JP2000245179A - Piezoelectric actuator, portable equipment, and clock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently transmit vibration of a piezoelectric element to a rotor. SOLUTION: A piezoelectric actuator A is provided with a plate-like diaphragm 10 and a stator 20. When the diaphragm 10 vibrates, a movable section 21 of the stator 20 makes a flexing vibration in the in-plane direction. An end part 21a of the movable section 21 is in contact with the outer surface of a rotor 30. Since the end part 21a has a curved surface, the movable section 21 can be kept in good contact with the rotor 30, even if there is variation in the installation accuracy of components. As a result, the rotor 30 can be rotated clockwise with a large driving force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator utilizing in-plane bending vibration, a portable device and a timepiece using the piezoelectric actuator.

[0002]

2. Description of the Related Art Various types of piezoelectric actuators utilizing the piezoelectric effect of a piezoelectric element have been developed in recent years because the piezoelectric element has excellent conversion efficiency from electric energy to mechanical energy and excellent responsiveness. This piezoelectric actuator is applied to fields such as a shutter mechanism of a camera, an ink jet head of a printer, and an ultrasonic motor. FIG. 16 is a plan view schematically showing an ultrasonic motor using a conventional piezoelectric actuator. This type of ultrasonic motor is of the so-called "stick type" type, in which the tip of a vibrating piece connected to a piezoelectric element is brought into contact with the side surface of the rotor with a slight inclination. The principle of rotation is that when the piezoelectric element expands and contracts due to the AC voltage from the oscillating unit and the vibrating piece reciprocates in the length direction, a component force is generated in the circumferential direction of the rotor and the rotor rotates.

[0003]

However, the displacement of the piezoelectric element is very small, depending on the applied voltage, and is usually about several μm. For this reason, it is desirable to amplify the displacement by some amplification mechanism and transmit the amplified displacement to the rotor. On the other hand, when the amplification mechanism is used, there is a problem in that energy is consumed to move itself, and efficiency is reduced. Also, small portable devices such as wristwatches and cameras are driven by batteries, so it is necessary to keep the drive voltage low. Therefore, when incorporating a piezoelectric actuator into such a portable device, it is particularly important to keep the drive voltage low.

In a calendar display mechanism for displaying the day, day of the week or the like in a wristwatch or the like, the rotational driving force of an electromagnetic step motor is intermittently transmitted to a date wheel and the like via a wheel train for moving hands. It is common to drive and drive a car. On the other hand, since a wristwatch is carried around a wrist with a belt, there has been a long-standing demand for a thin wristwatch for convenient carrying. For this purpose, it is necessary to reduce the thickness of the calendar display mechanism. However, since the step motor is configured by incorporating components such as a coil and a rotor in an out-of-plane direction, there is a limit in reducing the thickness thereof. For this reason, the conventional calendar display mechanism using the step motor has a problem that it is not structurally suitable for thinning.

In particular, a clock having a calendar display mechanism,
In order to share the mechanical system of hand movement (so-called movement) with a timepiece without such a display mechanism, it is necessary to configure a calendar display mechanism on the dial side. It is difficult to reduce the thickness to such an extent that it can be configured. Therefore, in the conventional timepiece, it is necessary to separately design and manufacture the mechanical system of the hand movement depending on the presence or absence of the display mechanism, which has been a problem in improving the productivity.

[0006] In a small portable device such as a wristwatch, a user often drops the portable device from his / her hand, and the portable device often hits the floor. For this reason, the piezoelectric actuator incorporated in such a portable device needs to be strong against an impact force.

The present invention has been made in view of the above circumstances, and has as its object to provide a piezoelectric actuator which can be driven at a low driving voltage, has a strong impact force, and is suitable for thinning. Another object is to provide a portable device and a clock using the same.

[0008]

In order to solve the above-mentioned problems, a piezoelectric actuator according to the present invention has a disk-shaped rotating body rotatably supported in an in-plane direction, and is in contact with an outer peripheral surface of the rotating body. A plate-shaped movable portion that rotates the rotating body by displacing the end portion in an in-plane direction, and a plate-shaped member coupled to the movable portion and provided with a piezoelectric element. And a vibration plate.

In the present invention, since the end of the movable portion and the outer peripheral surface of the rotating body are in contact with each other on a curved surface, the contact state does not change much even if the positional relationship between the rotating body and the movable portion slightly varies. Therefore, the allowable range of assembling accuracy can be increased, and a good contact state can be maintained even if the end is worn out due to wear. Here, the end of the movable portion may have a curved surface shape in an in-plane direction, or may have a curved surface shape in a direction perpendicular to the in-plane direction.

Further, in the piezoelectric actuator according to the present invention, the movable portion has an elongated shape in the longitudinal direction, and the center of rotation of the rotating body is shifted from a line extending from a center line connecting the centers in the width direction. It is preferable to dispose the rotator on the surface. In this case, the length required for disposing the piezoelectric actuator and the rotating body can be reduced, and downsizing is facilitated.

Further, in the piezoelectric actuator according to the present invention, the rotating body may have a V-shaped groove formed on an outer peripheral surface thereof. In this case, the state of contact between the rotating body and the movable portion can be kept even better, and the transmission efficiency between them can be improved. Further, since the end portion is supported by the V-groove, even if a large impact force is applied to the movable portion, the movable portion does not come off the rotating body. Therefore, a piezoelectric actuator that is strong against impact can be configured.

Further, in the piezoelectric actuator according to the present invention, it is preferable that the hardness of the outer peripheral surface of the rotating body is larger than the hardness of the end of the movable portion. In this case, when an impact force is applied to the piezoelectric actuator, the end of the movable portion is deformed, but the outer peripheral surface of the rotating body is not deformed. Therefore, it is possible to configure a piezoelectric actuator that is strong against an impact force without the outer peripheral surface of the rotating body being deformed and the end of the movable portion being cut there. It is preferable that a hardening process is performed on the outer peripheral surface of the rotating body.

Further, in the piezoelectric actuator according to the present invention, it is preferable that an end of the movable portion is formed of a wear-resistant material. In this case, wear of the end portion can be reduced, and a change with time in the contact state can be reduced.

Further, in the piezoelectric actuator according to the present invention, it is preferable that an outer peripheral surface of the rotating body or an end of the movable portion is subjected to a smoothing process for smoothing the surface. Thereby, the transmission efficiency of the driving force between the rotating body and the movable part can be increased.

Further, the piezoelectric actuator according to the present invention may include an urging means for urging the movable portion against the rotating body. In this case, the allowable range of the mounting position of the rotating body and the movable portion can be expanded, so that the piezoelectric actuator can be easily assembled. Furthermore, even if the end of the movable part is worn out due to wear,
A good contact state can be maintained.

Further, the piezoelectric actuator according to the present invention is characterized in that the driving means for supplying a driving signal of a frequency substantially equal to the natural vibration frequency of the primary vibration mode or the higher vibration mode to the piezoelectric element of the movable portion. It may be provided. In this case, a drive signal having a frequency substantially equal to the natural vibration frequency of the primary vibration mode or the higher vibration mode of the movable portion is applied to the piezoelectric element provided on the diaphragm. Therefore, the movable portion vibrates at a frequency substantially equal to the natural vibration frequency of the primary vibration mode or the higher vibration mode. When a structure vibrates at the frequency of the first-order vibration mode or higher-order vibration mode, its mechanical impedance is minimized, and a large displacement occurs. Therefore, according to the piezoelectric actuator of the present invention, it is possible to drive the rotating body by obtaining a large mechanical displacement even with a low driving voltage.

A portable device according to the present invention includes the piezoelectric actuator and a battery for supplying power to the piezoelectric actuator. In this case, since the piezoelectric actuator has extremely high energy efficiency, it can be used continuously for a long time. The battery may be a primary battery such as a dry battery or a mercury battery, or may be a large-capacity capacitor, a lithium-ion secondary battery, or a secondary battery having a storage capacity such as Ni-Cd.

The timepiece according to the present invention is characterized in that the piezoelectric actuator, a battery for supplying power to the piezoelectric actuator, a wheel train interlocking with the rotating body, and a ring-shaped calendar display rotating in conjunction with the wheel train. It is equipped with a car. As the calendar display car, there are day cars in addition to day cars. Since the piezoelectric actuator has a structure suitable for thinning, the entire timepiece can be thinned.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [1. First Embodiment] A piezoelectric actuator according to one embodiment of the present invention will be described below with reference to the drawings.

[1-1. Overall Configuration] FIG. 1 is a plan view of a piezoelectric actuator, and FIG. 2 is a side view thereof. As shown in the figure, the piezoelectric actuator A is roughly composed of a plate-shaped vibration plate 10, an L-shaped stator 20, and a rotor 30, and is mounted on the main plate 1.

First, the diaphragm 10 has a sandwich structure in which piezoelectric elements 11a and 11b are adhered to upper and lower surfaces of a shim portion 12, respectively. The shim 12 is made of, for example, a thin plate of phosphor bronze or the like, and functions as an elastic plate. With such a sandwich structure, the strength of the diaphragm 10 can be improved. Therefore, in a portable device such as a timepiece using the piezoelectric actuator A as a driving device, the durability against a large impact applied when the portable device is dropped can be improved. The materials of the piezoelectric elements 11a and 11b are quartz, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zirconate titanate, lead zinc niobate ((Pb (Zn1 / 3-Nb2 / 3) O3 1-x-Pb Ti O3
x) x depends on the composition. x = 0.09), and lead scandium niobate ((Pb {(Sc1 / 2Nb1 / 2) 1-xTix)} O3) x varies depending on the composition. X = 0.09) can be used. .

Next, the stator 20 includes a movable portion 21 having a rectangular shape, and a constricted portion 2 having a width smaller than the width of the movable portion 21.
2 and a spring portion 23 having a lever-like shape. The diaphragm 10 is connected to a side surface of the movable portion 21. For this reason, when the diaphragm 10 vibrates, the movable portion 21 is vibrated in the direction of arrow 200 in the figure, and a bending vibration in an in-plane direction (a direction parallel to the paper surface in FIG. 1) is excited there. In addition, regarding the bending vibration in the in-plane direction,
Details will be described later.

Further, since the width of the constricted portion 22 is smaller than that of the movable portion 21, the constricted portion 22 functions as an elastic body. For this reason, the constricted part 22 elastically connects the movable part 21 and the spring part 23. Therefore, when the movable portion 21 bends and vibrates in the in-plane direction, the constricted portion 22 is freely deformed according to the deflection of the movable portion 21.

Further, the spring portion 23 is provided with a through hole 23b through the constricted portion 22, into which a pin 24 is inserted. The pin 24 is fixed to the base plate 1, and its diameter is slightly smaller than the diameter of the through hole 23b. Therefore, the spring portion 23 is supported rotatably in the in-plane direction about the pin 24. A pin 25 serving as a pressing member for the spring portion 23 is fixed to the main plate 1 at a tip portion 23 a of the spring portion 23. Therefore, the spring portion 23 applies a counterclockwise force to the stator 20 about the pin 24. Thereby, the end 21 a of the movable portion 21 is pressed against the rotor 30. That is, the pin 24 functions as a supporting portion that rotatably supports the stator 20, and the spring portion 23 functions as a unit that urges the stator 20 to the rotor 30. By using such a biasing means, the dimensions of the components and the mounting of the components do not require very high precision, so that the piezoelectric actuator A can be simply configured.

Next, the rotor 30 has a shaft 31 at the center thereof. The shaft 31 is supported by a bearing (not shown) provided on the main plate 1. Therefore, the rotor 30 is rotatably supported by the main plate 1. Also. The rotor 30 has a cylindrical sliding part 3.
0a and flanges 30b, 30c provided on the upper and lower surfaces thereof, respectively.
And The flange portions 30b and 30c are formed of thin disks, and have a diameter slightly larger than the diameter of the sliding portion 30a. The end 21a is in contact with the sliding portion 30a, and the flanges 30b and 30c function as members for holding the end 21a. For this reason, even if a large impact force is applied to the movable portion 21 when it falls, the flange portion 30b, 30c prevents the end portion 21a from being excessively displaced and coming off.

[1-2. Contact Conditions Between Rotor and Movable Part] Now, the contact conditions between the rotor 30 and the movable part 21 will be described in detail. [1-2-1. Planar Contact Conditions] FIG. 3 is an enlarged plan view for explaining a planar contact state between the rotor 30 and the movable part 21. In FIG. 3, the flange portions 30b and 30c are omitted. As shown in this figure, the end 21a of the movable portion 21 that comes into contact with the rotor 30 has a curved shape when viewed in plan. When the end 21a is formed into a curved surface in this manner, the curved surface comes into contact with the curved surface, so that even if the positional relationship between the stator 20 and the rotor 30 varies somewhat, the contact state does not change much. Specifically, there are cases where the diameter of the through hole 23b is larger than the design value, or where the bearing of the rotor 30 has play.

Further, in this example, as shown in the figure, a normal J1 passing through the contact point P and a center line J2 of the movable portion 21 form an angle θa. That is, the rotor 30 is arranged so as to shift the rotation center of the rotor 30 from a line obtained by extending the center line J2. In this case, as compared with the case where θa = 0 (the case where the rotation center of the rotor 30 is on the center line J2), the rotor 30 is disposed at the constricted portion 22. Therefore, the length L required for disposing the piezoelectric actuator A and the rotor 30 can be reduced, and the size can be reduced. Further, the curved surface of the end 21a is formed by the rotor 30 and the end 21a.
a is set so as to be easily contacted. For this reason, the end 21
The radius of curvature of a is the distance from the pin 24, which is the center of rotation, to the contact point. However, since the rotor 30 and the end 21a need only be in contact with each other within a certain range, the radius of curvature may be reduced within the allowable range.

[1-2-2. Cross-Section Contact Conditions] Next, FIG. 4 is a cross-sectional view for explaining a cross-section contact state between the rotor 30 and the movable portion 21. As shown in FIG. 4A, the end 21a of the movable portion 21 has a curved surface when viewed in cross section. The end 21a has a projection 21a 'on its lower side.
Are formed. In addition, the protrusion 21a 'is formed when the stator 20 is manufactured by die cutting as described later. As described above, since the end portion 21a is formed to have a curved shape when viewed in cross section, the movable portion 21 and the rotor 30
Even if there is some variation in the contact angle with the contact, a good contact state can be maintained. On the other hand, as shown in FIG. 4 (b), when the end 21a is formed in a linear shape when viewed in cross section, the contact state greatly changes because the contact angle slightly varies. A change in the contact state causes uneven torque, which is not preferable. Here, in order to keep the contact angle constant, it is conceivable to provide a guide member for guiding the movable portion 21, but such a configuration increases the number of components and increases the cost of the piezoelectric actuator A. .
Therefore, by configuring the cross-sectional shape of the end portion 21a to be a curve, the allowable range of component attachment can be expanded and the cost of the piezoelectric actuator A can be reduced.

[1-2-3. Contact Conditions for Hardness] Next, contact conditions for hardness will be described. First, the hardness of the sliding portion 30 a of the rotor 30 is larger (harder) than the hardness of the end 21 a of the stator 20. This is to prevent the rotor 30 from being deformed when an impact force is applied to the piezoelectric actuator A. Assuming that the end 21a
Is larger than the hardness of the sliding portion 30a, the sliding portion 30a is deformed when the end 21a hits the rotor 30 with a large force. In this case, the sliding portion 30a often has a recess, although the manner of deformation depends on the magnitude of the impact force. Then, when the end 21a bites into this recess, the movement of the end 21a stops.

On the other hand, if the hardness of the sliding portion 30a is larger than the hardness of the end 21a, the end 21a is more deformed. However, even if the end 21a is deformed, the operation does not stop. Further, even if the concave portion and the convex portion are generated in the end portion 21a due to the deformation, the end portion 21a vibrates so as to hit the sliding portion 30a as long as the operation is continued, so that the convex portion gradually wears and finally disappears. Further, even if the concave portion is formed, the end portion 21a is urged to the rotor 30 by the spring portion 23, so that the end portion 21a and the sliding portion 30a cannot be in contact with each other due to the concave portion. . For the above reasons, in this example, the hardness of the sliding portion 30a is greater than the hardness of the end 21a.

Here, in order to obtain a large hardness, for example, super steel, ruby, iron, ceramic (aluminum oxide, silicon nitride), or duralumin may be used as the material of the sliding portion 30a. Further, a hardening process may be performed on the outer peripheral surface of the sliding portion 30a. Various types of curing treatments can be used. For example, DLC (D
(Sliding portion 30a containing aluminum), electroless nickel plating, chrome plating, ceramic spraying, or the like may be used.

On the other hand, although the hardness of the end portion 21a is smaller than the hardness of the sliding portion 30a, it is preferable to use, for example, a wear-resistant material such as polyimide resin, fluororesin (Teflon, PTFE), or nylon. In this case, the wear of the end 21a can be reduced, and the change over time in the contact state can be reduced.

[1-2-4. Contact Conditions for Surface Roughness]
Next, the contact condition relating to the surface roughness will be described. FIG. 5 shows the relationship between the surface roughness of the end portion 21a of the stator 20 or the sliding portion 30a of the rotor 30 and the minimum voltage of the drive signal V applied to the piezoelectric elements 11a and 11b required for driving the rotor 30. FIG. As shown in this figure, when the surface roughness exceeds 10 μm, the lowest voltage of the drive signal V sharply increases. This means that if the surface is not smooth, the transmission efficiency of the driving force decreases. In a portable device driven by a battery such as a wristwatch, the entire device needs to be operated by a low power supply voltage. Therefore, when the piezoelectric actuator A is incorporated in such a portable device and used, in particular, It is necessary to consider the voltage of the drive signal V. Therefore, in the present embodiment, a process for smoothing the contact surface of the end portion 21a or the sliding portion 30a is performed. As a process for smoothing the end portion 21a or the sliding portion 30a, there is a polishing process. Specifically, electrolytic polishing in which a metal is immersed in an electrolytic solution as an anode and a voltage is applied,
There is barrel polishing in which an abrasive and components are put in a container and the mixture is stirred to polish, or centerless polishing in which components are placed between two rotating cylindrical grindstones and the components are rotated while the components are rotated. .

[1-3. Manufacturing Method of Stator] Next, a manufacturing method of the stator 20 will be described. The stator 20 of this example is manufactured by a special press working method. FIG. 6 is a diagram illustrating a state of press working of the stator 20. As shown in this figure, when forming the end portion 21a of the stator 20, first, a semi-finished product 20 'of the stator 20 is placed on a lower mold Q inclined at an upper surface, and Semi-finished product 20 'by pushing down the upper mold R from
Is formed with an end 21a.

Here, the planar curved shape of the end 21a is formed by using the upper die Q and the lower die R corresponding to the shape. On the other hand, the cross-sectional curved shape of the end portion 21a utilizes a "drain" generated at the time of cutting. "Wall" is caused by the cutting edge of the mold biting into the material until the material cracks, and becomes large when the clearance is large or the material has a high viscosity. In this example, since the upper surface of the lower mold R is inclined, the semi-finished product 20 'is cut obliquely with respect to the thickness direction. By adding “who” to this, a cross-sectional curved shape of the end 21a is formed. In this example, the clearance, the inclination angle of the lower mold R, and the like are adjusted so as to obtain a desired curved surface. According to this manufacturing method, the polishing step can be omitted in order to obtain the curved shape of the end 21a, so that the stator 20 can be easily manufactured.

[1-4. Driving Circuit] Next, the driving circuit 100
Will be described. FIG. 7 shows the driving circuit 100 and the piezoelectric element 1.
It is a figure which shows the connection state with 1a, 11b. As shown in the figure, the shim portion 12 functions as a common electrode of the piezoelectric elements 11a and 11b, where
Is supplied, and the drive signal V is supplied to the piezoelectric elements 11a and 11b. In general, when the direction of the electric field applied to the piezoelectric element and the direction of displacement (strain direction) match, the longitudinal effect is used, and when the direction of the electric field and the direction of displacement are orthogonal, the lateral effect is used. Thus, the diaphragm 10 is vibrated. The polarization directions of the piezoelectric element 11a and the piezoelectric element 11b are set so that they are opposite to each other as shown by arrows in the figure. Therefore, when the drive signal V is applied, when one piezoelectric element extends in the longitudinal direction, the other piezoelectric element also extends in the longitudinal direction. Piezoelectric element 1
Since a voltage is applied to each of 1a and 11b, the voltage of the drive circuit can be used effectively. The connection shown in this figure is called a parallel connection. In the parallel connection, a large displacement can be obtained by low voltage driving. Therefore, it is suitable for application to portable equipment driven by a battery such as a watch.

The drive circuit 100 includes a separately-excited type and a self-excited type. First, FIG. 8A shows a block diagram of a separately-excited driving circuit. Oscillation circuit 1
The oscillation signal output from 01 is converted to a desired oscillation frequency by the frequency conversion circuit 102 to generate the drive signal V. In this case, the configuration can be simplified by using the oscillation circuit 101 also as a crystal oscillation circuit in a clock circuit for driving the hands, and using a frequency dividing circuit for the frequency conversion circuit 102. Next, FIG. 8B shows a block diagram of a self-excited drive circuit. In the self-excited type shown in the figure, a filter 104 is provided for a Colpitts oscillation circuit 103, and a drive signal V is applied to the piezoelectric elements 11a and 11b by positively feeding back only a signal of a predetermined frequency.

Now, the relationship between the frequency of the drive signal V and the structure of the movable section 21 will be described. Assuming that the stator 30 is a rigid body, the stator 20 is displaced around the constricted portion 22 as shown in FIG. In this case, when the diaphragm 10 is displaced, the displacement of the end portion 13 is amplified by the principle of leverage around the constricted portion 22, and the movable end 21
Is transmitted to However, since the stator 20 has a so-called cantilever structure, a large stress is applied to the constricted portion 22 serving as a support portion, and the stress escapes from the constricted portion 22 to increase energy loss. For this reason, there is a problem that conversion efficiency from electric energy to mechanical energy is reduced.

When the excitation frequency is gradually increased under the condition of a constant force with respect to a mechanical structure, the amplitude of the structure takes a maximum value at a certain frequency and then takes a minimum value. Repeat the response. That is, there are a plurality of frequencies at which the amplitude has a maximum, and the frequencies corresponding to the respective maximums are collectively referred to as a natural vibration frequency. The mode of vibration corresponding to the lowest natural frequency is referred to as a primary vibration mode, and the mode of vibration corresponding to the next lowest natural frequency is referred to as a secondary mode. It is known that when a structure vibrates at the natural vibration frequency of these vibration modes, its mechanical impedance is minimized, and a large displacement can be easily obtained with a small driving force.

The piezoelectric actuator A used in the present embodiment is constructed by paying attention to this point, and has a frequency substantially equal to the natural vibration frequency of the primary vibration mode or the higher vibration mode of the movable portion 21. Excites the movable part 21. FIG. 9B schematically shows the displacement of the movable portion 21 in the primary vibration mode, and FIG. 9C schematically shows the displacement of the movable portion 21 in the secondary vibration mode. It is a thing. As shown in FIGS. 9B and 9C,
The movable portion 21 vibrates while bending in the plane.

Here, assuming that the movable portion is vibrated in the n-th order vibration mode, the frequency of the drive signal V is set to be substantially equal to the natural vibration frequency of the n-th order mode. According to the piezoelectric actuator A, the movable portion 2
Since the mechanical impedance of 1 is minimized, a large displacement can be easily obtained with a small driving force. Although it depends on the damping coefficient of the movable part 21, the movable part 21 is generally regarded as a rigid body,
As compared with the case where the vibration is applied without considering the natural vibration frequency, a displacement several to several thousand times can be obtained.

[1-5. Operation of Piezoelectric Actuator] FIG.
When the drive signal V is applied to the piezoelectric element 11a (11b), the diaphragm 10 vibrates in the longitudinal direction. Then, diaphragm 10 pushes movable portion 21 in the direction of arrow 200, and in-plane bending vibration is excited in movable portion 21. Here, the drive signal V has a frequency substantially equal to the natural vibration frequency of the n-th vibration mode of the movable section 21. Therefore, an n-order vibration mode is excited in the movable portion 21. For example, if n = 2, as shown in FIG.
The movable part 21 bends and vibrates in the next vibration mode.

Since the end 21 a of the movable portion 21 is urged by the rotor 30 by the reaction force of the spring portion 23, the end 2 a
When 1a bends and vibrates in the in-plane direction, the sliding portion 30a of the rotor 30 is hit by the end 21a. This allows
A circumferential force is applied to the rotor 30, and the rotor 30 rotates clockwise.

[1-6. Modification of First Embodiment] [1-6-1. Modification of Rotor Shape] In the above example, the sliding portion 30a of the rotor 30 has a columnar shape. However, a rotor 32 shown in FIG. 10 may be used instead of the rotor 30. FIG. 10A is a plan view of the rotor 32 and the movable portion 21, and FIG. 10B is a side view thereof. As shown in the figure, the rotor 32 has a disk shape, and has a V-groove formed on the outer peripheral surface thereof. In this case, the end 21a of the movable portion 21 comes into contact with the first groove surface 32a and the second groove surface 32b forming the V groove. For this reason, the movable part 21 is automatically adjusted to the center of the V-groove, and a good contact state can be maintained.
The transmission efficiency between them is improved. Further, since the end 21a is supported by the first and second groove surfaces 32a, 32b,
Even if a large impact force is applied to the movable portion 21 when it falls, the movable portion 21 does not come off the rotor 32. Therefore, in this example, the flange 30
No special holding member such as b, 30c is required.

[1-6-2. Modification Example of Connection between Diaphragm and Stator] FIG. 11 is a plan view of a piezoelectric actuator according to a modification example, and FIG. 12 is a sectional view thereof. In this piezoelectric actuator, the diaphragm 10 and the stator 20 are connected by a constricted portion 13. The constricted portion 13 is formed as a part of the shim portion 12 and has a width equal to that of the diaphragm 10.
Is narrower than the width. Therefore, the constricted portion 13 functions as an elastic body.

As described above, the diaphragm 1 is provided through the constricted portion 13.
The reason why the stator 0 is connected to the stator 20 is as follows. That is, since the movable portion 21 of the stator 20 bends and vibrates in the in-plane direction, the diaphragm 10 is subjected to an in-plane force with the bending vibration of the movable portion 21, and moves in the direction of arrow 201 shown in FIG. Will be shaken. On the other hand, the vibration plate 10 vibrates in the longitudinal direction, but is shaken in the direction of the arrow 201, so that the center of gravity of the whole is shifted. For this reason,
The force applied to the fixing part increases, and the loss increases. Therefore, in this example, by providing a constricted portion 13 acting as an elastic body between the diaphragm 10 and the movable portion 21,
The movable portion 21 prevents the vibration plate 10 from being shaken and shifting the center of gravity of the whole.

[1-6-3. Modified Example Regarding Shape of Movable Part] In the first embodiment, the movable part 21 has substantially the same size as the diaphragm 10, but as shown in FIG. The size of the movable part 21 and the size of the diaphragm 10 may be different. FIG. 17 is a plan view of a piezoelectric actuator according to such a modification, and FIG. 18 is a cross-sectional view for explaining a cross-sectional contact state between the rotor 30 and the movable portion 21.

In FIG. 17 and FIG.
1 ', constricted portion 22', spring portion 23 ', support end 23c'
Is formed integrally with the shim 12 of the diaphragm 10.
A through hole 23b 'is formed in the support end 23c',
The pin 24 is inserted into the through hole 23b '. Pin 2
4 is fixed to a base plate (not shown), the diameter of which is
3b 'is slightly smaller. Therefore, the support end 23c 'is supported rotatably in the in-plane direction about the pin 24.

On the other hand, at the tip 23a 'of the spring portion 23',
A pin 25 serving as a holding member for the spring portion 23 'is fixed to a main plate (not shown). Therefore, the spring portion 23 'is
, And a counterclockwise force is applied to the diaphragm 10. Thus, the end 21 a of the movable portion 21 ′ is pressed against the rotor 30. That is, the pin 24 functions as a supporting portion that rotatably supports the stator 20 ′,
The spring portion 23 'functions as a means for urging the stator 20' against the rotor 30.

Further, since the cross-sectional shape of the end 21a of the movable portion 21 'is a curved shape as shown in FIG. 4 (a), there is some variation in the contact angle between the movable portion 21' and the rotor 30. Even if it is, a good contact state can be maintained.

With this configuration, the mass of the movable portion 21 'can be reduced, so that even if an impact is applied due to a drop or the like, the generated impact force can be reduced, and the piezoelectric actuator and the rotor can be damaged. Can be prevented.

[2. Second Embodiment] Next, a second embodiment relates to a timepiece incorporating the piezoelectric actuator described in the first embodiment. [2-1. Overall Configuration] FIG. 13 is a plan view showing a main configuration of a calendar display mechanism incorporating a piezoelectric actuator in a timepiece according to a second embodiment of the present invention. The piezoelectric actuator A of this example is the same as that described in the first embodiment except that the piezoelectric actuator A includes a small-diameter portion 3a fixed on the upper surface of the rotor 30 so as to be concentric with the rotor 30 and having teeth formed on the outer peripheral surface. It is configured similarly.

Next, the calendar display mechanism is connected to the piezoelectric actuator A, and is driven by its driving force. A main part of the calendar display mechanism is generally constituted by a reduction gear train for reducing the rotation of the rotor 30 and a ring-shaped date dial 50. The reduction gear train includes a date turning intermediate wheel 40 and a date turning wheel 60.

Here, the stator 20 is pressed against the rotor 30 with an appropriate pressing force in a stationary state. Therefore, when the stator 20 bends and vibrates in the in-plane direction,
The end 21a vibrates in the arrow direction X, and the rotor 30 rotates clockwise. The rotation of the rotor 30 is transmitted to the date driving wheel 60 via the date driving intermediate wheel 40, and the date driving wheel 6
0 causes the date dial 50 to rotate clockwise. As described above, the transmission of the force from the stator 20 to the rotor 30, the transmission of the force from the rotor 30 to the reduction gear train, and the transmission of the force from the reduction gear train to the date indicator 50 are all performed in the in-plane direction. Therefore, the thickness of the calendar display mechanism can be reduced.

FIG. 14 is a sectional view of a timepiece according to a second embodiment of the present invention. In the figure, a calender mechanism provided with the above-described piezoelectric actuator A is incorporated in the shaded portion, and its thickness is as thin as about 0.5 mm. A disk-shaped dial 70 is provided above the calendar display mechanism. A window 71 for displaying a date is provided on a part of the outer peripheral portion of the dial 70, and the window 71 is provided.
The date of the date wheel 50 can be seen from the. Also,
A movement 73 for driving the hands 72 and a drive circuit 100 (not shown) are provided below the dial 70.

In the above-described configuration, the piezoelectric actuator A has a configuration in which the diaphragm 10, the stator 20, and the rotor 30 are arranged in the same plane, instead of stacking coils and rotors in an out-of-plane direction as in a conventional step motor. It has become. Therefore, it is structurally suitable for thinning.
Therefore, the thickness of the calendar display mechanism can be reduced, and the thickness of the entire timepiece can be reduced.
Further, the movement 73 can be shared between a timepiece having a calendar display mechanism and a timepiece having no such display mechanism, and productivity can be improved.

[2-2. Calendar Display Mechanism] [2-2-1. Configuration of Calendar Display Mechanism] Next, the configuration of the calendar display mechanism will be described with reference to FIG. 13 and FIG. I do. In the figure, the ground plane 1 is
The first plate is a first bottom plate for arranging each component, and the main plate 1 ′ is a second bottom plate having a step partially with respect to the main plate 1. The date intermediate wheel 40 includes a large-diameter portion 4b and a small-diameter portion 4a which is fixed concentrically with the large-diameter portion 4b and has a slightly smaller diameter than the large-diameter portion 4b. Small diameter part 4a
Is cut out in a substantially square shape to form a cutout portion 4c. A bearing 4d is formed on the main plate 1 ', and a shaft 41 of the date turning intermediate wheel 40 is supported by the bearing 4d. Therefore, the date intermediate wheel 40 is provided rotatably with respect to the main plate 1 '.

Next, the date wheel 50 has a ring shape, and an internal gear 5a is formed on an inner peripheral surface thereof. The date wheel 60 has a five-tooth gear and meshes with the internal gear 5a. A shaft 61 is provided at the center of the date driving wheel 60.
Are provided, and the date wheel 60 is rotatably supported. The shaft 61 has a through hole 6 formed in the main plate 1 '.
It is loosely inserted in 2. The through hole 62 is formed to be long along the rotation direction of the date indicator 50.

Next, one end of the leaf spring 63 is connected to the main plate 1 '.
, And the other end is fixed to the shaft 61. Accordingly, the leaf spring 63 urges the shaft 61 and the date wheel 60 in the clockwise direction. Also, this leaf spring 63
The swinging of the date wheel 50 is also prevented by the urging action of.

Next, the leaf spring 64 has one end screwed to the main plate 1 'and the other end formed with a tip portion 64a bent in a substantially V-shape. Further, the contact 65
Means that the date-rotating intermediate wheel 40 rotates and the front end portion 64a
It is arranged so as to come into contact with the leaf spring 64 when it enters the position c. A predetermined voltage is applied to the leaf spring 64. When the leaf spring 64 contacts the contact 65, the voltage is also applied to the contact 65. Therefore, the date feeding state can be detected by detecting the voltage of the contact 65.
Note that a manually driven wheel that meshes with the internal gear 5a may be provided, and the date wheel 50 may be driven when the user performs a predetermined operation on the crown (not shown).

[1-3-2. Operation of calendar display mechanism]
The automatic calendar updating operation will be described with reference to FIG. At midnight on each day, it is detected that it is midnight, and the driving signal V
Is supplied to the piezoelectric elements 11a and 11b. Then, the end 21a of the stator 20 bends and vibrates in the in-plane direction. Accordingly, when the rotor 30 rotates clockwise, the date intermediate wheel 40 starts rotating counterclockwise.

Here, the drive circuit 100 is configured to stop supplying the drive signal V when the leaf spring 64 and the contact 65 come into contact with each other. When the leaf spring 64 and the contact 65 are in contact with each other, the distal end portion 64a enters the cutout portion 4c. Therefore, the date intermediate wheel 40 starts rotating from such a state.

Since the date driving wheel 60 is urged clockwise by the leaf spring 63, the small diameter portion 4a is
It rotates while sliding on the zero teeth 6a, 6b. When the notch 4c reaches the position of the tooth 6a of the date wheel 60 on the way, the tooth 6a meshes with the notch 4c. At that time, the circumscribed circle of the date driving wheel 60 has moved to the position indicated by C1.

Next, when the date driving intermediate wheel 40 continues to rotate counterclockwise, the date driving wheel 60 is rotated.
In conjunction with 0, it rotates clockwise by one tooth, that is, "1/5" circumference. Further, in conjunction with this, the date indicator 50
Is rotated clockwise by one tooth (corresponding to a date range of one day).

When the date intermediate wheel 40 continues to rotate counterclockwise and the notch 4c reaches the position of the tip 64a of the leaf spring 64, the tip 64a is moved to the notch 4c.
Get into it. Then, the leaf spring 64 and the contact 65 come into contact with each other, the supply of the drive signal V ends, and the rotation of the date intermediate wheel 40 stops. Therefore, the date intermediate wheel 40 is 1
One rotation per day. The number of days in the month is "3
On the last day of the month less than "1", the above operation is repeated a plurality of times, and the correct date based on the calendar is displayed by the date wheel 50.

By the way, the load of the piezoelectric actuator A1 is 1) during the first period until the tip end 64a of the leaf spring 64 enters the notch 4c and exits (at the start of rotation), and 2) at the notch 4c. Increases during the second period in which the date wheel 50 is engaged with the date wheel 60 to rotate the date wheel 50.
When the load on the piezoelectric actuator A1 increases, the current consumption increases, and the power supply voltage decreases. If the power supply voltage drops significantly, it will affect other circuits, and in the worst case, the hour and minute hands cannot be driven. However, in the mechanical system of this example, the first period and the second period do not overlap. In other words, the maximum torque required for detecting the date feed state and the maximum torque required for driving the date wheel 50 are shifted. Therefore, the peak current of the piezoelectric actuator A can be suppressed, and as a result, the timepiece can be reliably operated while maintaining the power supply voltage at a certain voltage value or higher.

[3. Modifications] (1) In each of the embodiments described above, the first and second order vibrations have been mainly described. However, the present invention is not limited to this. Of course, there may be.

(2) In each of the embodiments described above, the shim portion 12 and the stator 20 are formed of a single plate-like member, and the thin May be configured.
In this case, the main part of the piezoelectric actuator can be composed of two parts, so that the configuration can be extremely simplified.

(3) In each of the embodiments described above, the date wheel 50 of the calendar display mechanism is rotated. However, the day wheel may be rotated by a piezoelectric actuator. In addition to the watch's calendar display mechanism,
It can be used as a driving device for a device that displays the moon, year, age, sun position, as well as water depth, pressure, temperature, humidity, azimuth, speed, and the like. Further, it is needless to say that the present invention can be used as various driving devices other than the display device. For example, the present invention can be applied to a mechanism driving device incorporated in a picture book or a card. In particular, a piezoelectric actuator can be driven with a low drive voltage, and is therefore suitable for a portable device driven by a battery. The battery may be a primary battery such as a dry battery or a silver battery, or a secondary battery having a storage capacity such as a capacitor, a lithium ion secondary battery, or Ni-Cd.

(4) Needless to say, the piezoelectric actuator described in each modification of the first embodiment may be used in the calendar display mechanism of the timepiece described in the second embodiment.

[0071]

As described above, according to the present invention, since the movable portion and the rotating body are in contact with each other on the curved surfaces, the assembly accuracy of the piezoelectric actuator can be reduced. In addition, since the rotating body is made harder than the movable part, a piezoelectric actuator that is strong against impact can be provided. Also, since the movable part can be vibrated at a frequency that is a natural number times the natural vibration frequency, mechanical energy loss of the movable part can be reduced, and large displacement from the movable end can be achieved with high energy efficiency. Can be taken out. Further, the piezoelectric actuator of the present invention is suitable for thinning, and can be simply configured.

[Brief description of the drawings]

FIG. 1 is a plan view of a piezoelectric actuator according to a first embodiment of the present invention.

FIG. 2 is a side view of the piezoelectric actuator according to the embodiment.

FIG. 3 is an enlarged plan view for explaining a planar contact state between the rotor and the movable part according to the embodiment.

FIG. 4 is an enlarged plan view for explaining a planar contact state between the rotor and the movable part according to the embodiment.

FIG. 5 is a graph showing a relationship between a surface roughness of an end portion of a stator or a sliding portion 30a of a rotor and a minimum drive voltage according to the embodiment.

FIG. 6 is a diagram showing a state of press working of the stator according to the embodiment.

FIG. 7 is a diagram showing a connection state between the drive circuit and the piezoelectric element according to the same embodiment.

FIG. 8A is a block diagram in the case where the drive circuit of the embodiment is separately excited, and FIG. 8B is a circuit diagram in a case where the drive circuit is self-excited.

9A is a plan view showing vibration when the movable part is considered as a rigid body, FIG. 9B is a plan view showing primary vibration of the movable part, and FIG. 9C is a secondary view of the movable part. It is a top view which shows a vibration.

FIG. 10A is a plan view of a rotor and a movable section according to a modification of the embodiment, and FIG. 10B is a side view thereof.

FIG. 11 is a plan view of a piezoelectric actuator according to a modification of the embodiment.

FIG. 12 is a sectional view of a piezoelectric actuator according to a modified example of the embodiment.

FIG. 13 is a transparent plan view showing a main configuration of a calendar display mechanism in a timepiece according to a second embodiment of the present invention.

FIG. 14 is a sectional view of the timepiece according to the embodiment.

FIG. 15 is a perspective view showing a configuration example of a piezoelectric actuator A6 according to a sixth mode of the embodiment.

FIG. 16 is a plan view schematically showing an ultrasonic motor using a conventional piezoelectric actuator.

FIG. 17 is a plan view of a piezoelectric actuator according to a modification of the first embodiment of the present invention.

FIG. 18 is a sectional view of a piezoelectric actuator according to a modification of the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Vibration plate 11a, 11b ... Piezoelectric element 30, 32 ... Rotor (rotating body) 20 ... Stator (plate part) 21 ... Movable part 21a ... End part 23 ... Spring part (biasing means) 40 ... Date intermediate wheel ( Wheel train) 50: Date wheel (calendar display car) 60: Date wheel (wheel train) 100: Drive circuit (drive means) A: Piezoelectric actuator

Continued on the front page (72) Inventor Tsukasa Funasaka 3-5-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation (72) Inventor Makoto Furuhata 3-5-5 Yamato Suwa City, Nagano Prefecture Seiko Epson Corporation

Claims (14)

[Claims] 1. A disk-shaped rotator supported rotatably in an in-plane direction, and a curved end portion that comes into contact with an outer peripheral surface of the rotator, and the end portion extends in an in-plane direction. A piezoelectric actuator, comprising: a plate-shaped movable portion that rotates the rotating body by being displaced; and a plate-shaped diaphragm that is coupled to the movable portion and has a piezoelectric element. 2. The piezoelectric actuator according to claim 1, wherein an end of the movable portion has a curved shape in an in-plane direction. 3. The rotating body has a shape that is elongated in the longitudinal direction, and the rotating body is arranged so that the rotation center of the rotating body is shifted from a line extending a center line connecting the centers in the width direction. The piezoelectric actuator according to claim 2, wherein: 4. The piezoelectric actuator according to claim 1, wherein an end of the movable portion has a curved shape in a direction perpendicular to an in-plane direction. 5. The piezoelectric actuator according to claim 1, wherein a V-shaped groove is formed on an outer peripheral surface of the rotating body. 6. The piezoelectric actuator according to claim 1, wherein the hardness of the outer peripheral surface of the rotating body is larger than the hardness of the end of the movable portion. 7. The piezoelectric actuator according to claim 6, wherein a hardening process is performed on an outer peripheral surface of the rotating body. 8. The piezoelectric actuator according to claim 6, wherein an end of the movable portion is formed of a wear-resistant material. 9. The piezoelectric actuator according to claim 1, wherein a smoothing process for smoothing a surface is performed on an outer peripheral surface of the rotating body. 10. The piezoelectric actuator according to claim 1, wherein an end portion of the movable portion is subjected to a smoothing process for smoothing a surface. 11. The piezoelectric actuator according to claim 1, further comprising an urging unit that urges the movable portion toward the rotating body. 12. The device according to claim 1, further comprising a driving unit that supplies a driving signal having a frequency substantially equal to a natural vibration frequency of the movable portion to the piezoelectric element. Piezo actuator. 13. A portable device comprising: the piezoelectric actuator according to claim 12; and a battery for supplying power to the piezoelectric actuator. 14. A piezoelectric actuator according to claim 12, a battery for supplying electric power to the piezoelectric actuator, a wheel train interlocking with the rotating body, and a ring-shaped calendar display rotating in conjunction with the wheel train. A watch comprising a car.