member passed through the hole.

  When an alternating voltage having a predetermined frequency is applied between the external electrode 11e and the external electrode 11b, the laminated piezoelectric element 1 causes longitudinal vibration, and an alternating voltage having a predetermined frequency is applied between the external electrode 11e and the external electrodes 11a, 11c, 11d, and 11f. Is applied, the laminated piezoelectric element 1 generates bending vibration. FIG. 4 shows the amplitude distribution of vibration generated in the laminated piezoelectric element 1 at this time. A longitudinal displacement Ul with respect to the longitudinal direction of the laminated piezoelectric element 1 indicated by a coordinate x in FIG. 5 is shown in FIG. 4A, and a width (coordinate y) direction displacement Uw is shown in FIG. 4B. Here, the length in the longitudinal direction of the laminated piezoelectric element is represented by l, and the center in the longitudinal direction is represented by coordinate 0.

FIG. 5 shows a configuration example of a linear ultrasonic motor using the laminated piezoelectric element 1 of the present invention as a vibrating body. The rectangular laminated piezoelectric element 1 is provided with protrusions 2 a and 2 b and a shaft portion 3. The shaft portion 3 is provided with a hole portion 1h having a diameter smaller than those of the electrodes 10e, 10g, and 10i at the center portion serving as a node of longitudinal vibration and bending vibration excited by the laminated piezoelectric element 1, and the shaft portion 3 is joined. The protrusion 2 is provided at the antinode of bending vibration. The shaft 4a of the pressing member 4 has a step portion (not shown) and is guided by the guide hole 5a of the guide plate 5 so as to be movable only in the axial direction. A moving body 7 guided by the guide members 8a and 8b is provided under the protrusion 2, and the pressure member 4 engaged with the shaft portion 3 and the groove portion 4b is pressed by the pressurizing means 6 so that the shaft portion 3 is pressed. The protrusions 2 and the moving body 7 are in contact with each other while supporting the laminated piezoelectric element 1.
By simultaneously exciting the longitudinal vibration and the bending vibration, the protrusion 2 performs an elliptical motion consisting of a displacement in the longitudinal direction of the laminated vibrator 1 and a displacement in the width direction orthogonal thereto, and drives the moving body 7. By the way, the two vibration modes are not limited in their orders, and other modes may be used. Further, the moving body 7 may be fixed and the vibrating body itself may be driven.

  An example of a driving method of the multilayer piezoelectric element 1 is shown in FIG. A signal having a predetermined frequency generated by the oscillation circuit 12 is divided into a signal that does not pass through the transfer circuit 13 and a signal that does not pass through the transfer circuit 13, and is amplified to a predetermined output through the amplifier circuits 14a and 14b, and then applied to the laminated piezoelectric element 1. . That is, the external electrode 11e is set to GND, and a drive signal having a different phase, for example, a signal having a difference of 90 degrees or −90 degrees is applied between the external electrodes 11a, 11c, 11d, and 11f and the external electrode 11b to vertically Vibration and flexural vibration are excited. By reversing the phase by the transfer circuit 13, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 also changes.

By the way, in this embodiment, a laminated piezoelectric element applicable to an ultrasonic motor is shown as an example as a piezoelectric device. However, the piezoelectric device is not limited to an ultrasonic motor, and can be used for other piezoelectric devices such as transducers such as sensors and transformers. It may be a multilayer piezoelectric element. That is, any multilayer piezoelectric element having a hole or a recess can be applied to all cases.
(Embodiment 2)
The example which comprised the electronic device using the ultrasonic motor of this invention is demonstrated based on FIG. FIG. 7 is a block diagram in which the ultrasonic motor 100 driven by the drive circuit of the present invention is applied to a drive source of an electronic device. The laminated piezoelectric element 1 and the friction member 2 joined to the laminated piezoelectric element 1 are shown. The movable body 7 is frictionally driven by the transmission mechanism 32, the transmission mechanism 32 that operates integrally with the movable body 7, and the output mechanism 33 that operates based on the operation of the transmission mechanism 32. Here, an example in which the moving body 7 is a rotating body and the moving body 7 is rotated will be described.

  Here, the transmission mechanism 32 uses a transmission wheel such as a gear train and a friction wheel, for example. The output mechanism 33 serving as an operating unit includes a paper feed mechanism in a printer, a shutter drive mechanism, a lens drive mechanism, a film winding mechanism in a camera, a pointer in an electronic device and a measuring instrument, and an arm in a robot. In the mechanism and machine tool, a tooth feeding mechanism, a processing member feeding mechanism, and the like are used.

  Note that an electronic timepiece, a measuring instrument, a camera, a printer, a printing machine, a robot, a machine tool, a game machine, an optical information device, a medical device, a moving device, and the like can be realized as the electronic device in this embodiment. Furthermore, if the moving body 7 is provided with an output shaft and has a power transmission mechanism for transmitting torque from the output shaft, an ultrasonic motor driving device can be realized.

  By using the laminated piezoelectric element of the present invention, it can be applied to various piezoelectric devices such as ultrasonic motors, actuators, sensors, transformers and the like, and these piezoelectric devices can be applied as driving sources, sensors, and power sources for various electronic devices. is there.

It is a figure which shows the cross section of the multilayer piezoelectric element of this invention. It is a figure which shows the structure of the laminated piezoelectric element of this invention. It is a figure which shows the structure of the external electrode of the multilayer piezoelectric element of this invention. It is a figure which shows the vibration mode of the multilayer piezoelectric element of this invention. It is a figure which shows the structural example of the ultrasonic motor using the laminated piezoelectric element of this invention. It is a figure which shows the drive method of the ultrasonic motor using the laminated piezoelectric element of this invention. It is a block diagram of the electronic device which applied the ultrasonic motor using the multilayer piezoelectric element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric element 2 Friction member 3 Shaft part 4 Pressurizing member 6 Pressurizing means 7 Moving body 9a, 9b Insulating part 10a, 10b, 10c, 10d, 10e, 10f, 10g Electrode 11a, 11b, 11c, 11d, 11e, 11f External electrode

Claims (5)

In a piezoelectric device including a laminated piezoelectric element formed by laminating a plurality of piezoelectric elements having electrodes,
The laminated piezoelectric element includes a hole, a reinforcing electrode that is at least a part of the electrode and located in the hole, and an insulating part that insulates the reinforcing electrode from other electrodes. . In the piezoelectric device according to claim 1,
2. The piezoelectric device according to claim 1, further comprising a shaft portion connected to the hole portion.   2. The piezoelectric device according to claim 1, wherein the hole is provided at a vibration node of the laminated piezoelectric element.   2. The piezoelectric device according to claim 1, wherein the piezoelectric device is an ultrasonic motor that drives a moving body in contact with the laminated piezoelectric element by vibration of the laminated piezoelectric element.   5. An electronic apparatus comprising an operating unit driven by the ultrasonic motor according to claim 4.

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