JP3074379B2 - Rotary piezoelectric actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary piezoelectric actuator, and more particularly, to a rotary piezoelectric actuator in which the structure of a rotary moving body is devised in order to obtain stable rotation characteristics.

[0002]

2. Description of the Related Art Currently, OA equipment and information processing equipment have been miniaturized, and accordingly, rotary piezoelectric actuators have been receiving attention as a power source used for driving and transporting. As an example of such a rotary piezoelectric actuator, a micro piezoelectric motor developed by the present applicant is known (15th Sensor Symposium of the Institute of Electrical Engineers of Japan, TECHNICA).
L DIGEST pp 181-184 1997).

FIG. 6 is an assembly view of the micro piezoelectric motor. The micro piezoelectric motor 400 includes a shaft projection 4
It comprises a disk-shaped rotary moving body 401 having a rotating body 11, a vibrating body block 2, and a base chassis 3 that supports a shaft projection 411. The vibrating body block 2 is provided with three bending displacement mechanism sections 22 in which the piezoelectric elements 4 that generate expansion and contraction movements are attached to the support 21. The bending displacement mechanism 22 has a shape having a long side portion and a short side portion, and a short side end portion of this shape is fixed to the center portion 23 of the vibrating body block 2. The bending displacement mechanism 22 includes a rotating moving body 401.
Are arranged so as to coincide with the tangential direction of a circle included in the sliding portion 412.

Further, the rotating body 401 and the base chassis 3 are made of a magnet material generating a magnetic attraction force, and the rotating body 401 and the vibrating body block 2 are brought into contact with each other under a constant pressure. Further, the vibrating body block 2, particularly the bending displacement mechanism 2
For 2, a non-magnetic material is used so as not to be affected by the magnetic force of the magnet material. Shaft projection 41 of rotary moving body 401
1 is supported by a hollow shaft hole 25 of the vibrating body block 2. The main body of the rotary moving body 401 is formed of a metal or a resin, and a sliding surface 412 with the vibrating body block 2 is subjected to an oxide film treatment. In addition, a photofabrication technique such as etching is used for forming the rotating body 401 and the vibrating body block 2.

FIG. 7 is an explanatory diagram showing the operation principle of this micro piezoelectric motor. By applying a drive voltage of a specific frequency to the piezoelectric element 4, the piezoelectric element 4 expands and contracts in the direction of arrow A in the figure. Due to this expansion and contraction, the bending displacement mechanism 22
Vibrates in the direction of arrow B in the figure. When the bending displacement mechanism 22 vibrates, the tip of the bending displacement mechanism 22 contacts the rotary moving body 401. The contact direction is not perpendicular to the rotary moving body 401 but is the direction indicated by the arrow c in the figure. Since the tip of the bending displacement mechanism 22 is vibrating, the elliptical motion is repeated with respect to the rotary moving body 401. The elliptical movement of the tip of the bending displacement mechanism 22 is caused by the rotation
Only the force in the ch direction facing 1 is transmitted to the rotary moving body 401. For this reason, the rotary moving body 401 moves due to the lateral force component ch. Therefore, the rotary moving body 401 obtains a rotational force by the elliptical movement of the tip of the bending displacement mechanism 22.

[0006]

The supporting body 21 for mounting the piezoelectric element 4 of the conventional micro piezoelectric motor 400 and the vibrating body block 2 are configured so that the side in contact with and facing the rotary moving body is planar. Similarly, the rotary moving body also has a planar structure on the side facing the vibrator block. Therefore, the bending displacement mechanism 22 and the rotary moving body 401 always maintain a stable contact state under a constant pressurization, and the vibration state of the bending displacement mechanism 22 is directly transmitted to the rotary moving body. However, the vibrating body block 2
Is composed of a plurality of bending displacement mechanisms 22. Therefore, variations in the shape of each bending displacement mechanism unit 22 at the time of creation, the bonding state of the piezoelectric element 4 at the time of mounting, the geometrical tolerance between the vibrating body block 2 and the shaft projection 411,
There is a possibility that a variation in mounting that occurs when a means (an electrode, a wire, or the like) for transmitting a drive signal is formed. In particular, at the time of rotation of the rotary moving body, in order to provide a driving frequency for exciting the set vibration to each bending displacement mechanism unit 22,
It is anticipated that the variation in the vibration state of each bending displacement mechanism section 22 caused by the above-mentioned variation causes variation in the contact state between each bending displacement mechanism section 22 and the rotary moving body 401. Therefore, there is a high possibility that the rotation characteristics of the rotary moving body 401 become unstable. When changing the specifications and characteristics of the desired rotary piezoelectric actuator, the shape of the support such as the width direction and the curvature of the tip is changed. In this case as well, the above phenomenon is expected to be significant. When such a phenomenon occurs, stable driving force cannot be transmitted to the rotary moving body, and there is a possibility that rotation, torque unevenness, and positioning accuracy may deteriorate.

Further, when a beam portion having a long side portion as a free end and a short side portion as a fixed end is provided, the length of the beam portion is easily increased as compared with a configuration in which one end is fixed and the other end is free. Vibration at the free end can be increased. Further, by forming the short side portion at the node of the vibration mode at the long side portion having the free end (the portion that does not always vibrate), the long side portion can be held without obstructing the vibration of the long side portion. . However, although having such advantages, holding the long side at the short side excites not only bending vibration but also torsional vibration. There is a fear that the variation easily occurs.

Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a rotary piezoelectric actuator in which a rotary moving body can obtain stable rotation characteristics.

[0009]

According to a first aspect of the present invention, there is provided a rotary piezoelectric actuator having a beam portion extending in an inner circle tangential direction and having one end fixed and the other end free. And a vibrating body composed of a piezoelectric body spread for each beam portion of the support, and a rotating moving body having a shape that contacts only the designated area with the vibrating body during the rotational movement. It is.

According to a second aspect of the present invention, there is provided a rotary piezoelectric actuator comprising a long side portion and a short side portion, and the long side portion extends in a tangential direction of the inner circle and becomes a free end, and the short side portion becomes a fixed end. A vibrating body including a support having a beam portion, and a piezoelectric body spread for each beam portion of the support, and a rotary moving body having a shape that comes into contact with only the specified region with the vibrating body during rotational movement And with.

As described above, if the shape of the rotating body is defined so that the rotating body and the vibrating body always come into contact with each other in the designated area, the vibration of the vibrating body can be stably transmitted to the rotating body. In addition, the energy conversion efficiency from the vibrating body to the rotary moving body is stabilized. In addition, since stable driving force can be transmitted to the rotary moving body, rotation and torque unevenness can be reduced and positioning accuracy can be improved. Furthermore, even in the case of specification change or new design of the rotary actuator, since the contact state depends on the shape of the rotary moving body,
As described above, the specification of the stable rotation characteristics can be reproduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment.

(Embodiment 1) FIG. 1 is an assembly view showing a rotary piezoelectric actuator according to Embodiment 1 of the present invention. FIG. 2 is an explanatory cross-sectional view showing the rotary piezoelectric actuator shown in FIG. FIG. 2 schematically shows a cross section of the vibrating body block for convenience of explanation.

The rotary piezoelectric actuator 100
Hole 13 for sliding rotation using shaft projection 31 as a support shaft
Disk-shaped rotary moving body 1 having
And a base chassis 3 having a shaft projection 31. As shown in FIG. 2 and FIG.
Has a structure in which only the outer peripheral portion is thick and the vicinity of the hole 13 is thin. The rotary moving body 1 is provided with a surface having a step 14 between a thick part and a thin part facing the vibrator block 2. Further, the vibrating body block 2 is provided with three bending displacement mechanism portions 22 in which the piezoelectric elements 4 that generate expansion and contraction motion are attached to the support 21. The bending displacement mechanism 22 has a shape including a long side portion and a short side portion, and a short side end 22 a of this shape is fixed to the center portion 23 of the vibrating body block 2. The bending displacement mechanism 22 is evenly arranged along the outer circumference of the vibrating body block 2. The outer diameter is of the order of a few millimeters. Further, the bending displacement mechanism section 22 is disposed so as to coincide with the tangential direction of a circle included in the sliding section 12 on the lower surface of the rotary moving body. Therefore, when a rotary piezoelectric actuator is constituted by the above-described components, since only the outer peripheral portion of the rotary moving body 1 is thick, the rotary moving body 1 and the central portion 23 of the vibrating body block 2 in which friction that hinders the rotation operation is generated. The structure is such that no contact occurs. For this reason, the rotary moving body 1 is
, It always comes into contact with only the bending displacement mechanism 22 that generates the driving force. Further, when a pressure is applied between the rotary moving body 1 and the vibrating body block 2, the rotary moving body 1 and the bending displacement mechanism 22 come into a stable contact state.

Due to the elliptical motion drawn by the free end (long side portion) of the bending displacement mechanism 22, the rotary moving body 1 obtains a rotational force. Therefore, this affects the rotating operation in which the contact state between the bending displacement mechanism 22 and the rotary moving body 1 occurs. In the rotary piezoelectric actuator 100, the structure of the rotary moving body 1 ensures that the rotary moving body 1 and the bending displacement mechanism 22 are always in contact with each other in the assembled state, so that a stable rotation operation of the rotary moving body 1 is achieved. It becomes possible.

Further, the shape of the rotary moving body is not limited to FIG. 4 and 5 show examples of the shape of the rotary moving body.

FIG. 4 shows a sliding portion 212 of the rotary moving body 201.
This is an example in which a cross section on the side has a circular arc shape, and has a bending displacement mechanism portion 22 which is fixed at one end and free at the other end. FIG. 4A is an assembly view of the rotary piezoelectric actuator, and FIG. 4B is a cross-sectional view of the rotary moving body 201. Since the sliding portion 212 is at the top of the curvature, even if the contact state between the vibrator block and the rotary moving body slightly varies when the rotary piezoelectric actuator is formed or mounted, the bending displacement mechanism is required. The part and the rotary moving body 201 come into contact with each other. The bending displacement mechanism 2
2 has a structure in which one end is fixed and the other end is free, so that the vibration amplitude is smaller than that of the bending displacement mechanism portion including the long side portion and the short side portion, and it is difficult to obtain a large rotational force. However, in the structure in which one end is fixed and the other end is free, torsional vibration is less likely to occur, so that vibration at the free end is less likely to vary, and a stable rotational force is easily obtained. Therefore, the rotary piezoelectric actuator 200 is
Is constituted, the rotary moving body 201 and the bending displacement mechanism 22
Can be uniformly defined. For this reason, the contact state between the rotary moving body 201 and the bending displacement mechanism is kept constant, and the rotary moving body 201 can be rotated stably.

FIG. 5 shows the sliding portion 312 of the rotary moving body 301.
This is an example in which the cross section of FIG. FIG. 5A is an assembly diagram of a rotary piezoelectric actuator, and FIG.
1 is a sectional view of FIG. Since the sliding portion 312 is located at the top of the corner, even when the contact state between the vibrator block and the rotary moving body slightly varies when the rotary piezoelectric actuator is formed or mounted, the bending displacement is always required. The mechanism unit and the rotary moving body 301 come into contact with each other. Further, when the bending displacement mechanism section 22 is constituted by a long side portion and a short side portion, torsional vibration is easily generated at a free end of the long side portion. Therefore, the rotary piezoelectric actuator 300 is
Is constituted, the rotary moving body 301 and the bending displacement mechanism 22
Can be defined at the sliding portion 312 (corner vertex). For this reason, the contact state between the rotary moving body 301 and the bending displacement mechanism is kept constant, and the rotary moving body 301 can be rotated stably.

In the rotary piezoelectric actuator, the direction of rotation of the rotary moving body 1 is determined by the direction in which the free end of the bending displacement mechanism 22 extends. In this case, since the rotary moving body 1 is pivotally supported, if the motion trajectory of the bending displacement mechanism 22 is made to coincide with the motion trajectory of the rotary moving body 1, the bending displacement mechanism 22 moves to the rotary moving body 1. The exercise conversion becomes efficient. In FIG. 1, the bending displacement mechanism 22 extends counterclockwise. However, if the extending direction is reversed, the rotating direction of the rotary moving body 1 is reversed. Further, the rotation torque and the rotation speed of the rotary piezoelectric actuator 100 are determined by the distance from the rotation center to the bending displacement mechanism 22 and the shape and number of the bending displacement mechanism 22 provided in the vibrating body block 2. The distance from the rotation center to the bending displacement mechanism 22 and the shape and number of the bending displacement mechanism 22 are set based on the required specifications of the rotary piezoelectric actuator. At this time, since the natural frequency of each bending displacement mechanism 22 depends on the shape, it is determined to meet the specifications from the results of the simulation model and the experimental data.

The piezoelectric element 4 is a material having a function of generating distortion, a function of resonance, and a function of generating voltage. That is, it is a material that exhibits characteristics such that a stress or displacement is generated according to an applied voltage, a resonance phenomenon is generated according to the frequency of the applied voltage, and a voltage is generated according to the applied pressure. The piezoelectric element 4 of this example uses thin-film lead zircon titanate having a high piezoelectric constant. Further, barium titanate, lithium niobate, lead zirconate titanate, or the like may be used.
Also, instead of these piezoelectric ceramics, a functionally graded material or lithium niobate can be used.

The vibrator block 2 is made of a metallic or nonmetallic elastic material such as stainless steel, beryllium copper, phosphor bronze, brass, duralumin, titanium or silicon.
The rotating body 1 and the base chassis 3 are made of a magnet material generating a magnetic attraction force, and the rotating body 1 and the vibrating body block 2 are brought into contact with each other under a constant pressure. For example, a stainless steel-based magnet material is used for the rotating body 1 and a neodymium-based magnet material is used for the base chassis 3. Since the base chassis 3 is drawn toward the rotating body by the magnet material, stable adhesion between the sliding portion 12 of the rotating body 1 and the bending displacement mechanism 22 of the vibrating body block 2 can be obtained. Further, it is preferable to use a non-magnetic material for the vibrating body block 2, especially for the bending displacement mechanism 22, so as not to be affected by the magnetic force of the magnet material. As a pressing method, a method based on the weight of the rotary moving body 1 itself without using magnetism as described above,
There is a method of adding a mechanism such as a spring.

The shaft projection 31 of the base chassis 3 is rotatably supported in the hollow shaft hole 25 of the vibrating body block 2.
Conversely, a hollow shaft hole may be provided on the base chassis side, and a shaft projection may be provided on the vibrating body block side or on the rotary moving body. Since the sliding portion 12 of the rotary moving body 1 is a portion that rubs against the bending displacement mechanism portion 22, the sliding portion 12 satisfies requirements such as a large friction coefficient, excellent wear resistance, and a stable friction coefficient. It is preferable to use a material. For example, the main body of the rotating body 1 is formed of metal or resin, and the sliding surface 12 with the vibrating body block 2 is subjected to an oxide film treatment. Further, the sliding surface 12 may be formed using a cellulosic fiber, a carbon fiber, a composite material of whisker and phenol resin, or a composite material of polyimide resin and polyamide resin.

The rotary moving body 1 and the vibrating body block 2 can be formed by machining, but it is preferable to use a photofabrication technique such as etching.
This is because the use of a non-machining process can eliminate deformation, stress, and mechanical stress that occur during forming. In addition, due to the high precision of the parts, the assembling adjustment process of each element part can be minimized, and the function and reproducibility are stabilized. The bending displacement mechanism section 22 of this example is formed by etching a copper-based material having a thickness of about 100 microns.

The support 21 and the piezoelectric element 4 are integrated by bonding. The conditions required for such bonding are that the bonding layer be very thin, that the bonding layer be very hard and tough, and that the resistance near the resonance frequency be small after bonding between the support 21 and the piezoelectric element 4. That is. Support 21
A bonding interface exists between the piezoelectric element 4 and the piezoelectric element 4 even if the bonding is performed by direct bonding or bonding with an adhesive. This bonding interface
This is an important factor that determines the propagation characteristics between the support 21 and the piezoelectric element 4. For this reason, the properties of the adhesive and its thickness control are important. For example, a polymer adhesive represented by hot melt and epoxy resin is used as the adhesive. In this example, an epoxy-based adhesive is used to obtain an optimum film thickness. Note that the piezoelectric elements 4 may be directly joined without using an adhesive. Further, the piezoelectric element 4 may be provided by a process means for forming a thin film and a thick film.

The bending displacement mechanism 22 is a unimorph type composed of one piezoelectric element, a bimorph type composed of two piezoelectric elements, or a multimorph type composed of four or more piezoelectric elements. There are molds, and any of them may be used. The material of the piezoelectric element 4 and the support 21 and the method of bonding them are the same as those of the rotary piezoelectric actuator 10.
It is set by the displacement amount, force, responsiveness, and structural constraints of the bending displacement mechanism 22 required for zero. In the bending displacement mechanism section 22 of the present example, a unimorph type configuration is adopted. This is because it has characteristics that it is difficult to have hysteresis on the displacement voltage characteristics. In addition, the displacement amount is small as compared with the bimorph type, but the generated force is large, and the applied load and the pressing force of the rotary moving body are appropriate. Note that, depending on the specifications of the rotary piezoelectric actuator 100, it is possible to increase the displacement and the force by increasing the number of layers while maintaining a constant thickness by adopting a multimorph type. In addition, a taper can be provided from the fixed end to the free end of the bending displacement mechanism 22 to improve responsiveness. According to the vibrating body block 2 having such a configuration, the bending displacement of the bending displacement mechanism 22 can be excited very stably. Note that the arrangement, shape, number, and configuration of the bending displacement mechanism 22 of the vibrating body block 2 are not limited to the example illustrated in FIG.

Reference numeral 5 denotes a driver for driving the piezoelectric element 4, which obtains a driving frequency from a signal generator 6. In FIG.
The vibration behavior from the fixed end to the free end of the bending displacement mechanism 22 when an input signal is applied is shown. The left end to the right end of the horizontal axis is the effective length from the fixed end to the free end of the bending displacement mechanism 22. The vertical axis represents the vibration amplitude of the bending displacement mechanism 22. The positive and negative values indicated by the vertical axis indicate that the phase difference between the input signal and the tip of the vibrator is positive, and the phase difference that is 2π (180 °) different from the above-mentioned phase difference is negative. When the vibration amplitude is 0, it indicates that the vibration is not excited. Bending displacement mechanism 22
Generates vibrations in which minute displacements and forces are mixed depending on the application conditions of the input signal, and excites longitudinal motion and elliptical motion. At the free end of the bending displacement mechanism 22, the absolute value of the vibration amplitude becomes maximum, so that the motion is transmitted from the bending displacement mechanism 22 to the rotary moving body 1. Also, the rotation direction of the rotary moving body 1 is
Determined by the lateral component of the elliptical motion. For this reason, the bending displacement mechanism section 22 of the vibrating body block 2 is arranged according to the rotation direction required for the rotary moving body 1. The direction in which the bending displacement mechanism 22 is arranged determines whether the rotary moving body 1 rotates clockwise or counterclockwise.

The drive voltage and frequency input to the bending displacement mechanism 22 are adjusted to match the natural frequency according to the size and shape of the bending displacement mechanism 22. This is because the maximum amplitude of the bending displacement mechanism 22 can be obtained by setting the input signal near the resonance frequency. As the vibration mode of the vibrating body block 2, a motion mechanism using a primary vibration mode of displacement enlargement using the long side direction of the bending displacement mechanism 22 and a secondary or higher vibration mode can be effectively used. As a result of the experiment, in order to excite the rotational motion of the vibrating body block 2 stably, it is preferable to use the secondary vibration mode or more. Furthermore, by using the phase difference of the input signal, controlling the duty ratio, or using the multiple vibration mode, the rotating moving body 1 can be stably rotated.

By doing so, the energy conversion efficiency is stabilized. Further, since the contact position with the bending displacement mechanism 22 can be specified, a torque as designed can be obtained.

[0029]

As described above, in the rotary piezoelectric actuator according to the present invention, the shape of the rotating body is defined so that the rotating body comes into contact with only the designated area of the vibrating body. Vibration can be stably transmitted to the rotary moving body. In addition, stable driving can be performed without depending on the design change (width, thickness, tip shape, etc.) of the vibrating body shape expected when the specification of the rotary piezoelectric actuator is changed. As described above, the rotation and the generated torque of the rotary piezoelectric actuator can be stabilized, and the positioning accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is an assembly diagram showing a rotary piezoelectric actuator according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory sectional view showing the rotary piezoelectric actuator shown in FIG. 1;

FIG. 3 is a graph showing a vibration behavior from a fixed end to a free end of a bending displacement mechanism when an input signal is applied.

4A and 4B are an assembly view and a cross-sectional view illustrating an example of a shape of a rotary moving body.

5A and 5B are an assembly view and a cross-sectional view illustrating an example of the shape of the rotary moving body.

FIG. 6 is an assembly view showing an example of a conventional micro piezoelectric motor.

FIG. 7 is an explanatory view showing the operation principle of the micro piezoelectric motor shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 rotary piezoelectric actuator 1 rotary moving body 12 sliding portion 13 shaft hole 2 vibrating body block 3 base chassis 31 shaft protrusion 4 piezoelectric element 21 support 22 bending displacement mechanism 23 central part 25 hollow shaft hole 5 driver 6 signal generation vessel

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Satoshi Sato 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba Seiko Instruments Inc. (56) References JP-A-10-337052 (JP, A) JP-A-10-337059 (JP, A) JP-A-3-115892 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (2)

(57) [Claims] 1. A support having a beam portion fixed at one end and free at the other end and extending in a substantially tangential direction of a circle centered on the center of rotation , and a piezoelectric member spread for each beam portion of the support. A vibrating body, wherein at least the vibrating body includes
Rotary piezoelectric actuator to the rotating moving body having a convex shape for contact only with part of the area of the support, comprising the. 2. A beam portion comprising a long side portion and a short side portion, the long side portion extending in a substantially tangential direction of a circle centered on the center of rotation and having a free end and a short side portion being a fixed end. A vibrating body comprising a support, and a piezoelectric body spread for each beam portion of the support; and a vibrating body including at least the vibrating body during a rotational movement.
Rotary piezoelectric actuator to the rotating moving body having a convex shape for contact only with part of the area of the support, comprising the.