JP5491718B2 - Ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor, and more particularly, to an ultrasonic motor that generates a driving force when a laminated rectangular piezoelectric vibrator vibrates in a multiple vibration mode that combines a spread vibration mode and a bending vibration mode. .

  Conventionally, an ultrasonic motor that generates a driving force by forming a piezoelectric element in a rectangular shape and oscillating in a multiple vibration mode in which a primary longitudinal vibration mode (L1) and a secondary bending vibration mode (F2) are combined. It has been known. For example, Japanese Unexamined Patent Application Publication No. 2006-094597 discloses an ultrasonic transducer in which a plurality of piezoelectric bodies are stacked and driven in the L1F2 resonance mode. The ultrasonic transducer includes piezoelectric elements and internal electrodes that are alternately stacked, and includes an internal electrode group that is substantially divided into four along a second direction and a third direction orthogonal to the stacking direction. ing. In addition, the first external electrode group and the second external electrode group that are electrically connected to the internal electrode group, respectively. Then, by applying a voltage to the first and second external electrode groups, the longitudinal vibration mode generated in the second direction and the bending vibration mode generated in the third direction are excited simultaneously, thereby causing an elliptical Generate vibration.

JP-T-2007-538484 discloses a piezoelectric ultrasonic motor in which a vibrator is formed of a piezoelectric plate having a length L and a height H and is driven in a lame mode. In this piezoelectric ultrasonic motor, a primary asymmetric standing wave is excited by the piezoelectric plate, and the sliding tip makes an elliptical motion to generate a driving force.
JP 2006-094597 A Special table 2007-538484 gazette

  Conventionally, ultrasonic motors have been used for various purposes, but the main characteristics required for ultrasonic motors industrially are small size, high efficiency, and simple structure. Here, the fact that the ultrasonic motor is small means that the resonance frequency of the piezoelectric vibrator is as low as possible. Moreover, high efficiency means that the mechanical-electrical coupling coefficient of the piezoelectric vibrator is large.

  However, when the ultrasonic motor is driven in a multiple vibration mode that combines the primary longitudinal vibration mode (L1) and the secondary bending vibration mode (F2), the main surface is divided into four regions, Electric power must be arranged for each of the electrodes, and the electrodes positioned diagonally must be connected to each other, and the electrode structure must be complicated. Also, when trying to drive the ultrasonic motor in the lame mode, the resonance frequency is higher than in other modes, so when trying to drive at the same resonance frequency as other modes, use other modes. The ultrasonic motor becomes larger than the case, making it difficult to reduce the size. Furthermore, a rectangular and single-plate piezoelectric vibrator is configured with the above-described side ratio, and an ultrasonic motor in which this is laminated has not been performed.

  The present invention has been made in view of such circumstances, and a single-plate piezoelectric vibrator is configured with a side ratio different from the conventional one, and by laminating this, it is possible to reduce the size and improve the efficiency. An object of the present invention is to provide an ultrasonic motor that is high and has a simple structure.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the ultrasonic motor of the present invention is configured by stacking rectangular and single-plate piezoelectric vibrators to form a laminated piezoelectric vibrator, and the laminated piezoelectric vibrator combines a spreading vibration mode and a bending vibration mode. An ultrasonic motor that generates a driving force by oscillating in a multi-vibration mode, wherein one of the two sides of the single-plate piezoelectric vibrator has a side length L, and the other set Where w / L is a variable, w / L is a variable, and w / L is associated with the resonance frequency of the spreading vibration mode, and w / L is associated with the resonance frequency of the bending vibration mode. The single-plate piezoelectric vibrator is formed based on the value of w / L where the resonance frequency of the spreading vibration and the resonance frequency of the bending vibration are substantially the same. It is characterized by being laminated in the thickness direction.

  Thus, since the single-plate piezoelectric vibrator is formed based on the value of w / L in which the resonance frequency of the spreading vibration and the resonance frequency of the bending vibration are substantially the same, other modes, for example, The shape of the main surface of the single-plate piezoelectric vibrator can be made closer to a square than when driven in the L1F2 mode. As a result, the overall dimension does not become flat, and the depth dimension can be reduced. Thereby, it becomes possible to take a power input larger than the conventional one. In addition, by laminating a plurality of single-plate piezoelectric vibrators formed in this way in the thickness direction, a large electric field strength can be applied to the multilayer piezoelectric vibrator with the same input voltage as the single plate. The necessary power supply voltage can be reduced. As a result, it is possible to eliminate the step-up component required in the conventional ultrasonic motor, and to reduce the size of the driver board. As a result, a small driver system capable of multi-channel operation can be realized. The w / L value at which the resonance frequency of the spread vibration and the resonance frequency of the bending vibration are substantially the same means a range in which the single-plate piezoelectric vibrator functions practically as an ultrasonic motor. . Even if the resonance frequency of the spread vibration and the resonance frequency of the bending vibration are somewhat different, the value of w / L is substantially the same as long as the single-plate piezoelectric vibrator functions practically as an ultrasonic motor. It can be said that there is. Conversely, if the single-plate piezoelectric vibrator functions practically as an ultrasonic motor, the w / L value must be exactly the same as the resonance frequency of the spread vibration and the resonance frequency of the bending vibration. It doesn't have to be.

  (2) Further, the ultrasonic motor of the present invention is configured by stacking rectangular and single-plate piezoelectric vibrators to form a laminated piezoelectric vibrator, and the laminated piezoelectric vibrator has a spreading vibration mode and a bending vibration mode. Is an ultrasonic motor that generates a driving force by oscillating in a multi-vibration mode in which the length of one of the two sides of the single-plate piezoelectric vibrator is L, The length of the other side of the pair is w, w / L is a variable, w / L is associated with the resonance frequency of the spread vibration mode, and w / L is associated with the resonance frequency of the bending vibration mode. In this case, the single-plate piezoelectric vibrator is formed so that the value of w / L falls within the range of 0.75 to 0.90, and the single-plate piezoelectric vibrator is arranged in the thickness direction. It is characterized by being stacked in plural.

  Thus, the single-plate piezoelectric vibrator is formed so that the value of w / L falls within the range of 0.75 to 0.90. Therefore, when driven in another mode, for example, the L1F2 mode. In addition, the shape of the main surface of the single-plate piezoelectric vibrator can be made closer to a square. As a result, the overall dimension does not become flat, and the depth dimension can be reduced. As a result, the power input can be made larger than the conventional one. In addition, by laminating a plurality of single-plate piezoelectric vibrators formed in this way in the thickness direction, a large electric field strength can be applied to the multilayer piezoelectric vibrator with the same input voltage as the single plate. The necessary power supply voltage can be reduced. As a result, it is possible to eliminate the step-up component required in the conventional ultrasonic motor, and to reduce the size of the driver board. As a result, a small driver system capable of multi-channel operation can be realized.

  (3) Further, the ultrasonic motor of the present invention is configured by stacking rectangular and single-plate piezoelectric vibrators to form a laminated piezoelectric vibrator, and the laminated piezoelectric vibrator has a spreading vibration mode and a bending vibration mode. Is an ultrasonic motor that generates a driving force by oscillating in a multi-vibration mode in which the length of one of the two sides of the single-plate piezoelectric vibrator is L, The length of the other side of the pair is w, w / L is a variable, w / L is associated with the resonance frequency of the spread vibration mode, and w / L is associated with the resonance frequency of the bending vibration mode. In this case, the single-plate piezoelectric vibrator is formed so that the value of w / L is substantially 0.85, and a plurality of the single-plate piezoelectric vibrators are stacked in the thickness direction. It is characterized by having.

  As described above, the single-plate piezoelectric vibrator is formed so that the value of w / L is substantially 0.85. Therefore, the single-plate piezoelectric vibrator is more single-plate than when driven in other modes, for example, the L1F2 mode. The shape of the main surface of the piezoelectric vibrator can be made close to a square. As a result, the overall dimension does not become flat, and the depth dimension can be reduced. As a result, the power input can be made larger than the conventional one. In addition, by laminating a plurality of single-plate piezoelectric vibrators formed in this way in the thickness direction, a large electric field strength can be applied to the multilayer piezoelectric vibrator with the same input voltage as the single plate. The necessary power supply voltage can be reduced. As a result, it is possible to eliminate the step-up component required in the conventional ultrasonic motor, and to reduce the size of the driver board. As a result, a small driver system capable of multi-channel operation can be realized. Note that the value of w / L is substantially 0.85 means a range in which a single-plate piezoelectric vibrator practically functions as an ultrasonic motor. Even if the value of w / L is deviated around 0.85, if the single-plate piezoelectric vibrator functions practically as an ultrasonic motor, the value of w / L is substantially 0.85. It can be said that there is. Conversely, the value of w / L does not have to be exactly 0.85 if a single-plate piezoelectric vibrator functions practically as an ultrasonic motor.

  According to the present invention, the single-plate piezoelectric vibrator is formed based on the value of w / L at which the resonance frequency of the spreading vibration and the resonance frequency of the bending vibration are substantially the same. For example, the shape of the main surface of the single-plate piezoelectric vibrator can be made closer to a square than when driven in the L1F2 mode. As a result, the overall dimension does not become flat, and the depth dimension can be reduced. Thereby, it becomes possible to take a power input larger than the conventional one. In addition, by laminating a plurality of single-plate piezoelectric vibrators formed in this way in the thickness direction, a large electric field strength can be applied to the multilayer piezoelectric vibrator with the same input voltage as the single plate. The necessary power supply voltage can be reduced. As a result, it is possible to eliminate the step-up component required in the conventional ultrasonic motor, and to reduce the size of the driver board. As a result, a small driver system capable of multi-channel operation can be realized.

  Conventionally, piezoelectric transformers have realized high-operability piezoelectric transformers by using spreading vibration (contour vibration) and avoiding bending vibration (spurious vibration). That is, the piezoelectric transformer has taken measures to avoid bending vibration. The inventor paid attention to this point and found that a driving force is generated by vibrating a rectangular piezoelectric vibrator in a multiple vibration mode in which a spread vibration mode and a bending vibration mode are combined. In addition, the present inventor has known an ultrasonic motor in which two electrodes are arranged in parallel on one main surface of a piezoelectric vibrator. However, in a rectangular piezoelectric vibrator, a resonance frequency of spreading vibration is known. Focusing on the fact that an ultrasonic motor using the case where the resonance frequency of the bending vibration and the resonance frequency of the bending vibration are substantially the same has not been realized, the ultrasonic vibrator is formed by forming the piezoelectric vibrator based on the dimensions at that time. It has been found that miniaturization, high efficiency and simplification of the configuration of the motor can be realized, and further, a plurality of single-plate piezoelectric vibrators formed in this way are laminated in the thickness direction, so that the laminated type It has been found that a large electric field strength can be applied to a piezoelectric vibrator with the same input voltage as that of a single plate, and the present invention has been achieved.

  That is, the present invention forms a laminated piezoelectric vibrator by laminating rectangular and single-plate piezoelectric vibrators, and the laminated piezoelectric vibrator is in a multiple vibration mode combining a spreading vibration mode and a bending vibration mode. An ultrasonic motor that generates a driving force by vibration, wherein one of the two sides of the single-plate piezoelectric vibrator has a side length L, and the other side has a side length. When w / L is a variable and w / L is made to correspond to the resonance frequency of the spreading vibration mode, and w / L is made to correspond to the resonance frequency of the bending vibration mode, w / L is a variable. The vibrator is formed based on a value of w / L in which the resonance frequency of the spreading vibration and the resonance frequency of the bending vibration are substantially the same, and the single-plate piezoelectric vibrator is formed in the thickness direction. A plurality of layers are stacked.

  As a result, the inventor has made it possible to reduce the size, increase the efficiency, and simplify the configuration. In addition, the necessary power supply voltage can be reduced. Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  1 to 3 are plan views of a single-plate piezoelectric vibrator according to this embodiment. This single-plate piezoelectric vibrator 1 is made of piezoelectric ceramics and is polarized in a direction perpendicular to the paper surface. A known material such as lead zirconate titanate-based ceramics can be used for the single-plate piezoelectric vibrator 1. The single-plate piezoelectric vibrator 1 is manufactured according to a general ceramic manufacturing process, for example, a manufacturing process of forming (degreasing), firing, and processing of piezoelectric ceramic powder. By applying a silver paste in a predetermined pattern to the manufactured single-plate piezoelectric vibrator 1 by screen printing or the like and baking it, two electrodes to be described later can be provided on one main surface.

  Further, a sliding chip 2 for transmitting a driving force is provided in the central portion on the upper side with respect to the paper surface of the single-plate piezoelectric vibrator 1. The sliding tip 2 is made of a material having excellent wear resistance. For example, ceramic parts such as alumina, zirconia, silicon nitride, and silicon carbide, wear-resistant metal parts such as super-rigid, parts having a hard metal material coated with a ceramic thin film or a diamond thin film, and the like are preferably used.

  2 and 3, sliding chips 3a and 3b may be provided at both ends on the upper side with respect to the paper surface of the single-plate piezoelectric vibrator 1 as indicated by a dotted line. When the sliding chip 2 is provided at the upper central portion with respect to the paper surface of the single-plate piezoelectric vibrator 1, it is suitable for driving a rotating body such as a disk or a sphere, and the single-plate piezoelectric vibrator When the sliding tips 3a and 3b are provided at both ends on the upper side of the sheet of paper 1, it is suitable for driving a sliding body that operates linearly. Further, as shown in FIG. 1, the length of one side of the two sides of the rectangular and single-plate piezoelectric vibrator 1 is L, and the length of the other side is w. is there.

  FIG. 2 is a diagram illustrating a state in which the single-plate piezoelectric vibrator 1 is expanding and vibrating. This spreading vibration is vibration in which the rectangular, single-plate piezoelectric vibrator 1 repeatedly expands and contracts from the center toward the four sides. The potential distribution of the single-plate piezoelectric vibrator 1 becomes higher toward the end face with equipotential lines almost parallel. FIG. 3 is a diagram illustrating a state in which the single-plate piezoelectric vibrator 1 causes bending vibration. This bending vibration is a rectangular and single-plate piezoelectric vibrator 1 bent two-dimensionally, but in the potential distribution, potentials with opposite signs are generated at the output-side central portion and both sides in the width direction. When the expansion vibration mode shown in FIG. 2 and the bending vibration mode shown in FIG. 3 are combined (degenerated), the sliding tip 2 or the sliding tips 3a and 3b perform an elliptical motion, and a driving force is generated.

  Next, the driving principle of the ultrasonic motor according to this embodiment will be described. FIG. 4 is a diagram showing a frequency spectrum when a rectangular, single-plate piezoelectric vibrator is vibrated in an expansion vibration mode (Expand Mode) and a bending vibration mode (Flexural Mode). Of the two sets of sides of the rectangular and single-plate piezoelectric vibrator 1, the length of one set of sides is L, and the length of the other set of sides is w, as shown in FIG. , W / L is used as a variable, and w / L is associated with the resonance frequency of the spreading vibration mode of the single-plate piezoelectric vibrator, and w / L is associated with the resonance frequency of the bending vibration mode. In FIG. 4, L is fixed at 20 mm, and only w (Width) is changed. In this case, w is 17.0 mm, that is, the ratio of the two sides in the vertical and horizontal directions (hereinafter referred to as “side ratio”) w / L is about 0.85, the resonance frequencies of the two coincide, and the two vibrations Degenerate. The resonance frequency at this time is 107 kHz to 108 kHz.

  Thus, the side ratio is 0.85, and one side is a square having a length of about 20 mm, so that the size can be reduced.

  FIG. 5 is a diagram conceptually showing a laminated piezoelectric vibrator formed by laminating a plurality of single-plate piezoelectric vibrators 1 formed as described above in the thickness direction. In FIG. 5, a part is expressed by cutting. The laminated piezoelectric vibrator 50 includes a piezoelectric layer 51 in which a single-plate piezoelectric vibrator 1 is laminated and an inner layer electrode 52 provided between the piezoelectric layers. The laminated piezoelectric vibrator 50 includes an input electrode 53, two external extraction electrodes 54, and a ground electrode 55.

  For example, when the laminated piezoelectric vibrator 50 is configured by laminating the single-plate piezoelectric vibrator 1 in six layers, the single-plate piezoelectric vibrator 1 having an input voltage of 60 Vpp is the laminated piezoelectric vibrator. In the vibrator 50, the voltage could be reduced to 20Vpp. In this case, since the stacking direction and the displacement direction are perpendicular to each other, the “lateral effect” is used as the piezoelectric effect. Further, in order to further increase the efficiency, it is possible to adopt a configuration using the “vertical effect”. For example, the vertical effect can be used by stacking in the displacement direction. For example, when a single-plate piezoelectric vibrator is polarized in the vertical direction, the drive voltage needs to be 500 Vpp or more. On the other hand, by laminating single-plate piezoelectric vibrators at intervals of 0.5 mm to form a laminated piezoelectric vibrator, it becomes possible to drive with a drive voltage of 10 Vpp or less.

  FIG. 6 is a diagram showing a piezoelectric vibrator to which a cross finger electrode is attached. The piezoelectric vibrator 60 has a cross finger electrode 61 and a ground electrode 62. A similar effect can also be obtained by configuring a laminated piezoelectric vibrator using such a crossed finger electrode 61 and forming an ultrasonic motor by polarization in the direction of the interval between the crossed fingers. Further, the number of stacked layers is small, which is industrially advantageous.

Specifically, when the horizontal effect is used, d31 = 130 × 10 ⁻¹² m / V, and when the vertical effect is used, d33 = 290 × 10 ⁻¹² m / V. When the effect is used, the efficiency can be improved by about 2.2 times the lateral effect.

  FIG. 7A is a diagram showing impedance characteristics of an ultrasonic motor using a laminated piezoelectric vibrator laminated in six layers according to the present embodiment, and FIG. 7B shows impedance characteristics of the ultrasonic motor using a single-plate piezoelectric vibrator. FIG. Comparing the impedance characteristics of the two, as shown in FIGS. 7A and 7B, the impedance of the laminated piezoelectric vibrator laminated in six layers is one digit smaller than the impedance of the single-plate piezoelectric vibrator. Therefore, the input voltage for driving the laminated piezoelectric vibrator is obviously smaller than that of the single-plate piezoelectric vibrator.

  FIG. 8 is a diagram illustrating a schematic configuration of the ultrasonic motor device according to the present embodiment. In the ultrasonic motor device 80, the multilayer piezoelectric vibrator 50a slides the drive target 15 in the direction of the arrow A or B in FIG. 8 by the elliptical movement of the sliding tip 2a. The laminated piezoelectric vibrator 50a has electrodes as shown in FIG. 5, is supplied with voltage from two locations, and the center electrode is grounded.

  In FIG. 8, a driving device 70 includes a position sensor 31 that detects the position of the driven object 15, a resonance driving device 32 that resonates and drives an ultrasonic motor (laminated piezoelectric vibrator) 50a, and a direct current that drives the ultrasonic motor 50a. A DC drive device 33 for driving and a drive control device (CPU) 34 for sending a drive command signal to the resonance drive device 32 or the DC drive device 33 in accordance with a detection signal of the position sensor 31 are provided. The resonance driving device 32 and the DC driving device 33 share the amplifiers 35a and 35b. Further, the resonance driving device 32 includes a first feedback control device 36 and a phase control device 37. The DC drive device 33 includes a second feedback control device 38 and a signal inverter 39.

  Since the ultrasonic motor 50a is composed of a laminated piezoelectric vibrator, as described above, it is possible to exhibit the same driving force even when the driving voltage is smaller than that of a single-plate piezoelectric vibrator. For this reason, in the amplifiers 35a and 35b, it is not necessary to use a boosting component as in the prior art, and the amplifiers 35a and 35b can be downsized. More specifically, the amplifiers 35a and 35b according to the present embodiment are about 1/3 smaller in size than the conventional amplifier.

  As the position sensor 31, a non-contact optical sensor system using a laser is preferably used. For example, marking (not shown) for indicating the position of the driving object 15 is provided on the driving object 15, and the position sensor 31 detects the position of the driving object 15 from the reflected light pattern.

  When the first feedback control device 36 receives a command signal for resonantly driving the ultrasonic motor 50a from the drive control device (CPU) 34, the first feedback control device 36 generates a resonant drive signal for resonantly driving the ultrasonic motor 50a and amplifies it. Send to 35a, 35b. Further, the first feedback control device 36 receives the detection signal of the position sensor 31 and adjusts the moving speed of the driven object 15. Therefore, the first feedback control device 36 can appropriately change the waveform of the resonance drive signal (for example, change the zero-peak voltage value).

A resonance drive signal having the same waveform is output from the first feedback control device 36 to the amplifiers 35a and 35b. Therefore, the phase of the resonance drive signal sent to one amplifier, that is, the amplifier 35a, is shifted by 90 degrees by the phase controller 37 before being input to the amplifier 35a. For example, when the resonance drive signal output from the first feedback control device 36 is V = V ₀ sin (2πft), this resonance drive signal of V = V ₀ sin (2πft) is input to the amplifier 35b. However, a resonance drive signal of V = V ₀ cos (2πft) or V = −V ₀ cos (2πft) phase-controlled by the phase controller 37 is input to the amplifier 35a.

The resonance drive signal output from the first feedback control device 36 may be V = V ₀ cos (2πft). In this case, the phase controller 37 outputs a resonance drive signal of V = V ₀ sin (2πft) or V = −V ₀ sin (2πft).

  When the second feedback control device 38 receives a command signal for direct drive of the ultrasonic motor 50a from the drive control device (CPU) 34, the second feedback control device 38 generates a direct current voltage signal for direct drive of the ultrasonic motor 50a and amplifies it. Send to 35a, 35b. The second feedback control device 38 can receive a signal from the position sensor 31 and appropriately adjust the voltage value of the DC voltage signal and send it to the amplifiers 35a and 35b.

  The same DC voltage signal is output from the second feedback control device 38 to the amplifiers 35a and 35b. For this reason, the DC voltage signal sent to the amplifier 35a is inverted by the signal inverter 39 before being input to the amplifier 35a.

  As described above, according to this embodiment, the single-plate piezoelectric vibrator 1 is formed based on the value of w / L at which the resonance frequency of the spreading vibration and the resonance frequency of the bending vibration are substantially the same. Therefore, the shape of the main surface of the single-plate piezoelectric vibrator can be made closer to a square than when driven in another mode, for example, the L1F2 mode. As a result, the overall dimension does not become flat, and the depth dimension can be reduced. Thereby, it becomes possible to take a power input larger than the conventional one. Further, by stacking a plurality of single-plate piezoelectric vibrators 1 formed in this way in the thickness direction, a large electric field strength can be applied to the multilayer piezoelectric vibrator at the same input voltage as the single plate. This makes it possible to reduce the necessary power supply voltage. As a result, it is possible to eliminate the step-up component required in the conventional ultrasonic motor, and to reduce the size of the driver board. As a result, a small driver system capable of multi-channel operation can be realized.

It is a top view of the piezoelectric vibrator concerning this embodiment. It is a figure which shows a mode that the piezoelectric vibrator 1 is expanding and vibrating. It is a figure which shows a mode that the piezoelectric vibrator 1 is raising the bending vibration. It is a figure which shows a frequency spectrum when a rectangular-shaped piezoelectric vibrator is vibrated in an expansion vibration mode (Expand Mode) and a bending vibration mode (Flexural Mode). FIG. 3 is a diagram conceptually illustrating a stacked piezoelectric vibrator configured by stacking a plurality of single-plate piezoelectric vibrators in a thickness direction. It is a figure which shows the piezoelectric vibrator which attached the cross finger electrode. It is a figure which shows the impedance characteristic of the ultrasonic motor by the lamination type piezoelectric vibrator laminated | stacked on 6 layers which concern on this embodiment. It is a figure which shows the impedance characteristic of the ultrasonic motor by a single-plate piezoelectric vibrator. It is a figure which shows schematic structure of the ultrasonic motor apparatus which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single-plate piezoelectric vibrator 2 Sliding tip 2a Sliding tip 3a Sliding tip 3b Sliding tip 15 Drive target 31 Position sensor 32 Resonant drive device 33 DC drive device 35a Amplifier 35b Amplifier 36 Feedback control device 37 Phase control device 38 Feedback Control Device 39 Signal Inverter 50 Multilayer Piezoelectric Vibrator 50a Ultrasonic Motor (Multilayer Piezoelectric Vibrator)
51 Piezoelectric Layer 52 Inner Layer Electrode 53 Input Electrode 54 External Extraction Electrode 55 Ground Electrode 61 Piezoelectric Vibrator 61 Cross Finger Electrode 62 Ground Electrode 70 Drive Device 80 Ultrasonic Motor Device

Claims (2)

A rectangular single plate piezoelectric vibrator is laminated to form a laminated piezoelectric vibrator, and the laminated piezoelectric vibrator vibrates in a multiple vibration mode combining a spread vibration mode and a bending vibration mode, thereby driving force. An ultrasonic motor that generates
Of the two sets of sides of the single-plate piezoelectric vibrator, the length of one set of sides is L, the length of the other set of sides is w, w / L is a variable, and w / L When the resonance frequency of the spreading vibration mode is made to correspond, and w / L and the resonance frequency of the bending vibration mode are made to correspond,
The single plate piezoelectric vibrator is formed so that the value of w / L falls within a range of 0.75 to 0.90,
A plurality of the single-plate piezoelectric vibrators are stacked in the thickness direction,
The laminated piezoelectric vibrator is formed by a piezoelectric layer and an inner layer electrode provided between the piezoelectric layers, and has two external lead electrodes alternately arranged in parallel with a ground electrode as the inner layer electrode,
A first AC voltage is applied to one of the two external extraction electrodes,
The stacked piezoelectric vibrator is driven by applying a second AC voltage whose phase is shifted by π / 2 to the other of the two external extraction electrodes. Ultrasonic motor characterized by A rectangular single plate piezoelectric vibrator is laminated to form a laminated piezoelectric vibrator, and the laminated piezoelectric vibrator vibrates in a multiple vibration mode combining a spread vibration mode and a bending vibration mode, thereby driving force. An ultrasonic motor that generates
Of the two sets of sides of the single-plate piezoelectric vibrator, the length of one set of sides is L, the length of the other set of sides is w, w / L is a variable, and w / L When the resonance frequency of the spreading vibration mode is made to correspond, and w / L and the resonance frequency of the bending vibration mode are made to correspond,
The single-plate piezoelectric vibrator is formed such that the value of w / L is substantially 0.85,
A plurality of the single-plate piezoelectric vibrators are stacked in the thickness direction,
The laminated piezoelectric vibrator is formed by a piezoelectric layer and an inner layer electrode provided between the piezoelectric layers, and has two external lead electrodes alternately arranged in parallel with a ground electrode as the inner layer electrode,
A first AC voltage is applied to one of the two external extraction electrodes,
The stacked piezoelectric vibrator is driven by applying a second AC voltage whose phase is shifted by π / 2 to the other of the two external extraction electrodes. Ultrasonic motor characterized by

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