JP2015186329A - piezoelectric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric motor capable of stabilizing a vibration body, obtaining sufficient vibration characteristics and suppressing occurrence of a difference in brake force applied to rotation of a body to be driven in a forward direction and a reverse direction.SOLUTION: A piezoelectric motor comprises: a vibration body having a contact portion brought into contact with a body to be driven provided in a rotatable manner and a piezoelectric element provided at an opposite side of the contact portion to the body to be driven, vibrating by applying a voltage to the piezoelectric element and rotating the body to be driven by applying force to the body to be driven; a holding section holding the vibration body so as to allow the vibration body to vibrate; a base; and a pair of elastic bodies coupling the holding section and the base and biasing the contact portion toward the body to be driven via the holding section. An angle θ1 between a first straight line obtained by connecting a first portion where the pair of elastic bodies are fixed to the base and a second portion where the elastic bodies are fixed to the holding section and a third straight line perpendicular to a second straight line obtained by connecting an abutting portion against the contact portion of the body to be driven and a rotation center of the body to be driven is equal to 5° or less.

Description

  The present invention relates to a piezoelectric motor.

  The piezoelectric motor is a driving device having a piezoelectric element that converts a driving voltage such as a high-frequency AC voltage into mechanical vibration and a driven body that is driven by the piezoelectric element. As a form of this piezoelectric motor, a piezoelectric motor using a rotor or a longitudinal member as a driven body is known (see, for example, Patent Documents 1 and 2). The piezoelectric motor transmits bending vibration of a piezoelectric element via a convex portion protruding from a vibrating body including the piezoelectric element, and rotates the rotor in a predetermined direction.

  In recent years, attention has been paid to use of such a piezoelectric motor as a driving means of a robot hand (robot). Since a robot hand requires a precise and accurate operation, a piezoelectric motor used as a robot hand drive means is required to have a stable rotor rotation speed.

  In the piezoelectric motor described in Patent Document 1, the vibration pattern of the vibrating body is changed by selecting the energization pattern to each electrode of the vibrating body to change the direction of vibration of the convex portion of the vibrating body, thereby correcting the rotor. It is configured such that it can be rotated in either direction (counterclockwise or clockwise). Further, in the piezoelectric motor described in Patent Document 1, the vibrating body is biased toward the longitudinal driven body by a coil spring, and in the piezoelectric motor described in Patent Document 2, the vibrating body is directed toward the rotor by a plate spring. Energized.

JP 2013-230018 A Japanese Patent No. 3719061

  However, in the piezoelectric motor described in Patent Document 1, the vibrating body is biased toward the driven body having a long shape by the coil spring, so that the vibrating body is unstable and has a backlash. There was a problem that vibration characteristics could not be obtained.

  In addition, in the piezoelectric motor described in Patent Document 2, when the driving is performed as in Patent Document 1 so that the rotor can be rotated in both forward and reverse directions, the normal force of the rotor is used as a braking force when the piezoelectric motor is not driven. There is a problem that a difference occurs between the braking force with respect to the rotation in the direction and the braking force with respect to the rotation in the reverse direction.

  An object of the present invention is to stabilize a vibrating body, to obtain sufficient vibration characteristics, and to suppress a difference in braking force with respect to rotation of a driven body in the forward direction and the reverse direction. It is to provide a piezoelectric motor.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

(Application example 1)
A piezoelectric motor according to the present invention includes a contact portion that contacts a driven body that is rotatably provided, and a piezoelectric element that is provided on a side opposite to the driven body of the contact portion, and the piezoelectric element A vibrating body that vibrates by applying a voltage to the driven body and rotates the driven body by applying a force to the driven body;
A holding unit for holding the vibrating body so as to vibrate;
The base,
A pair of elastic bodies that connect the holding portion and the base and urge the contact portion toward the driven body via the holding portion;
A first straight line connecting a first portion fixed to the base of the elastic body and a second portion fixed to the holding portion of the elastic body, and the contact portion of the driven body An angle θ1 formed by a third straight line orthogonal to a second straight line connecting the contact portion and the rotation center of the driven body is 5 ° or less.

  Thereby, rattling of the vibrating body can be suppressed, the vibrating body can be stabilized, and sufficient vibration characteristics can be obtained.

  In addition, as a braking force when the piezoelectric motor is not driven, it is possible to suppress a difference between a braking force with respect to the forward rotation of the driven body and a braking force with respect to the reverse rotation of the driven body. it can.

(Application example 2)
In the piezoelectric motor according to the present invention, it is preferable that the first straight line and the third straight line are parallel to each other.

  Thereby, the effect which suppresses that a difference arises in the braking force with respect to the rotation of a to-be-driven body to the forward direction and the braking force with respect to the rotation of a to-be-driven body to the reverse direction can be improved.

(Application example 3)
In the piezoelectric motor according to the present invention, it is preferable that the driven body has a circular cross section.
Thereby, a to-be-driven body can be rotated smoothly.

(Application example 4)
A piezoelectric motor according to the present invention includes a contact portion that contacts a driven body that is movably provided, and a piezoelectric element that is provided on the opposite side of the contact portion from the driven body. A vibrating body that vibrates by applying a voltage to the movable body and moves the driven body by applying a force to the driven body;
A holding unit for holding the vibrating body so as to vibrate;
The base,
A pair of elastic bodies that connect the holding portion and the base and urge the contact portion toward the driven body via the holding portion;
A contact portion between a straight line connecting the first portion fixed to the base of the elastic body and the second portion fixed to the holding portion of the elastic body and the contact portion of the driven body The angle θ2 formed with the moving direction is 5 ° or less.

  Thereby, rattling of the vibrating body can be suppressed, the vibrating body can be stabilized, and sufficient vibration characteristics can be obtained.

  Further, as a braking force when the piezoelectric motor is not driven, it is possible to suppress a difference between a braking force for the forward movement of the driven body and a braking force for the reverse movement of the driven body. it can.

(Application example 5)
In the piezoelectric motor according to the present invention, it is preferable that the straight line and the moving direction are parallel to each other.

  Thereby, the effect which suppresses that a difference arises in the braking force with respect to the movement of a to-be-driven body to the forward direction, and the braking force with respect to the movement of a to-be-driven body to the reverse direction can be improved.

(Application example 6)
In the piezoelectric motor according to the present invention, the driven body preferably has a longitudinal cross-sectional shape.
Thereby, the driven body can be moved smoothly.

(Application example 7)
In the piezoelectric motor according to the present invention, it is preferable that the elastic body is a leaf spring.

  Thereby, the rattling etc. of a vibrating body can be suppressed and the effect of stabilizing a vibrating body can be improved.

(Application example 8)
In the piezoelectric motor according to the present invention, the vibrating body vibrates so as to draw a first elliptical locus such that the contact portion contacts and separates from the driven body;
The contact portion has a second vibration mode having a direction opposite to that of the first elliptical locus and oscillating so as to draw a second elliptical locus so as to contact and separate from the driven body. preferable.

  Thereby, the drive pattern in the apparatus using a piezoelectric motor can be increased, and the use of a piezoelectric motor can be expanded.

(Application example 9)
It is preferable to have the driven body.

  Thereby, a piezoelectric motor with a driven body can be provided without preparing a driven body separately, and the assembly work of the piezoelectric motor including the driven body can be easily performed.

It is a top view which shows 1st Embodiment of the piezoelectric motor of this invention. It is sectional drawing in the AA line in FIG. It is a perspective view of the vibrating body of the piezoelectric motor shown in FIG. It is a figure of the vibrating body for demonstrating operation | movement of the piezoelectric motor shown in FIG. It is a figure of the vibrating body for demonstrating operation | movement of the piezoelectric motor shown in FIG. It is a figure of the vibrating body for demonstrating operation | movement of the piezoelectric motor shown in FIG. It is a figure of the vibrating body for demonstrating operation | movement of the piezoelectric motor shown in FIG. It is a figure of the vibrating body for demonstrating operation | movement of the piezoelectric motor shown in FIG. It is a figure for demonstrating the state at the time of the stop of the piezoelectric motor different from this invention. It is a top view which shows 2nd Embodiment of the piezoelectric motor of this invention.

  Hereinafter, a piezoelectric motor of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<First Embodiment>
FIG. 1 is a plan view showing a first embodiment of the piezoelectric motor of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a perspective view of the vibrating body of the piezoelectric motor shown in FIG. FIG. 4 is a diagram of a vibrating body for explaining the operation of the piezoelectric motor shown in FIG. FIG. 5 is a diagram of a vibrating body for explaining the operation of the piezoelectric motor shown in FIG. FIG. 6 is a diagram of a vibrating body for explaining the operation of the piezoelectric motor shown in FIG. FIG. 7 is a diagram of a vibrating body for explaining the operation of the piezoelectric motor shown in FIG. FIG. 8 is a diagram of a vibrating body for explaining the operation of the piezoelectric motor shown in FIG. FIG. 9 is a diagram for explaining a state when the piezoelectric motor is stopped different from the present invention.

  In the following, for convenience of explanation, the upper side in FIGS. 2 and 3 is referred to as “upper” or “upper”, and the lower side is referred to as “lower” or “lower”.

  1 to 8 show the x axis, the y axis, and the z axis as three axes orthogonal to each other. A direction parallel to the x-axis is referred to as “x-axis direction”, a direction parallel to the y-axis is referred to as “y-axis direction”, and a direction parallel to the z-axis is referred to as “z-axis direction”. A plane defined by the x axis and the y axis is referred to as a “zy plane”, a plane defined by the y axis and the z axis is referred to as a “yz plane”, and a plane defined by the z axis and the x axis is referred to as “ xz plane ". Further, in the x direction, the x direction, and the z direction, the arrow tip side is defined as “+ (positive) side” and the arrow base end side is defined as “− (negative) side” (the same applies to FIG. 10 of the second embodiment).

  Further, in FIG. 9, not all members but members necessary for explanation are illustrated, and in FIG. 9 (b) and FIG. 9 (d), the deformation of the leaf spring is extremely reduced for easy understanding. It is shown.

-Basic configuration-
The piezoelectric motor 1 includes a vibrating portion 10 having a vibrating body 2 that vibrates by application of a voltage, a rotatable disk-shaped rotor (driven body) 5, and a support 6 that supports the vibrating portion 10 and the rotor 5. have. In other words, the rotor 5 is a driven body having a circular cross section.

  The piezoelectric motor 1 is a device that transmits power (driving force) to the rotor 5 to rotate (drive) by vibrating the vibrating body 2. Hereinafter, each part which the piezoelectric motor 1 has is demonstrated sequentially.

--Vibrating part 10--
The vibrating unit 10 connects the vibrating body 2, the holding unit (holding mechanism) 3 that holds the vibrating body 2 so as to be able to vibrate, the base 4, the holding unit 3, and the base 4. And a pair of leaf springs (elastic bodies) 71 and 72 for urging a later-described convex portion 26 of the vibrating body 2 toward the rotor 5.

--Vibrating body 2--
The vibrating body 2 has a rectangular plate shape, and includes four electrodes 21a, 21b, 21c and 21d, a plate-like piezoelectric element 22, a convex portion (contact portion) 26, and four pieces from the upper side of FIGS. A reinforcing plate (shim) 23 that is a diaphragm having a connecting portion 27, a plate-like piezoelectric element 24, and four electrodes 25a, 25b, 25c and 25d (in FIG. 3, the electrodes 25a and 25b are not shown) Only the reference numerals are shown in parentheses) in this order. In FIGS. 2 and 3, the thickness direction is exaggerated.

  The vibrating body 2 vibrates when the piezoelectric elements 22 and 24 are deformed by application of voltage, and transmits power to the rotor 5 via the convex portion 26 to rotate the rotor 5.

  The piezoelectric elements 22 and 24 each have a rectangular shape, and are fixed to both surfaces of the reinforcing plate 23.

  The piezoelectric elements 22 and 24 expand or contract in the longitudinal direction when a voltage is applied, and return to their original shapes when the voltage application is stopped.

  The constituent materials of the piezoelectric elements 22 and 24 are not particularly limited, respectively. Lead zirconate titanate (PZT), crystal, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, zinc Various materials such as lead niobate and lead scandium niobate can be used.

  On the upper surface of the piezoelectric element 22, the upper surface is divided into four rectangular areas approximately equally, and rectangular electrodes 21 a, 21 b, 21 c, and 21 d are provided in each of the divided areas. Similarly, on the lower surface of the piezoelectric element 24, the lower surface is substantially equally divided into four rectangular regions, and rectangular electrodes 25a, 25b, 25c, and 25d are respectively installed in the divided regions. Yes.

  Note that the electrode 21a and the electrode 25a, the electrode 21b and the electrode 25b, the electrode 21c and the electrode 25c, and the electrode 21d and the electrode 25d are arranged to face each other in the thickness direction of the vibrating body 2.

  As shown in FIG. 3, the electrodes 21a and 21c on one diagonal line and the electrodes 25a and 25c located on the back side of these electrodes are all electrically connected. Similarly, the electrodes 21b and 21d on the other diagonal line and the electrodes 25b and 25d located on the back side thereof are all electrically connected.

  The reinforcing plate 23 has a function of reinforcing the entire vibrating body 2 and prevents the vibrating body 2 from being damaged by over-amplitude, external force, or the like. The constituent material of the reinforcing plate 23 is not particularly limited, but for example, various metal materials such as stainless steel, aluminum or aluminum alloy, titanium or titanium alloy, copper or copper alloy are preferable.

  The reinforcing plate 23 is preferably thinner (smaller) than the piezoelectric elements 22 and 24. Thereby, the vibrating body 2 can be vibrated with high efficiency.

  The reinforcing plate 23 is grounded (connected to the ground potential), and also has a function as a common electrode for the piezoelectric elements 22 and 24. That is, a voltage is applied to the piezoelectric element 22 by a predetermined electrode among the electrodes 21a, 21b, 21c, and 21d and the reinforcing plate 23, and the piezoelectric element 24 is selected from the electrodes 25a, 25b, 25c, and 25d. A voltage is applied by the predetermined electrode and the reinforcing plate 23.

  The reinforcing plate 23 is not used as a common electrode for the piezoelectric elements 22 and 24. For example, between the reinforcing plate 23 and the piezoelectric element 22 and between the reinforcing plate 23 and the piezoelectric element 24, the piezoelectric element 22 and the piezoelectric element, respectively. A common electrode for the element 24 may be further provided.

  Further, a convex portion 26 is integrally formed at one end portion in the longitudinal direction of the reinforcing plate 23 (end portion on the rotor 5 side). In other words, each of the piezoelectric elements 22 and 24 is provided on the opposite side of the convex portion 26 from the rotor 5.

  The convex part 26 is located in the center of the vibrating body 2 in the width direction, and the tip thereof has a semicircular shape in plan view. Needless to say, the shape and position of the convex portion 26 are not limited to this.

  The convex portion 26 abuts on the rotor 5 or moves away from the rotor 5 when the vibrating body 2 vibrates.

  Further, at four positions of the reinforcing plate 23, connecting portions 27 for connecting the reinforcing plate 23 to the holding portion 3 are integrally formed so that the vibrating body 2 can vibrate. Each connecting portion 27 is arranged so as to be line-symmetric with each other at two places on the right side of the reinforcing plate 23 in FIG. 1 and two places on the left side.

-Holding part-
The holding unit 3 is configured so as not to hinder the vibration of the vibrating body 2 and holds the vibrating body 2 so as to be able to vibrate. The holding portion 3 includes a pair of support columns 31 and 32 arranged so as to be separated from each other, and a connecting portion 33 that connects an upper end portion of the support column 31 and a lower end portion of the support column 32. ing.

  The vibrating body 2 is disposed between the support column 31 and the support column 32, and the two connection portions 27 on the left side in FIG. 1 are fixed to the support column 31 with screws 115 and 117, respectively, and the two connection portions 27 on the right side in FIG. Are fixed to the column 32 by screws 116 and 118, respectively.

  The constituent material of the holding unit 3 is not particularly limited, and for example, various metal materials, various ceramic materials, and the like can be used.

-Base-
The base 4 supports the holding unit 3 holding the vibrating body 2 via a pair of leaf springs 71 and 72 and is fixed to the support 6. The shape of the base 4 is not particularly limited, but in the present embodiment, the shape of the cross section is a rod having a substantially rectangular shape, that is, a substantially rectangular parallelepiped that is long in one direction.

  The pair of leaf springs 71 and 72 are separated from each other, and connect the holding unit 3 and the base 4 with the entire holding unit 3 sandwiched therebetween. In this case, the first portion 711 which is one end (left side in FIG. 1) of the leaf spring 71 is fixed to the upper end of the base 4 with the screw 111, and the other end (right side in FIG. 1) of the leaf spring 71. ) Is fixed to the upper end of the support column 31 of the holding unit 3 with a screw 112. Similarly, a first portion 721 that is one end (left side in FIG. 1) of the leaf spring 72 is fixed to the lower end of the base 4 with a screw 113, and the other end of the leaf spring 72 (in FIG. 1). A second portion 722 which is an end portion on the right side) is fixed to the lower end portion of the support column 32 of the holding portion 3 with a screw 114.

  The leaf springs 71 and 72 are elastically deformed and urge the holding portion 3 holding the vibrating body 2 toward the rotor 5. That is, the leaf springs 71 and 72 urge the convex portion 26 of the vibrating body 2 toward the rotor 5 via the holding portion 3. Thereby, the power transmission to the rotor 5 by the vibrating body 2 can be performed efficiently.

  Further, the shape of the leaf springs 71 and 72 is not particularly limited, but in the present embodiment, it has an S shape. Each of the leaf springs 71 and 72 may have a flat plate shape in a natural state where no external force is applied, and may have an S-shape when attached and elastically deformed. Even if it is not in a natural state, it may be S-shaped.

  Further, the leaf spring 71 and the leaf spring 72 are set to have the same length. Further, the leaf spring 71 and the leaf spring 72 are arranged in parallel to each other. That is, a straight line (first straight line) 91 connecting the first portion 711 and the second portion 712 of the leaf spring 71 and a straight line (first straight line) connecting the first portion 721 and the second portion 722 of the leaf spring 72. 94) is parallel to 94.

  Further, as shown in FIG. 2, a through hole 713 larger than the convex portion 26 is provided at a position facing the convex portion 26 of the vibrating body 2 of the leaf spring 71, and the convex portion 26 performs elliptical motion. Also, the convex portion 26 does not interfere with the leaf spring 71.

  As described above, by using the pair of leaf springs 71 and 72, the dimension of the piezoelectric motor 1 in the width direction (the bending direction of the vibrating body 2) can be reduced, thereby reducing the size of the piezoelectric motor 1. be able to. Further, rattling or the like of the vibrating body 2 can be suppressed, the vibrating body 2 can be stabilized, and sufficient vibration characteristics can be obtained.

--rotor--
The rotor 5 is disposed in front of the vibration unit 10 having such a configuration in the X-axis direction.

  The rotor 5 is held so as to be rotatable in the forward direction (clockwise) and in the negative direction (counterclockwise) that is the opposite direction, with a rod-shaped shaft portion 51 erected on the support 6 as a rotation center.

And the convex part 26 contact | abuts repeatedly on the outer peripheral surface 52 of such a rotor 5 because the vibrating body 2 vibrates.
The basic configuration of the piezoelectric motor 1 has been described above.

--Drive--
Next, the operation of the piezoelectric motor 1 will be described.

  The piezoelectric motor 1 applies a positive voltage to the vibrating body 2 at a constant period to vibrate the vibrating body 2 so that the convex portion 26 draws an elliptical orbit, and rotates the rotor 5 by this vibration. Hereinafter, the reason why the convex portion 26 draws an elliptical orbit will be described with reference to FIGS.

-Movement of convex part-
As described above, the piezoelectric elements 22 and 24 repeat the application and release of a positive voltage (a positive charge is applied at a constant period) so that the piezoelectric elements 22 and 24 extend in the longitudinal direction and return to the original shape. (The operation of contracting from the stretched state) is repeated. Therefore, the electrodes 21a, 21b, 21c, 21d, 25a, 25b, 25c and 25d are energized at a constant cycle, and between these electrodes 21a, 21b, 21c, 21d, 25a, 25b, 25c and 25d and the reinforcing plate 23 When a positive voltage is applied to the piezoelectric element 22 at a constant period, the piezoelectric elements 22 and 24 repeat contraction and expansion.

  Along with these expansion and contraction, the entire vibrating body 2 performs stretching vibration (longitudinal vibration) as shown in FIGS. 4A and 4B in the XY plane.

  Further, when the frequency at which the voltage is applied is changed, the amount of expansion / contraction suddenly increases when a certain frequency is reached, and a kind of resonance phenomenon occurs. The frequency at which resonance occurs due to stretching vibration (resonance frequency) is determined by various conditions such as the physical properties of the vibrating body 2 and the dimensions (width W, length L, thickness T) of the vibrating body 2.

  On the other hand, when the electrodes 21a, 21c, 25a and 25c are energized at a constant cycle and a positive voltage is applied between the electrodes 21a, 21c, 25a and 25c and the reinforcing plate 23 at a constant cycle, the piezoelectric element 22 The portion corresponding to the electrodes 21a and 21c and the portion corresponding to the electrodes 25a and 25c of the piezoelectric element 24 repeat contraction and expansion.

  On the other hand, since the electrodes 21b, 21d, 25b and 25d are not energized, the portion corresponding to the electrodes 21b and 21d of the piezoelectric element 22 and the portion corresponding to the electrodes 25b and 25d of the piezoelectric element 24 expand and contract. Do not stretch or stretch.

  Along with such expansion and contraction, the entire vibrator 2 vibrates as shown in FIGS. 5A and 5B in the XY plane.

  Further, when the electrodes 21b, 21d, 25b and 25d are energized at a constant cycle, and a positive voltage is applied between these electrodes 21b, 21d, 25b and 25d and the reinforcing plate 23, the electrodes of the piezoelectric element 22 The portions corresponding to 21b and 21d and the portions corresponding to the electrodes 25b and 25d of the piezoelectric element 24 repeat contraction and expansion.

  On the other hand, since the electrodes 21a, 21c, 25a and 25c are not energized, the portion corresponding to the electrodes 21a and 21c of the piezoelectric element 22 and the portion corresponding to the electrodes 25a and 25c of the piezoelectric element 24 expand and contract. Do not stretch or stretch.

  Along with such expansion and contraction, the entire vibrator 2 undergoes bending vibration as shown in FIGS. 6A and 6B in the XY plane.

  5 and 6 also has a resonance frequency determined by various properties such as the physical properties of the vibrating body 2 and the dimensions (width W, length L, thickness T) of the vibrating body 2.

  As described above, both the resonance frequency of the stretching vibration shown in FIG. 4 and the resonance frequency of the bending vibration shown in FIG. 5 or 6 are the physical properties of the vibrating body 2 and the dimensions (width W, length L, thickness of the vibrating body 2). S) and the like. Therefore, if the dimensions (width W, length L, thickness T) of the vibrating body 2 are appropriately selected, the resonance frequencies can be matched or brought close to each other. When a voltage in the form of bending vibration as shown in FIG. 5 or 6 is applied to such a vibrating body 2 at the resonance frequency, the bending vibration shown in FIG. The stretching vibration shown in FIG.

  As a result, when a voltage is applied in the mode shown in FIG. 5, the vibrating body 2 has an elliptical orbit (first elliptical orbit) having a convex portion 26 with an arrow DL1 (clockwise in the drawing) as shown in FIG. ) Vibrate to draw. Such vibration is referred to as a first vibration mode.

  On the other hand, when a voltage is applied in the mode shown in FIG. 6, the vibrating body 2 has an elliptical orbit (second elliptical orbit) with the convex portion 26 having an arrow DR2 (counterclockwise in the drawing) as shown in FIG. ) Vibrate to draw. Such vibration is referred to as a second vibration mode.

  Although the above description has been made assuming that a positive voltage is applied to the vibrating body 2, the piezoelectric elements 22 and 24 are also deformed by applying a negative voltage. Therefore, bending vibration (and expansion / contraction vibration) may be generated by applying a negative voltage to the vibrating body 2, or bending vibration (and expansion / contraction) by applying an alternating voltage that repeats a positive voltage and a negative voltage. (Vibration) may be generated.

  In the above description, the voltage having the resonance frequency is applied. However, it is sufficient to apply a voltage having a waveform including the resonance frequency. For example, a pulse voltage may be used.

--Rotor movement--
The vibrating body 2 rotates the rotor 5 using the first vibration mode or the second vibration mode.

  Specifically, as shown in FIG. 7, when the vibrating body 2 is vibrated in the first vibration mode, the vibrating body 2 vibrates so that the convex portion 26 draws an elliptical orbit indicated by the arrow DL <b> 1. The frictional force received from the convex portion 26 rotates counterclockwise as indicated by an arrow SR in FIG.

  On the other hand, as shown in FIG. 8, when the vibrating body 2 is vibrated in the second vibration mode, the vibrating body 2 vibrates so that the convex portion 26 draws an elliptical orbit indicated by the arrow DR2, as shown in FIG. The rotor 5 rotates clockwise as indicated by an arrow SL in FIG.

  In this way, the rotor 5 rotates clockwise or counterclockwise by the vibration of the vibrating body 2.

  In such a piezoelectric motor 1, when viewed from the thickness direction of the reinforcing plate 23 (piezoelectric elements 22, 24), that is, when viewed from the direction of the rotation center axis 54 of the rotor 5, the first portion of the leaf spring 71. A straight line (first straight line) 91 that connects 711 and the second part 712, a straight line (first straight line) 94 that connects the first part 721 and the second part 722 of the leaf spring 72, and the convex portion 26 of the rotor 5. The angle θ1 formed by a straight line (third straight line) 93 orthogonal to a straight line (second straight line) 92 connecting the contact portion (contact point) 53 with the rotation center 50 of the rotor 5 is set to 5 ° or less. Has been. The angle θ1 is preferably 3 ° or less, more preferably 1 ° or less, and more preferably 0 °, that is, the straight line 91 and the straight line 93 are more preferably parallel. The angle θ1 of 5 ° or less includes the case where the angle θ1 is 0 °, that is, the case where the straight line 91 and the straight line 93 are parallel.

  If the angle θ1 is larger than the upper limit value, the braking force when the piezoelectric motor 1 is not driven is different between the braking force for the forward rotation of the rotor 5 and the braking force for the reverse rotation of the rotor 5. Will occur. The reason will be described below.

  As shown in FIG. 9A, when the piezoelectric motor 1 is stopped and the brake is applied by the frictional force between the convex portion 26 and the rotor 5, the rotor 5 is moved in the direction of the arrow 121 with respect to the rotor 5. When an external force is applied to the rotor 26, a force in the direction of the arrow 122 is applied from the rotor 5 to the convex portion 26, whereby a force in the direction of the arrow 122 is applied to the holding portion 3 holding the vibrating body 2. As a result, the leaf spring 71 is elastically deformed in the bending direction, as shown in FIG. 9B, thereby reducing the urging force of the leaf spring 71 and rotating the rotor 5 in the direction of the arrow 121. The braking force that prevents this is reduced. The same applies to the leaf spring 72.

  On the other hand, as shown in FIG. 9C, when the piezoelectric motor 1 is stopped and the brake is applied by the frictional force between the convex portion 26 and the rotor 5, the rotor 5 is moved to the arrow 123 with respect to the rotor 5. When an external force that rotates in the direction of is applied, a force in the direction of arrow 124 is applied from the rotor 5 to the convex portion 26, and thereby a force in the direction of arrow 124 is applied to the holding unit 3 that holds the vibrating body 2. As a result, the leaf spring 71 is elastically deformed in the extending direction as shown in FIG. 9 (d), thereby increasing the urging force of the leaf spring 71 and rotating the rotor 5 in the direction of the arrow 123. Increases the braking force to prevent The same applies to the leaf spring 72.

  In this way, there is a difference between the braking force for the forward rotation of the rotor 5 and the braking force for the reverse rotation of the rotor 5.

  However, in the piezoelectric motor 1, since the angle θ1 is set as described above, as a braking force when the piezoelectric motor 1 is not driven, a braking force against the forward rotation of the rotor 5 and a reverse direction of the rotor 5 are used. It is possible to suppress a difference from occurring in the braking force against rotation.

  In the present embodiment, the pressing direction (biasing direction) 95 of the vibrating body 2 by the leaf springs 71 and 72 and the straight lines 91 and 94 are not orthogonal to each other but are inclined at a predetermined angle.

  As described above, since the piezoelectric motor 1 uses the leaf springs 71 and 72, the vibration body 2 can be prevented from rattling and the vibration body 2 can be stabilized, and sufficient vibration characteristics can be obtained. .

  Further, as a braking force when the piezoelectric motor 1 is not driven, it is possible to suppress a difference between a braking force with respect to the forward rotation of the rotor 5 and a braking force with respect to the reverse rotation of the rotor 5. .

Second Embodiment
FIG. 10 is a plan view showing a second embodiment of the piezoelectric motor of the present invention.

  Hereinafter, the second embodiment will be described with a focus on the differences from the first embodiment described above, and the description of the same matters will be omitted.

  As shown in FIG. 10, the piezoelectric motor 1 according to the second embodiment includes a driven body having a longitudinal cross-sectional shape, that is, a slider 8 instead of the rotor 5 as a driven body.

  The slider 8 has a rod shape with a substantially square cross section, that is, a substantially rectangular parallelepiped that is long in one direction, and is movably installed in the longitudinal direction (axial direction). The piezoelectric motor 1 is a device that transmits (drives) power (driving force) to the slider 8 when the vibrating body 2 vibrates.

  The slider 8 is provided with two rollers 80a and 80b and two convex portions (movement restricting means) 83a and 83b that restrict the movement of the slider 8.

  The two rollers 80a and 80b are arranged in parallel in the left-right direction in FIG. The two rollers 80a and 80b are respectively arranged on one side (upper side in FIG. 10) of the slider 8 with shafts 81a and 81b positioned in the center in a posture parallel to the slider 8 and rotatable in both forward and reverse directions. It is supported.

  Further, grooves 82a and 82b are formed along the outer periphery on the peripheral surfaces (outer peripheral surfaces) of the rollers 80a and 80b, respectively. The slider 8 is disposed (positioned) in the groove 82a of the roller 80a and the groove 82b of the roller 80b.

  Further, the convex portion 83a is positioned at the left end portion in FIG. 10 with respect to the eight slider roller 80a, and the convex portion 83b is positioned at the right end portion in FIG. 10 with respect to the roller 80b of the slider 8.

  In addition, the position and number of convex parts are not restricted to this, For example, you may arrange | position between the two rollers 80a and 80b, and the number of convex parts may be one. Further, the number of rollers is not limited to this.

  In this piezoelectric motor 1, as in the first embodiment described above, when the reinforcing plate 23 (piezoelectric elements 22, 24) is viewed from the thickness direction, the straight lines 91 and 94 and the protrusions 26 of the slider 8 are in contact with each other. The angle θ2 formed with the moving direction 96 of the contact portion 84 (contact point) is set to 5 ° or less. Thereby, according to the piezoelectric motor 1, the effect similar to 1st Embodiment mentioned above is acquired. The angle θ2 is preferably set similarly to the angle θ1 in the first embodiment. In this case, θ1 in the first embodiment may be read as θ2, and the straight line 93 in the first embodiment may be read as the moving direction 96.

  Although the piezoelectric motor of the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. be able to. In addition, any other component may be added to the present invention.

  Further, the present invention may be a combination of any two or more configurations (features) of the above embodiments.

  Moreover, in the said embodiment, a to-be-driven body is a component of a piezoelectric motor, However In this invention, it is not limited to this, A to-be-driven body does not need to be contained in the component of a piezoelectric motor.

  In the above embodiment, the rotor and the slider are exemplified as the driven body. However, the driven body is not limited to this in the present invention. As a rotatable driven body, the shape of the cross section is not limited to the circular shape, and examples thereof include a polygon such as a decagon. Moreover, as a movable to-be-driven body, the shape of the cross section is not limited to the rectangle long in the said one direction, For example, the curved rod shape etc. are mentioned. Further, the driven body may be a rigid body or may have flexibility.

  Further, the use of the piezoelectric motor of the present invention is not particularly limited, and the piezoelectric motor of the present invention is a predetermined part of various devices such as driving of joints of various robots, driving of various end effectors such as hands. Can be used for driving.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric motor 10 ... Vibrating part 2 ... Vibrating body 21a, 21b, 21c, 21d ... Electrode 22, 24 ... Piezoelectric element 23 ... Reinforcing plate 25a, 25b, 25c, 25d ... Electrode 26 ... Convex part 27 ... Connecting part 3 ... Holding portions 31, 32 ... support 33 ... connecting portion 4 ... base 5 ... rotor 50 ... rotation center 51 ... shaft portion 52 ... outer peripheral surface 53 ... contact portion 54 ... rotation center shaft 6 ... supports 71, 72 ... leaf spring 711, 721 ... 1st part 712, 722 ... 2nd part 713 ... Through-hole 8 ... Slider 80a, 80b ... Roller 81a, 81b ... Shaft 82a, 82b ... Groove 83a, 83b ... Protruding part 84 ... Contact part 91-94 ... straight line 95 ... pressing direction 96 ... moving direction 111-118 ... screw 121-124 ... arrow

Claims (9)

A contact portion that contacts a driven body that is rotatably provided; and a piezoelectric element that is provided on a side opposite to the driven body of the contact portion, and is vibrated by applying a voltage to the piezoelectric element. A vibrating body that rotates the driven body by applying a force to the driven body;
A holding unit for holding the vibrating body so as to vibrate;
The base,
A pair of elastic bodies that connect the holding portion and the base and urge the contact portion toward the driven body via the holding portion;
A first straight line connecting a first portion fixed to the base of the elastic body and a second portion fixed to the holding portion of the elastic body, and the contact portion of the driven body A piezoelectric motor having an angle θ1 formed by a third straight line orthogonal to a second straight line connecting the contact portion and the rotation center of the driven body is 5 ° or less.   The piezoelectric motor according to claim 1, wherein the first straight line and the third straight line are parallel to each other.   The piezoelectric motor according to claim 1, wherein the driven body has a circular cross-sectional shape. A contact portion that comes into contact with a driven body that is movably provided, and a piezoelectric element that is provided on a side opposite to the driven body of the contact portion, and is vibrated by applying a voltage to the piezoelectric element. A vibrating body that moves the driven body by applying a force to the driven body;
A holding unit for holding the vibrating body so as to vibrate;
The base,
A pair of elastic bodies that connect the holding portion and the base and urge the contact portion toward the driven body via the holding portion;
A contact portion between a straight line connecting the first portion fixed to the base of the elastic body and the second portion fixed to the holding portion of the elastic body and the contact portion of the driven body An angle θ2 formed by the moving direction of the piezoelectric motor is 5 ° or less.   The piezoelectric motor according to claim 4, wherein the straight line and the moving direction are parallel to each other.   The piezoelectric motor according to claim 4, wherein the driven body has a longitudinal cross-sectional shape.   The piezoelectric motor according to claim 1, wherein the elastic body is a leaf spring. The vibrating body vibrates so as to draw a first elliptic locus such that the contact portion contacts and separates from the driven body; and
2. A second vibration mode in which the contact portion has a direction opposite to that of the first elliptical locus, and vibrates so as to draw a second elliptical locus so as to contact and separate from the driven body. The piezoelectric motor according to any one of 1 to 7.   The piezoelectric motor according to claim 1, comprising the driven body.

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