JP2008295287A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator and a driving method therefor which suppress current generated by the free oscillation of a piezoelectric element to reduce power consumption. <P>SOLUTION: A driving circuit generates a voltage waveform that forms a transition period of no voltage application between a first voltage level period and a second voltage level period that are different from each other. A voltage applied to the piezoelectric element 1 is controlled by the voltage waveform. Because the piezoelectric element 1 does not consume power during the transition period, power consumption can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator for impact driving a piezoelectric element and a driving method thereof.

  In order to provide the camera with an autofocus or zoom function, a mechanism for moving the optical lens along the optical axis is necessary, and a method using an electromagnetic motor has been conventionally known. In recent years, as seen in digital cameras and camera-equipped mobile phones, the miniaturization of devices has rapidly progressed. Accordingly, electro-mechanical conversion elements (hereinafter referred to as piezoelectric elements) represented by piezoelectric elements have been changed from electromagnetic motors. A voltage driven method has been proposed.

  For example, Patent Document 1 discloses a linear motor including a piezoelectric element, a friction member fixed to one end of the piezoelectric element, and a moving element pressed against the friction member. Furthermore, in Patent Document 1, by applying a voltage (for example, a sawtooth voltage) with a significantly different rise time and fall time to the piezoelectric element, the friction member fixed to the piezoelectric element moves in one direction opposite to the one direction. The speed is greatly varied, and as a result, the movable element that is the driven member is linearly moved in one specific direction. That is, Patent Document 1 discloses driving a moving element using a difference between a piezoelectric element and a frictional force due to a difference between a static friction coefficient and a dynamic friction coefficient, that is, impact driving.

  On the other hand, Patent Document 2 discloses a piezoelectric actuator that bonds a fixed member and a drive friction member to a piezoelectric element and vibrates the drive friction member. In Patent Document 2, by applying a rectangular wave to the piezoelectric element, the driven member is moved using the difference between the rectangular wave applied to the piezoelectric element and the frictional force, similar to the sawtooth wave of Patent Document 1. ing. That is, in Patent Document 2, the driven member is moved by changing the charge / discharge time in the polarization direction of the piezoelectric element and the charge / discharge time in the direction opposite to the polarization direction.

JP-A-3-289368 Japanese Patent No. 3171187

  In the piezoelectric actuator disclosed in Patent Document 2, charging and discharging in the polarization direction and charging and discharging in the direction opposite to the polarization direction are performed at substantially the same speed and with different driving times. The circuit configuration necessary for giving a large difference between the speed and the expansion / contraction speed can be simplified, and as a result, the piezoelectric actuator can be miniaturized.

  However, in this circuit configuration, charging / discharging is repeated continuously, and the power supply voltage is constantly applied to the piezoelectric element. Therefore, a current is constantly supplied from the power supply to cancel the charge generated by the free vibration of the piezoelectric element. Therefore, power consumption increases. For this reason, the circuit configuration of Patent Document 2 consumes a large amount of battery, and is not suitable for a device that requires downsizing, such as a mobile phone.

  An object of the present invention is to provide a piezoelectric actuator that can suppress current generated by free vibration of a piezoelectric element and reduce power consumption, and a driving method thereof.

  According to the first aspect of the present invention, in a driving method for driving the driven member by impact by applying a voltage to the piezoelectric element, the discontinuous voltage waveform that changes intermittently is supplied as the voltage. A drive method characterized by impact driving the drive member is obtained.

  According to a second aspect of the present invention, in the first aspect, the discontinuous voltage waveform includes a predetermined first voltage level period and a second voltage level period different from the first level. And there is a transition period in which no voltage is applied between the first and second voltage level periods.

  According to a third aspect of the present invention, there is provided the driving method according to the first or second aspect, wherein the first voltage level period and the second voltage level period are substantially the same. can get.

  According to a fourth aspect of the present invention, it includes a piezoelectric element and a voltage generation circuit that applies a voltage to the piezoelectric element, and the voltage generation circuit generates a discontinuous voltage waveform that changes intermittently. Is obtained.

  According to a fifth aspect of the present invention, in the fourth aspect, the voltage generation circuit includes a predetermined first voltage level period and a second voltage level period different from the first level; A piezoelectric actuator is obtained that generates a voltage waveform having a transition period in which no voltage is applied between the first and second voltage level periods.

  According to the sixth aspect of the present invention, the piezoelectric element, the driving member fixed to one end of the piezoelectric element, the support member fixed to the other end of the piezoelectric element, and the driving member to the driving member And a driven member engaged with a predetermined frictional force so as to be relatively movable in the moving direction, and the driven member moves reciprocally at different speeds due to expansion and contraction of the piezoelectric element to move the driven member. In the piezoelectric actuator to be applied, a constant voltage in the polarization direction is applied to the piezoelectric element to charge in the polarization direction, a first charge / discharge time for discharging in the opposite direction to the polarization direction, and in the polarization direction A second charge / discharge time for applying a constant voltage in the direction opposite to the polarization direction and charging in the direction opposite to the polarization direction, and a time during which the voltage is not applied and discharged in both directions. The piezoelectric actuator is obtained, characterized in that the charge and discharge time has a voltage generating circuit for generating a driving voltage is substantially the same.

According to the seventh aspect of the present invention, the resonance frequency of the piezoelectric actuator is fr, the anti-resonance frequency is fa, the first charge / discharge time is T1, the second charge / discharge time is T2, and the voltage is applied in both directions. When T3 is the time during which no voltage is applied or discharged,
T1 = T2 = (2n−1) / (2fr), (n = 1, 2, 3...)
T3 = (2m−1) / (2fa), (m = 1, 2, 3,...)
A piezoelectric actuator characterized by having a voltage generation circuit for generating a drive voltage such that

  According to the eighth aspect of the present invention, in the piezoelectric actuator driving method of moving the driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the resonance frequency and the antiresonance frequency of the piezoelectric actuator respectively. A driving method is characterized in that the driving member is moved by expanding and contracting the piezoelectric element for a fixed time.

According to the ninth aspect of the present invention, in the piezoelectric actuator that moves the driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the resonance frequency of the piezoelectric actuator is fr and the antiresonance frequency is fa. T1 is a time for applying a predetermined first voltage level to the piezoelectric element, T2 is a time for applying a second voltage level different from the first voltage level to the piezoelectric element, and When the time for stopping the voltage application is T3,
T1 = T2 = (2n−1) / (2fr), (n = 1, 2, 3...)
T3 = (2m−1) / (2fa), (m = 1, 2, 3,...)
Thus, a driving method can be obtained in which a voltage is applied to the piezoelectric element so that the driving member is moved by expanding and contracting the piezoelectric element.

  According to the tenth aspect of the present invention, in the piezoelectric actuator that moves the driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the voltage is applied to the piezoelectric element for a time determined by the resonance frequency of the piezoelectric actuator. And a voltage generation circuit for stopping the application of voltage to the piezoelectric element for a time determined by the anti-resonance frequency of the piezoelectric actuator.

According to the eleventh aspect of the present invention, in the piezoelectric actuator that moves the driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the resonance frequency of the piezoelectric actuator is fr and the antiresonance frequency is fa. T1 is a time for applying a predetermined first voltage level to the piezoelectric element, T2 is a time for applying a second voltage level different from the first voltage level to the piezoelectric element, and When the time for stopping the voltage application is T3,
T1 = T2 = (2n−1) / (2fr), (n = 1, 2, 3...)
T3 = (2m−1) / (2fa), (m = 1, 2, 3,...)
A piezoelectric actuator characterized by including a voltage generation circuit that generates such a voltage is obtained.

  According to the present invention, since the charging time applied from the power source to the piezoelectric element is shortened as compared with the conventional method, the power consumption can be reduced. Further, by providing a time during which no voltage is applied and discharged in both the polarization direction and the reverse direction, the driven member can be moved favorably. According to the present invention, it is possible to provide a driving method of a piezoelectric actuator with low power consumption, and it is possible to reduce the size of the device and the battery consumption.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a configuration diagram of a piezoelectric actuator used in the present invention, and includes an actuator unit 10 and a drive circuit unit 20. The actuator unit 10 is fitted with the piezoelectric element 1 that is vertically polarized in FIG. 1, the magnet 2 that is fixed to one end (here, the upper end) of the piezoelectric element, the moving ring 3 that is attracted to the magnet 2, and the moving ring 3. The movable body 4 includes a movable body 4 such as a lens unit that can move together with the movable ring 3, a support member (here, a housing) 5 that supports the lower end of the piezoelectric element 1, and a guide pin 6 that guides the movable body 4. ing. In the illustrated example, the driving member is configured by the magnet 2 fixed to the piezoelectric element 1, and the driven member is configured by the moving ring 3 and the moving body 4.

  On the other hand, the drive circuit unit 20 includes a control circuit 21 that generates a control signal necessary for driving the piezoelectric element 1, and a switch circuit 22 that charges and discharges the piezoelectric element 1 according to the control signal from the control circuit 21. It is out.

  The illustrated piezoelectric element 1 is displaced in the polarization direction (vertical direction in the figure) according to a discontinuous voltage controlled by turning on and off the switch in the switch circuit 22, and is a magnet fixed to the upper end of the piezoelectric element 1. 2 is moved up and down. As the magnet 2 moves, the moving ring 3 and the moving body 4 also move in the vertical direction. In the illustrated example, the magnet 2 is bonded to the upper end of the piezoelectric element 1 using an epoxy resin or the like.

  The material and structure of the piezoelectric element 1 can be appropriately selected as long as a predetermined displacement can be generated. However, in the present invention, a laminated piezoelectric ceramic that can obtain a large displacement output at a low voltage of about several V to several tens V is used. Is preferred.

  A general method may be used as a method of manufacturing the multilayer piezoelectric ceramic. For example, a ceramic green sheet having a predetermined thickness is manufactured by a method such as a doctor blade method, an Ag / Pd paste or a Cu paste is printed as an internal electrode in a predetermined shape by a screen printing method or the like, and then trimming and a predetermined number of layers are laminated To do. What is necessary is just to manufacture by the process of punching to a defined shape after a hot press, a binder removal, and a sintering.

  The material of the magnet 2 is not particularly limited, but it is preferable to use a neodymium-based magnet or a samarium-cobalt-based magnet in order to ensure a sufficient attractive force even when the size is reduced.

  Here, the moving ring 3 and the moving body 4 are separate members, but can be integrated as the same material.

  Next, in order to facilitate understanding of the driving method according to the present invention, a case where the piezoelectric actuator shown in FIG. 1 is driven by a conventional driving method will be described with reference to FIG. In FIG. 2, the height of the piezoelectric element 1 alone is about 1.5 mm, the height of the magnet is about 1 mm, and the resonance frequency is about 300 kHz. In this case, as shown in FIG. 2, the voltage waveform applied to the piezoelectric element 1 is a rectangular wave, the frequency of the rectangular wave voltage waveform, that is, the drive frequency is about 200 kHz, and the duty ratio is about 0.33 or 0.67. Then, the output displacement waveform of the piezoelectric element 1 becomes a sawtooth waveform due to the displacement of the harmonic component and the phase shift.

  As shown in FIG. 2, in the rectangular input voltage waveform, the output displacement waveform becomes a sawtooth waveform, so that the piezoelectric element slowly extends over time t1 and rapidly contracts at time t2. Here, if the input voltage is set so as to obtain an acceleration equal to or greater than the maximum static friction force generated between the moving ring 3 and the magnet 2 at time t2, both the moving ring 3 and the piezoelectric element 1 move at time t1. At time t2, slip occurs between the moving ring 3 and the piezoelectric element 1. By repeating this continuously, the moving ring 3 and the moving body 4 move in one direction with respect to the support member. That is, impact driving is performed. Further, when the input voltage is set so that the acceleration equal to or greater than the maximum static friction force generated between the moving ring 3 and the magnet 2 is obtained at both the times t1 and t2, the moving ring 3 has the time t1 and time. Although it moves while generating a slip between the piezoelectric elements 1 at any of t2, the time t1 and the time t2 are different, and thus by repeating this continuously, the moving ring 3 and the moving body 4 are moved. It moves substantially in one direction relative to the support member. Therefore, impact driving is also performed in this case.

  In any case, the speed and moving direction of the moving body can be controlled by changing the ratio between the time t1 and the time t2, that is, by changing the duty ratio of the input voltage waveform to the piezoelectric element 1.

  Next, examples of the piezoelectric actuator of the present invention will be described. As the piezoelectric element 1, a laminated piezoelectric ceramic element having a cross section of 1.0 × 1.0 mm and a height of 1.5 mm was prepared. This multilayer piezoelectric ceramic element generates a displacement of approximately 0.1 μm when a voltage of ± 3 V is applied. A neodymium magnet having a size of 1.0 mm × 1.4 mm and a height of 1.0 mm was bonded to one end of the piezoelectric ceramic element with a thermosetting epoxy resin. Further, a housing made of polycarbonate was produced as the support member 5 and bonded to the other end of the piezoelectric ceramic element with an epoxy resin.

  A moving body having an outer diameter of 7.5 mm, an inner diameter of 6.5 mm, and a height of 1.5 mm made of SUS430 was produced, and adhered to a holder made of polycarbonate with an epoxy resin. In addition, the actuator having the structure shown in FIG. 1 was manufactured by supporting the holder on a guide pin made of SUS304 and simultaneously adsorbing the magnet and the moving body by magnetic force. In this case, the movement stroke of the holder is about 0.5 mm, but the stroke can be further increased by increasing the height of the moving body.

  Further, as the switch circuit 22 of the drive circuit unit 20 that drives the actuator, a circuit as shown in FIG. 3 was produced. This switch circuit includes four switches Q1, Q2, Q3, and Q4 connected to both ends of the piezoelectric element 1 (PA). These switches Q1 to Q4 are connected to the control circuit 21 shown in FIG. It is turned on / off by the control signal. In this embodiment, as will be described later, the drive circuit unit 20 operates as a voltage generation circuit that generates a temporally discontinuous voltage waveform from the switch circuit 22 controlled by a control signal from the control circuit 21.

  Here, the switch circuit 22 according to the present invention is compared with a conventional switch circuit. First, as described in Patent Document 2, a case where the output voltage from the switch circuit 22 is controlled to change continuously will be described. In this case, the case where the switches Q1 and Q4 are turned on and the current path is formed from the power source Vp to the piezoelectric element 1 via the switches Q1 and Q4 is referred to as first driving means, while the switches Q2, Q3 A case where the current path is formed from the power source Vp to the piezoelectric element 1 via the switches Q2 and Q3 in the ON state is referred to as second driving means.

  Table 1 shows the on and off states of the switches Q1 to Q4 in the conventional switch circuit. As shown in Table 1, in the conventional switch circuit, since the piezoelectric element is driven by alternately driving the first driving means and the second driving means, one of the electrical terminals of the piezoelectric element is always provided. The power supply is connected. On the other hand, since the piezoelectric element is driven by the first and second driving means and is suddenly charged or discharged every time the switch state is changed, it vibrates at the resonance frequency fr after rapid expansion or rapid contraction. Here, fr is a resonance frequency when one end of the piezoelectric element is a fixed end and the driving member and the driven member are fixed to the other end. For this reason, in the conventional switch circuit, current is supplied from the power source so as to cancel the electric charge generated by the free vibration of the piezoelectric element and to keep the applied voltage to the piezoelectric element constant. End up.

  On the other hand, the driving method according to the present invention has a discontinuous voltage waveform having a period P1 of the first voltage level v1, a period P2 of the second voltage level v2, and a transition period P3 between the periods P1 and P2. Is applied to the piezoelectric element from the drive circuit unit 20, and the switch circuit 22 is controlled by the control circuit 21 so as to take an on / off state according to Table 2. In other words, the control circuit 21 generates a control signal (that is, a voltage waveform) that causes the switch circuit 22 to operate according to Table 2. The control circuit 21 that generates such a control signal can be easily obtained by combining, for example, a pulse generation circuit that generates a pulse in response to a user operation and a logic circuit that logically processes the generated pulse. Since it is realizable, description is abbreviate | omitted here.

  As shown in Table 2, in the first voltage level period P1, the switches Q1 and Q4 are turned on, a current path is formed from the power source Vp to the piezoelectric element via the switches Q1 and Q4, and In the second voltage level period P2, the switches Q2 and Q3 are turned on, and a current path is formed from the power source Vp to the piezoelectric element via the switches Q2 and Q3. In the transition period P3 between the first and second voltage level periods, the switches Q1 to Q4 are all turned off, and the piezoelectric element is placed in a state of being electrically disconnected from the switch circuit 22. However, since the electric charge charged in the piezoelectric element is stored and does not change, the voltage between the electric terminals of the piezoelectric element remains at the previous voltage level. That is, the voltage level applied to the piezoelectric element in the transition period P3 is substantially equal to the voltage level v1 in the immediately preceding first voltage level period P1. Therefore, in the transition period P3, power consumption due to charging / discharging from the power supply can be eliminated while maintaining the previous voltage level. Therefore, a discontinuous voltage waveform as shown by the voltage waveform Wv in FIG. 4 is output from the switch circuit 22 according to the driving method of the present invention. As shown, the first voltage level v1 differs in polarity from the second voltage level v2. Further, in FIG. 4, the first voltage level period P1 and the second voltage level period P2 are controlled to be substantially the same. In addition, during the first voltage level period P1, the piezoelectric element 1 is charged in the polarization direction of the piezoelectric element 1, for example, and during the second voltage level period P2, it is charged in the direction opposite to the polarization direction. In other words, the first voltage level period P1 and the second voltage level period P2 define the charge / discharge period of the piezoelectric element 1.

As described above, the driving method according to the present invention provides the transition period P3 in which the piezoelectric element is electrically disconnected from the switch circuit 22 between the first and second voltage level periods. As shown in the current waveform Wi, current supply from the power supply can be completely eliminated during the transition period P3. Accordingly, since no power is consumed by the piezoelectric element 1 during the transition period P3, power consumption can be reduced.

  In the driving method of the present invention described above, the piezoelectric element vibrates under the condition of constant electric field in the first and second voltage level periods P1 and P2, and the condition of constant electric flux density in the transition period P3. Vibrate. In other words, the driving method according to the present invention extends the piezoelectric element by extending and contracting the piezoelectric element for a time determined by the resonance frequency and the antiresonance frequency of the piezoelectric actuator in which the magnet 2 as the driving member is fixed. That is, the magnet 2 is moved.

  Therefore, when the resonance frequency of the piezoelectric element 1 (that is, the piezoelectric actuator) with the magnet 2 fixed is fr and the antiresonance frequency is fa, the vibration period is 1 / fr in the periods P1 and P2, and the period In P3, it is 1 / fa. Here, the antiresonance frequency fa of the piezoelectric element 1 used for the piezoelectric actuator is usually higher than the resonance frequency fr and smaller in amplitude.

  The driving method of the present invention will be described more specifically in view of the above points. With respect to the drive frequency fd of the piezoelectric actuator according to the present invention, the first voltage level period P1, the second voltage level period P2, and the transition period in order to move the moving body 4 efficiently using the resonance vibration of the piezoelectric element. P3 is set so as to satisfy the relationship of the following formula 1 in consideration of the vibration period in each period, and is operated near the drive frequency fd derived by the following formula 2, so that a piezoelectric with good operating characteristics is obtained. An actuator is obtained.

[Equation 1]
P1 = P2 = (2n−1) / (2fr), (n = 1, 2, 3...)
P3 = (2m−1) / (2fa), (m = 1, 2, 3,...)

[Equation 2]
fd = 1 / (P1 + P2 + P3)

  FIG. 5 shows, as an example of the driving voltage waveform of the piezoelectric actuator in the driving method of the present invention, the driving voltage waveform and the displacement of the piezoelectric element for about one cycle when n = 1 and m = 3 in the above equation 1. In this case, the period P1 = P2 = 1 / (2fr) and the period P3 = 5 / (2fa).

  In the figure, for example, when the voltage v1 is applied to the piezoelectric element at the point a, the piezoelectric element greatly expands at high speed while vibrating at the resonance frequency fr, and then decreases at the point b. Next, since all the switches of the switch circuit 22 are turned off at the point b and the transition period P3 is entered, the piezoelectric element continues to vibrate at the antiresonance frequency fa. When the voltage v2 is applied to the piezoelectric element at the point d where the reduction is changed to the extension, the piezoelectric element performs the reduction operation while vibrating at the resonance frequency fr from the displacement position to the point e. Then, when the voltage v1 is applied again to the piezoelectric element at the point e where the contraction operation ends and the expansion starts, the piezoelectric element again performs the expansion operation at a high speed. The expansion / contraction operation of the element is repeated. In the above-described expansion / contraction operation of the piezoelectric element, the extension operation between a and b is performed at a high speed, and the contraction operation between c and e is performed at a lower speed. Therefore, the expansion / contraction operation of the piezoelectric element causes the magnet to reciprocate. If it repeats, a slip will arise between the moving rings at the time of high speed extension between a and b, and a magnet and a moving ring will move together at the time of low speed reduction between c and e. Therefore, the moving ring moves in one direction as a whole. Alternatively, when slipping occurs between the moving ring even at a low speed reduction, the moving ring is moved by the time difference between ab and ce. Furthermore, between bc vibrating at the anti-resonance frequency fa, the displacement of the piezoelectric element is small, so that no slip occurs between the magnet and the moving ring, so the moving ring does not move.

  In FIG. 5, when the voltage level in the period P1 is changed to v2 and the voltage level in the period P2 is changed to v1 (that is, when the voltage waveform shown in FIG. 5 is inverted), the voltage in the transition period P3 The level becomes a voltage level v2 substantially equal to the immediately preceding period P1. When such a driving voltage is applied, the relationship between the above-described stretching vibrations is reversed, and the piezoelectric element is reduced at high speed between a and b and is extended at low speed between c and e. Therefore, the moving ring moves in the direction opposite to the above.

  FIG. 5 shows the case where n = 1 and m = 3 in Equation 1, but for example, if n = 2 and m = 2 in Equation 1, as shown in FIG. 6, it is compared with the case shown in FIG. Thus, a period corresponding to one period of the resonance frequency fr is added to each of the periods P1 and P2, and a period corresponding to one period of the anti-resonance frequency fa is reduced from the transition period P3. However, the phase of the vibration of the piezoelectric element at the end of each period is equal to that shown in FIG. Therefore, even in the case shown in FIG. 6, the movement is caused by the speed difference between the high speed extension between ab ′ and the low speed reduction between ce ′ by the same mechanism as that shown in FIG. The ring is moved.

  As described above, in any combination of n and m in Equation 1, the phase relationship between the drive waveform and the vibration of the piezoelectric element becomes equal, so that the moving ring can be moved stably. However, since the high-speed expansion and low-speed reduction operations of the piezoelectric element are performed once for each cycle (= P1 + P2 + P3 = 1 / fd) of the drive voltage waveform, when the drive time of one cycle becomes longer (when the drive frequency becomes lower). Although the driving efficiency per one cycle of the moving ring is lowered, the power consumption is also reduced at the same time, so that the driving waveform is set in consideration of the required operation characteristics of the piezoelectric actuator.

  Further, the condition shown in Formula 1 shows the condition for maximizing the speed difference between the high-speed expansion and the low-speed reduction of the piezoelectric element, and thus operating the moving body efficiently. Therefore, as each drive period of the drive voltage waveform deviates from the condition shown in Equation 1, the speed difference between the high speed extension and the low speed reduction of the piezoelectric element decreases, and accordingly, the moving efficiency of the moving body decreases. The moving speed of the moving body decreases. However, even if the condition shown in Equation 1 is not completely satisfied, if the condition shown in Equation 1 is satisfied to some extent, operation characteristics having no practical problem can be obtained. FIG. 7 shows the change in the speed of the moving body when the ratio of each drive period of the drive voltage waveform is fixed at a condition satisfying Equation 1 (P1: P2: P3 = constant) and the drive frequency fd is changed. Show. The speed of the moving body is maximized at the frequency f satisfying the condition of Equation 1, and shows a characteristic that the driving frequency decreases as the driving frequency goes away from f. From FIG. 7, the frequency at which the moving body can be driven is in the range of approximately 0.75 f ≦ fd ≦ 1.5 f. It is desirable to drive in the range of 0.8 f ≦ fd ≦ 1.4 f at which a speed of at least% is obtained.

  Next, measurement results of inrush current, current consumption, and power consumption in the actuator using the piezoelectric actuator in the driving method according to the present invention shown in Table 2 and the piezoelectric actuator in the conventional driving method shown in Table 1 will be described. Both input voltages to the actuator were set to ± 3V. The drive frequency fd was set to 80 kHz corresponding to the case where n = 1 and m = 3 in Equation 1. Table 3 compares the inrush current, current consumption, and power consumption of the actuator according to the present invention with the inrush current, current consumption, and power consumption of the conventional method. As is apparent from Table 3, according to the method of the present invention, the inrush current is reduced by 19.0%, the current consumption is reduced by 22.4%, and the power consumption is reduced by 16.5%. Recognize.

  Thus, since the drive circuit unit 20 of the piezoelectric actuator according to the present invention drives the actuator by supplying a discontinuous voltage waveform that changes intermittently to the piezoelectric element 1, a voltage pulse that changes continuously is applied. Power consumption can be reduced as compared with the applied prior art.

  The present invention can be applied not only to a piezoelectric actuator that drives an optical system used in a mobile terminal such as a mobile phone, but also to a piezoelectric actuator that drives a precision stage, a piezoelectric actuator that drives a magnetic head, and the like.

It is a figure which shows the structure of the piezoelectric actuator which concerns on this invention. It is a figure for demonstrating the normal drive method of the piezoelectric actuator shown by FIG. It is a figure explaining the structure of the switch circuit used in this invention. It is a figure which shows the relationship between the output voltage waveform of the switch circuit in the drive system by this invention, and the consumption current of an actuator. It is a figure which shows the relationship between the output voltage waveform of the switch circuit in the drive system by this invention, and the displacement of a piezoelectric element. It is a figure which shows the relationship between the output voltage waveform of the switch circuit in the drive system by this invention, and the displacement of a piezoelectric element. It is a figure which shows the relationship between the drive frequency of a piezoelectric actuator and the moving body speed which concern on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Magnet 3 Moving ring 4 Moving body 5 Support member (housing)
6 Guide Pin 10 Actuator 20 Drive Circuit 21 Control Circuit 22 Switch Circuit

Claims (11)

  In a driving method in which a driven member is impact driven by applying a voltage to a piezoelectric element, the driven member is impact driven by supplying an intermittently changing discontinuous voltage waveform as the voltage. Driving method.   2. The discontinuous voltage waveform according to claim 1, wherein the discontinuous voltage waveform includes a predetermined first voltage level period and a second voltage level period different from the first level, and the first and second voltage level periods. There is a transition period in which no voltage is applied between the driving methods.   3. The driving method according to claim 1, wherein the first voltage level period and the second voltage level period are substantially the same.   A piezoelectric actuator comprising: a piezoelectric element; and a voltage generation circuit for applying a voltage to the piezoelectric element, wherein the voltage generation circuit generates a discontinuous voltage waveform that changes intermittently.   5. The voltage generation circuit according to claim 4, wherein the voltage generation circuit includes a predetermined first voltage level period, a second voltage level period different from the first level, and the first and second voltage level periods. A piezoelectric actuator that generates a voltage waveform having a transition period in which no voltage is applied.   A piezoelectric element, a driving member fixed to one end of the piezoelectric element, a support member fixed to the other end of the piezoelectric element, and a predetermined movable body relative to the driving member in the moving direction. And a driven member engaged by a frictional force of the piezoelectric element, wherein the driven member moves the driven member by reciprocating displacement at different speeds due to expansion and contraction of the piezoelectric element. The first charge / discharge time for discharging in the direction opposite to the polarization direction and the discharge in the polarization direction and applying the constant voltage in the direction opposite to the polarization direction are applied. And the second charge / discharge time for charging in the opposite direction of the polarization direction and the time during which no voltage is applied or discharged in both directions, and the first and second charge / discharge times are substantially the same. The piezoelectric actuator, characterized in that a voltage generating circuit for generating a voltage. The resonance frequency of the piezoelectric actuator is fr, the anti-resonance frequency is fa, the first charge / discharge time is T1, the second charge / discharge time is T2, and the time during which no voltage is applied and discharged in both directions is T3. When
T1 = T2 = (2n−1) / (2fr), (n = 1, 2, 3...)
T3 = (2m−1) / (2fa), (m = 1, 2, 3,...)
The piezoelectric actuator according to claim 6, further comprising a voltage generation circuit that generates a drive voltage such that   In a piezoelectric actuator driving method for moving a driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the piezoelectric element is expanded and contracted for a time determined by a resonance frequency and an antiresonance frequency of the piezoelectric actuator. A driving method characterized by moving the driving member. In the piezoelectric actuator that moves the driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the resonance frequency of the piezoelectric actuator is fr and the antiresonance frequency is fa. The time for applying the voltage level is T1, the time for applying a second voltage level different from the first voltage level to the piezoelectric element is T2, and the time for stopping the voltage application to the piezoelectric element is T3. When
T1 = T2 = (2n−1) / (2fr), (n = 1, 2, 3...)
T3 = (2m−1) / (2fa), (m = 1, 2, 3,...)
The drive method according to claim 8, wherein the drive member is moved by applying a voltage to the piezoelectric element so as to be expanded and contracting the piezoelectric element.   In a piezoelectric actuator that moves a driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, a voltage is applied to the piezoelectric element for a time determined by the resonance frequency of the piezoelectric actuator, and the anti-resonance frequency of the piezoelectric actuator is A piezoelectric actuator comprising a voltage generation circuit that stops application of a voltage to the piezoelectric element for a time determined by: In the piezoelectric actuator that moves the driving member fixed to the piezoelectric element by expanding and contracting the piezoelectric element, the resonance frequency of the piezoelectric actuator is fr and the antiresonance frequency is fa. The time for applying the voltage level is T1, the time for applying a second voltage level different from the first voltage level to the piezoelectric element is T2, and the time for stopping the voltage application to the piezoelectric element is T3. When
T1 = T2 = (2n−1) / (2fr), (n = 1, 2, 3...)
T3 = (2m−1) / (2fa), (m = 1, 2, 3,...)
The piezoelectric actuator according to claim 10, further comprising a voltage generation circuit that generates a voltage such that

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