JP2005086991A - Piezo-electric actuator, motor, and apparatus equipped with piezo-electric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezo-electric actuator, a motor and an apparatus equipped with the piezo-electric actuator, capable of efficiently exciting bending secondary vibration. <P>SOLUTION: The piezo-electric device 22 is fixed at both sides of a rectangular reinforcement plate 21, and a protruding portion 23, which protrudes along a longitudinal direction of the piezo-electric device 22 from a short edge of the reinforcement plate 21, is provided. When the protruding portion 23 is brought into contact with a driven body and the piezo-electric device 22 is vibrated, the protruding portion 23 is vibrated, to drive the driven body with a friction force between protruding portion and the driven body. At this time, a length dimension L2 of the protruding portion 23 is formed longer than a width dimension W2. Compared to ones with the length dimension being smaller than the width dimension, since the center of gravity of the protruding portion 23 is disposed farther outward in the long-edge direction of the piezo-electric device 22, the inertia moment by the protruding portion 23 becomes large, and bending secondary vibration by the piezo-electric actuator 2 is facilitated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric actuator that drives a driven body by vibration of a piezoelectric element, a motor, and a device including the piezoelectric actuator.

  As a piezoelectric actuator that drives a driven body by vibration of a piezoelectric element, a protrusion is provided on the side surface of a rectangular flat plate-shaped piezoelectric element, and the protrusion is in contact with the driven body (for example, Patent Document 1), or a rectangular flat plate There is known a structure in which a reinforcing plate is laminated on a piezoelectric element and a protrusion formed integrally with the reinforcing plate is brought into contact (for example, Patent Document 2). These piezoelectric actuators are provided with urging means for urging the piezoelectric actuator in one direction in the in-plane direction of vibration, and the driven body is driven by the vibration of the protrusion and the urging force generated by the vibration of the piezoelectric element. To drive. At this time, the protrusion vibrates in the short side direction of the piezoelectric element, and drives the driven body in the driving direction by so-called bending vibration. Therefore, the bending behavior of the bending vibration excited by the piezoelectric actuator greatly affects the driving efficiency. That is, in order to improve the drive efficiency of the piezoelectric actuator, it is important to efficiently excite the flexural vibration in the piezoelectric element and draw the desired flexural vibration on the protrusion.

JP 7-184382 A (page 3-4, FIG. 2) JP 2001-286167 A (page 5-7, FIG. 1)

  However, in Patent Document 1, although the length dimension is mentioned with respect to the shape of the protrusion, the width dimension is not mentioned, and the appropriate shape of the protrusion is not disclosed. Therefore, even if the length dimension of the protrusion is set, the desired bending vibration cannot be obtained because the vibration behavior of the piezoelectric element varies depending on the width dimension. Also, in Patent Document 2, the shape of the protrusion is formed into a curved surface in a plan view, but there is no description about the size, and like the piezoelectric actuator of Patent Document 1, the vibration behavior of the piezoelectric element depends on the size of the protrusion. Are different, and good bending vibration cannot be obtained.

  The objective of this invention is providing the apparatus provided with the piezoelectric actuator, the motor, and the piezoelectric actuator which can obtain a bending vibration efficiently.

  A piezoelectric actuator of the present invention is a piezoelectric actuator that includes a piezoelectric element having a substantially rectangular plate shape and drives a driven body by exciting bending vibration that bends in the short side direction of the piezoelectric element. A protrusion that protrudes along the direction and contacts the driven body, and the dimension of the protrusion along the long side direction of the piezoelectric element is along the short side direction of the piezoelectric element at the connection portion with the piezoelectric element. It is characterized by being longer than the dimensions.

According to the present invention, the dimension along the long side direction of the piezoelectric element in the protrusion is longer than the dimension along the short side direction of the piezoelectric element at the connection portion with the piezoelectric element. Thus, the center of gravity of the protruding portion is arranged on the outer side in the long side direction of the piezoelectric element. As a result, when the piezoelectric element bends and vibrates, the distance from the node of the bending vibration to the center of gravity of the protrusion becomes longer, and the bending vibration of the piezoelectric element is easily excited. Therefore, bending vibration is more efficiently excited from the vibration of the piezoelectric element, and the driven body is driven efficiently.
Moreover, since the dimension along the long side direction of the piezoelectric element is long in the protruding portion, the distance from the bending vibration node to the tip of the protruding portion is also increased, and the vibration amplitude at the tip of the protruding portion is increased and the vibration speed is increased. As a result, the driven body can be driven at high speed.

In the present invention, the piezoelectric actuator includes longitudinal primary vibration that expands and contracts about the center of the long side of the piezoelectric element, and bending secondary that vibrates point-symmetrically about the center of the piezoelectric element in the short side direction of the piezoelectric element. It is desirable that the vibration is combined with the vibration.
According to the present invention, since the piezoelectric actuator excites the longitudinal primary vibration simultaneously with the bending secondary vibration, the tip of the protrusion vibrates while drawing a substantially elliptical orbit combining these vibrations. At this time, for example, if the projecting tip is brought into contact with the driven body and the piezoelectric actuator is urged toward the driven body with an appropriate urging force, the tip of the projecting portion is part of a substantially elliptical track and the driven body is integrated. Since it is driven in the direction, the driven body is driven stably.

In the present invention, it is desirable that the tip of the protruding portion is formed in a linear shape or an arc shape.
According to this invention, since the shape of the tip of the protrusion is appropriately set, the protrusion stably contacts the driven body, and the driving force is stabilized. For example, in the case where the tip of the protrusion is formed in a straight line, even if the tip of the protrusion is worn due to long-term use, the shape of the tip of the protrusion does not change, so that the driven body contacts at the same angle. Therefore, even during long-term use, fluctuations in the driving force are suppressed to a minimum, and the driving force is stabilized.
In addition, when the tip of the protruding portion is formed in an arc shape, the protruding portion makes point contact with the driven body, so that the abutting position on the driven body is stable and the pressing angle becomes constant. Power stabilizes.

In the present invention, it is desirable that the protrusions be provided at both ends of the piezoelectric element in the long side direction at point-symmetric positions with the approximate center of the piezoelectric element as the center.
Since one protrusion is used for driving the driven body, it is pressed against the driven body. Therefore, when a voltage is applied to the piezoelectric element to vibrate the piezoelectric element, the one protrusion is difficult to excite a desired vibration.
According to the present invention, since the protrusions are provided at both ends of the piezoelectric element in the long side direction, the other protrusion not pressed by the driven body excites vibration, and this vibration is transmitted to the entire piezoelectric element. This facilitates excitation of the entire piezoelectric element. That is, the startability of the piezoelectric actuator is improved.

In addition, since the protruding portions are provided at both ends of the piezoelectric element in the long side direction, the bending vibration is helped at both ends of the piezoelectric element in the long side direction, and the bending vibration of the entire piezoelectric actuator is easily excited and the amplitude is large. Become.
Furthermore, since the protrusion is provided at a point-symmetrical position with the approximate center of the piezoelectric element as the center, the vibration of the piezoelectric element becomes point-symmetrical with the approximate center as the center, and the vibration is balanced and stable driving is realized. The

A motor according to the present invention includes the above-described piezoelectric actuator and an output shaft that is rotationally driven by the piezoelectric actuator.
According to this invention, since the piezoelectric actuator drives the output shaft of the motor, the rotational drive is taken out from the output shaft. Since this motor includes the above-described piezoelectric actuator, the same effect as described above can be obtained, and the output shaft can be efficiently rotated by exciting the flexural vibration.

A device according to the present invention includes the piezoelectric actuator described above.
According to this invention, since the device includes the above-described piezoelectric actuator, the same effects as those described above can be obtained, bending vibration can be obtained efficiently, and driving efficiency can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the second embodiment and later described below, the same reference numerals are given to the same components and components having the same functions as those in the first embodiment described below, and description thereof will be simplified or omitted.

[First embodiment]
A first embodiment of the present invention will be described.
FIG. 1 shows a plan view of a drive mechanism (device) 1 according to the first embodiment. In FIG. 1, the drive mechanism 1 includes a piezoelectric actuator 2 having a piezoelectric element 22 and a support 3 that supports the piezoelectric actuator 2 so as to vibrate. The drive mechanism 1 is fixed to a fixed body 4 together with a disk-like driven body 100.

FIG. 2 shows an enlarged perspective view of the piezoelectric actuator 2 and the support 3. As shown in FIG. 2, the piezoelectric actuator 2 includes a reinforcing plate 21 formed in a substantially rectangular flat plate shape, and flat plate-shaped piezoelectric elements 22 provided on both the front and back surfaces of the reinforcing plate 21.
The reinforcing plate 21 is made of stainless steel or any other material, and projecting portions 23 that project along the long side direction are integrally formed at the approximate centers of the short sides on both sides.
FIG. 3 shows an enlarged plan view of the piezoelectric actuator 2. As shown in FIG. 3, the projecting portion 23 is formed in a substantially rectangular plane shape, and the tip portion has an arc shape having a larger arc radius than the size of the projecting portion 23. A length dimension (dimension in the direction along the long side direction of the reinforcing plate 21) L2 of the protrusion 23 is formed to be longer than a width dimension (dimension in the direction along the short side direction of the reinforcing plate 21) W2. ing.
Here, the width dimension W2 refers to the width dimension at the connection portion between the protrusion 23 and the piezoelectric element 22, and in the present embodiment, the protrusion 23 is formed integrally with the reinforcing plate 21, and therefore the width dimension W2 is In addition, the width dimension of the connection portion between the substantially rectangular portion of the reinforcing plate 21 and the protrusion 23 is referred to, and the width dimension of the connection portion between the protrusion 23 and the piezoelectric element 22 in a plan view of the piezoelectric actuator 2.
The width dimension W2 is preferably less than or equal to ½ of the width dimension W1 of the reinforcing plate 21. The total area of the two protrusions 23 is preferably smaller than 1/10 of the area of the piezoelectric element 22. By setting the projecting portion 23 to such a size and area, the projecting portion 23 does not excessively inhibit the vibration of the piezoelectric actuator 2 and the influence on the vibration behavior of the entire piezoelectric actuator 2 is reduced. The vibration behavior of the entire piezoelectric actuator 2 can be substantially set by the dimensions of the piezoelectric element 22 and the reinforcing plate 21.
Further, the ratio of the width dimension W2 to the length dimension L2 of the protrusion 23 is preferably such that the length dimension L2 is 1.5 or more when the width dimension W2 is 1, and is optimal when it is two. By setting the projecting portion 23 to such a dimension, a bending secondary vibration described later is more easily excited, and the driven body 100 increases in driving speed.

In the reinforcing plate 21, the tip of the protruding portion 23 is in contact with the outer periphery of the driven body 100, and the longitudinal direction of the reinforcing plate 21 is substantially perpendicular to the driven body 100 at the contact portion (that is, driven). (Along the radial direction of the body 100). Further, the reinforcing plate 21 is integrally formed with an arm portion 24 that protrudes outward in the width direction from the long side. These arm portions 24 project substantially at right angles to the long sides of the reinforcing plate 21, and holes 241 are formed in these end portions.
Here, the arm portion 24 is disposed at a position closer to the driven body 100 by a predetermined distance than the center of the reinforcing plate 21 in the long side direction. That is, the distance L3 from the center position of the arm portion 24 in the direction along the long side direction of the reinforcing plate 21 to the end portion of the long side of the reinforcing plate 21 is less than 1/2 of the length dimension L1 of the reinforcing plate 21. It is getting smaller. When a voltage is repeatedly applied to the piezoelectric element 22, the piezoelectric actuator 2 vibrates, but since one protrusion 23 is in contact with the driven body 100, the piezoelectric element 22 on the one protrusion 23 side vibrates. It becomes difficult to do. Therefore, the vibration behavior of the entire piezoelectric actuator 2 is not symmetric with respect to the center in the longitudinal direction, and the vibration node slightly moves to the driven body 100 side. This movement is obtained in advance by calculation or experiment, and the arm 24 is arranged at a position close to the driven body 100 by this movement, so that the arm 24 is arranged at a position corresponding to the vibration node, Vibration inhibition of the piezoelectric actuator 2 is prevented.

The piezoelectric element 22 is bonded to substantially rectangular portions on both sides of the reinforcing plate 21. That is, the piezoelectric element 22 is formed in a substantially rectangular shape having a width dimension W1 and a length dimension L1 in the same manner as the substantially rectangular portion of the reinforcing plate 21. The material of the piezoelectric element 22 is not particularly limited. Lead zirconate titanate (PZT (registered trademark)), crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zinc niobate Various types such as lead scandium niobate can be used.
On both surfaces of the piezoelectric element 22, nickel and gold are formed by a method such as plating, sputtering, or vapor deposition to form electrodes. A plurality of electrodes are formed by the electrodes being electrically insulated from each other by the grooves, and these electrodes are formed symmetrically about the center line along the longitudinal direction of the piezoelectric element 22. . That is, two grooves 25A are formed so as to divide the piezoelectric element 22 into approximately three equal parts in the width direction, and among the three electrodes divided by these grooves 25A, the longitudinal direction is further divided into approximately two equal parts. Thus, a groove 25B is formed. Five electrodes 22A, 22B, 22C, 22D, and 22E are formed on the surface of the piezoelectric element 22 by these grooves 25A and 25B.

Among these electrodes 22A, 22B, 22C, 22D, and 22E, a lead wire (not shown) that connects the electrodes 22A and 22E located at both ends on the diagonal line, and a lead wire (not shown) that connects the electrodes 22B and 22D ), A lead wire (not shown) connected to the electrode 22C, and a lead wire (not shown) connected to the reinforcing plate 21 are applied to a voltage applying device (not shown) to the piezoelectric element 22. Connected). Here, each lead wire is preferably connected in the vicinity of a vibration node of the piezoelectric actuator 2. That is, in the electrodes 22A, 22B, 22D, and 22E, it is desirable that the lead wire be connected to the vicinity of the groove 25B in the vicinity of the center in the long side direction of the piezoelectric element 22, and the lead wire of the electrode 22C is the length of the piezoelectric element 22. It is desirable to connect to a position corresponding to the position of the arm portion 24 in the side direction. Thereby, the vibration inhibition of the piezoelectric actuator 2 by the lead wire is well prevented.
These electrodes 22A, 22B, 22C, 22D, and 22E are similarly provided on both the front and back piezoelectric elements 22 provided with the reinforcing plate 21 interposed therebetween. For example, another electrode is provided on the back side of the electrode 22A. 22A is formed.

  Here, the dimensions, thicknesses, and electrode division forms of the piezoelectric element 22 are the so-called longitudinal primary vibration in which the piezoelectric element 22 expands and contracts in the longitudinal direction when a voltage is repeatedly applied to the piezoelectric element 22, and the piezoelectric element. It is appropriately set so that a so-called bending secondary vibration that bends in a direction orthogonal to the longitudinal vibration in the plane is point-symmetric with respect to the plane center of 22 at the same time. At this time, it is desirable that the resonance frequency of the longitudinal primary vibration and the resonance frequency of the bending secondary vibration are set to be close to each other, and the ratio of the resonance frequency of the bending secondary vibration to the resonance frequency of the longitudinal primary vibration is , Greater than 0.97 and not greater than 1.03. The length ratio of the long side (length dimension L1) to the short side (width dimension W1) of the piezoelectric element 22 is such that the length of the short side is 0.274 or more when the length of the long side is 1. It is desirable.

The ratio of the resonance frequency of the bending secondary vibration to the resonance frequency of the longitudinal primary vibration is 0.97 or less, and the ratio of the resonance frequency of the bending secondary vibration to the resonance frequency of the longitudinal primary vibration is greater than 1.03. In this case, the resonance point of the longitudinal primary vibration and the resonance point of the bending secondary vibration are separated from each other, and the protruding portion 23 cannot draw a good elliptical orbit.
The frequency of the voltage applied to the piezoelectric element 22 is between the resonance frequency of the longitudinal primary vibration and the resonance frequency of the bending secondary vibration, more preferably the resonance frequency of the longitudinal primary vibration, the longitudinal primary vibration, and the bending secondary vibration. A frequency at which both vibrations appear favorably between the anti-resonance frequencies is appropriately selected. In addition, the waveform of the voltage applied to the piezoelectric actuator 2 is not specifically limited, For example, a sine wave, a rectangular wave, a trapezoidal wave etc. are employable.

  Returning to FIG. 2, the support body 3 is a slide that is integrally formed between the pair of fixing portions 31 to which the piezoelectric actuator 2 is fixed, and is fixed to the fixing body 4 so as to be slidable. Part 32. A screw part 34 is formed in the fixing part 31 at a position corresponding to the hole 241 of the arm part 24. The piezoelectric actuator 2 is fixed to the fixing portion 31 by the screw 26 being screwed into the screw portion 34 through the hole 241.

  FIG. 4 shows a side sectional view of the drive mechanism 1. As shown in FIG. 4, the slide portion 32 is disposed in a slide groove 41 formed in a concave shape on the fixed body 4. In addition, a plurality of long holes 33 (two in the present embodiment) are formed at substantially the center in the width direction of the slide portion 32 along the contact direction of the protrusion 23 with respect to the driven body 100. A screw 421 passes through the long hole 33, and the screw 421 is screwed into a screw hole 42 formed in the fixed body 4. Thereby, the support body 3 can slide in the longitudinal direction of the long hole 33. That is, the protrusion 23 of the piezoelectric actuator 2 can be separated from the contact portion with the driven body 100 along the radial direction of the driven body 100.

The fixed portion 31 and the slide portion 32 are formed with a step. That is, the fixed portion 31 and the slide portion 32 form a concave portion in the center. Thereby, when the piezoelectric actuator 2 is attached to the fixed portion 31, a gap is formed between the piezoelectric actuator 2 and the slide portion 32, and even if the piezoelectric actuator 2 vibrates, it interferes with the screw 421 penetrating the slide portion 32. It is supposed not to.
As shown in FIG. 1 described above, the fixed portions 31 on both sides of the support 3 are respectively formed with spring mounting portions 35 protruding in a columnar shape on the side surfaces of the end opposite to the driven body 100 side. Yes. One end of a spring 36 is inserted into the spring mounting portion 35. The spring 36 is disposed so that its expansion / contraction direction is parallel to the separation direction of the piezoelectric actuator 2, and the other end is fixed to a locking piece 37 provided on the fixed body 4. Due to the spring force of the spring 36, the protrusion 23 of the piezoelectric actuator 2 is pressed against the driven body 100 with an appropriate biasing force.

  The driven body 100 is rotatably supported by a bearing pin 43 (FIG. 4) fitted to the fixed body 4. The driven body 100 is formed with a concave portion 101 having an arc-shaped cross section along the outer periphery, and the tip of the protruding portion 23 of the piezoelectric actuator 2 is in contact with the concave portion 101. The surface of the recess 101 is smoothly finished so as to reduce wear with the protrusion 23.

Such a driving mechanism 1 operates as follows.
FIG. 5 is a diagram showing the vibration behavior of the piezoelectric actuator 2. As shown in FIG. 5, an AC voltage is applied between the reinforcing plate 21 and the electrode on the surface of the piezoelectric element 22 by an applying device to vibrate the piezoelectric element 22. At this time, in the piezoelectric element 22, by selectively applying a voltage only to the electrodes 22A, 22E and the electrode 22C, the piezoelectric actuator 2 can be substantially centered in the longitudinal direction of the piezoelectric element 22 (approximately the center in the longitudinal direction) mainly by the electrode 22C. Longitudinal primary vibration that expands and contracts around a position closer to the driven body 100 than a predetermined distance) is excited. Also, the bending secondary vibration that bends along the direction orthogonal to the longitudinal primary vibration in the plane of the piezoelectric element 22, that is, the short direction of the piezoelectric element 22, is mainly excited by the electrodes 22 </ b> A and 22 </ b> E. By combining these longitudinal primary vibration and bending secondary vibration, the piezoelectric actuator 2 excites vibration that bends while expanding and contracting as shown by a two-dot chain line in FIG. 5, and the protrusion 23 combines these vibrations. It oscillates by drawing an elliptical orbit R. The protruding portion 23 is pressed against the concave portion 101 of the driven body 100 at a part of the elliptical orbit R, and intermittently rotates the driven body 100 in the circumferential direction by a frictional force with the driven body 100. By repeating this at a predetermined frequency, the driven body 100 rotates at a predetermined rotation speed in one direction.

Here, in a state where one protrusion 23 is in contact with the driven body 100, the piezoelectric element 22 is less likely to vibrate in the one protrusion 23, and there is no contact member in the other protrusion 23, so that it is free. It becomes. For this reason, when the piezoelectric actuator 2 to which a voltage is applied by the applying device is started, vibration is inhibited by contact with the driven body 100 at one protrusion 23, but vibration occurs according to the applied voltage at the other protrusion 23. Is excited. When this vibration is transmitted to the one projecting portion 23 and reaches a state in which a vibration sufficient to drive the driven body 100 is obtained, the one projecting portion 23 starts to vibrate. Note that a state in which vibration enough to drive the driven body 100 is obtained means that vibration obtained at the tip of one protrusion 23 due to vibration of the piezoelectric element 22 is piezoelectric at the contact portion between the protrusion 23 and the driven body 100. A state in which the urging force applied to the actuator 2 is overcome and an amplitude sufficient to leave the driven body 100 is obtained.
When one protrusion 23 starts to vibrate and the entire piezoelectric element 22 resonates, the vibration of the piezoelectric actuator 2 is in a steady state. In this steady state, the protrusion 23 vibrates in a substantially elliptical orbit R and drives the driven body 100 at a predetermined speed.

  When the driven body 100 is rotated in the opposite direction, the electrode of the voltage applied to the piezoelectric element 22 is switched symmetrically about the center line along the longitudinal direction of the piezoelectric actuator 2 as an axis. That is, when a voltage having a predetermined frequency is applied to the electrodes 22B and 22D and the electrode 22C of the piezoelectric element 22, the protruding portion 23 vibrates while drawing an elliptical orbit in the opposite direction. Thereby, the driven body 100 rotates in the opposite direction.

According to such a first embodiment, the following effects can be obtained.
(1) Since the length dimension L2 along the long side direction of the piezoelectric element 22 is longer than the width dimension W2 along the short side direction at the protrusion 23, the width dimension W2 is longer than the length dimension L2 in the same area. The center of gravity of the protruding portion 23 is arranged on the outer side with respect to the long side direction of the piezoelectric element 22 as compared with the portion.
FIG. 6 shows a diagram representing the amplitude of the bending secondary vibration of the piezoelectric actuator 2. As shown in FIG. 6, when the piezoelectric element 22 performs bending secondary vibration, the piezoelectric element 22 vibrates with three nodes A on the piezoelectric element 22. At this time, the distance from the node A close to the protrusion 23 to the center of gravity C is larger than that of the protrusion having the same area and the width dimension larger than the length dimension. Therefore, since the moment of inertia acting on the protrusion 23 becomes larger, the bending secondary vibration can be more easily excited in the piezoelectric actuator 2. Therefore, a favorable bending secondary vibration can be obtained, and the driven body 100 can be driven efficiently.

(2) Since the length dimension L2 of the protrusion 23 is longer than the width dimension W2, as compared with the protrusion having the same area and the length dimension shorter than the width dimension, from the bending secondary vibration node A to the tip of the protrusion 23 Can be made longer. Therefore, the amplitude of the bending secondary vibration obtained at the tip of the protrusion 23 can be further increased. Thereby, since the drive displacement of the driven body 100 by one amplitude of the protrusion part 23 can be enlarged, the driven body 100 can be driven at high speed.
In addition, since the vibration amplitude of the bending secondary vibration at the tip of the protrusion 23 is increased, for example, even when dust is attached to the driven body 100, it is possible to get over the dust with a large vibration amplitude. 100 can be driven well and stably. For example, even when the surface roughness of the driven body 100 is large, the driven body 100 can be driven satisfactorily because the vibration amplitude at the tip of the protrusion 23 is large. On the contrary, since the surface roughness of the driven body 100 can be increased, it is not necessary to strictly manage the surface roughness of the concave portion 101 of the driven body 100, and the manufacturing cost of the driven body 100 can be reduced.
Furthermore, since the length L2 of the protrusion 23 is relatively long, the piezoelectric element 22 does not come into contact with the driven body 100 even when the tip of the protrusion 23 is slightly worn due to long-term use, and the protrusion 23 is covered for a long time. The drive body 100 can be driven satisfactorily and the durability of the piezoelectric actuator 2 can be improved.

(3) Since the piezoelectric actuator 2 vibrates a combination of longitudinal primary vibration and bending secondary vibration, the projecting portion 23 draws an elliptical orbit R, so that the driven body 100 is made highly efficient with a part of the elliptical orbit R. Can be driven in one direction.
Further, the driven body 100 can be driven in both forward and reverse directions by switching the electrodes of the piezoelectric element 22.

(4) Since the tip of the projecting portion 23 is formed in an arc shape, it is possible to always make point contact with the driven body 100, obtain a stable pressing angle, and stabilize the driving force.
(5) The arm portion 24 is provided at a position closer to the driven body 100 by a predetermined distance than the substantially longitudinal center of the piezoelectric element 22. Therefore, since the distance from the protrusion 23 to the arm 24 is shortened, the protrusion 23 is driven by the vibration of the portion of the piezoelectric element 22 from the arm 24 to the protrusion 23 on the driven body 100 side. It is possible to prevent displacement with respect to 100. Thereby, the driving force of the piezoelectric actuator 2 can be stabilized and a high torque can be obtained.
Further, since one protrusion 23 is in contact with the driven body 100, the vibration node of the piezoelectric actuator 2 is shifted from the center in the long side direction of the piezoelectric element 22 toward the driven body 100. At this time, since the arm portion 24 is arranged at a position closer to the driven body 100 by this amount of deviation, the arm portion 24 can support the vibration node, and the inhibition of vibration by the arm portion 24 can be prevented.

(6) Since the protrusions 23 are provided at both ends of the reinforcing plate 21 in the long side direction, the moment of inertia is increased on both sides of the piezoelectric element 22, and a good bending secondary vibration can be obtained more efficiently.
Further, when the piezoelectric actuator 2 is started, the other protrusion 23 that is not in contact with the driven body 100 excites the bending secondary vibration well and transmits this vibration to the one protrusion 23. For this reason, compared with the case where the protrusion 23 is provided only on one side of the piezoelectric element 22, the entire piezoelectric element 22 resonates and enters a steady state, so that the startability of the piezoelectric actuator 2 can be improved. . Thereby, even when the applied voltage is low or a high starting torque is required, the engine can be started relatively quickly.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the second embodiment, the drive mechanism of the first embodiment is in contact with the inner peripheral side of the driven body.
FIG. 7 shows a plan view of the drive mechanism 1 according to the second embodiment, and FIG. 8 shows a side sectional view of the drive mechanism 1. 7 and 8, the piezoelectric actuator 2 and the support 3 are fixed to a disk-shaped fixed body 4, and an annular driven body 100 is equidistant from the outer periphery of the fixed body 4 in the circumferential direction. It is rotatably provided through a plurality of balls 44 arranged in the above. The plurality of balls 44 includes a groove 102 formed on the inner periphery of the driven body 100, an inclined portion formed on the outer periphery of the fixed body 4, and an inclined portion of an annular pressing plate 441 fixed to the fixed body 4. It fits in the groove | channel 102 by being pinched | interposed by. Further, an annular ball holding portion 442 is interposed between the fixed body 4 and the pressing plate 441. The ball holding portion 442 is formed with substantially the same number of semi-circular cutout portions as the balls 44 on the outer periphery, and the balls 44 are respectively disposed in the cutout portions, thereby maintaining a predetermined interval on the outer periphery of the fixed body 4. .

The reinforcing plate 21 of the piezoelectric actuator 2 is provided with a protrusion 23 only on one side of the short side. The protruding portion 23 protrudes from the approximate center of the short side of the reinforcing plate 21 along the longitudinal direction, and the tip is formed in an arc shape. As for the dimension of this protrusion part 23, the length dimension L2 is formed longer than the width dimension W2 similarly to the protrusion part 23 of 1st embodiment.
The number of electrodes provided on the surface of the piezoelectric element 22 is less than that of the piezoelectric element 22 of the first embodiment, and the electrodes 22A, 22C, and 22D of the first embodiment are coupled without being insulated by the groove 25A. A substantially T-shaped electrode 22F is formed.

A lead wire (not shown) connected to the electrodes 22B, 22E, 22F of the piezoelectric element 22 is connected to an application device (not shown) on the opposite side through a wiring hole 46 formed in the fixed body 4. The electrodes 22B and 22E are also connected to a detection device (not shown) that detects the vibration of the piezoelectric actuator 2 on the opposite side of the fixed body 4.
Each lead wire is preferably connected to the electrodes 22B, 22E, and 22F in the vicinity of the vibration node of the piezoelectric actuator 2.
The driven body 100 is formed with a concave portion 101 having an arcuate cross section along the inner periphery, and the protruding portion 23 of the piezoelectric actuator 2 is in contact with the concave portion 101.

In such a drive mechanism 1, when a voltage is applied to the electrodes 22 </ b> B and 22 </ b> F of the piezoelectric element 22, longitudinal primary vibration is excited in the piezoelectric actuator 2. Further, since no voltage is applied only to the electrode 22E, the vibration of the piezoelectric element 22 becomes asymmetrical, and the bending secondary vibration is excited in the piezoelectric actuator 2 at the same time. Due to these longitudinal primary vibration and bending secondary vibration, the protrusion 23 vibrates in an elliptical manner as in the first embodiment, and presses the driven body 100 from the inner peripheral side to rotate the driven body 100. .
At this time, no voltage is applied to the electrode 22E, but a minute displacement is generated in the piezoelectric element 22 in the portion of the electrode 22E due to the vibration of the entire piezoelectric actuator 2, and a minute voltage is generated. The detection device detects the minute voltage, grasps the vibration behavior of the piezoelectric actuator 2, and controls the vibration of the piezoelectric actuator 2 to have a predetermined vibration behavior by adjusting the voltage and frequency of the applied voltage. .
When the electrode to which the voltage is applied is switched to the electrodes 22E and 22F, the projecting portion 23 draws an elliptical orbit in the opposite direction and rotationally drives the driven body 100 in the opposite direction. In this case, the electrode 22B may be used as the detection electrode.

According to such a second embodiment, the following effects can be obtained in addition to the same effects as the effects (1) to (5) of the first embodiment.
(7) Since the length dimension L2 of the projecting portion 23 is long, the bending secondary vibration can be excited efficiently. Therefore, even when the electrodes 22B and 22E for exciting the bending secondary vibration are provided only on one side of the piezoelectric element 22 as compared with the electrodes 22A, 22B, 22D and 22E of the first embodiment, the bending The next vibration can be excited.
In addition, since the number of electrodes formed on the piezoelectric element 22 can be reduced, wiring can be reduced, the structure can be simplified, and vibration inhibition of the piezoelectric actuator 2 by wiring can be suppressed to a minimum.

[Third embodiment]
Next, a third embodiment of the present invention will be described. In the third embodiment, the piezoelectric actuator of the present invention is applied to a liquid ejection device.
FIG. 9 shows a liquid ejection device 50 according to the third embodiment. In FIG. 9, the liquid discharge device 50 includes a tube 51 through which liquid flows, a ball 52 that rolls on the tube 51 and sequentially sends the liquid inside, and presses the ball 52 toward the tube 51. A rotor (driven body) 53 that rolls while rotating and a piezoelectric actuator 2 that rotationally drives the rotor 53 are provided. A part of these tubes 51, the ball 52, the rotor 53, and the piezoelectric actuator 2 are accommodated in the base 54.

The protruding portions 23 of the piezoelectric actuator 2 are formed at both ends of the reinforcing plate 21 on a diagonal line so as to protrude in the long side direction from the short side of the reinforcing plate 21. As in the first embodiment and the second embodiment, these protrusions 23 are set such that the length dimension L2 is longer than the width dimension W2, the tip is formed in an arc shape, and one protrusion 23 is the rotor 53. It is contact | abutted to the outer peripheral side surface. Here, the piezoelectric actuator 2 is disposed such that the longitudinal direction is inclined at a predetermined angle with respect to the radial direction of the rotor 53.
An electrode is formed on the surface of the piezoelectric element 22, but in this embodiment, unlike the first embodiment, no groove is provided, and one electrode is formed on the entire surface of the piezoelectric element 22. The electrodes on the front and back surfaces of the piezoelectric element 22 are connected to an application device.
The piezoelectric actuator 2 is supported from both sides by an arm portion 24 at a substantially longitudinal center. The arm portion 24 is fixed to the base portion 54 with a screw 27 and is held so as to be rotatable about the screw 27. A substantially U-shaped urging member 28 is formed integrally with the arm portion 24, and the tip of a screw 29 is brought into contact with the end of the urging member 28 at a substantially right angle from the side surface. The screw 29 is screwed into the base portion 54, and the tip is supported so as to be able to advance and retreat toward the biasing member 28 side.

  When a voltage is applied to the electrodes of the piezoelectric element 22 to expand and contract the piezoelectric element 22, longitudinal primary vibration is excited in the piezoelectric actuator 2. At this time, since the protrusion 23 is provided asymmetrically with respect to the center line along the long side direction of the piezoelectric element 22, the weight of the piezoelectric actuator 2 is unbalanced, and the piezoelectric actuator 2 is bent twice. The next vibration is excited. The protrusion 23 vibrates along an elliptical orbit by these longitudinal primary vibration and bending secondary vibration, and rotates the rotor 53.

  When the rotor 53 rotates, the ball 52 rolls while crushing the tube 51 by the pressing force of the rotor 53. The liquid inside the tube 51 sandwiched between the two balls 52 is sequentially fed and discharged from the open end of the tube 51. Adjustment of the abutting force of the projecting portion 23 against the rotor 53 is performed by changing the urging force of the urging member 28 by rotating the screw 29 to advance and retract the tip. Due to the change of the urging force, the piezoelectric actuator 2 rotates around the screw 27, and the contact force to the rotor 53 is changed. When the protruding portion 23 is strongly pressed against the rotor 53, the portion of the elliptical orbit of the protruding portion 23 where the frictional force capable of driving the rotor 53 is increased, and the driving speed of the rotor 53 is increased.

According to the third embodiment, in addition to the same effects as the effects (1) to (4) and (6) of the first embodiment, the following effects can be obtained.
(8) Since the length dimension L 2 of the protrusion 23 is longer than the width dimension W 2, the piezoelectric element 22 interferes with the rotor 53 even if the long side direction of the piezoelectric actuator 2 is inclined with respect to the radial direction of the rotor 53. The piezoelectric actuator 2 can be arranged without doing so.
Further, since the piezoelectric actuator 2 is arranged so that the long side direction is inclined with respect to the radial direction of the rotor 53, the secondary bending vibration of the protruding portion 23 can be more easily generated by the reaction force from the rotor 53. Can do.

 (9) Since the piezoelectric actuator 2 excites the bending secondary vibration by the weight imbalance depending on the mounting position of the protrusion 23, the piezoelectric element 22 may be formed with one electrode. Therefore, the wiring and structure of the piezoelectric actuator 2 can be simplified, vibration inhibition of the piezoelectric actuator 2 can be satisfactorily prevented, and excitation can be performed with higher efficiency.

The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
The shape of the projecting portion of the piezoelectric actuator is formed in an arc shape in each embodiment, but is not limited thereto, and may be a shape as shown in FIGS. 10 to 12, for example.
In the protrusion part 23 shown by FIG. 10, the front-end | tip is formed in linear form. Even with such a protruding portion 23, if the length dimension L2 is formed longer than the width dimension W2, the center of gravity of the protruding portion 23 can be disposed more outward in the long side direction of the piezoelectric actuator 2, Bending secondary vibration can be excited efficiently. In addition, since the tip of the protruding portion 23 is formed in a straight line, even if the tip is worn slightly due to long-term use, the contact area to the driven body does not change greatly, so that stable driving over a long period of time is possible. You can gain power. And since the front-end | tip of the protrusion part 23 can be processed easily, manufacturing cost can be reduced.

  The shape of the protruding portion of the piezoelectric actuator may be a trapezoid as shown in FIG. 11 or a deformed shape as shown in FIG. In particular, in FIG. 12, the protruding portion 23 is formed so that the width dimension increases from the connecting portion to the rectangular portion of the reinforcing plate 21 toward the tip, and the tip is formed in a substantially arc shape. With such a shape, for example, even when there is no room in the longitudinal direction of the piezoelectric actuator 2, the center of gravity of the protruding portion 23 can be disposed outside the longitudinal direction of the piezoelectric actuator 2 while limiting the length L 2 to some extent. So it is useful.

  In the first embodiment and the second embodiment, the piezoelectric actuator 2 is arranged so that the long side direction thereof is along the radial direction of the driven body 100. However, the piezoelectric actuator 2 is not limited to this and is covered, for example, as in the third embodiment. You may arrange | position so that it may incline with respect to the radial direction of the drive body 100. FIG. In this case, the protrusion 23 can easily excite the secondary bending vibration by the reaction force from the driven body 100. For this reason, since the electrodes 22A, 22B, 22D, and 22E to which no voltage is applied in order to generate the bending secondary vibration can be reduced, the area of the electrodes used for driving can be increased and the driving force can be increased. can do.

You may set the dimension of a protrusion part suitably in the range from which a length dimension becomes longer than a width dimension. For example, if the weight of the protruding portion is increased or the length dimension is increased so that the center of gravity of the protruding portion is moved away from the node of the bending secondary vibration, the resonance frequency of the bending secondary vibration tends to decrease. By utilizing this, the dimension of the protrusion may be adjusted so that the resonance frequency of the longitudinal primary vibration and the resonance frequency of the bending secondary vibration are close to each other. By performing such adjustment, fine adjustment of a certain resonance frequency can be performed without changing the dimensions of the piezoelectric element and the reinforcing plate.
Further, the protruding portion is not limited to the one formed integrally with the reinforcing plate 21 of the above-described embodiment, and may be provided separately from the reinforcing plate 21. In this case, versatility can be improved because the shape and dimensions of the protrusions can be set and attached to the reinforcing plate having a common shape depending on the driving conditions of the piezoelectric actuator.

Or you may adjust the dimension of a piezoelectric actuator according to the dimension of a protrusion part.
FIG. 13 is a diagram illustrating an example of adjusting the dimensions of the protruding portion and the piezoelectric element 22. In FIG. 13, FIG. 13A is a diagram of the piezoelectric actuator of the present invention, and FIGS. FIG.
For example, in FIG. 13B, when the length of the protrusion 23 is made longer than that of the piezoelectric actuator 2 of FIG. 13A, the vibration amplitude of the bending secondary vibration becomes large. For this reason, the elliptical orbit drawn by the protrusion 23 has a component of bending secondary vibration larger than that of the elliptical orbit in the protrusion 23 in FIG. 13A, and the vibration component along the short side direction of the piezoelectric element 22. Becomes stronger. Furthermore, since the distance from the node of the bending secondary vibration to the tip of the protrusion 23 is large, the speed of the tip of the protrusion 23 is increased when vibrating at the same frequency. Useful. At this time, in order to prevent the vibration of the piezoelectric actuator 2 from the arm portion 24 to the protruding portion 23 from becoming unstable due to an increase in the length of the protruding portion 23, the arm portion 24 is moved in the longitudinal direction of the piezoelectric element 22. It may be provided on the side closer to the protrusion 23 than the center.
On the other hand, the piezoelectric actuator 2 in FIG. 13A has a component of longitudinal primary vibration larger than that of the piezoelectric actuator 2 in FIG. 13B, so that the pressing force against the driven body is increased. Therefore, it is useful when a high torque is required for driving the driven body, such as when the driven body is heavy.

  When the length dimension of the protrusion 23 is increased as shown in FIG. 13B, the resonance frequency of the bending secondary vibration of the piezoelectric actuator 2 is lowered. Here, in order to vibrate the piezoelectric actuator 2 near the resonance point of both the longitudinal primary vibration and the bending secondary vibration, it is desirable that the difference between the resonance frequency of the longitudinal primary vibration and the resonance frequency of the bending secondary vibration is smaller than 10 kHz. More desirably, it is less than 5 kHz. Therefore, when the difference between the resonance frequencies of both of the protrusions 23 becomes too large due to the change in the length of the protrusion 23, the width of the piezoelectric element 22 is increased as shown in FIG. Then, since the resonance frequency of the bending secondary vibration increases, the difference from the resonance frequency of the longitudinal primary vibration becomes small, and the piezoelectric actuator 2 can be vibrated well in the vicinity of both resonance points.

  In addition, in the piezoelectric actuator 2 of FIG. 13 (B) and FIG. 13 (C), the attachment position of the arm part 24 by the same distance as the length dimension of the protrusion part 23 of FIG. Is shifted to the protruding portion 23 side, the distance from the tip of the protruding portion 23 to the arm portion 24 does not change. Therefore, since the position of the driven body and the fixing position of the piezoelectric actuator 2 do not change for the piezoelectric actuators 2 having a plurality of types of dimensions, the common supporting body 3 can be used, and the fixing position of the supporting body 3 can be fixed. Therefore, the components other than the piezoelectric actuator 2 can be shared. On the other hand, piezoelectric actuators with multiple dimensions can be fixed to a common component, so that piezoelectric actuators can be selected and installed as appropriate for the intended use and usage conditions. Can be expanded, and versatility can be improved.

The piezoelectric actuator has been used as one that drives the rotating body in each embodiment. However, the piezoelectric actuator is not limited to this, and may be used as one that moves, for example, a rod-shaped member in the longitudinal direction. In addition, the piezoelectric actuator may be used for a motor having an output shaft as an output shaft by driving a rotating body and providing a shaft fixed to the rotating body.
In addition, the piezoelectric actuator is not limited to the motor, the drive mechanism of each embodiment, and the liquid ejection device, but may be applied to a toy car by using, for example, the driven body of the first embodiment as a wheel. It can be applied to various devices such as a watch hand drive and a date wheel drive actuator.

The best configuration, method and the like 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 invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations.
Therefore, the description limited to the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

In order to confirm the effect of the present invention, the following experiment was conducted.
(Example)
In the drive mechanism 1 that is substantially the same as that of the first embodiment, the length L1 of the piezoelectric element 22 is 7 mm and the width W1 is 2 mm. Further, the length dimension L2 = 0.45 mm of the protrusion 23 and the width dimension W2 = 0.5 mm were set. The pressing force of the protrusion 23 against the driven body 100 was 0.078 N, and a voltage of 5 V was applied to the piezoelectric element 22 to drive the driven body 100. At this time, the frequency of the applied voltage at which the driving speed of the driven body 100 was the highest was 270 kHz.

(Comparative example)
The length L2 of the protrusion 23 was set to 0.9 mm and the width W2 was set to 0.5 mm. In addition, the frequency of the voltage applied to the piezoelectric element 22 at which the driving speed of the driven body 100 was the highest was 286 kHz. Other conditions are the same as in the examples.

(Results of Examples and Comparative Examples)
In the driving mechanism 1 of the example, the driving speed of the driven body 100 was about 1.3 m / s.
On the other hand, in the driving mechanism 1 of the comparative example, the driving speed of the driven body 100 was about 0.5 m / s.
From the above, it can be seen that the drive speed of the driven body 100 can be increased when the length dimension L2 of the protrusion 23 is longer than the width dimension W2.

  The piezoelectric actuator of the present invention can be used for various devices such as a liquid ejection device, a toy car, a watch, etc., as well as a driving mechanism for driving a rod-shaped member or a rotating body.

The top view which shows the drive mechanism concerning 1st embodiment of this invention. The perspective view which shows a piezoelectric actuator and a support body. The enlarged plan view of a piezoelectric actuator. The sectional side view of a drive mechanism. The figure which shows the vibration behavior of a piezoelectric actuator. The figure which shows the vibration and displacement of a protrusion part. The top view which shows the drive mechanism concerning 2nd embodiment. The sectional side view of a drive mechanism. FIG. 9 is a plan view showing a liquid ejection device according to a third embodiment. The figure which shows the modification of the protrusion part of a piezoelectric actuator. The figure which shows another modification of the protrusion part of a piezoelectric actuator. The figure which shows another modification of the protrusion part of a piezoelectric actuator. The figure which shows the modification of the shape of a piezoelectric actuator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Drive mechanism (apparatus), 2 ... Piezoelectric actuator, 21 ... Reinforcement plate, 22 ... Piezoelectric element, 23 ... Projection part, 24 ... Arm part, 50 ... Liquid discharge apparatus (apparatus), 53 ... Rotor (driven body) , 100: driven body.

Claims (6)

A piezoelectric actuator comprising a substantially rectangular plate-like piezoelectric element, and driving a driven body by exciting bending vibration that is bent in the short side direction of the piezoelectric element,
Protruding portions that protrude along the long side direction of the piezoelectric element and are in contact with the driven body,
A dimension of the projecting portion along the long side direction of the piezoelectric element is longer than a dimension along the short side direction of the piezoelectric element at a connection portion with the piezoelectric element. The piezoelectric actuator according to claim 1,
The piezoelectric actuator includes a longitudinal primary vibration that expands and contracts around the approximate center of the long side of the piezoelectric element, and a bending secondary vibration that vibrates point-symmetrically around the approximate center of the piezoelectric element in the short side direction of the piezoelectric element. A piezoelectric actuator characterized by being configured to vibrate in combination with. The piezoelectric actuator according to claim 1 or 2,
The tip of the protrusion is formed in a linear shape or an arc shape. The piezoelectric actuator according to any one of claims 1 to 3,
The piezoelectric actuator is characterized in that the projecting portions are provided at both ends in the long side direction of the piezoelectric element at point-symmetrical positions about the approximate center of the piezoelectric element.   A motor comprising the piezoelectric actuator according to any one of claims 1 to 4 and an output shaft that is rotationally driven by the piezoelectric actuator.   The apparatus provided with the piezoelectric actuator in any one of Claims 1-4.

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