JP2009219280A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the driving efficiency of a piezoelectric actuator with a simple configuration. <P>SOLUTION: A through-hole 12 penetrating in an axial direction is formed on a cubic stator 11, and a shaft 13 is attached on the through-hole 12 so as to be freely linearly reciprocate. Piezoelectric ceramics 14 as vibration sources are each provided on the outer peripheral surface of the stator 11, two electrodes 15, 16 are formed in an axial direction on the outer surface of each of the piezoelectric ceramics 14, and the inside of each of the piezoelectric ceramics 14 is grounded via the stator 11. When an AC voltage having different phase is applied to each of the electrodes 15, 16, an elliptic movement of an axial direction is formed on the inner peripheral surface of the through-hole 12 and the shaft 13 is driven by friction in the axial direction. A slit 23 cut deep in the center direction is formed on the shaft 13, and this slit 23 works as a setting portion for setting frictional contact pressure between the outer peripheral surface of the shaft 13 and the inner peripheral surface of the stator 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator that drives a shaft straight or rotationally.

  A rotary ultrasonic motor is used to rotationally drive the driven member, and a linear ultrasonic motor is used to drive the driven member linearly. These actuators drive the driven member by converting the elastic vibration of the vibrating body into the motion of the driven member by a frictional force. The vibrating body is formed of an elastic body such as a metal and a piezoelectric element bonded thereto, and the ultrasonic motor is also referred to as a piezoelectric actuator.

  As a rotary-type piezoelectric actuator, Patent Document 1 discloses an ultrasonic motor having a disk-shaped stator having a vibrating body provided on the outer peripheral portion and a rotating shaft provided with a rotor that contacts the vibrating body. ing. As a linear type piezoelectric actuator, Patent Document 2 describes a linear motor in which a linear belt-like elastic body provided with a plurality of protrusions is vibrated by a piezoelectric vibrator and a moving body arranged on the protrusions is driven linearly. ing.

For an ultrasonic motor, a standing wave method in which an AC voltage is applied to a piezoelectric element and the driven member is driven by its elastic vibration, and an AC voltage having a predetermined phase difference is applied to a pair of piezoelectric elements. There is a traveling wave system in which a driven member is driven by a traveling wave generated by elastic vibration. In the traveling wave type ultrasonic motor, the driven member is driven in a direction opposite to the traveling direction of the traveling wave by frictional driving by the elliptical motion of the surface of the driven member.
JP-A-2-159984 JP 2001-21670 A

  Traveling wave type ultrasonic motors frictionally drive a moving body by the elliptical motion of the surface of a vibrating body as the traveling wave progresses, and a rotary piezoelectric actuator is used to efficiently apply this frictional force to the moving body. In Patent Document 1, a spring member such as a disc spring is assembled between the rotating shaft and the rotor as described in Patent Document 1. Also in the linear type piezoelectric actuator, a pressing force is applied to the belt-like elastic body by a spring member or the like to the moving body that is linearly driven.

  Piezoelectric actuators have the advantage that they can be reduced in size compared to electromagnetic or fluid actuators because they convert the elastic vibration of the vibrating body into rotational or linear motion of the driven member by friction. It has been put to practical use in camera autofocus mechanisms and surgical microscopes. However, in order to apply a frictional force between the vibrating body and the driven member, it is necessary to incorporate a spring member into the piezoelectric actuator, and there is a limit to downsizing the piezoelectric actuator. Moreover, since the structure of the vibrating body is different between the rotary type and the linear type, the basic structure is completely different from each other, and the rotary type and the linear type are not compatible.

  In order to reduce the size of the piezoelectric actuator and to achieve both linear drive and rotational drive with a single piezoelectric actuator, an outer periphery that forms a through hole in a cube-shaped stator and frictionally engages the inner peripheral surface of the through hole. There has been proposed a piezoelectric actuator in which a shaft-like driven member having a surface is provided and piezoelectric elements polarized in the thickness direction are attached to four outer peripheral surfaces surrounding the through hole of the stator.

  In this piezoelectric actuator, when sinusoidal AC voltages whose phases are different from each other by 90 ° are applied to the four piezoelectric elements provided in the circumferential direction, the piezoelectric elements rotate to the inner circumferential surface of the through hole of the stator by expansion and contraction in the width direction. An elliptical motion in the direction is generated, and the driven member is driven to rotate about its axis. Further, when two electrodes separated in the axial direction are provided on each of the piezoelectric elements and a sinusoidal AC voltage having a phase difference of 90 ° is applied to the two electrodes, the stator penetrates due to the expansion and contraction of each piezoelectric element in the axial direction. An elliptical motion in the axial direction is generated on the inner peripheral surface of the hole, and the driven member is linearly driven in the axial direction.

  However, in the above piezoelectric actuator, the vibration on the stator side is transmitted to the driven member by frictional force to drive the driven member. Therefore, in order to increase the driving efficiency, the outer peripheral surface of the driven member and the stator A mechanism for obtaining an appropriate frictional force between the inner peripheral surface of the through hole of the stator and the outer peripheral surface of the driven member or the inner peripheral surface of the through hole of the stator. In some cases, the driving force cannot be efficiently transmitted to the driven member.

  An object of the present invention is to improve the driving efficiency of a piezoelectric actuator with a simple configuration.

  The piezoelectric actuator of the present invention is a piezoelectric actuator that linearly drives a shaft in its axial direction, and has a through-hole having an inner peripheral surface that frictionally engages with the outer peripheral surface of the shaft, and the shaft can freely reciprocate linearly. A stator mounted on the stator, a piezoelectric element provided on the outer peripheral surface of the stator, and at least two electrodes that are electrically separated in the axial direction of the shaft and apply alternating voltages having different phases to the piezoelectric element. And a setting portion that is provided on at least one of the shaft and the stator and sets a frictional contact pressure between the outer peripheral surface of the shaft and the inner peripheral surface of the stator.

  The piezoelectric actuator according to the present invention is a piezoelectric actuator that linearly drives a shaft in its axial direction, and has a through hole having an inner peripheral surface that frictionally engages with the outer peripheral surface of the shaft, and the shaft can freely reciprocate linearly. A stator mounted on the stator, at least two piezoelectric elements provided in the axial direction of the shaft on the outer peripheral surface of the stator, electrodes for applying alternating voltages having different phases to the piezoelectric elements, the shaft, and the shaft It is provided in at least one of the stators, and has a setting part for setting a friction contact pressure between the outer peripheral surface of the shaft and the inner peripheral surface of the stator.

  The piezoelectric actuator of the present invention is a piezoelectric actuator that rotationally drives a shaft about its axis, and has a through hole having an inner peripheral surface that frictionally engages with the outer peripheral surface of the shaft, and the shaft is rotatably mounted. Stator, at least two piezoelectric elements respectively provided on the outer peripheral surface of the stator so as to be shifted from each other in the rotation direction of the shaft, and AC voltages having different phases are provided to the piezoelectric elements. It has an electrode for applying, and a setting part which is provided in at least one of the shaft and the stator and sets a friction contact pressure between the outer peripheral surface of the shaft and the inner peripheral surface of the stator.

  The piezoelectric actuator of the present invention is characterized in that the piezoelectric elements are provided on the stator so as to face each other around the shaft. In the piezoelectric actuator according to the aspect of the invention, the stator may be a substantially rectangular parallelepiped or a cube having a planar portion in the through hole forming direction, and the piezoelectric element is provided in each of the planar portions. .

  The piezoelectric actuator of the present invention is a piezoelectric actuator that linearly drives the shaft in its axial direction and rotationally drives its shaft center, and has a through hole having an inner peripheral surface that frictionally engages with the outer peripheral surface of the shaft, A stator on which the shaft is mounted so as to be linearly reciprocable and rotatable; a first piezoelectric element provided on an outer peripheral surface of the stator; and the first piezoelectric element that is electrically separated in an axial direction of the shaft. At least two electrodes for applying alternating voltages having different phases to each other, at least two second piezoelectric elements respectively provided on the outer peripheral surface of the stator so as to be shifted in the rotational direction of the shaft, and the second An electrode for applying an alternating voltage having a different phase to each of the second piezoelectric elements; and at least one of the shaft and the stator. It provided towards, and having a setting unit for setting the frictional contact pressure between the outer peripheral surface and the inner peripheral surface of said stator of said shaft.

  In the piezoelectric actuator according to the present invention, the electrodes provided in the second piezoelectric elements are electrically separated in the axial direction of the shaft. The piezoelectric actuator according to the present invention is characterized in that the first piezoelectric element and the second piezoelectric element are provided in the stator while being axially displaced from each other.

  The piezoelectric actuator of the present invention is characterized in that the first piezoelectric element and the second piezoelectric element are provided in the stator so as to be shifted from each other in the rotational direction. The piezoelectric actuator of the present invention is characterized in that the first piezoelectric element and the second piezoelectric element are provided on the stator so as to face each other with the shaft as a center.

  In the piezoelectric actuator according to the aspect of the invention, the setting portion may be a slit that is cut in a lateral direction in the shaft and extends in the axial direction, and sets the frictional contact pressure by elastic deformation of the shaft. In the piezoelectric actuator according to the aspect of the invention, the setting unit may be a slit that is cut in the stator in the lateral direction and extends in the axial direction, and sets the frictional contact pressure by elastic deformation of the stator. The piezoelectric actuator according to the present invention is characterized in that a slider made of a wear-resistant material is provided on one of the shaft and the stator.

  According to the present invention, since the setting portion for setting the frictional contact pressure between the outer peripheral surface of the shaft and the inner peripheral surface of the stator is provided on at least one of the shaft and the stator, the driving efficiency of the piezoelectric actuator is improved with a simple configuration. In addition, since it is not necessary to provide a spring member or the like for applying the frictional contact pressure, the size can be reduced.

  In addition, even when the outer peripheral surface of the shaft or the inner peripheral surface of the stator is worn, the outer peripheral surface of the shaft is pressed against the inner peripheral surface of the stator by frictional contact pressure, so that it is possible to prevent a decrease in drive efficiency. It becomes. In addition, by adjusting the frictional contact pressure, if the shaft and the stator are set to be in close contact with each other, the shaft is held by the stator even when stopped, so it is possible to prevent the shaft from moving when stopped. It becomes.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 is a perspective view of a piezoelectric actuator according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line 2-2 in FIG. 1, and FIG. 3 is a sectional view taken along line 3-3 of the stator in FIG. 4 is a circuit diagram showing a connection state between the piezoelectric actuator shown in FIG. 1 and an AC power supply, and FIG. 5 is a schematic sectional view showing an operation principle of the piezoelectric actuator shown in FIG.

  The piezoelectric actuator 10a is a piezoelectric actuator for linear drive, and has a substantially cubic metal stator 11 as shown in FIG. As shown in FIGS. 2 and 3, the stator 11 is formed with a through-hole 12 having a rectangular cross section penetrating in the axial direction (lateral direction in FIG. 3), and the through-hole 12 has a rectangular cross section extending in the axial direction. A hollow shaft 13 having a shape is slidably inserted. The outer peripheral surface of the shaft 13 as a driven member is frictionally engaged with the inner peripheral surface 12 a of the through hole 12, and the shaft 13 is mounted on the stator 11 so as to be linearly reciprocable.

  For example, phosphor bronze is used as the stator 11 in terms of wear resistance and vibration temperature characteristics, but the stator 11 is not limited to this. The shaft 13 is made of, for example, stainless steel or aluminum, but is not limited thereto. The through hole 12 and the shaft 13 are not limited to a rectangular cross section, and may be, for example, a circular cross section. The cross sectional shape is arbitrary, but when the rotation of the shaft 13 itself is restricted, the cross sectional shape is a quadrangle. Of course, any shape may be used as long as the shape is a square or a hexagon, and the shaft 13 is not limited to a hollow shape.

  The outer periphery of the stator 11 has four flat portions that are flat in the direction in which the through holes 12 are formed, corresponding to the inner peripheral surface 12a. As shown in FIG. A piezoelectric ceramic 14 as a source is attached by pasting or the like. The four piezoelectric ceramics 14 and the stator 11 form a linear motion vibrating body that drives the shaft 13 to move straight in the axial direction. The piezoelectric ceramics 14 are provided on the outer peripheral surface of the stator 11 so as to face each other around the shaft 13. The linearly acting stator 11 may have a shape having at least one plane portion so that at least one piezoelectric ceramic 14 is provided, and may be, for example, a substantially rectangular parallelepiped shape.

  Each piezoelectric ceramic 14 is polarized in the thickness direction. When a voltage in the same direction as the polarization direction is applied, the piezoelectric ceramic 14 contracts in the axial direction of the shaft 13, and when a voltage in the direction opposite to the polarization direction is applied, the axis of the shaft 13 is applied. Stretch in the direction. As the piezoelectric ceramic 14, barium titanate, lead titanium zirconate, or the like is used, but is not limited thereto.

  As shown in FIGS. 1 and 3, the outer surface of the piezoelectric ceramic 14 (the surface opposite to the stator 11) has two electrodes 15 and 16 that are electrically separated in the axial direction of the shaft 13. Electrodes are formed, and the electrodes 15 and 16 provided so as to be shifted from each other in the axial direction are connected to an electric circuit by lead wires (not shown). Two electrodes formed on the outer surface of the piezoelectric ceramic 14 for linear motion constitute a pair of electrodes, and in order to apply alternating voltages having different phases, at least two electrodes are necessary.

  On the other hand, an electrode 17 is formed on the inner surface of the piezoelectric ceramic 14 (the surface on the stator 11 side) corresponding to the electrodes 15 and 16, and the piezoelectric ceramic 14 is attached to the outer peripheral surface of the stator 11 via the electrode 17. ing. The electrode 17 is in electrical contact with the stator 11, and when the stator 11 is grounded, one side of each piezoelectric ceramic 14 is grounded.

  As shown in FIG. 4, each electrode 15 is connected to an AC power source 18, and each electrode 16 is connected to an AC power source 19. The AC power supplies 18 and 19 constitute a direct-acting power supply unit that applies sinusoidal AC voltages having the same resonance frequency and the same amplitude and different phases by 90 ° to the piezoelectric ceramics 14 via the electrodes 15 and 16. is doing.

  In this way, each piezoelectric ceramic 14 is provided with the two electrodes 15 and 16 that are electrically separated in the axial direction of the shaft 13, so that the first expansion region 20 provided with the first electrode 15 and the first expansion region 20 are provided. It has two expansion / contraction regions in the axial direction with the second expansion / contraction region 21 provided with the two electrodes 16, and these constitute a vibration source for linear motion. By attaching two piezoelectric ceramics to the flat portion of the outer surface of the stator 11 in the axial direction of the shaft 13, two expansion regions are provided in the axial direction so as to constitute a vibration source for linear motion. Also good. Alternatively, the electrode 17 may be formed of two electrodes corresponding to the electrodes 15 and 16, or one side of the piezoelectric ceramic 14 may be directly attached to the outer peripheral surface of the stator 11 without providing the electrode 17.

  The AC voltages of the AC power supplies 18 and 19 are sinusoidal and 90 ° out of phase with each other. As shown in FIG. 5, elastic vibrations due to expansion and contraction are generated in the expansion and contraction regions 20 and 21, respectively. FIGS. 5A to 5D show states of this elastic vibration every quarter period. When a voltage in a direction opposite to the polarization direction of the piezoelectric ceramic 14 is applied to the electrodes 15 and 16, the stretchable region 20. , 21 are stretched to the state shown in FIG. 5A, and when the voltage in the same direction as the polarization direction is applied to the electrode 15 and the voltage in the direction opposite to the polarization direction is applied to the electrode 16, the stretchable region 20 contracts. However, the stretchable region 21 is stretched to the state shown in FIG. Further, when a voltage in the same direction as the polarization direction of the piezoelectric ceramic 14 is applied to the electrodes 15 and 16, the stretchable regions 20 and 21 are both contracted to the state shown in FIG. 5C, and the electrode 15 is opposite to the polarization direction. When a voltage in the direction is applied and a voltage in the same direction as the polarization direction is applied to the electrode 16, the stretchable region 20 is stretched, but the stretchable region 21 is contracted to a state shown in FIG.

  By applying a sinusoidal AC voltage having a phase difference of 90 ° to the electrodes 15 and 16, the states shown in FIGS. 5A to 5D change continuously as described above, and an AC voltage is applied. While continuing, elastic vibration due to expansion and contraction is repeated. As shown in FIGS. 5A to 5D, the piezoelectric ceramic 14 expands and contracts in the axial direction of the shaft 13 on the inner peripheral surface 12 a of the through-hole 12. A wavefront of a traveling wave traveling in the left direction is formed.

  When the traveling wave formed on the inner peripheral surface 12a travels, the contact portion between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 changes continuously in the traveling direction. If this change is seen about any one point of the inner peripheral surface 12a of the through-hole 12, the elliptical motion is carried out counterclockwise in a figure with progress of a traveling wave. As shown in FIG. 5C, the inner peripheral surface 12a of the stator 11 and the outer peripheral surface of the shaft 13 come into contact with each other at the apex of the elliptical motion, and a frictional force opposite to the traveling direction of the traveling wave acts. The shaft 13 is friction-driven in the right direction in FIG. 5 which is opposite to the traveling direction of the traveling wave.

  In this way, a sinusoidal AC voltage having a phase difference of 90 ° is applied to the electrodes 15 and 16 formed by being electrically separated in the axial direction from the piezoelectric ceramic 14 provided on the outer peripheral surface of the stator 11. Thus, a wavefront of the traveling wave in the axial direction is formed on the inner peripheral surface 12a of the through hole 12, and an elliptical motion in the axial direction occurs on the inner peripheral surface 12a of the through hole 12. By this elliptical motion, the shaft 13 having the outer peripheral surface frictionally engaged with the inner peripheral surface 12a is friction-driven in the direction opposite to the traveling direction of the traveling wave. Accordingly, since the driving force can be transmitted to the entire outer peripheral surface of the shaft 13 existing in the through hole 12 of the stator 11 via the frictional force, the piezoelectric actuator 10a for driving the shaft 13 straightly in the axial direction thereof can be reduced in size. Can be Conversely, when the traveling direction of the traveling wave is reversed in the right direction in FIG. 5, the linear drive direction of the shaft 13 is reversed.

  As shown in FIG. 1, the shaft 13 is formed with a slit 23 that is cut in the central direction and extends in the axial direction. The slit 23 is a friction between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12 a of the stator 11. It is a setting unit that sets the contact pressure. By forming the slit 23 in the shaft 13, the shaft 13 can be elastically deformed in the direction of narrowing the interval between the slits 23. After the shaft 13 is mounted in the through hole 12 of the stator 11, the shaft 13 is elastically restored. An appropriate frictional contact pressure can be applied between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 by the force. Therefore, a frictional force can be generated with a simple configuration between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11, and the driving efficiency of the piezoelectric actuator 10a can be improved. Since the frictional contact pressure can be generated, it is not necessary to provide a spring member or the like for applying the frictional contact pressure, and the piezoelectric actuator 10a can be downsized.

  Further, since the outer peripheral surface of the shaft 13 is pressed against the inner peripheral surface 12a of the stator 11 by the frictional contact pressure, the driving efficiency is improved even when the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 are worn by use. A decrease can be prevented. Furthermore, if the shaft 13 is set so as to be strongly pressed against the inner peripheral surface 12a of the stator 11 by adjusting the frictional contact pressure, the shaft 13 has a holding force to hold the shaft 13 on the stator 11 even when stopped. Therefore, it is possible to prevent the movement of the shaft 13 at the time of stopping.

  Stoppers 24 projecting in the lateral direction (width direction) are attached to the outer peripheral surfaces of both axial end portions of the shaft 13, and the maximum displacement amount of the axial displacement of the shaft 13 is defined, and the stator 11 of the shaft 13. Prevents from falling out. The stopper 24 is not necessarily attached to the shaft 13, and may be attached to the outside of the stator 11 or the piezoelectric actuator 10a.

  Further, in this type of piezoelectric actuator, the expansion and contraction of the vibrating body that forms the traveling wave is on the order of microns, and the displacement amount in one cycle is extremely small. In order to prevent this vibration from propagating to other devices and a decrease in driving efficiency due to the vibration, the stator 11 is fixed via a vibration isolating support base 25. Note that the shaft 13 may be fixed via the anti-vibration support base 25.

  In the present embodiment, two electrodes 15 and 16 that are electrically separated are formed on the piezoelectric ceramic 14, and an AC voltage having a phase difference of 90 ° is applied to the electrodes 15 and 16, so that the inner circumference of the through-hole 12 Although the shaft 13 is driven linearly by generating an elliptical motion in the axial direction on the surface 12a, two piezoelectric ceramics are attached to the outer peripheral surface of the stator 11 in the axial direction of the shaft 13, and the two piezoelectric ceramics are attached to the two piezoelectric ceramics. An AC voltage having a phase difference of 90 ° may be applied to generate an elliptical motion in the axial direction on the inner peripheral surface 12a of the through hole 12 so that the shaft 13 is driven straight.

  6 is a perspective view of a piezoelectric actuator according to another embodiment of the present invention, FIG. 7 is a sectional view taken along line 7-7 in FIG. 6, and FIG. 8 is a connection between the piezoelectric actuator shown in FIG. It is a circuit diagram which shows a state. In these drawings, members common to the above-described piezoelectric actuator are given the same reference numerals.

  This piezoelectric actuator 10b is a piezoelectric actuator for rotational driving, and as shown in FIG. 7, a substantially cubic metal stator 11 is formed with a through-hole 12 having a circular cross section penetrating in the axial direction. . A hollow shaft 13 having a circular cross section extending in the axial direction is slidably inserted into the through hole 12. The shaft 13 as a driven member is frictionally engaged with an inner peripheral surface 12a of the through hole 12 via a slider, which will be described later, provided on the outer peripheral surface, and the shaft 13 is rotatably mounted on the stator 11. .

  The outer periphery of the stator 11 has four flat portions flattened in the direction in which the through-holes 12 are formed. Piezoelectric ceramics 28 as vibration sources are attached to the respective flat portions as shown in FIG. It is attached by etc. The four piezoelectric ceramics 28 and the stator 11 form a rotating vibrating body that rotates the shaft 13 about its axis. Since at least two piezoelectric ceramics 28 for rotation are required in the rotation direction of the shaft 13, the stator 11 for rotation has a shape having at least two plane portions provided so as to be shifted from each other in the rotation direction of the shaft 13. For example, a substantially rectangular parallelepiped shape may be used. Furthermore, in consideration of driving stability and the like, it is preferable to provide three or more, particularly four piezoelectric ceramics 28 for rotation in the rotation direction of the shaft 13, and the stator 11 is provided so as to be shifted from each other in the rotation direction. Further, it is preferable to have a shape having at least three, preferably four flat portions.

  The piezoelectric ceramics 28 are provided on the outer peripheral surface of the stator 11 so as to face each other with the shaft 13 as a center and are shifted from each other in the rotation direction of the shaft 13. Each piezoelectric ceramic 28 is polarized in the thickness direction. When a voltage in the same direction as the polarization direction is applied, the piezoelectric ceramic 28 contracts in the width direction orthogonal to the shaft 13, and when a voltage in the direction opposite to the polarization direction is applied, the shaft 13. It extends | stretches in the width direction orthogonal to.

  As shown in FIG. 7, electrodes 29 to 32 are formed on the outer surfaces (surfaces opposite to the stator 11) of the four piezoelectric ceramics 28 as rotation drive electrodes, which are electrically connected by lead wires (not shown). Connected to the circuit. On the other hand, the electrode 17 is formed on the inner surface of the piezoelectric ceramic 28 (the surface on the stator 11 side) corresponding to the electrodes 29 to 32, and the piezoelectric ceramic 28 is attached to the outer peripheral surface of the stator 11 via the electrode 17. It has been. The electrode 17 is in electrical contact with the stator 11, and one side of each piezoelectric ceramic 28 is in a grounded state by the stator 11 being grounded.

  As shown in FIG. 8, the electrodes 29 to 32 are connected to AC power sources 33 to 36, respectively. The AC power supplies 33 to 36 are rotating power supply units that apply sinusoidal AC voltages having the same resonance frequency and the same amplitude and different phases by 90 ° to the piezoelectric ceramics 28 via the electrodes 29 to 32. It is composed.

  As described above, the four piezoelectric ceramics 28 are arranged separately in the rotation direction, and thereby, the first stretchable region 37 provided with the first electrode 29 and the second electrode 30 are provided. The structure has a second stretchable region 38, a third stretchable region 39 provided with the third electrode 31, and a fourth stretchable region 40 provided with the fourth electrode 32.

  The AC voltages of the AC power sources 33 to 36 are 90 ° out of phase with each other, and generate elastic vibrations in the expansion / contraction regions 37 to 40 provided in the stator 11 while being shifted in the rotation direction of the shaft 13. Yes. On the inner peripheral surface 12a of the through-hole 12 of the stator 11, the wavefront of the traveling wave traveling in the counterclockwise rotation direction in FIG. 7 as the four piezoelectric ceramics 28 expand and contract in the width direction orthogonal to the shaft 13. Is formed. That is, the wave front of the traveling wave of the elastic vibration is formed on the inner peripheral surface 12a by the elastic vibration of each of the expansion / contraction regions 37 to 40 on the inner peripheral surface 12a. Due to the progress of the traveling wave, an elliptical motion is generated in the rotational direction on the inner peripheral surface 12a of the stator 11, and the direction of travel of the traveling wave is opposite between the inner peripheral surface 12a of the stator 11 and the outer peripheral surface of the shaft 13. The frictional force acts, and the shaft 13 is frictionally driven in the clockwise rotation direction opposite to the traveling direction of the traveling wave.

  In this way, by applying alternating voltages whose phases are different from each other by 90 ° to the electrodes 29 to 32 formed on the piezoelectric ceramics 28 provided on the outer peripheral surface of the stator 11 so as to be shifted from each other in the rotation direction, the through holes 12 are provided. A wavefront of a traveling wave in the rotational direction is formed on the inner peripheral surface 12a, and an elliptical motion in the rotational direction is generated on the inner peripheral surface 12a. By this elliptical motion, the shaft 13 having the outer peripheral surface frictionally engaged with the inner peripheral surface 12a is friction-driven in the direction opposite to the traveling direction of the traveling wave. Accordingly, since the driving force can be transmitted to the entire outer peripheral surface of the shaft 13 existing in the through hole 12 of the stator 11 via the frictional force, the piezoelectric actuator 10b that rotationally drives the shaft 13 about its axis is reduced in size. Can be Conversely, when the traveling direction of the traveling wave formed on the inner peripheral surface 12a is reversed in the clockwise direction in FIG. 7, the rotational driving direction of the shaft 13 is reversed.

  As shown in FIGS. 6 and 7, a slider 41 made of a wear-resistant material is provided on the outer peripheral surface of the shaft 13, and the shaft 13 is frictionally engaged with the inner peripheral surface 12 a of the through hole 12 via the slider 41. It is the composition which matches. Since the slider 41 reduces wear on the inner peripheral surface 12a of the through hole 12 and the outer peripheral surface of the shaft 13, it is possible to prevent a decrease in driving efficiency of the piezoelectric actuator 10b and to prevent sound during driving of the shaft 13. An effect is obtained.

  The shaft 13 and the slider 41 are formed with slits 23 that are cut in the center direction and extend in the axial direction. The slits 23 are formed between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12 a of the stator 11 via the slider 41. It is a setting unit for setting the friction contact pressure. By forming the slits 23 in the shaft 13 and the slider 41, the shaft 13 can be elastically deformed in the direction of narrowing the interval between the slits 23, and after the shaft 13 is mounted in the through hole 12 of the stator 11, the shaft 13 An appropriate frictional contact pressure can be applied between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12 a of the stator 11 via the slider 41 by the elastic restoring force 13. Therefore, a frictional force can be generated between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 via the slider 41, and the driving efficiency of the piezoelectric actuator 10b can be improved. Since the frictional contact pressure can be applied by the shaft 13 itself, it is not necessary to provide a spring member or the like for applying the frictional contact pressure, and the piezoelectric actuator 10b can be downsized.

  Further, since the outer peripheral surface of the shaft 13 is pressed against the inner peripheral surface 12a of the stator 11 by frictional contact pressure, the outer peripheral surface of the slider 41 provided on the shaft 13 and the inner peripheral surface 12a of the stator 11 are worn by use. In this case, it is possible to prevent the driving efficiency from being lowered. Furthermore, if the shaft 13 is set so as to be strongly pressed against the inner peripheral surface 12a of the stator 11 by adjusting the frictional contact pressure, the shaft 13 has a holding force to hold the shaft 13 on the stator 11 even when stopped. Therefore, it is possible to prevent the rotation of the shaft 13 at the time of stopping.

  Stoppers 24 projecting in the lateral direction (width direction) are attached to the outer peripheral surfaces of both axial ends of the shaft 13 to prevent the shaft 13 from coming off from the stator 11. Further, the stator 11 is fixed via a vibration isolation support base 25.

  9 is a perspective view of a piezoelectric actuator according to another embodiment of the present invention, FIG. 10 is a sectional view taken along line 10-10 in FIG. 9, and FIG. 11 is a sectional view taken along line 11-11 of the stator in FIG. FIG. 12 is a circuit diagram showing a connection state between the piezoelectric actuator shown in FIG. 9 and an AC power supply. In these drawings, members common to the above-described piezoelectric actuator are given the same reference numerals.

  This piezoelectric actuator 10c is a combined type piezoelectric actuator capable of both linear drive and rotational drive, and has two substantially cubic metal stator bodies 11a and 11b as shown in FIGS. The stator 11 is formed with a through hole 12 having a circular cross section that penetrates in the axial direction. The stator 11 is formed by connecting two stator bodies 11a and 11b in the axial direction by a connecting member 11c, and a shaft 13 having a circular cross section extending in the axial direction is slidably inserted into the through hole 12. Yes. The shaft 13 as a driven member is frictionally engaged with an inner peripheral surface 12a of the through hole 12 via a slider, which will be described later, provided on the outer peripheral surface of the shaft 13, and the shaft 13 is linearly reciprocable and rotatable with respect to the stator 11. It is attached to. The stator bodies 11a and 11b may be integrally formed without providing the connecting member 11c.

  The stator body 11a is a direct-acting stator, and has the same structure as the direct-acting stator 11 in the piezoelectric actuator 10a except for the shape of the through hole 12. Similarly, the stator body 11b is a rotating stator, and has the same structure as the rotating stator 11 in the piezoelectric actuator 10b as shown in FIG. Therefore, the description about the stator bodies 11a and 11b is omitted.

  As shown in FIG. 12, the power supply unit of the electric circuit connected to the piezoelectric actuator 10c has a sinusoidal wave shape that is 90 ° out of phase with the electrodes 15 and 16 provided on the first piezoelectric ceramic 14 of the stator body 11a. Rotation of applying AC voltages of sinusoidal shapes having phases different from each other by 90 ° to the AC power supplies 18 and 19 for direct acting to apply an AC voltage and the electrodes 29 to 32 provided on the second piezoelectric ceramic 28 of the stator body 11b. AC power sources 33 to 36 for use. The electric circuit is provided with a switch 47, which can be switched to either one of the direct-acting AC power supplies 18 and 19 and the rotating AC power supplies 33 to 36.

  As shown in FIG. 12, when the switch 47 is switched to the AC power supplies 18 and 19 for linear motion, electrodes are formed by being electrically separated in the axial direction from the piezoelectric ceramics 14 provided on the outer peripheral surface of the stator body 11a. A sinusoidal AC voltage having a phase difference of 90 ° is applied to 15 and 16 to form a wavefront of an axial traveling wave on the inner peripheral surface 12a of the through hole 12, and on the inner peripheral surface 12a of the through hole 12 An axial elliptical motion occurs. By this elliptical motion, the shaft 13 having an outer peripheral surface that frictionally engages with the inner peripheral surface 12a of the through hole 12 is frictionally driven in a direction opposite to the traveling direction of the traveling wave. That is, the shaft 13 is linearly driven in the axial direction.

  On the other hand, when the switch 47 is switched to the AC power sources 33 to 36 for rotation, the electrodes 29 to 32 formed on the piezoelectric ceramics 28 provided on the outer peripheral surface of the stator body 11b are shifted from each other in the rotation direction. Is applied to the inner circumferential surface 12a of the through hole 12 to form a wavefront of a traveling wave in the rotational direction, and an elliptical motion in the rotational direction is generated on the inner circumferential surface 12a. By this elliptical motion, the shaft 13 having the outer peripheral surface frictionally engaged with the inner peripheral surface 12a is friction-driven in the direction opposite to the traveling direction of the traveling wave. That is, the shaft 13 is driven to rotate about its axis.

  As described above, the first direct-acting piezoelectric element 14 provided on the outer peripheral surface of the stator 11 that is flat in the direction in which the through-hole 12 is formed and facing each other around the shaft 13 and the rotating first piezoelectric element 14 are provided. Since the two piezoelectric elements 28 are offset from each other in the axial direction, the entire outer peripheral surface of the shaft 13 existing in the through hole 12 of the stator 11 is caused by frictional force due to the elliptical motion generated on the inner peripheral surface 12a. Since the driving force can be transmitted, the piezoelectric actuator 10c can be reduced in size, and by switching the switch 47 of the electric circuit, the shaft 13 is linearly driven in the axial direction by one piezoelectric actuator 10c and is rotationally driven about the axis. can do.

  Similar to the piezoelectric actuator 10 b, a slider 41 made of an abrasion resistant material is provided on the outer peripheral surface of the shaft 13, and the shaft 13 frictionally engages with the inner peripheral surface 12 a of the through hole 12 via the slider 41. It has a configuration. Since the slider 41 reduces wear on the inner peripheral surface 12a of the through hole 12 and the outer peripheral surface of the shaft 13, it is possible to prevent a decrease in driving efficiency of the piezoelectric actuator 10c and to prevent sound during driving of the shaft 13. An effect is obtained.

  Further, the shaft 13 and the slider 41 are formed with slits 23 that are cut in the center direction and extend in the axial direction. The slits 23 are formed on the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 via the slider 41. It is a setting unit for setting the frictional contact pressure. By forming the slits 23 in the shaft 13 and the slider 41, the shaft 13 can be elastically deformed in the direction of narrowing the interval between the slits 23, and after the shaft 13 is mounted in the through hole 12 of the stator 11, the shaft 13 Due to this elastic restoring force, an appropriate frictional contact pressure can be applied between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12 a of the stator 11 via the slider 41.

  Therefore, a frictional force can be generated between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 via the slider 41, and the driving efficiency of the piezoelectric actuator 10c can be improved. Since the frictional contact pressure can be generated by the shaft 13 itself, there is no need to provide a spring member or the like for applying the frictional contact pressure, and the piezoelectric actuator 10c can be downsized.

  13 is a perspective view of a piezoelectric actuator according to another embodiment of the present invention, FIG. 14 is a sectional view taken along line 14-14 in FIG. 13, and FIG. 15 is a connection between the piezoelectric actuator shown in FIG. It is a circuit diagram which shows a state. In these drawings, members common to the above-described piezoelectric actuator are given the same reference numerals.

  This piezoelectric actuator 10d is a combined type piezoelectric actuator capable of both rectilinear driving and rotational driving, and has a metal stator 11 having a regular octagonal cross section as shown in FIGS. The stator 11 is formed with a through hole 12 having a circular cross section penetrating in the axial direction, and a shaft 13 having a circular cross section extending in the axial direction is slidably inserted into the through hole 12. The shaft 13 as a driven member is frictionally engaged with an inner peripheral surface 12a of the through-hole 12 through a slider, which will be described later, provided on the outer peripheral surface thereof, so that the shaft 13 can reciprocate and rotate linearly with the stator 11. Installed.

  The outer periphery of the stator 11 has eight flat portions that are flat in the formation direction of the through-holes 12 so as to correspond to the inner peripheral surface 12a. As shown in FIG. The first piezoelectric ceramics 14 and the second piezoelectric ceramics 28 are alternately provided, and a combination type vibration body is formed by the four piezoelectric ceramics 14 and 28 and the stator 11 respectively. The piezoelectric ceramics 14 and 28 are provided on the outer peripheral surface of the stator 11 so as to face each other with the shaft 13 as a center and shifted in the rotational direction of the shaft 13.

  The four piezoelectric ceramics 14 constitute direct-acting piezoelectric ceramics and have the same structure as the direct-acting piezoelectric ceramics 14 in the piezoelectric actuator 10a. Similarly, the four piezoelectric ceramics 28 constitute a rotating piezoelectric ceramic pair, and have the same structure as the rotating piezoelectric ceramic pair in the piezoelectric actuator 10b described above. Therefore, the description of the piezoelectric ceramics 14 and 28 is omitted.

  As shown in FIG. 15, the power supply unit of the electric circuit connected to the piezoelectric actuator 10d applies a sinusoidal AC voltage having a phase difference of 90 ° to the electrodes 15 and 16 provided on the piezoelectric ceramic 14 of the stator 11. AC power sources 18 and 19 for linear motion, and AC power sources 33 to 36 for rotation that apply sinusoidal AC voltages having phases different from each other by 90 ° to the electrodes 29 to 32 provided on the piezoelectric ceramics 28 of the stator 11. have. The electric circuit is provided with a switch 47, which can be switched to either one of the direct-acting AC power supplies 18 and 19 and the rotating AC power supplies 33 to 36.

  As shown in FIG. 15, when the switch 47 is switched to the AC power supply 18, 19 for direct acting, the piezoelectric ceramics 14 provided alternately on the outer peripheral surface of the stator 11 are electrically separated in the axial direction and formed. A sinusoidal AC voltage having a phase difference of 90 ° is applied to the electrodes 15 and 16, and a wavefront of an axial traveling wave is formed on the inner peripheral surface 12 a of the through hole 12, and the inner peripheral surface 12 a of the through hole 12. Then, elliptical motion in the axial direction occurs. By this elliptical motion, the shaft 13 having an outer peripheral surface that frictionally engages with the inner peripheral surface 12a of the through hole 12 is frictionally driven in a direction opposite to the traveling direction of the traveling wave. That is, the shaft 13 is linearly driven in the axial direction.

  On the other hand, when the switch 47 is switched to the AC power sources 33 to 36 for rotation, the electrodes 29 to 32 formed on the piezoelectric ceramics 28 alternately provided on the outer peripheral surface of the stator 11 are in a sine wave shape having phases different from each other by 90 °. Is applied to the inner peripheral surface 12a of the through-hole 12 to form a wavefront of a traveling wave in the rotational direction, and an elliptical motion in the rotational direction is generated on the inner peripheral surface 12a. By this elliptical motion, the shaft 13 having the outer peripheral surface frictionally engaged with the inner peripheral surface 12a is friction-driven in the direction opposite to the traveling direction of the traveling wave. That is, the shaft 13 is driven to rotate about its axis.

  In this manner, the first linear piezoelectric element 14 for linear motion and the second piezoelectric element 28 for rotation are provided on the outer peripheral portion of the stator 11 that is flat in the direction in which the through holes 12 are formed. Therefore, since the driving force can be transmitted to the entire outer peripheral surface of the shaft 13 existing in the through hole 12 of the stator 11 by the elliptical motion generated on the inner peripheral surface 12a, the piezoelectric actuator 10d can be downsized. In addition, by switching the switch 47 of the electric circuit, the shaft 13 can be driven linearly in the axial direction and rotationally driven around the axis by the single piezoelectric actuator 11d. In the present embodiment, four piezoelectric ceramics 14 and four piezoelectric ceramics 28 are alternately arranged on the outer peripheral surface of the octagonal stator 11 made of a cross section, but at least one piezoelectric ceramic 14 and at least two piezoelectric ceramics 28 are arranged. In consideration of the stability of rotational driving, it is preferable to provide three or more, especially four, ceramic ceramics 28 in the rotational direction of the shaft 13.

  Similar to the piezoelectric actuator 10 b, a slider 41 made of an abrasion resistant material is provided on the outer peripheral surface of the shaft 13, and the shaft 13 frictionally engages with the inner peripheral surface 12 a of the through hole 12 via the slider 41. It has a configuration. The slider 41 reduces wear on the inner peripheral surface 12a of the through-hole 12 and the outer peripheral surface of the shaft 13, so that it is possible to prevent a decrease in driving efficiency of the piezoelectric actuator 10d, and a soundproofing effect when the shaft 13 is driven. Is obtained.

  Further, the shaft 13 and the slider 41 are formed with slits 23 that are cut in the central direction and extend in the axial direction. The slits 23 are friction between the shaft 13 and the inner peripheral surface 12 a of the stator 11 via the slider 41. It is a setting unit that sets the contact pressure. By forming the slits 23 in the shaft 13 and the slider 41, the shaft 13 can be elastically deformed in the direction of narrowing the interval between the slits 23. After the shaft 13 is mounted in the through hole 12 of the stator 11, An appropriate frictional contact pressure can be applied between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12 a of the stator 11 via the slider 41 by the elastic restoring force 13.

  Therefore, a frictional force can be generated between the outer peripheral surface of the shaft 13 and the inner peripheral surface 12a of the stator 11 via the slider 41, and the driving efficiency of the piezoelectric actuator 10d can be improved. Since the frictional contact pressure can be generated by the shaft 13 itself, it is not necessary to provide a spring member or the like for applying the frictional contact pressure, and the piezoelectric actuator 10d can be downsized.

  FIG. 16 is a cross-sectional view showing a modification of the setting unit for setting the frictional contact pressure. The stator 11 shown in FIG. 16A is formed with a slit 45 extending in the axial direction from a pair of diagonals, and the slit 45 is formed on the outer peripheral surface of the shaft 13 and the inner periphery of the stator 11. It is a setting part which sets the friction contact pressure with the surface 12a. The stator 11 can be elastically deformed in the lateral direction by applying a compressive force in the lateral direction to the outer peripheral surfaces of the stator 11 by the slits 45 as indicated by arrows, and the outer peripheral surface of the shaft 13 and the inner peripheral surface of the stator 11. Appropriate frictional contact pressure can be applied to 12a. As shown in FIG. 16B, a slit 45 cut in the radial direction from the inner peripheral surface 12a and extending in the axial direction may be formed as a setting portion. The piezoelectric actuator is provided with at least one or both of a slit 23 formed in the shaft 13 and a slit 45 formed in the stator 11 as a setting unit for setting the frictional contact pressure.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the slider 41 may be provided on the inner peripheral surface 12a of the stator 11, the slider 41 may be partially cut away, or the slider 41 may be provided on the piezoelectric actuator 11a. Further, the electrodes 29 to 32 provided on the piezoelectric ceramic 28 are electrically separated in the axial direction in the same manner as the linear motion electrode pair having the electrodes 15 and 16, and are in phase with the axial electrode pair. The AC voltage may be applied.

It is a perspective view of the piezoelectric actuator which is one embodiment of the present invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. FIG. 3 is a cross-sectional view of the stator in FIG. 1 taken along line 3-3. It is a circuit diagram which shows the connection state of the piezoelectric actuator shown in FIG. 1, and alternating current power supply. It is a schematic sectional drawing which shows the principle of operation of the piezoelectric actuator shown in FIG. It is a perspective view of the piezoelectric actuator which is other embodiment of this invention. FIG. 7 is a cross-sectional view taken along line 7-7 in FIG. 6. It is a circuit diagram which shows the connection state of the piezoelectric actuator shown in FIG. 6, and alternating current power supply. It is a perspective view of the piezoelectric actuator which is other embodiment of this invention. FIG. 10 is a cross-sectional view taken along line 10-10 in FIG. 9. FIG. 11 is a sectional view of the stator taken along line 11-11 in FIG. 9. FIG. 10 is a circuit diagram showing a connection state between the piezoelectric actuator shown in FIG. 9 and an AC power supply. It is a perspective view of the piezoelectric actuator which is other embodiment of this invention. FIG. 14 is a sectional view taken along line 14-14 in FIG. 13. FIG. 14 is a circuit diagram of the piezoelectric actuator shown in FIG. 13. It is sectional drawing which shows the modification of the setting part which sets a friction contact pressure.

Explanation of symbols

10a to 10d Piezoelectric actuator 11 Stator 11a, 11b Stator body 11c Connecting member 12 Through hole 12a Inner peripheral surface 13 Shaft 14 Piezoelectric ceramics (first piezoelectric element)
15 to 17 Electrodes 18 and 19 AC power supply 20 and 21 Stretch region 23 Slit (setting unit)
24 Stopper 25 Anti-Vibration Support Base 28 Piezoelectric Ceramics (Second Piezoelectric Element)
29 to 32 Electrodes 33 to 36 AC power source 37 to 40 Stretchable region 41 Slider 45 Slit (setting unit)
47 switch

Claims (13)

A piezoelectric actuator that drives the shaft straight in its axial direction,
A stator having a through hole having an inner peripheral surface frictionally engaged with an outer peripheral surface of the shaft, the shaft being mounted so as to be linearly reciprocable;
A piezoelectric element provided on the outer peripheral surface of the stator;
At least two electrodes that are electrically separated in the axial direction of the shaft and for applying alternating voltages of different phases to the piezoelectric element;
A piezoelectric actuator, comprising: a setting portion that is provided on at least one of the shaft and the stator and sets a frictional contact pressure between an outer peripheral surface of the shaft and an inner peripheral surface of the stator. A piezoelectric actuator that drives the shaft straight in its axial direction,
A stator having a through hole having an inner peripheral surface that frictionally engages with an outer peripheral surface of the shaft;
At least two piezoelectric elements provided in the axial direction of the shaft on the outer peripheral surface of the stator;
Electrodes for applying alternating voltages having different phases to the piezoelectric elements;
A piezoelectric actuator, comprising: a setting portion that is provided on at least one of the shaft and the stator and sets a frictional contact pressure between an outer peripheral surface of the shaft and an inner peripheral surface of the stator. A piezoelectric actuator that rotationally drives a shaft about its axis,
A stator having a through hole having an inner peripheral surface frictionally engaged with the outer peripheral surface of the shaft, and the shaft rotatably mounted;
At least two piezoelectric elements respectively provided on the outer peripheral surface of the stator so as to be shifted from each other in the rotational direction of the shaft;
An electrode for applying an alternating voltage having a different phase to each piezoelectric element;
A piezoelectric actuator, comprising: a setting portion that is provided on at least one of the shaft and the stator and sets a frictional contact pressure between an outer peripheral surface of the shaft and an inner peripheral surface of the stator.   The piezoelectric actuator according to any one of claims 1 to 3, wherein the piezoelectric elements are provided on the stator so as to face each other with the shaft as a center.   5. The piezoelectric actuator according to claim 4, wherein the stator is a substantially rectangular parallelepiped or a substantially cubic body having a planar portion in a direction in which the through hole is formed, and the piezoelectric element is provided in each of the planar portions. A piezoelectric actuator. A piezoelectric actuator for driving the shaft straight in its axial direction and rotationally driving about its axis,
A stator having a through hole having an inner peripheral surface frictionally engaged with the outer peripheral surface of the shaft, the shaft being mounted so as to be linearly reciprocable and rotatable;
A first piezoelectric element provided on the outer peripheral surface of the stator;
At least two electrodes that are electrically separated in the axial direction of the shaft and apply alternating voltages of different phases to the first piezoelectric element;
At least two second piezoelectric elements respectively provided on the outer peripheral surface of the stator so as to be shifted from each other in the rotational direction of the shaft;
An electrode provided on each of the second piezoelectric elements, for applying an alternating voltage having a different phase to each of the second piezoelectric elements;
A piezoelectric actuator, comprising: a setting portion that is provided on at least one of the shaft and the stator and sets a frictional contact pressure between an outer peripheral surface of the shaft and an inner peripheral surface of the stator.   7. The piezoelectric actuator according to claim 6, wherein the electrodes provided on each of the second piezoelectric elements are electrically separated in the axial direction of the shaft.   8. The piezoelectric actuator according to claim 6, wherein the first piezoelectric element and the second piezoelectric element are provided in the stator while being axially displaced from each other.   8. The piezoelectric actuator according to claim 6, wherein the first piezoelectric element and the second piezoelectric element are provided in the stator while being shifted from each other in the rotational direction.   8. The piezoelectric actuator according to claim 7, wherein the first piezoelectric element and the second piezoelectric element are provided on the stator so as to face each other with the shaft as a center.   11. The piezoelectric actuator according to claim 1, wherein the setting portion is a slit that extends in an axial direction by being cut in a central direction of the shaft, and the frictional contact pressure is reduced by elastic deformation of the shaft. A piezoelectric actuator characterized by being set.   11. The piezoelectric actuator according to claim 1, wherein the setting portion is a slit that is cut in a central direction of the stator and extends in an axial direction, and the frictional contact pressure is reduced by elastic deformation of the stator. A piezoelectric actuator characterized by being set.   The piezoelectric actuator according to any one of claims 1 to 12, wherein a slider made of a wear-resistant material is provided on one of the shaft and the stator.

Images