JP2000188887A - Piezoelectric actuator and timepiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reversely rotate an object to be driven and, in addition, to reduce the thickness of the object by bringing a driving force transmitting member into contact with the object, in a first section in which the amplitude of the oscillation of the transmitting member increases when the member oscillates at a first frequency, or in a second section in which the amplitude decreases when the member oscillates at a second frequency. SOLUTION: Since the frequency of the driving signal of a piezoelectric actuator is normally set at a first frequency fs1, a stator 20 oscillates in a primary oscillation mode. In this case, a rotor receives a force Xa from the stator 20 and rotates in the direction shown by the arrow a1. When a user switches the frequency fs1 to a second frequency fs2 through prescribed operation, namely, when the stator 20 oscillates in a secondary oscillation mode, the rotor receives another force Xb from the stator 20 and reversely rotates. Since the rotating direction of the rotor can be inverted without providing any special mechanism, the thickness of a calendar displaying mechanism, etc., using this piezoelectric actuator can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator and a timepiece using the same.

[0002]

2. Description of the Related Art Various types of piezoelectric actuators utilizing the piezoelectric effect of piezoelectric elements have been developed in recent years because piezoelectric elements have 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. 17 is a diagram schematically showing an ultrasonic motor using a conventional piezoelectric actuator. The piezoelectric actuator 200 used for this ultrasonic motor has
The oscillating portion 201 includes a oscillating portion 201, a piezoelectric element 202 that expands and contracts by an AC voltage from the oscillating portion 201, and a vibrating piece 203. Here, the vibrating reed 203 has a base end portion fixed to the piezoelectric element 201 and a front end portion in contact with the surface of the rotor 204, and has a posture inclined by an angle θ with respect to a normal line of the rotor 204. I have. In such a configuration, the oscillation unit 201
When the piezoelectric element 202 expands and contracts due to an AC voltage from the rotor, the tip of the vibrating piece 203 strikes the surface of the rotor 204 as if poking, thereby driving the rotor 204 step by step.

[0004]

By the way, the above-mentioned piezoelectric actuator has been used for portable equipment, and is recently expected to be mounted particularly on a wristwatch. The details are as follows.

[0005] First, a wristwatch is worn by the user on the wrist and is carried, so that it is desired that the wristwatch be thin.
In order to make this wristwatch thinner, it is necessary to make the calendar display mechanism inside the wristwatch thinner. The existing calendar display mechanism is configured to intermittently transmit the rotational driving force of the electromagnetic step motor to the date indicator via a wheel train for hand movement, and to feed and drive the date indicator, thereby setting the date and day. Is generally switched sequentially.

Here, such a calendar display mechanism normally displays a date and a day of the week by rotating a date wheel in a fixed direction (forward direction), but sometimes corrects or adjusts the date display or the like. In order to do so, it is desirable that the date wheel can be rotated in a direction (reverse direction) opposite to the normal direction described above. The above-described step motor has an advantage that in such a case, the forward / reverse rotation can be switched by electric control.

However, since this step motor is constructed by combining various components such as a coil and a rotor in the thickness direction of the wristwatch, there is a limit to reducing the thickness. Therefore, it is difficult to meet the above demand for a thinner calendar display mechanism.

[0008] Some wristwatches have a product with a calendar display mechanism and others do not, but in order to improve productivity, a mechanical system (a so-called movement) is used between these two products. Common use is being considered. In order to make this movement common, it is necessary to arrange the calendar display mechanism on the dial side. But,
As long as the above-mentioned electromagnetic step motor is used, it is difficult to configure a thin calendar display mechanism that can be configured on the dial side.

For the above reasons, there is a demand for a thin drive means instead of a step motor, and a piezoelectric actuator has been expected as this drive means. However, a thin piezoelectric actuator that can meet such expectations has not been provided so far. This is due to the following reasons.

First, in the case of the piezoelectric actuator used in the above-described plucking type ultrasonic motor, it is necessary to change the inclination θ of the vibrating reed with respect to the surface of the rotor in order to rotate the rotor in the opposite direction. A mechanism (switching mechanism) for this switching is required.

The displacement of the piezoelectric element constituting the piezoelectric actuator caused by the application of a voltage is very small, and this displacement is usually about several μm. Therefore, in order to obtain a necessary driving force, some kind of amplifying mechanism for amplifying the displacement generated in the piezoelectric element and transmitting it to the driven object is required.

However, the switching mechanism and the amplification mechanism described above have a certain thickness. For this reason, it was difficult to make the piezoelectric actuator sufficiently thin.

Further, when the piezoelectric actuator is used in a portable device such as a wristwatch, the following problems must be solved.

First, a portable device such as a wristwatch generally uses a battery as a power source. Therefore, it is required that a piezoelectric actuator mounted on the device has low power consumption.

However, in the case of a piezoelectric actuator in which a switching mechanism or an amplification mechanism is added to a piezoelectric element, electric energy from a power source is converted into kinetic energy by the piezoelectric element, and the kinetic energy is driven via the switching mechanism or the amplification mechanism. Kinetic energy is lost in the switching mechanism or the amplification mechanism.

In the conventional piezoelectric actuator, the loss of the kinetic energy is large, and it is difficult to reduce the loss. For this reason, it is difficult to suppress power consumption to a sufficiently low level, and this has been one factor that hinders application of the piezoelectric actuator to portable devices such as wristwatches.

The present invention has been made under such a background, and is capable of reversing the rotational motion of a driven object and efficiently amplifying the vibration of the piezoelectric element and transmitting the amplified vibration to the driven object. It is another object of the present invention to provide a piezoelectric actuator suitable for thinning and a timepiece using the same.

[0018]

According to the present invention, there is provided a vibration plate having a piezoelectric element adhered to an elastic plate, and a long plate-like member which receives a pressure from the vibration plate on its side. A driving force transmitting member that bends and vibrates in an in-plane direction and drives a driven object by a side portion, and a drive having any one of a first frequency and a second frequency that is a natural vibration frequency of the driving force transmitting member. A driving circuit for supplying a signal to the piezoelectric element; and a switching unit for switching between the first and second frequencies. When vibration of the first frequency occurs in the driving force transmitting member, A first amplitude in which the amplitude of vibration of the driving force transmitting member increases as the driving force transmitting member advances along the longitudinal direction;
When the driving force transmitting member comes into contact with the object to be driven in the section of, and the driving force transmitting member generates a second frequency vibration, the driving force transmitting member moves along the longitudinal direction of the driving force transmitting member. According to another aspect of the present invention, there is provided a piezoelectric actuator, wherein the driving force transmitting member and the object to be driven come into contact with each other in a second section where the amplitude of the vibration of the force transmitting member decreases.

According to such a piezoelectric actuator, the vibration mode of the driving force transmitting member can be switched by switching the frequency of the generated driving signal, whereby the driving direction of the driven object can be reversed. .
Further, since the driving force transmitting member is vibrated at the natural vibration frequency of the driving force transmitting member, the internal loss of the driving force transmitting member can be greatly reduced. Therefore, there is an advantage that the displacement of the driving force transmitting member can be increased.

Here, the driving force transmitting member may have a projection on a side portion that comes into contact with the object to be driven. In this case, the amount of displacement of the driven object in the rotation direction can be further expanded and taken out. Therefore, there is an advantage that the drive target can be driven at a higher speed.

Further, the driving circuit has two resistors having different resistance values.
Having the above-described resistance, the switching means switching the first and second frequencies by selectively switching any one of the two or more resistances provided in the drive circuit. It may be. In this case, there is an advantage that any one of the drive signals of different frequencies can be selected and generated by a relatively easy configuration.

Further, the driving circuit has two or more capacitors having different capacities, and the switching means switches at least a part of the two or more capacitors to connect or not to the driving circuit. The first and second frequencies may be switched. Also in this case, there is an advantage that any one of the drive signals having different frequencies can be selected and generated by a relatively easy configuration.

Further, according to the present invention, there is provided any one of claims 1 to 4 between a movement for rotating a hand and a dial.
A timepiece, comprising: a calendar display mechanism including the piezoelectric actuator according to claim 1 and a calendar display wheel rotationally driven by the piezoelectric actuator. According to such a timepiece, the built-in piezoelectric actuator has a structure suitable for thinning, and a switching mechanism for reversing the rotation of the driven object is unnecessary, so that the entire timepiece can be thinned. Also, since the rotational movement of the driven object can be easily reversed,
There is an advantage that the date, day of the week, etc. displayed by the calendar display mechanism can be easily corrected.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. Such an embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.

A: First Embodiment A-1: Configuration of First Embodiment FIG. 1 is a plan view illustrating the configuration of a calendar display mechanism of a wristwatch using a piezoelectric actuator A1 according to an embodiment of the present invention. FIG. As shown in FIG. 1, the calendar display mechanism is a piezoelectric actuator A1 according to the present embodiment.
And a rotor 100 that is rotationally driven by the piezoelectric actuator A1, an intermediate wheel 101 that engages with the rotor 100, a date wheel 102 on which the date and day are written and that rotates in conjunction with the intermediate wheel 101, And a base (not shown) to be installed.

FIG. 2 is a sectional view showing the structure of a timepiece incorporating the calendar display mechanism. In the figure, the above-mentioned calendar display mechanism is incorporated in the shaded portion,
Its thickness is as thin as about 0.5 mm. This is because the piezoelectric actuator A1 for driving the date wheel 102 is configured in a plane. A disk-shaped dial 110 is provided above the calendar display mechanism (shaded portion). A window 111 for displaying a date is provided on a part of the outer peripheral portion of the dial 110, and the day and day of the day indicated on the date dial 102 can be seen through the window 111. . A movement 113 for driving the hands 112 and a drive circuit (not shown) to be described later are provided below the dial 110.
Is arranged.

FIG. 3A is a plan view of the piezoelectric actuator A1 according to the present embodiment as viewed from the dial 110 of the timepiece, and FIG. 3B is a line AA 'in FIG. 3A. FIG. As shown in FIGS. 3A and 3B, the piezoelectric actuator A1 according to the present embodiment includes a diaphragm 1
0, a stator 20, and a drive circuit 30. Further, the diaphragm 10 is joined to a side portion of the stator 20 at an end portion 13. Note that FIG.
3A, the drive circuit 30 and wiring shown in FIG. 3B are omitted for convenience.

The diaphragm 10 is a shim 1 made of a thin plate (about 0.05 to 0.2 mm thick) of phosphor bronze or the like.
The piezoelectric elements 11a and 11b each having a thickness of about 0.1 to 0.2 mm are bonded to both surfaces of the piezoelectric element 11. The piezoelectric elements 11a and 11b are attached to the shim 12 such that the polarization directions of the piezoelectric elements 11a and 11b are opposite to each other. As described above, the piezoelectric elements 11 are provided on both surfaces of the shim 12.
When the configuration provided with a and 11b is employed, it is possible to increase the durability against the impact generated when the timepiece provided with the piezoelectric actuator A1 falls. As the material of the piezoelectric elements 11a and 11b, various materials such as lead zirconate titanate, quartz, lithium niobate, barium titanate, lead titanate, metaniobate, and polyvinylidene fluoride can be used.

A wiring (parallel connection) as shown in FIG. 3B is provided between the diaphragm 11 and the drive circuit 30. The drive signal V generated by the drive signal 30 is applied between the shim 12 and the piezoelectric elements 11a and 11b.

The stator 20 functions as a driving force transmitting member for transmitting the vibration of the diaphragm 11 to the rotor 100, and as shown in FIG.
It has an elongated portion 22 having an elongated shape, a constricted portion 23 having a smaller width than other portions, and a fixing portion 24 fixed to the base of the calendar display mechanism by screws or the like. . In the following description, among the natural vibration frequencies of the stator 20 (details will be described later), the smallest one is a frequency fs1 (first frequency), and the next largest one is a frequency fs2 (second frequency). Call.

The long side portion 22 of the stator 20 is in contact with the rotor 100 to be driven, and the rotor 100 rotates with the vibration of the stator 20. The details of the rotation operation of the rotor 100 will be described later.

Next, the configuration of the drive circuit 30 will be described with reference to FIG. The drive circuit 30 is a circuit for generating a drive signal V for causing expansion and contraction vibration of the piezoelectric elements 11a and 11b. As shown in FIG. 4, the vibrator 11, the inverting amplifier 31, the feedback resistor 32, the amplifier 33, Element 34, capacitors 35 and 37 and resistor 36a
And 36b. Here, the vibrator 1
Reference numeral 1 is composed of the above-described piezoelectric elements 11a and 11b and a shim 12 sandwiched therebetween. One of the electrodes connected to the piezoelectric elements 11a and 11b is connected to the input terminal of the inverting amplifier 31, and the other electrode is connected to the output terminal of the amplifier 33. Is connected to the output terminal of the inverting amplifier 31. Further, a feedback resistor 32 is connected in parallel between the input terminal and the output terminal of the inverting amplifier 31.

The input terminal of the inverting amplifier 31 is grounded via a capacitor 35, the output terminal is connected to one end of a resistor 36a or 36b via a switching element 34, and the other end of these resistors is connected to a capacitor. It is grounded via 37. Here, the switching element 34
For example, by performing a predetermined operation on a switch provided on a wristwatch, the resistance 36a side or the resistance 36
It can be switched to any one of the b-side.

The driving circuit 30 is configured as described above.
The drive signal V is output to the piezoelectric element 11 by self-excited oscillation. Here, since the resistance connected to the inverting amplifier 41 is switched by switching the switching element 34, the amount of phase delay of the voltage at the output terminal of the inverting amplifier 41 changes, and as a result, the frequency of the drive signal V also changes. Becomes In the piezoelectric actuator according to the present embodiment, during normal use of the wristwatch, one end of the switching element 34 is connected to the resistor 36a, and in this case, the frequency of the drive signal V changes to the frequency fs1 described above.
The capacitances of the capacitors 35 and 37 and the size of the resistor 36a are set so as to be substantially equal to.

On the other hand, when the user performs a predetermined operation on a switch provided on the wristwatch, the connection of the switching element 34 is switched to the resistor 36b. In this case, the capacitances of the capacitors 35 and 37 and the size of the resistor 36b are set so that the frequency of the drive signal V becomes substantially equal to the frequency fs2. The above is the detailed configuration of the piezoelectric actuator A1 according to the present embodiment.

A-2: Operation of First Embodiment Next, the operation of the piezoelectric actuator A1 according to the present embodiment will be described. First, the piezoelectric elements 11a and 11b to which the drive signal V generated by the drive circuit 30 is applied are:
The diaphragm 10 vibrates in the longitudinal direction, and the diaphragm 10 vibrates longitudinally. The details are as follows.

As described above, the shim 12 functions as a common electrode for the piezoelectric elements 11a and 11b, and the shim 1
The drive signal V is applied between the piezoelectric element 2 and the piezoelectric elements 11a and 11b. Here, 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 the arrow in FIG. Therefore, when the drive signal V is applied, when one of the piezoelectric elements extends in the longitudinal direction, the other piezoelectric element also extends in the longitudinal direction. Therefore, when an AC voltage is applied to the piezoelectric elements 11a and 11b, the piezoelectric elements 11a and 11b
Is vertically vibrated in the plane to which the shim 12 belongs. The frequency of this oscillation is
The frequency of the drive signal V, that is, the frequency fs1 or fs2 of the natural vibration frequency of the stator 20. When such vibration occurs, the end 13 of the diaphragm 10
Presses the side of the stator 20 in the direction of the arrow shown in FIG.

When the pressure as described above is received from the diaphragm 10, the stator 20 undergoes bending vibration. Less than,
This bending vibration will be described in detail.

First, when the stator 20 is considered as a rigid body, the stator 20 receives the pressure from the diaphragm 10 as described above, and is displaced with the constricted portion 23 as a fulcrum as shown in FIG. . In this case, the displacement of the end portion 13 of the diaphragm 10 is amplified by this principle with the constricted portion 23 as a fulcrum, and transmitted to the long portion 22 and the tip portion 21 of the stator 20. However, since the stator 20 has a so-called cantilever structure, a large stress is generated in the constricted portion 23 serving as a support portion, and the force escapes from the constricted portion 23 to increase energy loss. For this reason, there is a problem that conversion efficiency from electric energy to mechanical energy is reduced.

By the way, when the excitation frequency is gradually increased while keeping the force applied to the mechanical structure constant, the amplitude of the structure becomes a maximum value at a specific frequency and then becomes a minimum value. Repeat the response. That is, there are a plurality of excitation frequencies whose amplitudes have a maximum value, and each such excitation frequency is called a natural oscillation frequency. Then, the mode of vibration when excited by the smallest natural vibration frequency (frequency fs1) among the natural vibration frequencies is represented by a primary vibration mode,
The mode of vibration when excited by the next highest natural vibration frequency (frequency fs2) is represented by a secondary vibration mode,.
That. When a structure vibrates at this natural vibration frequency, its mechanical impedance is minimized, so that a large displacement can be easily obtained with a small driving force.

In the piezoelectric actuator according to the present embodiment, as described above, the frequency of the drive signal V is set to the frequency fs1 or fs2 of the natural vibration frequency of the stator 20. Therefore, the diaphragm 10 to which the drive signal V is applied vibrates at the frequency fs1 or fs2, and this vibration is transmitted to the stator 20. As a result,
The stator 20 bends and vibrates in the primary vibration mode or the secondary vibration mode.

FIG. 5B shows that the frequency of the stator 20 is changed to the frequency fs.
FIG. 5C is a diagram schematically illustrating a mode of displacement of the stator 20 when the vibration is performed at 1 (that is, when the vibration is performed in the primary vibration mode), and FIG.
FIG. 6 is a diagram schematically illustrating a mode of displacement of a stator 20 when the vibration is applied in (i.e., when the vibration is performed in a secondary vibration mode). As shown in FIGS. 5B and 5C, the stator 20 vibrates while bending in a plane to which the stator 20 belongs. When the stator 20 vibrates in such a manner, the side of the long portion 22 is
It will be displaced so as to hit 00.

Here, the positional relationship between the stator 20 and the rotor 100 in the piezoelectric actuator A1 according to the present embodiment will be described in detail with reference to FIGS. 6 (a) and 6 (b). As described above, in the piezoelectric actuator A1 according to the present embodiment, the stator 20 vibrates in the primary or secondary vibration mode. FIG. 6A shows the stator 20.
FIG. 6B is a plan view showing a mode of displacement and a rotor 100 when vibrated in a primary vibration mode. FIG. 6B shows a mode of displacement and a rotor 100 when the stator 20 vibrates in a secondary vibration mode. FIG.

The piezoelectric actuator A1 according to the present embodiment
In the case where the stator 20 vibrates in the primary vibration mode, the amplitude of the vibration of the stator 20 increases as the stator 20 moves toward the tip 21 along the longitudinal direction (see FIG. 6A). In the section a1), the stator 20 and the rotor 100 come into contact with each other. In contrast,
When the stator 20 vibrates in the secondary vibration mode, a section in which the amplitude of the vibration of the stator 20 decreases as the stator 20 moves toward the tip 21 along the longitudinal direction (a section b1 shown in FIG. 6B). , The stator 20 and the rotor 100 come into contact with each other.

By arranging the stator 20 and the rotor 100 at such positions, when the stator 20 vibrates in the primary vibration mode, the rotor 100
0 and the direction of the force Xa received from the rotor 100 when the rotor 100 vibrates in the secondary vibration mode.
And the direction of the force Xb received from the motor becomes different. As a result, the rotor 1 is different between the case where the stator 20 vibrates in the primary vibration mode and the case where the stator 20 vibrates in the secondary vibration mode.
The rotation direction of 00 is reversed. Hereinafter, the rotor 10
The rotation operation of 0 will be described in detail. Hereinafter, a case where the stator 20 vibrates in the primary vibration mode and a case where the stator 20 vibrates in the secondary vibration mode will be described separately.

A. When the Stator 20 Vibrates in the Primary Vibration Mode In the piezoelectric actuator A1 according to the present embodiment, in normal use, the frequency of the drive signal V is set to the frequency fs1. It will vibrate. In this case, the rotor 100 receives the force Xa shown in FIG.
1 will be rotated. More specifically, the force Xa that the rotor 100 receives from the stator 20 is as shown in FIG.
As shown in (a), the radial component X of the rotor 100
a1 and a component Xa2 in the tangential direction of the rotor 100. Then, the rotor 100 applies this force X
Due to the component Xa2 in the tangential direction of a, the rotation is performed in the direction of arrow a1 in the figure.

Here, in the calendar display mechanism shown in FIG. 1, when the rotor 100 rotates in the direction of a1 as described above, the intermediate wheel 101 rotates in the direction of arrow a2, and the date wheel 102 It rotates in the direction of arrow a3. During normal use of the wristwatch, the calendar display mechanism operates in this manner, whereby the day, day, and the like displayed on the window are switched in order. That is,
For example, “31” → “1” → “2”.

B. When the stator 20 vibrates in the secondary vibration mode On the other hand, when the user performs a predetermined operation on a switch provided on the wristwatch, the frequency of the drive signal V is switched to the frequency fs2, When the stator 20 vibrates in the secondary vibration mode, the rotor 1
00 receives the force Xb shown in FIG. 6B from the stator 20, and rotates in the direction of the arrow b1. More specifically, the force Xb that the rotor 100 receives from the stator 20
7B, a radial component Xb1 of the rotor 100 and a tangential component Xb2 of the rotor 100, as shown in FIG.
And can be disassembled. And the rotor 100
Due to the tangential component Xb2 of the force Xb, the force Xb rotates in the direction of the arrow b1 in the figure.

In the calendar display mechanism shown in FIG. 1, when the rotor 100 rotates in the direction of b1 as described above, the intermediate wheel 101 rotates in the direction of the arrow b2, and the date wheel 102 It rotates in the direction of arrow b3. Therefore, the date displayed in the window changes from “2” to
The direction is switched in a direction opposite to the normal direction, such as “1” → “31”. As described above, the user rotates the date wheel 102 in a direction opposite to the normal direction by performing a predetermined operation on the switch provided on the wristwatch, thereby correcting or adjusting the display of the day or day. You can do it.

As described above, according to the piezoelectric actuator A1 of the present embodiment, the rotation direction of the rotor 100 can be reversed by switching the frequency of the drive signal V. As described above, in the piezoelectric actuator A1 according to the present embodiment, since the rotation direction of the rotor 100 can be reversed without providing a special mechanism, the thickness of a calendar display mechanism or the like using the piezoelectric actuator A1 can be reduced. This can contribute to the thickness of the wristwatch incorporating the calendar display mechanism.

B: Second Embodiment FIG. 8 is a plan view showing a configuration of a stator 40 used in a piezoelectric actuator A2 according to a second embodiment of the present invention. One end of the stator 20 in the piezoelectric actuator A1 according to the first embodiment is a free end,
The other end is a fixed end, and a constricted portion that is narrower than other portions is provided near the fixed end. On the other hand, as shown in FIG. 8, the stator 40 constituting the piezoelectric actuator A2 according to the present embodiment has end portions 41a and 41b which operate as free ends at both ends of a long portion 42 which is a rectangular plate member. And the constricted portion 43 and the fixed end 44 are provided on the side of the long portion 42. In the following, among the natural vibration frequencies of the stator 40, the lowest one is the frequency fs.
1 'and the next largest frequency will be described as a frequency fs2'. The other parts of the piezoelectric actuator A2 according to the present embodiment are the same as those of the piezoelectric actuator A1 according to the first embodiment, and thus description thereof will be omitted.

FIG. 9A shows a state where the stator 40 according to the present embodiment is vibrated at the frequency fs1 '.
FIG. 9B is a diagram schematically showing the mode of displacement of the rotor 40 and the mode of displacement of the stator 40 when the stator 40 is vibrated at the frequency fs2 ′.
It is a figure which shows 00 schematically.

The piezoelectric actuator A2 according to the present embodiment
The positional relationship between the stator 40 and the rotor 100 in
The positional relationship between the stator 20 and the rotor 100 in the piezoelectric actuator according to the first embodiment is substantially the same. That is, it is as follows.

When the stator 40 in the present embodiment vibrates in the primary vibration mode, the stator 40 moves toward the end 41a along the longitudinal direction of the stator 40.
In the section a2 where the amplitude of the vibration of the
0 comes into contact with the rotor 100. On the other hand, when the stator 40 vibrates in the secondary vibration mode,
The stator 40 and the rotor 100 come into contact in a section b2 where the amplitude of the vibration of the stator 40 decreases as it proceeds toward the end 41a along the longitudinal direction of the stator 40.

According to the present embodiment, the stator 4
FIG. 9A shows a case where 0 vibrates in the primary vibration mode.
Is applied to the rotor 100, and the rotor 100 rotates in the direction of the arrow a1 according to the same principle as in the first embodiment. On the other hand, when the stator 40 vibrates in the secondary vibration mode, a force Xb in the direction shown in FIG. 9B is applied to the rotor 100, and the rotor 100 is moved in the direction of the arrow b1. Rotate.

As described above, also in the piezoelectric actuator A2 according to the present embodiment, the same effects as those of the piezoelectric actuator A1 according to the first embodiment can be obtained.

C: Modifications Although one embodiment of the present invention has been described above, the above embodiment is merely an example, and various modifications may be made to the above embodiment without departing from the spirit of the present invention. be able to. For example, the following modifications can be considered.

<Modification 1> (1) In the first embodiment, the stator is configured such that one end is simply supported and the other end operates as a free end. In the second embodiment, Although both ends of the stator are configured to operate as free ends, the present invention is not limited to this, and the manner of supporting the stator may be simple support at both ends. FIG. 10 is a plan view illustrating the configuration of the piezoelectric actuator when both ends of the stator 60 are simply supported. As shown in FIG. 10, the ends 61a and 61b of the stator 60 are fixed to the base of the calendar display mechanism by screws or the like, and the width near the ends 61a and 61b is narrower than the other. Constrictions 62a and 62b are provided. FIG. 11A is a diagram illustrating a mode of vibration of the stator 60 when the stator 60 vibrates in the primary vibration mode, and the rotor 100, and FIG. FIG. 6 is a diagram showing a mode of displacement of a stator 60 when vibrated in the vibration mode of FIG. The positional relationship between the stator 60 and the rotor 100 in this modification is substantially the same as in each of the above embodiments. That is, it is as follows.

In this modification, when the stator 60 vibrates in the primary vibration mode, as shown in FIG. 11A, the amplitude of the vibration of the stator 60 increases as it goes toward the end 61a in the longitudinal direction of the stator 60. Section a where
At 3, the stator 60 and the rotor 100 come into contact. On the other hand, when the stator 60 vibrates in the secondary vibration mode, as shown in FIG. 11B, the amplitude of the vibration of the stator 60 increases as it proceeds toward the end 61a along the longitudinal direction of the stator 60. In the increasing section b3,
The stator 60 and the rotor 100 come into contact with each other.

In such a configuration, when the stator 60 vibrates in the primary vibration mode, a force Xa in the direction shown in FIG. 11A is applied to the rotor 100. It rotates in the direction of arrow b1. On the other hand, when the stator 60 vibrates in the secondary vibration mode, a force Xb in the direction shown in FIG. 11B is applied to the rotor 100, and the rotor 100 is moved in the direction of the arrow a1. Rotate.

(2) Further, a configuration may be adopted in which both ends of the stator are fixed ends. FIG. 12 is a plan view showing a configuration of a piezoelectric actuator according to the present modification. As shown in FIG. 12, the piezoelectric actuator according to the present modification has a configuration in which ends 71a and 71b of a stator 70 are fixed to a base of a calendar display mechanism by screws or the like.

FIG. 13 (a) is a diagram showing the manner of displacement of the stator 70 and the rotor 100 when the stator 70 vibrates in the primary vibration mode, and FIG. FIG. 7 is a diagram showing a mode of displacement of a stator 70 and a rotor 100 when vibrated in the vibration mode of FIG. As shown in FIGS. 13A and 13B, also in this modification, the contact position between the stator 70 and the rotor 100 is the same as that of the piezoelectric actuator shown in the above modification 1 (1). The direction of rotation of the rotor 100 is reversed between when the 70 vibrates in the primary vibration mode and when it vibrates in the secondary vibration mode.

As described above, the same effects as those of the piezoelectric actuators according to the above-described embodiments can be obtained by the piezoelectric actuator according to the present modification.

<Modification 2> As shown in FIG. 14, a configuration may be adopted in which a protrusion 50 that contacts the rotor 100 is provided on the side of the stator 20. According to the piezoelectric actuator of this modification, the amount of displacement of the rotor 100 in the rotation direction can be further expanded and taken out. Therefore, there is an advantage that the rotor can be rotated faster and can be driven by a low voltage as compared with the piezoelectric actuator without the projection 50.

In FIG. 14, the projection 50 is
Although the configuration is such that it protrudes in a direction perpendicular to the longitudinal direction of the stator 20, the present invention is not limited to this.
A configuration in which 0 protrudes may be adopted. Further, in FIG. 14, the rotor 100 and the protrusion 50 are configured to be in contact with each other on a perpendicular line from the center of the rotor 100 to the stator 20. However, the present invention is not limited to this. It is good also as a structure which the projection part 50 contacts. By doing so, the rotation speed or the driving force of the rotor 100 differs between the case where the rotor 100 is rotated in the forward direction and the case where the rotor 100 is rotated in the reverse direction.

<Modification 3> In the first embodiment, the frequency of the drive signal V is switched by switching the resistance connected to the output terminal of the inverting amplifier 31 in the drive circuit 30. The present invention is not limited to this. For example, the frequency of the drive signal V may be switched by switching a capacitor. FIG. 15A is a circuit diagram showing a configuration of the drive circuit 30 in this case. FIG.
As shown in (a), in the drive circuit 30 according to the present modification, by performing a predetermined operation on a switch provided on the wristwatch, the switching element 34 in the drive circuit 30 is switched. Accordingly, the configuration is such that any one of the capacitors 37a and 37b can be selectively connected. Thereby, the frequency of the drive signal is changed to the frequency fs1 (fs1 ′) or the frequency fs2 (f
s2 '). Even with such a configuration, the same effects as those of the above embodiments can be obtained.

The drive circuit 30 may have a configuration as shown in FIG. That is, in addition to the driving circuit 30 shown in FIG. 15A, the input terminal of the inverting amplifier 31 is connected to the capacitor 35a via the switching element 34a.
And 35b are provided. The switching elements 34 and 34a may be configured to switch in conjunction with each other,
It is good also as a structure which can be switched separately. Even in this case, the same effects as those of the above embodiments can be obtained.

<Modification 4> In each of the above embodiments,
A piezoelectric element is attached to both surfaces of the shim to form a diaphragm, and this diaphragm is connected in parallel to the drive circuit.However, a piezoelectric element is attached to only one side of the shim to form a diaphragm. The wiring between the diaphragm and the drive circuit may be configured in a mode (serial connection) as shown in FIG. With such a configuration, the piezoelectric element may be attached only to one surface of the shim portion, so that the manufacturing is facilitated and the wiring can be simplified.

<Modification 5> In each of the above embodiments,
Although the stator is configured to vibrate in the primary vibration mode or the secondary vibration mode, the present invention is not limited to this, and the vibration mode of the stator may be a higher vibration mode. Of course.

[0070]

As described above, according to the present invention,
By switching the frequency of the driving signal generated by the driving circuit, the vibration mode of the driving force transmitting member can be switched, and the vibration direction of the driven object can be reversed. The rotation of the rotor can be reversed without the provision. Further, since the stator is vibrated at its natural vibration frequency, the internal loss of the stator can be greatly reduced. Therefore,
The displacement of the stator can be increased.

In the case where a protruding portion which comes into contact with the rotor is provided on the side of the long portion, the displacement in the rotation direction of the rotor can be expanded and taken out. Can be rotated (claim 2).

Further, if a plurality of resistors or a plurality of capacitors are provided in the drive circuit and any one of them is selectively switched, the frequency of the drive signal can be switched by a relatively easy configuration. (Claims 3 and 4).

According to the piezoelectric actuator of the present invention, the rotation of the driven object can be reversed without providing a complicated switching mechanism. Therefore, when the piezoelectric actuator is used for a calendar display mechanism of a wristwatch, This can contribute to a reduction in the thickness of the wristwatch. In addition, since the driving target is reversed only by switching the resistance or the like provided in the driving circuit, the user can easily reverse the date indicator of the calendar display mechanism, thereby setting the date and day. Correction and adjustment can be easily performed (claim 5).

[Brief description of the drawings]

FIG. 1 is a plan view showing a main configuration of a calendar display mechanism incorporating a piezoelectric actuator in a timepiece according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the timepiece according to the first embodiment of the present invention.

FIG. 3A is a plan view showing the overall configuration of a piezoelectric actuator according to a first embodiment of the present invention,
FIG. 3B is a cross-sectional view taken along line AA ′ of FIG.

FIG. 4 is a circuit diagram showing a configuration of a drive circuit used in the piezoelectric actuator according to the first embodiment of the present invention.

FIG. 5A is a plan view showing vibration when the stator is considered as a rigid body, and FIG. 5B is a plan view showing an aspect when the stator vibrates in a primary vibration mode;
(C) is a plan view showing an aspect when the stator vibrates in the secondary vibration mode.

FIG. 6A is a plan view showing a mode of displacement of the stator when the stator vibrates in a primary vibration mode and a rotation direction of the rotor in this case, and FIG. FIG. 4 is a plan view showing a mode of displacement of a stator when vibrated at a direction and a rotation direction of a rotor in this case.

FIG. 7A is a diagram for explaining a rotational motion of a rotor when a stator vibrates in a primary vibration mode, and FIG. 7B is a diagram for explaining a rotor motion when the stator vibrates in a secondary vibration mode. It is a figure for explaining rotation movement.

FIG. 8 is a plan view illustrating an overall configuration of a piezoelectric actuator according to a second embodiment of the present invention.

FIG. 9A is a plan view showing the displacement of the stator when the stator vibrates in a primary vibration mode in the piezoelectric actuator according to the second embodiment and the rotation direction of the rotor in this case, and FIG. 4) is a plan view showing the displacement of the stator when the stator vibrates in the secondary vibration mode and the rotation direction of the rotor in this case.

FIG. 10 is a plan view showing a configuration of a modified example of the piezoelectric actuator according to the first and second embodiments of the present invention.

FIG. 11A is a plan view showing a state of displacement of a stator and a rotor when the stator vibrates in a primary vibration mode in the piezoelectric actuator according to the modification, and FIG. It is a top view which shows the aspect of the displacement of the stator when it vibrates in the next vibration mode, and a rotor.

FIG. 12 is a plan view illustrating a configuration of a modified example of the piezoelectric actuator according to the first and second embodiments of the present invention.

FIG. 13A is a plan view showing a mode of displacement of a stator and a rotor when the stator vibrates in a primary vibration mode in the piezoelectric actuator according to the modification, and FIG. It is a figure which shows the aspect of the displacement of a stator, and the rotor when it vibrates in the next vibration mode.

FIG. 14 is a plan view showing a configuration of a modified example of the piezoelectric actuator according to the first and second embodiments of the present invention.

FIG. 15 is a diagram showing a modified example of the drive circuit in the piezoelectric actuator according to the first and first embodiments of the present invention.

FIG. 16 is a cross-sectional view showing a configuration of a modification of the first and second embodiments of the present invention.

FIG. 17 is a view schematically showing an ultrasonic motor using a conventional piezoelectric actuator.

[Explanation of symbols]

10: diaphragm, 11: vibrator, 11a, 11b ...
Piezoelectric element, 12: Shim plate (elastic plate), 13: End portion of diaphragm, 20, 40, 60, 70 ... Stator (drive force transmitting member), 21: Tip portion, 22: Long Part, 23,
43, 62a, 62b ... constricted part, 24 ... fixed part, 3
0 ... Drive circuit, 31 ... Inverting amplifier, 32 ... Feedback resistor, 33 ... Amplifier, 34,34a ... Switching element, 35,35a, 35b, 37,37a, 37b ...
Capacitors, 36, 36a, 36b..., Resistors, 41a,
41b 61a, 61b, 71a, 71b ... end portions, 42
... Long part, 44 ... Fixed part, 50 ... Protrusion, 100
...... Rotor (drive target), 101 ... Intermediate wheel, 102 ...
… Date indicator (calendar display), 110… dial, 111
... window, 112 ... needle, 113 ... movement, A
1, A2, 200 ... piezoelectric actuator, 201 ...
Oscillator, 202, piezoelectric element, 203, vibrating piece, 20
4 ... rotor.

Continued on the front page (72) Inventor Taiji Hashimoto 3-3-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation (72) Inventor Makoto Furuhata 3-3-5 Yamato Suwa City, Nagano Prefecture Inside Seiko Epson Corporation F term (reference) 2H081 BB18 5H680 AA06 AA08 AA12 AA19 BC02 DD01 DD15 DD23 DD27 DD53 DD82 DD92 FF04 FF26 FF31 GG01 GG02 GG23

Claims (5)

[Claims] A vibration plate having a piezoelectric element adhered to an elastic plate; and a long plate-shaped member, which receives a pressure from the vibration plate on a side portion to bend and vibrate in an in-plane direction, A driving force transmitting member for driving a driving object by a side portion, and a driving signal having any one of a first frequency and a second frequency, which is a natural vibration frequency of the driving force transmitting member, is supplied to the piezoelectric element. A drive circuit; and a switching means for switching between the first and second frequencies. When vibration of the first frequency is generated in the drive force transmitting member, a longitudinal direction of the drive force transmitting member is provided. In the first section in which the amplitude of the vibration of the driving force transmission member increases as traveling along the driving force transmission member, the driving force transmission member comes into contact with the driven object, and vibration of the driving frequency transmission member has a second frequency. In some cases,
A piezoelectric actuator, wherein the driving force transmitting member and the object to be driven come into contact with each other in a second section in which the amplitude of the vibration of the driving force transmitting member decreases as the driving force transmitting member advances in the longitudinal direction. . 2. The piezoelectric actuator according to claim 1, wherein the driving force transmitting member has a protrusion on a side portion that comes into contact with the driven object. 3. The drive circuit has two or more resistors having different resistance values, and the switching means selectively switches any one of the two or more resistors provided in the drive circuit. The piezoelectric actuator according to claim 1, wherein the first and second frequencies are switched by: 4. The drive circuit has two or more capacitors having different capacities, and the switching means switches at least a part of the two or more capacitors to connect or not to be connected to the drive circuit. 3. The piezoelectric actuator according to claim 1, wherein the first and second frequencies are switched. 5. A piezoelectric actuator according to claim 1, between a movement for rotating a hand and a dial, and a calendar display wheel rotationally driven by the piezoelectric actuator. A timepiece provided with a calendar display mechanism having the following.