JP5760748B2 - Piezoelectric actuator driving method and driving unit - Google Patents

Description

  The present invention relates to a method for driving a piezoelectric actuator.

  As a piezoelectric actuator that drives a driven body (for example, a rotor), stretching vibration (also called longitudinal vibration) that causes the vibrating body to expand and contract in the length direction by a piezoelectric element (piezo element), and bending vibration that causes the vibrating body to bend in the plane direction Are known. For example, in Patent Document 1, the contact portion provided in the vibrating body is moved (elliptical motion) so as to draw a substantially elliptical trajectory by stretching vibration and bending vibration. Then, the driven body is driven by bringing the contact portion into contact with the driven body according to the elliptical motion.

JP 2007-166816 A

Conventionally, the shape of the orbit of elliptical motion was constant regardless of the driving speed of the driven body. For this reason, there is a possibility that the driven body cannot be driven stably. For example, when the driven body starts to move from the stopped state, if the amplitude of the refraction vibration is large, slipping may occur when the contact portion comes into contact with the driven body. Therefore, when the amplitude of the refractive vibration is reduced, the orbit of the elliptical motion is reduced and the amplitude of the stretching vibration is also reduced. In this case, as a result, the contact portion and the driven body are easily slipped, and there is a possibility that the slip cannot be suppressed. For example, when the amplitude of the refractive vibration is increased, the orbit of the elliptical motion is increased and the amplitude of the stretching vibration is also increased. In this case, the driven body is difficult to drive, and there is a possibility that energy is wasted in driving the driven body.
Therefore, an object of the present invention is to optimize driving of a driven body.

The main invention for achieving the above object is:
A piezoelectric actuator driving method comprising: a vibrating body that vibrates based on a driving signal supplied to a piezoelectric element; and transmitting the vibration of the vibrating body to a driven body to drive the driven body,
A first vibration mode for expanding and contracting the vibrating body in a direction crossing a driving direction of the driven body;
A second vibration mode in which the vibrating body is bent in the driving direction of the driven body, the second vibration mode being independent of the first vibration mode;
At the same time,
When accelerating or decelerating the driving of the driven body, the amplitude of vibration in the first vibration mode is set larger than in the case of driving the driven body at a constant speed, and in the second vibration mode. Reduce the amplitude of vibration,
This is a method for driving a piezoelectric actuator.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

It is a schematic block diagram of the drive unit using the piezoelectric actuator in this embodiment. It is a side view near the piezoelectric actuator in this embodiment. FIG. 3A is a simplified explanatory view of the longitudinal vibration mode, and FIG. 3B is a simplified explanatory view of the bending vibration mode. It is explanatory drawing of a motion of the contact part at the time of rotating a rotor. It is explanatory drawing of the locus | trajectory of an ellipse. It is explanatory drawing of the drive method of this embodiment. FIG. 6A shows an elliptical orbit in the acceleration / deceleration region, and FIG. 6B shows an elliptical orbit in the constant speed region.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A piezoelectric actuator driving method comprising: a vibrating body that vibrates based on a driving signal supplied to a piezoelectric element; and transmitting the vibration of the vibrating body to a driven body to drive the driven body,
A first vibration mode for expanding and contracting the vibrating body in a direction crossing a driving direction of the driven body;
A second vibration mode in which the vibrating body is bent in the driving direction of the driven body, the second vibration mode being independent of the first vibration mode;
At the same time,
When accelerating or decelerating the driving of the driven body, the amplitude of vibration in the first vibration mode is set larger than in the case of driving the driven body at a constant speed, and in the second vibration mode. Reduce the amplitude of vibration,
The driving method of the piezoelectric actuator characterized by this will become clear.

  According to such a driving method, when the driving of the driven body is accelerated or decelerated, the driven body and the vibrating body (contact portion) can be prevented from slipping and stably driven. Further, when driving the driven body at a constant speed, energy can be prevented from being wasted and the driving speed of the driven body can be increased. Therefore, the driving of the driven body can be optimized.

In this piezoelectric actuator driving method, the driving speed of the driven body is detected, and the amplitude of the vibration in the first vibration mode and the vibration in the second vibration mode are detected according to the detection result of the driving speed. It is desirable to change the amplitude of each.
According to such a driving method, the driving of the driven body can be controlled more reliably.

In this piezoelectric actuator driving method, it is preferable that the amplitude of the vibration in the second vibration mode is changed depending on the driving speed.
According to such a driving method, it is possible to change the driving speed while suppressing slippage between the driven body and the vibrating body (contact portion).

In this piezoelectric actuator driving method, it is desirable that the amplitude of vibration in the first vibration mode when the driving of the driven body is accelerated or decelerated is not more than a predetermined value.
According to such a driving method, occurrence of abnormal vibration can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

=== Embodiment ===
≪About the configuration of the drive unit≫
FIG. 1 is a schematic configuration diagram of a drive unit using a piezoelectric actuator in the present embodiment. FIG. 2 is a side view of the vicinity of the piezoelectric actuator in the present embodiment. In FIG. 2, illustration of a fixing member 25 described later is omitted for convenience. The drive unit of this embodiment is a unit for driving devices such as a micropump and a portable device.

  The drive unit of this embodiment shown in FIG. 1 includes a piezoelectric actuator 20, a rotor 30, a drive signal generation unit 100, a control unit 200, and a rotation speed detection unit 300.

  The piezoelectric actuator 20 vibrates based on a drive signal generated by a drive signal generation unit 100 described later, and rotates the rotor 30 (corresponding to a driven body) by the vibration. As shown in FIG. 1, the piezoelectric actuator 20 of the present embodiment is provided in a rectangular shape. In the following description, the long side direction is referred to as the longitudinal direction, and the short side direction is referred to as the width direction. The configuration of the piezoelectric actuator 20 will be described later.

  The rotor 30 is a cylindrical rotating body, and a rotating shaft 31 is provided at the center of the circle. The abutting portion 24 (described later) of the piezoelectric actuator 20 abuts on the rotor 30 according to the vibration of the piezoelectric actuator 20, whereby the rotor 30 rotates about the rotation shaft 31. In the present embodiment, the rotor 30 is controlled to rotate only in the counterclockwise direction in FIG. 1 (the arrow direction in the figure).

  The drive signal generation unit 100 generates a drive signal with a predetermined period. The drive signal generation unit 100 according to the present embodiment generates a rectangular wave drive signal that periodically switches between a high level and a low level. Note that the waveform of the drive signal is not limited to this, and may be, for example, a sine wave, a triangular wave, or a trapezoidal wave.

  The control unit 200 controls the driving of the piezoelectric actuator 20 by adjusting the waveform shape of the driving signal generated by the driving signal 100. The control unit 200 according to the present embodiment includes a first waveform adjustment unit 210 and a second waveform adjustment unit 220. Each adjustment unit includes a phase adjustment circuit (for example, a delay circuit) that adjusts the phase of the waveform of the drive signal, and an amplifier circuit that adjusts the voltage amplitude of the drive signal, and independently adjusts the waveform of the drive signal. To do. In the following description, the drive signal adjusted by the first waveform adjustment unit 210 is referred to as a first drive signal, and the drive signal adjusted by the second waveform adjustment unit 220 is referred to as a second drive signal. . The first drive signal and the second drive signal are signals having different waveform phases and amplitudes, and are both supplied to the piezoelectric actuator 20.

  The rotation speed detection unit 300 detects the rotation speed of the rotor 30 and outputs the detection result to the control unit 200. Based on the detection result of the rotation speed detection unit 300, the control unit 200 controls the driving of the piezoelectric actuator 20.

≪Piezoelectric actuator configuration≫
The piezoelectric actuator 20 includes piezoelectric elements 21 and 22, a reinforcing plate 23, a contact portion 24, and a fixing member 25.

  The reinforcing plate 23 is a rectangular plate member made of a metal such as aluminum. The reinforcing plate 23 is provided with a contact portion 24 and a fixing member 25 described later. Further, a grounding wire (not shown) is connected to the reinforcing plate 23, and the reinforcing plate 23 is grounded.

  The piezoelectric elements 21 and 22 are made of, for example, lead zirconate titanate, and are provided in the same rectangular shape as that of the reinforcing plate 23. As shown in FIG. 2, the piezoelectric element 21 is disposed on the upper surface side of the reinforcing plate 23, and the piezoelectric element 22 is disposed on the lower surface side of the reinforcing plate 23. That is, the reinforcing plate 23 is sandwiched between the piezoelectric element 21 and the piezoelectric element 22. Further, as shown in FIG. 1, a first electrode 26 is formed on the upper surface of the piezoelectric element 21 along the longitudinal direction at the central portion in the width direction. A pair of second electrodes 27 is formed on a diagonal line with the first electrode 26 interposed therebetween. Each of these electrodes is provided by forming, for example, a nickel plating layer and a gold plating layer on the surface of the piezoelectric element 21.

  Each second electrode 27 is arranged rotationally symmetrically with respect to the center of the surface of the piezoelectric element 21 and is electrically connected by a lead wire (not shown). The first electrode 26 is supplied with the first drive signal (the drive signal that has passed through the first waveform adjustment unit 210), and the second electrode 27 is supplied with the second drive signal (the drive through the second waveform adjustment unit 220). Signal).

  A third electrode 28 is provided on a diagonal line opposite to the pair of second electrodes 27. The third electrode 28 is a phase detection electrode provided to detect the phase of vibration of the vibrating body. The detection result by each third electrode 28 is output to the control unit 200.

  In addition, the same electrode as each electrode formed in the piezoelectric element 21 is also provided in the piezoelectric element 22 below the reinforcing plate 23 so as to have the same arrangement (see FIG. 2). Further, the same drive signal as that of each electrode of the piezoelectric element 21 is supplied to the first electrode 26 and the second electrode 27 of the piezoelectric element 22.

  The piezoelectric elements 21 and 22 and the reinforcing plate 23 vibrate when supplied with drive signals (first drive signal and second drive signal). Therefore, in the following description, the piezoelectric elements 21 and 22 and the reinforcing plate 23 are also referred to as vibrating bodies.

  The abutting portion 24 is provided at the center in the width direction on the short side of one side of the reinforcing plate 23 (on the rotor 30 side), and abuts on the rotor 30 according to the vibration of the vibrating body to rotate the rotor 30.

  The fixing members 25 are respectively provided in the central portions in the longitudinal direction on the long sides on both sides of the reinforcing plate 23. Each fixing member 25 is fixed to, for example, a base (not shown) by screws or the like. Thereby, the fixing member 25 supports the vibrating body. Moreover, it can also be used as an alternative member for the above-described ground wire.

≪About driving of piezoelectric actuator≫
The control unit 200 according to the present embodiment causes the vibrating body to vibrate in the longitudinal direction and the width direction based on the drive signal generated by the drive signal generation unit 100, thereby causing the contact portion 24 to elliptically move. Then, during this elliptical motion, the contact portion 24 is brought into contact with the rotor 30 to rotate the rotor 30. The control unit 200 has an acceleration region that accelerates from the stopped state to a predetermined speed, a constant speed region that maintains the predetermined speed, and a deceleration region that decelerates from the predetermined speed to the stopped state when the rotor 30 is rotated. Control is performed to rotate based on the speed profile. In the following description, the acceleration region and the deceleration region are collectively referred to as an acceleration / deceleration region.

  As described above, in this embodiment, the vibration mode in which the vibration body vibrates in the longitudinal direction (longitudinal vibration mode: corresponding to the first vibration mode) and the vibration mode in which the vibration body vibrates in the width direction (bending vibration mode: second). Two vibration modes (corresponding to vibration modes) are used. Each vibration mode will be described below.

<Vertical vibration mode>
FIG. 3A is a simplified explanatory diagram of the longitudinal vibration mode. When the control unit 200 supplies the first drive signal to the first electrode 26 of the piezoelectric element 21, the vibration in the longitudinal vibration mode in which the vibrating body expands and contracts along the longitudinal direction is excited. The amplitude of this vibration depends on the voltage amplitude of the first drive signal supplied to the first electrode 26. That is, the greater the voltage amplitude of the first drive signal, the greater the amplitude of vibration in the longitudinal vibration mode (hereinafter, also simply referred to as the amplitude of the longitudinal vibration mode). The mode amplitude is reduced.

<Bending vibration mode>
FIG. 3B is an explanatory diagram of the bending vibration mode. When the controller 200 supplies the second drive signal to the pair of second electrodes 27 of the piezoelectric element 21, each second electrode 27 expands and contracts in the longitudinal direction. That is, vibration in the longitudinal vibration mode occurs at the portion of the second electrode 27. On the other hand, in the portion of the third electrode 28, the vibration in the longitudinal vibration mode does not occur. As a result, as shown in FIG. 3B, vibration in a bending vibration mode that bends in a direction (width direction) orthogonal to the longitudinal direction is excited in the vibrating body. The amplitude of this vibration depends on the voltage amplitude of the second drive signal. That is, the greater the voltage amplitude of the second drive signal, the greater the amplitude of vibration in the flexural vibration mode (hereinafter also referred to simply as the amplitude of the flexural vibration mode). The mode amplitude is reduced.

  3A and 3B, only the upper surface side (piezoelectric element 21 side) of the vibrating body is shown, but the lower surface side (piezoelectric element 22 side) of the vibrating body has the same configuration, and the piezoelectric element 21 side. The longitudinal vibration mode and the bending vibration mode are excited in the same manner as in FIG. Specifically, the longitudinal vibration mode is excited by the first drive signal, and the bending vibration mode that is bent in the same direction as the bending of the piezoelectric element 21 is excited by the second drive signal.

<About elliptic motion>
FIG. 4 is an explanatory diagram of the movement (elliptical movement) of the contact portion 24 when the rotor 30 is rotated. FIG. 5 is an explanatory diagram of an elliptical locus.

  When the first drive signal is supplied to the first electrode 26 and the second drive signal is supplied to the second electrode 27, the contact portion 24 becomes an ellipse that combines the longitudinal vibration mode and the bending vibration mode as shown in FIG. Move so as to draw the locus (dotted line in the figure). When the abutting portion 24 draws this elliptical trajectory, the abutting portion 24 abuts on the rotor 30 at the end portion on the rotor 30 side in the longitudinal direction of the trajectory, and rotates the rotor 30 in the direction of the arrow.

  The longitudinal displacement (amplitude) in the elliptical locus shown in FIG. 5 depends on the amplitude of the longitudinal vibration mode. When this amplitude is large, the force (pressing force) for pressing the contact portion 24 against the rotor 30 increases. However, in this case, the reaction force that the contact portion 24 receives from the rotor 30 also increases. On the other hand, when the amplitude is small, the pressing force becomes low, and the contact portion 24 becomes slippery when contacting the rotor 30.

  On the other hand, the displacement amount (amplitude) in the width direction in the locus of the ellipse depends on the amplitude of the bending vibration mode. If this amplitude is large, the rotational speed of the rotor 30 can be increased. However, if this amplitude is increased when the rotation of the rotor 30 is not stable (for example, when it starts to move), the contact portion 24 and the rotor 30 become slippery. .

≪Comparative example≫
Assume that the rotor 30 is driven by an elliptical orbit having the same shape as the ellipse shown in FIG. 4 regardless of the rotational speed of the rotor 30. In this case, there is a possibility that the rotor 30 cannot be rotated stably.

  For example, when the orbit of the elliptical motion is reduced, the vibration in the longitudinal direction of the vibrating body (the amplitude of the longitudinal vibration mode) is also reduced. For this reason, for example, the contact portion 24 and the rotor 30 may be slippery in an acceleration / deceleration region where a pressing force is required. Moreover, if the orbit of the elliptical motion is reduced, the vibration in the width direction of the vibrating body (the amplitude of the refractive vibration mode) is also reduced. For this reason, there is a possibility that a desired rotation speed cannot be obtained in the constant speed range.

  On the other hand, when the orbit of the elliptical motion is increased, the vibration in the longitudinal direction of the vibrating body (the amplitude of the longitudinal vibration mode) also increases. For this reason, for example, in the constant speed region, the rotor 30 is difficult to rotate, and there is a possibility that energy is wasted when the rotor 30 rotates.

<< this embodiment >>
FIG. 6 is an explanatory diagram of the driving method of this embodiment. 6A shows an example of an elliptical orbit in the acceleration / deceleration region, and FIG. 6B shows an example of an elliptical orbit in the constant speed region.

  As described above, the control unit 200 of this embodiment includes the first waveform adjustment unit 210 and the second waveform adjustment unit 220. Then, the control unit 200 adjusts the waveform of the drive signal generated by the drive signal generation unit 100 in the first waveform adjustment unit 210 and the second waveform adjustment unit 220, respectively, and outputs the piezoelectric as the first drive signal and the second drive signal. It is output to the actuator 20. Thereby, the amplitude of the longitudinal vibration mode and the amplitude of the bending vibration mode are controlled separately.

  For example, in the acceleration / deceleration region, as shown in FIG. 6A, the longitudinal amplitude (longitudinal vibration mode amplitude) is increased, and the width direction amplitude (flexural vibration mode amplitude) is further decreased. That is, the control unit 200 increases the voltage amplitude of the first drive signal and decreases the voltage amplitude of the second drive signal. By doing so, the contact portion 24 can be strongly pressed against the rotor 30 and a strong force is not applied in the width direction, so the contact portion when the contact portion 24 and the rotor 30 are in contact with each other. 24 and the rotor 30 can be prevented from slipping.

  On the other hand, in the constant speed region, as shown in FIG. 6B, the longitudinal amplitude (longitudinal vibration mode amplitude) is reduced, and the width direction amplitude (flexural vibration mode amplitude) is increased. That is, the control unit 200 decreases the voltage amplitude of the first drive signal and increases the voltage amplitude of the second drive signal. By doing so, waste of energy (axial loss) due to pressing the contact portion 24 against the rotor 30 can be reduced, and a strong force can be applied in the width direction, so that the rotation speed can be increased.

  When the rotor 30 starts to move from the stopped state (acceleration region), the control unit 200 according to the present embodiment causes the contact portion 24 to move approximately elliptically so as to draw a trajectory indicated by a dotted line in FIG. 6A. At this time, a pressing force corresponding to the static friction coefficient of the rotor 30 is required in the longitudinal direction. For this reason, the amplitude in the longitudinal direction (the amplitude in the longitudinal vibration mode) is set so as to be equal to or greater than the pressing force. However, if the amplitude is too large, the vibrating body may cause abnormal vibration due to the reaction force from the rotor 30. For this reason, the amplitude of the longitudinal vibration mode is set to be smaller than the amplitude when the abnormal vibration occurs. This prevents abnormal vibration of the vibrating body.

  Based on the detection result of the rotation speed detection unit 300, the control unit 200 increases the amplitude of vibration in the bending vibration mode and decreases the amplitude of vibration in the longitudinal vibration mode as the rotation speed of the rotor 30 increases. By doing so, it is possible to increase the rotation speed while suppressing slippage. In addition, since the slip can be suppressed, the wear resistance of the contact portion 24 can be improved.

In the constant speed region, the control unit 200 maximizes the amplitude in the width direction (amplitude of the bending vibration mode) and minimizes the amplitude in the long side direction (the amplitude of the longitudinal vibration mode) as shown in FIG. 6B. Note that when the rotor 30 is stopped from the constant speed range (deceleration range), the control unit 200 performs a control opposite to the above.

  As described above, in the present embodiment, when the piezoelectric actuator 20 is driven, the longitudinal vibration mode in which the vibrating body is expanded and contracted in the longitudinal direction and the bending vibration mode in which the vibrating body is bent in the width direction are simultaneously and independently performed. It is done. In the case of accelerating or decelerating the rotation of the rotor 30 (acceleration / deceleration range), the longitudinal vibration mode has a larger amplitude and the bending vibration mode than in the case of rotating the rotor 30 at a constant speed (constant speed range). The amplitude is reduced.

  By doing so, it is possible to suppress slippage of the contact portion 24 and the rotor 30 in the acceleration / deceleration range, and it is possible to increase the rotation speed while suppressing energy consumption in the constant speed range. In this way, the driving of the rotor 30 by the piezoelectric actuator 20 can be optimized.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About driven objects>
In the piezoelectric actuator of the above-described embodiment, since the object to be driven (driven body) is the rotor 30, the rotor 30 is rotated by the contact portion 24. However, the present invention is not limited to this. For example, the driven body may be linearly driven by bringing the contact portion 24 into contact with a flat-plate driven body.

<About vibrating body>
In the above-described embodiment, the vibrating body is composed of the piezoelectric elements 21 and 22 and the reinforcing plate 23, but is not limited thereto. For example, the vibrating body may be configured by providing a piezoelectric element on one surface of the reinforcing plate 23. Or you may make it comprise a vibrating body only with a piezoelectric element, without using the reinforcement board 23. FIG. However, in this case, there is a possibility that bending is likely to occur. Also, for example, there is a risk of breaking when dropped or screwed. When the reinforcing plate 23 is sandwiched between the piezoelectric elements 21 and 22 as in the present embodiment, the fixing can be reliably performed, the strength can be increased, and the possibility of occurrence of cracks can be reduced.

  In this embodiment, aluminum is used for the reinforcing plate 23, but the reinforcing plate 23 may be formed using a metal other than aluminum. For example, 42Ni alloy may be used.

  In the present embodiment, lead zirconate titanate is used for the piezoelectric elements 21 and 22, but is not limited thereto. For example, quartz, lithium niobate, barium titanate, lead titanate, lead metaniobate, polyvinylidene fluoride, lead zinc niobate, lead scandium niobate, or the like may be used.

<About drive signal>
In the above-described embodiment, both the first drive signal and the second drive signal are generated by the drive signal generation unit 100, but the present invention is not limited to this. For example, a plurality of drive signal generation units may be provided to generate the first drive signal and the second drive signal separately. In this case, the waveform of each drive signal may be adjusted according to the detection result of the rotational speed of the rotor 30.

<Rotation of rotor>
In the above-described embodiment, the rotor 30 is rotated only in one direction (counterclockwise direction), but may be rotated in both directions. For example, an electrode similar to the pair of second electrodes 27 is provided at a position of the pair of third electrodes 28 on the diagonal, and the combination of the pair of second electrodes 27 that supplies the second drive signal is switched by a switch or the like. The rotation direction of the rotor 30 may be switched between the counterclockwise direction and the clockwise direction.

<About the rotation speed detector>
In the above-described embodiment, the rotational speed of the rotor 30 is detected by providing the rotational speed detector 300, but the rotational speed of the rotor 30 may not be detected. For example, the rotational speed of the rotor 30 may be estimated from the detection result of the third electrode 28 for phase detection, and the vibration of the vibrating body may be controlled based on the estimation result.

<About the amplitude of the longitudinal vibration mode>
In the above-described embodiment, the amplitude of the longitudinal vibration mode is changed according to the rotation speed of the rotor 30, but may be changed stepwise. For example, it may be changed in two stages: when the rotor 30 starts to move (large amplitude) and when the rotor 30 is rotating in a constant speed region (small amplitude).

20 piezoelectric actuators, 21, 22 piezoelectric elements, 23 reinforcing plates,
24 contact part, 25 fixing member,
26 1st electrode, 27 2nd electrode, 28 3rd electrode,
30 rotor, 31 rotation axis,
100 drive signal generation unit, 200 control unit,
210 first waveform adjustment unit, 220 second waveform adjustment unit,
300 Rotation speed detector

Claims (8)

A driving method of a piezoelectric actuator comprising a vibrating body having a piezoelectric element and transmitting the vibration of the vibrating body to a driven body to drive the driven body,
A first vibration mode in which the vibrating body expands and contracts the vibrating body in a direction intersecting a driving direction of the driven body; and a second vibration mode in which the vibrating body is bent in the driving direction of the driven body. , And vibrate simultaneously in a second vibration mode independent of the first vibration mode,
When accelerating or decelerating the driving of the driven body, the amplitude of vibration in the first vibration mode is set larger than in the case of driving the driven body at a constant speed, and in the second vibration mode. Reduce the amplitude of vibration,
A method for driving a piezoelectric actuator. It is a drive method of the piezoelectric actuator of Claim 1, Comprising:
Detecting the driving speed of the driven body, and changing the amplitude of vibration in the first vibration mode and the amplitude of vibration in the second vibration mode, respectively, according to the detection result of the driving speed;
A method for driving a piezoelectric actuator. A method for driving a piezoelectric actuator according to claim 2,
The method for driving a piezoelectric actuator, wherein the amplitude of vibration in the second vibration mode is changed depending on the driving speed. A method for driving a piezoelectric actuator according to any one of claims 1 to 3,
A method of driving a piezoelectric actuator, wherein an amplitude of vibration in the first vibration mode when accelerating or decelerating driving of the driven body is a predetermined value or less. A piezoelectric actuator having a piezoelectric element and comprising a vibrating body that vibrates based on a drive signal supplied to the piezoelectric element; and a transmission unit that transmits the vibration to a driven body;
A drive unit for supplying the drive signal to the piezoelectric actuator;
With
The drive unit includes a first drive signal for causing the vibrator to vibrate in a first vibration mode that expands and contracts in a direction intersecting the drive direction of the driven body, and the vibrator in the drive direction of the driven body. When the second driving signal for vibrating in the second vibration mode for bending the vibrating body is simultaneously supplied to accelerate or decelerate the driving of the driven body, the driven body is driven at a constant speed. than to, it supplies the first drive signal amplitude greater, and to supply the second drive signal low amplitude,
A drive unit characterized by that. The drive unit according to claim 5 ,
A speed detecting unit for detecting a driving speed of the driven body;
The drive unit supplies the first drive signal and the second drive signal, the amplitude of which is changed according to the detection result of the drive speed.
A drive unit characterized by that. The drive unit according to claim 6 ,
The drive unit supplies the second drive signal having an amplitude changed to depend on the drive speed;
A drive unit characterized by that. The drive unit according to any one of claims 5 to 7 ,
The drive unit supplies the first drive signal having an amplitude equal to or less than a predetermined value when accelerating or decelerating the drive of the driven body.
A drive unit characterized by that.