JP2009106041A - Surface acoustic wave actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the forecast of the limit of abrasion by forecasting the amount of abrasion of a contact section with the stator surface of a mobile by simple constitution, in a surface acoustic wave actuator. <P>SOLUTION: The surface acoustic wave actuator 1 includes: a stator 2 consisting of a piezoelectric substrate having a cross finger electrode 4 for exciting surface acoustic waves W; a high frequency power supply 11, which supplies the cross finger electrode 4 with power for excitation of surface acoustic waves; a mobile 3, which is driven by the surface acoustic waves W excited on the surface of a piezoelectric substrate (stator 2) by the cross finger electrode 4 and the high frequency power supply 11; an abrasion amount computer 12, which computes the amount of abrasion of the contact section, with the surface of the stator 2, of the mobile 3 in a unit drive cycle including acceleration and deceleration; an abrasion amount integrator 13, which integrates the computed amount of abrasion; and an output section 14, which displays the integrated amount of abrasion. Since the abrasion of the contact face of the mobile 3 arises at acceleration and deceleration, the integrated amount of abrasion is computed, based on the number of times of occurrence of unit drive cycles, the limit of abrasion is forecasted, and it is displayed on the output section 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave actuator.

  Conventionally, a linear motor type surface acoustic wave actuator using a Rayleigh wave which is a surface acoustic wave propagating on the surface of an elastic body is known. For example, the surface acoustic wave actuator shown in FIG. 13 includes a stator 92 made of a piezoelectric material, four crossing finger electrodes 4 arranged on the surface of the stator 92 (referred to as an XY plane), and the crossing finger electrodes 4. A high-frequency power source 95 to be excited, a change-over switch 96 that switches supply of electric power to each crossing electrode 4, and a mover 93 having a plurality of point contact portions arranged on the stator 92 are provided ( For example, see Patent Document 1).

  When a high-frequency voltage is applied to the above-described crossed finger electrode 4 (Interdigital transducer, IDT), the surface of the stator 92 made of a piezoelectric material is deformed and a surface acoustic wave W is excited as shown in FIG. The surface acoustic wave W is formed by elliptically moving each point (which can be considered as particles) on the surface of the stator 92 with a certain time lag. The surface acoustic wave W travels in the direction a1 indicated by the arrow by the elliptical motion of each particle. The particles at the top of the wave appearing at each wavelength λ have a velocity U opposite to the wave traveling direction.

The moving element 93 receives a driving force from each particle that moves at the speed U as described above via a frictional force, and moves in the direction of the speed U, that is, in the direction opposite to the traveling direction a1 of the surface acoustic wave W. . In the case of the arrangement of the cross finger electrode 4 and the movable element 93 shown in FIG. 13, the movable element 93 moves toward a virtual surface acoustic wave excitation source formed by synthesizing surface acoustic waves W from four directions. The moving speed increases as the excitation intensity of the synthesized surface acoustic wave, and accordingly, the high-frequency voltage value (amplitude value) supplied from the high-frequency power source 95 increases. That is, the moving element 93 in this surface acoustic wave actuator performs two-dimensional movement with variable speed on the XY plane by adjusting the traveling direction of the surface acoustic wave and the excitation intensity.
Japanese Patent No. 3466690

  However, in the conventional surface acoustic wave actuator as shown in FIG. 13 and Patent Document 1 described above, wear resulting from slippage between the surface of the stator 92 and the point contact portion of the mover 93 disposed thereon. There is no disclosure about the prediction of the lifetime based on. Since it is not practically preferable that the actuator suddenly becomes unusable during use, it is desired to realize a surface acoustic wave actuator capable of predicting the lifetime.

  The present invention solves the above-described problems, and provides a surface acoustic wave actuator that can predict the wear limit by predicting the wear amount of the contact portion of the mover with the stator surface with a simple configuration. For the purpose.

  In order to achieve the above object, a first aspect of the present invention is a stator comprising a piezoelectric substrate having a cross finger electrode for exciting a surface acoustic wave on the surface, and a power for exciting the surface acoustic wave. A surface acoustic wave actuator comprising: a high-frequency power source for supplying to a surface of the piezoelectric substrate; and a movable body driven by a surface acoustic wave excited on the surface of the piezoelectric substrate by the interdigitated electrode and the high-frequency power source. A drive amount calculation unit that calculates the amount of wear of the contact portion of the mover with the stator surface in the unit drive cycle, with the drive of the mover from the start of surface wave excitation to the stop of excitation as a unit drive cycle. A wear amount integrating unit that integrates the wear amount calculated by the wear amount calculating unit, and an output unit that displays the integrated wear amount integrated by the wear amount integrating unit. .

  According to a second aspect of the present invention, in the surface acoustic wave actuator according to the first aspect, an input unit for inputting a limit wear amount, an integrated wear amount integrated by the wear amount integration unit, and the input unit A life calculation unit that predicts the life of the moving element by comparing the input limit wear amount, and the life calculation unit moves the movement when the accumulated wear amount exceeds the limit wear amount. It is determined that the life of the child is almost exhausted, and this is notified to the outside via the output unit before the movable element becomes unusable.

  According to a third aspect of the present invention, in the surface acoustic wave actuator according to the first or second aspect, the high-frequency power source is driven under the same conditions when driven to move the movable element by a desired distance. The unit driving cycle is intermittently repeated, and power is supplied to the interdigitated electrodes so as to adjust the moving speed of the moving element according to the repetition interval, and the wear amount calculation unit repeats the unit driving cycle. The wear amount is calculated based on the number of times.

  According to a fourth aspect of the present invention, in the surface acoustic wave actuator according to the first or second aspect of the present invention, the surface acoustic wave actuator includes a speed measuring unit that measures a moving speed of the moving element, and the wear amount calculating unit is controlled by the speed measuring unit. An acceleration is calculated from the measured moving speed of the moving element, and the wear amount is calculated based on the integrated amount of the acceleration.

  According to a fifth aspect of the present invention, in the surface acoustic wave actuator according to the first or second aspect of the present invention, the surface acoustic wave actuator includes a speed measuring unit that measures a moving speed of the moving element, and the wear amount calculating unit is supplied by the high-frequency power source. Of the surface acoustic wave excited and the moving speed of the surface of the piezoelectric substrate along the propagation direction of the surface wave that moves with the surface acoustic wave excited by the power (hereinafter referred to as substrate particle velocity) ) And the moving speed of the moving element measured by the speed measuring unit and the speed of the substrate particle speed obtained using the relation from the magnitude of the supplied power The difference is obtained and the speed difference is integrated, and the wear amount is calculated based on the integrated amount.

  According to the first aspect of the present invention, since the user can recognize the time of the life based on the display of the accumulated wear amount, that is, predict the wear limit and take some measures for the life, the actuator is in use. The problem of suddenly becoming unusable can be avoided. Wear is mainly caused by slippage, and the slip occurs during acceleration / deceleration. The unit drive cycle includes acceleration / deceleration states at the start and stop of the movement of the mover. Therefore, the wear amount and the integrated wear amount can be calculated based on the number of occurrences of the unit drive cycle and the maximum applied voltage in the cycle. Therefore, the surface acoustic wave actuator of the present invention can predict the wear limit (life) by predicting the amount of wear of the contact portion of the mover with the stator surface with a simple configuration.

  According to the second aspect of the present invention, it is possible to set the limit wear amount in advance and set the time for replacement or repair of the surface acoustic wave actuator.

  According to the invention of claim 3, the unit drive cycle can be normalized by intermittently repeating the unit drive cycle under the same conditions, and the lifetime is predicted by the number of repetitions of the standardized unit drive cycle. Therefore, the wear amount and life of the contact portion can be predicted more precisely than in the case where the unit drive cycle is not standardized.

  According to the fourth aspect of the present invention, attention is paid to the details in the unit drive cycle, and the state relating to wear, that is, the acceleration / deceleration state is extracted to calculate the wear amount of the contact portion. Compared with the case where the wear amount is calculated by, for example, it can be calculated with higher accuracy. When the wear amount is calculated based on the accumulated amount of acceleration, the life can be predicted with the same accuracy as intermittent driving, regardless of the driving method by intermittent repetition of the standardized unit driving cycle, and many Wear progress due to intermittent driving can be avoided.

  According to the fifth aspect of the present invention, the wear amount of the contact portion is calculated by the integrated amount of the speed difference that can estimate the slip amount of the moving element, so that the wear amount can be calculated with higher accuracy. The integrated amount of the speed difference is an index that can directly quantify the sliding amount of the moving element. The substrate particle velocity can be obtained in advance as an amount related to the voltage applied to the interdigitated electrode. For example, the substrate particle velocity can be measured with a laser Doppler velocimeter.

  Hereinafter, a surface acoustic wave actuator according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a block configuration of the surface acoustic wave actuator according to the first embodiment, and FIG. 2 shows a definition of a unit driving cycle in the surface acoustic wave actuator.

  As shown in FIG. 1, the surface acoustic wave actuator 1 includes a stator 2 made of a piezoelectric substrate having a cross finger electrode 4 for exciting a surface acoustic wave W on the surface, and power for exciting the surface acoustic wave. A high-frequency power source 11 for supplying the electrode 4, and a movable body 3 driven by a surface acoustic wave W excited on the surface of the piezoelectric substrate (stator 2) by the interdigitated electrode 4 and the high-frequency power source 11. ing.

  The surface acoustic wave actuator 1 includes a wear amount calculation unit 12 that calculates a wear amount of a contact portion between the moving element 3 and the surface of the stator 2 in a unit driving cycle T (described later, FIG. 2), and a wear amount calculation unit 12. The wear amount integrating unit 13 for integrating the wear amount calculated by the above, an output unit 14 for displaying the integrated wear amount integrated by the wear amount integrating unit 13, the high frequency power source 11, the wear amount calculating unit 12, and the wear amount. The control part 10 which controls the integrating | accumulating part 13 and the output part 14 is provided.

The stator 2 may be a piezoelectric body itself such as lithium niobate (LiNbO ₃ ) or a thin film of PZT (lead zirconate titanate) that is a piezoelectric material on a silicon substrate or the like. Moreover, piezoelectric materials other than these can also be used. The surface shape of the stator 2 is not limited to a flat surface, and may be a cylindrical surface or other curved surface. The surface acoustic wave W is excited on such a plane or curved surface of the piezoelectric body or the surface of the film of the piezoelectric body formed on such a surface.

  The cross finger electrode 4 is formed on the surface of the stator 2 such that a pair of comb-like electrodes 41 are opposed to each other so that the comb teeth alternately enter. Twice the electrode pitch of the interdigitated electrode 4 (λ in the figure) matches the wavelength of the surface acoustic wave W to be excited.

  The mover 3 is provided in a surface wave generation region of the stator 2 in contact with the stator 2. The mover 3 moves relative to the stator 2. Usually, the stator 2 is fixed and the mover 3 moves. In the surface acoustic wave actuator 1, which is moved is relative, and the mover 3 is fixed and the stator 2 may move.

  The mover 3 is formed of a hard material such as silicon, for example. A plurality of protrusions for efficiently transmitting the kinetic energy of the surface acoustic wave W to the moving element 3 are provided on the contact surface of the moving element 3 with the stator 2. Such protrusions are manufactured by a silicon etching method when the movable element 3 is formed of silicon. Note that the material of the mover 3 may be a hard material as long as it is not silicon. Further, if the kinetic energy of the surface acoustic wave W can be efficiently transmitted to the moving element 3, the protrusion on the contact surface 32 is not necessary.

  The mover 3 is pressed against the stator 2 with a preload applied by a preload means (not shown). The mover 3 is driven by the frictional force based on this preload and moves on the stator 2. The surface acoustic wave W on the surface of the stator 2 needs to be excited against the preload, that is, with an energy capable of vibrating the lifter 3 by lifting it.

  In the surface acoustic wave actuator 1, the surface acoustic wave W is excited and a preload is applied to the movable body 3, so that the movable body 3 moves in the direction a 2, which is opposite to the traveling direction a 1 of the surface acoustic wave W. Move toward (V is the speed). Such a directional relationship is based on the fact that the surface acoustic wave W performs backward elliptical motion (see FIG. 11 and its description below).

As shown in FIG. 2, the unit drive cycle T is defined as a drive unit of the moving element 3 from the excitation start time t1 of the surface acoustic wave W to the excitation stop time t2. The waveform of the voltage E applied from the high-frequency power supply 11 to the cross finger electrode 4 is E = E ₀ · sin (ωt + α). Here, the waveform of the applied voltage E with respect to time t is represented by an amplitude E ₀ , an angular frequency ω that gives a wavelength λ, and an initial phase α that represents a phase change from a predetermined time.

In this figure, the applied voltage E is controlled by on / off switching, and the amplitude E ₀ is assumed to be constant from time t1 to time t2. This assumption is for illustrative purpose only, it is also possible to apply a voltage smoothly changes the amplitude E _0. In general, the voltage changes smoothly due to the presence of a time constant in the high-frequency power source 11.

The amplitude of the surface acoustic wave W excited by the stator 2 depends on the magnitude of the voltage applied from the high-frequency power source 1 to the cross finger electrode 4 (applied voltage amplitude E ₀ ). Determine the speed V. The length of the wave packet of the surface acoustic wave W corresponds to the voltage application time (also expressed as T, T = t2−t1). The moving distance (position) of the moving element 3 is determined by the amplitude E _{0 of the} applied voltage and the length of the applying time T.

  In the unit driving cycle T, as shown in FIG. 2, the speed of the moving element 3 is accelerated after the excitation start time t1, and the speed V increases (area a), and then becomes a constant speed (area b), and the excitation stops. After time t2, the vehicle is decelerated to zero (region c).

In such a surface acoustic wave actuator 1, wear of the contact surface of the moving element 3 with the stator 2 is mainly caused by slippage. The slip usually occurs during acceleration / deceleration. The unit drive cycle T shown in FIG. 2 includes acceleration / deceleration states (regions a and b) after the movement start time t1 of the moving element 3 and after the stop time t2. Considering this in reverse, it can be seen that the wear amount and the integrated wear amount can be calculated based on the number of occurrences of the unit drive cycle T and the maximum applied voltage (amplitude E ₀ ) in that cycle.

Therefore, the wear amount calculation unit 12 uses, for example, the number of movement starts as a relatively simple method of calculating the wear amount of the contact portion of the mover 3 with the surface of the stator 2 in the unit drive cycle T. The wear amount calculation based on the number of times is a sufficiently practical calculation method particularly when the applied voltage E is controlled by on / off switching and the amplitude E ₀ is assumed to be constant.

  In order to realize the above-described calculation method, for example, the relationship between the number of repetitions of the unit driving cycle T in the surface acoustic wave actuator 1 and the lifetime of the contact portion of the moving element 3 is determined in advance by measurement. Then, the wear amount calculation unit 12 detects the start of movement, the wear amount integration unit 13 integrates the number of times, and the number of times the output unit 14 is integrated, that is, the corresponding wear amount is displayed by some index. The wear limit (life) can be predicted by grasping the amount of wear of the contact portion between the moving element 3 and the surface of the stator 2 in the surface wave actuator 1. As an index for displaying the amount of wear, the number of times itself or a percentage display for the maximum possible number of times can be used.

  According to such a surface acoustic wave actuator 1, with a simple configuration, the user recognizes the time of the life based on the display of the accumulated wear amount, that is, predicts the wear limit, and takes some measures for the life. Therefore, the problem that the actuator suddenly becomes unusable during use can be avoided.

  The surface acoustic wave actuator 1 having the configuration shown in FIG. 1 can move the moving element 3 in the direction a2, but can move the moving element 3 only in one direction. Therefore, a return mechanism may be provided for bidirectional movement for moving the movable element 3 in the direction opposite to the direction a2. For example, it can be returned in the direction a1 by a return mechanism using an urging force such as a spring. Further, as a return mechanism, a return cross finger electrode may be provided on the direction a2 side. Such a surface acoustic wave actuator 1 capable of reciprocating will be described below.

(Modification of arrangement and structure of crossed finger electrodes)
3A to 3D show modifications of the arrangement and structure of the interdigital electrodes of the surface acoustic wave actuator. These surface acoustic wave actuators 1 are provided with crossed finger electrodes 4 as return mechanisms at both ends of a moving region of the moving element 3 so that the moving element 3 can move in both forward and reverse directions. Furthermore, these surface acoustic wave actuators 1 reflect a surface acoustic wave directed to the side opposite to the moving element 3 side of the interdigital finger electrode 4 to effectively use the energy (interdigital finger electrode 5, additional electrode). 43, the reflection part 40, etc.). The structure and arrangement of the crossed finger electrodes 4 and 5 are examples, and are not limited to those shown in these drawings.

  The cross finger electrode 5 in the surface acoustic wave actuator 1 shown in FIGS. 3A and 3B is a reflective electrode in which the adjacent cross finger electrode 4 for driving is a unidirectional cross finger electrode. These electrodes return the surface acoustic wave to the moving element 3 side by multiple reflection. Note that a ladder-type electrode may be used instead of such a comb-shaped electrode.

  Further, the driving cross finger electrodes 4 in the surface acoustic wave actuator 1 shown in FIGS. 3C and 3D each have a structure for forming a unidirectional cross finger electrode. In FIG.3 (c), the additional electrode 43 is arrange | positioned between a pair of individual electrodes which are mutually different polarities, and becomes a float potential and reflects a surface acoustic wave.

Further, in FIG. 3D, the reflection unit 40 arranges the electrodes of the crossed finger electrodes 4 having different polarities from each other at a predetermined interval. For example, a silicon oxide SiO ₂ film is formed on a surface region extending over a part of the surface of 2). The reflector 40 functions as a reflector by affecting the propagation of surface acoustic waves on the surface of the piezoelectric substrate. The cross finger electrode 4 combined with the reflection cross finger electrode 5, the additional electrode 43, the reflection portion 40, and the like described above can be regarded as a unidirectional cross finger electrode.

(Second Embodiment)
FIG. 4 shows a block configuration of a surface acoustic wave actuator according to the second embodiment. The surface acoustic wave actuator 1 of this embodiment is further provided with an input unit 15 and a life calculation unit 16 in the surface acoustic wave actuator 1 (FIG. 1) of the first embodiment described above. Is the same. A limit wear amount can be input from the input unit 15.

  The life calculation unit 16 compares the accumulated wear amount accumulated by the wear amount accumulation unit 13 with the limit wear amount input via the input unit 15 and predicts the life of the moving element 3. When the cumulative wear amount exceeds the limit wear amount, the life calculation unit 16 determines that the life of the mover 3 is about to expire and before the mover 3 becomes unusable, the output unit 14 To inform the outside through.

  According to the surface acoustic wave actuator 1 having such a configuration, the user can set the limit wear amount in advance and set the replacement or repair timing of the surface acoustic wave actuator 1.

(Third embodiment)
FIG. 5 shows the amplitude waveform of the applied voltage when the slider is intermittently driven in the surface acoustic wave actuator according to the third embodiment, and FIGS. 6A to 6F show examples of the intermittent drive. This is indicated by the change in the waveform and the speed of the slider. The surface acoustic wave actuator 1 of the present embodiment is different from the surface acoustic wave actuators 1 of the first and second embodiments in the amount of wear by the driving method of the moving element 3 (operation of the high frequency power supply 11) and the wear amount calculation unit 12. The calculation method is different, and the other points are the same.

  That is, the high frequency power source 11 intermittently repeats the above unit drive cycle T under the same conditions when driving to move the mover 3 by a desired distance, and the mover 3 according to the repetition interval. The cross finger electrode 4 is supplied with electric power so as to adjust the moving speed V of. Further, the wear amount calculation unit 12 calculates the wear amount based on the number of repetitions of the unit drive cycle T.

  In the movement of the moving element 3 by such intermittent driving, control is performed to repeat each unit driving cycle T under an applied voltage controlled so that the velocity waveforms in each unit driving cycle T are the same. Thereby, each unit drive cycle can be standardized and it can be set as the movement which controlled the movement distance (position) and movement speed with sufficient precision.

  FIG. 5 shows an example in which the moving element 3 moves by intermittent driving that is repeated four times from the time t3 to the time t4 with the unit driving cycle T sandwiched by the pause time Δt. If the speed change of each unit driving cycle T is made the same, the wear amount in each cycle can be made the same. Therefore, the wear amount of the contact portion of the moving element 3 can be calculated by counting the number of times of intermittent driving. Therefore, the wear limit at the life limit is set as a threshold value, and when the integrated wear amount exceeds the threshold value, it can be predicted that the life is reached. The amount of wear in each cycle is very small and difficult to measure. Therefore, the wear amount when the same operation is performed a plurality of times, for example, 1000 times, is measured, and a value obtained by dividing the wear amount by 1000 may be set as the wear amount per driving.

  Further, the moving amount of the moving element 3 in a certain time depends on the average speed in the entire moving time. As shown in FIGS. 6A to 6F, the average speed Vm can be adjusted by the interval of intermittent driving in intermittent driving. That is, if the time length and amplitude of the unit drive cycle T are made constant and the pause time Δt is lengthened, the average speed Vm can be slowed down, and if the pause time Δt is shortened, the average speed Vm can be quickened.

  According to such a surface acoustic wave actuator 1, the unit driving cycle T can be normalized by intermittently repeating the unit driving cycle T under the same conditions, and the lifetime can be predicted by the number of repetitions. The amount of wear and the life of the contact portion can be predicted more precisely than when based on a unit drive cycle without standardization.

(Fourth embodiment)
FIG. 7 shows a block configuration of the surface acoustic wave actuator according to the fourth embodiment, FIG. 8 shows a time change of acceleration of the moving element 3 in a unit driving cycle T, and FIG. 9 shows wear amount and acceleration used for life prediction. The relationship with the integrated amount is shown.

  The surface acoustic wave actuator 1 according to this embodiment is the same as the surface acoustic wave actuator 1 according to the second embodiment described above, but further includes a speed measuring unit 17 that measures the moving speed of the moving element 3. The life calculator 16 calculates the acceleration A from the moving speed V of the moving element 3 measured by the speed measuring unit 17 and predicts the life of the moving element 3 based on the integrated amount of the acceleration A. The other points are the same as those of the surface acoustic wave actuator 1 of the second embodiment.

  As described above, the life of the contact portion of the mover 3 is shortened when acceleration / deceleration is large. Therefore, the velocity of the moving element 3 is measured, the acceleration is obtained by differentiating the measurement result with respect to time, and the amount of wear is predicted. In FIG. 8, the wear amount calculation unit 12 obtains an area S1 surrounded by the acceleration curve and the time axis in the acceleration state a and an area S2 surrounded by the acceleration curve and the time axis in the deceleration state c, and sums them, S1 + S2, Is calculated as the amount of wear in the unit drive cycle T. The wear amount integrating unit 13 integrates each area Si to obtain an integrated amount S, S = ΣSi.

  As shown in FIG. 9, the life calculation unit 16 calculates the amount of wear at that time based on the relational expression S R and f of the amount of area S and the amount of wear R relating to acceleration / deceleration determined in advance, R = f (S). Therefore, the lifetime is calculated. Further, the life calculation unit 16 uses the wear amount of the life limit input separately through the input unit 15 as a threshold value, compares the accumulated wear amount R that can be predicted from the accumulated amount S of acceleration with the threshold value, and wear amount R If the value exceeds the threshold, it is predicted that the lifetime has come. It should be noted that the relational expression of R = f (S) is determined by measuring a plurality of integrated acceleration amounts and wear amounts and obtaining correlations.

  According to such a surface acoustic wave actuator 1, the state of acceleration / deceleration related to wear is extracted by paying attention to details in the unit drive cycle, and the wear amount and life of the contact portion are predicted. The amount of wear and life can be predicted more precisely than when the amount of wear and life are predicted from the whole, such as the number of driving cycles T. In addition, when the prediction is made based on the integrated amount of acceleration, the life prediction with high accuracy similar to the intermittent drive is possible without using the intermittent drive by intermittent repetition of the standardized unit drive cycle T as in the third embodiment. In addition, it is possible to prevent the progress of wear due to the multiple intermittent driving.

(Fifth embodiment)
FIG. 10 shows the time variation of the moving speed and the moving speed of the stator surface in the unit driving cycle of the surface acoustic wave actuator according to the fifth embodiment, and FIG. 11 is an enlarged view of the contact portion between the moving element and the stator. FIG. 12 shows the relationship between the wear amount used for life prediction and the integrated amount of speed difference.

  The surface acoustic wave actuator 1 of this embodiment includes a speed measuring unit 17 that measures the moving speed V of the moving element 3 as in the fourth embodiment described above, and the method of calculating the wear amount R depends on the acceleration. The point by speed is different from the fourth embodiment, and the other points are the same.

  In other words, the life calculation unit 16 is configured to measure the surface acoustic wave excitation power supplied from the high frequency power supply 11 and the piezoelectric substrate along the propagation direction of the surface wave moving with the surface acoustic wave excited by the power. The relationship between the moving speed U of the surface (hereinafter referred to as substrate particle speed U) is stored, and the moving speed V of the moving element 3 measured by the speed measuring unit 17 and the magnitude of the supplied electric power are used. The velocity difference between the substrate particle velocity U obtained by the relationship is obtained and the velocity difference is integrated, and the life of the movable element 3 is predicted based on the accumulated amount.

  The wear of the contact portion of the mover 3 is caused by the occurrence of slippage between the stator 2 and the mover 3, and the life is shortened if there is a lot of slip and wear. The sliding of the moving element 3 increases as the relative speed between the stator 2 and the moving element 3 increases. Therefore, by calculating the difference between the two (velocity V, substrate particle velocity U) and estimating the difference between them, slipping and wear The amount can be estimated.

  As shown in FIG. 3, the temporal changes in the speeds V and U correspond to changes in the magnitude of each other substantially corresponding to the acceleration state, the constant velocity motion state, and the deceleration state of the moving element 3 in the unit drive cycle T. Show. Therefore, the areas B1, B2, and B3 surrounded by the respective speed change curves and the time axis are obtained, and the total amount B obtained by integrating these B, B = B1 + B2 + B3 can be used as the slip amount, and hence the wear amount.

  The wear amount calculation unit 12 obtains the areas B1, B2, and B3 in FIG. 10 and calculates the wear amounts in the unit drive cycle T. The wear amount integration unit 13 integrates each area Bi to obtain an integration amount B, B = ΣBi.

  Here, the speeds V and U will be described with reference to FIG. On the surface of the stator 2 on which the surface acoustic wave W is excited, the particles at each point on the surface perform elliptical motions whose phases are adjacent to each other, thereby generating irregularities. The convex portion moves with a substrate particle velocity U opposite to the traveling direction a1 of the surface acoustic wave W. Further, the moving element 3 generates a velocity V due to the particle motion of the vibrator 3 and moves in the direction opposite to the traveling direction a1 of the surface acoustic wave W.

  The speed V of the moving element 3 is measured by the speed measuring unit 17. Further, the substrate particle velocity U is determined, for example, by the magnitude of the high-frequency voltage applied to the cross finger electrode 4 disposed on the vibrator 3. Therefore, the substrate particle velocity U can be estimated based on the value of the current flowing through the interdigitated electrode 4. The substrate particle velocity U can be directly measured by, for example, a laser Doppler velocimeter. Therefore, for example, by obtaining the relationship between the applied voltage or current value and the substrate particle velocity U in advance, the substrate particle velocity U is obtained based on the value of the current flowing through the interdigitated electrode 4.

  As shown in FIG. 12, the life calculation unit 16 calculates the amount of wear at that time based on a relational expression between the integrated amount B of the area related to the speed difference obtained in advance and the wear amount R, R = g (B). Therefore, the lifetime is calculated. Further, the life calculation unit 16 uses the wear amount of the life limit input separately through the input unit 15 as a threshold value, compares the accumulated wear amount R that can be predicted from the accumulated amount B of the speed difference with the threshold value, and wear amount If R exceeds the threshold, it is predicted that the lifetime has come. The relational expression of R = g (B) is determined by measuring a plurality of integrated amounts of the speed difference area and the wear amount to obtain a correlation.

  According to such a surface acoustic wave actuator 1, the wear amount R and the life of the contact portion are predicted by the integrated amount B of the speed difference that can estimate the slip amount of the moving element 3. Lifetime can be predicted more precisely. The accumulated amount B of the speed difference is an index that can directly quantify the slip amount of the moving element 3. The substrate particle velocity U can be obtained in advance as a relational quantity with respect to the voltage applied to the cross finger electrode 4 and the current value. Note that the integrated amount B takes into account not only the acceleration / deceleration state but also the slip (area B2) in the constant velocity moving body. In this respect, improvement of the life prediction accuracy is expected.

The present invention is not limited to the above-described configuration, and various modifications can be made. For example, although the first embodiment has been described on the assumption that the moving speed V of the moving element 3 is constant, the moving speed V of the moving element 3 may be variable. In order to make the speed V variable, the amplitude E ₀ may be changed. For example, a plurality of unit driving cycles T having different amplitudes E ₀ may be defined and distinguished, and the entire life prediction may be performed based on the life prediction for each unit driving cycle T. Further, the speed may be variable in one unit driving cycle T. In this case, the typical speed change pattern which varies according to the value of the amplitude E ₀ and the moving speed V, and the number of acceleration and deceleration, by previously measuring a relationship between the amount of wear, above It is possible to predict the lifespan.

The block block diagram about the surface acoustic wave actuator which concerns on the 1st Embodiment of this invention. The graph of the time change of the applied voltage waveform and moving element speed for demonstrating the unit drive cycle in a surface acoustic wave actuator same as the above. (A)-(d) is a top view which shows the modification of arrangement | positioning and structure of a cross finger electrode of a surface acoustic wave actuator same as the above. The block block diagram of the surface acoustic wave actuator which concerns on 2nd Embodiment. The graph of the time change of the amplitude waveform of the applied voltage for demonstrating the intermittent drive of the slider in the surface acoustic wave actuator which concerns on 3rd Embodiment. (A), (b), and (c) are graphs of changes over time in the amplitude waveform of the applied voltage for explaining an example of intermittent driving in the surface acoustic wave actuator, and (d), (e), and (f) are respectively (a) and (a). (B) The graph of the time change of the speed | velocity | rate of the slider corresponding to the intermittent drive of (c). The block block diagram of the surface acoustic wave actuator which concerns on 4th Embodiment. The graph of the time change of the acceleration of a slider in a unit drive cycle of a surface acoustic wave actuator same as the above. The graph which shows the relationship between the wear amount used for the lifetime prediction of a surface acoustic wave actuator same as the above, and the integrated amount of acceleration. The graph of the time change of the moving speed and the moving speed of the surface of a stator in the unit drive cycle of the surface acoustic wave actuator which concerns on 5th Embodiment. The expanded sectional view of the contact part of the slider and stator explaining the moving speed of the surface of the stator in the surface acoustic wave actuator same as the above. The graph which shows the relationship between the wear amount used for the lifetime prediction of a surface acoustic wave actuator same as the above, and the integrated amount of a speed difference. The top view which shows the example of the conventional surface acoustic wave actuator. The expanded sectional view of the piezoelectric substrate surface part explaining the excitation and propagation of a general surface acoustic wave.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface acoustic wave actuator 2 Stator 3 Mover 4 Cross finger electrode 11 High frequency power supply 12 Wear amount calculation part 13 Wear amount integration part 14 Output part 15 Input part 16 Life calculation part 17 Speed measurement part A Acceleration B Integration quantity (speed difference) of)
R Wear amount S Accumulated amount (acceleration)
T unit drive cycle U speed (of substrate particles)
V speed (of the mover)
W surface acoustic wave

Claims (5)

A stator composed of a piezoelectric substrate having a cross finger electrode on its surface for exciting a surface acoustic wave;
A high frequency power source for supplying surface acoustic wave excitation power to the interdigitated electrodes;
In a surface acoustic wave actuator comprising: a movable element driven by a surface acoustic wave excited on the surface of the piezoelectric substrate by the interdigitated electrode and the high frequency power source;
The amount of wear for calculating the amount of wear of the contact portion of the moving element with the stator surface in the unit driving cycle, wherein the driving of the moving element from the start of excitation of the surface acoustic wave to the stop of excitation is defined as a unit driving cycle. A calculation unit;
A wear amount integrating unit for integrating the wear amount calculated by the wear amount calculating unit;
The surface acoustic wave actuator comprising: an output unit that displays an accumulated wear amount accumulated by the wear amount accumulation unit. An input section for inputting the limit wear amount;
A life calculation unit that predicts the life of the moving element by comparing the accumulated wear amount accumulated by the wear amount accumulation unit and the limit wear amount input through the input unit;
The life calculating unit determines that the life of the moving element is about to expire when the accumulated wear amount exceeds the limit wear amount, and determines that the output unit before the moving element becomes unusable. The surface acoustic wave actuator according to claim 1, wherein the surface acoustic wave actuator is notified to the outside. The high-frequency power supply intermittently repeats the unit driving cycle under the same conditions when driving the movable element to move a desired distance, and adjusts the moving speed of the movable element according to the repetition interval. To supply power to the interdigitated electrodes,
The surface acoustic wave actuator according to claim 1, wherein the wear amount calculation unit calculates the wear amount based on the number of repetitions of the unit driving cycle. A speed measuring unit for measuring the moving speed of the moving element;
The wear amount calculation unit calculates an acceleration from a moving speed of the movable element measured by the speed measurement unit, and calculates the wear amount based on an integrated amount of the acceleration. The surface acoustic wave actuator according to claim 2. A speed measuring unit for measuring the moving speed of the moving element;
The wear amount calculation unit includes the piezoelectric substrate along the propagation direction of the surface wave that moves with the surface acoustic wave excited by the power and the surface acoustic wave excitation power supplied by the high-frequency power source. The relationship between the moving speed of the surface of the substrate (hereinafter referred to as substrate particle speed) and the moving speed of the moving element measured by the speed measuring unit and the magnitude of the supplied electric power is stored. The speed difference between the substrate particle speed obtained by use and the speed difference are calculated and the speed difference is integrated, and the wear amount is calculated based on the integrated amount. Surface acoustic wave actuator.

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