JP2012120313A - Ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic motor excellent in assembly facilitation.SOLUTION: An ultrasonic motor including a laminated piezoelectric element 40 having a cross section perpendicular to a central axis with a rectangular shape, a length ratio of a short side and a long side forming the rectangular shape set at a predetermined value, and elliptical vibration caused by simultaneous excitation of longitudinal vibration expanding and contracting in the central axis direction and torsional vibration with the central axis as a torsional axis comprises: a pressing shaft 22a, which is a shaft-like member, provided on the extension of the torsional axis in the laminated piezoelectric element 40; a hole part for inserting the pressing shaft 22a, provided at a position on the extension of the torsional axis of the laminated piezoelectric element 40 in a frames 31; a positioning pin 43 provided on the extension of the rotation axis of a rotor mechanism part 10 in the laminated piezoelectric element 40; and positioning-hole parts 14h and 15h for inserting the positioning pin 43, provided on the rotation axis and a surface facing the laminated piezoelectric element 40 in the rotor mechanism part 10.

Description

  The present invention relates to an ultrasonic motor that uses vibration of a vibrator such as a piezoelectric element.

  In recent years, ultrasonic motors using vibrations of vibrators such as piezoelectric elements have attracted attention as new motors that replace electromagnetic motors. Compared with conventional electromagnetic motors, this ultrasonic motor is capable of obtaining low speed and high thrust without gears, high holding force, long stroke and high resolution, quietness, and magnetism. This has the advantage of not generating noise.

In an ultrasonic motor, an ultrasonic transducer is pressed against a driven member that is a relative motion member through a driving element that is a friction member, thereby generating a frictional force between the driving element and the driven member. The driven member is driven by this frictional force.
For example, longitudinal vibration and torsional vibration are simultaneously generated in the ultrasonic vibrator to generate elliptic vibration in which these vibrations are combined in the ultrasonic vibrator, and the driven member is utilized using the elliptical vibration. An ultrasonic motor for driving the motor is known. As a technique relating to such an ultrasonic motor, for example, Patent Document 1 discloses the following technique.

  According to the technique disclosed in Patent Document 1, longitudinal vibration and twisting are applied to the rod-shaped elastic body by using the stretching vibration of two laminated piezoelectric elements arranged opposite to each other on the side surface of the rod-shaped elastic body. There has been disclosed an ultrasonic motor that simultaneously excites vibration and excites elliptical motion in a driver provided on an end face of the rod-shaped elastic body to rotate a rotor by the driver.

  Specifically, in the ultrasonic motor disclosed in Patent Document 1, a groove is provided in the rod-like elastic body in order to make the longitudinal vibration frequency and the torsional vibration frequency substantially coincide with each other. Then, by adjusting the position of the groove, the resonance frequency of the longitudinal vibration frequency and the torsional vibration frequency are substantially matched.

  Furthermore, a through hole is provided in the central portion of the rod-like elastic body along the length direction, and a shaft is inserted and fixed in the through hole. And the rotor supported on the basis of this shaft is rotated by the driver that has obtained the driving force from the above-described elliptical vibration.

JP-A-9-117168

By the way, it is difficult to say that the ultrasonic motor disclosed in Patent Document 1 is easy to assemble for the following reasons.
That is, in the ultrasonic motor disclosed in Patent Document 1, the laminated piezoelectric element and the rod-shaped elastic body must be bonded and fixed, and the frequency of longitudinal vibration and the frequency of torsional vibration are substantially matched. The fact that the groove portion must be formed in the rod-shaped elastic body reduces the ease of assembly. Such a poor assembling property may lead to variations or deterioration in the motor performance of the ultrasonic motor.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic motor that is easy to assemble.

In order to achieve the above object, an ultrasonic motor according to an aspect of the present invention includes:
The cross section perpendicular to the central axis has a rectangular shape, the ratio of the short side to the long side constituting the rectangular shape is set to a predetermined value, the vertical vibration that expands and contracts in the central axis direction, and the central axis is twisted. A vibrator whose elliptical vibration is excited by exciting the torsional vibration at the same time, and
A driver provided on a surface of the vibrator in which the elliptical vibration is excited;
A rotor mechanism that is in contact with the driver, is driven to rotate about the elliptical vibration of the vibrator as a drive source, and the central axis as a rotation axis;
A pressing portion that presses the vibrator toward the rotor mechanism portion;
A frame for holding the vibrator together with the rotor mechanism part and the pressing part;
A holder shaft that is a shaft-like member provided on an extension of the torsion shaft of the vibrator on a surface of the vibrator facing the pressing portion;
A holder shaft insertion hole that is provided at a position on the extension of the torsion shaft of the vibrator in the frame and into which the holder shaft is inserted;
On the surface of the vibrator facing the rotor mechanism, a positioning pin provided on an extension of the rotation shaft of the rotor mechanism,
A positioning hole portion provided on a surface of the rotor mechanism portion on the rotating shaft and facing the vibrator, and into which the positioning pin is inserted;
It is characterized by comprising.

  According to the present invention, it is possible to provide an ultrasonic motor that is easy to assemble.

1 is a perspective view showing a configuration example of an ultrasonic motor according to a first embodiment of the present invention. The disassembled perspective view about the rotor mechanism part vicinity of the ultrasonic motor which concerns on 1st Embodiment of this invention. 1 is an exploded perspective view of an ultrasonic motor according to a first embodiment of the present invention (a transmission member is not shown). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front sectional view of a vicinity of a rotor mechanism part of an ultrasonic motor according to a first embodiment of the present invention. The figure which shows the example of 1 structure of a laminated piezoelectric element. The perspective view which shows the vibration state of the laminated piezoelectric element in a vertical primary vibration mode with a broken line. The perspective view which shows the vibration state of the laminated piezoelectric element in a twist secondary vibration mode with a broken line. The figure which shows an example of the resonant frequency characteristic in each vibration mode of a laminated piezoelectric element. The perspective view which shows one structural example of the ultrasonic motor which concerns on 2nd Embodiment of this invention. The expansion perspective view of the press mechanism part vicinity of the ultrasonic motor which concerns on 2nd Embodiment of this invention. The perspective view which shows engagement with the holder and frame of the ultrasonic motor which concern on 2nd Embodiment of this invention. The perspective view which shows engagement with the holder and frame of the ultrasonic motor which concern on 2nd Embodiment of this invention.

Hereinafter, an ultrasonic motor according to an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a perspective view showing a configuration example of an ultrasonic motor according to the first embodiment of the present invention. FIG. 2 is an exploded perspective view of the vicinity of the rotor mechanism portion of the ultrasonic motor according to the first embodiment of the present invention. FIG. 3 is an exploded perspective view of the ultrasonic motor according to the first embodiment (the transmission member is not shown). FIG. 4 is a front sectional view of the vicinity of the rotor mechanism portion of the ultrasonic motor according to the first embodiment of the present invention.

As shown in FIG. 1, the ultrasonic motor according to the first embodiment includes a rotor mechanism unit 10, a transmission member 13, a pressing mechanism unit 20, a frame 31, and a laminated piezoelectric element 40.
The frame 31 includes a vibrating body housing frame 31P and a rotor mechanism housing frame 31R.

First, the frame 31 will be described in detail.
The vibrator housing frame 31P includes a first plate member 31P1 and a second plate member 31P2 which are a pair of plate members facing each other, and a third plate member 31P3 forming the bottom surface of the vibrator housing frame, Consists of.
The first plate-like member 31P1 is formed with a plurality of screw holes 31P1sh in the thickness direction for screwing a later-described restriction member 51a1, and a plurality of protrusions 51a1t provided on the restriction member 51a1. A plurality of through-holes 31P1th that are respectively inserted are provided.

  Similarly, the second plate-like member 31P2 has a plurality of screw holes (not shown) for screwing a later-described restricting member 51a2 formed in the thickness direction, and is provided in the restricting member 51a2. A plurality of through holes (not shown) through which the plurality of protrusions 51a2t are respectively inserted are provided.

In the third plate-like member 31P3, a pressing shaft insertion hole 31P3h into which a pressing shaft 22a of the holder 22, which will be described later, is inserted has a twisted shaft (twisted vibration) of the laminated piezoelectric element 40 disposed in the vibrator housing frame 31P. (Center axis of the) is provided at a position on the extension.
The rotor mechanism housing frame 31R includes a first U-shaped member 31R1 and a second U-shaped member 31R2, which are a pair of substantially U-shaped members facing each other. The first U-shaped member 31R1 and the second U-shaped member 31R2 include screw holes 31R1h and 31R2h for screwing the fixing plate 16 to a contact surface with the fixing plate 16 described later, and the fixing plate 16. Pins 31t1 and 31t2 to be inserted into the through holes 16ph1 and 16ph2 formed in the above are provided.

  The transmission member 13 includes a cylindrical shaft portion 13a and a gear portion 13g provided at one end of the shaft portion 13a. The transmission member 13 is formed with a through hole 13H having a diameter substantially the same as the outer diameter of an output shaft 15a of the output member 15 described later along the longitudinal direction of the shaft portion 13a.

Specifically, the through hole 13H is concentric with the central axis of the shaft portion 13a, and is a through hole having substantially the same diameter as the outer diameter of the output shaft 15a. An output shaft 15a is inserted and fixed (coupled) in the through hole 13H, and rotates according to the rotation of the output shaft 15a.
The transmission member 13 is disposed on a fixed plate 16 that is placed and fixed on the rotor mechanism housing frame 31R. An output shaft 15 a that is inserted into a through hole 16 </ b> H of the fixing plate 16 to be described later and exposed on the fixing plate 16 is inserted into and fixed (coupled) to the through hole 13 </ b> H of the transmission member 13. Thus, the transmission member 13 is disposed outside the frame 31 and rotates with the rotation of the output member 15.

  Here, between the fixed plate 16 and the transmission member 13, a spacer 19 is inserted through the output shaft 15a. The spacer 19 is an annular member disposed between the fixed plate 16 and the transmission member 13. By separating the fixed plate 16 and the transmission member 13, friction between the two during driving is reduced. It is a member to prevent.

By the way, the rotor mechanism unit 10 includes a bearing 12, a sliding plate 14, an output member 15, a fixed plate 16, and a spacer 19.
The bearing 12 has a first cylindrical portion 12c1 having an outer diameter substantially the same as an inner diameter (a diameter of the through hole 16H) of a cylindrical portion 16c of the fixing plate 16, which will be described later, and an outer diameter of the cylindrical portion 16c. And a second cylindrical portion 12c2 having an outer diameter. The inner diameter of the bearing 12 is substantially the same as an output shaft 15a of the output member 15 described later, and is inserted through the output shaft 15a.

  Specifically, the bearing 12 is a bearing member configured such that the inner peripheral surface thereof is rotatable, and the outer peripheral surface of the first cylindrical portion 12c1 is fixed to the inner peripheral surface of the cylindrical portion 16c of the fixed plate 16, The lower end surface of the second cylindrical portion 12c2 is in contact with the upper end surface of the output base portion 15b (details will be described later) of the output member 15.

  The sliding plate 14 is arranged so that one surface is in contact with a driver element 41 provided on the upper end surface of the laminated piezoelectric element 40, and the other surface is against the lower end surface of the output base portion 15 b constituting the output member 15. For example, it is a substantially annular member fixed by bonding or the like. By this sliding plate 14, the vibration of the laminated piezoelectric element 40 is transmitted to the output member 15 as a driving force through the driver 41. In other words, the sliding plate 14 and the output member 15 constitute one rotor.

  The output member 15 includes an output shaft 15a and a substantially disk-shaped output base portion 15b connected to one end surface (lower end surface) of the output shaft 15a. The output shaft 15a is inserted into the through hole 13H formed in the shaft portion 13a of the transmission member 13 as described above, and is fixed by, for example, adhesion.

  The output base 15b has a surface (lower end surface) opposite to the surface to which the output shaft 15a is connected fixed to the sliding plate 14 by, for example, adhesion. Specifically, the output base portion 15b is formed with a concave portion 15r having a diameter substantially the same as the outer diameter of the sliding plate 14 on the surface facing the sliding plate 14, and a sliding surface is formed on the surface of the concave portion 15r. The plate 14 is fitted and fixed by, for example, adhesion.

  In the sliding plate 14 and the output base 15b, through holes (positioning pin insertion holes 14h, 15h) into which positioning pins 43 (described later in detail) provided on the upper surface of the laminated piezoelectric element 40 are inserted are respectively laminated piezoelectric elements. It is formed on the 40 side surface. Specifically, the positioning pin insertion holes 14h and 15h are formed at positions corresponding to the central axes of the sliding plate 14 and the output base portion 15b (recessed portion 15r thereof), respectively. Although details will be described later, by assembling the positioning pin 43 into the positioning pin insertion holes 14h and 15h, the positional relationship between these members is necessarily optimized and assembled.

The output from the rotor mechanism portion 10 is transmitted to the outside by the gear portion 13g of the transmission member 13 through the transmission member 13 fixed (coupled) to the output shaft 15a of the output member 15 (the driving force is taken out). )
The fixed plate 16 includes a plate portion 16b and a cylindrical portion 16c provided on one surface of the plate portion 16b. The fixing plate 16 is formed with a through hole 16h having a diameter substantially the same as the outer diameter of the first portion 12c of the bearing 12 in the thickness direction. The inner peripheral surface of the through hole 16h and the first of the bearing 12 are formed. The outer peripheral surface of the portion 12c1 is fixed by, for example, adhesion. In other words, on the fixed plate 16, a rotor part set composed of the sliding plate 14 and the output member 15 fixed by bonding or the like is rotatably disposed via the bearing 12.

  Here, in the plate portion 16b, as described above, the through holes 16th1 and 16th2 into which the pins 31t1 and 31t2 provided in the rotor mechanism housing frame 31R are inserted, and the plate mounted on the rotor mechanism housing frame 31R. Through holes 16ph1 and 16ph2 for screwing the plate portion 16b to the rotor mechanism housing frame 31R are formed.

  As described above, the fixing plate 16 is aligned with respect to the pins 31t1 and 31t2 provided on the above-described rotor mechanism housing frame 31R, and is fixed to the rotor mechanism housing frame 31R by the screws sr. As a result, the driver 41 bonded and fixed to the laminated piezoelectric element 40 by the pressing force of the spring 21 to be described later pressurizing the laminated piezoelectric element 40 toward the rotor mechanism 10 is applied to the rotor surface (the surface of the sliding plate 14). Contact with appropriate pressure. Thereby, the elliptical vibration of the laminated piezoelectric element is transmitted to the rotor mechanism unit 10 as a driving force.

The pressing mechanism unit 20 includes a spring 21 and a holder 22.
The spring 21 is a member for pressing the laminated piezoelectric element 40 toward the rotor mechanism unit 10 and is positioned by the holder 22. The spring 21 is held in a bent state by the third plate-like member 31P3 of the vibrator housing frame 31P and the laminated piezoelectric element 40. Specifically, the spring 21 is, for example, a plate spring or a coil spring.

The holder 22 includes a pressing shaft 22a and a fixing portion 22f. Specifically, the pressing shaft 22a and the center axis in the longitudinal direction of the laminated piezoelectric element 40 (center axis of torsional vibration) are configured as follows.
The pressing shaft 22a is a shaft member through which the spring 21 is inserted. A fixing portion 22f, which will be described later, is provided at one end of the holder 22, and the other end is inserted into a pressing shaft insertion hole 31P3h formed in the third plate-like member 31P3 of the vibrating body housing frame 31P. As will be described in detail later, since the fixing portion 22f is fixed to the lower surface of the laminated piezoelectric element 40, the pressing shaft 22a of the holder 22 has a pressing shaft insertion hole provided in the third plate-like member 31P3 of the vibrator housing frame 31P. By being inserted into 31P3h, the position of the laminated piezoelectric element 40 is regulated and positioned (the laminated piezoelectric element 40 is regulated to move in a direction perpendicular to the direction of pressing by the spring 21).

  The fixing portion 22f has a pressing shaft 22a connected to one surface and the other surface corresponding to a node position of torsional vibration that is vibration in a direction contributing to driving on the lower surface of the laminated piezoelectric element 40 ( It is a plate-like member fixed by adhesion or the like in the vicinity of the center position in the width direction and the thickness direction.

  The fixing portion 22f is formed integrally with the pressing shaft 22a and is pressed toward the rotor mechanism portion 10 by the laminated piezoelectric element 40 and the spring 21 sandwiched and bent by the fixing portion 22f. Is done. That is, the laminated piezoelectric element 40 is pressed toward the rotor mechanism portion 10 by the spring 21 through the fixing portion 22f.

The holder 22 is made of a material (for example, a resin material) that reduces vibration transmission. Thereby, it is possible to reduce the vibration of the laminated piezoelectric element 40 from being transmitted to the vibrating body housing frame 31P.
The laminated piezoelectric element 40 is a vibrating body formed by laminating piezoelectric sheets, and is provided with a driver element 41 and positioning pins 43. Although the details will be described later, the ultrasonic motor is mounted using a holder 22 fixed to the lower end surface in the longitudinal direction of the laminated piezoelectric element 40 by bonding and a positioning pin 43 fixed to the upper end surface by bonding or the like. By assembling, the laminated piezoelectric element 40 is assembled in a state where the center axis (center axis in torsional vibration) and the center axis (rotation axis) of the rotor mechanism unit 10 coincide.

The driver element 41 is provided in the vicinity of the position where the optimal elliptical vibration is generated for driving on the upper surface of the laminated piezoelectric element 40 (the surface facing the rotor mechanism portion 10), and is provided on the sliding plate 14 of the rotor mechanism portion 10. In contact.
The positioning pin 43 protrudes perpendicularly to the upper surface on the center in the long side direction and the short side direction (the rotation axis (center axis) of the rotor mechanism unit 10) of the upper surface of the multilayer piezoelectric element 40. For example, it is fixed to the upper surface by adhesion or the like.

  The positioning pin 43 is inserted into the positioning pin insertion holes 14h and 15h of the sliding plate 14 and the output member 15 described above. When the rotor mechanism 10 (sliding plate 14 and output member 15) is disposed on the laminated piezoelectric element 40, the rotation pin of the rotor mechanism 10 is inserted by inserting the positioning pin 43 into the pin insertion holes 14h and 15h. And the center of the upper surface of the laminated piezoelectric element 40 coincide.

  The restricting member 51a1 is a plate-like member having a plurality (two in this example) of protrusions 51a1t provided in a convex manner in the thickness direction, and through holes 51a1h for screwing are formed in the thickness direction. Similarly, the restricting member 51a2 is a plate-like member in which a plurality of (in this example, two) protrusions 51a2t are provided so as to protrude in the thickness direction, and through holes 51a2h for screwing are formed in the thickness direction. ing.

  These restricting members 51a1 and 51a2 are arranged such that the protrusions 51a1t and 51a2t are in contact with the vicinity of the nodal position of torsional vibration on the main plane of the laminated piezoelectric element 40 (surface facing the vibrating body housing frame 31P). It is applied to the first plate-like member 31P1 and the second plate-like member 31P2 from the outside of the vibrator housing frame 31P, and is screwed and fixed by screws sr using the through holes 51a1h and 51a2h, respectively.

  As described above, the protrusions 51a1t and 51a2t of the regulating members 51a1 and 51a2 are fixed in a state of being in contact with the node position of the torsional vibration of the multilayer piezoelectric element 40 in the main plane of the multilayer piezoelectric element 40. The rotation of the laminated piezoelectric element 40 (same as the rotation of the transmission member 13) is performed without inhibiting the vibration of the laminated piezoelectric element 40 (without reducing the amplitude of torsional vibration excited on the end surface in the longitudinal direction of the laminated piezoelectric element 40). Direction rotation, rotation in a plane perpendicular to the direction of the pressing force of the spring 21) is restricted.

Hereinafter, an example of the laminated structure of the laminated piezoelectric element 40 will be described. FIG. 5 is a diagram illustrating a configuration example of the laminated piezoelectric element 40.
As shown in the figure, the laminated piezoelectric element 40 includes a first laminated part 411, a second laminated part 412, a third laminated part 413, a fourth laminated part 414, and a fifth laminated part 415. .

Specifically, the laminated structure of each of these laminated parts (the first laminated part 411, the second laminated part 412, the third laminated part 413, the fourth laminated part 414, and the fifth laminated part 415) is as follows. It is. In addition, the structure of the 1st piezoelectric sheet 401, the 2nd piezoelectric sheet 402, and the 3rd piezoelectric sheet 403 which comprise each lamination | stacking site | part is mentioned later.
<< 1st lamination part 411 >>
The first laminated portion 411 includes at least one third piezoelectric sheet 403 (in the case of a plurality of third piezoelectric sheets 403, the third piezoelectric sheets 403 are stacked in the thickness direction). .
<< 2nd lamination | stacking site | part 412 >>
The second laminated portion 412 is a portion laminated on the first laminated portion 411, and is formed by alternately laminating the first piezoelectric sheets 401 and the second piezoelectric sheets 402 in the thickness direction.
<< 3rd lamination | stacking site | part 413 >>
The third laminated portion 413 is a portion laminated on the second laminated portion 412 and is composed of at least one third piezoelectric sheet 403 (in the case of being composed of a plurality of third piezoelectric sheets 403, 3 piezoelectric sheets 403 are laminated in the thickness direction).
<< 4th lamination | stacking site | part 414 >>
The fourth laminated portion 414 is a portion laminated on the third laminated portion 413, and is formed by alternately laminating the first piezoelectric sheets 401 and the second piezoelectric sheets 402 in the thickness direction.
<< 5th lamination | stacking site | part 415 >>
The fifth laminated portion 415 is a portion laminated on the fourth laminated portion 414, and is composed of at least one third piezoelectric sheet 403 (in the case of being composed of a plurality of third piezoelectric sheets 403, 3 piezoelectric sheets 403 are laminated in the thickness direction).

Hereinafter, the first piezoelectric sheet 401, the second piezoelectric sheet 402, and the third piezoelectric sheet 403 will be described in detail.
The first piezoelectric sheet 401, the second piezoelectric sheet 402, and the third piezoelectric sheet 403 are rectangular sheet-like piezoelectric elements, for example, a hard lead zirconate titanate piezoelectric ceramic element (PZT). Consists of.

More specifically, on the electrode forming surface of the first piezoelectric sheet 401, a + phase first internal electrode 401a and a + phase second internal electrode 401c are arranged at a substantially central position in the longitudinal direction. They are provided symmetrically with respect to C (a line that bisects the short side).
Similarly, on the electrode formation surface of the second piezoelectric sheet 402, a first internal electrode 402a of a negative phase and a second internal electrode 402c of a negative phase are disposed at a center line C at a substantially central position in the longitudinal direction. They are provided symmetrically with respect to (a line that bisects the short side).

  Here, the + phase first internal electrode 401a includes an end portion 401ae that extends toward one short side of the first piezoelectric sheet 401 having a rectangular shape and is exposed. The + -phase second internal electrode 401c includes an end portion 401ce extending toward one short side of the first piezoelectric sheet 401 having a rectangular shape and exposed.

  Similarly, the negative-phase first internal electrode 402a includes an end portion 402ae extending toward one short side of the second piezoelectric sheet 402 having a rectangular shape and exposed. The -phase second internal electrode 402c includes an end portion 402ce extending toward one short side of the second piezoelectric sheet 402 having a rectangular shape and exposed.

  The external portion (outer surface) of the laminated piezoelectric element 40 is provided with external electrodes (not shown) that connect (short-circuit) the end portions 401ae, the end portions 401ce, the end portions 402ae, and the end portions 402ce. It has been. Here, in the laminated piezoelectric element 40, at least a portion where the + phase first internal electrode 401 a and the − phase first internal electrode 402 a are opposed to each other, and a + phase second internal electrode 401 c and the − phase first internal electrode 401 a. An activation region is formed in a portion where the second internal electrode 402c faces each other.

Specifically, there is a high level between the + phase first internal electrode 401a and the − phase first internal electrode 402a and between the + phase second internal electrode 401c and the − phase second internal electrode 402c. A voltage is applied and each electrode is polarized and piezoelectrically activated.
Each of the internal electrodes 401a, 401c, 402a, and 402c described above is a silver palladium alloy having a thickness of 4 μm, for example.

The third piezoelectric sheet 403 is a sheet-like member having the same shape as the first piezoelectric sheet 401 and the second piezoelectric sheet 402 and having no internal electrode.
As described above, in the laminated piezoelectric element 40, the insulating layer having no internal electrode is provided in the central portion in the lamination direction (thickness direction of the laminated piezoelectric element 40), and thereby the lamination direction (laminated piezoelectric element 40). The thickness direction of the piezoelectric activation region is divided into two. In addition, an insulating layer having no internal electrode is provided in the lowest part and the highest part in the stacking direction. Here, the electrode layer corresponding to the fourth laminated portion 414 is referred to as A phase, and the electrode layer corresponding to the second laminated portion 412 is referred to as B phase.

  FIG. 6A is a perspective view showing a vibration state of the multilayered piezoelectric element 40 in the longitudinal primary vibration mode by a broken line. FIG. 6B is a perspective view showing a vibration state of the multilayered piezoelectric element 40 in the torsional secondary vibration mode by a broken line. 6A and 6B, the state (shape) of the multilayer piezoelectric element 40 before vibration is indicated by a solid line, and the state (shape) of the multilayer piezoelectric element 40 during vibration in each vibration mode is indicated by a broken line.

Here, as shown in FIG. 6A and FIG. 6B, the length of the short side constituting the cross section orthogonal to the central axis 100c of the substantially rectangular parallelepiped laminated piezoelectric element 40 is a, the length of the long side is b, Let c be the height along the central axis 100c. However, the size relationship between the short side a, the long side b, and the height c is
a <b <c
Suppose that In the following description, the height c direction is defined as the vibration direction of the longitudinal primary vibration mode and the torsional axial direction of the torsional vibration.

In the ultrasonic motor according to the first embodiment, the resonance frequency of the longitudinal primary vibration mode is set by appropriately setting the values of the dimensions of the short side a, the long side b, and the height c of the laminated piezoelectric element 40. And the resonance frequency of the torsional secondary vibration mode or the torsional tertiary vibration mode are substantially matched.
6A and 6B, p1 and p2 indicate directions of torsional vibration, q indicates the direction of longitudinal vibration, and N indicates a vibration node.

In the longitudinal primary vibration shown in FIG. 6A, one node N exists at the center position in the height c direction of the laminated piezoelectric element 40. In the torsional secondary vibration shown in FIG. 6B, the node N exists at two positions in the height c direction.
Here, assuming that the height c of the multilayer piezoelectric element 40 is constant, the value of (short side length a / long side length b) is taken on the horizontal axis, and the value of the resonance frequency in each vibration mode is taken on the vertical axis. The characteristics shown in FIG. 7 can be obtained. Specifically, the following characteristics are obtained. That is,
The value of the resonance frequency in the longitudinal primary vibration mode does not depend on the value of (a / b) and takes a substantially constant value.
The value of the resonance frequency in the torsional primary vibration mode, the torsional secondary vibration mode, and the torsional tertiary vibration mode increases as the value of (a / b) increases.
The resonance frequency in the torsional primary vibration mode does not coincide with the resonance frequency in the longitudinal primary vibration mode regardless of the value of (a / b).
The resonance frequency in the torsional secondary vibration mode coincides with the resonance frequency in the longitudinal primary vibration mode in the vicinity where the value of (a / b) is 0.6.
The resonance frequency in the torsional tertiary vibration mode coincides with the resonance frequency in the longitudinal primary vibration mode in the vicinity where the value of (a / b) is 0.3.

Due to the above-described characteristics, the value of (a / b) is set as follows in the first embodiment. That is,
When the longitudinal primary vibration mode and the torsional secondary vibration mode are used, the length a of the short side of the multilayer piezoelectric element 40 is set so that the value of (a / b) is 0.55 to 0.65. The long side length b is set.

  That is, in the ultrasonic motor according to the first embodiment, the resonance between the longitudinal primary resonance vibration that expands and contracts in the direction of the center axis 100c of the multilayer piezoelectric element 40 and the torsional secondary resonance vibration that uses the center axis 100c as the torsion axis. The ratio (ratio) between the short side length a and the long side length b in the multilayer piezoelectric element 40 is set so that the frequencies substantially coincide.

Since the resonance frequency can be adjusted in this way, there is no need for special processing or the like for adjusting the resonance frequency, which is required in the prior art.
In the laminated piezoelectric element 40, the longitudinal primary resonance vibration that expands and contracts along the direction of the central axis 100c (rotation axis) and the torsional secondary resonance vibration with the central axis 100c as a torsion axis are excited simultaneously. These vibrations are combined to excite elliptical vibrations.

  Specifically, alternating voltages having different phases are applied to the internal electrodes of the A phase that is the electrode layer corresponding to the fourth laminated portion 414 and the B phase that is the electrode layer corresponding to the second laminated portion 412. By applying, longitudinal primary resonance vibration and torsional secondary resonance vibration are excited in the activation region polarized in the thickness direction (lamination direction) of the multilayer piezoelectric element 40, and elliptical vibration is generated on the end face of the multilayer piezoelectric element 40. Is excited, and the sliding plate 14 is rotationally driven by the driver 41. Thus, in the ultrasonic motor according to the first embodiment, driving is performed using the piezoelectric lateral effect of the laminated piezoelectric element 40.

  Specifically, longitudinal vibration is excited in the laminated piezoelectric element 40 by applying an alternating voltage having the same phase to the A phase and the B phase. Further, torsional vibration is excited in the laminated piezoelectric element 40 by applying an alternating voltage having a phase difference of 180 degrees (reverse phase) to the A phase and the B phase. Then, by applying an alternating voltage having a phase difference of 90 degrees between the A phase and the B phase, longitudinal vibration and torsional vibration are simultaneously excited in the laminated piezoelectric element 40, and elliptical vibration is excited at its end face.

  By the way, in the ultrasonic motor according to the first embodiment, as shown in FIGS. 5, 6A, and 6B, the positions where the internal electrodes 401a, 401c, 402a, and 402c are provided in each piezoelectric sheet are This position corresponds to the abdomen of torsional secondary vibration excited by the laminated piezoelectric element 40. In other words, each internal electrode 401a, 401c, 402a, 402c is provided at a position where the stress of the torsional secondary vibration is maximized.

As described above, according to the first embodiment, it is possible to provide an ultrasonic motor that is easy to assemble. Specifically, for example, an ultrasonic motor having the following effects can be provided.
Specifically, according to the first embodiment, an ultrasonic motor in which the positional relationship between the constituent members is optimized is assembled by the following very simple assembly operation. That is, the central axis of the torsional vibration of the laminated piezoelectric element 40 and the rotation of the rotor mechanism unit 10 are simply disposed in order from the bottom surface side (pressing mechanism unit 20 side) of the frame 31 with respect to the frame 31. An ultrasonic motor with the same axis is assembled.

  Specifically, the rotor mechanism unit 10 positioned by the fixed plate 16 in the state in which the laminated piezoelectric element 40 to which the holder 22 is attached and the spring 21 positioned by the holder 22 are disposed on the vibrating body housing frame 31P is disposed on the upper side. And fixed to the rotor mechanism housing frame 31R. Thereafter, the regulating members 51a1 and 51a2 are fixed to the first plate-like member 31P and the second plate-like member 31P of the vibrating body housing frame 31P, respectively. In such a very simple work process, an ultrasonic motor in which the central axis of the torsional vibration of the laminated piezoelectric element 40 and the rotation axis of the rotor mechanism unit 10 coincide is assembled.

In other words, in order to achieve the optimization of the positional relationship between the constituent members as described above (coincidence between the center axis of the torsional vibration of the laminated piezoelectric element 40 and the rotation axis of the rotor mechanism unit 10), the following is mainly performed. Constituent requirements have contributed greatly.
The pressing shaft 22a of the holder 22 fixed to the longitudinal end surface of the laminated piezoelectric element 40 by the fixing portion 22f is inserted into the pressing shaft insertion hole 31P3h provided in the third plate member 31P3 which is the bottom surface of the vibrator housing frame 31P. Insert.
The positioning pin 43 fixed to the laminated piezoelectric element 40 is inserted into the positioning pin insertion hole 15 h of the output member 15.
The pins 31t1 and 31t2 provided on the rotor mechanism housing frame 31R are inserted into the through holes 16th1 and 16th2 formed in the fixing plate 16.

  By assembling in this way, in the ultrasonic motor according to the first embodiment, the laminated piezoelectric element 40 and the frame 31 are positioned, and the laminated piezoelectric element 40 and the output member 15 are positioned (substantially (the laminated piezoelectric element 40). Positioning between the frame 31 and the fixed plate 16 (substantially positioning between the frame 31 and the rotor mechanism 10), that is, the center of the torsional vibration of the laminated piezoelectric element 40. Matching of the shaft and the rotation shaft of the rotor mechanism unit 10 is realized, and the positional relationship of the constituent members of the ultrasonic motor is optimized.

Further, for example, the following effects can be obtained.
Unlike the conventional technology, since the rectangular vibrating body (laminated piezoelectric element 40) is realized with a single member, the ease of assembly is also greatly improved in this respect.
・ Along with the reduction of assembly man-hours, the stability of motor performance is improved as the ease of assembly is improved.
-The number of parts of the ultrasonic motor is reduced and the cost is reduced.
The output member 15 is provided inside the frame 31, and the output member 15 rotates and drives the gear portion 13 g of the transmission member 13 provided outside the frame 31, so that the frame 31 is matched only to the outer diameter of the rotor mechanism portion 10. The ultrasonic motor itself can be easily downsized.

In addition, about the member which is contacting with respect to the laminated piezoelectric element 40, it is preferable to comprise with the material (for example, resin material) etc. which reduce transmission of a vibration. With this configuration, it is possible to further obtain an effect such as reducing the occurrence of abnormal noise.
[Second Embodiment]
Hereinafter, an ultrasonic motor according to a second embodiment of the present invention will be described. In order to avoid duplication of explanation, differences from the ultrasonic motor according to the first embodiment will be described. FIG. 8 is a perspective view showing a configuration example of the ultrasonic motor according to the second embodiment. FIG. 9 is an enlarged perspective view of the vicinity of the pressing mechanism portion of the ultrasonic motor according to the second embodiment of the present invention. FIG. 10 is a perspective view showing the relationship between the holder and the frame of the ultrasonic motor according to the second embodiment of the present invention. FIG. 11 is a perspective view showing the relationship between the holder and the frame of the ultrasonic motor according to the second embodiment of the present invention.

  In the ultrasonic motor according to the second embodiment, the holder 22 has the following configuration. That is, the holder 22 includes a pressing shaft 22a and a fixed protrusion 22t including protrusions 22t1 and 22t2. Specifically, the holder 22 is configured as follows so that the pressing shaft 22a and the central axis in the longitudinal direction of the laminated piezoelectric element 40 (central axis of torsional vibration) coincide.

  The pressing shaft 22a is a shaft member through which the spring 21 is inserted. One end of the pressing shaft 22a is provided with a fixing projection 22t fixed to the lower end surface of the laminated piezoelectric element 40, and the other end is a pressing formed on the third plate-like member 31P3 of the vibrating body housing frame 31P. The shaft is inserted into the shaft insertion hole 31P3h.

  By adopting such a configuration, when the pressing shaft 22a is inserted into the pressing shaft insertion hole 31P3h provided in the third plate-like member 31P3 of the vibrator housing frame 31P during assembly, the laminated piezoelectric element 40 is inevitably produced. Is regulated and positioning is performed (the laminated piezoelectric element 40 is regulated to move in a direction perpendicular to the direction of pressing by the spring 21).

  The fixed protrusion 22t is a rod-like member having convex portions 22t1 and 22t2 that are convex on the main plane side of the laminated piezoelectric element 40 as shown in FIG. The fixed protrusion 22t is a rod-like member fixed by bonding or the like in the vicinity of the position corresponding to the node position of torsional vibration on the lower end surface of the multilayer piezoelectric element 40.

  The protrusions 22t1 and 22t2 of the fixed protrusion 22t are respectively inserted into groove portions 31P1sl and 31P2sl provided in a vibrating body housing frame 31P described later (see FIG. 11). The protrusion 22t1 of the fixed protrusion 22t and the groove 31P1sl provided on the vibrating body housing frame 31P are engaged, and the protrusion 22t2 of the fixed protrusion 22t and the groove 31P2sl provided on the vibration body housing frame 31P. Are engaged with each other to restrict the rotation of the laminated piezoelectric element 40 (rotation in the same direction as that of the transmission member 13 and rotation in a plane perpendicular to the direction of the pressing force of the spring 21).

  As described above, according to the second embodiment, the same effects as the ultrasonic motor according to the first embodiment can be obtained, and the regulating members 51a1 and 51a2 in the ultrasonic motor according to the first embodiment are unnecessary. Thus, it is possible to provide an ultrasonic motor that has the effect of reducing the number of parts for restricting the position (supporting and holding) of the laminated piezoelectric element 40 and contributing to cost reduction.

As mentioned above, although this invention was demonstrated based on 1st Embodiment thru | or 2nd Embodiment, this invention is not limited to each embodiment mentioned above, In the range of the summary of this invention, various deformation | transformation and Of course, application is possible.
Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention can be achieved. In the case of being obtained, a configuration from which this configuration requirement is deleted can also be extracted as an invention.

    DESCRIPTION OF SYMBOLS 10 ... Rotor mechanism part, 12c1 ... 1st cylindrical part, 12c2 ... 2nd cylindrical part, 13 ... Transmission member, 13a ... Shaft part, 13g ... Gear part, 13H ... Through-hole, 14 ... Sliding plate, 14h. 15h ... Pin insertion hole, 15 ... Output member, 15a ... Output shaft, 15b ... Output base, 15r ... Recessed part, 15h ... Pin insertion hole, 16 ... Fixing plate, 16ph1.16ph2 ... Through hole, 16H ... Through hole, 16c ... Cylinder part, 16b ... Plate part, 16th1,16th2 ... Through hole, 19 ... Spacer, 20 ... Pressing mechanism part, 21 ... Spring, 22 ... Holder, 22a ... Pressing shaft, 22f ... Fixing part, 22t1,22t2 ... Convex part 22t ... fixed projection, 31 ... frame, 31P ... vibrator housing frame, 31R ... rotor mechanism housing frame, 31P1 ... first plate member, 31P2 ... second plate member, 31P3 ... third plate member, 31P3h ... Push shaft insertion hole, 31P1sh ... Screw hole, 31P1th ... Through hole, 31P ... Transducer housing frame, 31R1 ... No. U-shaped member, 31R2 ... 2nd U-shaped member, 31R1h, 31R2h ... Screw hole, 31t1, 31t2 ... Pin, 31P1 ... 1st plate-shaped member, 31P2 ... 2nd plate-shaped member, 31P3 ... 3rd plate-shaped member 31R ... Rotor mechanism housing frame, 31 ... Frame, 31P1sl, 31P2sl ... Groove, 40 ... Multilayer piezoelectric element, 41 ... Driver, 43 ... Positioning pin, 51a1, 51a2 ... Restriction member, 51a1t, 51a2t ... Projection, 51a1h, 51a2h ... through hole.

Claims (6)

The cross section perpendicular to the central axis has a rectangular shape, the ratio of the short side to the long side constituting the rectangular shape is set to a predetermined value, the vertical vibration that expands and contracts in the central axis direction, and the central axis is twisted. A vibrator whose elliptical vibration is excited by exciting the torsional vibration at the same time, and
A driver provided on a surface of the vibrator in which the elliptical vibration is excited;
A rotor mechanism that is in contact with the driver, is driven to rotate about the elliptical vibration of the vibrator as a drive source, and the central axis as a rotation axis;
A pressing portion that presses the vibrator toward the rotor mechanism portion;
A frame for holding the vibrator together with the rotor mechanism part and the pressing part;
A holder shaft that is a shaft-like member provided on an extension of the torsion shaft of the vibrator on a surface of the vibrator facing the pressing portion;
A holder shaft insertion hole that is provided at a position on the extension of the torsion shaft of the vibrator in the frame and into which the holder shaft is inserted;
On the surface of the vibrator facing the rotor mechanism, a positioning pin provided on an extension of the rotation shaft of the rotor mechanism,
A positioning hole portion provided on a surface of the rotor mechanism portion on the rotating shaft and facing the vibrator, and into which the positioning pin is inserted;
An ultrasonic motor comprising: 2. The ultrasonic motor according to claim 1, further comprising a regulating member that clamps a vicinity of a node position of the torsional vibration in the vibrator from the frame side. The ultrasonic motor according to claim 1, wherein the holder shaft is provided in the vicinity of a node position of the torsional vibration of the vibrator. The ultrasonic motor according to claim 1, wherein the positioning pin is provided in the vicinity of a node position of the torsional vibration of the vibrator. The frame is formed with a long hole-shaped slit whose longitudinal direction is the pressing direction by the pressing portion,
The holder shaft is provided with a rotation restricting convex portion that is inserted into the slit of the frame and engages with the slit to restrict the movement of the vibrator in a plane perpendicular to the pressing direction. The ultrasonic motor according to claim 1. A transmission member for transmitting the rotational driving force of the rotor mechanism to the outside of the frame;
A gear driven to rotate by the driving force transmitted to the outside of the frame by the transmission member;
The ultrasonic motor according to claim 1, comprising:

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