JP2008199700A - Ultrasonic motor, driving method thereof, and ultrasonic motor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor which can be driven with a simple power supply configuration, attached with a saved space and further stably stored. <P>SOLUTION: The ultrasonic motor 10 is provided with a rectangular planar piezoelectric plate 11 made of piezoelectric ceramics; four driving electrodes 12a-12d formed in two rows two columns on one main surface of the piezoelectric plate 11, and divided into two pairs of driving electrode sections by electrically the diagonally positioned two pairs; a common electrode formed on the other main surface of the piezoelectric plate so as to oppose the four driving electrodes 12a-12d with the piezoelectric plate sandwiched; and two heads 13a, 13b provided on both the ends of the side surface of the piezoelectric plate 11 and contacting an object 50 to be driven. In order to allow the ultrasonic motor 10 to simultaneously generate resonant vibrations of L1 and B2 modes, a predetermined voltage is applied to any one of the two driving electrode portions. During the voltage application, the other driving electrode portion is kept in a floating state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor using piezoelectric ceramics suitable for driving an XY stage and the like, a driving method thereof, and an ultrasonic motor apparatus for executing the driving method.

  Recently, ultrasonic motors using piezoelectric ceramics have been used for driving mechanisms such as an XY stage, a linear motor, and a rotary stage (see, for example, Patent Document 1).

  As shown in FIG. 3, the ultrasonic motor disclosed in Patent Document 1 includes four drive electrodes 92a formed in two rows and two columns on one main surface of a rectangular plate-shaped piezoelectric plate 91 made of piezoelectric ceramics. To 92d are formed, a full-surface electrode (ground electrode; not shown) is formed on the other main surface, and a head for contacting an end surface of the piezoelectric plate 91 with a driven body 99 such as an XY stage. (Sliding member) 93 is attached.

  The four drive electrodes 92a to 92d are electrically connected to each other located diagonally, and two sets of drive electrode portions 94 and 95 are configured. In addition, the ultrasonic motor 90 is held by applying a preload by the spring 96 in the width direction (X direction) of the piezoelectric plate 91 and simultaneously pressing the head 93 against the driven body 99 by the spring 97.

  In the ultrasonic motor 90, for example, a sine wave voltage is applied between one of the drive electrode portions 94 and 95 and the entire surface electrode, and the other drive electrode portion is in a floating state (a state where no voltage is applied). Thus, it can be driven. At this time, as shown in FIG. 4A, vibration in the expansion and contraction primary resonance (L1) mode occurs in the longitudinal direction of the piezoelectric plate 91, and as shown in FIG. B2) Mode vibration occurs.

  In the ultrasonic motor 90, an elliptical motion is generated in the head 93 due to the superposition (degeneration) of these vibration modes. The rotation direction of the elliptical motion can be reversed by switching the drive electrode portions 94 and 95 to which the voltage is applied. That is, whether the driven body 99 is moved in the + X direction or the −X direction is determined by which of the drive electrode portions 94 and 95 is applied with the drive voltage.

  However, the structure in which the head 93 is provided on the end face of the piezoelectric plate 91 has a structure in which the piezoelectric plate 91 protrudes with respect to the sliding surface of the driven body 99, so that a large installation space is required, and the apparatus is downsized. Is disturbed. Further, the holding of the piezoelectric plate 91 tends to become unstable.

  Therefore, as shown in FIG. 5, an ultrasonic motor 90A having a structure in which heads 93a and 93b are attached to both ends of a side surface of a piezoelectric plate 91 has been proposed (see, for example, Patent Document 2). In this ultrasonic motor 90A, a sine-shaped bending vibration is caused to occur on the piezoelectric plate 91 by applying a sine wave voltage whose phase is shifted by 90 degrees to the two sets of drive electrode portions 94 and 95 at the same time. Ellipse motions whose phases are shifted by 180 degrees are generated in the heads 93a and 93b, respectively. The direction in which the driven body 99 is moved can be selected depending on whether the phase shift is advanced or delayed.

However, this method complicates the power supply configuration. In order to prevent the vibration generated in the piezoelectric plate 91 from being hindered, it is preferable to hold the piezoelectric plate 91 at its central portion. However, such a holding method lacks anxiety, and the two heads 93 are equally distributed. It is difficult to press the driven body 99 with a strong force. Furthermore, processing such as providing a holding hole at the center of the piezoelectric plate 91 is required.
JP-A-7-184382 Japanese Patent Laid-Open No. 5-137359

  The present invention has been made in view of such circumstances, and is to provide an ultrasonic motor that can be driven with a simple power supply configuration, can be installed in a small space, and can be stably held. Objective. It is another object of the present invention to provide a method for driving the ultrasonic motor and an ultrasonic motor device for executing the driving method.

  According to a first aspect of the present invention, a rectangular flat plate-shaped piezoelectric plate made of piezoelectric ceramics, four drive electrodes formed in two rows and two columns on one main surface of the piezoelectric plate, and the piezoelectric plate A common electrode formed on the other main surface of the piezoelectric plate so as to be opposed to the driving electrode, and provided at both ends of the side surface of the piezoelectric plate, and pressed against a predetermined driven body with a predetermined force The four drive electrodes are electrically connected to each other at the diagonal positions and divided into two sets of drive electrode portions. One drive electrode portion has a predetermined number. An ultrasonic motor is provided in which no voltage is applied to the other drive electrode section while the above voltage is applied.

  In this ultrasonic motor, the value obtained by dividing the width of the piezoelectric plate by the length of the piezoelectric plate is preferably 0.272, whereby the L1 mode and the B2 mode are excited at the same frequency to obtain a large vibration displacement. Can do.

  According to a second aspect of the present invention, this ultrasonic motor driving method, that is, a rectangular plate-shaped piezoelectric plate made of piezoelectric ceramics and one main surface of this piezoelectric plate are provided in two rows and two columns, Four drive electrodes that are electrically connected to each other at diagonal positions and divided into two sets of drive electrode portions, and opposite to the drive electrodes with the piezoelectric plate sandwiched between the other main surfaces of the piezoelectric plate An ultrasonic motor comprising a common electrode provided to be arranged and two sliding members provided at both ends of the side surface of the piezoelectric plate, and a predetermined force applied to the driven body by the two sliding members. In the method of holding and driving in a state of being pressed, while applying a predetermined voltage to one of the two sets of drive electrodes, no voltage is applied to the other drive electrode portion. An ultrasonic motor driving method is provided.

  According to the third aspect of the present invention, the rectangular flat plate-shaped piezoelectric plate made of piezoelectric ceramics and the one formed on the main surface of the piezoelectric plate in two rows and two columns and located diagonally are electrically connected. Four drive electrodes connected to each other and divided into two sets of drive electrode portions, and a common electrode formed on the other main surface of the piezoelectric plate so as to face the four drive electrodes across the piezoelectric plate And an ultrasonic motor provided at both ends of the side surface of the piezoelectric plate and having two sliding members in contact with a predetermined driven body, and applying a predetermined voltage to one of the two driving electrode portions During the operation, an ultrasonic motor device including a drive power supply unit that does not apply a voltage to the other drive electrode unit is provided.

  In this ultrasonic motor apparatus, it is preferable that the drive power supply unit includes a single power supply and a switching unit that sets a voltage supply from the power supply to one of the two drive electrode units.

  The ultrasonic motor according to the present invention can be installed in a space-saving manner with respect to the driven body, can be stably held, and is driven by using one power source, so that the power supply configuration is simple. It has an excellent effect that it can be made.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an ultrasonic motor device. The ultrasonic motor device 100 includes an ultrasonic motor 10, a casing unit 20 for holding the ultrasonic motor 10, and a drive power supply unit 30 for driving the ultrasonic motor 10. As shown in FIG. 1, the three-dimensional orthogonal coordinate axes of the X axis, the Y axis, and the Z axis are defined.

  The ultrasonic motor 10 includes a rectangular plate-shaped piezoelectric plate 11 made of piezoelectric ceramics, and four drives formed in two rows and two columns on one main surface (Y-direction surface; Z-X surface) of the piezoelectric plate 11. The electrodes 12a to 12d, the common electrode (not shown) formed on the other main surface of the piezoelectric plate 11 so as to face the drive electrodes 12a to 12d across the piezoelectric plate 11, and the side surface (Z There are provided sliding members (hereinafter referred to as “heads”) 13a and 13b provided at both ends (X-direction ends) of the directional plane (XY plane).

  The piezoelectric ceramic material used for the piezoelectric plate 11 is not particularly limited, but lead zirconate titanate piezoelectric ceramics are usually used. The piezoelectric plate 11 preferably has a shape in which a value obtained by dividing the width (length in the Z direction) by the length (length in the X direction) is 0.272. By adopting such a shape, as described later, the L1 mode and the B2 mode can be excited at the same frequency to obtain a large vibration displacement.

  The driving electrodes 12a to 12d are electrically connected to each other at diagonal positions, and are divided into two sets of driving electrode portions, ie, a driving electrode 12a / 12d set and a driving electrode 12b / 12c set. A lead portion 15 for applying a drive voltage to the set of 12c is attached to the drive electrode 12c, and a lead portion 16 for applying a drive voltage to the set of the drive electrodes 12a and 12d is attached to the drive electrode 12d, respectively. .

  The drive electrodes 12a to 12d are equal in size, narrow as long as the gap width between the drive electrodes 12a to 12d does not cause dielectric breakdown, and the area occupied on the main surface of the piezoelectric plate 11 is as wide as possible. It is preferable that the vibration displacement clamp by the piezoelectric inactive region of the piezoelectric plate 11 is reduced.

  The casing portion 20 that holds the piezoelectric plate 11 includes a concave base portion 21, two first elastic members 22 a attached to the bottom wall of the base portion 21, and one side wall of the base portion 21. The attached second elastic member 22b and a columnar member 23 provided between the other side wall of the base portion 21 and the piezoelectric plate 11 are provided.

  The base 21 is made of engineering plastic or metal. As the first and second elastic members 22a and 22b, a coil spring, a leaf spring, an elastic resin (rubber), or the like is used. The two first elastic members 22 a are in contact with the side surface of the piezoelectric plate 11 where the heads 13 a and 13 b are not attached, and press the heads 13 a and 13 b against the driven body 50. The second elastic member 22b presses one end face (X direction plane; YZ plane) of the piezoelectric plate 11 in the X direction, whereby the piezoelectric plate 11 is connected to the base portion via the cylindrical member 23. 21 is pressed against the other side wall. The thickness (length) direction of the cylindrical member 23 is parallel to the Y direction, and is frictionally held between the side wall of the base portion 21 and the piezoelectric plate 11 by urging by the second elastic member 22b, and at the same time, The holding member that is not held is held so that it cannot move in the Z direction.

  The drive power supply unit 30 includes an AC power supply 31 and a switch 32. The AC power supply 31 outputs a sine wave voltage having a frequency for exciting the ultrasonic motor 10 to resonate in the L1 mode and the n-order (n is an integer) bending resonance mode. Preferably, a secondary bending resonance mode (the B2 mode described above with reference to FIG. 4B) is preferably used as the resonance mode of the nth order bending.

  When driving the ultrasonic motor 10, the switch 32 energizes one of the lead portions 15 and 16 with a voltage output from the AC power supply 31. That is, while a predetermined voltage is applied to one drive electrode portion of two sets of drive electrode portions (a set of drive electrodes 12a and 12d and a set of drive electrodes 12b and 12c), a voltage is applied to the other drive electrode portion. Is not applied. In FIG. 1, illustration of wiring between the AC power supply 31 and the common electrode is omitted (the same applies to FIGS. 2A and 2B described later).

  FIG. 2A schematically shows the movement of the ultrasonic motor 10 and the driven body 50 when a voltage is applied to the pair of drive electrodes 12a and 12d. When the L1 mode and, for example, the B2 mode resonance are simultaneously generated in the drive electrodes 12a and 12d, ideally, the diagonal length of the drive electrodes 12a and 12d of the piezoelectric plate 11 is expanded and contracted. Corresponding to this, shear deformation occurs in which the length in the diagonal direction where the drive electrodes 12b and 12c are provided expands and contracts.

  The displacement of the head 13a is indicated by arrows D1a and D1b according to this deformation, and the displacement of the head 13b is indicated by arrows D2a and D2b according to this deformation. Since the diagonal displacement amount of the drive electrodes 12a and 12d is larger than the diagonal displacement amount of the drive electrodes 12b and 12c, the displacement amount of the head 13a is larger than the displacement amount of the head 13b.

  When the head 13a is displaced in the direction of the arrow D1a approaching the driven body 50, the head 13b is displaced in the direction of the arrow D2a so as to be separated from the driven body 50, and conversely, the arrow in which the head 13a is separated from the driven body 50. When displacing in the direction of D1b, the head 13b is displaced in the direction of the arrow D2b so as to approach the driven body 50.

  The head 13a repeatedly strikes the driven body 50 by repeating the displacement of the arrows D1a and D1b at a constant short time interval according to the driving frequency. The striking force that the head 13a applies to the driven body 50 includes a leftward component in the X direction, and a frictional force acts between the head 13a and the driven body 50 at the moment of the hitting. It can be moved to the left in FIG. 2A.

  In addition, while the head 13 a strikes the driven body 50, the frictional force acting between the head 13 b and the driven body 50 may hinder the movement of the driven body 50. Further, when the displacement of the arrow D1b occurs in the head 13a, the displacement of the arrow D2b occurs in the head 13b. At this time, the head 13b may move the driven body 50 to the right. However, in reality, as shown in the embodiments described later, in view of the fact that the driven body 50 can be moved at a high speed, the braking force by the head 13b and the force for moving in the reverse direction are the same as the head 13a. It is considered to be extremely small compared to the driving force by.

  FIG. 2B schematically shows the movement of the ultrasonic motor 10 and the driven body 50 when a voltage is applied to the set of the drive electrodes 12b and 12c. At this time, the vibration generated in the ultrasonic motor 10 is symmetrical in the X direction in the form shown in FIG. 2A. That is, when the L1 mode and B2 mode resonances are simultaneously generated in the drive electrodes 12b and 12c, ideally, the diagonal length of the piezoelectric plate 11 where the drive electrodes 12b and 12c are provided expands and contracts. Corresponding to this, shear deformation occurs in which the length in the diagonal direction where the drive electrodes 12a and 12d are provided expands and contracts.

  The displacement of the head 13a is indicated by arrows D1a and D1b according to this deformation, and the displacement of the head 13b is indicated by arrows D2a and D2b according to this deformation. Since the diagonal displacement amount of the drive electrodes 12b and 12c is larger than the diagonal displacement amount of the drive electrodes 12a and 12d, the displacement amount of the head 13b is larger than the displacement amount of the head 13a.

  When the head 13b is displaced in the direction of the arrow D2b approaching the driven body 50, the head 13a is displaced in the direction of the arrow D1b so as to be separated from the driven body 50, and conversely the arrow in which the head 13b is separated from the driven body 50. When displacing in the direction of D2a, the head 13a is displaced in the direction of arrow D1a so as to approach the driven body 50.

  The head 13b repeatedly strikes the driven body 50 by repeating the displacement of the arrows D2a and D2b at regular short time intervals according to the driving frequency. The striking force applied to the driven body 50 by the head 13b includes a rightward component in the X direction, and a frictional force acts between the head 13b and the driven body 50 at the moment of the hitting. It can be moved to the right in FIG. 2A.

  The heads 13a and 13b actually have a motion to draw an elliptical trajectory whose major axis is in the directions of the arrows D1a, D1b, D2a, and D2b, depending on the shape system and the holding state of the ultrasonic motor 10, respectively. Although it may occur, even in that case, the driving characteristics of the driven body 50 are not greatly affected.

  The configuration of the drive power supply unit is not limited to that shown in FIG. 1. For example, the lead units 15 and 16 are each provided with an AC power supply connected via an on / off switch, and controlled by the on / off switch. It is good also as a structure which drives one of two sets of drive electrode parts.

  Next, a specific configuration and characteristics of the ultrasonic motor 10 will be described. A length of 16.5 mm × width 4.5 mm × thickness 3 mm (width / length = 0.272) of the piezoelectric plate 11 made of lead zirconate titanate-based piezoelectric ceramics is vertically 1.6 mm long. X Driving electrodes 12a to 12d having a width of 7.8 mm were formed, and a full surface electrode was formed on the other main surface. The drive electrodes 12a and 12d are connected, the drive electrodes 12b and 12c are connected, and lead portions 15 and 16 are provided on the drive electrodes 12c and 12d, respectively, and polarization treatment is performed in the thickness direction of the piezoelectric plate 11. . Further, alumina heads 13a and 13b were attached to both ends of the side surface of the piezoelectric plate 11 using an epoxy adhesive.

  The ultrasonic motor 10 thus manufactured is pressed against a metal slider 5 mm × 3 mm × 60 mm slidably held on a guide rail with a constant force, and a sine wave voltage having a frequency of 100 kHz and a voltage of 60 Vrms is applied to the lead portion 15. Thus, resonance vibrations in the L1 mode and the B2 mode were generated simultaneously. By adjusting the force for pressing the ultrasonic motor 10 against the slider, the slider could be moved at a maximum speed of 100 mm / sec.

The schematic block diagram of an ultrasonic motor. The figure which shows typically a motion of an ultrasonic motor and a to-be-driven body. The figure which shows typically another motion of an ultrasonic motor and a to-be-driven body. The top view which shows the structure of the conventional ultrasonic motor. The figure which shows the expansion-contraction primary resonance (L1) mode of a piezoelectric plate. The figure which shows the bending secondary resonance (B2) mode of a piezoelectric plate. The top view which shows the structure of another conventional ultrasonic motor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic motor, 11 ... Piezoelectric plate, 12a-12d ... Drive electrode, 13a * 13b ... Head, 15 * 16 ... Lead part, 20 ... Casing part, 21 ... Base part, 22a ... 1st elastic member, 22a DESCRIPTION OF SYMBOLS 2nd elastic member, 23 ... Cylindrical member, 30 ... Drive power supply part, 31 ... AC power supply, 32 ... Switch, 50 ... Driven object, 90 ... Ultrasonic motor, 91 ... Piezoelectric plate, 92a-92d ..., 93. 93a, 93b, head, 94, 95, drive electrode section, 96, 97, spring, 99, driven body, 100, ultrasonic motor device.

Claims (5)

A rectangular flat plate piezoelectric plate made of piezoelectric ceramic;
Four drive electrodes formed in two rows and two columns on one main surface of the piezoelectric plate;
A common electrode formed on the other main surface of the piezoelectric plate so as to face the drive electrode across the piezoelectric plate;
Two sliding members provided at both ends of the side surface of the piezoelectric plate and pressed against a predetermined driven body with a predetermined force,
The four drive electrodes are diagonally connected to each other and divided into two sets of drive electrode portions. While a predetermined voltage is applied to one drive electrode portion, the other is An ultrasonic motor, wherein no voltage is applied to the drive electrode portion.   The ultrasonic motor according to claim 1, wherein a value obtained by dividing the width of the piezoelectric plate by the length of the piezoelectric plate is 0.272. A rectangular plate-shaped piezoelectric plate made of piezoelectric ceramics and two main electrodes on one main surface of this piezoelectric plate are connected in two rows and two columns, and the diagonally-connected ones are electrically connected to two sets of drive electrode portions. Four divided drive electrodes, a common electrode provided to face the drive electrode with the piezoelectric plate sandwiched between the other main surface of the piezoelectric plate, and provided at both ends of the side surface of the piezoelectric plate, respectively. A method of driving an ultrasonic motor having two sliding members while holding the two sliding members pressed against a driven body with a predetermined force,
A method of driving an ultrasonic motor, wherein a voltage is not applied to the other drive electrode portion while a predetermined voltage is applied to one of the two sets of drive electrodes. A rectangular plate-shaped piezoelectric plate made of piezoelectric ceramic and two main electrodes formed in two rows and two columns on one main surface are electrically connected to each other so that two sets of drive electrode portions are connected to each other. Four divided drive electrodes, a common electrode formed on the other main surface of the piezoelectric plate so as to face the four drive electrodes across the piezoelectric plate, and both ends of the side surface of the piezoelectric plate An ultrasonic motor provided with two sliding members provided and pressed against a predetermined driven body with a predetermined force;
An ultrasonic motor apparatus comprising: a drive power supply unit that applies no voltage to the other drive electrode unit while a predetermined voltage is applied to one of the two drive electrode units.   5. The super power supply unit according to claim 4, wherein the drive power supply unit includes one power supply and a switching unit that sets a voltage supply from the power supply to one of the two drive electrode units. Sonic motor device.

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