JP4532175B2 - Piezoelectric actuator and drive device - Google Patents

Description

  The present invention relates to a piezoelectric actuator and a drive device that use shear displacement and thickness displacement of a piezoelectric body, which are used in a feeding device or the like.

  2. Description of the Related Art Conventionally, a piezoelectric actuator that connects a piezoelectric element that generates a shear displacement by applying a voltage and a piezoelectric element that generates a thickness displacement is known (for example, Patent Document 1). In the piezoelectric actuator of Patent Document 1, one of the drive legs that support the horizontal stage is obtained by connecting the piezoelectric bodies up and down, and one of the piezoelectric bodies is polarized in the vertical direction so as to be deformed in the expansion and contraction direction. . The other piezoelectric body is polarized in the horizontal direction so as to perform shear displacement. This piezoelectric actuator is configured so that three electrodes are provided so as to sandwich piezoelectric materials having different polarization directions, and by applying a voltage between the electrodes, each piezoelectric material can be expanded or contracted or sheared. Has been.

Also, some piezoelectric actuators are known that reduce the shake in the direction perpendicular to the displacement direction by adjusting the shape thereof (for example, Patent Document 2). The piezoelectric actuator described in Patent Document 2 grinds the side surface of the multilayer piezoelectric element, adjusts the shape so that the remaining surfaces are perpendicular to the surface, and the amount of elongation ΔL in the stacking direction is The ratio of the shake amount ΔR perpendicular to the stacking direction is 10% or less.
Japanese Examined Patent Publication No. 3-81119 JP 2003-46155 A

  As described above, there has been proposed a piezoelectric actuator in which piezoelectric bodies having different polarization directions are connected to increase a stroke when a driven body such as a stage is moved. In order to further speed up the movement of the driven body, there is a method of controlling the piezoelectric actuator at a high frequency to speed up the stage feed.

  However, when the vibration frequency is increased, resonance occurs in which the tip of the piezoelectric actuator swings in the direction perpendicular to the feed direction due to the shape of the piezoelectric actuator, and the driven body is slightly displaced in the direction perpendicular to the feed direction. In some cases, the displacement in the original feeding direction may not be ensured, and the drive is not stable. Therefore, in order to realize the control of the piezoelectric actuator at a high frequency, it is necessary to shift the resonance frequency in the shake direction perpendicular to the feed direction to the high frequency side and expand the non-resonance region to the high frequency side.

  An object of the present invention is to provide a piezoelectric actuator and a driving device that can increase the resonance frequency in the shake direction.

(1) In order to achieve the above object, a piezoelectric actuator of the present invention is a piezoelectric actuator comprising a rectangular expansion / contraction displacement portion and a rectangular shear displacement portion coupled in the expansion / contraction displacement direction of the expansion / contraction displacement portion. When the length in the displacement direction is H, the length in the shear displacement direction is L, the length in the direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction is W, the density is ρ, and the Young's modulus is Y, H, L, W, ρ, and Y satisfy the following relational expression: H ≦ 10 mm, L / W ≦ 2.5, ρ ≦ 8 × 10 ⁻³ kg / m ³ , and 65 GPa ≦ Y. It is said.

  As a result, the resonance frequency of the vibration in the direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction of the piezoelectric actuator becomes 12 kHz or more, and the non-resonance frequency region can be expanded. The piezoelectric actuator can be vibrated at a frequency of 10 kHz or more while suppressing the vibration in the vertical direction. As a result, for example, a piezoelectric actuator having a single vibration with a displacement in the shear displacement direction of 0.6 μm when a sinusoidal drive voltage with an amplitude of 100 V is applied is used for the stage feed device, and the stage is driven with the applied voltage. In this case, the stage drive can be stably controlled at a stage speed of 20 mm / s or more in the shear displacement direction. Therefore, it is possible to prevent the driven body from shifting in a direction perpendicular to the feed direction at a vibration speed in the normal feed direction, to ensure a stroke in the original feed direction, and to stabilize the vibration.

  (2) Further, in the driving device of the present invention, six piezoelectric actuators each including a rectangular expansion / contraction displacement section and a rectangular shear displacement section coupled in the expansion / contraction displacement direction of the expansion / contraction displacement section, and the piezoelectric actuator are fixed The piezoelectric actuators are arranged in two rows along the shear displacement direction and in three rows along a direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction. It is characterized by being arranged on a pedestal so as not to contact.

  Accordingly, the adjacent piezoelectric actuators can be alternately applied to the driven body every half cycle of the elliptical motion, and the driven body can be stably driven by the three-point support.

(3) In the driving device according to the present invention, the piezoelectric actuator has a length in the expansion / contraction displacement direction H, a length in the shear displacement direction L, and a direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction. When length is W, density is ρ, and Young's modulus is Y, H, L, W, ρ, and Y are H ≦ 10 mm, L / W ≦ 2.5, ρ ≦ 8 × 10 ⁻³ kg. / M ³ and 65 GPa ≦ Y,
It is characterized by satisfying the following relational expression.

  As a result, the driven body can be stably driven by the three-point support of the piezoelectric actuator. Furthermore, at the vibration speed in the normal feed direction, the driven body can be prevented from shifting in the direction perpendicular to the feed direction, the stroke in the original feed direction can be secured, and the vibration of the piezoelectric actuator can be stabilized. it can.

  According to the piezoelectric actuator according to the present invention, the resonance frequency of vibration in the direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction of the piezoelectric actuator is 12 kHz or more, and the non-resonance frequency region can be expanded. The piezoelectric actuator can be vibrated at a frequency of 10 kHz or more while suppressing vibration in a direction perpendicular to the direction and the shear displacement direction. As a result, for example, a piezoelectric actuator having a single vibration with a displacement in the shear displacement direction of 0.6 μm when a sinusoidal drive voltage with an amplitude of 100 V is applied is used for the stage feed device, and the stage is driven with the applied voltage. In this case, the stage drive can be stably controlled at a stage speed of 20 mm / s or more in the shear displacement direction. Therefore, it is possible to prevent the driven body from shifting in a direction perpendicular to the feed direction at a vibration speed in the normal feed direction, to ensure a stroke in the original feed direction, and to stabilize the vibration.

  Further, according to the driving device of the present invention, the adjacent piezoelectric actuators are alternately applied to the driven body every half cycle of the elliptical motion, and the driven body can be stably driven by the three-point support. it can.

  Further, according to the drive device according to the present invention, the driven body can be stably driven by the three-point support of the piezoelectric actuator. Furthermore, at the vibration speed in the normal feed direction, the driven body can be prevented from shifting in the direction perpendicular to the feed direction, the stroke in the original feed direction can be secured, and the vibration of the piezoelectric actuator can be stabilized. it can.

  Embodiments of the present invention will be described below with reference to the drawings. However, this is one embodiment, and the present invention is not limited to this embodiment.

(Embodiment 1)
FIG. 1 is a perspective view of the piezoelectric actuator 1. The piezoelectric actuator 1 includes a main body 2 and shim portions 3a and 3b. The shape of the main body 2 is rectangular, and a shear displacement portion 6 is connected to the expansion / contraction displacement portion 5 via a central plane electrode 4. The expansion / contraction displacement direction is the height direction from the fixed end of the piezoelectric actuator. The shear displacement direction is the deflection primary vibration direction of the piezoelectric actuator, and is the feed direction when the piezoelectric actuator is used for stage feed. The direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction is a shake direction with respect to the deflection primary vibration. As shown in FIG. 1, the length of the piezoelectric actuator 1 in the expansion / contraction displacement direction is H, the length in the shear displacement direction is L, and the length in the direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction is W. The expansion / contraction displacement part 5 has the piezoelectric bodies 7a and the planar electrodes 8a alternately stacked, and the shear displacement part 6 has the piezoelectric bodies 7b and the planar electrodes 8b alternately stacked. The piezoelectric body 7a is polarized in the expansion / contraction displacement direction, and the piezoelectric body 7b is polarized in the shear displacement direction. The material of the piezoelectric body 7a and the piezoelectric body 7b is a piezoelectric ceramic such as PZT. The material of the planar electrode is a conductor such as silver or palladium. For example, as for the shape and material of the piezoelectric actuator 1, H is 10 mm, L is 6 mm, W is 2.4 mm, the density is 8 × 10 ⁻³ kg / m ³ , and the Young's modulus is 65 GPa.

  By adopting such a shape, the resonance frequency of vibration in the direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction of the piezoelectric actuator 1 becomes 12 kHz or more, and the non-resonance frequency region can be expanded. The piezoelectric actuator 1 can be vibrated at a frequency of 10 kHz or more while suppressing vibration in a direction perpendicular to the direction and the shear displacement direction. As a result, for example, when the piezoelectric actuator 1 applies a sinusoidal drive voltage with an amplitude of 100 V, the displacement in the shear displacement direction is a single vibration of 0.6 μm, and this piezoelectric actuator 1 is fed to the stage. When the stage is driven by the above-mentioned applied voltage used in the apparatus, the stage drive can be stably controlled at a stage speed of 20 mm / s or more in the shear displacement direction. Therefore, it is possible to prevent the driven body from shifting in a direction perpendicular to the feed direction at a vibration speed in the normal feed direction, to ensure a stroke in the original feed direction, and to stabilize the vibration.

  The shim portions 3a and 3b are provided to be connected to both ends of the main body portion 2 in the expansion / contraction displacement direction, and the shape of the shim portion 3b provided on the end surface of the shear displacement portion 6 is the shape of a plate having protrusions. The shape of the shim portion 3a provided on the end surface of the displacement portion 5 is a plate shape. The shape of the plate having the protrusions of the shim portion 3b as shown in the drawing is an example, and may be a bowl shape or the like. The material of the shim portions 3a and 3b is an insulating material and is not particularly limited.

  On the side surfaces of the piezoelectric body 7a and the piezoelectric body 7b, a GND extraction electrode 21, an extension / displacement portion extraction electrode 22, and a shear displacement portion extraction electrode 23 are provided. Every other GND take-out electrode 21 is connected to the planar electrode 8a and the planar electrode 8b, and is also connected to the central planar electrode 4. The take-out electrodes 22 for the expansion / contraction displacement part are connected to the planar electrode 8a every other sheet. Every other shear displacement portion take-out electrode 23 is connected to the planar electrode 8b. As an example of the material of these extraction electrodes, there are conductors such as silver, palladium, and copper. The GND take-out electrode 21 is grounded via a lead wire 21a, the expansion / contraction displacement portion take-out electrode 22 is connected to an AC power source via the lead wire 22a, and the shear displacement portion take-out electrode 23 is connected via the lead wire 23a. The AC power source is connected to an AC power source having a phase difference of 90 °. Thereby, the piezoelectric actuator 1 can be vibrated so that the protrusion of the shim portion 3b draws an elliptical orbit. If the phase difference is in the vicinity of 90 °, the projection of the shim portion 3b can be moved in an elliptical orbit. In addition, by setting the phase difference due to the input voltage to each piezoelectric portion, it is possible to cause elliptical motion in either direction.

FIG. 2 is a schematic side view of the piezoelectric actuator 1 showing the polarization directions of the piezoelectric body 7a and the piezoelectric body 7b. As shown in FIG. 2, telescopic piezoelectric 7a forming the displacement portion 5 is polarized perpendicular to the direction P ₁ or P ₂ on the surface of the planar electrode 8a, the piezoelectric 7b is a plan for forming the shearing displacement portion 6 parallel to the electrode 8b, polarized in the direction parallel to Q ₁ or Q ₂ to one side of the rectangle. As shown in FIG. 2, four layers of the piezoelectric bodies 7a of the expansion / contraction displacement portion 5 are laminated here, and four layers of the piezoelectric bodies 7b of the shear displacement portion 6 are also laminated. However, the number of laminations is arbitrary, and the ratio of the number of laminations of the expansion / contraction displacement part 5 and the shear displacement part 6 may be different. Further, each may have a single layer structure instead of a laminated structure. In addition, about the expansion-contraction displacement part 5, the electrode may be formed in the inner-layer part by embedding the planar electrode 8a in the raw piezoelectric material 7a, and integrally baking.

  A method for manufacturing the piezoelectric actuator 1 will be described below. First, a piezoelectric actuator is designed in advance. For example, the length H of the piezoelectric actuator to be obtained is 10 mm, the length L of the shear displacement direction is 6 mm, and the length W of the shake direction is 2.4 mm. A PZT-based piezoelectric ceramic powder is mixed with a binder and an organic solvent to prepare a slurry.

  Next, using the slurry obtained by mixing, taking into consideration the height of the piezoelectric actuator to be obtained and the number of laminated layers, a raw sheet is produced with a doctor blade with a designed thickness. The flat electrode 8a is printed on the surface of the obtained raw sheet by a screen designed for electrode printing for the expansion / contraction displacement part and the shear displacement part, respectively. The raw sheets for the expansion / contraction displacement part are stacked, pressure-bonded, integrally fired, and processed into the designed shape. On the other hand, the raw sheet for the shear displacement portion is fired as a single plate and then processed into the designed shape.

  Next, the piezoelectric body of the expansion / contraction displacement portion 5 that is integrally fired is subjected to polarization processing in the stacking direction to produce the expansion / contraction displacement portion 5. On the other hand, the plates fired with a single plate for the shear displacement portion are each polarized so that the polarization direction is aligned with a predetermined plane direction when they are stacked, and are bonded with an adhesive so as to be laminated with electrodes sandwiched therebetween. The shear displacement portion 6 produced in this way is bonded to the expansion / contraction displacement portion 5 with the central plane electrode 4 made of phosphor bronze interposed therebetween, and the shim portions 3a and 3b are adhered to produce a piezoelectric actuator. . For the bonding, various resin adhesives are used. Here, the expansion / contraction displacement part 5 is produced by integral firing, but may be laminated by bonding and firing a single plate.

  The operation when an AC voltage is applied to the piezoelectric actuator 1 will be described below. When the piezoelectric actuator 1 is vibrated, the protrusions of the shim portion 3b draw a trajectory as shown in FIG. 3 over one period. FIG. 4 is a diagram showing the shape of the piezoelectric actuator 1 and the trajectory of the protrusion every quarter cycle. The piezoelectric actuator 1 is fixed on the pedestal 30. With respect to the piezoelectric actuator 1, a sine wave voltage is applied to the extraction electrode 22 for the expansion / contraction displacement portion, and a voltage whose phase of the sine wave is shifted by 90 ° is applied to the extraction electrode 23 for the shear displacement portion. By such a voltage input method, the expansion / contraction displacement section performs simple vibration of expansion / contraction displacement, and the shear displacement section 6 performs single vibration of shear displacement that is 90 ° out of phase with the expansion / contraction displacement of the expansion / contraction displacement section 5. Thus, as shown in FIG. 3, the protrusion of the shim portion 3b draws an elliptical trajectory of a path of A → B → C → D. Note that the trajectory of the protrusion is not necessarily an elliptical trajectory, and may be a rectangular trajectory by controlling the power source. If the phase difference of the applied voltage is in the vicinity of 90 °, the protrusion of the shim portion 3b can be moved along an elliptical orbit. Further, by setting the phase difference due to the input voltage in each piezoelectric portion, the piezoelectric actuator can be caused to make an elliptical motion in either direction.

  For example, when the piezoelectric actuator 1 is used to feed the stage, the piezoelectric actuator 1 operates as shown in FIG. 4 over one period. FIG. 4 shows the state of the piezoelectric actuator 1 every quarter cycle. As shown in FIG. 4, the shim portion 3 a on the expansion / contraction displacement portion 5 side of the piezoelectric actuator 1 is fixed to the pedestal 30, and the projection of the shim portion 3 b on the shear displacement portion 6 side contacts the stage 31, thereby 31 is driven. The operation of the piezoelectric actuator 1 at this time will be described below.

  FIG. 4A shows a state in which the expansion / contraction displacement portion 5 is fully extended, the shear displacement portion 6 is shear-displaced so as to send the shim portion 3b having the protrusion in the left direction, and the shear displacement speed is maximum. ing. The protrusion of the shim portion 3b hits the surface of the stage 31. FIG. 4B shows a state in which the contraction speed of the expansion / contraction displacement portion 5 is maximized, and the shear displacement portion has sent the shim portion 3b having a protrusion to the leftmost position. The protrusion of the shim portion 3b is separated from the surface of the stage 31. FIG. 4C shows a state in which the expansion / contraction displacement portion 5 is most contracted and the shear displacement portion 6 is sheared so as to send the shim portion 3b having a protrusion to the right, and the shear displacement speed is maximum. ing. The protrusion of the shim portion 3b is separated from the surface of the stage 31. FIG. 4D shows a state in which the extension speed of the expansion / contraction displacement portion 5 is maximized and the shear displacement portion has sent the shim portion 3b having a protrusion to the rightmost position. The protrusion of the shim portion 3b is separated from the surface of the stage 31.

(Embodiment 2)
In the first embodiment, the piezoelectric actuator 1 has been described. However, such a piezoelectric actuator may be fixed in a 3 × 2 arrangement on a pedestal to serve as a driving device. FIG. 5 is a perspective view of a driving device 40 including a piezoelectric actuator. The piezoelectric actuators 41 to 46 are piezoelectric actuators including the rectangular expansion / contraction displacement portion and the rectangular shear displacement portion described in the first embodiment. The pedestal 50 is made of SUS having a rectangular shape, a density of 7.93 × 10 ⁻³ kg / m ³ , and a Young's modulus of 210 GPa. The shape of the base 50 is, for example, 10 mm high, 14 mm wide, and 28 mm long. However, the shape and material of the pedestal 50 are sufficient as long as they do not cause deformation or resonance due to vibration of the piezoelectric actuator, and are not limited to the above. For example, the pedestal 50 may be made of ceramics. As shown in FIG. 5, the piezoelectric actuators 41 to 46 are arranged in two rows in the shaking direction and in three rows in the feeding direction at intervals that do not contact each other when vibrated, and are fixed to the pedestal 50. Yes.

  Next, the operation of the driving device 40 will be described. To each piezoelectric actuator of the driving device 40, an AC voltage having a phase difference of ½ cycle is applied to adjacent piezoelectric actuators to operate the driving device 40. For example, when the piezoelectric actuators 41, 43, and 45 shown in FIG. 5 are synchronized and vibrated at the same phase θ, the piezoelectric actuators 42, 44, and 46 are also synchronized and vibrated at the same phase θ + 180 °. 6 (a) and 6 (b) are plan views of the driving device 40 at a time point different from each other by a half cycle, and the piezo-electric actuators with diagonal lines indicate the piezo-electric actuators that are in contact with the stage that is the driven body. ing. Therefore, the driving device 40 drives the stage by alternately applying three piezoelectric actuators that are not adjacent to the stage. Thereby, adjacent piezoelectric actuators can be brought into contact with the driven body alternately every half cycle of the elliptical motion, and the stage can be stably fed by supporting three points.

  FIG. 7 is a schematic side view of the driving device 40 that performs the above-described operation. (A)-(d) of FIG. 7 has each shown the state for every 1/4 period when the drive device 40 is operated. The piezoelectric actuators installed adjacent to each other are vibrated while changing the phase by a half cycle, and the elliptical orbit of each piezoelectric actuator is repeated, whereby the stage 51 as a driven body is placed in one of the shear displacement directions of the piezoelectric actuator. Move. The arrows in the figure schematically represent the speed of each part. In FIG. 7, the piezoelectric actuators 42, 43, 45, 46 are omitted.

The present inventors have found that the resonance frequency in the shake direction of the piezoelectric actuator varies depending on the shape of the piezoelectric actuator. Therefore, by forming a piezoelectric actuator having an appropriate shape, the resonance frequency in the shake direction can be shifted to the high frequency side. When the resonance frequency is shifted to the high frequency side, as shown in FIG. 8, it is possible to enlarge the resonance region that becomes the base of the peak. For example, it is possible to a maximum driving frequency negligible vibrations shake directions increasing from X ₁ to X _2, avoiding the vibration direction of blur when caused to vibrate at frequencies of X ₁ to X _2. The difference between the resonance frequency and the maximum frequency that can be used as the non-resonance region is preferably about 2 kHz, for example.

  Based on this principle, a finite element method simulation was performed on a piezoelectric actuator by a computer in order to avoid resonance in the shake direction. MARC / MENTAT 2004 (MS Software Co., Ltd.) was used as a simulation program.

At the time of simulation, the shape and material data of the drive device having the same configuration as that of the drive device 40 were input, and the resonance frequency was examined. As a piezoelectric ceramic, a physical property value is input assuming that a PZT ceramic having a density of 7.6 × 10 ⁻³ kg / m ³ and a Young's modulus of 65 GPa is used, and the piezoelectric actuator has a density of 8.0 × 10 ⁻³ kg / m. ^{3. The} values were input so that the Young's modulus was 65 GPa, the stretch displacement direction length H was 4 to 10 mm, the shear displacement direction length L was 6 to 12 mm, and the blur direction length W was 2 to 12 mm. Assuming that the pedestal is made of SUS having a density of 7.93 × 10 ⁻³ kg / m ³ and a Young's modulus of 210 GPa, the length in the expansion / contraction displacement direction is 10 mm, the shear displacement direction length is 28 mm, and the blur direction length is 14 mm. did. The shape and material of the base are not particularly limited as long as the influence on the piezoelectric actuator can be ignored.

  FIG. 9 is a diagram showing the relationship between the shape of the piezoelectric actuator and the lowest resonance frequency. As shown in FIG. 9, the resonance frequency tends to increase as L / W decreases, and the resonance frequency tends to increase as H decreases. Further, the resonance frequency increases as the material density decreases, and the resonance frequency increases as the Young's modulus increases.

  On the other hand, a feed rate of 20 mm / s is generally desired in order for the stage feed device to sufficiently perform the function of stage feed in a process that is actually used. In the drive device using the piezoelectric actuator as described above, in order to obtain a feed rate of 20 mm / s, the displacement capacity when a sinusoidal drive voltage with an amplitude of 100 V is applied is 0.6 μm. The frequency needs to be 10 kHz or more. For this purpose, the minimum resonance frequency must be 12 kHz or more in consideration of the width from the peak to the base.

From the result of the above simulation, if the piezoelectric actuator has the characteristics of L / W ≦ 2.5, H ≦ 10 mm, ρ ≦ 8.0 × 10 ⁻³ kg / m ³ and 65 GPa ≦ Y, the minimum resonance The frequency becomes 12 kHz or more, and the drive device 40 can be vibrated at 10 kHz or more without causing resonance of lateral vibration. Therefore, it was proved that the stage feeding apparatus using this piezoelectric actuator can realize a feeding speed of 20 mm / s and can sufficiently perform the stage feeding function required in the actual process.

Similarly, from the above simulation results, if the piezoelectric actuator has the characteristics of L / W ≦ 2, H ≦ 10 mm, ρ ≦ 8.0 × 10 ⁻³ kg / m ³ and 65 GPa ≦ Y, the minimum The resonance frequency of the drive device 40 becomes 14 kHz or more, and the drive device 40 can be vibrated at 12 kHz or more without causing resonance of lateral vibration. Therefore, it has been proved that the stage feed device using this piezoelectric actuator can realize a feed speed of 25 mm / s and can perform the stage feed function required in the actual process with a margin.

1 is a perspective view of a piezoelectric actuator according to the present invention. 1 is a schematic side view of a piezoelectric actuator according to the present invention. It is a figure which shows operation | movement of the piezoelectric actuator which concerns on this invention. It is a figure which shows operation | movement of the piezoelectric actuator which concerns on this invention. It is a perspective view of the drive device concerning the present invention. It is a top view of the drive device concerning the present invention. It is a figure which shows operation | movement of the drive device which concerns on this invention. It is a figure which shows the vibration speed of the shake direction with respect to the drive frequency of a piezoelectric actuator. It is a figure which shows the result of simulation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 4 Planar electrode 5 Expansion / contraction displacement part 6 Shear displacement part 30 Base 40 Drive apparatus 41-46 Piezoelectric actuator 50 Base

Claims (2)

A piezoelectric actuator comprising a rectangular expansion / contraction displacement portion and a rectangular shear displacement portion coupled in the expansion / contraction displacement direction of the expansion / contraction displacement portion,
When the length in the elastic displacement direction is H, the length in the shear displacement direction is L, the length in the direction perpendicular to the elastic displacement direction and the shear displacement direction is W, the density is ρ, and the Young's modulus is Y ,
Said H, L, W, ρ and Y are
H ≦ 10 mm,
L / W ≦ 2.5,
ρ ≦ 8 × 10 ⁻³ kg / m ³ and 65 GPa ≦ Y,
By satisfying the relational expression,
A piezoelectric actuator characterized by shifting a resonance frequency in a shake direction perpendicular to a feed direction to a high frequency side . 6. The piezoelectric actuator according to claim 1 , comprising: a rectangular expansion / contraction displacement portion and a rectangular shear displacement portion coupled in the expansion / contraction displacement direction of the expansion / contraction displacement portion;
A pedestal on which the piezoelectric actuator is fixed;
The piezoelectric actuators are arranged on a pedestal so as not to contact each other in two rows along the shear displacement direction and in three rows along a direction perpendicular to the expansion / contraction displacement direction and the shear displacement direction. A drive device characterized by the above.

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