JP2004304963A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which has sufficient durability and allows reduction in size and thickness. <P>SOLUTION: A plurality of drive units 21 are provided in positions corresponding to a plurality of antinodes in bending vibration. Therefore, in one piezoelectric actuator 1, driving force can be applied to a driven body by a plurality of the drive units 21, and the durability can be enhanced as compared with cases where only one drive unit 21 is provided. Unlike conventional cases, where as many piezoelectric actuators 1 as drive units 21 are required, one piezoelectric actuator 1 is provided with a plurality of the drive units 21. Therefore, the number of piezoelectric actuators required can be reduced, and reduction in size and thickness can be facilitated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric actuator using a piezoelectric effect of a piezoelectric element.
[0002]
[Background Art]
A piezoelectric actuator using the piezoelectric effect of a piezoelectric element has excellent energy conversion efficiency and responsiveness from electrical energy to mechanical energy, and can easily obtain a low-speed, high-torque driving force. Therefore, piezoelectric actuators have attracted much attention in recent years as motive power in place of a DC motor unit having a speed reduction mechanism.
[0003]
As a conventional piezoelectric actuator, there is one in which a vibrating body is fixed on the upper surface of a disk-shaped piezoelectric element, and a rotor is driven by the vibration of the vibrating body (for example, Patent Document 1). Also, a piezoelectric actuator that divides the surface electrode of a thin piezoelectric element into five parts and applies a two-system voltage to vibrate the piezoelectric element to apply a driving force to a driven body (for example, Patent Document 2), There is a piezoelectric actuator that drives the same driven body with the piezoelectric element (for example, Patent Document 3). In any case, the piezoelectric actuator obtains a driving force by utilizing the piezoelectric effect of the piezoelectric element.
[0004]
[Patent Document 1]
JP 2000-308376 A
[Patent Document 2]
Japanese Patent No. 2722211
[Patent Document 3]
Japanese Patent No. 2980541
[0005]
[Problems to be solved by the invention]
A major difference between the piezoelectric actuator and the DC motor unit is that the piezoelectric actuator can achieve a high deceleration high torque without using a speed reduction mechanism, and the size and thickness can be reduced by the amount that the speed reduction mechanism is unnecessary.
However, Patent Literature 1 has a problem in that a space for disposing a disk-shaped piezoelectric actuator is required, and thus it is not possible to sufficiently cope with miniaturization. Further, if a pressure mechanism for biasing the piezoelectric actuator is incorporated in the driven body, the thickness increases accordingly, and it is difficult to reduce the thickness.
In Patent Literature 2, since a driving portion that applies a driving force to a driven body is also made of a piezoelectric element, the piezoelectric element may be damaged, and there is a problem in durability.
In Patent Literature 3, since only one protrusion is provided for one piezoelectric actuator, the protrusion is burdened and may be damaged, resulting in a problem in durability.
[0006]
An object of the present invention is to provide a piezoelectric actuator having sufficient durability and capable of realizing size reduction and thickness reduction.
[0007]
[Means for Solving the Problems]
The piezoelectric actuator of the present invention includes a vibrating body having a rectangular thin plate-shaped piezoelectric element having a longitudinal direction, and a driving unit that is in contact with a driven body, and the vibrating body includes longitudinal vibration and bending vibration. A piezoelectric actuator that vibrates in an in-plane direction with a combined vibration of the piezoelectric actuator and the piezoelectric actuator, wherein a plurality of the driving units are provided and provided at positions corresponding to antinodes of the bending vibration.
However, the respective vibration modes of the longitudinal vibration and the bending vibration here are arbitrary, and may be of any order.
According to the present invention, since the plurality of driving units are provided at positions corresponding to each antinode of the bending vibration, the driving force is applied to the driven body by the plurality of driving units for one piezoelectric actuator. The durability is better than in the case of a single part. Furthermore, unlike the conventional case where the number of piezoelectric actuators is required by the number of driving units, one piezoelectric actuator has a plurality of driving units, so the number of necessary piezoelectric actuators is reduced, and the size and thickness are reduced. Is promoted.
[0008]
In the present invention, it is preferable that the longitudinal vibration is a primary mode, and the bending vibration is a secondary mode.
According to the present invention, since the longitudinal vibration is in the primary mode and the bending vibration is in the secondary mode, the vibration of the driving unit is maximized, and a large driving force can be obtained.
[0009]
In the present invention, it is preferable that the vibrator is provided with a pair of protrusions at diagonal positions in a rectangular shape.
According to the present invention, since the protrusion is provided at a rectangular diagonal position of the piezoelectric actuator of the vibrator, the portion where the protrusion exists when a voltage is applied to the piezoelectric element of the vibrator is provided. In this case, the vertical vibration is suppressed due to the weight of the protrusion, etc., while the vertical vibration is excited in the portion where the protrusion does not exist, and the vibration becomes unbalanced in the entire vibrating body, and the bending vibration occurs in the width direction. . Therefore, longitudinal vibration and bending vibration can be generated by installing the protrusion on the vibrator, and there is no need to provide a complicated electrode on the piezoelectric element.
[0010]
In the present invention, it is preferable that the vibration of the vibrating body is adjustable by changing the frequency of a voltage applied to the surface of the piezoelectric element.
According to the present invention, since the vibration direction of the vibrating body can be changed only by changing the frequency of the voltage applied to the surface of the piezoelectric element, the vibrating body can be changed without any complicated mechanical variable means. The magnitude and direction of the driving force applied to the driven body can be adjusted by changing the vibration, and the rotation state of the driven body can be changed with a simple structure.
[0011]
In the present invention, it is preferable that a driving electrode is formed on a surface of the piezoelectric element along a substantially diagonal direction of a rectangular shape.
According to the present invention, by applying a voltage to the drive electrode formed in the substantially diagonal direction of the rectangular shape on the surface of the piezoelectric element, the piezoelectric element corresponding to the electrode formed in the substantially diagonal direction of the rectangular shape is applied. Since only the element portion vibrates and the piezoelectric element to which no voltage is applied does not perform a vibrating motion, the vibrating body as a whole generates a composite vibration of a longitudinal vibration and a bending vibration. At this time, the driving unit performs substantially elliptical vibration due to the composite vibration, and applies a driving force to the driven body in a part of the substantially elliptical motion.
Further, by applying a voltage in a direction symmetrical with respect to the center line between the substantially diagonal direction and the longitudinal direction of the vibrating body, the direction of the elliptical motion changes, so that the driving electrode to which the voltage is applied is changed. This makes it possible to change the driving direction given to the driven body.
[0012]
In the present invention, a plurality of electrodes are formed on the surface of the piezoelectric element, some of these electrodes are driving electrodes, and at least some of the remaining electrodes are displacement detection electrodes. preferable.
According to the present invention, since a part of the plurality of electrodes on the surface of the piezoelectric element serves as a displacement detection electrode, the magnitude of vibration of the vibrating body is detected by the displacement detection electrode, and this detection is performed. The voltage applied to the driving electrode can be adjusted by feedback control based on the magnitude of the vibration.
[0013]
In the present invention, assuming that the long side of the piezoelectric element is 1, the short side is formed to be 0.274 or more, and a protrusion is provided on the short side of the piezoelectric element, and the vertical side expands and contracts in the longitudinal direction of the piezoelectric element. The vibration ratio between the vibration and the bending vibration that bends in a direction orthogonal to the longitudinal vibration in a point symmetry with respect to the plane center of the piezoelectric element is a ratio of the resonance frequency of the bending vibration to the resonance frequency of the longitudinal vibration. , 1.00 and 1.03 or less.
According to the present invention, since the resonance frequencies of the longitudinal vibration and the bending vibration are close to each other, when the piezoelectric element is vibrated near these resonance frequencies, the longitudinal vibration and the bending vibration simultaneously appear, and the protrusion of the piezoelectric actuator and The drive unit vibrates in an elliptical orbit. With this elliptical trajectory, the driving unit can press and drive the driven body. At this time, since the piezoelectric element is excited near the respective resonance points of the longitudinal vibration and the bending vibration, the respective vibration amplitudes become large. Therefore, the amplitude of the elliptical trajectory of the driving section also increases, and the driven body can be driven with high efficiency.
[0014]
Here, when the short side of the piezoelectric actuator provided with the protrusion is smaller than 0.274, the resonance frequency of the longitudinal vibration becomes higher than the resonance frequency of the bending vibration, and a good elliptical orbit cannot be drawn. . At this time, the ratio of the resonance frequency of the bending vibration to the resonance frequency of the longitudinal vibration is 1.00 or less. When the ratio of the resonance frequency of the bending vibration to the resonance frequency of the longitudinal vibration is 1.03 or more, the resonance point of the longitudinal vibration is separated from the resonance point of the bending vibration, and the amplitudes of both vibrations are simultaneously improved. I can't.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of an apparatus having a piezoelectric actuator according to the first embodiment, FIG. 2 is an overall perspective view of the piezoelectric actuator, and FIG. 3 is a plan view of the piezoelectric actuator.
1 and 2, a piezoelectric actuator 1 includes a vibrating body 10 including a thin reinforcing plate 2 and a piezoelectric element 3 bonded to both surfaces of the reinforcing plate 2, and a support portion 23 that supports the vibrating body 10. It has.
[0016]
The vibrating body 10 is a laminated body having a longitudinal direction, and is formed in a rectangular shape such that a long side: short side has an aspect ratio of 7: 1.98.
The reinforcing plate 2 provided on the central layer of the vibrating body 10 is made of a material having conductivity and a predetermined strength, for example, stainless steel. A pair of substantially semicircular protrusions 22 are formed at diagonal positions at both short side ends of the reinforcing plate 2. In addition, a plurality of (in this embodiment, a pair) drive units 21 having a substantially semicircular shape are provided on one long side in accordance with antinodes of bending secondary vibration described later, and the drive units 21 are rotatably installed. It is in contact with the rotor 4 as a driven body at two places. Further, the support portion 23 is provided integrally at the center of the long side of the reinforcing plate 2 that does not have the drive portion 21. A support hole 231 is formed in the support part 23, and the support part 23 is attached to the attachment member 5 with an attachment screw 52 inserted through the support hole 231. The attachment member 5 has a pressing spring 51 and urges the piezoelectric actuator 1 attached to the attachment member 5 via the support portion 23 in the direction of the rotor 4.
The material of the piezoelectric element 3 is not particularly limited. Lead zirconate titanate (PZT (registered trademark)), quartz, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, zinc niobate Various materials such as lead and lead scandium niobate can be used.
[0017]
Electrodes 31 are formed on the front and back surfaces of the piezoelectric element 3 by plating, deposition, sputtering, or the like with nickel, gold, or the like (only the front surface is denoted by a reference numeral). Wiring is connected to an electrode 31 on the surface of the piezoelectric element 3 from a driving circuit (not shown), and the reinforcing plate 2 is electrically grounded.
The piezoelectric element 3 is joined to the reinforcing plate 2 by an adhesive. In the adhesive layer, the opposing surfaces of the reinforcing plate 2 and the electrode on the back side of the piezoelectric element 3 have microscopic irregularities, and the protrusions come into random contact with each other, so that the electrode and the reinforcing plate 2 Is conducting.
[0018]
FIG. 3 shows the movement of the projection 22 when a voltage is applied between the electrode 31 of the piezoelectric element 3 of the piezoelectric actuator 1 and the reinforcing plate 2. When a voltage is applied between the electrode 31 and the reinforcing plate 2, the piezoelectric element 3 starts to expand and contract. However, since the piezoelectric element 3 is formed in a rectangular shape, the expansion and contraction movement in the longitudinal direction becomes larger. The longitudinal primary vibration in the longitudinal direction is excited.
At this time, since the pair of projections 22 are formed at diagonal positions of the rectangle, the expansion and contraction movement is suppressed at the corners having the projections 22. As a result, a portion where the normal expansion and contraction motion is performed asymmetrically with respect to the center line of the piezoelectric element 3 which is parallel to the width direction and a portion where the expansion and contraction motion are suppressed appear. The secondary bending vibration is excited. The broken line A in FIG. 3 represents the magnitude of the displacement of the secondary bending vibration. The location where the displacement is maximum is the antinode, and the projection 22 is provided at a position corresponding to the antinode.
When the entire vibrating body 10 is viewed, these vertical primary vibrations and bending secondary vibrations are combined, and the drive unit 21 performs an elliptical motion as indicated by a broken line B. In a part of the elliptical motion, a driving force corresponding to the direction and the force is transmitted to the rotor 4. When the driving unit 21 draws an elliptical orbit, the driving force increases when the rotor 4 is sent, and when the driving unit 21 returns to the original position, the driving unit 21 moves away from the rotor 4 or the force in the returning direction decreases. Therefore, the rotor 4 can be driven efficiently. In addition, by providing the driving unit 21 at the antinode of the bending vibration, the amplitude and driving force of the driving unit 21 are increased, and the rotor 4 can be driven stably with high output. Further, such an effect can be obtained in any direction regardless of the direction of the elliptical orbit.
[0019]
The dimensions, thickness, and the like of the piezoelectric element 3 are appropriately set so that when a voltage is repeatedly applied to the piezoelectric element 3, longitudinal vibration and bending vibration simultaneously appear. At this time, the resonance frequency of the longitudinal vibration and the resonance frequency of the bending vibration are desirably set to be close to each other, and the ratio of the resonance frequency of the bending vibration to the resonance frequency of the longitudinal vibration is larger than 1.00. , 1.03 or less. The length ratio between the long side and the short side of the piezoelectric element 3 is desirably 0.274 or more, where 1 is the long side.
Here, the frequency of the voltage applied to the piezoelectric element 3 is such that both vibrations are between the resonance frequency of the longitudinal vibration and the resonance frequency of the bending vibration, more preferably between the anti-resonance frequency and the resonance frequency of the bending vibration. A frequency that appears well is appropriately selected. The waveform of the voltage applied to the piezoelectric actuator 1 is not particularly limited, and for example, a sine wave, a rectangular wave, a trapezoidal wave, or the like can be employed.
[0020]
FIG. 4 is a diagram illustrating the movement of the drive unit 21 when the voltage applied between the electrode 31 of the piezoelectric actuator 1 and the reinforcing plate 2 is changed.
FIG. 4 (A) is a diagram showing a locus of movement of the drive unit 21 when the resonance frequency is set to 278.75 kHz by adjusting the voltage applied to the electrode 31, and FIG. 4 (B) is a diagram showing a case where the resonance frequency is set to 280.75 kHz. FIG. 4C is a diagram illustrating a motion locus of the drive unit 21 when the resonance frequency is set to 282.00 kHz.
In FIG. 4A, when the resonance frequency is set to 278.75 kHz, the two driving units 21 can apply a clockwise driving force to the rotor 4 because the two driving units 21 perform an elliptical motion of pushing up to the upper left in FIG. .
In FIG. 4B, when the resonance frequency is changed to 280.75 kHz, the motion changes to an almost upward elliptical motion in FIG. At this time, one of the driving units 21 performs an elliptical motion of slightly pushing up to the upper left, so that the clockwise driving force is transmitted to the rotor 4 from the projection 22 at a low speed. Further, as compared with the case where the resonance frequency is 278.75 kHz, the urging force on the rotor 4 side is increased in the driving unit 21, so that a larger driving force can be obtained.
In FIG. 4C, when the resonance frequency is set to 282.00 kHz, the driving unit 21 changes to an elliptical motion in the upper right direction in FIG. Therefore, the rotor 4 obtains a counterclockwise driving force, and the rotation direction is reversed.
As described above, in the piezoelectric actuator according to the first embodiment, the direction and force of the elliptical motion of the drive unit 21 can be adjusted by changing the applied voltage to change the resonance frequency.
Also, since the phases of the two drive units 21 are different by 180 degrees, when one is in contact with the rotor 4, the other is away from the rotor 4. The driving force is given to the rotor 4.
[0021]
In the piezoelectric actuator according to the first embodiment, the following effects can be obtained.
(1) In the piezoelectric actuator 1, the two driving units 21 are provided at positions corresponding to the two antinodes of the secondary bending vibration. , A driving force is given to the motor, and the durability can be improved as compared with the case where one driving unit 21 is provided. Further, even in a device requiring a plurality of driving units, since one piezoelectric actuator has a plurality of driving units, the number of necessary piezoelectric actuators can be reduced, and miniaturization and thinning can be promoted.
(2) Since the vibration modes of the piezoelectric actuator 1 are primary longitudinal vibration and secondary bending vibration, the amplitude of the driving unit 21 can be increased, and the driving force can be further increased. Therefore, the rotor 4 can be driven at a constant rotation without stopping, and the driving stability can be remarkably improved.
(3) Since the piezoelectric actuator 1 has the protrusions 22 at diagonal positions in a rectangular shape, the protrusions 22 are present when a voltage is applied between the electrode 31 on the surface of the piezoelectric element 3 and the reinforcing plate 2. In the portion where the protrusion 22 is present, the longitudinal primary vibration is suppressed due to the weight of the protrusion 22 and the like, whereas in the portion where the protrusion 22 does not exist, the longitudinal primary vibration is excited. It becomes balanced and secondary bending vibration occurs in the width direction. Accordingly, the primary longitudinal vibration and the secondary bending vibration can be generated by installing the protrusion 22 on the piezoelectric actuator 1, and there is no need to provide a complicated electrode on the piezoelectric element 3, and the vibrating body 10 can be easily manufactured. it can.
[0022]
(4) The direction of the elliptical motion of the driving unit 21 can be changed by adjusting the frequency of the voltage applied between the electrode 31 and the reinforcing plate 2. This makes it possible to change the rotation state of the rotor 4 with a simple structure, such as adjusting the magnitude and direction of the driving force applied to the rotor 4 without a complicated mechanical variable means, and to enable reverse rotation. Become.
(5) The phases of the two drive units 21 are different by 180 degrees, and when one is in contact with the rotor 4, the other is separated from the rotor 4. By doing so, it is possible to substantially continuously apply a driving force to the rotor 4, and it is possible to obtain a larger driving force than in the case where only one driving unit 21 is provided. Further, since the driving unit 21 is divided into two parts to apply the driving force to the rotor 4 almost continuously, the rotation speed of the rotor 4 is likely to be constant, and if the rotation speed is constant, the rotation speed is maintained. The driving force required for the driving is small, and wear of the driving unit 21 can be prevented.
(6) Since the length dimension ratio of the vibrating body 10 is such that the long side: short side is 7: 1.98, the resonance frequencies of the longitudinal primary vibration and the bending secondary vibration are close to each other, and By vibrating the piezoelectric element in the vicinity of the resonance frequency, the piezoelectric element is excited in the vicinity of the respective resonance points of the longitudinal primary vibration and the bending secondary vibration, so that the respective vibration amplitudes are increased. Therefore, the amplitude of the elliptical trajectory of the driving section also increases, and the driven body can be driven with high efficiency.
[0023]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. Note that components that are the same as or similar to those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The same applies to a third embodiment described below.
FIG. 5 is a plan view of the piezoelectric actuator according to the second embodiment.
In the present embodiment, the electrode 31 on the surface of the piezoelectric element 3 is divided into three equal parts parallel to the longitudinal direction, and both ends of the divided electrode are equally divided into two equal parts parallel to the width direction. These divided electrodes 31A to 31E are insulated from each other, and wiring from a driving circuit (not shown) is connected to each of the electrodes 31A to 31E.
Further, in the second embodiment, the protrusions 22 are not formed on both short sides of the rectangular shape of the reinforcing plate 2.
[0024]
These electrodes 31A to 31E are formed by applying a voltage to electrodes along a diagonal direction of a rectangle, for example, electrodes 31A, 31C, and 31E in FIG. Appearing asymmetrically with respect to the centerline of the vibrating body 10, the longitudinal primary vibration and the bending secondary vibration are simultaneously excited as the whole vibrating body 10. The drive unit 21 draws an elliptical motion by combining the longitudinal primary vibration and the bending secondary vibration, and can transmit the driving force to the rotor 4 in a direction corresponding to the elliptical motion.
When a voltage is applied to the other diagonal electrode, that is, the electrodes 31B, 31C, and 31D, the bending secondary vibration of the opposite phase is excited, and the direction of the elliptical motion of the driving unit 21 is reversed.
Further, the electrode not used as the driving electrode is used as a displacement detection electrode, and the magnitude of vibration of the piezoelectric actuator 1 is detected by sending an electric signal generated according to the magnitude of vibration to a detection circuit (not shown). . The voltage applied to the driving electrode is adjusted by feedback control based on the magnitude of the detected vibration.
[0025]
According to the second embodiment, the following effects are obtained in addition to the effects (1), (2), (5), and (6) of the first embodiment.
(7) The electrode 31 on the surface of the piezoelectric element 3 is divided into three equal parts parallel to the longitudinal direction, and both ends of the divided electrode are equally divided into two parts parallel to the width direction. By applying a voltage to the electrodes located in the diagonal direction of the vibrating body 10 among the electrodes 31 to 31E, the driving unit 21 can be made to perform an elliptical motion, and a driving force corresponding to the elliptical motion can be obtained. Further, by switching the electrodes to electrodes in different diagonal directions and applying a voltage, the elliptical motion of the drive unit 21 can be reversed, and the rotor 4 can be reversed.
(8) Since the electrode to which no voltage is applied is used as the displacement detection electrode, the magnitude of the vibration of the vibrating body 10 can be detected, and the voltage applied to the electrode can be adjusted by feedback control based on the detection result. It can be driven under conditions.
[0026]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
The third embodiment uses the piezoelectric actuator 1 of the second embodiment described above as a pin actuator. FIG. 6 is a plan view of the piezoelectric actuator according to the present embodiment.
In FIG. 6, the piezoelectric actuator 1 of the third embodiment is configured to apply a driving force to a rod-shaped pin 6 that is in contact with a rotatably provided roller 41.
[0027]
One roller 41 is provided on the opposite side of the piezoelectric actuator 1 with the pin 6 interposed therebetween, and supports the pin 6.
The pin 6 is provided so as to be able to reciprocate in the axial direction by obtaining a driving force from the driving unit 21 of the piezoelectric actuator 1. The pins 6 are supported at three positions: two driving portions 21 provided on the piezoelectric actuator 1 and a roller 41 provided on the opposite side of the driving portion 21. The longitudinal direction of the piezoelectric actuator 1 is provided in the same direction as the axial direction of the pin 6.
[0028]
When a voltage is applied to the electrodes of the piezoelectric actuator 1, the piezoelectric actuator 1 performs an elliptical motion, whereby the pin 6 obtains a driving force and moves in a direction corresponding to the direction of the elliptical motion. That is, since the electrode 31 is divided into five, the pin 6 moves in both axial directions by changing the rotation direction of the elliptical motion of the drive unit 21 as described in the second embodiment.
[0029]
In the third embodiment, the following effects can be obtained in addition to the effects (1), (2), (5), and (6) of the first embodiment.
(9) Since the two drive units 21 are provided on the long side of the piezoelectric actuator 1, the drive unit 21 can support two places of the pin 6, and the roller 41 is driven with the pin 6 therebetween. It is only necessary to provide one on the opposite side of the portion 21. This can promote downsizing of the pin actuator and reduce the number of members.
[0030]
It should be noted that the present invention is not limited to the above-described embodiments, but includes modifications and improvements as long as the objects of the present invention can be achieved.
For example, in the first, second, and third embodiments, the vibration of the vibrating body 10 is a composite vibration of the longitudinal primary vibration and the bending secondary vibration, but the order of the vibration mode of each vibration is arbitrary. is there.
Further, the position of the projection at this time may be provided in accordance with the antinode of the bending vibration, and is not limited to two. For example, when the vibrating body performs a composite vibration of the fourth-order bending vibration, it is possible to provide two to four in accordance with the position of the antinode of the fourth-order bending vibration. In consideration of the above, it is sufficient that a plurality of them are arbitrarily provided.
[0031]
In the second and third embodiments, the piezoelectric element 3 is formed with the electrodes 31A to 31E that are divided into three equal parts in parallel with the longitudinal direction, and both ends are equally divided into two parts in parallel with the shorter side direction. Not limited to this. For example, there is a division method as shown in FIGS. FIG. 7A shows a dividing method in which the surface electrode of the piezoelectric element 3 is divided into three in parallel with the short side direction, and both ends are divided into two equal parts in parallel with the longitudinal direction. FIG. 7B illustrates a dividing method in which the surface electrode of the piezoelectric element 3 is divided by connecting the midpoint of the short side of the rectangle and the midpoint of the long side adjacent to the short side so that a diamond is drawn at the center. Is shown. FIG. 7C shows a dividing method in which the surface electrode is divided into four parts in parallel with the short side direction, and the two inner electrodes are further divided into two equal parts in parallel with the longitudinal direction.
In these examples, a longitudinal vibration and a bending vibration are excited by applying a voltage to the electrodes L and N shown in FIG. 7, and the driving unit 21 performs an elliptical motion by a combined vibration of these vibrations. Also, by applying a voltage to the electrodes M and N, the elliptical motion of reverse rotation is performed, and a driving force in the opposite direction is given to the driven body. In other words, the method of dividing the electrodes is arbitrary, as long as a composite vibration of longitudinal vibration and bending vibration can be obtained by applying a voltage.
[0032]
In the first, second, and third embodiments, the drive unit 21 is provided at two locations on one long side of the reinforcing plate 2 corresponding to the antinode position of the bending secondary vibration, and drives one rotor 4. However, it is not limited to this. For example, as shown in FIGS. 8A and 8B, the support portion 23A is provided substantially at the center of the vibrating body 10, and the driving portion 21 has one long side at one antinode of bending vibration and the other long side. It may be one provided at the antinode of the bending vibration on the side. Specifically, FIG. 8A illustrates a structure having a driving unit 21 near one side in the longitudinal direction of the vibrating body 10, and FIG. 8B illustrates a pair of driving units at positions that are line-symmetric with respect to the supporting unit 23 </ b> A. It has a structure in which the portion 21 is provided. In these structures, two rotors 4 can be driven for one piezoelectric actuator 1 by bringing one rotor into contact with each drive unit 21.
Further, as shown in FIG. 8C, a structure having one drive unit 21 on one long side and two drive units 21 on the other long side may be employed. In this case, one rotor 4 driven by these drive units 21 is provided on the long side provided with the two drive units 21, and only the drive unit 21 is provided on the long side provided with one drive unit 21. By arranging the driven rotors 4, two rotors 4 can be driven. Further, in the piezoelectric actuator 1, one rotor 4 can be brought into contact with each drive unit 21 to drive a total of three rotors 4 per one piezoelectric actuator 1.
Further, the drive units 21 may be provided corresponding to the positions of the antinodes of the bending vibration on both long sides. In this case, as shown in FIG. 8 (D), a structure in which each drive unit 21 drives one rotor 4 or as shown in FIG. 8 (E), one rotor 4 is driven by two drive units 21 It is possible to have a structure that allows it. In these modified examples, in some cases, the plurality of rotors 4 are driven by urging the rotor 4 toward the drive unit 21 side.
As described above, it is sufficient that a plurality of drive units are provided corresponding to the positions of antinodes of the bending vibration. In this manner, a plurality of rotors can be driven by one piezoelectric actuator. That is, another object of the present invention is to drive a plurality of driven members by one piezoelectric actuator, thereby promoting a reduction in the number of components and a reduction in the size of the entire device.
[0033]
In the first, second, and third embodiments, the vibrating body 10 is urged against the rotor 4 or the pin 6, but is not limited thereto. For example, in the first and second embodiments, the vibrating body 10 may be fixed and the rotor 4 may be urged toward the vibrating body 10, and in the third embodiment, the vibrating body 10 is fixed and the pin 6 is connected to the vibrating body. It may be biased to the 10 side.
[0034]
The best configuration and method for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the present invention has been particularly shown and described with particular reference to particular embodiments, but may be modified in form and form without departing from the spirit and scope of the invention. Those skilled in the art can make various modifications in terms of material, quantity, and other detailed configurations.
Therefore, the description of the shapes, materials, and the like disclosed above is merely an example for facilitating the understanding of the present invention, and does not limit the present invention. The description by the name of the member excluding some or all of the limitations such as is included in the present invention.
[0035]
【The invention's effect】
According to the present invention, since a plurality of driving units are mounted at positions corresponding to a plurality of antinodes of bending vibration, a driving force is applied to a driven body by a plurality of driving units for one piezoelectric actuator. In addition, the durability can be improved as compared with the case where there is one driving unit. Furthermore, unlike the conventional case where the number of piezoelectric actuators is required as many as the number of drive units, one piezoelectric actuator has a plurality of drive units, so the number of required piezoelectric actuators can be reduced, and the size and thickness can be reduced. The effect is that it can be promoted.
[Brief description of the drawings]
FIG. 1 is a plan view of an apparatus including a piezoelectric actuator according to a first embodiment.
FIG. 2 is an overall perspective view of a piezoelectric actuator according to the first embodiment.
FIG. 3 is a plan view of the piezoelectric actuator according to the first embodiment.
FIG. 4 (A) is a diagram showing the movement of a driving unit when the resonance frequency is set to 278.75 kHz by adjusting the voltage applied to the electrodes, and FIG. 4 (B) is a diagram showing the case where the resonance frequency is set to 280.75 kHz. The figure which showed the movement of the drive part, (C) The figure which showed the movement of the drive part when the resonance frequency was set to 282.00 kHz.
FIG. 5 is a plan view of a piezoelectric actuator according to a second embodiment.
FIG. 6 is a plan view of a pin actuator according to a third embodiment.
FIG. 7 is a view showing a modified example of the piezoelectric actuator of the second embodiment.
FIG. 8A is a plan view of a modified example of a structure having a driving unit near one side in the longitudinal direction of the vibrating body, and FIG. 8B is a diagram illustrating a pair of driving units at positions that are line-symmetric with respect to substantially the center of the vibrating body. (C) is a plan view of a modified example of a structure in which one part is provided, and (C) is a plan view of a modified example of a structure having one driving part on one long side and two driving parts on the other long side. () Is a plan view of a modification of a structure in which each driving unit drives one driven body, and (E) is a plan view of a modification of a structure in which two driving units drive one driven body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator, 10 ... Vibrating body 21 ... Drive part, 22 ... Projection part, 3 ... Piezoelectric element, 31, 31A, 31B, 31C, 31D, 31E ... Electrode

Claims (7)

A rectangular thin plate-shaped piezoelectric element having a longitudinal direction, and a vibrating body having a driving unit that is in contact with the driven body, the vibrating body is a composite vibration of longitudinal vibration and bending vibration, and A piezoelectric actuator that vibrates in an in-plane direction,
A piezoelectric actuator, wherein a plurality of the driving units are provided at positions corresponding to antinodes of the bending vibration. The piezoelectric actuator according to claim 1,
The piezoelectric actuator is characterized in that the longitudinal vibration is in a first mode and the bending vibration is in a second mode. The piezoelectric actuator according to claim 1 or 2,
A piezoelectric actuator, wherein the vibrator is provided with a pair of protrusions at diagonal positions in a rectangular shape. The piezoelectric actuator according to any one of claims 1 to 3,
A piezoelectric actuator, wherein the vibration of the vibrating body is adjustable by changing the frequency of a voltage applied to the surface of the piezoelectric element. The piezoelectric actuator according to any one of claims 1 to 4,
A piezoelectric actuator, wherein a driving electrode is formed on a surface of the piezoelectric element along a substantially diagonal direction of a rectangular shape. The piezoelectric actuator according to any one of claims 1 to 5,
A plurality of electrodes are formed on the surface of the piezoelectric element, some of these electrodes are driving electrodes, and at least some of the remaining electrodes are displacement detection electrodes. Actuator. The piezoelectric actuator according to any one of claims 1 to 6,
Assuming that the long side of the piezoelectric element is 1, the short side is formed to be 0.274 or more, a protrusion is provided on the short side of the piezoelectric element, and the longitudinal vibration that expands and contracts in the longitudinal direction of the piezoelectric element; The vibration ratio between the bending vibration and the bending vibration bending in a direction orthogonal to the longitudinal vibration in a point symmetry with respect to the plane center of the piezoelectric element is such that the ratio of the resonance frequency of the bending vibration to the resonance frequency of the longitudinal vibration is 1.00. A piezoelectric actuator characterized by being set to be larger and 1.03 or less.

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